Papers by Keyword: Electron Transfer

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Authors: Jun Hui Xiang, Zhi Zhang, Fu Shi Zhang, Shoji Kaneko, Masayuki Okuya, Hui Ping Zhang
Abstract: For the first time, it was found that low-valence additives could be employed to improve the conversion efficiency of dye sensitized solar cell. It was experimentally discovered that by forming nonstoichiometric compound, Ti3+ was located in the lattice of TiO2 film, generating surplus electrons within the film and affecting the morphology of TiO2 particle. The improvement of the conversion efficiency of the solar cell was mainly due to the increase of short circuit current along with the content of Ti3+. The surface of the TiO2 particle became more coarsely after TiCl3 added and the absorbed dye molecules was increased. It was another reason of the improvement of conversion efficiency.
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Authors: Hiroshi Imahori
Abstract: Recently, dye-sensitized solar cells have attracted much attention relevant to global environmental issues. So far ruthenium(II) bipyridyl complexes have proven to be the most efficient TiO2 sensitizers in dye-sensitized solar cells. However, the highest power conversion efficiency has been stagnated in recent years. More importantly, considering that ruthenium is rare and expensive, novel dyes without metal or using inexpensive metal are desirable for highly efficient dye-sensitized solar cells. To fulfill the requirement, it is crucial to develop inexpensive novel dyes that exhibit high efficiencies in terms of light-harvesting, charge separation, and charge collection. Porphyrins are important classes of potential sensitizers for highly efficient dye-sensitized solar cells owing to their photostability and potentially high light-harvesting capabilities that would allow applications in thinner, low-cost dye-sensitized solar cells. However, typical porphyrins possess an intense Soret band at 400 nm and moderate Q bands at 600 nm, which does not match solar energy distribution on the earth. Therefore, the unmatched light-harvesting property relative to the ruthenium complexes has limited the cell performance of porphyrin-sensitized TiO2 cells. Elongation of the -conjugation and loss of symmetry in porphyrins cause broadening and red-shift of the absorption bands together with an increasing intensity of the Q bands relative to that of the Soret band. On the basis of the strategy, the cell performance of porphyrin-sensitized solar cells has been improved remarkably by the enhanced light absorption. The efficiency of porphyrin-sensitized solar cells could be improved significantly if the dyes with larger red and near-infrared absorption could be developed.
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Authors: Edgar Patiño, Arvids Stashans, Risto M. Nieminen
1325
Authors: Alain Bergel
Abstract: Microbial biofilms produce electrochemical interactions with metal surfaces by following a wide variety of different electron exchange pathways. Reviewing the mechanisms identified in the biocorrosion of steels leads us to distinguish direct and indirect mechanisms for biofilm-catalysed cathodic reactions. Indirect mechanisms are due to the production of metal oxides or hydrogen peroxide (aerobic corrosion) or metal sulphides (anaerobic corrosion), which further react with the metal surface. Direct mechanisms involve adsorbed biocompounds, generally enzymes or their active sites, which catalyse the cathodic reduction of oxygen for aerobic biocorrosion or the proton/water reduction in anaerobic processes. Recent studies dealing with the role of hydrogenases in anaerobic corrosion have shed light on the important role of phosphate species via so-called cathodic deprotonation. Advances in the development of microbial fuel cells have also resulted in new concepts, mainly for oxidation processes. Some microbial cells have been shown to be able to produce their own electron mediators. Others can transfer electrons directly to electrodes through membrane-bound electron shuttles or achieve long-range transfer through conductive pili.
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Authors: Taku Murase, Hidenobu Umeda
Abstract: The decrease of initial relative permeability at 103-106Hz is observed in MgCuZn or MnMgCuZn ferrites. By measuring the temperature dependence of loss factor, the gradual deterioration of initial relative permeability is attributed to a relaxation phenomenon. The relaxation phenomena of MnMgCuZn ferrites occur in the condition of the stoichiometoric composition and the higher sintering temperatures. The activation energies of the relaxation phenomena are calculated to be 0.3-1.0eV. The relaxation times at infinite temperature are calculated to be 10-12-10-16 second. The initial relative permeability of MgCuZn or MnMgCuZn ferrites with the relaxation phenomena is higher than the value calculated from the resonance frequency and Snoek’s limit law.
521
Authors: Zhong Xu, Quan Fu Wang, Ning Li, Jian Wei Zhao
Abstract: Following the previous study [Chemistry Letters 2007, 10, 1278.] on specific electron transport pathway in porphyrin, the electron transfer through oligomeric porphyrin molecular wires was studied in this work using first principle density function theory and non-equilibrium Green’s function calculations. The effects of chain length on the transportation behavior were discussed in terms of the electronic structures and transmission spectra. Through the analysis of spatial distribution of molecular frontier orbit we found that with the chain length increased, the whole delocalization of molecular frontier orbit enlarged, so e-transitivity became better. The results demonstrated that the frontier orbital energy gap decreased when the chain length increased, so that it should be conductive to electronic transmission. We presumed that the oligomeric porphyrin can be used to make moleculer electronic devices.
1126
Authors: Manoranjan Behera, Shanker Ram
Abstract: Since the discovery, gold nanoparticles (GNPs) have been attracting scientific and research communities owing to their biocompatibility, excellent thermal conductivity, low cytotoxicity, ease of processability, and highly functionalization capability. In this report, we discuss synthesis of gold nanoparticles with poly(vinyl pyrrolidone) (PVP) in 1–butanol from gold hydroxide, a new precursor salt. An emergence of a strong surface plasmon absorption band at 535 nm confirms formation of GNPs in the colloidal solution. The stability of Au colloid was studied by using UV–Visible and zeta potential measurements. The interfacial interaction between GNP and PVP molecules was studied in terms of Fourier transform infrared and X–ray photoemission spectrum (XPS). Marked enhancement in some of the vibrational bands (e.g., C=O, C–H, and C–N stretching) of PVP molecules in presence of GNPs reveals existence of an interaction between this two major constituents. However a small red-shift in the C=O stretching frequency of pyrrolidone group of PVP molecule implies that a weak interaction occurs via O–atom of carbonyl group. Appearance of Au4f doublet band at 82.7 and 86.4 eV in XPS spectrum with a chemical shift of 3.7 eV further confirms formation of GNPs by reduction of Au3+ to Au0 chemical state in presence of PVP. A noticeable negative shift in the binding energies of Au4f doublet band as compared to bulk Au atom suggests an interfacial interaction between GNP and PVP molecules. Transmission electron microscopic images propose that Au crystalline core is covered by an amorphous layer of PVP molecules.
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