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Applied Surface Science (v.274, #)

Editorial Board (pp. ii).

Theoretical study on the reactivity of the surface of pure oxides: The Influence of the support and oxygen vacancies by Walter G. Reimers; Miguel A. Baltanás; María Marta Branda (pp. 1-6).

► The presence of oxygen vacancies both on ceria and gallia surfaces becomes these surfaces more reactive. ► Supported films are very reactive to oxidize CO and CO₂ molecules, and also to dissociate the H₂ molecule. ► Thin films of Ga₂O₃ and ZnO grown onto ceria are higher suitable catalysts than the unsupported oxides. ► The higher interaction with the studied molecules is mainly the presence of reduced cations on the surface.The surface reactivity of three oxides widely used as heterogeneous catalysts, CeO₂ (ceria), Ga₂O₃ (gallia), and ZnO, with CO, CO₂, and H₂ was investigated. The most stable perfect (dehydroxylated) oxide surfaces, surfaces that contain oxygen vacancies, and monolayers of Ga₂O₃ and ZnO epitaxially grown over CeO₂(111) were investigated using DFT calculations. As expected, CO₂ exhibited the highest adsorption energies on almost every surface. The only observed exceptions were the ZnO surfaces, viz., the ZnO(0001) perfect surface and a ZnO monolayer grown on ceria, with which the CO molecule interacts more strongly and generates CO₂ species. In contrast, H₂ interacts weakly with the majority of the surfaces, with the exception of gallia/ceria, where this molecule dissociates. The oxides become considerably more reactive when oxygen vacancies are present on the surface. The reactivity of the CeO₂(111) and Ga₂O₃(100) surfaces that contain oxygen vacancies increases up to ten-times with respect to the perfect surfaces. In addition, both Ga₂O₃ and ZnO also exhibit an important increase of their reactivity when they are supported on ceria. Thin films of these oxides that are epitaxially grown onto ceria surfaces have shown to be highly suitable catalysts for oxidizing CO and CO₂ molecules and for dissociating the H₂ molecule.

Keywords: Pure oxides; Supported oxides; DFT; Reactivity; Adsorption; Gallia; Ceria; Zinc oxide

Synthesis and characterization of cesium molybdo vanado phosphate immobilized on platelet SBA-15: An efficient inorganic composite ion-exchanger for gadolinium ion sorption by H. Aghayan; A.R. Khanchi; A.R. Mahjoub (pp. 7-14).

Display Omitted► Immobilization of Cs₂H₂PMo₁₁VO₄₀ onto platelet mesoporous silica SBA-15 was performed. ► Two-step aqueous impregnation method used for supporting Cs₂H₂PMo₁₁VO₄₀ onto mesopore. ► Adsorption behavior of sample for gadolinium removal was investigated. ► Adsorption capacity of mesoporous silica by supporting of Cs₂H₂PMo₁₁VO₄₀ was increased.A series of cesium molybdo vanado phosphate (CsMVP) supported on platelet SBA-15 (SBA-15–% xCsMVP, x=20, 30, 40 and 50wt.%) was synthesized to develop an efficient inorganic composite ion-exchanger for gadolinium ion removal from aqueous solution. The preparation has been carried out using two-step aqueous impregnation methods. The obtained products were characterized by inductively coupled plasma (ICP), XRD, N₂ adsorption–desorption isotherms, scanning electron microscopy (SEM) and FT-IR. In order to examine adsorption behavior of this compound on gadolinium removal, the effect of heteropoly metalate loading, pH, contact time, concentration of metal ion and temperature were investigated under batch system conditions. The SBA-15–30%CsMVP showed maximum adsorption capacity toward gadolinium removal. The results suggested that this methodology provides the general synthesis of supported heteropolymetalate with large surface areas, and ordered nano porous structures that can be used as inorganic composite ion-exchanger for efficient removal of gadolinium ions from aqueous solution.

Keywords: Mesoporous silica; SBA-15; Ion exchange; Gadolinium

Characterization of Nb SRF cavity materials by white light interferometry and replica techniques by Chen Xu; Charles Reece; Michael Kelley (pp. 15-21).

► SRF accelerator cavity interior surface topography provides a key link between processing (fabrication) and performance. ► Topography data analysis by extensions of power spectral distribution (PSD) methods yields important new insights. ► Application of replica methods substantially overcomes the problem of access to the cavity interior surface. ► WLI offers an enormous increase in the rate at which topography data can be acquired, greatly expanding its usefulness.Much work has shown that the topography of the interior surface is an important contributor to the performance of Nb superconducting radiofrequency (SRF) accelerator cavities. Micron-scale topography is implicated in non-linear loss mechanisms that limit the useful accelerating gradient range and impact cryogenic cost. Aggressive final chemical treatments in cavity production seek to reliably obtain “smoothest” surfaces with superior performance. Process development suffers because the cavity interior surface cannot be viewed directly without cutting out pieces, rendering the cavities unavailable for further study. Here we explore replica techniques as an alternative, providing imprints of cavity internal surface that can be readily examined. A second matter is the topography measurement technique used. Atomic force microscopy (AFM) has proven successful, but too time intensive for routine use in this application. We therefore introduce white light interferometry (WLI) as an alternative approach. We examined real surfaces and their replicas, using AFM and WLI. We find that the replica/WLI is promising to provide the large majority of the desired information, recognizing that a trade-off is being made between best lateral resolution (AFM) and the opportunity to examine much more surface area (WLI).

Keywords: Particle accelerator; Surface topography; Topography measurement; SRF accelerator

Orientation dependence of subsurface deformation in dry sliding wear of Cu single crystals by S. Yu. Tarasov; D.V. Lychagin; A.V. Chumaevskii (pp. 22-26).

► We study orientation dependence of strain in copper single crystals in dry sliding. ► We found differences in strain patterns between1¯11- and [110]-single crystals. ► As shown, severe deformation results in formation of a lip for both orientations. ► Morphology of this lip depends on the single crystal orientation and slip systems.Copper single crystals grown according to the Bridgman method and having their axes1¯11 or [110] aligned with the normal load axis were used for dry sliding experiments. As shown, sliding-induced severe plastic deformation occurred in the subsurface of single crystals and caused formation of a lip by mechanism of texture formation. The SEM structure of this lip was found to be composed of fragments with their shapes dependent on the single crystal orientation with respect to normal load and friction force. These fragments may be referred to as wear particles generated by shearing in planes parallel to the worn surface.

Keywords: Single crystal; Subsurface deformation; Dry sliding conditions; Orientation; Strain localization

Solid–liquid–solid process for forming free-standing gold nanowhisker superlattice by interfering femtosecond laser irradiation by Y. Nakata; N. Miyanaga; K. Momoo; T. Hiromoto (pp. 27-32).

► Perfectly aligned gold nanowhisker superlattice was fabricated via solid–liquid–solid process induced by interfering femtosecond laser. ► The shape is defined by liquid motion and not by crystallographic growth although its structure is polycrystalline. ► The smallest curvature radius of its vertex was 3.4nm, and the period of the nanowhisker superlattice was 2.2μm. ► The processing speed exceeds 1cm²/s.One-dimensional nanomaterial superlattices are fundamental components in plasmonics, nanophotonics, and nanoelectronics. Bottom-up techniques such as vapour–liquid–solid (VLS) and chemosynthesis have been used to fabricate the structure but are nonoptimal for controlling alignment and size. Here we report the fabrication of gold nanowhisker superlattice, based on a novel mechanism termed solid–liquid–solid (SLS). An interfering femtosecond laser pulse induces fluid flows of nanosize gold, which is followed by droplets pinching off from them and freezing of a free-standing nanowhisker superlattice fixed on a substrate. The shape is defined by liquid motion and not by crystallographic growth although its structure is polycrystalline. The smallest curvature radius of its vertex was 3.4nm, which is one-half of the smallest nanorods fabricated by chemosynthesis. SLS process is a superior alternative to sequential bottom-up processes involving catalyst fabrication, bottom-up synthesis, purification, alignment, stabilization, and preservation.

Keywords: Gold nanowhisker superlattice; Solid–liquid–solid mechanism; Femtosecond laser; Interference

Chitosan polymer as support to IgG immobilization for piezoelectric applications by Rosângela Ferreira Frade de Araújo; Cosme Rafael Martínez; Karla Patrícia de Oliveira Luna; Renata Maria Costa Souza; Danyelly Bruneska; Rosa Fireman Dutra; José Luiz de Lima Filho (pp. 33-38).

► Chitosan backbone showed to be efficient for IgG immobilization using a gold support. ► Highest concentration of NaOH on chitosan film favored a better IgG immobilization. ► The response in QCM analysis was not as predicted by the Sauerbrey equation. ► A significant variation in the crystal frequency occurred by using 2μg/mL IgG.Immunoenzymatic assays using gold plates and quartz crystal microbalance (QCM) analysis were carried out in order to evaluate chitosan/IgG interaction. Two chitosan solutions (S1 and S2) were prepared with different concentrations of NaOH (0.8% – S1 and 8% – S2). Absorbances 3-fold higher were obtained when chitosan (S2) was used as support when compared with direct IgG adsorption on gold. S1 on gold showed a better stability (at 22°C, for 72h) for IgG immobilization when compared with S2. However, S1 was used on QCM analysis and the IgG adsorption led to a non-Sauerbrey response, in which the mass on the electrode surface promote a proportional increase in the crystal resonant frequency. Direct IgG adsorption on gold electrode led to a 14.19% (±2.43) increase in crystal frequency. When S1 was used as a support for IgG, a better immobilization occurred, causing a 24.34% (±0.75) variation in crystal frequency. The structure of chitosan was shown to be efficient for IgG immobilization both in the immunoenzymatic method and in the QCM system.

Keywords: Abbreviations; QCM; quartz crystal microbalance; S1; chitosan film prepared with 0.8% NaOH; S2; chitosan film prepared with 8% NaOH; ELISA; enzyme-linked immunoabsorbent assay; OPD; ortofenilenodiamine; ANOVA; analysis of variance; HSD; honestly significant differenceAntibody; Chitosan; Gold; Immobilization; QCM

Synthesis of ZnO/CdSe hierarchical heterostructure with improved visible photocatalytic efficiency by Yao Wu; Fang Xu; Defu Guo; Zhiyong Gao; Dapeng Wu; Kai Jiang (pp. 39-44).

► ZnO/CdSe heterostructure was synthesized via a facile aqueous reaction. ► CdSe nanoparticles are dispersed on the nanoplates of ZnO microspheres. ► Enhanced photocatalytic efficiency under visible light region was obtained compared to pure ZnO.ZnO/CdSe hierarchical heterostructure was prepared using pompon-like ZnO as substrate materials, and hexagonal CdSe nanoparticles were dispersed on the ZnO plates. The hybrid ZnO/CdSe samples were intensively investigated by XRD, SEM, TEM, HRTEM, PL and UV–vis absorption spectrum. The photocatalytic experiments confirm that ZnO/CdSe heterostructure exhibits improved photocatalytic efficiency compared to pure ZnO under visible light irradiation. CdSe nanoparticles are believed to serve as photosensitizers to extend the absorption spectrum to visible light region. In addition, the incorporation of CdSe can suppress the recombination of photogenerated electron-hole pairs, which contributes to the enhancement of photocatalytic efficiency.

Keywords: ZnO/CdSe; Heterostructure; Photocatalytic

Effect of calcination temperature on the H₂O₂ decomposition activity of nano-crystalline Co₃O₄ prepared by combustion method by M.Th. Makhlouf; B.M. Abu-Zied; T.H. Mansoure (pp. 45-52).

Display Omitted► Spinel Co₃O₄ nano-particles were synthesized by combustion method using urea as a combustion fuel. ► The estimated particle size using both XRD and TEM were in the range 8–34nm depending upon calcination temperature. ► The H₂O₂ decomposition over Co₃O₄ nano-particles was found to decrease with the crystallites sized increase.Cobalt oxide nano-particles were prepared by combustion method using urea as a combustion fuel. The effects of calcination temperature, 350–1000°C, on the physicochemical, surface and catalytic properties of the prepared Co₃O₄ nano-particles were studied. The products were characterized by thermal analyses (TGA & DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Textural features of the obtained catalysts were investigated using nitrogen adsorption at −196°C. X-ray diffraction confirmed that the resulting oxide was pure single-crystalline Co₃O₄ nano-particles. Transmission electron microscopy indicating that, the crystallite size of Co₃O₄ nano-crystals was in the range of 8–34nm. The catalytic activities of prepared nano-crystalline Co₃O₄ catalysts were tested for H₂O₂ decomposition at 35–50°C temperature range. Experimental results revealed that, the catalytic decomposition of H₂O₂ decreases with increasing the calcination temperature. This was correlated with the observed particle size increase accompanying the calcination temperature rise.

Keywords: Nano crystalline cobalt oxide; Spinels; Urea; Combustion method; H; ₂; O; ₂; decomposition

Interaction of 157nm excimer laser on pristine and radiation exposed CR39 polymer by R. Zakaria; R.M. Scott (pp. 53-59).

► Surface modification on (CR39) has been investigated using VUV F₂ laser. ►We report cones formation and threshold calculation on the pristine surface. ► We observed the changes on surface after exposed to alpha radiation²²⁶Ra. ► We used chemical etching process to reveal micron size tracks and changes after laser treatment. ► Surface morphology's were also observed at different time of exposure.Surface modification effect of VUV 157nm laser on solid state nuclear track detector di-glycol carbonate (CR39), has been investigated. It covers some preliminary work on ablating pristine surface where ablation threshold obtained at this wavelength and polymer surface exposed to alpha radiation with close contact of²²⁶Ra prior to laser treatment. Two sets of samples were prepared; the first set of samples were exposed to either 1, 5 and 10s of radiation and the second set had samples exposed to 10s of radiation followed by laser treatment. A chemical etching process was used to reveal micron size tracks in the CR39 polymeric detector and for comparison with ablation on the pristine surface, one sample without etching process has been prepared. Changes on the surface of the detector were observed, revealing the tracks density at different time exposure and the effects of laser treatment with and without chemically etched. Analysing modification on this polymer detector confirm that it is a useful substrate when interact with the VUV 157nm laser.

Keywords: 157; nm laser; Polymer ablation

Enhancement of up-conversion emissions in ZnO: Er³⁺–Yb³⁺ after Gd₂O₃ surface modification by Cong Han; Yuanbao Du; Xiuqing Meng; Fengmin Wu; Yunzhang Fang (pp. 60-63).

► ZnO: Er³⁺–Yb³⁺/Gd₂O₃ core/shell nanoparticles are synthesized via a seeded. ► ZnO: Er³⁺–Yb³⁺ acts as seed and Gd₂O₃ as shell. ► Visible up-conversion (UC) emissions are observed in the seed sample. ► Gd₂O₃ shell surface modification enhances the UC emission evidently. ► The intensity of UC emission increase with the increase of Gd₂O₃ deposition times.ZnO: Er³⁺–Yb³⁺/Gd₂O₃ core/shell nanoparticles are synthesized via a seeded deposition process with ZnO: Er³⁺–Yb³⁺ nanoparticles as seeds and Gd₂O₃ as shells, respectively. Analyses on phase and structures indicate that the Gd₂O₃ shell is around 1nm in thickness. Raman signals change with the increase of Gd₂O₃ shell deposition times, which are the synergistic results of phonon confinement effect and interface strain. Visible up-conversion (UC) emissions are observed in the seed samples, after Gd₂O₃ surface modification, great enhancement of the UC emissions are observed. The detail is discussed.

Keywords: Nanoparticles; Up-conversion; Seed deposition; Sol–gel

Influence of growth ambient on the surface and structural properties of vanadium oxide nanorods by Li-Chia Tien; Yu-Jyun Chen (pp. 64-70).

► The structural and surface properties of V₂O₅ nanorods were studied by XPS and RS. ► Controlling of growth ambient enhance surface stoichiometry of V₂O₅ nanorods. ► Partially reduced surface can be obtained under reducing ambient. ► The surface non-stoichiometry may be correlated with structural disorder.The influence of growth ambient on the surface and structural properties of vanadium oxide nanorods have been studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (RS). The vanadium oxide nanorods, which were synthesized through an ambient controlled vapor transport process, exhibit different surface electronic properties depending upon the growth ambient. The Raman data indicates that the as-grown samples are orthorhombic V₂O₅ phase with a small variation of stoichiometry. Under highly oxidative conditions, nearly stoichiometry sample can be grown. If the samples were grown under less oxidizing conditions, an increase of structural disorder was observed. The observed V 2p core level spectra of both samples showed a single peak with chemical shifts corresponding to the V⁵⁺ and V⁴⁺. XPS results suggested that the highly oxidized vanadium ions (V⁵⁺) are gradually reduced to lower oxidation state (V⁴⁺) with the decreases of ambient oxygen levels during growth. The results clearly show that surface non-stoichiometry may be correlated with structural disorder of V₂O₅ nanorods. The growth ambient and post-annealing may influence the vanadium oxidation state and subsequent surface reactivity significantly.

Keywords: Nanorods; Vanadium oxide; XPS; Raman

Wettability and XPS analyses of nickel–phosphorus surfaces after plasma treatment: An efficient approach for surface qualification in mechatronic processes by L. Vivet; A.-L. Joudrier; M. Bouttemy; J. Vigneron; K.L. Tan; J.M. Morelle; A. Etcheberry; L. Chalumeau (pp. 71-78).

► Plasma induced transformations of NiP surface properties and composition have been studied. ► The plasma treatment provokes a strong increase of the polar fraction of the superficial tension. ► Benefit of the plasma treatment for electronic and mechatronic assembly processes achieved under ambient conditions is demonstrated. ► This effect is correlated with the elimination of the carbon contamination of the surface. ► In the same time the oxidation and nitridation of the underneath NiP metal surface occurs. ► Benefit of the plasma treatment on solderability depends on the balance between these effects.Electroless nickel-high-phosphorus Ni–P plating is known for its physical properties. In case of electronic and mechatronic assembly processes achieved under ambient conditions the wettability of the Ni–P layer under ambient temperature and ambient air stays a point of surface quality investigation. This contribution will be devoted to the study of the surface properties of Ni–P films for which we performed air plasma treatment. We focus our attention on the evolution of the surface wettability, using the classical sessile drop technique. Interpreting the results with the OWRK model we extract the polar and disperse surface tension components from which we deduced typical evolution of the surface properties with the different treatment settings. By controlling the variations of the parameters of the plasma exposure we are able to change the responses of our Ni–P sample from total hydrophobic to total hydrophilic behaviours. All the intermediate states can be reached by adapting the treatment parameters. So it is demonstrated that the apparent Ni–P surface properties can be fully adapted and the surface setting can be well characterized by wettability measurements. To deep our knowledge of the surface modifications induced by plasma we performed parallel SEM and XPS analyses which provide informations on the structure and the chemical composition of the surface for each set of treatment parameters. Using this double approach we were able to propose a correlation between the evolution of surface chemical composition and surface wettability which are completely governed by the plasma treatment conditions. Chemical parameters as the elimination of the carbon contamination, the progressive surface oxidation, and the slight incorporation of nitrogen due to the air plasma interaction are well associated with the evolution of the wettability properties. So a complete engineering for the Ni–P surface preparation has been established. The sessile drop method can be considered as a very efficient method to propose qualification of treatments onto Ni–P surfaces before performing electronic and mechatronic assembly processes that are achieved under ambient conditions.

Keywords: NiP coating; Wetability; Bare dice glueing; Resin deposition; Potting; Plasma treatment; Sessile drop test

Selectively grown vertical silicon nanowire p–n⁺ photodiodes via aqueous electroless etching by Hyonik Lee; Juree Hong; Seulah Lee; Sung-Dae Kim; Young-Woon Kim; Taeyoon Lee (pp. 79-84).

► Simple method to selectively grow vertically-aligned SiNWs by photolithography and aqueous electroless etching. ► The use of SU-8-2002 provides a high selectivity for the etching reaction on the exposed surface of (100) Si substrate. ► p–n⁺ junction SiNW photodiode arrays were fabricated and their electrical and optical properties were measured. ► SiNW photodiode exhibited higher performances compared to those of the planar device.A facile method to selectively grow vertically-aligned silicon nanowires (SiNWs) which can inherit the doping concentration from its mother wafer, with controllable length, is demonstrated using the combination of photolithography and aqueous electroless etching. The use of SU-8-2002, a chemically and mechanically robust photoresist (PR) material, provided a high selectivity for the etching reaction on the exposed surface of 1-μm-thick n⁺ doped p-type (100) Si substrate, resulting in the fabrication of ∼30-μm-long vertically-aligned SiNW photodiode arrays on the desired locations, while the areas covered with SU-8-2002 remained unreacted. Optical and field emission scanning electron microscope analyses confirmed that SiNWs were selectively grown while retaining the shape of the PR patterns. The electrical and optical measurements of the fabricated p–n⁺ junction SiNW photodiodes were compared to those of reference planar p–n⁺ junction Si photodiodes: the current density of the p–n⁺ junction SiNW photodiodes was approximately 3 times greater than that of the planar counterpart at the forward bias of 5V, which can be attributed to the high density of defect states on the rough surfaces of the synthesized SiNWs, leading to the increased recombination efficiencies for the injected carriers. In addition, the photoresponse of the p–n⁺ SiNW photodiode arrays was 3.4 times higher than that of the planar device at −3.5V due to the increase in the light scattering.

Keywords: Selectively grown silicon nanowires; Silicon nanowire photodiode; Nanowire devices; Seletive growth nanowires

Complementary resistive switching mechanism in Ti-based triple TiO_x/TiN/TiO_x and TiO_x/TiO_xN_y/TiO_x matrix by Ah Rahm Lee; Yoon Cheol Bae; Hyun Sik Im; Jin Pyo Hong (pp. 85-88).

► CRS characteristics are demonstrated in Pt/TiO_x/TiN/TiO_x/Pt and Pt/TiO_x/TiO_xN_y/TiO_x/Pt configurations. ► The observed CRS can be attributed to the combined effects of redox reactions and the formation of a conducting path. ► Control of the current level and threshold voltages by means of oxygen content in the middle layer.We report the complementary resistive switching (CRS) origins of two hetero TiO_x/TiN/TiO_x and TiO_x/TiO_xN_y/TiO_x matrix, allowing for the possible memory operation without the use of selection device. Each matrix consisted of anti-serially combined bipolar switching elements 1 and 2, where one bipolar switching element 1 was Pt/top TiO_x/bottom TiN or TiO_xN_y, and the other switching element 2 was top TiN or TiO_xN_y/bottom TiO_x/Pt. The electrical properties of the two matrices suggested that the nature of CRS behaviors was based on a combination of the filamentary conduction paths in the top and bottom TiO_x layers and the redox reaction induced by oxygen ion drift at the interfaces of the middle TiN and TiO_xN_y layers.

Keywords: ReRAM; Complementary resistive switching; Resistive switching; CRS; Titanium oxide

Influence of thermal treatment on thermo-mechanical stability and surface composition of carbon fiber by J.J. Sha; J.X. Dai; J. Li; Z.Q. Wei; J.-M. Hausherr; W. Krenkel (pp. 89-94).

For investigating the influence of thermal treatment on the thermo-mechanical stability and the carbon fiber's surface composition, the T300 carbon fibers were thermally treated at temperatures ranging from 600°C to 1500°C. After treatment, the thermal stability and microstructure were analyzed by mass change and XRD measurement. The mechanical properties and the surface composition of carbon fibers were measured as a function of temperature by the single filament tensile test technique and ESCA analysis, respectively. The results indicated that T300 fiber had good thermal stability and high temperature mechanical properties. To some extent, the high temperature treatment could lead to a further graphitization of carbon fiber. The surface composition measured by ESCA revealed that the oxygen concentrations on the surface of fibers significantly decreased from 17.97% for as-received fiber to 1.97% for 1500°C treated fibers. But the relative content of graphite-like carbon increased from 42.97% for as-received fibers to 53.13% for 1500°C treated fibers. Such composition would result in a decreased surface activity of carbon fiber.

Keywords: Carbon fiber; Thermal treatment; Surface composition; Thermo-mechanical stability

Microstructure and physical properties of sol gel derived SnO₂:Sb thin films for optoelectronic applications by S. Sujatha Lekshmy; Georgi P. Daniel; K. Joy (pp. 95-100).

Color images of SnO2:Sb thin films (a) 0mol%, (b) 1mol%, (c)3mol%, (d) 5mol% Sb.Display Omitted► SnO₂:Sb thin films were deposited on glass substrates by sol–gel method. ► This film showed an inhibition of grain growth with increase in Sb concentration. ► These films acquire n-type conductivity due to non- stoichiometry and by the addition of Sb. ► The films exhibit a band gap widening which is important in window layer coating. ► The intense UV PL emission leads to generation of solid state lighting in LED. ► The rms roughness value of SnO₂:Sb thin films are found to 1% of film thickness which makes them suitable for optoelectronic applications.Antimony doped tin oxide thin films were deposited on glass substrates by sol-gel dip coating technique. X-ray diffraction pattern showed the deterioration of the crystallinity of the films with increase in antimony doping concentration. Atomic force microscopy studies showed an inhibition of grain growth with increase in Sb concentration.The rms roughness value of SnO₂:Sb thin films are found to 1% of film thickness which makes them suitable for optoelectronic applications. The film surface revealed positive skewness and high kurtosis values which make them favorable for tribological applications. The lowest resistivity (about10⁻⁵Ωm) was obtained for the 5mol% Sb doped SnO₂: Sb films. These films acquire n-type conductivity due to non- stoichiometry (oxygen vacancies and interstitial tin atoms) and by the addition of Sb. The optical properties of the films have been studied from transmission spectra. An average transmittance of >80% (in UV–vis region) was observed for all the films. Optical band gap energy of SnO₂:Sb films were found to vary in the range of 3.69–3.97eV with the increase in Sb doping concentration. Photoluminescence spectra of the films exhibited an increase in the emission intensity with increase in antimony doping concentration which is due the combined effect of charge balance and decrease in grain size. The enhancement of PL intensity in the antimony doped SnO₂ thin films make it suitable for generation of solid state lighting in light emitting diode.

Keywords: SnO; ₂; Thin films; Sol gel dip coating; Optical properties; Conductivity; Photoluminescence

Antibacterial characteristics of electroless plating Ni–P–TiO₂ coatings by Qi Zhao; Chen Liu; Xueju Su; Shuai Zhang; Wei Song; Su Wang; Guiling Ning; Junwei Ye; Yuan Lin; Weitao Gong (pp. 101-104).

•A range of Ni–P–TiO₂ nano-composite coatings were prepared on stainless steel 316L using electroless plating technique.•The Ni–P–TiO₂ coatings reduced bacterial adhesion by up to 75%, compared with stainless steel.•The electron donor surface energy of the Ni–P–TiO₂ coatings increased significantly with increasing TiO₂ content.•The number of adhered bacteria decreased with increasing electron donor surface energy of the coatings.•The Ni–P–TiO₂ coatings have potential applications in heat exchangers and pipelines etc. to reduce biofouling formation.Electroless Ni–P coatings have been widely used in the chemical, mechanical and electronic industries due to their excellent corrosion and wear resistance. Many studies reported that the incorporation of nano-sized particles TiO₂ into Ni–P matrix greatly improved their anti-corrosion and anti-wear resistance. However no studies have been reported on their anti-bacterial property. In this paper, the Ni–P–TiO₂ nano-composite coatings were prepared on stainless steel 316L using electroless plating technique. The experimental results showed that the Ni–P–TiO₂ coatings reduced the adhesion of three bacterial strains ( Pseudomonas fluorescens, Cobetia and Vibrio) by up to 75% and 70% respectively, as compared with stainless steel and Ni–P coatings. The electron donor surface energy of the Ni–P–TiO₂ coatings increased significantly with increasing TiO₂ content after UV irradiation. The number of adhered bacteria decreased with increasing electron donor surface energy of the coatings.

Keywords: Ni–P–TiO; ₂; Nano-composite coatings; Surface energy; Bacterial adhesion

Processing condition influence on the characteristics of gold nanoparticles produced by pulsed laser ablation in liquids by R.G. Nikov; A.S. Nikolov; N.N. Nedyalkov; P.A. Atanasov; M.T. Alexandrov; D.B. Karashanova (pp. 105-109).

► Au colloids were prepared by nanosecond laser ablation of solid in water. ► The influence of laser wavelength on the particle size distribution was studied. ► The formation of nanowires using 355 and 532nm laser wavelengths was observed. ► Unfocused laser illumination of the colloid leads to nanowires disintegration. ► Optical transmission spectra of the samples were measured from 300 to 900nm.A study is presented of Au nanoparticles (NPs) created by nanosecond pulsed laser ablation of a solid target in double distilled water. The influence was examined of the laser wavelength on the size, shape and optical properties of the resulting NPs. Three different wavelengths: the fundamental ( λ=1064nm), second ( λ_SHG=532) and third ( λ_THG=355) harmonic of a Nd:YAG laser at the same fluence were utilized to produce various colloids. Ablation at the wavelength of 532nm was investigated in more detail to reveal the influence of self-absorption by the already created NPs on their characteristics. The colloid produced was irradiated by λ_irrad=532nm (laser energy 40mJ) at different times up to 25min after the end of ablation. The initial structure of welded NPs forming wires was modified. Transmission electron microscopy and optical transmission measurements were used to evaluate the shape and size distribution of the NPs.

Keywords: Au nanoparticles; Nanowires; Nanosecond laser ablation; Aqueous colloids; Chain fragmentation; Optical extinction spectra

Bio-template-assisted synthesis of hierarchically hollow SiO₂ microtubes and their enhanced formaldehyde adsorption performance by Yao Le; Daipeng Guo; Bei Cheng; Jiaguo Yu (pp. 110-116).

•Hierarchical hollow SiO₂ microtubes (HHSM) are prepared using CTAB and bio-template poplar catkin (PC) as co-templates.•Amine-modified HHSM samples present good formaldehyde adsorption capacity.•The maximum formaldehyde adsorption capacity (20.65mg/g adsorbent) was obtained on the P0.3-50 sample.•The maximum adsorption capacity is due to the synergistic effects of amine groups of TEPA and the high specific surface area of the sample.The indoor air quality is crucial for human health, taking into account that people often spend more than 80% of their time in houses, offices and cars. Formaldehyde (HCHO) is a major pollutant and long-term exposure to HCHO may cause health problems such as nasal tumors and skin irritation. In this work, for the first time, hierarchically hollow silica microtubes (HHSM) were synthesized by a simple sol–gel and calcination method using cetyltrimethyl ammonium bromide (CTAB) and bio-template poplar catkin (PC) as co-templates and the PC/SiO₂ weight ratio R was varied from 0, 0.1, 0.3 and 1. The prepared samples were further modified with tetraethylenepentamine (TEPA) and characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), and N₂ physisorption techniques. This was followed by formaldehyde adsorption tests at ambient temperature. The results showed that all the prepared HHSM samples contained small mesopores with peak pore size at ca. 2.5nm and large several tens of nanometer-sized pores on the tube wall. The R exhibited an obvious influence on specific surface areas and the sample prepared at R=0.3 exhibited highest specific surface area (896m²/g). All the TEPA-modified samples exhibited enhanced formaldehyde adsorption performance. The maximum HCHO adsorption capacity (20.65mg/g adsorbent) was achieved on the sample prepared at R=0.3 and modified by 50wt.% TEPA. The present study will provide new insight for the utilization of bio-template used for the fabrication of inorganic hollow tubes with high HCHO adsorption performance for indoor air purification.

Keywords: Silica tubes; Hollow; TEPA; Adsorption; Formaldehyde

Anatase TiO₂ single crystals with dominant {001} facets: Facile fabrication from Ti powders and enhanced photocatalytical activity by Min Liu; Hongmei Li; Yangsu Zeng; Tongcheng Huang (pp. 117-123).

•Anatase TiO₂ single crystals with 75% {001} facets were fabricated from Ti powders successfully.•The influence of the experimental factors was systematically studied.•The anatase TiO₂ single crystals show a superior photocatalytic activity.•This work opens a brand new avenue to prepare TiO₂ single crystals from low-cost Ti powders.Anatase TiO₂ single with dominant {001} facets were fabricated from Ti powders through a facile hydrothermal method. The obtained TiO₂ single crystals have a remarkable ~75% fraction of {001} facets. The crystallographic structure of the anatase products and the influence of the experimental factors, such as the reaction temperatures, the amount of precursor, and the reaction time, on the morphology and the exposed facets were investigated systematically by X ray diffraction, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy spectra. Owing to the highly reactive dominant {001} facets and the high crystallinity, the obtained anatase TiO₂ products exhibited significantly superior activities compared with commercial P25 titania nanoparticles in the photocatalytic degradation of methylene blue dye.

Keywords: Ti powders; TiO; ₂; single crystals; {0; 0; 1} Facets; Enhanced photocatalytical activity

Reactive wetting in liquid magnesium/silica and magnesium/silicon systems by Laixin Shi; Ping Shen; Dan Zhang; Erting Dong; Qichuan Jiang (pp. 124-130).

•Silica is well wetted by molten Mg.•Interfacial reaction leads to the formation of a periodically layered structure.•Formation mechanism was discussed based on thermodynamic and kinetic considerations.•Rapid wetting is mainly attributed to the formation of Mg₂Si at the interface.The reactive wetting of SiO₂ and Si by molten Mg in a flowing Ar atmosphere was studied using an improved sessile drop method. The initial contact angles in the Mg/SiO₂ system decreased from 56° to 35° as temperature increased from 973K to 1073K, and they decreased very rapidly with time during isothermal holding. The interfacial reaction led to the formation of a distinct reaction zone, consisting mainly of a thin Mg₂Si layer, an MgO layer, a periodic alternatively arranged MgO and Mg₂Si layer, and an aggregated Mg₂Si–MgO mixture layer. The formation mechanism of these complex structures was discussed based on thermodynamic and kinetic considerations. Moreover, the effect of the interfacial reaction on the wetting improvement was examined and the primary contribution was ascribed to the formation of Mg₂Si at the interface, which was further demonstrated by the result in the Mg/Si system.

Keywords: Wetting; Reaction; Mg; SiO; ₂

Simple synthesis of layered CeO₂–graphene hybrid and their superior catalytic performance in dehydrogenation of ethylbenzene by Qiang Ling; Ming Yang; Richuan Rao; Hongxiao Yang; Qingyun Zhang; Huade Liu; Aimin Zhang (pp. 131-137).

•Layered CeO₂/graphene exhibits excellent catalytic oxidative performance.•High catalytic activity is owing to larger surface and steadily dispersed CeO₂.•Acrylamide plays a crucial role for the formation of the layered hybrid material.In this work, we reported a facile synthesis of layered CeO₂ nanomaterials on reduced graphene via using acrylamide (AM) as complex precipitant. The characterized results indicated that the CeO₂ nanoparticles (NPs) with about 4–6nm are dispersed uniformly on the surface of graphene and still keep same NPs size and similar layered morphology after calcination at 550°C in the atmosphere of argon. The superior catalytic performance of the prepared CeO₂–RGO-5 in dehydrogenation of ethylbenzene (EB) can be attributed to its high specific surface area offered by the unique two-dimensional layered structure and their steadily dispersed NPs obtained by adding of enough AM.

Keywords: CeO; ₂; –graphene; Layered structure; Acrylamide (AM); Ethylbenzene (EB) Dehydrogenation (DH)

Enhanced activity of Pd nanoparticles supported on Vulcan XC72R carbon pretreated via a modified Hummers method for formic acid electrooxidation by Jianyu Cao; Lingzheng Song; Jiali Tang; Juan Xu; Wenchang Wang; Zhidong Chen (pp. 138-143).

Display Omitted•XC72R carbon was pretreated by a modified Hummers method and adopted as the support.•Surface carboxyl groups significantly increase after pretreatment.•The Pd nanoparticles on pretreated XC72R display high electrocatalytic activity.Vulcan XC72R carbons were pretreated using a modified Hummers method and adopted as the support of palladium nanoparticles for formic acid electrooxidation. XPS analysis was used to investigate the surface species of the pretreated XC72R (XC72R-O), indicating a significant increase in the content of surface carboxyl groups. The structural properties of Pd nanoparticles deposited on the XC72R-O (Pd/XC72R-O) were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and their electrochemical performance was evaluated by cyclic voltammetry (CV) and chronoamperometry. Pd nanoparticles in the Pd/XC72R-O display an average size of ~6.7nm with narrow size distribution. Electrochemical studies for formic acid oxidation reveal that the Pd/XC72R-O presents much higher electrocatalytic activity than that of the Pd/XC72R and commercial Pd/C, which may be due to the formation of carboxyl groups enhanced the interaction between the Pd particles and the carbon support, facilitating the dispersion of Pd particles and the formation of preferred plane orientation available for electrocatalytic reaction.

Keywords: Carbon support; Modified Hummers method; Palladium nanoparticles; Electrooxidation; Direct formic acid fuel cell

Microstructural, mechanical and oxidation features of NiCoCrAlY coating produced by plasma activated EB-PVD by Jian He; Hongbo Guo; Hui Peng; Shengkai Gong (pp. 144-150).

•NiCoCrAlY coatings are produced by plasma activated electron beam-physical vapor deposition (PA EB-PVD).•The novel coatings show a terraced substructure on the surface of each grain.•The toughness of the coatings produced by PA EB-PVD gets remarkably improved.•The novel coatings exhibit excellent isothermal oxidation resistance at 1373K.NiCoCrAlY coatings produced by electron beam-physical vapor deposition (EB-PVD) have been extensively used as the oxidation resistance coatings or suitable bond coats in thermal barrier coating (TBC) system. However, the inherent imperfections caused by EB-PVD process degrade the oxidation resistance of the coatings. In the present work, NiCoCrAlY coatings were creatively produced by plasma activated electron beam-physical vapor deposition (PA EB-PVD). The novel coatings showed a terraced substructure on the surface of each grain due to the increased energy of metal ions and enhanced mobility of adatoms. Also a strong (111) crystallographic texture of γ/γ′ grains was observed. The toughness of the coatings got remarkably improved compared with the coatings deposited by conventional EB-PVD and the oxidation behavior at 1373K showed that the novel coatings had excellent oxidation resistance. The possible mechanism was finally discussed.

Keywords: Coating; Structure; Oxidation; Plasma activated electron beam physical vapor deposition (PA EB-PVD)

Surface modification of calcium hydroxyapatite by grafting of etidronic acid by Masseoud Othmani; Abdallah Aissa; Christophe Goze Bac; Férid Rachdi; Mongi Debbabi (pp. 151-157).

•Our studies of apatite–etidronic acid hybrid compounds highlight the influence of apatitic surface in grafting process.•We showed that the apatitic surface possesses two different functional groups CaOH and POH acting as the active sites.•Synthesizing CaHAp-(ETD) composites offers a relevant tool as possible application as biomaterials to repair bone tissues.The surface of prepared calcium hydroxyapatite CaHAp has been modified by grafting the etidronic acid (ETD). For that purpose, CaHAp powders have been suspended in an aqueous etidronate solution with different concentrations. The obtained composites CaHAp-(ETD) were characterized by TEM and AFM techniques to determinate morphological properties and were also characterized by XRD, IR, NMR and chemical and thermal analysis to determinate their physico-chemical properties and essentially the nature of the interaction between the inorganic support and the grafted organic ETD. After reaction with ETD, XRD powder analysis shows that the apatitic structure remains unchanged with slight affectation of its crystallinity. The presence of etidronate fragment bounded to hydroxyapatite was confirmed by IR and solid-state NMR spectroscopy. TEM and AFM techniques indicate that the presence of etidronate changes the morphology of the particles. Basing on the obtained results, a reactional mechanism was proposed to explain the formation of covalent CaOP_org bonds on the hydroxyapatite surface between the superficial hydroxyl groups (CaOH) of the apatite and phosphonate group (POH) of etidronate.

Keywords: Hydroxyapatite; Etidronic acid; Surface modification; Grafting; Biomaterials

Mechanochemical approach for synthesis of layered double hydroxides by Xiaoqing Zhang; Shuping Li (pp. 158-163).

A mechanochemical method, which involves manually grinding and afterwards hydrothermal treatment, is developed to prepare uniform and high crystalline LDHs particles, the hydrothermal treatment is found to be beneficial for the crystallinity and regularity of LDHs particles.Display Omitted•Hydrothermal treatment is beneficial for crystallization and regularity of LDHs.•Combination of grinding and hydrothermal treatment leads to uniform particles.•The degree of precursors to LDHs after grinding depends on their melting points.•Intercalation of water layer has been proved after hydrothermal treatment.In this paper, a mechanochemical approach is used to prepare layered double hydroxides (LDHs). This approach involves manually grinding the precursor, nitrates and then the hydrothermal treatment. The study indicates that grinding leads to the incomplete formation of LDHs phase, LDHs-M. The reaction degree of precursor salts to LDHs after grinding depends on the melting points of the precursors. As expected, hydrothermal treatment is beneficial for the good crystallization and regularity of LDHs. Especially, the effect of hydrothermal treatment has been emphatically explored. The hydration of LDHs-M, increment of zeta potentials and the complete exchange of NO₃⁻ by CO₃²⁻ anions occur successively or in parallel during the hydrothermal treatment. It can be found that combination of grinding and hydrothermal treatment gives rise to the formation of uniform and monodispersed particles of LDHs.

Keywords: Layered compounds; Mechanochemical approach; Hydrothermal treatment; Grinding

Molecular dynamic simulation of binary Zr_xCu100−_x metallic glass thin film growth by Lu Xie; Pascal Brault; Anne-Lise Thomann; Larbi Bedra (pp. 164-170).

•MD simulation of Zr_xCu100−_x metallic glass thin film shows amorphous structure for 3< x<95.•Simulated and experimental X-ray diffraction patterns are close together.•Radial distribution functions display the crystalline–amorphous transition.In this work, we employed classical molecular dynamics simulations model to study Zr_xCu100−_x (3≤ x≤95) metallic glass films deposited on a silicon (100) substrate. Input data were chosen to fit with the experimental operating conditions of a magnetron sputtering deposition system. The growth evolution is monitored with variable compositions of the incoming atom vapor. The Zr–Zr, Cu–Cu and Zr–Cu interactions are modeled with the Embedded Atom Method (EAM), the Si–Si interaction with Tersoff potential, the Zr–Si and Cu–Si interactions with Lennard-Jones (12-6) potential. Different film morphology and structure were detected and analyzed when the Zr to Cu ratio is varied. The results are compared with X-ray diffraction and scanning electron microscopy analyses of experimentally deposited thin films by magnetron sputter deposition process. Both simulation and experiment results show that the structure of the Zr_xCu100−_x film varies from crystalline to amorphous depending on the elemental composition.

Keywords: Molecular dynamics simulation; Thin film growth; Metallic glass; Alloy; Sputtering deposition

Effect of hydrogen plasma treatment on nano-structured TiO₂ films for the enhanced performance of dye-sensitized solar cell by Hyung Jin Kim; Jumi Kim; Byungyou Hong (pp. 171-175).

•We present an efficient method to improve the efficiency and stability of DSSC.•We utilized a low temperature RF plasma-enhanced chemical vapor deposition system to treat hydrogen plasma TiO₂ film.•DSSC with plasma-treated TiO₂ exhibited high performance with an increase in J_sc and V_oc.We report an efficient method to improve the efficiency and stability of DSSC with nano-structured TiO₂. A low temperature RF plasma-enhanced chemical vapor deposition (PECVD) system was utilized for hydrogen plasma treatment on nano-structured TiO₂ film. We confirmed that the efficiency of DSSCs was significantly dependent on the plasma power. This increased the hydrophilic property, the excess electrons and dye adsorption on its surface. The relative change in surface chemistry and hydrophilic characteristics with plasma treatment was investigated using various analysis methods. In our study, we showed that DSSC with plasma-treated TiO₂ had a power conversion efficiency of 6.94%, which is 21% higher than that without plasma treatment. It was found that the plasma treatment caused both increased dye adsorption and significant longer electron lifetime.

Keywords: Dye-sensitized solar cells (DSSCs); Nano-structured TiO; ₂; film; Plasma treatment

Modification of SrTiO₃ surface by nitrogen ion bombardment for enhanced photocatalysis by Tao Sun; Ming Lu (pp. 176-180).

•Simultaneous incorporation of nitrogen ions and surface defects into SrTiO₃.•Achieving a fairly strong and broadband photocatalysis in SrTiO₃.•Demonstrating a synergetic method to improve the photocatalytic ability of SrTiO₃.Modification of SrTiO₃ (STO) surface by nitrogen ion bombardment was performed in order to achieve a strong and broadband photocatalysis in STO via incorporations of nitrogen ions and surface defects. Enhanced UV photocatalysis and a fairly strong visible-light one were observed in nitrogen ion-bombarded STO. UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy, cross-sectional transmission electron microscopy, atomic force microscopy and contact angle measurements were performed. The characterization results revealed that nitrogen ions and surface defects were introduced simultaneously. The incorporated nitrogen ions were found to narrow the band gap of STO, and the surface defects acted as extra adsorptive sites, which make a strong and broadband photocatalysis possible. Our work indicates that nitrogen ion bombardment is an effective method to enhance the photocatalytic ability of STO in a synergetic manner.

Fabrication of bioactive titania coating on nitinol by plasma electrolytic oxidation by H.T. Siu; H.C. Man (pp. 181-187).

•Thick and porous TiO₂ was fabricated on NiTi by plasma electrolytic oxidation.•By using an appropriate electrolyte and a low voltage, anatase was formed.•The corrosion resistance in Hanks’ solution is significantly improved.•The surface Ni content is greatly reduced.•The plasma-electrolytic oxidized NiTi possesses high apatite-forming ability.Surface modification was attempted on Nitinol (NiTi) by plasma electrolytic oxidation (PEO) in aqueous solutions of sodium sulphate and sodium hydroxide (Na₂SO₄-NaOH) using an AC power supply. A thick and porous oxide layer with micron-sized pores was formed on the Nitinol substrate, with the thickness of the oxide layer ranging from a few μm to over 10μm, depending on the processing time. X-ray diffraction (XRD) analysis confirmed that the oxide formed was anatase. Potentiodynamic polarization tests in Hanks’ solution showed that the corrosion resistance of PEO-coated Nitinol was much higher than that of the substrate. More importantly, the apatite-forming ability of the PEO-treated NiTi was found to be enhanced. This could be attributed to the anatase crystalline structure of the titanium oxide and the porous structure that facilitates the anchorage of the hydroxyapatite particles.

Keywords: Nickel Titanium (NiTi); Plasma Electrolytic Oxidation (PEO); Titanium Oxide; Corrosion; Apatite

Preparation of photoluminescent single crystalline MgO nanobelts by DC arc plasma jet CVD by Mingji Li; Xiufeng Wang; Hongji Li; Hairong Di; Xiaoguo Wu; Changri Fang; Baohe Yang (pp. 188-194).

•MgO nanobelts were grown by DC arc plasma jet CVD process for the first time.•The growth time of nanobelts does not exceed 5min.•The formation of nanobelts does not dependent on the reported growth mechanism.•Tadpole, dendrite, belt, and rod-like crystallites were prepared.•The as-prepared MgO nanobelts exhibit a strong blue-green emission.Magnesium oxide (MgO) nanostructures were synthesized by DC arc plasma jet chemical vapor deposition, which possesses the advantages of being simple, economical, fast, effective and environmentally benign. The formation of “tadpole”-, dendrite-, belt- and rod-like MgO nanostructures was confirmed by scanning electron microscopy and high-resolution transmission electron microscopy. Powder X-ray diffraction analysis revealed that the nanostructures consist of cubic phase MgO. Nanobelts that were 30–50nm wide with a width/thickness ratio of 1–2 were synthesized in just 5min. Most of the nanobelts were connected to others, and the connected nanobelts possessed a single-crystal structure. A formation mechanism for MgO nanostructures was proposed. Fourier transform infrared spectra indicated the adsorption of water and CO₂ on the MgO surface. The nanobelts exhibited relatively strong blue-green luminescence.

Keywords: MgO; Nanostructures; DC arc plasma jet CVD; Growth mechanism; Photoluminescence properties

Characterization of atomic structure of oxide films on carbon steel in simulated concrete pore solutions using EELS by H. Burak Gunay; Pouria Ghods; O. Burkan Isgor; Graham J.C. Carpenter; Xiaohua Wu (pp. 195-202).

•Atomic structure of oxides on carbon steel in concrete pore solutions is studied.•Effects of pore solution composition and chloride are investigated.•Inner film was mainly Fe^IIO and became unprotective after chloride exposure.•Chlorides induce valence state transformation of oxides from Fe^II to Fe^III.•Chemical compositions of the oxide films vary in different pore solutions.The atomic structure of oxide films formed on carbon steel that are exposed to highly alkaline simulated concrete pore solutions was investigated using Electron Energy Loss Spectroscopy (EELS). In particular, the effect of chloride exposure on film structure was studied in two types of simulated pore solutions: saturated calcium hydroxide (CH) and a solution prepared to represent typical concrete pore solutions (CP). It was shown that the films that form on carbon steel in simulated concrete pore solutions contained three indistinct layers. The inner oxide film had a structure similar to that of Fe^IIO, which is known to be unstable in the presence of chlorides. The outer oxide film mainly resembled Fe₃O₄ (Fe^IIO·Fe₂^IIIO₃) in the CH solution and α-Fe₂^IIIO₃/Fe₃O₄ in the CP solution. The composition of the transition layer between the inner and outer layers of the oxide film was mainly composed of Fe₃O₄ (Fe^IIO·Fe₂^IIIO₃). In the presence of chloride, the relative amount of the Fe^III/Fe^II increased, confirming that chlorides induce valence state transformation of oxides from Fe^II to Fe^III, and the difference between the atomic structures of oxide film layers diminished.

Keywords: EELS; Passive film; Carbon steel rebar; Corrosion; Chloride; Concrete

Nanocrystalline biphasic resorbable calcium phosphate (HAp/β-TCP) thin film prepared by electron beam evaporation technique by K. Elayaraja; V. Sarath Chandra; M.I. Ahymah Joshy; R.V. Suganthi; K. Asokan; S. Narayana Kalkura (pp. 203-209).

•First report of BCP deposited by e-beam evaporation technique.•Cost effective and versatile technique to prepare BCP thin film.•Has resorbable β-TCP and HAp phases with enhanced in vitro bioactivity.•Hydrophilic BCP surface found to enhance the cell attachment and apatite growth.•Partial absorbability and bioactivity of the layer could assist the bone regeneration.Biphasic calcium phosphate (BCP) thin film having resorbable β-tricalcium phosphate (β-TCP) and non-resorbable hydroxyapatite (HAp) phases having enhanced bioactivity was synthesized by electron beam evaporation technique. Nanosized BCP was deposited as a layer (500nm) on (001) silicon substrate by electron beam evaporation and crystalline phase of samples were found to improve on annealing at 700°C. Uniform deposition of calcium phosphate on silicon substrate was verified from elemental mapping using scanning electron microscope (SEM-EDX). Annealing of the samples led to a decrease in surface roughness, hydrophobicity and dissolution of the coating layer. Amoxicillin loaded thin films exhibited significant bacterial resistance. In addition, BCP thin films did not exhibit any cytotoxicity. Antibiotics incorporated BCP coated implants might prevent the post-surgical infections and could promote bone-bonding of orthopedic devices.

Keywords: Biomaterials; Electron beam evaporation; Wettability; Bioactivity; Drug delivery system

Effect of fiber surface on flexural strength in carbon fabric reinforced epoxy composites by Thatiane Brocks; Maria Odila Hilário Cioffi; Herman Jacobus Cornelis Voorwald (pp. 210-216).

•The interface of two composites processed by RTM was analyzed with flexural test, SEM and DMA.•To explain the difference on results between T800HB and IM7 carbon fiber surfaces, both were analyzed with FTIR and SEM.•Although both have showed good results, the IM7 fiber showed high interfacial adhesion.•The reason for this results was attributed to IM7 surface coating.The effect of carbon fiber surface characteristics on flexural properties of structural composites is studied in this work. Two types of intermediate modulus carbon fibers were used: T800HB and IM7. Results revealed that higher mechanical properties are linked with higher interfacial adhesion. Morphologies and chemical compositions of commercial carbon fibers (CF) were characterized by Fourier Transformed Infra Red (FTIR) and Scanning Electronic Microscopy (SEM). Comparing the results, the T800HB apparently has more roughness, since the IM7 seems to be recovered for a polymeric film. On other hand, the IM7 one shows higher interactivity with epoxy resin system Cycom 890 RTM. Composites produced with Resin Transfer Molding (RTM) were tested on a flexural trial. Interfacial adhesion difference was showed with SEM and Dynamic Mechanical Analyses (DMA), justifying the higher flexural behavior of composites made with IM7 fibers.

Keywords: Surface properties; Interfacial adhesion; Structural composites; Flexural properties

NO₂ detection by nanosized AlN sheet in the presence of NH₃: DFT studies by Somayeh F. Rastegar; Ali Ahmadi Peyghan; H.R. Ghenaatian; Nasser L. Hadipour (pp. 217-220).

•Adsorption of NH₃ and NO₂ molecules on aluminum nitride nanosheet was investigated.•It was revealed that the conductivity of AlN may be increased upon NO₂ adsorption.•The AlN sheet might selectively detect the NO₂ molecule in the presence of NH₃.Adsorption of NH₃ and NO₂ molecules on aluminum nitride (AlN) nanosheets was investigated by using density functional calculations. Equilibrium geometries, stabilities, and electronic properties of NH₃ and NO₂ adsorptions on the surface of an AlN surface were identified. The adsorption energies were calculated to be about −91.84 and −95.02kJ/mol for NH₃ and NO₂ corresponding to the most stable configurations, respectively. It was revealed that the electrical conductivity of the sheet may be increased upon the NO₂ adsorption, being insensitive toward NH₃ adsorption. Thus, the AlN sheet may selectively detect NO₂ molecules in the presence of NH₃ molecules.

Keywords: Ammonia; Nitrogen dioxide; DFT; Graphene like; B3LYP

Fluorinated saccharides on the Si(001) surface by Anna Szwajca; Magdalena Rapp; Monika Bilska; Maciej Krzywiecki; Henryk Koroniak (pp. 221-230).

The attachment of saccharide molecules directly to silicon surface was studied. The resulting monolayers were characterized by AFM, XPS, ATR infrared spectroscopy and surface wettability.•The attachment of five different fluorinated pentofuranoses directly to silicon Si(001) surface have been describe.•The structural contribution of OH group as a unit of sugar bonded to the surface was evaluated and improved by XPS analysis.•The CA analysis was performed at saccharide layers with a different number of fluorine atoms.•The computational study was performed providing a molecular level description of monolayer structure on Si(001).The attachment of saccharide molecules directly to silicon surface has been for the first time. Oxygen free silicon surface was functionalized with monosacharides thanks to UV irradiation in acetonitryl solution (254nm). Selected derivatives of pentofuranose were protected at the C-1 and C-2 position. The remaining hydroxyl group at C-3 or C-5 was suitable for direct attachment to H-terminated Si(001) surface via SiOC bonds. The binding energy of the saccharide to the Si surface was investigated by quantum mechanical calculations method. The Parametric Method 5 (PM5) calculations confirmed that the formation of SiOC bonds was chemically possible. Synthesis of new fluorinated carbohydrates has been described. The resulting monolayers were characterized by Atomic Force Microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Attenuated Total Reflection (ATR) infrared spectroscopy. The effect of incorporating fluorine atom or CF₃ group into self-assembled monosaccharide monolayers was studied using a water contact angle measurements. The resulting surface wettability of different fluorinated components on one kind of planar substrate enables an answer which of derivative is required for the preparation of the hydrophobic monolayer.

Keywords: Si(0; 0; 1); Self-assembled monolayer; Surface analysis; Fluorinated pentofuranose; Semiempirical calculations

Microstructure, mechanical and tribological behavior of MoN_x/SiN_x multilayer coatings prepared by magnetron sputtering by Guojun Zhang; Tianxiang Fan; Tao Wang; Hailin Chen (pp. 231-236).

•MoN_x/SiN_x coatings are deposited in multilayer structure by magnetron sputtering.•SiN_x monolayers have been crystallized and grown coherently with MoN_x monolayers in the coatings.•The friction coefficient of MoN_x/SiN_x multilayer coatings is about 0.53 lower than MoN_x coating of about 0.72 on average.MoN_x/SiN_x multilayer coatings and MoN_x coating were prepared with direct current magnetron sputtering system. The coatings were characterized by X-ray diffraction, transmission electron microscopy, nano-indentation and pin on disk tribotester. The X-ray diffraction and transmission electron microscopy results demonstrated, that phase of multilayer coatings were composed of γ-Mo₂N and amorphous SiN_x. The MoN_x coating showed higher microhardness of about 29GPa than MoN_x/SiN_x multilayers about 27GPa. The MoN_x/SiN_x multilayers show better tribological properties with lower friction coefficient of about 0.53 and higher wear resistance. The wear resistance of MoN_x/SiN_x multilayers was reduced with the microstructure change from crystalline to amorphous.

Keywords: MoN; _x; /SiN; _x; Nanomultilayer; Magnetron sputtering; Microhardness

Effect of the surface topographic modification on cytocompatibility of hardened calcium phosphate cement by Jiyan Li; Fupo He; Jiandong Ye (pp. 237-240).

•The surface of hardened CPC was covered by regular blade-like HA crystals after modified by PEG.•The surface roughness of CPC-P was similar to that of CPC-W.•Ion concentration and pH value of the soaking solution of CPC-P and CPC-W were without significant difference.•Regular blade-like structure was in favor of MC3T3-E1 cells.As cells are inherently sensitive to local nanoscale patterns of topography, the aim of this study was to determine the effect of the topographic modification of hardened calcium phosphate cement on cell response which was conducted with MC3T3-E1 cells. The results exhibited that the samples with regular blade-like crystalline structure had better cell response (cell attachment, viability, proliferation and differentiation) compared to those with irregular blade-like crystalline structure. The method of topographic modification is promising for developing a novel biomaterial of hardened calcium phosphate cement for bone repair.

Keywords: Calcium phosphate cement; Topography; Cell response

Polymer grafting surface as templates for the site-selective metallization by Fang Yang; Peiyuan Li; Xiangcheng Li; Lini Huo; Jinhao Chen; Rui Chen; Wei Na; Wanning Tang; Lifang Liang; Wei Su (pp. 241-247).

•A novel convenient method for electroless copper deposition on flexible polymeric material based on N-containing polyemer modification is reported.•The formation of polymer modified polymeric substrate is confirmed by ATR FT-IR and contact angle analysis.•The formation of Pd-activated polymeric substrate is confirmed by XPS, SEM and contact angle analysis.•The electroless-plated copper film on polymeric substrate is characterized by SEM, TEM, contact angle and XRD analysis.We report a simple, low-cost and universal method for the fabrication of copper circuit patterns on a wide range of flexible polymeric substrates. This method relies on procedures to modify the polymeric substrates with grafted polymer template to form surface-bound N-containing groups, which can bind palladium catalysts that subsequently initiate the site-selective deposition of copper granular layer patterns. The fabrications of patterned copper films were demonstrated on three kinds of flexible polymeric films including poly(imide) (PI), poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) with minimum feature sizes of 200μm. The films were characterized by ATR FT-IR, contact angle, XPS, XRD, TEM, SEM. Furthermore, the copper layered structure shows good adhesion with polymeric film. This method, which provides a promising strategy for the fabrication of copper circuit patterns on flexible polymeric substrates, has the potential in manufacturing conductive features adopted in various fields including modern electronics, opto-electronics and photovoltaic applications.

Keywords: Metallic pattern; Polymeric substrate; Palladium; Electroless plating

Effect of surface modification of fiber post using dopamine polymerization on interfacial adhesion with core resin by Yan Li; Qian Chen; Mi Yi; Xuegang Zhou; Xinzhi Wang; Qing Cai; Xiaoping Yang (pp. 248-254).

•A kind of bioadhesive, dopamine, was first reported as the surface modifier of fiber posts.•The polydopamine-coated fiber posts were tested having strong interfacial adhesion with composite resins using pull-out test.•The results suggested the feasibility to prevent failure in endodontically treated teeth due to dislodgement of fiber post by using dopamine surface modification.The purpose of this study is to evaluate the effects of surface modification of fiber posts using dopamine polymerization on their interfacial adhesion with core resins. The fiber posts were surface-coated with polydopamine via the oxidization polymerization of dopamine in aqueous solution. Two commercial composite resins (3M ESPE and paracore) were used to build up the cores around the post heads (modified and unmodified). Pull-out tests were conducted, and the maximum failure load (N) and the failure modes were recorded to compare the interfacial adhesion between fiber post and resin core. The results demonstrated that the tensile forces needed to damage the retention of fiber post increased from 228.6±10.9N to 276.3±14.7N in the 3M ESPE group, from 216.5±17.4N to 277.2±14.3N in the paracore group, when polydopamine-coated fiber posts were applied. No significant difference had been found between the different resin groups. The observation of the surface morphology of both fiber posts and cores after adhesive failure clearly confirmed that the presence of polydopamine interlayer had acted as a binder to bond fiber post and resin together. This study would be valuable for endodontically treatments to reduce the chances of detachment of resin core from the fiber post or dislodgement of fiber posts from the canal.

Keywords: Glass fiber post; Polydopamine; Surface modification; Core resin; Interfacial adhesion

Light induced enhancement of minority carrier lifetime of chemically passivated crystalline silicon by S. Aouida; N. Bachtouli; B. Bessais (pp. 255-257).

•In this work we present the light effect on chemically passivated silicon surface.•The passivation behavior is sensitive to silicon surface state and illumination.•Minority carrier lifetime measurements vary from 2μs to 40μs for un-passivated and chemically passivated silicon samples, respectively.•Light enhances the passivation effect by the formation of silicon-ethoxylate group SiOC₂H₅.•We propose a mechanism to the passivation effect based on carrier-induced dissociation of I₂.In this work we present light effects on chemically passivated silicon surface. Di-iodine–ethanol (I–E) mixtures were used to passivate silicon dangling bonds. The passivation quality is sensitive to both silicon surface state and light irradiation. The minority carrier lifetime values vary from 2μs for unpassivated surfaces to about 40μs for chemically passivated ones. FTIR investigations show that light irradiation catalyses the passivation effect by forming the silicon-ethoxylate group (SiOC₂H₅). We suggest a mechanism to explain the passivation effect based on carrier-induced dissociation of I₂.

Keywords: Silicon surface; Minority carrier lifetime; Chemical passivation

High-temperature oxidation behavior of hot-dipped aluminide mild steel with various silicon contents by Wei-Jen Cheng; Chaur-Jeng Wang (pp. 258-265).

•Silicon changed the microstructure and phase constitution of aluminide steel.•Aluminide steel with lower silicon has better isothermal oxidation resistance.•Aluminide steel with higher silicon has better cyclic oxidation resistance.•Formation of voids and cracks increased the oxidation rate of aluminide steel.Mild steel was coated by hot-dipping into molten baths containing pure aluminum, Al–2.5Si, Al–5Si and Al–10Si (wt.%) at 700°C for 180s. Isothermal and cyclic oxidations were carried out at 750°C in static air to study the oxidation behavior of the hot-dipped aluminide steel with various silicon contents. The results of isothermal oxidation show the weight gains of the aluminide steel followed a parabolic law. The isothermal oxidation rates of the aluminide steel specimens were directly proportional to the silicon content in the aluminide layers. The reason for the aluminide steel with high silicon possessing a high isothermal oxidation rate is that the silicon addition in the molten bath caused a reduction in the aluminide layer thickness and the formation of phase transformation induced voids in the aluminide layer. The results, after cyclic oxidation, show the weight gains of the aluminide steel specimens were larger than those after isothermal oxidation. Because the aluminide layer with low silicon was mainly composed of a thick brittle Fe₂Al₅ phase, thermal stress was easily generated in the aluminide layer and caused the formation of vertical cracks when the aluminide steel underwent cyclic oxidation. Once cracks appeared, the weight gains of the aluminide steel specimens were accelerated. Thus, mild steel after hot-dipping in pure aluminum, which had the thickest Fe₂Al₅ layer, possessed the worst resistance to cyclic oxidation.

Keywords: Mild steel; Hot-dip aluminizing; Silicon content; High-temperature oxidation

Effect of aging treatment on the in vitro nickel release from porous oxide layers on NiTi by Z. Huan; L.E. Fratila-Apachitei; I. Apachitei; J. Duszczyk (pp. 266-272).

•Nickel release from NiTi surfaces treated by plasma electrolytic oxidation was assessed in vitro.•The treatment enhanced nickel release relative to non-treated surfaces.•Aging in boiling water under optimal conditions proved a suitable post-treatment for decreasing nickel release.Despite the ability of creating porous oxide layers on nickel–titanium alloy (NiTi) surface for biofunctionalization, the use of plasma electrolytic oxidation (PEO) has raised concerns over the possible increased levels of Ni release. Therefore, the primary aim of this study was to investigate the effect of aging in boiling water on Ni release from porous NiTi surfaces that have been formed by the PEO process. Based on different oxidation conditions, e.g. electrolyte composition and electrical parameters, three kinds of oxide layers with various characteristics were prepared on NiTi substrate. The process was followed by aging in boiling water for different durations. The Ni release was assessed by immersion tests in phosphate buffer saline and the Ni concentration was measured using the flame atomic absorption spectrometry. The results showed that aging in boiling water can significantly reduce the Ni release from oxidized porous samples, given that the duration of the treatment is finely adjusted according to the parameters of the as-formed oxide layer. Surface examination of the samples before and after aging in boiling water suggested that such a treatment is non-destructive while improving the corrosion resistance of oxidized samples, as evidenced by potentiodynamic polarization tests. The results of this study indicate that water boiling may be a suitable post-treatment required to minimize Ni release from porous oxides produced on NiTi by PEO for biomedical applications.

Keywords: Nickel–titanium alloy; Plasma electrolytic oxidation; Ni ion release; Aging in boiling water; Corrosion

A facile one-step approach to synthesizing ZnO/graphene composites for enhanced degradation of methylene blue under visible light by M. Ahmad; E. Ahmed; Z.L. Hong; J.F. Xu; N.R. Khalid; A. Elhissi; W. Ahmed (pp. 273-281).

•Synthesis of ZnO/graphene composite photocatalysts by facile one-step approach.•Enhanced visible light absorption of ZnO by graphene modification.•Excellent photocatalytic performance of composites over pure ZnO.A series of visible light-responsive ZnO/graphene composite photocatalysts were successfully synthesized by a facile single step solvothermal method, using ethylene glycol as a solvent and a reducing agent. Successful deposition of wurtzite ZnO nanoparticles onto the graphene was confirmed by high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). UV–vis diffuse reflectance spectroscopy (DRS) showed that the as-prepared ZnO/graphene composite photocatalysts had enhanced visible light absorption and also exhibited a red-shift of the band-edge as compared with the pure ZnO. Fluorescence emission spectra showed that ZnO/graphene composites caused improved charge separation when compared with the pure ZnO. The photocatalysis experiment demonstrated that graphene has an important role in the enhancement of photocatalytic performance and the ZG-4 composite attained a maximum degradation efficiency of almost 100% under visible light irradiation for 90min as compared with pure ZnO (58%). The enhancement in photocatalytic activity is likely to be due to the synergistic effect of improved adsorptivity of dyes, enhanced visible light absorption and effective charge separation.

Keywords: ZnO; Graphene; Methylene blue; Solvothermal; Photocatalysis

Role of base pressure on the structural and nano-mechanical properties of metal/diamond-like carbon bilayers by Neeraj Dwivedi; Sushil Kumar; Hitendra K. Malik (pp. 282-287).

•Metal/DLC bilayers.•Effect of base pressure.•Nano-mechanical properties.•Hard and superhard coatings.The influence of base pressure on the structural and nano-mechanical properties of plasma produced metal (Cu and Ti)/diamond-like carbon (DLC) bilayers is reported. All of these samples show the formation of micro and nano-structured morphology with very low average roughness (less than 1nm). The Cu/DLC and Ti/DLC bilayers deposited at low base pressure exhibit comparatively higher hardness and better nano-mechanical properties than the ones grown at higher base pressure. Highest hardness as ~49GPa is obtained in Ti/DLC bilayer grown at low base pressure condition. Several other nano-mechanical parameters are also examined and correlated with each other. Present investigation will be useful to understand the role of base pressure on the properties of DLC coatings and may enhance its industrial application in term of hard and protective coatings.

Keywords: DLC; Nano-mechanical properties, Nanoindentation

Hydrophilic polysulfone film prepared from polyethylene glycol monomethylether via coupling graft by Ruikui Du; Baojiao Gao; Yanbin Li (pp. 288-294).

•The hydrophilic modification of polysulfone membrane was realized.•The PSF-g-PEG membrane was obtained.•The contact angle of PSF-g-PEG membrane declines rapidly with the increase of PEG grafting degree.•The PSF-g-PEG membrane processes excellent antifouling ability for proteins.In the presence of acid-acceptor Na₂CO₃, the nucleophilic substitution between chloromethylated polysulfone (CMPSF) and polyethylene glycol monomethylether (PEGME) was conducted. Polyethylene glycol (PEG) was coupling-grafted onto the side chains of polysulfone (PSF) so that the graft copolymer PSF-g-PEG was prepared and the hydrophilic modification of polysulfone membrane material was realized. The chemical structure of PSF-g-PEG was characterized by FTIR and¹H NMR. The influence of the main factors on the coupling graft reaction was investigated. The water static contact angle of PSF-g-PEG membrane was determined and its property of resisting protein pollution was examined by using bovine serum albumin (BSA) as a model protein. The experimental results show that the coupling graft reaction between CMPSF and PEGME can proceed successfully, and the reaction of chloromethyl groups of CMPSF with the hydroxyl end groups of PEGME is a typical SN1 nucleophilic substitution reaction. The polarity of the solvents and the reaction temperature greatly influence the reaction. The suitable solvent is dimethyl acetamide with stronger polarity and 70°C is a suitable reaction temperature. After reaction of 36h, the grafting degree of PEG can reach 48g/100g and the product yield is about 73.6%. The contact angle of PSF-g-PEG membrane declines rapidly with the increase of PEG grafting degree, displaying the obvious enhancement of the hydrophilicity. The adsorption capacity of BSA on PSF-g-PEG membrane decreases remarkably with the increase of PEG grafting degree, showing excellent antifouling ability of PSF-g-PEG membrane for proteins.

Keywords: Polysulfone; Polyethylene glycol; Coupling graft; Hydrophilic modification; Protein adsorption

Removal of hardness agents, calcium and magnesium, by natural and alkaline modified pumice stones in single and binary systems by Mohammad Noori Sepehr; Mansur Zarrabi; Hossein Kazemian; Abdeltif Amrane; Kamiar Yaghmaian; Hamid Reza Ghaffari (pp. 295-305).

•Ca²⁺ and Mg²⁺ were removed by raw and modified pumice in single and binary system.•Maximum adsorption capacity was 57.27mg/g for Ca²⁺ by raw pumice.•Maximum adsorption capacity was 62.34mg/g for Ca²⁺ by modified pumice.•Maximum adsorption capacity was 44.53mg/g for Mg²⁺ by raw pumice.•Maximum adsorption capacity was 56.11mg/g for Mg²⁺ by modified pumice.Natural and alkaline modified pumice stones were used for the adsorption of water hardening cations, Ca²⁺ and Mg²⁺. The adsorbents were characterized using XRF, XRD, SEM and FTIR instrumental techniques. At equilibrium time and for 150mg/L of a given cation, removal efficiencies were 83% and 94% for calcium and 48% and 73% for magnesium for raw and modified pumices, respectively. The optimal pH for raw and modified pumices were found to be 6.0, leading to the removal of 79 and 96% of calcium and 51 and 93% of magnesium by 10g/L of raw and modified pumice adsorbents, respectively. Maximum adsorption capacities were 57.27 and 62.34mg/g for Ca²⁺ and 44.53 and 56.11mg/g for Mg²⁺ on the raw and modified pumices, respectively. Ca²⁺ and Mg²⁺ adsorption capacities of the pumice adsorbents decreased in the presence of competing cations. Less than 300min were needed to achieve 99 and 92% desorption of the adsorbed Ca²⁺ and 100 and 89% of the adsorbed Mg²⁺ from the natural and modified pumices, respectively. After treating synthetic water solution simulating an actual water stream with the alkali-modified pumice, total hardness of the treated sample met the required standard for drinking water, namely below 300mg/L of CaCO₃ (297.5mg/L). The studied pumice adsorbents, and especially the treated pumice, can be therefore considered as promising low cost adsorbents, suitable for the removal of hardness ions from drinking water.

Keywords: Calcium; Magnesium; Adsorption; Modification; Batch system

On the properties of aluminium doped zinc oxide thin films deposited on plastic substrates from ceramic targets by M. Girtan; A. Vlad; R. Mallet; M.A. Bodea; J.D. Pedarnig; A. Stanculescu; D. Mardare; L. Leontie; S. Antohe (pp. 306-313).

•Al:ZnO are successfully prepared on cheap and flexible PET substrates at room temperature.•The figure of merit of such PLD grown films (5.6×10⁻³Ω⁻¹) is among the best values reported so far.•The properties of AZO films are found out to depend on the laser fluence employed in PLD.•PLD is a promising technique with potential applications for plastic solar cells.We report on the deposition of Al doped ZnO (AZO) thin films on unheated polyethylene terephthalate (PET) substrates by pulsed laser deposition technique using a UV excimer laser and Al₂O₃:ZnO ceramic targets (1.5 and 2wt% Al₂O₃). The deposited AZO films have been investigated by atomic force microscopy, scanning electron microscopy, X-ray diffraction, and optical spectrophotometry. Films present excellent optical and electrical properties (transmission in the visible range T>85%; resistivity at room temperature ρ=1.3×10⁻³Ωcm) as electrodes for plastic solar cells. A good correlation was found between deposition conditions (laser fluence) and structural, morphological, optical and electrical properties.

Keywords: Plastic solar cells; Plastics optoelectronics

Thermal decomposition behaviors and kinetic properties of 1,8-naphthalic anhydride loaded dense nano-silica hybrids by Jinpeng Wang; Jihong Sun; Feng Wang; Bo Ren (pp. 314-320).

Display Omitted•The luminescent dense nano-silica hybrid via grafting 1,8-naphthalic anhydride.•Apparent activation energy of the thermal decomposition performances was evaluated according to Kissinger and Flynn-Wall-Ozawa principles.•Both dynamic-based control and diffusion-based control would be important during the thermal decomposition process of hybrids DNSS.A certain amount of (3-aminopropyl)triethoxysilane (APTES) and various capacity of 1,8-naphthalic anhydride (NA) were employed to modify and then graft onto the surface of the dense nano-silica spheres (DNSS) via a post-grafting method, and thereby, a novel luminescent density nano-silica hybrid materials have been successfully synthesized. Meanwhile, the structures and properties of obtained hybrid DNSS were characterized by XRD, TEM, N₂ sorption, FT-IR, and TG analysis. Furthermore, the thermal stability of before and after modification were demonstrated by using both Kissinger methods and Ozawa–Flynn–Wall methods. Particularly, the thermal decomposition behaviors of amino-modified groups and NA-grafted organic molecules were emphasized based on the TG and DTG analysis and then the related mechanism was put forward according to Coats and Redfern methods. Finally, as a comparison, the obtained results and the proposed decomposition mechanism of hybrid DNSS with non-pores were discussed with that of mesopores silicas in details.

Keywords: Nano-silica; Hybrids; Thermal decomposition; Apparent activation Energy

Preparation and photocatalyic properties of TiO₂-P25 film prepared by spray pyrolysis method by J. Dostanić; B. Grbić; N. Radić; S. Stojadinović; R. Vasilić; Z. Vuković (pp. 321-327).

•TiO₂ films were prepared by immobilizing Degussa P25 powders on stainless steel.•The spray pyrolysis technique was used for film preparation.•The photoactivities of films decreased with increase in calcinations temperature.•The films showed lower photoactivity then corresponding powders.TiO₂ films were synthesized by immobilization of Degussa P25 powders on stainless steel support by spray pyrolysis technique. After preparation, the films were annealed at different temperatures in order to obtain materials with different morphological, structural, and textural properties. The photocatalytic activity of obtained films was investigated by monitoring the degradation of arylazo pyridone dye. The results showed that with increasing annealing temperature the photoactivity of films decreased. A comparative photocatalytic activity of the synthesized films and corresponding commercial powders was evaluated under the same experimental conditions. Films generally showed lower photoactivity than powders, due to mass transfer limitations inside film layer, smaller surface exposure to light, and possible presence of metal ions in film layer.

Keywords: TiO; ₂; film; Photocatalysis; Spray pyrolysis; Photoactivity; Stainless steel

Preparation of Cu-loaded SrTiO₃ nanoparticles and their photocatalytic activity for hydrogen evolution from methanol aqueous solution by Duc-Nguyen Bui; Jin Mu; Lei Wang; Shi-Zhao Kang; Xiangqing Li (pp. 328-333).

•Cu was deposited on SrTiO₃ nanoparticles using in situ photo-deposition method.•Cu–SrTiO₃ displayed high photocatalytic activity for H₂ evolution.•Metallic Cu is an efficient alternative to Pt for SrTiO₃.Cu-loaded SrTiO₃ nanoparticles (Cu–SrTiO₃) were prepared using a simple in situ photo-deposition method and their photocatalytic activity for hydrogen evolution from methanol aqueous solution was evaluated. The results characterized with XRD, TEM, XPS and EDX indicated that the as-synthesized sample was composed of metallic Cu and cubic SrTiO₃, and the metallic Cu was homogeneously loaded on the surface of SrTiO₃ nanoparticles. Under UV light irradiation, Cu–SrTiO₃ displayed much higher photocatalytic activity for hydrogen evolution and excellent stability in comparison with pure SrTiO₃ nanoparticles. The results further confirmed that the efficient separation of photogenerated electron/hole pairs was critical for the enhanced photocatalytic activity of Cu–SrTiO₃. Moreover, the rate of hydrogen evolution of 0.5wt.% Cu–SrTiO₃ is comparable with that of 0.5wt.% Pt–SrTiO₃ photocatalyst under optimum conditions, implying that the metallic Cu is an efficient alternative to Pt as a co-catalyst on SrTiO₃. The high photocatalytic activity, low cost and chemical stability mean that the Cu-loaded SrTiO₃ is a potential catalyst for the photocatalytic hydrogen evolution from methanol aqueous solution.

Keywords: Cu co-catalyst; SrTiO; ₃; nanoparticles; Photocatalysis; Hydrogen

Microstructure and wear properties of WC particle reinforced composite coating on Ti6Al4V alloy produced by the plasma transferred arc method by Osman Nuri Çelik (pp. 334-340).

•WC particle reinforced composite coatings were produced on Ti6Al4V alloy by plasma transferred arc method.•All PTA processes performed at 70A, 80A, and 90A increased the surface hardness and the wear resistance of the alloy.•The composite coating produced at 70A exhibited better wear resistance than the coatings produced at 80A and 90A.The microstructure and wear properties of a WC particle reinforced composite coating produced by the plasma transferred arc (PTA) method on Ti6Al4V alloy were investigated in this study. PTA processing was carried out using argon as the plasma gas at arc current values of 70A, 80A and 90A. Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to characterize the microstructure of the composite layer formed on the surface of a Ti6Al4V substrate. The results indicate that the WC, TiC and W₂C carbide phases formed in the composite layers produced by PTA on the surface of the Ti6Al4V alloy. The distributions and volume fractions of these phases were found to vary with the arc current values. Wear tests were performed under dry sliding conditions using a linear ball-on-disc geometry. The microhardness and wear resistances of all of the composite layers produced by the PTA process were enhanced relative to those of the Ti6Al4V substrate. The homogeneity and volume fractions of the carbide phases in the composite layers were responsible for the improvement in the wear resistance of the alloy. The wear test results indicate that the alloy modified at 70A shows better wear resistance than the alloys modified at 80A and 90A.

Keywords: Ti6Al4V; Wear; Plasma transferred arc

Structure and optical properties of ternary alloy BeZnO and quaternary alloy BeMgZnO films growth by molecular beam epitaxy by Longxing Su; Yuan Zhu; Quanlin Zhang; Mingming Chen; Tianzhun Wu; Xuchun Gui; Bicai Pan; Rong Xiang; Zikang Tang (pp. 341-344).

•Be_xZn1−_xO and Be_xMg_yZn1− x−_yO were prepared by molecular beam epitaxy.•Quaternary alloy Be_xMg_yZn1− x−_yO exhibits a better result in crystal quality.•Quaternary alloy Be_xMg_yZn1− x−_yO exhibits a better result in band gap modulation.•We first report of MSM structure UV detectors based on Be_xMg_yZn1− x−_yO alloys.Ternary alloy BeZnO and quaternary alloy BeMgZnO films were prepared on sapphire (001) substrate by radio-frequency plasma-assisted molecular beam epitaxy (RF-PAMBE). Based on X-ray diffraction (XRD) analysis, no phase segregation is observed for all the alloys. However, Be_xZn1−_xO alloys exhibit a constantly worse crystal quality than Be_xMg_yZn1− x−_yO alloys at the similar incorporation contents (i.e. x in BeZnO approximately equals to x+ y in BeMgZnO). Optical transmittance spectra were recorded to determine the energy band gap of the films. BeMgZnO was revealed more effective in widening the band gap. Finally, BeZnO and BeMgZnO based MSM structure UV detectors were fabricated. BeMgZnO alloys with better crystal quality showed a favorable optical response and the cutoff wavelength shifted continuously to deep ultraviolet range, while BeZnO based detectors were found no response. This is the first report on BeMgZnO based UV detector, which is a meaningful step forward to the real application.

Keywords: BeZnO; BeMgZnO; Crystal quality; Band-gap; MSM detector

The passive film characterization and anodic polarization behavior of 11% Cr ferritic/martensitic and 15% Cr oxide dispersion strengthened steels in different electrolytic solutions by S. Ningshen; M. Sakairi; K. Suzuki; S. Ukai (pp. 345-355).

•The passive film of F/M and ODS steels is evaluated in different electrolytic media.•The XPS analysis shows that the passive film has Fe₂O₃ and Cr₂O₃ along with Y₂O₃.•Low pitting corrosion resistance was observed in chloride media.•Presence of Cl⁻ significantly reduces the pitting corrosion in both the steels.•The SEM micrographs shows severe pitting corrosion attack in chloride solutions.The ferritic/martensitic (F/M) and oxide dispersion strengthened (ODS) steels are the most promising candidate materials for future nuclear power plants. In the present work, the passive film compositions and its correlation with anodic polarization behavior of 11% Cr F/M and 15% Cr ODS steels was examined in different electrolytic solutions of borate buffer, acidic, acidified chloride and in chloride solution. The X-ray photoelectron spectroscopy analysis of the passive film reveals the existence of the layers of Cr₂O₃ and Fe₂O₃ and in 15% Cr ODS steel along with Y₂O₃. The open circuit potential and potentiodynamic anodic polarization measurements show that pitting corrosion resistance is strongly dependent on electrolytic solutions and passive film compositions. The ODS steel indicated increased breakdown potential and wider passive range as compared to F/M steel in chloride containing media. In a non-chloride environment, this difference is not prominent. However, low pitting corrosion resistance of both steels in chloride solutions was attributable to Cl⁻ and microstructural inhomogeneity. The SEM micrographs of surface morphology of corrosion attack showed severe pitting corrosion attack in chloride solutions. The anodic polarization behavior of F/M and ODS steels in different electrolytic solutions was studied for this work in relation to passive film compositions.

Keywords: Corrosion; F/M steel; ODS steel; Passive films; Pitting corrosion; XPS

Surface nitriding on Ti–6Al–4V alloy via friction stir processing method under nitrogen atmosphere by Bo Li; Yifu Shen; Weiye Hu (pp. 356-364).

•Surface nitriding layer on Ti alloy was produced via friction stir processing method.•Nitrogen gas was introduced to a rapid thermal reaction on activated metal surface.•A nitride particle reinforced composite-like structure formed beneath TiN layer.The solid-state friction stir processing (FSP) was introduced to surface nitriding on Ti–6Al–4V substrate under nitrogen atmosphere. Under the optimized process conditions, a sound and thick nitriding layer was successfully prepared and detailed by XRD, SEM and EDS methods. The outer thin layer on the top surface crowns was mainly TiN phase with refined grains in size of 2–3μm. After removing the crowns, a more than 150μm thick nitriding layer was remained with a composite-like structure. The transition layer contained numerous fine and uniformly dispersive nitride particles embedded in the Ti matrix with a certain solid solution of Ti(N). The micro-hardness of the top surface was ~1105HV_0.2. Furthermore, the formation mechanisms including rapid thermalchemical reaction, nitrogen diffusion and nitride particle dispersion were discussed in detail.

Structural, optical and electrical properties of cerium and gadolinium doped CdO thin films by L.L. Pan; G.Y. Li; J.S. Lian (pp. 365-370).

•Highly textured cerium and gadolinium co-doped CdO films were deposited on glass substrates by RF magnetron sputtering.•The average optical transmittance of co-doped CdO films was over 80% in the UV–vis spectral regions.•The optical band gap of the co-doped CdO films was increased from 2.59eV to 2.99eV.•The doped CdO films show low electrical resistivity of 3.11×10⁻⁴Ωcm and high carrier concentration of 6.34×10²⁰cm⁻³.Cadmium oxide thin films doped with different concentration of cerium (Ce) and gadolinium (Gd) have been prepared by radio frequency magnetron (RF) sputtering. Thin films are deposited on glass substrates at a substrate temperature of 400°C and pressure of 0.1mbar in Ar:O₂=4:1 atmosphere. The structural, optical and electrical properties of deposited film are studied. X-ray diffraction reveals that Ce and Gd doped CdO films have good crystallinity and are apt to grow on (200) orientation with increasing Ce and Gd doping concentrations. These films are highly transparent with an average transmittance over 80%. With a moderate doping (0.4at.% Ce and 0.8at.% Gd), the optical band gap ( E_g) blue-shift from 2.59eV to 2.99eV. The electrical conductivity increases with increasing Ce and Gd doping concentrations, but for higher doping concentration (0.5at.% Ce and 1.0at.% Gd), the conductivity decreases. The increase in carrier concentration due to Ce and Gd doping is the main reason responsible for the increase of and conductivity and the blue shift of band gap.

Keywords: Cadmium oxide; Radio frequency magnetron sputtering; Transparent conductor oxide; Band gap; Hall effect

Temperature-dependent growth and properties of W-doped ZnO thin films deposited by reactive magnetron sputtering by Chi Zhang; Xin-liang Chen; Xin-hua Geng; Cong-sheng Tian; Qian Huang; Ying Zhao; Xiao-dan Zhang (pp. 371-377).

•W-doped ZnO (WZO) films were deposited by reactive magnetron sputtering.•Substrate temperatures have key influences on the properties of WZO films.•Low sheet resistance and high transmittance were obtained at 300°C.•W element exists only in the oxidized state of W⁶⁺ in WZO thin films.•WZO films are promising TCO layers for solar cells.Tungsten doped zinc oxide (WZO) thin films have been deposited by pulsed direct-current (DC) reactive magnetron sputtering technique. The microstructure, surface morphology, optical and electrical properties of WZO thin films were investigated at different substrate temperatures. Experimental results indicate that the substrate temperature is the key factor for fabricating high quality WZO thin films. The WZO thin films exhibit hexagonal wurtzite structure with (002) preferential growth orientation, and become more smooth at a much higher temperature. The optimized WZO thin film obtained at the substrate temperature of 300°C exhibits a high Hall mobility of 27.5cm²V⁻¹s⁻¹, a low sheet resistance of 23.3Ω/□, and an average transmittance of 82.0% in the wavelength range from 400 to 1500nm. The X-ray photoelectron spectroscopy (XPS) reveals that W element exists only in the oxidized state of W⁶⁺ in WZO thin films obtained at all the substrate temperatures, and Zn exists in a mixture state of oxidized and metallic formation.

Keywords: Reactive magnetron sputtering; ZnO thin films; W-doping; Substrate temperature; Solar cells

Interaction of micro-discharges in heptane with metallic multi-layers by A. Hamdan; J.-N. Audinot; C. Noel; F. Kosior; G. Henrion; T. Belmonte (pp. 378-391).

•Interactions of discharges in heptane with thin films of copper, aluminum and iron, or show specific behaviors.•At low impact energy, melting of surface is not always assured and surface stress may be invoked to explain how the shape of the surface is defined.•At intermediate energy, melting occurs, leading to the synthesis of external beads by Marangoni's convection.•At high energy, the shape of the impact is defined by the pressure release when the discharge stops.•Multilayers can be designed to improve the way the energy of the plasma is deposited.Interaction of discharges in heptane with magnetron-sputtered thin films made of aluminum, copper or iron is studied in a pin-to-plate configuration. The behavior of discharges on thin films can be used to better understand the interaction of discharges with given surfaces and it might also improve the reproducibility of the impacts in order to better control their shape. Single layers and bilayers of metals are characterized after impact by SEM, AFM, micro-EDX and nano-SIMS analyses. Discharges last typically for a few hundreds of nanoseconds and dissipated energies range between 1 and 100mJ. We show that at low impact energy, copper and aluminum are heated and stretched by surface stress. At intermediate energy, melting occurs, leading to the synthesis of external beads by Marangoni's convection. At high energy, the shape of the impact is defined by the pressure release when the discharge stops. When iron is deposited onto silicon, dewetting is an important mechanism. The columnar structure of the deposit may have two distinct roles. On the one hand, gases trapped in intercolumnar boundaries can produce tiny holes. On the other hand, the shock wave can abrade the outermost and less cohesive part of the film if it is made of columns separated by large porosities.

Keywords: Microplasma; Plasma in liquids; Plasma–surface interaction; Thin filmsPACS; 47.55.dr Interactions with surfaces; 52.80.Wq Discharge in liquids and solids

Nanometer scale chemistry and microstructure of CrN/AlN multilayer films by Jianliang Lin; Hunter B. Henderson; Michele V. Manuel; William D. Sproul (pp. 392-396).

•Nanoscale resolution chemistry and microstructure of CrN/AlN films were studied using advanced microscopy.•The interface between CrN and AlN nanolayers contains a graded elemental distribution.•The rapid repetition of high interfacial energy across the nanolayers is critical for the coherent epitaxial growth in the film.Nanometerscale multilayer CrN/AlN thin films were deposited by pulsed DC magnetron sputtering. Nanoscale resolution chemistry and microstructure of CrN/AlN films with modulation periods ( Λ) of 4nm and 18nm were studied using advanced microscopy and diffraction. At the nanometer level, the interface between the CrN and AlN nanolayers contains a concentration gradient of Al and Cr. Inter-diffusion of Cr and Al atoms into the AlN and CrN layers was identified. Microstructural characterization revealed the CrN nanolayers epitaxially stabilize the AlN layers (2nm) to a cubic structure for the Λ=4nm film. The rapid repetition of the interfacial energy across the AlN nanolayers is critical for the coherent epitaxial growth. The film at Λ=4nm exhibited a superhardness of 42GPa. In contrast, the AlN layers (12.5nm) exhibited a hexagonal structure in the Λ=18nm film as the bulk energy becomes dominating, in which misorientated and incoherent interfaces were found. The hardness of the film dropped down to 23GPa.

Preparation of the photosensitive copper complex and CuO film pattern by H.L. Zhang; G.Y. Zhao; L.Z. Xu (pp. 397-400).

•Acrylic acid (AA) as chemical modifier was used to prepare the copper complex.•The copper complex is photosensitive to UV-light.•The patterned CuO film was fabricated by chemically modified sol–gel method.The precursor solution was prepared with copper acetate (Cu(OAc)₂) as the start material, acrylic acid (AA) as the chemical modifier, and absolute methanol (MEOH) as the solvent. AA reacted with Cu(OAc)₂ to form the copper complex with the photosensitivity. In the complex, Cu ion is coordinated with two hydroxy oxygen atoms of AA. The coated gel film using this precursor solution exhibited photosensitivity to UV light at around 245nm. Based on the photosensitivity, the patterned CuO film was fabricated.

Keywords: PACS; 78.30.Jw; 82.50.HpChemical modification; Copper complex; photosensitivity; CuO film pattern

Status report of the Thomson spectrometer for LILIA experiment by M. Maggiore; G.A.P. Cirrone; F. Romano; A. Caruso; G. Caruso; A. Longhitano; G. Messina; S. Passarello; D. Rizzo; S. Salomone; E. Zappalà (pp. 401-404).

► We provided the study and design of a compact spectrometer for the analysis of ion beams produced by laser target interaction. ► The spectrometer has been designed with a view to a possible application for high energy beam resolution. ► A detailed study about the electromagnetic modelling and beam optic as well were done.LILIA is an experiment of light ions acceleration trough laser interaction with thin metal targets to be done at the FLAME facility, which is now running in INFN-LNF of Frascati (Rome). In the framework of LILIA, the LNS is involved in the design and construction of a spectrometer based on the Thomson's configuration in order to diagnostic the ion ejection from the laser-generated plasma. The main goal is to realize a compact system which is both very practical and optimized with regard to the mass and energy resolution of particles obtained by laser–plasma interactions. The preliminary design has to be able to analyze and resolve beams of protons and ions up the total energy of 10MeV. However, the technical choices adopted in this prototype have to be applied for the final device concerning a challenging spectrograph able to analyze beams of 150MeVof total energy. The magnetic and the electric part have been built and these have been assembled. The vacuum and the high voltage test have been accomplished out and also the magnetic measurements. The results will be presented and discussed.

Keywords: Laser driven beams; Spectrometer

Characterization of critically cleaned sapphire single-crystal substrates by atomic force microscopy, XPS and contact angle measurements by Dan Zhang; You Wang; Yang Gan (pp. 405-417).

► We evaluated many reported methods for cleaning sapphire substrates using comprehensive surface analysis techniques. ► We found that reported methods did not perform well in terms of removing both organic and particulate contaminants. ► We proposed a new wet-cleaning method showing outstanding performance for cleaning sapphire substrates.A contaminant-free surface of single-crystal α-Al₂O₃ (or sapphire) substrates is key to the experimental studies of its surface and interfacial properties at ambient conditions. Here we critically evaluated methods reported in the literature using comprehensive surface analysis techniques including atomic force microscopy, XPS and contact angle measurements. We found that reported methods did not perform well in terms of removing both organic and particulate contaminants from the (0001) basal surface. After thoroughly examining the cleaning effect of various chemical solutions and UV light and plasma irradiation, and based on modified RCA cleaning protocols, we proposed a new wet-cleaning method showing outstanding cleaning performance. This new reliable method will be very useful for the next-step surface chemistry study of single-crystal α-Al₂O₃. It was also demonstrated that AFM, due to its high spatial resolution and sensitivity as a local probe technique, was an indispensable tool for surface contamination control studies.

Keywords: Alpha alumina; α-Al; ₂; O; ₃; Sapphire; Contamination control; Wet cleaning method; UV-ozone cleaning; Plasma cleaning; AFM; XPS; Contact angle measurements

Determination of functionalized gold nanoparticles incorporated in hydrophilic and hydrophobic microenvironments by surface modification of quartz crystal microbalance by Tsui-Hsun Wu; Shu-Chuan Liao; Ying-Fang Chen; Yi-You Huang; Yi-Syuan Wei; Shu-Ju Tu; Ko-Shao Chen (pp. 418-424).

► Plasma deposition method was used to immobilize Au electrode of a QCM. ► Au electrode surface modification measured in hydrophobic and hydrophilic microenvironment. ► MUA-AuNPs and DCT-AnNPs immobilized on Au electrode surface to quantify AuNP mass.In this study, plasma deposition methods were used to immobilize Au electrode of a quartz crystal microbalance (QCM) to create different microenvironments for mass measurement of various modified Au nanoparticles (AuNPs). AuNPs were modified by 11-mercaptoundecanoic acid (MUA) and 1-decanethiol (DCT) for potential applications to drug release, protective coatings, and immunosensors. We aimed to develop a highly sensitive and reliable method to quantify the mass of various modified AuNPs. The surface of AuNPs and Au electrode was coated with polymer films, as determined by Fourier transform infrared spectroscopy and atomic force microscopy. Measurements obtained for various AuNPs and the plasma-treated surface of the Au electrode were compared with those obtained for an untreated Au electrode. According to the resonant frequency shift of QCM, a linear relationship was observed that significantly differed for AuNPs, MUA-AuNPs, and DCT-AuNPs ( R² range, 0.94–0.965, 0.934–0.972, and 0.874–0.9514, respectively). Compared to inductively coupled plasma and micro-computerized tomography, the QCM method with plasma treatment has advantages of real-time monitoring, greater sensitivity, and lower cost. Our results demonstrate that surface modifications measured by a QCM system for various modified AuNPs were reliable.

Keywords: Plasma deposition; Quartz crystal microbalance; 11-Mercaptoundecanoic acid; 1-Decanethiol; Au nanoparticles; Inductively coupled plasma

Erratum for article published as 266 (2013) 380–385 by Xiaohua Yu; Benkang Chang (pp. 425-425).

Corrigendum to “Effect of strontium ions on the early formation of biomimetic apatite on single crystalline rutile” [Appl. Surf. Sci. 266 (2013) 199–204] by Carl Lindahl; Håkan Engqvist; Wei Xia (pp. 426-426).

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Applied Surface Science (v.274, #)