Electronic absorption spectra and energy gap studies of Er3+ ions in different chlorophosphate glasses

Spectroscopic properties of Er3+ ions in different chlorophosphate glasses 50P2O5-30Na2HPO4-19.8RCl (R = Li, Na, K, Ca and Pb) are studied. The direct and indirect optical band gaps (Eopt) and the various spectroscopic parameters (E1, E2, E3, and zeta4f and alpha) are reported. The oscillator strengths of the transitions in the absorption spectrum are parameterized in terms of three Judd-Ofelt intensity parameters (omega2, omega4 and omega6). These intensity parameters are used to predict the transition probabilities (A), radiative lifetimes (tauR), branching ratios (beta) and integrated cross sections (sigma) for stimulated emission. Attention has been paid to the trend of the intensity parameters over hypersensitive transitions and optical band gaps. The lifetimes and branching ratios of certain transitions are compared with other glass matrices.     

Oxidation of toluidine blue by chlorite in acid and mechanisms of the uncatalyzed and Ru(III)-catalyzed reactions: a kinetic approach

The complex mechanism of the uncatalyzed and Ru(III)-catalyzed oxidation of toluidine blue [(7-amino-8-methylphenothiazin-3-ylidene)dimethyl ammonium chloride, TB(+)Cl(-)] (λ(max) = 626 nm) by acidic chlorite is elucidated by a kinetic approach. Both the uncatalyzed and catalyzed reactions had a first-order dependence on the initial ClO(2)(-) and H(+) concentrations ([ClO(2)(-)](0) and [H(+)](0), respectively). The catalyzed reaction had a first-order dependence on the initial Ru(III) concentration ([Ru(III)](0)). The overall reaction of toluidine blue and chlorite ion was as follows: TB(+) + 5ClO(2)(-) + H(+) = P + 2ClO(2) + 2HCOOH + 3Cl(-) + H(2)O, where P is (7-amino-8-methyl-5-sulfoxophenothiazin-3-ylidene)amine. Consistent with the experimental results, the pertinent reaction mechanisms are proposed.     

Quantum confinement effects in highly conducting,ultrathin polyaniline films pursued through spectroscopic investigations

Polyaniline (PANI) is well-known for its remarkable electrical and optical properties which find immense applications in polymer optoelectronics. Though extensive work has been reported in polyaniline samples both in bulk and thin film forms, much attention has not been paid to investigate the quantum confinement effects in ultrathin polyaniline films. The present work is devoted to the search for quantum confinement effects in ultrathin polyaniline films having nanometer thickness, prepared from m-cresol, through conventional and less sophisticated spectroscopic techniques. Remarkable blue-shift has been observed in the absorption spectrum of these samples. Much intense photo-luminescent emission with considerable blue-shift observed in these ultrathin films is cited as the clear evidence for confinement effects.     

Volumetric and Viscometric Properties of Propanoic Acid in Equimolar Mixtures of N,N-dimethyl Formamide + Alkanols at T/K = 303.15, 313.15, and 323.15

The densities, ρ, and viscosites, η, of mixtures of propanoic acid with equimolar mixtures of N,N-dimethyl formamide + methanol/ethanol/1-propanol, over the entire composition range of propanoic acid and including the pure liquids, have been measured at the temperatures T/K = 303.15, 313.15, and 323.15. From this experimental data, the excess molar volume, $ V_{\text{m}}^{\text{E}} $ , deviation in viscosity, Δη, and excess Gibbs energy of activation of viscous flow, ΔG ^*E, have been determined at all three temperatures. The influence of temperature on these mixtures has been studied in terms of molecular interactions. The calculated deviation and excess parameters have been fitted to a Redlich–Kister type polynomial and the corresponding standard deviations were also evaluated. Negative values of $ V_{\text{m}}^{\text{E}} $ and positive values of Δη and ΔG ^*E are observed at all temperatures over the entire composition range in the mixtures studied. The observed negative and positive values of various excess and deviation parameters are attributed to the existence of strong interactions, like dipole–dipole interactions, H-bonding between the carbonyl group of acid molecules and hydroxyl group of alcohol groups, geometrical fitting of smaller molecules into the voids created by larger molecules in the liquid mixtures. The strength of these interactions in the mixtures was found to decrease with the rise in temperature and increase with an increase of chain length of the alcohols. The derived partial molar volumes and excess partial molar volumes also support the $ V_{\text{m}}^{\text{E}} $ results. The experimental viscosity data of all of these liquid mixtures have been correlated with four viscosity models, those of Grunberg and Nissan, Hind et al., Katti and Chaudhri, and Heric and Brewer. The Katti and Chaudhri model was found to be in good agreement with the experimental values.     

Ultrasonic velocities, densities, and excess molar volumes of binary mixtures of N,N-dimethyl formamide with methyl acrylate, or ethyl acrylate, or butyl acrylate, or 2-ethyl hexyl acrylate at T = 308.15 K

Ultrasonic velocities, u, densities, ρ, of binary mixtures of N,N-dimethyl formamide (DMF) with methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), and 2-ethyl hexyl acrylate (EHA), including pure liquids, over the entire composition range have been measured at T = 308.15 K. Using the experimental results, the excess molar volume, , partial molar volumes, , , and excess partial molar volumes, , have been calculated. Molecular interactions in the systems have been studied in the light of variation of excess values of calculated properties. The excess properties have been fitted to Redlich–Kister type polynomial and the corresponding standard deviations have been calculated. The positive values of indicate the presence of dispersion forces between the DMF and acrylic ester molecules. Further theoretical values of sound velocity in the mixtures have been evaluated using various theories and have been compared with experimental sound velocities to verify the applicability of such theories to the systems studied. Theoretical ultrasonic velocity data have been used to study molecular interactions in the binary systems investigated.     

Unoriented two-stage DEA: The case of the oscillating intermediate products

Data envelopment analysis (DEA) allows us to evaluate the relative efficiency of each of a set of decision-making units (DMUs). However, the methodology does not permit us to identify specific sources of inefficiency because DEA views the DMU as a “black box” that consumes a mix of inputs and produces a mix of outputs. Thus, DEA does not provide a DMU manager with insight regarding the internal source of the organization’s inefficiency.     

Microwave Assisted Synthesis and Antimicrobial Activity of Novel Pyrrolidine Derivatives

Microwave assisted synthesis of 1-acetyl-2-benzylpyrrolidine-2-carboxylic acid and its derivatives has been developed with highly encouraging yields. 2-Benzyl-tert-butylpyrrolidine-1,2-dicarboxylate is used as an initial compound in the four steps synthesis of the target compounds. Structures of the products 5a–5h have been confirmed by spectroscopic methods. According to antimicrobial tests 1-acetyl-2-benzylpyrrolidine-2-carboxamide 5c is determined to be the most potent product.