Current Physical Chemistry - Volume 4, Issue 3, 2014

Impedance measurements on poly(o-aminophenol) (POAP) film electrodes in solutions of different pH were carried out. Impedance spectra were interpreted in terms of the modified electron hopping model described in F.J. Rodríguez Nieto, R. Tucceri, J. Electroanal. Chem., 416(1996), 1. An increase of the metal/POAP interfacial resistance with an increase of pH was obtained. With regard to the bulk charge-transport process, a decrease in the electron diffusion coefficient with an increase of pH was extracted from the fitting procedure. The change of the charge-transport and charge-transfer parameters with the increase in pH was attributed to an increase in the electron hopping distance between adjacent redox sites in POAP films. Impedance results are in agreement with potentiodynamic surface resistance measurements carried out in [10].

Rechargeable magnesium batteries have attracted attention for use in the nextgeneration power storage applications. V2O5 xerogel, which has a high capacity, is expected to be an active cathode material for magnesium rechargeable batteries. However, it faces the problem of degradation due to desorption of structural water. A vanadium pentoxide xerogel containing sulfur (S-V2O5 gel) was prepared by a new composition process and evaluated by structural analysis, and its electrode performance was analyzed. Structural analysis by X-ray diffraction, differential thermal analysis, and scanning electron microscopy showed that the bulk S-V2O5 gel adopted a V2O5 xerogel-like structure with a layer structure in a stable planar direction with added sulfur, and that the surface was a reformed hard amorphous structure due to treatment with a low-temperature plasma generated using carbon felt (CF-MWP). Charge-discharge tests revealed a specific capacity of 450 mAh g-1, and cyclic voltammetry was almost perfectly stabilized after the second cycle.

Surface pressure-area isotherms and hysteresis of Langmuir films of 2-[(Octadecylimino) methyl]phenol (ODIMP) alone and mixed with octadecylamine (ODA) are described. Mixed surface films of ODIMP and ODA behave differently depending on whether the components are spread on the surface individually or what is spread instead is a previously mixed bulk solution. Hysteresis curves for pure ODIMP and both types of mixed films show that irreversible changes take place during the first compression, as isotherms obtained during the subsequent cycles have entirely different characteristics. A pure ODIMP monolayer irreversibly forms a bilayer during the first compression. Separately spread mixed films retain characteristics of the individual components, indicating non-homogeneity in the monolayer. Calculated areas per molecule of the film are consistent with the ODIMP part of the film collapsing and forming a bilayer as in its pure film. On the other hand, when a premixed solution is spread, there is no indication of a bilayer being formed. Instead, ODIMP is squeezed out of the film as it is being compressed.

Thermoelectric materials have attracted great interest during the last several decades because of their high potential for generating clean energy through devices containing no moving parts or maintenance. They are governed by the Seebeck and Peltier effects which refer to the generation of electrical energy through a temperature difference between two junctions and vice versa respectively. However, the major drawback to these devices is the lower efficiency compared to other approaches. Recently, the advancements in the field of nanotechnology have allowed the development of new materials with superior properties to increase the thermoelectric efficiency in terms of the figure of merit allowing commercially viable thermoelectric devices to exist. This review article summarizes the main thermoelectric materials studied in the past few years and focuses on perovskite oxide based materials. Approaches to improve the thermoelectric performance of these materials are also listed. Finally, the current state of the thermoelectric field of study is also considered and future research is discussed.

Spin-polarized current and tunneling magnetoresistance (TMR) are studied for two lengths of phenyl based molecules using Green's function formalism. The Hückel method is used for describing the Hamiltonian of the molecules. Our results show that an increase in length of the BPDT molecule leads to an increase in the spin-polarized current and a decrease in the TMR at higher voltages.

The kinetics and mechanism of oxidation of sulfanilic acid by hexacyanoferrate (III) catalyzed by osmium (VIII) and ruthenium (III) respectively have been studied spectrophotometrically. The uncatalyzed reaction simultaneously occurring in absence of these catalysts is suspected due to catalysis by any trace metal-ion present as an impurity either in the reagents or water. The rate of the reaction was also retarded by hexacyanoferrate (II). The energy and entropy of activation were calculated in these reactions. A plausible reaction mechanism has been suggested in each case accounting for all the experimental observations.

The kinetics and mechanism of oxidation of paracetamol (PCM) by thallium (III) in acid perchlorate medium has been studied. The reaction exhibits first order kinetics with respect to the oxidant but a complex dependence of the substrate. The rate is reduced by an increase in the hydrogen ion concentration in a complex manner. A plausible reaction mechanism has been suggested to account for experimental observations.