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Abstract : Phycocyanin as Potential Natural Dye for its Use in Photovoltaic Cells
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Abstract: Phycocyanin, a blue protein extracted from Spirulina spp, shows promising characteristics that made it suitable for its use as natural dye in photovoltaic devices as the dye sensitized solar cells. In this work, a study of the aqueous solution-phase photochemistry, photophysics, spectroscopy, voltammetry and thermal stability of phycocyanin is presented. Suitable redox potentials (Eox = 1.2 V vs. Ag/AgCl) and a value of 1.96 V for E0,0 (i.e., the energy difference between the vibrationally relaxed levels of the first electronic excited state, S1, and the ground state, S0 of phycocyanin), allows the calculation of energetic profiles that in comparison with the conduction band of the anatase-TiO2 and I-/I3- electrolyte, could predict electron transfer with these components of the cell. The data reported herein should not only help to evaluate the potential use of phycocyanin as sensitizer for solar cells, but should also help in the development of novel solar cells where the photoinduced behavior of this protein can be controlled. Keywords: Natural dye, DSSC, energy level diagram, phycocyanin.Download Full Article |
Abstract : Density Measurement for the Binary Mixtures of Ionic Liquid 1-ethyl- 3-methylimidazolium Diethylphosphate and Water (Methanol or Ethanol) at 1atm and (293.15 to 333.15) K
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Abstract: The density data for the binary mixtures of an ionic liquid (IL), 1-ethyl-3-methylimidazolium diethylphosphate [EMIM][DEP], and water (methanol or ethanol) were measured at 1 atm as a function of composition in the temperature range of (293.15 to 333.15) K using a vibrating-tube densimeter. The excess molar volumes (VE) and other thermodynamic properties were derived from the density data. All VE values are negative for the binary mixtures in the whole composition range, and reach to the maximum at the mole fraction of IL of ca. 0.3. The VE values decrease with increasing temperature for the aqueous solution of ILs, but increase with the increasing temperature for the IL solutions of methanol or ethanol. The excess molar volumes were correlated successfully by an empirical equation with the maximum average absolute relative deviation within 0.02%. Keywords: Density, excess volume, ionic liquid, water, methanol, ethanol.Download Full Article |
Abstract : Valid Entropy-Enthalpy Compensation: Its True Physical-Chemical Meaning
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Abstract: The notion of entropy-enthalpy compensation (EEC) is well known and hotly debated up to now. Nevertheless, any valid EEC phenomenon ought to have in sooth a definite physical-chemical sense. The roots of the latter are discussed here in detail. Keywords: Enthalpy, entropy, compensation, free energy, exergy, availability,thermodynamics.Download Full Article |
Abstract : Determination of Aggregation Numbers of Bile Salt Micelles with the Depression of the Solution Freezing Point
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Abstract: The special geometry of the steroid skeleton causes formation of bile acid anion micelles with small aggregation numbers, in contrast to aliphatic amphiphiles. Relative to the tendency to reduce membrane toxicity, pharmacological investigations of bile acids are mainly concerned with their oxo derivatives. Since micelles of these bile acids have been insufficiently studied, the objective of this work is the determination of aggregation numbers of corresponding micelle monomers. The aggregation numbers were determined using the freezing point depression of the solutions by applying the appropriate equations of Debye-Hückel, Guggenheim and Gibbs-Duhems, and using pNa data measured with a Na-selective electrode. Depending on the structure of the bile acid anion, the values obtained for the aggregation numbers were in the range from 2.09 to 3.44. The increase in number of oxo groups in the molecule is accompanied by a decrease in hydrophobicity of the convex side of the steroid skeleton of the bile acid anion, resulting in a lower aggregation number. Keywords: Micelles, bile salts, aggregation number, steroid skeleton, critical micellar concentration.Download Full Article |
