Solar Energy Materials and Solar Cells, Dec 1, 2007
The electrodeposition of CuInSe 2 is investigated to improve the stoichiometric properties of CuI... more The electrodeposition of CuInSe 2 is investigated to improve the stoichiometric properties of CuInSe 2 layers on indium tin oxide (ITO)coated glass substrates and to develop one-step electrodeposition method for solar cell applications. XPS was utilized for the characterization of the surface properties of CuInSe 2 layers. The influence of the complexing agent, e.g. benzotriazole, bulk concentration of Cu and Se and deposition potentials on the stoichiometric properties, are discussed.
Solar Energy Materials and Solar Cells, Dec 1, 2007
The electrodeposition of CuInSe 2 is investigated to improve the stoichiometric properties of CuI... more The electrodeposition of CuInSe 2 is investigated to improve the stoichiometric properties of CuInSe 2 layers on indium tin oxide (ITO)coated glass substrates and to develop one-step electrodeposition method for solar cell applications. XPS was utilized for the characterization of the surface properties of CuInSe 2 layers. The influence of the complexing agent, e.g. benzotriazole, bulk concentration of Cu and Se and deposition potentials on the stoichiometric properties, are discussed.
A facile route for the electrochemical generation of an olefin metathesis catalyst from methylene... more A facile route for the electrochemical generation of an olefin metathesis catalyst from methylene chloride solution of WCl 6 was described. It was found that reductive, oxidative and pulse electrolysis produced the same intermediate. This electrolysis intermediate incorporates olefin into its structure possibly forming a metal Á/olefin complex, which decomposes into catalytically active metal carbene type species. ESCA, NMR and ESR methods were used to elucidate the structure of the catalyst system. The catalyst was applied in the metathesis of 1-octene and 2-octene without any need for a co-catalyst. Highly specific products with high yields were obtained.
A facile route for the electrochemical generation of an olefin metathesis catalyst from methylene... more A facile route for the electrochemical generation of an olefin metathesis catalyst from methylene chloride solution of WCl 6 was described. It was found that reductive, oxidative and pulse electrolysis produced the same intermediate. This electrolysis intermediate incorporates olefin into its structure possibly forming a metal Á/olefin complex, which decomposes into catalytically active metal carbene type species. ESCA, NMR and ESR methods were used to elucidate the structure of the catalyst system. The catalyst was applied in the metathesis of 1-octene and 2-octene without any need for a co-catalyst. Highly specific products with high yields were obtained.
The new macroazoinitiators containing poly (propylene glycol), (PPG), with molecular weight 400 a... more The new macroazoinitiators containing poly (propylene glycol), (PPG), with molecular weight 400 and 2000, having hydrophilic character, were synthesized and polymerized with styrene to prepare PS-b-PPG block copolymers. Cast Wlms and e-spun Wlms were prepared and contact angles of these Wlms with water drop were measured to examine hydrophilic/ hydrophobic behavior of the copolymers. Each e-spun Wlm with average Wber diameters from 0.25 to 2.20 m was prepared in N,N-dimethylformamide (DMF) under controlled electrospinning process parameters such as polymer concentration, applied voltage and tip-to-collector distance. Scanning electron microscope (SEM) images of the electrospun Wlms were taken to determine the Wber diameters. Surface compositions of the block copolymers were also determined by using an electron spectrometer with Mg K X-rays. NMR, and FT-IR spectroscopic, and GPC measurements were employed to characterize and determine the PPG contents (6-43%). From the results, electrospinning process increased the hydrophilic properties of the block copolymers obtained, compared their cast Wlm forms. Our results suggest that these polymers are favorable in biological applications in cases where high ratio of the surface to volume and hydrophilicity are required simultaneously. Both chemical structure and topology of the Wlms are important in wetting and hydrophobicity.
The new macroazoinitiators containing poly (propylene glycol), (PPG), with molecular weight 400 a... more The new macroazoinitiators containing poly (propylene glycol), (PPG), with molecular weight 400 and 2000, having hydrophilic character, were synthesized and polymerized with styrene to prepare PS-b-PPG block copolymers. Cast Wlms and e-spun Wlms were prepared and contact angles of these Wlms with water drop were measured to examine hydrophilic/ hydrophobic behavior of the copolymers. Each e-spun Wlm with average Wber diameters from 0.25 to 2.20 m was prepared in N,N-dimethylformamide (DMF) under controlled electrospinning process parameters such as polymer concentration, applied voltage and tip-to-collector distance. Scanning electron microscope (SEM) images of the electrospun Wlms were taken to determine the Wber diameters. Surface compositions of the block copolymers were also determined by using an electron spectrometer with Mg K X-rays. NMR, and FT-IR spectroscopic, and GPC measurements were employed to characterize and determine the PPG contents (6-43%). From the results, electrospinning process increased the hydrophilic properties of the block copolymers obtained, compared their cast Wlm forms. Our results suggest that these polymers are favorable in biological applications in cases where high ratio of the surface to volume and hydrophilicity are required simultaneously. Both chemical structure and topology of the Wlms are important in wetting and hydrophobicity.
Journal of Electroanalytical Chemistry, Apr 1, 2001
Electrooxidation of methanol was realised on platinum and perchlorate anion doped polypyrrole fil... more Electrooxidation of methanol was realised on platinum and perchlorate anion doped polypyrrole film electrodes in acidic media. A systematic kinetic investigation was performed and optimum experimental conditions for the preparation of the electrocatalytic system were determined. The presence of ClO 4 -anions was confirmed by XPS analysis of the doped polymer matrix.
Journal of Electroanalytical Chemistry, Apr 1, 2001
Electrooxidation of methanol was realised on platinum and perchlorate anion doped polypyrrole fil... more Electrooxidation of methanol was realised on platinum and perchlorate anion doped polypyrrole film electrodes in acidic media. A systematic kinetic investigation was performed and optimum experimental conditions for the preparation of the electrocatalytic system were determined. The presence of ClO 4 -anions was confirmed by XPS analysis of the doped polymer matrix.
Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectrosco... more Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectroscopy, XPS, and the Auger electron spectroscopy, AES, are given. Their utilization in material characterization are introduced through examples with application of these techniques to various surface related problems.
Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectrosco... more Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectroscopy, XPS, and the Auger electron spectroscopy, AES, are given. Their utilization in material characterization are introduced through examples with application of these techniques to various surface related problems.
Carbon monoxide adsorption on a Ru/SiO 2 catalyst was followed by IR spectroscopy to investigate ... more Carbon monoxide adsorption on a Ru/SiO 2 catalyst was followed by IR spectroscopy to investigate the active sites. Using this catalyst, ammonia synthesis was achieved at 350ЊC in an N 2 /H 2 gas mixture (N 2 /H 2 Ϸ 3 : 1) for different reaction times. In addition to NH 3 other NH x (x 1,2) species were also observed. CO adsorption after NH 3 production was also performed to investigate the change in nature of the active sites. Based on the experimental evidence participation of Ru 0 sites in ammonia synthesis was confirmed and a partial oxidation of the reduced Ru sites during the synthesis was observed.
Carbon monoxide adsorption on a Ru/SiO 2 catalyst was followed by IR spectroscopy to investigate ... more Carbon monoxide adsorption on a Ru/SiO 2 catalyst was followed by IR spectroscopy to investigate the active sites. Using this catalyst, ammonia synthesis was achieved at 350ЊC in an N 2 /H 2 gas mixture (N 2 /H 2 Ϸ 3 : 1) for different reaction times. In addition to NH 3 other NH x (x 1,2) species were also observed. CO adsorption after NH 3 production was also performed to investigate the change in nature of the active sites. Based on the experimental evidence participation of Ru 0 sites in ammonia synthesis was confirmed and a partial oxidation of the reduced Ru sites during the synthesis was observed.
Analytical and Bioanalytical Chemistry, Jun 1, 1996
Electrochemically prepared films of conducting polymers of polypyrrole and polythiophene and thei... more Electrochemically prepared films of conducting polymers of polypyrrole and polythiophene and their blends with polyamide have been investigated by X-ray photoelectron spectroscopy. In the N1s region of the spectra of films containing polypyrrole the peak corresponding to N> at 402.0 eV is separated from that of neutral N. The intensity of the N> peak can be correlated with the electrical conductivity of the films and the spectroscopically derived ratio of F/N> is close to 4 indicating that one BF\ dopant ion is incorporated for every oxidized nitrogen center. In the spectra of films of polythiophene and its blends peaks corresponding to S and S> can not be resolved but again the F/C ratio correlates with the electrical conductivity. S , . Su ¨zer ( )
Ag-Cu nanoalloys were synthesized by chemical co-reduction of their metal salts in aqueous soluti... more Ag-Cu nanoalloys were synthesized by chemical co-reduction of their metal salts in aqueous solution with hydrazine hydrate, in the presence of complexing agent and stabilizer, preventing the oxidation of copper, as revealed by XPS. Their antibacterial behavior was tested against Escherichia coli strains, attesting far better ability of the Ag-Cu compared to Ag-only nanoparticles. Single metal nanoparticles have recently been in focus for their particle characteristics, size dependent properties, easy synthesis and chemical modifications. They also exhibit increased photochemical activity, modified chemical, biomedical and biological properties due to their high surface to volume ratios and unique properties that are different from their bulk. Preparation and characterization of the monometallic nanoparticles using different synthesis methods have been investigated for many years, whereas metal nanoalloy syntheses have not been as widespread due to handling problems and difficulties in preparation. Copper-only and silver-only nanoparticles (NPs) can be synthesized by the chemical reduction of copper and silver ions, which are produced by dissolving the salts of copper and silver in aqueous media, with the help of a reducing agent according to different procedures. Silver and copper alloy nanoparticles can also be prepared by co-reduction of their salts in aqueous solutions. The aqueous chemical reduction method is preferred over other nanoparticle preparation techniques because of its ease of application, variation in particle characteristics and different experimental parameters such as concentration, temperature and pH. 7 For the synthesis of the silver and copper nanoalloys (NAs) the main problems encountered are their high air sensitivity, low stability, and reactivity of the copper nanoparticles that cause the formation of copper oxide in the end product. To suppress the oxidation problem of copper in the nanoalloy synthesis, purging of the reaction media with inert gases, use of non-aqueous media, very strong reducing agents, complexing agents, surfactants and different kinds of stabilizers are the commonly employed procedures to prevent oxide formation both during preparation and storage.
A noncontact chemical and electrical measurement technique of XPS is performed to investigate a n... more A noncontact chemical and electrical measurement technique of XPS is performed to investigate a number of devices under operation. The main objective of the technique is to trace chemical and location specified surface potential variations as shifts of the XPS peak positions under operating conditions. To implement the technique we apply D.C. (Voltage-Contrast XPS) and/or A.C. (Dynamical XPS) voltage biases externally, and extract chemically resolved static and/or time-resolved electrical properties of materials and devices made from them. Details of the technique, and applications to a number of graphene-based devices configured in a transistor geometry with and without gating will be presented.
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