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Applied Surface Science (v.266, #)

Editorial Board (pp. ii).

Crystalline silicon solar cells with micro/nano texture by Dimitre Z. Dimitrov; Chen-Hsun Du (pp. 1-4).

► Combined micro/nano scale texture was produced on crystalline silicon surface ► The micro/nano scale texture features antireflection properties ► Solar cells with this texture are shown improved blue-response and conversion efficiency.Crystalline silicon solar cells with two-scale texture consisting of random upright pyramids and surface nanotextured layer directly onto the pyramids are prepared and reflectance properties and I– V characteristics measured. Random pyramids texture is produced by etching in an alkaline solution. On top of the pyramids texture, a nanotexture is developed using an electroless oxidation/etching process. Solar cells with two-scale surface texturization are prepared following the standard screen-printing technology sequence. The micro/nano surface is found to lower considerably the light reflectance of silicon. The short wavelengths spectral response (blue response) improvement is observed in micro/nano textured solar cells compared to standard upright pyramids textured cells. An efficiency of 17.5% is measured for the best micro/nano textured c-Si solar cell. The efficiency improvement is found to be due to the gain in both J_sc and V_oc.

Keywords: Crystalline silicon solar cell; Texturization; Nano structure; Antireflection

Interphase chemistry of Si electrodes used as anodes in Li-ion batteries by Catarina Pereira-Nabais; Jolanta Światowska; Alexandre Chagnes; François Ozanam; Aurélien Gohier; Pierre Tran-Van; Costel-Sorin Cojocaru; Michel Cassir; Philippe Marcus (pp. 5-16).

► XPS and ToF-SIMS study of solid electrolyte interphase layer on Si thin film and Si nanowires electrodes is presented. ► Modification of Si electrode surface morphology is evidenced by SEM micrographs. ► Organic part of solid electrolyte interphase is present at the outer- and inorganic part in the innermost surface. ► Different thickness of solid electrolyte interphase is observed in a function of type of electrolytes.The effect of the Si electrode morphology (amorphous hydrogenated silicon thin films – a-Si:H as a model electrode and Si nanowires – SiNWs electrode) on the interphase chemistry was thoroughly investigated by the surface science techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS analysis shows a strong attenuation and positive shift of the Si 2p peaks after a complete charge/discharge performed in PC- and EC:DMC-based electrolytes for both electrodes (a-Si:H and SiNW), confirming a formation of a passive film (called solid electrolyte interphase – SEI layer). As evidenced from the XPS analysis performed on the model electrode, the thicker SEI layer was formed after cycling in PC-based electrolyte as compared to EC:DMC electrolyte. XPS and ToF-SIMS investigations reveal the presence of organic carbonate species on the outer surface and inorganic salt decomposition species in the inner part of the SEI layer. Significant modification of the surface morphology for the both electrodes and a full surface coverage by the SEI layer was confirmed by the scanning electron microscopy (SEM) analysis.

Keywords: Solid electrolyte interphase layer; Lithium-ion battery; Si thin films and Si nanowires; XPS; ToF-SIMS

Reaction between NiO and Al₂O₃ in NiO/ γ-Al₂O₃ catalysts probed by positronium atom by C.Y. Li; H.J. Zhang; Z.Q. Chen (pp. 17-21).

► We studied the reaction between NiO and Al₂O₃ in NiO/ γ-Al₂O₃ catalysts using positronium atom as a new probe. ► After annealing the catalyst above 600°C, reaction between NiO and Al₂O₃ occurs, which leads to the formation of NiAl₂O₄. ► The NiAl₂O₄ resultant weakens the spin-conversion effect of positronium, which results in the abnormal increase of ortho-positronium lifetime. ► Our results show that the positronium can be used as a sensitive probe for the detection of chemical reaction occurred in catalysts.NiO/ γ-Al₂O₃ catalysts with NiO content of 9wt% and 24wt% were prepared by solid state reaction method. They are annealed in air at temperatures from 100°C to 1000°C. Positron lifetime spectra were measured to study the microstructure variation during annealing process. Four positron lifetime components were resolved with two long lifetime τ₃ and τ₄, which can be attributed to the ortho-positronium lifetime in microvoids and large pores, respectively. It was found that the longest lifetime τ₄ is rather sensitive to the chemical environment of the large pores. The NiO active centers in the catalysts cause decrease of both τ₄ and its intensity I₄, which is due to the spin-conversion of positronium induced by NiO. However, after heating the catalysts above 600°C, abnormal increase of the lifetime τ₄ is observed. This is due to the formation of NiAl₂O₄ spinel from the reaction of NiO and γ-Al₂O₃. The generated NiAl₂O₄ weakens the spin-conversion effect of positronium, thus leads to the increase of o-Ps lifetime τ₄. Formation of NiAl₂O₄ is further confirmed by both X-ray diffraction and X-ray photoelectron spectroscopy measurements.

Keywords: NiO/Al; ₂; O; ₃; Catalysts; Positronium; Reaction

Ultrasonic-assisted synthesis of core–shell structure CePO₄:Tb/GdPO₄ and GdPO₄/CePO₄:Tb nanophosphors and their photoluminescence properties by Yao-yao Fan; Zong-chao Hu; Jian Yang; Chao Zhang; Ling Zhu (pp. 22-26).

Conversion from core to shell has resulted in a profound change in photoluminescence intensity.Display Omitted► CePO₄:Tb/GdPO₄ and GdPO₄/CePO₄:Tb nanobars were obtained by ultrasonic-assisted synthesis. ► Conversion from core to shell has resulted in a profound change in photoluminescence intensity. ► [102] and [200] of CePO₄:Tb/GdPO₄ and GdPO₄/CePO₄:Tb crystals prefer to choose to grow. ► A possible mechanism of CePO₄:Tb/GdPO₄ is proposed for the highest photoluminescence intensity. ► GdPO₄ as the role of shielding effect in CePO₄:Tb/GdPO₄ can improve photoluminescence intensity.CePO₄:Tb, CePO₄:Tb/GdPO₄, GdPO₄/CePO₄:Tb and (Ce, Tb, Gd)PO₄ (4–8)nm×(35–73)nm sized nanobars with the hexagonal crystal system have been obtained by ultrasonic-assisted synthesis and characterized by X-ray diffraction (XRD), FT-IR spectrum, transmission electron microscopy (TEM), photoluminescence (PL). The shell thickness of CePO₄:Tb/GdPO₄ and GdPO₄/CePO₄:Tb core/shell structure is 1.04nm and 1.10nm respectively. Under ultraviolet excitation, these nanophosphors show Tb³⁺ characteristic emission,⁵D₄–⁷F_J ( J={6, 5, 4, 3}) and the fluorescence of CePO₄:Tb/GdPO₄ and GdPO₄/CePO₄:Tb increases superficially compared with CePO₄:Tb and the co-precipitated (Ce, Tb, Gd)PO₄. The photoluminescence intensity of CePO₄:Tb/GdPO₄ is 33 times, 7 times, 2 times as high as that of CePO4:Tb, GdPO4/CePO4:Tb and (Ce, Tb, Gd)PO₄, respectively. It is worth mentioning that the increasing amount of intensity of CePO₄:Tb/GdPO₄ is double than that of GdPO₄/CePO₄:Tb. A possible formation mechanism for the fluorescent efficiency enhancement has been proposed. The results are helpful in developing effective phosphors and have potential applications in field emission display (FED) and plasma display panels (PDP).

Keywords: Ultrasonic; Core–shell structure; Photoluminescence; Nanophosphors

Superhydrophobic surfaces by replication of micro/nano-structures fabricated by ultrafast-laser-microtexturing by Barada K. Nayak; Paul O. Caffrey; Christian R. Speck; Mool C. Gupta (pp. 27-32).

► We demonstrate a simple method of producing superhydrophobic surfaces. ► No additional coatings required to achieve CA greater than 154°. ► CA can be controlled by changing the height of the microtextures in PDMS. ► A minimum texture height of about 4.2μm is needed to enter into Cassie regime. ► Replication process is applicable to other polymeric and plastic materials.We report a simple and inexpensive method of producing superhydrophobic surfaces by directly replicating micro/nano-structures on to poly(dimethylsiloxane) (PDMS) from a replication master prepared by ultrafast-laser microtexturing process. No additional coatings on PDMS have been required to achieve contact angles greater than 154°. The contact angle can be controlled by changing the height of the microtextures in PDMS. Very low optical reflection properties of micro/nano textured surfaces combined with superhydrophobic characteristics make it an attractive encapsulating material for photovoltaics and other applications. Additionally, this replication method can be applied for large scale production of micro/nano textured superhydrophobic surfaces for commercial applications.

Keywords: Ultrafast lasers; Surface texture; Superhydrophobic surfaces; Contact angle

Preparation of polystyrene/SiO₂ microsphere via Pickering emulsion polymerization: Synergistic effect of SiO₂ concentrations and initiator sorts by Haiou Zhou; Tiejun Shi; Xun Zhou (pp. 33-38).

Polystyrene/SiO₂ microsphere with different morphology under variational Pickering emulsion polymerization conditions.Display Omitted► Polystyrene (PS)/SiO₂ microspheres with different morphology were prepared via Pickering emulsion polymerization. ► The formation mechanisms of PS/SiO₂ microspheres with different morphology were investigated. ► It was found that SiO₂ concentrations and initiator sorts would synergistically impact on the morphology of the products.In this paper, polystyrene (PS)/SiO₂ microspheres were successfully prepared via Pickering emulsion polymerization stabilized solely by ethacryloxypropyltrimethoxysilane (MPTMS) modified SiO₂ nanoparticles. The formation mechanisms of PS/SiO₂ microspheres with different morphology were investigated under various Pickering emulsion polymerization conditions. The results showed that SiO₂ concentrations and initiator sorts would synergistically impact on the morphology of products corresponding to distinct formation mechanisms. When SiO₂ concentrations was low and water-solute initiator potassium persulfate (KPS) was used, aqueous nucleation was dominant, which was deduced to the formation of dispersive microspheres sparsely anchored by SiO₂ particles. When SiO₂ concentrations was increased and oil-solute initiator azobisisobutyronitrile (AIBN) was applied, nucleation in oil phase prevailed which lead to the formation of microspheres densely packed by SiO₂ particles.

Keywords: Pickering emulsion polymerization; Polystyrene/SiO; ₂; microsphere; Morphology

Single-phase and well-dispersed Cu_1.75S nanocrystals by ambient pressure diethylene glycol solution synthesis by Xuerong Zheng; Zhengguo Jin; Hui Liu; Yueqiu Wang; Xin Wang; Haiyan Du (pp. 39-45).

► Single-phase, well-dispersed Cu_1.75S nanocrystals were synthesized by diethylene glycol based solution process. ► Influence of hydrazine, ethylenediamine additions and synthetic temperature on nanocrystals growth was investigated. ► Flaky-shaped Cu_1.75S nanocrystals with narrow size distribution were obtained at refluxing temperature 200°C and above. ► The DEG solvent phase synthesis is a green, cheap and facile route to prepare Cu_1.75S nanocrystals.Single-phase, well-dispersed Cu_1.75S nanocrystals were synthesized by an ambient pressure, hydrazine hydrate and ethylenediamine co-assisted diethylene glycol based solution chemical process using copper chloride and thioacetamide as precursors at the temperature range from 180 to 210°C. Influence of hydrazine hydrate and ethylenediamine adding amounts, synthetic temperature on crystal growth, size distribution and optical properties of the synthesized Cu_1.75S nanocrystals were investigated by XRD, TEM, HRTEM, EDX and UV–vis measurements. The synthetic reaction at above 200°C grew flaky-shaped nanocrystals with relatively narrow size distribution. The formation of single-phase Cu_1.75S nanocrystals in the diethylene glycol based solution process might be involved in the presence of intermediate [Cu(en)_n]¹⁺ and [Cu(NH₃)₄]²⁺ complexes in reaction solution, providing a stable Cu(I) and Cu(II) valent-mixed precursor.

Keywords: Cu; _1.75; S nanocrystals; Solution synthesis; Diethylene glycol solvent; Crystal growth

Characterization for N- and P-type 3C-SiC on Si (100) substrate with thermal anneal and pulsed excimer laser anneal by Kung-Yen Lee; Yu-Hao Chang; Yan-Hao Huang; Chih-Fang Huang; Cheng Yueh Chung; Feng Zhao (pp. 46-50).

► Laser pulses move damage in Al-implanted samples to the higher angles in XRD spectra. ► Laser pulses reduce damage in N-implanted samples at the same angles in XRD spectra. ► FTIR and Raman show laser irradiation creates damage on Al- and N-implanted samples. ► Damage in the reststrahlen band in Al-implanted samples is recovered by laser pulses. ► Numbers of laser shots significantly affect damage recovery in the reststrahlen band.Thermal and pulsed excimer laser treatments have been applied for the post-implant anneals of Al- and N-implanted 3C-SiC samples to recover crystal damage caused by the ion implantation. FTIR reflectivity spectra show that the thermal anneal carried out at 1350°C for 30min has the better damage recovery in a range of the reststrahlen bands of both Al- and N-implanted samples. However, shoulders in the XRD spectra caused by the implantation indicate that a thermal anneal cannot completely recover the damage throughout an entire sample. For the Al-implanted samples, laser pulses with various energy densities can move shoulders to higher 2 θ angles and then merge shoulders with the major peaks at the total energy density of 583.7J/cm². 150 shots of laser pulses at the energy density of 256mJ/cm² and combining with other energy densities can be used to recover damage in a range of the reststrahlen band which is induced by laser irradiation. Furthermore, the damage caused by the implantation in N-implanted samples is not close to the major peak in the XRD spectra, which can be improved by the laser pulses as well, but not moved to higher 2 θ angles. However, the applied energy densities create extra damage in a range of the reststrahlen band.

Keywords: 3C-SiC; FTIR; XRD; Raman; Pulsed excimer laser; Anneal

Improving hydrophobicity of laser textured SiC surface with micro-square convexes by Chunhong Ma; Shaoxian Bai; Xudong Peng; Yonggang Meng (pp. 51-56).

.Display Omitted► The aim was to control water condensation on silicon carbide (SiC) seal surfaces. ► The testing substrate material was reaction bonded SiC. ► The SiC surface was laser textured with micro-square-convexes. ► The wetting behavior changed from hydrophilic to hydrophobic after laser surface texturing. ► The contact angle increased from 89.8° to 119°.In this paper, wetting behavior of laser micro-square-convexed silicon carbid (SiC) surfaces was studied, so as to achieve laser processed texture to improve hydrophobicity effectively. Micro-square textures of different roughness were fabricated by fiber optic laser. Then static angles and contact angles evolution over time were measured with a video contact angle analyzer. The results show that micro-square convex effectively changed wetting behavior of SiC surface, and the surfaces translated from hydrophilic to hydrophobic after laser processing. Hydrophobicity property increased with increase of surface roughness. The contact angle increased from 100.2° to 119° with increasing roughness from 1μm to 3μm, comparing to the untextured smooth surface of 89.8°. It may be expected to use the laser micro-protuberant structure to control the condensation of water droplets on the SiC surfaces.

Keywords: Laser surface texturing; Silicon carbide; Wettability; Contact angle

The biocompatibility of hydroxyapatite film deposition on micro-arc oxidation Ti6Al4V alloy by Rui Luo; Zhongde Liu; Feixiang Yan; Yang Kong; Yingtao Zhang (pp. 57-61).

We designed HA film by micro-arc oxidation and hydrothermal synthesis. The biocompatibility of three specimens was tested using anti-hematolysis tests, anti-coagulation tests, anti-platelet adhesion and cytotoxicity tests. Results show that hydrothermal synthesis treated samples have the better blood biocompatibility and histocompatibility than Ti6Al4V substrate alloy and micro-arc oxidation treated alloy.Display Omitted► The bioactive ceramic film was prepared by micro-arc oxidation (MAO) and hydrothermal synthesis (HS). ► Anti-hematolysis, anti-coagulation, anti-platelet adhesion and cytotoxicity tests were all used to test the biocompatibility of specimens. ► The hematolysis rate of hydroxyapatite (HA) film is only 0.994%, which cannot lead to acute hematolysis action. ► The HA modified layer shows toxicity grade 0 that means it cannot induce the cytotoxic effect.Among the titanium alloys employed as implant materials, the Ti6Al4V alloy is still widely used. Micro-arc oxidation (MAO) was used to prepare ceramic oxide layer containing calcium and phosphor on surface of Ti6Al4V alloy and then the specimens were hydrothermal synthesis (HS) treated, and then a thin hydroxyapatite ((Ca₁₀(PO₄)₆(OH)₂, HA) film was deposited on the surface. The biocompatibility of Ti6Al4V alloy, MAO alloy and sample treated by hydrothermal synthesis were evaluated. The biocompatibility of three specimens was tested using anti-hematolysis tests, anti-coagulation tests, anti-platelet adhesion and cytotoxicity tests. Specimens coated with HA film exhibited significant improved anti-hemolytic reaction, and the hematolysis ratio was 0.994% (less than 5%), which indicated that this type of samples could not induce acute hematolysis. And coagulation did not occur within 50min on the HA layer. There was almost no platelet adhered on the surface. The toxicity was ranked as 0 grades which indicated that it could not induce the cytotoxic effect. This demonstrates that the HA film can significantly improve the biocompatibility properties.

Keywords: Titanium alloy; Hydroxyapatite film; Biocompatibility

Substrate surface effect on the structure of cubic BN thin films from synchrotron-based X-ray diffraction and reflection by X.M. Zhang; W. Wen; X.L. Li; Q. He; X.T. Zhou (pp. 62-66).

► BN films with different substrate roughness were analyzed by synchrotron X-rays. ► More cBN phase formed near the surface than substrate in the as-deposited film. ► With substrate roughness increase, more hBN phase formed in the film. ► Synchrotron-based GI-XRD and XRR are powerful tools for characterizing BN films.Cubic BN (cBN) thin films prepared by mass-selected ion beam deposition technique (MSIBD) on Si substrates with different surface roughness were studied by synchrotron-based grazing incidence X-ray diffraction (GI-XRD) and X-ray reflectivity (XRR) measurements. The BN films are mostly composed of two phases. One is cBN phase, the other is hexagonal BN (hBN) phase. The cubic phase content of the thin films is dependent on the roughness of their corresponding substrates. The smooth substrate surface is helpful for the nucleation of the cBN phase. cBN phase is mostly grown in the near surface region of the films and there is a hBN interlayer at the film–substrate interface. GIXRD and XRR are proved to be powerful tools for analyzing the structure of the cBN thin films.

Keywords: BN film; Synchrotron; Grazing incidence X-ray diffraction (GI-XRD); X-ray reflectivity (XRR)

Antibacterial action of silver-doped activated carbon prepared by vacuum impregnation by Ying Zhao; Zi-qiang Wang; Xin Zhao; Wei Li; Shou-xin Liu (pp. 67-72).

► The Silver-containing activated carbon (Ag/AC) exhibits control release of silver and long-term high antibacterial action. ► The inhibition of growth to antibacterial activity because of the higher silver content and smaller size of the silver particles. ► The Ag/AC composites showed a lower release rate of silver because a strong interaction between the silver particles and carbon. ► It shows promise for purification of drinking water.Silver-containing activated carbon (Ag/AC) exhibiting controlled release of silver and antibacterial action was prepared by vacuum impregnation using acetate silver as a precursor. The antibacterial activity toward E. coli and resistance to water erosion were investigated with the view of water purification. N₂ adsorption at 77K, scanning electron microscopy and X-ray diffraction were used to characterize the surface morphology and crystalline properties of the Ag/AC samples. As the concentration of CH₃COOAg increased, the samples change from exhibiting no antibacterial activity to inhibition of bacteria growth and then to antibacterial activity because of the higher silver content and smaller size of the silver particles. The Ag/AC composites showed a lower release rate of silver than that of a composite prepared by a traditional AgNO₃ impregnation method, which suggests a strong interaction between the silver particles and carbon. Because the Ag particles block the pores of AC, the BET surface area, total pore volume and average pore diameter of the Ag/AC samples decreased as the concentration of the CH₃COOAg solution increased. The higher antibacterial activity and controlled release of silver by Ag/AC containing 1.65wt % silver means that it shows promise for purification of drinking water.

Keywords: Vacuum impregnation; Activated carbon; Silver; Antibacterial; Controlled release

Microscopic observations of osteoblast growth on micro-arc oxidized β titanium by Hsien-Te Chen; Chi-Jen Chung; Tsai-Ching Yang; Chin-Hsin Tang; Ju-Liang He (pp. 73-80).

► Anatase-rich TiO₂ and rutile-rich TiO₂ coatings were successfully grown on β-Ti alloy. ► Rutile-rich TiO₂ coatings achieved an enhanced in vitro biocompatibility. ► The osteoblast and TiO₂ interaction is fully explored in this study. ► Osteoblast grows into MAO-TiO₂ structure and no micro-gap found on rutile-rich TiO₂. ► MAO can be a novel surface-modification method on β-Ti alloy for medical implants.Titanium alloys are widely used in orthopedic and dental implants, owing to their excellent physical properties and biocompatibility. By using the micro-arc oxidation (MAO), we generated anatase-rich (A-TiO₂) and rutile-rich (R-TiO₂) titanium dioxide coatings, individually on β-Ti alloy, in which the latter achieved an enhanced in vitro and in vivo performance. Thoroughly elucidating how the osteoblasts interact with TiO₂ coatings is of worthwhile interest. This study adopts the focused ion beam (FIB) to section off the TiO₂ coated samples for further scanning electron microscope (SEM) and transmission electron microscope (TEM) observation. The detailed crystal structures of the TiO₂ coated specimens are also characterized. Experimental results indicate osteoblasts adhered more tenaciously and grew conformably with more lamellipodia extent on the R-TiO₂ specimen than on the A-TiO₂ and raw β-Ti specimens. FIB/SEM cross-sectional images of the cell/TiO₂ interface revealed micro gaps between the cell membrane and contact surface of A-TiO₂ specimen, while it was not found on the R-TiO₂ specimen. Additionally, the number of adhered and proliferated cells on the R-TiO₂ specimen was visually greater than the others. Closely examining EDS line scans and elemental mappings of the FIB/TEM cross-sectional images of the cell/TiO₂ interface reveals both the cell body and interior space of the TiO₂ coating contain nitrogen and sulfur (the biological elements in cell). This finding supports the assumption that osteoblast can grow into the porous structure of TiO₂ coatings and demonstrating that the R-TiO₂ coating formed by MAO serves the best for β-Ti alloys as orthopedic and dental implants.

Keywords: Micro-arc oxidation (MAO); Titanium dioxide (TiO; ₂; ); Focus ion beam (FIB); Osteoblast; Microscopic observation

Construct Scaffold-like delivery system with poly (lactic-co-glycolic) microspheres on micro-arc oxidation titanium by Lin Wang; Huade Zheng; Chang Du; Zhifeng Shi; Li Ren; Yingjun Wang (pp. 81-88).

► A scaffold-like delivery system with poly (lactic-co-glycolic) (PLGA) microspheres was prepared on MAO-Ti surface. ► This system could be stable on the porous MAO-Ti surface up for 6 weeks. ► In this system, not only the PLGA microspheres could control the release of BSA, but also the MAO-Ti could regulate the pH value during degradation. ► This system could improve the proliferation of HBMSCs.In this paper, we present the first report about constructing a scaffold-like delivery system with poly (lactic-co-glycolic) (PLGA) microspheres on micro-arc oxidation titanium (MAO-Ti). The results show that this system could be stable on the porous MAO-Ti surface up for 6 weeks. Not only the system could control the release of model protein BSA, but also the MAO film could regulate the pH value of the solution which would decrease by the degradation of PLGA microspheres. In addition, compared to MAO-Ti, this system loaded with BSA could improve the proliferation of HBMSCs after 3 or 7 days culture.

Keywords: Micro-arc oxidation; Titanium; Poly (lactide-co-glycolide); Controlled release

Improvement in electrical characteristics of HfO₂ gate dielectrics treated by remote NH₃ plasma by Li-Tien Huang; Ming-Lun Chang; Jhih-Jie Huang; Hsin-Chih Lin; Chin-Lung Kuo; Min-Hung Lee; Chee Wee Liu; Miin-Jang Chen (pp. 89-93).

► We report the structural and electrical characteristics of nitrided hafnium oxide (HfO₂) gate dielectrics. ► The nitridation process was conducted in the remote NH₃ plasma at a low temperature under various radio-frequency powers. ► Significant decrease in the capacitance equivalent thickness, leakage current density, and interfacial layer thickness of the nitrided HfO₂ gate dielectrics were achieved. ► The enhancement and decrease of the photoluminescence intensity from Si was also observed as a result of the hydrogen passivation and depassivation effects at the HfO₂/Si interface.We report the structural and electrical characteristics of hafnium oxide (HfO₂) gate dielectrics treated by remote NH₃ plasma under various radio-frequency (RF) powers at a low temperature. Significant increase of effective dielectric constant ( k_eff), decrease of capacitance equivalent thickness (CET), reduction in leakage current density, and suppression of the interfacial layer thickness were observed with the increase of the RF power in the remote NH₃ plasma treatment. The effects of hydrogen passivation and depassivation on the HfO₂/Si interface due to the remote NH₃ plasma treatment were also observed by the variation of photoluminescence (PL) intensity, indicating that the PL measurement is applicable to probe the interfacial properties. An ultrathin interfacial layer (∼0.3nm), a high k_eff, (20.9), a low leakage current density (9×10⁻⁶A/cm²), and a low CET (1.9nm) in the nitrided HfO₂ film were achieved, demonstrating that the nitridation process using remote NH₃ plasma under a high RF power at a low temperature is a promising way to improve in electrical properties of high-K gate dielectrics.

Keywords: Hafnium oxide; Atomic layer deposition; Nitridation; NH; ₃; Remote plasma

Preparation of aqueous dispersion of thermoplastic sizing agent for carbon fiber by emulsion/solvent evaporation by Isabelle Giraud; Sophie Franceschi-Messant; Emile Perez; Colette Lacabanne; Eric Dantras (pp. 94-99).

Display Omitted► Aqueous dispersions of PEI were prepared as sizing agent by emulsion/solvent evaporation. ► PEI particles stabilized by SDS as surfactant led to stable dispersions. ► SEM observations of PEI sized carbon fiber PEEK composites showed a continuous interface.In this work, different sizing agent aqueous dispersions based on polyetherimide (PEI) were elaborated in order to improve the interface between carbon fibers and a thermoplastic matrix (PEEK). The dispersions were obtained by the emulsion/solvent evaporation technique. To optimize the stability and the film formation on the fibers, two surfactants were tested at different concentrations, with different concentrations of PEI. The dispersions obtained were characterized by dynamic light scattering (DLS) and the stability evaluated by analytical centrifugation (LUMiFuge). The selected dispersions were tested for film formation ability by scanning electron microscopy (SEM), and the sizing performance was assessed by observation of the fiber/matrix interface by SEM. The results revealed that an aqueous dispersion of PEI, stabilized by sodium dodecyl sulfate as the surfactant, led to very stable sizing agent aqueous dispersion with ideal film formation and better interface adhesion.

Keywords: Sizing; Carbon fibers; Composites; Thermoplastic polymer; Aqueous dispersion; Emulsion/solvent evaporation

Structural and magnetic properties of annealed FePt/Ag/FePt thin films by O.P. Pavlova; T.I. Verbitska; I.A. Vladymyrskyi; S.I. Sidorenko; G.L. Katona; D.L. Beke; G. Beddies; M. Albrecht; I.M. Makogon (pp. 100-104).

► Layered stacks FePt(15nm)/Ag( x)/FePt(15nm) ( x=0, 3, 30nm) were prepared by magnetron sputtering onto thermally oxidized monocrystalline Si substrate. ► Heat treatment was carried out in high vacuum in temperature range of 100–900°C. ► Characterization of the films was conducted by means of XRD, AFM, SNMS, SQUID. ► Introducing of Ag intermediate layer improves the L1₀ phase formation kinetic. ► We report transition from chemically disordered A1 phase to chemically ordered L1₀ phase in FePt thin films.Layer stacks of FePt(15nm)/Ag( x)/FePt(15nm) with various Ag interlayer thicknesses ( x=0, 3, and 30nm) were deposited at room temperature onto SiO₂(100nm)/Si(001) substrates. These films were post-annealed in a temperature range of 100°C–900°C for 30s under high vacuum condition. The influence of the Ag interlayer on the L1₀(FePt)_FCT phase formation and its related structural and magnetic properties were investigated. The onset of chemical ordering of FePt single layers is observed at annealing temperatures between 600°C and 700°C. Increasing the Ag interlayer thickness to 30nm reduces the ordering temperature of the L1₀(FePt)_FCT phase formation by about ∼100°C. Higher annealing temperatures lead to a further increase in volume fraction of the ordered L1₀(FePt)_FCT phase but also to the diffusion of Ag towards the free surface as probed by secondary neutral mass spectrometry. In addition, due to the limited solvability of Ag into the FePt phase, Ag is expected to be located at the grain boundaries.The increasing volume fraction of the L1₀(FePt)_FCT phase is also reflected in the increasing coercivity of the films which reaches values of up to ∼19kOe after annealing at 900°C. Furthermore, in this case similar M-H hysteresis loop were recorded when the field is applied in the film plane and perpendicular to it. This isotropic behavior is in agreement with the coexistence of L1₀ ordered grains which are randomly oriented.

Keywords: L; 1; ₀; FePt; Chemical ordering; Secondary neutral mass spectrometry; Magnetic coercivity

A simple approach to fabricate stable superhydrophobic glass surfaces by Haiyan Ji; Gang Chen; Jin Yang; Jie Hu; Haojie Song; Yutao Zhao (pp. 105-109).

► Superhydrophobic glass surfaces were fabricated by a simple method. ► Hierarchical structure with nanorods and pores was constructed on the glass surface. ► The superhydrophobicity is stable under different pH values and storage time. ► This facile method may have extensive applications in self-cleaning glass.We present a facile method to fabricate superhydrophobic glass surface via one-step hydrothermal method and chemical modification. The etched glass surface shows the hierarchical textured morphology as well as the multiple scales of roughness and large numbers of nanorods and pores. The formation mechanism of the hierarchically structured surface is discussed in detail. After surface modification with vinyltriethoxysilane, the glass surface exhibits stable superhydrophobicity with a high contact angle of 155° and a low sliding angle of 5°. A water droplet of 10μL can bounce away from the surface when it vertically hit the superhydrophobic glass surface. Moreover, the contact angle of the superhydrophobic glass surface under different pH values and storage time are measured to study the stability of the superhydrophobic property.

Keywords: Superhydrophobic; Glass; Stable; Contact angle

Effect of thermoplastic coating on interfacial adhesion of oxygen-plasma-pretreated PBO/PPESK composites by Xiangyi Zhang; Ping Chen; Debin Han; Qi Yu; Zhenfeng Ding; Xiuling Zhu (pp. 110-117).

Display Omitted► Two thermoplastic resins were coated to improve the adhesion of PBO and PPESK. ► The coatings were chemically bonded and physically absorbed onto the fiber. ► The ILSS increased with an 80.8% increment after coating. ► The enhancement of the interfacial was caused mainly by molecular entanglement.To improve the interfacial adhesion of PBO/PPESK composite, thermoplastic resins were coated onto the fiber surface after plasma pretreatment. Two coating resins applied in this study were chemically linked with the plasma pretreated fibers, which was confirmed by X-ray photoelectron spectroscopy. The fiber surface morphologies and wettability were analyzed by scanning electron microscope (SEM) and dynamic contact angle analysis, respectively. The interfacial adhesion performance of the PBO fiber-reinforced PPESK composite was measured by interlaminar shear strength (ILSS) and water absorption tests. Fracture mechanisms of the composites were examined by SEM. The results indicated that after coating the surface wettability was improved and the ILSS had an increment of 80.8% for phenolphthalein poly (ether ketone) coating and 30.3% for phenolphthalein poly (ether sulfone) coating.

Keywords: PBO fiber; Surface treatment; Plasma-induced coating; XPS; SEM

Surface modification of oil fly ash and its application in selective capturing of carbon dioxide by Ali L. Yaumi; Ibnelwaleed A. Hussien; Reyad A. Shawabkeh (pp. 118-125).

Display Omitted► A large surface area of activated ash with well-defined particle sizes and porous structure was obtained from waste oil fly ash. ► This activated ash provided high adsorption capacity for carbon dioxide compared to conventional adsorbents. ► Removal of CO₂ by the treated ash is an endothermic process which can be used at high temperatures.Oil fly ash from power generation plants was activated with 30% NH₄OH and used for selective adsorption of carbon dioxide from CO₂/N₂ mixture. The treated samples were characterized for their surface area, morphology, crystalline phase, chemical composition and surface functional groups. Energy dispersive X-ray analysis showed an increase in the carbon contents from 45 to 73wt% as a result of leaching out metal oxides. XRD proved that chemical activation of ash resulted in diminishing of major crystalline phases of zeolite, and other alumino-silicates leaving only quartz and mullite. BET analysis showed an increase in surface area from 59 to 318m²/g after chemical activation and the pore volume increased from 0.0368 to 0.679cm³/g. This increase in pore volume is supported by the results of SEM, where more micropores were opened with well-defined particle sizes and porous structure. The TGA of the treated fly ash showed stability at higher temperature as the weight loss decreased with increasing temperature. For treated ash, the FTIR displayed new peaks of amine functional group. The treated ash was used for the removal of CO₂ from CO₂/N₂ mixture and the maximum adsorption/capturing capacity was found to be 240mg/g. This capacity increases with increase in initial gas concentration, inlet flow rate and temperature suggesting the endothermic nature of the interaction between the gas molecules and the surface of the ash.

Keywords: Fly ash; Adsorption; Carbon dioxide; Chemical treatment; CO; ₂; capturing

Fabrication of TiO₂ film with different morphologies on Ni anode and application in photoassisted water electrolysis by Hongbo He; Aiping Chen; Hui Lv; Haijun Dong; Ming Chang; Chunzhong Li (pp. 126-131).

.Display Omitted► The anode of an alkaline electrolytic cell for water electrolysis was modified by TiO₂ photocatalysts with different morphologies. ► The WEAP was based on the traditional water electrolysis; Ni and Ni-Cr alloy were anode and cathode, respectively. ► The H₂-production rate in WEAP with the anode modified by ordered TiO₂ nanotube arrays increased by 139%.The anode of an alkaline electrolytic cell for water electrolysis was modified by TiO₂ photocatalysts with different morphologies. The water electrolysis was coupled with photocatalytic decomposition of water by irradiation of UV light on the modified anode. And a feasible process for the hydrogen production of water electrolysis assisted by photocatalysis (WEAP) was proposed and experimentally confirmed. The results show that the highly ordered, vertically oriented tubular arrays structure on Ni anode surface has better hydrogen production performance than random TiO₂. In WEAP process, the maximum rate of hydrogen production is 2.77ml/(h*cm²) when the anode modified by ordered TiO₂ nanotube arrays, compared to traditional alkaline electrolytic cell for water electrolysis with Ni anode, H₂-production rate increased by 139%.

Keywords: Morphology of TiO; ₂; film; Water electrolysis; Photocatalysis; Hydrogen

Controllable atomic layer deposition of one-dimensional nanotubular TiO₂ by Xiangbo Meng; Mohammad Norouzi Banis; Dongsheng Geng; Xifei Li; Yong Zhang; Ruying Li; Hakima Abou-Rachid; Xueliang Sun (pp. 132-140).

► One-dimensional TiO₂ nanotubes were synthesized by atomic layer deposition (ALD). ► Two substrates were used in ALD-TiO₂, anodic aluminum oxide (AAO) and carbon nanotubes (CNTs). ► The two routes resulted in pure TiO₂ nanotube arrays and coaxial TiO₂-CNT nanotubes, respectively. ► The TiO₂ nanotubes could be tuned from amorphous to crystalline phase in the range 150–250°C. ► The TiO₂ nanotubes could also be controlled on their wall thickness.This study aimed at synthesizing one-dimensional (1D) nanostructures of TiO₂ using atomic layer deposition (ALD) on anodic aluminum oxide (AAO) templates and carbon nanotubes (CNTs). The precursors used are titanium tetraisopropoxide (TTIP, Ti(OCH(CH₃)₂)₄) and deionized water. It was found that the morphologies and structural phases of as-deposited TiO₂ are controllable through adjusting cycling numbers of ALD and growth temperatures. Commonly, a low temperature (150°C) produced amorphous TiO₂ while a high temperature (250°C) led to crystalline anatase TiO₂ on both AAO and CNTs. In addition, it was revealed that the deposition of TiO₂ is also subject to the influences of the applied substrates. The work well demonstrated that ALD is a precise route to synthesize 1D nanostructures of TiO₂. The resultant nanostructured TiO₂ can be important candidates in many applications, such as water splitting, solar cells, lithium-ion batteries, and gas sensors.

Keywords: Atomic layer deposition; Titanium oxide; Nanotubes; Anodic aluminum oxide; Carbon nanotubes

Hydrophilicity, photocatalytic activity and stability of tetraethyl orthosilicate modified TiO₂ film on glazed ceramic surface by Peng Zhang; Jie Tian; Ruifen Xu; Guojun Ma (pp. 141-147).

► P25-TiO₂/TEOS film was prepared onto glazed ceramic surface by a simple method. ► The hydrophilicity and photocatalytic activity were studied under visible light. ► P25-TiO₂/TEOS film shows higher photocatalytic activity and good stability.A new, simple, and low-cost method has been developed to enhance the surface properties of TiO₂ film. Degussa P25-TiO₂ nanoparticles were modified by tetraethyl orthosilicate (TEOS) on glazed ceramic tiles. Effects of tetraethyl orthosilicate modification on microstructure, crystal structure, hydrophilicity, photocatalytic activity and stability of the film were investigated. The obtained results showed that P25-TiO₂/TEOS particles exhibited better dispersion, higher surface area, bigger surface roughness and smaller particle size comparing to pure P25-TiO₂ particles, which resulted in better hydrophilicity after 10 days in a dark place and higher photocatalytic activity under visible light irradiation. 68% of Rhodamine B was degraded by P25-TiO₂/TEOS film in 25h with the light intensity of 5000±500lx, and degradation rate reached to 82% with the light intensity of 10,000±1000lx. Furthermore, two fundamentally different systems, in which the films recycle for repetitive degradation after soaked in dye solution and for discoloration after depositing dye on the surfaces, respectively, were measured to confirm that P25-TiO₂/TEOS film showed excellently stable performances. Therefore the P25-TiO₂/TEOS film we obtained has good washing resistance and would be a promising candidate for practical applications.

Keywords: P25-TiO; ₂; Tetraethyl orthosilicate; Hydrophilicity; Photocatalytic activity; Stability; Ceramic

Fe₂O₃ particles enwrapped by graphene with excellent cyclability and rate capability as anode materials for lithium ion batteries by Wei Xiao; Zhixing Wang; Huajun Guo; Xinhai Li; Jiexi Wang; Silin Huang; Lei Gan (pp. 148-154).

A facile hydrothermal method is employed to prepare Fe₂O₃/graphene composites with different contents of graphene which is determined by thermogravimetric analysis(TG). While the X-ray diffraction (XRD) indicates the presence of hematite, the graphene and Fe₂O₃ are demonstrated to be existed via Fourier transform infrared spectra (FI-IR) and Raman spectroscopic analysis. Furthermore, the scanning electron microscopy (SEM) and transmission electron microscope (TEM) also illustrate the good combination of graphene and Fe₂O₃, especially for the composite with graphene mass content of 30%. After performed as anode for lithium ion battery, Fe₂O₃/graphene composite with graphene mass content of 30% exhibits outstanding cyclability with highly reversible charge capacity of 1069mAhg⁻¹ after 50 cycles, at current density of 50mAg⁻¹. And when the current density is increased to 1000mAg⁻¹, it could still retain charge capacity of 534mAhg⁻¹. Meanwhile, the critical role of graphene to the electrochemical performance of composites has also been proven.Display Omitted► A simple PVP-assisted hydrothermal method was employed to prepare Fe₂O₃/graphene composites. ► Fe₂O₃ particles are uniformly enwrapped by graphene. ► Excellent electrochemical performances of composites could be attributable to synergic effects between Fe₂O₃ and graphene. ► The effects of graphene on electrochemical properties of composites have been investigated.A facile hydrothermal method is employed to prepare Fe₂O₃/graphene composites with different contents of graphene which is determined by thermogravimetric analysis (TG). While the X-ray diffraction (XRD) indicates the presence of hematite, the graphene and Fe₂O₃ are demonstrated to be existed via Fourier transform infrared spectra (FI-IR) and Raman spectroscopic analysis. Furthermore, the scanning electron microscopy (SEM) and transmission electron microscope (TEM) also illustrate the good combination of graphene and Fe₂O₃, especially for the composite with graphene mass content of 30%. After performed as anode for lithium ion battery, Fe₂O₃/graphene composite with graphene mass content of 30% exhibits outstanding cyclability with highly reversible charge capacity of 1069mAhg⁻¹ after 50 cycles, at current density of 50mAg⁻¹. And when the current density is increased to 1000mAg⁻¹, it could still retain charge capacity of 534mAhg⁻¹. Meanwhile, the critical role of graphene to the electrochemical performance of composites has also been proven.

Keywords: Lithium ion batteries; Anode; Hematite; Graphene; Hydrothermal method

Preparation of amino-functionalized silica in aqueous conditions by Fabrice Cuoq; Armand Masion; Jérôme Labille; Jérôme Rose; Fabio Ziarelli; Benedicte Prelot; Jean-Yves Bottero (pp. 155-160).

► Grafting of silane in water is as efficient as grafting in toluene after rinsing. ► A partial mono-layer system is reached with water grafting. ► A 3D network system is reached with toluene grafting before rinsing. ► Reactivity of amino-groups of grafted silane was easily proved with salicylaldehyde.Silica particle surfaces were modified with 3-aminopropyltriethoxysilane (APTES) for the fabrication under mild conditions of amino-functionalized silica particles which can be applied in a number of processes, e.g. chromatography. Surface activation was carried out in water at natural pH and in toluene on non-preheated silica in order to compare the grafting efficiency in these two solvents. No successive thermal treatments were carried out after grafting. Grafting extents were then calculated using solid state TOC measurements. Grafting extents of APTES in water and anhydrous solvent were surprisingly found to be the same after a simple rinsing step (i.e. 2.10±0.09μmol/m²). Thus, in our case, the use of anhydrous solvent is an unnecessary precaution if the silica is further used in water since equivalent grafting extents of APTES are obtained with a simple and eco-friendly grafting process.

Keywords: Abbreviations; APTES; 3-aminopropyltriethoxysilane; SA; salicylaldehyde; U360; Ultrasil 360Water; APTES; Anhydrous; Silica; Functionalization; Grafting

Nanostructured Ag₄O₄ thin films produced by ion beam oxidation of silver by D. Dellasega; C.S. Casari; F. Vario; C. Conti; C.E. Bottani; A. Li Bassi (pp. 161-169).

► Nanostructured Ag films are irradiated by oxygen ion beams with kinetic energy in the range 50–300eV. ► Nanostructured Ag₄O₄ layers are obtained. ► Morphology and crystalline phase of the oxide depend on ion energy and Ag film morphology. ► Tetragonal and monoclinic Ag₄O₄ crystalline structures are obtained. ► Oxidation with atomic oxygen leads to the formation of peculiar Ag₄O₄ lamellar nanostructures.We report on the synthesis of nanostructured Ag₄O₄ by thermal evaporation of silver films followed by oxidation with beams of oxygen ions with different kinetic energy in the 50–300eV range. This method, which combines simplicity and versatility, allows to control the oxide structural properties, and in particular to obtain Ag₄O₄ thin films characterized by different nanoscale morphologies and crystalline structure, depending on the pristine silver layer morphology and on the energy of the oxygen ions. Monoclinic and tetragonal Ag₄O₄ phases, or a mixture of the two, can be obtained. The nanoscale porosity of the material makes it interesting for applications where surface mediated Ag ion release plays a crucial role.

Keywords: Thin films; Silver oxide; Tetragonal phase; Oxygen ions

Titanium interlayer to improve the adhesion of multilayer amorphous boron carbide coating on silicon substrate by E. Vassallo; R. Caniello; A. Cremona; D. Dellasega; E. Miorin (pp. 170-175).

► Boron-based coatings can be very useful in neutrons detection application. ► B-based coatings with a multilayer structure do not present stress phenomena. ► Ti interlayer decreases the internal stress at the substrate–film interface, thus smoothing the difference in lattice parameters between the growing film and substrate.Boron-based coatings can be very useful in neutrons detection application. Here, stable boron carbon (B-C) films in nanometer scale were deposited on silicon substrates with titanium interlayer by RF plasma magnetron sputtering. Ti interlayer is likely to decrease the internal stress at the substrate–film interface, thus smoothing the difference in lattice parameters between the growing film and substrate. The B-C/Ti/Si coatings were characterized using SEM, EDS, AFM and XRD. The enhancement in adhesion of the B-C film to the substrate was analyzed by a scratch tester measurements.

Keywords: Boron carbide; Titanium interlayer; Plasma sputtering; Plasma chemical vapor deposition; Internal stress; Roughness

Cell viability and adhesion on diamond-like carbon films containing titanium dioxide nanoparticles by C.C. Wachesk; C.A.F. Pires; B.C. Ramos; V.J. Trava-Airoldi; A.O. Lobo; C. Pacheco-Soares; F.R. Marciano; N.S. Da-Silva (pp. 176-181).

► The increasing concentration of TiO₂ nanoparticles in DLC films enhanced the mitochondrial activity on these samples. ► The pseudoconfluent layer of elongated and adherent cells demonstrated very good adhesion on the coatings. ► The increasing concentration of TiO₂ decreases the LDH activity on these samples and shown the integrity of plasma membrane. ► A high cell attachment was obtained on TiO₂-DLC (0.5g/L).The combination of low friction, wear resistance, high hardness, biocompatibility and chemical inertness makes diamond-like carbon (DLC) films suitable in a numerous applications in biomedical engineering. The cell viability and adhesion of L929 mouse fibroblasts was investigated using two different colorimetric assays: (i) 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT), and (ii) lactate dehydrogenase (LDH). The films were growth on 316L stainless steel substrates using plasma enhanced chemical vapor deposition technique from a dispersion of TiO₂ nanopowder in hexane. The increasing concentration of TiO₂ nanoparticles in DLC films enhanced the mitochondrial activity and decreases the LDH activity on these samples. Fluorescence and scanning electron microscopy corroborate the results. These experiments show the potential use of DLC and TiO₂-DLC films in biomedical applications.

Keywords: Diamond-like carbon; TiO; ₂; nanoparticles; Cell viability; Fibroblasts

DFT study on the functionalization of a BN nanotube with sulfamide by Javad Beheshtian; Ali Ahmadi Peyghan; Mohammad Bigdeli Tabar; Zargham Bagheri (pp. 182-187).

► A BN nanotube functionalization with sulfamide is investigated using DFT. ► Electronic properties of the tube are slightly changed upon the functionalization. ► The work function is slightly decreased, facilitating the field electron emission. ► Functionalization with sulfamide may be a way for purification of BN nanotubes.Surface modification of a boron nitride nanotube (BNNT) with sulfamide molecule has been investigated in terms of its energetic, geometric, and electronic properties using B3LYP and PBE density functionals. The sulfamide molecule can be physically adsorbed on the tube surface or chemically diffuse into its wall, accompanied by the release of one NH₃ molecule. Calculated density of states show that the electronic properties of the BNNT are slightly changed upon the chemical modification. Accordingly, HOMO–LUMO energy gap of the tube is changed by about −4.8 to +10.5%, predicted using the B3LYP functional with 6-31G (d) basis set. Moreover, the work function is slightly decreased which may facilitate the field electron emission from the BNNT surface. Preservation of the electronic properties of the BNNT coupled with the enhanced solubility suggests that chemical modification of the BNNTs with sulfamide may be an effective way for their purification.

Keywords: Chemical functionalization; DFT; Nanostructure; B3LYP; Adsorption; Surface

Synthesis of silver nanoparticles on reduced graphene oxide under microwave irradiation with starch as an ideal reductant and stabilizer by Yujie Han; Zhimin Luo; Lihui Yuwen; Jing Tian; Xingrong Zhu; Lianhui Wang (pp. 188-193).

► A facile microwave method for synthesizing RGO/Ag NPs was developed. ► Starch as an ideal reductant and stabilizer is environmentally friendly. ► Ag⁺ and graphene oxide were reduced simultaneously assisted by microwave. ► RGO/Ag NPs shows higher antibacterial activity against Pseudomonous aeruginosa.A facile aqueous solution procedure has been developed to synthesize silver nanoparticles (Ag NPs) on reduced graphene oxide (RGO) (RGO/Ag NPs) with starch as an ideal reductant and stabilizer in one pot under microwave irradiation. Graphene oxide and Ag(NH₃)₂⁺ were reduced simultaneously by starch in the process of forming Ag NPs. The size of Ag NPs decorated on the RGO sheets is about 20–50nm and the average size of Ag NPs on RGO is 34nm calculated by X-ray diffraction. RGO and RGO/Ag NPs prepared with starch show good stability in aqueous solution. With the decoration of Ag NPs on RGO, Raman intensity of RGO increased evidently. Antimicrobial activity of RGO/Ag NPs was investigated against the gram negative bacteria Pseudomonous aeruginosa. The minimum inhibitory concentration (MIC) of RGO/Ag NPs is 0.2wt%. The antimicrobial activity of RGO/Ag NPs is stronger than Ag NPs because of the synergic effect of RGO and Ag NPs.

Keywords: Reduced graphene oxide; Silver nanoparticles; Starch; Antimicrobial

Room temperature radio-frequency plasma-enhanced pulsed laser deposition of ZnO thin films by S.-H. Huang; Y.-C. Chou; C.-M. Chou; V.K.S. Hsiao (pp. 194-198).

► ZnO thin film was deposited by RF. plasma-enhanced pulsed laser deposition. ► The depositions were performed at room temperature under low-vacuum conditions. ► The oxygen pressure reduced defects effectively and increased the deposition rate.In this study, we compared the crystalline structures, optical properties, and surface morphologies of ZnO thin films deposited on silicon and glass substrates by conventional pulsed laser deposition (PLD) and radio-frequency (RF) plasma-enhanced PLD (RF-PEPLD). The depositions were performed at room temperature under 30–100mTorr pressure conditions. The RF-PEPLD process was found to have deposited a ZnO structure with preferred (002) c-axis orientation at a higher deposition rate; however, the RF-PEPLD process generated more defects in the thin films. The application of oxygen pressure to the RF-PEPLD process reduced defects effectively and also increased the deposition rate.

Keywords: Pulsed laser deposition; Radio frequency plasma; Zinc oxide; Thin film

Effect of strontium ions on the early formation of biomimetic apatite on single crystalline rutile by Carl Lindahl; Håkan Engqvist; Wei Xia (pp. 199-204).

► Sr ion influences the early apatite formation. ► Adsorption rate of ions on different crystal faces is different. ► Adsorption of Sr ion on the surfaces was almost as fast as the adsorption of Ca ion.Single crystalline rutile is a good model to investigate the growth mechanism of hydroxyapatite on bioactive Ti surfaces. Previous studies have shown the difference on different crystalline rutile faces in the early stage and during the growth of HAp crystals from simulated body fluids. It is known that the biological apatite crystal is an ion-substituted apatite. Ion substitution will influence the HAp crystal growth and morphology. In the present study, the effect of strontium ions on the adsorption of Ca and phosphate ions on three different faces of single crystalline rutile substrates has been investigated. The ion adsorption is the crucial step in the nucleation of HAp crystals on specific surfaces. Single crystalline rutile surfaces ((110), (100) and (001)) were soaked in phosphate buffer solutions containing calcium and strontium ions for different time periods. The results showed that the adsorption of Sr, Ca and P is faster on the (110) surface than on the (100) and (001) surfaces. Almost same amount of Sr ion was adsorbed on the surfaces compared to the adsorption of Ca ion. Strontium ion influenced the biological apatite formation in the early stage in this study.

Keywords: Single crystalline rutile; Apatite; Strontium; Ion adsorption

Nickel adsorption and incorporation on a 2×2- T₄ GaN(0001) surface: A DFT study by Rafael González-Hernández; William López-Pérez; Jairo Arbey Rodríguez M. (pp. 205-208).

Display Omitted► Adsorption, diffusion and incorporation of nickel atoms on the 2×2-T4 GaN(0001) surface were theoretically studied. ► Ni adsorption process is energetically more favorable that the Ni incorporation in interstitial and Ga-substitutional sites. ► Ni surface adsorption is more favorable in moderate and extreme Ga-rich conditions. ► Our DFT calculations predict the interface formation of NiGax/GaN layer growth, before the Ni film formation on GaN.We have performed first-principles calculations of energetic stability and electronic structure of nickel adsorption and incorporation on a 2×2 reconstructed GaN(0001) surface. Our total energy results show that the most stable positions of a Ni adatom on the reconstructed 2×2- T₄ GaN(0001) surface are at theH3a0 and T₄ adsorption sites. We found that the Ni adatom diffusion energy barrier between theH3a0 and T₄ sites is around 0.16eV, which is an indication of a significant Ni adatom diffusion on this surface. In addition, calculating the relative surface energy of several configurations, we constructed a phase diagram showing the energetically most stable surfaces as a function of the Ga chemical potential. Based on these results, we found that Ni adsorption is energetically more favorable compared with Ni incorporation in the Ga-substitutional and interstitial sites. In addition, confirming previous experimental results, we found that the growth of NiGa_x and Ni monolayers on the GaN(0001) surface is possible.

Keywords: Density functional theory; Surface states; GaN surface

Thermal stability and effect of substrate temperature of TiSiBC hard nanocomposite coatings on microstructure, mechanical, thermal behaviour deposited by magnetron sputtering by S.K. Mishra; P. Mahato; B. Mahato; L.C. Pathak (pp. 209-213).

► TiSiBC nanocomposite films deposited at different temperature are studied. ► TEM studies confirmed the presence of fine crystallites in amorphous matrix. ► Optimum temperatures were around 400–450°C for higher modulus and hardness. ► The film deposited at 400°C was smooth with the average roughness 11nm. ► Thermally stability of film was excellent and found stable up to 900°C in air.The TiSiBC nanocomposite thin films deposited on steel (SS 304) at different substrate temperatures have been investigated. TEM analysis showed that film morphology consist of very fine grain size in the range of 10nm. With the increase of substrate temperature the crystallinity of the film was also increased. At 500°C substrate temperature other crystalline phase containing Ti and Si also appear along with the TiB₂. The optimum temperatures were around 400–450°C, where the film had higher hardness and modulus, further increase of temperature led to decrease in the hardness and modulus, which is due to formation of softer phases. The film deposited at 400°C was smooth with the average engineering roughness of about 11nm. The nanocomposite film was thermally stable in air up to 900°C with little decrease in hardness.

Keywords: TiSiBC; Nanocomposite; Nanoindentation; Thermal stability

Preparation of magnetic nickel hollow fibers with a trilobe structure using cellulose acetate fibers as templates by Changfeng Zeng; Ping Li; Lixiong Zhang (pp. 214-218).

► Nickel hollow fibers with trilobe shape in cross section were prepared. ► Cellulose acetate fibers from cigarette filters were used as the template. ► Monolithic nickel structures were also obtained. ► Magnetic ZSM-5 coating on Ni hollow fibers were then fabricated.Nickel hollow fibers with trilobe shape in cross section and monolithic nickel structures composed of trilobe shaped nickel hollow fibrous networks were prepared by using cellulose acetate fibers from cigarette filters as the template. Magnetic ZSM-5/Ni hollow fibers were then fabricated by using the nickel-based hollow fibers as the support. The samples were characterized by scanning electron microscopy, energy dispersive X-ray spectrometer, and X-ray diffraction. The results indicate that nickel hollow fibers and ZSM-5/Ni hollow fibers retain the morphology of the cellulose acetate fibers, and the monolithic nickel structures can be prepared by pre-shaping the cellulose acetate fibers. The thickness of the nickel layer can be regulated by controlling the electroless plating times. The saturation magnetization and coercivity of the trilobe shaped nickel hollow fibers and ZSM-5/Ni hollow fibers are 27.78 and 21.59emu/g and 78 and 61Oe, respectively.

Keywords: Cellulose acetate fiber; Electroless plating; Nickel hollow fiber; Trilobe structure; Magnetization

Simple quantification of surface carboxylic acids on chemically oxidized multi-walled carbon nanotubes by Hyejin Gong; Seong-Taek Kim; Jong Doo Lee; Sanggyu Yim (pp. 219-224).

Display Omitted► Simple and rapid quantification of acidic groups on oxidized MWCNT surfaces has been proposed. ► The quantification was performed using pH measurements and pre-determined p K_a value. ► The results were consistent with those obtained from XPS and titration. ► Variations in acid concentrations as a function of the type of oxidants and oxidation time were also investigated.The surface of multi-walled carbon nanotube (MWCNT) was chemically oxidized using nitric acid and sulfuric–nitric acid mixtures. Thermogravimetric analysis, transmission electron microscopy and infrared spectroscopy revealed that the use of acid mixtures led to higher degree of oxidation. More quantitative identification of surface carboxylic acids was carried out using X-ray photoelectron spectroscopy (XPS) and acid–base titration. However, these techniques are costly and require very long analysis times to promptly respond to the extent of the reaction. We propose a much simpler method using pH measurements and pre-determined p K_a value in order to estimate the concentration of carboxylic acids on the oxidized MWCNT surfaces. The results from this technique were consistent with those obtained from XPS and titration, and it is expected that this simple quantification method can provide a cheap and fast way to monitor and control the oxidation reaction of MWCNT.

Keywords: Multi-walled carbon nanotube; Surface functionalisation; Acid quantification; X-ray photoelectron spectroscopy

Superhydrophobicity determines the buoyancy performance of kapok fiber aggregates by Xiaoyan Zhang; Wangyang Fu; Chunting Duan; Hong Xiao; Meiwu Shi; Ning Zhao; Jian Xu (pp. 225-229).

Display Omitted► Superhydrophobicity determines the buoyancy performance of natural kapok fibers. ► The superhydrophobicity of individual kapok fibers was investigated. ► We modeled the buoyancy performance of the fiber aggregates by looking into their superhydrophobicity and density. ► Experimental buoyancy performance of kapok fiber aggregates was carried out. ► A good agreement between our theoretical analysis and experimental observations was found.Superhydrophobicity is commonly regarded as a surface property that has important consequences for self-cleaning applications. Here we show interestingly that the superhydrophobicity is closely connected to the bulk buoyancy performance of kapok fiber aggregates, a natural material endowed with superhydrophobicity and extraordinary high porosity. First of all, we have determined the superhydrophobicity of a single kapok fiber, which can be ascribed to its micro-nano-binary structure (MNBS) and the thin hydrophobic paraffinic wax layer covered on the surface. Second, based on classic capillary and wicking theory, the buoyancy performance of the kapok fiber aggregates can be modeled and we demonstrate that their buoyancy performance is actually determined by the superhydrophobicity of individual kapok fibers. Our results also suggest an optimized density ∼0.015gcm⁻³ for using kapok fiber aggregates as the lightest natural buoyancy.

Keywords: Superhydrophobicity; Natural buoyancy material; Kapok fiber; Low density

Investigation on the sulfur state and phase transformation of spent and regenerated S zorb sorbents using XPS and XRD by Limei Qiu; Kang Zou; Guangtong Xu (pp. 230-234).

► Industrial S zorb sorbents are investigated, which is of great practicability. ► XPS, XRD, Ar⁺ ion profiling XPS and in situ XPS are applied to investigate the sorbent. ► The influence of the conversion between sulfide and sulfate on the activity is employed. ► The formation of spinel species is the major reason of the disactivation.A series of industrial S zorb sorbents extracted from production line were characterized by XPS and XRD. The formation of ZnAl₂O₄ and Zn₂SiO₄ is the major reason for the deactivation of spent sorbent. The stability of the Zn-containing spinel species leads to the decrease of the desulfurization efficiency of regenerated sorbent. The chemical states of sulfur atom were examined by XPS. The depth distribution of sulfur species and the reductive behavior of sulfate in H₂ atmosphere were explored using Ar⁺ etching XPS and in situ XPS. The formation of sulfate species in the regeneration process decreases the content of ZnO in the surface significantly and should be avoided. XPS and XRD are excellent tools to follow the sulfur chemical states and phase evolution of S zorb sorbent, respectively, which provide important information for the investigation of deactivation pathways and regenerated mechanisms for S zorb sorbent.

Keywords: S zorb sorbent; Characterization; Deactivation pathway; Regeneration mechanism

Hydrophobic acrylic hard coating by surface segregation of hyper-branched polymers by Masayuki Haraguchi; Tomoyasu Hirai; Masaaki Ozawa; Katsuaki Miyaji; Keiji Tanaka (pp. 235-238).

One step preparation of functional surface.Display Omitted► HBP was preferentially segregated to the surface. ► A water-repellent acrylic hard coating material was prepared. ► HBP removal from the surface was suppressed due to three-dimensional network.The ability of hyperbranched polymers (HBPs) to preferentially segregate to the surface of its matrix owing to its unique structure makes it a good candidate as a surface modifier. One particular challenge in its application as an efficient surface modifier, however, is its possible elimination from the surface due to the lack of attachments between a HBP (modifier) and its host material (polymer matrix). Here, we present a novel approach to efficiently prevent the removal of HBPs from the surface of its host material by directly reacting a HBP containing fluoroalkyl segments (F-HBP) to a multi-functional acrylate monomer prior to curing. We also have characterized surface structure and wettability of the acrylic hard coating material by X-ray photoelectron spectroscopic and contact angle measurements, respectively. The results show that since F-HBP was segregated at the surface, the surface became hydrophobic and more stable. Thus, we claim that our approach results in the formation of a water-repellent acrylic hard coating material.

Keywords: Hyperbranched polymer; Surface modifier; Curing reaction; Hard coat

A new striped-phase of decanethiol self-assembled monolayers on Au(111) formed at a high solution temperature by Waleed Azzam; Lo’ay Al-Momani (pp. 239-244).

Display Omitted► Preparation of Decanethiol SAMs at different solution temperatures. ► Formation of a new striped phase. ► Observation of four different molecular heights per c(4×2) unit cell.Self-assembled monolayers (SAMs) of decanethiol (C10) on Au(111) prepared at room temperature (RT), 60°C, and 70°C have been investigated using high resolution scanning tunneling microscopy (STM). For SAMs prepared at RT, the c(4×2) superlattice of the basic(3×3)R30° structure was hardly observed in small-scale STM images. Increasing the solution temperature to 60°C results in formation of SAMs having large ordered domains of the c(4×2) superlattice. In contrast to the previous studies, our results indicate the presence of four different topographical heights for the C10 molecules per c(4×2) unit cell. Preparation of C10 SAMs from 70°C of solution temperature leads to the formation of new striped phase with(43×23)R30° unit cell. The area of a single molecule in the(43×23)R30° striped structure amounts to 57.73Å², which is about 167% larger than that (21.6Å²) for a molecule in the c(4×2) structure.

Keywords: STM; SAMs; Decanethiol; Monolayer; Phase; Solution temperature

Key technique for texturing a uniform pyramid structure with a layer of silicon nitride on monocrystalline silicon wafer by Bohr-Ran Huang; Ying-Kan Yang; Wen-Luh Yang (pp. 245-249).

► A new approach for texturing uniform pyramid structures using silicon nitride. ► Silicon nitride of varying thicknesses, resulting in various pyramid structures. ► Uniform and higher surface coverage of pyramids possess the lower average reflectivity.A new approach for texturing uniform pyramid structures is proposed with technique using a layer of silicon nitride (Si₃N₄). This technique eliminates the pre-treatment processes of native oxide etching or acid etching and improves on the conventional texturization process. Si₃N₄ layers with thicknesses of 14nm, 40nm, 50nm, 73nm, 82nm and 102nm are coated on a monocrystalline silicon wafer, serving as an effective mask in the texturization process. Observation of the influence of the Si₃N₄ thickness on pyramid morphology and reflectivity shows that good surface coverage (94.7%) with a small uniform pyramid size (∼2.6μm) on the silicon surface results in improved reflectance properties (12.3%). This simple technique could potentially be used in the texturization processes for commercial optoelectronic devices and sensor applications.

Keywords: Pyramid structure; Silicon nitride (Si; ₃; N; ₄; ); Texturization; Reflectivity

Formation and characterization of titania coatings with cortex-like slots formed on Ti by micro-arc oxidation treatment by Zhenfei Liu; Weiqiang Wang; Huiying Liu; Tongyue Wang; Min Qi (pp. 250-255).

Display Omitted► A cortex-like slots TiO₂ coating formed on Ti under micro-arc oxidation treatment. ► We have discussed evolution of morphology of TiO₂ coatings. ► This TiO₂ coating shows superior surface wettability. ► The cell growth of the cortex-like coating shows cell ingrowth into the deep slots.Using sodium tetraborate as electrolyte, a porous titania (TiO₂) coating with a novel morphology of cortex-like slots was successfully prepared on the Ti surface through micro-arc oxidation (MAO). The effect of MAO treating time on surface layer was investigated. In this paper, we compared the cortex-like coatings with the conventional volcanic coatings. Results show that the cortex-like coatings with interconnected pores and slots have better wettability than volcanic coatings. The cell responses of TiO₂ coatings, examined by culturing MG-63 cells on the samples, revealed that both cortex-like coating and volcanic coating presented good cell attachment after culturing for 1, 5 and 7 days, suggesting good biocompatibility. However, the cell growth of cortex-like coating occurred with cell ingrowth into the deep slots, which is different from that of the conventional volcanic coating. Results of this study indicated that the cortex-like coating was conducive to cell retention and implant stabilization.

Keywords: Micro-arc oxidation; Porous titania coatings; Cortex-like slots; Surface wettability

Application of multireflection grazing incidence method for stress measurements in polished Al–Mg alloy and CrN coating by M. Marciszko; A. Baczmański; K. Wierzbanowski; M. Wróbel; C. Braham; J.-P. Chopart; A. Lodini; J. Bonarski; L.Tarkowski; N. Zazi (pp. 256-267).

► Grazing incident X-ray diffraction enables stress measurements in surface layers. ► Göbel mirror significantly reduces the uncertainty of determined stresses. ► Using multireflection grazing incidence method the peak broadening can be analysed. ► Mechanical polishing can produce stress gradient in the surface layer. ► Compressive stress in the CrN film deposited on the steel substrate is generated.Multi-reflection grazing incidence geometry, referred to as MGIXD, characterized by a small and constant incidence angle, was applied to measure low surface stresses in very thin layers of Al–Mg alloy and CrN coating. These two materials were selected in order to deal with the low and high levels of residual stress, respectively. The influence of different mechanical treatments on residual stresses was studied for Al–Mg samples. It was found that both rolling and mechanical polishing influence the distribution and amplitude of residual stress in surface layers. In the case of CrN coating, a very high compressive stress was generated during the deposition process. The stress distributions determined by the MGIXD method is in good agreement with the classic sin² ψ technique results for all studied samples. In performing stress measurements for a powder sample, it was found that the application of the Göbel mirror in the incident beam strongly reduces statistical and misalignment errors. Additionally, the root mean square values of the third order lattice strain within diffracting grains were determined.

Keywords: Thin film; Residual stresses; X-ray diffraction; Grazing incidence method; Göbel mirror

Impact of n-heptane as surfactant in the formation of CdO nanowires through microwave combustion by D. Sathya Raj; R. Jayaprakash; T. Prakash; Sanjay kumar; G. Neri; T. Krishnakumar (pp. 268-271).

Formation of wires for the cadmium oxide semiconductors is carried using a novel microwave-assisted combustion route. The TEM micrographs represent the wire like structural formation of prepared CdO sample. From the micrographs it could be seen that the wires possessing diameter of 25–30nm are acknowledged with tiny particles having 8–20nm crystallite sizes.Display Omitted► Synthesized CdO wires with tiny particles on its surface. ► Wires with diameters 25–30nm and tiny particles are of 8–20nm in size. ► Good thermal stability of the prepared CdO sample observed from TG analysis.A microwave-assisted combustion route for the preparation of cadmium oxide (CdO) nanowire is carried and its characterization results are discussed. This method resembles a supportive way in the formation of CdO nanowire which is confirmed with the structure and morphological analysis carried for the prepared sample. Microwave combustion method is a cost effective and less time consumption to achieve CdO nanowires. The controlled shapes and size are attained due to microwave irradiation. Yielded sample is investigated with Fourier transformation infra-red (FTIR) spectra, X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX) spectra and transmission electron microscopy (TEM) with SAED pattern. The formation of CdO phase with a face centered cubic structure is confirmed from XRD spectra and the presence of CdO metallic bond is also confirmed with FTIR spectra. The formation of CdO nanowires is visualized through the TEM images and presence of elements is also recorded from EDX spectra.

Keywords: Microwave combustion; FCC; CdO nanowires

Adsorption behavior of antimony(III) oxyanions on magnetite surface in aqueous organic acid environment by Vinit K. Mittal; Santanu Bera; S.V. Narasimhan; S. Velmurugan (pp. 272-279).

This study describes possible adsorption, dissolution and complexation processes with Sb(III) and Fe₃O₄ during chemical decontamination.Display Omitted► Adsorption of Sb(III) on Fe₃O₄ at low pH occurs with the formation of Fe–O–Sb complex via inner-sphere surface interaction. ► Adsorption Sb(III) on Fe₃O₄ surface was very low in tartaric acid medium among the verities of organic acids studied. ► The presence of complexing agent phenathroline in tartaric acid medium reduced Sb(III) adsorption further on Fe₃O₄ surface. ► Adsorption of Sb(III) on Fe₃O₄ surface increases in the presence of MoO₄²⁻ and Mn²⁺ in tartaric acid medium. ► Surface chemical modification of Fe₃O₄ by Lauric acid or benzoic acid delayed Sb(III) adsorption on magnetite surface.Antimony(III) adsorption is observed on magnetite (Fe₃O₄) surface under acidic and reducing condition through surface hydroxyl (SOH) groups bonding on Fe₃O₄ surface. Desorption of adsorbed Sb(III) is observed from Fe₃O₄ surface along with iron release in organic acid at 85°C after 5h of experiment. Tartaric acid (TA) shows minimum Sb(III) adsorption on Fe₃O₄ among the organic acid studied. The reason is TA having two sets of adjacent functional groups viz. OCOH and COH which are responsible for the formation of five-membered bidendate chelate with Sb(III). Other oxyanions, cations or complexing agents along with TA influences the Sb(III) adsorption on Fe₃O₄. The surface of magnetite is modified by the addition of fatty acids viz. Lauric acid, benzoic acid to bind the SOH groups present on the surface. This results in delaying the process of adsorption without changing the quantity of saturation adsorption of Sb(III) on Fe₃O₄ surface.

Keywords: Antimony; Adsorption; Oxyanions; Surface complexes; ICP-AES; X-ray photoelectron spectroscopy

Effective water disinfection using silver nanoparticle containing silica beads by Dang Viet Quang; Pradip B. Sarawade; Sun Jeong Jeon; Sang Hoon Kim; Jong-Kil Kim; Young Gyu Chai; Hee Taik Kim (pp. 280-287).

► In this study, we report an effective water disinfection method using Ag-NPBs. ► Filters can inactivate. ► 99% of the E. coli with a contact time of several seconds. ► Ag-NPBs have an antibacterial capacity of 4.5L/g. ► Ag-NPBs with size 0.5–1mm can be easily integrated into various filtration systems.The shortage of safe drinking water in developing countries and at the sites of natural disaster has spurred scientists to develop more effective materials for water disinfection at the point of use. In the present study, silver nanoparticle supported silica beads (Ag-NPBs) with sizes ranging from 0.5 to 1mm were prepared, and their potential for water disinfection was examined. Escherichia coli was utilized to assess water disinfection potential by flow tests using a filter column filled with Ag-NPBs. Ag-NPBs inactivated>99% of E. coli with a contact time of several seconds when the input water had a bacterial load of approximately 10⁶ colony-forming units per mL. Ag-NPBs have an antibacterial capacity of 4.5L/g. The effect of ammonium and urea on the release rate of silver into filtrate was investigated. The results suggest that Ag-NPBs could be an effective material for water disinfection.

Keywords: Silica beads; Silver nanoparticles; Water disinfection; Antibacterial material

Relationship between the electrochemical behavior of multiwalled carbon nanotubes (MWNTs) loaded with CuO and the photocatalytic activity of Eosin Y-MWNTs-CuO system by Duc-Nguyen Bui; Shi-Zhao Kang; Lixia Qin; Xiang-Qing Li; Jin Mu (pp. 288-293).

Nyquist plots of impedance spectra of (a) MWNTs, (b) MWNTs-3% CuO, (c) MWNTs-5% CuO, (d) MWNTs-6% CuO and (e) MWNTs-7% CuO coated electrodes in 0.1mol(L(1 NaOH solution at 25°C.Display Omitted► The electrochemical behavior of MWNTs loaded with CuO was explored. ► A relation between electrochemical behavior and photocatalytic activity was found. ► Fast electron transfer causes high photocatalytic activity of Eosin Y-MWNTs-CuO.The photocatalytic system containing Eosin Y, multiwalled carbon nanotubes (MWNTs) and CuO (Eosin Y-MWNTs-CuO) was fabricated; meanwhile its photocatalytic activity for hydrogen evolution from triethanolamine (TEOA) aqueous solution was evaluated. Under visible light irradiation, the amount of hydrogen (H₂) evolution increased greatly due to introduction of CuO in the photocatalytic system. Moreover, the electrochemical behavior of MWNTs loaded with CuO was explored using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results clearly indicate that there is a strong relationship between the electrochemical behavior of MWNTs-CuO and the photocatalytic activity of Eosin Y-MWNTs-CuO, and the high photocatalytic activity of Eosin Y-MWNTs-CuO may mainly originate from the efficient electron-transfer in the system.

Keywords: Multiwalled carbon nanotubes; CuO; Electrochemical behavior; Photocatalysis, Hydrogen

Surface acid etching of (BiO)₂CO₃ to construct (BiO)₂CO₃/BiOX (X=Cl, Br, I) heterostructure for methyl orange removal under visible light by Jing Cao; Xin Li; Haili Lin; Benyan Xu; Shifu Chen; Qingmei Guan (pp. 294-299).

Novel (BiO)₂CO₃/BiOX (X=Cl, Br, I) heterostructured photocatalysts synthesized through one-step acid etching method displayed the enhanced photocatalytic activity than pure (BiO)₂CO₃ and the corresponding BiOX (X = Cl, Br, I) for the degradation of MO under visible light (l>400 nm). Comparatively, (BiO)₂CO₃/BiOI revealed the best photocatalytic activity among (BiO)₂CO₃/BiOCl, (BiO)₂CO₃/BiOBr and (BiO)₂CO₃/BiOI, which is largely attributed to the excellent separation of photocarriers through the p–n junction and its good visible light absorption.Display Omitted► (BiO)₂CO₃/BiOX (X=Cl, Br, I) were synthesized through acid etching method. ► (BiO)₂CO₃/BiOX displayed higher activity than single (BiO)₂CO₃ and BiOX. ► (BiO)₂CO₃ and BiOX constructed efficient p–n junction (BiO)₂CO₃/BiOX. ► (BiO)₂CO₃/BiOX p–n junction facilitated the separation of electrons and holes.A series of (BiO)₂CO₃/BiOX (X=Cl, Br, I) heterostructured photocatalysts were synthesized through acid etching method and characterized by XRD, DRS, SEM and HRTEM, respectively. Under visible light ( λ>400nm), (BiO)₂CO₃/BiOX displayed much higher photocatalytic activity than pure (BiO)₂CO₃ and corresponding BiOX for the degradation of methyl orange (MO). The photocatalytic activities of the as-prepared samples increased following this order: (BiO)₂CO₃/BiOCl<(BiO)₂CO₃/BiOBr<(BiO)₂CO₃/BiOI. The enhanced photocatalytic activities could be attributed to the function of heterojunction interface between (BiO)₂CO₃ and BiOX. Moreover, except for the role of heterostructure, the excellent photocatalytic performance of (BiO)₂CO₃/BiOI also originated from its good visible light absorption.

Keywords: (BiO); ₂; CO; ₃; Acid etching method; Photocatalytic activity; Heterostructure

Hierarchical structure of Co₃O₄ nanoparticles on Si nanowires array films for lithium-ion battery applications by Fu Sun; Kai Huang; Yuping Liu; Tian Gao; Yunan Han; Jianxin Zhong (pp. 300-305).

► A large-area and well-aligned Si nanowire arrays are fabricated employing electroless-etching procedure. ► Cobalt nanoparticles are grafted onto Si nanowires through the electroless metal deposition method.► The cobalt nanoparticles are converted into cobalt oxide through annealing in the air. ► The as-prepared Co₃O₄@Si composited nanostructure displays better Lithium-ion battery performance compared with commercial Co₃O₄ powders.The Co₃O₄@Si nanowires configuration was successfully fabricated by employing the electroless metal deposition (EMD) technology and the following annealing in air. The nanostructure exhibits a uniform Co₃O₄ nanoparticles grafting on the solution-etched aligned Si nanowires. What is more important, the cost-effective and uncomplicated fabrication strategy as well as the obtained unique architecture will lead to perfect performance in many applications. When functioned as anode electrodes in lithium-ions battery, the Co₃O₄@Si nanowires configuration displays an excellent Lithium-ion battery performance with larger reversible capacity, more comforting cyclic performance and better rate capability compared with the commercial Co₃O₄ powders.

Keywords: Cobalt oxide; Nanoparticles; Lithium ion battery; Electroless metal deposition

Interfacial microstructure and properties of poly (phenylene benzobisoxazole) fiber grafted with graphene oxide via solvothermal method by Y.W. Li; F. Zhao; Y.J. Song; J. Li; Z. Hu; Y.D. Huang (pp. 306-312).

Display Omitted► A facile one-pot process for grafting GO onto PBO fiber surface using solvothermal method was proposed. ► Solvothermal method provides a supercritical fluid ambient for forming a hierarchical structure on the surface of PBO fiber. ► The hierarchical structure effectively enhanced the interfacial adhesion between PBO fibers and matrix. ► The enhancement effect mainly comes from the increasing chemical bonding, improving wettability and mechanical interlocking.An effective approach for grafting graphene oxide (GO) onto poly (phenylene benzobisoxazole) (PBO) fiber surface through ethanediamine as linkage using solvothermal method was proposed. Grafting GO onto the PBO fiber surface was an attempt to improve the interfacial properties between PBO fibers and epoxy matrix. Experimental results reveal that GO was grafted uniformly on the PBO fiber surface through chemical bonds. The polar functional groups and surface energy of PBO fiber were obviously increased after the grafting process. Results of the mechanical property tests show the interfacial shear strength increased obviously and single fiber tensile strength have not any discernable decrease after the grafting process. GO effectively enhanced the interfacial adhesion of PBO fiber-reinforced composite by increasing chemical bonding, improving wettability and mechanical interlocking.

Keywords: PBO fiber; Graphene oxide; Solvothermal method; Surface grafting; Interfacial property

Poly(acrylic acid) brushes pattern as a 3D functional biosensor surface for microchips by Yan-Mei Wang; Yi Cui; Zhi-Qiang Cheng; Lu-Sheng Song; Zhi-You Wang; Bao-Hang Han; Jin-Song Zhu (pp. 313-318).

► The convenient method of microcontact printing(μCP) was used for fabricating 3D PAA brushes pattern surface. ► Protein immobilization enhancement based on 3D PAA brushes pattern surface was found in model protein immunoassay. ► HBsAg concentration array chip based on 3D PAA brushes pattern surface was developed for label-free assaying of HBsAb. ► The linearity range for HBsAb assay is wider than that of conventional ELISA method.Poly(acrylic acid) (PAA) brushes, a novel three dimensional (3D) precursor layer of biosensor or protein microarrays, possess high protein loading level and low non-specific protein adsorption. In this article, we describe a simple and convenient way to fabricate 3D PAA brushes pattern by microcontact printing (μCP) and characterize it with FT-IR and optical microscopy. The carboxyl groups of PAA brushes can be applied to covalently immobilize protein for immunoassay. Thriving 3D space made by patterning PAA brushes thin film is available to enhance protein immobilization, which is confirmed by measuring model protein interaction between human immunoglobulin G (H-IgG) and goat anti-H-IgG (G-H-IgG) with fluorescence microscopy and surface plasmon resonance imaging (SPRi). As expected, the SPRi signals of H-IgG coating on 3D PAA brushes pattern and further measuring specific binding with G-H-IgG are all larger than that of 3D PAA brushes without pattern and 2D bare gold surface. We further revealed that this surface can be used for high-throughput screening and clinical diagnosis by label-free assaying of Hepatitis-B-Virus surface antibody (HBsAb) with Hepatitis-B-Virus surface antigen (HBsAg) concentration array chip. The linearity range for HBsAb assay is wider than that of conventional ELISA method.

Keywords: Poly(acrylic acid) brushes; Microcontact printing; Surface plasmon resonance imaging; Hepatitis B virus; 3-Dimension

Lotus-like paper/paperboard packaging prepared with nano-modified overprint varnish by Wenting Chen; Xinling Wang; Qingsheng Tao; Jinfang Wang; Zhen Zheng; Xiaoliang Wang (pp. 319-325).

As the most consumption packaging material, the application of paper/paperboard largely confined due to the inferior water resistance performance. This paper provides a preparation method of a functional overprint varnish in aim to significantly abate the wettability of the printed packaging. The prominent water repellency of the varnish, as well as its inhibition of frost formation, is rendered by its unique nano-structrured bio-mimicking lotus-like morphology. Meanwhile the transparency and the application process of the varnish are well preserved.Display Omitted► A lotus-like paper surface rendered by functional overprint varnish. ► Nano-structrured superhydrophobic surface with high transparency. ► Extremely water resistant property to the paper and paperboard packaging. ► The unique function of anti-fouling ► A strong ability to restrain and delay frost formation.Paper/paperboard has great advantages over plastics as packaging material in terms of cost and sustainability. However, the application of paper/paperboard packaging is limited due to their inferior water resistance performance. Here we report a functional overprint varnish prepared with the aim to significantly abate the wettability of the printed packaging. The prominent water repellency of the varnish is rendered by its unique nano-structured morphology, a technology bio-mimicking lotus surface. The frost formation on the applied packaging is also inhibited. Moreover, the transparency and the application process of the varnish are retained. We expect such varnish has high potential for expanding the application field of paper/paperboard packaging, especially for uses requiring a strict standard of water resistance.

Keywords: Paper and paperboard; Packaging; Varnish coating; Nano-structured; Water resistance; Anti-frost

Spectral and nonlinear optical transmission studies of Zr⁴⁺-doped TiO₂ nanoparticles by K. Mani Rahulan; L. Devaraj Stephen; Charles Christopher Kanakam (pp. 326-331).

► Zr⁴⁺ doped TiO₂ nanoparticles were synthesized by sol–gel method. ► The increase of Zr⁴⁺ doping decreased the particle growth, and enhanced “blue-shift” in the UV–vis absorption spectra. ► The fluorescence lifetime decreases with the increase in Zr⁴⁺ concentration. ► At lower concentration of Zr⁴⁺ the particles exhibit three-photon absorption while for at higher concentration the data fitted to saturable absorption followed by two-photon absorption.Zr⁴⁺-doped TiO₂ nanoparticles with a homogeneous anatase structure were synthesized through sol–gel technique. The crystalline phase and particle sizes of the resultant particles were investigated by X-ray diffraction (XRD), Raman and transmission electron microscopy (TEM) techniques. Results indicated that Zr⁴⁺ was incorporated into the lattice and interstices of titania nanocrystals. The amount of Zr⁴⁺ doping decreased the size of particle, and enhanced “blue-shift” in the UV–vis absorption spectra. The optical limiting property of the samples was assessed by a Z-scan technique in which the Zr⁴⁺/TiO₂ nanoparticles dispersed in ethylene glycol were excited at 532nm using 7ns Nd:YAG laser pulses. Experimental results indicated that at 0.5 and 1.0mol% doping of Zr⁴⁺ the particles exhibit three-photon absorption while for at 2.0 and 3.0mol% dopant concentration the data fitted to saturable absorption followed by two-photon absorption.

Keywords: Nanoparticles; Sol–gel process; Optical limiting; Saturable absorption

Ultraviolet, visible, and near infrared photoresponse properties of solution processed graphene oxide by Xiang Qi; Xianghua Zou; Zongyu Huang; Long Ren; Guolin Hao; Yundan Liu; Xiaolin Wei; Jianxin Zhong (pp. 332-336).

Display Omitted► Photoresponse properties of solution processed graphene oxide were studied. ► GO devices have high sensitivity, high-speed and superior reproducibility as a visible and near infrared photodetector. ► The responsivity and external quantum efficiency are found to be reached about 95.8mA/W and 26.2%, respectively, for incident wavelength of 455nm.The photoresponse properties of solution processed graphene oxide (GO) ranged from ultraviolet–visible–near infrared regime are studied. Photoelectrochemical results indicate that the as-prepared GO devices have excellent sensitivity, high-speed and superior reproducibility as a visible and near infrared photodetector. Especially, the responsivity and external quantum efficiency are found to be about 95.8mA/W and 26.2%, respectively, for incident wavelength of 455nm at 0.8V bias voltage. Resulting from the degradation of GO under UV irradiation, the GO devices exhibit unstable photoresponse performance, as well as high UV photosensitivity.

Keywords: Graphene oxide; Optoelectronic; Responsivity

Silver nanoparticles incorporated onto ordered mesoporous silica from Tollen's reagent by M. Zienkiewicz-Strzałka; S. Pasieczna-Patkowska; M. Kozak; S. Pikus (pp. 337-343).

Display Omitted► In this work SBA-15 materials with silver nanostructures were synthesized and characterized. ► Tollen's reagent [Ag(NH₃)₂]⁺ was used as a silver precursor. ► New method of the synthesis AgCl nanoparticles was proposed. ► Small silver nanoparticles or nanowires depending on the metal loading amount were obtained.Noble metal nanostructures supported on mesoporous silica are bridge between traditional silica adsorbents and modern catalysts. In this work the Ag/SBA-15 mesoporous materials were synthesized and characterized. Various forms of nanosilver supported on ordered mesoporous template have been successfully obtained via proposed procedures. In all synthesized materials, Tollen's reagent (diammine silver complex [Ag(NH₃)₂]⁺) was used as a silver source. Silver nanoparticles were prepared by reduction of ammoniacal silver complex by formaldehyde in the solution of stabilizer. After reduction, Ag nanoparticles could be deposited on SBA-15, or added during traditional synthesis of SBA-15 giving silver or silver chloride nanoparticles in the combination with porous silica. Silver nanostructures as nanoparticles or nanowires were also embedded onto the SBA-15 by incipient wetness impregnation of silver ions. Absorbed silver ions were next reduced under hydrogen at high temperature.There are many advantages of utilized ammoniacal silver complex as a silver source. Proposed method is capable to synthesis of various metal nanostructures with controlled composition and morphology. The silver ammonia complex is composed of two ions surrounding and protecting the central silver ion, so it is possible to obtain very small nanoparticles using simple approach without any functionalization of external and internal surface of SBA-15. This approach allows obtaining greatly small silver nanoparticles on SBA-15 (4nm) or nanowires depending on the metal loading amount. Moreover, the colloidal silver solution prepared from Tollen's reagent, in the presence of triblock copolymer, remains stable for a long time. Reduction of Tollen's reagent to silver colloidal solution seems to be efficient, fast and interesting approach for the preparation of supported silver nanostructures Obtained samples were characterized by powder X-ray diffraction, small angle X-ray scattering (SAXS), UV–vis spectroscopy, transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms and photoacoustic spectroscopy (PAS).

Keywords: Silver nanoparticles; SBA-15; Adsorption; Ag-SBA-15; Tollen's reagent

Evaporation and removal mechanism of phosphorus from the surface of silicon melt during electron beam melting by Shuang Shi; Wei Dong; Xu Peng; Dachuan Jiang; Yi Tan (pp. 344-349).

► Phosphorus can be removed to less than 0.07×10⁻⁴wt.% by electron beam melting. ► The phosphorus content decreases rapidly at first and then tends to level out. ► Phosphorus evaporation in the melt free surface follows the first order kinetics. ► The mass transfer coefficients of phosphorus in silicon are calculated and discussed. ► The removal of phosphorus is controlled by both diffusion and evaporation.An experimental investigation into the removal of phosphorus from molten silicon using electron beam melting has been carried out. The time variation of phosphorus content is obtained at the electron beam power of 9, 15, and 21kW, respectively. The results show that, at a constant power, the content of phosphorus decreases rapidly within the range of approximately 0–900s after silicon is melted completely, and then tends to level out with further extension of the melting time. The content of phosphorus is decreased from 33.2×10⁻⁴wt.% to 0.07×10⁻⁴wt.% after 1920s at a power of 21kW, which achieves the target for solar-grade silicon of less than 0.1×10⁻⁴wt.%. Moreover, the removal reaction of phosphorus by evaporation from the surface of silicon melt during electron beam melting occurs in accordance with the first order kinetics. The mass transfer coefficients in different removal steps are calculated and discussed, which indicate the removal reaction of phosphorus is controlled by both the transport of phosphorus atom from the bulk to the melt free surface and the vaporization from the free melt surface into the gas phase.

Keywords: Electron beam melting; Evaporation; Removal mechanism; Phosphorus; Silicon

Theoretical study of oxidation–reduction reaction of Fe₂O₃ supported on MgO during chemical looping combustion by Wu Qin; Qiuluan Chen; Yang Wang; Changqing Dong; Junjiao Zhang; Wenyan Li; Yongping Yang (pp. 350-354).

► Properties of Fe₂O₃/MgO composite. ► CO/O₂ adsorption on Fe₂O₃/MgO composite. ► Mechanism of CO oxidation by Fe₂O₃ related to the fuel reactor of the CLC system. ► Mechanism of Fe₂O₂ oxidation by O₂ related to the air reactor of the CLC system.We applied density-functional theory (DFT) in periodic system to investigate the two reactions (CO+Fe₂O₃/MgO→CO₂+Fe₂O₂/MgO, O₂+Fe₂O₂/MgO→O+Fe₂O₃/MgO) in chemical looping combustion system. While Fe₂O₃ was supported on MgO(100) surface Fe₂O₃ gathered together to form a cluster shape on MgO(100), denoted as Fe₂O₃/MgO, where the Fe₂O₃ was activated by MgO(100). Then CO interacted with Fe₂O₃/MgO and carbonate generated during a stepwise reaction with the calculated maximum barrier energy of 0.95eV, far less than that of the reaction between CO and the pure Fe₂O₃ cluster (2.59eV). CO was oxidized by Fe₂O₃/MgO and then Fe₂O₃/MgO transformed into the reduced state Fe₂O₂/MgO, corresponding to the reaction in the fuel reactor in the CLC system. Then the breaking of the adsorbed O₂ molecule on Fe₂O₂/MgO made an O atom bind to a Fe site with the barrier energy of 0. 20eV, which played as the key step for the oxidizing of Fe₂O₂/MgO by O₂ into Fe₂O₃/MgO, corresponding to the reaction in the air reactor in the CLC system.

Keywords: Chemical-looping combustion; Fe; ₂; O; ₃; MgO; CO; DFT

Structural and dielectric properties of Ti and Er co-doped HfO₂ gate dielectrics grown by RF sputtering by Murad Ali Khaskheli; Ping Wu; Ram Chand; Xianfei Li; Hui Wang; Shiping Zhang; Sen Chen; Yili Pei (pp. 355-359).

► HfTiErO_x gate dielectrics were prepared by employing growth parameters on Si(100) using RF sputtering at 100°C substrate temperature. ► XRD pattern confirms the crystalline structure and XPS results showed that HfTiErO chemical bond may be existed. ► C– V measurements reveal that improved flatband voltage shift, hysteresis voltage and interface-state density (Dit) in contrast of other samples.This work reports on the structural and dielectric properties of high-k Ti and Er co-doped HfO₂ (HfTiErO_x) gate dielectrics deposited on Si(100) substrates by RF sputtering. Results indicate that the capacitance value of HfTiErO_x gate dielectric at 100°C substrate temperature is higher and exhibits a lower hysteresis voltage as well as interface trap density compared to HfO₂, HfErO_x and HfTiO_x films at the same conditions in capacitance–voltage ( C– V) curves. Furthermore, the structural, chemical compositions and photonics properties of these films have been explored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Photo luminous (PL) measurements. The results are well attributed to crystalline HfTiErO_x microstructure thus new chemical bonding of HfTiErO may exit. PL spectra of all the prepared samples exhibit peaks in range of ∼2.82 to ∼3.03eV which is attributed to oxygen vacancies.

Keywords: High-k dielectrics; Thin films; HfTiErO; _x; Substrate temperature; Sputtering

Functionalized graphene nanoplatelets for enhanced mechanical and thermal properties of polyurethane nanocomposites by Santosh Kumar Yadav; Jae Whan Cho (pp. 360-367).

► An effective way to fabricate high performance polymer nanocomposites via incorporation of the functionalized graphene nanoplatelets. ► Homogeneous dispersion of graphene nanoplatelets in the polymer matrix and interface control in the nanocomposites. ► An improvement in the mechanical properties, thermal stability, and shape recovery properties.In the evolution of high performance graphene-based polymer nanocomposites, homogeneous dispersion of graphene nanoplatelets in the polymer matrix and exact interface control are difficult to achieve due to the potent interlayer cohesive energy and surface inactiveness of the nanocomposites. Herein, we present an effective way to fabricate high performance polyurethane (PU) nanocomposites via the incorporation of functionalized graphene nanoplatelets (f-GNP) during in situ polymerization. The f-GNP/PU nanocomposites exhibited a significant improvement in terms of their mechanical, thermal, and shape recovery properties. The modulus of the f-GNP/PU nanocomposites at 2wt% graphene nanoplatelets loading is ten times greater than that of the pure PU sample. The breaking stress and shape recovery showed a highly improving trend with increasing wt% of f-GNP. An unprecedented enhancement of thermal stability at 30°C compared to the pure PU is also found at 2wt% loading of f-GNP via in situ polymerization.

Keywords: Polyurethane; Nanocomposites; Functionalization; Graphene nanoplatelets; Mechanical properties

The effect of adding PDMS-OH and silica nanoparticles on sol–gel properties and effectiveness in stone protection by Dan Li; Feigao Xu; Zhenghua Liu; Jiaqi Zhu; Qingjian Zhang; Li Shao (pp. 368-374).

► Preparation of TEOS–SiO₂–PDMS-OH hybrid gels using DBTL as a catalyst. ► Thermal properties of TEOS–PDMS hybrid gels were characterized. ► Acid rain resistance property of hybrid agents for carbonate stone was evaluated.Inorganic–organic hybrid crack-free xerogels were obtained using di- n-butyltin dilaurate (DBTL) as a catalyst containing tetraethoxyorthosilicate (TEOS) and hydroxyl-terminated polydimethylsiloxane (PDMS-OH) as an additive. We studied the effect of gelling time and sol pH on DBTL concentration. The xerogels’ structure was studied by FTIR, TGA–DTA and SEM techniques. The results showed that the catalyst (DBTL) would substantially shorten the gelling time of the sol. With the addition of PDMS-OH, the viscosity of the sol increased while the gel time decreased. In addition, we noticed an improvement in the cracking of the xerogel with the addition of PDMS-OH. However, the xerogels were opaque when mole ratio of PDMS/TEOS is higher than 0.153. Addition of silica nanoparticles at 0.1% (w/v) in sol could increase xerogels’ surface roughness and hydrophobicity and did not change color of the xerogels. The protective performance evaluated by its ability to resist acid rain revealed that the protective effects were satisfying.

Keywords: Crack-free; PDMS-OH; Silica nanoparticles

Superparamagnetic iron oxide nanoparticles prepared by using an improved polyol method by Baolin Zhang; Zhijiang Tu; Fangyuan Zhao; Jun Wang (pp. 375-379).

Schematic illustration of the synthesis of PEG/PVP-coated SPIONs.Display Omitted► Superparamagnetic iron oxide nanoparticles were synthesized by thermal decomposition of Fe(acac)₃ in PEG containing PVP or PEI. ► The nanoparticles are jointly coated by PEG/PVP or PEG/PEI. ► The nanoparticles showed high dispersion stability in water and in PBS. ► The properties of nanoparticles were tuned by PVP or PEI.Superparamagnetic iron oxide nanoparticles were synthesized by thermal decomposition of iron (III) acetylacetonate (Fe(acac)₃) in PEG containing poly(vinyl pyrrolidone) (PVP) or poly(ethylene imine) (PEI). The morphologies and phase compositions of the nanoparticles were determined by transmission electron microscopy and X-ray diffraction, respectively. The surface coating of the nanoparticles was recognized using Fourier transform infrared spectroscopy and the presence of the surface coating was confirmed by Thermogravimetric analyses. Magnetic properties were measured using superconducting quantum interference device. The zeta potentials and hydrodynamic sizes of the nanoparticles were determined using nano-particle and zeta potential analyzer. The superparamagnetic iron oxide nanoparticles with sizes from 4.1nm to 14.9nm were prepared in the present work, which could be tuned by varying factors such as the reaction temperature, the reaction time, and the PVP or PEI contents. The superparamagnetic nanoparticles were jointly coated with PEG/PVP or PEG/PEI. With hydrodynamic sizes smaller than 40nm and neutral or positive zeta potentials these superparamagnetic iron oxide nanoparticles exhibited higher dispersion stability in deionized water and in phosphate buffered saline as compared with the superparamagnetic iron oxide nanoparticles coated with PEG alone. This work demonstrates that superparamagnetic iron oxide nanoparticles with modulated properties can be prepared simply by using the improved polyol method.

Keywords: Superparamagnetic iron oxide nanoparticles; Thermal decomposition; PEG; PVP; PEI; Dispersion stability

Study on the electron structure and optical properties of Ga_0.5Al_0.5As(100) β₂(2×4) reconstruction surface by Xiaohua Yu; Yujie Du; Bengkang Chang; Zhonghao Ge; Honggang Wang; Meishan Wang (pp. 380-385).

► The build of Ga_0.5Al_0.5As(100) β₂(2×4) reconstruction surface. ► The analysis of the photoelectric emission properties of the surface. ► The comparison of the optical properties of the surface and the bulk.Using quantum mechanics GASTEP software package based on the first principle density function theory (DFT), the electronic structure and optical properties of Ga_0.5Al_0.5As(100) β₂(2×4) reconstruction surface are calculated. Result shows that Ga_0.5Al_0.5As(100) β₂(2×4) reconstruction surface is stable. The calculated work function of Ga_0.5Al_0.5As(100) β₂(2×4) reconstruction surface is 4.811eV. The band gap of the surface is smaller than the bulk. During the formation of the surface, the electrons move into the bulk and a band-binding region is formed. The absorption peaks move to the high-energy edge and the reflectivity decreases, the static dielectric constant decreases, metal reflective properties region of the surface moves to the low-energy edge and is smaller than the bulk.

Keywords: Ga; _0.5; Al; _0.5; As(1; 0; 0) β; ₂; (2; ×; 4) reconstruction; The first principle; Electron structure; Optical propertiesPACS; 71.55.Eq; 78.20.Ci

Fabrication of millimeter scale nanochannels using the AFM tip-based nanomachining method by Y.Q. Geng; Y.D. Yan; X.S. Zhao; Z.J. Hu; Y.C. Liang; T. Sun; S. Dong (pp. 386-394).

► An AFM-based nanomachining method is used to fabricate large scale nanochannels. ► Chip formation states and variations in the machined depth and width are studied. ► The machining parameters to obtain the required machined depth and R_a are given. ► A nanochannels array with 1mm in length and 180nm in depth is machined. ► A three dimensional ladder-type nanochannel is manufactured.A novel nanomachining method based on the atomic force microscope (AFM) is presented to process millimeter scale nanochannels on the surface of the aluminum alloy. Effects of the machining parameters including the machining velocity, the normal load and the feed rate on chip formation mechanism and the machined results are investigated. Results show that more and longer continuous belt-type chips are achieved with a higher machining velocity than a lower one because the higher machining velocity will bring more heat which results in a larger adhesion force between removed materials. There is a significant difference of chip states between the light load and the heavy load which is induced by different removal states. The percentage of the ploughing and cutting states with different feed rates in each scratch plays the key role in this method which has a significant effect on the removal chip states as well as the machined depth of the nanochannels. Moreover, relationships between the depths and surface roughness and the machining parameters are provided. Finally, a nanochannels array and a 3D ladder-type channel with a millimeter scale are obtained successfully indicating the capability of fabrication of the millimeter scale nanochannels using this method.

Keywords: Atomic force microscope (AFM); Nanochannel; Cutting; Ploughing

The fabrication of controlled coral-like Cu₂O films and their hydrophobic property by Yanbo Ding; Yao Li; Lili Yang; Zhenyu Li; Wuhong Xin; Xin Liu; Lei Pan; Jiupeng Zhao (pp. 395-399).

► The controlled coral-like Cu₂O film is firstly reported. ► Multi-patterned Cu₂O films are obtained by governing the time or additive. ► The contact angle of the Cu₂O films is discussed. ► The formation mechanism of multi-patterned Cu₂O is demonstrated.In this paper, we report on the nanostructured Cu₂O film with controllable coral-like morphology in the presence of CuCl₂ by electrodeposition without using any performed template. Four types of patterned Cu₂O films including grains-like, agaric-like, frutex-like and coral-like films were achieved by governing the time or additive. The coral patterned Cu₂O film is for the first time found here. Additionally, possible growth mechanism for multi-patterned Cu₂O is discussed via preferential growths induced by selective absorption of Cl⁻ ions in the present reaction system. The resulting pattered films displayed tunable hydrophobic and even superhydrophobic properties owing to their special surface with micro-/nanostructures after simple surface modification. These experimental results prove a versatile and facile strategy for Cu₂O films with special and complex architectures which may highlights their potential applications in self-cleaning equipment due to the improved surface activity.

Keywords: Coral-like; Contact angles; Superhydrophobic; Electrodeposition

The impact of thermal annealing on the morphology of sputter deposited platinum clusters into anodic aluminum oxide pores by Sujuan Wu; Pascal Brault; Cong Wang; Blandine Courtois (pp. 400-404).

► Plasma sputtered Pt growth in cylindrical anodic aluminum oxide nanopores. ► Annealing effects on cluster morphology: Pt cluster melting above 600°C. ► Cluster to thin film transition via capillary effects of fused Pt above 600°C.The influence of post deposition annealing (PDA) up to temperatures of T_PDA=900°C on the morphology and agglomeration behavior of ambient temperature sputter deposited platinum onto anodic aluminum oxide templates is investigated. Both cluster agglomeration and diffusion processes occur on the surface and on the inner channel walls. When the annealing temperature is less than 400°C, particles are diffusing inside the channels. Around T_PDA=400°C, a particle agglomeration process is taking place. A diffusion process is playing an important role and the Pt particles are able to reach a depth of 12μm. The surface morphology exhibits a remarkable change for annealing temperature above 600°C, where Pt is migrating on the outermost surface for forming flat films. When further enhancing T_PDA to 900°C, the particles on the surface and in the channels agglomerate together to form separated large flat islands. Moreover, the maximum channel depth where platinum is present is around 12μm.

Keywords: Deposition; Sputtering; Nanoparticles; Porous materials; Thin films; Interfaces

Adsorption of formaldehyde and formyl intermediates on Pt, PtRu-, and PtRuMo-alloy surfaces: A density functional study by Wahyu Tri Cahyanto; Ganes Shukri; Mohammad Kemal Agusta; Hideaki Kasai (pp. 405-409).

► We have studied the binding configuration of formaldehyde and formyl adsorption on Pt-, PtRu and PtRuMo surfaces. ► Different adsorption type of formaldehyde and formyl on Pt and on Pt-alloy surfaces were observed. ► The interaction strength of both formaldehyde and formyl with the surface is following this order PtRuMo>PtRu>Pt. ► Ru and Mo have fewer filled d-orbital; alloying them to Pt surface shifts the d-band higher.Stable binding configuration for formaldehyde (H₂CO) and formyl (HCO) adsorption on Pt, PtRu, and PtRuMo are studied within the frame of density functional theory (DFT). We address this study to investigate the role of Ru and Mo on the binding characteristic of formaldehyde and formyl adsorption with respect to interaction strength and charge analysis. Several binding conformation on all possible surface adsorption sites are considered in determining the most stable adsorption geometry on three surfaces. Our results show that the presence of Ru in PtRu and Mo in PtRuMo stabilize the formaldehyde and formyl, which are indicated by stronger bond strength. Further electronic structure analysis shows that the addition of Ru in PtRu and Mo in PtRuMo modifies the electronic structure of Pt's surface significantly. The presence of both impurities shifted the derived anti-bonding state – which is originally located below the fermi level in pure Pt surface – to be above the fermi level in PtRu and PtRuMo systems. This fact explains the stronger adsorption found on PtRu & PtRuMo as compared to pure Pt surface.

Keywords: Formaldehyde; Formyl; Binding configuration; Density functional theory; PtRu; PtRuMo

Preparation of photoactive nitrogen-doped rutile by D. Dolat; D. Moszyński; N. Guskos; B. Ohtani; A.W. Morawski (pp. 410-419).

Display Omitted► Photoactive N-doped rutile TiO₂ catalysts were obtained by annealing in NH₃ flow. ► Band-gap narrowing and better visible light absorption properties were revealed. ► Ti⁴⁺ to Ti³⁺ ions reduction was confirmed by EPR studies. ► Photoactivity of rutile depends inverse-proportionally on nitrogen concentration.An easy way of preparing highly N-doped rutile photocatalysts (N–TiO₂/R) in tubular furnace in a constant ammonia (NH₃) flow at 800–1000°C temperature range is presented. New materials were compared to TiO₂ samples prepared at the same temperatures in air atmosphere as well as to the starting material. Complete transformation of amorphous and anatase phases to rutile was confirmed by XRD method. Successful incorporation of relatively high amounts of nitrogen (up to 17% at.), in form of either TiO₂(N), TiO_xN_y or TiN, on photocatalysts’ surface and in their lattice was confirmed using XPS and XRD analysis. Also presence of Ti³⁺ was revealed by EPR studies. In contrast to pristine TiO₂, the UV–vis/DR absorption spectra of N-modified photocatalysts extended significantly into the visible light region. Whereas nitrogen concentration as well as visible light absorption were found to increase with increasing modification temperature, photocatalytic activity was, on the contrary decreasing. This may be due to the very high nitrogen concentration, obtained at higher modification temperature, as well as the presence of small amount of conductive TiN phase on the N–TiO₂/1000°C photocatalyst surface. The artificial solar light activity of new photocatalysts after thermal treatment in NH₃ increased in comparison to starting material, due to nitrogen modification and presence of Ti³⁺ ions. Activity under UV(-vis) light, though, decreased after modification procedure, probably due to smaller surface areas of new photocatalysts and complete anatase to rutile transformation.

Keywords: Rutile-TiO; ₂; Photocatalysis; N-doping; Semiconductors; Catalytic properties; Electronic paramagnetic resonance (EPR)

Influence of surface nitriding treatment on rolling contact behavior of Fe-based plasma sprayed coating by Piao Zhong-yu; Xu Bin-shi; Wang Hai-dou; Wen Dong-hui (pp. 420-425).

► The dense nitriding layer was deposited on Fe-based sprayed coating. ► RCF lifetime of the coating with nitriding layer was lower. ► Cohesive delamination was the main failure mode of the coating with nitriding layer. ► Microdefects and high brittleness are the main failure reason.Fe–Cr coating was prepared by plasma spraying process. Gas nitriding treatment was conducted on the coating. Rolling contact fatigue (RCF) experiments were conducted using a ball-on-disc setup. RCF lifetime of the coating was calculated by two-parameter Weibull distribution. The worn morphologies of the coating were observed. Correlative failure mechanism was investigated based on fracture analysis and theoretical calculation. Results showed that the dense nitriding layer with high microhardness was formed on Fe-based coating surface. Unfortunately, the deposition of nitriding layer decreases RCF lifetime of the coating. The coating with nitriding layer always failed owing to cohesive delamination. The “born” microdefect and high brittleness of nitriding layer are the main reasons for the failures under rolling contact.

Keywords: Rolling contact fatigue; Plasma sprayed coating; Fe-based alloy; Nitriding layer

Physicochemical properties of phospholipid model membranes hydrolyzed by phospholipase A₂ (PLA₂) in the presence of cholesterol at different temperatures by Małgorzata Jurak; Aleksandra Szcześ; Emil Chibowski (pp. 426-432).

Display Omitted► Presence of cholesterol in lipid membranes regulates the PLA₂ activity. ► Cholesterol in the phospholipid membrane influences its surface free energy and stability. ► Electron–donor parameter may be an indicator of the hydrolysis effectiveness.The physicochemical studies of the model biological membranes were undertaken to seek for correlations between the bilayer composition, the temperature 20°C and 37°C, the time of the enzymatic catalysis process, the surface free energy, as well the electron–donor interactions (the hydrogen bonding). The phospholipase A₂ (PLA₂) action on supported lipid bilayer and lipid vesicles was compared. The investigated liposomes and supported bilayers were composed of two phospholipids (1,2-dipalmitoyl- sn-glycero-3-phosphatidylcholine – DPPC and 1,2-dioleoyl- sn-glycero-3-phosphatidylcholine – DOPC), which differ in hydrocarbon chains saturation, and mixed phospholipid/cholesterol systems. The results show that the changes of electron–donor parameter of the films during their hydrolysis process may be an indicator of the presence of polar products of catalysis in the membrane. Furthermore, the presence of cholesterol in phospholipid membranes and the temperature increase regulate the enzyme action what is reflected in the changes of thermodynamic parameters of the supported lipid bilayers, as well as in the size and polydispersity of the corresponding liposomes.

Keywords: Phospholipase A; ₂; Surface free energy; Electron–donor interactions; Liposomes

Facile single-step ammonia heat-treatment and quenching process for the synthesis of improved Pt/N-graphene catalysts by Bin Xiong; Yingke Zhou; Ryan O’Hayre; Zongping Shao (pp. 433-439).

► A facile single-step heat-treatment and quenching process is developed to prepare composite catalyst. ► Simultaneous reduction and functional doping of graphene oxide, and loading of Pt catalyst are realized. ► Well-dispersed electrocatalysts of Pt nanoparticles on nitrogen-doped graphene are obtained. ► The composite catalysts present excellent catalytic activity for methanol electro-oxidation. ► The facile process is promising to synthesize other graphene based composite electrocatalysts.In this work, we present a facile route to prepare electrocatalysts for methanol oxidation. The catalyst synthesis route involves the simultaneous reduction and nitrogen doping of graphene oxide (GO) along with the reduction of H₂PtCl₆ to Pt by a facile ammonia gas heat-treatment and quenching process. The resulting catalysts are characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy while their electrocatalytic activity toward the oxidation of methanol is evaluated by cyclic voltammetry. The obtained Pt/graphene composites consist of crystalline Pt nanoparticles in the range of 1–4nm which are well-dispersed on the N-doped graphene sheets. The best Pt/N-graphene catalyst composite is obtained after a 5min ammonia treatment at 800°C followed by rapid ammonia gas quenching at room temperature. This catalyst demonstrates superior catalytic activity for methanol electro-oxidation, with a peak current density of 0.218Amg_Pt⁻¹, which is about five times higher than an undoped (hydrogen treated and quenched) Pt/graphene control catalyst. The excellent electrocatalytic performance of the ammonia quenched catalyst is attributed to the nitrogenous functional groups and dopants in the graphene sheets that are formed during the facile quenching process in ammonia.

Keywords: Platinum; Nitrogen-doped graphene; Heat treatment; Methanol oxidation; Electrocatalyst

Effects of power on properties of ZnO thin films grown by radio frequency magnetron sputtering by Ya-Jun Zhao; Da-Yong Jiang; Man Zhao; Rui Deng; Jie-Ming Qin; Shang Gao; Qing-Cheng Liang; Jian-Xun Zhao (pp. 440-444).

► The RF power play an important role in ZnO films during the growth process. ► Films deposited at 150W showed the best crystalline and optical properties. ► The mechanism can be explained by a qualitative model and dynamics equations.Zinc oxide (ZnO) thin films have been grown on quartz substrates by using the radio frequency (RF) magnetron sputtering technique with different sputtering power, which was adjusted widely from 10 to 200W. It was found that the sputtering power play an important role in the growth process of the film. The characteristic features of crystallinity, absorption and photoluminescence (PL) were examined. Furthermore, the surface morphology of the films was also observed by using atomic force microscopy (AFM). Upon increasing the power during the growing process, the films deposited at a RF power of 150W showed the best crystal quality and optical properties. The inflection point at 150W is detectable. This tendency is estimated to result from the enhancing of the particles sputtered from the ZnO target induced by the enlarging power. These results demonstrate that there is an optimal power operating window for sputtering technique. The physical mechanism for this has been explained by a straightforward qualitative model and dynamics equations.

Keywords: ZnO; Power; Magnetron sputtering

A simple immersion approach for fabricating superhydrophobic Mg alloy surfaces by Jinlong Song; Yao Lu; Shuai Huang; Xin Liu; Libo Wu; Wenji Xu (pp. 445-450).

► A simple immersion approach was developed to fabricate superhydrophobic Mg alloy surfaces. ► The approach only needs 10min to get the roughness required by superhydrophobicity. ► A layer of green film was obtained after immersion in the aqueous CuSO₄ solution. ► Superhydrophobicity can be obtained on the surfaces only containing micrometer-scale structures.A simple immersion approach for fabricating superhydrophobic Mg alloy surfaces is present here. Micro/nanometer-scale rough structures composed of micrometer-scale island-like rough structures and nanometer-scale sheets are generated on the Mg alloy surfaces after immersion in the aqueous CuSO₄ solution. After ultrasonic cleaning, the micro/nanometer-scale rough structures are disappeared, whereas the lump-like rough structures appear on the Mg alloy surfaces. After modification with stearic acid, the as-prepared micro/nanometer-scale rough structures and the micrometer-scale lump-like rough structures all show superhydrophobicity. The contact angles of the water droplet on the aforementioned two structures are respectively 151.3° and 161.8°. The rolling angles are respectively 3° and 13°. The results indicate that the cooperation of suitable rough structures and stearic acid modification is responsible for the obtained superhydrophobicity on the Mg alloy surfaces.

Keywords: Superhydrophobic surface; Mg alloy; Immersion

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Applied Surface Science (v.266, #)