Current Physical Chemistry - Volume 7, Issue 1, 2017

The use of the semi empirical (SE) quantum harmonic approach for calculating the proton's mean kinetic energy, Ke(H), of systems containing hydrogen bonds (HB), is reviewed. The value of Ke(H) provides very interesting information on the proton dynamics, anharmonicity, and quantum effects. This method uses the IR/Raman and inelastic neutron scattering frequencies of the system as input data and assumes the harmonic approximation. The systems studied encompass a wide range of HBs strengths, from weak occurring in e.g. pure H2O phases and Silanol groups, via moderate, as in ferro-electric KDP-type crystals, to strong ones as in highly compressed ice VII and the superprotonic Rb3H(SO4)2 conductor. The comparison of SE results with electron (ECS) and neutron (NCS) Compton scattering measurements revealed many cases of very good agreements. In recent years, however, unusual Ke(H) values, using NCS, were reported in confined water within ≤ 20 Å size cavities such as in carbon nanotubes (CNTs) and in Beryl crystal. The Ke(H) values were found to depart strongly from those of the non-confined water. In an attempt to understand those anomalies, SE study was carried out, focusing on nano-confined samples meeting the ≤ 20Å size criteria, including carbon nanotubes, Beryl and Bikitaite. These calculations failed to reproduce the NCS anomalies. Possible sources for the discrepancies were discussed and further research to reconcile this open question was proposed.

Background: Olivine structured LiMnPO4 is a pioneering energy-storage material of Li+-ion batteries. Its synthesis in a shape of small plates (large free-surfaces) bonding over a C-sp2 surface layer is demanded in harvesting its functional properties. Objective: In situ synthesis of grafted LiMnPO4 of nanopaltes with a C-sp2& surface layer, with tailored impedance properties. Method: A simple hydrothermal reaction is explored in a solution LiOH·H2O, MnSO4·H2O and H3PO4 with sodium dodecyl sulphate (a surfactant) to synthesize LiMnPO4 of small plates. A phase pure LiMnPO4 is obtained in 8-12 h heating a precursor solution at 150°C in an autoclave, and then washing a recovered powder in hot water. Results: The sample LiMnPO4 contains nanoplates of a Pmnb orthorhombic crystal structure, 20-40 m2/g surface area, 30-40 nm thickness, and self-assemblies. The lattice parameters a = 0.6104 nm, b = 1.0468 nm and c = 0.4758 nm describe a marked 0.43 % lattice expansion over the bulk phase, with an enhanced aspect ratio c/a = 0.7795 above the bulk value 0.7777, which likely promotes the charge-carrier dynamics. In the HRTEM images, the LiMnPO4 plates wear a GO-surface layer of a conductive 2D-network with sp2-C electrons. Uniquely, a cell made of the sample yields largely enhanced (i) conductivity of Li+ ions and electrons at a 10-6 S-cm-1 scale and (ii) Li+ diffusion coefficient 3.291x10-14 cm2s-1 at room temperature. Conclusion: The results describe LiMnPO4 nanoplates with an inbuilt surface C-sp2 layer extend fast charge diffusion kinetics useful for powerful Li+- ion batteries.

Background: The organic molecules represent one of the most active classes of compounds, and they have been widely used as active materials for important applications. In this study, the organic molecules and their derivatives with electron withdrawing groups in different positions were investigated to elucidate the influence of substituted groups on electronic and optical properties. Objective: In order to guide the synthesis of novel materials, some new organic compounds are designed as good candidates for nanoelectronics and solar cell applications. Methods: All the calculations are based on the density functional theory (DFT) at the B3LYP/6-31G level through the Gaussian 09W program package. Results: The optimized structures, total energies, electronic states (HOMO and LUMO), energy gaps and the absorption thresholds were performed. This study clarified that the electronic and optical properties are sensitive to the type and position of substituted subgroups. This leads to significant changes in the charge transport and the absorption spectra. The results showed a decrease in energy gaps and the presence of the electron withdrawing groups (such as CClO radical) leads to the absorption threshold in the visible region of the spectrum. Conclusion: The study of structural, electronic and optical properties for these molecules could help to design more efficient functional organic materials, and these properties play a key role in a variety of nanoelectronics and solar cells applications.

Bisphenol A (BPA) is a monomer that is used in the production of polycarbonate plastics. Polycarbonate plastics are used to manufacture a lot of common consumer goods, including eating utensils. The voltammetric behavior of BPA has been investigated using a modified carbon paste electrode in a Britton–Robinson (BR) buffer. A rapid quantitative determination of BPA in polycarbonate products due to an incomplete polymerization reaction has been examined using cyclic voltammetry and differential pulse voltammetry at a modified carbon paste electrode. The optimum voltammetric response was achieved in a pH 9 BR buffer. Additions of BPA using a quantitative voltammetric determination exhibited a linear detection range between 1.0x10-8 M and 2.7x10-4 M BPA. The limit of detection and the limit of quantification were found to be 1.1x10-9 M and 3.7x10-9 M, respectively. The method developed was successfully applied to the determination of BPA content of real samples.

Cloud point extraction (CPE) was used to extract uranium (VI) from an aqueous solution in acetate media. The methodology used is based on the formation of uranyl-ionic liquid (I) complexes and uranyl-D2EHPA soluble in a micellar phase of non-ionic surfactant (Triton X-100). The uranium (VI) complexes are then extracted into the surfactant-rich phase at ambient temperature. The ionic liquid (IL) used as a chelating agent was synthesized and characterized in this study. It is composed of N-butyl N'-triethoxy methyl imidazolium cation and anion diethylhexylphosphate (D2EHPA-H). The effect of the ionic liquid IL on the extraction efficiency was studied in the presence and in the absence of IL's cation in acetate medium.

Glycine (Gly) is one of the amino acids, commonly found in proteins, coded by codons GGU, GGC, GGA and GGG. Glycine is the unique non-optically active amino acid. The Gly-ferricyanide reaction catalyzed by Pd(II), under pseudo-first-order conditions, has been spectrophotometrically monitored at the ferricyanide λmax of 303 nm at constant temperature. The experimental rate law for the reaction is: rate = kı [Fe(CN)63-] [Gly]x [H+]y[Pd(II)]z, where x, y and z are fractional orders. Additionally, the effect on the rate of adding the reduction product, [Fe(CN)64-], has been found to be negligible. Variations of the ionic strength and the dielectric constant of the reaction medium have an effect on the rate. Activation parameters have been evaluated using Arrhenius and Eyring plots. A suitable mechanism has been presented and the derived rate law is consistent with the kinetic data.

Background: The study of the effect of external electric field on the structure and reactivity of fatty acids and their glycerides is now extended to selected derived lipids. Objectives: The present study involves computations of changes in energy and dipole moments, charge density and bond lengths of β-carotene (a carotenoid), cholesterol (a sterol), sphingosine and ceramide (sphingolipids) and phosphatidylcholine (a phospholipid) in the external electric field of 0.00, 5.14, 25.70 and 51.40 MV/cm. Method: The computations were performed applying HyperChem 8.0 software together with the PM3 method for optimization of the conformation of the molecules. Results: The raise in the EEF strength to 5.14 MV/cm has a subtle effect on the molecular energy of the lipids under study. A slight tendency in decreasing that energy can, however, be observed. On elevating the strength up to 25.70 MV/cm that decrease in molecular energy was more significant. Conclusions: Observed changes evoked by the EEF were specific for particular molecules. They resulted mainly from the polarization of the bonds and to a lesser extent from steric deformations of the molecules.