Current Physical Chemistry - Volume 7, Issue 3, 2017

Background: A molecular iodine catalyzed synthesis of quinoxalines with phenylenediamines (1) and epoxides (2), mediated by visible-light under open atmosphere in the absence of a photoredox catalyst, has been developed. Methods: Good to excellent yield of the desired products was obtained at room temperature. We have also extended our protocol by the utilization of phenacyl bromide (3). Result: Use of photochemical activated pathway showed a considerable advantage over previously reported methods for the synthesis of highly significant heterocycles.

Background: Strontium titanate (SrTiO3, STO) has a typical perovskite structure with unique physical and chemical properties, being widely used as a functional material in electronic, piezoelectric and photocatalytic devices. Method: Combining existing properties with high specific area and regular geometric morphology to attain more accurate characteristics, nanoscale SrTiO3 has been generated. Observation: This review introduces STO and doped nonstoichiometric STO nanomaterials, especially barium strontium titanate (BST). Furthermore, nano-STO morphology control in solvothermal synthesis and self-assembly in fabrication are discussed. Result: The relevant applications such as in transistors and memory devices, thermoelectric ceramics, and solar cells are also addressed.

Background: Advanced veterinary medical care's promote progress to improve the health of our animals and enhance the efficiency of animal husbandry. Drugs present in tissue can be ingested by humans, after being added to feed or premixed with it to prevent various intestinal disorders. Objective: Diaveridine HCl (DVD), diaminopyimidine antimicrobial agent, has been electroanalyzed at electrochemically activated ultrafine urethane (UT) electrode using square wave voltammetry with well-known high sensitivity. Method: The optimum conditions for electrochemical activation of UT electrode have been explored. The effects of electrolyte pH and instrumental parameters on the electrochemical behavior of DVD are optimized. Results: At the optimum conditions, the rectilinear range for the DVD analysis was constructed and found to extend over the range 1.68-16.4 μM. Both relative standard deviation and confidence limit for six replicate measurements were calculated. Conclusion: The electrochemical pre-treatment of UT via cycling of electrode in the potential range -0.2-1.9 V was found to be the optimum; the maximum negative potential shift with the larger peak current was obtained at the modified electrode at the optimum pH (8.3).

Aims: Experimental and computational studies of a series of multi-halogenated boron subphthalocyanine (Cl-BsubPcXn) derivatives are reported. This family of compounds with various degrees of chlorine or fluorine peripheral substitution (n = 4, 8, or 12) was studied by density functional theory (B3LYP model) in order to characterize the optimized geometries and electronic structures. Method: The boron subphthalocyanines with one, two and three fully fluorinated rings (Cl- BsubPcF4, Cl-BsubPc F8, and Cl-BsubPcF12 respectively) were prepared in a single pot synthesis, purified, and characterized. Observation: While the yields (0.6%, 5.2%, 1.9% respectively) are low, this is the first report of isolated separation and characterization of these subphthalocyanine structures. Result: Absorption spectroscopy and electrochemical studies confirmed that the ring substitution has a strong effect on the electronic properties of Cl-BsubPcXn. Cyclic voltammetry and UV-Vis support theoretical results where bandgaps decreased as the degree of fluorine substitution increased.

History: A new series of Dy³⁺ ions doped lead fluoroborate glasses containing different alkaline earth oxides of composition 20PbF2-10Li2O-5RO-5ZnO-59B2O3-1Dy2O3 (R = Ba, Sr and Ca; abridged as PLRZFB: Dy) were prepared by conventional melt quenching method. Method: The non-crystalline nature and the glass transition temperatures (Tg) of the prepared glass samples were confirmed through XRD studies and DSC analysis respectively. The EDS analysis was performed to know the elements present in the prepared glass compositions. The Judd-Ofelt (JO) intensity parameters determined from the absorption spectra were used to investigate the symmetry orientation of the Dy- ligand field environment. Various radiative parameters were determined using J-O parameters for different Dy³⁺ emission transitions. Objective: Photoluminescence spectra exhibit emission bands in the blue, yellow and red regions. Stimulated emission cross section (σPE) branching ratio (βexp), yellow to blue intensity (Y/B) ratio and Dy - O bond covalence were estimated from the luminescence spectra. The nature of the decay curves of p>4F9/2 level of Dyp>3+ ions was analyzed. Conclusion: Finally the effect of different alkaline earth metal oxide modifiers on the luminescence properties of PLZFB: Dy glass system was analyzed. Among the prepared glasses, PLSrZFB: Dy glass possesses higher values of AR, βr, σPE and η indicating its usefulness for the development of optical, display and LED devices in the visible region.

Method: Nanocrystalline powder of 10 mol% indium oxide doped ceria is synthesized by mechanically alloying the stiochiometric powder mixture of CeO2 and In2O3 within 5 h of milling in open air. Further milling up to 8 h confirms the stable cubic structure of the compound with increase in milling time. Objective: Detailed structure and microstructure of the compound have been characterized by Rietveld powder structure and microstructure refinement method using XRD data and analyzing HRTEM images. Effect of In2O3 doping on electrical conductivity of nanocrystalline CeO2 is studied by measuring the electrical conductivity of the compound in the temperature range 300°C-600°C. The DC conductivity of doped ceria (σdc ~ 3x10-4 S/cm at 540°C for doped ceria) has been enhanced to ~100 times in comparison to that of the undoped ceria (σdc~ 4x10-6 S/cm at 540°C) nanoparticles has been found. Conclusion: This significant increment in electrical conductivity has been interpreted through the microstructure characterization of the doped compound.

Aims: Present study explores two important nonlinear optical (NLO) properties of impurity doped quantum dots (QDs) under the purview of hydrostatic pressure (HP) and temperature. Method: The NLO properties are the total optical absorption coefficient (TOAC) and the total optical refractive index change (TRIC). Simultaneously, the role of Gaussian white noise on these optical properties has also been minutely examined. A change in HP and temperature affects the above NLO properties reflected through alteration of peak height and peak position. Objective: Under a given temperature and HP, the magnitude of above NLO properties has been found to be severely depleted in the presence of noise and the extent of depletion prominently depends on the mode through which noise is applied to the system. Result: The study highlights important interplay between HP, temperature and noise (obviously taking care of its mode of application) that finally governs the profiles of TOAC and TRIC of doped QD systems.

Aims: Reactions of manganese(III)-porphyrins have been reported as possible models for closely related and biologically significant systems. Method: In this study, a stock solution of manganese(III) sulfate was prepared using a standard method of anodic oxidation of manganese(II) in H2SO4. The Indigo carmine (IC)-Mn(III) reaction catalyzed by Ru(III), under pseudo-first-order conditions, has been spectrophotometrically monitored at the IC λmax IC (610 nm) at constant temperature. The experimental rate law for the reaction is: rate = k' [IC][H+]x[Ru(III)]y, where x and y are fractional orders. Objective: The reaction rate shows a zero-order dependence on the concentration of the oxidant, Mn(III), indicating its involvement in fast steps following the slow step. Additionally, the effect on the rate of adding the reduction product, Mn(II), has been found to be negligible. Variations of the ionic strength and the dielectric constant of the reaction medium have negligible effect on the rate. Result: Based on the effect of temperature, activation parameters have been evaluated using Arrhenius and Erying plots. A suitable mechanism has been presented. The rate law derived is consistent with experimental data.