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Applied Surface Science (v.258, #17)

Morphology-tunable assembly of periodically aligned Si nanowire and radial pn junction arrays for solar cell applications by Xiaocheng Li; Kun Liang; Beng Kang Tay; Edwin H.T. Teo (pp. 6169-6176).

Display Omitted► PASiNW arrays are fabricated via a templated catalytic chemical etching process. ► The diameter, length, packing density and the shape of SiNWs are precisely controlled. ► Current debate on formation mechanism of SiNW and the role of silver are clarified. ► Diameter and interspace of SiNW significantly affect the efficiency of solar cell. ► A high PCE of 4.1% is achieved for PASiNW radial pn junction-based solar cell.Large-area periodically aligned Si nanowire (PASiNW) arrays have been fabricated on Si substrates via a templated catalytic chemical etching process. The diameter, length, packing density, and even the shape of Si nanowires (SiNWs) could be precisely controlled and tuned. A local coupling redox mechanism involving the reduction of H₂O₂ on silver particles and the dissolution of Si is responsible for formation of SiNWs. With the as-prepared SiNWs as templates, three kinds of PASiNW radial pn junction structures were fabricated on Si substrates via a solid-state phosphorous diffusion strategy and their applications in solar cells were also explored. The PASiNW radial pn junction-based solar cell with big diameter and interspace shows the highest power conversion efficiency (PCE) of 4.10% among the three kinds of devices. Further optimization, including surface passivation and electrode contact, is still needed for the higher efficiency PASiNW radial pn junction-based solar cells in the future.

Keywords: Si nanowire; Chemical etching; Periodicity; Solar cell; Radial; pn; junction

Synthesis, characterization of core–shell carbon-coated CaSnO₃ nanotubes and their performance as anode of lithium ion battery by Xiaoyan Hu; Ting Xiao; Wei Huang; Wei Tao; Bojun Heng; Xinqi Chen; Yiwen Tang (pp. 6177-6183).

► We design a strategy to obtain carbon-coated CaSnO₃ nanotubes directly via a solvothermal synthesis. ► The uniform carbon-coating layer plays essential roles of a good conductor and a structure buffer. ► It shows enhanced cycling performance in term of cycling stability.In this paper, we design a strategy to obtain core–shell carbon-coated CaSnO₃ nanotubes (hereafter C-CTO NTs) directly via a facile subsequent solvothermal synthesis using CaSn(OH)₆ nanotubes as precursor in a mixed ethanol and water solvent. The mixed solvent not only facilitates the phase transformation of CaSnO₃ from CaSn(OH)₆ to take place quickly, but also retains the tube-shaped morphology. The uniform decoration of C shell on the surface of CaSnO₃ nanotubes (hereafter CTO NTs) was confirmed by EELS (electron energy loss spectroscopy). Moreover we found that the uniform carbon-coating layer on the surface of CTO NTs played roles of a good conductor and a structure buffer to alleviate the strains from the volume variation of CTO NTs cores. So the core–shell structure possesses both the electroactivity of C and the advantages of nanotube structure. When used as an anode for Li ion battery, it shows enhanced cycling performance in term of cycling stability over bare CTO NT electrode and CaSnO₃ nanocube (hereafter CTO NC) electrode. To our best knowledge, this is the first attempt to use C-CTO NTs as an anode in Li ion battery.

Keywords: Core–shell carbon-CaSnO; ₃; nanotubes; Solvothermal synthesis; Mixed ethanol and water solvent; Tubular structure maintenance

Hydrothermal synthesis of β-NaYF₄ nanotubes by in situ ion exchange reaction using Y(OH)₃ nanotubes as templates by Lina Liu; Chunhe Zang; Yongsheng Zhang (pp. 6184-6189).

► Hexagonal NaYF₄ nanotubes were prepared through in situ ion exchange reaction. ► The as-prepared β-NaYF₄ preserved the basic morphology of the initial Y(OH)₃ nanotubes. ► β-NaYF₄ nanotubes could only be obtained at proper pH value. ► Yb³⁺/Er³⁺ codoped NaYF₄ emitted bright green and red light.In this article, we reported the synthesis of uniform hexagonal NaYF₄ (β-NaYF₄) nanotubes through in situ ion exchange reaction using Y(OH)₃ nanotubes as templates via a facile hydrothermal route. The structure and morphology of the products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the as-prepared β-NaYF₄ with a length of about 4μm, an external diameter of about 160nm, and a thickness of about 50nm preserved the basic morphology of the initial Y(OH)₃ nanotubes. The influence of pH value of the precursor on the morphology and structure of the products was also studied, and the results indicated that β-NaYF₄ nanotubes could only be obtained at proper pH value. The strength of acids adjusting the pH value of the precursor had no influence on the morphology and structure of the products. Additionally, the upconversion luminescence properties of Yb³⁺/Er³⁺ codoped β-NaYF₄ were investigated. Yb³⁺/Er³⁺ codoped NaYF₄ emitted bright green and red light, both of which were two-photon processes.

Keywords: Nanotubes; Upconversion; β-NaYF; ₄; Template

Effects of anodic oxidation and hydrothermal treatment on surface characteristics and biocompatibility of Ti–30Nb–1Fe–1Hf alloy by Shih-Fu Ou; Hsin-Hua Chou; Chao-Sung Lin; Ching-Jui Shih; Kuang-Kuo Wang; Yung-Ning Pan (pp. 6190-6198).

► A new electrolyte was developed to promote the Ca/P of the anodic oxide film. ► The new electrolyte results in an adherent Ca–P containing oxide film. ► The hydrothermally treated surface promotes the attachment of cells.Anodic oxidation followed by hydrothermal treatment has been widely applied for surface modification of titanium alloys to precipitate a crystalline hydroxyapatite (HA) layer in order to achieve improved osteoconduction. A majority of the studies in the literature imposed relatively high powers to enhance Ca and P in the anodic oxide film (AOF). However, high powers have been found to cause deterioration of the adhesive strength in one of the author's previous study. In this study, a new electrolyte comprising calcium acetate monohydrate (CA), β-glycerophosphate disodium pentahydrate (β-GP) and HA powder was developed, and the Ti–30Nb–1Fe–1Hf alloy was anodized in this HA-containing electrolyte to a relatively low voltage. Results show that the AOF anodized in the HA-containing electrolyte exhibits a better HA forming ability during hydrothermal treatment, attributing to the presence of HA powder in the electrolyte that effectively enhances both the Ca content and Ca/P ratio in the AOF. On the other hand, the adhesive strength was little affected due to the decrease in size of the craters residing in the AOF. With respect to the biological responses, not much difference in biocompatibility of the treated and untreated Ti–Nb surfaces was obtained. However, the anodized and hydrothermally treated surface promotes the attachment of cells.

Keywords: Anodic oxidation; Hydrothermal treatment; Hydroxyapatite; Ti–Nb alloy

Growth and characterization of La_0.85Sr_0.15MnO₃ thin films for fuel cell applications by Dongbo Zhang; Lei Yang; Ze Liu; Kevin Blinn; Jae-Wung Lee; Meilin Liu (pp. 6199-6203).

► The LSM films were prepared by rf-magnetron sputtering and process parameters (work pressure and substrate temperature) were studied. ► The microstructure and morphology of LSM films were tested by SEM, Raman and XRD and its electrical properties were studied. ► The results show that high quality (dense and uniform) LSM films with desired thickness, morphology, and microstructure critically influence the electrochemical properties.Thin films of La_0.85Sr_0.15MnO₃ (LSM) are deposited on (100) silicon wafer and YSZ (yttria-stabilized zircornia) electrolyte substrates by magnetron sputtering using a single-phase LSM target. The conditions for sputtering are systematically studied, including substrate temperature (from room temperature to 600°C), the argon background pressure (from 1.2×10⁻² to 3.0×10⁻²mbar), and deposition time. Results show that the optimal conditions for producing a dense, uniform, and crack-free LSM film include a substrate temperature of 600°C and an argon pressure of 1.9×10⁻²mbar. Further, a testing cell with a dense LSM film, an YSZ electrolyte membrane, and a porous LSM counter electrode is prepared and the electrochemical properties of the dense LSM film on YSZ substrate are studied. It was found that the thickness, morphology, and microstructure of LSM films critically influence the electrochemical properties.

Keywords: La; _0.85; Sr; _0.15; MnO; ₃; Thin film; Solid oxide fuel cell; Sputtering; Cathode

Hydrothermal preparation of ZnO-reduced graphene oxide hybrid with high performance in photocatalytic degradation by Xun Zhou; Tiejun Shi; Haiou Zhou (pp. 6204-6211).

► The one step hydrothermal method with ammonia used in this manuscript can reduce graphene oxide (GO) and anchor ZnO nanostuctures to reduced graphene oxide (RGO) sheets synchronously. ► The morphology of ZnO in ZnO–RGO can be changed by adjusting mass ratio between Zn(NO₃)₂·6H₂O and GO used for preparation of ZnO–RGO. ► The ZnO–RGO can hinder the recombination of photo electrons and holes to enhance the photocatalytic degradation of methylene blue.Hydrothermal method was utilized to prepare reduced graphene oxide (RGO) and fabricate ZnO–RGO hybrid (ZnO–RGO) with zinc nitrate hexahydrate and graphene oxide (GO) as raw materials under pH value of 11 adjusted by ammonia water. During the process of reduction of GO, hydrothermal condition with ammonia provided thermal and chemical factors to synthesize RGO. The retained functional groups on RGO planes played an important role in anchoring ZnO to RGO, which was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy and photoluminescence spectra. The various mass ratios of zinc nitrate hexahydrate to GO used to prepare ZnO–RGO impacted significantly on the morphology of ZnO nanostructures such as nanoparticles and nanorods. And, the RGO sheets wrapped ZnO nanoparticles and nanorods very tightly. After the emission of photo electrons from ZnO, RGO in ZnO–RGO can effectively transfer the photo electrons to exhibit a high performance and reproducibility in photocatalytic degradation toward methylene blue (MB) absorbed on the surface of RGO through π–π conjugation.

Keywords: Hydrothermal; ZnO; Reduced graphene oxide; Photocatalytic degradation; Methylene blue

Effects of hydrogen and substrate temperature on the chemical bonding and optical properties of germanium carbon films deposited by reactive sputtering by Xing-Sen Che; Zheng-Tang Liu; Yang-Ping Li; Ning Wang (pp. 6212-6216).

► Germanium carbon films were prepared by reactive sputtering in a CH₄+H₂+Ar mixture. ► Deposition rate, chemical bonding and optical properties were investigated. ► The effects of composition and chemical bonding on optical gap were investigated. ► we found that high H₂ can broaden the optical band gap.Germanium carbon (Ge1−_xC_x) films were prepared by radio frequency (RF) reactive magnetron sputtering of a pure Ge (111) target in a CH₄+H₂+Ar mixture and their composition, chemical bonding, optical properties were investigated as a function of substrate temperature and gas flow ratio of H₂/(CH₄+Ar). The results show that the deposition rate decreased almost linearly with increasing the substrate temperature and gas flow ratio. And the optical gap of the Ge1−_xC_x films decreased from 1.5 to 0.9eV due to the drop in the carbon content of the films as the substrate temperature was increased with the relative content of GeC bonds decreasing. The optical gap first decreased and then increased as the gas flow ratio was increased from 0 to 1.125. Through the analysis of XPS spectrum, it is found that the formation of GeC bonds in the films was promoted both by low substrate temperature and by high atomic hydrogen content in the working gas mixture near the growth surface. Especially in high H₂ concentration, the optical gap shows an abnormal increase due to the increase of the formation of sp³-hybridized C and high concentration of CH bonds.

Keywords: Germanium carbon; Magnetron sputtering; Chemical bonding; Optical band gap

Facile fabrication of freestanding through-hole ZrO₂ nanotube membranes via two-step anodization methods by Dong Fang; Suqin Liu; Zhiping Luo; Chuanxi Xiong; Weilin Xu (pp. 6217-6223).

► Freestanding and tubular ZrO₂ membrane was prepared by anodization. ► Two methods were used to fabricate the two-end opened ZrO₂ membranes. ► Potential shock method and reducing potential method were adopted. The growth mechanisms of the two-end opened ZrO₂ nanotube arrays were investigated.Highly ordered freestanding tubular zirconia (ZrO₂) membrane was prepared via an electrochemical anodization of zirconium (Zr) substrate in non-aqueous electrolytes (mixture of formamide and glycerol (weight ratio=1:1) containing 1wt% NH₄F and 3wt% H₂O). Two methods were used to fabricate the two-end opened ZrO₂ membranes, one is a potential shock method and another is a reducing potential method. The two-end opened ZrO₂ membrane was produced through the detachment of the existing self-organized ZrO₂ tubular layer from Zr substrate or sub tubular layer. The microstructures and morphologies of the samples were studied by scanning electron microscopy and the growth mechanisms of the two-end opened ZrO₂ nanotube arrays were investigated.

Keywords: ZrO; ₂; Through-hole nanotube; Anodization; Membrane; Mechanism; Scanning electron microscopy

Thermal stability of {110} facet terminated gold nanobelts by Ying Chen; Srdjan Milenkovic; Achim Walter Hassel (pp. 6224-6231).

Display Omitted► {110} faceted gold nanowire iso-oriented arrays were produced. ► Thermal stability of gold nanowires is studied using an FE-SEM with heating stage. ► Free standing gold nanowires are compared with those in substrate contact. ► The decay mechanism is a transformation through {111} facets to Rayleigh instabilities.A precise knowledge and understanding of the thermal stability of nanowires is a prerequisite for the reliable implementation of nanowire-based devices. Single crystalline Au nanobelts with {110} surface either in free standing arrays with identical crystallographic orientation or lying on the substrate were prepared by a combination of directional eutectoid decomposition followed by phase selective etching process. The thermal stability in the temperature range 500–700°C of the obtained free standing and lying Au nanobelts were investigated in situ with a scanning electron microscope equipped with a high temperature stage. The results suggested that free standing Au nanobelts undergo morphological evolution in a different way compared with the substrate contacted lying Au nanobelts. The free standing Au nanobelts broke more easily and decayed into a chain of nanospheres following Rayleigh instability after the belt morphology changed into cylindrical wires; whereas the Au nanobelts lying on the substrate decayed into irregular particles. These findings clearly support a surface energy minimization driven mechanism. Only after transformation into a mainly {111} terminated structure formation of Rayleigh instabilities are observed.

Keywords: Gold nanobelts; Metal nanowires; Thermal stability; Rayleigh instabilities

The effect of acidity of electrolyte on the porosity and the nanostructure morphology of electrolytic manganese dioxide by H. Adelkhani (pp. 6232-6238).

► Electrolytic manganese dioxides are electrodeposited from a MnSO₄ solution at fixed pH (2, 3, 4, 5, and 6) and unfixed pH. ► The nanostructure morphology and porosity (hysteresis behavior and specific surface area) of the samples have been studied. ► The acidity of electrolyte (pH) has strong influence on the characteristic of Electrolytic manganese dioxides.The effects of acidity of electrolyte (pH) on the hysteresis behavior, the specific surface area, and nanostructure morphology of electrolytic manganese dioxides (EMDs) have been studied by using the Barrett–Joyner–Halenda (BJH) analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) images analysis. EMD samples are electrodeposited at a variable pH (6 to 1) and many fixed pH (2, 3, 4, 5, and 6). Results indicate that pH play key roles in the characteristics of EMD. The samples obtained at low pH (2 and 3) show multi-branched morphology and represent a H4 hysteresis loop. At pH 4 and 5, a uniform and dense structure of MnO₂ is obtained without hysteresis behavior. The sample electrodeposited at pH 6 shows a regular reticulate, that its adsorption–desorption isotherm show hysteresis behavior. By electrodeposition at a variable pH, the sample shows a cauliflower-like and multi-branched form. From the viewpoint of classification of isotherm, pH strongly affects on Type of isotherm. The results show that γ-MnO₂ is as main-product of electrodeposition and α-MnO₂ and β-MnO₂ were obtained as side-product at low and high pH, respectively.

Keywords: Electrodeposition; MnO; ₂; pH; Sorption; Nanostructure

Investigation of the doped transition metal promotion effect on CO₂ chemisorption on Ni (111) by Wei Xie; Wenjing Sun; Wei Chu; Chengfa Jiang; Ying Xue (pp. 6239-6245).

► The different H values lead to the different most stable chemisorbed structures. ► The strongest electron transfer is caused by the same chemisorbed structure. ► The higher H value of doped transition metal atom means they bond with CO₂ easier. ► We explain the La's high ability of hider carbon deposition in the experiment by the calculation of CO₂ dissociative.The chemisorption of CO₂ on the pure Ni (111) and doped Ni (111) by transition metal (Co, Rh, Cr, Ce, La) were investigated by using the generalized gradient approximation (GGA) and the Perdew–Burke–Emzerhof (PBE) functional. The optimized structure of doped metal surface showed that Rh, Cr, Ce, La atoms upward shift from the surface of Ni (111) plane, while the atom radius of Co is the minimum offset which lead to the height is −0.03Å. The ability of CO₂ chemisorption follows the order of La/Ni (111)>Ce/Ni (111)>Cr/Ni (111)>Co/Ni (111)>pure Ni (111). It is exothermic when CO₂ chemisorbed on Cr/Ni (111) Ce/Ni (111) and La/Ni (111), while it is endothermic on the Co/Ni (111) and pure Ni (111). CO₂ molecular chemisorbed on all the metal surfaces are negatively charged, result from the electron transfer between the metal surfaces and the CO₂ molecular. The transition metals La, Ce and Cr can promote the transformation of electron and make the CO bonds longer than the pure Ni (111). We also analyzed the dissociation of CO₂ on the Ni-based surface and found that the La/Ni (111) surface is the preference surface for the dissociation of CO₂, which improved the ability to hinder carbon deposition.

Keywords: Density functional theory; Chemisorptions; Doped Ni-based surface; Transition metal catalysis; Ni-based catalysis; Simulation; The activity and dissociation of CO; ₂

Characterization of azo dyes on Pt and Pt/polyaniline/dispersed Pt electrodes by J. Molina; J. Fernández; A.I. del Río; J. Bonastre; F. Cases (pp. 6246-6256).

Display Omitted► Platinum nanoparticles have been dispersed on polyaniline coatings. ► Platinum coatings have been characterized morphologically by means of SEM and AFM. ► XPS was employed to measure the oxidation state of the elements and the composition of the coatings. ► SECM measurements were employed to measure the electroactivity of the coatings. ► Amaranth and procion orange MX-2R dyes have been electrochemically characterized on Pt and Pt–Pani–dispersed Pt electrodes.The electrochemical characterization of two organic dyes (amaranth and procion orange MX-2R) has been performed on Pt electrodes and Pt electrodes coated with polyaniline and dispersed Pt. Electrodes with different Pt loads have been synthesized and characterized obtaining that a load of 300μgcm⁻² was the optimum one. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was employed to observe the distribution and morphology of the Pt nanoparticles. The electroactivity of the electrodes has also been characterized by means of scanning electrochemical microscopy (SECM). The chemical characterization of Pt dispersed Pani coated Pt electrodes (Pt–Pani–Pt) was performed by means of X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of the dyes has been performed by means of cyclic voltammetry. Voltammograms have shown that the presence of the dyes diminishes characteristic Pt oxidation and reduction peaks. However, redox processes due to the dyes, appeared in the voltammograms. The different species responsible of these redox processes were generated in the vicinity of the electrode and were not adsorbed on the electrode surface since after stirring, the different redox processes disappeared. Characterization with different scan rates showed that redox processes of both dyes were controlled by diffusion.

Keywords: Dispersed platinum; Polyaniline; Scanning electrochemical microscopy; Atomic force microscopy; Dye; Cyclic voltammetry

Optoelectronic and thermoelectric properties in Ga doped β- PbS₂ nanostructured thin films by R. Geethu; Rajani Jacob; T. Shripathi; G.S. Okram; V. Ganesan; Shilpa Tripathi; Anees Fatima; P.V. Sreenivasan; K.S. Urmila; B. Pradeep; Rachel Reena Philip (pp. 6257-6260).

► An initiating study on the effect of Ga doping on the optoelectronic and thermoelectric properties of β-PbS₂ thin films. ► The films were characterized by XRD, XPS, SEM, AFM. ► Higher bandgap observed for Ga doped β-PbS₂ film compared to β-PbS₂ film. ► Thermopower measurements yielded E_F value and the scattering mechanisms in the film.Lead sulphide nanostructured thin films were grown on soda lime glass substrates by chemical bath deposition. The films were then doped with gallium using vacuum evaporation technique. X-ray diffraction (XRD) established the structural type of the host films to be tetragonal β-PbS₂ with average grain size of the order of 15nm. The nanostructure of films was further confirmed from scanning electron and atomic force micrographs. The shift in the binding energies of the 4f and 4d states of lead, 2p state of sulphur and the 2p states of Ga from their elemental binding energy values, determined from X-ray photoelectron spectroscopy (XPS), indicated intact chemical bonding in the compound. Compositional analysis showed about 0.01% doping of Ga into PbS₂. Low temperature thermopower measurements indicated p-type conductivity for the films with Fermi level positioned at about 0.017eV above the maxima of valence band. Optical absorption studies in conjunction with photo sensitivity measurements established its pertinence in junction formation in photovoltaic applications due to the blue shift in the band gap to 2.37eV and the increased photoconductivity of the films.

Keywords: PACS; 73.50.Lw; 61.05.cp; 68.37.Hk; 68.37.PsThin films; X-ray photoelectron spectroscopy; X-ray diffraction; Optical properties; Thermopower

The Cu₂ZnSnSe₄ thin films solar cells synthesized by electrodeposition route by Ji Li; Tuteng Ma; Ming Wei; Weifeng Liu; Guoshun Jiang; Changfei Zhu (pp. 6261-6265).

► It is the first report of fabricating Cu₂ZnSnSe₄ solar cells by electrodeposition route. ► CZTSe formation mechanism at different temperature was studied in this paper. ► A Cu₂ZnSnSe₄ solar cell was fabricated and achieved an conversion efficiency of 1.7%.An electrodeposition route for preparing Cu₂ZnSnSe₄ thin films for thin film solar cell absorber layers is demonstrated. The Cu₂ZnSnSe₄ thin films are prepared by co-electrodeposition Cu–Zn–Sn metallic precursor and subsequently annealing in element selenium atmosphere. The structure, composition and optical properties of the films were investigated by X-ray diffraction (XRD), Raman spectrometry, energy dispersive spectrometry (EDS) and UV–VIS absorption spectroscopy. The Cu₂ZnSnSe₄ thin film with high crystalline quality was obtained, the band gap and absorption coefficient were 1.0eV and 10⁻⁴cm⁻¹, which is quite suitable for solar cells fabrication. A solar cell with the structure of ZnO:Al/i-ZnO/CdS/Cu₂ZnSnSe₄/Mo/glass was fabricated and achieved an conversion efficiency of 1.7%.

Keywords: Cu; ₂; ZnSnSe; ₄; Thin films; Electrodeposition; Selenization; Capacitance–voltage

Analysis of plasma-mediated ablation in aqueous tissue by Jian Jiao; Zhixiong Guo (pp. 6266-6271).

► We postulate that a critical seed free electron density exists due to multiphoton ionization to trigger avalanche ionization. ► The evolution of plasma formation is solved analytically for the first time. ► The analysis is applied to ablation in corneal epithelium and validated via comparison with experimental data. ► This model is further extended to the estimation of crater size in the ablation of tissue-mimic PDMS.Plasma-mediated ablation using ultrafast lasers in transparent media such as aqueous tissues is studied. It is postulated that a critical seed free electron density exists due to the multiphoton ionization in order to trigger the avalanche ionization which causes ablation and during the avalanche ionization process the contribution of laser-induced photon ionization is negligible. Based on this assumption, the ablation process can be treated as two separate processes – the multiphoton and avalanche ionizations – at different time stages; so that an analytical solution to the evolution of plasma formation is obtained for the first time. The analysis is applied to plasma-mediated ablation in corneal epithelium and validated via comparison with experimental data available in the literature. The critical seed free-electron density and the time to initiate the avalanche ionization for sub-picosecond laser pulses are analyzed. It is found that the critical seed free-electron density decreases as the pulse width increases, obeying atp−5.65 rule. This model is further extended to the estimation of crater size in the ablation of tissue-mimic polydimethylsiloxane (PDMS). The results match well with the available experimental measurements.

Keywords: Ablation; Ultrafast laser; Biological tissue

Oxidation behavior of multiwall carbon nanotubes with different diameters and morphology by Ilya Mazov; Vladimir L. Kuznetsov; Irina A. Simonova; Andrey I. Stadnichenko; Arkady V. Ishchenko; Anatoly I. Romanenko; Evgeniy N. Tkachev; Olga B. Anikeeva (pp. 6272-6280).

► We study oxidation of MWNT with different diameters and morphology. ► Oxidation induces defects and formation of oxygen-containing surface groups. ► Amount of surface functions depends of MWNT's and oxidizer's nature. ► Oxidation decreases conductivity of MWNT and changes its type. ► Commonly used oxidation step of MWNT must be used with caution.Multiwall carbon nanotubes (MWNT) with three medium diameters (20–22, 9–13, and 6–8nm) and different morphology were chemically oxidized using concentrated nitric acid, mixture of nitric and sulfuric acids (“mélange” solution) and mixture of sulfuric acid and hydrogen peroxide (“piranha” solution). Influence of MWNT type and structure as well as type of oxidizer on the surface composition and structure of nanotubes after oxidation was investigated. Acid–base titration, X-ray photoelectron spectroscopy and thermal gravimetric analysis were used for quantitative and qualitative investigation of surface group composition of initial and oxidized nanotubes. Amount of oxygen-containing groups on the surface of oxidized MWNT depends on the type of initial MWNT. It was found that ratio of different oxygen containing groups is less dependent on the type of oxidizer. Electrophysical properties of initial and oxidized nanotubes were investigated in temperature range 4–293K and main types of electrical conductivity were determined. It was shown that oxidation results in decrease in electrical conductivity of all samples with simultaneous change in the conductivity mechanism. Dispersive behavior of initial and oxidized nanotubes in different commonly used solvents was investigated. It was shown that oxidation leads to the improvement of sedimentation stability of MWNT in polar solvents.

Keywords: Carbon nanotubes; Oxidation; Functionalization; Acid–base titration

Damage tolerance of Ti₃SiC₂ to high energy iodine irradiation by Lei. Zhang; Q. Qi; L.Q. Shi; D.J. O’Connor; B.V. King; E.H. Kisi; D.K. Venkatachalam (pp. 6281-6287).

► In this paper, it was the first time to find that a TiC or/and 3C-SiC (cubic β) nanocrystalline phase was formed under high fluence 2MeV I²⁺ irradiation to Ti₃SiC₂ MAX phase. ► However, a complete phase decomposition by irradiation did not take place even at 10.3dpa. ► Post irradiation annealing to temperatures of 500–800°C results in crystal regrowth of Ti₃SiC₂ and TiC phasesThe microstructure of high fluence 2MeV I²⁺ irradiated Ti₃SiC₂ has been studied by grazing incident X-ray diffraction (GIXRD) using synchrotron radiation. The shift and broadening of the observed diffraction peaks are due to a variety of defects ranging from atomic to micron scale in size. The observation of the surface micrograph reveals the microcrack formation at grain boundaries due to high irradiation damage. The Raman spectrum of Ti₃SiC₂ was measured and compared with that of TiC_0.67. It was found that a TiC nanocrystalline phase was formed under the high dose irradiation. However, a complete decomposition by irradiation did not take place even at 10.3dpa. Post irradiation annealing to temperatures of 500–800°C results in crystal regrowth of Ti₃SiC₂ and TiC phases.

Keywords: PACS; 29.20.dk; 61.80.Jh; 78.70.Bj; 81.05.JeMAX phase; Ion irradiation; X-ray diffraction

Structural characteristics of mixed oxides MO_x/SiO₂ affecting photocatalytic decomposition of methylene blue by V.M. Gun’ko; J.P. Blitz; B. Bandaranayake; E.M. Pakhlov; V.I. Zarko; I.Ya. Sulym; K.S. Kulyk; M.V. Galaburda; V.M. Bogatyrev; O.I. Oranska; M.V. Borysenko; R. Leboda; J. Skubiszewska-Zięba; W. Janush (pp. 6288-6296).

► Thermal treatment of SiO₂/TiO₂ mixed oxides result in separation of the SiO₂ and TiO₂ phases providing an increased TiO₂ anatase crystalline phase content. ► The increased anatase content after thermal treatment is correlated with the increased photocatalytic degradation ability of these materials with the organic dye methylene blue. ► The photocatalytic degradation ability did not directly correlate with properties other than crystallinity for any of the mixed oxides studied (CeO₂/SiO₂, CeO₂, ZrO₂/CeO₂/SiO₂, TiO₂/Fe₂O₃/SiO₂). These properties included surface area, particle size, zeta potential, surface charge density, and calculated band gap energy.A series of photocatalysts based on silica (nanoparticulate) supported titania, ceria, and ceria/zirconia were synthesized and characterized by a variety of techniques including surface area measurements, X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential, surface charge density, and photocatalytic behavior toward methylene blue decomposition. Thermal treatment at 600°C increases the anatase content of the titania based catalysts detected by XRD. Changes in the infrared spectra before and after thermal treatment indicate that at low temperature there are moreSiOTi bonds than at high temperature. As these bonds break upon heating the SiO₂ and TiO₂ separate, allowing the TiO₂ anatase phase to form. This results in an increased catalytic activity for the thermally treated samples. Nearly all titania based samples exhibit a negative surface charge density at pH 7 (initial pH of photocatalytic studies) which aids adsorption of methylene blue. The crystallinity of ceria and ceria/zirconia based catalysts are in some cases limited, and in others non-existent. Even though the energy band gap ( E_g) can be lower for these catalysts than for the titania based catalysts, their photocatalytic properties are inferior.

Keywords: PACS; 61.43.Gt (Powders porous materials); 68.08.-p (Liquid–solid interfaces); 68.43.-h (Chemisorption/physisorption: adsorbates on surfaces); 68.35.Md (Surface thermodynamics surface energies)Fumed silica substrate; Grafted titania; Ceria; Ceria–Zirconia; Structural characteristics; Crystallinity; Methylene blue; Photocatalysis

Effect of annealing ambient on electrical and optical properties of Ga-doped Mg_xZn1−_xO films by Jinming Liu; Xiaoru Zhao; Libing Duan; Huinan Sun; Xiaojun Bai; Liu Chen; Changle Chen (pp. 6297-6301).

► Ga-doped Mg_xZn1−_xO films post-annealed in different ambient are investigated. ► Electrical and optical properties of the films are studied. ► Provide tradeoffs of the films with different optical transparency and resistivity.2at.% Ga-doped Mg_xZn1−_xO ( x=0–8%) films have been prepared by sol–gel dip-coating method, and the effects of three different post annealing ambient: (a) vacuum annealing under air pressure of ∼10⁻²Pa; (b) annealing in nitrogen atmosphere, and (c) annealing in argon-hydrogen (96%argon+4%hydrogen) atmosphere on the electrical and optical properties of the films are investigated. When treated by these three different post-annealing ambient, both the resisitivity and band gap of the films increase with Mg doping contents increasing from 0 to 8at.%. The vacuum annealed films show much lower resistivity than those treated in nitrogen or argon–hydrogen atmosphere, and the transmittance of the vacuum annealed films (∼70%) is also lower than those annealed by the other two methods (∼90%) in visible region. It shows that different post annealing ambient and ion doping could modify the optoelectronic properties of ZnO films.

Keywords: Ga doping; Mg; _x; Zn; 1−; _x; O films; Sol–gel; Annealing process

Combination of static time of flight secondary ion mass spectrometry and infrared reflection–adsorption spectroscopy for the characterisation of a four steps built-up carbohydrate array by Gemma Leone; Marco Consumi; Stefania Lamponi; Agnese Magnani (pp. 6302-6315).

► In this study we realised a four step built-up carbohydrate array. ► ToF-SIMS and RAIRS confirmed the bond and a correct orientation. ► PCA and cluster analysis confirmed the validity of the results. ► The discriminating action of the supports versus cell adhesion was demonstrated.Carbohydrate microarrays are essential tools to determine functions of glycans. In this work we analysed the applicability of a four-step procedure, previously used to monolayers [G. Leone, M. Consumi, A. Tognazzi, A. Magnani, Realisation and chemical characterisation of a model system for saccharide-based biosensor, Thin Solid Films 519 (2010) 462–470], for the realisation of micropatterned substrates. The applicability was demonstrated by a combination of static time of flight secondary ion mass spectrometry and infrared reflection–adsorption spectroscopy (ToF-SIMS) which permitted not only to confirm the functionalisation of the substrates but also to detect the orientation of bound molecules. The ToF-SIMS raw data were also analysed by principal component analysis and cluster analysis to minimise the bias and confirm the validity of the results. The discriminating action of the modified supports versus cell adhesion was also demonstrated.

Keywords: SAMs; Click-chemistry; ToF-SIMS; RAIRS; Saccharides

Effect of electroplating polyaniline on electrochemical kinetics of La–Mg–Ni-based hydrogen storage alloy by Wenzhuo Shen; Shumin Han; Yuan Li; Shuqin Yang; Qi Miao (pp. 6316-6320).

► Technique of PANI electroplated La–Mg–Ni-based hydrogen storage alloy is found. ► PANI films are deposited on the surface of the alloy uniformly. ► Electrochemical kinetics property of La–Mg–Ni-based alloy is improved by PANI-coated. ► Suitable time of PANI-coated technique is about 2min.A new polyaniline (PANI)-coated technique is adopted for the La–Mg–Ni-based alloy La_0.80Mg_0.20Ni_2.70Mn_0.10Co_0.55Al_0.10 in order to advance its electrochemical kinetic characteristics. In this treatment, the aniline monomers are electroplated on the alloy particles to form polyaniline films. FE-SEM observation and UV–vis analysis results revealed that the coral-like atrovirens PANI particles are deposited on the surface of the alloy. Through the PANI-coating the capacity retention rate at the 200th cycle of the La–Mg–Ni-based alloy electrodes amounts up from original 82.3% to 86.4% and the high rate discharge ability increased from 24.7% to 35.6% at a discharge current density of 1500mAg⁻¹. Linear polarization, anodic polarization and cyclic voltammetry measurements suggest that charge-transfer resistance decreases and the hydrogen absorption rate of the alloys increases after PANI-coating.

Keywords: Hydrogen storage alloy; Polyaniline; Surface treatment; Electrochemical characteristics; Kinetics

Modification of an enzyme electrode by electrodeposition of hydroquinone for use as the anode of a glucose fuel cell by Takashi Kuwahara; Hiraku Yamazaki; Mizuki Kondo; Masato Shimomura (pp. 6321-6325).

► An enzyme electrode was modified with polyhydroquinone (PHQ) by electrodeposition. ► The electrodeposited PHQ functioned as an electron-transferring mediator. ► The PHQ-modified enzyme electrode was used as an anode of a biofuel cell.An electrode having immobilized glucose oxidase (GOx) was modified with polyhydroquinone (PHQ), which was employed as an electron-transferring mediator, by a simple electrochemical method and used as the anode of a glucose fuel cell. The GOx-immobilized electrode was fabricated by attaching polyallylamine (PAAm) and then GOx covalently onto a gold electrode covered with a monolayer formed with 3-mercaptopropionic acid. Subsequently, the GOx-immobilized electrode (GOx/PAAm electrode) was modified with PHQ by electrodeposition of hydroquinone. The cyclic voltammogram of the modified electrode (PHQ/GOx/PAAm electrode) in a phosphate buffer solution (0.10M, pH 7.0) showed redox peaks due to the electrodeposited PHQ, whereas no redox peaks were found for the GOx/PAAm electrode in the buffer solution containing p-benzoquinone (BQ). The onset potential of glucose oxidation with the PHQ/GOx/PAAm electrode became ca. 0.2V more negative than that observed with the GOx/PAAm electrode in the presence of BQ. The glucose fuel cell equipped with the PHQ/GOx/PAAm electrode as an anode gave a 3 times larger power output than the cell with the GOx/PAAm electrode using dissolved quinone as the mediator.

Keywords: Biofuel cell; Electrodeposition; Electron transfer; Glucose oxidase; Hydroquinone

A simple method to synthesize modified Fe₃O₄ for the removal of organic pollutants on water surface by Ling Zhu; Chuanhao Li; Juan Wang; Hui Zhang; Jian Zhang; Yuhua Shen; Cun Li; Cuiping Wang; Anjian Xie (pp. 6326-6330).

► Fe₃O₄ was prepared by a partial oxidation of Fe²⁺ in air without N₂ gas protection. ► Different morphologies of Fe₃O₄ were obtained via adjusting the alkali source. ► Modified Fe₃O₄ can easily be synthesized by interaction betweenCOO⁻ and FeOH. ► Sodium oleate modified Fe₃O₄ is both super-hydrophobic and lipophilic. ► Modified Fe₃O₄ shows an important application in the removal of organic pollutants.In this article, a simple, economic and environment-friendly approach is explored to prepare Fe₃O₄ nanoparticles by using air oxidation at room temperature. Furthermore, the Fe₃O₄ magnetic nanoparticles (MNPs) have been modified with sodium oleate successfully to form super-hydrophobic surfaces. The alkali source played an important role in controlling the morphologies of Fe₃O₄ MNPs. Either Fe₃O₄ MNPs or sodium oleate modified Fe₃O₄ MNPs possessed good magnetic property, and the as-prepared modified Fe₃O₄ nanoparticles are both hydrophobic and lipophilic. Therefore, Fe₃O₄/sodium oleate could be dispersed stable in the oil medium and have been applied in the cleanup engine oil from the water surface. It will open up a potential and broad application in wastewater treatment.

Keywords: Magnetic materials; Surface; Nanoparticles; Hydrophobic; Lipophilic; Oil removal

Corrosion behavior of titanium alloy Beta-21S coated with diamond like carbon in Hank's solution by L. Mohan; C. Anandan; V.K. William Grips (pp. 6331-6340).

► Carbon ion implantation leads to carbide formation and facilitates DLC deposition on titanium alloy. ► Corrosion resistance of the implanted layer in Hanks solution is lower than the substrate. ► Corrosion resistance is restored by deposition of DLC coating on the implanted layer. ► XPS results show that during corrosion process, the carbide is replaced by oxide.Diamond like carbon (DLC) coatings posses high hardness and low friction coefficient and also biocompatible, hence, they are of interest for enhancing the wear and corrosion resistance of bio-implant materials. Beta stabilized titanium alloys are attractive for biomedical applications because of their high specific strength and low modulus. In this work Beta-21S alloy (Ti–15Mo–3Nb–3Al–0.2Si) was implanted with carbon ions by plasma immersion ion implantation using methane and hydrogen gas mixture followed by DLC deposition by plasma enhanced chemical vapour deposition (PECVD). The implanted layers enabled deposition of adherent diamond-like carbon coatings on the titanium alloy which was otherwise not possible. The corrosion behavior of the treated and untreated samples was investigated through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies in simulated body fluid (Hank's solution). XPS, micro Raman and EDAX investigation of the samples showed the formation of a thin oxide layer on the treated samples after corrosion experiments. Corrosion resistance of the DLC coated sample is comparable with that of the untreated samples. Electrochemical impedance data of the substrate and implanted samples were fitted with two time constant equivalent circuits and that of DLC coated samples with two-layer model.

Keywords: Diamond like carbon; Titanium alloy; XPS; Plasma immersion ion implantation; Corrosion

Adsorption and surface reaction of bis-diethylaminosilane as a Si precursor on an OH-terminated Si (001) surface by Seung-Bin Baek; Dae-Hee Kim; Yeong-Cheol Kim (pp. 6341-6344).

The adsorption energy and reaction energy barrier between BDEAS and OH-terminated Si (001) surface were 0.60eV and 0.52eV, respectively. When the surface reaction energy barrier was lower than the adsorption energy, BDEAS would react with the surface instead of being desorbed.Display Omitted► Initial reaction mechanism between BDEAS and Si (001) surface was investigated. ► Adsorption configuration affects adsorption energy and reaction energy barrier. ► Adsorption energy should be higher than reaction energy barrier for ALD reaction.The adsorption and the surface reaction of bis-diethylaminosilane (SiH₂[N(C₂H₅)₂]₂, BDEAS) as a Si precursor on an OH-terminated Si (001) surface were investigated to understand the initial reaction mechanism of the atomic layer deposition (ALD) process using density functional theory. The bond dissociation energies between two atoms in BDEAS increased in the order of SiH, SiN, and the rest of the bonds. Therefore, the relatively weak SiH and SiN bonds were considered for bond breaking during the surface reaction. Optimum locations of BDEAS for the SiH and SiN bond breaking were determined on the surface, and adsorption energies of 0.43 and 0.60eV, respectively, were obtained. The SiH bond dissociation energy of the adsorbed BDEAS on the surface did not decrease, so that a high reaction energy barrier of 1.60eV was required. On the other hand, the SiN bond dissociation energy did decrease, so that a relatively low reaction energy barrier of 0.52eV was required. When the surface reaction energy barrier was higher than the adsorption energy, BDEAS would be desorbed from the surface instead of being reacted. Therefore, the SiN bond breaking would be dominantly involved during the surface reaction, and the result is in good agreement with the experimental data in the literature.

Keywords: Bond dissociation energy; Adsorption; Surface reaction; Bis; -diethylaminosilane; Atomic layer deposition; Density functional theory

Fly ash adsorbents for multi-cation wastewater treatment by Maria Visa; Luminita Isac; Anca Duta (pp. 6345-6352).

Class “F” fly ash (FA), collected from the Central Heat and Power (CHP) Plant Brasov (Romania), with oxides composition SiO₂/Al₂O₃ over 2.4 proved good adsorbent properties. A new adsorbent material, FA-Z, was obtained from this fly ash and was investigated as substrate for complex adsorption processes in a three-component pollutant system, containing lead, zinc and cadmium cations. The adsorption studies proved that the novel material is highly active in lead removal from mixtures also containing cadmium and zinc, on a broad concentration range and after a low contact time.Display Omitted► The FA-Z was investigated for adsorption processes in a tricomponent pollutant system. ► The process selectivity was analyzed considering ionic radii of cations. ► The results were compared with those for micro- and macroporous cation exchangers. ► The FA-Z can replace the synthetic ion exchanger in cations selective adsorption.Class “F” fly ash (FA), collected from the Central Heat and Power (CHP) Plant Brasov (Romania), with oxides composition SiO₂/Al₂O₃ over 2.4 proved good adsorbent properties, and was further used for obtaining a new substrate with good adsorption capacity for heavy metals from multi-cation wastewater treatment. Firstly, the new adsorbent was characterized by AFM, XRD, DSC, FTIR and the surface energy was evaluated by contact angle measurements. The experimental data suggested that the new type of substrate is predominant crystalline with highly polar surface.The substrate was used for removing the Pb²⁺, Cd²⁺ and Zn²⁺ cations from mixed solutions. The results show high efficiency and selective adsorption the Pb²⁺ and Zn²⁺ cations.The optimized adsorption parameters were further used in thermodynamic and kinetic studies of the adsorption processes. The Langmuir and Freundlich models were used to describe the processes. The pseudo-second order kinetics could well model all the processes, indicating a surface concentration of the adsorption sites with the same order of magnitude as the cation concentrations.

Keywords: Fly ash; Heavy metals; Adsorption; Wastewater treatment

In vitro degradation of biodegradable polymer-coated magnesium under cell culture condition by Liping Xu; Akiko Yamamoto (pp. 6353-6358).

► Degradation behavior of 4 kinds of polymer-coated Mg under cell culture condition. ► All kinds of polymer coating effectively decreased Mg²⁺ release. ► SEM and EDX analysis revealed corrosion layer underneath the polymer coating. ► X-ray CT showed corrosion depth of PLLA-coated Mg 3 times smaller than PCL-coated.Magnesium (Mg) coated with four kinds of polymers, poly (l-lactic acid) (PLLA)-high molecular weight (HMW), PLLA-low molecular weight (LMW), poly (ɛ-caprolactone) (PCL)-HMW and PCL-LMW, and uncoated Mg were immersed under cell culture condition to study the degradation/corrosion behavior of the polymer-coated Mg. The releases of Mg²⁺ are measured during the immersion. Surface morphology and chemical composition are observed and identified by SEM and EDX. The tomography is obtained by X-ray CT observation and degradation rate is calculated by image analysis after 10-day immersion. All kinds of polymer-coated Mg showed significantly low release of Mg²⁺ ( p<0.05) in the whole immersion process comparing to that of uncoated Mg. In SEM and EDX results show, a corrosion layer can be observed on both polymer-coated and uncoated Mg after immersion. There is no obvious difference on the morphology and chemical composition of the corrosion layer between polymer-coated and uncoated Mg, indicating the corrosion/degradation process and corrosion product of Mg substrate are not changed by the polymer films under the present condition compared with uncoated Mg. Concerning the tomography and degradation rate of 10-day immersion, it can be found that the polymer-coated Mg shows a significantly low corrosion rate ( p<0.05) compared with that of uncoated Mg. PLLA coated Mg shows relatively uniform corrosion than PCL coated Mg and uncoated Mg. The largest pitting corrosion depth of PCL-LMW is about 3 times as large as the PLLA-LMW, which might be attributed to the difference of polymer microstructure. It is suggested that PLLA coating might be a suitable option for retarding the loss of mechanical properties of Mg substrate.

Keywords: Magnesium; Surface modification; Biodegradable polymer coating; Degradation/corrosion; Cell culture condition

Facile fabrication and characterization of poly(tetrafluoroethylene)@polypyrrole/nano-silver composite membranes with conducting and antibacterial property by Zhiquan Shi; Hui Zhou; Xutang Qing; Tingyang Dai; Yun Lu (pp. 6359-6365).

► We prepared two kinds of poly(tetrafluoroethylene)@ polypyrrole/nano-silver composite membranes. ► Both of them have suitable for gas/solid isolation with bi-functionality of conducting and antibacterial property. ► They can annihilate the bacteria filled in the air at the same time of air filtration due to the existence of nano-silver.Porous poly(tetrafluoroethylene) (PTFE) membranes play an important role in air purification and separation engineering. To achieve the bi-functionality of conducting and antibacterial property, two kinds of poly(tetrafluoroethylene)@ polypyrrole/nano-silver composite membranes have been prepared. One involves hydrophobic polypyrrole/nano-silver composite with hollow capsule nanostructures immobilized on the surface of the PTFE membranes. The other is a type of composite membranes with polypyrrole/nano-silver composite wholly packed on the fibrils of the expand PTFE membrane to form core/shell coaxial cable structures. The structure and morphology of the two kinds of composite membranes have been characterized by FTIR, UV–vis, XRD, TGA and SEM measurements. Possible formation mechanisms of the hollow capsules and the core/shell nanocable structures have been discussed in detail. The antibacterial effects of composite membranes are also briefly investigated.

Keywords: Poly(tetrafluoroethylene); Silver; Polypyrrole; Conducting polymers; Antimicrobial activity

Improving the controlled release of water-insoluble emodin from amino-functionalized mesoporous silica by Yunqiang Xu; Chunfeng Wang; Guowei Zhou; Yue Wu; Jing Chen (pp. 6366-6372).

► Amino-functionalized SBA-15 were prepared by co-condensation of TEOS and APTES. ► Functionalized SBA-15 were employed for the controlled release of emodin. ► Drug loading capacities were depended on the surface areas and pore diameters of the carriers. ► Functionalization of mesoporous SBA-15 could efficiently retard drug release and prolong release time period.Several types of amino-functionalized mesoporous silica, including F5-SBA-15, F10-SBA-15, and F15-SBA-15 were prepared through co-condensation of tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES) in varying molar ratios (5mol%, 10mol%, and 15mol%) via a hydrothermal process. The materials obtained were characterized by means of small-angle X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption–desorption, Fourier transformed infrared spectra, and X-ray photoelectron spectroscopy. Increasing APTES molar ratios decreased the degree of orderliness of the functionalized mesoporous silica. Pure and amino-functionalized SBA-15 samples were employed as supports for the controlled release of water-insoluble drug emodin. Loading experiments showed that drug loading capacities mainly depended on the surface areas and pore diameters of the carriers. Controlled release profiles of emodin-loaded samples were studied in phosphate buffered saline (PBS, pH 7.4), and results indicated that the emodin release rate could be controlled by surface amino-functionalized carriers. Emodin loaded on functionalized mesoporous supports exhibited a lower release rate than that of loaded on pure SBA-15, emodin loaded on F10-SBA-15 showed the smallest release amount (71.74wt%) after stirring in PBS for 60h. Findings suggest that functionalized mesoporous SBA-15 is a promising carrier for achieving prolonged release time periods.

Keywords: Amino-functionalized mesoporous silica; Co-condensation; Controlled release; Water-insoluble; Emodin

Alteration of Mn exchange coupling by oxygen interstitials in ZnO:Mn thin films by Usman Ilyas; R.S. Rawat; Y. Wang; T.L. Tan; P. Lee; R. Chen; H.D. Sun; Fengji Li; Sam Zhang (pp. 6373-6378).

► Oxygen rich ZnO:Mn thin films deposition by simple spin coating technique. ► Incorporation of tetrahedral Mn²⁺ ions at lattice sites Zn²⁺ ions without any impurity phase formation. ► Enhanced optical transparency and optical band gap with increasing Mn doping concentration. ► Deep level emissions in yellow spectral region confirmed the presence of oxygen interstitials. ► Origin of ferromagnetism in Mn-defect pair exchange coupling with oxygen interstitials.The un-doped and Mn doped ZnO thin films, with oxygen rich stoichiometry, were deposited onto Si (100) substrate using spin coating technique. The structural analysis revealed the hexagonal wurtzite structure without any impurity phase formation. A consistent increase in cell volume with the increase in Mn doping concentration confirmed the successful incorporation of bigger sized tetrahedral Mn²⁺ ions (0.83Å) in ZnO host matrix that was also endorsed by the presence of Mn 2p_3/2 core level XPS spectroscopic peak. Extended deep level emission (DLE) spectra centered at ∼627nm confirmed the presence of oxygen interstitials. Moreover, the magnetic measurements of field dependent M– H curves revealed the origin of ferromagnetic ordering from Mn-defect pair exchange coupling with oxygen interstitials in ZnO host matrix.

Keywords: ZnO:Mn thin films; Spin coating technique; Oxygen interstitials; Dilute magnetic semiconductors (DMS); Room temperature ferromagnetism (RTFM)

Removal of nanoparticles from a silicon wafer using plasma shockwaves excited with a femtosecond laser by Jung-Kyu Park; Ji-Wook Yoon; Sung-Hak Cho (pp. 6379-6383).

Display Omitted► The experimental setup for the removal of nanoparticles using plasma shockwaves formed by a femtosecond pulsed laser. ► Removal of PSL nanoparticles from the silicon wafer surface as a function of the gap distance and particle counting. ► The removal efficiency of the nanoparticles reached 95% without surface damage when the gap distance was 150μm.Experiments on the cleaning effect of 100nm-sized polystyrene latex (PSL) particles on silicon wafers using plasma shockwaves excited via a femtosecond (130fs) Ti:Sapphire laser ( λ_p=790nm) are reported. By the scan of wafer using the X–Y–Z stage during excited plasma shockwave, the removal variation of nanoparticles on surface was observed in situ before and after plasma shockwave occurred. The cleaning efficiency was strongly dependent on the gap distance between the plasma formation point and the surface. The removal efficiency of the nanoparticles reached 95% without surface damage when the gap distance was 150μm.

Keywords: Dry cleaning; Laser cleaning; Nanoparticle removal; Femtosecond laser; Plasma shockwave

Friction and wear behavior of nanosilica-filled epoxy resin composite coatings by Yingke Kang; Xinhua Chen; Shiyong Song; Laigui Yu; Pingyu Zhang (pp. 6384-6390).

► The SiO₂ may possess desired activity and functionality toward strengthening EP matrix. ► The wetting behavior and the tribological character were dicussed. ► The optimum of the lowest coefficient of friction of the epoxy-nanosilica composite films were found out.Hydrophilic silica nanoparticles (abridged as nano-SiO₂) surface-capped with epoxide were dispersed in the solution of epoxy resin (abridged as EP) in tetrahydrofuran under magnetic stirring. Resultant suspension of nano-SiO₂ in EP was then coated onto the surface of glass slides and dried at 80°C in a vacuum oven for 2h, generating epoxy resin-nanosilica composite coatings (coded as EP/nano-SiO₂). EP coating without nano-SiO₂ was also prepared as a reference in the same manner. A water contact angle meter and a surface profiler were separately performed to measure the water contact angles and surface roughness of as-prepared EP/nano-SiO₂ composite coatings. The friction and wear behavior of as-prepared EP/nano-SiO₂ composite coatings sliding against steel in a ball-on-plate contact configuration under unlubricated condition was evaluated. Particularly, the effect of coating composition on the friction and wear behavior of the composite coatings was highlighted in relation to their microstructure and worn surface morphology examined by means of scanning electron microscopy. Results indicate that EP/nano-SiO₂ composite coatings have a higher surface roughness and water contact angle than EP coating. The EP-SiO₂ coatings doped with a proper amount of hydrophilic SiO₂ nanoparticles show lower friction coefficient than EP coating. However, the introduction of surface-capped nanosilica as the filler results in inconsistent change in the friction coefficient and wear rate of the filled EP-matrix composites; and it needs further study to achieve well balanced friction-reducing and antiwear abilities of the composite coatings for tribological applications.

Keywords: Epoxy resin; Silica nanoparticle; Composite coating; Friction and wear behavior

First-principles study of CO and NO adsorption on transition metals doped (8,0) boron nitride nanotube by You Xie; Yi-Ping Huo; Jian-Min Zhang (pp. 6391-6397).

► The combining processes of CO and NO gas adsorption on TM-doped (8,0) BNNT are exothermic, accompanying with larger formation energies and charges transfer. ► The NO adsorption is more stable than CO adsorption on TM-doped (8,0) BNNT. ► The adsorption of CO and NO molecules leads to different magnetic and electronic properties.To explore the novel application of boron nitride nanotube (BNNT), we have investigated the structural, magnetic and electronic properties of CO and NO molecules adsorption on transition metals (TM=V, Cr, Mn, Fe, Co or Ni) doped (8,0) BNNT using first-principle calculations. The combining processes of all gas adsorption on TM-doped BNNT are exothermic, accompanying with larger formation energies and charges transfer showing that both CO and NO molecules present strong chemical interaction with the TM-doped BNNT, and the adsorption of NO is more stable than that of CO. The presence of CO molecule almost does not change the magnetic properties of the TM-BNNT systems. But the adsorption of NO gas on different sites of different TM doped BNNT has different magnetic moment. The adsorption of CO and NO molecules on TM-doped BNNTs leads to different electronic structure properties of BNNTs. Therefore, the TM-doped BNNT can be used as CO and NO gas sensor manufacturing raw materials, and it may be a potential material for nanodevice applications.

Keywords: Gas adsorption; Transition metal doping; Boron nitride nanotube; Electronic structure; First-principles

Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive by Jian-Hua Li; Mi-Zi Li; Jing Miao; Jia-Bin Wang; Xi-Sheng Shao; Qi-Qing Zhang (pp. 6398-6405).

► A novel amphiphilic zwitterionic copolymer PVDF-g-PSBMA was firstly synthesized by ATRP. ► The PVDF-g-PSBMA was used as membrane additive to prepare PVDF-g-PSBMA/PVDF blend membrane. ► The surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface property.An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR–ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane–coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

Keywords: PVDF membrane; Amphiphilic zwitterionic copolymer; Hydrophilicity; Anti-fouling ability

Fractal analysis of engineering ceramics ground surface by Xiaohu Liang; Bin Lin; Xuesong Han; Shangong Chen (pp. 6406-6415).

► In general, the texture in engineering ceramics surface is fine and dense, when the fractal dimension is high. ► The size order of fractal dimension is steel, zirconia, silicon nitride and alumina. It is the same as the order of fracture toughness of four materials. ► With the higher value of the fractal dimensions, they can indicate the better wear resistance for the same material.Traditional methods of roughness characterization cannot properly reflect the differences between metal and engineering ceramics surfaces. Therefore, fractal method is introduced to characterize the engineering ceramics ground surface in this paper. This article compares various methods to calculate profile dimension. By comparison, the variation method is suitable for extracting fractal dimension of engineering ceramics ground surface. The precision of variation method is further improved by modifying the error. In view of engineering ceramics ground surface, we have analyzed the relationship between fractal dimension and traditional roughness parameters, surface texture, surface function and material property using modified variation method.

Keywords: Engineering ceramics; Grinding; Fractal analysis; Surface topography

Mechanism of wettability transition in copper metal foams: From superhydrophilic to hydrophobic by Mahmood R.S. Shirazy; Sonia Blais; Luc G. Fréchette (pp. 6416-6424).

Display Omitted► We corrected a misconception on the role of oxides on wettability in heat pipes. ► Time of spreading of a droplet is used to measure the rate of hydrophilicty loss. ► Samples in ambient air become hydrophobic but not in pure air or nitrogen. ► XPS and TOF-SIMS show carbon content increases when samples are in ambient air. ► We show the link between increasing the carbon and hydrophobicity in foams.Hydrophilicity is a necessary condition for wicking materials such as copper metal foams used in heat pipes. Unfortunately hydrophilic copper metal foams become hydrophobic when exposed to room ambient air. This wettability transition is commonly explained by the formation of copper oxides on the surface; however copper oxides are known to be hydrophilic. An experimental study is conducted to explain this controversy. Effect of different atmospheres on the rate of hydrophilicity loss is studied by a novel approach which is to measure the spreading time of droplet on the foam surface. Also, surface characterization techniques such as XPS and TOF-SIMS are used to characterize the time dependent impact of the ambient air on the morphology and chemical composition of the copper metal foams. The hydrophobicity mechanism of copper metal foams is found to be dominated by surface chemistry and not its morphology (Wenzel type). Results show that oxidation is not the reason for this hydrophilic to hydrophobic change but rather, adsorption of volatile organic compounds (VOCs) on the copper foam's surface. This explanation is further supported by observing the same wettability change towards hydrophobicity when immersing hydrophilic copper metal foams in a liquid VOC (α-pinene).

Keywords: Heat pipe; Wick; Metal foam; Wetting; Hydrophilicity; Organic compound

Al–Cu intermetallic coatings processed by sequential metalorganic chemical vapour deposition and post-deposition annealing by Lyacine Aloui; Thomas Duguet; Fanta Haidara; Marie-Christine Record; Diane Samélor; François Senocq; Dominique Mangelinck; Constantin Vahlas (pp. 6425-6430).

► Sequential MOCVD of Al and Cu metals. ► Process feasibility ensured by appropriate selection of Al and Cu MOCVD precursors. ► Al/Cu ratio and annealing temperature drives the nature of Al–Cu phases. ► In situ monitored post deposition annealing allows formation of targeted Al–Cu phases.Sequential processing of aluminum and copper followed by reactive diffusion annealing is used as a paradigm for the metalorganic chemical vapour deposition (MOCVD) of coatings containing intermetallic alloys. Dimethylethylamine alane and copper N,N′-di-isopropylacetamidinate are used as aluminum and copper precursors, respectively. Deposition is performed on steel and silica substrates at 1.33kPa and 493–513K. Different overall compositions in the entire range of the Al–Cu phase diagram are obtained by varying the relative thickness of the two elemental layers while maintaining the overall thickness of the coating close to 1μm. As-deposited films present a rough morphology attributed to the difficulty of copper to nucleate on aluminum. Post-deposition annealing is monitored by in situ X-ray diffraction, and allows smoothening the microstructure and identifying conditions leading to several Al–Cu phases. Our results establish a proof of principle following which MOCVD of metallic alloys is feasible, and are expected to extend the materials pool for numerous applications, with innovative thin film processing on, and surface properties of complex in shape parts.

Keywords: Aluminides; Intermetallics; Chemical vapour deposition; Coatings; Annealing

Graded porous glasses for antireflective applications formed by chemical treatment by Ying Du; Hongbo He; Yunxia Jin; Fanyu Kong; Heyuan Guan; Zhengxiu Fan (pp. 6431-6435).

► Antireflective structures were prepared on borosilicate glass using aqueous solutions ► We analyze the morphology, composition and optical property of glasses before and after etching. ► Etching effects depend on glass composition, solution concentration and etching time. ► The transmittance of glass substrate can be improved after chemical treatment, and the laser-induced damage threshold of graded porous glass is much higher than that of antireflective coatings. ► The SEM and EDS results revealed a significant corrosion process in the solution.Porous glass surface can be achieved by the neutral-solution etch process, which has been reported to be effective in suppressing light reflection from glasses. Samples of a commercial borosilicate glass were submitted to a static aqueous corrosion at 87°C for several hours for introducing porosity on glass surface. Morphology, composition and optical properties of the surface, which were analyzed by scanning electron microscope (SEM), energy dispersive spectrum (EDS) and spectrometer, can be controlled by changing both the neutral-solution concentration and etching time. The results show that the transmittance of glass substrate can be improved after chemical treatment, and the laser-induced damage threshold of graded porous glass is much higher than that of antireflective coatings. The SEM and EDS results revealed a significant corrosion process in the solution, and determined the relationship between the graded porosity and refractive index of glasses.

Keywords: Antireflection microstructure; Optical property; Laser-induced damage threshold; Morphology

A combination of electroless and electrochemical etching methods for enhancing the uniformity of porous silicon substrate for light detection application by N. Naderi; M.R. Hashim (pp. 6436-6440).

► A combination of electroless and electrochemical etching of silicon is introduced. ► A novel parameter called delay-time ( T_d) is optimized prior to applying pulsed current. ► The uniformity of fabricated porous silicon is enhanced by applying T_d=2min. ► The optimized porous structures show a noticeable Raman shift with small FWHM, representing good crystalline quality. ► Efficient photodetectors are fabricated on nano-structured porous silicon by a combination of electroless and electrochemical etching of silicon substrate.This paper reports on a combination of electroless and electrochemical etching of a silicon surface for enhancing the uniformity of fabricated porous silicon substrate and improving the sensitivity of photodetectors. Photo-assisted pulsed electrochemical etching of silicon is modified by introducing a novel parameter called delay time ( T_d), along with cycle time and pause time, of pulsed current, which can affect the morphology of pores. This technique offers the possibility of growing photoluminescent materials with uniform pores and selective wavelength emission. A sample with a T_d of 2min shows a significant increase in the intensity of the Raman spectrum (10 times stronger than that of the sample without T_d at 518.2cm⁻¹) due to the enhanced surface-assisted multi-phonon processes in porous film. A red-shift of 2.5cm⁻¹ and a peak broadening of 1.4 times are also observed for this porous sample compared with those of crystalline silicon. Porous surface properties and the performance of the optimized PS as photodetectors are discussed.

Keywords: Porous silicon; Electrochemical anodization; Raman spectroscopy; FTIR; MSM photodetectors

Grafting molecularly imprinted poly(2-acrylamido-2-methylpropanesulfonic acid) onto the surface of carbon microspheres by Yongzhen Yang; Yan Zhang; Sha Li; Xuguang Liu; Bingshe Xu (pp. 6441-6450).

Display Omitted► Molecularly imprinted polymer on carbon microsphere surface was obtained for adsorbing dibenzothiophene. ► The optimized conditions of grafting poly(2-acrylamido-2-methylpropanesulfonic acid) were obtained. ► The dynamic adsorption efficiency was 46%. ► This novel surface molecular imprinted material with priority adsorption is of importance for deep desulfurization of oil.Poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) was grafted on the surface of carbon microspheres (CMSs), which were modified in prior by a mixed acid (HNO₃ and H₂SO₄) oxidation and 3-methacryloxypropyl trimethoxysilane silanization. Then, the molecularly imprinting polymerization was carried out towards the macromolecule PAMPS grafted on the surface of CMSs using dibenzothiophene (DBT) as template, ethylene dimethacrylate as cross-linking agent and (NH₄)₂S₂O₈ (APS) as initiator to prepare surface molecularly imprinted polymer (MIP-PAMPS/CMSs) for adsorbing DBT. The optimized conditions of grafting PAMPS, including AMPS dosage, APS content, reaction temperature and reaction time, were emphasized in this paper. The morphology of the samples was characterized by field emission scanning electron microscopy. The functional groups were analyzed qualitatively by Fourier transform infrared spectrometry. The grafting degree of PAMPS was investigated by thermogravimetry. The results show that the preferable AMPS dosage, APS content, reaction temperature and time were 5g, 0.15g, 70°C and 12h, respectively, for preparing PAMPS/CMSs composite on the basis of 1.0g of silanized-CMSs. The absorbing characteristic of MIP-PAMPS/CMSs toward DBT was studied preliminarily with dynamic adsorption. In the experiment of dynamic adsorption, MIP-PAMPS/CMSs and non-imprinted polymer (NIP-PAMPS/CMSs) were compared with respect to their rapid adsorption in 1mmol/L of DBT solution in n-hexane. When the first 1mL of 1mmol/L DBT solution was injected and flowed through a column packed with 0.1g of MIP-PAMPS/CMSs, the content of DBT reduced to 0.265mmol/L, that is, decreased significantly from 279 to 74ppm. When 3mL of DBT solution was flowed through the packed column, the adsorption of MIP-PAMPS/CMSs toward DBT reached saturation with the maximum adsorption amount of 1.38×10⁻²mmol/g and the overall adsorption efficiency of 46%, while NIP-PAMPS/CMSs adsorbed only 1.66×10⁻³mmol/g of DBT. It is suggested that the MIP-PAMPS/CMSs had much better adsorption property towards DBT than NIP-PAMPS/CMSs.

Keywords: 2-Acrylamido-2-methylpropanesulfonic acid; Grafting; Carbon microspheres; Surface molecularly imprinted polymer; Adsorption

Gallium vacancies related yellow luminescence in N-face GaN epitaxial film by Huayong Xu; Xiaobo Hu; Xiangang Xu; Yan Shen; Shuang Qu; Chengxin Wang; Shuqiang Li (pp. 6451-6454).

► Yellow luminescence in N-face n-type GaN was characterized. ► Outstanding increase of yellow luminescence in N-face GaN was observed after KOH etching. ► Correlation between the intensity of the YL and the concentration of Ga vacancies at the surface of KOH-etched n-face GaN was derived. ► Direct evidence shows that the yellow luminescence in n-type GaN is related to the Ga vacancies.To investigate the mechanism of the yellow luminescence (YL) in GaN, N-face GaN epitaxial film was prepared by wafer bonding and laser lift off from sapphire substrate. The exposed N-polar surface could be etched with potassium hydroxide aqueous solution. Intriguingly, we observed the yellow-to-band-edge luminescence ratio increased by 3.2 times after KOH etching. Since KOH etching is dislocation selective and changes the surface states of GaN, we associated the outstanding increase of YL to the presence of surface states instead of dislocations. It is further confirmed by X-ray photoelectron spectroscopy studies that the Ga vacancies dominate the YL in GaN.

Keywords: GaN; Yellow luminescence; Ga vacancy; XPS

Self assembly of positively charged carbon nanotubes with oppositely charged metallic surface by Ji-Young Hwang; Mohamed Eltohamy; Hae-Won Kim; Ueon Sang Shin (pp. 6455-6459).

.Display Omitted► Surface modification of implants (or scaffolds) with CNTs. ► Negatively charged surface of implants (or scaffolds). ► Coating of positively modified CNTs (CNT-Cl) by self assembly. ► New surface properties such as electrical conductivity, nanotopography, and favorable wettability.Surface modification of implants (or scaffolds) with CNTs is one of the most effective methods to create important surface properties such as electrical conductivity, new nanotopography, and favorable wettability, leading to effective control of the initial response of cells. A simple strategy to coat carbon nanotubes (CNTs) on the negatively charged and curved surface with a complex nanotopography of metal oxides and metallic substrates that are usually used as implants and scaffolds for medical purposes was developed. Positively modified CNTs (CNT-Cl) were used to ionically attach to the oppositely charged surface of the substrates. Model substrates such as TiO₂ and SiO₂ powders, Ti disc, and Ti-implants, which were curved, nano-structured and porous figures, were dipped into positively modified CNT solution (CNT-Cl/THF) and dried to create a uniform CNT-Cl coating layer. The uniformity of the CNT-Cl layer was confirmed by SEM images, and the physicochemical properties of the new surface were analyzed by XPS and contact angle measurement.

Keywords: Surface modification; Implants; Carbon nanotubes; Self assembly

Multi-modal TiO₂–LaFeO₃ composite films with high photocatalytic activity and hydrophilicity by Kun Gao; Shudan Li (pp. 6460-6464).

► TiO₂–LaFeO₃ film and LaFeO₃–TiO₂ film have been synthesized for the first time. ► The introduction of LaFeO₃ changed the micro-structure, the surface acidity and the interfacial charge transfer process of composite films. ► TiO₂–LaFeO₃ film and LaFeO₃–TiO₂ film exhibited superior photocatalytic activity and hydrophilicity.In this paper, a series of multi-modal TiO₂–LaFeO₃ composite films have been successfully synthesized through a two-step method. The resultant films were characterized in detail by several testing techniques, such as X-ray diffraction (XRD), ultraviolet–visible diffuse reflection spectrum (UV–vis DRS), photoluminescence spectrum (PL), surface photovoltage spectroscopy (SPS) and water contact angle measurements. The photocatalytic activity of different films was evaluated for degrading Methylene Blue (MB) aqueous solution. Hydrophilicity of the obtained TiO₂–LaFeO₃ composite films was also investigated. The results show that TL film and LT film exhibited superior photocatalytic activity and hydrophilicity.

Keywords: Oxides; Thin films; Surface properties; Optical properties; Photocatalytic activity

Efficient removal of aniline by a water-compatible microporous and mesoporous hyper-cross-linked resin and XAD-4 resin: A comparative study by Guqing Xiao; Liping Long (pp. 6465-6471).

In view of the high toxicity of nitrobenzene, a novel water-compatible microporous and mesoporous hyper-cross-linked resin modified with phenolic hydroxyl group GQ-03 was synthesized with the solvent of 1,2-dichloroethane. GQ-03 displayed higher adsorption capacity than XAD-4 because of the size matching between the pore diameter of GQ-03 and the molecular size of aniline, and hydrogen bonding between GQ-03 and aniline. As an ideal adsorbent for the removal of aniline, GQ-03 shows an excellent adsorption behavior and acceptable adsorption time.Display Omitted► In view of the toxicity of nitrobenzene, 1,2-dichloroethane was used as solvent. ► The BET surface area of water-compatible GQ-03 is up to be 1154.45m²/g. ► The microporous and mesoporous structure, and hydrogen bonding bring larger adsorption capacity. ► GQ-03 shows an excellent adsorption behavior as an ideal adsorbent.A novel water-compatible microporous and mesoporous hyper-cross-linked resin modified with phenolic hydroxyl group (named as GQ-03) was synthesized to remove aniline in aqueous solution as compared with XAD-4. The maximum adsorption capacity of GQ-03 emerged at the molecular state for both aniline and p-cresol while the pH dependency trend of aniline adsorbed onto XAD-4 was accordant with the dissociation curve of aniline. The ionic strength influenced the adsorption obviously. The pseudo-first-order rate equation could describe the adsorption process of aniline onto GQ-03 in two stages while this equation could characterize the entire adsorption process of XAD-4. The adsorption isotherms could be correlated to the Freundlich model, higher K_F and n values for GQ-03 than XAD-4. The breakthrough capacity and the total adsorption capacity of GQ-03 and XAD-4 was up to 47.2mgmL⁻¹ and 28.3mgmL⁻¹, 271.7mgmL⁻¹ and 115.6mgmL⁻¹, respectively. The size matching between the pore diameter of GQ-03 and the molecular size of aniline, and hydrogen bonding between GQ-03 and aniline resulted in the larger adsorption capacity.

Keywords: Hyper-cross-linked resin; XAD-4; Aniline; Adsorption

Refractory nanoporous materials fabricated using tungsten atomic layer deposition on silica aerogels by Anil U. Mane; John P. Greene; Jerry A. Nolen; Uma Sampathkumaran; Thomas W. Owen; Ray Winter; Jeffrey W. Elam (pp. 6472-6478).

Atomic layer deposition of conformal tungsten films on silica aerogels enables the synthesis of refractory nanoporous materials with tunable density and pore size. These materials maintain their mesoporosity even after heating to 1500°C in vacuum.Display Omitted► Silica aerogels were coated using tungsten atomic layer deposition (ALD). ► High porosity and surface area of aerogels were preserved during ALD. ► Monolith density could be tuned from 0.3 to 5.0g/cc. ► Nanoporous monoliths survived high temperature vacuum heating to 1500°C. ► Useful as rare-isotope catchers for short-lived radioactive isotope beams.We report an approach for preparing refractory nanoporous materials using high surface area silica aerogels as templates for the growth of conformal tungsten (W) coatings by atomic layer deposition (ALD). Nanoporous silica aerogel monoliths were prepared with a variety of initial pore sizes and initial densities in the range of 0.3–0.5g/cc using porogen extraction methods. Next, W ALD using Si₂H₆ and WF₆ reactants at 200°C was employed to coat the inner surfaces of the silica aerogels. After coating, scanning electron microscopy revealed a microstructure in which the ALD W completely encapsulated the silica aerogel micro-cells. The porosity of the aerogels was preserved during the first 10 W ALD cycles allowing the density to be controlled by adjusting the number of W ALD cycles to achieve densities as high as 5g/cc. Nitrogen adsorption surface area measurements revealed a gradual decrease in the surface area of the silica aerogels with increasing numbers of W ALD cycles, consistent with a partial filling of the aerogel voids. The high density nanoporous tungsten monoliths survived high temperature vacuum heating (1500°C) making them promising candidates for solid rare-isotope catchers that can be used in the production of short-lived radioactive isotope beams in facilities such as the facility for rare isotope beams (FRIB).

Keywords: Atomic layer deposition; Aerogel; Tungsten; Spallation target; Nanomaterial

Effects of boron doping in TiO₂ nanotubes and the performance of dye-sensitized solar cells by Alagesan Subramanian; Hong-Wen Wang (pp. 6479-6484).

► The effects of boron doping into TiO₂ nanotubes have been presented. ► Boron doping contributed to the conduction band shift in TiO₂. ► The boron-doped TiO₂ nanotube electrodes showed an enhanced performance compare to those of undoped TNAs. ► Effective retardation of the charge recombination reaction was observed in boron-doped TiO₂ electrode.Titanium nanotubes doped with boron used as the photoelectrode for dye-sensitized solar cells were investigated. The materials were characterized by SEM, XRD, and UV–vis spectroscopy and their photoconversion efficiencies were evaluated. The chemical compositions of TiO₂ nanotubes (TNA) and boron doped TNA (B-TNA) were identified by the energy dispersive X-ray spectroscopy (EDS). XRD evidenced the presence of anatase as the main phase and presented the existence of boron elements at interstitial sites between the TiO₂ lattices. The UV–vis spectra indicated the narrowing of band gap upon doping boron into titanium nanotubes. The photovoltaic properties were measured by a current–voltage meter under AM1.5 simulated light radiation. The boron-doped TiO₂ nanotube arrays showed an enhanced performance with a photocurrent density of 7.85±0.20mA/cm² and an overall conversion efficiency ( η) of 3.44±0.10%. The enhanced performance was attributed to the enhanced electron injection rate and retardation of the charge recombination, which could be due to perfect matching between the LUMO of dye molecules and the conduction band of TiO₂. Electrochemical impedance spectroscopy (EIS) measurement indicated the longer electron lifetime and reduced TiO₂/dye/electrolyte interface resistance for boron doped TiO₂ nanotubes than that of undoped TiO₂ nanotubes.

Keywords: Boron doping; TiO; ₂; nanotube; Dye-sensitized solar cell

Chemical and structural analysis of the bone-implant interface by TOF-SIMS, SEM, FIB and TEM: Experimental study in animal by Anders Palmquist; Lena Emanuelsson; Peter Sjövall (pp. 6485-6494).

► Time of flight-secondary ion mass spectroscopy (TOF-SIMS) is a valuable tool for assessing the chemical aspects of the bone-implant interface. ► TOF-SIMS analysis could be done in combination with other techniques such as light and electron microscopy. ► Chemical and structural analysis from macro to nano could be achieved by combining different techniques. ► Sample preparation induce artifacts which has to be considered for each analysis.Although bone-anchored implants are widely used in reconstructive medicine, the mechanism of osseointegration is still not fully understood. Novel analytical tools are needed to further understand this process, where both the chemical and structural aspects of the bone-implant interface are important. The aim of this study was to evaluate the advantages of combining time-of-flight secondary ion mass spectroscopy (TOF-SIMS) with optical (LM), scanning (SEM) and transmission electron microscopy (TEM) techniques for studying the bone-implant interface of bone-anchored implants. Laser-modified titanium implants with surrounded bone retrieved after 8 weeks healing in rabbit were dehydrated and resin embedded. Three types of sample preparation were studied to evaluate the information gained by combining TOF-SIMS, SEM, FIB and TEM. The results show that imaging TOF-SIMS can provide detailed chemical information, which in combination with structural information from microscopy methods provide a more complete characterization of anatomical structures at the bone-implant interface. By investigating various sample preparation techniques, it is shown that grinded cross section samples can be used for chemical imaging using TOF-SIMS, if careful consideration of potential preparation artifacts is taken into account. TOF-SIMS analysis of FIB-prepared bone/implant cross section samples show distinct areas corresponding to bone tissue and implant with a sharp interface, although without chemical information about the organic components.

Keywords: Osseointegration; Interface analysis; Time of flight-secondary ion mass spectroscopy (TOF-SIMS); Transmission electron microscopy (TEM); Focused ion beam (FIB)

Surface state of Y₃(Al,Ga)₅O₁₂:Tb phosphor under electron beam bombardment by A. Yousif; H.C. Swart; O.M. Ntwaeaborwa (pp. 6495-6503).

► The chemical stability of Y₃(Al,Ga)₅O₁₂:Tb phosphor was tested under prolonged electron beam exposure. ► The CL intensity of the Y₃(Al,Ga)₅O₁₂:Tb stabilized after removal of the chemisorbed species. ► X-ray photoelectron spectroscopy results suggested electron-beam induced formation of new interleave oxide layers. ► The interleave oxide layers acted as a protective layer inhibiting further CL intensity degradation. ► A lowering in the work function due to the new surface layers lead to an increase in the number of electrons for CL excitation.The surface state of Y₃(Al,Ga)₅O₁₂:Tb phosphor was determined before and after 27h of prolonged electron beam exposure. The electron irradiation was carried out at a base pressure of 2.3×10⁻⁸Torr and an oxygen pressure of 1.0×10⁻⁶Torr. New surface layers were formed after the chemisorbed species were removed as a result of electron stimulated surface chemical reactions. The rate of the removal of the chemisorbed species from the phosphor's surface during prolonged electron irradiation was affected by the background working atmosphere as measured with Auger electron spectroscopy combined with cathodoluminescence (CL) spectroscopy. The CL intensity of the Y₃(Al,Ga)₅O₁₂:Tb stabilized after removal of the chemisorbed species and stayed constant during further electron irradiation, indicating that this phosphor is good for the technology used in field emission displays. There was an increase in the Al, Y, O and Tb Auger peak intensities pointing to the formation of a complicated surface structure that was probably a combination of more than one chemical compound. X-ray photoelectron spectroscopy results suggested electron-beam induced formation of new interleave oxide layers, such as AlO_x, YO_x and Y(Al,Ga)O₃ on the surface. These oxide layers acted as a protective layer inhibiting further CL intensity degradation during prolonged electron irradiation.

Keywords: AES; NanoSAM; Photoluminescence; Cathodoluminescence; XPS; ESSCR; Electron degradation; Y; ₃; (Al,Ga); ₅; O; ₁₂; :Tb

The enhanced characteristics of osteoblast adhesion to porous Zinc–TiO₂ coating prepared by plasma electrolytic oxidation by Zhenxiang Zhang; Beibei Gu; Wenjie Zhang; Guangyu Kan; Junying Sun (pp. 6504-6511).

► Porous Zn–TiO₂ coating was prepared by plasma electrolytic oxidation in a novel Ca, P, Zn-containing electrolyte. ► Characteristics of the Zn-containing TiO₂ coating were investigated. ► Adhesion of MC3T3-E1 cells on Zn–TiO₂ coating, as well as its possible signal transduction pathway involved are discussed.Zinc-incorporated TiO₂ coating (Zn–TiO₂) was prepared on titanium (Ti) plate by plasma electrolytic oxidation (PEO) technique in the Ca, P, Zn-containing electrolyte. The surface topography, phase and element composition of the coatings were characterized by scanning electron microscopy, X-ray diffraction and energy dispersive spectrometer, respectively. Osteoblast-like MC3T3-E1 cell adhesion on Ti, TiO₂ and Zn–TiO₂ surfaces was evaluated and its possible signal transduction pathway involved was confirmed by the sequential gene expressions of integrin β₁, α₁, α₃ and α₅, focal adhesion kinase (FAK), and extracellular regulated kinases (ERK, including ERK1 and ERK2). The obtained results showed that Zn was successfully incorporated into the porous TiO₂ coating, which did not alter apparently its surface topography and phase composition. The adhesion of MC3T3-E1 cells on Zn-incorporated TiO₂ coating was significantly enhanced compared with that on the Zn-free TiO₂ coating and pure Ti plate. In addition, the enhanced cell adhesion on Zn–TiO₂ coating may be mediated by integrin (subunits β₁ and α₅) binding and subsequent signal transduction pathway (involving FAK and ERK1). The present work suggests that the Zn-incorporated porous TiO₂ coating produced by PEO technique is promising as a candidate for orthopedic implant applications.

Keywords: Key words; Plasma electrolytic oxidation; Zinc; TiO; ₂; Osteoblast; Adhesion

Microbiologically influenced corrosion (MIC) in stainless steel heat exchanger by E. Huttunen-Saarivirta; M. Honkanen; T. Lepistö; V.-T. Kuokkala; L. Koivisto; C.-G. Berg (pp. 6512-6526).

► Results from microstructural characterization of the corroded heat exchanger are reported. ► The bulk material contained austenite and ferrite, with the latter being preferentially attacked. ► Corrosion had occurred as microbiologically influenced corrosion (MIC). ► A mechanism by which the corrosion attack had proceeded is suggested.Corrosion attack in the form of corrosion product tubercles was observed in an AISI 304 (EN 1.4301) stainless steel heat exchanger only after 36 months of service. Failure analyses revealed that in one of the attacked areas corrosion had penetrated the entire wall thickness of 6.2mm, but in most of the cases it reached the depth of 2–4mm. In this paper, we report the results from a thorough microstructural characterization of the corroded heat exchanger carried out with optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffractometry (XRD).Microstructural studies by OM, SEM and XRD revealed a two-phase structure of austenite and ferrite in the bulk material, as well as the preferential attack of the ferrite phase. SEM surface studies disclosed bacteria in and close to the attacked areas. Cross-sectional SEM examinations showed the distribution and composition of corrosion products within and underneath the tubercles. TEM and XRD studies gave information about the amorphous and/or nanocrystalline nature of some of the formed corrosion products. These results are discussed in this paper and, based on them, the main corrosion mechanism for the observed attack is suggested. Further, explanations for the propagation of corrosion along the ferrite phase are presented.

Keywords: Stainless steel; Microbiological corrosion; Passivation; Austenite; Ferrite

Synthesis and tribological properties of diamond-like carbon films by electrochemical anode deposition by Yang Li; GuiFeng Zhang; XiaoDuo Hou; DeWei Deng (pp. 6527-6530).

► Nanocrystalline diamond particles obtained by electrochemical deposition. ► Previous work: high applied potential: 1000–3000V, 10h; our work: low voltage: 400V, 4h. ► A growth mechanism for the anode deposition was proposed.Diamond-like carbon films (DLC) are deposited on Ti substrate by electrochemical anodic deposition at room temperature in pure methanol solution using a pulsed DC voltage at a range from 200V to 2000V. Raman spectroscopy analysis of the films reveals two broaden characteristic absorption peaks centred at ∼1350cm⁻¹ and 1580cm⁻¹, relating to D- and G-band of typical DLC films, respectively. A broad peak centred at 1325–1330cm⁻¹ is observed when an applied potential is 1200V, which can confirm that the deposited films contained diamond structure phase. Tribological properties of the coated Ti substrates have been measured by means of a ball-on-plate wear test machine. A related growth mechanism of DLC films by the anodic deposition mode has also been discussed.

Keywords: Diamond-like carbon; Anode deposition; Tribological property

Study on fabrication of the superhydrophobic sol–gel films based on copper wafer and its anti-corrosive properties by Youhua Fan; Changzhu Li; Zejun Chen; Hong Chen (pp. 6531-6536).

Morphology of the superhydrophobic copper wafers surface.Display Omitted► In this paper, a stable superhydrophobic film was prepared on copper wafer substrate by a simple sol–gel method via hydrolysis of vinyltrimethoxysilane (VTES). ► The surface morphological study showed that different structures, such as pyramid-shaped protrusions or nipple-shaped protrusions or ball-shaped silica particles distributed on the copper substrate. ► The films showed a good superhydrophobic property, which had a high CA of larger than 155.4°. ► The superhydrophobic film held a good anti-corrosive property, the CA was 151.6° for the copper wafer even with immersion periods up to 14 days in the 3.5wt.% NaCl solution, pointing to promising future applications.In the present study, superhydrophobic copper wafer was prepared by a sol–gel deposition method. Different molar ratios of vinyltrimethoxysilane (VTES), ethanol (EtOH), water (H₂O) and ammonia water (NH₃·OH) were involved in this research. The morphologies, chemical compositions and hydrophobicity of the films were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX), Fourier transfer infrared spectrometer (FTIR) and water contact angle measurement (CA). It was shown by the surface morphological study that different structures, such as pyramid-shaped protrusions, nipple-shaped protrusions or ball-shaped silica particles, were distributed on the copper substrate. The films had a high water contact angle larger than 155.4°. The durability properties revealed that the films had a good superhydrophobicity deposited in 3.5wt.% sodium chloride solution for up to 14 days.

Keywords: Key words; Superhydrophobic; Copper wafer; Sol–gel deposition; Anti-corrosive properties

Ga-doped ZnO films deposited with varying sputtering powers and substrate temperatures by pulsed DC magnetron sputtering and their property improvement potentials by Sanghun Lee; Dongkeun Cheon; Won-Jeong Kim; Moon-Ho Ham; Woong Lee (pp. 6537-6544).

► ZnO:Ga transparent electrode films by pulsed DC magnetron sputtering. ► Synergistic contribution of sputtering power and temperature in combination. ► 100nm-thick film fulfilled required properties with improvement margins. ► Dopant Ga as electron donor and carrier suppressor deactivating oxygen vacancy. ► Necessity of careful control of doping efficiency for optimal properties.Ga-doped ZnO (GZO) transparent conductive oxide (TCO) films were deposited on glass substrates by pulsed DC magnetron sputtering with varying sputtering power and substrate temperature while fixing the Ga concentration in the sputtering target. The application of higher sputtering power by pulsed DC magnetrons sputtering at a moderate temperature of 423K results in increased carrier concentration and mobility which accompanied improved doping efficiency and crystalline quality. Substrate temperature was found to be the more dominant parameter in controlling the electrical properties and crystallinity, while the sputtering power played synergistic auxiliary roles. Electrical and optical properties of the GZO TCO films fulfilled requirements for transparent electrodes, despite relatively low substrate temperature (423K) and small thickness (100nm). In an attempt to improve the electrical properties of the GZO films by hydrogen-treatment, it was observed that the substitutional Ga plays the complex role of carrier generator as donor and carrier suppressor deactivating the oxygen vacancy simultaneously, which would complicate the property improvement by increasing doping efficiency.

Keywords: Transparent conductive oxide (TCO); Ga-doped ZnO (GZO); Pulsed DC magnetron sputtering; Post-annealing in hydrogen

Enhanced uniformity and durability of antisticking layer in imprinting stamps by Moon Jae Lee; Sang Uk Cho; Sang Mae Lee; Chang Seok Kim; Myung Yung Jeong (pp. 6545-6549).

► A fluorinated self-assembled monolayer (SAM) is used as an antisticking layer in NIL. ► We formed the antisticking layer with the 0.5nm uniformity via stamp tilt and rotation. ► To enhance durability, we treated the stamp surface before and after treatment. ► We identified that the durability of antisticking layer was dramatically improved.In the nanoimprint lithography (NIL) stamp, a fluorinated self-assembled monolayer (SAM) is used as an antisticking layer. The uniformity and durability of the antisticking layer should be improved for achieving an effective fabrication of imprinted devices. In order to achieve these goals, we manufactured a vaporized SAM coating system with tilt and rotation functions, and we uniformly formed the antisticking layer on the stamp surface. The antisticking layer was with the 0.5nm uniformity and the almost the same thickness of coating and re-coating. Moreover, to enhance durability, we conducted the pre-treatment before SAM coating and post-treatment after SAM coating – plasma cleaning, re-coating, deionized (DI) water deposition and annealing. The content of fluorine increased with re-coating, we could infer that the density of the antisticking layer increased via re-coating. To inspect the lifetime of the SAM-coated stamp, we measured the stamp surface contact angle in every five thermal NIL and identified that the durability of antisticking layer was dramatically improved.

Keywords: Nanoimprint lithography (NIL); Self-assembled monolayers (SAM); Antisticking layer

Effect of complexing agents and pH on microstructure and tribological properties of Co–W coatings produced by double pulse electrodeposition by Feng-hua Su; Can-sen Liu; Ping Huang (pp. 6550-6557).

The correlations among the electrodepositing condition that varied with the complexing agent or pH value, the microstructure and the tribological properties of the deposited Co–W coatings were established. The differences of the tribological properties for Co–W coatings from different baths were attributed to their different hardness, crystal structure and morphological characterizations, which can be optimized by the electrodepositing condition, i.e., the complexing agent and pH value in bath.Display Omitted► The Co–W coatings were produced by dual-pulse electrodeposition from aqueous bath with cobalt sulphate and sodium tungstate. ► The correlation between the electrodepositing condition, the microstructure and the tribological properties of the Co–W deposits were established. ► The Co–W alloy coating obtained excellent tribological performances and high hardness by careful control of the electrodeposition condition.The Co–W coatings were produced by double pulse electrodeposition from aqueous bath with cobalt sulphate and sodium tungstate. Effect of complexing agent and pH value in the plating bath on the microstructure, morphology and hardness of the electrodeposited Co–W coatings were investigated using an X-ray diffraction (XRD), scanning electron microscope (SEM) and a Vickers hardness tester, respectively. The friction and wear properties of the Co–W coatings deposited from different baths were evaluated with a ball-on-disk UMT-3MT tribometer. The correlation among the electrodepositing condition that varied with the complexing agent or pH value, the microstructure and the tribological properties of the deposited Co–W coatings were discussed. The results show that the complexing agent and pH value significantly affect the microstructure and tribological properties of the electrodeposited Co–W coatings. The sodium citrate is the best complexing agent to improve the tribological properties of the electrodeposited Co–W coatings at pH 6.0, followed by the sodium gluconate. The Co–W coatings electrodeposited from the near neutral bath can obtain better tribological properties than those deposited from strong acid or strong alkaline bath. The differences of the tribological properties for Co–W coatings from different baths were attributed to their different hardness, crystal structure and morphological characterizations, which can be optimized by the electrodepositing condition, i.e., the complexing agent and pH value in bath.

Keywords: Co–W coatings; Electrodeposition; Microstructure; Tribology

Electrodeposited AgInSe₂ onto TiO₂ films for semiconductor-sensitized solar cell application: The influence of electrodeposited time by Lung-Chuan Chen; Yi-Ching Ho; Ru-Yuan Yang; Jean-Hong Chen; Chao-Ming Huang (pp. 6558-6563).

► AgInSe₂ with tetragonal body structure was successfully electrodeposited on TiO₂/ITO. ► The prepared AgInSe₂ film exhibits n-type semiconductor behavior with two band gap energies around 1.27–1.80eV. ► The electrodeposited time of 45min results in the highest photocurrent, fill factor, and solar to electricity conversion efficiency of the AgInSe₂-based semiconductor-sensitized solar cells. ► The AgInse₂ film with an electrodeposited time of 45min displays the longest electron lifetime and slowest open circuit voltage decay rate.The influence of electrodeposited time (EDT) on Ag–In–Se species growth onto TiO₂ films for possible semiconductor-sensitized solar cells (SSSCs) application was investigated. XRD analysis illustrated that the Ag–In–Se film was predominantly comprised by AgInSe₂ species with tetragonal body structure and crystal size of 6.05–7.50nm when EDT was in the region of 15–60min at a bias of −1.25V (verse Hg/Hg₂SO₄ (MSE)). Scanning electron microscope (SEM) indicated a high porosity of AgInSe₂/ITO morphology, permitting electrolytes freely percolated through these films. The prepared AgInSe₂ films exhibited n-type semiconductor behavior with two band gap energies at 1.27 and 1.80eV. Photoelectrochemical measurement reflected that open circuit potential varied little with EDT, however, significant change was associated with short circuit current and fill factor (FF), causing the AgInSe₂/TiO₂ films with EDT of 45min exhibited the best solar to electricity conversion efficiency of 0.26%. The AgInSe₂/TiO₂ films with EDT of 45min demonstrated the longest electron lifetime according to the open circuit voltage decay analysis.

Keywords: Key words; Electrodeposition; AgInSe; ₂; Sensitized solar cells; Titanium dioxide

In situ synthesis of TiO₂/polyethylene terephthalate hybrid nanocomposites at low temperature by Xinyan Peng; Enyong Ding; Feng Xue (pp. 6564-6570).

► TiO₂ nanoflowers were in situ grown on PET non-woven fabric at 70°C within 4.5h. ► NCC pre-grafted on PET promotes the nucleation and crystal growth of TiO₂ at low temperature. ► The TiO₂/PET nanocomposites exhibits good self-cleaning property under solar light.TiO₂ nanoflowers were in situ grown on polyethylene terephthalate (PET) non-woven fabric by hydrolysis of TiCl₄ in aqueous solution in the presence of nanocrystal cellulose grafted PET fabric (NCC-g-PET) at a low temperature of 70°C. Nanocrystal cellulose (NCC) pre-grafted on PET fabric acted as hydrophilic substrate and morphology inducing agent to promote the nucleation and crystal growth of TiO₂. Detailed information on the synthetic process was presented. The resulting samples were characterized using FE-SEM, EDS, ATR-IR, Raman microscopy, XRD and TG analysis. The photocatalytic activity of the samples was evaluated by the degradation of orange methyl under solar light. Characteristic results indicate that rutile TiO₂ nanoflowers have grown abundantly on PET non-woven fabric, and the established hydrogen bonding strengthens the interfacial interaction between the inorganic particles and the polymeric substrates. The methyl orange decoloration test under natural solar light demonstrates that this TiO₂/PET hybrid nanocomposites exhibit excellent self-cleaning performance which is expected to have a good potential for commercialization.

Keywords: Synthesis; Polyesters; Nanocomposites; Surface modification; Catalyst; Titania

Molecular beam epitaxial growth and characterization of GaSb layers on GaAs (001) substrates by Yanbo Li; Yang Zhang; Yuwei Zhang; Baoqiang Wang; Zhanping Zhu; Yiping Zeng (pp. 6571-6575).

► High quality GaSb layers have been grown on GaAs (001) substrates. ► The influence of the GaAs substrate surface treatment, growth temperature, and V/III flux ratios on the crystal quality and the surface morphology of GaSb epilayers has been investigated. ► It has been found that the Sb-rich GaAs substrate surface preparation can promote the growth of high-quality GaSb material. ► The p-type nature of the unintentionally doped GaSb has been studied and the main native acceptor in the GaSb is the Ga antisite (Ga_Sb) defect.We report on the growth of GaSb layers on GaAs (001) substrates by molecular beam epitaxy (MBE). We investigate the influence of the GaAs substrate surface treatment, growth temperature, and V/III flux ratios on the crystal quality and the surface morphology of GaSb epilayers. Comparing to Ga-rich GaAs surface preparation, the Sb-rich GaAs surface preparation can promote the growth of higher-quality GaSb material. It is found that the crystal quality, electrical properties, and surface morphology of the GaSb epilayers are highly dependent on the growth temperature, and Sb/Ga flux ratios. Under the optimized growth conditions, we demonstrate the epitaxial growth of high quality GaSb layers on GaAs substrates. The p-type nature of the unintentionally doped GaSb is studied and from the growth conditions dependence of the hole concentrations of the GaSb, we deduce that the main native acceptor in the GaSb is the Ga antisite (Ga_Sb) defect.

Keywords: Molecular beam epitaxy; Gallium arsenide; Gallium antimonide

Preparation and tribological characterization of amorphous carbon nitride coatings in a RF PECVD–DC PVD hybrid coating process by Pengfei Wang; Takanori Takeno; Koshi Adachi; Hiroyuki Miki; Toshiyuki Takagi (pp. 6576-6582).

► CN_x coatings were successfully prepared using a hybrid coating process with the combination of RF PECVD and DC magnetron co-sputtering of graphite target at different N₂/Ar flow ratios. ► The structural properties of CN_x coating were greatly affected by the N₂/Ar flow ratio. ► Friction coefficients of CN_x coatings in air and N₂ gas stream showed less dependency on the N₂/Ar flow ratio. ► The friction behaviors of CN_x coatings are mainly controlled by the tribo-films on the mating surfaces.Amorphous carbon nitride (CN_x) coatings were prepared on Si (100) substrates using a unique hybrid coating process with the combination of radio frequency plasma enhanced chemical vapor deposition (RF PECVD) and DC magnetron co-sputtering of graphite target at different N₂/Ar flow ratios. The structural properties (i.e. deposition rate, composition and bonding structure, residual stress, hardness, and surface morphology) of those CN_x coatings were greatly affected by the N₂/Ar flow ratio. However, the friction behaviors of the CN_x coatings in air and N₂ gas stream showed less dependency on the N₂/Ar flow ratio. The friction coefficients of CN_x coatings sliding against AISI 52100 pins in air and N₂ gas stream were in the ranges of 0.17–0.19 and 0.33–0.42, respectively. The analyses of the worn surfaces from optical microscopy and Raman spectroscopy suggested that the friction behaviors of the CN_x coatings are mainly controlled by the tribo-films on the pin surfaces other than the composition and bonding structure of the coatings. Specifically, the moderate friction coefficients (0.17–0.19) in air are attributed to the formation of a polymer-like carbon tribo-film, whereas the high friction coefficients (0.33–0.42) in N₂ gas stream are due to the directly sliding between CN_x coating and steel pin surface.

Keywords: Carbon nitride; PECVD; PVD; Friction; Tribo-film

Preparation and evaluation of hollow molecular imprinted polymer for adsorption of dibenzothiophene by Wenming Yang; Lukuan Liu; Wei Zhou; Wanzhen Xu; Zhiping Zhou; Weihong Huang (pp. 6583-6589).

► H-MIP was prepared by surface imprinting technique combined with removing carrier process. ► The kinetics and isotherms for the adsorption towards DBT of the polymer was adopted. ► The selectivity performance of H-MIP was favorable.Hollow molecular imprinted polymer (H-MIP) was prepared using dibenzothiophene as template molecule, 4-vinylpyridine as functional monomer and K₂Ti₄O₉ as carrier by surface imprinting technique combined with removing carrier process. The polymer was characterized by means of nitrogen adsorption, Fourier transform infrared spectrometry and scanning electron microscopy. H-MIP was provided with larger surface areas and pore features. The adsorption process was spontaneous by thermodynamic analysis. The adsorption process followed pseudo-second-order model by kinetics analysis and Freundlich equation by isotherm analysis. The selectivity performance of H-MIP was favorable.

Keywords: Surface imprinted polymer; Adsorption; Dibenzothiophene; Desulfurization; Potassium tetratitanate

Growth and analysis of GaN nanowire on PZnO by different-gas flow by L. Shekari; H. Abu Hassan; S.M. Thahab; A.J. Ghazai; Z. Hassan (pp. 6590-6594).

► This research introduces an easy and safe method to grow high quality GaN NWs, as without using NH₃ gas. Using just Ar gas, makes the experiment more easier and safer which have never been done before. The obtained results are in agreement with experimental and other published data and also a cheap method to grow GaN NWs, but we achieved a good result as well. This is a new growth process to decrease the cost, complexity of growth of GaN NWs. ► GaN NWs are prepared by Thermal Evaporation method, which is believed to have never been done before using these variable gas flows. ► Instead of being easy, this is a controllable method to synthesize highly crystalline GaN NWs by thermal evaporation; by changing the flow of gas, amount of powder, and the duration of growth.In this research we have used an inexpensive method to fabricate highly crystalline GaN nanowires (NWs) on porous zinc oxide (PZnO) on Si (111) wafer by thermal evaporation using commercial GaN powder, either in argon (Ar) gas atmosphere or a combination of Ar and nitrogen (N₂) gas atmosphere without any catalyst. Micro structural studies by scanning electron microscopy (SEM) and transmission electron microscope (TEM) measurements reveal the role of different gas flowing, in the nucleation and alignment of the GaN NWs. The GaN NWs different diameters ranging between 50 and 200nm for the NWs grown under flow of mix gases, but the NWs which were grown under Ar gas only, have uniform diameter of around 50–60nm, also their lengths are almost the same (around 10μm). Further structural and optical characterizations were performed using high resolution X-ray diffraction (HR-XRD), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence (PL) spectroscopy. Results indicated that the NWs are of single-crystal hexagonal GaN with [0001] and[101¯1] growth directions for NWs grown under Ar and mixed gas flow.

Keywords: Nanowires; Characterization; Single crystal growth; GaN

Study of the photocatalytic activity of nanocrystalline S, N-codoped TiO₂ thin films and powders under visible and sun light irradiation by Mohsen Behpour; Vajiheh Atouf (pp. 6595-6601).

► Homogeneous and transparent S, N-codoped TiO₂ thin films were prepared by sol gel dip coating method. ► The equivalent powders were obtained by aging the residual sol of pure and modified TiO₂. ► Sol gel method can produce crack-free and homogeneous doped TiO₂ thin films with high photocatalytic activity. ► The thin films and powders exhibit excellent photocatalytic activity for degradation of methyl orange under both visible and sun light irradiation.Homogeneous and transparent sulfur and nitrogen (S, N)-codoped TiO₂ nanocrystalline thin films were deposited on glass substrates by sol gel dip coating method using thiourea (Tu) as a source of sulfur and nitrogen. The surface structure of the films was modified by addition of different concentrations of polyethylene glycol (PEG) into the TiO₂ sol. The equal powders of pure and modified TiO₂ were also prepared to compare of their photocatalytic activity with films.The films and powders were characterized by different techniques like diffuse reflectance UV–Vis spectroscopy (DRS), X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX).DRS exhibited a shift in optical absorption wavelength to visible region and XRD analysis showed that only the anatase TiO₂ formed in both of film and powder. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) as a model. The modified TiO₂ films and powders showed excellent visible-light photocatalytic ability for the degradation of MO under both irradiation of visible and sun light. So that, up to 96% MO can be decomposed in sun light only within 3h in the presence of a modified TiO₂ film consist of Tu/TiO₂ molar ratio of 0.45 and 0.9g PEG. On the other hand, MO solution was discolored completely under sun light in 75min in the presence of the modified TiO₂ powder.

Keywords: S, N-codoped TiO; ₂; Photocatalytic activity; Thiourea; Polyethylene glycol; Visible light; Sun light

Influence of sodium borate concentration on properties of anodic coatings obtained by micro arc oxidation on magnesium alloys by R.F. Zhang; S.F. Zhang; Y.L. Shen; L.H. Zhang; T.Z. Liu; Y.Q. Zhang; S.B. Guo (pp. 6602-6610).

► Sodium borate decreases the electrical conductivity of an alkaline solution. ► Sodium borate can cause intensive spark discharge on sample surface during MAO. ► The boron content of anodic coatings is within the range of 0.84–5.10at.%. ► The coatings formed in solutions containing sodium borate consist of Mg₃B₂O₆.The influence of sodium borate concentration on the formation and properties of anodic coatings obtained by micro arc oxidation (MAO) on magnesium alloys was systematically studied in an alkaline solution with addition of 0–40g/L sodium borate. It is shown that sodium borate can decrease the solution conductivity, take part in the coating formation and increase the coating thickness. With the increase of sodium borate concentration, the boron content in the coatings increases in the range of 10–20g/L but decreases within the range of 20–40g/L. Sodium borate cannot further improve the corrosion resistance attributed to the development of porous or rough anodic coatings.

Keywords: Magnesium alloy; Micro arc oxidation; Electrolyte; Sodium borate

Theoretical modelling of iron nitriding coupled with a nanocrystallisation treatment. Application to numerical predictions for ferritic stainless steels by B. Panicaud; M. Chemkhi; A. Roos; D. Retraint (pp. 6611-6620).

► Nitriding on ferritic steels is modelled by a simultaneous multiscale/multiphysics approach. ► A duplex nanocrystallisation/nitriding treatment is investigated. ► Numerical results show a significant influence of nanocrystallisation on penetration depth.This paper analyses a recently developed duplex process combining nitriding with nanocrystallisation. A model is proposed to show how nitrogen diffusion mechanisms are modified within ferritic steels due to the nanostructure near the top surface. This model is based on micro-mechanical and micro-physical approaches, and also on the thermodynamics of irreversible processes. It takes into account size effects influencing the nitrogen diffusion, including mechanical stresses at the different length scales. Several models are investigated and numerical applications are performed. The results are compared to literature in order to demonstrate the generality of the present methodology.

Keywords: Nitriding; Scale transition methods; Nanocrystallisation; Diffusion; Stress effects

Theoretical studies of the magnetism of the first-row adatom on the ZnO nanotube by Feng Li; Changwen Zhang; Peiji Wang; Ping Li (pp. 6621-6626).

Display Omitted► The magnetism of the first-row adatom on the ZnO nanotube is investigated. ► H-, Be-, and B-adsorption on the ZnO nanotube cannot induce the magnetism. ► Li-, C-, N-, O-, and F-adsorption on the ZnO nanotube can induce the magnetism.On the basis of density functional theory (DFT) methods, we study the magnetic properties and electronic structures of the adsorbed ZnO nanotube by various first-row atoms (H, Li, Be, B, C, N, O, and F). It is found that the eight atoms which have been studied can be effectively adsorbed by the ZnO nanotube with the adsorption energy ranging from 1.53 to 6.79eV. Furthermore, the adsorption of Li, C, N, O, F atoms can induce magnetization, whereas no magnetism is observed when H, Be, and B atoms are absorbed on the ZnO nanotube.

Keywords: ZnO nanotube; Magnetism; Ab initio calculation; Adatoms

Photoelectrochemical properties of polypyrrole/TiO₂ nanotube arrays nanocomposite under visible light by Yichao Jia; Peng Xiao; Huichao He; Jianyu Yao; Feila Liu; Zhifeng Wang; Yanhong Li (pp. 6627-6631).

► PPy as sensitizer directly synthesized onto TiO₂NTs by potentiostatic method. ► Sensitization effect was evaluated under the visible light illumination. ► Discussed the relationship between sensitization effect and modification amount. ► Sensitization effect was improved under visible light duo to the heterojunction formed.In this study, different amount of polypyrrole (PPy) were electropolymerized on highly ordered TiO₂ nanotube arrays (TiO₂NTs) anodized by Ti foil in aqueous solution containing fluoride. In order to improve the conductivity of PPy, an anionic surfactant sodium dodecyl benzene sulfonate (SDBS) was used as doping during electropolymerization. The PPy modified TiO₂NTs was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR) and UV–vis spectroscopy (UV–vis). The results indicated that there might exist a strong interaction between TiO₂NTs and PPy. Photoelectrochemical response showed that PPy/TiO₂NTs electropolymerized for 30s presented the maximum IPCE 1.81% under 550nm visible light. The results were ascribed to the presence of narrow band gap p-type conducting polymer semiconductor PPy enhancing visible-light absorption and decreasing the recombination of photo electron–hole result in enhanced photocurrent. These results have implications for the use of PPy/TiO₂NTs as a photoswitch or solar cell.

Keywords: TiO; ₂; nanotube arrays; Polypyrrole; Electropolymerization; Photoelectrochemical response

Electrodeposition of hierarchical Ag nanostructures on ITO glass for reproducible and sensitive SERS application by Jun-Cao Bian; Zhong-Dong Chen; Zhe Li; Fei Yang; Hai-Yan He; Juan Wang; Jeannie Ziang Yie Tan; Jie-Liang Zeng; Rui-Qun Peng; Xi-Wen Zhang; Gao-Rong Han (pp. 6632-6636).

► Relatively uniform hierarchical Ag nanostructures were electrodeposited on ITO glass. ► The size RSD of the hierarchical Ag nanostructures is about 28.8%. ► A low precursor concentration and complexing agent were used. ► The RSD of SERS intensity (rhodamine 6G, R6G) for 1651cm⁻¹ band is about 14.9%. ► The detectable concentration of R6G can be 10⁻¹⁰M at least.In this paper, electrodeposition of relatively uniform hierarchical Ag nanostructures (the RSD of size is about 28.8%) on ITO glass has been achieved via utilizing low precursor concentration and complexing agent without any surfactant. The RSD of SERS intensity (rhodamine 6G, R6G) for 1651cm⁻¹ band is about 14.9% and the detectable concentration of R6G can be 10⁻¹⁰M at least, indicating the hierarchical Ag nanostructures on ITO glass good candidate for reproducible and sensitive SERS application.

Keywords: Hierarchical Ag nanostructures; Electrodeposition; SERS; Reproducibility; Sensitivity

Epoxidation of soybean oil catalyzed by peroxo phosphotungstic acid supported on modified halloysite nanotubes by Junqing Jiang; Yanwu Zhang; Liwei Yan; Pingkai Jiang (pp. 6637-6642).

Display Omitted► A natural halloysite nanotubes with end-opening acted as the support of catalysts. ► The mass transfer was enhanced by combination of mechanical and ultrasonic agitation. ► The catalyst can be recovered by centrifugation as deposit easily. ► The catalyst can be reused for three times with enough catalytic activity. ► The catalyst can be regenerated with the same catalytic activity by re-exchange of {PO₄[W(O)(O₂)₂]₄}³⁻.{PO₄[W(O)(O₂)₂]₄}³⁻ was supported onto modified halloysite nanotubes (HNTs) to prepare heterogeneous catalysts and these catalysts were applied in epoxidation of soybean oil. To enhance the cohesive force between {PO₄[W(O)(O₂)₂]₄}³⁻ and HNTs, quaternary amino groups were anchored onto HNTs through silylation of N-(2-aminoethyl)-3-aminopropyl trimethoxysilane and alkylation of amino groups. Further {PO₄[W(O)(O₂)₂]₄}³⁻ was supported onto HNTs by ion exchange. The heterogeneous catalysts were characterized by FTIR, TGA, XRF and TEM–EDS. Then the catalytic behaviour to epoxidation of soybean oil was studied in detail. The results show that the introduction of phase transfer agent during preparation of the catalysts is very effective to improve catalytic activity and mechanical agitation combining with ultrasonic agitation is the best agitation way. The catalytic reactivity increased as reaction time increased. Moreover, the catalysts can be easily recovered from the reaction system by centrifugation as deposit and recycled three times without obviously decreasing the catalytic activity. Through re-exchange of {PO₄[W(O)(O₂)₂]₄}³⁻, the heterogeneous catalyst can be regenerated without catalytic activity loss.

Keywords: Peroxo phosphotungstic acid; Halloysite nanotubes; Heterogeneous catalyst; Epoxidation; Soybean oil

High performance ethanol sensing films fabricated from ZnO and In₂O₃ nanofibers with a double-layer structure by Xiao-Juan Zhang; Guan-Jun Qiao (pp. 6643-6647).

► Double-layer structure is firstly employed in nanofiber-based gas sensors. ► Decreased optimum temperature and enhanced sensitivity are obtained. ► Response and recovery times are only 1 and 2s to 100ppm ethanol, respectively. ► Effects of the layer structure on sensor performance are discussed.ZnO and In₂O₃ nanofibers are synthesized via electrospinning methods, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), infrared (IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The nanofibers are deposited on ceramic substrates to form sensing films with various structures (ZnO nanofiber films, ZnO–In₂O₃ nanofiber films, and ZnO–In₂O₃–ZnO nanofiber films), and their sensing properties are investigated at different temperatures. Compared with ZnO nanofiber films and ZnO–In₂O₃–ZnO nanofiber films, the obtained ZnO–In₂O₃ nanofiber films exhibit improved and excellent sensing properties to ethanol. The highest sensitivity (the ratio of sensor resistance in air to that in target ambience) of 25 is obtained when the ZnO–In₂O₃ films are exposed to 100ppm ethanol at 210°C, while the corresponding values are only 8 for ZnO nanofiber films at 300°C and 17 for ZnO–In₂O₃–ZnO nanofiber films at 210°C. Rapid sensing reactions are also obtained as the response and recovery times of ZnO–In₂O₃ nanofiber films to 100ppm ethanol are only about 2 and 1s, respectively. These high sensing performances are explained by referring the heterocontacts formed by the double-layer structure.

Keywords: Semiconductors; Sensitivity; Sensing films; Gas sensors; Chemical sensors

Synthesis, studies and growth mechanism of ferromagnetic NiFe₂O₄ nanosheet by P. Sivakumar; R. Ramesh; A. Ramanand; S. Ponnusamy; C. Muthamizhchelvan (pp. 6648-6652).

The morphology of the as-prepared sample is determined by HR-SEM, TEM and HRTEM. The morphology of the as prepared NiFe₂O₄ is sheet-like structure. HR-TEM shows clear lattice fringes of each nanoparticle. This is interpreted as oriented attachment and sample as sheet-like morphology. From the HR-TEM observations of single sheet-like nanostructures, and the fringe spacing is measured to be 0.291nm and 0.0.248nm, which confirms that the nanosheet is single crystal with lattice fringes being (220) and (311) planes.Display Omitted► Single-phase NiFe₂O₄ powders have been synthesised by a wet chemical route. ► XRD, FTIR, TGA, HR-SEM, TEM, HR-TEM and VSM study. ► The structural and magnetic properties of NiFe₂O₄ nanosheet. ► PVP plays an important role for the formation of the sheet-like nanostructure. ► Both TEM and HR-SEM image for NiFe₂O₄ nanocomposite shows the sheet-like nanostructure.Nickel ferrite (NiFe₂O₄) nanoparticles were prepared by a simple and cost-effective method using nickel nitrate, ferric nitrate, ethylene glycol and citric acid via polyvinylpyrrolidone (PVP) assisted sol–gel auto-combustion method. The structure, composition, morphology and magnetic properties of the gel precursor were characterised XRD confirmed the formation of single phase NiFe₂O₄ with space group Fd3m and inverse spinel structure and the crystallite size was found to be 29nm. The FT-IR showed absorption bands, which were assigned to the vibration of tetrahedral and octahedral complexes. The thermal decomposition of the gel precursors was investigated by TGA. HR-SEM and TEM images showed sheet-like nanostructure. The magnetic properties of these nanosheets were studied for the enlightening ferromagnetic behaviour at room temperature. The magnetic saturation ( M_s=41.70emug⁻¹), remanent magnetisation ( M_r=7.57emug⁻¹) and coercive force ( H_c=162.47Oe), were determined.

Keywords: NiFe; ₂; O; ₄; Nanostructure; Polymer; Chemical synthesis; VSM

Effect of Ti additive on (Cr, Fe)₇C₃ carbide in arc surfacing layer and its refined mechanism by Yefei Zhou; Yulin Yang; Jian Yang; Feifei Hao; Da Li; Xuejun Ren; Qingxiang Yang (pp. 6653-6659).

TiC particles distribute in/around M7C3 carbide. Moreover, TiC act as heterogeneous nuclei of the M7C3 is medium effective. Therefore, the M7C3 carbide has been refined.Display Omitted► Ti additive was added in the hypoeutectic HCCI arc surfacing layer. ► M₇C₃ carbide in arc surfacing microstructure of hypoeutectic HCCI has been refined with 2wt.% Ti additive. ► TiC carbide can be observed in/around the M₇C₃ carbide. ► TiC as heterogeneous nuclei of the Cr₇C₃ is medium effective.Arc surfacing layer of hypoeutectic high chromium cast iron (HCCI) expects refiner carbides in the microstructure to improve its mechanical properties. In this paper, Ti additive as a strong carbide forming element was added in the hypoeutectic HCCI arc surfacing layer. Microstructure of titaniferous hypoeutectic HCCI was studied by optical microscopy, X-ray diffraction and field emission scanning electronic microscopy with energy dispersive spectrometer. Furthermore, the M(M=Cr, Fe)₇C₃ carbide refinement mechanism was explained by the phase diagram calculation and lattice misfit theory. The results show that, the M₇C₃ carbide in arc surfacing microstructure of hypoeutectic HCCI has been refined with 2wt.% Ti additive, and TiC carbide can be observed in/around the M₇C₃ carbide. With Ti addictive increasing, the micro-hardness along the depth in profile section of layer becomes more uniform, and the wear resistance has been improved. According to the phase diagram calculation, MC carbide precipitates prior to M₇C₃ carbide in Fe–Cr–C–Ti alloy. In addition, the lattice misfit between (110)_TiC and(010)Cr7C3 is 9.257%, which indicates that the TiC as heterogeneous nuclei of the M₇C₃ is medium effective. Therefore, the M₇C₃ carbide can be refined.

Keywords: Arc surfacing layer; High chromium cast iron; Carbide; Phase diagram; Titanium

Synthesis and properties of core-shell magnetic molecular imprinted polymers by Limin Chang; Shaona Chen; Xin Li (pp. 6660-6664).

A general fabricating protocol for the preparation of core-shell magnetic molecularly imprinted polymers is reported.Display Omitted► Core-shell magnetic molecularly imprinted polymers (MIPs) for chlorinated phenols recognition has been prepared. ► The resultant polymers showed a high saturation magnetization value and short response time. ► The MIPs showed excellent recognition and selection properties toward imprinted molecule over structurally related compound. ► The effective method might helpful to prepare magnetic MIPs with high affinity, selectivity and easy separation.A general fabricating protocol for the preparation of core-shell magnetic molecularly imprinted polymers (MIPs) for chlorinated phenols recognition is described. In this protocol, Fe₃O₄ magnetic nanoparticles were first prepared using the chemical co-precipitation method. Then, the obtained magnetic nanoparticles were coated with a silica shell through modified Stöber method. Finally, MIP films were coated onto the surface of silica-modified magnetic nanoparticles by surface molecular imprinting technique. The resultant polymers showed a high saturation magnetization value (31.350emug⁻¹), and short response time (30s). Meanwhile, the as-synthesized magnetic MIPs showed an excellent recognition and selection properties toward imprinted molecule over structurally related compounds.

Keywords: Molecularly imprinted polymers; Magnetic; Chlorinated phenols; Hybrid

Structure and surface nanomechanics of poly(l-lactide) from thermally induced phase separation process by Jundong Shao; Cong Chen; Yingjun Wang; Xiaofeng Chen; Chang Du (pp. 6665-6671).

Display Omitted► Early stage evolution of structure and nanoscale property in TIPS process. ► Nanofiber initiate from crystalline grains and assembled with a bunch of thinner ones. ► Crystallization result in more chain entanglement and decrease chain mobility. ► Chain packing has a direct functional consequence in the nanomechnical properties. ► Nanofiber have more significant plastic deformation and creep.The surface morphology, crystalline structure and nanomechanical properties of poly(l-lactide) (PLLA) samples prepared via thermally induced phase separation (TIPS) process have been investigated by scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), force spectroscopy and nanoindentation. Typical nanofibrous scaffold was obtained at −24°C (NF sample) while a denser matrix with some plateletlike structure was obtained at 15°C (PL sample). The NF sample has a higher crystallinity with α′-form crystals while the PL sample has α-form crystals embedded in a largely amorphous matrix. The two kinds of samples have differences in the chain conformation with a more restricted backbone vibration and stiffened segmental motion in NF samples. The NF samples have a higher adhesion force although both samples showed a heterogeneous distribution of adhesion force on the surface based on force spectroscopy analysis. The alternating distribution of domains with higher and lower adhesion force exhibited a banded pattern on PLLA nanofibre. This pattern is proposed to reflect the distribution of crystal-rich and amorphous-rich domains in the semicrystalline samples. AFM-based nanoindentation test indicated that the nanofibrous NF samples can have more significant plastic deformation and creep than the largely amorphous PL samples. The sliding of the crystal-rich domains along the fibrils would account for this increased plasticity of the nanofiber.

Keywords: Poly(; l; -lactic acid) nanofibers; Thermally induced phase separation; AFM; Nanoindentation

Fabrication and characterization of hybrid micro/nano-structured hydrophilic titania coatings deposited by suspension flame spraying by Jianhui Yuan; Qing Zhan; Qiang Lei; Siyue Ding; Hua Li (pp. 6672-6678).

► A novel flame spray approach using suspension/powder feedstock was proposed. ► Controllable hybrid micro/nano-structured titania coatings was deposited. ► The coatings are super hydrophilic. ► Relative contents of anatase and rutile in the titania coatings can be tailored. ► Effect of the hybrid structures on coating mechanical properties was elucidated.Nanostructured titania coatings have been a research focus for many years owing to their excellent photocatalytic activity. The major persistent challenge yet is development of competitive deposition techniques for fabricating the nanostructured coatings. Here we report a novel deposition approach by flame spraying the mixtures of nano titania-contained suspension and micron-sized titania powders feedstock. Promising hybrid micro/nano-structured TiO₂ coatings comprising micron-sized splats (50–80μm) and nano particles (10–40nm) were successfully produced. Anatase-rutile ratio and proportion of the nanostructures in the coatings can be tailored in a wide range depending on the concentration of nano TiO₂ particles (10–30nm in size) in the starting suspension. Up to 30wt.% of anatase in the coatings was achieved. The hybrid micro-/nano-structured TiO₂ coatings exhibit super-hydrophilic performances (∼0° contact angle). Effect of the suspension concentration (concentration of the nano titania particles in the suspension) on the microstructure and mechanical properties of the coatings was also investigated. Compared to the coating deposited using the suspension alone, the hybrid micro/nano-structured TiO₂ coatings exhibited markedly enhanced adhesive strength (by up to 1.8 times) and microhardness (by 9 times). The behavior between the TiO₂ particles with micro- and nano-sizes was also elucidated.

Keywords: Suspension flame spraying; TiO; ₂; Micro/nano-structure; Hydrophilic coating; Mechanical properties

Adsorption and corrosion-inhibiting effect of 2-(2-{[2-(4-Pyridylcarbonyl)hydrazono]methyl}phenoxy)acetic acid on mild steel surface in seawater by Baoyu Liu; Hongxia Xi; Zhong Li; Qibin Xia (pp. 6679-6687).

► One synthesized organic compound was experimentally and theoretically investigated. ► The investigated compound showed chemisorption on the surface. ► The adsorption of the inhibitor on steel surface obeys Langmuir adsorption isotherm. ► Employing Gaussian DFT method for quantum chemical study of inhibitor. ► The adsorption behaviour of the studied inhibitor on iron surface has been studied using molecular dynamics method.The corrosion inhibition property of a Hydrazone derivative, namely 2-(2-{[2-(4-Pyridylcabonyl)hydrazono]methyl}phenoxy)acetic acid (PMA) for mild steel surface corrosion in synthetic seawater medium was analyzed by weight loss, electrochemical techniques (potentiodynamic polarization and electrochemical impedance), the experimental results suggest that PMA is a good corrosion inhibitor and the inhibition efficiency increased with the increase of PMA concentration, while the adsorption followed the Langmuir isotherm. X-ray photoelectron spectroscopy, scanning electron microscopy, theoretical calculation of electronic density, molecular electrostatic potential and molecular dynamics were carried out to establish mechanism of corrosion inhibition for mild steel with PMA in synthetic seawater medium. The inhibition action of the compound was assumed to occur via adsorption on the steel surface through the active centres in the molecule. The results indicated that the corrosion inhibition is due to the formation of a chemisorbed film on the steel surface.

Keywords: Corrosion inhibitor; Mild steel; DFT; Molecular dynamics

Adsorption of formaldehyde (HCOH) molecule on the SiC sheet: A first-principles study by Lizhi Wang (pp. 6688-6691).

Display Omitted► The C atom of the SiC sheet is the active adsorption site compared with the Si site. ► Adsorption of HCOH molecule could affect the electronic properties of the SiC sheet by strong interactions. ► The SiC sheet is expected to be a novel sensor to detect HCOH gas.We investigated the adsorption of HCOH molecule on the SiC sheet using density functional theory (DFT) calculations. It is found that the C atom of the SiC sheet is the active adsorption site and the HCOH molecule prefers to the C atom rather than the O and H atoms close to the SiC sheet. The calculated charge-transfer, electronic density difference image and the densities of states (DOS) show that the HCOH molecule could be firmly adsorbed by the SiC sheet and the electronic properties of the SiC sheet are affected by the adsorption of HCOH molecule. The SiC sheet would be promising candidate to detect the HCOH gas.

Keywords: Density functional theory (DFT); SiC sheet; Adsorption; HCOH molecule

Study on structures and photoluminescence of nitrogenated carbon nanotip arrays synthesized by plasma assisted hot filament chemical vapor deposition by Chun Dang; Biben Wang (pp. 6692-6696).

► Nitrogenated carbon nanotip arrays were grown by plasma assisted hot filament CVD. ► The photoluminescence of NCNAs with different structures was studied. ► The emission bands are related to the size of sp² carbon clusters. ► The photoluminescence intensity is related to the light trapping of NCNAs.Nitrogenated carbon nanotip arrays (NCNAs) with different structures were synthesized by plasma assisted hot filament chemical vapor deposition using methane, hydrogen and nitrogen as the reaction gases. The structural and compositional properties of NCNAs were studied using field emission electron scanning microscopy, micro-Raman spectroscopy, X-ray photoelectron spectroscopy, respectively. The photoluminescence (PL) of NCNAs with different structures was measured at room temperature using the excitation sources with the wavelengths of 325nm. The PL results exhibit that the NCNAs generate both of the emission bands centered about 2.47 and 3.07eV, but there are differences in the PL bands and intensities for the NCNAs with different structures. According to the growth conditions, the difference in the structures of NCNAs was studied. Combined the structures with the compositions of NCNAs, the generation of the differences in the PL bands and intensities of different NCNAs was investigated.

Keywords: Nitrogenated carbon nanotip arrays; sp; ²; clusters; Lone pair electrons; Photoluminescence

Effect of powders refinement on the tribological behavior of Ni-based composite coatings by laser cladding by Lingqian Wang; Jiansong Zhou; Youjun Yu; Chun Guo; Jianmin Chen (pp. 6697-6704).

► Effect of milling time on the size, morphology, uniformity of the powders was investigated. ► Consecutive evolution trend of properties of a series of coatings was presented. ► The final optimized processing parameters selected play a basal role in further researches. ► Changes of friction and wear mechanism of coatings with powders of different sizes were discussed.NiCr+Cr₃C₂+Ag+BaF₂/CaF₂ composite coatings were produced on stainless steel (1Cr18Ni9Ti) substrates by laser cladding. Corresponding powders were prepared by high-energy ball milling technique. The friction and wear behavior at room temperature was investigated through sliding against the Si₃N₄ ball. The morphologies of the wear debris, worn surfaces of both samples and the Si₃N₄ ball were analyzed by scanning electron microscopy and three dimensional non-contact surface mapping. Results showed that milling time had a great effect on the size, morphology, uniformity of the powders as well as the microstructure and properties of laser cladding coatings. The wear mechanism of the coatings is dominated by abrasive wear, plastic deformation and slight adhesive wear. The consecutive evolution trend of friction coefficient, wear rate as well as microhardness of the serials of coatings produced with powders of different sizes was presented.

Keywords: High-energy ball milling; Powder sizes; Laser cladding; Friction and wear behavior

One-step solvothermal syntheses and microwave electromagnetic properties of organic magnetic resin/Fe₃O₄ hybrid nanospheres by Junji Wei; Rui Zhao; Yingqing Zhan; Fanbin Meng; Xulin Yang; Mingzhen Xu; Xiaobo Liu (pp. 6705-6711).

Novel hybrid nanospheres composed of organic magnetic resin and Fe₃O₄ (OMR/Fe₃O₄) were prepared via an effective solvothermal route. The morphology and structure of the hybrid nanospheres were characterized by Fourier transform infrared spectrophotometer (FTIR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). These results showed that the as-prepared nanospheres were well-defined in size (200–230nm) and shape. Base on these results, the formation process was discussed. Magnetization measurement showed that the saturation magnetization and coercive force of the hybrid nanospheres were 62.6emug⁻¹ and 163.5Oe at 300K, respectively. The microwave absorption properties were measured by a vector network analyzer and the data indicated that the addition of organic magnetic resin has greatly affected the microwave electromagnetic properties of the hybrid nanospheres. The as-prepared hybrids displayed different electromagnetic properties from conventional nano-Fe₃O₄ particles. The loss in magnetism exhibited two obvious peaks: one appeared at 4.0–5.0GHz, the other sharp peak appeared around 9.0–12.0GHz. The former peak was attributed to the natural properties of the Fe₃O₄ and the latter was owing to the interface effects between OMR and Fe₃O₄ particles.

Keywords: Nanocomposites; Ferromagnetism; Microwave electromagnetic properties; Bisphthalonitrile-benzoxaine resin containing ferrocene; Physical adsorption

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Applied Surface Science (v.258, #17)

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Applied Surface Science (v.258, #17)