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Applied Surface Science (v.257, #18)

Control of wettability of hydrogenated amorphous carbon thin films by laser-assisted micro- and nanostructuring by Wilhelm Pfleging; Robert Kohler; Maika Torge; Vanessa Trouillet; Friederike Danneil; Michael Stüber (pp. 7907-7912).

► Formation of artificial microstructures in a-C:H films with low hydrogen content. ► Surface energy increases linearly with laser energy dose. ► Micro- and nanostructures for the formation of hydrophilic and hydrophobic surfaces.A flexible and rapid surface functionalization of amorphous carbon films shows a great potential for various application fields such as biological surfaces and tribological systems. For this purpose, the combination of thin film deposition and subsequent laser material processing was investigated. Amorphous carbon layers doped with hydrogen were deposited on silicon wafers by reactive direct-current magnetron sputtering. Films with three different hydrogen contents were synthesized. Subsequent to the thin film deposition process, UV laser material processing at wavelengths of 193nm or 248nm was performed with respect to chemical surface modification and surface structuring on micro- and nanometer scale. Depending on structure size and laser-induced chemical surface modification the adjustment of the surface energy and wetting behaviour in a broad range from hydrophobic to hydrophilic was possible. The chemical modification and the ablation mechanisms near the ablation threshold were strongly influenced by the hydrogen content in amorphous carbon thin films.Structural and chemical information of the as-deposited and modified films was obtained by Raman spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements.

Keywords: Laser ablation; Modification; Amorphous carbon; Thin films; Surface energy

Removal of organic dye by air and macroporous ZnO/MoO₃/SiO₂ hybrid under room conditions by Mengjia Yuan; Shengtian Wang; Xiaohong Wang; Lingling Zhao; Tianhong Hao (pp. 7913-7919).

A new macroporous ZnO/MoO₃/SiO₂ hybrid was synthesized by a method involving sol–gel technology and biomimetic synthesis. The catalyst was proved to be an high active and stable heterogeneous catalyst for CWAO of ST under extremely mild conditions.Display Omitted► The macroporous catalyst is synthesized by the mushroom as the biological template. ► The degradation reactions by air and the catalyst are studied under room conditions. ► High catalytic effect and stability are proved the catalytic activity of the catalyst. ► The investigation of ZnO/MoO₃/SiO₂ exhibits academic and industrial values.A new macroporous ZnO/MoO₃/SiO₂ hybrid was synthesized by a method involving sol–gel technology and biomimetic synthesis. It was characterized by Elemental analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS) and scanning electron microscopy (SEM). Chemical degradation of 0.3g/L Safranin T (ST) by air oxidation over macroporous ZnO/MoO₃/SiO₂ hybrid was studied. It was found that the decolorization efficiency and the chemical oxygen demand (COD) removal of ST reached above 95.3% and 93.2%, respectively, within 25min at room temperature and atmospheric pressure. And the organic pollutant was mineralized to simple inorganic species such as HCO₃⁻, Cl⁻ and NO₃⁻, while the total organic carbon (TOC) decreased 95.4%. The structure and morphology of the catalyst were still stable after six cycling runs and the leaching test showed negligible leaching effect.

Keywords: Catalytic wet air oxidation; Organic dye; Degradation; Heterogeneous catalysis

An in vitro controlled release study of valproic acid encapsulated in a titania ceramic matrix by M.J. Uddin; D. Mondal; C.A. Morris; T. Lopez; U. Diebold; R.D. Gonzalez (pp. 7920-7927).

► A nanoparticulate TiO2 matrix was loaded with valproic acid (VPA). ► The release of VPA into methanol was monitored over long time periods. ► The kinetics of the release were analyzed. ► Theresults suggest that VPA-TiO2 implants can be used as nanocarriers for the treatment of epilepsy.Despite the therapeutic efficacy of valproic acid towards numerous diseases, its poor bioavailability and systemic side effects pose significant barriers to long term treatment. In order to take advantage of controlled release implants of valproic acid, the drug was encapsulated into titania ceramic matrices via a sol–gel process. The integrity and structure of valproic acid-containing matrices were characterized through the use of FESEM, TEM, and BET analyses. In vitro controlled release studies and kinetic analyses were performed under ambient conditions (25°C, atmospheric pressure) and controlled release behaviors were studied using a GC–MS method. Results showed first order dependence in the rate of valproic acid release as a function of drug concentrations in the titania ceramic device. A marked dependence on the surface area and pore size distribution with drug loading was also observed. This research opens new possibilities for the design of novel time-delayed controlled release systems for valproic acid encapsulates.

Keywords: Controlled release; Valproic acid; TiO; ₂; Titania matrix and antiepileptic drug

Low-cost one-step fabrication of superhydrophobic surface on Al alloy by Youfa Zhang; Jie Wu; Xinquan Yu; Hao Wu (pp. 7928-7931).

► Superhydrophobic al alloy surface is fabricated by a fast immersion method only using some cheap materials, such as hydrochloric acid and myristic acid. ► The binary structures at micro- and nano scales is due to the cooperation of etching of Cl⁻ and hydrophobic tails of the formed Al(CH₃(CH₂)₁₂COO)₃. ► The process could be extended to other long-chain fatty acids.A stable superhydrophobicity on aluminum alloy has been rendered by a low-cost one-step method, simply immersing the substrates in a solution containing hydrochloric acid and fatty acid molecules. The formation mechanism of such a surface was proposed by SEM morphology and EDS results. The resulting surface shows superhydrophobicity and low adhesion. This low cost and facile process provides a real feasible avenue for large-scale production of superhydrophobic surfaces.

Keywords: Low cost; Immersion; Superhydrophobicity; Myristic acid

Effect of post heat treatment on microstructure and photocatalytic activities of TiO₂ nanoribbons by Lin Zhu; Lixin Cao; Ge Su; Wei Liu; Liang Song; Hui Liu; Bohua Dong (pp. 7932-7937).

► TiO₂ nanoribbons were synthesized by a modified hydrothermal method. ► After post heat treatment, plenty of holes were observed on the surface of nanoribbons. ► The size of the holes increased with the calcination temperature increasing. ► The samples annealed at 800°C for 1.5h and 600°C for 2.5h showed the best photocatalytic activity.Low-dimensional TiO₂ nanoribbons were synthesized by a simple one-step hydrothermal method. The TiO₂ nanoribbons were calcined over the temperature range 200–800°C in order to enhance their photocatalytic properties by altering their crystal phase and increasing crystallization. Effects of hydrothermal temperature, calcinated temperature and calcination time on the formation of nanostructures have been observed and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The (BET) specific surface area of the samples which with different post treatments were determined by N₂ absorption–desorption experiment. In addition, photocatalytic activities of the nanoribbons were evaluated by photodegradation of organic dyes methyl orange under the radiation of UV light. The results reveal that the post-treatments have great effects on the microstructures and the photocatalytic activities of TiO₂ nanoribbons.

Keywords: Hydrothermal; Nanoribbon; Photocatalytic activity; TiO; ₂

Theoretical study of the adsorption of DOPA-quinone and DOPA-quinone chlorides on Cu (100) surface by Shuang-Kou Chen; Bo-Chu Wang; Tai-Gang Zhou; Wen-Zhang Huang (pp. 7938-7943).

► We theoretically studied three adsorption modes for DOPA-quinone and DOPA-quinone-Cl on Cu (100) surface. ► Two molecules could absorb on the Cu (100) only via hydroxyl oxygen-side vertical adsorption mode. ► When DOPA-quinone modified by HOCl, the adsorption capacity weakened. So the anti-foul goal had been achieved.The marine mussel secreted adhesive proteins and could bind strongly to all kinds of surfaces. Studies indicated that there was an unusual amino acid 3,4-dihydroxy-l-phenylanine (DOPA). DOPA could be oxidized to DOPA-quinone easily, which had a superior ability to on surface directly. The technology of electrolyzing seawater was employed to generate HOCl solution to react with DOPA-quinone and form DOPA-quinone chlorides (DOPA-quinone-Cl) to hinder the adhesion. However, the detailed hinder-mechanism remained unknown to be fully explained. Herein, using quantum chemical density functional theory methods, we have systematically studied three kinds of adsorption for DOPA-quinone and DOPA-quinone-Cl on Cu (100) surface: hydroxyl oxygen-side vertical, carbonyl oxygen-side vertical, amino N-terminal vertical adsorptions and carried out geometry optimization and energy calculation. The results showed that two molecules could absorb on the Cu (100) through hydroxyl oxygen-side vertical adsorption, while the other two kinds of adsorption could not form an effective adsorption. Calculations of adsorption energy for hydroxyl oxygen-side vertical adsorption indicated that: after HOCl modification, adsorption energy decreased from −247.2310kJ/mol to −177.0579kJ/mol for DOPA-quinone and DOPA-quinone-Cl; and the Mulliken Charges Populations showed that the electrons transferred from surface to DOPA-quinone-Cl was less than that to DOPA-quinone, namely, the fewer the number of electrons transferred, the weaker interaction between molecular and surface. After the theoretical calculation, we found that the anti-foul goal had been achieved by electrolysis of seawater to generate HOCl to modify DOPA-quinone, which led to the reduction of adsorption energy and transferred electrons.

Keywords: Density functional theory; Dopa quinone; Surface adsorption; Anti-fouling

Functionalization of PET and PA6.6 woven fabrics by R. Bessada; G. Silva; M.C. Paiva; A.V. Machado (pp. 7944-7951).

► PET and PA6.6 fabric samples were continuously treated in air, under atmospheric pressure DBD discharge, in industrial conditions. ► The treated samples showed significant improvement in wettability and spreading of distilled water after treatment. ► XPS results showed that treated PA6.6 surfaces presented new oxidation products even after one month stored. ► FTIR spectra showed chemical changes after treatment, revealing the formation of new polar groups like carboxylic acids and amide groups (in PA6.6 case) and the break of covalent bonds present on PET and PA6.6 substrate surfaces.In the present work as received woven fabrics of polyethylene terephthalate (PET) and polyamide 6.6 (PA6.6) were exposed to a continuous dielectric barrier discharge (DBD), in air at atmospheric pressure, at selected discharge power values and conveyor speeds. The chemical modification of the fabric surface was studied by contact angle analysis, attenuated total reflection (ATR)-FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). The results confirmed that the treatment changed the fabric surface chemistry, increasing its wettability by polar liquids and its oxygen content. Contact angle results showed different behaviour of the two polymer fabrics toward ageing effects; while PET showed a contact angle increase along the subsequent days of treatment, the PA6.6 fabric maintained its hydrophilicity even 15 days after treatment. The surface morphology analysed by scanning electron microscopy (SEM), did not show any significant difference before and after treatment.

Keywords: Dielectric barrier discharge (DBD); Surface treatment; Textiles; Poly(ethylene terephtalate) (PET); Polyamide 6.6 (PA6.6); Wettability

Preparation of nano-structured Pt–YSZ composite and its application in oxygen potentiometric sensor by Xia ChaoYang; Lu XuChen; Yan Yan; Wang TiZhuang; Zhang ZhiMin; Yang SuPing (pp. 7952-7958).

► We have fabricated Pt–YSZ composite with carbon black and the precursors such as chloroplatinic acid, zirconyl nitrate and yttrium nitrate. ► The as-prepared Pt–YSZ composite consists of cubic crystalline YSZ of 5–10nm in diameter and Pt particles of 25–35nm in diameter, and there has an uniform Pt/YSZ interface distribution in the composite. ► The Pt–YSZ composite electrodes exhibits excellent electrochemical performance when evaluated by EIS measurements. ► The introduction of the nano-structured Pt–YSZ composite into the oxygen potentiometric sensor can reduce sensor's operating temperature to be about 380°C, and also can reduce sensor's response time to be about 5s at 400°C.Nano-structured Platinum–Yttria Stabilized Zirconia (YSZ) composites for oxygen potentiometric sensors were directly prepared with carbon black and the precursors such as chloroplatinic acid, zirconyl nitrate and yttrium nitrate. The as-prepared Pt–YSZ composite consisted of cubic crystalline YSZ and Pt particles, and the particle sizes of Pt catalyst and YSZ electrolyte were about 25–35 and 5–10nm, respectively. The Pt–YSZ composite electrodes exhibited excellent electrochemical performances when evaluated by EIS measurements. The introduction of the nano-structured Pt–YSZ composite into the oxygen potentiometric sensor can reduce sensor's operating temperature to be about 380°C, and also can reduce sensor's response time to be about 5s at 400°C. The oxygen potentiometric sensors incorporating nano-structured Pt–YSZ composites exhibited longer lifetime than those employing pure Pt as the sensing electrodes.

Keywords: Oxygen potentiometric sensor; Pt–YSZ; Composite

Adsorption behavior of weak hydrophilic substances on low-energy surface in aqueous medium by Wang Hui; Guo Chao; Fu Jiangang; He Zhangxing; Liang Wei; Chen Xiaolei; Zhuang Caihong (pp. 7959-7967).

There is a clear corresponding relationship between the free energy and hydrophile index of material surface, and the specific relationship is close to a simple linear relationship.Display Omitted► The adsorption of weak hydrophilic substance on low-energy surface can not be neglected. not like dealing with the high-energy surface system. ► A simple linear relationship exist between the interfacial interactive free energy and the hydrophilic index. ► The Lewis acid–base interaction is the main responsible for the absorption of weak hydrophilic substance on low-energy surface in aqueous medium.Through the methods such as measurements of contact angle and surface tension, calculations of surface energy and interfacial interaction free energy, and four weak hydrophilic substances (WHS) were taken as research objects, some interesting conclusions were obtained as follow. In aqueous medium, the WHS give priority to adsorb on low-energy surface that is low polar or particularly non-polar. There is a clear corresponding relationship between the free energy and Lewis base component γ⁻ or the hydrophile index of low-energy surface, and the specific relationship is obtained. Finally, we find hydrophobic attractive force of the Lewis acid–base interaction is mainly responsible for the absorption of WHS on low-energy surface. In short, an initial insight into adsorption behavior of WHS on low-energy surface is demonstrated in this paper.

Keywords: Weak hydrophilic substances (WHS); Adsorption; Low-energy surface (LES); Contact angle; Surface energy

Preparation of highly dispersed Pt-SnO_x nanoparticles supported on multi-walled carbon nanotubes for methanol oxidation by Chuangang Hu; Yanxia Cao; Lin Yang; Zhengyu Bai; Yuming Guo; Kui Wang; Pengle Xu; Jianguo zhou (pp. 7968-7974).

► HQ functionalization process preserves the integrity and electronic structure of MWCNTs. ► The preparaed Pt-SnO_x nanoparticles are well dispersed on the HQ-MWCNTs with an average diameter of ca. 2.2nm. ► The Pt-SnO_x/HQ-MWCNTs catalyst displays superior electrocatalytic activity and stability for the methanol oxidation, the forward peak current density of Pt-SnO_x/HQ-MWCNTs catalyst is ca. 1.9 times of that of JM commercial 20% Pt/C catalyst.To maximize the utilization of catalysts and thereby reduce the high price, a new strategy was developed to prepare highly dispersed Pt-SnO_x nanoparticles supported on 8-Hydroxyquinoline (HQ) functionalized multi-walled carbon nanotubes (MWCNTs). HQ functionalized MWCNTs (HQ-MWCNTs) provide an ideal support for improving the utilization of platinum-based catalysts, and the introduction of SnO_x to the catalyst prevents the CO poisoning effectively. The as-prepared catalysts are characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It is found that the HQ functionalization process preserves the integrity and electronic structure of MWCNTs, and the resulting Pt-SnO_x particles are well dispersed on the HQ-MWCNTs with an average diameter of ca. 2.2nm. Based on the electrochemical properties characterized by cyclic voltammetry and chronoamperometry, the Pt-SnO_x/HQ-MWCNTs catalyst displays better electrocatalytic activity and stability for the methanol oxidation. It is worth mentioning that the forward peak current density of Pt-SnO_x/HQ-MWCNTs catalyst is ca. 1.9 times of that of JM commercial 20% Pt/C catalyst, which makes it the preferable catalyst for direct methanol fuel cells.

Keywords: 8-Hydroxyquinoline; Multi-walled carbon nanotubes; Platinum; Sn oxides; Methanol oxidation

Co₃O₄–ZnO hierarchical nanostructures by electrospinning and hydrothermal methods by Muzafar A. Kanjwal; Faheem A. Sheikh; Nasser A.M. Barakat; Ioannis S. Chronakis; Hak Yong Kim (pp. 7975-7981).

► The nanofibers from colloidal solution of mixture containing Cobalt acetate, poly vinyl alcohol, and zinc powder were successfully achieved by electrospinning. ► These nanofibers after calcinations at 600°C for 1h, containing the zinc nanoparticles have been exploited as the seeds to grow nanobranches followed by hydrothermal technique. ► The produced hierarchical structure might be utilized in many exciting fields such as dye degradation, photoluminescence, etc.A new hierarchical nanostructure that consists of cobalt oxide (Co₃O₄) and zinc oxide (ZnO) was produced by the electrospinning process followed by a hydrothermal technique. First, electrospinning of a colloidal solution that consisted of zinc nanoparticles, cobalt acetate tetrahydrate and poly(vinyl alcohol) was performed to produce polymeric nanofibers embedding solid nanoparticles. Calcination of the obtained electrospun nanofiber mats in air at 600°C for 1h, produced Co₃O₄ nanofibers with rough surfaces containing ZnO nanoparticles (i.e., ZnO-doped Co₃O₄ nanofibers). The rough surfaced nanofibers, containing ZnO nanoparticles (ZnNPs), were then exploited as seeds to produce ZnO nanobranches using a specific hydrothermal technique. Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to characterize the as-spun nanofibers and the calcined product. X-ray powder diffractometery (XRD) analysis was used to study the chemical composition and the crystallographic structure.

Keywords: Zinc oxide; Zinc nanoparticles; Electrospinning; Hydrothermal; Cobalt oxide

Synthesis and characterization of hexagonal nano-sized nickel selenide by simple hydrothermal method assisted by CTAB by Azam Sobhani; Fatemeh Davar; Masoud Salavati-Niasari (pp. 7982-7987).

► NiSe nanostructures were synthesized by hydrothermal method. ► CTAB as capping agent plays a crucial role on the morphology of products. ► Reaction time and reductant agent can be affected on morphology of products.Nano-sized nickel selenide powders have been successfully synthesized via an improved hydrothermal route based on the reaction between NiCl₂·6H₂O, SeCl₄ and hydrazine (N₂H₄·H₂O) in water, in present of cetyltrimethyl ammonium bromide (CTAB) as surfactant, at various conditions. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray energy dispersive spectroscopy analysis. Effects of temperature, reaction time and reductant agent on the morphology, the particle sizes and the phase of the final products have been investigated. It was found that the phase and morphology of the products could be greatly influenced by these parameters. The synthesis procedure is simple and uses less toxic reagents than the previously reported methods. Photoluminescence (PL) was used to study the optical properties of NiSe samples.

Keywords: NiSe nanostructures; Hydrothermal; CTAB

Synthesis of SnO₂/ZnO composite nanofibers by electrospinning method and study of its ethanol sensing properties by Hamed Akbari Khorami; Mansoor Keyanpour-Rad; Mohammad Reza Vaezi (pp. 7988-7992).

► In this paper, we report the synthesis of SnO₂/ZnO composite nanofibers via electrospinning SnO₂/ZnO composite nanofibers with good distribution of diameter size and the average diameter size of about 75nm were synthesized via the electrospinning method. Polyvinyl alcohol, zinc acetate and stannous chloride were used as the precursors. The ethanol sensor based on these nanofibers showed a good and desirable sensing behavior such as high sensitivity, quick response and recovery times at optimum temperature of 360°C.In this paper, we report the synthesis of SnO₂/ZnO composite nanofibers via electrospinning method. Polyvinyl alcohol (PVA)/zinc acetate/stannous chloride nanofibers were electrospun using a solution containing PVA, zinc acetate and stannous chloride in distilled-water followed by calcination at 650°C for 2h, obtaining the related composite nanofibers. The nanofibers were characterized by simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared spectroscopy (FTIR). Ethanol sensing of the nanofibers showed a good and desirable sensing behavior such as high sensitivity, quick response and recovery times.

Keywords: Gas sensor; Ethanol sensing; Electrospinning; Composite nanofibers; SnO; ₂; /ZnO

Structural, optical and electrical properties of amorphous silicon thin films prepared by sputtering with different targets by Yi Qin; Tao Feng; Zhiqiang Li; Zhuo Sun (pp. 7993-7996).

► a-Si films were prepared with polycrystalline and monocrystalline silicon target. ► The structural, optical and electrical properties of the films are studied. ► Polycrystalline silicon target is superior to monocrystalline one.Amorphous silicon (a-Si) films were prepared by sputtering method with polycrystalline and monocrystalline silicon targets. Structural, optical and electrical properties of the a-Si films have been systematically studied. The deposition power is from 100 to 200W. Compared with the a-Si films deposited by using monocrystalline silicon target, the a-Si films prepared with polycrystalline silicon target exhibit better growth property, similar optical band gap, and own the highest mobility of 1.658cm²/Vs, which make a good match with the optimal window of optical band gap for a-Si solar cells. The results indicated that the polycrystalline silicon target is superior to the monocrystalline silicon target when used to prepare a-Si films as the intrinsic layer in a-Si solar cells.

Keywords: Amorphous silicon; Sputtering; Optical band gap; Mobility; Solar cell

Improvement of water and oil repellency on wood substrates by using fluorinated silica nanocoating by Chien-Te Hsieh; Bi-Sheng Chang; Jia-Yi Lin (pp. 7997-8002).

. Photographs of surface repellency toward different types of liquids: (a) coffee, (b) red wine, (c) coke, (d) milk, and (e) soya sauce, on F-silica coated wooden surface. The satisfactory result clearly demonstrates that this efficient approach contributes significantly to anti-contamination coatings on wooden surfaces.Display Omitted► A one-step fabrication of fluoro-containing silica coating on wooden substrates was investigated. ► The silica spheres play a crucial role in improving the repellency toward water and oil droplets. ► The multi-functional coating on wooden substrates delivers a promising feasibility on the woodworks.We have investigated a one-step fabrication of fluoro-containing silica coating on wooden substrates, showing multi-functions including super repellency toward water and sunflower oil, low sliding angles, good durability, and low adsorption capacity of moisture. The repellent slurry, consisting of well-mixing silica nanospheres and perfluoroalkyl methacrylic copolymer, is simply prepared and subsequently sprayed over wooden substrates with good adhesion. It has shown that the decoration of silica nanospheres on microscaled wooden texture acts as a crucial role in improving the repellency toward water and sunflower oil droplets. The maximal contact angles can reach as high as 168.3° and 153.6° for water and sunflower oil drops, respectively. These analyses of wetted fraction and work of adhesion also demonstrate the improved repellency due to the addition of silica. This improvement of the repellencies is ascribed to the fact that the drops partially sit on F-coated silica spheres, leaving a layer of air underneath the droplet (i.e., Cassie state). On the basis of the results, the multi-functional coating on wooden substrates delivers a promising commercial feasibility on a variety of woodworks.

Keywords: Wooden substrate; Superhydrophobic coating; Oil repellency; Sliding angle; Contact angle; Silica nanospheres

Influence of strain/stress on the nonlinear-optical properties of sprayed deposited ZnO:Al thin films by K. Bahedi; M. Addou; M. El Jouad; Z. Sofiani; H. EL Oauzzani; B. Sahraoui (pp. 8003-8005).

► ZnO:Al 3at.% thin films show a free strain/stress. ► The strain/stress of the films can influence the crystallinity and the THG. ► The higher third order nonlinear optical susceptibility is obtained for a lower strain/stress value.Nanocrystalline ZnO:Al thin films were deposited by reactive chemical pulverization spray pyrolysis technique on heated glass substrates at 450°C to study their crystalline structure, composition, strain, stress, roughness characteristics and nonlinear optical susceptibility as a function of Al concentration (0, 2, 3, 5at.%). The films were characterized by X-ray diffractometer (XRD), EDAX 9100 analyser, atomic force microscopy (AFM) and third harmonic generation (THG). The Al (3at.%) doped ZnO thin films exhibited the lower strain/stress than undoped films. The nonlinear properties of the ZnO:Al thin films have been found to be influenced by the films strain/stress.

Keywords: ZnO; Al; Spray pyrolysis; THG; Stress; Thin films

Synthesis of anatase TiO₂ nanowires by modifying TiO₂ nanoparticles using the microwave heating method by Li Li; Xiaomei Qin; Guobing Wang; Limin Qi; Guoping Du; Zhijuan Hu (pp. 8006-8012).

► Anatase TiO₂nanowires with diameter of 5–10 nm have been synthesized by microwave heating method. ► The reaction condition was controlled at 500 W, 0.5– 3.0 Mpa, and 40– 70 min. ► The surface morphology, the structural and phase identification are investigated. ► The effects of reaction time, pressure, and different post treatments are discussed.Anatase TiO₂ nanowires with a diameter of 5–10nm and length of 500nm to 2μm have been successfully synthesized by modifying TiO₂ nanoparticles (P25) using the microwave heating method. The microwave power, reaction pressure, and reaction time for the synthesis of TiO₂ nanowires were 500W, 0.5–3.0MPa (corresponding to a temperature range of 175–260), and 40–70min, respectively. X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and the BET techniques were used to investigate the phase structures, morphologies, and specific surface areas of the TiO₂ nanowires. The effects of reaction time, pressure, and different post-treatment processes on the microstructures of TiO₂ nanowires were discussed. It has been shown that the microwave heating method is efficient in transforming TiO₂ nanoparticles to anatase TiO₂ nanowires.

Keywords: Microwave heating method; TiO; ₂; Nanowires; Nanoparticles; Microstructures

Multi-layered Ag film pattern printed by spatially modulated pulsed laser beam by Seongsu Kim; Hyeongjae Lee; Myeongkyu Lee (pp. 8013-8016).

► Double-layered Ag film patterns are deposited by parallel laser printing ► The printed pattern is mechanically robust and exhibits good electrical contact ► The thickness of the first layer is a crucial factor affecting the mechanical stability ► A very low threshold pulse energy density allows printing over 5cm×5cm by a single pulse.Ag film solution-deposited on the glass source substrate was selectively transferred onto a receiver substrate by a spatially modulated pulsed ultraviolet laser beam. After printing a line pattern, an additional layer was orthogonally printed over the first layer. It was found that the thickness of the first layer is a crucial factor affecting the mechanical stability of the overall pattern. When the first layer was thicker than 0.7μm, the second layer was cracked at the junction edges regardless of its thickness. This is attributed to the vertical elongation of the second layer at the edge areas. As long as the first layer remains below 0.7μm thick, however, a very thick additional layer could be printed without any cracks. The printed patterns were mechanically robust and exhibited good electrical contact between the layers. The threshold pulse energy density for printing was measured to be 10mJ/cm² and this threshold level made it possible to print over square centimeters by a single pulse.

Keywords: Laser printing; Multi-layered film; Metallization

Adsorption of nicotine from aqueous solution onto hydrophobic zeolite type USY by Natasa Lazarevic; Borivoj Adnadjevic; Jelena Jovanovic (pp. 8017-8023).

► The isotherms of nicotine adsorption can be modeled by the Freudlich adsorption isotherm. ► The adsorbed nicotine molecules are in the form of the separated two-dimensional clusters (0.05≤ θ≤0.3). ► The continual two-dimensional layer of nicotine adsorbed is formed ( θ=0.5). ► The three-dimensional layer of adsorbed nicotine with structure different then the liquid nicotine is created ( θ≥0.7).The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite–nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine.

Keywords: Nicotine; Adsorption; Zeolite; Density distribution function; Entropy of adsorption

Te/C coaxial nanocable as a supporting material for loading ultra-high density Pt nanoparticles at room temperature by Rongbo Zheng; Kang Zheng; Hui Fu (pp. 8024-8027).

Display Omitted► Te/C nanocables were used as supporting materials to attach Pt NPs. ► Ultra-high density Pt NPs with size of about 3nm were attached at room temperature. ► The amount of Pt NPs could be controlled via changing the amount of Te/C nanocables.We have developed a facile procedure to load ultra-high density Pt NPs with the size of about 3nm on the surface of Te/C coaxial nanocable based on the –OH, –COOH hydrophilic groups on the carbon surface through directly mixing the Te/C coaxial nanocable, H₂PtCl₆, HCOOH and water at room temperature. Comparing with carbon nanotubes, the present procedure needed neither complex functionalization process nor any additional linkers. Notably, the amount of Pt NPs on the surface of coaxial nanocables could be easily controlled via changing the amount of Te/C coaxial nanocables in the mixture.

Keywords: Platinum; Te/C Nanocables; Room temperature

Novel urchin-like Pd nanostructures prepared by a simple replacement reaction and their catalytic properties by Zhipeng Cheng; Jiming Xu; Hui Zhong; XiaoZhong Chu; Juan Song (pp. 8028-8032).

Display Omitted► Novel urchin-like Pd nanostructures were firstly synthesized using a simple replacement reaction. ► Numerous one-dimensional Pd nanorods radiate from the center of the aluminum templates. ► The urchin-like Pd nanostructures can accelerate the thermal decomposition of ammonium perchlorate.Novel urchin-like Pd nanostructures were firstly synthesized using a simple replacement reaction between Al and PdCl₂ aqueous solution at room temperature without the assistance of any surfactant or ligand. Their phase structure, morphology, specific surface area, and catalytic property were characterized by XRD, TEM, EDS, BET and DSC/TG. The results show numerous one-dimensional Pd nanorods radiate from the center of the aluminum templates to form an urchin-like shape with a diameter of ∼0.5–1.0μm. The as-prepared urchin-like Pd nanostructures can serve as a promising additive to accelerate the thermal decomposition of ammonium perchlorate (AP), a key oxidizer in composite solid propellants.

Keywords: Pd nanostructure; Urchin-like; Ammonium perchlorate; Catalytic property

The electrical and magnetic properties of epitaxial orthorhombic YMnO₃ thin films grown under various oxygen pressures by Zhong Chen; Chun-Lu Ma; Fei-Xiang Wu; Y.B. Chen; Jian Zhou; Guo-Liang Yuan; Zheng-Bin Gu; Shan-Tao Zhang; Yan-Feng Chen (pp. 8033-8037).

► Orthorhombic YMnO₃ thin films were grown under various oxygen pressures. ► Oxygen pressure dependent leakage current and magnetic behavior were observed. Resistive switching behavior was obtained only in films grown under 30Pa O₂. ► The results are discussed by considering the effects of oxygen vacancy on properties.Orthorhombic YMnO₃ thin films were epitaxially grown on bare and LaNiO₃ buffered (001)–SrTiO₃ substrates by pulsed laser deposition under various oxygen pressures from 5 to 30Pa. The crystal structure and microstructure of these films have been characterized by both X-ray diffractions and transmission electron microscopy. The leakage current, modeled as the space charge limited current (SCLC) mechanism, decreased significantly with the increase of oxygen content. It is further found that the magnetic property of films is greatly enhanced in YMnO₃ films grown under high oxygen pressure, which can be explained decreased oxygen vacancies. In addition, bipolar switching behavior was obtained only in the films grown under 30Pa oxygen pressure, which is attributed to the decrease of voltage-driven oxygen vacancy migration.

Keywords: YMnO; ₃; Oxygen vacancy; Leakage current; Magnetic; Resistive switching

Analyses of residual iron in carbon nanotubes produced by camphor/ferrocene pyrolysis and purified by high temperature annealing by E.F. Antunes; V.G. de Resende; U.A. Mengui; J.B.M. Cunha; E.J. Corat; M. Massi (pp. 8038-8043).

► We analyzed iron-containing phases in multiwall carbon nanotubes (MWCNTs) by thermogravimetric analysis, Mössbauer spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. ► The MWCNTs were produced by camphor/ferrocene and purified by high temperature thermal annealing in an oxygen-free atmosphere (N₂ or vacuum). ► The vacuum treatments provided MWCNTs with a purity degree higher than 99%. ► We included a brief description of iron removal mechanism, emphasizing the mobility of iron atoms through graphitic sheets and the large contact angle of iron clusters on MWCNT surfaces at high temperatures.A detailed analysis of iron-containing phases in multiwall carbon nanotube (MWCNT) powder was carried out. The MWCNTs were produced by camphor/ferrocene and purified by high temperature annealing in an oxygen-free atmosphere (N₂ or VC). Thermogravimetric analysis, Mössbauer spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy enabled the evaluation of the residual iron in MWCNTs after purification. The VC treatments provided MWCNTs with a purity degree higher than 99%. Moreover, Raman spectroscopy revealed a significant improvement in graphitic ordering after thermal annealing. A brief description of the mechanism of iron removal was included. We highlight the mobility of iron atoms through graphitic sheets and the large contact angle of iron clusters formed on MWCNT surfaces at high temperatures.

Keywords: Carbon nanotubes; Purification; Annealing; Mossbauer spectrocopy; Camphor; XPS

Influence of substrate temperature on surface textured ZnO:Al films etched with NaOH solution by Ying Wang; Yousong Gu; Shou Peng; Wanyu Ding; Hualin Wang; Weiping Chai (pp. 8044-8047).

► In our work, Al-doped ZnO (ZnO:Al, AZO) thin films with good optical and electrical characteristics have been prepared by direct current pulse magnetron sputtering. ► Surface textured AZO films have been obtained by etching with NaOH solution at room temperature. ► And the influence of substrate temperature on surface textured AZO films etched with NaOH solution has been investigated. ► According to the results, the AZO film deposited at 270°C displayed the best light trapping ability.Transparent conducting Al-doped ZnO (ZnO:Al, AZO) thin films with good optical and electrical characteristics were prepared by direct current pulse magnetron sputtering. Textured surfaces of AZO films were obtained by etching with NaOH solution successfully and the effect of substrate temperature on the surface texture was investigated. The surface is covered with craters after etching with 5% NaOH solution, and the crater diameter decreases gradually as substrate temperature increases. For AZO film deposited at 270, the crater diameters is 0.5–1μm, which is an effective surface texture for light trapping.

Keywords: ZnO:Al; Texture; Light trapping; Haze

Nanocrystalline hard chromium electrodeposition from trivalent chromium bath containing carbamide and formic acid: Structure, composition, electrochemical corrosion behavior, hardness and wear characteristics of deposits by F.I. Danilov; V.S. Protsenko; V.O. Gordiienko; S.C. Kwon; J.Y. Lee; M. Kim (pp. 8048-8053).

► The Cr–C electrodeposits have a nanocrystalline type of structure. ► Carbon is present as chromium carbide. ► The deposits exhibit an absence of the active dissolution range in acid solution. ► The hardness and wear characteristics were investigated.The paper is devoted to the structure, composition and properties investigations of coatings obtained from a sulfate trivalent chromium bath containing formic acid and carbamide as the complexing agents. The results indicate that the deposits have a nanocrystalline type of structure—there are regions with atomic ordered arrangement in bulk material with the average size of 3–5nm. Carbon is present as chromium carbide within the coating and it is distributed uniformly inside of the deposit. The deposits under study exhibit particular electrochemical behavior (absence of the active dissolution range in acid solution). The hardness of these coatings does not differ noticeably from that typical of coatings obtained in Cr(VI)-based baths. The wear characteristics of the deposits from the proposed bath are somewhat better than in the case of a common hexavalent chromium bath.

Keywords: Trivalent chromium bath; Hard chromium electrodeposition; Nanocrystalline coatings; Hardness; Wear characteristics

Hydrogen template assisted electrodeposition of sub-micrometer wires composing honeycomb-like porous Pb films by Serhiy Cherevko; Xiaoli Xing; Chan-Hwa Chung (pp. 8054-8061).

► We study the effect of hydrogen co-deposition on porous Pb morphology. ► Growth of Pb wires and particles is controlled by H⁺ content in electrolyte. ► The obtained wires are single crystalline branches of dendrites. ► Dendrites overgrow hydrogen bubbles and form highly porous foams.High surface area porous Pb films are electrodeposited using a hydrogen bubble dynamic template. The influence of the experimental parameters on the morphology features such as the pore size, wall thickness, and sub-micrometer size features is investigated. Two structural transformations between sub-micrometer wires and particles obtained by adjusting the HClO₄ concentration are observed. At a low HClO₄ concentration, the growth of sub-micrometer wires is favored. The deposition of particles or wires covered by particles is observed at higher H⁺ concentrations. The addition of sodium citrate as an additive facilitates the preservation of Pb in the form of wires. Adjusting the concentration of Pb(ClO₄)₂·3H₂O influences the mass transfer of Pb and affects its morphology. At low concentrations, the deposition of porous Pb films composed of porous wires is shown. The additional deposition of particles on wires is observed at high concentrations. The formation process of honeycomb-like porous structures is revealed by analysis of films deposited during different deposition time. The influence of the current density on the micro and sub-micrometer scale morphologies is presented.

Keywords: Porous lead; Hydrogen template; Pb wires

Analyses of surface temperatures on patterned sapphire substrate for the growth of GaN with metal organic chemical vapor deposition by Zheng Li; Yuxuan Jiang; Tongjun Yu; Zhiyuan Yang; Yuebin Tao; Chuanyu Jia; Zhizhong Chen; Zhijian Yang; Guoyi Zhang (pp. 8062-8066).

► Surface temperature of PSS for GaN growth by MOCVD is studied by FEM simulations. ► The relation of surface temperature of PSS and the forced convection conditions is discussed. ► The effects of PSS topographies and scales on surface temperature are presented.The surface temperature of cone-shaped patterned sapphire substrate (PSS) in GaN epitaxial growth by MOCVD and its relation to forced convection conditions and substrate surface topography were systematically investigated. Calculations using finite element method (FEM) exhibited that increase of substrate thickness would reduce surface temperature variation on PSS in typical growth condition. A hydrodynamics model under different chamber conditions is established, suggesting that carrier gas's velocity V_∞ plays a significant role on surface temperature of PSS in comparison with planar substrate. Also, carrier gas's pressure P_carrier is found to be another important factor on surface thermal distribution. Results of temperatures of surface with different pattern topographies suggested that an ideal PSS structure can confine the in-cell temperature discrepancy on surface into less than 0.4K. Pattern scales of PSS and their influence on surface temperature variation were also discussed.

Keywords: Patterned sapphire substrate; Surface temperature; GaN; MOCVD

Electroless plating of copper on surface-modified glass substrate by Wei Su; Libei Yao; Fang Yang; Peiyuan Li; Juan Chen; Lifang Liang (pp. 8067-8071).

► A novel method for electroless copper deposition on glass material is reported. ► The formation of modified-glass substrate is confirmed. ► The surface morphology of the electroless plated copper film is characterized. ► The chemical composition of the copper-metalized glass surface is determined.This work focuses on developing a novel convenient method for electroless copper deposition on glass material. This method is relied on the formation of amino (NH₂)-terminated film on the surface of glass substrate, by coating polyethylenimine (PEI) on glass matrix and using epichlorohydrin (ECH) as cross-linking agent. The introduced amino groups can effectively adsorb the palladium, the catalysts which could initiate the subsequent Cu electroless plating, onto the glass substrate surface. Finally, a copper film is formed on the palladium-activated glass substrate through copper electroless plating and the surface-coppered glass material is therefore acquired. X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscopy (SEM) images combined with energy diffraction X-ray (EDX) analysis demonstrate the successful copper deposition on the surface of glass substrate.

Keywords: Electroless deposition; Copper; Amine modification; Glass substrate

Tunable photocatalytic selectivity of fluoropolymer PVDF modified TiO₂ by Liqun Ye; Changjun Yang; Lihong Tian; Ling Zan; Tianyou Peng (pp. 8072-8077).

Display Omitted► Fluoropolymer was used to modify TiO₂ firstly. ► PVDF/TiO₂ shows high photocatalytic selectivity by degrading mixed solution of cationic dyes MB and anionic dyes MO. ► The selectivity can be tuned by changing the PVDF modification amount.Fluoropolymer poly-vinylidene-fluoride modified TiO₂ (PVDF/TiO₂) were prepared via a simple chemisorption approach and characterized by thermo gravimetric analyse, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and photoluminescence spectra. The modified mechanism and the photocatalytic selectivity of the PVDF/TiO₂ were studied. The existence of Ti-F coordination bond on the interface between TiO₂ and PVDF was confirmed. For the PVDF modification, the photocatalytic degradation (PCD) of cationic dye was greatly enhanced, and the PCD of anionic dye was obviously inhibited. PVDF/TiO₂ shows high photocatalytic selectivity than that of TiO₂ by degrading mixed solution of cationic dyes MB and anionic dyes MO. The selectivity can be tuned by changing the PVDF modification amount.

Keywords: TiO; ₂; PVDF; Photocatalytic; Selectivity

Femtosecond pulsed laser deposition of Ge quantum dot growth on Si(100)-(2×1) by Ali Oguz Er; Hani E. Elsayed-Ali (pp. 8078-8084).

► In this manuscript we report on our observation of germanium quantum dot formation on Si (100)-(2×1) by using femtosecond pulsed laser deposition (PLD). ► We have studied the shape transition of Ge quantum dots at different thicknesses and showed that using femtosecond pulses significantly reduces the epitaxial temperature compared to nanosecond PLD, MBE and CVD. ► We explain the mechanism responsible for the morphology change and epitaxial growth temperature.Ge quantum dots were grown on Si(100)-(2×1) by femtosecond pulsed laser deposition at various substrate temperatures using a femtosecond Ti:sapphire laser. In situ reflection high-energy electron diffraction and ex situ atomic force microscopy were used to analyze the film structure and morphology. The morphology of germanium islands on silicon was studied at different coverages. The results show that femtosecond pulsed laser deposition reduces the minimum temperature for epitaxial growth of Ge quantum dots to ∼280°C, which is 120°C lower than previously observed in nanosecond pulsed laser deposition and more than 200°C lower than that reported for molecular beam epitaxy and chemical vapor deposition.

Keywords: Quantum dots; Self-assembly; Pulsed laser deposition; RHEED; AFM

Unusual piezoresponse behavior across the grain boundary of PbMg_1/3Nb_2/3O₃–0.33PbTiO₃ thin films by X. Leng; H.R. Zeng; X.M. Li; Y. He; K.Y. Zhao; W. Wang (pp. 8085-8088).

► Piezoresponse behavior of PMN–0.33PT thin film was investigated via PFM. ► Piezoresponse enhancement was observed across the grain boundary in PMN–PT thin film. ► This is ascribe to incompatibility-induced stress. ► The stress also contributes to local imprint behavior.Ferroelectric PbMg_1/3Nb_2/3O₃–0.33PbTiO₃ (PMN–0.33PT) polycrystalline thin film near MPB was grown on Ir with LaNiO₃ buffer layer by pulsed laser deposition technology. Piezoresponse force microscopy (PFM) was employed to investigate the role of grain boundary on the domains formation and their local physical properties in PMN–PT thin film. Unusual piezoresponse behaviors were firstly observed across the grain boundary of PMN–PT thin film via PFM. Such abnormal phenomenon is ascribed to the structural incompatibility-induced local stress across the grain boundary, which gives a deep influence on the local imprint behavior of PMN–PT thin film.

Keywords: PbMg; _1/3; Nb; _2/3; O; ₃; –PbTiO; ₃; (PMN–PT) thin film; Ferroelectric domains; Grain boundary; Piezoresponse force microscopy (PFM)

Improved surface-enhanced Raman scattering of patterned gold nanoparticles deposited on silicon nanoporous pillar arrays by Wei Fen Jiang; Xing Fu Li; Hong Tao Cai; Xin Jian Li (pp. 8089-8092).

► A new synthesized composite structure, a patterned gold/silicon nanoporous pillar array (Au/Si-NPA) made by depositing Au on Si-NPA using conventional thermal evaporation method, can be used as a surface-enhanced Raman scattering (SERS) substrate. Its surface component and morphology were analyzed by X-ray diffraction and field-emission scanning electron microscopy, respectively. It was found that the surface was a continuous Au nanoparticle film evenly covered the surface of Si/NPA. The composite structure is strongly SERS active using rhodamine 6G as probe molecules, which is mainly due to the patterned hierarchical Au structure, and good reproducibility which is attributed to Au nanoparticles with narrow particle-size distribution uniformly coated on the surface.Large-area silicon nanoporous pillar arrays (Si-NPA) uniformly coated with gold nanoparticles was synthesized, and surface-enhanced Raman scattering of rhodamine 6G adsorbed on these gold nanoparticles were studied and compared. It's found that Au/Si-NPA substrate has a significantly high Raman signal sensitivity and good homogeneity. These are attributed to gold nanoparticles with narrow particle-size distribution uniformly coated on the surface and to the enlarged specific surface area for adsorption of target molecules brought by the porous silicon pillars.

Keywords: Surface-enhanced Raman scattering; Silicon nanoporous pillar array; Evaporation

Solvent vapor induced morphology transition in thin film of cylinder forming diblock copolymer by Yuhu Li; Haiying Huang; Tianbai He; Yumei Gong (pp. 8093-8101).

The morphology formation and transition of thin film of polystyrene– block–poly(methyl methacrylate) diblock copolymer annealed under 1,1,2-trichloroethane, toluene, and their binary mixed solvent vapors is investigated by using OM and TEM. A morphology evolution with increasing the annealing solvent vapor pressure and a series of morphologies depending on the solvent vapor preferential affinities have been observed.The morphology formation and transition of thin film of a cylinder-forming polystyrene– block–poly(methyl methacrylate) (PS– b–PMMA) diblock copolymer annealed under 1,1,2-trichloroethane (Tri-CE), toluene (Tol), and their binary mixed solvent vapors is investigated by using optical microscopy (OM) and transmission electronic microscopy (TEM). By modulating the annealing solvent vapor pressure and the preferential affinities, a detailed morphology evolution with increasing the vapor pressure and a series of morphologies depending on the preferential affinities have been observed. A phase diagram by plotting the morphologies as a function of the annealing solvent vapor pressure and its preferential affinity is subsequently constructed.

Keywords: Controlled solvent vapor pressure annealing; Diblock copolymers; Self-assembly

Effect of Pt and Ti on Ni/Ag/(Pt or Ti)/Au p-ohmic contacts of GaN based flip-chip LEDs by Hong Joo Song; Cheong Hyun Roh; Hong Goo Choi; Min-Woo Ha; Cheol-Koo Hahn; Jung Ho Park; Jun Ho Lee (pp. 8102-8105).

► In this paper, we report the dependence of Ni/Ag/diffusion barrier (D.B)/Au p-ohmic contact on Pt^D.B and Ti^D.B for GaN based flip-chip light emitting diodes (FC LEDs). ► The reflectance and contact resistivity of p-ohmic contact were analyzed by confocal laser scanning microscopy (CLSM) and SIMS depth profile. ► Pt^D.B and Ti^D.B showed the clearly different effect on the atomic distribution, which influenced on reflectance and contact resistivity of p-ohmic contact. ► We especially focused on the interface between p-electrode and p-GaN contact layer, which was analyzed by CLSM and SIMS depth profile in details, and identified the origins of properties. ► We think that our experimental results and interpretation could be of much help in understanding the roles of two kinds of diffusion barrier, Pt and Ti, on the p-ohmic contact based on Ni/Ag.In this paper, we report the dependence of Ni/Ag/diffusion barrier (D.B)/Au p-ohmic contact on Pt^D.B and Ti^D.B for GaN based flip-chip light emitting diodes (FC LEDs). It is shown that D.B metals have strongly influenced on the reflectance and contact resistivity of contacts. We present these results are caused by the variation of the morphology and atomic distribution due to D.Bs. The roles of Pt^D.B and Ti^D.B on Ni/Ag/D.B/Au p-GaN ohmic contacts are analyzed using the confocal laser scanning microscopy (CLSM) measurement and the secondary ion mass spectroscopy (SIMS) profiles in details.

Keywords: GaN; Flip-chip (FC); p; -Ohmic contact; Silver (Ag); Specific contact resistivity; Reflectance; Surface morphology

Synthesis and CO₂ capture property of high aspect-ratio Li₂ZrO₃ nanotubes arrays by Limin Guo; Xiaohui Wang; Caifu Zhong; Longtu Li (pp. 8106-8109).

Display Omitted► High aspect-ratio Li₂ZrO₃ nanotubes were prepared by hydrothermal method using ZrO₂ nanotubes layers as templates. That was not reported before. ► The Li₂ZrO₃ nanotubes had a uniform morphology, tetragonal structure and high specific surface area. ► Comparing to the nanoparticle or bulk Li₂ZrO₃, the nanotubal nature gives rise to improve the CO₂ capture capacity of the layers. ► The tetragonal crystalline structure and introduction of ZrO₂ crystal in the layers were also responsible to their high CO₂ capture nature.High aspect-ratio Li₂ZrO₃ nanotubes were prepared by hydrothermal method using ZrO₂ nanotubes layers as templates. Characterizations of SEM, XRD, TEM and CO₂ adsorption were performed. The results showed that tetragonal Li₂ZrO₃ nanotubes arrays containing a little monoclinic ZrO₂ can be obtained using this simple method. The mean diameter of the nanotubes is approximately 150nm and the corresponding specific surface area is 57.9m²g⁻¹. Moreover, the obtained Li₂ZrO₃ nanotubes were thermally analyzed under a CO₂ flow to evaluate their CO₂ capture property. It was found that the as-prepared Li₂ZrO₃ nanotubes arrays would be an effective acceptor for CO₂ at high temperature.

Keywords: Zirconia; Li; ₂; ZrO; ₃; nanotubes; Hydrothermal; CO; ₂; sorption

Valence band offset of GaN/diamond heterojunction measured by X-ray photoelectron spectroscopy by K. Shi; X.L. Liu; D.B. Li; J. Wang; H.P. Song; X.Q. Xu; H.Y. Wei; C.M. Jiao; S.Y. Yang; H. Song; Q.S. Zhu; Z.G. Wang (pp. 8110-8112).

► XPS was used to measure the energy discontinuity in the GaN/diamond heterostructure. ► The valence band offset was determined to be 0.38 ± 0.15 eV and a type- II heterojunction with a conduction band offset of 2.43±0.15 eV was obtained.XPS was used to measure the energy discontinuity in the GaN/diamond heterostructure. The valence band offset (VBO) was determined to be 0.38±0.15eV and a type-II heterojunction with a conduction band offset (CBO) of 2.43±0.15eV was obtained.

Keywords: Valence band offset; GaN/diamond heterojunction; XPS; Conduction band offset

Effect of nickel doping on the photocatalytic activity of ZnO thin films under UV and visible light by Nina V. Kaneva; Dimitre T. Dimitrov; Ceco D. Dushkin (pp. 8113-8120).

Display Omitted► The addition of Ni²⁺ ions to the initial solution modifies the the ganglia-like hills and wrinkles morphology of the films. ► Amount of nickel doping strongly affect the photocatalytic activity of ZnO films under both, the UV and visible light iradiation. ► The concentration of MG by ZnO films decreases even in darkness.Nanostructured ZnO thin films with different concentrations of Ni²⁺ doping (0, 1, 5, 10 and 15wt.%) are prepared by the sol–gel method for the first time. The thin films are prepared from zinc acetate, 2-methoxyethanol and monoethanolamine on glass substrates by using dip coating method. The films comprise of ZnO nanocrystallites with hexagonal crystal structure, as revealed by X-ray diffraction. The film surface is with characteristic ganglia-like structure as observed by Scanning Electron Microscopy. Furthermore, the Ni-doped films are tested with respect to the photocatalysis in aqueous solutions of malachite green upon UV-light illumination, visible light and in darkness. The initial concentration of malachite green and the amount of catalyst are varied during the experiments. It is found that increasing of the amount of Ni²⁺ ions with respect to ZnO generally lowers the photocatalytic activity in comparison with the pure ZnO films. Nevertheless, all films exhibit a substantial activity under both, UV and visible light and in darkness as well, which is promising for the development of new ZnO photocatalysts by the sol–gel method.

Keywords: ZnO thin films; Ni(II); Doping; Zinc oxide; Visible light; UV; Photocatalysis; Malachite green; Sol–gel method

Enhanced visible light photocatalytic properties of Fe-doped TiO₂ nanorod clusters and monodispersed nanoparticles by Y. Liu; J.H. Wei; R. Xiong; C.X. Pan; J. Shi (pp. 8121-8126).

► The Fe-TiO₂ nanorod clusters and monodispersed nanoparticles were prepared in this paper. ► The microstructures and morphologies can be controlled by restraining the hydrolytic reaction rates. ► The modified morphologies enhance the specific surface areas of the prepared photocatalysts. ► Fe³⁺-dopant promotes the visible light utility and enhances the quantum efficiency of TiO₂. ► The Fe-doped photocatalysts show high photocatalytic activities under visible light.In order to get photocatalysts with desired morphologies and enhanced visible light responses, the Fe-doped TiO₂ nanorod clusters and monodispersed nanoparticles were prepared by modified hydrothermal and solvothermal method, respectively. The microstructures and morphologies of TiO₂ crystals can be controlled by restraining the hydrolytic reaction rates. The Fe-doped photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectroscopy (UV–vis), N₂ adsorption–desorption measurement (BET), and photoluminescence spectroscopy (PL). The refinements of the microstructures and morphologies result in the enhancement of the specific surface areas. The Fe³⁺-dopants in TiO₂ lattices not only lead to the significantly extending of the optical responses from UV to visible region but also diminish the recombination rates of the electrons and holes. The photocatalytic activities were evaluated by photocatalytic decomposition of formaldehyde in air under visible light illumination. Compared with P25 (TiO₂) and N-doped TiO₂ nanoparticles, the Fe-doped photocatalysts show high photocatalytic activities under visible light.

Keywords: Fe-doped TiO; ₂; Monodispersed nanoparticles; Nanorod clusters; Photocatalytic activities; Formaldehyde; Visible light

Structural transition and blue emission in textured and highly transparent spray deposited Li doped WO₃ thin films by M. Kovendhan; D. Paul Joseph; E. Senthil Kumar; A. Sendilkumar; P. Manimuthu; S. Sambasivam; C. Venkateswaran; R. Mohan (pp. 8127-8133).

► Doping of Li (0–5wt%) in WO₃ thin films leads to structural change from orthorhombic to tetragonal phase. ► XRD patterns suggest textured growth for Li doped films. ► Li-doped films revealed greater transparency. ► Direct and indirect bandgaps were found to blue shift with Li doping. ► Photoluminescence spectra show pronounced blue emission with Li doping.The effect of Li (0–5wt%) doping on the properties of WO₃ thin films deposited using an automated homemade spray pyrolysis unit is studied. Change in structural and optical properties is observed on doping with Li. The XRD patterns shows that undoped WO₃ film has an orthorhombic phase while the Li (1–5wt%) doped WO₃ films have tetragonal phase. The SEM and AFM images confirm relatively smooth surface of Li doped WO₃ films compared to undoped WO₃ film. Transmission spectra reveal that the transparency of the Li-doped films is much greater than that of undoped film. From the transmission data, the direct, indirect bandgap and phonon energies were calculated. Room temperature photoluminescence spectra showed pronounced blue emission on doping with Li.

Keywords: Spray pyrolysis; Tungsten oxide; Lithium; Textured growth; Optical transparency; Photoluminescence

Mechanical reliability of transparent conducting IZTO film electrodes for flexible panel displays by Young Sung Kim; Woo Jin Hwang; Kyung Tae Eun; Sung-Hoon Choa (pp. 8134-8138).

► Amorphous IZTO films fabricated at room temperature showed the best properties at oxygen partial pressure of 3%. ► IZTO films have a better mechanical durability compared to ITO films for both outer and inner bending tests. ► IZTO films exhibit better feasibility than ITO films for use as transparent conducting electrodes in flexible display devices.The mechanical reliability of transparent In–Zn–Sn–O (IZTO) films grown using pulsed DC magnetron sputtering with a single oxide alloyed ceramic target on a transparent polyimide (PI) substrate at room temperature is investigated. All IZTO films deposited at room temperature have an amorphous structure. However, their optical and electrical properties change depending on the oxygen partial pressure applied during depositing process. At an oxygen partial pressure of 3%, the films exhibit a resistivity of 8.3×10⁻⁴Ωcm and an optical transmittance of 86%. Outer bending tests show that the critical bending radius decreases from 10mm to 7.5mm when the oxygen partial pressure increases from 1% to 3%. In the inner bending test, the critical bending radius is independent of oxygen partial pressure at 3.5mm, indicating excellent film flexibility. In the dynamic fatigue test, the electrical resistance of the films reduces by less than 1% for more than 2000 bending cycles. These results suggest that IZTO films have excellent mechanical durability and flexibility in comparison to ITO films.

Keywords: Transparent conducting oxide; Zinc doped In oxide (IZTO); Film; Mechanical reliability; Flexible panel display

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Applied Surface Science (v.257, #18)

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Applied Surface Science (v.257, #18)