Showing papers in "Applied Surface Science in 2009"

Effect of TiO2 nanoparticles on the surface morphology and performance of microporous PES membrane

Abstract: PES–TiO2 composite membranes were prepared via phase inversion by dispersing TiO2 nanopaticles in PES casting solutions. The crystal structure, thermal stability, morphology, hydrophilicity, permeation performance, and mechanical properties of the composite membranes were characterized in detail. XRD, DSC and TGA results showed that the interaction existed between TiO2 nanopaticles and PES and the thermal stability of the composite membrane had been improved by the addition of TiO2 nanopaticles. As shown in the SEM images, the composite membrane had a top surface with high porosity at low loading amount of TiO2, which was caused by the mass transfer acceleration in exposure time due to the addition of TiO2 nanopaticles. At high loading amount of TiO2, the skinlayer became much looser for a significant aggregation of TiO2 nanopaticles, which could be observed in the composite membranes. EDX analysis also revealed that the nanoparticles distributed in membrane more uniformly at low loading amount. Dynamic contact angles indicated that the hydrophilicity of the composite membranes was enhanced by the addition of TiO2 nanopaticles. The permeation properties of the composite membranes were significantly superior to the pure PES membrane and the mean pore size also increased with the addition amount of TiO2 nanopaticles increased. When the TiO2 content was 4%, the flux reached the maximum at 3711 L m−2 h−1, about 29.3% higher than that of the pure PES membrane. Mechanical test also revealed that the mechanical strength of composite membranes enhanced as the addition of TiO2 nanopaticles.

Ice adhesion on super-hydrophobic surfaces

Abstract: In this study, ice adhesion strength on flat hydrophobic and rough super-hydrophobic coatings with similar surface chemistry (based on same fluoropolymer) is compared. Glaze ice, similar to naturally accreted, was prepared on the surfaces by spraying super-cooled water microdroplets at subzero temperature. Ice adhesion was evaluated by spinning the samples at constantly increasing speed until ice delamination occurred. Super-hydrophobic surfaces with different contact angle hysteresis were tested, clearly showing that the latter, along with the contact angle, also influences the ice–solid adhesion strength.

Superhydrophobic surfaces fabricated by microstructuring of stainless steel using a femtosecond laser

Abstract: Fabrication of superhydrophobic surfaces induced by femtosecond laser is a research hotspot of superhydrophobic surface studies nowadays. We present a simple and easily-controlled method for fabricating stainless steel-based superhydrophobic surfaces. The method consists of microstructuring stainless steel surfaces by irradiating samples with femtosecond laser pulses and silanizing the surfaces. By low laser fluence, we fabricated typical laser-induced periodic surface structures (LIPSS) on the submicron level. The apparent contact angle (CA) on the surface is 150.3°. With laser fluence increasing, we fabricated periodic ripples and periodic cone-shaped spikes on the micron scale, both covered with LIPSS. The stainless steel-based surfaces with micro- and submicron double-scale structure have higher apparent CAs. On the surface of double-scale structure, the maximal apparent CA is 166.3° and at the same time, the sliding angle (SA) is 4.2°.

Characterization and degradation behavior of AZ31 alloy surface modified by bone-like hydroxyapatite for implant applications

Abstract: Hydroxyapatite (HA) coating on AZ31 alloy substrate was prepared by a cathodic electrodeposition method. The as-deposited specimen was then post-treated with hot alkali solution to improve the corrosion resistance and bioactivity for implant applications. The microstructure and composition of HA coating, as well as its degradation behavior in simulated body fluid (SBF) were investigated. It reveals that the as-deposited coating consists of dicalcium phosphate dehydrate (DCPD, CaHPO4·2H2O) and HA. While 10 μm-thick nanowhisker HA coatings doped with Na+, Mg+, HPO42−and CO32− can be found after NaOH alkali treatment, which exhibits a very similar composition of natural bone. The post-treated coating was composed of needle-like particles with 1000 nm in length and 35 nm in diameter, having a slenderness ratio of about 28.6. Electrochemical tests shows that the Ecorr of Mg substrate significantly increased from −1.6 to −1.42 V after surface modified by HA coatings. There was obvious mass gain on post-treated specimen immersed in SBF during the first 30 days due to the Ca–P–Mg deposition. The HA-coated AZ31 alloy could slow down the degradation rate and effectively induce the deposition of Ca–P–Mg apatite in SBF, showing a good bioactivity.

The effect of heat treatment on the physical properties of sol-gel derived ZnO thin films

Abstract: Zinc oxide (ZnO) thin films were deposited on microscope glass substrates by sol–gel spin coating method. Zinc acetate (ZnAc) dehydrate was used as the starting salt material source. A homogeneous and stable solution was prepared by dissolving ZnAc in the solution of monoethanolamine (MEA). ZnO thin films were obtained after preheating the spin coated thin films at 250 °C for 5 min after each coating. The films, after the deposition of the eighth layer, were annealed in air at temperatures of 300 °C, 400 °C and 500 °C for 1 h. The effect of thermal annealing in air on the physical properties of the sol–gel derived ZnO thin films are studied. The powder and its thin film were characterized by X-ray diffractometer (XRD) method. XRD analysis revealed that the annealed ZnO thin films consist of single phase ZnO with wurtzite structure (JCPDS 36-1451) and show the c-axis grain orientation. Increasing annealing temperature increased the c-axis orientation and the crystallite size of the film. The annealed films are highly transparent with average transmission exceeding 80% in the visible range (400–700 nm). The measured optical band gap values of the ZnO thin films were between 3.26 eV and 3.28 eV, which were in the range of band gap values of intrinsic ZnO (3.2–3.3 eV). SEM analysis of annealed thin films has shown a completely different surface morphology behavior.

Electrical conductivity and optical properties of ZnO nanostructured thin film

Abstract: The electrical conductivity, structural and optical properties of ZnO nanostructured semiconductor thin film prepared by sol–gel spin coating method have been investigated The X-ray diffraction result indicates that the ZnO film has the polycrystalline nature with average grain size of 28 nm The optical transmittance spectrum indicates the average transmittance higher than 90% in visible region The optical band gap, Urbach energy and optical constants (refractive index, extinction coefficient, real and imaginary parts of the dielectric constant) of the film were determined The electrical conductivity of the film dependence of temperature was measured to identify the dominant conductivity mechanism The conductivity mechanism of the film is the thermally activated band conduction The electrical conductivity and optical results revealed that the ZnO film is an n-type nanostructured semiconductor with a direct band gap of about 330 eV at room temperature

Fabrication of cyclodextrin-functionalized superparamagnetic Fe3O4/amino-silane core–shell nanoparticles via layer-by-layer method

Abstract: This paper presents a feasible protocol for the preparation of a novel versatile nanocomposite possessing superparamagnetism via a layer-by-layer method. We combined (3-aminopropyl)triethoxysilane-coated magnetic Fe 3 O 4 nanoparticles (APTES-MNPs) with β-cyclodextrin (β-CD). The following unusual features were integrated in a single nano-system : (a) the silane coating outside the magnetic Fe 3 O 4 cores derived from the hydrolysis of APTES acted as a coupling agent and provided amino group (–NH 2 ) for linking the CD molecule; (b) the outermost CD moieties can function as inclusion sites and specific containers for drugs and biomolecules; (c) the innermost magnetic cores were able to sense and respond to an externally applied magnetic field and their behaviors in vivo or in vitro can be artificially manipulated and navigated. The obtained nanocomposite turned out to be superparamagnetic with a relatively high saturation magnetization value of 69 emu g −1 , which implies potentially promising applications in magnetic drug delivery technology and bioseparation.

Silver nanoparticle supported on halloysite nanotubes catalyzed reduction of 4-nitrophenol (4-NP)

Abstract: The silver nanoparticles with about 10 nm diameter were immobilized onto the halloysite nanotubes (HNTs) via the in situ reduction of AgNO3 by polyol process. The silver nanoparticles supported halloysite nanotubes (Ag/HNTs), with Ag content of about 11%, were used for the catalyzed reduction of 4-nitrophenol (4-NP) with NaBH4 in alkaline aqueous solutions. The effect of the reduction of 4-NP catalyzed by the catalysts in the presence of variable concentration NaBH4 was investigated. It was found that the reduction rate increased with the increasing of the amounts of NaBH4. And the larger amounts of NaBH4 reduced the induction time.

Characterization and corrosion behavior of hydroxyapatite coatings on Ti6Al4V fabricated by electrophoretic deposition

Abstract: In order to increase the bone bioactivity of the metallic implants, hydroxyapatite (HA) is often coated on their surface so that a real bond with the surrounding bone tissue can be formed. Plasma spraying of HA coatings is currently the only commercial process in use but long-term stability of plasma sprayed coatings could be a problem because of their high degree of porosities, poor bond strength, presence of a small amount of amorphous phase with non-stoichiometric composition, and non-uniformity. In the present study, cathodic electrophoretic deposition (EPD) has been attempted for depositing HA coatings on Ti6Al4V followed by vacuum sintering at 800 °C. Submicron HA powders with different morphologies including spherical, needle-shaped and flake-shaped were used in the EDP process to produce dense coatings. Moreover, carbon nanotubes (CNTs) were also used to reinforce the HA coating for enhancing its hardness. The surface morphology, compositions and microstructure of the HA coated Ti6Al4V were investigated by electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffractometry, respectively. Electrochemical corrosion behavior of the HA coatings in Hanks’ solution at 37 °C was investigated by means of open-circuit potential measurement and cyclic potentiodynamic polarization tests. Surface hardness, adhesion strength and bone bioactivity of the coatings were also studied. All HA coated specimens had a thickness of about 10 μm and free of cracks, with corrosion resistance higher than that of the substrate and adhesion strength higher than that of plasma sprayed coating. The enhanced properties could be attributed to the use of submicron-sized HA particles in the low-temperature EDP process. Among the three types of HA powder, spherical powder yielded the densest coating whereas the flake-shaped powder yielded the most porous coatings. Compared with monolithic HA coating, the CNT-reinforced HA coating markedly increased the coating hardness without compromising the corrosion resistance or adhesion strength.

Physical aspects of the pulsed laser deposition technique: The stoichiometric transfer of material from target to film

Abstract: The physical processes of pulsed laser deposition (PLD) change strongly from the initial light absorption in a target to the final deposition and growth of a film. One of the primary advantages of PLD is the stoichiometric transfer of material from target to a film on a substrate. Even for a stoichiometric flow of material from a multicomponent target, the simultaneous arrival of the target atoms is not sufficient to ensure a stoichiometric film growth. The laser fluence has to be sufficiently high to induce ablation rather than pure evaporation from target, but a high fluence may lead to preferential (self)sputtering and possibly implantation of the light atoms in the film. A background gas of a sufficiently high pressure may reduce sputtering of the film, but may lead the preferential diffusion of the light component to the substrate. The importance of these processes during the entire PLD process will be discussed.

Effects of CO2 activation on porous structures of coconut shell-based activated carbons

Abstract: In this paper, textural characterization of an activated carbon derived from carbonized coconut shell char obtained at carbonization temperature of 600 °C for 2 h by CO2 activation was investigated The effects of activation temperature, activation time and flow rate of CO2 on the BET surface area, total volume, micropore volume and yield of activated carbons prepared were evaluated systematically The results showed that: (i) enhancing activation temperature was favorable to the formation of pores, widening of pores and an increase in mesopores; (ii) increasing activation time was favorable to the formation of micropores and mesopores, and longer activation time would result in collapsing of pores; (iii) increasing flow rate of CO2 was favorable to the reactions of all active sites and formation of pores, further increasing flow rate of CO2 would lead carbon to burn out and was unfavorable to the formation of pores The degree of surface roughness of activated carbon prepared was measured by the fractal dimension which was calculated by FHH (Frenkel–Halsey–Hill) theory The fractal dimensions of activated carbons prepared were greater than 26, indicating the activated carbon samples prepared had very irregular structures, and agreed well with those of average micropore size

Preparation and characterization of modified nano-porous PVDF membrane with high antifouling property using UV photo-grafting

Abstract: In this study, the poly(vinylidene fluoride) (PVDF) membrane was prepared via immersion precipitation technique and modified by UV photo-grafting of hydrophilic monomers on the top membrane surface. Acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) as acrylic monomers and 2,4-phenylenediamine (PDA) and ethylene diamine (EDA) as amino monomers were used at different concentrations to modify the membrane and improve the hydrophilicity with less fouling tendency. Moreover the presence of benzophenon as photo-initiator for grafting the hydrophilic monomers onto PVDF membrane surface was elucidated. The virgin and modified PVDF membranes were characterized by contact angle, ATR–FTIR, SEM and cross-flow filtration. The contact angle measurements demonstrated that the hydrophilicities of the membranes were significantly enhanced by UV photo-grafting of hydrophilic monomers onto the membrane surface. The ATR–FTIR confirmed the occurrence of modification on PVDF membrane by UV photo-grafting. The pure water flux of membranes was declined by UV photo-grafting but the milk water permeation and protein rejection were slightly improved. Moreover the antifouling properties and flux recovery of PVDF membrane were improved by UV photo-grafting of hydrophilic monomers.

Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl2 activation

Abstract: In this study, pomegranate seeds, a by-product of fruit juice industry, were used as precursor for the preparation of activated carbon by chemical activation with ZnCl2. The influence of process variables such as the carbonization temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons was studied. When using the 2.0 impregnation ratio at the carbonization temperature of 600 °C, the specific surface area of the resultant carbon is as high as 978.8 m2 g−1. The results showed that the surface area and total pore volume of the activated carbons at the lowest impregnation ratio and the carbonization temperature were achieved as high as 709.4 m2 g−1 and 0.329 cm3 g−1. The surface area was strongly influenced by the impregnation ratio of activation reagent and the subsequent carbonization temperature.

Room-temperature deposition of transparent conducting Al-doped ZnO films by RF magnetron sputtering method

Abstract: Transparent conductive Al-doped zinc oxide (AZO) films with highly (0 0 2)-preferred orientation were deposited on quartz substrates at room temperature by RF magnetron sputtering. Optimization of deposition parameters was based on RF power, Ar pressure in the vacuum chamber, and distance between the target and substrate. The structural, electrical, and optical properties of the AZO thin films were investigated by X-ray diffraction, Hall measurement, and optical transmission spectroscopy. The 250 nm thickness AZO films with an electrical resistivity as low as 4.62 × 10−4 Ω cm and an average optical transmission of 93.7% in the visible range were obtained at RF power of 300 W, Ar flow rate of 30 sccm, and target distance of 7 cm. The optical bandgap depends on the deposition condition, and was in the range of 3.75–3.86 eV. These results make the possibility for light emitting diodes (LEDs) and solar cells with AZO films as transparent electrodes, especially using lift-off process to achieve the transparent electrode pattern transfer.

Effect of thickness on structural, optical and electrical properties of nanostructured ZnO thin films by spray pyrolysis

Abstract: Transparent conducting zinc oxide thin films were prepared by spray pyrolytic decomposition of zinc acetate onto glass substrates with different thickness. The crystallographic structure of the films was studied by X-ray diffraction (XRD). XRD measurement showed that the films were crystallized in the wurtzite phase type. The grain size, lattice constants and strain in films were calculated. The grain size increases with thickness. The studies on the optical properties show that the direct band gap value increases from 3.15 to 3.24 eV when the thickness varies from 600 to 2350 nm. The temperature dependence of the electrical conductivity during the heat treatment was studied. It was observed that heat treatment improve the electrical conductivity of the ZnO thin films. The conductivity was found to increase with film thickness.

Effect of current density on the microstructure and corrosion behaviour of plasma electrolytic oxidation treated AM50 magnesium alloy

Abstract: Plasma electrolytic oxidation (PEO) of an AM50 magnesium alloy was accomplished in a silicate-based electrolyte using a DC power source. Coatings were produced at three current densities, i.e. 15 mA cm−2, 75 mA cm−2, and 150 mA cm−2 and were characterised for thickness, roughness, microstructural morphology, phase composition, and corrosion resistance. Even though the 15 min treated coatings produced at higher current density levels were thicker, they showed poor corrosion resistance when compared to that of the coatings obtained at 15 mA cm−2. Short-term treatments (2 min and 5 min) at 150 mA cm−2 yielded coatings of thickness and corrosion resistance comparable to that of the low current density coatings. The superior corrosion resistance of the low thickness coatings is attributed to the better pore morphology and compactness of the layer.

Molecular dynamics simulation of femtosecond ablation and spallation with different interatomic potentials

Abstract: Fast heating of target material by femtosecond laser pulse (fsLP) with duration τ L ∼ 40 – 100 fs results in the formation of thermomechanically stressed state. Its unloading may cause frontal cavitation of subsurface layer at a depth of 50 nm for Al and 100 nm for Au. The compression wave propagating deep into material hits the rear-side of the target with the formation of rarefaction wave. The last may produce cracks and rear-side spallation. Results of MD simulations of ablation and spallation of Al and Au metals under action fsLP are presented. It is shown that the used EAM potentials (Mishin et al. and our new one) predict the different ablation and spallation thresholds on absorbed fluence in Al: ablation F a = 60 { 65 } mJ/cm2and spallation F s = 120 { 190 } mJ/cm2, where numbers in brackets { } show the corresponding values for Mishin potential. The strain rate in spallation zone was 4.3 × 1 0 9 1/s at spallation threshold. Simulated spall strength of Al is 7.4{8.7} GPa, that is noticeably less than 10.3{14} GPa obtained from acoustic approximation with the use of velocity pullback on velocity profile of free rear surface. The ablation threshold F a ≈ 120 mJ/cm2 and crater depth of 110 nm are obtained in MD simulations of gold with the new EAM potential. They agree well with experiment.

The role of pH variation on the growth of zinc oxide nanostructures

Abstract: In this paper we present a systematic study on the morphological variation of ZnO nanostructure by varying the pH of precursor solution via solution method. Zinc acetate dihydrate and sodium hydroxide were used as a precursor, which was refluxed at 90 °C for an hour. The pH of the precursor solution (zinc acetate di hydrate) was increased from 6 to 12 by the controlled addition of sodium hydroxide (NaOH). Morphology of ZnO nanorods markedly varies from sheet-like (at pH 6) to rod-like structure of zinc oxide (pH 10–12). Diffraction patterns match well with standard ZnO at all pH values. Crystallinity and nanostructures were confirmed by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) pattern, which indicates structure grew along [0 0 0 1] direction with an ideal lattice fringes distance 0.52 nm. FTIR spectroscopic measurement showed a standard peak of zinc oxide at 464 cm −1 . Amount of H + and OH − ions are found key to the structure control of studied material, as discussed in the growth mechanism.

Superhydrophobic silica films by sol–gel co-precursor method

Abstract: Wetting phenomena of water droplets on solid are of crucial concern in our daily life as well as in engineering and science. The present paper describes the room temperature synthesis of superhydrophobic silica films on glass substrates using trimethylethoxysilane (TMES) as a co-precursor. The coating sol was prepared by keeping the molar ratio of tetraethoxysilane (TEOS) precursor, methanol (MeOH) solvent, water (H2O) constant at 1:38.6:8.68, respectively, with 2 M NH4OH throughout the experiments and the TMES/TEOS molar ratio (M) was varied from 0 to 1.1. It was found that with an increase in M value, the hydrophobicity of the films increased, however the optical transmission decreased from 88% to 82% in the visible range. The hydrophobic silica films retained their hydrophobicity up to a temperature of 275 °C and above this temperature the films became superhydrophilic. The hydrophobic silica films were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared (FT-IR) spectroscopy, percentage of optical transmission, humidity test and static and dynamic contact angle measurements.

Effect of contact angle hysteresis on water droplet evaporation from super-hydrophobic surfaces

Abstract: Small water drops demonstrate different evaporation modes on super-hydrophobic polymer surfaces with different hysteresis of contact angle. While on the high-hysteresis surface evaporation follows the constant-contact-diameter mode, the constant-contact-angle mode dominates on the low-hysteresis surface. These modes were previously reported for smooth hydrophilic and hydrophobic surfaces, respectively. The experimental data are compared to the previous models describing spherical cap drops that evaporate in different modes, and good fitting is obtained.

Manufacturing of fine-structured 3D porous filter elements by selective laser melting

Abstract: Selective laser melting (SLM) allows manufacturing porous 3D parts with customized near-net shape and internal geometry designed at the stage of their computer modeling. The relations between laser operational parameters, computer design of the manufacturing object, composition and microstructure of the obtained fine porous structures are discussed. A series of experiments are carried out on PHENIX PM-100 machine to analyze the influence of the manufacturing strategy on anisotropy and regularity of the internal structure of samples from stainless steel, nickel alloys and metal-polymer powders. The issues of accurate reproduction of the parts geometry, strategy of manufacturing thin-walled 3D filters and filters with customized pattern of the micron-sized channels are addressed. Effect of the porous structure on the material filtering performance is analyzed in order to optimize and diversify design of the porous materials for a given application and to improve their operational behavior.

Synthesis of ZnO2 nanoparticles by laser ablation in liquid and their annealing transformation into ZnO nanoparticles

Abstract: A pulsed laser emitting UV radiations generated by the third harmonic of Nd:YAG was applied for the synthesis of nano-structured ZnO 2 and ZnO. For the synthesis of nanoparticles of ZnO 2 , a high-purity metallic plate of Zn target was fixed at the bottom of a glass cell, in the presence of deionized water mixed with oxidizing agent H 2 O 2 , under repeated laser irradiation. The optical properties, size and the morphology of the synthesized ZnO 2 and ZnO by laser ablation was influenced strongly by post-annealing conditions which is not previously reported. By annealing ZnO 2 at 200 °C for 8 h, the product (ZnO 2 ) synthesized primarily was converted completely to ZnO. By variation of the annealing temperatures from 200 to 600 °C, the grain size of ZnO changes from 5 to 19 nm with a change in lattice parameters, the band gap and some other optical properties of nano-ZnO.

Engineering the Maxwell-Wagner polarization effect

Abstract: Layered structures, when supporting the Maxwell–Wagner polarization mechanism, exhibit very large effective electric permittivity and thus can be used for miniaturizing purposes. However, the large interfacial dimensions evolved, limit the Maxwell–Wagner polarization at relatively low frequencies. Any element or mechanism that causes a spatial variation of charge density, contributes to the dielectric susceptibility of a medium. Thus, intentionally planted polarization states can be used for further exploiting the Maxwell–Wagner polarization mechanism.

Physics and chemistry of silicene nano-ribbons

Abstract: We review our recent discovery of silicene in the form of silicon nano-ribbons epitaxially grown on silver (1 1 0) or (1 0 0) surfaces, which paves the way for the growth of graphene-like sheets. We further draw some perspectives for this unique novel material upon mild hydrogenation.

Degradation and biocompatibility of porous nano-hydroxyapatite/polyurethane composite scaffold for bone tissue engineering

Abstract: Porous scaffold containing 30 wt% nano-hydroxyapatite (n-HA) and 70 wt% polyurethane (PU) from castor oil was prepared by a foaming method and investigated by X-ray diffraction (XRD), Fourier transform infrared absorption (FTIR), scanning electron microscopy (SEM) techniques. The results show that n-HA particles disperse homogeneously in the PU matrix. The porous scaffold has not only macropores of 100–800 μm in size but also a lot of micropores on the walls of macropores. The porosity and compressive strength of scaffold are 80% and 271 kPa, respectively. After soaking in simulated body fluid (SBF), hydrolysis and deposition partly occur on the scaffold. The biological evaluation in vitro and in vivo shows that the n-HA/PU scaffold is non-cytotoxic and degradable. The porous structure provides a good microenvironment for cell adherence, growth and proliferation. The n-HA/PU composite scaffold can be satisfied with the basic requirement for tissue engineering, and has the potential to be applied in repair and substitute of human menisci of the knee-joint and articular cartilage.

First-principles molecular dynamics simulation of O2 reduction on nitrogen-doped carbon

Abstract: Density-functional calculations were performed to examine oxygen reduction reactions (ORRs) on N-doped graphene sheets. We found that O2 adsorption becomes energetically favorable as the number of N around a C C bond increases. Pathways for both 4e− and 2e− reductions were identified. The possibility of O poisoning was suggested after calculating the reversible potential of each reduction step.

Electrodeposited ruthenium oxide thin films for supercapacitor: Effect of surface treatments

Abstract: Amorphous and porous ruthenium oxide thin films have been deposited from aqueous Ru(III)Cl 3 solution on stainless steel substrates using electrodeposition method. Cyclic voltammetry study of a film showed a maximum specific capacitance of 650 F g −1 in 0.5 M H 2 SO 4 electrolyte. The surface treatments such as air annealing, anodization and ultrasonic weltering affected surface morphology. The supercapacitance of ruthenium oxide electrode is found to be dependent on the surface morphology.

Versatile synthesis of rectangular shaped nanobat-like CuO nanostructures by hydrothermal method; structural properties and growth mechanism

Abstract: This paper describes a simple and versatile method for growing highly anisotropic rectangular shaped nanobat-like CuO nanostructures by simple, low temperature and cost effective hydrothermal method. Field emission scanning electron microscopy illustrated that these CuO nanostructures have diameter of ∼70 nm, thickness of ∼8 nm and length of ∼174 nm. Structural analysis reveals that the CuO nanostructures have a high crystal quality with monoclinic crystal structure. X-ray photoelectron spectroscopy studies demonstrate that the sample is composed of CuO. The Raman study also indicates the single phase property and high crystallinity of as-grown CuO nanostructures. The plausible growth mechanism for the formation of nanobat-like CuO structure is proposed.

Surface modification of a biomedical polyethylene terephthalate (PET) by air plasma

Abstract: In this work, low-pressure air plasma has been used to improve polyethylene terephthalate (PET) surface properties for technical applications. Surface free energy values have been estimated using contact angle value for different exposure times and different test liquids. Surface composition and morphology of the films were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Surface topography changes related with the etching mechanism have been followed by weight loss study. The results show a considerable improvement in surface wettability and the surface free energy values even for short exposure times in the different discharge areas (discharge area, afterglow area and remote area), as observed by a remarkable decrease in contact angle values. Change of chemical composition made the polymer surfaces to be highly hydrophilic, which mainly depends on the increase in oxygen-containing groups. In addition to, the surface activation and AFM analyses show obvious changes in surface topography as a consequence of the plasma-etching mechanism.

Influence of the OH groups on the photocatalytic activity and photoinduced hydrophilicity of microwave assisted sol–gel TiO2 film

Abstract: In the present work the influence of the OH groups on the photocatalytic activity and the photoinduced hydrophilicity of microwave assisted sol–gel TiO 2 films was investigated. The prepared TiO 2 films were characterized using XRD and AFM. Furthermore, the surface of the TiO 2 films was examined by help of XPS in order to determine the amount of OH groups before and after UV irradiation at different humidities. The activity of the TiO 2 films was determined using stearic acid as a model compound and the photoinduced superhydrophilicity was investigated through contact angle measurements. The results of this investigation showed that the microwave assisted sol–gel technique produces highly homogeneous and efficient TiO 2 films without the need for heat treatment for crystallization. Based on the conducted experiments it is suggested that the amount of OH groups on the TiO 2 surface highly influence the photocatalytic activity and the photoinduced superhydrophilicity and that the two mechanisms may be closely related. It is suggested that the superhydrophilicity is obtained through a combination of photocatalytic degradation of organic contaminants and surface structural changes in form of an increased amount of OH-groups.