Electrochemical growth and characterization of iron doped cadmium sulfide thin films

Cadmium Sulfide and Ferrous doped Cadmium Sulfide thin films have been prepared on different substrates using an electrodeposition technique. Linear sweep voltammetric analysis has been carried out to determine deposition potential of the prepared films. X-ray diffraction analysis showed that the prepared films possess polycrystalline nature with hexagonal structure. Surface morphology and film composition have been analyzed using Scanning electron microscopy and Energy dispersive analysis by X-rays. Optical absorption analysis showed that the prepared films are found to exhibit Band gap value in the range between 2.3, 2.8 eV for Cadmium Sulfide and Ferrous doped Cadmium Sulfide.     

Electrochemical study of 7α,12,20-O-trimethyl-conacytone in acetonitrile

An electrochemical study of the electroreduction in anhydrous acetonitrile of 7α,12,20-O-trimethyl-conacytone, an abietane quinoid diterpene derivative from the natural product 7α-O-methyl-conacytone, showed two reduction signals. At the first reduction step, fast chemical reactions involving the loss of the methoxyl group located at C-7 with simultaneous regeneration of the quinoid moiety were observed. This electrogenerated quinone is reduced again, at the same potential used with the former quinone, resulting in a two-electron peak. These results were obtained by cyclic voltammetry and double-step chronoamperometry experiments. The electrolysis under methylating conditions of 7α-O-methyl-conacytone, at potential values of the second electron transfer, generates as major products, methoxy-hydroquinone, where the methoxy group at C-7 is lost, which is in agreement with the proposed mechanism. Therefore, the second reduction signal was attributed to the reduction of semiquinone intermediates by a mechanism not elucidated.     

Gold nanowire array electrode for non-enzymatic voltammetric and amperometric glucose detection

The non-enzymatic voltammetric and amperometric detection of glucose using a gold nanowire array electrode is described. The voltammetric detection of glucose was performed by cyclic and differential-pulse voltammetry. The detection of glucose by partial and direct oxidation of glucose during the anodic and cathodic potential sweeps was shown in cyclic voltammetry. An unusual decrease in overpotential for partial oxidation of glucose on a Au NW array electrode was observed. A linear differential-pulse voltammetric response for partial oxidation of glucose was observed up to a glucose concentration of at least 20 mM with a sensitivity of 41.9 μA mM⁻¹ cm⁻² and detection limit below 30 μM (signal-to-noise ratio of 3) for glucose oxidation at low potentials, where the influence of possible intermediates can be avoided. The amperometric response was also linear up to a glucose concentration of 10 mM with a sensitivity of 309.0 μA mM⁻¹ cm⁻². The wide dynamic range and high sensitivity, selectivity and stability, as well as good biocompatibility of the Au NW electrode make it promising for the fabrication of non-enzymatic glucose sensors.     

Characterization of nickel-bearing ferrites obtained as by-products of hydrochemical wastewater purification processes

The efficiency of the ‘ferrite process’ for the purification of wastewater heavily contaminated with nickel is evaluated, and the solid residues formed are characterised. The efficiency of the purification process is always above 99.9% for Fe²⁺/Ni²⁺ ratios greater than 3. The tested Fe²⁺/Ni²⁺ molar ratios (15/1, 7/1 and 3/1) yielded three different nickel ferrites. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES), potentiometric titration, X-ray fluorescence (XRF), X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) yielded Ni_xFe_1−x^IIFe₂^IIIO₄ (x=0.18, 0.40 and 0.65, respectively) as the most probable stoichiometry, and inverse spinel as the most probable structure. Heating at 600 °C causes the transformation of the solids into a mixture of NiFe₂O₄, α-Fe₂O₃ and NiO. Electrochemical analysis of the solid nickel ferrites was performed using carbon paste electrodes (CPEs) in HClO₄ and HCl media. In each case, the first cyclic voltammogram showed the participation of solid species in the electrochemical transformation process, since the shape of the redox peaks could be related to the structure and stoichiometry of the ferrites. In second and successive scans, the voltammograms indicated the redox couples Fe_ads³⁺+1e⁻⇔Fe_ads²⁺ (0.525 V vs. Ag/AgCl) and Ni_ads²⁺+2e⁻⇔Ni(s) (−0.470 V) in HClO₄, and FeCl_2,ads⁺+1e⁻⇔FeCl_ads⁺+Cl⁻ (0.475 V) and NiCl_x,ads^(x−2)−+2e⁻⇔Ni(s)+xCl⁻ (−0.550 V) in HCl.     

铜(Ⅱ)-丁二肟配合物体系的电化学吸附伏安法的研究

本文研究了在四硼酸钠(pH10.4)介质中,铜(Ⅱ)—丁二肟配合物的电化学吸附伏安行为,发现于-0.50V(vs.SCE)处进行配合物还原富集,再由-0.20V处静置后进行阴极扫描,于-0.30V处得一灵敏峰.铜浓度在4.0×10~(-9)～2.5×10~(-7)mol·dm~(-3)范围内与峰电流呈线性关系,富集2min检测限为2.0×10~(-9)mol·dm~(-3).用于实样测定结果满意.     

Synthesis, characterization, electrochemistry and spectroelectrochemistry of novel soluble porphyrazines bearing unsaturated functional groups

Metalloporphyrazines with a 2-methyl-2-pentenyl group fused to each pyrrole unit were synthesized starting with the corresponding unsaturated dicarbonitrile derivative. The new compounds were characterized by elemental analysis together with FTIR, ¹H-NMR, and UV-Vis spectroscopy and via voltammetric and spectrochemical methods. Electrochemical and spectroelectrochemical measurements demonstrate that while metal-free and magnesium porphyrazines gave common porphyrazine (Pz) ring-based electron-transfer reactions, incorporating redox active metal center, Co^II, into the porphyrazine core extended the redox activity of the ring system with reversible metal-based reduction and oxidation couples of the metal center in addition to the common Pz ring-based electron transfer processes. The unsaturated functional groups of the porphyrazines did not alter the common electrochemical behavior of the complexes. An in situ electrocolorimetric method, based on the 1931 CIE (Commission Internationale de l’Eclairage) system of colorimetry, was applied to investigate the color of the electro-generated anionic and cationic forms of the complexes for possible electrochromatic applications.     

Preparation of platinum-doped hollow spheres and their electrocatalytic activity in water electrolysis

Pure TiO₂ hollow spheres were prepared by using poly(styrene-methacrylic acid) latex particles as template; thereafter, titania hollow spheres were coated by platinum with an appropriate amount of choloroplatinic acid solution to obtain Pt/TiO₂ catalysts. The morphology and structure of nonstructural Pt/TiO₂ hollow spheres were characterized by BET, XRD, TGA, SEM and TEM analysis. In the samples, a remarkably uniform layer of Pt consisting of particles from 5 to 70 nm in size was formed over TiO₂ hollow spheres. We found the electrocatalytic nature of the samples by cyclic voltammetric experiment in acidic solution. The anodic peak current density of 20 wt% Pt-loaded TiO₂ hollow particles was observed 2.5 times higher than that of 5 wt% Pt/TiO₂ in the same experimental condition. Also, the anodic current density of 20 wt% Pt/TiO₂ hollow spheres calcined at various temperatures followed the order: 400 °C≈500 °C>600 °C. The electrocatalytic activity of the Pt-loaded TiO₂ hollow spheres depends on the amount of atomic platinum present in the sample; a higher concentration of platinum results in a larger current density value in anodic sweep, resulting in more oxygen production during electrolysis. Pt/TiO₂ hollow sphere catalysts have also shown long term electrocatalytic stability in acidic media.     

Preparation and characterization of a PtRu/C nanocatalyst for direct methanol fuel cells

PtRu/C nanocatalysts were prepared by changing the molar ratio of citric acid to platinum and ruthenium metal salts (CA:PtRu) from 1:1, 2:1, 3:1 to 4:1 using sodium borohydride as a reducing agent. Transmission electron microscopy analysis indicated that well-dispersed smaller PtRu particles (2.6 nm) were obtained when the molar ratio was maintained at 1:1. X-ray diffraction analysis confirmed the formation of PtRu alloy; the atomic percentage of the alloy analyzed by the energy dispersive X-ray spectrum indicated an enrichment of Pt in the nanocatalyst. X-ray photoelectron spectroscopy measurements revealed that 83.34% of Pt and 79.54% of Ru were present in their metallic states. Both the linear sweep voltammetry and chronoamperometric results demonstrated that the 1:1 molar ratio catalyst exhibited a higher methanol oxidation current and a lower poisoning rate among all the other molar ratios catalysts. The CO stripping voltammetry studies showed that the E-TEK catalyst had a relatively higher CO oxidation current than did the 1:1 molar ratio catalyst. Testing of the PtRu/C catalysts at the anode of a direct methanol fuel cell (DMFC) indicated that the in-house PtRu/C nanocatalyst gave a slightly higher performance than did the E-TEK catalyst.     

化学法改性电池锰粉的研究

本文对干电池用天然锰粉进行了化学法改性,使不同品位的天然锰粉的电性能得到了改善,实验采用薄层电池恒阻放电以及循环伏安法评价锰粉的电性能。     

锌电极电化学行为研究(Ⅴ)——有机缓蚀剂对碱液中无汞锌膏电极充放电的影响

利用电化学阻抗技术及循环伏安法,对碱性电液中无汞锌膏电极的电化学行为进行了研究,并讨论了一些有机缓蚀剂对静置、充电和放电状态下的无汞锌膏电极的阻抗行为及循环伏安行为的影响及缓蚀机理。