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Applied Surface Science (v.258, #5)

Contents Contd... (pp. i).

Enhancement of surface properties of oil fly ash by chemical treatment by Reyad Shawabkeh; Muhammad J. Khan; Abdulhadi A. Al-Juhani; Hamad I. Al-Abdul Wahhab; Ibnelwaleed A. Hussein (pp. 1643-1650).

► Treatment of OFA with mixture of H₂SO₄/HNO₃, and air yield carboxylic functionalized OFA and high surface area. ► Modified OFA is used with polymer composite to reduce agglomeration in polymer applications. ► Modified OFA is more compatible with nonpolar polymers.In this study, surface modification of oil fly ash (OFA), a by-product generated by oil power plants, was achieved by chemical treatment. A mixture of sulfuric and nitric acids was used to modify the surface in order to attach a carboxylic functional group to the surface of OFA. The goal of surface modification of OFA is to make its surface more compatible with nonpolar polymers in order to produce OFA/polymer composite materials with improved dispersion of OFA, and to increase OFA surface area in order to support its use as adsorbent materials in adsorptive separation and purification applications. Different acid compositions were used for treatment by gradually increasing the nitric acid concentration from 0 to 20%. Also, the effect of oxidation on surface modification was examined by introducing air to enhance the oxidation of OFA. FTIR analysis was performed to identify the different functional groups attached to OFA surface before and after the chemical treatment. Evaluation of different structural changes during the surface modification was investigated by XRD analysis. Surface morphology and spot analysis was studied by SEM technique to identify the composition of different elements present in the OFA such as carbon, oxygen and sulfur. BET analysis showed major increase in surface area after modification as well as pore size and micropore volume of OFA particles. The maximum increase in surface area was obtained with 15vol.% HNO₃. Also, carboxylic functionalization of OFA was enhanced when air was injected.

Keywords: Ash; Acid treatment; Surface modification; Oxidation

Diffusion of Li⁺ ion on graphene: A DFT study by Jiming Zheng; Zhaoyu Ren; Ping Guo; Li Fang; Jun Fan (pp. 1651-1655).

► The electronic structure of boron doped graphene and the potential barrier of lithium diffusion on the different number of boron doped graphene are studied and analyzed. ► The graphene has changed from semimetal to semiconductor with the increasing number of doped boron atoms. ► The grapheme with an electron-deficient system is more conducive to the adsorption of lithium-ion. ► The potential barrier for lithium diffusion on boron doped graphene is higher than that of intrinsic graphene.Density functional theory investigations show that the Li⁺ ion is stabilized at the center of hexagonal carbon ring with the distance of 1.84Å from graphene surface. The potential barrier of Li⁺ ion diffusion on the graphene surface, about 0.32eV, is much lower than that of Li⁺ ion penetrating the carbon ring which is 10.68eV. When a vacancy of graphene exists, potential barrier about 10.25eV for Li⁺ ion penetrating the defect is still high, and the ability of the vacancy to sizing the Li⁺ ion is also observed. Electronic densities of states show that the formation of a localized bond between Li atom and edge carbon of vacancy is the main reason for high potential barrier when Li⁺ ion penetrate a vacancy. While Coulomb repulsion is the control factor for high potential barrier in case of Li⁺ ion penetrating a carbon ring.

Keywords: Adsorption; Charge transfer; Diffusion path; First principle method

Characterization and photocatalytic activity of Zn²⁺–TiO₂/AC composite photocatalyst by Xincheng Lu; Jianchun Jiang; Kang Sun; Dandan Cui (pp. 1656-1661).

► Zn²⁺–TiO₂ deposited on activated carbon as photocatalyst. ► Toluene as a pollution target to evaluate the photocatalytic activity of photocatalyst. ► Zn²⁺-doping reduces the crystallite size of TiO₂ and induces the generation of photo-holes. ► Zn²⁺-doping increases the oxidation and reduction of the hole–electron pairs. ► Zn²⁺–TiO₂/AC photocatalyst has higher photocatalytic activity than TiO₂.Activated carbon (AC) supported Zn²⁺–TiO₂ photocatalyst was prepared by sol–gel method. The prepared samples were characterized by X-ray diffraction, scanning electron micrograph, nitrogen absorption, diffuse reflectance UV/VIS and X-ray photoelectron spectroscopy. Using toluene as a pollution target, the photocatalytic activity of photocatalyst was evaluated. The results showed that prepared photocatalyst was obviously helpful for the removal of toluene in air. The photocatalytic degradation of toluene by Zn²⁺–TiO₂/AC reached 100% for 40min and remained 75% after 160min, while degradation by TiO₂ was only 30%. It indicated that the photocatalytic activity of prepared photocatalyst was enhanced. It is due to Zn²⁺-doping increased the oxidation and reduction of hole–electron pairs, which was the important factor in heterogeneous photocatalysis.

Keywords: Photocatalytic activity; Activated carbon; Zn; ²⁺; –TiO; ₂; Photocatalysis; Toluene

SERS activity of Au nanoparticles coated on an array of carbon nanotube nested into silicon nanoporous pillar by Wei Fen Jiang; Yan Feng Zhang; Yu Sheng Wang; Lei Xu; Xin Jian Li (pp. 1662-1665).

► A novel structure, Au covered on a nest-shaped carbon nanotube array is made. ► The Au nanoparticle film is relatively uniform with a thickness less than 20nm. ► The composite structure is strongly SERS active using R6G as probe molecules. ► It could clearly detect R6G up to 10⁻⁸M. ► The excellent property is attributed to the enlarged surface area brought by CNTs.A novel composite structure, Au nanoparticles coated on a nest-shaped array of carbon nanotube nested into a silicon nanoporous pillar array (Au/NACNT/Si-NPA), was fabricated for surface-enhanced Raman scattering (SERS). The morphology of the Au/NACNT/Si-NPA composite structure was characterized with the aid of scanning electron microscopy, X-ray diffraction instrumentation and Transmission electron microscopy. Compared with SERS of rhodamine 6G (R6G) adsorbed on SERS-active Au substrate reported, the SERS signals of R6G adsorbed on these gold nanoparticles were obviously improved. This was attributed to the enlarged specific surface area for adsorption of target molecules brought by the nest-shaped CNTs structure.

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

Use of quartz crystal nanobalance to study the binding and stabilization of albumin and doxycycline on a thin layer of hydroxyapatite by Sunita Prem Victor; Chandra P. Sharma; K. Sreenivasan (pp. 1666-1669).

Display Omitted► Hydroxyapatite (HA) was coated on quartz crystal by deposition technique. ► Albumin adsorption on HA coated quartz was monitored by quartz crystal nanobalance. ► Doxycycline used to facilitate as specific interaction sites for albumin binding. ► Albumin adsorption on HA coated quartz immobilized with doxycycline was monitored by quartz crystal nanobalance. ► The albumin deposited shows a substantial increase and is retained for an enhanced period of time.This study reports the use of quartz crystal nanobalance (QCN) to study the adsorption of two model molecules namely albumin and doxycycline by hydroxyapatite (HA). The work focuses on the deposition of a stable coating of HA on the quartz crystal, modification of the coating using doxycycline and its subsequent effects on albumin adsorption. The uniformity and thickness of the HA coating has been studied using atomic force microscopy (AFM). The functional groups to ascertain the presence of the selected moieties have been characterized by Raman spectroscopy. The results indicate that the mass of albumin deposited on the surface of the HA coated quartz crystal functionalized with doxycycline shows a substantial increase when compared to the standard HA coated quartz crystal. The adsorbed albumin has also been found to be retained for an enhanced period of time. This surface immobilization of doxycycline and subsequent albumin adsorption seem to be a promising approach to confer biomaterials with antithrombogenic and antibacterial surfaces.

Keywords: Quartz crystal nanobalance; Hydroxyapatite; Albumin; Doxycycline

Bilayer porous scaffold based on poly-(ɛ-caprolactone) nanofibrous membrane and gelatin sponge for favoring cell proliferation by Zhihua Zhou; Yang Zhou; Yiwang Chen; Huarong Nie; Yang Wang; Fan Li; Yan Zheng (pp. 1670-1676).

Bilayer porous scaffolds based on poly-(ɛ-caprolactone) (PCL) electrospun membranes and gelatin (GE) sponges were fabricated through surface modification. GE sponges were stably anchored on PCL membrane surface with the aid of grafted GE molecules and crosslink of GE coat and grafted GE molecules. It showed excellent hydrophilic surface, desirable mechanical strength and better cell affinity.Display Omitted► Bilayer porous scaffolds based on poly-(ɛ-caprolactone) (PCL) electrospun membranes were fabricated through surface modification. ► Gelatin (GE) sponges were stably anchored on membrane surface with the aid of grafted GE molecules and crosslink. ► It showed excellent hydrophilic surface, desirable mechanical strength and better cell affinity.Electrospun poly-(ɛ-caprolactone) (PCL) nanofibers has been widely used in the medical prosthesis. However, poor hydrophilicity and the lack of natural recognition sites for covalent cell-recognition signal molecules to promote cell attachment have limited its utility as tissue scaffolds. In this study, Bilayer porous scaffolds based on PCL electrospun membranes and gelatin (GE) sponges were fabricated through soft hydrolysis of PCL electrospun followed by grafting gelatin onto the fiber surface, through crosslinking and freeze drying treatment of additional gelatin coat and grafted gelatin surface. GE sponges were stably anchored on PCL membrane surface with the aid of grafted GE molecules. The morphologies of bilayer porous scaffolds were observed through SEM. The contact angle of the scaffolds was 0°, the mechanical properties of scaffolds were measured by tensile test, Young's moduli of PCL scaffolds before and after hydrolysis are 66–77.3MPa and 62.3–75.4MPa, respectively. Thus, the bilayer porous scaffolds showed excellent hydrophilic surface and desirable mechanical strength due to the soft hydrolysis and GE coat. The cell culture results showed that the adipose derived mesenchymal stem cells did more favor to adhere and grow on the bilayer porous scaffolds than on PCL electrospun membranes. The better cell affinity of the final bilayer scaffolds not only attributed to the surface chemistry but also the introduction of bilayer porous structure.

Keywords: Bilayer porous scaffold; Poly-(ɛ-caprolactone) nanofibrous membrane; Gelatin sponge

Carbon fractals grown from carbon nanotips by plasma-enhanced hot filament chemical vapor deposition by B.B. Wang; G.B. Dong; X.Z. Xu (pp. 1677-1681).

► The carbon fractals were grown from carbon nanotips in PEHFCVD system. ► The formation mechanism of carbon fractals was studied. ► The formation is related to the tip damage and electron emission of carbon nanotips.Carbon nanomaterials with different structures were prepared in a custom-designed plasma-enhanced hot filament chemical vapor deposition system using methane, hydrogen and nitrogen. They were investigated by scanning electron microscopy (SEM) and micro-Raman spectroscopy. The SEM images show that the smooth carbon nanotips are formed under a high bias current and the carbon fractals can grow from the tips of the carbon nanotips under a low bias current. The results of micro-Raman spectroscopy indicate that the graphitization of the carbon nanomaterials was improved by ion bombardment. Combined the ion bombardment, electric field enhancement and electron emission mechanisms, the formation model of the carbon fractals was suggested.

Keywords: Carbon nanotips; Carbon fractals; Ion bombardment

Covalent marriage of multi-walled carbon nanotubes (MWNTs) and β-cyclodextrin (β-CD) by silicon coupling reagents by Lu Shao; Chenzhong Mu; Hongpeng Du; Zbigniew Czech; Huachuan Du; Yongping Bai (pp. 1682-1688).

► Amino-functional multi-walled carbon nanotubes (MWNTs) are linked up with β-cyclodextrin (β-CD) utilizing a novel grafting reagent. ► The synthesized hybrid porous materials have the unique pore and surface characteristics. ► The novel materials demonstrate the good adsorption for removing the resorcinol in water and have potentials in environmental applications.In this study, β-cyclodextrin (β-CD) polymer was covalently bonded to multi-walled carbon nanotubes (MWNTs) with the aid of γ-glycidoxypropyltrimethoxysilane (GPTMS) for the fabrication of novel porous materials with special surface properties. The success of synthesis and physicochemical properties of β-CD polymer grafted MWNTs (MWNTs-g-CDP) were characterized by FT-IR, XPS, TGA, TEM and BET. The novel materials were further utilized to remove the typical contaminant of resorcinol in industrial wastewater. The results illustrated that MWNTs-g-CDP possessed much higher adsorption capability and demonstrated the shorter saturation adsorption time than that of pristine MWNTs. Therefore, MWNTs-g-CDP with the unique pore and surface characteristics may have great potentials in environmental applications.

Keywords: Carbon nanotube; Modification; Cyclodextrin; Nanocomposites

Analysis of machining characteristics in electrochemical etching using laser masking by Hong Shik Shin; Do Kwan Chung; Min Soo Park; Chong Nam Chu (pp. 1689-1698).

► Changes in characteristics of recast layer formation were investigated according to the laser masking conditions. ► The protective effects of the recast layer were investigated according to the electrochemical etching conditions. ► The oxidized recast layer with a thickness of 500nm was verified to yield a superior protective effect.Electrochemical etching using laser masking (EELM), which is a combination of laser beam irradiation for masking and electrochemical etching, allows the micro fabrication of stainless steel without photolithography technology. The EELM process can produce various micro patterns and multilayered structures. In this study, the machining characteristics of EELM were investigated. Changes in characteristics of recast layer formation and the protective effect of the recast layer according to the laser masking conditions and electrochemical etching conditions were investigated by field emission scanning electron microscopy (FE-SEM), focused ion beam (FIB) and X-ray photoelectron spectroscopy (XPS). The oxidized recast layer with a thickness of 500nm was verified to yield a superior protective effect during electrochemical etching and good form accuracy. Finally, micro patterns and structures were fabricated by EELM.

Keywords: Laser masking; Electrochemical etching; Recast layer; EELM; Micro fabrication; Micro patterning; Multilayered structures

Effects of deposition parameters on tantalum films deposited by direct current magnetron sputtering in Ar–O₂ mixture by Y.M. Zhou; Z. Xie; H.N. Xiao; P.F. Hu; J. He (pp. 1699-1703).

► This investigation indicated that the electrical properties and microstructure of the tantalum films sputter-deposited in argon-oxygen mixture were dependent on the sputter power and temperature in the range of 300–650°C. The films deposited at substrate temperatures in range of 300–500°C were composed of β phase of Ta, whereas the samples at 650°C contained both α phase and β phase of Ta. ► This study indicated that the oxygen and other impurity in the films was decreased as the increase of sputter power and the O/Ta ratio decrease and grain size reduction were related to a change of electrical properties of the samples. ► This paper also present that the increase of the sputtering power gave rise to an increase of the temperature coefficient of resistance (TCR) of the deposited tantalum films and the major role on the electrical properties of these deposited samples was due to the oxygen and other impurity content and grain size in the films rather than to growth orientation.The structure, composition, and temperature coefficient of resistance of tantalum films sputtered in Ar–O₂ mixture were studied as a function of deposition parameters and substrates temperature. As the sputtering power increased from 25 to 100W, the samples deposited at 300°C only consisted of the β phase, the preferred-growth orientation of films changed from (200) to (202) and the temperature coefficient of resistance reduced from −289.8 to −116.7ppm/°C. The decrease of the oxygen and other impurity in the films was observed as the increase of the sputtering power. In addition, the O/Ta ratio decrease and grain size reduction in the films related to a change of electrical resistivity were observed at substrate temperatures in the range of 300–500°C. These results suggested that the electrical properties were due to the oxygen and other impurity content and grain size in the films rather than to growth orientation. At 650°C, the deposited films contained both partial stable body-centered-cubic α phase with low resistivity and tetragonal β phase of Ta. The presence of α phase of Ta causes a sharp decrease of the electrical resistivity and a significant change in the microstructure of the samples.

Keywords: Tantalum; Deposition by sputtering; X-ray diffraction; Crystal structure

Forming mechanism of nitrogen doped graphene prepared by thermal solid-state reaction of graphite oxide and urea by Zhigang Mou; Xiaoye Chen; Yukou Du; Xiaomei Wang; Ping Yang; Suidong Wang (pp. 1704-1710).

► N doping is based on oxygen-containing groups of GO and amino-groups of urea. ► There is a thermal transformation of N bonding configurations in graphene structure. ► High concentrations (∼10at.%) of N are incorporated into graphene lattice.Nitrogen doped graphene was synthesized from graphite oxide and urea by thermal solid-state reaction. The samples were characterized by transmission electron microscopy, atomic force microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectra, element analysis, and electrical conductivity measurement. The results reveal that there is a gradual thermal transformation of nitrogen bonding configurations from amide form nitrogen to pyrrolic, then to pyridinic, and finally to “graphitic” nitrogen in graphene sheets with increasing annealing temperature from 200 to 700°C. The products prepared at 600°C and 700°C show that the quantity of nitrogen incorporated into graphene lattice is ∼10at.% with simultaneous reduction of graphite oxide. Oxygen-containing functional groups in graphite oxide are responsible for the doping reaction to produce nitrogen doped graphene.

Keywords: Graphene; Graphite oxide; Urea; Nitrogen doping; Mechanism

Albumin adsorption on oxide thin films studied by spectroscopic ellipsometry by P. Silva-Bermudez; S.E. Rodil; S. Muhl (pp. 1711-1718).

► Bovine Serum Albumin adsorption on metal oxide thin films: Ta, Nb, Zr and Ti oxides. ► Adsorption is highly dependent on the films wettability. ► Hydrophobicity notoriously increases Bovine Serum Albumin adsorption. ► On the hydrophilic character films, adsorption increases with surface roughness. ► Adsorption on the hydrophilic films increases with surface energy polar component.Thin films of tantalum, niobium, zirconium and titanium oxides were deposited by reactive magnetron sputtering and their wettability and surface energy, optical properties, roughness, chemical composition and microstructure were characterized using contact angle measurements, spectroscopic ellipsometry, profilometry, X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The purpose of the work was to correlate the surface properties of the films to the Bovine Serum Albumin (BSA) adsorption, as a first step into the development of an initial in vitro test of the films biocompatibility, based on standardized protein adsorption essays. The films were immersed into BSA solutions with different protein concentrations and protein adsorption was monitored in situ by dynamic ellipsometry; the adsorption-rate was dependent on the solution concentration and the immersion time. The overall BSA adsorption was studied in situ using spectroscopic ellipsometry and it was found to be influenced by the wettability of the films; larger BSA adsorption occurred on the more hydrophobic surface, the ZrO₂ film. On the Ta₂O₅, Nb₂O₅ and TiO₂ films, hydrophilic surfaces, the overall BSA adsorption increased with the surface roughness or the polar component of the surface energy.

Keywords: Protein adsorption; Ellipsometry; Metal oxide thin film; Albumin

Facile synthesis and photocatalytic activity of hierarchical WO₃ core–shell microspheres by Liang Zhang; Xincun Tang; Zhouguang Lu; Zhimin Wang; Lianxing Li; Yuanhua Xiao (pp. 1719-1724).

► Hierarchical WO₃ core–shell microspheres was prepared by a facile template-free precipitation method. ► It eliminated disadvantages related to high cost and tedious synthetic procedures for usage of templates. ► The core was composed of aggregated nanoparticles encapsulated by a hierarchical shell layer self-assembled by ultrafine nanoplates. ► The photocatalytic activity of WO₃ was explored. ► It shows superior photocatalytic activities for the degradation of the rhodamine B (RhB) aqueous.In this work, we present a facile template-free precipitation method for the large-scale preparation of hierarchical WO₃ core–shell microspheres in which the core was composed of aggregated nanoparticles encapsulated by a hierarchical shell layer self-assembled by ultrafine nanoplates with a thickness of about 15nm. The products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry and thermogravimetry (TG/DSC). The experimental parameters affecting the morphology were discussed in detail. We found that the concentration of citric acid and pH value of the reaction solution had profound effects on the morphology of the products. In addition, a formation mechanism was proposed for producing hierarchical WO₃ core–shell microspheres. Furthermore, the obtained hierarchical WO₃ core–shell microspheres showed superior photocatalytic activities for the degradation of rhodamine B (RhB) under visible light irradiation.

Keywords: Tungsten trioxide (WO; ₃; ); Hierarchical; Core–shell; Precipitation; Photocatalysts; Pollutant treatment

Development of cholesterol biosensor with high sensitivity using dual-enzyme immobilization into the mesoporous silica materials by Kazuki Murai; Katsuya Kato (pp. 1725-1732).

► Immobilization of dual-enzyme onto mesoporous silica material was influenced by size of mesopore. ► Catalytic activity of dual-enzyme was increased when enzymes were adjacently immobilized on mesoporous silica material. ► Secondary and tertiary structures of cholesterol esterase immobilized on mesoporous silica materials were not significantly different by comparison with native cholesterol esterase.Mesoporous silica (MPS) materials with different pore diameters were synthesized by a sol–gel method where organic templates such as cationic surfactant (cetyltrimethylammonium bromide) and triblock co-polymer of (poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (Pluronic P123, EO₂₀PO₇₀EO₂₀)), were used. MPS surface was organo-functionalized using a silane coupling reagent (ethyl-, phenyl-, or 3-mercaptpropyltriethoxysilane). Dual-enzyme, cholesterol esterase (10.0nm×5.4nm×11.0nm) and cholesterol oxidase (6.8nm×8.5nm×8.8nm), was immobilized on MPS materials by physical adsorption. Amount of dual-enzyme immobilized on all MPS materials, having a different pore size (2.7, 6.4, 12.4, 14.7, and 22.6nm), and organo-functionalized MPS was similar (CE: 1.5mg/mg silica and CO: 0.01mg/mg silica). High activity of dual-enzyme was obtained by adjacently immobilizing on MPS materials. Its activity on MPS-2 (pore diameter: 6.4nm) or MPS-5 (pore diameter: 22.6nm) showed approximately 60% of native activity. Moreover, dual-enzyme immobilized on MPS with highly hydrophobic organo-functional groups (phenyl- or mercaptopropyl-group) exhibited higher activity than that on no-substituted MPS. Relative activity of dual-enzyme immobilized on organo-functionalized MPS-2 increased from 58% to 93%, under the optimum conditions.

Keywords: Immobilization; Enzyme; Mesoporous silica; Cholesterol; Biosensor

Decay processes of photoluminescence in a nanocrystalline SiC thin film by Wei Yu; Xinzhan Wang; Chunling Geng; Xueqin Lve; Wanbing Lu; Guangsheng Fu (pp. 1733-1737).

► Intense blue-white light emission is observed in a nanocrystalline SiC thin ﬁlm. ► The optical emission of the film mainly occurs in the quantum states of 3C–SiC nanocrystals. ► Triple-exponential photoluminescence decay processes with nanosecond-order are obtained.Nanocrystalline (nc)-SiC film has been deposited by helicon wave plasma enhanced chemical vapor deposition technique and intense blue-white light emission is obtained. Microstructure analyses show that the 3C–SiC particles are embed in amorphous SiC matrix, and the average size of the nc-SiC is 3.96nm. The photon energy of the main photoluminescence (PL) band is higher than the band gap of bulk SiC, which indicates that the optical emission mainly occurs in quantum states of 3C–SiC nanocrystals. In addition, the band tail states of amorphous SiC also contribute to the optical emission. Three decay processes are obtained from time-resolved PL spectra by deconvolution treatment, and the decay components correspond to the quantum confinement effect (QCE), surface states of nc-SiC particles, and band tail of amorphous SiC, respectively. The fractional integrated PL intensity of QCE related decay process decreases dramatically in the lower PL photon energy, indicating that the QCE mainly contributes to the short wavelength optical emission.

Keywords: Nanocrystalline silicon carbide; Time-resolved photoluminescence; Quantum confinement effect

Photocatalytic degradation of methylene blue in water solution by multilayer TiO₂ coating on HDPE by Jussi Kasanen; Janne Salstela; Mika Suvanto; Tuula T. Pakkanen (pp. 1738-1743).

► Photocatalytically effective TiO₂-based multilayer coating can be prepared on HDPE.► Over 90% of methylene blue degrades in 6h. ► Polyurethane assists methylene blue adsorption and degradation. ► Pseudo-first order rate constant of k_obs=0.43h⁻¹ is obtained for degradation.A multilayer photocatalytic TiO₂ coating on a high-density polyethylene (HDPE) disk was found to degrade aqueous methylene blue in a batch reactor study. The TiO₂ coating was fabricated by a low-temperature method using polyurethane resin (PU) as a barrier layer for HDPE and as a binding agent for two TiO₂ layers. Adequate adhesion between the HDPE substrate and PU barrier in aqueous environment was ensured with an oxygen plasma treatment.The photocatalytic effect of immersed TiO₂ coating on the degradation of methylene blue in aqueous solution was monitored by UV–vis spectrometry as a function of UV-illumination time. Samples were allowed to adsorb methylene blue in the dark for 1h before the UV-degradation experiments were started. The percentages of methylene blue degraded during 6h UV illumination ( λ=365nm) varied from 80% to 92%. The degradation followed pseudo-first order reaction kinetics, and the observed rate constants ( k_obs) were between 0.27 and 0.43h⁻¹.

Keywords: Coatings; Methylene blue; Photocatalysis; Polymers; Surface morphology; TiO; ₂

Impedometric anion sensing behaviour of In_xGa1−_xN films grown by modified activated reactive evaporation by S.R. Meher; Kuyyadi P. Biju; Mahaveer K. Jain (pp. 1744-1749).

► Impedometric anion sensing behaviour of InGaN thin films has been studied for the first time. ► The InGaN based anion sensors were found to have good sensitivity with faster response and recovery time. ► The film with 63% indium was found to have the highest sensitivity for all the anions due to the presence of large active surface area and donor states.In the present work, In_xGa1−_xN films with different indium compositions ( x=0.88, 0.63, 0.36 and 0.18) were prepared on glass substrates using a commercially viable technique known as modified activated reactive evaporation. Electrochemical impedance was used to investigate the anion sensing properties of these films for KCl, KI and KNO₃ salt solutions of different molar concentrations. The anion sensing behaviour of InGaN films is attributed to the presence of high n-type background carrier concentration and positively charged surface donor states. The InGaN based anion sensors were found to have good sensitivity with faster response and recovery time. The film with x=0.63 was found to have the highest sensitivity for all the anions due to the presence of more active surface area together with large number of surface donor states.

Keywords: InGaN; Anion sensing; Semiconductors; Thin films; Impedance spectroscopy

Finite element simulation and analytical analysis for nano field emission sources that terminate with a single atom: A new perspective on nanotips by Moh’d Rezeq (pp. 1750-1755).

► Analytical and numerical analyses to single atom tip (FIM/FEM) images at different applied voltages, have been performed. ► The analyses exhibit the significant effect of the tip base on the electric field of the nanotip apex. ► The analyses help to estimate the tip shape at a mesoscopic scale. ► These models correct the misconception about single atom tips that are widely thought to be extremely sharp.Nanotips are highly demanded for various applications in nanotechnology. For instance, nanotips with a single atom end can be used as a source of self collimated electron or ion beams. Such tips are usually characterized in the field ion microscope (FIM) or the field emission microscope (FEM), where only a top view can be captured and analyzed. We have noticed that single atom tips fabricated by different methods produce electrons in FEM mode, or ions in FIM mode, at a wide range of applied voltages for the respective mode. In this work we present numerical and analytical analyses to the distribution of the electric field in the vicinity of the nanotip apex that holds the topmost single atom. We demonstrate that although the electric field is relatively enhanced by the nano protrusion it is still significantly dominated by the tip base. The analyses explicitly show that nanotips with broad bases produce even less field than some modest tips, at the same applied voltage. This pronounced effect of the tip base accounts for the relatively high voltages needed at the imaging threshold field. The results reveal that single atom tips are not necessarily sharp at a mesoscopic scale and the tip sharpness has to be determined from the combination of the nanotip apex (FIM or FEM) image and the applied voltage.

Keywords: Nanotip and single atom tip; Nano fabrication; Field emission; Nano electron and ion source; Nanotechnology

Comparison of surface damage under the dry and wet impact: Molecular dynamics simulation by Ruling Chen; Min Liang; Jianbin Luo; Hong Lei; Dan Guo; Xiao Hu (pp. 1756-1761).

Molecular dynamic simulation was applied in analyzing the difference of surface damage during the impact of a large silica cluster on a crystal silicon substrate in dry and wet condition, respectively. The simulation results show that the damage of silicon substrate under the dry impact is more severe than that under the wet impact. A reason is that the water film buffers the impact of the incident cluster at the init stage under the wet impact. The more important reason is that the water film might be solidified into a continuous thin film at the cluster deformation stage. So, the considerable great impact energy of the cluster will be absorbed by the water film and transformed into thermal dissipation of energy between the simulation ensemble and the water film.

Keywords: Surface damage; Energy transfer; Crystalline silicon; Dry and wet impact; Molecular dynamics simulation

Properties of nanocrystalline Al–Cu–O films reactively sputtered by DC pulse dual magnetron by J. Blažek; J. Musil; P. Stupka; R. Čerstvý; J. Houška (pp. 1762-1767).

► The effect of Cu addition in Al₂O₃ on its properties. ► The structure changes from Al₂O₃ through Al–Cu–O solid solution to CuAl₂O₄. ► Hardness of Al–Cu–O films increases with increasing Cu content. ► Hard Al–Cu–O films exhibit enhanced resistance to cracking compared to pure Al₂O₃.The article reports on the effect of the addition of copper in the Al₂O₃ film on its mechanical and optical properties. The Al–Cu–O films were reactively co-sputtered using DC pulse dual magnetron in a mixture of Ar+O₂. One magnetron was equipped with a pure Al target and the second magnetron with a composed Al/Cu target. The amount of Al and Cu in the Al–Cu–O film was controlled by the length of pulse at the Al/Cu target. The Al–Cu–O films with ≤16at.% Cu were investigated in detail. The addition of Cu in Al₂O₃ film strongly influences its structure and mechanical properties. It is shown that (1) the structure of Al–Cu–O film gradually varies with increasing Cu content from γ-Al₂O₃ at 0at.% Cu through (Al8−2_x,Cu3_x)O₁₂ nanocrystalline solid solution to CuAl₂O₄ spinel structure, (2) the Al–Cu–O films with ≥3at.% Cu exhibit (i) relatively high hardness H increasing from ∼15GPa to ∼20GPa, (ii) enhanced elastic recovery W_e increasing from ∼67% to ∼76% with increasing Cu content from ∼5 to ∼16at.% Cu and (iii) low values of Young's modulus E* satisfying the ratio H/ E*>0.1 at ≥5at.% Cu, and (3) highly elastic Al–Cu–O films with H/ E*>0.1 exhibit enhanced resistance to cracking during indentation under high load.

Keywords: Al; ₂; O; ₃; -based films; Cu addition; Mechanical properties; Elasticity; Resistance to cracking; Pulse reactive sputtering

Fabrication, structure and luminescence properties of polycrystalline Tb³⁺-doped Lu₂SiO₅ films by Pechini sol–gel method by Si-qing Shen; Qing Ma; Zhi-bin Xu; Jian-jun Xie; Ying Shi; Jian Wang; Fei Ai (pp. 1768-1771).

► Tb:Lu₂SiO₅ films are firstly successfully fabricated on silicon (111) substrates by Pechini sol–gel method combined with the spin-coating technique. The method is simple, cheap and nontoxic. ► Tb:Lu₂SiO₅ films are crystallized into A-type LSO phase at 1000°C, followed by a phase transition from A-type LSO to B-type LSO occurred at 1100°C. ► The AFM observation reveals that the phosphor films are uniform and crack-free.Tb³⁺-doped lutetium oxyorthosilicate (Tb:Lu₂SiO₅, LSO) films have been successfully fabricated on carefully cleaned silicon (111) substrates by Pechini sol–gel method combined with the spin-coating technique. X-ray diffraction (XRD), photoluminescence (PL) spectra and atomic force microscopy (AFM) were employed to characterize the resultant films. XRD patterns indicated that the films were crystallized into A-type LSO phase at 1000°C, followed by a phase transition from A-type LSO to B-type LSO occurred at 1100°C. The AFM observation revealed that the phosphor films were uniform and crack-free, consisting of closely packed grains with an average size of 200–300nm. The PL spectra showed the characteristic emission⁵D₄→⁷F_J ( J=3–6) for Tb³⁺, The lifetime of Tb³⁺ in Tb:LSO films was 2.33ms. The effect of heat-treatment temperature on the luminescent properties was also investigated.

Keywords: Lu; ₂; SiO; ₅; Tb; ³⁺; Sol–gel; Luminescence; Fabrication

A simple solution-immersion process for the fabrication of superhydrophobic cupric stearate surface with easy repairable property by Jian Li; Xiaohong Liu; Yinping Ye; Huidi Zhou; Jianmin Chen (pp. 1772-1775).

► A superhydrophobc cupric stearate surface has been fabricated by a simple and time-saving solution-immersion process. ► The fabrication of superhydrophobic surface involves a one-step process. ► The damaged superhydrophobic surface can restore superhydrophobicity by immering the surface into stearic acid solution again.The present work reports a simple and time-saving method to fabricate cupric stearate film on zinc substrate by a solution-immersion process. Superhydrophobic surfaces are conventionally prepared employing two steps: roughening a surface and lowering its surface energy. The fabrication of superhydrophobic cupric stearate surface is reported using a one-step process by immersing a zinc plate coated with copper into the stearic acid solution, simplifying the complexity of two different steps involved in the conventional methods. The surface of the zinc plate coated with copper is found to be covered with low surface energy cupric stearate film providing the water contact angle of 160±1° with the rolling off properties. In addition, the damaged superhydrophobic surface can restore superhydrophobicity property by immersing the surface into the stearic acid solution again.

Keywords: Superhydrophobic; Water contact angle; Stearic acid; Repairable

Cystamine immobilization on TiO₂ film surfaces and the influence on inhibition of collagen-induced platelet activation by Yujuan Zhou; Yajun Weng; Liping Zhang; Fengjuan Jing; Nan Huang; Junying Chen (pp. 1776-1783).

► A new method for improving the haemocompatibility of inorganic materials by exploiting endogenous NO donor is reported. ► Cystamine is successfully immobilized on TiO₂ film surface via polydopamine as a linker. ► NO release was evaluated and confirmed by cGMP analysis. ► Collagen-induced platelet activation is significantly inhibited on cystamine modified surfaces.Poor haemocompatibility is a main issue of artificial cardiovascular materials in clinical application. Nitric oxide (NO), produced by vascular endothelial cells, is a well known inhibitor of platelet adhesion and activation. Thus, NO-releasing biomaterials are beneficial for improving haemocompatibility of blood-contacting biomedical devices. In this paper, a novel method was developed for enhancement of haemocompatibility by exploiting endogenous NO donors. TiO₂ films were firstly synthesized on Si (100) wafers via unbalanced magnetron sputtering technology, and then polydopamine was grafted on TiO₂ films and used as a linker for further immobilization of cystamine. The obtained surfaces were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. NO generation is evaluated by saville-griess reagents, and it shows that cystamine immobilized samples are able to catalytically generate NO by decomposing endogenous S-nitrosothiols (RSNO). In vitro platelet adhesion results reveal that cystamine modified surfaces can inhibit collagen-induced platelet activation. ELISA analysis reveals that cGMP in platelets obviously increases on cystamine immobilized surface, which suggests the reducing of platelet activation is through NO/cGMP signal channel. It can be concluded that cystamine immobilized surface shows better blood compatibility by catalyzing NO release from the endogenous NO donor. It may be a promising method for improvement of haemocompatibility of blood-contacting implants.

Keywords: Cystamine; Nitric oxide; Catalytic generation; Cyclic guanosine monophosphate; Collagen-induced platelet activation

Improving the visible transmittance of low-e titanium nitride based coatings for solar thermal applications by M. Yuste; R. Escobar Galindo; S. Carvalho; J.M. Albella; O. Sánchez (pp. 1784-1788).

► We study three different strategies in order to improve the optical properties of TiN layers as low-e coatings. ► We deposit TiN, TiAlN coatings and TiO₂/TiN/TiO₂ multilayers by reactive magnetron sputtering. ► Post deposition annealing treatments improve in a 10% the TiN visible transmittance while keeping constant the emittance. ► Multilayers structures present the best results by improving a 30% the TiN visible transmittance without degrading the emittance.Low-emissivity (low-e) coatings on glass are nowadays extensively used for energy saving applications in architectural windows and on solar thermal collectors. In this work the feasibility of TiN-based layers as low-e coatings has been studied. TiN samples were deposited by reactive magnetron sputtering and, in order to improve their optical properties (transmission in the visible range, T and emissivity, ɛ), we have investigated the changes in optical response following three different approaches: (i) post-deposition annealing treatments up to 500°C, (ii) doping the TiN layers with aluminium (target composition: Ti/Al=90/10, 75/25 and 50/50) and (iii) deposition of antireflective coatings of TiO₂ in multilayers structures. The crystalline structure and chemical composition of the multilayers were studied by X-Ray Diffraction and Rutherford Backscattering Spectroscopy, respectively. Spectroscopic Ellipsometry, Fourier Transform Infrared Spectroscopy and direct emissivity measurements were employed to determine the optical properties T and ɛ. We have concluded that the most noticeable improvement has been obtained by the deposition of multilayers structures increasing in a 30% the original transmittance of the single TiN coatings.

Keywords: Low-emissivity; TiN; Magnetron sputtering

Effect of substrate bias voltage on the structure, electric and dielectric properties of TiO₂ thin films by DC magnetron sputtering by M. Chandra Sekhar; P. Kondaiah; S.V. Jagadeesh Chandra; G. Mohan Rao; S. Uthanna (pp. 1789-1796).

► TiO₂ films were deposited by DC magnetron sputtering at different substrate bias voltages. ► The leakage current density decreased with the substrate bias voltage. ► Conduction mechanisms in TiO₂ films were Schottky effect and Fowler–Nordheim effect. ► Dielectric constant increased with the substrate bias voltage. ► Optical band decreased with the increase of substrate bias voltage.Titanium dioxide (TiO₂) films have been deposited on glass and p-silicon (100) substrates by DC magnetron sputtering technique to investigate their structural, electrical and optical properties. The surface composition of the TiO₂ films has been analyzed by X-ray photoelectron spectroscopy. The TiO₂ films formed on unbiased substrates were amorphous. Application of negative bias voltage to the substrate transformed the amorphous TiO₂ into polycrystalline as confirmed by Raman spectroscopic studies. Thin film capacitors with configuration of Al/TiO₂/p-Si have been fabricated. The leakage current density of unbiased films was 1×10⁻⁶A/cm² at a gate bias voltage of 1.5V and it was decreased to 1.41×10⁻⁷A/cm² with the increase of substrate bias voltage to −150V owing to the increase in thickness of interfacial layer of SiO₂. Dielectric properties and AC electrical conductivity of the films were studied at various frequencies for unbiased and biased at −150V. The capacitance at 1MHz for unbiased films was 2.42×10⁻¹⁰F and it increased to 5.8×10⁻¹⁰F in the films formed at substrate bias voltage of −150V. Dielectric constant of TiO₂ films were calculated from capacitance–voltage measurements at 1MHz frequency. The dielectric constant of unbiased films was 6.2 while those formed at −150V it increased to 19. The optical band gap of the films decreased from 3.50 to 3.42eV with the increase of substrate bias voltage from 0 to −150V.

Keywords: Sputtering; Structure; Leakage current; Dielectric constant; Optical properties

Fabrication of CuO/T-ZnOw nanocomposites using photo-deposition and their photocatalytic property by J. Wang; X.M. Fan; D.Z. Wu; J. Dai; H. Liu; H.R. Liu; Z.W. Zhou (pp. 1797-1805).

► Largely enhanced photocatalytic properties. ► CuO exist on the surface of T-ZnOw either as leaf-like platelets or as nano-needles. ► Both the molar ratio of Cu/Zn and the concentration of PEG have profound influence on the photocatalytic activity of the CuO/T-ZnOw nanocomposites.CuO/tetrapod-like ZnO whisker (T-ZnOw) nanocomposites were successfully synthesized using a simple photo-deposition method. Some nanocomposites exhibit remarkably improved photocatalytic property, while the extents of the improvements vary with different Cu/Zn molar ratios and polyethylene glycol (PEG) concentrations. Moreover, it is found that excessively high Cu/Zn molar ratio or PEG concentration would reduce the photocatalytic property of the nanocomposites. A direct relationship between the morphology and the photocatalytic property of CuO/T-ZnOw was established and then analyzed by discussing the photocatalytic mechanism of the CuO/T-ZnOw nanocomposites.

Keywords: CuO/T-ZnOw nanocomposites; Cu/Zn molar ratio; PEG concentration; Photocatalytic property

Growth behavior and magnetic property of electroless NiCoFeP films by W.L. Liu; S.H. Hsieh; H.C. Yan; W.J. Chen (pp. 1806-1812).

► The electroless NiCoFeP films are deposited on Si substrate in a plating bath with pH value of 9. ► At the initial stage (about 10s) in the plating process, the film contains only Ni-rich phase. ► At the latter stage (about 30s), the film contains Ni-rich phase and Co-rich phase. ► The Ms and Hc of electroless NiCoFeP films varied from 525 to 1546emu/cm³ and from 51.4 to 88.5Oe, respectively.The electroless NiCoFeP films were deposited on a silicon substrate in a bath containing Ni²⁺, Co²⁺, and Fe²⁺ ions with a concentration ratio of 1:1.9:1.2. These films were characterized by using transmission electron microscope, energy dispersive X-ray spectrometer, and alternating gradient magnetometer for their microstructure, crystal structure, and magnetic properties. The result showed that the film deposited at the initial stage (about 10s) consists of only one phase with a crystal structure of FCC Ni and a composition about Ni (69at%), Co (19at%), Fe (4at%), and P (7at%); The film deposited at the latter stage (about 30s) consists of two phase, one is similar to that of initial stage and the other has crystal structure of HCP Co with a composition about Ni (35at%), Co (44at%), Fe (19at%), and P (2at%). The saturation magnetization and coercivity of electroless NiCoFeP films vary from 525 to 1546emu/cm³ [0.68–2.01T] and from 51.44 to 88.5Oe [4.09–7.04kA/m], respectively.

Keywords: NiCoFeP films; Electroless plating; Growth behavior; Magnetic property

Thermal diffusion of Co into sputtered ZnO:Co thin film for enhancing visible-light-induced photo-catalytic activity by Chi-Yuan Kao; Jiunn-Der Liao; Chia-Wei Chang; Ru-Yang Wang (pp. 1813-1818).

► ZnO based visible-light photo-catalyst is realized by diffusing Co into ZnO:Co. ► Diffused Co/ZnO:Co narrows its band gap as a visible-light driven photo-catalyst. ► Grain sizes of diffused Co/ZnO:Co affect the absorption edge red-shift. ► Photo-degradation and bacteria inactivation occur on the diffused Co/ZnO:Co.ZnO has received a lot of attention in for the degradation and complete mineralization of environmental pollutants. In this study, efficient ZnO-based visible-light photocatalysts are synthesized via a low-cost method by increasing the Co concentration at the outermost surface of ZnO:Co thin film under an annealing process. The simply adjusted Co concentration gradient (≈1.5% increase) into the surface of ZnO:Co is driven by thermal diffusion. Co ions substitute Zn sites in the ZnO lattice. The band gap narrowed due to sp–d exchange interactions between the conduction band electrons and the d electrons of Co. The annealing process enhances the grain size and the degree of crystallinity of the diffused Co/ZnO:Co, which contributes to the absorption edge red-shift. Photocatalytic activities such as the photo-degradation of methylene blue and the inactivation of bacteria are obviously enhanced. The proposed low-cost method significantly increases the efficiency of ZnO for the generation of the photocatalytic effect under visible-light exposure.

Keywords: Zinc oxide (ZnO); Thermal diffusion; Photocatalytic activity; Visible-light exposure

Effect of nitrogen partial pressure on Al–Ti–N films deposited by arc ion plating by Fei Cai; Shihong Zhang; Jinlong Li; Zhong Chen; Mingxi Li; Lei Wang (pp. 1819-1825).

► We prepared the Al–Ti–N films with high Al contents by multi-arc ion plating. ► We examined the structure of the Al–Ti–N films by XRD and XPS. ► We systematically evaluated the macroparticles, hardness and adhesion strength of the Al–Ti–N films.AlTiN films with different nitrogen partial pressures were deposited using arc ion plating (AIP) technique. In this study, we systematically investigated the effect of the nitrogen partial pressure on composition, deposition efficiency, microstructure, macroparticles (MPs), hardness and adhesion strength of the AlTiN films. The results showed that with increasing the nitrogen partial pressure, the deposition rate exhibited a maximum at 1.2Pa. Results of X-ray photoelectron spectroscopy (XPS) analysis revealed that AlTiN films were comprised of Ti–N and Al–N bonds. XRD results showed that the films exhibited a (111) preferred growth, and AlTi₃N and TiAl_x phases were observed in the film deposited at 1.7Pa. Analysis of MPs statistics showed MPs decreased with the increase in the nitrogen partial pressure. In addition, the film deposited at 1.2Pa possessed the maximum hardness of 38GPa and the better adhesion strength.

Keywords: AlTiN film; Macroparticles; Nanoindentation; Adhesion

Optical properties and color generation mechanism of porous anodic alumina films by Qin Xu; Hui-Yuan Sun; Yu-Hua Yang; Li-Hu Liu; Zi-Yue Li (pp. 1826-1830).

► Porous anodic alumina thin films with iridescent colors are fabricated electrochemically in phosphoric acid electrolyte. ► Compared to the color saturation of alumina films fabricated in oxalic acid electrolyte, the saturation obtained using phosphoric acid was enhanced dramatically. ► The mechanisms behind this observation are discussed, and the microstructure and optical characteristics of the films are characterized.Porous anodic alumina thin films with iridescent colors were fabricated electrochemically in phosphoric acid electrolyte. Compared to the color saturation of alumina films fabricated in oxalic acid electrolyte, the saturation obtained using phosphoric acid was enhanced dramatically. The mechanisms behind this observation are discussed, and the microstructure and optical characteristics of the films are characterized. Multicolor patterns were obtained by an organics-assisted process for which details are given.

Keywords: Alumina films; Electrochemical oxidization; Porous material; Optical properties

Electrodeposition of silver nanoparticle arrays on ITO coated glass and their application as reproducible surface-enhanced Raman scattering substrate by Jun-Cao Bian; Zhe Li; Zhong-Dong Chen; Hai-Yan He; Xi-Wen Zhang; Xiang Li; Gao-Rong Han (pp. 1831-1835).

► In this study, a double-potentiostatic method is used for preparation of dense and uniform silver nanoparticle arrays. ► The silver nanoparticle arrays contain large amount of hot spots. ► As-deposited samples exhibit significant SERS effect with excellent reproducibility.In this paper, a double-potentiostatic method is used for preparation of highly efficient and uniform surface-enhanced Raman scattering (SERS) substrate. The method takes advantage of the quick nucleation and slow growth process, yielding silver nanoparticle arrays (NAs) containing large amount of hot spots, which bring about these dense silver NAs for reproducible SERS application.

Keywords: Silver; Nanoparticle arrays; Double-potentiostatic; Electrodeposition; SERS

Effect of ultrasound on the structural and textural properties of copper-impregnated cerium-modified zirconium-pillared bentonite by Fatma Tomul (pp. 1836-1848).

The figure shows HK micropore and BJH mesopore size distributions of Zr-, Ce/Zr- and Cu@Ce/Zr-pillared-bentonite samples synthesized by applying conventional and ultrasonic treatment during the intercalation stage. The micro- and mesopore distributions for all samples are not uniform across samples prepared by both methods, and it can be observed that they include micro- and mesopores with diameters of 0.3–2.0 and 2.0–30.0nm.Display Omitted► Zr-, Ce/Zr- and Cu@Ce/Zr-pillared bentonite were prepared via conventional and ultrasonic treatment during the intercalation stage. ► It was found that using ultrasonic treatment at the intercalation stage caused a considerable decrease in the required synthesis time. ► The ultrasonically processed samples possessed characteristics that were comparable to those of conventionally treated samples.In this study, the synthesis of zirconium-pillared bentonite modified with cerium was performed via two different methods by the application of conventional and ultrasonic treatments during the intercalation stage. To synthesise copper-impregnated pillared clays by wet impregnation, cerium-modified zirconium-pillared clays were used as supportive materials after being calcined at 300°C. Ultrasonic treatment significantly decreased the required processing time compared with the conventional treatment of the synthesised pillared bentonites. Chemical analysis confirmed the incorporation of Zr⁴⁺, Ce⁴⁺ and Cu²⁺ species into the pillared bentonites. X-ray diffraction (XRD) patterns of zirconium- and cerium/zirconium-pillared bentonites prepared by conventional treatment show that one large d-spacing above 3.5nm corresponds to the mesoporous delaminated part, and another small d-spacing above 1.7nm is indicative of the microporous pillared part. Zirconium- and cerium/zirconium-pillared bentonites prepared via ultrasonic treatment exhibited similar results, with the same high d-spacing but with a second low-intensity d-spacing above 1.9nm. The delaminated structures of the pillared bentonites synthesised by both methods were conserved after copper impregnation. Nitrogen-adsorption isotherm analysis showed that the textural characteristics of products synthesised by ultrasonic treatment were comparable to those of products synthesised by conventional treatment. Fourier-transform infrared spectroscopy (FTIR) analyses showed the presence of Brønsted- and Lewis-acid sites, and zirconium-pillared clays synthesised by conventional treatment exhibited increased numbers of Brønsted- and Lewis-acid sites after cerium addition and copper impregnation. However, the products synthesised by ultrasonic treatment exhibited an increased number of Brønsted- and Lewis-acid sites after cerium addition, but a decreased number of acid sites after copper impregnation.

Keywords: Bentonite; Ce/Zr-pillared clays; Ultrasonic treatment; Structural properties

Laser scribing of gallium doped zinc oxide thin films using picosecond laser by Anna Risch; Ralf Hellmann (pp. 1849-1853).

► Rear side processing has a higher ablation rate as compared to front side ablation. ► Optimized ablation quality was achieved by ultraviolet rear side processing. ► Optimized lines have smooth groove bottoms, steep groove walls and small ridges.We report on a comprehensive study of picosecond laser scribing of gallium doped zinc oxide (GZO) thin films deposited on glass substrates using 355nm, 532nm and 1064nm radiation, respectively. In this study, we investigated the influence of front side and rear side irradiation and determined single pulse ablation thresholds for all three wavelengths. Good ablation quality with full electrical isolation, steep groove walls and a smooth groove bottom was achieved by 355nm rear side processing with a scanning speed of 224mm/s. Ridges at the groove rims were found to be between 15nm and 45nm high. At similar scanning speed, laser scribing using 532nm and 1064nm radiation resulted in a lower ablation quality due to a higher roughness of the groove bottoms or higher ridges at the groove rims.

Keywords: Picosecond laser; Gallium doped zinc oxide (GZO); Laser scribing

Treatment of PVC using an alternative low energy ion bombardment procedure by Elidiane C. Rangel; Nazir M. dos Santos; José Roberto R. Bortoleto; Steven F. Durrant; Wido H. Schreiner; Roberto Y. Honda; Rita de Cássia C. Rangel; Nilson C. Cruz (pp. 1854-1861).

► Effect of ion bombardment in argon plasmas on the PVC thermodynamical properties. ► Hydrophilic surfaces after treatment are ascribed to polar group incorporation and Cl loss. ► All the surfaces become hydrophobic after aging in atmospheric conditions. ► Further chemical alterations and formation of specific patterns on the surface. ► Surface properties depend on total energy deposited by ionic impacts.In many applications, polymers have progressively substituted traditional materials such as ceramics, glasses, and metals. Nevertheless, the use of polymeric materials is still limited by their surface properties. Frequently, selective modifications are necessary to suit the surface to a given application. Amongst the most common treatments, plasma immersion ion implantation (PIII) has attracted the attention of many researchers owing to its versatility and practicality. This method, however, requires a power supply to provide high voltage (tens of kV) negative pulses, with a controlled duty cycle, width and frequency. Owing to this, the implementation of PIII on the industrial scale can become economically inviable. In this work, an alternative plasma treatment that enables low energy ion bombardment without the need of a high voltage pulse generator is presented. To evaluate the efficiency of the treatment of polymers, polyvinylchloride, PVC, specimens were exposed to 5Pa argon plasmas for 3600s, at excitation powers, P, of between 10 and 125W. Through contact angle and atomic force microscopy data, the influence of P on the wettability, surface free energy and roughness of the samples was studied. Surface chemical composition was measured by X-ray photoelectron spectroscopy, XPS. To evaluate the effect of aging under atmospheric conditions, contact angle and XPS measurements were performed one and 1334 days after the treatment. The plasma potential and ion density around the driven electrode were determined from Langmuir probe measurements while the self-bias potential was derived with the aid of an oscilloscope. From these data it was possible to estimate the mean energy of ions bombarding the PVC surface. Chlorine, carbon and oxygen contamination were detected on the surface of the as-received PVC. Upon exposure to the plasma, the proportion of chlorine was observed to decrease while that of oxygen increased. Consequently, the wettability and surface energy increased after the treatment but such modifications were not stable after aging: the contact angle increased for all the samples, modifying the initially hydrophilic surface into a highly hydrophobic one. Consistently, the surface composition also changed after aging: there was carbon enrichment due to further losses of oxygen and chlorine. Another relevant factor for the elevation of θ was the change in morphology induced by the treatment. At greater powers, the uniform matrix of the PVC was transformed into a columnar structure containing randomly distributed sharp pillars. Interpretation of such results is proposed in terms of the total energy deposited in the solid by ionic collisions.

Keywords: PACS; 52.77.Dq; 68.08.Bc; 68.35.CtPVC; Ion bombardment; Plasma treatment; Wettability; Roughness

Possible stibnite transformation at the friction surface of the semi-metallic friction composites designed for car brake linings by V. Matějka; Y. Lu; P. Matějková; B. Smetana; J. Kukutschová; M. Vaculík; V. Tomášek; S. Zlá; Y. Fan (pp. 1862-1868).

► Transformation of Sb₂S₃ in semi-metallic fiction composites for car brake lining. ► Antimony formation during friction process of brake linings. ► Alloying of iron from steel wool by antimony and ɛ-FeSb and FeSb₂ formationAfter a friction process several changes in phase composition of friction composites are often registered. High temperature, accompanied by high pressure induced during braking can cause initiation of chemical reactions which do not run at room or elevated temperatures under the atmospheric pressure. Most of the studies in the field of tribochemistry at friction surfaces of automotive semi-metallic brake linings deal with phenolic resin degradation and corrosion of metallic components. The paper addresses the formation of elemental antimony as well as the alloying process of iron with antimony observed on the surface of laboratory prepared semi-metallic friction composites containing stibnite. The role of alumina abrasives in the process of stibnite transformation is also discussed and mechanism of stibnite transformation was outlined.

Keywords: Semi-metallic friction composite; Tribochemistry; Stibnite; Antimony

Facile and low cost chemosynthesis of nanostructured PbS with tunable optical properties by S.B. Pawar; J.S. Shaikh; R.S. Devan; Y.R. Ma; D. Haranath; P.N. Bhosale; P.S. Patil (pp. 1869-1875).

► Synthesized nanosphere and nano cubo-octahedron PbS thin films with tunable optical properties. ► Effect of deposition time on the structure, morphology and optical properties was investigated. ► The possible growth mechanism of nanosphere and nano cubo-octahedron is proposed.The present work reports on the chemosynthesis of nanocrystalline lead sulphide (PbS) thin films by a facile and cost-effective chemical bath deposition (CBD) method onto soda-lime glass substrates. The X-ray diffraction (XRD) pattern shows the formation phase pure PbS with cubic crystal structure. Electronic structures and chemical states of PbS film have been performed by X-ray photoelectron spectroscopy (XPS). Field emission-scanning electron microscopy (FESEM) images show the transition from granular-to-cubic-to-cubo-octahedra like surface morphology with the increase in the deposition time from 20 to 90min. The UV–vis–NIR absorption spectra of PbS thin films are measured, and a classical Tauc approach was employed to estimate their band gap energies. The increase in band gap energy from 0.99 to 2.06eV with the reduction in crystallite size evinces quantum size effect. This work demonstrates a simple and effective solution approach to deposit PbS nanostructured thin films having predominant quantum confinement. This approach would be helpful in nano-PbS sensitized oxide based solar cells, which are recently under intensive investigations.

Keywords: Chemical bath deposition of PbS; Quantum size effect; Optical; PL; XRD; XPS; FT-IR

Studying the effects of the addition of TiN nanoparticles to Ni–P electroless coatings by Iman R. Mafi; Changiz Dehghanian (pp. 1876-1880).

► The surface morphology and deposition rate of Ni–P/TiN nano-composite electroless coatings were investigated. ► The addition of TiN nano particles to the Ni–P matrix enhanced the hardness of the coatings. ► Heat treatment at 400°C improved the hardness of coatings while the hardness of specimens after heat treatment at 200°C remained unchanged. ► The addition of TiN nano particles to the Ni–P matrix adversely affected the corrosion properties. ► Heat treatment at 200°C improved the corrosion properties of the Ni–P specimen while heat treatment at 400°C had a negative effect on the corrosion properties of both Ni–P and Ni–P/TiN systems.The effects of the addition of nano TiN on the surface morphology, deposition rate, hardness and corrosion properties of Ni–P electroless coatings were studied. Heat treatment was conducted to compare the corrosion and hardness behavior of the coatings before and after heat treatment. It was observed that the incorporation of TiN particles into the coating has an adverse effect on the corrosion properties of the specimens. The hardness of the specimens increased dramatically by adding TiN. Furthermore, the hardness of the specimens increased after conducting the heat treatment. The corrosion and hardness behavior of the Ni–P system after heat treatment largely depended on the temperature of heat treatment. The heat treatment temperatures at which the desired corrosion and hardness properties were expected were determined.

Keywords: Electroless deposition; Composite coating; TiN; Nano-composite; Corrosion resistance; Polarization; Impedance

Effect of post annealing temperature on structural and optical properties of ZnCdO thin films deposited by sol–gel method by Amanpal Singh; Dinesh Kumar; P.K. Khanna; Bhubesh Chander Joshi; Mukesh Kumar (pp. 1881-1887).

Ternary ZnCdO thin films oriented along c-axis have been successfully deposited on p-Si (100) substrates using sol–gel spin coating route. To optimize most suitable annealing temperature for the Zn1−_xCd_xO thin films; these films with selected cadmium content x=0.10 were treated at annealing temperatures from 300°C up to 800°C in oxygen ambient after deposition. The structural and optical properties of deposited thin films have been characterized by X-ray diffraction, energy dispersive spectroscopy, atomic force microscopy, UV–Vis spectroscopy, and photoluminescence spectra. The results show that the obtained films possess high crystallinity with wurtzite structure. The crystallite size, lattice parameters, lattice strain and stress in the deposited films are determined from X-ray diffraction analysis. The band gap energy increased as a function of annealing temperatures as observed from optical reflectance spectra of samples. The presence of Cd in the deposited films is confirmed by energy dispersive spectrum and it is observed that Cd re-evaporate from the lattice with annealing. The photoluminescence measurements as performed at room temperature did not exhibit any luminescence related to oxygen vacancies defects for lower annealing temperatures, as normally displayed by ZnO films. The green yellow luminescence associated to these defects was observed at higher annealing temperatures (≥700°C).

Keywords: Zinc oxide; Sol–gel; Photoluminescence; UV–Vis spectroscopy

Encapsulating MAl₂O₄:Eu²⁺, Dy³⁺ (M=Sr, Ca, Ba) phosphors with triethanolamine to enhance water resistance by Ping Ting Ji; Xiang Ying Chen; Ye Qin Wu (pp. 1888-1893).

Encapsulation of aluminate phosphors with triethanolamine can effectively enhance the water resistance.Display Omitted► Phosphors were prepared by a co-precipitation synthesis and postannealing approach. ► 8-Hydroxyquinoline and sodium oxalate were used as precipitants. ► Encapsulation of phosphors with triethanolamine can enhance the water resistance.Traditional aluminates phosphors with persistent luminescence are chemically unstable to water or moisture. Thus, how to improve the water-resistance of these phosphors is becoming a key issue in their practical applications. In this work, a series of alkaline earth aluminate phosphors including MAl₂O₄:Eu²⁺, Dy³⁺ (M=Sr, Ca, Ba) have been prepared by a co-precipitation synthesis and postannealing approach, using 8-hydroxyquinoline and sodium oxalate as precipitants. The samples before and after encapsulation were well characterized by means of XRPD, FESEM, FT-IR, TGA-DTG and PL techniques as well as water resistance measurements. The precipitants involved can react with Al³⁺ and Sr²⁺ (or Ca²⁺, Ba²⁺) to form complex compounds in aqueous solution, which further convert into porous phosphors by postannealing method under reducing atmosphere. Next, triethanolamine encapsulation at room temperature was conducted onto their surfaces to improve the water resistance. The results reveal that the encapsulation of aluminate phosphors with triethanolamine can effectively enhance the water resistance, and minimally affect on persistent phosphorescence.

Keywords: Aluminate phosphors; Encapsulation; Triethanolamine; Water resistance; Co-precipitation

Erratum to “Effect of sizing on carbon fiber surface properties and fibers/epoxy interfacial adhesion” [Appl. Surf. Sci. 257 (2011) 6980–6985] by Zhishuang Dai; Fenghui Shi; Baoyan Zhang; Min Li; Zuoguang Zhang (pp. 1894-1894).

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Applied Surface Science (v.258, #5)