Surface modification of electrodeposited p-CulnSe2 thin films with selenium and ruthenium

Changes in the surface composition of electrodeposited p-CulnSe₂ (CIS) thin films with electrodeposited selenium and ruthenium chemically adsorbed, improve the cathodic photocurrent response in sulphuric acid solution. The structural and chemical composition of the as-deposited and modified surface have been determined by X-ray diffraction and atomic absorption spectrometry before and after illumination. The estimates of the optical band gap have been analysed and discussed in terms of bulk modifications arising from the indium released, and its substitution by selenium or ruthenium.     

Influence of processing method on the properties of hydroxyapatite nanoparticles in the presence of different citrate ion concentrations

The objective of this study was to investigate the effect of processing methods on the formation of ultra fine hydroxyapatite (HAp) nanoparticles in the presence of citrate ions and analyze their various physical properties. The addition of the citrate ions was found to reduce the size and prevent the agglomeration of HAp particles dramatically in the high gravity (HG) method compared to precipitation method. In precipitation method, the particle size reduced from 300 ± 70 nm to 90 ± 20 nm with the addition of citrate ions. In high gravity method, the particle size decreased more significantly from 80 ± 10 nm to 13 ± 5 nm with the addition of citrate ions. Furthermore, more uniform size distribution of nanoparticles was achieved in high gravity method. X-ray diffraction of nanoparticles prepared in both method exhibited slight shift of peaks to the higher angle with the addition of citric acid, indicating the incorporation of carbonate (CO₃) content in the HAp nanoparticles irrespective of the particle size. The mechanical properties of HWMPE matrix composite reinforced with nanoparticles was examined and this nanocomposite with nanoparticles prepared in high gravity method with the addition of citrate ions showed increased mechanical strength due to the considerable reduction in the particle size and higher uniformity of the particles. In vitro cellular analyses of the nanoparticle prepared in high gravity with the addition of citrate ions also displayed the most pronounced spreading of cell growth.     

Photoelectrochemical solar cells using electrodeposited GaAs and AlSb semiconductor films

Electrodeposited GaAs and AlSb thin film semiconductors were prepared under various deposition conditions. Reasonable stoichiometry could be attained as revealed by EDAX studies. The best stoichiometry was obtained are Ga_1·04As_0·96 and Al_1·12Sb_0·88. The band gap of the GaAs and AlSb films was ∼1·5 eV and 1·6 eV respectively. The electrochemical and photoelectrochemical studies on these films are reported with different redox-couples in aqueous and non-aqueous medium.     

Photoelectrochemical (PEC) studies on CdSe thin films electrodeposited from non-aqueous bath on different substrates

Thin films of CdSe were deposited by potentiostatic mode on different substrates such as stainless steel, titanium and fluorine tin-oxide (FTO) coated glass using non-aqueous bath. The preparative parameters were optimized to get good quality CdSe thin films. These films were characterized by X-ray diffraction (XRD), optical absorption and photoelectrochemical (PEC) techniques. XRD study revealed that the films were polycrystalline in nature with hexagonal phase. Optical absorption study showed that CdSe films were of direct band gap type semiconductor with a band gap energy of 1·8 eV. PEC study revealed that CdSe film deposited on FTO coated glass exhibited maximum values of fill factor (FF) and efficiency (η) as compared to the films deposited on stainless steel and titanium substrate.     

Preparation and characterization of pulse-plating electrodeposited CuInSe2 thin films

CuInSe₂ thin films were electrodeposited on an indium-tin-oxide glass substrate by a pulse-plating technique from an aqueous electrolyte solution, containing CuSO₄, InCl₃ and SeO₂ with the pH adjusted to 1.5 at room temperature. The deposited and heat-treated films were characterized structurally using X-ray diffraction (XRD), scanning electron microscopy (SEM) and auger electron spectroscopy (AES) analysis. The optical and the electrical properties of the films were also examined. When the film was submitted to heat-treatment above 300 C in air for 1 h, the sample showed a chalcopyrite structure and n-type conductivity with a carrier concentration of ~ 10¹⁷ cm^–3 and a band-gap (direct allowed transition) energy of 0.99 eV.     

An investigation of structure and electrical characteristics of lanthanum strontium manganite nanopowders with different Sr2+ ion concentrations

Generally, the efficiency of solid oxide fuel cells is heavily dependent on the electrocatalytic activity of the cathode toward the oxygen reduction reaction. In order to achieve a better cathode performance, La_xSr_1-xMnO₃ (LSM) nanopowders with different Sr²⁺ ion contents varying from 0.2 to 0.8 have been synthesized using the coprecipitation method. The obtained nanoparticles were characterized by x-ray diffraction, field emission scanning electron microscopy, and electrochemical impedance spectroscopy. It was found that the LSM nanoparticles seemed to exhibit high polarization resistance with the increase of the Sr²⁺ ion molar ratios. The crystallite size was found to increase from 16.4 to 24.3 nm with increasing Sr²⁺ content from 0.2 to 0.8. The lattice parameters were decreased with Sr²⁺ ion content which may be caused by an increase in internal stress with the increasing grain size of LSM. Meanwhile, the real part impedance (Z′) was increased from 10 (Ω) at 0.2 Sr²⁺ to 24 (Ω) at 0.8 Sr²⁺ ion ratio. Alternatively, |Z| of prepared sample was increased from 12 to 26 (Ω) by increasing Sr²⁺ ion molar ratios from 0.2 to 0.8.     

Structural characterization of electrodeposited boron

Structural characterization of electrodeposited boron was carried out by using transmission electron microscopy and Raman spectroscopy. Electron diffraction and phase contrast imaging were carried out by using transmission electron microscopy. Phase identification was done based on the analysis of electron diffraction patterns and the power spectrum calculated from the lattice images from thin regions of the sample. Raman spectroscopic examination was carried out to study the nature of bonding and the allotropic form of boron obtained after electrodeposition. The results obtained from transmission electron microscopy showed the presence of nanocrystallites embedded in an amorphous mass of boron. Raman microscopic studies showed that amorphous boron could be converted to its crystalline form at high temperatures.     

Photoelectrochemical characterization of sintered n-CdS pellet

From an analysis of the photoeffects at the n-CdS pellet - $\text{S}\text{2?}\text{S}\text{2?}$ electrolyte interface, solid state parameters of the CdS pellet, e.g., flat band potential, donor density, minority carrier diffusion length and depletion layer width have been evaluated. It is stressed that PEC measurements may also be adopted for the determination of bandgap and transition mode of the semiconductor.     

Structural and spectroscopic ellipsometry characterization for electrodeposited ZnO growth at different hydrogen peroxide concentration

This work deals with textural and optical characterization of zinc oxide (ZnO) layers obtained by potentiostatic electroplating at various hydrogen peroxide concentrations (from 0 up to 5 mM). The electrodeposition process was studied by cyclic voltametry and chronoamperometry. The [002] preferred growth orientation of hexagonal phase is obtained for the lowest hydrogen peroxide concentration (1 mM), while additionally X-ray diffraction peaks are observed for hydrogen peroxide concentration ranging from 3 to 5 mM. The optical constants and the thickness of films were determined by spectroscopic ellipsometry measurements. The refractive index of all thin films shows normal dispersion behavior. It was also found that refractive index values decrease with increasing hydrogen peroxide concentration. Further, it was revealed that the changes in the optical properties are correlated to the changes in the surface structure.     

Electrochemical characterization of electrodeposited carbon nanotubes

Carbon nanotubes were electrodeposited in acetonitrile solution at room temperature using Cu, and Fe-Ni nanoparticles as nucleation sites on HF-etched Si(100) wafer substrate. The electrochemical behavior of the deposition was investigated by voltammetry and chronoamperometry techniques. In order to obtain the optimum growth condition, the deposition critical parameters including current density range, potential and time were studied and calculated. Carbon nanotubes with approximate external diameter of 40-100 nm were fabricated under potentiostatic condition and diffusion control at − 20 V in 4-6 h. The film crystallinity was investigated by means of X-ray diffraction and the tubes structure was revealed using scanning electron microscope and transmission electron microscope images. Raman spectroscopy was also employed to characterize the nanostructural features and single wall carbon nanotubes were detected.     

Preliminary characterization of electrodeposited W2C coatings for wear applications

The recent development of hard adherent W₂C coatings by the simultaneous electrochemical reduction of tungstate (WO₄^2-) and carbonate (CO₃^2-) ions in a molten fluoride bath is described. The elements tungsten and carbon thus formed on the cathode combine in a subsequent chemical step to form the carbide. The structure of the deposit depends on the length of the plating time as well as melt composition and electrochemical parameters such as current and voltage. In pin-on-disk-type wear tests some fragmentation of the coating and abrasive wear were observed.     

柠檬酸银纳米乳液的合成与表征

为了制备纳米层级有机酸银乳液，并考察其在制备纳米导电银膜方面的应用，在聚乙烯吡咯烷酮（PVP）存在的条件下，于水中通过硝酸银与柠檬酸钠反应，合成了柠檬酸银纳米乳液。将柠檬酸银纳米乳液涂布在PET片基上，并用抗坏血酸（Vc）水溶液对其进行还原，制备了纳米导电银膜。通过红外光谱仪、热分析仪、X射线衍射仪、激光粒度仪、紫外．可见光分光光度计、扫描电镜（SEM）等，对柠檬酸银纳米乳液，以及导电银膜性能进行了测试和表征。发现PVP保护的柠檬酸银乳液，粒度分布均匀。SEM观察表明，柠檬酸银呈长径比为5：1的棒状生长，直径约为20nm。银膜的UV-Vis吸收峰位于430nm，表明其具有纳米结构，表面电阻为2.42kΩ/cm。     

Photoelectrochemical characterization of Bi2Se3 thin films deposited by SILAR technique

Bi₂Se₃ thin films have been deposited by simple and less investigated successive ionic layer adsorption and reaction (SILAR) technique onto fluorine-doped tin oxide (FTO) coated glass substrates at room temperature (27 °C). The X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies indicate that Bi₂Se₃ thin films are nanocrystalline. These films are used for photoelectrochemical (PEC) characterization in cell with configuration as n-Bi₂Se₃/0.1 M polysulfide/C. The studies such as current–voltage characteristics in dark and light, photovoltaic power output, transient photoresponse, and capacitance–voltage have been carried out. The study reveals that fill factor and power conversion efficiency of the cell are low (0.43 and 0.032%, respectively).The flat bond potential is found to be −0.04 V (SCE).     

Optical characterization of titania thin films produced by the solgel method and doped with co(2+) at different concentrations

We report some preliminary results on the fabrication and optical characterization of high-refractive-index thin films of titania doped with Co(2+). These films were supported on silica platesthat were chemically activated to attach both phases. The titania films were produced by the solgel method at room temperature and slowly annealed from room temperature to 230 degrees C; their thickness was approximately 600 ?. The optical characterizations were obtained by the use of spectroscopic ellipsometry, where the dielectric function of the material was obtained as a function of the wavelength. Additionally, the ellipsometric function was modeled to obtain the porosity of the films and their thickness.     

Photoelectrochemical response studies of W deposited TiO2 nanotubes via thermal evaporation technique

Titania (TiO₂) nanotube arrays were successfully formed by anodising titanium (Ti) foil in a standard two-electrode bath in 1?M of glycerol (HOCH₂CH(OH)CH₂OH) containing 0.5?wt% ammonium fluoride (NH₄F). It was observed that such anodisation condition resulted in self-organised of TiO₂ nanotubes with the average pore sizes of approximately 90?nm and the length was approximately 1?µm. In this study, various thicknesses of tungsten (W) were deposited on TiO₂ nanotubes via thermal evaporation technique to investigate the photoelectrochemical (PEC) response and hydrogen generation rate. The improvement in PEC response was found by using a photoanode of 2.5?nm W deposited TiO₂ nanotubes as compared to the pure TiO₂ nanotubes. It was believed that a shallow trap was provided for charge carrier to inhibit the recombination and eventually extend the lifetime of charge carrier. In contrast, the higher deposition of W on TiO₂ nanotubes resulted in lower PEC response because it acts as charge carrier recombination center. The experiment results show that the maximum photocurrent density of 0.9?mA/cm² and maximum hydrogen production rate of 12?µL/cm²/min was achieved using 2.5?nm W deposited TiO₂ nanotubes.     

The biochemical response to different Cr and Cd concentrations in soils amended with organic wastes

The effects of adding municipal solid waste (MSW) or poultry manure (PM) on the biochemical properties of a soil polluted with Cr and Cd were studied. Soil was mixed with Cr(NO₃)₃ and Cd(NO₃)₂ to give three concentrations (0, 100, and 250 mg Cr kg⁻¹ and 0, 100, and 250 mg Cd kg⁻¹) in the soil, which was then treated with MSW at a rate of 10% or PM at a rate of 7.6%. The pH and biochemical parameters were measured at 0 and 120 days. An unamended and no-polluted soil was used as control. Compared with the non-polluted soil, for the 250 mg Cd kg⁻¹ treatment the microbial biomass-C, dehydrogenase, urease, β-glucosidase, phosphatase, and arylsulphatase activities decreases 23%, 26.2%, 36%, 34.8%, 18.4%, and 15.8%, respectively, whereas for 250 mg Cr kg⁻¹ treatment the biochemical parameters were slightly lowest than for 250 mg Cd kg⁻¹ treatment. For 250 mg Cr kg⁻¹ soil + 250 mg Cd kg⁻¹ soil treatment, the inhibition percentages of the biochemical parameters increased. After the application of organic wastes in Cr + Cd polluted soil, the inhibition of biochemical properties was greater with the MSW amendment than with PM, possibly due to its higher humic acid concentration.     

Photoelectrochemical characterization of p-type silicon electrodes covered with tunnelling nitride dielectric films

The photoelectrochemical behaviour of p-Si(100) single crystal electrodes in aqueous solution, covered with a very thin nitride film, was studied. The silicon surface nitridation was achieved in a N₂-H₂ plasma at floating potential. The as-grown insulating Si₃N₄ layers, with thickness inferior to 3.1 nm, allow the electrons to tunnel in the presence of an electric field by the Fowler-Nordheim tunnelling mechanism. However, the p-Si(100)/Si₃N₄-electrolyte interface generated lower photocurrent densities than those generated by naked p-Si(100) electrodes. In contrast, the nitridated silicon surface displayed a significant stability improvement in aqueous electrolyte (neutral pH). An overvoltage higher than 0.6 V for water oxidation on a p-Si(100) covered with a 2.4 nm Si₃N₄ layer was measured. The results show that silicon covered with a nitridated thin film may be useful to stabilize electrodes in photoelectrochemical applications.     

Structural and magnetic characterization of electrodeposited Ni/Cu multilayers

Ni/Cu multilayers were electrodeposited from a single solution electrolyte by galvanostatic method. Interface roughness, magnetization and magneto-transport studies of Ni/Cu multilayers on Si(1 1 1)/Ti/Cu substrate were carried out for samples deposited from three different electrolytes, viz. pure sulphate, sulphate–citrate and sulphate-polyethylene glycol-8000 (PEG-8000). The top Ni-layer morphology of these samples was characterized by atomic force microscope (AFM). Detailed analysis of the morphological data showed a typical two-dimensional fractal growth pattern in all the three cases. The structural parameters like interface roughness, density and thicknesses of Ni and Cu layers were extracted from neutron reflectivity (NR) study. The order of interface roughness obtained from NR and AFM was found to be quite close. The sample deposited from sulphate–citrate electrolyte was found to have minimum interface roughness. The polarized neutron reflectometry (PNR) measurement showed reduced magnetic moment value (∼0.41 ± 0.01 μ_B) for nickel layers compared to bulk value in all the three samples. The magnetoresistance (MR) of these samples were measured at room temperature. An attempt has been made to explain the observed MR results in terms of granular structure and scattering mechanism involving super-paramagnetic and ferromagnetic particles in these samples.