Applied Surface Science (v.258, #15)

Calculation of surface entropy of liquid transition and noble metals by R.C. Gosh; M.R. Amin; A.Z. Ziauddin Ahmed; Ishtiaque M. Syed; G.M. Bhuiyan (5527-5532).
► The applicability of hard–sphere interaction is tested on liquid metal's surface. ► The theory works well for the liquid noble metals. ► More sophisticated theory is required for liquid transition metals.The surface entropies of liquid transition and noble metals Fe, Co, Ni, Cu, and Ag have been investigated. Surface entropy expression involving hard–sphere (HS) interaction in closed form is used. Since the HS diameter depends on metallic properties and temperature, the temperature dependent effective HS diameter is determined from a well-known perturbation theory, linearized Weeks–Chandler–Andersen (LWCA) and integral equation theory, variational modified hypernetted chain (VMHNC). Theoretical calculations are compared with the available experimental data, and found good agreement for some concerned systems.
Keywords: Transition metal; Noble metal; Hard–sphere diameter; Packing fraction; Surface entropy;

► Silver nanoparticles were made by electrolysis method. ► The SERS spectra of three kinds of Azo-dye molecules were gained. ► The SERS spectra these Azo-dye molecules were calculated by Gauss’98 software.Silver nanoparticles were prepared by an electrolysis method. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to detect the morphology of these particles. Based on this high active surface enhanced Raman scattering (SERS) substrate, three kinds of azo-dye molecules (Methyl Yellow, Methyl Red and Sudan Red 1) were carefully studied. Using the Gaussian’98 software, we gained the calculation result of these three kinds of azo-dye molecules, and found that the calculation results had good concordance with the experimental one. The detection limit of azo-dye molecules on the silver nanoparticles can go down to 10−5  mol/l, which indicated that these particles were an active SERS substrate.
Keywords: SERS; Azo-dye molecules; Electrolysis; Silver nanoparticles;

Cleavable porous silicon based hybrid material for pre-enrichment of trace heavy metal ions by Shaoyuan Li; Wenhui Ma; Yang Zhou; Yanfeng Wang; Wei Li; Xiuhua Chen (5538-5542).
► Cleavable groups was successfully graft on porous silicon surface. ► The hybrid possessed a similar preferential adsorption trend for studied metal ions. ► At pH = 5.0, the most efficient pre-enrichment for Cd was obtained. The paper reports on the preparation of the cleavable porous silicon (PSi) based hybrid material and application in pre-enrichment of trace heavy metal ions. The cleavable groups (benzimidazoledithio) were grafted on the PSi surface by a stepwise covalent process. PSi was first obtained by anodization of bulk silicon wafers and was subsequently silanized by 3-mercaptopropyltriethoxysilane (MPTS) to synthesize MPTS-PSi, the MPTS-PSi was further converted into pyridyldithio-terminated PSi (PDT-PSi), and finally, the PDT-PSi reacted with 2-mercaptobenzimidazole to form the benzimidazoledithio modified PSi (BDT-PSi). Scanning electron microscopy (SEM) was used to characterize the morphology of freshly prepared and modified PSi. Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy were performed to confirm the effectiveness of each step graft. According to the UV–vis spectra analysis, the disulfide linkage of BDT-PSi can be dissociated in presence of reduced glutathione (GSH). The pre-enrichment efficiency of BDT-PSi was investigated at the different pH for the different metal species (Cd, Hg, Pb, Cu and Co). The results show that the BDT-PSi possesses a similar preferential adsorption trend (Cd > Cu ≫ Hg ∼ Pb ∼ Co) at different pH (from 2.0 to 6.0). At pH 5.0, the best pre-enrichment efficiency for Cd ions is observed, the concentration of Cd is increased more than ten times and the recovery is found to be 95.4%.
Keywords: Porous silicon; Cleavable modification; Selective pre-enrichment; Cadmium ions;

► The relative activity of immobilized trypsin onto chitosan modified microsphere was higher than that onto no-chitosan grafted microspheres. ► Zeta potential was used to evaluate the immobilization of trypsin. ► The surface biocompatibility of PSt-GMA microspheres is improved suitably for enzyme immobilization.The carrier's surface biocompatibility plays a vital role in biochemical and biomedical fields. In this study, chitosan (CS) was used as a modified material to improve the surface biocompatibility of the microspheres. The particle size, size distribution and zeta potentials of these microspheres were measured before and after immobilized trypsin. Enzyme activity and zeta potential of immobilized trypsin were used to evaluate the immobilization. The experimental results showed that the enzyme activity of immobilized trypsin onto chitosan modified microspheres (CMMs) was higher than that onto no-chitosan modified microspheres (NCMs), even can approximately retain 80% of free trypsin. Meanwhile, electrostatic force was found to have the significance in the immobilization of trypsin. This work demonstrates that chitosan can improve the surface biocompatibility of carrier and provide a suitable surface for enzyme immobilization. Therefore, it is being used to its potential in preparation of the functional carriers required by high throughput screening of drugs (HTS) based on scintillation proximity assay (SPA) method.
Keywords: Chitosan modified microspheres; Carrier's surface biocompatibility; Enzyme immobilization; PSt-GMA microsphere; Electrostatic force; Zeta potential;

► We study the effect of surface roughness on the tungsten nanoneedles formation. ► Tungsten nanoneedles are self-assembled on tungsten surface with high roughness (Rz = 8.9 nm). ► A specific surface without nanoneedles formed on tungsten surface with low roughness (Rz = 1.4 nm) ► The nanoneedles are formed via self-organization processes, not by direct beam writing.The effect of surface roughness on the morphological evolution of polycrystalline tungsten during bombardment by focused ion beam has been investigated. The nanoneedles were self-assembled on the mechanically polished tungsten surface with high roughness (Rz = 8.9 nm). In contrast, a specific surface without nanoneedles was formed on the electrochemically polished tungsten surface with low roughness (Rz = 1.4 nm) although all bombardment parameters except for surface roughness were the same. The concave–convex surface morphology significantly influences nanoneedle formation due to its effect on the dynamic competition between the roughening and smoothing process. This discovery shows the importance of original surface roughness in controlling the morphological evolution of tungsten during ion irradiation and suggests a means for fabricating tungsten nanoneedles that might be used in quantum, photon and electron devices.
Keywords: Tungsten; Nanostructure; Focused ion beam; Self-organization; Surface roughness;

► By controlling hydrophilic character of the plasma treated polymer surface we may influence on adhesion properties. ► Oxygen plasma treated polymer surface prevents physical adhesion of streptavidin. ► Streptavidin can be successfully attached to polymer surface only by chemical coupling using special reagents.Immobilization of protein streptavidin to the surface of polystyrene (PS) polymer was studied by X-ray photoelectron spectroscopy (XPS). Two different protocols were used to attach streptavidin to the PS surface: physical adsorption and chemical coupling. In both cases the surface properties of PS samples were modified by exposure to cold oxygen plasma for 10 s. Plasma was created in oxygen at 75 Pa by en electrode-less RF discharge. The RF generator operated at 27.12 MHz and the nominal power was about 120 W. The electron temperature was about 3 eV, the plasma density was about 3 × 1015  m−3 and the neutral oxygen atom density was about 3 × 1021  m−3. Oxygen plasma treatment caused formation of O-rich functional groups on the surface of PS. The concentration of oxygen was determined by XPS and was about 28 at.%. A thin film of streptavidin was deposited by physical adsorption and chemical bonding. The appearance of streptavidin on the surface was determined from XPS spectra measuring the ratio between N and C peaks. The plasma treatment caused poor adsorption and but strong chemisorption of streptavidin. The results were explained by specific interaction of protein with polar functional groups on the surface of PS after plasma treatment.
Keywords: Plasma; Polymer; Surface functionalization; Protein; Adsorption; Biomedical application;

Thermal etching of SiC by N.G. van der Berg; Johan B. Malherbe; A.J. Botha; E. Friedland (5561-5566).
► Defects in SiC such as twins and stacking faults were observed using an in-lens SEM. Usually TEM is necessary to observe these defects. ► Thermal etching of SiC starts at lower temperatures than previously reported. ► Decomposition of SiC starts at lower temperatures than previously reported. ► Thermal etching is suggested as an alternative polishing method for SiC. ► 3D nano-structures develop on SiC due to decomposition.Thermal etching of SiC or its decomposition at high temperatures is of significance because of the many industrial applications of SiC at high temperatures. The effect of vacuum annealing at relatively high temperatures (1200–1800 °C) on the surface microstructure of 6H-SiC and polycrystalline SiC was investigated using a modern high resolution scanning electron microscope (FEG-SEM) with an in-lens detector. Crystal defects such as stacking faults and twins on the SiC surfaces were easily observed in this system. Thermal etching of SiC already started at 1200 °C with evidence of step bunching and grain boundary grooving. Preferred etching occurred on certain crystal surfaces of polycrystalline SiC. Significant decomposition of SiC occurred at 1800 °C. The resulting decomposition structures have possible nanotechnological applications.
Keywords: Thermal etching; SiC; Decomposition; Vacuum annealing; Step bunching; Grain boundary grooving; SEM;

Thermal stability of magnetron sputtered amorphous Si2C by R. Gustus; W. Gruber; L. Wegewitz; H. Schmidt; W. Maus-Friedrichs (5567-5573).
► We investigated the thermal stability of thin films of amorphous Si2C at 800 °C. ► The films were investigated by means of XPS, XRD, AFM, SEM and AES. ► Annealing led to the formation of new Si―C bonds. ► Crystallization of silicon took place during thermal annealing. ► Small particles of silicon were formed on the surface of the film.The thermal stability of amorphous Si2C films was studied by means of X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Grazing Incidence X-ray Diffractometry (GIXRD), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The films were deposited by magnetron sputtering onto silicon single crystals. The as-deposited films show a homogenous amorphous structure with a variety of bonding states reaching from homonuclear silicon-like Si―Si over mixed Si―Si―C to heteronuclear Si―C bonds. Annealing at 800 °C for 1 h leads to a depletion of Si―Si―C bonding states and to the formation of additional Si―C bonds. AFM and SEM images showed particles with a remarkable faceting on the surface of the annealed film. In accordance with GIXRD and AES measurements, these observations confirmed the crystallization of silicon during thermal annealing. Besides, no crystallized silicon carbide could be detected.
Keywords: Silicon carbide; Amorphous films; Crystallization; Sputter-deposition;

► Polyamide 6 films were treated with different environmental humidity, respectively. ► We investigated the effect of different environmental humidity on the surface modification of atmospheric pressure plasma. ► The environmental humidity has effectiveness on the polymer surface modification with atmospheric pressure plasma.The environmental humidity (EH) may have potential influence on atmospheric pressure plasma treatment. In order to investigate how the environmental humidity affects atmospheric pressure plasma treatment, polyamide 6 (PA 6) films were treated by helium/oxygen (He/O2) plasmas using atmospheric pressure plasma jet (APPJ) at different environmental humidity. The plasma treated samples had lower contact angles than the control. Atomic force microscopy (AFM) showed increased surface roughness, while X-ray photoelectron spectroscopy (XPS) revealed increased oxygen contents after the plasma treatments. The plasma treated films had higher T-peel strength than that of the control as revealed by T-peel strength tests. It was shown that the addition of environmental humidity increased effectiveness of the plasma in polymer surface modification after the treatment.
Keywords: Plasma; Polyamide; Environmental humidity (EH); XPS;

Modulation of anisotropic crystalline in a-plane GaN on HT-AlN buffer layer by H. Long; T.J. Yu; H. Fang; Z.J. Yang; G.Y. Zhang (5579-5582).
a-Plane GaN was investigated in its strains and crystalline quality. ► Crystalline anisotropy can be improved using HT-AlN buffer. ► Strain transforms along [0 0 0 2] from compression to tensile using HT-AlN buffer. ► The contraction of lattice along [ 1 0 1 ¯ 0 ] induces the transformation of compression into tensile along [0 0 0 2].( 1 1 2 ¯ 0 ) a-plane gallium nitride has been investigated by Raman spectroscopy and X-ray diffraction. Strains of a-plane GaN grown on LT-GaN nucleation layer were both compressive along [ 1 1 ¯ 0 0 ] and [0 0 0 2] orientations. However, strains of GaN epitaxied on HT-AlN buffer were tensile along [0 0 0 2] and compressive along [ 1 1 ¯ 0 0 ] GaN orientation. The crystalline anisotropy and quality were also improved by the HT-AlN layer. Atomic force microscopy was utilized for analyzing the HT-AlN buffer layer. We ascribed this divergence of strain and improvement of crystalline to the thermal expansion and lattice mismatch effects of HT-AlN buffer during the metalorganic vapor phase epitaxy.
Keywords: Strains; Crystallites; Metalorganic vapor phase epitaxy; Semiconducting III–V materials;

► Application of a novel cladding technique has been illustrated. ► Domestic microwave oven at 900 W was used to develop composite clads. ► Confirms metallurgical bonding of clads to substrate. ► Flexural behavior of the clads has been analyzed using bend test and fractography. ► Clads exhibit uniform microstructure and good adhesion with the substrate.A domestic multimode microwave applicator was used to develop carbide reinforced (tungsten-based) metal–matrix composite cladding on austenitic stainless steel substrate. Cladding was developed through microwave irradiation of the preplaced clad materials at 2.45 GHz for 420 s. Clads show metallurgical bonding with substrate by partial dilution of materials. Back scattered images of clad section confirm uniformly distributed reinforced particles in the metallic matrix. Presence of WC, W2C, NiSi, NiW and Co3W3C phases was detected in the clad. Flexural characteristics show two distinct load transitions attributable to deformations of the matrix and the reinforced particles. Clads fail at the upper transition load; further load is taken by the SS-316 substrate. Clads exhibit good stiffness and good adhesion with the substrate. Multi directional cracks were observed at the clad surface; on further loading, cracks get propagated into the clad thickness without getting peeled-off. Mechanism of clad development has been introduced.
Keywords: Surface modification; Microwave heating; Composite cladding; Microstructure; Flexural strength;

► A high quality of ITO film deposited on PET substrate at room temperature was achieved by a commercial RF-assisted DC magnetron sputter. ► A moderate sputtering rate and denser microstructure of ITO films can be achieved by this unique sputter. ► The electrical resistivity was obtained a minimum value of 5.3 × 10−4  Ω cm by wisely adjusting to a 50% RF portion of the total power. ► The electrical resistivity and optical transmission of ITO films were further improved to 3.9 × 10−4  Ω cm and 90% by flowing 2 sccm of O2 gas. ► This research dominates the feasibility of in-line mass production of ITO-coated PET films at room temperature for OLED and touch panel applications.A unique design of RF (radio frequency) assisted DC (direct current) sputter was employed to deposit ITO (indium tin oxide) films on PET (polyethylene terephtalate) substrate. Effects of different RF portions of total power and oxygen gas flow on the properties of the films were investigated. It was found that the films became denser as the applied RF portion of the total power increased. This is due to higher momentum energy transfer by impinging ions increasing adatom diffusion on the films. Thus, a larger grained and less porous microstructure was presented in the films deposited at higher RF portions of the total power. However, a rougher surface morphology and minor crystallization was also found in the films prepared at 100% RF power. By wisely adjusting to a 50% RF portion of the total power, the electrical resistivity can reach a minimum value of 5.4 × 10−4  Ω cm associated with the carrier concentration of 7.0 × 1020  cm−3 and mobility of 17.4 cm2  V−1  s−1, respectively. In addition, the oxygen gas concentration in the sputtering chamber was found to play a key role in determining the quality of the films. As oxygen gas flowed at 2 sccm, the electrical resistivity was decreased to 3.9 × 10−4  Ω cm at a 50% RF portion of the total power. The electrical conduction mechanism, based on the grain boundary scattering, was correlated to the microstructure of the films in terms of grain size.
Keywords: ITO films; PET (polyethylene terephtalate); Grain boundary scattering;

Chemical and microstructural characterization of rf-sputtered BaTiO3 nano-capacitors with Ni electrodes by James N. Reck; Rebecca Cortez; S. Xie; Ming Zhang; Matthew O’Keefe; Fatih Dogan (5599-5604).
► Sputter deposited BaTiO3 nano-capacitors ∼100 nm thick were characterized. ► AFM and SEM confirmed the films to be smooth and conformal with no macro-defects such as pores or cracks. ► TEM and XRD indicate the films were either amorphous or nanocrystalline. ► XPS showed the films had excess oxygen and Ba:Ti ratios ranging from 0.78 to 1.1. ► No correlation between the chemical/microstructural features and dielectric properties (permittivity up to ∼1000 and losses below 0.1).Chemical and microstructural evaluation techniques have been used to characterize sputter deposited 100–150 nm thick BaTiO3 nano-capacitors with 30 nm thick Ni electrodes fabricated on Si/SiO2 wafers. More than 99% of devices had resistance > 20 MΩ. Electrodes were found to have a roughness, R a, of about 0.66 ± 0.04 nm, and the BaTiO3 had a R a value of 1.3 ± 0.12 nm. Characterization of the BaTiO3 film chemistry with X-ray Photoelectron Spectroscopy (XPS) showed the films had excess oxygen and Ba:Ti ratios ranging from 0.78 to 1.1, depending on sputtering conditions. X-ray diffraction showed a broad peak between approximately 20° and 35° 2θ, indicating the films were either amorphous or contained grain sizes less than 5 nm. Focused ion beam images confirmed the presence of smooth, conformal films, with no visible signs of macro-defects such as pin-holes, cracks, or pores. High resolution transmission electron microscopy (TEM) and electron diffraction patterns confirmed the presence of a nearly amorphous film with limited short range order. No correlation was found between the chemical and microstructural studies with the dielectric permittivity (280–1000), loss (0.02–0.09), and/or resistivity (8.7 × 1010–1.5 × 1012  Ω cm) values.
Keywords: Sputtering; Capacitors; Nano-technology; Dielectric;

Characterization of SiC in DLC/a-Si films prepared by pulsed filtered cathodic arc using Raman spectroscopy and XPS by C. Srisang; P. Asanithi; K. Siangchaew; A. Pokaipisit; P. Limsuwan (5605-5609).
► DLC/a-Si films were prepared by pulsed filtered cathodic arc. ► Carbon atoms impinging on a-Si layer act not only as a carbon source for DLC formation, but also as a source for SiC formation which may potentially increase adhesive strength, hardness and wear resistance over the films. ► The formation of SiC was confirmed using Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).DLC/a-Si films were deposited on germanium substrates. a-Si film was initially deposited as a seed layer on the substrate using DC magnetron sputtering. DLC film was then deposited on the a-Si layer via a pulsed filtered cathodic arc (PFCA) system. In situ ellipsometry was used to monitor the thicknesses of the growth films, allowing a precise control over the a-Si and DLC thicknesses of 6 and 9 nm, respectively. It was found that carbon atoms implanting on a-Si layer act not only as a carbon source for DLC formation, but also as a source for SiC formation. The Raman peak positions at 796 cm−1 and 972 cm−1 corresponded to the LO and TO phonon modes of SiC, respectively, were observed. The results were also confirmed using TEM, XPS binding energy and XPS depth profile analysis.
Keywords: Diamond-like carbon; Amorphous silicon; Silicon carbide; Pulsed filtered cathodic arc;

► Spectroscopic properties of NaGdF4:Eu3+(Er3+) nanoparticles are systematically studied. ► Fluorescence as a reliable tool for determination of the species present on the NC's surface. ► The NOBF4 treatment removes effectively the oleate ligands from the surface of NCs. ► Only the synthesis of NaGdF4 in inorganic medium yields the organic ligand-free sample.For electronic or biomedical applications it is desirable to have ligand-free water-dispersible nanocrystals (NCs). The commonly used FTIR spectroscopy often provides a direct evidence for molecules on the surface. In some cases, however, the strong bands of solvent molecules may obscure the peaks of surface bounded ligands. We show that in this regard the emission spectroscopy may be used as a more reliable probing tool. The relevant information can be obtained from emission and excitation spectra, emission decay times as well as from analysis of relative efficiency of excitation energy transfer from Gd3+ to Eu3+ ions. Using these methods we tested samples obtained by various synthetic routes and indicated that only nitrosonium tetrafluoroborate (NOBF4) removes successfully the organic ligands from the nanocrystals surface, yielding organic ligand-free NCs dispersible in aqueous solutions. The conclusions drawn from emission spectroscopy are useful for interpretation of results of FTIR, Raman and NMR studies. The detailed assignment of FTIR peaks for oleate-capped and oleate-free NCs is also provided. Finally, we point to the risk of drawing erroneous conclusions about colloidal stability of nanocrystals if refractive indexes of NCs and medium are similar.
Keywords: Surface ligands; Nanocrystals; Nanofluorides; Fluorescence; Colloids;

Wetting properties of gas diffusion layers: Application of the Cassie–Baxter and Wenzel equations by Valérie Parry; Grégory Berthomé; Jean-Charles Joud (5619-5627).
Display Omitted► We study the wetting properties of as received and aged gas diffusion layers. ► We use the Wilhelmy plate method with water at various temperature from 5 to 60 °C. ► We discuss our results in the frame of the Wenzel and Cassie–Baxter wetting regimes. ► We analyse how water temperature and ageing alter the wetting of gas diffusion layers.In this paper, the wetting behaviours of as received and aged commercial 10% PTFE loaded gas diffusion layer were studied using the Wilhelmy plate method with liquid water temperature ranging from 5 to 60 °C. Comparison were made with an untreated sample and a PTFE smooth plate. These experimental results, supported by chemical and morphological surface characterizations, were discussed in the frame of the Wenzel and Cassie–Baxter regimes.For each wetting regime, surface fraction of solid, PTFE and carbon fibres and/or roughness coefficient were estimated by solving a system of Cassie–Baxter and/or Wenzel equations. The transition to one wetting regime to the other is also commented.Finally, the effects of ageing and of water temperature were studied. Ageing was found to alter the wetting behaviour of the GDL through its chemical degradation. An erosion and the crazing of the PTFE coating and an oxidation of the carbon fibres were pointed out. The decrease of the water surface tension linked to an increase of its temperature is also shown to lead to a better wetting and to an increase of the solid surface fraction value. This effect is reinforced by GDL ageing.
Keywords: Contact angle; Wilhelmy plate; Hysteresis; Gas diffusion layer; PEMFC; ESEM;

Metal-assisted electroless etching of silicon in aqueous NH4HF2 solution by Naima Brahiti; Sihem-Aissiou Bouanik; Toufik Hadjersi (5628-5637).
► A non-HF based solution was developed to elaborate different shapes of Si nanostructures by the metal-assisted chemical etching process. ► Metal-assisted electroless etching of silicon was investigated in new chemical solution containing NH4HF2. ► It was shown that silicon nanowires are fabricated either by one-step or two-step metal-assisted chemical etchings. ► It was shown that the increase of NH4HF2 in the etching solution leads to the increase of etching rate.One-step and two-step metal-assisted electroless chemical etchings of p-type silicon substrate in new solutions were investigated. In the one-step etching process, the etching is performed in NH4HF2/AgNO3 solution. On the other hand, the two-step etching process involves chemical deposition of noble metal onto silicon substrate surface followed by electroless etching in NH4HF2/H2O2 solution. The effect of several parameters on the morphology of etched layer was studied namely: pH of etching solution for the two cases and the etching temperature, the concentration of NH4HF2 and the type of metal deposited on silicon surface for second case. It is shown that the morphology depends strongly on etching parameters where different nanostructure shapes can be formed. An important result is that silicon nanowires are formed at pH = 4 and pH ≤ 2 for the first and second case, respectively.
Keywords: Silicon nanostructures; Silicon nanowires; Metal-assisted electroless etching; Catalyst;

► First-principle calculation of the formation and interface energy for the growth of AlN on VN and TiN, and for VN on TiN. ► Role and magnitude of the interaction between the growth surface and the interface with substrate, as determined from first-principle calculations. ► Theoretical critical thickness for the growth of rocksalt AlN on VN and on TiN, and phase transformation into the stable wurtzite structure.We perform first-principle density-functional theory calculations using the full-potential linearized augmented plane wave method to investigate the formation, atomic and electronic structure, and stability of the metal–nitride interface systems, (1 0 0) AlN/TiN, AlN/VN, and VN/TiN in the rocksalt structure. We also determine the surface, interface, and strain energies, of the constituent materials, as well as the layer-dependent interaction energy between the adlayer surface and the interface. We find that this latter interaction, while typically not taken into account, plays an important role in terms of the formation energy for the initial stages of film growth. Using these energy quantities we calculate the film formation energy as a function of thicknesses, where we find that the growth of TiN on VN has the lowest formation energy, followed respectively by AlN on VN, and AlN on TiN. The formation energy of the latter two systems is notably higher due to the significantly higher energy of the metastable rocksalt phase of AlN compared to the stable wurtzite structure. From our calculations, together with experiment, we can predict the values of the interface energy of wurtzite-AlN on VN(1 0 0) and TiN(1 0 0).
Keywords: Atomic structure; Interface energy; Metal nitrides; Nanostructured materials; Hard coatings; Density functional theory;

Photoelectron emission from Cs3Sb coated on a cathode tip by Takayoshi Kimoto; Yoshihiro Arai; Kuniaki Nagayama (5646-5653).
Display Omitted► We developed an equipment to coat photoemissive material on a small area of a cathode tip for TEM in high vacuum and to detect photoelectrons from coated material. ► Cs3Sb emitting photoelectrons was formed at −20 °C from the layers of Sb, Cs and Sb which were deposited on a cathode tip at −20 °C with the developed equipment. ► Lifetime tests of Cs3Sb photocathode were performed at −20 °C and 11 °C. ► The effects of vacuum level, temperature and anode voltage on photoemission from Cs3Sb were also examined.We developed vacuum deposition equipment for coating a photoemissive material on a cathode tip for TEM in high vacuum. For practical reasons, we firstly examined whether Cs reacts chemically with Sb at low temperature. Photoelectrons were emitted from the as-deposited layers of Sb, Cs and Sb deposited on the cathode tip at −20 °C less than 0.5 h after the second Sb deposition. Since the quantum efficiency calculated from the photocurrent was much more than 104 times as large as that of substrate materials, we concluded that Cs3Sb film was formed by the reaction of Cs and Sb at −20 °C. The quantum efficiency of the Cs3Sb 2 h after the second Sb deposition was 0.021–0.029%, but it decreased rapidly with time at temperatures of both about −20 °C and about 10.5 °C at the vacuum level of 1.2–1.4 × 10−7  Pa. Photoelectrons were successfully detected from the Cs3Sb coated on a small area of 70 μm in diameter over the cathode tip whose diameter was 0.2 mm. It was also determined that photoelectrons emitted from Cs3Sb decreased with anode voltage from 0.1 to 0.4 kV, but increased from 0.4 to 7 kV.
Keywords: Photoelectron; Cs3Sb; Reaction of Cs and Sb; Vacuum deposition; Photocathode for TEM; Lifetime test;

Nanoporous silicon membrane for fuel cells realized by electrochemical etching by M. Jaouadi; W. Dimassi; M. Gaidi; R. Chtourou; H. Ezzaouia (5654-5658).
► Porous silicon membrane was fabricated entirely by electrochemical. ► The thickness of grooves and porosity become more when applied current density. ► The roughness is extremely low after dissolution of silicon. ► Double porous silicon layer is realized with different porosity on both sides.In this work we propose a simple method to realize nanoporous silicon proton exchange membranes for fuel cells. The electrochemical etching allows in a single step, the grooving of the membrane and the realization of double porous silicon (PS) layer.We have studied the impact of the different electrochemical conditions: current density, the electrolyte concentration (ethanoic HF) and the anodization time leading to optimal thickness (of 50–90 μm) and nanoporosity for silicon microstructures. The experimental techniques employed for surface studies and depths of groove in silicon are mainly scanning electronic microscopy (SEM) and atomic force microscopy (AFM) which give information of the silicon microstructures. Photoluminescence (PL) measurements of porous silicon membrane were carried out in order to investigate the optical properties of the PS.
Keywords: Fuel cells; Membrane; Nanoporous silicon; Electrochemical etching;

Display Omitted► Role of plasma ions on the growth and the optical properties of TiO2 films. ► Nanocrystalline rutile TiO2 with crystallinity retained over a range of ion energy. ► Highly transparent TiO2 of small crystallite size is promising as optical coating. ► Ion energy influences the dispersion parameters of the films.TiO2 films are deposited by direct current reactive magnetron sputtering with radio frequency substrate bias. Plasma ions are accelerated towards the substrate due to the negative self bias developed at the substrate. X-ray diffraction pattern reveals that the films deposited at the floating potential (−35 V) of the substrate are amorphous, and broad, low intensity rutile peaks of TiO2 are observed for the films deposited with the substrate bias (self bias in the range −40 to −100 V). A gentle ion bombardment of the growing surface improves the crystallinity of the films. The films are nanocrystalline and rutile phase is retained in the self bias range −40 to −100 V. Films are highly transparent to visible and near infrared and ultraviolet light is effectively filtered out. The optical constants are extracted by the Swanepoel method and the optical dispersion parameters are determined by employing the Wemple–DiDomenico single oscillator model. Inherent good adhesion of plasma based deposits, small crystallite size, high level of transmittance in the visible region and colorless appearance may enhance the performance of the films as optical coatings.
Keywords: Rutile TiO2; Reactive sputtering; Substrate bias; Ion energy; Optical dispersion;

Display Omitted► We report morphological evolution on sapphire (1 −1 0 2) surfaces during annealing in air. ► Anisotropy of the surface occasionally appears as elongation of atomic-height islands and voids near the step edges. ► On another case, the anisotropy induces spontaneous formation of a comb-shaped surface. ► It has phase-separated surface with two domains characterized by different hydrophilicity.Morphology of vicinal sapphire (1 −1 0 2) surfaces was observed in air by atomic force microscopy (AFM) after annealing at temperatures between 1073 K and 1273 K. Surfaces of one type of the samples exhibited high densities of islands and voids with single-atomic height near the step edges at the early stage of annealing, and the crystallographic anisotropy appears as their elongated shapes. During the subsequent annealing, their densities were decreased through the Ostwald ripening process, and finally they were incorporated into the upper and lower terraces. On surfaces of another type of the samples, a comb-shaped pattern consisting of parallel-striped domains running along the [1 −1 0 −1] direction appeared upon the annealing at 1273 K for 3 h. Difference in hydrophilicity was observed between the striped domains and the other areas using frictional force microscopy, which detects the amount of adsorbed water on the surface through meniscus force. The striped pattern that is one of the features of the surface anisotropy is considered to be formed because the surface energy can be decreased when two striped stress domains are alternately arranged.
Keywords: Surface structure; Step arrangement; Surface chemistry; Aluminum oxide; Atomic force microscopy;

Monitoring the formation of inorganic fullerene-like MoS2 nanostructures by laser ablation in liquid environments by Giuseppe Compagnini; Marco G. Sinatra; Gabriele C. Messina; Giacomo Patanè; Silvia Scalese; Orazio Puglisi (5672-5676).
Display Omitted► Fullerene-like nanoparticles are obtained by laser ablation of MoS2 in liquid. ► The presence of MoO x plays a crucial role in the formation pathway. ► Absence of dissolved oxygen in the liquid inhibits the formation of IF nanoparticles.Laser ablation of solid targets in liquid media is emerging as a simple, clean and reproducible way to generate a large number of intriguing nanometric structures with peculiar properties. In this work we present some results on the formation of MoS2 fullerene-like nanoparticles (10–15 nm diameter) obtained by the ablation of crystalline targets in water. Such a top–down approach can be considered greener than standard sulphidization reactions and represents an intriguing single step procedure. The generation of the MoS2 nanostructures is in competition with that of oxide clusters and strongly depends on the oxidative environment created by the plasma plume. The size, shape and crystalline phase of the obtained nanoparticles are studied by microscopy while X-Ray Photoelectron Spectroscopy is used to investigate the chemical state of produced nanostructures and to propose mechanisms for their growth.
Keywords: Laser ablation; Transition metal chalcogenide; Inorganic fullerene; XPS;

Effects of the melt state on the microstructure of a Sn–3.5%Ag solder at different cooling rates by Xiaoyun Li; Fangqiu Zu; Wenlong Gao; Xiao Cui; Lifang Wang; Guohua Ding (5677-5682).
► Liquid–liquid structure transition (LLST) does occur in lead-free Sn–3.5%Ag solder. ► The increases of solid–liquid interface energy results in the melts need a larger undercooling to nucleate and a slower rate to grow when the melt experiences LLST. ► The solidification microstructures of Sn–3.5%Ag alloy are refined when the melt experiences LLST. ► When LLST occurs, the eutectic growth pattern would be changed.The effects of the melt state on the microstructure of Sn–3.5%Ag solder were investigated at two different cooling rates. The results show the solid–liquid interface energy is found to increase when the alloy is melted at above liquid–liquid structure transition (L-LST) temperature. Consequently, the melts require a larger undercooling to nucleate and a slower rate to grow. Finally, the solidification microstructures of the Sn–3.5%Ag alloy are refined. During L-LST, the eutectic growth pattern changes from a metastable cellular eutectic growth into a rod-like regular eutectic in some grains. L-LST refines the microstructure, inevitably leading to increased microhardness. At different cooling rates, the effects of the melt state on the microstructure and microhardness of Sn–3.5%Ag solder are similar.
Keywords: Sn–3.5%Ag solder; Liquid–liquid structure transition; Melt state; Microstructure; Eutectic growth pattern;

► We prepare multilayer films of Ag/Si and Ag/SiN x by magnetron sputtering technique. ► We study the atomic oxygen (AO) resistance of Ag/Si film and Ag/SiN x . ► Nanoscaled Si or SiN x protective layer can provide better protection to Ag films against oxidation caused by AO irradiation. ► Ag/Si and Ag/SiN x films show the better lubricating performance before and after AO irradiation than pure Ag film.The Ag film, and double layer films of Ag/Si and Ag/SiN x were deposited by magnetron sputtering technique. The atomic oxygen (AO) irradiation tests were conducted using a ground AO simulation facility. The microstructure and composition of these films before and after AO irradiation tests were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), respectively, atomic force microscope (AFM) and scanning electron microscopy (SEM), respectively. Then the protective effects of nanoscaled amorphous Si and SiN x layers on the atomic oxygen resistant property of Ag film were investigated. The results show that nanoscaled Si or SiN x protective layer can provide better protection to Ag film against oxidation caused by AO irradiation. The silica layer formed on the surface of amorphous protective layers during AO exposure process plays the key role in protecting Ag film from oxidation. On the other hand, the tribological performance of Ag film and the multilayer films was comparatively studied using a ball-on-disc tribometer in vacuum condition. The tribotest results indicate that Ag/Si and Ag/SiN x films show the better lubricating performance before and after AO irradiation than pure Ag film.
Keywords: Atomic oxygen resistance; Tribological properties; Ag film; Amorphous Si and SiN x protective film;

► Synthesis of Si nanowire arrays by catalysis etching in a new chemical solution Ag2O–HF–H2O. ► Spectroscopic-ellipsometry study of catalytic-etched Si nanowire surface. ► Demonstration of the effectiveness of SPM cleaning for Si nanowire synthesis.An etchant system, Ag2O–HF–H2O, was used to fabricate vertically aligned Si nanowire (SiNW) arrays on Si wafers. The synthesis was based on catalytic etching and produced large-area brushlike SiNWs on Si wafers. The Ag2O concentration was varied from 0.001 to 0.1 mol/L and various synthesis conditions were optimized. The synthesized SiNWs were investigated by Fourier-transform infrared spectroscopy analysis, optical absorption, and contact-angle measurements. Spectroscopic ellipsometry was also used to assess the surface roughness produced in the early stage of etching. The optical measurements revealed that the SiNWs have high optical absorbance from the far infrared to ultraviolet regions. Passive HF etching of the SiNWs changed their wettability from superhydrophilic (∼0°) to highly hydrophobic (∼135°). The effect of sulfuric peroxide mixture (SPM) cleaning on the SiNW formation properties was also examined.
Keywords: Si nanowire; Catalytic etching; Ag2O; Spectroscopic ellipsometry; Optical absorption; Wettability;

► Storing Matter is a novel technique that can improve the sensitivity during SIMS analysis. ► The influence of the oxidation of a Si collector on the secondary ion yields of In and Au deposits is analyzed. ► Surfaces with very different levels of oxidation led to modified secondary ions yields. ► The oxidation generated on a Si0 collector under vacuum is not enough to induce relevant changes.Storing Matter is a new technique developed to avoid the matrix effect appearing during secondary ion mass spectrometry (SIMS) analysis by decoupling the sputtering step of the sample to be analyzed from the subsequent analysis step by SIMS. Prior to the analysis, the emitted matter is deposited at a sub-monolayer level on a well known collector, whose oxidation state may influence the secondary ion yields of the deposit.The aim of this work is to study the influence of the oxidation of a Si collector on the secondary ion yields of In and Au deposits analyzed in positive and negative modes, respectively. We have observed in our study that extreme variations of the level of oxidation alter the ion yield, although the oxidation generated on a Si0 collector under vacuum is not enough to induce relevant changes.
Keywords: SIMS; Storing Matter; Oxidation; Auger;

► Synthesis of flower-like SnO2 single crystals. ► As-synthesized flower-like SnO2 single crystals exhibit higher photoactivity than granular SnO2 and P25. ► OH• and h+ are the main active species in photocatalysis of SnO2.Flower-like SnO2 single crystals were successfully synthesized using hydrothermal method and characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FESEM) and UV–vis diffuse reflectance (DRS). As-synthesized flower-like SnO2 single crystals exhibited higher photoactivity (about 2.2 times) than granular SnO2 for degradation of Rhodamine B (RhB) dye. The trapping experiment showed that the holes (h+) and hydroxyl radical (•OH) were the main active species in the photodegradation process.
Keywords: SnO2; Flower-like; Environmental performance; Photocatalytic mechanism;

Evolution of the Al2O3/Ge(1 0 0) interface for reactively sputter-deposited films submitted to postdeposition anneals by Nicolau Molina Bom; Gabriel Vieira Soares; Cristiano Krug; Rafael Peretti Pezzi; Israel Jacob Rabin Baumvol; Claudio Radtke (5707-5711).
► Al2O3 sputter deposited on Ge. ► Evidence of a GeO2 interlayer in as-deposited samples. ► Ar and forming gas annealings reduced the amount of oxidized Ge. ► Remaining transition layer consisted of aluminum germanates. ► Al2O3/Ge is more stable than Al2O3/Si in the absence of an oxidizing agent.Al2O3 was deposited by pulsed DC reactive sputter on Ge(1 0 0) aiming at producing layers with reduced OH and H2O content in comparison with water-based atomic layer deposition. In this way, the intrinsic interaction of Al2O3 with Ge could be probed. Photoelectron spectroscopy showed evidence of a GeO2 interlayer in as-deposited samples. Thermal annealing in Ar or forming gas for 30 min at 350 °C reduced the amount of oxidized Ge, i.e. significant activity took place at the Al2O3/Ge interface irrespective of annealing ambient. The remaining transition layer consisted essentially of aluminum germanates. Analysis of Si companion samples indicates that in the absence of an oxidizing agent, Al2O3/Ge is more stable than Al2O3/Si.
Keywords: Germanium; Aluminum oxide; Thin oxide film; X-ray photoelectron spectroscopy (XPS); Nuclear reaction profiling (NRP);

Synthesis and characterization of monodisperse porous α-Al2O3 nanoparticles by Xinghua Su; Shuanfa Chen; Zhenjun Zhou (5712-5715).
The SEM micrograph of the monodisperse porous α-Al2O3 nanoparticles.Display Omitted► Monodisperse α-Al2O3 nanoparticles were prepared by the simple homogeneous precipitation method and subsequent heat-treatments. ► The particle size of porous α-Al2O3 nanoparticles can be controlled. The pore sizes of porous α-Al2O3 nanoparticles were approximately 6–14 nm. ► It is demonstrated that shrinkage and sintering of precursor particles resulted in the porous structure of α-Al2O3 nanoparticles. ► The monodisperse porous α-Al2O3 nanoparticles have great potential to be applied in gas separation, catalyst supports and filters in a high temperature environment.Monodisperse porous α-Al2O3 nanoparticles with variable sizes were prepared by the homogeneous precipitation method and subsequent heat-treatments. The crystalline phases, morphologies and pore size distributions of the samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and N2 adsorption/desorption. The diameters of porous α-Al2O3 nanoparticles obtained with an Al3+ concentration of 10 mmol/L were in the range of 200–500 nm, and the diameters of porous α-Al2O3 nanoparticles obtained with an Al3+ concentration of 0.5 mmol/L were in the range of 40–70 nm. The pore sizes of porous α-Al2O3 nanoparticles were approximately 6–14 nm. The porosity developed during the heating process due to phase transformation and shrinkage of precursor particles. The monodisperse porous α-Al2O3 nanoparticles have great potential to be applied in gas separation, catalyst supports and filters in a high temperature environment.
Keywords: α-Al2O3; Nanoparticles; Monodisperse; Porous;

Research on PEG modified Bi-doping lead dioxide electrode and mechanism by Weihua Yang; Wutao Yang; Xiaoyan Lin (5716-5722).
► Bi–PbO2 electrode modified with different concentrations of PEG was prepared. ► Morphology of Bi–PbO2 film was greatly changed by adulteration of PEG. ► Bi–PbO2 electrode modified with 8 g L−1 PEG exhibits the highest electro-catalytic activity for phenol degradation. ► PEG modified Bi–PbO2 electrode owns higher oxygen evolution potential and more negative flatband potential. ► PEG modification significantly reduces the adsorption resistance of Bi–PbO2 electrode for hydroxyl radicals (·OH).Bi-doping PbO2 electrode, which is called Bi–PbO2 for short, modified with different concentrations of polyethylene glycol (PEG) was prepared by electrodeposition method in this paper. The microstructure and electrochemical properties of the different modified electrodes were investigated using scanning electron microscopy, X-ray diffraction, Mott–Schottky, electrochemical impedance spectroscopy and linear sweep voltammetry techniques. The results show that adulteration of PEG has a noticeable improvement in the morphology of Bi–PbO2 electrode which can greatly decrease its particle size and enlarge its active surface area. Phenol degradation experiments reveal that the modified electrodes have excellent electro-catalytic activity and stability, and the optimal adulterate concentration of PEG is 8 g L−1. Electrochemical performance tests show that the modified electrodes exhibit more negative flatband potential (E fb), larger adsorption pseudo capacitance, lower adsorption resistance and higher oxygen evolution potential, and these characteristics promote the electro-catalytic activity of the Bi–PbO2 electrode. Finally, accelerated lifetime tests demonstrate that PEG modification can highly lengthen the service life of Bi–PbO2 electrode in its practical application.
Keywords: Lead dioxide; Bismuth; Polyethylene glycol; Modification mechanism; Mott–Schottky;

A ZnO-based nanocomposite coating with ultra water repellent properties by Gelareh Momen; Masoud Farzaneh (5723-5728).
► A stable nanocomposite coating with ultra water repellent properties was prepared. ► The water droplet easily rolled off and bounce on the coated glass surface. ► The synergistic effect of micro-nano structure was produced by SR/ZnO/SiO2 composite. ► The stability of coating was studied against adverse environmental influences.In this paper a simple and low-cost approach for the elaboration of a superhydrophobic nanocomposite coating is reported. This method can be used for preparing self-cleaning superhydrophobic coatings on large areas for different kinds of substrates. The synergistic effect of the micro-nano-binary scale roughness was produced by a silicone rubber/ZnO/SiO2 composite. A high static contact angle of about 162° and low contact angle hysteresis of about 7.5° was obtained for the prepared superhydrophobic surface on which water droplets were observed to easily roll off and bounce. This type of coating showed exceptional stability against UV exposure, humidity and heating. Also, good stability was observed after immersion in different aqueous solution.
Keywords: Superhydrophobic coating; ZnO; UV; Stability; Nanoparticle;

Investigations of ZnO nanostructures grown on patterned sapphire using different precursors in aqueous solutions by Naisen Yu; Bin Dong; WenWen Yu; Boya Hu; Yongqiang Zhang; Yan Cong (5729-5732).
► ZnO nanostructures are grown using zinc acetate and zinc nitrate as precursors on patterned sapphire substrate by aqueous method. ► It has been found that the distinct surface morphologies of ZnO nanostructures grown by different precursors. ► Both ZnO samples show remarkable photocatalytic activity, in particular, ZnO nanoflowers arrays exhibit an outstanding photocatalytic activity.ZnO nanostructures are grown using zinc acetate and zinc nitrate as precursors on patterned sapphire substrate by aqueous method in this paper. Structural and optical properties of ZnO nanostructures are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and photoluminescence (PL). The photocatalytic activities of the as-prepared samples are evaluated by photocatalytic decolorization of Methyl orange. It has been found that the distinct surface morphologies of ZnO nanostructures grown by different precursors. ZnO nanoflowers arrays with a hexagonal wurtzite structure are grown by using zinc nitrate as precursors, whereas ZnO nanorods/film hybrid structures are achieved by zinc acetate. Meanwhile, both ZnO samples show remarkable photocatalytic activity, in particular, ZnO nanoflowers arrays exhibit an outstanding photocatalytic activity. This behavior is mainly due to the high surface-to-volume ratio and high content of oxygen vacancy, which is also confirmed by photoluminescence. This investigation may provide guidance for the morphology-controlled synthesis of ZnO nanostructures grown on patterned sapphire and their application in the treatment of organic pollutants.
Keywords: ZnO nanostructures; Aqueous solutions; Different precursors;

► We studied the nanostructural CuS thin films by spray pyrolysis method. ► For the first time we used copper acetate as the precursor. ► XRD data show various growth conditions lead to polycrystalline/amorphous films. ► By PL spectra we found the presence of quantum confined effects caused by nano grains. ► Hall effect data including hole density and their mobilities are presented.Copper sulphide (CuS) thin films have been deposited on glass substrates by spray pyrolysis method using an aqueous solutions of copper (II) acetate and thiourea with different Cu to S molar ratios (0.33 and 0.43) at various substrate temperatures of 260, 285 and 310 °C. The structural, optical and electrical characterizations have been carried out using XRD, UV–Vis. transmittance/reflectance, PL spectra and Hall effect measurements. These characterizations indicated the formation of a CuS single phase (covellite) with polycrystalline nature with preferred orientation along (1 0 2) plane, except one with amorphous nature. Optical studies showed that the deposited layers have a relatively high absorption coefficient (5 × 104 to 1 × 105  cm−1) in the visible range, with an effective optical band gap of ∼2.4–2.6 eV. The Hall effect data showed that all the grown samples have a degenerate p-type conductivity with a hole concentration of ∼1.8 × 1020 to 1.7 × 1021  cm−3.
Keywords: Semiconductors; Nanostructures; Optical properties; Electrical properties; Spray pyrolysis;

► Al2O3–YAG composite coatings were successfully fabricated by EPD in a seeded boehmite sol and pressure filtration microwave sintering. ► The cyclic oxidation tests demonstrate that both of the oxidation and spallation resistances of coatings were greatly improved. ► The reduction of weight gain and enhanced adherence of TGO are determined by the Al2O3 sealing effect and reactive element effects. ► This composite coating could be considered as a new kind of diffusion barrier in thermal barrier coatings.Al2O3–YAG (Y3Al5O12) composite coatings were successfully fabricated on NiCoCrAlY alloy substrates by electrophoretic deposition (EPD) in Y3+ doped composite sol–gel suspensions and pressure filtration microwave sintering (PFMS). The composite coating was dense, crack-free and had good adherence with substrate even after cycling oxidation at 1000 °C for 200 h. Filed emission SEM showed that nano-size YAG particles were embedded in α-Al2O3 matrix. The high-temperature cyclic oxidation tests revealed that the oxidation resistance and spallation resistance were greatly improved. The oxidation resistance of alloy is mainly determined by α-Al2O3 sealing effect and reactive elements effects (REE) on the thermally grown oxide (TGO) scale. Moreover, the enhanced fracture toughness and strength of this composite coating can be attributed to the nano/submicro composite structure and YAG particles toughening effects.
Keywords: Al2O3–YAG; Composite coating; Cyclic oxidation resistance; REE; Toughening effects;

Study on microwave absorbing properties of carbonyl–iron composite coating based on PVC and Al sheet by Duan Yuping; Wu Guangli; Gu Shuchao; Li Shuqing; Ma Guojia (5746-5752).
Display Omitted► Polyvinyl chloride sheet as coating baseplate. ► Bruggeman's equation for the calculation of electromagnetic parameters. ► PVC-based coating exhibits high performance in the lower frequency region of 2–6 GHz. ► PVC-based coating could remedy the deficiency of the common metal-based coating.To suppress the increasingly terrible electromagnetic pollution, microwave absorption coatings based on polyvinyl chloride (PVC) sheet have been fabricated, employing polyurethane varnish (PU) as matrix and carbonyl–iron particle (CIP) as absorbent. The morphology, static magnetic and microwave absorption properties of CIP were characterized by scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA), respectively. Bruggeman's equation was introduced to calculate the electromagnetic parameters of materials in the frequency range of 2–18 GHz and the loss mechanisms were discussed. Furthermore, the microwave absorption properties of composite coatings with different component content and thickness were investigated. The results show that the electromagnetic properties of the composite heavily depended on the particle loadings. The minimum reflection peaks of the coatings shift towards the lower frequency region with the increase of CIP content or coating thickness. PVC-based coatings with a component content of 1:7 (PU:CIP mass ratio) in CIP/PU layer, exhibit a minimum reflection loss value of −29 dB at 4 GHz and a permissible reflection loss (RL ≤ −10 dB) frequency band of 2–6 GHz, which is much better than the performance of the common metal-based coatings in the lower frequency.
Keywords: Coating; Microwave absorption; PVC-based; Carbonyl–iron particle; Bruggeman's equation;

In6Se7 thin films by heating thermally evaporated indium and chemical bath deposited selenium multilayers by R.E. Ornelas; D. Avellaneda; S. Shaji; G.A. Castillo; T.K. Das Roy; B. Krishnan (5753-5758).
► This paper reports preparation of In6Se7 thin films by a non-toxic process of selenization using chemical bath deposited selenium. ► The structure, morphology, optical and electrical properties of In6Se7 thin films are described in this article. ► X-ray diffraction studies showed the formation of monoclinic In6Se7. ► The effect of indium layer thickness and selenium deposition time on the structure, electrical and optical properties of In6Se7 thin films is described. ► This material is having good scope as a photovoltaic material.Indium selenide (In6Se7) thin films were prepared via selenization of thermally evaporated indium thin films by dipping in sodium selenosulphate solution followed by annealing in nitrogen atmosphere. First, indium was thermally evaporated on glass substrate. Then, the indium coated glass substrates were dipped in a solution containing 80 ml 0.125 M sodium selenosulphate and 1.5 ml dilute acetic acid (25%) for 5 min. Glass/In–Se layers were annealed at 200–400 °C in nitrogen atmosphere (0.1 Torr) for 30 min. X-ray diffraction studies showed the formation of monoclinic In6Se7. Morphology of the thin films formed at different conditions was analyzed using Scanning electron microscopy. The elemental analysis was done using Energy dispersive X-ray detection. Electrical conductivity under dark and illumination conditions was evaluated. Optical band gap was computed using transmittance and reflectance spectra. The band gap value was in the range 1.8–2.6 eV corresponding to a direct allowed transition. We studied the effect of indium layer thickness and selenium deposition time on the structure, electrical and optical properties of In6Se7 thin films.
Keywords: In6Se7 thin films; Chemical bath deposition; XRD; Photoconductivity;

Effects of oxygen/argon ratio and annealing on structural and optical properties of ZnO thin films by Bing Zhou; Aleksandr V. Rogachev; Zhubo Liu; Dzmitry G. Piliptsou; Hongjun Ji; Xiaohong Jiang (5759-5764).
► ZnO thin films were prepared at various O2/Ar ratios by RF magnetron sputtering. ► Green emission band observed at the ZnO films with O2/Ar flow ratio of 35/35 was attributed the OZn and O i -related emission. ► Moderate annealing temperature can increase the transmittance and PL emission of ZnO films.Zinc oxide (ZnO) thin films were prepared on quartz substrate using radio frequency magnetron sputtering at various oxygen/argon (O2/Ar) flow ratios. The structural and optical properties of ZnO films were investigated in dependence of O2/Ar ratio and annealing temperature by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman scattering spectroscopy, UV–visible spectroscopy and photoluminescence (PL) spectroscopy. XPS spectra showed that the peak positions of the O1s and Zn 2p shifted to opposite directions of binding energy with increasing O2/Ar flow ratio, and the as-deposited ZnO films changed from the Zn-rich to O-rich. Raman spectra revealed that ZnO films consisted of wurtzite structure exhibited high crystalline quality and c-axis preferred orientation after annealing at 420 °C. The transmittance and energy band gap (E g) of the as-deposited ZnO films increased with increasing O2/Ar flow ratio. As the films were annealed, the E g decreased first and then increased with annealing temperature. The PL spectra indicated that all films exhibited a violet emission peak and the ZnO films prepared at O2/Ar = 35/35 showed an additional green emission. The origin of both emission peaks and the change in the intensity with O2/Ar ratio and annealing temperature were discussed.
Keywords: ZnO thin films; RF magnetron sputtering; Transmittance; Band gap; Photoluminescence;

A novel method for synthesis of size-controlled L10 FePt nanoparticles by Fereshteh Azarkharman; Esmaiel Saievar Iranizad; Seyed Ali Sebt (5765-5769).
.Display Omitted► The effect of HF on silicon surface causes the surface sufficiency for bonding to FePt NPs. ► Bonding of NPs to the surface prevent their coalescence during annealing at 600 °C. ► L10 FePt nanocrystals are synthesized and they are single size. ► Chemical ordered fct FePt NPs are 15 nm and ferromagnetic at room temperature. ► A surface with uniform distribution of ferromagnetic FePt nanocrystals were synthesized.Monodisperse FePt nanoparticles with an average particle size of 2.7 nm are synthesized by a polyol process and an etched silicon structure is also formed by an electrochemical process in HF acid. Then, the etched silicon surface as a substrate is coated with FePt nanoparticles. Chemical bonding between nanoparticles and the etched silicon surface prevents the coalescence of the particles during thermal annealing. Annealing at 600 °C for 1 h under a reducing atmosphere (90Ar% + 10H2%) leads to realize phase transformation from fcc to fct L10 structure and the magnetic behavior changes from the superparamagnetic into the ferromagnetic one. After annealing, the coercivity reaches a maximum value of 3.3 kOe for particles coated on the etched wafer. Furthermore, the monosize nanoparticles with an average size of 15 nm are distributed uniformly on the etched silicon surface. So, after phase transition to L10, the FePt nanoparticle size limits to the average value (15 nm).
Keywords: FePt nanoparticles; L10 structure; Size control; Annealing; Polyol method;

Orientation control in L10 FePt films by using magnetic field annealing around Curie temperature by Liwang Liu; Hua Lv; Wei Sheng; Yuanfu Lou; Jianmin Bai; Jiangwei Cao; Bin Ma; Fulin Wei (5770-5773).
► We report a new method to improve (0 0 1) texture of L10 FePt films. ► Annealing at its T c in a magnetic field is used to control the texture of FePt films. ► Why the magnetic field is effective around T c is analyzed on viewpoint of the energy.A new method to improve (0 0 1) texture of L10 FePt films was reported. In this work, in order to obtain the perpendicular orientation of L10 FePt films, the FePt films were annealed at 700 °C (T A1) for 30 min and then annealed at T A2 (430–600 °C) for an hour either in a magnetic field of ∼3500 Oe along the normal direction of the films (Route A) or without magnetic field (Route B). Compared with the Route B, I (0 0 1)/I (1 1 1) showed a peak value of 7 when T A2 was around 478 °C (around the Curie temperature of L10 FePt films) and the AFM image of FePt sample was annealed around 478 °C showed an obvious change of grains through Route A. It is related to the following reason: when the temperature is near Curie temperature of L10 FePt films, the thermal disturbing term is close to the exchange energy of the magnetization, therefore, the magnetic field of ∼3500 Oe is effective for promoting the preferential growth direction of L10 structure.
Keywords: FePt; Magnetic field annealing; Exchange energy; Curie temperature;

Growth of carbon nanotubes on Si/SiO2 wafer etched by hydrofluoric acid under different etching durations by Lling-Lling Tan; Siang-Piao Chai; Abdul Rahman Mohamed (5774-5777).
► Etching Si/SiO2 wafer with 48–50% HF generates SiO2 nanoparticles. ► Metal-catalyst-free growth of CNTs on SiO2 nanoparticles is demonstrated. ► TEM shows the presence of SWCNTs on Si/SiO2 wafer etched at 1 min after CVD.The preparation of SiO2 nanoparticles for the metal-free catalyst growth of carbon nanotubes (CNTs) was investigated. SiO2 nanoparticles were generated by etching Si/SiO2 wafers with 48–50% hydrofluoric acid. Etching duration was varied to study its effects on the generation of the SiO2 nanoparticles. Atomic force microscopy characterization showed that etching at 1 min was the most effective considering the significant numbers of SiO2 nanoparticles obtained under this condition. The wafer etched at 1 min after chemical vapor deposition at 900 °C for 1 h demonstrated a low I D/I G from Raman analysis which establishes that CNTs with highly ordered graphitic structures were grown. Raman analysis also showed a strong radial breathing mode peak in the low-frequency range for the substrate following the 1 min etching process after the reaction.
Keywords: Carbon nanotubes; Chemical vapor deposition; Silicon wafer; Etching; Methane decomposition;

Sulfur dioxide and nitrogen dioxide adsorption on zinc oxide and zirconium hydroxide nanoparticles and the effect on photoluminescence by Jagdeep Singh; Anupama Mukherjee; Sandip K. Sengupta; Jisun Im; Gregory W. Peterson; James E. Whitten (5778-5785).
► Exposure of zinc oxide and zirconium hydroxide particles to SO2 and NO2 results in adsorbed SO3 and NO3, respectively. ► The amount of adsorbed SO3 and NO3 is enhanced by hydration of the samples prior to reactive gas exposure. ► Adsorption results in changes in the photoluminescence spectra of ZnO and Zr(OH)4.Nanoparticulate zinc oxide and micron-size zirconium hydroxide powders have been exposed to sulfur dioxide and nitrogen dioxide by flowing the gases, diluted with nitrogen, over powder samples. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and thermogravimetric analysis (TGA) indicate strongly bound, chemisorbed SO3 and NO3 surface species. Two pre-treatments of the nanoparticulate ZnO samples prior to gas exposure have been investigated: (1) drying overnight in a vacuum oven and (2) hydrating the samples by placing them overnight in water-saturated air. A dramatic difference in reactivity of ZnO is observed, with approximately two-fold and ten-fold greater uptake of NO2 and SO2, respectively, measured by XPS for the hydrated samples relative to the dried ones. Transmission electron microscopy (TEM) demonstrates that the greater uptake arises from a morphology change in the case of the hydrated samples. For zirconium hydroxide, no morphology change is observed for hydrated samples, and SO4 (ads), in addition to SO3 (ads), is indicated by XPS. ZnO and Zr(OH)4 both exhibit photoluminescence (PL) spectra, with peak intensities that change dramatically due to hydration and subsequent exposure to SO2 and NO2 gases. Dosing of the powders with these gases effectively reverts the PL spectra to those corresponding to less hydration.
Keywords: Metal oxide; Photoelectron spectroscopy; Photoluminescence; Sensor;

Ultrasonic nanowelding of SiC microparticles on Al surface by Bo Zhao; Yanfang Wang; Chang Liu; Liying Zhang; Xuan Liu; Yafei Zhang (5786-5789).
► Ultrasonic nanowelding was developed to coat SiC particles on Al surface. ► SiC particles were bonded and compacted well with the Al substrate. ► The microhardness and anticorrosion properties were improved after nanowelding.Ultrasonic nanowelding technique was used to coat silicon carbide (SiC) particles on aluminium (Al) substrate. Both sparse SiC particles and dense particle coating layers were fabricated on Al surface. Detailed analysis shows that SiC particles are bonded and compacted well with the Al surface after the ultrasonic nanowelding process, but no structural transformation and chemical combination at the interface between SiC and Al were observed. The samples of the SiC coatings nanowelded on Al surface possess high hardness, and bigger SiC particle size results in higher hardness values. Corrosion tests reveal that the corrosion resistant properties of Al are improved with the nanowelded SiC coatings.
Keywords: Ultrasonic nanowelding; SiC; Al;

Full depth profile of passive films on 316L stainless steel based on high resolution HAXPES in combination with ARXPS by W. Fredriksson; S. Malmgren; T. Gustafsson; M. Gorgoi; K. Edström (5790-5797).
► Depth profiles of passive films and the chemical content underneath the film on stainless steel by combining ARXPS and HAXPES. ► Nickel is enriched underneath the passive film in the bulk. ► Three different chromium oxides were found in the high resolution HAXPES spectra.Depth profiles of the passive films on stainless steel were based on analysis with the non-destructive hard X-ray photoelectron spectroscopy (HAXPES) technique in combination with the angular resolved X-ray photoelectron spectroscopy (ARXPS). The analysis depth with ARXPS is within the passive film thickness, while the HAXPES technique uses higher excitation energies (between 2 and 12 keV) also non-destructively probing the chemical content underneath the film. Depth profiles were done within and underneath the passive film of 316L polarized in acidic solution.The passive film thickness was estimated to 2.6 nm for a sample that was polarized at 0.6 V and the main component in the passive film is, as expected, chromium. From the high resolution HAXPES spectra we suggest chromium in three different oxidation states present. Also for iron three oxides were detected. Gradients of chromium and iron concentrations and oxidation states within the film and an enrichment of nickel within a 0.5 nm layer directly underneath the passive film are some of the results discussed.
Keywords: Stainless steel; XPS; HAXPES; Passive film;

Chemical mechanical polishing of stainless steel foil as flexible substrate by Xiaokai Hu; Zhitang Song; Weili Liu; Fei Qin; Zefang Zhang; Haibo Wang (5798-5802).
► Stainless steel foils are polished to be used as flexible substrates. ► The surface roughness can be reduced to 0.7 nm by chemical mechanical polishing. ► The acidic slurries containing oxidant can produce the greatest removal rate. ► The microscopic defects are always present within the polished surface. ► The electrochemical corrosion happens locally owing to manganese richness.Stainless steel foils as thin as 120 μm are polished to meet the requirement of low roughness for fabricating flexible thin-film transistors on them used in display or sensor. Using the colloidal silica as abrasives in the chemical mechanical polishing (CMP) procedure, different slurries are evaluated in terms of material removal rates (MRRs). Preliminary CMP tests show that the slurries containing oxidant with the pH less than 2.0 produce the greatest removal rate, and accordingly the mechanism of material removal is proposed. The surface topography of stainless steel before and after polishing is characterized by optical image, scanning electron microscopy and atomic force microscopy image. The surface roughness can be reduced from the unpolished 13.6 nm to the polished 0.7 nm. However, it's found that the microscopic defects of 1–2 μm in size are always present within the polished surface, and the electrochemical cause of their occurrence is suggested according to elementary mapping analysis.
Keywords: Chemical mechanical polish; Stainless steel; Flexible substrate; Colloidal silica; Electrochemical corrosion;

Improvement of photocatalytic activity of brookite titanium dioxide nanorods by surface modification using chemical etching by Linjie Zhang; Victor M. Menendez-Flores; Naoya Murakami; Teruhisa Ohno (5803-5809).
Display Omitted► Brookite TiO2 nanorods were easily etched from the tip faces in H2O2–NH3 solution and exposed new surfaces after etching. ► Brookite TiO2 nanorods were stable against H2SO4 at room temperature, while were greatly etched in H2SO4 at 200 °C. ► The formation of new exposed crystal faces by H2O2–NH3 etching improved separation of redox sites due to its high oxidation ability.Surface morphology of brookite titanium dioxide (TiO2) nanorods was modified by chemical etching with aqueous hydrogen (H2O2)–ammonia (NH3) or sulfuric acid (H2SO4) solution. The brookite nanorods after chemical etching were characterized by TEM, SAED, FE-SEM, XRD and specific surface area measurements. Brookite nanorods after chemical etching with H2O2–NH3 solution exposed new crystal faces in the tips, and nanorods with sharper tips were observed. On the other hand, etching with H2SO4 at 200 °C induced morphological changes in the tip faces and broadened the angle between tip faces as a result of dissolution along the [0 0 1] direction, though brookite nanorods were only slightly etched after etching with H2SO4 at room temperature. Photocatalytic activity of brookite nanorods was tested by toluene decomposition in gas phase under ultraviolet irradiation. Brookite nanorods etched with H2O2–NH3 solution showed higher photocatalytic activity than that of brookite nanorods before etching. In the case of H2SO4 etching at 200 °C, brookite nanorods after etching exhibited lower photocatalytic activity. One reason for this may be that the formation of newly exposed crystal faces by H2O2–NH3 etching improved separation of redox sites due to their strong oxidation ability.
Keywords: Photocatalyst; Brookite nanorods; Chemical etching; Redox site; Photocatalytic activity;

Mechanical and optical characteristics of multilayer inorganic films on polyimide for anti-atomic-oxygen erosion by Yongxian Huang; Xiubo Tian; Shixiong Lv; Ricky K.Y. Fu; Paul K. Chu (5810-5814).
► Multilayer inorganic films were fabricated for protection against atomic oxygen in LEO. ► Higher level of optical transmittance and anti-AO erosion properties were matched with the mechanical stability. ► The FVAPIID process will be promising for fabricating inorganic films on polymer substrate for anti-AO erosion.Multilayer inorganic silica/alumina films with excellent mechanical, optical and anti-atomic-oxygen erosion characteristics were fabricated by the hybrid implanting and depositing processes of Al/Si plasmas on polyimide. The multilayer films exhibited an excellent mechanical stability, demonstrating that balanced internal stresses and alternating bonding structures were crucial for enhancing mechanical stability. The multilayer inorganic films exhibited higher optical transmittance. The slight change surface morphology and high mechanical stability of polyimide covered with multilayer silica/alumina films suggest that the techgnique used is an effective method to protect polymer materials which are applied to thermal control system of spacecrafts in low Earth orbit.
Keywords: Polyimide; Multilayer; Inorganic films; Erosion; Optical properties;

Superhydrophobic terpolymer nanofibers containing perfluoroethyl alkyl methacrylate by electrospinning by Ugur Cengiz; Merih Z. Avci; H. Yildirim Erbil; A. Sezai Sarac (5815-5821).
Display Omitted► Random terpolymers of perfluoromethacrylate, BA with MMA were synthesized in scCO2. ► Molecular weight and concentration were most important parameter on fiber morphology. ► Highest water θ results were obtained on the lotus-like hierarchical fiber surface.A new statistical terpolymer containing perfluoroethyl alkyl methacrylate (Zonyl-TM), methyl methacrylate and butyl acrylate, poly(Zonyl-TM–ran-MMA–ran-BA) was synthesized in supercritical carbon dioxide at 200 bar and 80 °C using AIBN as an initiator by heterogeneous free radical copolymerization. Nanofibers of this terpolymer were produced by electrospinning from its DMF solution. The structural and thermal properties of terpolymers and electrospun poly(Zonyl-TM–MMA–BA) nanofibers were analyzed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and differential scanning calorimetry. Nanofiber morphology was investigated by scanning electron microscopy. Electrospun nanofiber layer was found to be superhydrophobic with a water contact angle of 172 ± 1° and highly oleophobic with hexadecane, glycerol and ethylene glycol contact angles of 70 ± 1°, 167 ± 1° and 163 ± 1° respectively. The change of the contact angle results on the electrospun fiber layer and flat terpolymer surfaces by varying feed monomer composition were compared and discussed in the text.
Keywords: Nanofibers; Electrospinning; Superhydrophobic; Perfluoroacrylates; Supercritical carbon dioxide;

In situ synthesis of zero-valent silver nanoparticles in polymethylmethacrylate under high temperature by Yuanlu Xiong; Guoqiang Luo; Cheng Chen; Huan Yuan; Qiang Shen; Meijuan Li (5822-5826).
Display Omitted► Stable zero-valent Ag nanoparticles are synthesized in PMMA by one step approach under high temperature. ► The size and shape can be controlled by reaction time. ► The competitive growth of Ag nanoparticles with the lacking of additional Ag source is discussed. ► A new mechanism of shape conversion of Ag nanoparticles is proposed.In this work, the silver nanoparticles were synthesized in polymethylmethacrylate (PMMA) matrix under high temperature with polyvinylpyrrolidone (PVP) as additional stabilizer and N,N-dimethylformamide (DMF) as reaction medium. The UV–vis spectroscopy and transmission electron microscopy (TEM) were adopted to investigate the growth and shape conversion of Ag nanoparticles with the lacking of additional Ag source. The results showed that the stable zero-valent Ag in PMMA was obtained successfully. Two types of Ag nanoparticles, single-crystal and twinned ones, could form in the initial period. While the twinned ones will gradually disappear along with the reaction processed, the single-crystal ones could survive and slowly grow by consuming the Ag atoms which were etched form twinned ones. The single-crystal ones will take shape conversion from sphere to nanocube with nearly the same particle size after the total disappearance of twinned ones. The size and shape of Ag nanoparticles can be well controlled by reaction time. The high viscosity PMMA matrix plays the important role of controlling the growth of the Ag nanoparticles, and the PVP takes the responsibility of the shape conversion.
Keywords: Nanoparticle; Morphology; Growth; Shape conversion;

Synergistic effects of Fe and graphene on photocatalytic activity enhancement of TiO2 under visible light by N.R. Khalid; Zhanglian Hong; E. Ahmed; Yuewei Zhang; He Chan; M. Ahmad (5827-5834).
► Synthesis of GR-Fe/TiO2 composite photocatalyst by simple hydrothermal method. ► Bang gap narrowing due to synergistic effects of Fe and graphene. ► Photocatalytic activity enhancement of composite catalyst over pure TiO2.A novel visible light-responsive GR-Fe/TiO2 composite photocatalyst was successfully synthesized by a simple hydrothermal method. Successful deposition of anatase TiO2 nanoparticles onto the graphene is confirmed by transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). UV–vis diffuse reflectance spectroscopy (DRS) shows that compared with the pure TiO2, the resulting GR-Fe/TiO2 composite photocatalysts exhibit enhanced visible light absorption with the increasing Fe dopant. Fluorescence emission spectra show that GR-Fe/TiO2 composites possess improved charge separation than both GR-TiO2 and pure TiO2. The photocatalysis experiment demonstrates that GR-Fe/TiO2 composites have a ten-fold photocatalytic activity enhancement over pure TiO2 for the degradation of methyl orange. The enhanced photocatalytic activity may be attributed to the synergistic effect of improved adsorptivity of dyes, enhanced visible light absorption and effective charge separation.
Keywords: Graphene; Fe-doped TiO2; Hydrothermal; Synergistic effect; Photocatalysis;

A first principles study of a piece of carbon nanoribbon on nickel along the zigzag edge by Yao Cai; Mingtian Zhao; Wei Xiao; Kyeongjae Cho (5835-5840).
► The adsorption of zigzag graphene on Ni (1 0 0) is stronger than that on Ni (1 1 1). ► The edge effect of the zigzag graphene on Ni surfaces can be ignored. ► The zigzag graphene adsorption on steps is strong than the edge adsorption. ► Stronger adsorption at the steps benefit the CNT growth. ► Step adsorption may control the CNT diameter for CNT growth on Ni particles.The adsorption of a piece of graphene nanoribbon on Ni surfaces, edges, and steps along the zigzag edge are studied with first principle calculations. The absolute value of the adsorption energy per contacting point on the (1 0 0) surface is higher than that on the (1 1 1) surface. The edge effects on the graphene adsorption on one side of various edges can be ignored because the cohesive energies and the bond lengths do not change too much on edges compared with that on the bare surfaces. The vertical edge adsorption is not as strong as the one side edge adsorption. For the step adsorption, extra Ni―C bonds form at the interface, the absolute values of the adsorption energies on steps increase and the C―C bond lengths near interfaces are longer than that on the surfaces and edges. For carbon nanotube (CNT) or graphene growth on Ni nanoparticles, steps are at the outside portions of the particles between different facets. Since stronger adsorption and longer C―C bond length near the interface, especially on the steps, may benefit the CNT growth, it can help us understand the relationship between the diameter of CNTs and the size of the Ni particles.
Keywords: Graphene; Carbon nanotubes; Nanoribbon; Nickel; First principles; Edge; Step; Adsorption;

Fabrication of PP-g-PEGMA-g-heparin and its hemocompatibility: From protein adsorption to anticoagulant tendency by Jing Jin; Wei Jiang; Qiang shi; Jie Zhao; Jinghua Yin; Paola Stagnaro (5841-5849).
► Surface grafting on PP via O2 plasma pretreatment combining with UV-irradiated technique. ► We gave a definition of anti-protein adsorptive factor r to evaluate the thrombogenic tendency. ► Protein adsorption depended on graft density, molecular weight and the type of the protein. ► Heparinized PP exhibited very low platelet adhesion and a high bioactivity.We described a two-step process to fabricate the heparinized polypropylene (PP) film using cyanuric chloride (CC) as a trifunctional reagent and poly (ethylene glycol) methacrylate (PEGMA) as a spacer. The modified PP films were characterized by attenuated total reflectance FT-IR and X-ray photoelectron spectroscopy; the content of PEGMA and heparin were determined by gravimetric method and a toluidine blue assay, respectively. For the PP-g-PEGMA films, it was found that small size protein BSA tended to adsorb on the surface of low molecular weight monomer grafted PP, whereas big spindle-shaped fibrinogen tended to adsorb on the surface of high molecular weight monomer grafted PP. We gave a definition of anti-protein adsorptive factor r with two model proteins, albumin and fibrinogen. The results by platelet adhesion and plasma recalcification time (PRT) experiments indicated that the factor r could be used to quantitatively evaluate the anticoagulant tendency of PP-g-PEGMA modified films. For the PP-g-PEGMA-g-heparin modified films, the surface was proved to have a high bioactivity by the adsorption of AT III assay and very low platelet adhesion. It indicated that immobilization of heparin on the PP film with PEGMA as a spacer was an effective way to improve the hemocompatibility of PP.
Keywords: Hemocompatibility; Heparin; PEG; Polypropylene; Protein adsorption;

Ferromagnetism in nanocrystalline nickel incorporated diamond-like carbon thin films by R. Paul; M.K. Sharma; R. Chatterjee; S. Hussain; R. Bhar; A.K. Pal (5850-5857).
► Nanoparticulated Ni incorporated diamond like carbon films by plasma CVD. ► No presence of NiC. ► Increase in ferromagnetism with increased Ni content. ► Decrease in ferromagnetism due to increase in NiO. ► Curie temperature above RT.Nanocrystalline nickel (Ni) impregnated diamond-like carbon (NiDLC) films were deposited on glass substrates by using capacitatively coupled plasma chemical vapour deposition. Ni nanocrystallite content was modulated by varying the relative amount of argon in the methane and argon plasma. The chemical composition, structural, microstructural and magnetic studies in these NiDLC films were carried out. Presence of Ni―C bonding states could not be supported as no peak related to the characteristic Ni3C phase was present even in the samples with highest Ni content. DLC matrix became more graphitic in nature with increasing Ni content. This observation was in conformity with the findings from the XPS and FTIR studies as well. Magnetization in the films decreased with increase in temperature. Values of the coercive fields were measured under both increasing and decreasing applied magnetic fields. The difference in the coercive fields increased slowly for films containing increased amount of nickel particles in the DLC matrix and then increased significantly for films containing 0.69 At% of nickel.
Keywords: Diamond-like carbon; Nanocrystalline; Plasma CVD; Raman spectroscopy;

Synthesis and photocatalytic property of lead molybdate dendrites with exposed (0 0 1) facet by Muhammad Hashim; Chenguo Hu; Xue Wang; Xiaoyan Li; Donglin Guo (5858-5862).
High photocatalytic activity of PbMoO4 dendritic crystals prepared by the CMS method has been found due to the exposure of (0 0 1) facet.Display Omitted► PbMoO4 dendritic crystals are synthesized by the composite molten salt method for the first time. ► The dendritic plane is exposed on (0 0 1) facet. ► Well recyclability with a stable catalytic activity is found compared with P25 and TiO2 nanoparticles. ► Multi-atomic centers on (0 0 1) facet are the origin of active sites for hydrophilicity and adsorption of O2.PbMoO4 dendrites have been synthesized by the composite molten salt method at 180 °C. The dendritic plane is exposed on (0 0 1) facet. PbMoO4 dendritic crystals exhibited high photocatalytic activity through the degradation of rhodamine B under the irradiation of the simulated sunlight, mainly due to the exposed facet (0 0 1). The (0 0 1) facet is assumed to provide more multi-atomic centers (PbMo4), which are the origin of the active sites for hydrophilicity and adsorption of O2 and the cause of the high photocatalytic activity. The photocatalytic activity of the PbMoO4 dendrites was also compared with those of the conventional catalysts, P25 (21 nm) and TiO2 nanoparticles (50–200 nm).
Keywords: Lead molybdate; Composite molten salt method; Photocatalytic property;

Anatase TiO2 hollow microspheres with exposed {0 0 1} facets: Facile synthesis and enhanced photocatalysis by Xiaoliang Wang; Huanlong He; Yan Chen; Jinqiu Zhao; Xiangyi Zhang (5863-5868).
Display Omitted► TiO2 hollow spheres with exposed (ca. 60%) {0 0 1} facets were synthesized. ► A plausible mechanism for formation of the TiO2 hollow spheres is discussed. ► The products show enhanced photocatalytic activity for degradation methylene blue.Anatase TiO2 hollow microspheres with a high percentage of exposed {0 0 1} facets have been successfully synthesized by a one-step hydrothermal strategy in the presence of hydrogen peroxide and hydrofluoric acid solution. It is found that both HF and H2O2 play an essential role in the formation of TiO2 hollow polyhedron TiO2 microspheres with exposed {0 0 1} facets. A plausible mechanism for formation of the TiO2 hollow spheres with exposed {0 0 1} facets by dissolution–recrystallization and Ostwald ripening is proposed based on the experimental observations. The products exhibited enhanced photocatalytic activities for degradation of methylene blue dye present in aqueous solution under ultraviolet light irradiation at ambient temperature.
Keywords: Anatase TiO2; {0 0 1} facets; Hollow structures; Photocatalytic activity;

► The effects of K2ZrF6 in the electrolyte on characteristics of the MAO coatings were investigated. ► More uniform and compact MAO coating was obtained due to the addition of K2ZrF6. ► γ-Al2O3/t-ZrO2 nanocomposite MAO coating was prepared in the electrolyte with 6.0 g/L K2ZrF6. ► Abrasive resistance of the MAO coatings was improved due to the addition of K2ZrF6.Al2O3/ZrO2 composite coating was prepared on 2A70 aluminum alloy by microarc oxidation (MAO) in a phosphate electrolyte containing K2ZrF6. The effects of K2ZrF6 in the electrolyte on the coating thickness, surface morphology, elemental composition and abrasive resistance were investigated. The results indicated that the MAO coating thickness increase due to the addition of K2ZrF6 in the electrolyte. In the electrolyte containing 6.0 g/L K2ZrF6, the coating was the most uniform and compact. The MAO coating formed in the electrolyte without K2ZrF6 was mainly composed of γ-Al2O3 and a little α-Al2O3. Zirconium in the form of t-ZrO2 was detected in the MAO coatings formed in the electrolyte containing K2ZrF6, and the Zr content increases with increasing concentration of K2ZrF6. A γ-Al2O3 and t-ZrO2 nanocomposite coating was formed in the electrolyte containing 6.0 g/L K2ZrF6, and which exhibited the highest abrasive resistance.
Keywords: Aluminum alloy; Microarc oxidation; Composite coating; Zirconia;

Liquid phase surface alloying of AZ91D magnesium alloy with Al and Ni powders by Mohammad Reza Elahi; Mahmoud Heydarzadeh Sohi; Abdolghayoom Safaei (5876-5880).
► TIG surface alloying of AZ91D with Al + Ni caused formation of hard intermetallics. ► The hardness of the alloyed layer reached to 162 HV which was twice of that of AZ91D. ► Wear rate of alloyed layer was reduced to half of the wear rate of untreated AZ91D.In this paper, liquid phase surface alloying of AZ91D magnesium alloy was carried out by pre-placing of Al and Ni powder mixture and subsequent tungsten inert gas (TIG) melting process. The effects of TIG processing parameters on both microstructures and resulting hardness were investigated. Microstructures of alloyed layers were studied by optical microscope, and scanning electron microscope equipped with energy dispersive X-ray spectroscopy (EDS) analyzer, and the phases were identified by X-ray diffraction analysis. The microhardness of the surface alloyed layer was also measured. The surface hardness was increased from 80 HV0.1 for AZ91D magnesium alloy to as high as 162 HV0.1 for alloyed sample due to the formation of Mg17Al12 and AlNi3 intermetallic compounds in the alloyed region and structural refinement. Hardness improvement reduced the wear rate of the surface alloyed layer to almost half of that of the untreated substrate.
Keywords: Magnesium alloy; Surface alloying; TIG; Microstructure; Wear;

Display Omitted► A series of Ag/Si nanoporous pillar arrays (Ag/Si-NPAs) were prepared controllably. ► The SERS detection of rhodamine 6G with a concentration of 10−15  M was performed. ► The SERS effect depended highly upon the size of the deposited silver particles. ► The optimal silver particle size for obtaining strong SERS effect was ∼35–55 nm.A series of silver/silicon nanoporous pillar arrays (Ag/Si-NPAs) were prepared by an immersion-plating method through controlling the immersing times and their surface-enhanced Raman scattering (SERS) behaviors to rhodamine 6G (R6G) were contrastively studied. With a concentration of 10−15  M, the identification of R6G could be performed by all the samples, but the corresponding peak intensities varied largely. This phenomenon was attributed to the size difference of the deposited silver nanoparticles, and the optimal size range for obtaining the strongest SERS signal was determined to be ∼35–55 nm. Ag/Si-NPA might be an effective substrate for performing highly sensitive SERS detections.
Keywords: Surface-enhanced Raman scattering (SERS); Silicon nanoporous pillar array (Si-NPA); Ag/Si-NPA; Rhodamine 6G (R6G);

Photon energy conversion via localized surface plasmons in ZnO/Ag/ZnO nanostructures by Tian Ning Xu; Lian Hu; Shu Qiang Jin; Bing Po Zhang; Xi Kun Cai; Hui Zhen Wu; Chen Hua Sui (5886-5891).
► We demonstrate great enhancement of visible light emission in ZnO/Ag/ZnO nanostructures. ► The enhancement originates from localized surface plasmon of Ag islands. ► The enhancement are influenced by Ag island sizes and ZnO capping layer. ► The experimental results can be interpreted with theoretical calculation.Localized surface plasmons mediated photon energy conversion in ZnO/Ag/ZnO nanostructures has been investigated. Ag nano islands immersed in ZnO cause a great enhancement of visible light emission where silicon solar cells have maximum response, compared to that of ZnO single layer or Ag/ZnO bilayer structures. It is found that the visible light emission enhancement ratio increases with the thickness of the ZnO capping layer and an enhancement ratio of tenfold for 100 nm ZnO is realized. Furthermore, the intensity and peak wavelength of visible light emission are also influenced by the sizes of Ag islands. The observation of photoluminescence from ZnO/Ag/ZnO nanostructures is interpreted with theoretical calculation of localized surface plasmon resonance. The observed large enhancement of visible light emission may have potential applications in high efficiency solar cells by conversion of ultraviolet to visible light.
Keywords: ZnO; Sandwiched metallic nanostructures; Localized surface plasmons; Luminescence;

► The penetration depth and substrate surface damage increase with increasing cluster size. ► The self-diffusion coefficient and the penetration depth of a cluster significantly increase with temperature. ► The number of volcano-like defects and the penetration depth increase with incident energy. ► High sputtering yield can be obtained by increasing the incident energy at high temperature.The bombardment process of a Ni cluster onto a Cu (0 0 1) surface is studied using molecular dynamics (MD) simulations based on the tight-binding second-moment approximation (TB-SMA) many-body potential. The effects of incident cluster size, substrate temperature, and incident energy are evaluated in terms of molecular trajectories, kinetic energy, stress, self-diffusion coefficient, and sputtering yield. The simulation results clearly show that the penetration depth and Cu surface damage increase with increasing incident cluster size for a given incident energy per atom. The self-diffusion coefficient and the penetration depth of a cluster significantly increase with increasing substrate temperature. An incident cluster can be scattered into molecules or atoms that become embedded in the surface after incidence. When the incident energy is increased, the number of volcano-like defects and the penetration depth increase. A high sputtering yield can be obtained by increasing the incident energy at high temperature. The sputtering yield significantly increases with cluster size when the incident energy is above 5 eV/atom.
Keywords: Bombardment; Temperature; Cluster size; Kinetic energy; Molecular dynamics;

Laser-assisted nanostructuring of Tungsten in liquid environment by E.V. Barmina; E. Stratakis; M. Barberoglou; V.N. Stolyarov; I.N. Stolyarov; C. Fotakis; G.A. Shafeev (5898-5902).
Display Omitted► Nanostructures (NS) are generated on W surface ablated by short pulses in ethanol. ► Density of NS depends on delay between two fs pulses. ► NS on W show reduced efficient work function in comparison with flat surface.Formation of surface nanostructures on Tungsten target immersed into liquids is experimentally studied under its exposure to femtosecond laser pulses with different durations. In particular, nanotexturing of Tungsten upon its exposure to delayed femtosecond pulses is investigated. Two different types of morphological features are observed, namely periodic ripples and nanostructures. Field emission scanning electron microscopy shows that the density of nanostructures as well as their morphology depends on the time delay between pulses and reaches its maximum at 1 ps delay. Thermionic emission of nano-structured W cathode is investigated. The work function of nanostructured W surface is measured to be 0.3 eV lower than that of the pristine surface.
Keywords: Laser; Tungsten; Liquid; Nanostructures; Ripples; Work function;

Computational study of cis-oleic acid adsorption on Ni(1 1 1) surface by S. Simonetti; S. Ulacco; G. Brizuela; A. Juan (5903-5908).
► The adsorption process is more favorable through C=C group than ―COOH group. ► The C=C bond is bound at a height of 1.10 Å above the surface plane of Ni(1 1 1). ► The main interaction is through Ni p and Ni d bonding with C p orbitals. ► The Ni―H bonding plays a minor role.In the present work, the Atom Superposition and Electron Delocalization method has been applied in order to study the adsorption of cis-oleic acid on Ni(1 1 1) surface. This molecule presents two active functional groups, C=C (in the middle) and ―COOH (at one end). Therefore, it is important to explore adsorption on the metal surface through the C=C bond in a geometry parallel to the surface and also in a vertical one with ―COOH pointing at Ni atoms. Our results indicate that the parallel geometry is more stable than the vertical one and C=C bond adsorption dominates the process. Energetic results show a strong interaction with the metallic surface. Ni―Ni, C=C, and C―C bonds are weakened upon adsorption because of a bonding interaction between carbons and nickel surface. We found that Ni 5d z 2 and 5d yz orbitals play an important role in the bonding between C p x , p z orbitals and surface, and the same happens with Ni 6p x and Ni 6p z . A small Ni―H interaction is also detected.
Keywords: Oleic acid; Adsorption; Nickel; Molecular orbital method;

The influence of synthesis condition and aging process of silver nanocrystals on the formation of silver nanorods by Wanzhong Zhang; Xueliang Qiao; Qingyuan Chen; Yuchun Cai; Haiqiang Chen (5909-5913).
Silver nanocrystals obtained by different temperatures, different NaBH4 addition methods and different aging times have significant influence on the formation of silver nanorods by a seed-mediated growth approach.Display Omitted► The particle size and crystal defect of seeds are determined by the synthesis methods. ► The differences in crystal defects determine the possibility of selective adsorption. ► The large and heavily aged nanocrystals are best suitable for acting as silver seeds. ► The use of seeds obtained by addition of NaBH4 all at once produces most Ag nanorods. ► Particle size, crystal defect and aging time of silver seeds are the key factors.Silver nanocrystals with controlled particle size were prepared by reduction of silver nitrate with sodium borohydride in the presence of trisodium citrate and then silver nanorods were synthesized by using the nanocrystals as seeds. The aging has obvious influence on the small nanocrystals but little influence on the large nanocrystals, implying different structural defects on the crystal surfaces of the two kinds of nanocrystals. The use of silver nanocrystals prepared by addition of NaBH4 all at once and prepared at 0 °C helps produce the most silver nanorods with maximum aspect ratio. Only the smaller and slightly aged nanocrystals can be used as seeds for the formation of silver nanorods with high aspect ratio. The effects of concerned parameters of silver seeds can be applied to the synthesis of other anisotropic nanomaterials by a seed-mediated growth approach.
Keywords: Silver nanocrystals; Synthesis; Aging effect; Nanorods; Crystal growth;

Heat and mass transfer in laser dissimilar welding of stainless steel and nickel by Yaowu Hu; Xiuli He; Gang Yu; Zhifu Ge; Caiyun Zheng; Weijian Ning (5914-5922).
► We simulated heat and mass transfer, fluid flow during laser dissimilar welding. ► Fluid flow significantly influences temperature field close to the heat source. ► Mass transport is more quickly at the top surface than cross section. ► The speed of mass transport is the highest during the initial stage of melting.Laser spot welding of stainless steel–nickel dissimilar couple has been studied experimentally and numerically. A three-dimensional heat and mass transfer model is used to simulate the welding process, based on the solution of the equations of mass, momentum, energy conservation and solute transport in weld pool. The calculated fusion zone geometry and element distributions are in good agreement with the corresponding experimental results. The role of fluid flow on temperature field and its evolution is analyzed by comparing two cases with and without considering convection. Temperature fields far away from the weld pool are quite similar, but exhibit large difference close to the heat source. During the early stage after formation of weld pool, the distribution of element Fe in weld pool is non-uniform, due to insufficient time for mixing. The speed for mass transport is the highest during the initial stage of weld pool formation and it decreases with time. Both heat and mass transport are significantly influenced by convection during laser spot welding of stainless steel and nickel.
Keywords: Laser dissimilar welding; Heat transfer; Mass transfer; Fluid flow;