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Applied Surface Science (v.273, #)

Editorial Board (pp. ii).

Modification of polyimide wetting properties by laser ablated conical microstructures by Brandon T. Least; David A. Willis (pp. 1-11).

► Cone-shaped microstructures were generated on polyimide by low-fluence laser ablation. ► Contact angle of water on polyimide was altered, depending on nature of the cone density. ► Maximum contact angle of 118° was achieved for densely packed cones, while a decrease in contact angle to as low as 47° was achieved for low density of cones. ► Wenzel mode wetting behavior was observed due to a combination of surface texturing and alteration in oxygen content of ablated surface.Laser texturing of Kapton^® HN polyimide was performed by low-fluence ablation using a pulsed, frequency tripled (349nm) Nd:YLF laser. The laser was scanned in two dimensions in order to generate texture over a large area. The laser overlap percentage and fluence were varied and the resulting texture was studied. The texture features were inspected by electron microscopy and energy dispersive X-Ray spectroscopy (EDS), while the static contact angle of de-ionized water was measured by a contact angle goniometer. Rounded bump features were formed at all fluences, which decreased in areal density with fluence and number of laser pulses. Conical microstructures or “cones” were also formed at most fluences. Cones were larger than the bumps and thus had lower areal density, which increased as a function of the number of laser pulses. The polyimide was hydrophilic before texturing, with a contact angle of approximately 76°. For most of the experimental conditions the contact angle increased as a result of texturing, with the contact angle exceeding 90° for some textured surfaces, and reaching values as high as 118°. In general, the surfaces with significant increases in contact angle had high density of texture features, either bumps or cones. The surfaces that experienced a decrease in contact angle generally had low density of texture features. The increase in contact angle from a wetting ( θ<90°) to a nonwetting surface ( θ>90°) cannot be explained by texturing alone. EDS measurements indicate that textured regions had higher carbon content than the untextured regions due to depletion of oxygen species. The increase in carbon content relative to the oxygen content increased the native contact angle of the surface, causing the transition from hydrophilic to hydrophobic behavior. The contact angle of a textured surface increased as the relative spacing of features (diameter to spacing) decreased.

Keywords: Laser ablation; Polyimide; Contact angle; Texturing; Hydrophobic; Hydrophilic; Pulsed laser

Studies on the optoelectronic properties of the thermally evaporated tin-doped indium oxide nanostructures by Ko-Ying Pan; Liang-Da Lin; Li-Wei Chang; Han C. Shih (pp. 12-18).

► An accurate composition of ITO nanorods was synthesized directly by one-step thermal evaporation. ► The optoelectronic properties of ITO nanorods are better than it of In₂O₃ nanorods, nanotowers due to doping tin. ► The electrical resistivity of In₂O₃ nanorods is 20 times higher than it of ITO nanorods. ► The electrical resistivity of In₂O₃ nanorods is 10 times higher than it of In₂O₃ nanotowers. ► The CL spectrum of ITO nanorods causes a blue-shift.Indium oxide (In₂O₃) nanorods, nanotowers and tin-doped (Sn:In=1:100) indium oxide (ITO) nanorods have been fabricated by thermal evaporation. The morphology, microstructure and chemical composition of these three nanoproducts are characterized by FE-SEM, HRTEM and XPS. To further investigate the optoelectronic properties, the I– V curves and cathodoluminescence (CL) spectra are measured. The electrical resistivity of In₂O₃ nanorods, nanotowers and ITO nanorods are 1.32kΩ, 0.65kΩ and 0.063kΩ, respectively. CL spectra of these three nanoproducts clearly indicate that tin-doped (Sn:In=1:100) indium oxide (ITO) nanorods cause a blue shift. No doubt ITO nanorods obtain the highest performance among these three nanoproducts, and this also means that Sn-doped In₂O₃ nanostructures would be the best way to enhance the optoelectronic properties. Additionally, the growing mechanism and the optoelectronic properties of these three nanostructures are discussed. This study is beneficial to the applications of In₂O₃ nanorods, nanotowers and ITO nanorods in optoelectronic nanodevices.

Keywords: Indium oxide (In; ₂; O; ₃; ); Sn-doped indium oxide (ITO); Thermal evaporation; Cathodoluminescence (CL); Optoelectronic

Fabrication of two domain Cu₂O(011) films on MgO(001) by pulsed laser deposition by Yajun Fu; Hongwei Lei; Xuemin Wang; Dawei Yan; Linhong Cao; Gang Yao; Changle Shen; Liping Peng; Yan Zhao; Yuying Wang; Weidong Wu (pp. 19-23).

► The single orientated Cu₂O(011) films with two kinds of domains were successfully fabricated by PLD. ► The deposition process was monitored by in situ RHEED; oxidation state of Cu for the as grown films was investigated by in situ XPS and XAES. ► The in-plane and out-of-plane orientation of Cu₂O(011) films were determined, the formation mechanism was also discussed. ► The optical band gap was determined by using the linear extrapolation method from the ( αE)² versus photon energy plot since.Single oriented Cu₂O(011) films were fabricated on MgO(001) substrates at temperature from 450 to 600°C by pulsed laser deposition. In situ X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy showed that the oxidation state of Cu should be Cu¹⁺. In situ reflection high-energy electron diffraction, ex situ X-ray diffraction and cross-sectional transmission electron microscopy have been used to characterize the structural properties of deposited Cu₂O films. The coexistence of two kinds of domains in the Cu₂O films was observed. The in-plane orientation relationships for the two kinds of domains are Cu₂O[100]||MgO[110] and Cu₂O[100]||MgO[1−10], respectively. The formed rotation domains, which perpendicular to each other, can be attributed to the mismatch of rotational symmetry at interface between Cu₂O and MgO. The strip-like surface morphology of Cu₂O films was investigated by atomic force microscopy and scanning electron microscopy. The band gap of Cu₂O films was determined by using the linear extrapolation method.

Keywords: Cu; ₂; O; MgO; PLD; Orientation relationships

Co-culture of vascular endothelial cells and smooth muscle cells by hyaluronic acid micro-pattern on titanium surface by Jingan Li; Guicai Li; Kun Zhang; Yuzhen Liao; Ping Yang; Manfred F. Maitz; Nan Huang (pp. 24-31).

The morphology and behavior of SMC were regulated by HMW-HA. Hyaluronidase was used to decompose HMW-HA to LMW-HA. Subsequently, EC adhesion took place selectively on LMW-HA coated zones of titanium substrate micro-patterned with strips of LMW-HA and SMC, and the EC and SMC ordered co-culture system was achieved.Display Omitted► The parallel micro-stripes of HMW-HA are successfully prepared on TiOH surface. ► The HMW-HA stripes can effectively regulate the morphology and behavior of SMC. ► EC can be cultured along the LMW-HA from HMW-HA and regulated by SMC. ► The new EC/SMC co-culture model may be useful for studying their interactions.Micro-patterning as an effective bio-modification technique is increasingly used in the development of biomaterials with superior mechanical and biological properties. However, as of now, little is known about the simultaneous regulation of endothelial cells (EC) and smooth muscle cells (SMC) by cardiovascular implants.In this study, a co-culture system of EC and SMC was built on titanium surface by the high molecular weight hyaluronic acid (HMW-HA) micro-pattern. Firstly, the micro-pattern sample with a geometry of 25μm wide HMW-HA ridges, and 25μm alkali-activated Ti grooves was prepared by microtransfer molding (μTM) for regulating SMC morphology. Secondly, hyaluronidase was used to decompose high molecular weight hyaluronic acid into low molecular weight hyaluronic acid which could promote EC adhesion. Finally, the morphology of the adherent EC was elongated by the SMC micro-pattern. The surface morphology of the patterned Ti was imaged by SEM. The existence of high molecular weight hyaluronic acid on the modified Ti surface was demonstrated by FTIR. The SMC micro-pattern and EC/SMC co-culture system were characterized by immunofluorescence microscopy. The nitric oxide release test and cell retention calculation were used to evaluate EC function on inhibiting hyperplasia and cell shedding, respectively.The results indicate that EC in EC/SMC co-culture system displayed a higher NO release and cell retention compared with EC cultured alone. It can be suggested that the EC/SMC co-culture system possessed superiority to EC cultured alone in inhibiting hyperplasia and cell shedding at least in a short time of 24h.

Keywords: Co-culture; Micro-pattern; Hyaluronic acid; Endothelial cells; Biomaterials

Substrate material affects wettability of surfaces coated and sintered with silica nanoparticles by Kang Wei; Hansong Zeng; Yi Zhao (pp. 32-38).

► We coated silica nanoparticles on glass, polyimide and copper substrates at different concentrations and performed a thermal sintering process for nanoparticles immobilization. ► We examined the surface morphologies and surface elements of above mentioned substrates. ► We examined the surface wettability of the above mentioned substrates. ► Copper surface has a significantly greater contact angle than the other two substrates at the same nanoparticles concentrations. ► Nano-roughening of copper surface due to thermal sintering helps to develop hierarchic micro/nanostructures, and is believed contribute to the wettability difference. Such nano-roughened features were not found in glass/polyimide substrates. ► Substrate material and the surface preparation approach must be appropriately selected by considering the possible surface topography evolution during surface functionalization and subsequent use.Silica nanoparticles coating and sintering is a widely-used approach for creating hydrophobic and superhydrophobic surfaces. The role of substrate material in this process, however, has not been thoroughly investigated. In this work, the role of substrate material is examined by measuring surface wettability of three different substrate materials (glass, polyimide and copper) under systematically varied conditions. These surfaces are modulated from hydrophilic (water contact angle (WCA)<90°) to superhydrophobic (WCA>150°) by coating and sintering silica nanoparticles, followed by assembling a layer of fluorine compound. Static WCA characterization shows that surface wettability is not solely dependent on the concentration of the coating colloidal, but is also on the substrate material. In particular, copper substrate exhibits a larger WCA than glass and polyimide substrates. Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and Atomic Force Microscopy (AFM) characterizations show that the substrate material-dependent wettability is attributed to thermal-induced nanostructures on the copper surface, which contributes to the hierarchical micro-/nano- topography. This finding is important for designing hydrophobic/superhydrophobic surfaces comprised of different materials, especially those that would experience thermal cycles in surface functionalization and subsequent use.

Keywords: Wettability; Thermal sintering; Substrate material; Nanoparticles; Grain growth

Dependence of precursor composition on patterning and morphology of sol–gel soft lithography based zinc zirconium oxide thin films by Susanta Bera; Moumita Pal; Saswati Sarkar; Sunirmal Jana (pp. 39-48).

► Film surface pattern formation depends on precursor solution composition. ► Films are crystalline, enriched with hexagonal ZnO below 55mol% ZOO in precursors. ► ZnO crystal shape changes from spherical to rod to sunflower-like particles. ► Water and chloride contents from ZOO are found to control the film characteristics.Array-like surface patterned zinc zirconium oxide thin films (135–163nm thickness) on soda lime silica glass substrate were prepared by sol–gel soft lithography from the precursor solutions (8wt% equivalent metal oxides) having zinc acetate dihydrate (ZA) and zirconium oxychloride octahydrate (ZOO=0–100mol% w.r.t. ZA) in ethanol-2-butanol medium with acetylacetone. The ZOO concentration in solutions strongly influenced the pattern formation, crystallinity, morphology and optical property of the films. The films were crystalline in nature and enriched with only h-ZnO or a mixture of h-ZnO and c-ZrO₂ below 55mol% of ZOO content. On increasing ZOO concentration, a systematic change in morphology of h-ZnO nano/micro crystals from spherical to rod-shaped to sunflower-like particles was evident from electron microscopes (FESEM and TEM). Below 30 and above 65mol% of ZOO, light surface patterns formed. However, the films from 30 to 65mol% ZOO containing solutions evident distinct surface patterns with average periodicity, 1.5μm and peak height, 20–70nm by AFM measurements. The films were also characterized by UV–vis and FTIR spectral studies. Water and chloride contents from ZOO in the precursor solutions found to play a key role for generation of the film characteristics.

Keywords: Sol–gel soft lithography; Thin films; Surface patterning; Morphology

Electrochemical anodic oxidation of nitrogen doped carbon nanowall films: X-ray photoelectron and Micro-Raman spectroscopy study by A. Achour; S. Vizireanu; G. Dinescu; L. Le Brizoual; M.-A. Djouadi; M. Boujtita (pp. 49-57).

► Surface oxidation and morphology modification of CNW films was controlled. ► The CNW specific capacitance was enhanced in ranges ([0–1] and [0–1.5] vs. SCE). ► Conversion of pyridinic nitrogen to pyridonic nitrogen upon cycling is revealed.Unintentional nitrogen doped carbon nanowall (CNW) films were oxidized through anodic polarization in different applied potential windows, in a mild neutral K₂SO₄ electrolyte solution. Applied potentials in the range of [0–1], [0–1.5] and [0–2]V vs. SCE were explored. The films were characterized with X-ray photoelectron (XPS) and Micro-Raman spectroscopy, in order to investigate the surface chemistry and structural changes after treatment, respectively. The XPS analysis revealed that this electrochemical treatment leads to an increase of oxygen functional groups, and influences the nitrogen proportion and bonding configuration (such as pyridinic/pyridonic nitrogen) on the film surface at room temperature. In particular, an obvious enhancement of pyrrolic/pyridonic nitrogen doping of CNWs via electrochemical cycling in the range of [0–1.5] and [0–2] V vs. SCE was achieved. Such enhancement happened, because of the oxidation of nitrogen atoms in pyridine as a result of OH ions injection upon electrochemical cycling. Micro-Raman analysis indicates structural quality degradation with increasing the applied potential window. Moreover, the electrochemical capacitance of CNW films was increased after treatment in the range of [0–1] and [0–1.5] and decreased in the range of [0–2]V vs. SCE. The results show that harsh oxidation happened in the range [0–2]V.

Keywords: CNW; Electrochemical oxidation; Carbon doped nitrogen; X-ray photoelectron spectroscopy (XPS); Pyridinic/pyridonic nitrogen; Electrochemical capacitance

Low temperature wet etching to reveal sub-surface damage in sapphire substrates by Purushottam Kumar; Jinhyung Lee; Gwangwon Lee; Suhas Rao; Deepika Singh; Rajiv K. Singh (pp. 58-61).

► Low temperature wet etching was studied to reveal sub-surface damage in sapphire. ► Etching in H₂SO₄ at temperatures ≥125°C and 3:1 H₂SO₄–H₃PO₄ at temperatures ≥75°C was found to reveal sub-surface damage as scratches. ► This technique can be used to observe very low density of sub-surface damage. ► The depth of surface and sub-surface damaged layer was 1.6 and 2.2μm respectively for wafers lapped with 1μm diamond particles.Low temperature wet etching using various etchants was investigated to reveal sub-surface damage in sapphire wafer induced during lapping. Surface scratches during wafer preparation is conveniently observed using optical or atomic force microscopy whereas sub-surface damage to crystal requires techniques such as X-ray diffraction, Raman spectroscopy etc. In this study, sub-surface damage in sapphire was revealed as shallow scratches by etching in H₂SO₄ at temperatures ∼125°C and 3:1 H₂SO₄–H₃PO₄ at temperatures ∼75°C. These etching conditions showed no measurable etch rate of sapphire and also did not affect the pristine sapphire surface. The heavily damaged and sub-surface damaged layer was determined to be 1.6±0.1 and 2.2±0.1μm deep by repeated chemical mechanical polishing and etching of sapphire wafer lapped with 1μm diamond abrasive.

Keywords: Sapphire; Sub-surface damage; Wet etching

Microstructure and properties of composite polyetheretherketone/Bioglass^® coatings deposited on Ti–6Al–7Nb alloy for medical applications by Tomasz Moskalewicz; Sigrid Seuss; Aldo R. Boccaccini (pp. 62-67).

Display Omitted► Composite coatings consist of Bioglass^® particles embedded in a PEEK matrix. ► Coatings are micro-porous, the volumetric porosity is 28%. ► Diffusion of Na from the glass to the PEEK matrix after heat-treatment. ► EPD is very useful to deposit porous PEEK/Bioglass^® coatings on titanium alloy.Composite polyetheretherketone (PEEK)/Bioglass^® coatings were electrophoretically deposited on two phase α+β Ti–6Al–7Nb titanium alloy substrates. A heat treatment was performed to improve the adhesion of the coatings to the substrate. The microstructure of the coatings and substrate was examined by light microscopy, scanning- and transmission electron microscopy methods as well as by X-ray diffractometry. Coatings deposited from suspensions with PEEK/Bioglass^® weight ratio of 0.3 showed the best quality. Coatings of 40μm thickness, exhibiting uniform porosity, without any cracks or presence of large voids were produced. The microstructure of the coatings was observed to be composed of Bioglass^® particles fairly homogeneously embedded in a PEEK matrix. STEM-EDX line analysis revealed diffusion of Na from the glass to the PEEK matrix after heat-treatment. The results demonstrate that electrophoretic deposition (EPD) is a very useful method to deposit uniform and reproducible microporous composite PEEK/Bioglass^® coatings on titanium alloy substrate for biomedical applications.

Keywords: Titanium alloy; EPD; Composite coating; PEEK; Bioglass; Microstructure

Removal of uranium from aqueous solution by a low cost and high-efficient adsorbent by Yun-Hai Liu; You-Qun Wang; Zhi-Bin Zhang; Xiao-Hong Cao; Wen-Bin Nie; Qin Li; Rong Hua (pp. 68-74).

► Low-cost and high-efficient hydrothermal carbon with carboxylic group was prepared. ► The adsorption process is endothermic and spontaneous in nature. ► The sorption capacity and selectivity for U(VI) are improved after carboxylation.In this study, a low-cost and high-efficient carbonaceous adsorbent (HTC-COOH) with carboxylic groups was developed for U(VI) removal from aqueous solution compared with the pristine hydrothermal carbon (HTC). The structure and chemical properties of resultant adsorbents were characterized by Scanning electron microscope (SEM), N₂ adsorption–desorption, Fourier transform-infrared spectra (FT-IR) and acid–base titration. The key factors (solution pH, contact time, initial U(VI) concentrations and temperature) affected the adsorption of U(VI) on adsorbents were investigated using batch experiments. The adsorption of U(VI) on HTC and HTC-COOH was pH-dependent, and increased with temperature and initial ion concentration. The adsorption equilibrium of U(VI) on adsorbents was well defined by the Langmuir isothermal equation, and the monolayer adsorption capacity of HTC-COOH was found to be 205.8mg/g. The kinetics of adsorption was very in accordance with the pseudo-second-order rate model. The adsorption processes of U(VI) on HTC and HTC-COOH were endothermic and spontaneous in nature according to the thermodynamics of adsorption. Furthermore, HTC-COOH could selectively adsorption of U(VI) in aqueous solution containing co-existing ions (Mg²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Mn²⁺). From the results of the experiments, it is found that the HTC-COOH is a potential adsorbent for effective removal of U(VI) from polluted water.

Keywords: Hydrothermal carbonization; Selective adsorption; U(VI); Surface functionalization

Anomalous conformational transitions in cytochrome C adsorbing to Langmuir–Blodgett films by Kamatchi Sankaranarayanan; B.U. Nair; A. Dhathathreyan (pp. 75-81).

Display Omitted► Cationic lipid triggers the helix to beta transitions in Cytochrome C. ► Water entrainment near the polar planes of the lipid leads to Protein dehydration. ► Fibrillar pattern with spacing of 0.41nm typical of β strand is seen.Helix to beta conformational transitions in proteins has attracted much attention due to their relevance to fibril formation which is implicated in many neurological diseases. This study reports on unusual conformational transition of cytochrome C adsorbing to hydrophilic surface containing pure cationic lipid and mixed Langmuir–Blodgett films (LB films) of cationic and neutral lipids. Evidence for conformational changes of the protein from its native helical state to beta sheet comes from Circular dichroic spectroscopy (CD spectroscopy). Analysis of these samples using High resolution TEM (HRTEM) shows a typical fibrillar pattern with each strand spacing of about 0.41nm across which can be attributed to the repeat distance of interdigitated neighboring hydrogen-bonded ribbons in a beta sheet. Changes in contact angles of protein adsorbing to the LB films together with the increased mass uptake of water using quartz crystal microbalance (QCM) confirm the role of positive charges in the conformational transition. Dehydration of the protein resulting from the excess water entrainment in the polar planes of the cationic lipid in hydrophilic surface seems to trigger the refolding of the protein to beta sheet while it retains its native conformation in hydrophobic films. The results suggest that drastic conformational changes in CytC adsorbing to cationic lipids may be of significance in its role as a peripheral membrane protein.

Keywords: LB films; Cytochrome C; Helix to beta; Destabilization; Cationic lipids

Synthesis and photocatalytic application of Au/Ag nanoparticle-sensitized ZnO films by Lan Chen; ThanhThuy Tran. T; Chen’an Huang; Jiezhen Li; Lijuan Yuan; Qingyun Cai (pp. 82-88).

► A new Au–Ag-ZnO film photocatalyst was fabricated by a facile three-step synthesis approach. ► The photocatalyst was applied in MO degradation with higher photocatalytic ability. ► Photocatalytic process with excellent stability was established.Here it is demonstrated that the Au–Ag-ZnO architecture can be immobilized on indium tin oxide (ITO) substrate through a facile three-step synthesis approach. A series of ZnO films with different modifications of Au and Ag were applied to study the effect of Ag and Au nanoparticles on the morphology, optical properties and photocatalytic activity. An annealing treatment of the ZnO nanosheets before Ag–Au deposition is found to play an important role in the properties of the Au–Ag-deposited ZnO nanosheet (Au–Ag-ZnO). The annealing treatment results in a significant increase in the surface area of ZnO, and consequently an increase in the depositing amount of Ag nanoparticles. The Au–Ag-ZnO film shows nearly twice the photocatalytic efficiency than pure ZnO, and much higher efficiency comparing with the Ag-ZnO film in the photocatalytic degradation of methyl orange (MO) under UV illumination in aqueous solutions.

Keywords: ZnO; Nanosheets; Au; Ag; Photocatalytic; Methyl orange (MO)

Surface-roughness-assisted formation of large-scale vertically aligned CdS nanorod arrays via solvothermal method by Minmin Zhou; Shancheng Yan; Yi Shi; Meng Yang; Huabin Sun; Jianyu Wang; Yao Yin; Fan Gao (pp. 89-93).

Display Omitted► CdS nanorod arrays were synthesized on several different substrates. ► The morphology of the substrate was quite critical for the CdS seed layers. ► The morphology of all the substrates were studied by atomic force microscopy. ► Each sample had a non-linear I– V characteristic for a −2V to 2V sweep. ► The optical properties of the samples were tested.Large-scale cadmium sulfide (CdS) nanorod arrays were successfully synthesized on several different substrates through solvothermal reaction. During the growth experiments, we observed that the adhesion strength of the CdS nanorod arrays to different substrates differed dramatically, causing some of the CdS coating being easily flushed away by deionized water (DI water). With doubts and suspicions, we seriously investigate the original morphology of all the substrates by using atomic force microscopy (AFM). The phase, morphology, crystal structure and photoelectric property of all the products were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and current–voltage ( I– V) probe station. The growth mechanism of solvothermal reaction was proposed on the basis of all the characterizations. Our approach presents a universal method of liquid phase epitaxy of 1D material on a wide range of substrates of any shape.

Keywords: CdS nanorod; Surface roughness; Seed layer; Solvothermal reaction

Deuterium plasma exposure on rhodium: Reflectivity monitoring and evidence of subsurface deuteride formation by Baran Eren; Marco Wisse; Laurent Marot; Roland Steiner; Ernst Meyer (pp. 94-100).

► Deuterium plasma exposure of Rh films results in a reversible degradation of the reflectivity. ► Deuterium acts as an electron donor, filling the Rh 4d states above the Fermi level. ► The obtained Rh/D system can be denoted as RhD_x. ► After storage in air, initial band structure and reflectivity of Rh are recovered.The effects of low flux, low temperature deuterium plasma (LTP) exposure on nanocrystalline rhodium (Rh) films are investigated. The exposures do not cause any surface damage on the nanoscale and the specific electrical resistivity of the films remains invariant during exposures. However, the spectral reflectivity of Rh decreases during exposure and recovers very slowly during subsequent storage in high vacuum. This drop in the reflectivity can be associated with a formation of a subsurface rhodium deuteride (RhD_x, x≤2), which has optical constants different to those of Rh. After air storage of the exposed samples, the Rh surface gets depopulated of deuterium adsorbates due to a catalytic reaction taking place between oxygen and deuterium, which results in a diffusion of the incorporated deuterium first to the surface and then into the air. Consequently, the reflectivity is rapidly recovered. Comparison of the ultraviolet photoelectron spectroscopy (UPS) measurements performed before and after plasma exposure reveals an increase in the work function which is attributed to deuterium adsorbates on the surface. Changes in the valence band structure were also observed with UPS measurements, lending support to the suggestion of subsurface RhD_x formation. Deuterium atoms in Rh are electron donors filling the 4d states above the Fermi level, thus reducing optical transitions.

Keywords: Rhodium; Hydride; Deuteride; Plasma; Reflectivity; ITER

Ultrafast laser parallel microprocessing using high uniformity binary Dammann grating generated beam array by Zheng Kuang; Walter Perrie; Dun Liu; Stuart P. Edwardson; Yao Jiang; Eamonn Fearon; Ken G. Watkins; Geoff Dearden (pp. 101-106).

► We demonstrated ultrashort pulse laser parallel processing using diffractive beam-array generated by binary Dammann gratings. ► The beam-array machined holes had high uniformity (hole diameter variation <4%) by slightly defocusing the 0-th order. ► Parallel surface patterning of ITO with periodic structures was demonstrated using the beam array.Ultrafast laser parallel processing using diffractive multi-beam patterns generated by a spatial light modulator (SLM) has demonstrated a great increase in processing throughput and efficiency. Applications ranging from surface thin film patterning to internal 3D refractive index modification have been recently reported with the parallel processing technology. Periodic and symmetrical geometry design (e.g. N×M beam array) of the multi-beam pattern must be avoided to guarantee the required high uniformity in these applications, which, however, limited the processing flexibility. In this paper, Dammann gratings are used to create diffractive 1×5 and 5×5 beam arrays for the parallel processing. The 0-th order, observed slightly stronger than the other higher orders, can be adjusted by superimposing a Fresnel zone lens (FZL) and tuning the degree of defocusing at the processing plane. The uniformity (presented by the variation of the machined hole diameter) is measured to be <4% after the adjustment. Additionally, a parallel surface patterning of indium tin oxide (ITO) thin film with periodic array structures was demonstrated using the Dammann grating generated beam array without requiring the complicated geometry separation and the time-consuming positioning.

Keywords: Ultrafast laser; Special Light Modulator; Dammann grating

Metal-assisted homogeneous etching of single crystal silicon: A novel approach to obtain an ultra-thin silicon wafer by Fan Bai; Meicheng Li; Dandan Song; Hang Yu; Bing Jiang; Yingfeng Li (pp. 107-110).

► Homogeneous etching of silicon is achieved, it offers a simple route to get ultra-thin silicon wafer with thickness below 50μm. ► The surface of the ultra-thin silicon wafer is smooth at the nanometer scale across a large wafer area, and its surface roughness is around 10nm. ► Any thickness of silicon wafer within 30–180μm can be obtained by this method.Homogeneous etching of silicon is achieved through one-step metal-assisted chemical etching (MACE), which offers a simple route to obtain the ultra-thin silicon wafer with thickness below 50μm. The surface of the ultra-thin silicon wafer obtained by this method is smooth at the nanometer scale, and its surface roughness is around 10nm. The homogenous etching mechanism is discussed in terms of the hole injection principle. It's found that the introduction of a high concentration of H₂O₂ facilitates the uniform distribution of the holes injected on the silicon surface, causing the homogeneous etching of the silicon. Meanwhile, the thinning is uniform across a large wafer area, and ultra thin silicon wafers up to 4in. in diameter were obtained. Furthermore, any thickness of silicon wafer within 30–180μm can be obtained by modulating the etching process accurately.

Keywords: Thin silicon wafer; Homogeneous etching; Holes; MACE

Theoretical study on electronic structure and optical properties of Ga_0.75Al_0.25N(0001) surface by Yang Mingzhu; Chang Benkang; Hao Guanghui; Guo Jing; Wang Honggang; Wang Meishan (pp. 111-117).

In order to study the surface of Ga1−_x Al_x N photocathodes theoretically, atomic structure, band structure, density of state, surface energy, work function and optical properties of Ga_0.75Al_0.25N(0001) surface are calculated using the plane-wave pseudo-potential method based on the density function theory. It is found that the Ga_0.75Al_0.25N(0001) surface is not flat, the Al atom is more close to N atoms while the Ga atoms are far away from N layer. The surface charges shift from bulk to surface by the effect of dipole moment, the charges of Ga atoms in the top-most layer decrease while that of Al atom change little. The surface energy and work function of Ga_0.75Al_0.25N(0001) are 2.169J/m² and 4.36eV respectively. The absorption coefficient of Ga_0.75Al_0.25N(0001) surface is lower than bulk Ga_0.75Al_0.25N. This provides a theoretical basis for the design and application of Ga1−_x Al_x N photocathodes.

Keywords: Ga; _0.75; Al; _0.25; N(0; 0; 0; 1) surface; Work function; Electronic structure; Optical properties

Effects of particle size and pH value on the hydrophilicity of graphene oxide by Xuebing Hu; Yun Yu; Weimin Hou; Jianer Zhou; Lixin Song (pp. 118-121).

► Effects of particle size and pH value on the hydrophilicity of graphene oxide are investigated with measuring the water contact angle. ► The water contact angle of different graphene oxides decreases from 61.8° to 11.6°. ► The hydrophilicity of graphene oxide is sensitive to particle size and pH value.Graphene-based material has attracted extensive attention from both experimental and theoretical scientific communities due to its extraordinary properties. As a derivative of graphene, graphene oxide has also become an attractive material and been investigated widely in many areas since the ease of synthesizing graphene oxide and its solution processability. In this paper, we prepared graphene oxide by the modified Hummers method. The hydrophilicity of graphene oxide with different particle sizes and pH values was characterized with water contact angle. And we find the water contact angle of the different graphene oxides decreases from 61.8° to 11.6°, which indicates graphene oxide has the excellent hydrophilicity. The X-ray photoelectron spectroscopy, zeta potential and dynamic light scattering measurements were taken to study the chemical state of elements and the performances of graphene oxide in this experiment. The results show the hydrophilicity of graphene oxide is sensitive to particle size and pH value, which result in the variations of the ionizable groups of graphene oxide. Our work provides a simple ways to control the hydrophilicity of graphene oxide by adjusting particle size and pH value.

Keywords: Graphene oxide; Hydrophilicity; Particle size; pH value

Study on laser surface remelting of plasma-sprayed Al–Si/1wt% nano-Si₃N₄ coating on AZ31B magnesium alloy by Yaqiong Ge; Wenxian Wang; Xin Wang; Zeqin Cui; Bingshe Xu (pp. 122-127).

► As-plasma-sprayed Al–Si/1wt% nano-Si₃N₄ coating was successfully remelted by laser. ► The laser remelted coating possessed an excellent metallurgical bonding to substrate. ► Some special structure existed in the composite coating. ► The remelted coating was mainly composed of Al, AlN, Al₉Si, Al_3.21Si_0.47 and Mg₂Si. ► Microhardness of remelted coating was enhanced to the range of 200–514HV_0.05.Plasma sprayed micro-structured Al–Si based and 1wt% nano-structured Si₃N₄ coating was successfully fabricated on an AZ31B magnesium alloy using a high efficiency supersonic atmosphere plasma spraying system, and then the as-sprayed coating was remelted by a continuous wave CO₂ laser. The remelted coating was investigated by optical microscope, scanning electron microscope, energy-dispersive spectroscopy, X-ray diffractometer and Vickers microhardness tester. The results indicated that the laser remelted coating possessed an excellent metallurgical bonding to the substrate. A finer dendritic structure was exhibited after laser remelting. The nano-Si₃N₄ decomposed fully in the coating, and the remelted coating was mainly composed of Al, AlN, Al₉Si, Al_3.21Si_0.47 and Mg₂Si. Moreover, the microhardness of remelted coating was enhanced to 200–514HV_0.05, which was much higher than that of the substrate(about 50 HV_0.05).

Keywords: AZ31B magnesium alloy; Laser remelting; Plasma spraying; Nano-Si; ₃; N; ₄

Tensile property of low carbon steel with gridding units by Chuanwei Wang; Hong Zhou; Zhihui Zhang; Zhengjun Jing; Dalong Cong; Chao Meng; Luquan Ren (pp. 128-134).

► Tensile properties of BCLR steel with gridding units were studied and compared. ► Gridding units were found to have significant influences on tensile properties. ► Different trends existed in the strength and ductility with unit distance narrowing. ► Strengthening and toughening mechanisms of gridding BCLR steel were discussed.Although much effort has been devoted to the mechanical properties of biomimetic coupled laser remelting (BCLR) processed steels, our understanding to the strengthening and toughening mechanisms of it has still remained unclear. To address it, here we studied the roles played by the gridding units of BCLR steels. Tensile tests show that the gridding units have a significant influence on the tensile properties. Interestingly, such an influence is essentially decided by the unit distance of gridding units. The strength increases with the unit distance narrowing while the ductility first increases with it up to a maximum then decreases. The mechanism behind these changes is attributed to the combined effects of the microstructure changes in the units and the stress transition throughout the BCLR samples.

Keywords: Tensile properties; Biomimetic; Laser remelting; Low carbon steel

Processable polyaniline/titania nanocomposites with good photocatalytic and conductivity properties prepared via peroxo-titanium complex catalyzed emulsion polymerization approach by Yuzhen Li; Yuan Yu; Liangzhuan Wu; Jinfang Zhi (pp. 135-143).

The homogeneous polyaniline (PAni)/TiO₂ nanocomposites were synthesized via a facile emulsion polymerization with the assistance of peroxo-titanium complex (PTC), where PTC was used as both the TiO₂ precursor and the oxidant for the polymerization of PAni/TiO₂ nanocomposites.Display Omitted► PTC was used as both the TiO₂ precursor and the oxidant for the polymerization of PAni/TiO₂ nanocomposites. ► Anatase TiO₂ were well-dispersed in the PAni chains without aggregation. ► The TiO₂ were anchored on the polymer chains through chemical interactions. ► The PAni/TiO₂ composites could be well dispersed in common solvent, and showing good photocatalytic and conductivity properties.The homogeneous polyaniline (PAni)/TiO₂ nanocomposites were successfully synthesized via a facile emulsion polymerization with the assistance of peroxo-titanium complex (PTC), where PTC was used as both the TiO₂ precursor and the oxidant for the polymerization of PAni/TiO₂ nanocomposites. Comprehensive analysis indicated that anatase TiO₂ nanocrystals (about 4–6nm) were well-dispersed in the PAni chains without aggregation, and the TiO₂ were anchored on the polymer chains through chemical interactions, such as TiONC and TiOC, which made the PAni/TiO₂ composite possess better thermal stability. The PAni/TiO₂ composite could be well dispersed in common solvent, such as acetone, and stay stability without any precipitation for a month. Since the PAni/TiO₂ composite could be well dispersed in common solvent, the PAni/TiO₂ dispersion may be coated on the surface of Poly (ethylene terephthalate) (PET) film, showing good processable properties, and the prepared PAni/TiO₂/PET films exhibit good photocatalysis and best conductivity (2.08×10⁻²scm⁻¹), when the molar ratio of aniline (AN) and Ti in the PAni/TiO₂ composite is 1/1. The possible reaction mechanism was also discussed. The facile synthesized method proposed can also be used for the preparation of other conducting polymer/semiconductor nanocomposites.

Keywords: Polyaniline; Anatase; Nanocomposite; Homogeneous; Photocatalyst; Conductivity

Role of the surface polarity in governing the luminescence properties of ZnO nanoparticles synthesized by Sol–gel route by A. Sharma; S. Dhar; B.P. Singh (pp. 144-149).

► Luminescence properties of the washed and unwashed ZnO nanoparticles are different. ► It is explained in terms of the dissimilar nature of the surface charge polarity. ► Zeta potential study shows that the intrinsic surface of ZnO nanoparticles have negative polarity. ► Hydroxyl groups are found to be the primary cause for GL emission for these ZnO nanoparticles. ► The origin for the remnant GL emission which survives the evacuation is found to be different.ZnO nanoparticle samples, which are synthesized by a sol–gel route and collected after various stages of a washing procedure, are systematically investigated using a variety of experimental techniques. The study shows that while the surface charge polarity is positive for the as-grown (unwashed) particles, the surface turns negatively charged when the particles are sufficiently washed. This dissimilar surface charge polarity has been found to result in markedly different luminescence characteristics for the two cases (washed and unwashed). Our study of the luminescence properties under different surrounding conditions furthermore reveals that the major source for the GL emission for these nanoparticles is the hydroxyl groups, which are physisorbed on the surface.

Keywords: 78.55.Et; 78.67.Bf; 73.20.Hb; 61.72.ujZnO; Photoluminescence; Hydroxyl groups; Surface charge

Photochromism of amorphous molybdenum oxide films with different initial Mo⁵⁺ relative concentrations by Mehdi Rouhani; Yong L. Foo; Jonathan Hobley; Jisheng Pan; Gomathy Sandhya Subramanian; Xiaojiang Yu; Andrivo Rusydi; Sergey Gorelik (pp. 150-158).

Display Omitted► The effect of defects on optical properties of virgin and photo-colored MoO₃ thin films ► Raman spectroscopy was used to confirm that the results of XPS were consistent with the bulk of the films. ► The absorption coefficient of as-deposited films increases with Mo⁵⁺ content. ► The temporal evolutions of absorption coefficients for all the films show initial fast rise. ► Mo⁵⁺ content of the films increases after UV irradiation except for the film with the highest initial Mo⁵⁺ content.We report the effect of deposition conditions on the intrinsic color and photochromic properties of amorphous MoO₃ thin films (a-films) deposited by R.F. unbalanced magnetron sputtering. Optical transmission spectroscopy was used to measure optical properties of the films. The conversion between Mo⁶⁺ and Mo⁵⁺ for as-deposited and UV irradiated films was characterized using XPS. Raman spectroscopy was used to confirm that the results of XPS were consistent with the bulk of the films. It is shown that absorption coefficient of as-deposited films increases with Mo⁵⁺ content. The temporal evolution of absorption coefficients for all films under UV light irradiation is measured using optical transmission spectroscopy. The largest change in absorption was observed for the film with the highest initial Mo⁵⁺ content. The temporal evolution of absorption coefficients for all the films shows initial fast rise within first minute of irradiation. XPS and Raman results show that for all films Mo⁵⁺ content increases as a result of UV irradiation except for the film with the highest initial Mo⁵⁺ content, for which the Mo⁵⁺ content decreases relative to Mo⁶⁺ despite the fact that the absorption of the film continues to rise. Further understanding of this mechanism is important since it will lead to enhanced photochromism and extend the photo-colorability of the films beyond the point at which the conversion of Mo⁶⁺ to Mo⁵⁺ is saturated.

Keywords: Molybdenum oxide; Photochromism; Thin film; Mo; ⁵⁺; Raman spectroscopy; XPS; Oxygen vacancies; Absorption coefficient

Synthesis and characterization of AgBr/AgNbO₃ composite with enhanced visible-light photocatalytic activity by Cheng Wang; Jia Yan; Xiangyang Wu; Yanhua Song; Guobin Cai; Hui Xu; Jiaxiang Zhu; Huaming Li (pp. 159-166).

► The novel AgBr/AgNbO₃ composite was synthesized by two-step method. ► The photo-degradation process followed a pseudo-first-order reaction. ► The AgBr/AgNbO₃ exhibited a higher photocatalytic activity than the pure AgNbO₃. ► AgBr was doped to promote the separation of photo-generated electron–hole.A novel AgBr/AgNbO₃ composite was synthesized by a two-step method. The physical and chemical properties of catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), diffuse-reflection spectra (DRS), and photocurrent techniques. The photocatalytic performance of the samples was evaluated by photocatalytic oxidation of methylene blue (MB) dye under visible-light irradiation. The XRD, SEM-EDS, and XPS analyses indicated that the heterojunction structure had formed in the composite. The DRS analysis showed that AgBr formed on the surface of AgNbO₃ had promoted the optical absorption in the visible region and made it possible to enhance the photocatalytic activity. The results indicated that the AgBr/AgNbO₃ heterojunction had exhibited a much higher photocatalytic activity than the pure AgNbO₃. The mechanism of the AgBr/AgNbO₃ composite with enhanced heterojunction photocatalytic activity was researched.

Keywords: AgBr/AgNbO; ₃; Photocatalytic; Visible-light; Methylene blue

The effect of oxidation treatment with supercritical water/hydrogen peroxide system on intersurface performance for polyacrylonitrile-based carbon fibers by Linghui Meng; Dapeng Fan; Chunhua Zhang; Zaixing Jiang; Yudong Huang (pp. 167-172).

► We provide a new surface treatment method for carbon fiber. ► Using supercritical fluid as the medium of oxidation treatment contributes to achieve a better control of the oxidizing reactions. ► Surface appearance of oxidized carbon fibers changed obviously.In order to improve the interfacial properties between carbon fibers and epoxy matrix, supercritical water and hydrogen peroxide were used as oxidation medium for the oxidation treatment for carbon fibers. Analysis results of X-ray photoelectron spectroscopy suggest that the oxygen content on the carbon fibers’ surfaces increases by these oxidation treatments. Scanning electron microscope and atomic force microscopy images indicate that the surface appearance of oxidized carbon fibers obviously changed. The maximal interlaminar shear strength and interface shear strength of carbon fiber/epoxy resin composite in which the fibers were treated by the supercritical water and hydrogen peroxide systems reaches 70.46MPa and 106.66MPa, increases by 13.4% and 29.6% respectively compared with untreated carbon fibers.

Keywords: Carbon fiber; Oxidation; Surface treatment; Supercritical water

Validity of “sputtering and re-condensation” model in active screen cage plasma nitriding process by A. Saeed; A.W. Khan; F. Jan; M. Abrar; M. Khalid; M. Zakaullah (pp. 173-178).

► The nitrogen mass transfer mechanism in active screen cage plasma has been investigated. ► A new modified model for nitrogen mass transfer mechanism in ASPN is proposed. ► The effect of processing duration on microhardness is investigated.The validity of “sputtering and re-condensation” model in active screen plasma nitriding for nitrogen mass transfer mechanism is investigated. The dominant species including NH, Fe-I, N₂⁺, N-I and N₂ along with H_α and H_β lines are observed in the optical emission spectroscopy (OES) analysis. Active screen cage and dc plasma nitriding of AISI 316 stainless steel as function of treatment time is also investigated. The structure and phases composition of the nitrided layer is studied by X-ray diffraction (XRD). Surface morphology is studied by scanning electron microscopy (SEM) and hardness profile is obtained by Vicker's microhardness tester. Increasing trend in microhardness is observed in both cases but the increase in active screen plasma nitriding is about 3 times greater than that achieved by dc plasma nitriding. On the basis of metallurgical and OES observations the use of “sputtering and re-condensation” model in active screen plasma nitriding is tested.

Keywords: Plasma nitriding; Active screen cage; Micro-hardness

Fabrication of chitosan-silver nanoparticle hybrid 3D porous structure as a SERS substrate for biomedical applications by Gyeong-Bok Jung; Ji-Hye Kim; Jin Sik Burm; Hun-Kuk Park (pp. 179-183).

► We developed novel silver nanoparticle hybridized 3D porous chitosan SERS substrate. ► Thiolated single stranded DNA was measured at a low concentration of 5pM. ► Chitosan-Ag NPs SERS substrate has a simple, low-cost, large-area and excellent biocompatibility.We propose a simple, low-cost, large-area, and functional surface enhanced Raman scattering (SERS) substrate for biomedical applications. The SERS substrate with chitosan-silver nanoparticles (chitosan-Ag NPs) hybrid 3D porous structure was fabricated simply by a one-step method. The chitosan was used as a template for the Ag NPs deposition. SERS enhancement by the chitosan-Ag NPs substrate was experimentally verified using rhodamine B as an analyte. Thiolated single stranded DNA was also measured for atopic dermatitis genetic markers (chemokines CCL17) at a low concentration of 5pM. We successfully designed a novel SERS substrate with silver nanoparticle hybridized 3D porous chitosan that has the potential to become a highly sensitive and selective tool for biomedical applications.

Keywords: Surface enhanced Raman scattering; Micro-porous structured chitosan; Silver nanoparticle

Superhydrophobic film fabricated by controlled microphase separation of PEO–PLA mixture and its transparence property by Pihui Pi; Wei Mu; George Fei; Yulin Deng (pp. 184-191).

Transparent surperhydrophobic film could be fabricated by controlling the phase separation of two homopolymer mixture solution followed by hydrophobic coating.Display Omitted► Phase separation in PEO and PLA coating film has been used to create desired nano- to microporous structure ► A superhydrophobic surface was obtained by controlling the coating film structure ► Porous structure of the coating film is very important for superhydrophobic thin film fabrication.Instead of block copolymers that have been widely used in controlling thin film morphology, a mixture of two homopolymers has been used in this study to create desired nano- to microporous structure. By further modifying the nano-sized porous structured surface, a superhydrophobic surface was obtained. Experimentally, a chloroform solution containing a mixture of polylactic acid (PLA) and polyethylene oxide (PEO) was first coated on glass slides. Because of the dissimilarity of PLA and PEO, a microphase separation happened and the PEO formed microdomains in the coating layer during the film drying. Because PEO is water soluble but PLA is water-insoluble, the PEO microdomains could be washed out with water but PLA remained, resulted in a porous and rough PLA film. By two or three layer coating and washing, nano-sized roughness was obtained. A thin layer of fluorinated acrylic resin was further deposited on the rough surface. Because of the synergistic effect of surface roughness and hydrophobic, a superhydrophobicicity layer was obtained.

Keywords: Superhydrophobic, Phase separation; Microdomain; Transparent; Coating

Experimental study of corrosion behavior for burnished aluminum alloy by EWF, EBSD, EIS and Raman spectra by Lv Jinlong; Luo Hongyun; Xie Jinpeng (pp. 192-198).

► The electron work function of 2024 aluminum alloy decreased due to burnish process. ► The burnish process and higher burnish force improved corrosion resistance. ► The current efficiency and passive film thickness were affected by burnish process.The effect of burnish process on 2024 aluminum alloy was studied by electron work function and electron backscattered diffraction (EBSD). Moreover, the corrosion resistance of thin passive films formed on 2024 aluminum alloy in borate buffer solutions was studied by the electrochemical impedance spectroscopy (EIS), the Mott–Schottky plots and the galvanostatic techniques. The composition of passive films was analyzed by Raman spectra. The results obtained indicated that the impedance increased due to burnish and this was attributed to decreased electron work function and higher current efficiency in the burnished aluminum alloy which led to thicker passive films. It was further supported by Raman spectra experiment. Moreover, the donor and acceptor concentration of passive films and their the semiconductor type have changed due to burnish.

Keywords: Electron work function; Electron backscattered diffraction; Electrochemical impedance spectroscopy; Raman spectra; Burnish

The effect of surface texturing on reducing the friction and wear of steel under lubricated sliding contact by Wei Tang; Yuankai Zhou; Hua Zhu; Haifeng Yang (pp. 199-204).

► The surface texturing can reduce the friction and wear. ► The change of dimple area fraction can lead to dramatic reduction in the friction and wear. An optimum dimple area fraction is found. ► A numerical model of the load carrying capacity of the multi-dimples is developed.Surface texturing is a widely used approach to improve the load capacity, the wear resistance, and the friction coefficient of tribological mechanical components. This study experimentally investigates the effect of surface texturing on reducing friction and wear. A numerical model of the load carrying capacity of multi-dimples is developed to analyze the relevant mechanism, and the effect of surface texturing on different dimple area fractions is evaluated to determine the optimal dimple pattern. The results show that surface texturing is important for reducing friction and wear. Changes in dimple area fraction can dramatically reduce friction and wear. The results indicate a 5% optimal dimple area fraction can generate the greatest hydrodynamic pressure compared with other fractions and can reduce friction and wear up to 38% and 72%, respectively. The theoretical model and the experimental results are found to be closely correlated. The generation of hydrodynamic pressure, the function of micro-trap for wear debris and the micro-reservoirs for lubricant retention are the main causes for the reduction in the friction and wear of the surface texturing.

Keywords: Surface texturing; Friction reduction; Wear reduction; Load carrying capacity

Synthesis of fluorinated nano-silica and its application in wettability alteration near-wellbore region in gas condensate reservoirs by M.A. Mousavi; Sh. Hassanajili; M.R. Rahimpour (pp. 205-214).

► Wettability alteration to gas wetness is proposed to Sarkhun rock in this study. ► We have prepared fluorinated silica nanoparticles to alter rock wettability. ► The effect of this method is evaluated by various tests. ► Water contact angle of 147° and n-decane contact angle of 61° were measured on the core surface after treatment.Fluorinated silica nanoparticles were prepared to alter rock wettability near-wellbore region in gas condensate reservoirs. Hence fluorinated silica nanoparticles with average diameter of about 80nm were prepared and used to alter limestone core wettability from highly liquid-wet to intermediate gas-wet state. Water and n-decane contact angles for rock were measured before and after treatment. The contact angle measured 147° for water and 61° for n-decane on the core surface. The rock surface could not support the formation of any water or n-decane droplets before treatment. The functionalized fluorinated silica nanoparticles have been confirmed by the CF bond along with SiOSi bond as analyzed by FT-IR. The elemental composition of treated limestone core surface was determined using energy dispersive X-ray spectroscopy analyses. The final evaluation of the fluorinated nanosilica treatment in terms of its effectiveness was measured by core flood experimental tests.

Keywords: Surface modification; Fluorinated nano-silica; Hydrophobicity; Oleophobicity

Effect of wettability on surface morphologies and optical properties of Ag thin films grown on glass and polymer substrates by thermal evaporation by Jing Lv (pp. 215-219).

► The subject matter (the influence of Ag surface morphology and substrate on the reflectance and the transmittance) is timely. ► The effect of the wettability on the morphology and optical properties of Ag/glass and Ag/polymer structures was studied by atomic force microscopy and spectrophotometry. ► The investigation results show that the wettability of Ag grains with polymer is stronger than with glass. ► The strong wettability activates the nonlinear optical properties of Ag grains grown on polymer substrates, which result in the strong absorbance in short wavelength. ► The surface morphology affects on the reflectance, and the transmittance is more influenced by the substrate material.A series of Ag films with different thicknesses were deposited on BK-7 glass, PET and PC substrates under identical conditions by thermal evaporation. The effect of the wettability on the morphology and optical properties of Ag/glass and Ag/polymer films was studied by atomic force microscopy and spectrophotometry. The experimental results show that the wettability of Ag grains with polymer is stronger than with glass, which results in the aggregation of bigger grains in initial layer. During deposition the interaction of interlayer plays an important role for the formation of the surface morphology. The strong wettability activates the nonlinear optical properties of Ag grains grown on polymer substrates, which result in the strong absorbance in short wavelength. The effect of the bare substrate on the transmittance of Ag films is more obvious than the reflectance. With the increasing of the thickness, the effect of the wettability on the morphology and optical properties of Ag films decline. In this experiment when the thickness is above 50nm, the effect almost vanished.

Keywords: PACS; 68.37.Ps; 68.55.−a; 78.68.+mWettability; Ag thin films; Substrate material; Surface morphologies; Optical properties

Dynamics of porphyrin adsorption on highly oriented pyrolytic graphite monitored by scanning tunnelling microscopy at the liquid/solid interface by Q. Ferreira; A.M. Bragança; N.M.M. Moura; M.A.F. Faustino; L. Alcácer; J. Morgado (pp. 220-225).

Sequential STM images (35nm×35nm) of ZnOEP assembly on HOPG where three different phases are identified ( α, β, and γ) which change with the time.Display Omitted► STM images of Zn(II)-octaethylporphyrin monolayer were obtained in real time. ► Polymorphic behaviour of zinc(II)-octaethylporphyrin (ZnOEP) was identified. ► A phenomenological expression was proposed to explain the ZnOEP phase transition. ► STM images of Zn(II)- meso-tetradodecylporphyrin monolayer were obtained. ► The effect of the porphyrins alkyl substituents was discussed.Scanning tunnelling microscopy (STM) at solid/tetradecane interface is used to study the dynamics of zinc(II)-octaethylporphyrin (ZnOEP) and zinc(II)- meso-tetradodecylporphyrin (ZnTDP) adsorption on the surface of highly oriented pyrolytic graphite (HOPG). ZnOEP exhibits a polymorphic behaviour, with a first metastable phase remaining for the first 2h. This initial α-phase is then converted into a β-phase, where all porphyrins lie parallel to the substrate with a hexagonal arrangement, in agreement with previous reports. At variance with this behaviour, no metastable phases are found during ZnTDP adsorption under the same conditions. We consider that this different behaviour is due to the combination of a stronger interaction and lower mobility of ZnTDP on the HOPG surface.

Keywords: Self assembly; Polymorphism; Porphyrins; Monolayers; Scanning tunneling microscopy at solid/liquid interface

One-pot synthesis of peacock-shaped TiO₂ light scattering layer with TiO₂ nanorods film for dye-sensitized solar cells by Hyun Sik Kim; Young-Jea Kim; Wonjoo Lee; Soon Hyung Kang (pp. 226-232).

Peacock-shaped TiO₂ nanobundles consisting of small-sized nanorods above the compact TiO₂ nanorod film prepared by one-pot hydrothermal method.Display Omitted► Hydrothermal synthesis was used to make bilayered TiO₂ film. ► Dual functional peacock-shaped light scattering layer was formed upon the compact TiO₂ film. ► Acid (HCl and CH₃COOH) control in the solution affects the morphological properties. ► Bilayered film exhibits the sharp increase in conversion efficiency (3.93%) versus (1.49%) of TiO₂ NRs film.A titanium dioxide (TiO₂) film, showing distinctive functions and morphology, was prepared using the hydrothermal method by controlling the ratio of HCl:CH₃COOH in acidic medium. A one-dimensional (1-D) TiO₂ nanorod (NR) film was synthesized with a length of 2μm using a 1:2 ratio of HCl:CH₃COOH, whereas a 1-D TiO₂ NR film with peacock shaped TiO₂ nanobundles as a light scattering layer (LSL) was acquired by employing a 2:1 ratio of HCl:CH₃COOH. This LSL exhibited remarkable dual functions with respect to high light harvesting, which was attributable to the large surface area of the micrometer-sized TiO₂ nanobundles, consisting of small-sized TiO₂ NRs of 30–40nm in diameter and a light scattering effect in the long wavelength region of 550–700nm. Accordingly, the dual functions of the LSL resulted in a sharp increase in conversion efficiency (3.93%) that was about twice that (1.49%) of TiO₂ NR film synthesized using a 1:2 ratio of HCl:CH₃COOH. In particular, a considerably enhanced short-circuit photocurrent ( J_sc) was mainly responsible for the resulting increase in overall efficiency with a moderate increase in fill factor and slightly reduced open-circuit voltage.

Keywords: Hydrothermal synthesis; Dye-sensitized solar cells; Light scattering layer; Photoanode

Photoluminescence and I– V characteristics of the carbonized silicon nanoporous pillar array by Haiyan Wang; Renzhong Xue; Zijiong Li; Yongqiang Wang (pp. 233-236).

► The surface of silicon nanoporous pillar array is carbonized to 3C–SiC simply. ► Strong photoluminescence in the UV-blue region is observed in SiC/Si-NPA. ► Obvious rectification and low leakage current are obtained from SiC/Si-NPA.A layer of nanocrystalline 3C–SiC film was synthesized on silicon nanoporous pillar array (Si-NPA) by thermally carbonizing the surface of Si-NPA in a graphite crucible and a 3C–SiC/Si nanoheterojunction (named SiC/Si-NPA) was fabricated. Room-temperature photoluminescence of SiC/Si-NPA was studied and strong light emissions peaked at 383, 402 and 420nm were observed from SiC/Si-NPA when it was excited by 300nm fluorescent light. The I– V characteristics of SiC/Si-NPA were measured. Obvious rectification behavior and low leakage current were found in the prepared SiC/Si-NPA diodes. Based on the I– V measurements the conduction mechanism in SiC/Si-NPA under positive applied voltage was explained. Our results indicate that SiC/Si-NPA might be a valuable heterostructure nanosystem to be further probed for achieving enhanced optical and electrical properties.

Keywords: 3C–SiC nanocrystals; Silicon nanoporous pillar array; Photoluminescence; I; –; V; characteristics

Uniform β-Co(OH)₂ disc-like nanostructures prepared by low-temperature electrochemical rout as an electrode material for supercapacitors by Mustafa Aghazadeh; Hamid Mohammad Shiri; Abbas-Ali Malek Barmi (pp. 237-242).

Display Omitted► Low-temperature cathodic electrodeposition form cobalt nitrate bath resulted uniform cobalt hydroxide nanodiscs. ► A maximum specific capacitance of 736.5Fg⁻¹ was achieved. ► The mechanism of Co(OH)₂ electrodeposition was proposed and confirmed by CHN and FTIR analyses.Uniform nanostructures of cobalt hydroxide were successfully prepared by a low-temperature electrochemical method via galvanostatically deposition from a 0.005M Co(NO₃)₃ bath at 10°C. The XRD and FT-IR analyses showed that the prepared sample has a single crystalline hexagonal phase of the brucite-like Co(OH)₂. Morphological characterization by SEM and TEM revealed that the prepared β-Co(OH)₂ was composed of uniform compact disc-like nanostructures with diameters of 40–50nm. The electrochemical performance of the prepared β-Co(OH)₂ was evaluated using cyclic voltammetry and charge–discharge tests. A maximum specific capacitance of 736.5Fg⁻¹ was obtained in aqueous 1M KOH with the potential range of −0.2–0.5V ( vs. Ag/AgCl) at the scan rate of 10mVs⁻¹, suggesting the potential application of the prepared nanostructures as an electrode material in electrochemical supercapacitors. The results of this work showed that the low-temperature cathodic electrodeposition method can be recognized as a new and facile route for the synthesis of cobalt hydroxide nanodiscs as a promising candidate for the electrochemical supercapacitors.

Keywords: β-Co(OH); ₂; Cathodic Electrodeposition; Nanodiscs; Supercapacitors

Microstructure and magnetic properties of L1₀ FePt–MgO/Fe–MgO thin films by Liwang Liu; Qi Li; Honggang Dang; Liang Hao; Jiangwei Cao; Yanbo Li; Ying Wang; Jianmin Bai; Fulin Wei (pp. 243-246).

► The FePt–MgO films preserving good perpendicular anisotropy have been prepared. ► The FePt grains distribute uniformly in MgO matrix and the grains size close to 5.4nm. ► The relatively small α value 2.0 is obtained and magnetic domain size is about 99nm. ► The microstructure and magnetic properties of FePt–MgO/Fe–MgO bilayers were studied.The L1₀ FePt–MgO/Fe–MgO bilayers were fabricated on thermal oxide silicon substrate by using magnetron sputtering. The TEM image shows that the FePt–MgO single layer has small and uniform granular grain. In the FePt–MgO/Fe–MgO bilayer system, with increasing Fe layer thickness, the grain size become larger and the grain boundary become obscure, while the magnetization process transforms from a coherent magnetization to an exchange spring behavior, and finally a two-phase magnetization reversible process.

Keywords: L; 1; ₀; FePt; Microstructure; TEM; Coercivity; Exchange coupling; Magnetic domain

Reactive growth of MgO overlayers on Fe(001) surfaces studied by low-energy electron diffraction and atomic force microscopy by Antoni Tekiel; Shawn Fostner; Jessica Topple; Yoichi Miyahara; Peter Grütter (pp. 247-252).

► Reactive growth of ultra-thin MgO films on the Fe(001) surface was investigated. ► This method gives full control over the gaseous species that reach the surface. ► Preparation required a protocol that prevents overoxidation of the Fe(001) surface. ► The effect of annealing during and after the growth was studied. ► The reactive deposition method can produce terraces as large as 10nm.Ultra-thin MgO films grown reactively on the Fe(001) surface by evaporation of magnesium in an atmosphere of molecular oxygen have been investigated by low energy electron diffraction and non-contact atomic force microscopy. Preparation of structurally stable crystalline films requires a protocol that prevents an excessive interfacial reaction between oxygen and the Fe(001) surface, but at the same time provides a sufficient amount of oxygen in order to grow a stoichiometric MgO film. The proper ratio between the magnesium deposition rate and the oxygen pressure has been determined, as well as measures to prevent initial interfacial oxidation of the substrate. The effect of both post-annealing and an increased substrate temperature during the growth has been studied. We demonstrate that the reactive deposition method, which gives full control over the gaseous species that reach the surface, can produce terraces that have an average size of 10nm (on an 8 monolayer thick film), which is a significant improvement compared to other preparation methods, such as thermal or electron beam evaporation of MgO.

Keywords: Magnesium oxide; Iron; Reactive growth; Magnetoelectronics; Ultra-thin insulating film; LEED; AFM

The hydrogen generation from alkaline NaBH₄ solution by using electroplated amorphous Co–Ni–P film catalysts by Yueping Guo; Qinghua Feng; Jiantai Ma (pp. 253-256).

► The amorphous Co–Ni–P films were electrodeposited on Cu sheets. ► The deposit plating rate and the catalytic activities for NaBH₄ hydrolysis were investigated. ► The highest hydrogen generation rate of 3636mL(ming-catalyst)⁻¹ was obtained. ► The activation energy ( E_a) for the NaBH₄ hydrolysis was 38kJmol⁻¹.The amorphous Co–Ni–P films were electroplating on Cu sheets. The effects of NiSO₄ concentrations on the deposit plating rate and the catalytic activities for NaBH₄ hydrolysis were investigated. The surface morphology and phase structure of the deposited Co–Ni–P films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The composition was analyzed by energy dispersive spectrometer (EDX). Experimental results showed that adding NiSO₄ in Co–P bath could increase the deposition rate. When 0.01M of NiSO₄ was used, the highest deposition rate and the highest hydrogen generation rate of 3636mL(ming-catalyst)⁻¹ were obtained. The activation energy ( E_a) for the NaBH₄ hydrolysis was 38kJmol⁻¹, which was comparable to the value of noble metal catalysts.

Keywords: Co–Ni–P films; Sodium borohydride; Hydrogen generation; Electrodeposition

Upconversion properties in hexagonal-phase NaYF₄:Er³⁺/NaYF₄ nanocrystals by off-resonant excitation by Xianjia Luo; Katsuhiro Akimoto (pp. 257-260).

Display Omitted► Upconversion in NaYF₄:Er³⁺/NaYF₄ nanocrystals excited at 1620nm were observed. ► An off-resonant absorption peak at around 1600nm was observed. ► The off-resonant absorption is phonon assisted. ► Upconversion intensity excited at 1620nm strongly depends on temperature. ► Upconversion under off-resonant excitation involves phonon-assisted transitions.Upconversion (UC) emissions in the hexagonal phase of NaYF₄:10%Er³⁺/NaYF₄ core/shell nanocrystals have been observed by off-resonant excitation at 1620nm, whose energy is lower than that corresponding to the lowest f–f transition of Er³⁺ (⁴I_15/2→⁴I_13/2). The UC emission spectrum consists of five main peaks at around 1540 (⁴I_13/2→⁴I_15/2), 980 (⁴I_11/2→⁴I_15/2), 800 (⁴I_9/2→⁴I_15/2), 660 (⁴F_9/2→⁴I_15/2) and 540nm (⁴S_3/2→⁴I_15/2). The infrared absorption spectrum shows a weak peak at around 1600nm which is separated from the⁴I_15/2→⁴I_13/2 absorption peak by 315cm⁻¹, and phonon bands of NaYF₄ has been observed at about 300cm⁻¹ in the Raman spectrum. From these results, the UC emission is interpreted to involve a phonon-assisted excitation process. The UC emission intensity under off-resonant excitation at 1620nm exhibits a much stronger temperature dependence than that under resonant excitation at 1550nm, which is consistent with the phonon-assisted interpretation.

Keywords: Upconversion; NaYF; ₄; :Er; ³⁺; Off-resonant excitation; Phonon-assisted transition; Temperature dependence

Pt and Pd as catalyst deposited by hydrogen reduction of metal salts on WO₃ films for gasochromic application by N. Tahmasebi Garavand; S.M. Mahdavi; A. Iraji zad (pp. 261-267).

Display Omitted► WO₃ films were prepared by pulsed laser deposition (PLD) method. ► Pt NPs was deposited onto the WO₃ films through hydrogen reduction of PtCl₂ at 200°C. ► Gasochromic performance of samples was studied at temperature range of 30–200°C.In this study, tungsten oxide films were deposited by pulsed-laser deposition (PLD) technique. The as-deposited films were annealed at 250°C in air for 1h. The surface morphology, microstructure, crystalline phase, and chemical composition of the films were characterized by SEM, XRD and XPS techniques. Pt nanoparticles were deposited onto the tungsten oxide films through a two-step process. First of all, a layer of PtCl₂ was coated on the WO₃ surface by drop-drying the PtCl₂ solution onto the WO₃ surface at 60°C. Consequently, the reduction of the PtCl₂ into the metallic Pt nanoparticles was performed at 200°C. In this study, the effect of the temperature during hydrogen reduction of PtCl₂ as well as the influence of operating temperature on the gasochromic performance of Pt–WO₃ samples were investigated. Results revealed that the gasochromic responses of the Pt–WO₃ samples have attained approximately a constant value at temperatures above 90°C. On the other hand, their responses are insignificant at temperatures below 90°C. Additionally, for the sake of comparison, some results of the gasochromic performance of Pd-WO₃ films were presented.

Keywords: Pulsed-laser deposition; Tungsten oxide film; Platinum; Gasochromic

Comparative study on catalyst-free formation and electron field emission of carbon nanotips and nanotubes grown by chemical vapor deposition by B.B. Wang; K. Zheng; R.W. Shao (pp. 268-272).

► Catalyst-free growth of carbon nanotips and nanotubes was comparatively studied.► Their formation relates the change of carbon film with temperature. ► The electron field emission of carbon nanotips and nanotubes is studied.► The structure of carbon nanotips is stable during electron emission.The catalyst-free growth of carbon nanotips and nanotubes on silicon substrate pre-deposited with carbon film was realized under different temperatures in plasma-enhanced hot filament chemical vapor deposition system, in which methane, nitrogen and hydrogen were used as the reactive gases. The structure and composition of synthesized carbon nanotips and nanotubes were investigated using field emission scanning electron microscope, transmission electron microscope and micro-Raman spectroscopy, respectively. The results indicate that the carbon nanotips are formed at about 800°C while the carbon nanotubes are formed about 900°C. According to the ion bombardment effect and the diffusion at different temperatures, the catalyst-free formation of carbon nanotips and nanotubes was comparatively studied. The transformation from carbon film to spherical carbon particles at a high temperature results in the formation of carbon nanotubes depending on the diffusion of carbon. At a low temperature, the carbon film still locates at the substrate and leads to the formation of carbon nanotips relying on the sputtering-etching of etching ions and the deposition of carbonaceous ions. In addition, the electron field emission characteristics of carbon nanotips and nanotubes were investigated. The results indicate that there is much difference in the electron field emission properties for the carbon nanotips and nanotubes. According to the thermal effect produced by Joule heat during electron emission, the difference was interpreted.

Keywords: Carbon nanotips; Carbon nanotubes; Temperature; Diffusion; Thermal effect

Preparation and luminescence properties of Tb³⁺ doped SiO₂ film on TiO₂ nanotube arrays by Yibo Shang; Enzhou Liu; Xiaoyun Hu; Hui Miao; Lu Zhang; Suchang Zhan; Ruonan Ji; Dekai Zhang; Jun Fan; Lunming Xu (pp. 273-277).

Display Omitted► Tb-doped SiO₂ films on TiO₂ nanotube arrays were prepared by anodization sol–gel method. ► The SiOTi chemical bond was formed in the interface between Tb-doped SiO₂ films and TiO₂ nanotube arrays. ► TiO₂ nanotube arrays fabricated in NH₄Cl+H₂O electrolytes improved the luminous efficiency of Tb-doped SiO₂ films.TiO₂ nanotube arrays (TiO₂ NTs) are fabricated by anodic oxidation of titanium in NH₄Cl+H₂O and NH₄F+HOCH₂CH₂OH electrolytes respectively, then TiO₂ NTs coated with Tb³⁺ doped SiO₂ films (Tb–SiO₂/TiO₂ NTs) are prepared by sol–gel method and dip-coating process. The luminescence properties of Tb–SiO₂/TiO₂ NTs are investigated by fluorescence spectrometer. Results show that TiO₂ NTs can improve the luminescence properties of Tb–SiO₂, especially the TiO₂ NTs fabricated in NH₄Cl+H₂O electrolyte. The emission intensity of Tb–SiO₂ on the TiO₂ NTs fabricated in NH₄Cl+H₂O electrolyte is five times to that on the pure titanium sheet. Additionally, the effect of TiO₂ NTs preparation conditions on the Tb–SiO₂ luminescence properties is analyzed in detail, and the luminescence enhancement mechanism of Tb–SiO₂ on TiO₂ NTs is explained.

Keywords: TiO; ₂; nanotube arrays; Surface; Rare-earth; Luminescent films; Sol–gel method; Luminescence enhancement

A facile method for synthesis of N-doped TiO₂ nanooctahedra, nanoparticles, and nanospheres and enhanced photocatalytic activity by Jimin Du; Guoyan Zhao; Yunfeng Shi; HaoYang; Yaxiao Li; Gaigai Zhu; Yanjun Mao; Rongjian Sa; Weiming Wang (pp. 278-286).

► N-doped TiO₂ nanooctahedra, nanoparticles and nanospheres were successfully synthesized through nitrification of the corresponding TiO₂ nanostructures in the presence of ammonia gas at 700°C for 30min. ► UV–vis absorption results show that all the as-synthesized N-doped TiO₂ samples present red-shift absorption up to ∼410nm, which can be ascribed to the addition energy level between TiO₂ valence and conducion band. ► Amongst as-synthesized samples, the N-doped TiO₂ nanooctahedra show the best behavior under UV–vis and visible light irradiation due to the exposed {101} facets. ► Therefore, N-doped TiO₂ nanooctahedra can be a promising photocatalyst in photodegradation for organic compounds, photoredox for carbon oxide and so on under UV–vis irradiation.N-doped TiO₂ nanooctahedra, nanoparticles and nanospheres were successfully synthesized through nitrification of the corresponding TiO₂ nanostructures in the presence of ammonia gas at 700°C for 30min. The crystal phase and compositions of N-doped TiO₂ samples were confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The product morphology was characterized with scanning microscopy (SEM) and transmission electron microscopy (TEM). UV–vis absorption results show that all the as-synthesized N-doped TiO₂ samples present red-shift absorption up to ∼410nm, which can be ascribed to the addition energy level between TiO₂ valence and conducion band. Surface areas of all samples were measured through nitrogen absorption–desorption isothermal. In order to evaluate the photocatalytic activity of N-doped TiO₂ samples, photodecomposition for methyl orange (MO) was performed under UV–vis light irradiation for 30min, indicating that N-doped TiO₂ nanooctahedra with the exposed {101} crystallized surfaces show good photocatalytic behavior in comparison with other samples.

Keywords: N-doped TiO; ₂; Photocatalyst; Nitrification; Enhancement

Surface characteristics of etched parylene-C films for low-damaged patterning process using inductively-coupled O₂/CHF₃ gas plasma by Yong-Hyun Ham; Dmitriy Alexandrovich Shutov; Kwang-Ho Kwon (pp. 287-292).

► We investigated pattering processes of organic materials. ► We attempted to conduct a simplified model-based analysis of the CHF₃/O₂ plasma. ► A small addition of CHF₃ to the O₂ plasma produced a high etch rate. ► The surface energy was decreased with increasing fluorocarbon containing gas. ► The decreased surface energy is related to the functional groups of CF_x polymer.We investigated the effectiveness of CHF₃ admixture in O₂ plasma for a low damage patterning process. We used inductively-coupled plasma (ICP) etching of parylene-C thin films with O₂/CHF₃ gas mixtures. Plasma diagnostics were performed by using a double Langmuir probe. Also in order to examine the relationship between the plasma and surface energy, we attempted to conduct a simplified model-based analysis of the CHF₃/O₂ plasma.The surface energy decreased as the admixture fraction increased with fluorocarbon containing gas. The decreased surface energy is related to the functional groups of CF_x polymer at binding energy of around 290eV and low ion physical damage. We observed that a small addition of CHF₃ to O₂ plasma produced a high etch rate, low surface energy, and low roughness compared to pure oxygen plasma.

Keywords: Parylene-C; O; ₂; /CHF; ₃; Surface characteristics; Etch, ICP

Divacancy-assisted transition metal adsorption on the BN graphene and its interaction with hydrogen molecules: a theoretical study by Ying Chen; Hongmei Wang; Hongxia Wang; Jing-xiang Zhao; Qing-hai Cai; Xiao-Guang Wang; Yi-hong Ding (pp. 293-301).

► The considered transition metals can be stably adsorbed on BN graphene with divacancy. ► TM adsorption has an obvious effect on the electronic and magnetic properties of defective BN. ► The dispersed Sc, V, and Cr on DV-BN graphenes are suitable candidates for hydrogen storage.We have performed first-principles calculations to study the chemical functionalization of the BN graphene with divacancy (DV) defect by 12 different transition metal (TM) atoms, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pt, and Au. The results indicate that the DV defect can assist the adsorption of TM atoms on BN graphene. Moreover, some impurity bands are induced within the band gap of DV-BN graphene, leading to the modification of its electronic properties in various ways. Interestingly, Ti- and Co-adsorbed DV-BN graphenes are found to possess ferromagnetic characteristic, while antiferromagnetic state is preferred for V-, Mn-, and Fe-functionalized DV-BN graphenes, and the paramagnetic state is the ground state for Sc-, Cr-, Ni-, Cu, Zn-, Pt-, and Au-decorated DV-BN graphenes. Finally, aiming at evaluating the potential of these functionalized BN graphenes in hydrogen storage, we study their interaction with H₂ molecules. It is found that the dispersed Sc, V, and Cr on DV-BN graphene are able to adsorb up to three H₂ molecules as strongly as 0.25–0.58eV/H₂, suggesting that the three nanomaterials may be suitable candidates for hydrogen storage.

Keywords: Adsorption; Band-structure; Ab initio calculations; Nanostructures; Hydrogen storage

Phosphorus-doped graphene and (8, 0) carbon nanotube: Structural, electronic, magnetic properties, and chemical reactivity by Hong-mei Wang; Hong-xia Wang; Ying Chen; Yue-jie Liu; Jing-xiang Zhao; Qing-hai Cai; Xuan-zhang Wang (pp. 302-309).

► P dopant drastically changes the geometrical structure of graphene or CNT. ► P-doping induces localized electronic states into graphene and CNTs, thus modifying the electronic properties by producing n-type behavior. ► Due to P doping, the graphene and CNT exhibit magnetic nature. ► The chemical reactivity of graphene or CNT toward O₂, NO, and NO₂ is enhanced in various ways after P doping.Recently, doping non-carbon atoms into graphene or carbon nanotube (CNT) has attracted considerable attention due to its effectiveness to change or tailor their electronic and magnetic properties as well as chemical reactivity. In this work, we present a density functional theory study of the recently synthesized phosphorus (P) doped graphene and CNT. Particular attention is paid to studying the effects of P-doping on the structural, electronic, and magnetic properties as well as chemical reactivity of graphene or CNT. The results show that P dopant drastically changes the geometrical structure of graphene or CNT, rendering P and its neighboring C atoms protrude from the sidewall of CNT and graphene. Moreover, P-doping induces localized electronic states into graphene and CNTs, thus modifying the electronic properties by producing n-type behavior. Meanwhile, due to P doping, the graphene and CNT exhibit magnetic nature with spin net moment of 1.02 and 0.99 μ_B, respectively. In order to evaluate the chemical reactivity of the two nanostructures, their interactions with several gas molecules, including NH₃, H₂O, O₂, NO₂, and NO, are further calculated. Our results may be useful not only for deeply understanding the properties of CNTs and graphenes, but also for developing various novel nanodevices.

Keywords: P-doping; Graphene; CNT; Density functional theory

Titanium bone implants with superimposed micro/nano-scale porosity and antibacterial capability by B.S. Necula; I. Apachitei; L.E. Fratila-Apachitei; E.J. van Langelaan; J. Duszczyk (pp. 310-314).

This study aimed at producing a multifunctional layer with micro/nano-interconnected porosity and antibacterial capability on a rough macro-porous plasma sprayed titanium surface using the plasma electrolytic oxidation process. The layers were electrochemically formed in electrolytes based on calcium acetate and calcium glycerophosphate salts bearing dispersed Ag nanoparticles. They were characterized with respect to surface morphology and chemical composition using a scanning electron microscope equipped with the energy dispersive spectroscopy and back scattering detectors. Scanning electron microscopy images showed the formation of a micro/nano-scale porous layer, comprised of TiO₂ bearing Ca and P species and Ag nanoparticles, following accurately the surface topography of the plasma sprayed titanium coating. The Ca/P atomic ratio was found to be close to that of bone apatite. Ag nanoparticles were incorporated on both on top and inside the porous structure of the TiO₂ layer.

Keywords: Plasma electrolytic oxidation; Plasma sprayed; Superimposed porosity; Antibacterial implants; Silver nanoparticles

Electron scattering at surfaces and grain boundaries in thin Au films by Ricardo Henriquez; Marcos Flores; Luis Moraga; German Kremer; Claudio González-Fuentes; Raul C. Munoz (pp. 315-323).

► We measured the resistivity of gold films varying film thickness and grain size. ► We examine resistivity data using theories of electron-grain boundary scattering. ► Mayadas's theory describes the same resistivity data using different parameters. ► Mayadas's theory leads to a sizable increase of resistivity in small grained films. ► Palasantzas's theory leads to a film resistivity that is identical to the bulk.The electron scattering at surfaces and grain boundaries is investigated using polycrystalline Au films deposited onto mica substrates. We vary the three length scales associated with: (i) electron scattering in the bulk, that at temperature T is characterized by the electronic mean free path in the bulk ℓ₀( T); (ii) electron-surface scattering, that is characterized by the film thickness t; (iii) electron-grain boundary scattering, that is characterized by the mean grain diameter D. We varied independently the film thickness from approximately 50nm to about 100nm, and the typical grain size making up the samples from 12nm to 160nm. We also varied the scale of length associated with electron scattering in the bulk by measuring the resistivity of each specimen at temperatures T, 4K< T<300K. Cooling the samples to 4K increases ℓ₀( T) by approximately 2 orders of magnitude. Detailed measurements of the grain size distribution as well as surface roughness of each sample were performed with a Scanning Tunnelling Microscope (STM). We compare, for the first time, theoretical predictions with resistivity data employing the two theories available that incorporate the effect of both electron-surface as well as electron-grain boundary scattering acting simultaneously: the theory of A.F. Mayadas and M. Shatzkes, Phys. Rev. 1 1382 (1970) (MS), and that of G. Palasantzas, Phys. Rev. B 58 9685 (1998). We eliminate adjustable parameters from the resistivity data analysis, by using as input the grain size distribution as well as the surface roughness measured with the STM on each sample. The outcome is that both theories provide a fair representation of both the temperature as well as the thickness dependence of the resistivity data, but yet there are marked differences between the resistivity predicted by these theories. In the case of the MS theory, when the average grain diameter D is significantly smaller than ℓ₀(300)=37nm, the electron mean free path in the bulk at 300K, the effect of electron-grain boundary scattering dominates the increase in resistivity of the film over the bulk, and the electronic mean free path, ℓ_D(4), computed from Drude's model at 4K, is similar to the grain diameter D. The increase in resistivity attributable to electron-grain boundary scattering can be as large as 220 at low temperatures, for samples made out of 12nm grains. On the contrary, when D is significantly larger than ℓ₀(300), then electron-surface scattering dominates the increase in resistivity. When D is comparable to ℓ₀(300), there is a cross over where both electron-surface and electron-grain boundary scattering do contribute to increasing the resistivity of the film over that of the bulk. These predictions are in sharp contrast with those based upon the theory of Palasantzas, that predicts an increase in resistivity—attributable to electron-grain boundary/surface scattering—that turns out to be essentially unity regardless of the size of the grains making up the sample.

Keywords: PACS; 73.50.−h; 73.61.−rResistivity; Electron-surface scattering; Electron-grain boundary scattering

Characterization of transparent conductive delafossite-CuCr1−_xO₂ films by Hong-Ying Chen; Kuei-Ping Chang; Chun-Chao Yang (pp. 324-329).

► The CuCr1−_xO₂ films with x<0.25 are successfully deposited by low-cost sol–gel processing. ► Pure CuCrO₂ phase exists in the CuCr1−_xO₂ films below x≤0.20. ► The chemical states of Cu and Cr in pure CuCrO₂ phase are +1 and +3 valence. ► The stoichiometry in CuCr1−_xO₂ films enhances the electrical conductivity of the films.In this study, the CuCr1−_xO₂ films with x=0.00–0.25 were prepared on a quartz substrate by sol–gel processing. The films were first deposited onto a quartz substrate by spin-coating. The specimens were annealed at 500°C in air for 1h and post-annealed in N₂ at 700°C for 2h. As the films were post-annealed in N₂, a pure delafossite-CuCrO₂ phase appeared in the CuCr1−_xO₂ films below x=0.20. However, an additional CuO phase appeared at x=0.25. The pure delafossite-CuCrO₂ phase can exist within x≤0.20 in CuCr1−_xO₂ films. The binding energies of Cu-2p_3/2 and Cr-2p_3/2 in the CuCr1−_xO₂ films with the pure delafossite-CuCrO₂ phase were 932.1±0.2eV and 576.0±0.2eV, respectively. The surface exhibited elongated grain features when the pure delafossite-CuCrO₂ phase was present in the CuCr1−_xO₂ films. The maximum transmittance of the CuCr1−_xO₂ films with the pure delafossite-CuCrO₂ phase was approximately 80%, which moved toward the visible region with the increasing x-value. The film absorption edges were observed at 400nm, which were sharper with the increasing x-value. The optical bandgaps of CuCr1−_xO₂ films with the pure delafossite-CuCrO₂ phase were approximately 3.0eV. The electrical conductivity of CuCr1−_xO₂ films with the pure delafossite-CuCrO₂ phase was 1.1×10⁻³Scm⁻¹ ( x=0.00), and increased to 0.16Scm⁻¹ ( x=0.20). The corresponding carrier concentration of CuCr1−_xO₂ films with the pure delafossite-CuCrO₂ phase was 2.8×10¹⁴cm⁻³ ( x=0.00), and markedly increased to 1.8×10¹⁶cm⁻³ ( x=0.20). The Cr-deficient condition in delafossite-CuCrO₂ films enhances film electrical conductivity and carrier concentration, but retains the film's high-visible transparency.

Keywords: Delafossite; CuCrO; ₂; p-type; Sol–gel processes; Thin films; Stoichiometry

The structure of Pd–M supported catalysts used in the hydrogen transfer reactions (M=In, Bi and Te) by Izabela A. Witońska; Michael J. Walock; Piotr Dziugan; Stanisław Karski; Andrei V. Stanishevsky (pp. 330-342).

► Pd–M support (M=In, Bi and Te) catalysts show high activity and selectivity in the hydrogen transfer reactions. ► After catalysts activation in H₂ the formation of intermetallic phases was observed. ► Formation of the intermetallic compounds and their composition was examined by XRD, XPS, SIMS-ToF. ► Intermetallic Pd_xM_y compounds can modify the catalytic properties of studied systems. ► The knowledge of the composition of Pd_xM_y compounds is important in the optimization of hydrogen transfer catalysts.Palladium catalysts promoted with a second metal demonstrate good activity and selectivity in many important oxidation and reduction reactions. The influence of co-metal on the catalytic performance of Pd depends on interaction between the two components and by the chemical state of both the Pd and co-metal. The understanding of the nature of such interaction is important in the optimization of such catalysts and development of new Pd-based catalyst systems with improved performance and stability. In this study, the surface structure and chemical states in several Pd–M/supported catalysts (where M=In, Bi, and Te) were experimentally investigated by using time-of-flight secondary ion mass spectroscopy (ToF-SIMS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It has been found that the formation of the intermetallic compounds and their composition can be responsible for a reduction or increase of catalytic activity and selectivity previously observed for the studied Pd–M systems.

Keywords: Intermetallic compounds on the bimetallic supported catalysts; Palladium bimetallic catalysts; XPS; SIMS-ToF

Labile Zn ions on octacalcium phosphate-derived Zn-containing hydroxyapatite surfaces by Yoshitomo Honda; Takahisa Anada; Shinji Morimoto; Osamu Suzuki (pp. 343-348).

► Zinc (Zn)-containing octacalcium phosphate (OCP) and its hydrolyzed Ca-deficient hydroxyapatite (HA) were prepared. ► Zn release was investigated by comparing the solubilities of the crystals in physiological environments, such as medium. ► Some of Zn ions are present as a labile state on these calcium phosphate surfaces. ► Zn ions on the crystal surfaces are released if cysteine and histidine are present under co-existence of other amino acids.We previously synthesized and characterized zinc-containing octacalcium phosphate (OCP) and its hydrolyzed Ca-deficient hydroxyapatite (HA). In the present report, we attempted to define the state of Zn in the OCP-derived Zn-calcium phosphates (CaPs) in relation to the presence of specific amino acids. Zn-containing OCPs were prepared in solutions that included Zn ions up to a concentration of 3.5mM, and their hydrolyzates [hydrolyzed (hy)-Zn-CaP] were obtained in hot water. The materials were characterized by x-ray diffraction and scanning electron microscopy. The concentration of Ca and Zn ions at room temperature was determined by analyzing the supernatant after incubating the materials in α-minimal essential medium (α-MEM) and HEPES buffer including cysteine, histidine, lysine, aspartic acid, and glutamic acid. Zn ions were more dissolved in α-MEM than HEPES buffer in the absence of amino acids. The inclusion of the amino acids enhanced Zn dissolution by several hundred fold, even in HEPES buffer. Among the amino acids, both cysteine and histidine enhanced the release of Zn. The effect was particularly remarkable with cysteine even in the presence of the other amino acids tested. These results indicate that Zn ions are present as a surface labile pool, which tends to be preferentially desorbed by cysteine, a ubiquitous molecule present in serum.

Keywords: Hydroxyapatite; Octacalcium phosphate; Zinc; Amino acids; Surface exchange

Phosphorus doped TiO₂ as oxygen sensor with low operating temperature and sensing mechanism by Zhizhong Han; Jiejie Wang; Lan Liao; Haibo Pan; Shuifa Shen; Jianzhong Chen (pp. 349-356).

Display Omitted► This work firstly reports an oxygen sensor based on phosphorus doped TiO₂. ► The sensitivity and selectivity of TiO₂ are enhanced by phosphorus doping. ► The operating temperature is low, and the response time is short. ► The mechanism of oxygen sensing improvement with phosphorus doping is researched. ► Based on this work, nonmetal doping could be as a new filed for gas sensor.Nano-scale TiO₂ powders doped with phosphorus were prepared by sol–gel method. The characterization of the materials was performed by XRD, BET, FT-IR spectroscopy, Zeta potential measurement and XPS analysis. The results indicate that the phosphorus suppresses the crystal growth and phase transformation and, at the same time, increases the surface area and enhances the sensitivity and selectivity for the P-doped TiO₂ oxygen sensors. In this system, the operating temperature is low, only 116°C, and the response time is short. The spectra of FT-IR and XPS show that the phosphorus dopant presents as the pentavalent-oxidation state in TiO₂, further phosphorus can connect with Ti⁴⁺ through the bond of TiOP. The positive shifts of XPS peaks indicate that electron depleted layer of P-doped TiO₂ is narrowed compared with that of pure TiO₂, and the results of Zeta potential illuminate that the density of surface charge carrier is intensified. The adsorptive active site and Lewis acid characteristics of the surface are reinforced by phosphorus doping, where phosphorus ions act as a new active site. Thus, the sensitivity of P-doped TiO₂ is improved, and the 5mol% P-doped sample has the optimal oxygen sensing properties.

Keywords: TiO; ₂; Oxygen sensor; Phosphorus doping; Low operating temperature; Sensing mechanism

Structure–activity relationship of CuO/MnO₂ catalysts in CO oxidation by Kun Qian; Zhaoxia Qian; Qing Hua; Zhiquan Jiang; Weixin Huang (pp. 357-363).

Display Omitted► Efficient CuO/MnO₂ catalysts have been developed for CO oxidation. ► CuO/MnO₂ catalysts with CuO loading of 1–40% exhibit almost the same catalytic performance toward CO oxidation. ► The CuO–MnO₂ interface is the active site for CO oxidation in CuO/MnO₂ catalysts. ► CO oxidation over CuO/MnO₂ catalysts likely follows the interfacial reaction mechanism.A series of CuO/MnO₂ catalysts with different CuO loadings were synthesized by the incipient wetness impregnation method. The catalysts were characterized by N₂ adsorption–desorption isotherms, powder X-ray diffraction, X-ray photoelectron spectroscopy, H₂-temperature programmed reduction, CO-temperature programmed reduction and scanning electron microscope. The CuO/MnO₂ catalysts with CuO loading of 1–40% exhibit almost the same catalytic performance toward CO oxidation while those with higher CuO loadings exhibit a much poorer catalytic activity. The structural characterization results demonstrate that the CuO–MnO₂ interface is the active site for CO oxidation in CuO/MnO₂ catalysts and CO oxidation over CuO/MnO₂ probably follows the interfacial reaction mechanism in which CO chemisorbed on CuO reacts with oxygen species on MnO₂ at the CuO–MnO₂ interface.

Keywords: CuO/MnO; ₂; catalysts; CO oxidation; Interfacial catalysis

Synthesis of nanocrystalline TiC reinforced W nanocomposites by high-energy mechanical alloying: Microstructural evolution and its mechanism by Guoquan Zhang; Dongdong Gu (pp. 364-371).

► TiC/W nanocomposites were prepared by high-energy mechanical alloying from micrometer-scaled feedstock. ► Nanocrystalline W matrix and nanoscale TiC reinforcing particles were simultaneously formed. ► Interesting evolutions of phase and microstructure of the nanocomposites were disclosed. ► Predominant mechanisms behind the microstructural development were elucidated.High-energy mechanical alloying (MA) of a micrometer-scaled W and TiC powder mixture was performed to prepare TiC/W nanocomposites. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and laser particle size analysis were used to study the morphological change and microstructural evolution occurred during MA process. It showed that the powder particles experienced a continuous refinement during 0–35h milling; on increasing the applied milling time up to 45h, the particles had a tendency to coarsen. The 35h milled powder had a considerably refined particle morphology, showing a narrow size distribution ( D₂₅=0.47μm, D₅₀=0.61μm, D₇₅=0.74μm, and D₉₀=0.86μm) and a significantly elevated specific surface area of 4154.86 m²/kg. The TEM results revealed that the particles of 35h milled product consisted of a large number of ultrafine crystallites of W and TiC with sizes less than 20nm and the nanometer-sized TiC particulates were dispersed uniformly throughout the W matrix. The analysis of XRD spectra by Scherrer equation indicated that the average crystallite sizes of the W and TiC constituents in the 35h milled powder were 8.5nm and 13.6nm, respectively, showing a good agreement with the experimental results. On further increasing the milling time up to 45h, the partial amorphization of W constituent occurred in the milled powder. Formation mechanisms and theoretical basis for microstructural development and phase change in the milled powders were elucidated.

Keywords: Mechanical alloying; Tungsten; Nanocrystalline; Nanocomposites; Microstructure; Amorphization

Capacitive humidity-sensing properties of Zn₂SiO₄ film grown on silicon nanoporous pillar array by Wen Chuang Wang; Yong Tao Tian; Kun Li; Er Yang Lu; Dong Shang Gong; Xin Jian Li (pp. 372-376).

The capacitance of Zn₂SiO₄/Si-NPA increases monotonically with RH in the range from 11% to 95%. The maximum increment is 8042% according to the changing from 11% to 99%. The response and recovery time was less than 1min.Display Omitted► A Zn₂SiO₄ film was grown on silicon nanoporous pillar array (Si-NPA) for humidity detection. ► Zn₂SiO₄/Si-NPA humidity sensor showed high sensitivity, quick response and slight hysteresis. ► Zn₂SiO₄/Si-NPA might be a promising material for fabricating practical humidity sensors.A Zn₂SiO₄ thin film was grown on silicon nanoporous pillar array (Si-NPA) via a chemical vapor deposition method, and the capacitive humidity-sensing properties of Zn₂SiO₄/Si-NPA were investigated at room temperature. With the relative humidity (RH) changing from 11% to 95%, the capacitance of the sensor increased from 1.67 to 135.97nF at the testing frequency of 20Hz, and an overall increment of 8042% was obtained. The response and recovery time was measured to be 48 and 32s, respectively. The sensor showed a maximum humidity hysteresis of 1.99% at 75% RH. These results indicated that Zn₂SiO₄/Si-NPA might be a promising material for fabricating high-performance capacitive humidity sensors.

Keywords: Silicon nanoporous pillar array (Si-NPA); Zn; ₂; SiO; ₄; /Si-NPA; Chemical vapor deposition; Capacitive humidity sensor

Marble protection: An inorganic electrokinetic approach by Paola Meloni; Francesco Manca; Gianfranco Carcangiu (pp. 377-385).

► COM precipitation on marble from ammonium oxalate solution. ► Innovative electro-mediated ammonium oxalate treatment for stone conservation. ► SEM characterization of electrokinetically consolidated marble sample. ► Electrokinetic process as a cost effective and efficient way to consolidate marble.The influence of an electric potential difference in an aqueous solution was studied as a method for depositing a calcium oxalate coating over a weathered carbonatic stone. Samples of weathered Carrara white marble were treated at 15 and 50°C for 5h in an electrokinetic cell, specifically conceived for this study, containing a solution of ammonium oxalate (4% by weight), and were subsequently characterised by scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis and mercury intrusion porosimetry. The electrokinetic treatment proved to be a cost effective and time saving process, able to produce a thick and homogeneous calcium oxalate coating over the stone surface that improves its chemical and physical resistance in low pH environments, and is able to protect the stone from the by-products of urban pollution.

Keywords: Ammonium oxalate treatment; Stone conservation; Marble protection; Electrokinetic treatment

Imaging the electronic structure of carbon nanotubes decorated with Fe₂O₃ nanoparticles by Yuting Nie; Lili Bai; Jing Gao; Jinyin Liu; Guanqi Zhao; Tian Xie; Xu-Hui Sun; Jun Zhong (pp. 386-390).

Display Omitted► Carbon nanotubes with Fe₂O₃ nanoparticles were imaged by scanning transmission X-ray microscopy. ► The results for Fe₂O₃-out-CNTs revealed the existence of an amorphous carbon coating on CNTs. ► The surface oxidation of Fe₂O₃-in-CNTs showed a heterogeneous distribution. ► The oxidization of CNTs may favor the internal Fe₂O₃ decoration of CNTs.Carbon nanotubes (CNTs) with external and internal decoration of Fe₂O₃ nanoparticles (NPs) were imaged by scanning transmission X-ray microscopy (STXM) with a concurrent identification of the electronic structure. For Fe₂O₃ outside CNTs, a carbon coating on CNTs was observed while for Fe₂O₃ inside CNTs, pure CNTs without carbon coating could be clearly identified. Surface oxidation of CNTs with internal decoration of Fe₂O₃ NPs was also found which showed a heterogeneous distribution. Further experiments suggest that the oxidization of CNTs may favor the internal Fe₂O₃ decoration of CNTs.

Keywords: Key words; X-ray absorption near-edge structure (XANES); Carbon nanotubes; Nanoparticles; Surface oxidation; Scanning transmission X-ray microscopy (STXM)

On the growth and photocatalytic activity of the vertically aligned ZnO nanorods grafted by CdS shells by M. Zirak; O. Moradlou; M.R. Bayati; Y.T. Nien; A.Z. Moshfegh (pp. 391-398).

Vertically aligned ZnO@CdS core–shell nanorods were synthesized via combined sol–gel/hydrothermal/SILAR method and their photocatalytic activity under UV- and visible-irradiation was carefully investigated and compared.Display Omitted► Vertically aligned ZnO@CdS core–shell nanorods were synthesized by a facile combined method. ► Photocatalytic activity of samples were examined under UV and visible light. ► The MB degradation mechanism was carefully investigated. ► The results were compared under UV and visible irradiation for the first time.We have studied systematically photocatalytic properties of the vertically aligned ZnO@CdS core–shell nanorods where the features were grown through a multistep procedure including sol–gel for the formation of ZnO seed layer, hydrothermal process to grow ZnO nanorods, and successive ion layer adsorption and reaction (SILAR) process to deposit CdS nanoshells onto the ZnO nanorods. Formation of the ZnO seed layer and vertically aligned ZnO nanorods ( d∼40nm) with a hexagonal cross-section was confirmed by AFM and SEM imaging. Successful capping of ZnO nanorods with homogeneous CdS nanocrystallites (∼5nm) was ascertained by HRTEM diffraction and imaging. Optical properties of the samples were also studied using UV–vis spectrophotometry. It was found that the absorption edge of the CdS shell has a red shift when its thickness increases. Photocatalytic activity of the samples was examined by photodecomposition of methylene blue under UV and visible lights where the maximum reaction rate constant was found to be 0.012min⁻¹ under UV illumination and 0.007min⁻¹ under visible light. The difference in catalytic activities of the ZnO@CdS core–shell nanorods under UV and visible irradiations was explained based upon the electronic structure as well as the arrangement of the energy levels in the ZnO@CdS core–shells. It is shown that the structure and photocatalytic efficiency of the samples can be tuned by manipulating the SILAR variables.

Keywords: Core–shell; Nanorod; Photocatalytic activity; Visible irradiation

Time dependency of the hydrophilicity and hydrophobicity of metallic alloys subjected to femtosecond laser irradiations by P. Bizi-bandoki; S. Valette; E. Audouard; S. Benayoun (pp. 399-407).

► Femtosecond laser texturing of metallic alloys were carried out. ► A multi-scale topography made of periodic undulations was induced. ► The surface wettability passed from hydrophilicity to hydrophobicity, over time. ► This modification is due to a combined effect of surface topography and chemistry. ► The chemical effect is related to the formation and the removal of functional groups.Surfaces of metallic alloys were laser-processed with femtosecond laser pulses of 800nm, with different power densities. The effect of time on the wettability of these surfaces was investigated. A multi-scale roughness made of undulations was created after the laser processing. This specific surface topography allowed the occurrence of a Wenzel's state. This state clearly explains the high hydrophilicity and hydrophobicity observed respectively one day after laser treatment and several days later. The change from hydrophilicity to hydrophobicity occurred over time and is due to surface chemistry modifications. The creation of new hydrophobic functional groups on aluminum alloy surface, for example, was proposed to be responsible for the hydrophobic behavior observed on these surfaces.

Keywords: Femtosecond laser; Multi-scale roughness; Hydrophilicity; Hydrophobicity; Metallic alloys; Chemical modifications

Structure and tribological properties of MoCN-Ag coatings in the temperature range of 25–700°C by D.V. Shtansky; A.V. Bondarev; Ph.V. Kiryukhantsev-Korneev; T.C. Rojas; V. Godinho; A. Fernández (pp. 408-414).

► MoCN-Ag nanocomposite coatings for tribological applications. ► Low friction coefficients in the temperature ranges of 25–100°C and 400–700°C. ► Carbon phase improves tribological properties at low temperatures. ► Ag, MoO_x and AgMo_xO_y phases serve as lubricants above 400°C.The preparation of hard coatings with low friction coefficient over a wide temperature range is still a challenge for the tribological community. The development of new nanocomposite materials consisting of different metal-ceramic phases, each of which exhibiting self-lubricating characteristics at different temperatures, may help to solve this problem. We report on the structure and tribological properties of MoCN-Ag coatings deposited by magnetron co-sputtering of Mo and C (graphite) targets and simultaneous sputtering of an Ag target either in pure nitrogen or in a gaseous mixture of Ar+N₂. The structure and elemental composition of the coatings were studied by means of X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, Raman spectroscopy, and glow discharge optical emission spectroscopy. The tribological properties of the coatings against an Al₂O₃ ball were investigated first at discrete temperatures of 25, 500, and 700°C, and then during continuous heating in the temperature range of 25–700°C. The coating structure and their respective wear tracks were also examined to elucidate their phase transformations during heat treatments. The lowest friction coefficients (<0.4) were observed in the temperature ranges of 25–100°C and 400–700°C and can be explained by the presence of a free amorphous carbon phase, which served as a lubricant at low temperatures, and by a positive role of silver and two phases forming at elevated temperatures, molybdenum oxide and silver molybdate, which provided lubrication above 400°C. In the temperature range between 100 and 400°C, the friction coefficient was relatively high. This problem is to be addressed in future works.

Keywords: Sputtering; Nanocomposite MoCN-Ag coatings; Structure; Tribological properties

Charge transfer and band bending at Au/Pb(Zr_0.2Ti_0.8)O₃ interfaces investigated by photoelectron spectroscopy by Nicoleta G. Apostol; Laura E. Stoflea; George A. Lungu; Cristina Chirila; Lucian Trupina; Raluca F. Negrea; Corneliu Ghica; Lucian Pintilie; Cristian M. Teodorescu (pp. 415-425).

► First follow-up by XPS, with detailed curve fitting, of the interface Au/PZT. ► Nearly perfect composition transfer from the target to the PZT film by pulsed laser deposition. ► A 0.94eV binding energy difference between P⁽⁺⁾ and P⁽⁰⁾ areas of the PZT surface. ► Evidence of 0.45eV band bending toward higher binding energies with Au deposition.The growth of gold layers on Pb(Zr,Ti)O₃ (PZT) deposited on SrTiO₃ is investigated by X-ray photoelectron spectroscopy in the Au thickness range 2–100Å. Two phases are identified, with compositions close to nominal PZT. The ‘standard’ phase is represented by all binding energies (Pb 4f, Ti 2p, Zr 3d, O 1s) sensibly equal to the nominal values for PZT, whereas the ‘charged’ phase exhibits all core levels are shifted by ∼1eV toward higher binding energies. By taking into account also scanning probe microscopy images together with recent photoemission results, the ‘charged’ phase belongs to P⁽⁺⁾ regions of PZT, whereas the ‘normal’ phase corresponds to regions with no net ferroelectric polarization perpendicular to the surface. Au deposition proceeds in a band bending of Φ_PZT−Φ_Au∼0.4–0.5eV for both phases, identified as similar shifts toward higher binding energies of all Pb, Ti, Zr, O core levels with Au deposition. The Au 4f core level exhibits also an unusually low binding energy component 1eV below the ‘nominal’ Au 4f binding energy position (metal Au). This implies the existence of negatively charged gold, or electron transfer from PZT to Au, although the ‘normal’ PZT phase have a higher work function, as it is derived from the band bending. Most probably this charge transfer occurs toward Au nanoparticles, which have even higher ionization energies. High resolution transmission electron microscopy evidenced the formation of such isolated nanoparticles.

Keywords: Ferroelectrics; XPS; PZT; Band bending; Schottky diode; PFM; HRTEM

Fabrication and corrosion resistance of HVOF-sprayed Ni₂Si intermetallic compound by M.M. Verdian; K. Raeissi; M. Salehi (pp. 426-431).

► Ni₂Si intermetallic coatings were produced by HVOF spraying. ► A bulk Ni₂Si was used as a reference for corrosion tests in 70% H₂SO₄. ► Corrosion rate of HVOF coatings was much lower than that of substrate. ► Both HVOF Ni₂Si and bulk Ni₂Si showed active–passive behavior. ► There was a small performance gap between coating and reference material.In this study, Ni₂Si powders were deposited onto 420 stainless steel substrate using high velocity oxy-fuel (HVOF) process. The coatings were characterized by X-ray diffractometery, optical and scanning electron microscopy and microhardness measurements. Tafel polarization tests and electrochemical impedance spectroscopy (EIS) measurements were employed to study corrosion performance of the coatings in 70% H₂SO₄ media at room temperature. Here, a dense sintered Ni₂Si was used as reference material. The results showed the phase composition of HVOF coating is similar to that of feedstock powders. The corrosion rate of HVOF Ni₂Si coatings was much lower than that of 420 stainless steel substrate but slightly higher than that of bulk Ni₂Si. Further investigation showed that both thermally sprayed and sintered (reference) Ni₂Si alloys exhibited similar anodic polarization behavior including a narrow active section followed by a wide passive region.

Keywords: Protective coatings; Intermetallic; HVOF; Corrosion; Electrochemical impedance spectroscopy; Ni; ₂; Si

A surface-conducted field emission device with suspended graphene cathodes by Chaoxing Wu; Fushan Li; Yongai Zhang; Tailiang Guo (pp. 432-436).

► A surface-conducted field emission device based on graphene cathode is fabricated. ► The Graphene cathode is suspended on tetrapod-like zinc oxide (T-ZnO) nanostructure. ► High electric field can be achieved at the graphene edges. ► High emission efficiency can be achieved by coating MgO film on T-ZnO nanostructure.A surface-conducted field emission device using suspended graphene film as field emitter is fabricated, where the tetrapod-like zinc oxide (T-ZnO) nanostructure is used as surface conducting emitter and supporting structure for the suspended graphene film. The suspended graphene film locates parallely to the gate electric field, leading to high local electric field at the graphene edges. High emission efficiency (30%) is obtained at low operation bias (<150V) by depositing magnesium oxide film on the surface of T-ZnOs nanostructure.

Keywords: Graphene; Surface-conducted; Field emission device; T-ZnOs; MgO

Electronic structure and optical band gap of silver photo-diffused Ge₂Sb₂Te₅ thin film by S. Kumar; D. Singh; R. Thangaraj (pp. 437-443).

► Amorphous chalcogenides were investigated in this work. ► Carried out photo-doping of Ag into Ge-Sb-Te films by illuminating thermally evaporated GST:Ag bilayer. ► Photo-induced silver diffusion effects were investigated in the created thin films. ► Increase in the optical band gap on silver photo-diffusion is due to decrease in the density of defect states.Thin films of amorphous chalcogenide with composition of Ge₂₂Sb₂₂Te₅₆ (thickness d=250nm) and silver film (thickness d=50nm) on top of chalcogenide film were deposited by thermal evaporation technique. Photo-diffusion of Ag into the amorphous Ge₂Sb₂Te₅ thin films has been carried out by illuminating the prepared Ge-Sb-Te:Ag bilayer with halogen lamp. The photo-diffused silver depth profile was traced by means of Time of Flight Secondary Ion Mass Spectroscopy. The films remain amorphous after Ag photo-diffusion into the amorphous Ge₂Sb₂Te₅ films. The composition of Ge₂Sb₂Te₅ thin films and the amount of Ag photo-diffused has been gathered from Electron Probe Micro-analyzer having a Wavelength Dispersive Spectrometer. The composition of the films was found to be very close to the bulk used to deposit films and the amount of Ag photo-diffused was ∼5.20at.%. Changes in the electronic structures of Ge₂Sb₂Te₅ film on Ag photo-diffusion were studied using X-ray photoelectron spectroscopy. The incorporation of silver also increases the optical band gap of the film due to the decrease in the density of defect states on Ag photo-diffusion.

Keywords: Chalcogenides; Interfaces; Diffusion; Photoelectron spectroscopy

Superhydrophilic properties of plasma-treated Posidonia oceanica by Hernando S. Salapare III; Ma. Gregoria Joanne P. Tiquio; Henry J. Ramos (pp. 444-447).

► Plasma treatment of Posidonia oceanica resulted to stable superhydrophilic surfaces. ► O₂ plasma treatment showed greater sample weight loss than Ar plasma treatment. ► Surface roughness effects vary for the O₂ and Ar plasma treatment. ► Increase in the surface roughness leads to the decrease in the water contact angle. ► CH₂ and C–H groups were absent from the FT-IR of the superhydrophilic samples. Posidonia oceanica samples were exposed to argon and oxygen plasma at varying plasma energies. The untreated and treated samples were characterized to study the weight loss, wettability, surface roughness, and surface chemical functionalities. It was observed that oxygen plasma treatment showed greater weight loss than the argon plasma treatment. Superhydrophilic surfaces ( θ<5°) were achieved at 180kJ argon-plasma treatment and 6kJ and18kJ oxygen-plasma treatments. The surface roughness increases as the plasma energies were increased for the argon-plasma treatment; however, opposite trend was seen for the oxygen-plasma treatment. The –CH₂ groups and the aliphatic C–H groups were absent from the FT-IR spectra of the superhydrophilic samples.

Keywords: Superhydrophilic surface; Plasma; Surface modification; Posidonia oceanica

Equilibrium and kinetic studies of C.I. Basic Blue 41 adsorption onto N, F-codoped flower-like TiO₂ microspheres by Yinhua Jiang; Yingying Luo; Fumei Zhang; Leiqun Guo; Liang Ni (pp. 448-456).

. N, F-codoped flower-like TiO₂ microsphere, a novel three-dimensional porous material with large adsorption capacity, was first synthesized as a new high efficiency adsorbent for dye removal.Display Omitted► A novel 3D N, F-codoped flower-like TiO₂ structure was successfully synthesized. ► The as-prepared samples showed high absorption capacities for dye CB41. ► The adsorption of CB41 onto NFT-1 fitted well with Langmuir model. ► The pseudo-second order kinetic model described well for CB41absorption onto NFT-1. ► The adsorption process was feasibility, spontaneous and endothermic in nature.Three-dimensional (3D) N, F-codoped flower-like TiO₂ microspheres were successfully synthesized by a hydrothermal method combined with calcination process. The as-prepared samples were characterized by XRD, FE-SEM and EDS. The adsorption abilities of prepared samples were investigated for the removal of C.I. Basic Blue 41(CB41) from aqueous solution. The FE-SEM and adsorption results showed that doping amount of NH₄F affected the morphologies of samples and sample NFT-1 with the structure of 3D flower-like microsphere had the highest adsorption amount of CB41. The effects of varying parameters such as pH, contact time, initial dye concentration and temperature on the CB41 adsorption onto NFT-1 were further examined. Equilibrium data correlated with Langmuir, Freundlich and Temkin isotherms. The Langmuir isotherm showed the best fit to the equilibrium data. The kinetic experimental data were analyzed by three kinetic models including the pseudo-first-order model, the pseudo-second-order model and the intraparticle diffusion model to access the adsorption mechanism and the potential rate-controlling step. The pseudo-second-order kinetic model described best for the adsorption of CB41 on NFT-1 and the intraparticle diffusion was not the only rate-controlling step. The thermodynamics parameters as positive values of Δ H° and negative values of Δ G° showed that the adsorption process was endothermic and spontaneous in nature.

Keywords: N, F-codoped; Flower-like TiO; ₂; microspheres; Adsorption; Isotherm; Kinetic

Effect of annealing temperature on the microstructural, optical and electrical properties of CeO₂ nanoparticles by chemical precipitation method by R. Suresh; V. Ponnuswamy; R. Mariappan (pp. 457-464).

Display Omitted► Cerium oxide nanoparticles prepared by chemical precipitation method. ► This method is widely adopted in laboratories because of its low preparation cost. ► The activation energy is found to be 1.004eV from XRD studies.Highly uniform and well-dispersed cerium oxide nanoparticles are successfully synthesized by simple precipitation method using cerium nitrate and ammonia. Effect of annealing temperature on the crystallite growth of cerium oxide nanoparticles is investigated by PL, XRD, FTIR, SEM, TEM, XPS, TG–DTA and I– V studies. Cubic fluorite crystallites are detected by X-ray diffraction pattern with preferred orientation along (111) direction. Annealing temperature affects the crysrallinity and structural parameters like grain size, texture coefficient, and dislocation density. The activation energy of cerium oxide (CeO₂) nanoparticles during annealing is found to be 1.004eV. PL spectra revealed that strong and broad emission band is observed at 425nm due to the presence of blue shift in the visible region. Large agglomerated spheroid crystallites are obtained with the typical size in the range 4–12nm. XPS spectrum confirms the existence of Ce⁴⁺ oxidation states in Cerium oxide nanoparticles. The activation energy is calculated as 0.984eV.

Keywords: Cerium oxide; Optical; Structural; Electrical properties

Investigation of performance degradation in metallized film capacitors by M. Godec; Dj. Mandrino; M. Gaberšček (pp. 465-471).

► Capacitors that perform differently differ in surface morphologies of metalized foils. ► Hexagonal ZnO monocrystallites were discovered on the surfaces of the poorly performing capacitors. ► AES was used to distinguish oxide/metallic state of Zn and Al. ► On the surface, Zn corresponds to ZnO, deeper, to metallic Zn; Al corresponds to oxidized Al throughout. ► Corrosion resistivity in air is increased by increasing Al concentration up to 5wt.%.Zn–Al metallized film capacitors in two different production stages were investigated to explain the decrease of capacitors performance with time. Unsealed and sealed capacitors with different aluminium content in metallization layer were investigated. Scanning electron microscopy (SEM) was used to image the surface of the metallization layers, energy dispersive X-ray spectroscopy (EDS) was used to determine the chemical composition and Auger electron spectroscopy (AES) was used to determine the chemical composition of the top of the metallization layers as well as to estimate the degree of oxidation. It was found that air humidity degraded the metallization layer of unsealed capacitors, especially at lower Al contents. Sealed capacitors were exposed to high electric fields, typical for standard usage. It was found – rather unexpectedly – that the performance was decreased by increasing Al content. A crystallographic explanation was proposed.

Keywords: Al; Zn; Metallized foil capacitor; Oxidation; AES

Ethylene oxide- block-butylene oxide copolymer uptake by silicone hydrogel contact lens materials by Yuchen Huo; Howard Ketelson; Scott S. Perry (pp. 472-477).

► Silicone hydrogel materials were examined following copolymer solution treatments. ► Both surface adsorption and bulk absorption of the copolymer was observed. ► The extent of adsorption and absorption differed greatly between hydrogels. ► Molecular concentration gradient of the copolymer was apparent in all hydrogels. ► The results indicated that the copolymer interaction was material-dependent.Four major types of silicone hydrogel contact lens material have been investigated following treatments in aqueous solutions containing poly(ethylene oxide) and poly(butylenes oxide) block copolymer (EO–BO). The extent of lens surface modification by EO–BO and the degree of bulk uptake were studied using X-ray photoelectron spectroscopy (XPS) and ultra-performance liquid chromatography (UPLC), respectively. The experimental results suggest that different interaction models exist for the lenses, highlighting the influence of both surface and bulk composition, which greatly differs between the lenses examined. Specifically, lenses with hydrophilic surface treatments, i.e., PureVision^® (balafilcon A) and O₂OPTIX (lotrafilcon B), demonstrated strong evidence of preferential surface adsorption within the near-surface region. In comparison, surface adsorption on ACUVUE^® Oasys^® (senofilcon A) and Biofinity^® (comfilcon A) was limited. As for bulk absorption, the amount of EO–BO uptake was the greatest for balafilcon A and comfilcon A, and least for lotrafilcon B. These findings confirm the presence of molecular concentration gradients within the silicone hydrogel lenses following exposure to EO–BO solutions, with the nature of such concentration gradients found to be lens-specific. Together, the results suggest opportunities for compositional modifications of lenses for improved performance via solution treatments containing surface-active agents.

Keywords: Silicone hydrogel; XPS; UPLC; Contact lens; Diblock copolymer solution; Amphiphilic surfactant

Ultrasonically sprayed ZnO:Co thin films: Growth and characterization by Barbaros Demirselcuk; Vildan Bilgin (pp. 478-483).

► The effect of Co doping on the physical properties of the ZnO films was reported. ► The XRD results indicated that all the films were polycrystalline. ► The optical results confirm the Co²⁺ ion substitution for Zn²⁺ ion in ZnO lattice. ► The Co doping decreased the electrical conductivity of the undoped ZnO films. ► AFM measurements were performed to obtain the surface roughness for the films.In this work, undoped and cobalt-doped ZnO thin films were deposited at 275±5°C on glass substrates by the ultrasonic spray pyrolysis technique. The structural, electrical, optical and surface characterization of the films as a function of the cobalt concentration in the spraying solution were studied by means of x-ray diffractometer, current–voltage characteristics, UV–vis spectrophotometer and atomic force microscope, respectively. X-ray diffraction reveals that the films are polycrystalline in nature with preferred orientations of (002) for the ZnO:Co (0, 2, 4at.%) and (100) for the ZnO:Co (6at.%). The optical transmittance of all films was studied as a function of wavelength in the range of 300–1100nm. They exhibit high transparency in the visible wavelength region with some interference fringes and sharp ultraviolet absorption edges. The optical band gap and Urbach energy values of the films were found in the range of 3.250–3.301eV and 90–230meV, respectively. The electrical studies for all films were carried out by using conductivity-temperature measurements and it was seen that the electrical conductivity of ZnO films decreases slightly depending on the increasing of Co doping. Also, Co doping increases both energies of donor-like traps and activation energy for ZnO films. The surface morphology was analyzed by atomic force microscope and a strong dependence on the cobalt incorporation was found.

Keywords: Zinc oxide; Co doped zinc oxide; Optical properties; Electrical conductivity; XRD; AFM

Graphene–nickel composites by Da Kuang; Liye Xu; Lei Liu; Wenbin Hu; Yating Wu (pp. 484-490).

► Graphene/nickel composites were produced through electrodeposition. ► Graphene influenced the preferred orientation of Ni growth in the composites. ► A significant improvement in the thermal conductivity of the composites was found. ► Hardness value of the composites was almost 4-fold higher than that of pure Ni.Graphene/nickel composites were prepared by electrodeposition in a nickel sulfamate solution with graphene oxide (GO) sheets in suspension. Raman spectra demonstrated that the GO sheets had been reduced during the electrodeposition process and the graphene content was 0.12wt%. X-ray diffraction patterns showed the preferred orientation of nickel growth changing from (200) to (111) in the composites. Transmission and scanning electron microscopy images were used to help explain how the introduction of graphene substrates leads to the change of preferred orientation. Measurements showed the thermal conductivity of the composites to be about 15% more than that of pure nickel electrodeposits. Significant improvement was also demonstrated in the hardness measured by nanoindentation.

Keywords: Graphene/Ni composites; Thermal properties; Microstructure; Electrodeposition; Nanomechanical properties

Room-temperature preparation and properties of cadmium sulfide thin films by ion-beam sputtering deposition by Guang-Xing Liang; Ping Fan; Zhuang-Hao Zheng; Jing-Ting Luo; Dong-Ping Zhang; Chao-Ming Chen; Peng-Ju Cao (pp. 491-495).

► CdS thin film is prepared by a dry and in situ preparation by ion-beam sputtering at room temperature. ► A mixed cubic and hexagonal wurtzite structure and a smooth surface morphology. ► High absorption in the visible spectrum and of n-type conductivity. ► After annealed at 100°C, optimized properties can be found.Deposition of cadmium sulfide (CdS) thin film on BK7 glass substrates has been prepared by a dry and in situ fabrication process with ion-beam sputtering deposition at room temperature. The structural, optical and electrical properties of CdS thin film were investigated. X-ray diffraction (XRD) analysis indicates the formation of polycrystalline CdS film with the mixed structure of cubic and hexagonal wurtzite phase. The Raman peaks are observed at 304cm⁻¹ and 606cm⁻¹, and these peaks are identified as the first and second order LO optical phonons form of the CdS film. Energy dispersive X-ray Spectrometer (EDS) shows no other impurity elements, except Cd and S. The as-deposited film exhibits good transfer of the sintered target material with almost the same Cd/S ratio. Scan electron microscopy (SEM) and atomic force microscopy (AFM) reveal that the CdS thin film has a smooth surface and exhibited an obvious columnar growth indicating the c-axis preferred orientation. The detected room-mean-square (RMS) roughness by AFM is 0.76nm. Optical transmission and absorption spectroscopy measurement reveal high absorption and energy band gap is of about 2.32eV. The CdS thin film is of n-type conductivity and the resistivity is found to be in the order of 10⁴Ωcm. The CdS films annealed at 100°C were demonstrated to be improvement in structural, electrical and optical properties.

Keywords: CdS thin film; Ion-beam sputtering deposition; Microstructure; Optical and electrical properties

Role of the Si–Si bond stability in the first stages of Ti diffusion on a Si(111) 2×1 surface. A periodic DFT study by Rafael Añez; Anibal Sierraalta; Miguel A. San-Miguel; Javier Fdez. Sanz (pp. 496-501).

► Ti adsorption on a bare Si(111) surface. ► Ti forms polar covalent bonds with Si atoms on the surface. ► At low temperature, a stable TiSi monolayer is formed by Ti deposition on the Si(111) surface. ► Remaining Si–Si bonds in the TiSi interface play an important role for the Ti diffusion on the Si(111) surface.A periodic Density Functional Theory (DFT) study, using Generalized Gradient Approximation (GGA), of the Ti deposition on a clean 2×1 reconstructed Si (111) surface was carried out. Results indicate that as in the case of the Si(001) surface, a TiSi monolayer is formed at 6.8×10¹⁴Tiatomcm⁻² which shows its high reactivity in presence of Ti even at RT. However, the TiSi interface on the Si(111) presents Ti–Ti and Si–Si interactions forming atom rows in a zigzag arrangement. Ti deposition on the TiSi interface suggests that remaining Si–Si bonds on the surface could play a very important role in the Ti diffusion on the Si surface.

Keywords: Ti deposition; TiSi interface; Si(1; 1; 1); Si(0; 0; 1); DFT calculations

The effects of low power density CO₂ laser irradiation on graphene properties by Ting Huang; Jiangyou Long; Minlin Zhong; Juan Jiang; Xiaohui Ye; Zhe Lin; Lin Li (pp. 502-506).

► Graphene structure was modified in a controlled manner by CO₂laser irradiation. ► Thermal effect played an important role in CO₂ laser irradiation on graphene. ► CO₂ laser may enable high-efficiency and economical modification of graphene.We report the investigations on structural modifications in monolayer graphene induced by low-power-density CO₂ laser irradiation (2–60W/cm²). Observed modifications in graphene include the disassembly of crystalline graphene into nanocrystalline structure and the generation of amorphous carbon. It was found that thermal effect played an important role during laser irradiation. By adjusting laser power density, irradiation time and temperature, the structure of graphene can be modified accordingly in a controlled manner. Our approach may enable high-efficiency and economical modification of large-area graphene, which relies on large-area irradiation using low-power-density laser.

Keywords: Graphene; Laser irradiation; Thermal annealing; Raman spectrum; XPS

Comparison between FTIR and XPS characterization of amino acid glycine adsorption onto diamond-like carbon (DLC) and silicon doped DLC by Mukhtar H. Ahmed; John A. Byrne; J.A.D. McLaughlin; Abdelbary Elhissi; Waqar Ahmed (pp. 507-514).

► Diamond-like carbon (DLC) synthesized and characterized, DLC surface modified with silicon (Si-DLC). ► Adsorption study using amino acid glycine. ► Investigation of glycine configuration using spectroscopic ellipsometry, FTIR and X-ray photoelectron spectroscopes (XPS). ► Mechanism of adsorption investigated change due to esterification of carboxyl species. ► Small amount of silicon content DLC enhance the glycine adsorption.Diamond-like carbon (DLC) coatings are extremely useful for creating biocompatible surfaces on medical implants. DLC and silicon doped DLC synthesized on silicon wafer substrate by using plasma enhanced chemical vapour deposition (PECVD). The adsorption of glycine onto prepared samples has been investigated with a range of surface analysis techniques. The effects of surface morphology on the interaction of glycine with doped and undoped DLC films have been investigated. The chemical composition of the surface before and after adsorption was analyzed using X-ray photoelectron spectroscopy (XPS). For undoped DLC the spectra show peaks at 285eV (C 1s), 532eV (O 1s) and in the case of Si-doped DLC films a band at ∼100eV (Si 2p) is observed. Following exposure to solutions containing (0.001M) glycine, for undoped DLC the peaks at ∼285.0, ∼399 and ∼532eV reduced in intensity and for Si-DLC samples, the peak at 100eV was reduced. This gives an indication of the quantitative change in the amounts of C, N and O on the surfaces. From Fourier transform infrared (FTIR) spectrum, the peaks occur the following functional groups were assigned as COOR, COŌ,NH₃⁺, NH₂, CH and CCN. Both XPS and FTIR spectroscopy confirm that glycine was bound onto the surfaces of the DLC and Si-DLC films via interaction of ionized carboxyl groups and the amino group did not play a significant role in the adsorption of glycine. These results from SE show that an adsorbed layer of glycine is higher at low silicon doping whilst increased doping levels led to a reduced adsorption compared to undoped DLC. Therefore doping of DLC may provide an approach to controlling the protein adsorption.

Keywords: Silicon doped diamond-like carbon Si-DLC; FTIR; XPS; Spectroscopic ellipsometry; Glycine adsorption

Catalyst-assisted vertical growth of carbon nanotubes on Inconel coated commercial copper foil substrates versus sputtered copper films by Gowtam Atthipalli; Hao Wang; Jennifer L. Gray (pp. 515-519).

► Growth comparison of multi-walled carbon nanotubes on Cu foils and sputtered Cu films ► The substrate surface plays a vital role in the catalyst distribution, CNT density, and graphitic crystallinity ► Grain size of Cu substrate, surface asperities affect CNT density and alignment ► Quantitative analysis of the density and alignment of CNTs shows that the smooth, sputtered Cu is better than rough Cu foil.We have compared the growth of multi-walled carbon nanotubes using thermal chemical vapor deposition (CVD) on two types of substrates, copper foils and sputtered copper films. In both cases an initial 12nm thin film of Inconel is first deposited on the Cu before growing the nanotubes. The Inconel thin film can act as both a catalyst for nanotube growth as well as a support for the additional Fe catalyst that is supplied in the form of ferrocene during CVD growth. The surfaces of the underlying copper substrates are very different and play a role in the resulting carbon nanotube density. A quantitative analysis of the density and alignment of the resulting carbon nanotubes using scanning electron microscopy shows that the smooth surface of the sputtered copper substrate leads to improvement in vertical growth and density of nanotubes as opposed to the much rougher electropolished Cu foil. We show that this is related to the differences in catalyst islands distributions and graphitic crystallinity seen on the surfaces of the two types of substrates after heating the samples in the CVD chamber. This demonstrates that the surface of the starting substrate plays an important role in the subsequent catalyst surface distribution and therefore the resulting nanotube density.

Keywords: Carbon nanotubes; Sputtering (PVD); Chemical vapor deposition (CVD); Scanning electron microscopy (SEM); Raman microscopy

Grain and grain boundary characters in surface layer of untreated and plasma nitrocarburized 18Ni maraging steel with nanocrystalline structure by M.F. Yan; Y.Q. Wu; R.L. Liu (pp. 520-526).

► Sizes of γ′-Fe₄N and α-Fe grains in the surface layer of the steel are nanoscale. ► Number fractions of CSL and low angle boundaries for α-Fe grains reduce. ► γ′-Fe₄N grain boundaries are made up of high angle, low angle and CSL boundaries.The nanocrystallized 18Ni maraging steel was plasma nitrocarburized at 460°C for 4h in a mixture gas of N₂, H₂ and C₂H₅OH. The surface phase compositions of the specimens were analyzed using X-ray diffractometer. The grain shape and size, and grain boundaries in the subsurface layers of the samples were characterized by electron backscattering diffraction and transmission electron microscopy. The results show that the nitrocarburized layers are composed of α-Fe, γ′-Fe₄N and FeN_0.049 phases. Most α-Fe and γ′-Fe₄N grains show in columnar shape. The major and minor axes of some α-Fe grains are elongated and shortened after nitrocarburizing, respectively. In the subsurface layers of the untreated and nitrocarburized specimens, the average areas of γ′-Fe₄N and α-Fe grains both with a dimension of nanometer are 0.395μm² and 0.397μm², respectively. The γ′-Fe₄N grain boundaries are mainly high angle boundaries with a very small fraction of low angle boundaries. Coincidence site lattice boundaries in the subsurface layer of the untreated specimen are composed mainly of Σ3, Σ11 and Σ13b, and their fraction decreases after nitrocarburizing.

Keywords: Nanocrystalline; Plasma nitrocarburizing; Electron backscattering diffraction; Grain boundary

Study of Pt–Rh/CeO₂–ZrO₂–M_xO_y (M=Y, La)/Al₂O₃ three-way catalysts by Guo Jiaxiu; Shi Zhonghua; Wu Dongdong; Yin Huaqiang; Gong Maochu; Chen Yaoqiang (pp. 527-535).

Display Omitted► CeO₂–ZrO₂–M_xO_y oxides have a face-centered cubic fluorite structure and are nanosize. ► Fresh and aged CZYL has 105 and 60m²/g surface area and 460 and 390μmol/g OSC. ► T₅₀ of fresh Pt–Rh/CZYL/LA is 170°C for CO, 222°C for C₃H₈ and 189°C for NO. ► WGS and SR are relate to the OSC and oxygen mobility of oxygen storage materials. ► Reducibility of noble metals and dissociatively adsorbed O₂ are related to activity.CeO₂–ZrO₂–M_xO_y (M=Y; La) mixed oxides, prepared by co-precipitation method and characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Raman spectra (RM) and oxygen pulse reaction, were comparatively investigated to elucidate the combinational effects of Y and/or La oxide promoters on the catalytic activity and anti-aging performance of monolithic cordierite honeycomb catalysts with low Pt and Rh content. The catalytic activities, water-gas shift (WGS) and steam reforming reaction (SR) were studied under a simulated gas mixture. The catalysts were also characterized by H₂-temperature-programmed reduction (H₂-TPR) and O₂-temperature-programmed desorption (O₂-TPD). The results showed that the prepared CeO₂–ZrO₂–M_xO_y oxides have a face-centered cubic fluorite structure and are nanosize. La³⁺ ions can significantly improve thermal stability and efficiently retard CeO₂–ZrO₂ crystal sintering and growth. Doped CeO₂–ZrO₂ with Y³⁺ and La³⁺ has 105 and 60m²/g surface area and 460 and 390μmol/g OSC before and after aging. The T₅₀ of fresh Pt–Rh/CZYL/LA is 170°C for CO, 222°C for C₃H₈ and 189°C for NO, and shift to 205, 262 and 228°C after hydrothermal aging, which are better than those of Pt–Rh/CZY/LA or Pt–Rh/CZL/LA. WGS and SR are relate to the OSC of oxygen storage materials and absorbed oxygen species on the catalyst surface and affect the three-way catalytic activities of catalysts. The reductive property of noble metals and the dissociatively adsorbed O₂ on the surface of catalysts are closely related to the catalytic activities.

Keywords: Three-way catalysts; Water-gas shift; Steam reforming; Ceria–zirconia

Influence of roughness on surface instability of medical grade cobalt–chromium alloy (CoCrMo) during contact corrosion–fatigue by Jae Joong Ryu; Pranav Shrotriya (pp. 536-541).

► We investigated influence of residual stress of implant surface on environmental corrosion. ► Localized stress developed during contact fatigue accelerates preferential corrosion pit at surface troughs. ► A new method was suggested to evaluate thermodynamic driving forces of implant surface. ► We developed predictive model of roughness evolution by contact corrosion–fatigue.Surface roughness and contact load play a major role in contact corrosion–fatigue phenomena that accelerates corrosion pits on the stressed surface area. The local yielding and stress concentration will be produced when the rough surface is brought into cyclic contact. Subsequently, the selective electrochemical attacks on the stressed surface will lead to the roughness evolution during environmental corrosion. The continuous roughness evolution by the stress-assisted dissolution will ultimately nucleate microcracks on the surface. In this article, a new evaluation method was introduced to identify the thermodynamic driving forces responsible for the stress-assisted dissolution. In order for complete understanding of the mechanical and electrochemical response of materials surface during contact corrosion–fatigue, finite element calculations and contact corrosion–fatigue experiments were performed on textured medical grade cobalt–chromium–molybdenum (CoCrMo) specimen surfaces. Consequently, the quantitative model of roughness evolution was developed to predict contact corrosion–fatigue damage of CoCrMo surface.

Keywords: Surface roughness; Contact corrosion–fatigue; Stress-assisted dissolution; Bio-implant

Selective sensing of copper and mercury ions with pyrene-functionalized fluorescent film sensor containing a hydrophilic spacer by Yuan Cao; Liping Ding; Wenting Hu; Lin Wang; Yu Fang (pp. 542-548).

Display Omitted► A pyrene-functionalized fluorescent SAM film sensor was prepared and characterized. ► The film sensor exhibits high selectivity and sensitivity toward Cu(II) and Hg(II) ions in the form of inorganic salts in aqueous solution. ► The functional subunits and polarity of the spacer play an important role in adjusting the sensing properties of fluorescent SAM sensors. ► To our knowledge, this is the first fluorescent SAM sensor for Hg(II) ion.A fluorescent film sensor for Cu(II) and Hg(II) ions was designed and prepared by chemical attaching pyrene moieties on an epoxy-terminated surface via a long flexible and hydrophilic spacer. The chemical attachment of pyrene moieties on the surface was verified by contact angle, XPS, and fluorescence characterization. The fluorescence responses of the present film to a series of metal ions in aqueous solution indicate that this film sensor is sensitive to both copper and mercury ions. Presence of other metal ions, including Ni(II), Fe(III), Pb(II), Mg(II), Ba(II), Zn(II), La(II) and Eu(II), has little effect upon the fluorescence emission of the film. The sensitivity of the present film sensor is quite high toward both Cu(II) and Hg(II) ions in the form of inorganic salts as revealed by the large K_SV values. Moreover, the presence of organic anions produces little influence on the sensitivity of the film sensor toward metal ions, suggesting the introduction of the hydrophilic spacer weakens the spacer layer screening effect in aqueous solution. The novel fluorescent film sensor may have potentials as Cu(II) and Hg(II) sensors to probe natural environments.

Keywords: Fluorescence; Sensor; Film; Self-assembled monolayer; Metal ions

Towards understanding hydrophobic recovery of plasma treated polymers: Storing in high polarity liquids suppresses hydrophobic recovery by Edward Bormashenko; Gilad Chaniel; Roman Grynyov (pp. 549-553).

Polar molecules of liquid suppress hydrophobic recovery of a polymer substrate.Display Omitted► Hydrophobic recovery of air plasma treated polyethylene films was studied. ► Plasma treated polymer films were immersed into liquids with various polarities. ► Immersion into high polarity liquids slowed markedly the hydrophobic recovery. ► Hydrophobic recovery is governed by the dipole–dipole interaction of molecules of polymer and liquid. ► Cooling renders restoring of hydrophobicity of plasma irradiated films.The phenomenon of hydrophobic recovery was studied for cold air plasma treated polyethylene films. Plasma-treated polymer films were immersed into liquids with very different polarities such as ethanol, acetone, carbon tetrachloride, benzene and carbon disulphide. Hydrophobic recovery was studied by measurement of contact angles. Immersion into high polarity liquids slows markedly the hydrophobic recovery. We relate this slowing to dipole–dipole interaction of polar groups of the polymer with those of the liquids. This kind of interaction becomes decisive when polar groups of polymer chains are at least partially spatially fixed.

Keywords: Cold plasma; Polyethylene; Wetting; Hydrophobic recovery; Polar liquids; Dipole–dipole interaction

Properties of ultrathin Pb layers on the Ni₃Al(111) face by K. Miśków; A. Krupski (pp. 554-561).

► 2-DIM growth of the first Pb monolayer takes place for 200K≤ T≤650K. ► For RT, flat three atomic-layer-high islands seem to grow. ► The ordered LEED patterns are observed. ► Lead atoms and Ni₃Al(111) face form a Pb–Ni₃Al(111) surface alloy. ► The stacking fault is formed in the Ni₃Al(111)–Pb interface region.The atomic structure and morphology of ultrathin Pb layers deposited on the Ni₃Al(111) face in ultrahigh vacuum at the substrate temperature, ranging from 200K to 950K, were investigated with the use of Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and directional elastic peak electron spectroscopy (DEPES). The analysis of AES measurements indicates that two-dimensional growth of the first Pb monolayer ‘wetting layer’ takes place for substrate temperature 200K≤ T≤650K. For T=200K, lead on the Ni₃Al(111) grows layer-by-layer, while for T=300K flat three atomic-layer-high islands seem to grow after the completion of the first lead monolayer. Above 350K, the Stranski–Krastanov growth mode is observed. The ordered LEED patterns corresponding to p(4×4) and p(√3×√3)R30° structures are observed. AES and LEED data indicate that lead atoms and the Ni₃Al(111) face form a Pb-Ni₃Al(111) surface alloy. The DEPES results show that the stacking fault abcabcBACBAC or abcabcACBACB is formed in the Ni₃Al(111)–Pb interface region.

Keywords: Lead; Nickel; Aluminium; Alumina; Crystal growth; Metal–metal interfaces; Electron–solid interactions; Scattering; Diffraction; Low index single crystal surface; Crystalline structure; Auger electron spectroscopy (AES); Low-energy electron diffraction (LEED); Directional elastic peak electron spectroscopy (DEPES)

Functionalization of PDMS modified and plasma activated two-component polyurethane coatings by surface attachment of enzymes by Alexej Kreider; Katharina Richter; Stephan Sell; Mandus Fenske; Christian Tornow; Volkmar Stenzel; Ingo Grunwald (pp. 562-569).

Display Omitted► The described technique allows the biofunctionalization of a two-component polyurethane (2C-PUR) coating. ► Creation of functional groups on the surface by migrating PDMS and plasma treatment. ► 2C-PUR systems with PDMS displayed a higher stability over a time period of at least 28h. ► Chemical immobilization (chemisorption) of the enzyme to the surface showed statistically significant higher biological activity.This article describes a new strategy for coupling the enzyme horseradish peroxidase to a two-component polyurethane (2C-PUR) coating. A stable polymer conjugate was achieved by combining the enzyme and the 2C-PUR coating which was modified with poly(dimethylsiloxane) (PDMS), located at the surface. An atmospheric pressure plasma jet system was used to convert alkyl groups from the PDMS into polar silanol functionalities. This conversion was proven by X-ray photoelectron spectroscopy and dynamic contact angle measurements. In addition, the stability of the activated 2C-PUR surface containing silanol groups was determined by measuring the contact angle as a function of time. Compared to the non-modified 2C-PUR systems the one with PDMS displayed a higher stability over a time period over 28h. In a silanization process the coating was treated with (3-aminopropyl) trimethoxysilane and the enzyme was subsequently immobilized to the coating via the cross linker glutaraldehyde to receive new biomimetic catalytic/enzymatic functions. The chemical immobilization (chemisorption) of the enzyme to the surface showed statistically significant higher biological activity as compared to references samples without using a cross linker (physisorption). The presented technique offers the opportunity to design new and smart multifunctional surface coatings which employ biomimetic capabilities.

Keywords: Enzyme immobilization; PDMS; Two-component polyurethane (2C-PUR/2K-PUR); Plasma treatment; Biofunctionalization; Surface coating

Tribological and stability investigations of alkylphosphonic acids on alumina surface by M. Cichomski; K. Kośla; J. Grobelny; W. Kozłowski; W. Szmaja (pp. 570-577).

► Alumina surface modification by alkylphosphonic acids was investigated. ► The effectiveness of modification was monitored by the contact angle measurements. ► The modification procedure correctness was characterized by XPS, ToF-SIMS, FT-IR measurements. ► The tribological performance of modified alumina in mili Newton load range was studied. ► The stability of alkylphosphonic acids on alumina surface were monitored.Alumina substrates are commonly used for various micro-/nanoelectromechanical systems (MEMS/NEMS). For efficient and lifetime longevity of these devices, lubricant films of self-assembled monolayers (SAMs) with nanometer thickness are increasingly being employed. In the present paper, we report preparation, tribological and stability investigations of alkylphosphonic acids on the alumina surface.The alkylphosphonic acids were prepared on the alumina surface using the liquid phase deposition method. The effectiveness of modification of the alumina surface by alkylphosphonic acids was investigated using water contact angle measurements, secondary ion mass spectrometry, X-ray photoelectron and infrared spectroscopy.Frictional behavior in milinewton load range was studied by microtribometry. It is shown that surface modification of the alumina surface by alkylphosphonic acids reduces the coefficient of friction values compared to the unmodified alumina. In comparison to the non-modified alumina surface, all tested alkylphosphonic acids cause a decrease in the friction coefficients in friction tests for counterparts made from different materials, such as steel, zirconia and silicon nitride. It is also found that the alumina surface modified by alkylphosphonic acids with longer chain has a higher degree of hydrophobicity and lower coefficient of friction. The best frictional properties are obtained for the system consisting of the alumina surface modified by n-octadecylphosphonic acid and silicon nitride counterpart.Stability tests in different environmental conditions: laboratory, acidic and alkaline solutions were also monitored.

Keywords: Alkylphosphonic acids; Alumina surface; Tribology; X-ray photoelectron spectroscopy; Time of flight secondary ion mass spectrometry; Fourier transform infrared spectroscopy

Surface interactions, corrosion processes and lubricating performance of protic and aprotic ionic liquids with OFHC copper by Tulia Espinosa; José Sanes; Ana-Eva Jiménez; María-Dolores Bermúdez (pp. 578-597).

► Relationship between surface interaction, corrosion and lubrication performance. ► Use of new protic ammonium ionic liquids. ► Effect of the number of ammonium protons and of the anion composition.In order to select possible candidates for use as lubricants or as precursors of surface coatings, the corrosion and surface interactions of oxygen-free high conductivity (OFHC) copper with two new protic (PIL) and four aprotic (APIL) room-temperature ionic liquids have been studied. The PILs, with no heteroatoms in their composition, are the triprotic di[(2-hydroxyethyl)ammonium] succinate (MSu) and the diprotic di[bis-(2-hydroxyethyl)ammonium] adipate (DAd). The four APILs contain imidazolium cations with short or long alkyl chain substituents and reactive anions: 1-ethyl-3-methylimidazolium phosphonate ([EMIM]EtPO₃H); 1-ethyl-3-methylimidazolium octylsulfate ([EMIM]C₈H₁₇SO₄); 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM]BF₄) and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF₆). Contact angles between the ionic liquids and OFHC copper surface were measured. Mass and roughness changes of OFHC copper after 168h in contact with the ionic liquids have been determined. Copper surfaces were studied by XRD, SEM–EDX and XPS surface analysis. FTIR spectra of the liquid phases recovered after being in contact with the copper surface were compared with that of the neat ionic liquids. The lowest corrosion rate is observed for the diprotic ammonium adipate PIL (DAd), which gives low mass and surface roughness changes and forms adsorbed layers on copper, while the triprotic ammonium succinate salt (MSu) produces a severe corrosive attack by reaction with copper to form a blue crystalline solid, which has been characterized by FTIR and thermal analysis (TGA). All imidazolium APILs react with copper, with different results as a function of the anion. As expected, [EMIM]C₈H₁₇SO₄ reacts with copper to form the corresponding copper sulphate salt. [EMIM]EtPO₃H produces severe corrosion to form a phosphonate–copper soluble phase. [HMIM]BF₄ gives rise to the highest roughness increase of the copper surface. [HMIM]PF₆ shows the lowest mass and roughness changes of the four imidazolium ionic liquids due to the formation of a solid layer containing phosphorus and fluorine. The results described in the present study are in agreement with the outstanding good tribological performance of the diprotic ammonium adipate (DAd) ionic liquid for the copper–copper contact, in pin-on-disc tests, preventing wear and giving a very low friction coefficient of 0.01. Under the same conditions, [HMIM]PF₆ gives a friction value of 0.03, while the reactivity of MSu towards copper produces maximum friction peaks of 0.05. In contrast with the absence of surface damage on copper, an abrasive wear mechanism is observed for MSu and [HMIM]PF₆. The results confirm a better lubricating performance for a lower corrosion rate.

Keywords: Copper; Ionic liquids; Surface interactions; Corrosion; Lubrication

The inter-metallic oxide of ZnO/ITO/ZnO tri-layer films using a heat-induced diffusion mechanism by Kuan-Jen Chen; Fei-Yi Hung; Truan-Sheng Lui; Sheng-Po Chang; Wen-Lung Wang (pp. 598-602).

Display Omitted► The study presents the interface diffusion behavior based on ZnO/In/ZnO and ZnO/ITO/ZnO tri-layer films. ► The heat-induced thermal diffusion caused an intense inter-metallic oxide (IMO) in the interface and a doping layer. ► IMO and doping layer that enhanced the electrical conductivity. ► The formation of IMO and good contact behavior can also improve the film transmittance.This study presents a bias-crystallization mechanism (BCM) that is based on ZnO/In/ZnO tri-layer film and thermal annealing treatment on ZnO/ITO/ZnO tri-layer films. After biasing (40V, 0.025A), the resistivity of the ZnO/In/ZnO sample was reduced to 1.35×10⁻²Ωcm. Bias-induced Joule heat and indium ion diffusion were critical factors with regard to decreasing resistivity. When substituted for the metal indium layer, the ZnO/ITO (13nm)/ZnO thin film demonstrated comparatively better electrical properties and optical transmittance. During thermal annealing, the indium and tin atoms in the ITO structure diffused into the ZnO matrix and improved the conductivity of the tri-layer film. Inter-metallic oxide (IMO) was formed in the interface between the ZnO and the interlayer, and it dominated the crystallization characteristics as well as the optical and electrical properties of the tri-layer films.

Keywords: Bias-crystallization mechanism (BCM); Joule heat; Diffusion; Inter-metallic oxide (IMO)

Effect of the cathodic polarization on structural and morphological proprieties of FTO and ITO thin films by C.C. Plá Cid; E.R. Spada; M.L. Sartorelli (pp. 603-606).

► Transparent and conductive electrodes ITO and FTO used in association at electrochemical techniques. ► Structural and chemical stability needs to be evaluated in working conditions. ► XRD and SEM elucidate the nature of the changes in crystalline structure, morphology and chemical composition.This paper deals on the influence of the potentiodynamic stress on structural and morphological proprieties of fluorine-doped tin oxide (FTO, SnO₂:F) and indium tin oxide (ITO, In₂O₃:Sn) commercial substrates. The potential range is between 0.0 and −2.0 (V/SCE) using an electrolyte with neutral pH. The electrochemical behavior was investigated from cyclic voltammetry technique and chronopotentiometric curves. These electrochemical results were associated to the X-ray diffraction (XRD) spectra and morphology images acquired by scanning electron microscopy (SEM). The main results show that structural and morphological properties of FTO substrates after cathodic polarization remain near constant when compared with ITO films. The ITO substrates show morphological changes after treatment and the XRD patterns indicate the formation of a crystalline structure with In metallic characteristic, at neutral pH.

Keywords: Cathodic polarization; Transparent conducting oxide; X-ray diffraction; Scanning electron microscopy; Morphology

Sensitivity of photoelectron energy loss spectroscopy to surface reconstruction of microcrystalline diamond films by Denis G.F. David; Marie-Amandine Pinault-Thaury; Dominique Ballutaud; Christian Godet (pp. 607-612).

► Evaluation of PEELS sensitivity using diamond surface reconstruction. ► Energy loss analysis of diamond surface reconstruction without graphitization. ► Simulation of energy loss at 11 and 19eV by surface plasmon excitation in graphite.In X-ray Photoelectron Spectroscopy (XPS), binding energies and intensities of core level peaks are commonly used for chemical analysis of solid surfaces, after subtraction of a background signal. This background due to photoelectron energy losses to electronic excitations in the solid (surface and bulk plasmon excitation, inter band transitions) contains valuable information related to the near surface dielectric function ɛ( ħω). In this work, the sensitivity of Photoelectron Energy Loss Spectroscopy (PEELS) is investigated using a model system, namely the well-controlled surface reconstruction of diamond. Boron-doped microcrystalline thin films with a mixture of (111) and (100) preferential orientations were characterized in the as-grown state, with a partially hydrogenated surface, and after annealing at 1150°C in ultra high vacuum. After annealing, the bulk (σ+π) plasmon of diamond at 34.5eV is weakly attenuated but no evidence for surface graphitization is observed near 6eV, as confirmed by electronic properties. Unexpected features which appear at 10±1eV and 19±1eV in the energy loss distribution are well described by simulation of surface plasmon excitations in graphite-like materials; alternatively, they also coincide with experimental inter band transition losses in some graphene layers. This comparative study shows that the PEELS technique gives a clear signature of weak effects in the diamond surface reconstruction, even in the absence of graphitization. It confirms the sensitivity of PEELS acquisition with standard XPS equipment as a complementary tool for surface analysis.

Keywords: XPS; Electron energy loss; Plasmon; Diamond; Surface reconstruction

Cu₂ZnSnSe₄ thin films prepared by selenization of one-step electrochemically deposited Cu–Zn–Sn–Se precursors by Mingming Meng; Lei Wan; Peng Zou; Shiding Miao; Jinzhang Xu (pp. 613-616).

► Selenization one-step electrochemical deposition Cu–Zn–Sn–Se precursors to fabricate CZTSe thin films for the first time. ► Studied the effect of different rate of each element in electrolyte and the influence of pH. ► Prepared Cu₂ZnSnSe₄ that is pure and close to stoichiometric. ► Proved the structure of CZTSe is Kesterite-type.In this research a non-vacuum strategy was reported in facile preparation of kesterite-type Cu₂ZnSnSe₄ (CZTSe) thin films via selenization of one-step electrochemically prepared Cu–Zn–Sn–Se precursors. The Cu–Zn–Sn–Se precursor films were prepared by electrochemical deposition from electrolytes containing CuSO₄, ZnSO₄, SnCl₄ and H₂SeO₃, and the substrate is a Mo coated soda-lime glass. The CZTSe thin films were obtained by annealing the electrochemically deposited films in the selenium vapors at the temperature of 550°C. The crystal phases, micro-structures, chemical compositions and optical properties of CZTSe films have been studied by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma optical emission spectrometer (ICP-OES), Raman scattering spectrum, and UV–vis absorption spectroscopic means. The results revealed that the electrolytes with Cu:Zn:Sn:Se molar ratio of 3:70:20:3 yields nearly pure phase of kesterite, and a band gap of 0.94eV was determined by spectroscopic measurements.

Keywords: Cu; ₂; ZnSnSe; ₄; Electrodeposition; Thin films; Solar energy materials

A hybrid approach to determine critical and erosion velocities in the cold spray process by A. Moridi; S.M. Hassani-Gangaraj; M. Guagliano (pp. 617-624).

► Obtaining critical and erosion velocities in cold spray process. ► A new combined numerical-analytical model is proposed. ► The model considers porosity of the particles and adhesion phenomena. ► Equations for calculating critical/erosion velocity for Cu and SS316 are proposed. ► Equations are function of particle's porosity, temperature and diameter.Cold spray is a coating process in which bonding is obtained when the impact velocity of small particles exceeds a critical value called critical velocity (CV) but it is less than an upper limit beyond which erosion happens. The success of the cold spray process mainly depends on the correct choice of the process velocity which should be set to be between CV and erosion velocity (EV), that are influenced by many parameters. This justifies the interest of many researchers to define models for the CV assessments. In the present work, we propose a new model, combination of numerical and analytical solutions, to calculate not only the CV but also EV. Compared with previous works, porosity of particles and adherence phenomena between particle and the substrate have been taken into account as a novelty. Results of the proposed approach have been compared with experimental data and good agreement was found. Finally, based on the procedure results, a representative equation was established for calculating critical and erosion velocities as a function of particle porosity, diameter and temperature for Cu and stainless steel 316L particles.

Keywords: Cold spray; Critical velocity (CV); Erosion velocity (EV); Finite element model; Analytical solution; Porosity

Characterization of nanoscale clusters fabricated by pulsed laser irradiation of thin Au films by Yi Fang; Yanbing Hou; Feng Teng; Zhidong Lou; Aiwei Tang; Bo Zhang; Lingchuan Meng; Yu Ning; Longfeng Lu (pp. 625-631).

► Uniformly distributed Au NCs with mean diameter in the 10–25nm were fabricated. ► The evolution of Au structure was recorded in crossing of structural and optical characterization. ► Three processes for the evolution of Au film by laser irradiation have been proposed. ► The melt dynamics and temperature changes of Au film are quantitatively evaluated.The characterization of Au nanoclusters (AuNCs) on indium-tin-oxide (ITO) substrates fabricated by nanosecond pulsed laser irradiations of thin Au films is reported. By several hundreds of pulsed laser irradiations of 2.5×10⁷Wcm⁻² and 5×10⁷Wcm⁻² intensity in 1min, the nanoscale clusters are formed in an ultrafast melting, collecting, growing-up and solidification process of 5, 7.5 and 10nm Au films. The mean diameter and size distribution of nanoclusters are quantified by the statistical analysis on scanning electron microscopy (SEM) images. The melt dynamics and temperature changes of Au film under pulsed laser irradiation are obtained by quantitative evaluation. The extinction spectra of the initial Au films and formed Au nanoclusters on the ITO surface have also been measured. It has been found that the mean diameter, the surface density and extinction spectra of the induced AuNCs are influenced by the thickness of Au films and the laser intensity. The evolutional mechanism of the nanoscale clusters formation is discussed by the comparison on the morphology of the Au films with and without laser irradiations.

Keywords: Au nanoclusters; Pulsed laser irradiation; Extinction curve

FTIR-ATR spectroscopy in thin film studies: The importance of sampling depth and deposition substrate by G. Laroche; J. Fitremann; N. Gherardi (pp. 632-637).

► The substrate properties must be considered for the analysis of FTIR-ATR spectra. ► Band assignment depends strongly on the used FTIR measurement mode. ► FTIR-ATR spectroscopy is powerful for the study of thin film molecular organisation. ► Townsend DBD leads to more ordered SiO_xH_y layers than filamentary DBD.Fourier transform infrared (FTIR) spectroscopy in the attenuated total reflectance mode (ATR) was used to characterise SiO_xH_y thin films deposited on either polypropylene foil or silicon wafers through a cold atmospheric plasma discharge. Compared to a classical transmission spectrum with transverse (TO) vibrational modes, the FTIR-ATR spectra revealed modified and/or exhibited additional features caused by either the non-orthogonal angle of incidence of the infrared radiation with respect to the sample normal or the partial light reflection on the deposition substrate. On one hand, recording the infrared spectra with an angle of incidence other than 90° produced a longitudinal (perpendicular to the sample normal) component in the electric field of the incident light, which enabled the detection of longitudinal (LO) vibrational modes. On the other hand, the transverse vibrational modes of thin films deposited on silicon were slightly extinguished with a concomitant increase of the spectral intensity of the LO features, due to both the partial withdrawing between the incident and reflected electric fields of the infrared light lying in the sample plane and, the addition of those perpendicular to this sample plane. These data thus clearly show the enormous potential of FTIR-ATR to characterise thin film molecular order, provided that a prior comprehensive analysis is performed on the sampling depth and the light reflection on the deposition substrate.

Keywords: Fourier transform infrared spectroscopy; Molecular order; Longitudinal optical vibrational mode; Transverse optical vibrational mode; LO/TO; SiO; _x; H; _y; thin film

Enhanced photocatalytic activity of titania with unique surface indium and boron species by Yanlong Yu; Enjun Wang; Jixiang Yuan; Yaan Cao (pp. 638-644).

Display Omitted► The doping energy level will result in an enhanced visible light photocatalysis. ► Both the doped indium ions in the catalyst exist as unique O–In–Cl_x surface species. ► The doping B ions exist in interstitial mode and as B₂O₃ surface species.Indium and boron co-doped TiO₂ photocatalysts were prepared by a sol–gel method. The structure and properties of photocatalysts were characterized by XRD, BET, XPS, UV–vis DRS and PL techniques. It is found that boron is mainly doped into the lattice of TiO₂ in interstitial mode, while indium is present as unique chemical species of O–In–Cl_x ( x=1 or 2) on the surface. Compared with pure TiO₂, the narrowness of band gap of TiO₂ doped with indium and boron is due to the mixed valence band formed by B2p of interstitial doped B ions hybridized with lattice O2p. And the surface state energy levels of O–In–Cl_x ( x=1 or 2) and B₂O₃ species were located at about 0.4 and 0.3eV below the conduction band respectively, which could lead to significant absorption in the visible-light region and facilitated the effectually separation of photogenerated carriers. Therefore, indium and boron co-doped TiO₂ showed the much higher photocatalytic activities than pure TiO₂, boron doped TiO₂ (TiO₂–B) and indium doped TiO₂ (TiO₂–In) under visible and UV light irradiation.

Keywords: TiO; ₂; 4-Chlorophenol degradation; Unique O–In–Cl; _x; (; x; =; 1 or 2) surface species; Visible photocatalytic activity

Magnetic properties and microstructure of Tb_xDy1−_xFe₂ thin films sputtered on Pt/TiO₂/SiO₂/Si substrate by Jiang Zhu; Christophe Cibert; Bernadette Domenges; Rachid Bouregba; Gilles Poullain (pp. 645-651).

► Tb_xDy1−_xFe₂ thin films are grown on Pt/TiO₂/SiO₂/Si substrate by sputtering. ► Ferromagnetic properties are investigated while changing the deposition conditions. ► Magnetization of 680emu/cm³ is achieved in a 140nm thick TERFENOL-D film. ► The microstructure of the films are investigated by XRD and TEM. ► The good ferromagnetic properties are related to crystallization of nano-grains.Tb_xDy1−_xFe₂ thin films are grown on Pt/TiO₂/SiO₂/Si substrate by multi-target sputtering. In order to achieve the best magnetic properties, samples grown while heating the sample holder (in situ films) are compared to those prepared at room temperature followed by thermal annealing. The effect of Tb, Dy and Fe content is also examined. It is found that the magnetic properties are very sensitive to the deposition parameters. Magnetization value as high as 680emu/cm³ with very low coercivity is achieved in a 140nm thick film whose composition (Tb_0.3Dy_0.7)Fe₂ corresponds to the TERFENOL-D formulation. Observation of soft ferromagnetism and high magnetization are related to crystallization of nano-grains (size 7–10nm) as deduced from microstructure investigation by X ray diffraction and transmission electron microscopy. It is shown the possibility of growing TERFENOL-D thin films with properties suitable for observation of extrinsic magneto-electric coupling in future thin film devices combining piezoelectric and magnetostrictive materials on metallized silicon substrate.

Keywords: Ferromagnetism; Magnetization; TERFENOL-D; Microstructure; Thin film; Sputtering

A facile fabrication of light diffusing film with LDP/polyacrylates composites coating for anti-glare LED application by Shisen Song; Yaojie Sun; Yandan Lin; Bo You (pp. 652-660).

► A novel light diffusing film was fabricated by a facile coating technique with hemispherical surface convex micro-structure using LDP/polyacrylate composite coating. ► The modification made the LDP a better dispersion and incorporating with polyacrylate polymer chain, resulting in both high transmittance and light-diffusing effect of the film. ► The film shows a good performance for anti-glare LED application.In this paper, we present a facile coating technique to fabricate the light diffusing film with hemispherical surface convex micro-structure. The coating was prepared by different ratio of light-diffusing particles (LDP)/polyacrylates composites via in situ radical polymerization, with the H₂SO₄ and vinyl triethoxysilane (A-151) pretreatment made the LDP better dispersed and incorporated with polyacrylate polymer chains. When the mass ratio (LDP/polyacrylate) was 0.5, the film obtained the highest light-diffusing effect and more than 90% transmittance due to the formation of hemispherical surface convex micro-structure. The light diffusing films have excellent anti-glare property if applied to LED light system.

Keywords: Light diffusing film; In situ radical polymerization; Anti-glare; LED application

CdS nanocrystals/TiO₂/crosslinked chitosan composite: Facile preparation, characterization and adsorption-photocatalytic properties by Huayue Zhu; Ru Jiang; Ling Xiao; Li Liu; Chunhua Cao; Guangming Zeng (pp. 661-669).

► CdS nanocrystals were deposited on TiO₂/crosslinked chitosan composite. ► CdS/TiO₂/CS NCFs showed enhanced photocatalytic activity. ► The photocatalytic decolorization reached 99.1% by CdS/TiO₂/CS NCFs ► Photocatalytic decolorization of methyl orange by CdS/TiO₂/CS NCFs obeyed L-H mechanism.CdS nanocrystals deposited on TiO₂/crosslinked chitosan composite (CdS/TiO₂/CSC) were prepared in an attempt to photocatalyze decolorization of water soluble azo dye in aqueous solution under simulated solar light irradiation. CdS/TiO₂/CSC was characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The characterization results proved that CdS nanocrystals has successfully been deposited on/in TiO₂/crosslinked chitosan composite. The adsorption ability of CdS/TiO₂/CSC was approximately 2.66mg methyl orange (a typical water soluble azo dye) per gram. The photocatalytic decolorization of methyl orange solution reached 99.1% by CdS/TiO₂/CSC after simulated solar light irradiation for 210min. Kinetics analysis indicated that photocatalytic decolorization of methyl orange solution by CdS/TiO₂/CSC obeyed first-order kinetic Langmuir-Hinshelwood mechanism ( R²>0.997). CdS/TiO₂/CSC exhibited enhanced photocatalytic activity under simulated solar light irradiation compared with photocatalysts reported before and the photocatalytic activity of CdS/TiO₂/CSC maintained at 89.0% of initial decolorization rate after five batch reactions. The presence of NO₃⁻ accelerated the decolorization of methyl orange solution by CdS/TiO₂/CSC, while SO₄²⁻ and Cl⁻ had an inhibitory effect on the decolorization of methyl orange. Therefore, present experimental results indicated to assess the applicability of CdS/TiO₂/CSC as a suitable and promising photocatalyst for effective decolorization treatment of dye-containing effluents.

Keywords: Adsorption; Photocatalysis; Azo dye; CdS; TiO; ₂

Structural properties and growth evolution of diamond-like carbon films with different incident energies: A molecular dynamics study by Xiaowei Li; Peiling Ke; He Zheng; Aiying Wang (pp. 670-675).

► The dependence of films properties on different incident energies was investigated. ► The compressive stress originated from the decrease of both bond angles and lengths. ► The growth mechanism was clarified based on the atomic motion mechanism.Structural properties and growth evolution of diamond-like carbon (DLC) films with different incident energies were investigated systematically by the molecular dynamics simulation using a Tersoff interatomic potential for carbon-carbon interaction. The results revealed that the density, sp³ fraction and residual compressive stress as a function of incident energy increased firstly and then decreased; when the incident energy was 70eV/atom, the density could reach to 3.0g/cm³ with the maximal compressive stress of 15.5GPa. Structure analysis indicated that the deviation of both bond angles and lengths from the equilibrium position led to the generation of a large residual stress, while the high compressive stress mainly attributed to the decrease of both bond angles and lengths among carbon atoms. The growth of DLC films underwent a formation process of “Line-Net” structure accompanied with the interaction of many atomic motion mechanisms, and the “Point” stage was only found for DLC films with low incident energy.

Keywords: Diamond-like carbon; Molecular dynamics simulation; Residual stress; Growth mechanism

Titania–supported silver nanoparticles: An efficient and reusable catalyst for reduction of 4-nitrophenol by S.P. Deshmukh; R.K. Dhokale; H.M. Yadav; S.N. Achary; S.D. Delekar (pp. 676-683).

Schematic representation for synthesis of silver nanoparticles.Display Omitted► Environmentally benign and efficient method ► Stable silver NPs better for catalysis ► Elemental silver NPs instead of their oxides ► Effective capping of silver NPs by sodium dodecyl sulfate in aqueous medium ► Excellent catalyst towards reduction of p-nitrophenol to p-aminophenol at RT.Supported silver nanoparticles were synthesized via in situ sol–gel followed by reduction method with dextrose as reductant and sodium dodecyl sulfate as stabilizer. The synthesized nanoparticles were characterized by X–ray diffraction, transmission electron microscopy, Fourier transform Infra-Red spectroscopy and UV–visible measurements. The XRD peaks confirm the metallic face-centered cubic silver particles. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption maxima at 412nm; which shifted to the longer wavelengths after supported on titania host lattice. TEM showed the spherical nanoparticles with size in the range of 18–23nm. An efficient and simple method was reported for the reduction of 4-nitrophenol using titania-supported silver nanoparticles at room temperature. The reaction was first order with respect to the concentration of 4-nitrophenol with higher efficiency. Titania supported silver nanoparticles are reusable and stable heterogeneous catalyst.

Keywords: Supported nanoparticles; Chemical synthesis; Electron microscopy; Optical properties; Catalytic properties

Magnetic composite ZnFe₂O₄/SrFe₁₂O₁₉: Preparation, characterization, and photocatalytic activity under visible light by Taiping Xie; Longjun Xu; Chenglun Liu; Yuan Wang (pp. 684-691).

► A simple synthesis process for ZnFe₂O₄/SrFe₁₂O₁₉ Composite was reported. ► The composite with uniform tetrahedral structure has a better magnetic properties. ► The composite has excellent magnetic and photocatalytic properties. ► The composite showed a higher activity for the photodegradation of MB under visible light irradiation. ► The synthesis process facilitates mass production for various composite materials.One-step chemical coprecipitation with high-temperature sintering method was employed for preparing magnetic composite ZnFe₂O₄/SrFe₁₂O₁₉ including a hard-magnetic phase (SrFe₁₂O₁₉) and a soft-magnetic phase (ZnFe₂O₄). The magnetic composite was characterized by FTIR, XRD, SEM, BET, XPS, VSM, and UV–vis. The testing results showed that the saturation magnetization ( M_s), remanent magnetization ( M_r), and coercivity ( H_c) were 34.95emu/g, 18.31emu/g, and 2254.54G, respectively, indicating that the composite possessed excellent magnetic properties and a greater capacity for anti-demagnetize. The properties of the composite were favourable to its separation, recycling, and reuse after reaction. The photocatalytic performance of the composite was studied by the degradation reaction of methylene blue under visible light irradiation. The experimental results revealed that the degradation rate was still more than 70% when the composite was reused for four times. In addition, this research was expected to provide a promising method to prepare various composite materials with multi-functional components.

Keywords: Magnetic composite; ZnFe; ₂; O; ₄; /SrFe; ₁₂; O; ₁₉; One-step chemical coprecipitation; Methylene blue; Magnetic; Photocatalytic

Super-mercuryphobic and hydrophobic diamond surfaces with hierarchical structures: Vanishment of the contact angle hysteresis with mercury by Juan V. Escobar; Cristina Garza; Juan Carlos Alonso; Rolando Castillo (pp. 692-701).

Display Omitted► We measure contact angles with water and mercury on progressively rougher surfaces. ► Substrate is boron doped diamond: polished, microcrystalline and oxidized. ► Oxidized surface has pyramids decorated with 100nm protrusions, giving low adhesion. ► Contact angle hysteresis vanishes for mercury drops on the oxidized diamond film. ► Contact angle for mercury is above 175 degrees.Increased roughness is known to enhance the natural wetting properties of surfaces, making them either more hydrophobic or more hydrophilic. In this work we study the wetting properties of water and mercury drops in contact with boron doped diamond films with progressively increased surface roughnesses. We show how thermal oxidation of a microcrystalline film creates pyramids decorated with sub-micron protrusions that turn its naturally mercuryphobic surface into super-mercuryphobic. With this liquid, we observe the vanishment of the contact angle hysteresis that is expected for rough surfaces as the contact angle approaches 180˚, making small drops of mercury roll along out of the surface at an apparent zero tilt-angle. In contrast, the incorporation of nano-globules on the oxidized surface through a silanization process is necessary to increase the hydrophobic properties of the film for which the contact angle with water reaches 138°. The wetting states that dominate in each case are discussed.

Keywords: Contact angle hysteresis; Mercury; Diamond; Adhesion; Wetting; Mercuryphobic; Hydrophobic; Lotus effect

Crystallization behaviors and electric properties of (Pb_0.8Ca_0.2)TiO₃ thin films prepared by a sol–gel route by Q.G. Chi; H.F. Zhu; J.Q. Lin; C.T. Chen; X. Wang; Y. Chen; Q.Q. Lei (pp. 702-705).

► The (Pb_0.8Ca_0.2)TiO₃ thin films were prepared by a sol–gel technique. ► The influence of pyrolysis temperature on crystallization behavior was investigated. ► The film pyrolyzed at 450°C could be crystallized at a low temperature. ► The film pyrolyzed at 450°C exhibited high (100) orientation and enhanced electric properties.The pure tetragonal perovskite (Pb_0.8Ca_0.2)TiO₃ (PCT) thin films deposited on (111)Pt/Ti/SiO₂/Si substrate were successfully achieved by a sol–gel route, and the influence of pyrolysis temperature on crystallization behaviors and electric properties of the PCT films was investigated. It was found that the film pyrolyzed at 450°C could be crystallized at temperature as low as 450°C, while the film pyrolyzed at 350°C is amorphous under the same crystallization temperature. It was also found that the PCT films pyrolyzed at different temperatures could be fully crystallized when the crystallization temperature was raised to 600°C, and compared to the film pyrolyzed at 350°C, the film pyrolyzed at 450°C exhibited higher (100) orientation and possessed enhanced electric properties (remanent polarization ∼19.5μC/cm², piezoelectric constant ∼125pm/v, pyroelectric coefficient ∼310μC/m²K).

Keywords: PCT thin films; Pyrolysis temperature; Orientation; Low-temperature crystallization; Electric properties

Synthesis, characterization, and mercury adsorption properties of hybrid mesoporous aluminosilicate sieve prepared with fly ash by Minmin Liu; Li-an Hou; Beidou Xi; Ying Zhao; Xunfeng Xia (pp. 706-716).

► Adsorption of mercury. ► Impregnation of A zeolite on MCM-41. ► Prepared with fly ash.A novel hybrid mesoporous aluminosilicate sieve (HMAS) was prepared with fly ash and impregnated with zeolite A precursors. This improved the mercury adsorption of HMAS compared to original MCM-41. The HMAS was characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, Fourier transform infrared (FTIR) analysis, transmission electron microscopy (TEM) images and²⁹Si and²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra. These showed that the HMAS structure was still retained after impregnated with zeolite A. But the surface area and pore diameter of HMAS decreased due to pore blockage. Adsorption of mercury from aqueous solution was studied on untreated MCM-41and HMAS. The mercury adsorption rate of HMAS was higher than that of origin MCM-41. The adsorption of mercury was investigated on HMAS regarding the pH of mercury solution, initial mercury concentration, and the reaction temperature. The experimental data fit well to Langmuir and Freundlich isotherm models. The Dublin–Radushkevich isotherm and the characterization show that the mercury adsorption on HMAS involved the ion-exchange mechanisms. In addition, the thermodynamic parameters suggest that the adsorption process was endothermic in nature. The adsorption of mercury on HMAS followed the first order kinetics.

Keywords: MCM-41; Fly ash; Mercury adsorption; Isotherms; Mesoporous sieve

Thermoplastic polymers surfaces for Dip-Pen Nanolithography of oligonucleotides by Raffaella Suriano; Serena Biella; Federico Cesura; Marinella Levi; Stefano Turri (pp. 717-722).

Display Omitted► Thermoplastic polymers substrates have been used in nanolithography experiments. ► DPN technique is applied for deposition of end-group modified oligonucleotides. ► Array composed of 441 spots with a diameter smaller than 200nm was obtained.Different thermoplastic polymers were spin-coated to prepare smooth surfaces for the direct deposition of end-group modified oligonucleotides by Dip-Pen Nanolithography. A study of the diffusion process was done in order to investigate the dependence of calibration coefficient and quality of deposited features on environmental parameters (temperature, relative humidity) and ink's molecular weight and functionality. The optimization of the process parameters led to the realization of high quality and density nanoarrays on plastics.

Keywords: Surface; Polymer; Dip Pen Nanolithography; Oligonucleotides; Nanoarray

Effect of [Al] and [In] molar ratio in solutions on the growth and microstructure of electrodeposition Cu(In,Al)Se₂ films by Kuo-Chan Huang; Chien-Lin Liu; Pin-Kun Hung; Mau-Phon Houng (pp. 723-729).

► The chemical reaction mechanism and element's reduction potential in solutions can be realized by cyclic voltammetric studies. ► The constituent and surface morphology of Cu(In,Al)Se₂ films are investigated by adjusting the aluminum and indium concentrations. ► The XRD peaks shift and decrease in lattice constants, showing the incorporation of Al atoms in CIS lattice to form CIAS crystals. ► The optical energy band gap of Cu(In,Al)Se₂ films can be successfully controlled from 1.17eV to 1.48eV by adjusting the aluminum and indium concentrations.In this paper, the cyclic voltammetric studies were used to realize the element's reduction potential and chemical reaction mechanism for presuming the formation routes of quaternary Cu(In,Al)Se₂ crystals. Thereafter, the prior adjustment of deposited potential from −0.6V to −1.0V can be identified a suitable potential as co-electrodeposition. The material characteristics of Cu(In,Al)Se₂ films are dominated by the percentage of aluminum content. Thus, the influence of aluminum and indium concentrations in solutions on the percentage composition, surface morphology, structural and crystal properties, and optical energy band gap of Cu(In,Al)Se₂ films were investigated. Energy dispersive X-ray spectroscopy (EDS) indicated that the ratio of Al to (Al+In) in Cu(In,Al)Se₂ films varied from 0.21 to 0.42 when adjusting aluminum and indium concentrations in solutions. Scanning electron microscopy (SEM) shows that the surface morphology changed from round-like structures into cauliflower-like structures and became rough when the aluminum concentration increased and indium concentration decreased in solutions. X-ray diffraction (XRD) patterns revealed three preferred growth orientations along the (112), (204/220), and (116/312) planes for all species. The ( αhυ)² versus hυ plots (UV–Visible) shows that the optical energy band gap of the Cu(In,Al)Se₂ films can be successfully controlled from 1.17eV to 1.48eV by adjusting the aluminum and indium concentrations. Furthermore, the shift of the (112) peak in the XRD patterns and variation of optical band gap are evidence that the incorporation of aluminum atoms into the crystallitic CuInSe₂ forms Cu(In,Al)Se₂ crystals.

Keywords: Cu(In,Al)Se; ₂; Cyclic voltammerty; Surface morphology; Optical energy band gap

Regular growth combined with lateral etching in diamond deposited over silicon substrate by using hot filament chemical vapor deposition technique by M. Ali; M. Ürgen (pp. 730-734).

•First time regular growth combined with lateral etching in diamond film deposited over Si.•Regular growth combined with lateral etching initiated over polycrystalline diamond film.•The cyclic formation of steps in diamond crystallite and their mode are discussed.Hot filament chemical vapor deposition has proved to be an attractive method for growing diamond films with good quality and higher growth rate. Diamond films were produced at deposition parameters under which, it is possible to have regular growth combined with lateral etching (RGCLE). Fracture cross-section SEM images showed that RGCLE initiated over polycrystalline diamond film and proceeded by the growth of consecutive steps in each crystallite, which terminated with square/rectangle shaped facets. All the diamond films exhibit RGCLE but with different type of growth behavior. Present work discusses the cyclic formation of the steps in diamond crystallites and RGCLE modes. RGCLE in diamond film may find important applications where heat absorption and dissipation are key issues.

Keywords: CVD; Thin film; Growth rate; Crystal structure; Surface morphology

Impact of proton diffusion and the hydrogen photospillover upon the photochromic sensitivity of the WO₃ films and the WO₃ double-layer structures by A.I. Gavrilyuk (pp. 735-747).

Display Omitted•Hydrogen photochromism in WO₃ films was investigated.•It was shown that the photochromic sensitivity of the films is massively impacted by proton diffusion.•The proton diffusion was provided by forming of water proton conducting wires in the film pores.•The proton conducting wires make it possible for hydrogen to flow between the layers in the double layer structures.It has been shown that the hydrogen photochromism, i.e., photochromism arising in WO₃ films due to hydrogen atoms detached from hydrogen donor molecules under the action of light, is massively impacted by proton diffusion. The control of the diffusion can be established by the combined use of two types of hydrogen-containing molecules; one (organic) playing the role of the hydrogen donor, whereas the other (water) provides pathways for the proton diffusion. The film morphology highly influences formation of the proton conducting water wires in pores of the WO₃ films. The spirit is that the hydrogen photospillover is used here: the hydrogen atoms detached from the hydrogen donor molecules adsorbed on the surface of the highly disordered WO₃ films flow to the polycrystalline WO₃ films along the special water pathways that are formed in the highly disordered films. The hydrogen spillover triggered by light makes it possible to create the photochromic systems with enhanced photochromic sensitivity and special optical characteristics of the photochromic state.

Keywords: Photochromism; Hydrogen; Proton diffusion; Color centers; Hydrogen spillover

Synthesis of silver-incorporated hydroxyapatite nanocomposites for antimicrobial implant coatings by Xiangmei Liu; Yanan Mou; Shuilin Wu; H.C. Man (pp. 748-757).

•A facile chemical reduction method to synthesize a silver incorporated HA nanocomposite on implant surface.•The diameter of the formed Ag particles is 20–30nm and the particles are firmly attached on the HA particle.• In vitro bacteria adhesion results proved a significant enhancement in the antibacterial property.Because of excellent osteoconductivity and resorbability, hydroxyapatite (HA) is commonly used as a bone substitute material or implant coating. Both ionic and metallic silver are considered to have a broad spectrum of antimicrobial properties especially associated with biomaterial-related infections. The present work proposes a facile chemical reduction method to synthesize an Ag incorporated HA nanocomposite. Ammoniacal silver solution was firstly prepared and then added into the HA solution, followed by hydrazine hydrate (N₂H₄·H₂O) being used to reduce the silver ions to metallic silver. The formed Ag nanoparticles had diameters of 20–30nm and were firmly attached on the HA particle surfaces. This approach can also keep the integrity of the HA chemical structure and the morphology. The strain Escherichia coli was used to evaluate the antibacterial effect of the nanocomposite. An In vitro bacterial adhesion study indicated a significant enhancement in the antibacterial property of silver containing HA.

Keywords: Hydroxyapatite; Nanocomposite; Silver; Antibacterial; Implant

A synergistic combination of tetraethylorthosilicate and multiphosphonic acid offers excellent corrosion protection to AA1100 aluminum alloy by Viviane Dalmoro; João H.Z. dos Santos; Elaine Armelin; Carlos Alemán; Denise S. Azambuja (pp. 758-768).

•Sol–gel films formed by phosphonic acids and TEOS are powerful aluminum-protecting systems.•Phosphonic acids increase the hydrophobicity of silica network.•Incorporation of phosphonic acids favors the coverage of the aluminum during the silanization.This work describes a new mechanism for the incorporation of organophosphonic acid into silane self-assembly monolayers, which has been used to protect AA1100 aluminum alloy. The protection improvement has been attributed to the fact that phosphonic structures promote the formation of strongly bonded and densely packed monolayer films, which show higher surface coverage and better adhesion than conventional silane systems. In order to evaluate the linking chemistry offered by phosphonic groups, two functionalized organophosphonic groups have been employed, 1,2-diaminoethanetetrakis methylenephosphonic acid (EDTPO) and aminotrimethylenephosphonic acid (ATMP), and combined with tetraethylorthosilicate (TEOS) films prepared by sol–gel synthesis. Results suggest that phosphonic acids may interact with the surface through a monodentate and bidentate coordination mode and, in addition, form one or more strong and stable linkages with silicon through non-hydrolysable bonds. Therefore, the incorporation of a very low concentration of phosphonic acids on TEOS solutions favors the complete coverage of the aluminum substrate during the silanization process, which is not possible using TEOS alone. The linking capacity of phosphonic acid has been investigated by FTIR-RA spectroscopy, SEM and EDX analysis, X-ray photoelectron spectroscopy (XPS), and quantum mechanical calculations. Finally, electrochemical impedance spectroscopy has been used to study the corrosion protection revealing that EDTPO-containing films afforded more protection to the AA1100 substrate than ATMP-containing films.

Keywords: Tetraethylorthosilicate; Organophosphonic acid; Sol–gel synthesis; Aluminum alloy; Electrochemical impedance spectroscopy

Preparation and characterization of PVA–I complex doped mesoporous TiO₂ by hydrothermal method by Shi Qian; Jiang Caiyun; Wang Yuping; Yang Weiben; Yang Chun (pp. 769-775).

•The anatase TiO₂ nanoparticles can be produced using PVA and iodine complex as modifier by lower temperature hydrothermal method.•The thermal stability of iodine of catalyst is enhanced because of PVA.•The visible light activity of catalysts is improved because of the synergy of iodine and carbon.Polyvinyl alcohol [PVA]–iodine complex doped mesoporous TiO₂ (PIT) and iodine doped (IT) catalysts were prepared by hydrothermal method, using tetrabutyl titanate as precursor, potassium iodate and iodine as iodine sources. The as-prepared PIT and IT catalysts were characterized by UV–vis, XRD, FESEM, BET, TG/DTA, XPS and photoluminescence (PL) spectroscopy. Production ofOH radicals on the surface of photocatalyst was detected by the PL technique using terephthalic acid as a probe molecule. The influences of calcinated temperature on the structure and properties of the catalysts were investigated. The photocatalytic activity of catalysts was evaluated through photocatalytic decolorization of methylene blue (MB) aqueous solution. The results showed that PIT samples were anatase mesoporous TiO₂ and their iodine content and mesoporous structure were influenced by calcinated temperature. Particle size of PIT samples was smaller than that of IT as a result of the PVA skeleton and regular structure. Because of the complexation of iodine and PVA, thermostability of iodine is improved and the amount of iodine in PIT calcinated at 200°C (PIT-200) is higher than that of IT calcinated at same temperature. Light absorption range and intensity of PIT-200 has been greatly improved due to the synergy of iodine and carbon. The efficiency of photocatalysis for MB is greatly improved with TiO₂ modified by PVA–I complex under simulated sun light irradiation.

Keywords: PVA–iodine complex; TiO; ₂; Thermostability; Hydrothermal method; Visible light

Highly transparent and thermally stable superhydrophobic coatings from the deposition of silica aerogels by Jinbin Lin; Hongling Chen; Ting Fei; Chang Liu; Jinlong Zhang (pp. 776-786).

Transparent superhydrophobic coatings, having high water contact angle (>160°), low sliding angle (<5°) and high transparency (transmittance closes to 90%), were prepared by using poly(methylhydrosiloxane) (PMHS) and tetraethoxysilane (TEOS) as precursors based on a simple sol–gel process. The high volume-fraction porosity structure and low surface energy are responsible for the superhydrophobicity of coating in this paper.•Transparent superhydrophobic coatings were prepared by a simple sol–gel method.•High SSA and low surface energy built the superhydrophobicity of coating.•Appropriate surface area (SSA) achieves superior superhydrophobicity coating.•The nanocoating could switch from superhydrophobic to superhydrophilic by heating.Transparent superhydrophobic coatings, having high water contact angle (>160°) and low sliding angle (<5°), were prepared by using poly(methylhydrosiloxane) (PMHS) and tetraethoxysilane (TEOS) as precursors based on a simple sol–gel process. The influence of different mass ratios of PMHS to TEOS on the transparency and superhydrophobicity of resulting coatings was investigated herein to get the optimum performance coating. The structure, composition and morphology of optimum performance coating were characterized by various technologies including Fourier transform infrared (FT-IR) spectroscopy, thermal analysis, BET,²⁹Si CP MAS NMR, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The optimum performance coating exhibits superhydrophobicity (CA, 164.7° and SA, 2.7°), a high transparency (transmittance closes to 90%) and a good thermal stability (up to 400°C). Note that the optimum coating directly from sol–gel process exhibits poor moisture resistance. The low surface energy and high volume-fraction porosity structure are responsible for the superhydrophobicity, transparency and thermal stability of the as-prepared coating, while the poor moisture is attributed to the untreated hydroxyl groups on the surface of coating. The moisture resistance of coating can be improved by further treated by cetyltrimethoxylsilane (CTMS), and the coating could switch from superhydrophobic (164.7°) to superhydrophilic (0°) after heat-treating at 600°C.

Keywords: Transparent; Superhydrophobic; Coating; Silica aerogel; Moisture resistance

Active screen plasma nitriding enhances cell attachment to polymer surfaces by Georgia Kaklamani; James Bowen; Nazia Mehrban; Hanshan Dong; Liam M. Grover; Artemis Stamboulis (pp. 787-798).

•Active screen plasma nitriding of ultra-high molecular weight poly(ethylene).•Nitrogen-containing functional groups incorporated into surface.•NIH 3T3 fibroblast attachment and proliferation over 28 days.•Extensive spectroscopic and visualisation study of polymer surface.Active screen plasma nitriding (ASPN) is a well-established technique used for the surface modification of materials, the result of which is often a product with enhanced functional performance. Here we report the modification of the chemical and mechanical properties of ultra-high molecular weight poly(ethylene) (UHMWPE) using 80:20 (v/v) N₂/H₂ ASPN, followed by growth of 3T3 fibroblasts on the treated and untreated polymer surfaces. ASPN-treated UHMWPE showed extensive fibroblast attachment within 3h of seeding, whereas fibroblasts did not successfully attach to untreated UHMWPE. Fibroblast-coated surfaces were maintained for up to 28 days, monitoring their metabolic activity and morphology throughout. The chemical properties of the ASPN-treated UHMWPE surface were studied using X-ray photoelectron spectroscopy, revealing the presence of CN, CN, and CN chemical bonds. The elastic modulus, surface topography, and adhesion properties of the ASPN-treated UHMWPE surface were studied over 28 days during sample storage under ambient conditions and during immersion in two commonly used cell culture media.

Keywords: Active screen plasma nitriding; Atomic force microscopy; Fibroblast; Interferometry; Nanoindentation; X-ray photoelectron spectroscopy

Comparative investigation on HVOF sprayed carbide-based coatings by Mingxiang Xie; Shihong Zhang; Mingxi Li (pp. 799-805).

•We prepared the WC-base and Cr₃C₂-base coatings with different binder phases by HVOF.•We investigated the structure, porosity, micro-hardness, fracture toughness and adhesion strength of coatings.•We comparatively evaluated the tribological properties of the four coatings at 500°C.In this work, WC-17Co, WC-10Co-4Cr, WC-12Co and Cr₃C₂-25NiCr coatings were deposited on stainless steel using WOKAStar-640 HVOF spraying system. Three WC-based coatings were studied and compared with a chromium carbide-based coating. The microstructure, porosity, micro-hardness, indentation fracture toughness and adhesion strength of the coatings were investigated. The wear test was done by using silica grits as abrasive medium using a load of 20N. The result shows that HVOF sprayed carbide-based coating possesses low porosity, high micro-hardness and high adhesion strength. Three WC-based coatings have higher micro-hardness and indentation fracture toughness compared to the Cr₃C₂-25NiCr coating. HVOF sprayed carbide coating has good wear resistance under 500°C. The decarburization of WC-based coating has great effect on coating wear resistance. In addition, WC-17Co coating has best wear resistance.

Keywords: Carbide-based coatings; HVOF spray processes; Wear resistance

Realizing a variety of carbon nanostructures at low temperature using MW-PECVD of (CH₄+H₂) plasma by Amit Banerjee; Debajyoti Das (pp. 806-815).

•Variety of carbon nanostructures grown at low temperature (200–250°C) using MW-PECVD of (CH₄+H₂) plasma.•Highly polycrystalline spherical nano-diamonds (size ~13nm, density ~8×10⁸cm⁻²) produced with graphitic inclusions.•Rectangular plate-like and rod-like nanostructures grown on substrates with irregular scratches.•Amorphous carbon wrinkles formed by controlling the flow rate of the precursors.Various process conditions are summarized that allocate different carbon nanostructures (spherical nano-diamonds, nano-plates, nano-rods, a-C wrinkles, etc.) grown at low temperature, by micro-wave plasma enhanced CVD (MW-PECVD) of CH₄/H₂ mixture. At an optimized MW power of 500W, gas pressure of 30Torr and at only 200°C temperature, spherical shaped homogeneously distributed nano-structures of average size ~120nm, embedded within a matrix made of fine-grain nanocrystallites were produced. The spherical structures were found to increase in number density with elevation of temperature. With pretreatment of the substrate by mechanical scratching nano-plate and nano-rod like structures could also be grown. Further, amorphous carbon wrinkles were formed by controlling the flow rate of the precursors. The bulk material was found to improve in crystallinity with the increment of pressure and highly polycrystalline nano-diamonds (111), along with graphitic [(100), (004)] inclusions, with an average size of 13nm and number density ~8×10⁸cm⁻² were grown at 70Torr, at a low substrate temperature of 250°C. In view of basic understanding of the structure and the growth mechanism of these various nano-structures of carbon a detailed study was performed using Micro-Raman, FE-SEM and HR-TEM characterizations.

Keywords: Spherical nano-diamond; Carbon nanostructures; Low-temperature synthesis; MW-PECVD; HRTEM; Raman studies

Nanoindentation behaviors of amorphous carbon films containing nanocrystalline graphite and diamond clusters prepared by radio frequency sputtering by Xue Fan; Kenji Nose; Dongfeng Diao; Toyonobu Yoshida (pp. 816-823).

•Ion energy and temperature decided nanostructures of amorphous carbon (a-C) film by RF sputtering.•Nanocrystalline graphite (NCG) and diamond (NCD) clusters were embedded in a-C.•High elastic recovery was achieved by NCG not by NCD.•NCD accounted for the brittle fractures in nanoindentation.Amorphous carbon (a-C) films were prepared by a radio-frequency sputtering method. Nano structures in the films were controlled by changing the ion irradiation energy and deposition temperature. It was found that nanocrystalline graphite and diamond clusters were embedded in the pure amorphous structure with sizes of approximately 5nm. a-C films contained nanocrystalline graphite clusters (a-C:NCG) were obtained with the ion energy ranging from 50 to 120eV and temperature in 300–370K. a-C film contained nanocrystalline diamond clusters (a-C:NCD) was obtained with 120eV at 570K. Nanoindentation behaviors of these carbon films were compared with pure amorphous structured carbon film. The percentage of elastic recoveries of a-C:NCD, a-C, and a-C:NCG films were obtained to be 81.9%, 84.3%, and 87.5%, respectively. Pop-in steps with about 3nm displacement appeared in loading curves for a-C:NCG film, and 10nm for a-C:NCD film. These results showed that the nanoindentation behaviors of amorphous carbon film containing cross-linked nanocrystalline graphite clusters is better than that of diamond clusters.

Keywords: Nanocrystalline; Carbon film; Amorphous; Graphite; Diamond; Nanoindentation

Preparation and characterization of ZnO-deposited DBD plasma-treated PP packaging film with antibacterial activities by Sutida Paisoonsin; Orathai Pornsunthorntawee; Ratana Rujiravanit (pp. 824-835).

•In this study, PP film with antibacterial activities was successfully fabricated.•ZnO particles were incorporated into PP film with the aid of DBD plasma treatment.•After DBD plasma treatment, ZnO deposition on PP surface was significantly enhanced.•ZnO-deposited PP showed antibacterial activities with and without exposure to UV.Zinc oxide (ZnO)-deposited polypropylene (PP) packaging film was prepared with the aid of dielectric barrier discharge (DBD) plasma treatment. The surface hydrophilicity of PP film was found to increase after the DBD plasma treatment due to the presence of oxygen-containing functional groups on the DBD plasma-treated PP surface. Although the surface roughness of the DBD plasma-treated PP film gradually increased with increasing plasma treatment time, the DBD plasma treatment insignificantly affected the mechanical properties of the PP film. The DBD plasma treatment time was found to be optimized at 10s. The DBD plasma-treated PP film was further immersed in an aqueous zinc nitrate (Zn(NO₃)₂) solution at different concentrations before being converted to ZnO particles with the use of a 2.5M sodium hydroxide (NaOH) solution, followed by sonication. The highest amount of ZnO deposited on the DBD plasma-treated PP surface was about 0.26wt.% at the optimum Zn(NO₃)₂ concentration of 0.5M. The ZnO-deposited DBD plasma-treated PP film showed good antibacterial activities against gram-positive Staphylococcus auerus and gram-negative Escherichia coli.

Keywords: Zinc oxide; Polypropylene; Dielectric barrier discharge; Antibacterial activities

Formation of complex bis(β-mercaptobenzothiazole)–zinc(II) films by pulsed laser deposition by Kejie Zhang; M.A. Yarmolenko; A.A. Rogachev; Bing Zhou; Xiaohong Jiang; Ruiqi Shen; Xiaoheng Liu (pp. 836-840).

The preparation of Zn(MBT)₂ thin film by pulsed laser deposition approach with original Zn(MBT)₂ powder as the precursor. Photoluminescence result shows that the as-prepared film has good fluorescence response at both UV and visible wavelength.Display Omitted► Zn(MBT)₂ film has been successfully deposited onto silicon substrate by pulsed laser deposition method. ► The structure of this complex could not be damaged during the pulsed laser deposition process. ► PL result shows that the as-prepared film has good fluorescence response at both UV and visible wavelength.Bis(β-mercaptobenzothiazole)–zinc (Zn(MBT)₂) films were successfully deposited onto silicon substrate by pulsed laser deposition (PLD) method using Zn(MBT)₂ powder as the raw material. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ﬁeld emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and room-temperature photoluminescence (PL) spectroscopy were used to characterize the as-prepared product. The obtained results indicate the structure and composition of Zn(MBT)₂ are preserved during the mild PLD process. The approach provides new possibility to produce special metal complex film material.

Keywords: Zn(MBT); ₂; films; Pulsed laser deposition; Complex

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Applied Surface Science (v.273, #)