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Applied Surface Science (v.258, #8)

Preparation of hybrid bimodal mesoporous silicas loaded with various capacity of 1,8-naphthalic anhydride and their luminescent properties by Yuzhen Li; Jihong Sun; Li Zhang; Lin Gao; Xia Wu (pp. 3333-3339).

The PL spectra indicated that the luminescence intensity of LHMS decreased at the beginning and later increased with the increasing of the loading NA amount. Meantime, with the loading NA amount decreased, the blue-shift effectiveness of the position of the emission peak was remarkable.Display Omitted► The novel luminescent hybrid bimodal mesoporous silicas (LHMS) were synthesized through two-step route. ► The luminescent behaviors of LHMS. ► Remarkable blue-shift effectiveness.The novel luminescent hybrid bimodal mesoporous silicas (LHMS) modified with different amount of (3-aminopropyl)triethoxysilane (APTES) on the mesoporous surface and then loaded with various capacity of 1,8-naphthalic anhydride (NA) were synthesized through two-step route. The relative hybrid materials were characterized by XRD, N₂ adsorption–desorption isotherms,²⁹Si NMR, TG and PL, and the results show that the bimodal pore system is a suitable host matrix for the fluorescent materials. After modification by using propylamine group as a linker, the surface area and the pore volume of resultant samples decreased with the increasing concentration of APTES in tetrahydrofuran solution and the amount of the NA, respectively. The luminescent behaviors of LHMS indicated that the fluorescence intensity and position of emission spectra depended on the various preparation parameters, especially including the concentration of APTES in the tetrahydrofuran solution during the modification process and mass ratio of NA with the modified mesoporous silicas. Particularly, their blue-shift effectiveness of the position of the emission peak was remarkable with the loading NA amount decreased. The detailed mechanism was also discussed.

Keywords: Bimodal mesoporous silicas; Fluorescent signaling; Covalent anchoring

Synthesis of efficient TiO₂-based photocatalysts by phosphate surface modification and the activity-enhanced mechanisms by Liqiang Jing; Xu Qin; Yunbo Luan; Yichun Qu; Mingzheng Xie (pp. 3340-3349).

► Surface modification with phosphate increases thermal stability of anatase. ► Modified TiO₂ exhibits much high photocatalytic activity compared with TiO₂. ► Activity enhancement is mainly attributed to the increased charge separation rates.A simple strategy to greatly increase the thermal stability of nanocrystalline anatase has been put forward to fabricate efficient TiO₂-based photocatalysts under ultraviolet irradiation, via the surface modification with phosphate anions. The results show that the increased anatase thermal stability is attributed to the roles of the phosphate modification effectively inhibiting the contacts among anatase nanocrystals. Compared to un-modified TiO₂, the modified TiO₂ calcined at high temperature (over 700°C) exhibits much high photocatalytic activity for degrading Rhodamine B (or phenol) solution, even superior to the commercial P25 TiO₂. The activity enhancement is mainly attributed to the increased separation rate of photogenerated charge carriers on the basis of the measurements of steady state- and transient state-surface photovoltage spectroscopy. This work would provide a practical route to reasonably design and synthesize high-performance TiO₂-based nanostructured photocatalysts with high anatase thermal stability.

Keywords: TiO; ₂; Surface modification; High thermal stability; Photoinduced charge separation; Photocatalysis

A threshold of Vo⁺/Vo⁺⁺ to room temperature ferromagnetism of hydrogenated Mn doped ZnO nanoparticles by K. Yuan; Q.X. Yu; Q.Q. Gao; J. Wang; X.T. Zhang (pp. 3350-3353).

► Mn doped ZnO nanoparticles were prepared by co-precipitation method. ► And the doped nanoparticles exhibit obvious ferromagnetism after hydrogenating. ► With the Mn ions concentration increasing, the magnetization of the hydrogenated Zn1−_xMn_xO increased. ► Analysed photoluminescence spectra showed the relationship between charged Vo defects and magnetization. ► We used bound-magnetic-polarons model and long-rang interaction theory explained our results.Hydrogenated Mn doped Zn1−_xMn_xO ( x=0.03, 0.04, 0.08) nanoparticles were prepared by co-precipitation method. With the increase of Mn ions concentration, the magnetization of the hydrogenated Zn1−_xMn_xO increased. Photoluminescence spectra of samples annealed in Ar and H₂ respectively were performed and the visible bands were fitted with Gaussian analysis. It is concluded that the sharp magnetization enhancement could be attributed to the long-rang interaction between bound-magnetic-polarons led by the singly charged oxygen vacancy (Vo⁺).

Keywords: ZnO; Nanoparticle; Ferromagnetism; Photoluminescence; Oxygen vacancy; Gaussian analysis

Fresnel absorption of 1μm- and 10μm-laser beams at the keyhole wall during laser beam welding: Comparison between smooth and wavy surfaces by Alexander F.H. Kaplan (pp. 3354-3363).

► Laser welding: direct absorption at the keyhole surface is modelled. ► Surface waves heavily modulate direct absorption compared to a smooth capillary. ► Waves rapidly cause local shadowing regions, redistributing the energy. ► 10μm-lasers loose much of their stable high direct absorption at wavy surfaces. ► 1μm-lasers experience an absorption increase at wavy surfaces.The angle-dependent absorption of laser beams at metal surfaces is described by the Fresnel-equations. During keyhole laser welding the essential interaction takes place at very striping angles of incidence of the order of 1–8 degrees at the front of the vapour capillary, called the keyhole. For a smooth vapour capillary, laser beams with a wavelength of about 1μm operate in a Fresnel-regime where the absorptance increases with the angle of incidence at the wall, towards the weak Brewster-angle maximum. In contrast, for 10μm-lasers high absorptance around the more pronounced Brewster-angle peak takes place. From high speed imaging keyhole surface waves were observed. Mathematical modelling of the laser-keyhole interaction demonstrates that already relatively little waviness of the melt surface at the keyhole strongly modulates the angles of incidence and in turn the Fresnel-absorption due to varying angles of incidence, soon also leading to shadow zones. Due to this local variation of the angle of incidence the absorptance tends towards the angle-averaged value, with the consequence that for 1μm-lasers the direct absorptance and in turn the penetration depth increases, particularly at low welding speed, while for 10μm-lasers it generally decreases.

Keywords: Laser welding; Keyhole; Model; Wave; Hump; Fresnel absorption; Absorptance

A DFT study the solvent effects of H₂ adsorption on Cu( h k l) surface by Zhijun Zuo; Wei Huang; Peide Han (pp. 3364-3367).

► DFT-COSMO method was used to examine H₂ adsorption on Cu( h k l) surface. ► H₂ can not be parallel adsorbed on Cu( h k l) surface and only vertical adsorption in gas phase. ► Solvent effects improve the ability of H₂ activation when H₂ vertically adsorb on Cu( h k l) surface. ► H–H bond of H₂ parallel adsorption on Cu( h k l) surface is broken spontaneously due to solvent effects.Density functional theory (DFT) combined with conductor-like solvent model (COSMO) have been performed to study the solvent effects of H₂ adsorption on Cu( h k l) surface. The result shows H₂ can not be parallel adsorbed on Cu( h k l) surface in gas phase and only vertical adsorbed. At this moment, the binding energies are small and H₂ orientation with respect to Cu( h k l) surfaces is not a determining parameter. In liquid paraffin, when H₂ adsorbs vertically on Cu( h k l) surface, solvent effects not only influences the adsorptive stability, but also improves the ability of H₂ activation; When H₂ vertical adsorption on Cu( h k l) surface at 1/4 and 1/2 coverage, H–H bond is broken by solvent effects. However, no stable structures at 3/4 and 1 ML coverage are found, indicating that it is impossible to get H₂ parallel adsorption on Cu( h k l) surfaces at 3/4 and 1 ML coverages due to the repulsion between adsorbed H₂ molecules.

Keywords: DFT; H; ₂; Cu; Solvent effects; Adsorption

Study on Fe–Al–Si in situ composite coating fabricated by laser cladding by Long-zhi Zhao; Ming-Juan Zhao; De-Ying Li; Jian Zhang; Guang-Yao Xiong (pp. 3368-3372).

► Fe–Al–Si composite coatings were prepared by laser cladding. ► The composite coating is uniform, free of crack and porosity. ► The Fe–Al–Si composite coatings consist mainly of Fe, SiO₂ and Al₂Fe₃Si₄. The hardness and wear resistance of coating significantly improved.Fe–Al–Si in situ composite coating was fabricated on the surface of ASTM A283Gr.D steel by laser cladding with the preplaced powder. The influence of powder composition, laser power and scanning speed on microstructure, microhardness and wear resistance were investigated in this paper. The results show that Fe–Al–Si in situ composite coating with the good metallurgical bond mainly consists of Fe, SiO₂ and Al₂Fe₃Si₄ intermetallic compound. With the increase of laser power and scanning speed, the grain size of coating gets the minimum value. With the increase of laser power and scanning speed, microhardness and wear resistance both get the peak vaule, and their value are three times and 3.5 times those of substrate, respectively. The optimum parameters are followed as: the ratio of the preplaced composite powder: 8:1:1, laser power: 1600W and scanning speed: 400mm/min.

Keywords: Laser cladding; Fe–Al–Si in situ composite coating; Microhardness; Wear resistance

Self-assembly growth and electron work function of copper phthalocyanine films on indium tin oxide glass by Mingshan Xue; Zhonghao Jiang; Wen Li; Guangli Bi; Junfei Ou; Fajun Wang; Changquan Li (pp. 3373-3377).

► Growth and work function of copper phthalocyanine films on ITO were investigated. ► α-form crystalline CuPc films with well order were obtained. ► The decrease of the EWF with the increase of film thickness was observed. ► The evolution of the EWF was associated with the changes of surface morphology and electronic behaviors.Organic semiconductor materials are becoming a promising subject of not only scientific interest but also potential applications in the field of new energy resources. In this study, the copper phthalocyanine (CuPc) films as an excellent organic semiconductor were self-assembly grown on indium tin oxide glass by electrodeposition, the structural and electronic properties were investigated using various techniques. The results demonstrated that ordered α-form crystalline CuPc films were obtained. The decrease of electron work function of CuPc films with the increase of film thickness was found, which was obviously dependent on the surface morphology. The understanding of these behaviors of CuPc films will be significant for designing related photoelectric devices.

Keywords: Work function; Electronic structures; Copper phthalocyanine

Interaction of platelets, fibrinogen and endothelial cells with plasma deposited PEO-like films by Zhilu Yang; Jin Wang; Xin Li; Qiufen Tu; Hong Sun; Nan Huang (pp. 3378-3385).

► The plasma polymerized PEO-like films. ► The addition of O₂ can increase the COC content. ► The PEO-like film with 70% COC content was obtained while had a good stability. ► The PEO-like film has good hemocompatibility and strong cell repulsive behavior. ► It shows a potential candidate for the application in anti–fouling biomedical device.For blood-contacting biomedical implants like retrievable vena cava filters, surface-based diagnostic devices or in vivo sensors, limiting thrombosis and cell adhesion is paramount, due to a decrease even failure in performance. Plasma deposited PEO-like films were investigated as surface modifications. In this work, mixed gas composed of tetraethylene glycol dimethyl ether (tetraglyme) vapor and oxygen was used as precursor. It was revealed that plasma polymerization under high ratio of oxygen/tetraglyme led to deposition of the films that had high content of ether groups. This kind of PEO-like films had good stability in phosphate buffer solution. In vitro hemocompatibility and endothelial cell (EC) adhesion revealed low platelet adhesion, platelet activation, fibrinogen adhesion, EC adhesion and proliferation on such plasma deposited PEO-like films. This made it a potential candidate for the applications in anti-fouling surfaces of blood-contacting biomedical devices.

Keywords: PEO-like film; Plasma polymerization; Platelet; Protein adsorption; Endothelial cell

TiO₂ activation using acid-treated vermiculite as a support: Characteristics and photoreactivity by Ling Jin; Bin Dai (pp. 3386-3392).

► Vermiculite treated by different acids, nitric acid was superior over sulfuric acid. ► Acid activated vermiculite was successfully used to immobilize TiO₂. ► The substituted partly isopropyl alcohol with Cl⁻ in titanium chloride as TiO₂ precursor. ► The photoreactivity of different TiO₂/vermiculite was compared.Vermiculite was treated by sulfuric or nitric acid aqueous solutions with different concentration. These modified materials as the promising supports, were used to immobilize TiO₂. TiO₂ was prepared by the precursor, which was obtained by substituting partly isopropyl alcohol with Cl⁻ in titanium chloride {[Ti(IV)(OR)_nCl_m] ( n=2–3, m=4− n)}. The TiO₂/vermiculite composites were characterized by X-ray diffraction, scanning electron microscopy, and the nitrogen absorption. Their photocatalytic activity was evaluated by removal of methylene blue (MB). The pure anatase type crystalline phase was well deposited on the supports. The concentrations of acid for treatment had a significant influence on pore sizes and surface area of vermiculite. The treatment process changed microstructure of vermiculite, modified its characteristics, and farther improved the catalytic activity and absorption capacity of TiO₂/vermiculite composites. The treatment effect of nitric acid was superior to that of sulfuric acid.

Keywords: Vermiculite; TiO; ₂; Photocatalysis; Adsorption

Resistivity of thin gold films on mica induced by electron–surface scattering: Application of quantitative scanning tunneling microscopy by Marcelo E. Robles; Claudio A. Gonzalez-Fuentes; Ricardo Henriquez; German Kremer; Luis Moraga; Simón Oyarzun; Marco Antonio Suarez; Marcos Flores; Raul C. Munoz (pp. 3393-3404).

We report a comparison between the resistivity measured on thin gold films deposited on mica, with predictions based upon classical theories of size effects (Drude's, Sondheimer's and Calecki's), as well as predictions based upon quantum theories of electron–surface scattering (the modified theory of Sheng, Xing and Wang, the theory of Tesanovic, Jaric and Maekawa, and that of Trivedi and Aschroft). From topographic images of the surface recorded with a Scanning Tunneling Microscope, we determined the rms roughness amplitude, δ and the lateral correlation length, ξ corresponding to a Gaussian representation of the average height–height autocorrelation function, describing the roughness of each sample in the scale of length set by the Fermi wave length. Using ( δ, ξ) as input data, we present a rigorous comparison between resistivity data and predictions based upon the theory of Calecki as well as quantum theoretical predictions without adjustable parameters. The resistivity was measured on gold films of different thickness evaporated onto mica substrates, between 4K and 300K. The resistivity data covers the range 0.1< x( T)<6.8, for 4K< T<300K, where x( T) is the ratio between film thickness and electron mean free path in the bulk at temperature T. We experimentally identify electron–surface and electron–phonon scattering as the microscopic electron scattering mechanisms giving rise to the macroscopic resistivity. The different theories are all capable of estimating the thin film resistivity to an accuracy better than 10%; however the mean free path and the resistivity characterizing the bulk turn out to depend on film thickness. Surprisingly, only the Sondheimer theory and its quantum version, the modified theory of Sheng, Xing and Wang, predict and increase in resistivity induced by size effects that seems consistent with published galvanomagnetic phenomena also arising from electron–surface scattering measured at low temperatures.

Keywords: Resistivity induced by electron-surface scattering; Classical theories and quantum theories of size effects; Surface roughness measured with a STM; Parameters describing the surface roughness; rms roughness amplitude and lateral correlation lengthPACS; 73.50.−h; 73.61.−r

Enhancing the hydrogen storage capacity of Pd-functionalized multi-walled carbon nanotubes by Priyanka Singh; Mukta V. Kulkarni; Suresh P. Gokhale; Samir H. Chikkali; Chandrashekhar V. Kulkarni (pp. 3405-3409).

.Display Omitted► Improved hydrogen storage capacity of carbon nanotubes. ► PVP capping of Pd-nanoparticles. ► 2.3 times more hydrogen storage. ► Increasing the efficiency of sustainable energy sources.We demonstrate that the hydrogen storage capacity of multi-walled carbon nanotubes can be enhanced by polyvinylpyrrolidone functionalization. The polyvinylpyrrolidone acts as a stabilizing agent for Pd-nanoparticles, reduces their size and facilitates their uniform and enhanced loading onto multi-walled carbon nanotubes. According to sorption studies, the polyvinylpyrrolidone capping and consequent nanostructural modification enables 2.3 times more hydrogen adsorption than mere Pd-functionalization of multi-walled carbon nanotubes. Corresponding morphological changes before and after polyvinylpyrrolidone capping, characterized using Raman Spectroscopy, X-ray diffraction, TEM and thermal analysis techniques, are also presented. The results contribute towards increasing the efficiency of hydrogen based sustainable energy sources.

Keywords: Abbreviations; MWCNT; multi-walled carbon nanotubes; PVP; polyvinylpyrrolidone; Pd-nanoparticles; palladium nanoparticlesHydrogen based energy sources; Hydrogen storage capacity; Multiwalled carbon nanotubes; Pd functionalization; PVP capping

Metal-nanoparticle-induced crystallization of amorphous Ge film using ferritin by Mutsunori Uenuma; Bin Zheng; Takanori Imazawa; Masahiro Horita; Takashi Nishida; Yasuaki Ishikawa; Heiji Watanabe; Ichiro Yamashita; Yukiharu Uraoka (pp. 3410-3414).

► Ferritin can form Ni nanoparticle inside its vacant cavity by biomineralization. ► Ni nanoparticles enable to crystallize a-Ge film. ► Crystalline quality was equivalent with that of conventional method. ► Ni contamination was reduced by more than one order of magnitude.The metal-induced lateral crystallization (MILC) of an amorphous Ge (a-Ge) thin film using Ni nanoparticles (NPs) was investigated. Ni-NPs were formed and evenly distributed onto a 30nm thick a-Ge film by cage-shaped protein. After complete elimination of protein shell, crystal growth was performed at 400°C. Raman spectra and electron backscatter diffraction (EBSD) studies revealed that a poly-Ge film with a maximum grain size approximately 1μm was successfully formed. The Ni contamination in the poly-Ge film was reduced by more than one order of magnitude compared with that in the case of a conventional MILC process.

Keywords: Germanium; Crystallization; Nanoparticle; Ferritin

Correlation between bioactivity and structural properties of titanium dioxide coatings grown by atomic layer deposition by I.P. Grigal; A.M. Markeev; S.A. Gudkova; A.G. Chernikova; A.S. Mityaev; A.P. Alekhin (pp. 3415-3419).

► TiO₂ was grown on Ti and Si by ALD in the range of the reaction cycles N=100–2000. ► TiO₂ coatings reveal polycrystalline structure at the value of N≥300. ► The TiO₂ coatings bioactivity was evaluated by hydroxyapatite forming ability in SBF. ► Amorphous TiO₂ coating did not induce the hydroxyapatite growth. ► TiO₂ anatase bioactivity was confirmed by the hydroxyapatite forming on its’ surfaces.TiO₂ coatings were grown on Ti and Si by Atomic Layer Deposition (ALD) from titanium ethoxide and water at 300°C in a wide range of the reaction cycles number N=100–2000. TiO₂ coatings were found to be amorphous at low value of N<300 while the coatings grown at N≥300 revealed anatase polycrystalline structure. The TiO₂ coatings bioactivity was evaluated by hydroxyapatite forming ability by the technique of soaking in Simulated Body Fluid (SBF). Correlation between bioactivity and structural properties of TiO₂ was determined. X-ray diffraction and scanning electron microscopy with electron probe microanalysis showed that amorphous TiO₂ coating did not induce the hydroxyapatite growth whereas anatase resulted in the hydroxyapatite forming on the samples surfaces which confirmed TiO₂ anatase bioactivity.

Keywords: Atomic layer deposition; Anatase; Bioactivity, Hydroxyapatite

In vitro corrosion and biocompatibility study of phytic acid modified WE43 magnesium alloy by C.H. Ye; Y.F. Zheng; S.Q. Wang; T.F. Xi; Y.D. Li (pp. 3420-3427).

Phytic acid (PA) conversion coating on WE43 magnesium alloy was prepared by the method of immersion. The influences of phytic acid solution with different pH on the microstructure, properties of the conversion coating and the corrosion resistance were investigated by SEM, FTIR and potentiodynamic polarization method. Furthermore, the biocompatibility of different pH phytic acid solution modified WE43 magnesium alloys was evaluated by MTT and hemolysis test. The results show that PA can enhance the corrosion resistance of WE43 magnesium especially when the pH value of modified solution is 5 and the cytotoxicity of the PA coated WE43 magnesium alloy is much better than that of the bare WE43 magnesium alloy. Moreover, all the hemolysis rates of the PA coated WE43 Mg alloy were lower than 5%, indicating that the modified Mg alloy met the hemolysis standard of biomaterials. Therefore, PA coating is a good candidate to improve the biocompatibility of WE43 magnesium alloy.

Keywords: Magnesium alloy; Phytic acid; Corrosion; Biocompatibility

Solvent-free synthesis of oxides for CuInSe₂ thin films fabrication by Guilin Chen; Guoshun Jiang; Weifeng Liu; Xiangzhou Chen; Changfei Zhu (pp. 3428-3432).

► Synthesis of monodisperse oxides by solvent-free solid state reaction for CuInSe₂ thin films has been described. ► Fixing Cu:In ratio molecularly by concentrating Cu–In solution into eutectoid salt before solid state reaction. ► Three categories of mixed salt-type were used to fabricate oxides with different mixing degree. ► The results also show that near stoichiometric CIS films with micron-sized dense grains are obtained in our work.A low-cost non-vacuum process for fabrication of CuInSe₂ (CIS) films by solvent-free mechanochemical method and spin-coating process is described. First, highly monodisperse Cu, In oxides nanoparticles are synthesized via a facile, solvent-free route, which is the first applied in the CIS solar cells. Second, the oxide particulate precursors are deposited in a thin layer by spin-coating technique. Finally, the dry layers are sintered into CIS thin films with composition control by sequential reduction and selenization. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), it is found that near stoichiometric CIS films with a micron-sized dense grains are obtained in our work. Three types of mixed nitrates are used to fabricate oxides, the influence of the degree of mixing on the CIS films have been investigated.

Keywords: CIS thin films; Solvent-free synthesis; Oxides; Selenization

Enhancement of Ti-containing hydrogenated carbon (TiC:H) films by high-power plasma-sputtering by Jyh Gwo; Chun-Lin Chu; Ming-Jui Tsai; Shyong Lee (pp. 3433-3437).

► A high power pulsed magnetron sputtering was explored in depositing TiC:H thin film on a stainless steel 304. ► The sputtering processed TiC:H thin film/stainless steel 304 system exhibits minimal residual stress. ► The TiC:H thin film adheres firmly to the substrate showing the effectiveness of this process.Ti-containing amorphous hydrogenated carbon (TiC:H) thin films were deposited on stainless steel SS304 substrates by high-power pulsed magnetron sputtering (HPPMS) in an atmosphere of mixed Ar and C₂H₂ gases using titanium metal as the cathodic material. The multilayer structure of the deposited film had a TiTiCDLC gradient to improve adhesion and reduce residual stress. This study investigates the effects of substrate bias and target-to-substrate distance on the mechanical properties of TiC:H films. Film properties, including composition, morphology, microstructure, mechanical, and tribology, were examined by glow discharge spectroscopy (GDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and a nanoindenter and a pin-on-disk tribometer. Experiments revealed impressive results.

Keywords: High-power pulsed magnetron sputtering; Me; DLC; Diamond-like carbon

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction by Baojiang Jiang; Chungui Tian; Lei Wang; Li Sun; Chen Chen; Xiaozhen Nong; Yingjie Qiao; Honggang Fu (pp. 3438-3443).

► Concentrate ammonia-assisted hydrothermal method to fabricate N-doped graphene. ► Simultaneous N-doping and reduction of GO. ► The high doping levels of N within products are achieved. ► N-doped graphenes exhibit high capacitive performance and cycle stability.In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180°C for 12h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Keywords: Nitrogen-doped; Grapheme; Hydrothermal; Supercapacitor

Stability of La₂O₃ and GeO₂ passivated Ge surfaces during ALD of ZrO₂ high- k dielectric by O. Bethge; C. Henkel; S. Abermann; G. Pozzovivo; M. Stoeger-Pollach; W.S.M. Werner; J. Smoliner; E. Bertagnolli (pp. 3444-3449).

► Comparative XPS analysis of the chemical stability of La₂O₃ and GeO₂ Ge surface passivation during ALD of ZrO₂. ► Comparative electrical characterization of La₂O₃ and GeO₂ Ge surface passivations in MOS capacitors. ► Decomposition of the 1.5nm thick initial GeO₂ interface layer during ALD of 6.5nm ZrO₂ indicated by TEM and XPS. ► Changing of the Ge oxidation states during ALD of ZrO₂ on interfacial GeO₂ indicated by XPS. ► Detection of zirconia germanate inside the ZrO₂ matrix by XPS independently from surface passivation.La₂O₃ grown by atomic layer deposition (ALD) and thermally grown GeO₂ are used to establish effective electrical surface passivations on n-type (100)-Ge substrates for high- k ZrO₂ dielectrics, grown by ALD at 250°C substrate temperature. The electrical characterization of MOS capacitors indicates an impact of the Ge-surface passivation on the interfacial trap density and the frequency dependent capacitance in the inversion regime. Lower interface trap densities can be obtained for GeO₂ based passivation even though a chemical decomposition of the oxidation states occur during the ALD of ZrO₂. As a consequence the formation of a ZrGeO_x compound inside the ZrO₂ matrix and a decline of the interfacial GeO₂ are observed. The La₂O₃ passivation provides a stable amorphous lanthanum germanate phase at the Ge interface but also traces of Zr germanate are indicated by X-ray-Photoelectron-Spectroscopy and Transmission-Electron-Microscopy.

Keywords: ALD; ZrO; ₂; La; ₂; O; ₃; GeO; ₂; Ge; MOS capacitor

Structural and electrical properties of AlN films deposited using reactive RF magnetron sputtering for solar concentrator application by A. Kale; R.S. Brusa; A. Miotello (pp. 3450-3454).

► We deposited AlN coating using RF magnetron sputtering. ► Al interlayer was deposited to improve film bonding to substrate. ► The deposition conditions were optimized in order to achieve the smooth coating. ► Electrical properties depend on interlayer.AlN is an interesting material with some excellent properties like high hardness (>11GPa), high temperature stability (>2400°C), good electrical resistivity (>10¹⁰Ωcm), and good thermal conductivity (>100W/mK). These properties make it useful in the field of photo voltaic systems. Cooling of solar cells in solar concentrator application is of major concern because high temperature reduces their efficiency. In the present work we deposited AlN coating, with and without an Al interlayer, on various substrates like Si, quartz, and copper using RF magnetron sputtering. Deposition conditions such as Al interlayer (deposition time=5–20min), Ar:N₂ ratio (N₂%=0–75%) and substrate bias (0 and −50V) were changed in order to study their effect on coating properties. Coating surface roughness increased from 0.05 to 0.15μm with increase in Al interlayer thickness. The coating thickness decreased from 4.4 to 3.1μm with increase in N₂ gas % and films grew in (002) orientation. Films deposited on copper using Al interlayer showed good electrical resistance of ∼10¹³Ω. Films deposited on copper without Al interlayer showed presence of voids or micro cracks and poor electrical properties. AlN films deposited at −50V bias show cracking and delamination.

Keywords: PVD; AlN; Surface finish; Electrical insulation

Structural and electronic properties of cubic SrHfO₃ surface: First-principles calculations by Qi-Jun Liu; Zheng-Tang Liu; Ji-Chao Chen; Li-Ping Feng; Hao Tian; Wei Zeng (pp. 3455-3461).

Display Omitted► Density functional theory has been used to study cubic SrHfO₃ (001) surface. ► There is the same changed trend of interplanar distance for two slabs. ► Band gaps of surface systems are reduced by comparison with those of bulk system. ► SrO-terminated slab is more stable.Structural, electronic and chemical bonding properties of the (001) surface of cubic SrHfO₃ have been investigated with both SrO and HfO₂ termination using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory. The relaxed structures of two slabs have been analyzed, which shows the interplanar distance of two slabs has the same changed trend. The electronic band structures and density of states of two slabs have been discussed, showing the reduced band gaps by comparison with those of bulk system. The chemical bonding between Sr and O between the surface layer and subsurface layer as well as Hf and O has been increased. The surface energy, work function and stability have been calculated, which indicates SrO-terminated slab is more stable.

Keywords: Density-functional theory; Surface energy; Work function; SrHfO; ₃

Effect of oxyfluorination on gas sensing behavior of polyaniline-coated multi-walled carbon nanotubes by Jumi Yun; Ji Sun Im; Hyung-Il Kim; Young-Seak Lee (pp. 3462-3468).

. The introduced hydrophilic functional groups on carbon nanotubes using oxyfluorination allowed the thickness controlled polyaniline for the sensitivity of gas sensor.Display Omitted► Thickness controlled polyaniline coating on the surface of MWCNTs by oxyfluorination. ► The oxyfluorinated MWCNTs showed the improvement in the dispersion stability. ► Improved gas sensing sensitivity with quick response time. ► Mechanism of hydrophilic functional groups introduced electrode for gas sensing.Polyaniline-coated multi-walled carbon nanotubes were prepared by in situ chemical polymerization method for the novel sensing materials of ammonia gas. The thickness of the polyaniline coatings was controlled by the oxyfluorination treatment on the multi-walled carbon nanotubes. The oxyfluorination with higher oxygen content produced the more hydrophilic functional groups on the surface of multi-walled carbon nanotubes. Both the resistivity change and the response time were significantly improved with high repeatability using the more hydrophilic multi-walled carbon nanotubes which were modified with oxyfluorination.

Keywords: Gas sensor; Polyaniline; Multi-walled carbon nanotubes; Oxyfluorination; Ammonia

Preparation of continuous TiO₂ fibers by sol–gel method and its photocatalytic degradation on formaldehyde by Yang You; Shiying Zhang; Long Wan; Difa Xu (pp. 3469-3474).

► The continuous TiO₂ fiber has a length of several meters. ► The polymer titanate collosol with molar ratio R≤2 presents great spinnability. ► The continuous TiO₂ fiber is a radial close-packed product of nano-particles. ► The formaldehyde degradation of the continuous TiO₂ fiber is studied.The continuous TiO₂ fibers were prepared by sol–gel method using the tetrabutyl orthotitanate as the precursor. The sol-formation process is studied by FT-IR spectroscopy. The synthesized continuous TiO₂ fibers were characterized using SEM, HRTEM and XRD. Results demonstrate that the titanate sol has good spinnability when R≤2 ( R=H₂O:Ti(OC₄H₉)₄, molar ratio). The fibers have the length of several meters and the diameter of about 30μm. The fibers are a radial close-packed product of nano-particles with high crystallinity. The continuous TiO₂ fibers are co-crystal including anatase phase and rutile phase. The formaldehyde degradation ratio of continuous TiO₂ fiber was 98.6%.

Keywords: Continuous TiO; ₂; fibers; Sol–gel method; Photocatalyst; Formaldehyde degradation

Comparative investigation of the c(2×2)-Si/Cu(011) and (√3×√3)R30°-Cu₂Si/Cu(111) surface alloys using DFT by I.G. Shuttleworth (pp. 3475-3484).

► Energetic arguments show that Si ions drive their local bonding towards hexagonal (111) rather than rectangular (011) co-ordinations. ► The c(2×2)-Si/Cu(011) contains significant Cu 3d charge density rearrangements in the surface and second layers due to the lowering of surface Cu periodicity during alloying.The electronic structure of the c(2×2)-Si/Cu(011) surface alloy has been investigated and compared to the structures seen in the three phases of the (√3×√3)R30°Cu₂Si/Cu(111) system, using LCAO-DFT. The weighted surface energy increase between the alloyed Cu(011) and Cu(111) surfaces is 126.7meV/Si atom. This increase in energy for the (011) system when compared to the (111) system is assigned to the transition from a hexagonal to a rectangular local bonding environment for the Si ion cores, with the hexagonal environment being energetically more favorable. The Si 3s state is shown to interact covalently with the Cu 4s and 4p states whereas the Si 3p state, and to a lesser extent the Si 3d state, forms a mixture of covalent and metallic bonds with the Cu states. The Cu 4s and 4p states are shown to be altered by approximately the same amount by both the removal of Cu ion cores and the inclusion of Si ion cores during the alloying of the Cu(011) surface. However, the Cu 3d states in the surface and second layers of the alloy are shown to be more significantly altered during the alloying process by the removal of Cu ion cores from the surface layer rather than by the addition of Si ion cores. This is compared to the behavior of the Cu 3d states in the surface and second layers of the each phase of the (√3×√3)R30°-Cu₂Si/Cu(111) alloy and consequently the loss of Cu–Cu periodicity during alloying of the Cu(011) surface is conjectured as the driving force for changes to the Cu 3d states. The accompanying changes to the Cu 4s and 4p states in both the c(2×2)-Si/Cu(011) and (√3×√3)R30°-Cu₂Si/Cu(111) alloys are quantified and compared. The study concludes with a brief quantitative study of changes in the bond order of the Cu–Cu bonds during alloying of both Cu(011) and Cu(111) surfaces.

Keywords: Surface alloy; Cu(0; 1; 1); c; (2; ×; 2); Copper silicide; PDOS; COOP; LCAO; DFT

ZnO hedgehog-like structures for control cell cultivation by Neda Neykova; Antonín Brož; Zdeněk Remeš; Karel Hruška; Marie Kalbáčová; Alexander Kromka; Milan Vaněček (pp. 3485-3489).

Display Omitted► We grow biocompatible zinc oxide hedgehog-like structures on glass substrates. ► We use hydrothermal method at low temperature at different reaction times. ► The increase of the reaction time resulted in the change of ZnO morphology. ► We examine the effect of ZnO microstructures on the cultivation of osteosarcoma cells (SAOS-2). ► Additionally, we measure the optical absorption.Growth of biocompatible zinc oxide hedgehog-like structures on glass substrates using hydrothermal method at low temperature is demonstrated. The as-grown samples are characterized by scanning electron microscopy and Raman spectroscopy. The optical absorption of the as-grown ZnO microstructures measured with photothermal deflection spectroscopy showed very low optical absorption and strong scattering making ZnO microrods an ideal diffuser in the visible and near IR regions. In addition, the effect of ZnO microstructures on the cultivation of osteosarcoma cells (SAOS-2) is presented. During the 48h cultivation period, no toxic effect of ZnO as a chemical agent on SAOS-2 cells was observed.

Keywords: Zinc oxide; Hedgehog-like structures; Hydrothermal method; Osteosarcoma cells; Cell adhesion; Scanning electron microscopy; Raman spectroscopy; Photothermal deflection spectroscopy

Surface sprouting growth of Na₂Nb₂O₆·H₂O nanowires and fabrication of NaNbO₃ nanostructures with controlled morphologies by Ang Yu; Jieshu Qian; Lei Liu; Hao Pan; Xingfu Zhou (pp. 3490-3496).

We demonstrated the fabrication of one-dimensional Sandia octahedral molecular sieves (SMOS) Na₂Nb₂O₆·H₂O nanowires via the sprouting growth from the metallic niobium surface. Na₂Nb₂O₆·H₂O nanowires were hydrothermally synthesized in the 15M NaOH solution at 423K, which can be easily converted into NaNbO₃ nanowires by calcination, while the NaNbO₃ cubes were obtained at a higher temperature of 453K.Display Omitted► Na₂Nb₂O₆·H₂O nanowires were synthesized via the surface sprouting growth mechanism. ► Temperature play great roles in the morphology of the nanostructured materials. ► Na₂Nb₂O₆·H₂O nanowires can be easily converted into NaNbO₃ nanowires by calcination.The one-dimensional (1D) Sandia octahedral molecular sieves (SOMS) Na₂Nb₂O₆·H₂O nanowires were prepared by the reaction of Nb powder with NaOH via a one-step hydrothermal methods. The products were characterized by SEM, TEM, XRD, IR and EDX. A plausible sprouting growth mechanism is proposed for the formation of Na₂Nb₂O₆·H₂O nanowires based on the systematic investigation. Na₂Nb₂O₆·H₂O nanoribbons-based complex flowerlike structure were first grew on the metallic niobium surface, the growth process of SOMS nanowire is similar to the plant seed sprouting and growing, Na₂Nb₂O₆·H₂O nanowires were finally formed at the depletion of metallic niobium powder. In the end, we showed that Na₂Nb₂O₆·H₂O nanowires is hydrothermally synthesized in the 15M NaOH solution at 423K, which can be easily converted into NaNbO₃ nanowires by calcination, while the NaNbO₃ cubes were obtained through the same hydrothermal process at a higher temperature of 453K.

Keywords: SOMS nanowire; NaNbO; ₃; nanostructures; Surface sprouting growth; Hydrothermal synthesis

Efficient fluorescence of dissolved CaF₂:Tb³⁺ and CaF₂:Ce³⁺, Tb³⁺ nanoparticles through surface coating sensitization by Limei Song; Lei Xue (pp. 3497-3501).

► Dissolved oleic acid-modified CaF₂:Tb³⁺ and CaF₂:Ce³⁺, Tb³⁺ nanoparticles were synthesized. ► The oleic acid sensitized emission of Tb³⁺ was observed. ► CaF₂:Tb³⁺ nanoparticles with 10mol% Tb³⁺ concentrations possess the highest emission intensity. ► The emission intensity of CaF₂:Ce³⁺, Tb³⁺ nanoparticles is about 4.5 times that of CaF₂:Tb³⁺ (10mol%) nanoparticles.Oleic acid (OA)-modified CaF₂:Tb³⁺ nanoparticles with various Tb³⁺ concentrations and CaF₂:Ce³⁺, Tb³⁺ nanoparticles were synthesized. The as-prepared nanoparticles were shown to be well dissolved in some common organic solvents, such as chloroform and toluene. The nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The investigation of fluorescence properties of CaF₂:Tb³⁺ nanoparticles showed that the Tb³⁺ ions could be sensitized efficiently by the surface coating of OA and CaF₂:Tb³⁺ nanoparticles with 10mol% Tb³⁺ concentrations possess the highest emission intensity. The comparison of emission for CaF₂:Ce³⁺, Tb³⁺ and CaF₂:Tb³⁺ (10mol%) nanoparticles revealed that the emission intensity of the former is about 4.5 times as strong as that of the latter.

Keywords: CaF; ₂; nanoparticles; Oleic acid; Luminescence; Terbium; Cerium

Fractal analysis and atomic force microscopy measurements of surface roughness for Hastelloy C276 substrates and amorphous alumina buffer layers in coated conductors by F. Feng; K. Shi; S.-Z. Xiao; Y.-Y. Zhang; Z.-J. Zhao; Z. Wang; J.-J. Wei; Z. Han (pp. 3502-3508).

► The surface roughness of four samples were prepared and analyzed by AFM. ► The surfaces of amorphous alumina layers were found to be fractal in nature. ► The surfaces of Hastelloy substrates were not fractal. ► The flatten modification of AFM images was discussed.In coated conductors, surface roughness of metallic substrates and buffer layers could significantly affect the texture of subsequently deposited buffer layers and the critical current density of superconductor layer. Atomic force microscopy (AFM) is usually utilized to measure surface roughness. However, the roughness values are actually relevant to scan scale. Fractal geometry could be exerted to analyze the scaling performance of surface roughness. In this study, four samples were prepared, which were electro polished Hastelloy C276 substrate, mechanically polished Hastelloy C276 substrate and the amorphous alumina buffer layers deposited on both the substrates by ion beam deposition. The surface roughness, described by root mean squared (RMS) and arithmetic average ( R_a) values, was analyzed considering the scan scale of AFM measurements. The surfaces of amorphous alumina layers were found to be fractal in nature because of the scaling performance of roughness, while the surfaces of Hastelloy substrates were not. The flatten modification of AFM images was discussed. And the calculation of surface roughness in smaller parts divided from the whole AFM images was studied, compared with the results of actual AFM measurements of the same scan scales.

Keywords: Fractal; Atomic force microscopy; Surface roughness; Coated conductor

Migration of indium ions in amorphous indium–gallium–zinc-oxide thin film transistors by Jiyeon Kang; Kyeong-Ju Moon; Tae Il Lee; Woong Lee; Jae-Min Myoung (pp. 3509-3512).

► Migration of In was observed in indium–gallium–zinc-oxide thin film transistors. ► In migration accompanied performance degradation in terms of threshold voltage shift. ► Momentum transfer by injected electrons as suggested as possible mechanism.Electromigration of In in amorphous indium–gallium–zinc-oxide thin film transistors under repeated switching operation was investigated by analyzing the distribution of component elements. During the repeated switching operations up to 300 times, threshold voltage of this device increased gradually implying alteration to the internal device structures. Energy dispersive X-ray spectroscopy revealed noticeable redistribution of metallic components, especially In, in the channel layer beneath the source electrode during switching operations by the migration of metallic ions away from the source electrode, which is attributed to electromigrations similar to those observed in organic light emitting diodes having indium tin oxide electrodes.

Keywords: Thin film transistors; Indium compounds; Electromigration; Amorphous semiconductors

Chitosan hydrogel films as a template for mild biosynthesis of CdS quantum dots with highly efficient photocatalytic activity by Ru Jiang; Huayue Zhu; Jun Yao; Yongqian Fu; Yujiang Guan (pp. 3513-3518).

► CdS quantum dots were prepared in situ in crosslinked chitosan hydrogel films. ► CdS QDs exhibited a good photocatalytic activity. ► Dye photodegradation followed pseudo-first-order kinetics. ► CdS QDs/chitosan composite films were suitable for potential application.Cadmium sulfide (CdS) semiconducting quantum dots (QDs) were prepared using in situ synthesizing method in crosslinked chitosan hydrogel films under relative mild experimental conditions and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results confirmed that crosslinked chitosan hydrogel films provided a confined matrix for CdS QDs growth in uniform size through chelation and electrostation between cadmium ions and amino groups in chitosan chains. The CdS QDs/chitosan composite films exhibited a highly efficient photocatalytic activity for decolorization of methyl orange (MO) solution under visible light irradiation. The good linearity relationship between ln( C₀/ C_i) and irradiation time ( t) indicated that the decolorization of MO dye under present experimental conditions followed pseudo-first-order kinetics. These results suggested that CdS QDs/chitosan composite films were suitable material for potential application in decolorization of organic dye pollutants under visible light irradiation.

Keywords: CdS quantum dots; Methyl orange; Photocatalysis; Visible light; Chitosan

Silver nanostructure arrays abundant in sub-5nm gaps as highly Raman-enhancing substrates by Jun Wang; Liqing Huang; Lin Yuan; Lihua Zhao; Xuehong Feng; Weiwei Zhang; Lipeng Zhai; Jian Zhu (pp. 3519-3523).

► A simple method to fabricate Ag nanostructures with narrow gaps was proposed. ► Controlling template temperature and deposited thickness lead to gap's formation. ► The SERS enhancement factors reach 10⁷ due to existence of numerous sub-5nm gaps. ► High gaps density and narrow gaps size could improve substrates’ SERS activity.Two types of highly Raman-enhancing arrays substrates were fabricated using anodic aluminum oxide (AAO) templates by controlling the AAO template temperature and evaporated silver thickness during e-beam evaporating: complex patterned Ag nanoparticle arrays abundant in sub-5nm gaps (type I); hexagonal Ag nanopore arrays (type II). The surface enhanced Raman scattering (SERS) enhancement factors (EF) of both substrates are estimated experimentally to exceed 10⁵, especially that of type I reaches 10⁷ due to the existence of numerous sub-5nm gaps. The simulation using finite-difference time-domain (FDTD) method confirmed that gap effect has significantly improved the substrates’ SERS activity.

Keywords: Gap effect; Surface enhanced Raman scattering (SERS); Electron beam evaporation

The role of poly(methacrylic acid) conformation on dispersion behavior of nano TiO₂ powder by Bimal P. Singh; Sasmita Nayak; Samata Samal; Sarama Bhattacharjee; Laxmidhar Besra (pp. 3524-3531).

► Stability maxima, optimum dosages can be derived from the potential characteristic. ► Free energy of adsorption(ΔGSP°) data by electrokinetic and adsorption compare well. ► Low pH more coiling of polymer, high pH extended configuration stable suspension. ► Conformation of polymer at S/L interface is important for stable dispersibility.To exploit the advantages of nanoparticles for various applications, controlling the dispersion and agglomeration is of paramount importance. Agglomeration and dispersion behavior of titanium dioxide (TiO₂) nanoparticles was investigated using electrokinetic and surface chemical properties. Nanoparticles are generally stabilized by the adsorption of a dispersant (polyelectrolyte) layer around the particle surface and in this connection ammonium salt of polymethacrylic acid (Darvan C) was used as dispersant to stabilize the suspension. The dosages of polyelectrolyte were optimized to get best dispersion stability by techniques namely particle charge detector (13.75mg/g) and adsorption (14.57mg/g). The surface charge of TiO₂ particles changed significantly in presence of dispersant Darvan C and isoelectric point (iep) shifted significantly towards lower pH from 5.99 to 3.37. The shift in iep has been quantified in terms of free energy of interaction between the surface sites of TiO₂ and the adsorbing dispersant Darvan C. Free energies of adsorption were calculated by electrokinetic data (−9.8 RT unit) and adsorption isotherms (−10.56 RT unit), which corroborated well. The adsorption isotherms are of typical Langmuir type and employed for calculation of free energy. The results indicated that adsorption occurs mainly through electrostatic interactions between the dispersant molecule and the TiO₂ surface apart from hydrophobic interactions.

Keywords: TiO; ₂; nanoparticle; Dispersion; Stability; Dispersant; Free energy of interaction; Conformation; Adsorption

Investigation of the pore blockage of a Brazilian dolomite during the sulfation reaction by Ivonete Ávila; Paula M. Crnkovic; Fernando E. Milioli; Kai H. Luo (pp. 3532-3539).

► TG analyses were applied to investigate the sulfur sorption reactivity by dolomite. ► The pore blockage of dolomite was demonstrated by porosimetry tests. ► The best fits for experimental data were given by the exponential decay. ► The high temperature was more effective than the time of thermal exposure. ► It was possible to quantify the reactivity decrease of dolomite for SO₂ sorption.The influence of the temperature and reaction time on the sulfation process of a dolomite is investigated in this paper. The sulfation effectiveness was evaluated and correlated with changes in the physical characteristics of a Brazilian dolomite during the reactive process. Calcination and sulfation experiments were performed under isothermal conditions for dolomite samples with average particle sizes of 545μm at temperatures of 750°C, 850°C and 950°C at different times of sulfation. Thermogravimetric tests were applied to establish the reactivity variation of the dolomite in function of the time in the sulfation reaction and evaluate the methodology of the samples preparation. Porosimetry tests were performed to study the pore blockage of dolomite during the sulfation reaction. The highest values of BET surface area were 25.55m²/g, 29.55m²/g and 12.62m²/g for calcined samples and after their sulfation processes, conversions of 51.5%, 61.9% and 42.8% were obtained at 750°C, 850°C and 950°C, respectively. Considering the process as a whole, the best fit was provided by a first-order exponential decay equation. Moreover, the results have shown that it is possible to quantify the decreasing in the dolomite reactivity for sulfur dioxide sorption and understand the changes in the behavior of the sulfation process of limestones when applied to technologies, as fluidized bed combustor, in which sulfur dioxide is present.

Keywords: Pore blockage; Dolomite; Sulfation; Thermal decomposition; BET surface area

Finite element simulation of stress distribution and development in 8YSZ and double-ceramic-layer La₂Zr₂O₇/8YSZ thermal barrier coatings during thermal shock by L.Wang; Y. Wang; W.Q. Zhang; X.G. Sun; J.Q. He; Z.Y. Pan; C.H. Wang (pp. 3540-3551).

► Double-ceramic-layer thermal barrier coatings. ► Finite element simulation. ► Effect of defects on the thermal shock behavior. ► Crack propagation patterns and failure model.In this paper, the thermal stress of the double-ceramic-layer (DCL) La₂Zr₂O₇/8YSZ thermal barrier coatings (TBCs) fabricated by atmospheric plasma spraying (APS) during thermal shock has been calculated. The residual stress of the coating after being sprayed has been regarded as the initial condition of the first thermal cycle. The characteristic of the stress development during the thermal cycle has been discussed, and the influence of the defects on the failure mode during the thermal cycle has also been discussed systematically. Finite element simulation results show that there exist higher radial thermal shock stresses on the ceramic layer surface of these two coatings. There also exist higher thermal stress gradient at the interface between the ceramic layer and the metallic layer. Higher thermal stress in 8YSZ/NiCoCrAlY coating lead to the decrease of thermal shock property as compared to that of LZ/8YSZ/NiCoCrAlY coating. The addition of LZ ceramic layer can increase the insulation temperature, impede the oxygen transferring to the bond coating and can also reduce the thermal stress. Considering from the aspects of thermal insulation ability and the thermal shock resistance ability, DCL type LZ/8YSZ TBCs is a more promising coating material compared with the single-ceramic-layer (SCL) type 8YSZ TBCs for the application.

Keywords: Thermal barrier coatings; Thermal shock; Finite element simulation; Crack

Thickness measurement of a thin hetero-oxide film with an interfacial oxide layer by X-ray photoelectron spectroscopy by Kyung Joong Kim; Seung Mi Lee; Jong Shik Jang; Mona Moret (pp. 3552-3556).

► Thickness of the HfO₂ layers in HfO₂/SiO₂/Si(100) films were measured by XPS. ► The contribution of the interfacial SiO₂ layer to the thickness of the HfO₂ overlayer was counterbalanced. ► The thickness levels of the HfO₂ overlayers showed a small standard deviation of 0.03nm in a series of HfO_2/SiO_2/Si(100) films. ► The thickness of HfO₂ overlayers in a series of HfO₂/SiO_2/Si(100) films was verified by mutual calibration with XPS and TEM. ► The effective attenuation length of the photoelectrons could be determined.The general equation T_ove= Lcos θln( R_exp/ R₀+1) for the thickness measurement of thin oxide films by X-ray photoelectron spectroscopy (XPS) was applied to a HfO₂/SiO₂/Si(100) as a thin hetero-oxide film system with an interfacial oxide layer. The contribution of the thick interfacial SiO₂ layer to the thickness of the HfO₂ overlayer was counterbalanced by multiplying the ratio between the intensity of Si⁴⁺ from a thick SiO₂ film and that of Si⁰ from a Si(100) substrate to the intensity of Si⁴⁺ from the HfO₂/SiO₂/Si(100) film. With this approximation, the thickness levels of the HfO₂ overlayers showed a small standard deviation of 0.03nm in a series of HfO₂ (2nm)/SiO₂ (2–6nm)/Si(100) films. Mutual calibration with XPS and transmission electron microscopy (TEM) was used to verify the thickness of HfO₂ overlayers in a series of HfO₂ (1–4nm)/SiO₂ (3nm)/Si(100) films. From the linear relation between the thickness values derived from XPS and TEM, the effective attenuation length of the photoelectrons and the thickness of the HfO₂ overlayer could be determined.

Keywords: PACS; 68.55.jd; 77.84.Bw; 79.60.−i; 06.20.F−Thickness measurement; HfO; ₂; XPS; Standard metrology

Studies on wettability, mechanical and tribological properties of the polyurethane composites filled with talc by Gai Zhao; Tingmei Wang; Qihua Wang (pp. 3557-3564).

► Polyurethane filled with talc was synthesized by pre-polymer method. ► The COF decreased with the increasing of applied load and sliding speed. ► The roughness would increase after friction, thus resulted in increasing of the CA. ► The CA decreased with the increasing of the talc content.A series of polyurethane (PU)/talc composites modified by a high molecular weight hydroxyl-terminated polydimethylsiloxane (HTPDMS) were prepared. The effect of the talc content on the mechanical, wettability and tribological properties of the PU composites was studied. Tensile strength of the PU composites reached to the maximum after adding 5% talc. The water contact angles (CA) of the original surfaces and worn surfaces of the polyurethane composites were measured. The experimental results indicated that the contact angles of the worn surface increased after friction. The friction and wear experiments were tested on a MRH-3 model ring-on-block test rig at different sliding speeds and loads under dry sliding and water lubrication. Experimental results revealed that the talc contributed to largely improve the tribological properties of the PU composites. The coefficient of friction (COF) of the composites increased with increasing talc. Scanning electron microscopic (SEM) investigations showed that the worn surfaces of the talc filled PU composites were smoother than pure polyurethane under given load and sliding speed.

Keywords: Polymer–matrix composite; Boundary lubrication; Surface analysis; Wear testing

Effect of growth pressure on the morphology evolution and doping characteristics in nonpolar a-plane GaN by Keun Man Song; Jong Min Kim; Bong Kyun Kang; Chan Soo Shin; Chul Gi Ko; Bo Hyun Kong; Hyung Koun Cho; Dae Ho Yoon; Hogyoung Kim; Sung Min Hwang (pp. 3565-3570).

Nonpolar a-plane GaN layers grown on r-plane sapphire substrates were examined by using a two-step growth process. The higher initial growth pressure for the nucleation layer resulted in the improved crystalline quality with lower density of both threading dislocations and basal stacking faults. This was attributed to the higher degree of initial roughening and recovery time via a growth mode transition from three-dimensional (3D) to quasi two-dimensional (2D) lateral growth. Using Hall-effect measurements, the overgrown Si doped GaN layers grown with higher initial growth pressure were found to have higher mobility. The scattering mechanism due to the dislocations was dominant especially at low temperature (<200K) for the lower initial growth pressure, which was insignificant for the higher initial growth pressure. The temperature-dependent Hall-effect measurements for the Mg doped GaN with a higher initial growth pressure yielded the activation energy and the acceptor concentration to be 128meV and 1.2×10¹⁹cm⁻³, respectively, corresponding to about 3.6% of activation at room temperature. Two-step growth scheme with a higher initial growth pressure is suggested as a potential method to improve the performance of nonpolar a-plane GaN based devices.

Keywords: PACS; 85.30.De; 81.05.Ea; 73.30.+y a; -plane GaN; Crystalline quality; Mobility; Two-step growth

In vitro corrosion behavior of Ti-O film deposited on fluoride-treated Mg–Zn–Y–Nd alloy by S.S. Hou; R.R. Zhang; S.K. Guan; C.X. Ren; J.H. Gao; Q.B. Lu; X.Z. Cui (pp. 3571-3577).

► Mg alloy substrate under composite coating has an largely improved corrosion resistance, potential to meet the requirement of long-term mechanical of Mg alloy. ► Since substrate is well protected by composite coating, Ti-O film can keep the surface integrity, hence to function as a coating with good biocompatibility. ► Pitting corrosion was found on the composite coating, resulting in more milder and slower corrosion with time. This may be beneficial to stent degradation.In this paper, a new composite coating was fabricated on magnesium alloy by a two-step approach, to improve the corrosion resistance and biocompatibility of Mg–Zn–Y–Nd alloy. First, fluoride conversion layer was synthesized on magnesium alloy surface by immersion treatment in hydrofluoric acid and then, Ti-O film was deposited on the preceding fluoride layer by magnetron sputtering. FE-SEM images revealed a smooth and uniform surface consisting of aggregated nano-particles with average size of 100nm, and a total coating thickness of ∼1.5μm, including an outer Ti-O film of ∼250nm. The surface EDS and XRD data indicated that the composite coating was mainly composed of crystalline magnesium fluoride (MgF₂), and non-crystalline Ti-O. Potentiodynamic polarization tests revealed that the composite coated sample have a corrosion potential ( E_corr) of −1.60V and a corrosion current density ( I_corr) of 0.17μA/cm², which improved by 100mV and reduced by two orders of magnitude, compared with the sample only coated by Ti-O. EIS results showed a polarization resistance of 3.98kΩcm² for the Ti-O coated sample and 0.42kΩcm² for the composite coated sample, giving an improvement of about 100 times. After 72h immersion in SBF, widespread damage and deep corrosion holes were observed on the Ti-O coated sample surface, while the integrity of composite coating remained well after 7d. In brief, the data suggested that single Ti-O film on degradable magnesium alloys was apt to become failure prematurely in corrosion environment. Ti-O film deposited on fluoride-treated magnesium alloys might potentially meet the requirements for future clinical magnesium alloy stent application.

Keywords: Mg–Zn–Y–Nd alloy; Degradable stents; Ti-O film; Fluoride layer; Corrosion resistance

Water-dispersible hydroxyapatite nanoparticles synthesized in aqueous solution containing grape seed extract by Ruchao Zhou; Shaoxiong Si; Qiyi Zhang (pp. 3578-3583).

► A methodology of water-dispersible grape seed polyphenol (GSP) modified hydroxyapatite nanoparticles (nHAp). ► GSP graft ratio is up to 44.3%, phenolic hydroxyls introduced onto the surface of nHAp particles. ► The zeta potential value is up to −26.1mV while the pure nHAp is −0.36mV.A novel and effective method for the preparation of water-dispersible nano-hydroxyapatite (nHAp) particles was reported. nHAp was prepared in the presence of grape seed polyphenol (GSP) solution with different concentrations. Chemical precipitation method was adopted to produce pure nHAp and modified nHAp (nHAp-GSP) at 60°C for 2h. The chemical nature of the products was detected by Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Moreover, the crystal structure and morphology of particles was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the spherical nHAp particles with a diameter of 20–50nm could be synthesized at 60°C. The zeta potential values of pure nHAp and nHAp-GSP are −0.36mV and −26.1mV respectively. According to the sedimentary time, the colloidal stability of nHAp-GSP in water could be improved dramatically with the increase of GSP content and the particles tended to exist as dispersive nanoparticles without aggregation. All the results indicated that GSP exhibited strong binding to nHAp and enhanced the colloidal stability of nHAp particles.

Keywords: Hydroxyapatite; Surface modification; Grape seed polyphenol; Dispersion; Colloidal stability

Effect of surface roughness on nucleation and growth of vanadium pentoxide nanowires by Li-Chia Tien; Yu-Jyun Chen (pp. 3584-3588).

► The effect of surface roughness on subsequent growth of V₂O₅ nanowire is examined. ► The control of surface roughness and etching conditions is shown to provide an effective method for increasing the density of nucleation sites. ► The obtained V₂O₅ nanowires are orthorhombic structure with high aspect ratio and large number density. ► PL results show intense visible emission, which is attributed to different inter-band transitions between the V 3d and O 2p band.The effect of surface roughness on subsequent growth of vanadium pentoxide (V₂O₅) nanowires is examined. With increasing surface roughness, both the number density and aspect ratio of V₂O₅ nanowires increase. Structures and morphology of obtained nanowires were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The nanowires are approximately 40–90nm in diameter and 2μm in length. X-ray diffraction (XRD) analysis indicates that the obtained nanowires are orthorhombic structure with (001) out-of-plane orientation. The luminescence property of V₂O₅ nanowires has been investigated by photoluminescence (PL) at 150K and 300K. PL results show intense visible emission, which is attributed to different inter-band transitions between the V 3 d and O 2 p band. This simple fabrication approach might be useful for fabrication of large area V₂O₅ nanowires arrays with high density.

Keywords: Surface roughness; Vanadium oxide; Nanowires; Photoluminescence

Multipulse irradiation of silicon by femtosecond laser pulses: Variation of surface morphology by S. Lugomer; A. Maksimović; B. Farkas; Z. Geretovszky; T. Szörényi; A.L. Tóth; Z. Zolnai; I. Bársony (pp. 3589-3597).

► Multipulse processing of Si by fs UV laser and evolution of surface structures. ► Multiscale structures range from nm to hundreds of micrometers. ► Generation of “carpet-like” pattern of spikes in the center of the spot. ► Evolution of a liquid foam layer on the silicon surface. ► Generation of surface tension waves at the peripheral region of the spot.The multipulse interaction of ultraviolet femtosecond laser pulses with silicon and generation of surface structures in a large area spot (≳1mm²) has been studied. The evolution of multiscale structures at the constant fluence strongly depends on the number of pulses, N. For N<200, the “carpet-like” pattern of nano-, and micro-spikes is generated by the bubble explosion in a thin surface foam layer. The accumulation of bubbles and their explosion due to repetition of laser pulses cause damped membrane-like oscillations of the silicon surface. For 200≤ N, bifurcation of surface morphology takes place: (i) the surface tension waves of the wavelength ∼200μm appear in the peripheral region of the spot. Generated by the surface thermal gradient in the liquid foam layer, they spread from the hot centerline towards the periphery of the spot. The change of their wavelength with propagation distance indicates onset of the Eckhaus instability caused by the phase modulation in multipulse interaction. (ii) Deep caverns appear in a highly superheated silicon layer in the central region of the spot due to the fast gas–liquid phase separation and the fragmentation process.

Keywords: Femtosecond laser interaction; Silicon surface modification; Nonlinear surface processes; Scanning electron microscopy; Atomic force microscopy

Effect of pulse repetition rate and number of pulses in the analysis of polypropylene and high density polyethylene by nanosecond infrared laser induced breakdown spectroscopy by Flavio O. Leme; Quienly Godoi; Paulo H.M. Kiyataka; Dario Santos Jr.; José A.M. Agnelli; Francisco J. Krug (pp. 3598-3603).

► LIBS is an important tool for the direct determination of elements in solid materials. ► The analytical performance depends on laser pulse characteristics. ► SEM and perfilometry were useful to evaluate features of laser craters in PP and HDPE. ► Pulse repetition rate affects crater geometry which depends on polymer properties.Pulse repetition rates and the number of laser pulses are among the most important parameters that do affect the analysis of solid materials by laser induced breakdown spectroscopy, and the knowledge of their effects is of fundamental importance for suggesting analytical strategies when dealing with laser ablation processes of polymers. In this contribution, the influence of these parameters in the ablated mass and in the features of craters was evaluated in polypropylene and high density polyethylene plates containing pigment-based PbCrO₄. Surface characterization and craters profile were carried out by perfilometry and scanning electron microscopy. Area, volume and profile of craters were obtained using Taylor Map software. A laser induced breakdown spectroscopy system consisted of a Q-Switched Nd:YAG laser (1064nm, 5ns) and an Echelle spectrometer equipped with ICCD detector were used. The evaluated operating conditions consisted of 10, 25 and 50 laser pulses at 1, 5 and 10Hz, 250mJ/pulse (85Jcm⁻²), 2μs delay time and 6μs integration time gate. Differences in the topographical features among craters of both polymers were observed. The decrease in the repetition rate resulted in irregular craters and formation of edges, especially in polypropylene sample. The differences in the topographical features and ablated masses were attributed to the influence of the degree of crystallinity, crystalline melting temperature and glass transition temperature in the ablation process of the high density polyethylene and polypropylene. It was also observed that the intensities of chromium and lead emission signals obtained at 10Hz were two times higher than at 5Hz by keeping the number of laser pulses constant.

Keywords: LIBS; Laser induced breakdown spectroscopy; Laser pulse repetition rate; Craters characterization; High density polyethylene; Polypropylene

Synthesis of snowflake-like multi-layered ZnO with controllable pore sizes and its photocatalytic property by Qiang Jing; Wuyou Fu; Wancheng Li; Haibin Yang; Minghui Li; Jinwen Ma; Xiaoming Zhou; Meiling Sun; Hui Zhao; Yanyan Zhang; Wenyan Zhao; Lina Zhang; Hui Chen (pp. 3604-3610).

Display Omitted► The pore size of the multi-layered ZnO is roughly controlled by just regulating the calcination temperature. ► The surface-to-volume ratio of the samples decrease with the increase in calcination temperature. ► The surface-to-volume ratio is not the decisive factor and the pores sizes also play a very important role in the whole catalytic activity. ► ZnO obtained at 550°C shows strongest catalytic ability and good recycling ability and demonstrates good catalytic ability in the sunlight.Snowflake-like multi-layered ZnO with porous structure is synthesized through a facile hydrothermal process and followed by calcinating process. The pore size of the multilayered ZnO is controlled by just regulating the calcination temperature. X-diffraction (XRD) patterns reveal that the precursor obtained by hydrothermal method is zinc hydroxide carbonate (ZnHC)¹1Zinc hydroxide carbonate (ZnHC)., after being calcinated, pure wurtzite ZnO is got. TEM and SEM demonstrate the existence of the porosity and the variation of the pore size (ranges from tens of nanometers to hundreds of nanometers). The photocatalytic property is investigated by Xenon Lamp and sunlight.

Keywords: Microporous materials; Multilayers; Chemical synthesis; Heat treatment; Photocatalysis; Photoluminescence spectroscopy

Influence of Sb in synthesize of ZnO nanowire using sandwich type substrate in carbothermal evaporation method by I.A. Palani; K. Okazaki; D. Nakamura; K. Sakai; M. Higashihata; T. Okada (pp. 3611-3616).

► Synthesis of Sb doped ZnO nanowire by sandwich substrate in carbothermal evaporation method. ► The horizontally oriented Sb doped ZnO nanowires with a diameter of 1μm. ► Diffusion of Sb in ZnO lattice is confirmed through TEM, XRD and Raman spectrum. ► Neutral–acceptor–bound exciton (A⁰X) with donor acceptor pair (DAP) observed in PL.The paper deals with synthesis of Sb doped ZnO nanowire by considering Si coated with Sb and Au as substrate using carbothermal evaporation method. The horizontally oriented Sb doped ZnO nanowires with a diameter of 1μm synthesized at 900°C, which is quite high as compared to the Pure ZnO nanowires generated without the influence of Sb at 900°C. The nanowire synthesized at 900°C showed a measurable lower angle of about 0.06° from XRD and suppression of A₁T and E₁(L0) modes in Raman spectroscopic, this confirms the incorporation of Sb in ZnO lattice. The strong exciton emission and weak deep-level emission from room temperature PL and Strong emission attributed to the radiant recombination from neutral–acceptor–bound exciton (A⁰X) peak accompanied by two strong and broad emission of donor acceptor pair (DAP) from low temperature PL, this confirms the use of Sb as an acceptor for ZnO.

Keywords: ZnO; Sb; Nanowires; Optical properties; Raman spectroscopy

Adsorption of ammonia on vanadium–antimony mixed oxides by Hernan Seitz; Estefanía Germán; Alfredo Juan; Beatriz Irigoyen (pp. 3617-3623).

► The N atom is oriented toward surface, while interacts using its N(2p_z) orbital. ► The main orbital interaction occurs between N and V (for the Lewis acid site), and between N and H4 (for the Brønsted acid site). ► On Lewis acid sites, the surface V atom interacts with the N(2p_z) orbital, using its V(3dz2) orbital. ► There is no other N-surface interactions both on Lewis or Brønsted sites and from the point of view of bonding, the NH₃ adsorption is weak.We analyzed the adsorption of ammonia (NH₃) on the VSbO₄(110) catalyst surface using density functional theory (DFT) calculations. We followed the evolution of the chemical bonds between different atoms of the resulting NH₃/VSbO₄ system and the changes in the electronic structure of the catalyst. NH₃ preferential adsorption geometries were analyzed through the crystal orbital overlap population (COOP) concept and the density of states (DOS) curves. The VSbO₄(110) surface exhibits Lewis and Brønsted acid sites on which the ammonia molecule can interact. On the Lewis acid site, NH₃ adsorption resulted in the interaction between the N and a surface V-isolated cation. On Brønsted acid site, N interacted with a surface H coming from the chemical dissociation of water. The COOP analysis indicate that NH₃ interaction on the VSbO₄(110) surface is weak. In addition, the DOS curves show more developed electronic interactions for NH₃ adsorption on Lewis acid site than over Brønsted acid site.

Keywords: VSbO4; Sb; V; NH; ₃; DFT

Adsorption of 2,4,6-trinitrotoluene on carboxylated porous polystyrene microspheres by Zhengfang Ye; Qingqiang Meng; Shengtao Lu (pp. 3624-3628).

► Fast adsorption of TNT using PA–PSt. ► High adsorption capacity of PA–PSt for TNT. ► Completely remove TNT using PA–PSt column. ► Fast regeneration of PA–PSt with acetone.Large-pore-size (150nm) polystyrene (PSt) microspheres were carboxylated with phthalic anhydride (PA) through Friedel–Crafts acetylation to study the adsorption of 2,4,6-trinitrotoluene (TNT) on this material from aqueous solution. The scanning electron microscope (SEM) images and mercury porosimetry measurements (MPM) of the microspheres showed that the pore structure was unchanged during the reaction. High adsorption capacity (11.2mgg⁻¹ of suction-dried adsorbent) and adsorption rate (33.9mgg⁻¹h⁻¹) for TNT were observed during the study. As shown by the adsorption isotherm, the adsorption of TNT on PA–PSt can be described by the Freundlich adsorption equation, indicating heterogeneous adsorption process. On-column adsorption of TNT on PA–PSt and elution indicated that TNT can be completely removed from aqueous solution and condensed into acetone.

Keywords: 2,4,6-Trinitrotoluene (TNT); Carboxylation; Porous polystyrene microspheres; Adsorption

Influence of deposition parameters on hard Cr–Al–N coatings deposited by multi-arc ion plating by Lei Wang; Shihong Zhang; Zhong Chen; Jinlong Li; Mingxi Li (pp. 3629-3636).

► We prepared Cr–Al–N films at various deposition parameters by multi-arc ion plating. ► We examined the phase structures of Cr–Al–N films by XRD and XPS. ► We systematically evaluated macroparticles, hardness and adhesion strength of Cr–Al–N films.The Cr–Al–N coatings were synthesized at various substrate bias voltages and nitrogen partial pressures by multi-arc ion plating (M-AIP). The relationships between deposition parameters and coating properties were investigated. Morphologies, phase structures, hardness and adhesion strength of the coatings were analyzed by SEM, XRD, XPS, nano-indenter and scratch tester. The results indicated that with the increase of substrate bias voltages, the surface macroparticles and deposition rate reduced mainly for the resputtering phenomenon. The (Cr, Al)N solid-solution phase kept unchanged, but the Cr₂N and AlN phases disappeared gradually. Due to the change of phase structures and residual compressive stress, the hardness values decreased and the adhesion strength decreased initially and then increased. Similarly, with the increase of nitrogen partial pressures, the phase structures of CrAlN coatings varied from Cr+Cr₂N+(Cr,Al)N to Cr₂N+(Cr,Al)N. The surface macroparticles increased due to the decreasing resputtering efficiency, and the deposition rate increased initially and then decreased due to the resputtering phenomenon. With increasing nitrogen partial pressures, adhesion strength decreased initially and then increased. The microhardness increased mainly due to the increase of Cr₂N contents and decrease of metal macroparticles.

Keywords: Bias voltage; Nitrogen partial pressure; Cr–Al–N films; Multi-arc ion plating

Evolution of self-assembled Ge/Si island grown by ion beam sputtering deposition by Jie Yang; Yingxia Jin; Chong Wang; Liang Li; Dongping Tao; Yu Yang (pp. 3637-3642).

► The Ge/Si islands were prepared by ion beam sputtering deposition. ► The intermixing led to the reappearance of low aspect ratio islands. ► Short islands did not grow along the constant ratio of 11:1 (diameter:height). ► The islands always grew faster in the vertical direction. ► The inter-diffusion, surface diffusion and amount of Ge determined the evolution.The effect of temperature and Ge coverage on the evolution of self-assembled Ge/Si islands grown by ion beam sputtering deposition is studied. Atomic force microscopy and Raman spectroscopy are used to analyze the island morphology and the intermixing between Si and Ge. The experiments are presented in two aspects. First, when the temperature is increased, intermixing is promoted, resulting in the reappearance of low aspect ratio islands. Second, a different evolution pathway is observed, in which short islands initially don’t grow along the constant ratio of 11:1 (diameter:height) and the islands always grow faster in vertical direction. In summary, the interdiffusion, surface diffusion, and amount of Ge determines the evolution of Ge/Si islands.

Keywords: Nanostructures; Ion beam sputtering deposition; Self-assembly; Atomic force microscopy; Raman

Superhydrophobic nickel films fabricated by electro and electroless deposition by Feifei Tian; Anmin Hu; Ming Li; Dali Mao (pp. 3643-3646).

► Nickel nanocone arrays are fabricated on Cu substrate by electrodeposition. ► Hemispherically topped nickel nanocones are obtained by coupling electroless deposition. ► A water contact angle of 153.6° is finally achieved after firstly electrodeposition and secondly electroless deposition at optimized conditions.In this work, a superhydrophobic nickel surface is fabricated by coupling electro and electroless deposition without chemical modification. SEM study reveals that electrodeposited nickel surface is characterized by nanocone arrays and has a contact angle of about 135°. After adding electroless deposition, as the second step, hemispherically topped nickel nanocone arrays are formed which leads to a high contact angle of 153.6°. That is, nickel surface has successfully transformed from hydrophobic to superhydrophobic. This transition is investigated both from the aspects of chemical composition and surface structure and proves the latter is the dominant factor. The present study inspires us to do more research about the creation of rough surfaces and enriches our comprehension about superhydrophobicity.

Keywords: Nickel; Electroless deposition; Electrodeposition; Superhydrophobicity; Microstructure; Surfaces

Highly ordered anodic TiO₂ nanotube arrays and their stabilities as photo(electro)catalysts by Lingjie Li; Zhuqing Zhou; Jinglei Lei; Jianxin He; Shengtao Zhang; Fusheng Pan (pp. 3647-3651).

► Highly ordered TiO₂ nanotube arrays are anodically fabricated within a large domain. ► The arrays photoelectrocatalytically degrade MO pollutants with a high efficiency. ► The arrays have highly stabilities on morphology and structure. ► The arrays can be reused many time as good photo(electro)catalysts.Highly ordered TiO₂ nanotube arrays with an average diameter of 230nm, a wall thickness of 30nm and a length of 1.8μm were fabricated within a large domain by electrochemically anodizing of a titanium foil in a mixed solution of glycerol and NH₄F aqueous electrolyte. The TiO₂ nanotubes exhibit an anatase structure after annealing at 450°C in air for 3h. The direct photolysis (DP), photocatalytic (PC), electrocatalytic (EC) and photoelectrocatalytic (PEC) activities of the TiO₂ nanotube arrays were investigated using methyl orange (MO) as the model pollutant. The degradation of MO in PC process is faster than that in DP process, which confirms the photocatalysis of TiO₂ nanotube arrays. The degradation rate in PEC process is much higher than those in EC and PC processes, which demonstrates the synergetic effect between PC and EC processes. The synergetic factor is 4.1, which suggests that the synergetic effect is strong. Moreover, the stabilities of morphology, structure and photo(electro)catalytic degradation performance of the TiO₂ nanotube arrays were studied in order to evaluate their applicability as photo(electro)catalysts. The photo(electro)catalytic experiments bring neither morphological nor structural modifications to the nanotube arrays. The photo(electro)catalytic degradation rates of the TiO₂ nanotube arrays maintain stable in 10 cycles, which indicates that the TiO₂ nanotube arrays are appropriate to be applied as photo(electro)catalysts.

Keywords: TiO; ₂; nanotube; Anodization; Photo(electro)catalytic activity; Pollutant degradation; Stability

A novel methodology based on contact angle hysteresis approach for surface changes monitoring in model PMMA-Corega Tabs system by Stanisław J. Pogorzelski; Zdzisław Berezowski; Paweł Rochowski; Janusz Szurkowski (pp. 3652-3658).

Display Omitted► Contact angle hysteresis (CAH) with inclined plate on Corega/PMMA were measured. ► CAH Chibowski's approach was used to determine wettability parameters. ► Wettability variation was attributed to exposure time and polarity of liquids. ► It stands a tool for tracing surface erosion of dentures cleanser-treated.The aim of the paper is to propose a quantitative description of dental surface modifications, resulting from application of Corega and oral cavity liquids, with several surface parameters derived from liquid/solid contact angle measurements. In particular, to predict the long-term effectiveness of denture cleansers in prosthetics, it is necessary to determine surface wettability variations for model dental materials/probe liquid systems related to the contamination effect caused by substances found in the oral cavity. A novel simple low-cost methodology, based on liquid drop contact angle hysteresis CAH approach developed by Chibowski, was adopted to trace solid surface free energy changes in the model PMMA-Corega Tabs interfacial layer. Contact angle and its hysteresis were studied with a sessile drop-inclined plate method in contact with a cleanser (Corega Tabs) and model liquids found in the oral cavity. The apparent solid surface free energy, adsorptive film pressure, work of adhesion and spreading were derived from contact angle hysteresis data for both model solid surfaces (reference) and samples affected by different reactive liquids for a certain time. A time-dependent surface wettability changes of dentures were expressed quantitatively in terms of the corresponding variations of the surface energy parameters which turned out to be unequivocally related to the cleanser exposure time and polarity of the liquids applied to the dental material.The novel methodology appeared to be a useful tool for long term surface characterization of dental materials treated with surfactants-containing liquids capable of forming adhesive layers. The time of optimal use and effectiveness of cleansers are also reflected dynamically in the corresponding variations of the surface wettability parameters. Further studies on a large group of dental surface-probe liquid systems are required to specify the role played by other important factors (liquid polarity, pH and temperature).

Keywords: Dental materials; Oral cavity contaminants; Contact angle hysteresis; Surface free energy; Surface modification; Cleanser effectiveness

Preparation, magnetic and electromagnetic properties of polyaniline/strontium ferrite/multiwalled carbon nanotubes composite by Yuqing Li; Ying Huang; Shuhua Qi; Lei Niu; Yinling Zhang; Yanfei Wu (pp. 3659-3666).

► Synthesizing polyaniline/strontium ferrite/MWCNT composites by in situ polymerization. ► With excellent magnetic and electromagnetic properties. ► The particular coating structure of PANI and Sr-ferrite. ► Great interest for magnetic material and microwave absorbers.Strontium ferrite particles were firstly prepared by sol–gel method and self-propagating synthesis, and then the polyaniline/strontium ferrite/multiwalled carbon nanotubes composites were synthesized through in situ polymerization approach. Structure, morphology and properties of the composite were characterized by various instruments. XRD analysis shows that the output of PANI increases with the increase of the content of MWCNTs, due to the large surface area of MWCNTs. Because of the coating of PANI, the outer diameter of MWCNTs increases from 10nm to 20–40nm. The electrical conductivity of the composites increases with the amount increase of MWCNTs and reaches 7.2196S/cm in the presence of 2g MWCNTs. The coercive force of the composites prepared with 2g MWCNTs is 7457.17Oe, which is much bigger than that of SrFe₁₂O₁₉ particles 6145.6Oe, however, both the saturation magnetization and the remanent magnetization of the composite become much smaller than those of SrFe₁₂O₁₉ particles. The electromagnetic properties of the composite are excellent in the frequency range of 2–18GHz, which mainly depend on the dielectric loss in the range of 2–9GHz, and mainly on the magnetic loss in the range of 9–18GHz.

Keywords: Strontium ferrite; Polyaniline; Carbon nanotubes; Magnetic properties; Electromagnetic properties; In situ polymerization

Removal of lead from aqueous solutions by using the natural and Fe(III)-modified zeolite by Milan Kragović; Aleksandra Daković; Živko Sekulić; Marina Trgo; Marin Ugrina; Jelena Perić; G. Diego Gatta (pp. 3667-3673).

► In this paper sorption of lead by the natural and Fe(III)-modified zeolite was investigated. ► Fe(III)-modified zeolite was synthesized under strongly basic conditions. ► The effects of sorbents dose and the initial lead concentrations on its sorption by two sorbents were studied. ► Much higher sorption of lead was achieved with Fe(III)-modified zeolite (natural zeolite – 66mg/g; Fe(III)-modified zeolite – 133mg/g). ► The best fit of experimental data was obtained with Freudlich sorption model.In the present study, the sorption of lead by the natural and Fe(III)-modified zeolite (clinoptilolite) is described. The characterization of the natural zeolite-rich rock and the Fe(III)-modified form was performed by chemical analysis, point of the zero charge (pH_pzc), X-ray powder diffraction, applying the Rietveld/RIR method for the quantitative phase analysis, and scanning electron microscopy. The effects of sorbents dose and the initial lead concentrations on its sorption by two sorbents were investigated. For both sorbents, it was determined that at lower initial concentrations of lead, ion exchange of inorganic cations in zeolites with lead, together with uptake of hydrogen dominated, while at higher initial lead concentrations beside these processes, chemisorption of lead occurred. Significantly higher sorption of lead was achieved with Fe(III)-modified zeolite. From sorption isotherms, maximum sorbed amounts of lead, under the applied experimental conditions, were 66mg/g for the natural and 133mg/g for Fe(III)-modified zeolite. The best fit of experimental data was achieved with the Freundlich model ( R²≥0.94).

Keywords: Natural zeolite; Fe(III)-modified zeolite; Heavy metals; Lead; Sorption

Characterization of Zr–Si–N films deposited by cathodic vacuum arc with different N₂/SiH4 flow rates by G.P. Zhang; E.W. Niu; X.Q. Wang; G.H. Lv; L. Zhou; H. Pang; J. Huang; W. Chen; S.Z. Yang (pp. 3674-3678).

► In this paper, we investigate the microstructure and mechanical properties of Zr–Si–N films deposited with different N₂/SiH₄ flow rates while keeping other parameter constant during the deposition process. ► The phase structure, surface and cross-section morphologies. ► The mechanical properties are systematically studied.Zr–Si–N films were deposited on silicon and steel substrates by cathodic vacuum arc with different N₂/SiH₄ flow rates. The N₂/SiH₄ flow rates were adjusted at the range from 0 to 12sccm. The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), hardness and wear tests. The structure and the mechanical properties of Zr–Si–N films were compared to those of ZrN films. The results of XRD and XPS showed that Zr–Si–N films consisted of ZrN crystallites and SiN_x amorphous phase. With increasing N₂/SiH₄ flow rates, the orientation of Zr–Si–N films became to a mixture of (111) and (200). The column width became smaller, and then appeared to vanish with the increase in N₂/SiH₄ flow rates. The hardness and Young's modulus of Zr–Si–N films increased with the N₂/SiH₄ flow rates, reached a maximum value of 36GPa and 320GPa at 9sccm, and then decreased 32GPa and 305GPa at 12sccm, respectively. A low and stable of friction coefficient was obtained for the Zr–Si–N films. Friction coefficient was about 0.1.

Keywords: Zr–Si–N films; Cathodic vacuum arc; N; ₂; /SiH; ₄; flow rates

Single step thermal decomposition approach to prepare supported γ-Fe₂O₃ nanoparticles by Geetu Sharma; P. Jeevanandam (pp. 3679-3688).

► A simple low temperature thermal decomposition approach for the synthesis of MgO supported γ-Fe₂O₃ nanoparticles. ► Effect of nanocrystalline versus macro-crystalline MgO as the support has been investigated for the first time. ► Stabilization of γ-Fe₂O₃ phase on the supports up to temperature as high as 1150°C is observed.γ-Fe₂O₃ nanoparticles supported on MgO (macro-crystalline and nanocrystalline) were prepared by an easy single step thermal decomposition method. Thermal decomposition of iron acetylacetonate in diphenyl ether, in the presence of the supports followed by calcination, leads to iron oxide nanoparticles supported on MgO. The X-ray diffraction results indicate the stability of γ-Fe₂O₃ phase on MgO (macro-crystalline and nanocrystalline) up to 1150°C. The scanning electron microscopy images show that the supported iron oxide nanoparticles are agglomerated while the energy dispersive X-ray analysis indicates the presence of iron, magnesium and oxygen in the samples. Transmission electron microscopy images indicate the presence of smaller γ-Fe₂O₃ nanoparticles on nanocrystalline MgO. The magnetic properties of the supported magnetic nanoparticles at various calcination temperatures (350–1150°C) were studied using a superconducting quantum interference device which indicates superparamagnetic behavior.

Keywords: Supported magnetic nanoparticles; Thermal decomposition method; Superparamagnetism

Synthesis and characterization of core–shell structured SiO₂@YVO₄:Yb³⁺,Er³⁺ microspheres by Yanjie Liang; Jun Ouyang; Hongyou Wang; Weili Wang; Pengfei Chui; Kangning Sun (pp. 3689-3694).

► SiO₂ spheres were coated by up-conversion phosphors via a sol–gel technique. ► Bright green luminescence is observed under the excitation of a 980nm laser diode. ► The photoluminescence intensity increases with the number of coatings.In this paper, the core–shell structured SiO₂@YVO₄:Yb³⁺,Er³⁺ microspheres have been successfully prepared via a facile sol–gel process followed by a heat treatment. X-ray diffraction, field emission scanning electron microscopy, energy disperse X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence spectra were used to characterize the samples. The results reveal that the SiO₂ spheres have been successfully coated by YVO₄:Yb³⁺,Er³⁺ phosphors to form core–shell structures and the size of obtained microspheres has a uniform distribution. Additionally, the samples exhibit bright green luminescence under the excitation of a 980nm laser diode. The photoluminescence intensity increases with the number of coatings. These core–shell structured SiO₂@YVO₄:Yb³⁺,Er³⁺ microspheres may have great potential in the fields of infrared detection and display devices.

Keywords: YVO; ₄; :Yb; ³⁺; ,Er; ³⁺; Up-conversion; Sol–gel; Luminescence

Zinc oxide's hierarchical nanostructure and its photocatalytic properties by Muzafar A. Kanjwal; Faheem A. Sheikh; Nasser A.M. Barakat; Xiaoqiang Li; Hak Yong Kim; Ioannis S. Chronakis (pp. 3695-3702).

► The nanofibers from colloidal solution of mixture containing Zinc acetate, poly vinyl alcohol, and zinc powder, were successfully achieved by electrospinning. ► These nanofibers after calcinations at 500°C for 90min, containing the zinc nanoparticles has been exploited as the seeds to grow nanobranches followed by hydrothermal technique. ► The produced hierarchical structure could be utilized in many exciting fields such as dye degradation, photoluminescence, etc.In this study, a new hierarchical nanostructure that consists of zinc oxide (ZnO) was produced by the electrospinning process followed by a hydrothermal technique. First, electrospinning of a colloidal solution that consisted of zinc nanoparticles, zinc acetate dihydrate and poly(vinyl alcohol) was performed to produce polymeric nanofibers embedding solid nanoparticles. Calcination of the obtained electrospun nanofiber mats in air at 500°C for 90min produced pure ZnO nanofibers with rough surfaces. The rough surface strongly enhanced outgrowing of ZnO nanobranches when a specific hydrothermal technique was used. Methylene blue dihydrate was used to check the photocatalytic ability of the produced nanostructures. The results indicated that the hierarchical nanostructure had a better performance than the other form.

Keywords: Zinc oxide; Zinc nanoparticles; Electrospinning; Hydrothermal; Methylene blue

Surface decoration of carbon nanosheets with amino-functionalized organosilica nanoparticles by M. Baikousi; K. Dimos; A.B. Bourlinos; R. Zbořil; I. Papadas; Y. Deligiannakis; M.A. Karakassides (pp. 3703-3709).

► Development of new hybrid carbonaceous nanosheets decorated with amino-functionalized organosilica nanoparticles. ► The organosilica modified carbon nanosheets remain the unique nearly 2D morphology of the pristine carbonaceous material. ► The materials were characterized by means a variety of spectroscopic and microscopy methods to study their structure, properties and morphology. ► The developed functionalization procedure of the betaine-derived carbon nanosheets would be applicable for the surface modification of other carbon nanostructures.Carbonaceous nanosheets decorated with amino-functionalized organosilica nanoparticles have been synthesized by a direct pyrolysis of betaine at 400°C in air, followed by a simple surface treatment with ([3-(2-aminoethylamino) propyl]trimethoxysilane under reflux conditions. Both pristine and organosilica modified carbon nanosheets (OMCNs), were characterized by Fourier-transform infrared (FTIR), Raman, and electron paramagnetic resonance (EPR) spectroscopies, transmission electron microscopy and thermal analysis methods. The experimental data reveal a dramatic increase in the number of radical centers on the surface of the developed OMCN hybrid. The organosilica nanoparticles, ranging in size between 3 and 15nm, are spherical and homogenously anchored on the surface of carbon nanosheets. The formation of COSi bridges between carbon sheets and the organosilica nanoparticles has been supported by FTIR and EPR. These nanoparticles are bound to the nanosheet surface together with individual functional organosilane groups at a spacing of about 4Å distance. The final hybrid is the complex nanosystem composed of 2D carbon nanosheets, spherical organosilica nanoparticles and immobilized amino organosilane molecules.

Keywords: Carbon; Nanosheets; Nanoparticles; Organosilica; Modification; ESR; Properties

Preparation and characterization of Mg-doped ZnO thin films by sol–gel method by Kai Huang; Zhen Tang; Li Zhang; Jiangyin Yu; Jianguo Lv; Xiansong Liu; Feng Liu (pp. 3710-3713).

► Mg segregates in the form of MgO in the ZnO thin film with Mg:Zn=0.08. ► The band gap increases from 3.26 to 3.34eV with increasing Mg concentration. ► A strong ultraviolet emission and a weak blue emission are observed.Undoped and Mg-doped ZnO thin films were deposited on Si(100) and quartz substrates by the sol–gel method. The thin films were annealed at 873K for 60min. Microstructure, surface topography and optical properties of the thin films have been measured by X-ray diffraction (XRD), atomic force microscope (AFM), UV–vis spectrophotometer, and fluorophotometer (FL), respectively. The XRD results show that the polycrystalline with hexagonal wurtzite structure are observed for the ZnO thin film with Mg:Zn=0.0, 0.02, and 0.04, while a secondary phase of MgO is evolved for the thin film with Mg:Zn=0.08. The ZnO:Mg-2% thin film exhibits high c-axis preferred orientation. AFM studies reveal that rms roughness of the thin films changes from 7.89nm to 16.9nm with increasing Mg concentrations. PL spectra show that the UV–violet emission band around 386–402nm and the blue emission peak about 460nm are observed. The optical band gap calculated from absorption spectra and the resistivity of the ZnO thin films increase with increasing Mg concentration. In addition, the effects of Mg concentrations on microstructure, surface topography, PL spectra and electrical properties are discussed.

Keywords: Mg-doped ZnO; Sol–gel method; Surface topography; Optical properties

The dehydrogenation of CH₄ on Rh(111), Rh(110) and Rh(100) surfaces: A density functional theory study by Baojun Wang; Luzhi Song; Riguang Zhang (pp. 3714-3722).

Display Omitted► CH and CH₂ is the most abundant species for CH₄ dissociation on Rh catalyst. ► Rh catalyst can resist the carbon deposition in the CH₄ dehydrogenation. ► CH₄ dehydrogenation on Rh(100) surface is the most preferable pathway.CH₄ dehydrogenation on Rh(111), Rh(110) and Rh(100) surfaces has been investigated by using density functional theory (DFT) slab calculations. On the basis of energy analysis, the preferred adsorption sites of CH_x ( x=0–4) and H species on Rh(111), Rh(110) and Rh(100) surfaces are located, respectively. Then, the stable co-adsorption configurations of CH_x ( x=0–3) and H are obtained. Further, the kinetic results of CH₄ dehydrogenation show that on Rh(111) and Rh(100) surfaces, CH is the most abundant species for CH₄ dissociation; on Rh(110) surface, CH₂ is the most abundant species, our results suggest that Rh catalyst can resist the carbon deposition in the CH₄ dehydrogenation. Finally, results of thermodynamic and kinetic show that CH₄ dehydrogenation on Rh(100) surface is the most preferable reaction pathway in comparison with that on Rh(111) and Rh(110) surfaces.

Keywords: CH; ₄; Dehydrogenation; Rh surface; Density functional theory

Magnetic irreversibility of the Fe antidot arrays film by depositing on the porous alumina templates by Changjun Jiang; Wenwen Wei; Qingfang Liu; Dangwei Guo; Desheng Xue (pp. 3723-3725).

► Fe antidot arrays were fabricated by sputtering onto porous alumina templates, which was cheap and manipulated easily comparing with those of electron-beam lithography or focused ion beam milling. ► Investigation of magnetic properties dependence of the temperature in antidot arrays due to the existence of the holes, especially those in low temperature with characterized size near several hundreds of nanometers. ► The magnetic irreversibility of antidot arrays and continuous film were investigated by the ZFC and FC magnetization curves.An Fe layer was sputter-deposited onto porous alumina templates and Kapton respectively. Fe layer on the porous alumina templates formed an antidot arrays nanostructure, while Fe layer on the Kapton substrate formed a continuous film. Scanning electron microscopy and grazing incidence X-ray diffraction were employed to characterize the morphology and crystal structure of the Fe antidot arrays and continuous film, respectively. The temperature dependence of magnetic properties was shown in the temperature range 2–300K. The irreversibility of the magnetization of Fe antidot arrays film, as measured in zero-field cooling (ZFC) and field cooling (FC) states, was attributed to the pinning effect of the holes.

Keywords: Magnetic irreversibility; Low-temperature; Antidot arrays; Fe

Graphene oxide with improved electrical conductivity for supercapacitor electrodes by Z.J. Li; B.C. Yang; S.R. Zhang; C.M. Zhao (pp. 3726-3731).

► Few-layer graphene oxide (FLG) has been synthesized with a high electrical conductivity. ► The specific capacitance of 180Fg⁻¹ is obtained for the FLG in a 1M Na₂SO₄ aqueous. ► The FLG sheets have a great potential as high-performance electrochemical supercapacitors.Predominant few-layer graphene (FLG) sheets of high electrical conductivity have been synthesized by a multi-step intercalation and reduction method. The electrical conductivity of the as-synthesized FLG is measured to be ∼3.2×10⁴Sm⁻¹, comparable to that of pristine graphite. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman analysis reveal that the as-synthesized FLG sheets have large areas with single and double layers. The specific capacitance of 180Fg⁻¹ is obtained for the FLG in a 1M Na₂SO₄ aqueous electrolyte by integrating the cyclic voltammogram. The good capacitive behavior of the FLG is very promising for the application for next-generation high-performance electrochemical supercapacitors.

Keywords: Graphene oxide; Supercapacitor; Electrical conductivity

Influence of various thickness metallic interlayers on opto-electric and mechanical properties of AZO thin films on PET substrates by R.C. Chang; T.C. Li; C.W. Lin (pp. 3732-3737).

Various thickness metallic interlayers to improve the opto-electric and mechanical properties of aluminum-doped zinc oxide (AZO) thin films deposited on flexible polyethylene terephtalate (PET) substrates are studied. The effects of the interlayers on the resistance and transmittance of the AZO thin films are discussed. The result shows that the metallic interlayers effectively improve the electric resistance but reduce the optical transmittance of the AZO thin films. These phenomena become more obvious as the interlayer thickness increases. However, the AZO with an aluminum interlayer still behaves an acceptable transmittance. Moreover, mechanical tests indicate that the aluminum interlayer increases the hardness and modulus, and reduce the residual stress of the AZO thin films. In contrast, the silver and copper interlayers decrease the AZO's mechanical properties. Comparing to those without any interlayer, the results show that the best interlayer is the 6nm thick aluminum film.

Keywords: AZO thin film; PET substrate; Interlayer; Mechanical property; Opto-electric property

The role of copper species on Cu/γ-Al₂O₃ catalysts for NH₃–SCO reaction by Chunxia Liang; Xinyong Li; Zhenping Qu; Moses Tade; Shaomin Liu (pp. 3738-3743).

UV–vis spectra, XRD, H₂-TPR, TEM and ESR were used to characterize a series of Cu/γ-Al₂O₃ catalysts, which were prepared by incipient wetness impregnation using copper nitrate, copper acetate or copper sulfate as precursors, to study the role of Cu species on Cu/γ-Al₂O₃ catalysts for NH₃–SCO reaction. It was found that the mixture of CuO phase and CuAl₂O₄ phase formed on various Cu/γ-Al₂O₃ catalysts, and the Cu species and dispersion had significant influence on the Cu/γ-Al₂O₃ activity. Highly dispersed CuO phase on the support would be related with its high activity for the NH₃–SCO reaction.

Keywords: NH; ₃; –SCO; Cu/γ-Al; ₂; O; ₃; Dispersion; Copper species

Color-tunable magnetic and luminescent hybrid nanoparticles: Synthesis, optical and magnetic properties by Lei Lou; Ke Yu; Yiting Wang; Ziqiang Zhu (pp. 3744-3749).

► Color-tunable magnetic and luminescent hybrid nanoparticles are synthesized in a simple and effective method. ► Hybrid nanoparticles remain the optical properties from QDs, displaying multicolor under UV excitation. ► Hybrid nanoparticles inherit the superparamagnetic properties originated from Fe₃O₄. ► Polyethyleneimine is used to avoid aggregation, attach QDs and transfer the surface properties of QDs from hydrophobic to hydrophilic.A facile method for synthesizing color-tunable magnetic and luminescent hybrid bifunctional nanoparticles is presented. A series of CdSe/ZnS core–shell quantum dots (QDs) with different sizes were successfully fabricated and self-assembled to Fe₃O₄ magnetic nanoparticles (MNP), which were subsequently coated with a polyethyleneimine (PEI) layer to prevent large aggregates. The hydrophobic QDs capped with trioctylphosphine oxide (TOPO) formed a coating surrounding MNP, and were transferred into hydrophilic phase by PEI with high efficiency. The samples were characterized by TEM, FT-IR, XRD, EDS, UV–vis spectrophotometer, fluorescent spectrophotometer and PPMS. Results show that the original properties of the nanoparticles were well-preserved in the hybrid structure. All MNP-QDs hybrid nanoparticles showed paramagnetic behavior and the nanocomposites were still highly luminescent with no shift in the PL peak position.

Keywords: PACS; 75.50.Gg; 73.21.La; 61.41.+e; 74.25.Gz; 74.25.HaFe; ₃; O; ₄; Quantum dots; Polyethyleneimine; Luminescence; Magnetic

Synthesis and conformational characterization of functional di-block copolymer brushes for microarray technology by Gabriele Di Carlo; Francesco Damin; Lidia Armelao; Chiara Maccato; Selim Unlu; Philipp S. Spuhler; Marcella Chiari (pp. 3750-3756).

► Microarray glass slides were functionalized with block polymer brushes. ► The coating was characterized by Self Spectral Interference Fluorescence Microscopy. ► Coating composition and morphology were assessed by X-ray Photoelectron Spectroscopy.Surface initiated polymerization (SIP) coupled with reversible addition-fragmentation chain transfer polymerization (RAFT) was used to functionalize microarray glass slides with block polymer brushes. N,N-dimethylacrylamide (DMA) and N-acryloyloxysuccinimide (NAS) ( graft-poly[DMA- b-(DMA- co-NAS)]) brushes, with di-block architecture, were prepared from a novel RAFT chain transfer agent bearing a silanating moiety (RAFT silane) directly anchored onto the glass surfaces. Conformational characterization of the coatings was performed by Self Spectral Interference Fluorescence Microscopy (SSFM), an innovative technique that describes the location of a fluorescent DNA molecule relative to a surface with sub-nanometer accuracy. X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were used to characterize the coatings composition and morphology.

Keywords: Surface initiated polymerization; Reversible addition–fragmentation chain transfer polymerization (RAFT); Block copolymers; Polymer brushes; DNA microarray

Microstructure and wear behaviors of laser clad NiCr/Cr₃C₂–WS₂ high temperature self-lubricating wear-resistant composite coating by Mao-Sheng Yang; Xiu-Bo Liu; Ji-Wei Fan; Xiang-Ming He; Shi-Hong Shi; Ge-Yan Fu; Ming-Di Wang; Shu-Fa Chen (pp. 3757-3762).

► WS₂ is utilized to produce high temperature self-lubricant wear-resistant composite coating by laser cladding. ► Noticeably, the coating added withWS₂ has a higher microhardness because of the formation of the hard phase (Cr,W)C. ► The average friction coefficients both decrease with the rising of temperature, but the wear rates both increase. ► The coating added with WS₂ has a lower friction coefficient whatever at ambient, 300°C, 600°C, and a lower wear rate only at 300°C.The high temperature self-lubricating wear-resistant NiCr/Cr₃C₂–30%WS₂ coating and wear-resistant NiCr/Cr₃C₂ coating were fabricated on 0Cr18Ni9 austenitic stainless steel by laser cladding. Phase constitutions and microstructures were investigated, and the tribological properties were evaluated using a ball-on-disc wear tester under dry sliding condition at room-temperature (17°C), 300°C and 600°C, respectively. Results indicated that the laser clad NiCr/Cr₃C₂ coating consisted of Cr₇C₃ primary phase and γ-(Fe,Ni)/Cr₇C₃ eutectic colony, while the coating added with WS₂ was mainly composed of Cr₇C₃ and (Cr,W)C carbides, with the lubricating WS₂ and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of two coatings both decrease with the increasing temperature, while the both wear rates increase. The friction coefficient of laser clad NiCr/Cr₃C₂–30%WS₂ is lower than the coating without WS₂ whatever at room-temperature, 300°C, 600°C, but its wear rate is only lower at 300°C. It is considered that the laser clad NiCr/Cr₃C₂–30%WS₂ composite coating has good combination of anti-wear and friction-reducing capabilities at room-temperature up to 300°C.

Keywords: High temperature wear-resistant composite coating; Solid lubrication; Laser cladding; WS; ₂

Polymer-templated mesoporous carbons synthesized in the presence of nickel nanoparticles, nickel oxide nanoparticles, and nickel nitrate by Jerzy Choma; Katarzyna Jedynak; Michal Marszewski; Mietek Jaroniec (pp. 3763-3770).

.Display Omitted► Ni-containing carbons were obtained by soft-templating using various Ni precursors. ► Synthesis was performed in the presence of Ni and NiO nanoparticles and Ni(NO₃)₂. ► Additional advantage of incorporating Ni is partial graphitization of carbon. ► Post-synthesis impregnation with Ni(NO₃)₂ gave mesoporous carbons with NiO.Mesoporous carbon composites, containing nickel and nickel oxide nanoparticles, were obtained by soft-templating method. Samples were synthesized under acidic conditions using resorcinol and formaldehyde as carbon precursors, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock co-polymer Lutrol F127 as a soft template and nickel and nickel oxide nanoparticles, and nickel nitrate as metal precursors. In addition, a one set of samples was obtained by impregnation of mesoporous carbons with a nickel nitrate solution followed by further annealing at 400°C. Wide angle X-ray powder diffraction along with thermogravimetric analysis proved the presence of nickel nanoparticles in the final composites obtained using nickel and nickel oxide nanoparticles, and Ni(NO₃)₂ solution. Whereas, the impregnation of carbons with a nickel nitrate solution followed by annealing at 400°C resulted in needle-like nickel oxide nanoparticles present inside the composites’ pores. Low-temperature (−196°C) nitrogen physisorption, X-ray powder diffraction, and thermogravimetric analysis confirmed good adsorption and structural properties of the synthesized nickel–carbon composites, in particular, the samples possessed high surface areas (>600m²/g), large total pore volumes (>0.50cm³/g), and maxima of pore size distribution functions at circa 7nm. It was found that the composites were partially graphitized during carbonization process at 850°C. The samples are stable in an air environment below temperature of 500°C. All these features make the synthesized nickel–carbon composites attractive materials for adsorption, catalysis, energy storage, and environmental applications.

Keywords: Mesoporous carbons; Soft-templating synthesis; Block copolymer, Nickel and nickel oxide nanoparticles; Adsorption properties

Microemulsion synthesis, characterization of bismuth oxyiodine/titanium dioxide hybrid nanoparticles with outstanding photocatalytic performance under visible light irradiation by Zhang Liu; Xiaoxin Xu; Jianzhang Fang; Ximiao Zhu; Jinhui Chu; Baojian Li (pp. 3771-3778).

Display Omitted► BiOI/TiO₂ hybrid nanoparticles were synthesized by a reverse microemulsion method. ► BiOI/TiO₂ composites were characterized by various characterization technologies. ► BiOI/TiO₂ presented outstanding visible-light-induced photocatalytic performance. ► The photoactivity of BiOI/TiO₂ is highly affected by its mole ratios. ► Possible photocatalytic mechanism was proposed based on the experimental studies.Reverse microemulsions, consisting of n-hexanol, Triton X-100, Cyclohexane and aqueous salt solutions, were used to synthesize BiOI, TiO₂ and BiOI/TiO₂ hybrid nanoparticles at room temperature. The particles had been characterized by X-ray powder diffraction, FT-IR spectra, TG-DSC analysis, nitrogen sorption, electron microscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic properties of those particles were evaluated by degradation of methyl orange under visible light irradiation. The BiOI/TiO₂ composites showed about 5 times higher photocatalytic performances than BiOI when the mole ratio of BiOI to TiO₂ was 75%. The remarkable enhancement in the visible light photocatalytic activities of the BiOI/TiO₂ heterostructures could be first attributed to the effective electron–hole separations at the interfaces of the two semiconductors, which facilitated the transfer of the photoinduced carriers. Meanwhile, the heterojunction formed between BiOI and TiO₂ would further retard the recombination of photoinduced carriers. In addition, high degree of crystallization, bimodal porous structure, relative large specific surface area, and appropriate energy band gap have great contribution to the enhancement of photocatalytic performance.

Keywords: Microemulsion; BiOI/TiO; ₂; heterostructure; Visible light; Methyl orange; Degradation

Surface-initiated addition polymerization of norbornene by a Pd(II) catalyst bearing acetylacetone ligand on the glass slide by Xiaohui He; Kaiti Wang; Yiwang Chen; Bin Yuan (pp. 3779-3784).

► A Pd(II) acetylacetone based catalyst was used to surface-initiate the polymerization of norbornene onto the glass slide. ► Vinyl-type addition polynorbornene layer was obtained on the glass slide surface. ► The thickness of polynorbornene layers were increased with the increasing of polymerization time.A Pd catalyst bearing acetylacetone ligand [(CH₃CO)₂CHPdCl₂] was covalently attracted onto the surface of glass slides, and then these Pd-terminated glass slides were immersed into a toluene solution of norbornene (NB) to produce a vinyl-type addition polynorbornene (PNB) layer on the surface of glass slides. It was found that the contract angles of the PNB-terminated glass slides surface increased with the increasing of polymerization time, and the thickness of the PNB layers were approximately 0–44.0μm when the polymerization time was 0.5–24h. The researching on etching also has been operated.

Keywords: Surface modification; Polymer brush; Addition polymerization

Plasmon based antireflection coatings containing nanostructured Ag and silica medium by Xinxing Sun; Xiaohong Chen; Zhejuan Zhang; Zhuo Sun (pp. 3785-3788).

► The antireflection (AR) coatings of Ag nanowires and silica composite were enhanced. ► The optimal transmittance values of AR coatings with 0.10wt.% Ag is 95.7%. ► The enhanced transmittance of the AR coatings is ascribed to plasmon effect. ► Another enhanced transmittance factor is the lesser refractive indices of coatings. ►The transmittance and scattering of the antireflection (AR) coatings based on nanostructured Ag and silica medium were enhanced by the exploitation of the localized surface plasmon resonance (LSPR). The transmittance and scattering values of AR coatings are relative to the annealing temperature, Ag concentration and thickness of AR coatings. The transmittance values of 95.7% and 97.2% of AR coatings with 0.10wt.% Ag and annealed at 400°C were obtained in the visible wavelength for a single-side and double-side coated glass slides, respectively. The enhanced transmittance and scattering of the AR coatings are primarily attributable to the large forward scattering of nanostructured Ag and the lesser refractive indices of Ag/SiO₂ coatings.

Keywords: PACS; 73.20.Mf; 78.20.Ci; 78.67.−n; 81.07.−bAntireflection coating; Nanostructured Ag; SiO; ₂; Localized surface plasmon resonance

Fabrication and characterization of electrospun orthorhombic InVO₄ nanofibers by Lingjun Song; Suwen Liu; Qifang Lu; Gang Zhao (pp. 3789-3794).

In this paper, citric acid was used as a ligand for getting a transparent homogeneous precursor solution and further ensured homogeneous precursor sol for electrospining. Polyvinyl pyrrolidone (PVP, K-30) was used as a binder and a structure guide reagent because it could form one-dimensional structure in the electrospinning process if the viscosity of the sol was suitable. Finally, the novel orthorhombic InVO₄ nanofibers were prepared successfully by annealing electrospun precursor fibers at 700°C. Photocatalytic experiment on methyl orange solution under visible light showed that orthorhombic InVO₄ nanofibers had a potential application in wastewater-treatment.Display Omitted► In this paper, orthorhombic InVO₄ nanofibers were successfully prepared by annealing the electrospun precursor fibers. ► Citric acid was used as a ligand, it could react with metal salts to get a clear homogeneous precursor solution. ► PVP (K-30), one kind of water-soluble polymers, was used as a binder. Meanwhile, PVP was used as a structure guide reagent.The novel orthorhombic InVO₄ nanofibers have been successfully synthesized by annealing electrospun precursor fibers. Citric acid was used as a ligand for it could react with metal salts to get a transparent homogeneous precursor solution and homogeneous precursor sol for electrospining. Polyvinyl pyrrolidone (PVP, K-30) was used as a binder and a structure guide reagent because it was one kind of water-soluble polymers. It is easy to gain one-dimensional materials while the viscosity of the citrate/PVP sol was suitable. The structure, morphology and photocatalytic properties of the nanofibers were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electron microscopy (SEM) analysis, UV–vis spectrophotometer and fluorescence spectrophotometer. The nanofibers calcined at 700°C were orthorhombic InVO₄ with a width in the range of 30–100nm and length in micron-grade. This one-dimensional pure orthorhombic InVO₄ had the higher photocatalytic activity under visible light irradiation. The photo-degradation rate of nitrobenzene aqueous solution under visible light reached 69% after 6h. It is obvious that the orthorhombic InVO₄ nanofibers have a potential application in wastewater-treatment.

Keywords: Orthorhombic InVO; ₄; Electrospinning technique; Sintering; Nanofibers

The investigation of room temperature ferromagnetism in (100) oriented BaNb₂O₆ PLD films on LaAlO₃ (100) substrate by Ensi Cao; Yongjia Zhang; Lin Ju; Lihui Sun; Hongwei Qin; Jifan Hu (pp. 3795-3799).

► BaNb₂O₆ epitaxial films have been successfully grown on LaAlO₃ (100) substrate by PLD. ► Room temperature ferromagnetism (RTFM) has been observed in all the samples. ► The observed RTFM in BaNb₂O₆ films is predominantly induced by oxygen vacancies. ► Ab inito calculations are performed to verify our prediction.(100) oriented BaNb₂O₆ films have been successfully grown on LaAlO₃ (100) substrate at 750°C or 450°C in vacuum by pulsed laser deposition. The deposited BaNb₂O₆ PLD films exhibit room-temperature ferromagnetism. Ab initio calculations demonstrate that stoichiometric BaNb₂O₆ and that with barium vacancy are nonmagnetic, while oxygen and niobium vacancy can induce magnetism due to the spin-polarization of Nb s electrons and O p electrons respectively. Moreover, ferromagnetic coupling is energetically more favorable when two Nb/O vacancies are located third-nearest-neighbored. The observed room temperature ferromagnetism in BaNb₂O₆ films should be mainly induced by oxygen vacancies introduced during vacuum deposition, with certain contribution by Nb vacancies.

Keywords: PLD film; Room-temperature ferromagnetism; Oxygen vacancy; Ab initio

X-ray photoelectron spectroscopy study of cubic boron nitride single crystals grown under high pressure and high temperature by Lixin Hou; Zhanguo Chen; Xiuhuan Liu; Yanjun Gao; Gang Jia (pp. 3800-3804).

► Unintentionally doped cubic boron nitride single crystals are investigated by XPS. ► Nitrogen vacancy (V_N) is the main native defect. ► The chemical state of carbon as the main impurity in the cBN samples is analyzed.The defects, impurities and their bonding states of unintentionally doped cubic boron nitride (cBN) single crystals were investigated by X-ray photoelectron spectroscopy (XPS). The results indicate that nitrogen vacancy (V_N) is the main native defect of the cBN crystals since the atomic ratio of B:N is always larger than 1 before Ar ion sputtering. After sputter cleaning, around 6at% carbon, which probably comes from the growth chamber, remains in the samples as the main impurity. Carbon can substitute nitrogen lattice site and form the bonding states of CBN or CB, which can be verified by the XPS spectra of C1s, B1s and N1s. The C impurity (acceptor) and N vacancy (donor) can compose the donor–acceptor complex to affect the electrical and optical properties of cBN crystals.

Keywords: Cubic boron nitride; XPS; Single crystal; Impurities; Defects

Improvement of mechanical and tribological properties in steel surfaces by using titanium–aluminum/titanium–aluminum nitride multilayered system by L. Ipaz; J.C. Caicedo; J. Esteve; F.J. Espinoza-Beltran; G. Zambrano (pp. 3805-3814).

► The novel [Ti–Al/Ti–Al–N]_n nanometric multilayer was deposited by co-sputtering. ► The modulation period effect on mechanical and tribological properties was studied. ► The interfaces dissipate energy in plastic deformation process. ► Hardness and friction coefficient increase with the decrease of bilayer period ( Λ).Improvement of mechanical and tribological properties on AISI D3 steel surfaces coated with [Ti–Al/Ti–Al–N]_n multilayer systems deposited in various bilayer periods ( Λ) via magnetron co-sputtering pulsed d.c. method, from a metallic binary target; has been studied in this work exhaustively. The multilayer coatings were characterized in terms of structural, chemical, morphological, mechanical and tribological properties by X–ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy, nanoindentation, pin-on-disc and scratch tests, respectively. The failure mode mechanisms were studied by optical microscopy. Results from X-ray diffraction analysis revealed that the crystal structure of TiAl/TiAlN multilayer coatings has a tetragonal and FCC NaCl-type lattice structures for Ti–Al and Ti–Al–N, respectively, i.e., it was found to be non-isostructural multilayers. An enhancement of both hardness and elastic modulus up to 29GPa and 260GPa, respectively, was observed as the bilayer periods ( Λ) in the coatings were decreased. The sample with a bilayer period ( Λ) of 25nm and bilayer number n=100 showed the lowest friction coefficient (∼0.28) and the highest critical load (45N), corresponding to 2.7 and 1.5 times better than those values for the coating deposited with n=1, respectively. These results indicate an enhancement of mechanical, tribological and adhesion properties, comparing to the [Ti–Al/Ti–Al–N]_n multilayer systems with 1 bilayer at 26%, 63% and 33%, respectively. This enhancement in hardness and toughness for multilayer coatings could be attributed to the different mechanisms for layer formation with nanometric thickness such as the novel Ti–Al/Ti–Al–N effect and the number of interfaces that act as obstacles for the crack deflection and dissipation of crack energy.

Keywords: Multilayers; Coatings; Vacuum deposition; Crystal structure; Mechanical properties; Tribology; Wear

An ion-imprinted amino-functionalized silica gel sorbent prepared by hydrothermal assisted surface imprinting technique for selective removal of cadmium (II) from aqueous solution by Hong-Tao Fan; Jing Li; Zhan-Chao Li; Ting Sun (pp. 3815-3822).

► We develop a new Cd(II)-imprinted amino-functionalized silica gel sorbent. ► Hydrothermal-assisted heating enables increase of adsorption capacity. ► Langmuir adsorption model is more favorable than Freundlich adsorption model. ► Kinetic studies indicate that the adsorption follow a pseudo-second-order model. ► The adsorption process of Cd(II) is spontaneous and endothermic.A new ion-imprinted amino-functionalized silica gel sorbent was synthesized by the hydrothermal-assisted surface imprinting technique using Cd²⁺ as the template, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AAAPTS) as the functional monomer, and epichlorohydrin as the cross-linking agent (IIP-AAAPTS/SiO₂) for the selective removal of Cd²⁺ from aqueous solution, and was characterized by FTIR, SEM, nitrogen adsorption and the static adsorption–desorption experiment method. The specific surface area of the IIP-AAAPTS/SiO₂ sorbents was found to be 149m²g⁻¹. The results showed that the maximum static adsorption capacities of IIP-AAAPTS/SiO₂ sorbents by hydrothermal heating method and by the conventional heating method were 57.4 and 31.6mgg⁻¹, respectively. The IIP-AAAPTS/SiO₂ sorbents offered a fast kinetics for the adsorption and desorption of Cd(II). The relative selectivity coefficients of IIP-AAAPTS/SiO₂ sorbents for Cd²⁺/Co²⁺, Cd²⁺/Ni²⁺, Cd²⁺/Zn²⁺, Cd²⁺/Pb²⁺ and Cd²⁺/Cu²⁺ were 30.68, 14.02, 3.00, 3.12 and 6.17, respectively. IIP-AAAPTS/SiO₂ sorbents had a substantial binding capacity in the range of pH 4–8 and could be used repeatedly. Equilibrium data fitted perfectly with Langmuir isotherm model compared to Freundlich isotherm model. Kinetic studies indicated that adsorption followed a pseudo-second-order model. Negative values of Δ G° indicated spontaneous adsorption and the degree of spontaneity of the reaction increased with increasing temperature. Δ H° of 26.13kJmol⁻¹ due to the adsorption of Cd²⁺ on the IIP-AAAPTS/SiO₂ sorbents indicated that the adsorption was endothermic in the experimental temperature range.

Keywords: Cadmium; 3-[2-(2-Aminoethylamino)ethylamino]propyl-trimethoxysilane; Hydrothermal-assisted; Ion imprinted

Evaluation of copper ion of antibacterial effect on Pseudomonas aeruginosa, Salmonella typhimurium and Helicobacter pylori and optical, mechanical properties by Young-Hwan Kim; Yu-ri Choi; Kwang-Mahn Kim; Se-Young Choi (pp. 3823-3828).

► Copper sol was coated on glass substrate by spin coating method. ► Copper ion coated glass demonstrated 99.9% of antibacterial effect. ► Transmittance of silver ion coated glass was 90.02%. ► Mechanical property of glass substrate was enhanced by copper ion coating.Antibacterial effect on Pseudomonas aeruginosa, Salmonella typhimurium and Helicobacter pylori of copper ion was researched. Also, additional effects of copper ion coating on optical and mechanical properties were researched as well. Copper ion was coated on glass substrate as a thin film to prevent bacteria from growing. Cupric nitrate was used as precursors for copper ion. The copper ion contained sol was deposited by spin coating process on glass substrate. Then, the deposited substrates were heat treated at the temperature range between 200°C and 250°C. The thickness of deposited copper layer on the surface was 63nm. The antibacterial effect of copper ion coated glass on P. aeruginosa, S. typhimurium and H. pylori demonstrated excellent effect compared with parent glass. Copper ion contained layer on glass showed a similar value of transmittance compared with value of parent glass. The 3-point bending strength and Vickers hardness were 209.2MPa, 540.9kg/mm² which were about 1.5% and 1.3% higher than the value of parent glass. From these findings, it is clear that copper ion coating on glass substrate showed outstanding effect not only in antibacterial activity but also in optical and mechanical properties as well.

Keywords: Antibacterial activity; Copper ion; Spin coating; Optical property; Mechanical property

Optical properties and chemical structures of Kapton-H film after proton irradiation by immersion in a hydrogen plasma by Jingwei Shi; Chunzhi Gong; Xiubo Tian; Shiqin Yang; Paul K. Chu (pp. 3829-3834).

► Proton irradiation on polyimide films is conducted by immersing the samples in hydrogen plasma. ► The spectral transmittance decreases in the wavelength of 500–2000nm after proton irradiation. ► Surface etching and the polymer chains breakage make finger-like bulges emerge in the surface of the sample. ► The content of C element increases, while that of N and O elements decreased after proton irradiation.Proton irradiation of Kapton-H films was physically simulated in plasma immersion configuration with hydrogen plasmas. Hydrogen ion was implanted into the samples biased to a negative pulse of 20kV. Optical transmittance of the sample in the wavelength region of 200–2500nm was determined by a UV–vis–NIR scanning spectrophotometer, and the functional group evolution was examined by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was utilized to determine the roughness and morphology of the samples, and the bulk modification was analyzed by FTIR. The experimental results showed the optical transmittance of the treated sample in the wavelength of 500–2000nm weakened after proton irradiation, and decreased with the increase of irradiation time. Finger-like bulges emerged on the surface of the sample irradiated by ion irradiation for 30min, and became bigger and denser with the increase of the irradiation time. The content of C element of the sample increased after proton irradiation, while that of N and O elements decreased because of the bonds breakage of CO, COC and CN during irradiation process.

Keywords: Proton irradiation; Kapton-H; Hydrogen plasma immersion configuration; Optical transmittance; Bonds breakage

A superoleophobic textile repellent towards impacting drops of alkanes by Georg R.J. Artus; Jan Zimmermann; Felix A. Reifler; Stuart A. Brewer; Stefan Seeger (pp. 3835-3840).

► Coating with silicone nanofilaments and fluorination yields superoleophobicity. ► Superoleophobic fabric achieves highest possible oil-repellency grade of 8. ► Inclined fabric repels impacting drops of alkanes. ► Fabric displays a plastron when immersed in hexadecane.A commercially available polyester fabric has been rendered superoleophobic by coating with silicone nanofilaments and subsequent plasma fluorination. The treated samples show outstanding oil-repellency. They achieve the highest possible oil-repellency grade of 8, repel impacting drops of alkanes and show a plastron layer in hexadecane. The oil repellency is shown to depend on the topography of the silicone nanofilament coating.

Keywords: Superoleophobic; Textile; Coating; Silicone; Nanofilaments; Shedding angle

Nanoporous structures of polyimide induced by Ar ion beam irradiation by Sk. Faruque Ahmed; Kwang-Ryeol Lee; Ju-il Yoon; Myoung-Woon Moon (pp. 3841-3845).

The surface morphology evolution of polyimide (PI) that was treated with an Ar ion beam was explored using a hybrid ion beam system. A hole-like nanostructure formed on PI during the Ar ion beam treatment at a lower fluence, but PI formed 3D porous nanostructures with a mean diameter of ∼90nm at a higher fluence. The chemical binding energy and the composition of the Ar ion irradiated PI were analyzed using FT-IR and XPS spectra, which revealed that the polymer chain scissioning increased with increasing Ar ion treatment duration, i.e., fluence. The surface hardness and the elastic modulus of PI increased from 1.17 to 1.62GPa and 4.06 to 5.41GPa, respectively, with respect to the Ar ion beam treatment duration.

Keywords: Ar ion beam; Polyimide; 3D porous nanostructure; Hardness

Scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry study on the enhanced visible photocatalytic mechanism of carbon–TiO₂ nanohybrids by Hai Ming; Hengchao Zhang; Zheng Ma; Hui Huang; Suoyuan Lian; Ying Wei; Yang Liu; Zhenhui Kang (pp. 3846-3853).

Display Omitted► Carbon–TiO₂ nanohybrids (CTs) have been successfully prepared. ► CTs show excellent photocatalytic abilities in visible light. ► Scanning transmission X-ray microscopy was used to study CTs. ► The mechanism of enhanced visible photocatalytic ability of CTs was investigated.Carbon–TiO₂ nanohybrids (CTs, 5–10nm TiO₂ nanocrystals evenly dispersed on carbon film) have been successfully prepared via a mild, one-step hydrothermal approach. The interactions and electronic structures of carbon and TiO₂ nanoparticles and the enhanced visible photocatalytic mechanism were investigated by scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry in detail. Meanwhile, it was demonstrated that the as-obtained CTs had a large BET specific surface area of 304.6m²/g and showed excellent photocatalytic abilities towards organic (Rhodamine B, benzene) and inorganic pollutant (K₂Cr₂O₇) degradation in visible light. This work provided a new approach for the high performance catalyst design towards new energy sources and environmental issues.

Keywords: Titanium dioxide; Nanohybrids; Photocatalyst; Scanning transmission X-ray microscopy

Electrochemical performance of Sn–Sb–Cu film anodes prepared by layer-by-layer electrodeposition by Qianlei Jiang; Ruisheng Xue; Mengqiu Jia (pp. 3854-3858).

► The Sn–Sb–Cu film was prepared by layer-by-layer electrodeposition. ► Sn–Sb–Cu electrode was annealed to restrain the pulverization. ► The annealed Sn–Sb–Cu anode shows high reversible capacity and good capacity retention.A novel layer-by-layer electrodeposition and heat-treatment approach was attempted to obtain Sn–Sb–Cu film anode for lithium ion batteries. The preparation of Sn–Sb–Cu anodes started with galvanostatic electrochemically depositing antimony and tin sequentially on the substrate of copper foil collector. Sn–Sb and Cu–Sb alloys were formed when heated. The SEM analysis showed that the crystalline grains become bigger and the surface of the Sn–Sb–Cu anode becomes more denser after annealing. The energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis showed the antimony, tin and copper were alloyed to form SnSb and Cu₂Sb after heat treatment. The X-ray photoelectron spectroscopy (XPS) analysis showed the surface of the Sn–Sb–Cu electrode was covered by a thin oxide layer. Electrochemical measurements showed that the annealed Sn–Sb–Cu anode has high reversible capacity and good capacity retention. It exhibited a reversible capacity of about 962mAh/g in the initial cycle, which still remained 715mAh/g after 30 cycles.

Keywords: Sn–Sb–Cu film anode; Layer-by-layer electrodeposition; Heat-treatment; Lithium ion batteries

Improvement of amine-modification with piperazine for the adsorption of CO₂ by Xue Quanmin; Wu Di; Zhou Yaping; Zhou Li (pp. 3859-3863).

► Both selectivity and capacity of CO₂ adsorption were considerably increased when PZ (piperazine) was added in MDEA (methyldiethylamine) that used to modify adsorbent surface. ► The adsorbent saturated with CO₂ was regenerated at ambient temperature through nitrogen purge. ► PSA (pressure swing adsorption) experiments illustrated the potential application of the modified adsorbent.Both selectivity and capacity of CO₂ adsorption were considerably increased when PZ (piperazine) was added in MDEA (methyldiethylamine) that used to modify the surface of silica gels. The adsorbent saturated with CO₂ was regenerated at ambient temperature through nitrogen purge. A set of PSA (pressure swing adsorption) operation with 200 cycles was carried out and applicability of the modified adsorbent was thus illustrated. The CO₂ content in the column-top stream decreased from 13% to below 0.05% at steady state.

Keywords: Adsorption; CO; ₂; Amine-modification; Piperazine; Improvement

Influence of substrate bias voltage on structure and properties of the CrAlN films deposited by unbalanced magnetron sputtering by Yanhong Lv; Li Ji; Xiaohong Liu; Hongxuan Li; Huidi Zhou; Jianmin Chen (pp. 3864-3870).

► The relationship between structure and properties of CrAlN film is investigated. ► The microstructure of the CrAlN is analyzed in detail as a function of the bias voltage. ► The mechanism of the evolution of the mechanical properties is expounded. ► The CrAlN film shows excellent wear resistance and low friction coefficient at −100V. ► The corrosion resistance is influenced by Al content and structure of the film.The CrAlN films were deposited on silicon and stainless steel substrates by unbalanced magnetron sputtering system. The influence of substrate bias on deposition rate, composition, structure, morphology and properties of the CrAlN films was investigated. The results showed that, with the increase of the substrate bias voltage, the deposition rate decreased accompanied by a change of the preferred orientation of the CrAlN film from (220) to (200). The grain size and the average surface roughness of the CrAlN films declined as the bias voltage increases above −100V. The morphology of the films changed from obviously columnar to dense glass-like structure with the increase of the bias voltage from −50 to −250V. Meanwhile, the films deposited at moderate bias voltage had better mechanical and tribological properties, while the films deposited at higher bias voltage showed better corrosion resistance. It was found that the corrosion resistance improvement was not only attributed to the low pinhole density of the film, but also to chemical composition of films.

Keywords: CrAlN films; Microstructure; Mechanical properties; Corrosion resistance

Deposition of titanium nitride and hydroxyapatite-based biocompatible composite by reactive plasma spraying by Radu Alexandru Roşu; Viorel-Aurel Şerban; Alexandra Ioana Bucur; Uţu Dragoş (pp. 3871-3876).

► Titanium nitride and hydroxyapatite based composite layers obtained by reactive plasma spraying. ► Deposition of the composites onto a titanium substrate at different spraying distances. ► Characterization of the coatings roughness as function of the spraying distances.Titanium nitride is a bioceramic material successfully used for covering medical implants due to the high hardness meaning good wear resistance. Hydroxyapatite is a bioactive ceramic that contributes to the restoration of bone tissue, which together with titanium nitride may contribute to obtaining a superior composite in terms of mechanical and bone tissue interaction matters.The paper presents the experimental results in obtaining composite layers of titanium nitride and hydroxyapatite by reactive plasma spraying in ambient atmosphere. X-ray diffraction analysis shows that in both cases of powders mixtures used (10% HA+90% Ti; 25% HA+75% Ti), hydroxyapatite decomposition occurred; in variant 1 the decomposition is higher compared with the second variant. Microstructure of the deposited layers was investigated using scanning electron microscope, the surfaces presenting a lamellar morphology without defects such as cracks or microcracks. Surface roughness values obtained vary as function of the spraying distance, presenting higher values at lower thermal spraying distances.

Keywords: Reactive plasma spraying; Hydroxyapatite; Titanium nitride

Optical and electrical properties of nonstoichiometric a-Ge1−_xC_x films prepared by magnetron co-sputtering by J.Q. Zhu; C.Z. Jiang; J.C. Han; H.L. Yu; J.Z. Wang; Z.C. Jia; R.R. Chen (pp. 3877-3881).

► The effect of the Ge/C ratio on chemical bonding, optical and electrical properties of germanium carbide films that is rarely reported in literature is represented in this article. ► The chemical bonding and microstructure characterization are focused in detail. ► The relationship between chemical bonding and optoelectronic properties is discussed in detail.Amorphous non-hydrogenated germanium carbide (a-Ge1−_xC_x) films have been prepared by magnetron co-sputtering method in a discharge of Ar. The dependence of structural and chemical bonding properties on the Ge/C ratio ( R) has been investigated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The relationship between the chemical bonding and the optical and electrical properties of the a-Ge1−_xC_x films has also been explored. It has been shown that the refractive index of the films increases from 2.9 to 4.4 and the optical gap decreases from 1.55 to 1.05eV as R increases from 1.22 to 5.67. Moreover, the conductivity σ increases clearly and the activation energy E_a decreases with the increasing R owing to the reduction of sp³ CGe bonds. The a-Ge1−_xC_x films exhibit refractive index and optical gap values changing with x in a wide range, which may make a-Ge1−_xC_x films good candidates in the fields of protection coatings for IR windows and electronic devices.

Keywords: Magnetron co-sputtering; Germanium carbide; Chemical bonding; Optical properties; Electrical properties

Influence of [S₂O₃²⁻]/[Sm³⁺] on Sm₂S₃ thin films deposited by liquid phase deposition method on self-assembled monolayers by Hou Yan-chao; Huang Jian-feng; Zhou Xuan; Cao Li-yun; Wu Jian-peng (pp. 3882-3887).

► Denser and smoother Sm₂S₃ thin films. ► Sm₂S₃ thin films with orientation growth along (011) direction. ► The influence of the [S₂O₃²⁻]/[Sm³⁺]. ► Liquid phase deposition method on self-assembled monolayers. ► Red photoluminescence properties.Sm₂S₃ thin films were prepared on Si (100) substrates using SmCl₃ and Na₂S₂O₃ as precursors by liquid phase deposition method on self-assembled monolayers. The influence of the molar concentration ratio of [S₂O₃²⁻]/[Sm³⁺] on the phase compositions, surface morphologies and optical properties of the as-deposited films were investigated. The as-deposited Sm₂S₃ thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet–visible (UV–vis) and photoluminescence spectrum (PL). Results show that it is important to control the [S₂O₃²⁻]/[Sm³⁺] during the deposition process and monophase Sm₂S₃ thin films with orientation growth along (011) direction can be achieved when [S₂O₃²⁻]/[Sm³⁺]=2.0, pH 3.0, with citric acid as a template agent. The as-deposited thin films exhibit a dense and crystalline surface morphology. Good transmittance in the visible spectrum and excellent absorbency of ultraviolet light of the thin films are observed, and the band gap of the thin films first decrease and then increase with the increase of the [S₂O₃²⁻]/[Sm³⁺]. The as-deposited thin films also exhibit red photoluminescence properties under visible light excitation. With the increase of the [S₂O₃²⁻]/[Sm³⁺] in the deposition solution, the PL properties of Sm₂S₃ thin films are obviously improved.

Keywords: Sm; ₂; S; ₃; Self-assembled monolayers; Liquid phase deposition; Thin films

Contact ratio of rough surfaces with multiple asperities in mixed lubrication at high pressures by Huaping Xiao; Dan Guo; Shuhai Liu; Guoshun Pan; Xinchun Lu (pp. 3888-3896).

► We realize high experimental pressure up to 3GPa. ► We acquire the profile of contact region between two solid surfaces employing light interference method. ► We investigate the relationship between contact ratio and many impact factors. ► We summarize a formula to calculate contact ratio under different conditions.Relative optical intensity interference was used to measure the lubrication film thickness when four kinds of polyalphaolefin (PAO) were used as lubricants confined between a smooth sapphire disc surface and a rough steel ball surface. Maximum Hertz contact pressure up to 3GPa was applied in the central part of the contact region in mixed lubrication. It was found that the contact ratio (the ratio of real contact region to the whole nominal contact region) is related to the film thickness, the applied pressure, the surface roughness and the rolling speed, and so on. Contact ratio evidently reduces as lubrication film thickness or rolling speed increases. Quantitative relationship between the contact ratio and the influence factors was summarized based on the nonlinear fitting of experimental measurements. A formula was put forward to calculate the contact ratio at high pressure conditions according to the current experimental results.

Keywords: Contact ratio; Mixed lubrication; High pressure; Multiple asperities

A simplified method for synthesis of Fe₃O₄@PAA nanoparticles and its application for the removal of basic dyes by Yin-Yin Xu; Min Zhou; Hui-Juan Geng; Jun-Jie Hao; Qian-Qian Ou; Sheng-Da Qi; Hong-Li Chen; Xing-Guo Chen (pp. 3897-3902).

► A simplified method was used to synthesis the Fe₃O₄@PAA NPs.► The as synthesized magnetic NPs had relatively large specific surface area and good magnetic responsiveness.► As magnetic adsorbents, the Fe₃O₄@PAA NPs could be used to adsorb basic dyes from water solution.► The adsorption equilibrium could be reached in a short time.A simplified method for synthesis of polyacrylic acid-bound iron oxide magnetic nanoparticles (Fe₃O₄@PAA NPs) was reported. The as-prepared nanoparticles were characterized by TEM, FT-IR, VSM and XRD. Characterization results indicated that PAA was successfully introduced onto the surface of Fe₃O₄ and did not cause any changes in magnetic property. The Fe₃O₄@PAA NPs were used to adsorb rhodamine 6G (R6G) as a model basic dye pollutant from aqueous solution. Kinetics data and adsorption isotherms were better fitted by pseudo-second-order kinetic model and Langmuir isotherm, respectively. The adsorption equilibrium could be reached at about 20min, showing that the as-prepared adsorbent exhibited extremely rapid adsorption rate. The aqueous solution of the Yellow River was chosen as the test sample, and the results showed that the magnetic adsorbent was efficient for the removal of the basic dye in the real sample.

Keywords: Adsorption; Magnetic separation; Basic dye; Polyacrylic acid

Effects of electron irradiation on the properties of GZO films deposited with RF magnetron sputtering by Y.S. Kim; S.B. Heo; H.M. Lee; Y.J. Lee; I.S. Kim; M.S. Kang; D.H. Choi; B.H. Lee; M.G. Kim; Daeil Kim (pp. 3903-3906).

► GZO films were deposited by electron beam assisted RF magnetron sputtering. ► The effect of electron irradiation on the properties of GZO films was investigated. ► The work-function is increased with electron irradiation energy.Transparent conductive GZO films were deposited on polycarbonate substrates by electron beam assisted radio frequency (RF) magnetron sputtering and then the influence of electron irradiation on the structural, optical and electrical properties of GZO films was investigated by using X-ray diffractometry, UV–vis spectrophotometry, four point probes, atomic force microscopy and UV photoelectron spectroscopy. Sputtering power was kept constant at 3W/cm² during deposition, while electron irradiation energy varied from 450 to 900eV.Electron irradiated GZO films show larger grain sizes than those of films prepared without electron irradiation, and films irradiated at 900eV show higher optical transmittance in the visible wavelength region and lower sheet resistance (120Ω/□) than other films. The work-function is also increased with electron irradiation energy. The highest work-function of 4.4eV was observed in films that were electron irradiated at 900eV.

Keywords: GZO; Electron irradiation; XRD; Figure of merit; Work-function

Nucleation, growth and properties of Co nanostructures electrodeposited on n-Si(111) by Mohamed Redha Khelladi; Loubna Mentar; Amor Azizi; Figen Kadirgan; Guy Schmerber; Aziz Dinia (pp. 3907-3912).

► Nanocrystalline Co thin films were electrodeposited directly on n-Si(111) substrate from Watts bath. ► At the initial stages, the nucleation and growth kinetics of Co is characterized by an instantaneous nucleation mechanism followed by a 3D island growth. ► The phase structures of the films consisted of a mixture of hcp and fcc Co phases. ► The film thickness affected the films saturation magnetization and its coercivity.In the present work, cobalt thin films deposited directly on n-Si(111) surfaces by electrodeposition in Watts bath have been investigated. The electrochemical deposition and properties of deposits were studied using cyclic voltammetry (CV), chronoamperometry (CA), ex situ atomic force microscopy (AFM), X-ray diffraction (XRD) and alternating gradient field magnetometer (AGFM) techniques. The nucleation and growth kinetics at the initial stages of Co studied by current transients indicate a 3D island growth (Volmer–Weber); it is characterized by an instantaneous nucleation mechanism followed by diffusion limited growth. According to this model, the estimated nucleus density and diffusion coefficient are on the order of magnitude of 10⁶cm⁻² and 10⁻⁵cm²s⁻¹, respectively. AFM characterization of the deposits shows a granular structure of the electrodeposited layers. XRD measurements indicate a small grain size with the presence of a mixture of hcp and fcc Co structures. The hysteresis loops with a magnetic field in the parallel and perpendicular direction and showed that the easy magnetization axis of Co thin film is in the film plane.

Keywords: Electrodeposition; Cobalt; Nucleation; Structure

Sputter deposition of indium tin oxide onto zinc pthalocyanine: Chemical and electronic properties of the interface studied by photoelectron spectroscopy by Jürgen Gassmann; Joachim Brötz; Andreas Klein (pp. 3913-3919).

► Sputter deposition of ITO has been performed on top of the organic semiconductor (ZnPc). ► Interface formation was investigated by in situ XPS. ► No chemical reaction at the interface, i.e. no sputter damage, is observed. ► The barrier height for hole injection (0.9eV) does not depend on the deposition sequence of the layers. ► Sputtered ITO layers should be feasible as top electrodes for inverted, stacked and fully transparent OLEDs.The interface chemistry and the energy band alignment at the interface formed during sputter deposition of transparent conducting indium tin oxide (ITO) onto the organic semiconductor zinc phtalocyanine (ZnPc), which is important for inverted, transparent, and stacked organic light emitting diodes, is studied by in situ photoelectron spectroscopy (XPS and UPS). ITO was sputtered at room temperature and a low power density with a face to face arrangement of the target and substrate. With these deposition conditions, no chemical reaction and a low barrier height for charge injection at this interface are observed. The barrier height is comparable to those observed for the reverse deposition sequence, which also confirms the absence of sputter damage.

Keywords: Indium tin oxide (ITO); Zinc phtalocyanine (ZnPc); Photoelectron spectroscopy; Magnetron sputtering; Energy band alignment; Inverted OLED

Surface grafting density analysis of high anti-clotting PU-Si-g-P(MPC) films by Chun-Yan Lu; Ning-Lin Zhou; Ying-Hong Xiao; Yi-Da Tang; Su-Xing Jin; Yue Wu; Jun Zhang; Jian Shen (pp. 3920-3926).

► We prepared a kind of high anti-clotting PU-Si-g-P(MPC) films. ► Structures of polymer brushes and properties depend greatly on grafting density. ► ImageJ 1.44e software combining SEM/AFM were adopted to calculate grafting density. ► This method was fit to materials with great thickness, rough or non-uniform surfaces.Well-defined zwitterionic polymer brushes with good blood compatibility were studied, grafted from polyurethane (PU) substrate (PU-Si-g-P(MPC)) by surface-initiated reverse atom transfer radical polymerization (SI-RATRP). We found that the structure of polymer brushes and hence their properties greatly depend on the grafting density. To solve the problems of the normal method for grafting density measurement, i.e., more requirements for qualified and proficient instrument operator, we established an effective and feasible way instead of the conventional method of spectroscopic ellipsometer combined with gel permeation chromatograph (ELM/GPC) to calculate the grafting density of PU-Si-g-P(MPC) films by using a software named ImageJ 1.44e in combination with scanning electronic microscope (SEM) or atomic microscope (AFM). X-ray photoelectron spectroscopy (XPS), SEM and AFM were employed to analyze the surface topography and changes of elements before and after graft modification of the synthetic PU-Si-g-P(MPC) biofilms.

Keywords: 2-(Methacryloyloxy) ethyl phosphorylcholine (MPC); Grafting density; ImageJ; SEM; XPS

Synthesis, characterization and application of iodine modified titanium dioxide in phototcatalytical reactions under visible light irradiation by Segomotso Bagwasi; Baozhu Tian; Feng Chen; Jinlong Zhang (pp. 3927-3935).

► I-TiO₂ nanoparticles were prepared by simple hydrolysis calcination method. ► Iodine exists in two different states assigned to I⁵⁺ and I⁻ in I-TiO₂. ► I⁵⁺ was doped in the lattice while I⁻ was dispersed on the surface of the catalyst. ► I-TiO₂ degraded AO7, 2,4-DCP and MO under visible light effectively. ► AO7 degradation followed indirect oxidation via hydroxyl radicals.Iodine doped titanium dioxide has been successfully prepared by simple hydrolysis of tetrabutyl titanate in the presence of iodic acid. The adopted method allowed for the production of spherical iodine doped titaniun dioxide nanoparticles with varied amount of iodine content. Analysis by X-ray diffraction, Raman, transmission electron microscopy as well as UV–vis DRS revealed that titanium dioxide nanostructures were doped with iodine which existed in two different valence states I⁵⁺ and I⁻. The iodine in the form of I⁵⁺ is believed to have doped into the lattice whereas I⁻ was well dispersed on the surface of TiO₂ probably as iodine adducts hence rendering it to be highly absorbing in visible light region. The I-TiO₂ exhibited improved photocatalytic activity toward degradation of acid orange 7 (AO7), methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP) under visible light over the pristine TiO₂ prepared by the same method. High catalytic properties are attributed to iodine doping which led to high specific surface area, absorption in visible region as well as alleviation of charge carrier recombination. The most probable route undertaken in the degradation of AO7 is through indirect oxidation by the hydroxyl radicals.

Keywords: TiO; ₂; Iodine modification; Visible light; Photocatalyst; Organic pollutants

The effect of riblets in rectangular duct flow by Brian Dean; Bharat Bhushan (pp. 3936-3947).

► A flow cell for riblet study was designed and is discussed. ► The effect of riblet surfaces on rectangular duct pipe flow was studied. ► Pressure drop across test sections is compared and discussed.Much is known about the benefits of surface structures which mimic the riblets found on the skin of fast swimming sharks. Structures have been fabricated for study and application which replicate and improve upon the natural shape of the shark skin riblets, providing a maximum drag reduction of nearly 10% in external turbulent fluid flow. Mechanisms of fluid drag in turbulent flow and riblet-drag reduction theories from experiment and simulation are discussed. A brief review of riblet performance studies is given, and optimal riblet geometries are defined for external flow. A discussion of the structure of internal turbulent fluid flow is provided, and existing data for riblet drag reduction benefit is presented. A flow cell for studying riblet effects in internal rectangular duct flow is discussed, and data collected using several riblet surfaces fabricated for the flow cell is presented and analyzed. A discussion of the effects of the riblets on fluid flow is given, and conclusions are drawn about the possible benefits of riblets in internal fluid flow.

Keywords: Shark skin; Drag reduction; Riblets; Biomimetics; Turbulent flow; Internal flow

Effect of degumming time on silkworm silk fibre for biodegradable polymer composites by Mei-po Ho; Hao Wang; Kin-tak Lau (pp. 3948-3955).

► In this paper, a cleaner and environmentally friendly surface modification technique for tussah silk in polymer based composites is proposed. ► The effectiveness of different degumming parameters such as surface purity, degumming time and temperature on tussah silk are discussed through the analyses of their mechanical and morphological properties. ► It was found that the mechanical properties of tussah silk are affected by the degumming time due to the change of the fibre structure and fibroin alignment.Recently, many studies have been conducted on exploitation of natural materials for modern product development and bioengineering applications. Apart from plant-based materials (such as sisal, hemp, jute, bamboo and palm fibre), animal-based fibre is a kind of sustainable natural materials for making novel composites. Silkworm silk fibre extracted from cocoon has been well recognized as a promising material for bio-medical engineering applications because of its superior mechanical and bioresorbable properties. However, when producing silk fibre reinforced biodegradable/bioresorbable polymer composites, hydrophilic sericin has been found to cause poor interfacial bonding with most polymers and thus, it results in affecting the resultant properties of the composites. Besides, sericin layers on fibroin surface may also cause an adverse effect towards biocompatibility and hypersensitivity to silk for implant applications. Therefore, a proper pre-treatment should be done for sericin removal. Degumming is a surface modification process which allows a wide control of the silk fibre's properties, making the silk fibre possible to be used for the development and production of novel bio-composites with unique/specific mechanical and biodegradable properties. In this paper, a cleaner and environmentally friendly surface modification technique for tussah silk in polymer based composites is proposed. The effectiveness of different degumming parameters including degumming time and temperature on tussah silk is discussed through the analyses of their mechanical and morphological properties. Based on results obtained, it was found that the mechanical properties of tussah silk are affected by the degumming time due to the change of the fibre structure and fibroin alignment.

Keywords: Silk; Biodegradation; Hydrophilicity; Surface treatment; Biocompatibility

Electrochemical and SERS spectroscopic investigations of 4-methyl-4H-1,2,4-triazole-3-thiol monolayers self-assembled on copper surface by Ying-Cheng Pan; Ying Wen; Rui Zhang; Ying-Ying Wang; Zong-Rang Zhang; Hai-Feng Yang (pp. 3956-3961).

Display Omitted► 4-Methyl-4H-1, 2, 4-triazole-3-thiol (4-MTTL) has been modified at the copper surface. ► SERS analysis indicated that 4-MTTL film was adsorbed on Cu surface via S⁶ and N² atoms. ► The 4-MTTL film was proved to protect copper electrode from corrosion in KCl solution.Electrochemically anticorrosive behaviors of 4-methyl-4H-1,2,4-triazole-3-thiol (4-MTTL) monolayers self-assembled on copper surface have been investigated by electrochemical impedance spectroscopy (EIS), electrochemical polarization measurement and surface-enhanced Raman scattering (SERS) spectroscopy. The EIS mechanism of the copper surface adsorbed with 4-MTTL monolayers was fitted with the mode of R( QR)( QR)( CR). The electrochemical polarization experimental results indicated the high inhibitive efficiency of about 81.1%. Potential dependent SERS result suggests that 4-MTTL molecule was anchored at the copper surface via S⁶ and N² atoms with a tilted orientation, which resulting in a strong interaction between the 4-MTTL molecule and copper surface. The molecule tended to experience a transition state of the adsorption at the copper surface via S⁶ atom only as the potential applied at −0.5V vs. SCE.

Keywords: 4-Methyl-4H-1,2,4-triazole-3-thiol; Copper; Self-assembled monolayers; Surface-enhanced Raman scattering; Electrochemistry

Microstructure and electromagnetic characteristics of BaTiO₃/Ni hybrid particles prepared by electroless plating by Guiqin Wang; Lixin Ma; Yongfeng Chang; Chao Liu (pp. 3962-3966).

► Hybrid particles consisting of dielectric loss of BaTiO₃ and magnetic loss of Ni have been successfully prepared through electroless depositing Ni on BaTiO₃ particles. ► Microstructure at different stages of the electroless plating was investigated. ► Influence of the Ni content on the electromagnetic and microwave absorption properties of the hybrid particles was also studied. ► Electromagnetic and microwave absorption performances can readily be tuned by changing Ni content.To improve the microwave absorption ability, hybrid particles containing both dielectric loss of BaTiO₃ and magnetic loss of Ni were fabricated via electroless Ni plating on BaTiO₃ particles. A continuous Ni coating was successfully covered on the surface of the BaTiO₃. The effect of the Ni content on complex permittivity, complex permeability, and microwave absorption properties of BaTiO₃/Ni hybrid particles was investigated. The real ( ɛ′) and imaginary ( ɛ″) parts of complex permittivity as well as imaginary part of complex permeability ( μ″) were found to increase with an increase in Ni content, while the variation of the real part of complex permeability ( μ′) with Ni content was non-linear. The microwave absorption performances could readily be tuned base on the changing Ni content of the hybrid particles. The optimal absorption performances were attained when the content of Ni reached 38.9wt% in hybrid particles.

Keywords: BaTiO; ₃; /Ni hybrid particles; Electroless plating; Electromagnetic parameters; Microwave absorption; Reflection loss

Ion irradiation induced evolution of nanostructure in a graded multi-trilayer system by Sumalay Roy; J. Ghatak; B.N. Dev (pp. 3967-3974).

► Ion irradiation induced modifications in Pt/Ni/C multi-trilayers. ► Analysis by X-ray reflectivity, X-ray standing wave and transmission electron microscopy techniques. ► Ion irradiation causes complete Pt–Ni mixing at high ion fluence. ► At high ion fluence Pt–Ni nanoparticles embedded in a C matrix are formed.Nanostructural modifications in a double-graded Pt/Ni/C multi-trilayer, due to irradiation by an energetic ion-beam, have been analyzed using X-ray reflectivity (XRR), X-ray standing wave (XSW) and cross-sectional transmission electron microscopy (X-TEM) techniques. 2MeV Au²⁺ ions were rastered on Pt/Ni/C multi-trilayer samples producing a uniformly irradiated area at ion-fluences ranging from 1×10¹⁴ions/cm² to 2×10¹⁵ions/cm². Ion irradiation induced modifications of microstructural parameters, e.g., layer thicknesses and electron densities of individual layers and interface roughnesses have been obtained from XRR analysis. Pt- and Ni-fluorescence yield from the as-deposited sample under the XSW condition show the distinct existence of Pt and Ni layers. The almost indistinguishable Pt- and Ni-fluorescence data over the first order Bragg peak from the sample irradiated at the highest ion-fluence, suggest complete mixing of Pt and Ni. Strong mixing between Pt and Ni in the ion irradiated samples is also corroborated by XRR results. X-TEM studies reveal the individual layer structure in the as-deposited sample. This layer structure is lost in the sample irradiated at the highest ion fluence indicating a complete mixing between Pt and Ni layers and nanoscale grain growth of Pt–Ni alloys. Additionally, formation of Pt–Ni alloy nano-clusters in the C-layers is observed. The results are understood in the light of the positive heat of mixing between Pt and C, and Ni and C and the negative heat of mixing between Pt and Ni. The effect of heat of mixing becomes dominant at high fluence irradiation.

Keywords: Graded multilayer; X-ray reflectivity; X-ray standing wave; Ion-beam induced modifications; Transmission electron microscopy

Numerical investigation on thermal properties at Cu–Al interface in micro/nano manufacturing by Liqiang Zhang; Ping Yang; Min Chen; Ningbo Liao (pp. 3975-3979).

► We proposed a hybrid model by integrating TTM (two-temperature model) and MD (molecular dynamics). ► We investigated the properties on interface of dissimilar materials under thermal flux conditions. ► We detected the fantastic change on Cu–Cu interface and Cu–Al interface. ► We investigated the propagation mechanisms of nanocracks. ► It implies a potential method for design interface structure in micro/nano manufacturing.A hybrid model by integrating TTM (two-temperature model) and MD (molecular dynamics) is proposed to investigate the properties on interface of dissimilar materials under thermal flux conditions. This model can describe the electron phonon coupling and phonon scattering at the interface of different metals easily. By comparing the Cu–Cu interface and Cu–Al interface, the atoms of the Cu–Cu interface at different sides tend to move together; while, the atoms displacements of Cu and Al are opposite along the interface, which may cause stress and voids at the interface. Moreover, the propagation mechanisms of nanocracks and the corresponding change of temperature distribution and thermal flux are investigated. The results show that the interfaces of dissimilar materials are prone to crack initiations, leading to delaminations because of the high temperature. All these are useful for understanding the deformation and failure of the interfaces structures. It implies a potential method for design and analysis of interface structure in micro/nano manufacturing.

Keywords: MD (molecular dynamics); TTM (two-temperature model); Nanocracks; Interface; Thermal flux; Failure

Reaction mechanism for CO oxidation on Cu(311): A density functional theory study by Shuping Liu; Peng Jin; Ce Hao; Donghui Zhang; Xueming Yang; Shuling Chen (pp. 3980-3985).

.Display Omitted► The CO oxidation on Cu(311) surface was investigated by density functional theory computations. ► O₂ dissociation is highly dependent on the orientation and site of the adsorbed oxygen molecule. ► The energetically most favorable site for CO molecule on Cu(311) is the step edge. ► The reaction barrier of CO+O→CO₂ is about 0.3eV lower than that of CO+O₂→CO₂+O.The microscopic reaction mechanism for CO oxidation on Cu(311) surface has been investigated by means of comprehensive density functional theory (DFT) calculations. The elementary steps studied include O₂ adsorption and dissociation, dissociated O atom adsorption and diffusion, as well as CO adsorption and oxidation on the metal. Our results reveal that O₂ is considerably reactive on the Cu(311) surface and will spontaneously dissociate at several adsorption states, which process are highly dependent on the orientation and site of the adsorbed oxygen molecule. The dissociated O atom may likely diffuse via inner terrace sites or from a terrace site to a step site due to the low barriers. Furthermore, we find that the energetically most favorable site for CO molecule on Cu(311) is the step edge site. According to our calculations, the reaction barrier of CO+O→CO₂ is about 0.3eV lower in energy than that of CO+O₂→CO₂+O, suggesting the former mechanism play a main role in CO oxidation on the Cu(311) surface.

Keywords: Density functional computations; Oxygen; Copper; Surface reaction; Carbon monoxide; Oxidation; Chemisorption; Dissociation

Effect of oxygen atmosphere on the structure and refractive index dispersive behavior of KTa_0.5Nb_0.5O₃ thin films prepared by PLD on Si(001) substrates by Wenlong Yang; Zhongxiang Zhou; Bin Yang; Yongyuan Jiang; Yanbo Pei; Hongguo Sun; Ying Wang (pp. 3986-3990).

► Pure perovskite phase and crack-free KTa_0.5Nb_0.5O₃ films were prepared by PLD. ► Structure and optical properties were found sensitive to oxygen atmosphere. ► Refractive indexes dispersive behavior was analyzed by Cauchy dispersion model.KTa_0.5Nb_0.5O₃ thin films were deposited on Si(001) substrates by pulsed laser deposition (PLD) with different oxygen pressures (10Pa, 15Pa, 20Pa, 25Pa and 30Pa). The effect of oxygen atmosphere on the structure and refractive indices of the films were studied. It is found that the phase structure, the scale of the grains, the surface roughness and the optical properties of the films are sensitive to oxygen atmosphere variation. The refractive indices of the films were investigated by ellipsometer and the dispersive behavior was analyzed by Cauchy dispersion model. The films grown with 15Pa oxygen pressure show the pure perovskite structure and the dispersion behaviors possess the normal dispersion shape; and other influence on the quality and properties of KTa_0.5Nb_0.5O₃/Si(001) films were discussed.

Keywords: Oxygen atmosphere; KTa; _0.5; Nb; _0.5; O; ₃; thin film; Microtopography; Refractive index dispersion; Cauchy dispersion model

Study of high-temperature hydrogen reduced Pt⁰/TiO₂ by X-ray photoelectron spectroscopy combined with argon ion sputtering—Diffusion-encapsulation effect in relation to strong metal–support interaction by Jingwei Zhang; Min Zhang; Zhensheng Jin; Jingju Wang; Zhijun Zhang (pp. 3991-3999).

The schematic illustration of SMSI-R (a) and SMSI-O (b).Display Omitted► The Ti_xO_y of low-valence can transfer onto the surface of Pt⁰ particulates. ► The Pt⁰ atom can be diffused into the lattice of TiO₂, occupies the oxygen vacancy. ► A localized PtTi⁴⁺ can be formed via Pt⁰ accepting one electron from the adjacent Ti³⁺. ► The SMSI-O results in the increase of the photo-catalytic activity of Pt⁰/TiO₂. ► The SMSI-R leads to the decrease of the photo-catalytic activity of Pt⁰/TiO₂.X-ray photoelectron spectroscopy combined with Ar⁺ ion sputtering has been used to analyze the variation in the valence and concentration of Pt, Ti, and O of Pt⁰/TiO₂ reduced by H₂ at elevated temperature. It is confirmed that titanium oxide of low-valence is transferred onto the surface of Pt⁰ particulates to encapsulate the surface via a strong metal–support interaction under reducing atmosphere. It is also found for the first time that Pt⁰ atom is diffused into the lattice of TiO₂ to occupy the oxygen vacancy (V_O) and accept one electron from adjacent Ti³⁺ forming a localized Pt⁻Ti⁴⁺ bond. This differs from the strong metal–support interaction under oxidizing atmosphere. Namely, although the Pt⁰ atom is also diffused into the lattice of TiO₂ under oxidizing atmosphere, it replaces Ti atom and forms a Pt²⁺O²⁻ bond. Moreover, the strong metal–support interaction under oxidizing atmosphere results in increased photocatalytic activity of Pt⁰/TiO₂, while the strong metal–support interaction under reducing atmosphere leads to decreased photocatalytic activity of Pt⁰/TiO₂.

Keywords: Pt; ⁰; /TiO; ₂; Reduction; Strong metal–support interaction; XPS-Ar; ⁺; ion sputtering study; Photocatalytic activity

Buffer-layer enhanced crystal growth of BaB₆ (100) thin films on MgO (100) substrates by laser molecular beam epitaxy by Yushi Kato; Ryosuke Yamauchi; Hideki Arai; Geng Tan; Nobuo Tsuchimine; Susumu Kobayashi; Kazuhiko Saeki; Nobutaka Takezawa; Masahiko Mitsuhashi; Satoru Kaneko; Mamoru Yoshimoto (pp. 4000-4004).

Display Omitted► Crystalline BaB₆ thin films can be fabricated by inserting buffer layer. ► BaB₆ thin films without the buffer layer develop as polycrystalline films. ► Buffer layer is considered to greatly affect the initial growth of BaB₆ thin films. ► Crystalline BaB₆ thin films exhibit n-type semiconducting behavior.Crystalline BaB₆ (100) thin films can be fabricated on MgO (100) substrates by inserting a 2–3nm-thick epitaxial SrB₆ (100) buffer layer by pulsed laser deposition (PLD) in ultra-high vacuum (i.e., laser molecular beam epitaxy). Reflection high-energy electron diffraction and X-ray diffraction measurements indicated the heteroepitaxial structure of BaB₆ (100)/SrB₆ (100)/MgO (100) with the single domain of the epitaxial relationship. Conversely, BaB₆ thin films without the buffer layer were not epitaxial instead they developed as polycrystalline films with a random in-plane configuration and some impurity phases. As a result, the buffer layer is considered to greatly affect the initial growth of epitaxial BaB₆ thin films; therefore, in this study, buffering effects have been discussed. From the conventional four-probe measurement, it was observed that BaB₆ epitaxial thin films exhibit n-type semiconducting behavior with a resistivity of 2.90×10⁻¹Ωcm at room temperature.

Keywords: PACS; 68.55.−a; 68.55.ag; 73.61.−r; 81.10.Aj; 81.15.Fg; 81.15.KkAlkaline-earth hexaboride; BaB; ₆; Laser MBE; Epitaxial thin film; Buffer layer; Electrical property

Electrodeposited Ni–Co films from electrolytes with different Co contents by Ali Karpuz; Hakan Kockar; Mursel Alper; Oznur Karaagac; Murside Haciismailoglu (pp. 4005-4010).

► Properties of electrodeposited Ni–Co films were investigated as a function of Co concentration in sulfamate–sulfate bath. ► Except for boric acid, no additive was used to get coherent and quality Ni–Co structures. ► The properties were affected by different Co contents in the film, which can be controlled by the Co concentration. ► Also, optimum film composition for applied experimental conditions was determined by considering obtained film properties.The properties of electrodeposited Ni–Co films produced from electrolyte consisted of nickel sulfamate, cobalt sulfate and boric acid were investigated as a function of Co content in the films. The compositional analysis performed by an energy dispersive X-ray spectroscopy demonstrated that the Co content of the films increases as the cobalt sulfate concentration in the electrolyte increases. The anomalous codeposition behavior was observed for all concentrations. The crystal structure was analyzed using an X-ray diffraction technique. The face centered cubic (fcc) structure was observed in the films containing from 0at.% Co to 58at.% Co. For the higher atomic Co contents (64at.% and 80at.%), a mixed phase of dominantly fcc and hexagonal closed packed (hcp) structure was observed although the (10.0) and (10.1) hcp peaks had minor intensities in the patterns. Surface micrographs obtained from a scanning electron microscope revealed that the film surface has a rougher appearance as the Co content increases. Magnetic measurements showed that the saturation magnetization gradually increased with increasing Co content of the films. The coercivity, H_c can be controlled by the structural parameters such as average grain size and crystal structure. The results also indicated that the optimum film composition was 28–40at.% Co since the lower H_c and higher magnetoresistance (MR) values with very smooth or slightly granular surfaces were achieved at this Co content. It is revealed that Co content has an important effect on structural, magnetic and MR properties of the Ni–Co films.

Keywords: Cobalt alloys; Magnetic analysis; Magnetoresistance; Structural analysis

Acetic acid mediated interactions between alumina surfaces by Kimiyasu Sato; Hüseyin Yılmaz; Atsuko Ijuin; Yuji Hotta; Koji Watari (pp. 4011-4015).

► Interaction forces between alumina surfaces mediated by acetic acid were studied. ► Repulsive forces due to steric repulsion and electrostatic repulsion dominated the interaction. ► Rheological study on alumina slurry containing acetic acid supported the finding.Low-molecular-weight organic acids have been known to modify colloidal stability of alumina-based suspensions. We investigated interaction forces between alumina surfaces mediated by acetic acid which is one of the simplest organic acids. Forces between alumina surfaces were measured using the colloid-probe method of atomic force microscope (AFM). Repulsive forces attributed to steric repulsion due to adsorbed molecules and electrostatic repulsion dominated the interaction. Results of rheological characterization of the alumina slurry containing acetic acid supported the finding.

Keywords: Surface force; Alumina; Acetic acid; Atomic force microscope; Colloid-probe

Low-temperature solvothermal synthesis of visible-light-responsive S-doped TiO₂ nanocrystal by Guidong Yang; Zifeng Yan; Tiancun Xiao (pp. 4016-4022).

Display Omitted► Nanosized titania was prepared successfully by low-temperature solvothermal method. ► The as-prepared samples are characterized by XRD, XPS, Raman spectroscopy, FT-IR, SEM and UV–vis DRS spectrophotometer. ► S⁶⁺ substituted for Ti⁴⁺ cation in the crystal lattice. ► The sample shows higher photocatalytic activity under visible light irradiation.In this work, a low-temperature solvothermal method has been developed to synthesize visible-light-responsive S-doped TiO₂ nanocrystal photocatalyst, using thiourea as the sulfur source to enhance sulfur incorporation into TiO₂ lattice. The effects of different S:Ti molar ratio on the crystal structure, chemical composition, surface property and catalytic performance have been studied. X-ray photoelectron spectroscopy (XPS) analysis and Fourier transform infrared (FT-IR) spectra displayed that the TiO₂ was modified by the S element incorporated into the TiO₂ network to form TiOS bond, which therefore led to the formation of intermediate energy level just above the O 2p valance band, and caused the absorption edge of TiO₂ to shift into the visible light region up to 500nm. Characterization results show that the pure nanocrystal anatase structure, with both the degree of S doping and oxygen vacancies makes contribution to the exceptional photocatalytic activity of TONS in visible-light degradation of Methylene Blue (MB) and phenol molecules.

Keywords: Sulfur; Doping; TiO; ₂; Visible light; Photocatalysis; Solvothermal

Preparation and characterization of bipolar membranes modified by photocatalyst nano-ZnO and nano-CeO₂ by Ting-jin Zhou; Yan-yu Hu; Ri-yao Chen; Xi Zheng; Xiao Chen; Zhen Chen; Jie-qiong Zhong (pp. 4023-4027).

► Nano-ZnO–CeO₂ coupled semiconductor was added into the bipolar membrane (BPM).Nano-ZnO–CeO₂ had good photocatalytic property for water splitting in the interlayer, and greatly reduced the membrane impedance of the BPM. ► Furthermore, nano-ZnO–CeO₂ could improve the mechanical properties and hydrophilicity of the BPM.Nano-ZnO–CeO₂ coupled semiconductor was added into the chitosan (CS) anion exchange membrane layer to prepare the PVA–CMC/nano-ZnO–CeO₂–CS (here, PVA: polyvinyl alcohol; CMC: carboxymethyl cellulose) bipolar membrane (BPM), and the prepared BPM was characterized by SEM, J– V characteristics, electronic universal testing machine, contact angle measurement and so on. Experimental results showed that nano-ZnO–CeO₂ exhibited better photocatalytic property for water splitting at the interlayer of BPM than nano-ZnO or nano-CeO₂, which could greatly reduce the membrane impedance of the BPM. Under the irradiation of high-pressure mercury lamps, the cell voltage of PVA–CMC/nano-ZnO–CeO₂–CS BPM decreased by 0.7V at the current density of 60mA/cm², and the cell voltages of PVA–CMC/nano-ZnO–CS BPM and PVA–CMC/nano-CeO₂–CS BPM were only reduced by 0.3V and 0.5V, respectively. Furthermore, the hydrophilicity, and mechanical properties of the modified BPM were increased.

Keywords: Bipolar membrane; Photocatalysis; Water splitting; Nano-ZnO; Nano-CeO; ₂

The influence of annealing treatments on the properties of Ag:TiO₂ nanocomposite films prepared by magnetron sputtering by R.C. Adochite; D. Munteanu; M. Torrell; L. Cunha; E. Alves; N.P. Barradas; A. Cavaleiro; J.P. Riviere; E. Le Bourhis; D. Eyidi; F. Vaz (pp. 4028-4034).

► Vacuum annealing treatments were performed on the Ag:TiO₂ system. ► The effect on the morphological, structural and mechanical properties was studied. ► The annealing treatments above 300°C led to: - slight variations of the nanohardness and reduced Young modulus; - redistribution of the residual stresses, the crystallization of Ag metallic particles and the dielectric matrix. ► Ag:TiO₂ thin films represent an interesting alternative for decorative applications.The present paper reports on the preparation and characterization of DC reactive magnetron sputtered Ag:TiO₂ nanocomposite coatings, with a silver content of about 8at.% (average estimation). The as-deposited samples were subjected to annealing, in a protective atmosphere, at temperatures ranging from 200 to 800°C. Morphology, structure, hardness and friction behaviour were characterised after each heat treatment. The cross-sections of the films were studied by transmission electron microscopy (TEM). X-ray diffraction (XRD) was used to determine the thin-film structure and crystallinity as a function of annealing temperature. XRD analysis confirmed the presence of silver in all the samples and the crystallization of the TiO₂ matrix for the samples annealed at temperatures above 300°C. These structural changes were also followed by significant morphological variations, which resulted in the change of the mechanical properties of the films (hardness and Young's modulus) as well as of their tribological behaviour.

Keywords: Magnetron sputtering; Mechanical properties; Tribological properties; Decorative thin films; Silver; TiO; ₂

Electrochemical corrosion behavior of Ti–24Nb–4Zr–8Sn alloy in a simulated physiological environment by Y. Bai; S.J. Li; F. Prima; Y.L. Hao; R. Yang (pp. 4035-4040).

► Electrochemical corrosion behavior of the Ti–24Nb–4Zr–8Sn alloy is investigated. ► Ti–24Nb–4Zr–8Sn alloy exhibits the excellent passivation performance. ► Its corrosion current is comparable to that of pure titanium. ► A single passive layer is presented on the surface of Ti–24Nb–4Zr–8Sn alloy.Electrochemical corrosion behavior of a biomedical titanium alloy Ti–24Nb–4Zr–8Sn in weight percent was investigated in a phosphate buffered saline solution at 37°C utilizing open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Both commercially pure titanium and Ti–6Al–4V alloy were also investigated to make a comparison. The results show that all the samples were spontaneously passivated once immersion into the electrolyte. Ti–24Nb–4Zr–8Sn alloy exhibited a much wider passive region compared with pure titanium and Ti–6Al–4V and also relatively low corrosion current density which is comparable to that of pure titanium in the buffered saline solution, which was attributed to a stable passive film mainly consisted of titanium oxide and niobium oxide on its surface. The EIS results indicated the presence of a single passive layer with thickness ∼2nm for Ti–24Nb–4Zr–8Sn and pure titanium but a duplex film consisting an inner barrier layer and an outer porous layer on Ti–6Al–4V alloy with thickness of ∼3nm and ∼2.5nm, respectively.

Keywords: Titanium alloy; Polarization; EIS; Passive film

In vitro biocompatibility evaluation of ePTFE graft with controlled release of heparin from mesoporous material by Kun Li; Yu Zhou; Jia yuan Yang; Jian hua Zhu; Chang jian Liu (pp. 4041-4047).

Heparin-loaded mesoporous-expanded poly(tetrafluoroethylene) (ePTFE) vascular prosthesis are prepared and the biocompatibility is studied by contact angle, heparin release, platelet resistance, chromogenic assay, endothelial progenitor cells (EPCs) proliferation and produced-NO function, illustrating the relationship between the performance of artificial vessels and their mesostructure.Display Omitted► Using in situ synthesis of mesoporous silica on ePTFE grafts to create mesoporous vascular prosthesis. ► Adjusting the mesostructure through controlling the synthetic condition of mesoporous silica. ► Improved biocompatibility owning to the controlled release of heparin. ► Closed relationship between the mesostucture and the biocompatibility.Heparin-loaded mesoporous-expanded poly(tetrafluoroethylene) (ePTFE) vascular prosthesis (HMVP- n) are prepared and the biocompatibility is studied by contact angle, heparin release, platelet resistance, chromogenic assay, endothelial progenitor cells (EPCs) proliferation and produced-NO function, in order to illustrate the relationship between the performance of artificial vessels and their mesostructure. Through in situ synthesis of mesoporous silica on ePTFE grafts, different mesoporous silica materials can be uniformly coated on the surface as well as the internal fibers of the artificial vessels to give various mesoporous vascular prosthesis, named as MVP- n. Structure analysis through scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX) analysis and nitrogen sorption experiment indicates that different MVP- n series own the similar n_F/ n_Si ratio of both surface and cross-section, large Brunauer-Emmett-Tellerand (BET) surface area and average pore size located in meso range but different textural properties. Owning to the existence of mesostucture, controlled release and high bioactivity of heparin can be achieved, and the biocompatibility greatly enhance: surface hydrophilicity increases; no adherent platelet was observed on the surface of HMVP- n when they contacted with platelet-enriched plasma; endothelial progenitor cells proliferous potential and produced-NO function exhibit better endothelial coverage of grafts. And the performance is closely related to the mesostructure, suggesting a new way to improve the biocompatibility of biomaterials through controlling their mesostructure.

Keywords: Mesoporous silica; Expanded poly(tetrafluoroethylene); Heparinization; Biocompatibility; Endothelialization

A comparative study of pyrolyzed and doped cobalt-polypyrrole eletrocatalysts for oxygen reduction reaction by Wei Feng; Hengyi Li; Xuan Cheng; Ting-Chu Jao; Fang-Bor Weng; Ay Su; Yu-Chun Chiang (pp. 4048-4053).

► The use of different dopants in the preparation of pyrolyzed Co-PPy/C cathode catalysts. ► The electrocatalytic activities of non-doped and doped catalysts toward oxygen reduction reaction (ORR) were compared. ► The electron numbers of ORR were evaluated. ► The influences of dopants in structure and surface properties of catalyst and support were examined.The pyrolyzed carbon supported cobalt polypyrrole (Co-PPy/C) catalysts were prepared without or with three selected dopants, namely, sodium dodecylbezene sulfonate (DBSNa), sodium paratoluene sulfonate (TSNa) and sodium bezene sulfonate (BSNa), respectively, through chemical oxidation with ferric chloride as an oxidant. The structure, surface and electrochemical properties of the obtained catalysts were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmitt–Teller (BET) analysis, cyclic voltammetry, rotating disc electrode technique and Raman spectroscopy. The introduction of dopants increased the surface concentrations of nitrogen and cobalt which would provide more active sites for oxygen reduction reaction (ORR), and enhanced the graphitization degree of carbon support which would improve the electron conductivity. The electron numbers of ORR for the non-doped and doped Co-PPy/C were evaluated to be 2.7–3.1, respectively. The pyrolyzed BSNa-doped Co-PPy/C exhibited the best electrocatalytic activity toward ORR due to its higher surface areas, larger amounts of micropores, as well as relatively higher nitrogen and cobalt contents.

Keywords: Proton exchange membrane fuel cells; Cobalt polypyrrole catalyst; Dopant; Oxygen reduction reaction

Preparation and characterization of montmorillonite modified by phosphorus–nitrogen containing quaternary ammonium salts by Guobo Huang; Jianrong Gao; Xu Wang (pp. 4054-4062).

► A novel class of PNQAS were synthesized and characterized. ► PNQAS-MMT were prepared and through ion exchange of Na-MMT with PNQAS. ► The thermal stability for PNQAS-MMT was investigated by TGA.A novel class of phosphorous–nitrogen containing quaternary ammonium salts (PNQAS) were synthesized and used as modifiers for sodium montmorillonite (Na-MMT). Montmorillonites modified by PNQAS (PNQAS-MMT) were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dispersibility measurement and thermogravimetric analysis (TGA). The results show that the PNQAS have been intercalated into the montmorillonite layers successfully and the basal spacing of PNQAS-MMT is 1.70–2.65nm. The XRD results show that the basal spacing of PNQAS-MMT reaches a maximum when PNQAS/CEC molar ratio is above 1.2. The increase of chain length of PNQAS is beneficial to expand the interlayer space of the MMT. The TEM and dispersibility measurement results show that PNQAS-MMT have stronger hydrophobicity and better dispersion than Na-MMT. The TGA results reveal that the thermal stability for PNQAS-MMT is affected by the structure and composition of intercalated PNQAS cations. The T_inital of PNQAS-MMT is between 286°C and 385°C, which can be applied to the modification of the polymer as a halogen-free flame retardant.

Keywords: Phosphorous–nitrogen; Montmorillonite; Surface modification

Water condensation on superhydrophobic aluminum surfaces with different low-surface-energy coatings by Long Yin; Yuanyi Wang; Jianfu Ding; Qingjun Wang; Qingmin Chen (pp. 4063-4068).

The influence of environmental conditions on the wettability of superhydrophobic aluminum surfaces with different low-surface-energy coatings is investigated in the temperature range of −10 to 30°C under RH of 30, 60 and 90%.Display Omitted► Superhydrophobic Al surfaces with different coatings are prepared by etching. ► Contact and sliding angles are tested under controlled environmental conditions. ► Condensation causes an increased wettability under high RH. ► The loss of water repellency triggered by water condensation is restorable.In this work, we have fabricated superhydrophobic aluminum surfaces by a facile chemical etching method. Surface morphology and composition were studied by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). To comparatively investigate the effect of environmental factors on superhydrophobic behaviors of surfaces with different low-surface-energy coatings under controllable condensation conditions, contact and sliding angles were measured from −10°C to 30°C under relative humidity (RH) of 30, 60 and 90%, respectively. The calculation of the solid–liquid contact area fraction quantitatively explained the increased wettability characterized by descending contact angle and ascending sliding angle under low temperature and high humidity, and indicated a transition of the equilibrium state from Cassie–Baxter to Wenzel on rough surfaces. The wettability restoration test showed that the loss of superhydrophobicity during condensation could be recovered completely after a drying process at room temperature.

Keywords: Superhydrophobic; Condensation; Contact angle; Sliding angle; Surface temperature; Relative humidity

Molecular gating of transistors by amine-terminated layers by O. Shaya; I. Amit; H. Einati; L. Burstein; Y. Shacham-Diamand; Y. Rosenwaks (pp. 4069-4072).

► Molecular-gated transistors were measured during APTMS self-assembly. ► I– V characteristics enable the study of threshold-voltage shift in-situ. ► Surface charging occurs only after exposure to air and is probably a result of it.Self-assembly of amine-terminated layers on a transistor gate dielectric leads to gating of the transistor even without the use of a reference electrode or any voltage drop across the organic layer. This effect was studied using in situ electrical measurements, Kelvin probe force microscopy and X-ray photoelectron spectroscopy of (3-aminopropyl)-trimethoxysilane (APTMS) gated transistors. Current–voltage characteristics measured during the self-assembly process showed that the gating occurs only following exposure of the device to ambient humidity. X-ray photoelectron spectroscopy measurements of the layers showed a high percentage of protonated amine groups on the surface. Therefore, it is concluded that the charging of the amine group due to protonation under ambient conditions is the cause for the molecular-gating.

Keywords: APTMS; MOCSER; Polar organic layers; Molecular-gated transistors

Features of structural reorganization in bulk III–V compounds induced by weak magnetic fields by R. Red’ko (pp. 4073-4078).

► In this study we examine the interaction of WMF with GaAs, InP and GaP. ► General features of induced transformation are similar. ► We propose to use WMF-action as the method of non-equilibrium centers detection.The long-term transformations of defect structure in GaP, GaAs and InP single crystals treated with pulsed weak magnetic fields are obtained. The treatments were performed in two regimes, namely, single-pulse ( τ=30ms) and multi-pulse ( τ=1.2ms) ones, at varying magnitude of magnetic induction. The defect structure transformations were inferred from the radiative recombination spectra in the 0.6–2.5μm range at 77–300K as well as Raman scattering and morphology investigations. A possible mechanism of observed modifications related to the electron spin transformation is discussed.

Keywords: Photoluminescence; Weak magnetic field; Impurity-defect composition

Improvement of suspension stability and electrophoresis of nanodiamond powder by fluorination by H. Huang; Y.H. Wang; J.B. Zang; L.Y. Bian (pp. 4079-4084).

Figures show that the aggregate particle size reduced from several hundred nanometers (a) to less than 40nm after fluorination (d and e). Some monodisperse particles of F-ND were observed in (c). The pristine ND clusters were drastically deagglomerated by the surface fluorination.Display Omitted► The F-ND was prepared by annealing in fluorine gas and periodically feeding. ► The aggregate ND particle size was reduced to ∼40nm by fluorination. ► The dispersion of F-NDs in the ethanol or distilled water was improved. ► The surface charge of ND particle became negative after fluorination.Fluorinated nanodiamond (F-ND) was prepared by annealing ND in fluorine gas. The fluorine gas was periodically fed to ensure uniform exposure of every diamond nanoparticle in homogenous reactive ambience. The characteristics of the F-ND particles were investigated by the following methods: Fourier-transform infrared absorption spectroscopy, energy-dispersive X-ray spectrometer, X-ray diffraction, and transmission electron microscopy. The results showed that the fluorine atoms were chemically adsorbed on the surface of the ND particles and consequently formed CF bonds. Fluorine of 6.4wt.% was detected on the F-ND surface. The aggregated ND particles were disintegrated by the fluorination and the size of aggregated ND was reduced from approximately several hundred nanometers to about 40nm. The stability of the F-ND suspension in distilled water or ethanol was higher than that of the pristine ND suspension. The anodic electrophoretic deposition of the F-ND particles was derived using ethanol suspension, indicating that the F-ND particles were negatively charged.

Keywords: Nanodiamond; Fluorination; Disintegration; Dispersivity; Electrophoresis

Desorption and photodegradation of methylene blue from modified sugarcane bagasse surface by acid TiO₂ hydrosol by Jun-Xia Yu; Ru-An Chi; Jia Guo; Yue-Fei Zhang; Zhi-Gao Xu; Chun-Qiao Xiao (pp. 4085-4090).

► Modified sugarcane bagasse was prepared to improve its sorption for methylene blue. ► The capacity of modified biosorbent for dye was 12 times than the unmodified sorbent. ► TiO₂ hydrosol was used as a self-cleaning eluent to regenerate dye loaded biosorbent. ► 78.3% of the absorbed dye could be desorbed and then photodegraded by TiO₂ hydrosol.Waste sugarcane bagasse (SCB) was modified by pyromellitic dianhydride to improve its adsorption capacity for cationic dyes. Results showed that the adsorption capacity of the modified SCB for methylene blue was 564mgg⁻¹, which was about 12 times than that obtained on the unmodified SCB. Methylene blue loaded modified SCB was regenerated by a self-clean eluent: TiO₂ hydrosol with pH ranged from 1 to 4, and HNO₃ solution with the same pH range was tested at the same time for comparison. Results showed that desorption kinetics of methylene blue in the hydrosol systems fit two-step kinetic model and controlled mainly by the slow step. As a self-clean eluent, acid hydrosol could firstly desorb and then photodegrade methylene blue under sunlight irradiation. After five desorption–photodegradation cycles, 78.3% of the absorbed dyes could be desorbed by using hydrosol (pH 2) as eluent. The hydrosol could be continuously used in desorption and photodegradation process, which would economize large volume of the eluent and moreover it would not bring secondary pollution.

Keywords: TiO; ₂; hydrosol; Sugarcane bagasse; Biosorption; Photodegradation; Methylene blue

Erratum to “Finite element simulation and analytical analysis for nano field emission sources that terminate with a single atom: A new perspective on nanotips” [Appl. Surf. Sci. 258 (2011) 1750–1755] by Moh’d Rezeq (pp. 4091-4091).

Natively textured surface Al-doped ZnO-TCO layers with gradual oxygen growth for thin film solar cells via magnetron sputtering by Xin-liang Chen; Fei Wang; Xin-hua Geng; De-kun Zhang; Chang-chun Wei; Xiao-dan Zhang; Ying Zhao (pp. 4092-4096).

Natively textured surface aluminum doped zinc oxide (ZnO:Al) transparent conductive oxide (TCO) thin films have been directly deposited via pulsed direct current magnetron reactive sputtering on glass substrates. Gradual oxygen growth (GOG) techniques were developed in the reactive sputtering process for textured ZnO:Al thin films in reactive magnetron sputtering. The light-scattering ability and optical transmittance of the natively textured ZnO:Al TCO thin films can be improved through gradual oxygen growth methods while maintaining a low sheet resistance. Typical natively textured ZnO:Al TCO thin film with crater-like surface exhibits low sheet resistance (Rs∼4Ω), high transmittance ( Ta>85%) in visible optical region and high haze value (12.1%). The natively ZnO:Al thin films are promising TCO materials for thin film solar cells.

Keywords: Zinc oxide thin films; Magnetron sputtering; Natively textured surface; Gradual oxygen growth; Solar cells

Tailoring phase and oxidation states of Cu by varying oxygen gas flow rates in rf sputter deposition for photovoltaic devices by Kyounga Lim; Juyun Park; Rex D. Ramsier; Do-Geun Kim; Jae-Wook Kang; Yong-Cheol Kang (pp. 4097-4099).

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Applied Surface Science (v.258, #8)