Polymeric stabilization of hybrid nanocomposites: a comparison between in situ and ex situ-grown CuInS2 in poly(3-hexylthiophene) polymer

CuInS₂ (CIS) particles were directly synthesized in P3HT matrix with different concentrations ratio of P3HT and CIS (1:2, 1:4, and 1:8) by decomposition of copper indium xanthate (CIX). Here, copper indium xanthate and P3HT were mixed homogeneously in o-dichlorobenzene (DCB), which induced the formation of the CIS nanoparticles by the thermal decomposition of the precursor compound in situ at temperatures as low as 110 °C. The effects of the precursor concentration on the size of the CIS nanoparticles was studied by microstructure investigations (TEM, AFM, XRD) and UV–vis measurements show that these CIS composites possess a direct bandgap energy higher than 1.45 eV depending on the concentration of P3HT. PL quenching of P3HT polymer (i.e., higher accessible fraction of fluorophores) was found to be more for in situ rather than ex situ conditions for comparable CIX concentrations or particle size. This can be attributed to the fact that in in situ synthesis, P3HT act as surface directing template for CIS nanoparticles which is not so in the case of ex situ synthesis. Due to this, the polymeric stabilization of the CIS nanocomposites is better realized for in situ synthesis as compared to ex situ synthesis.     

Organic Synthesis Using Ptc-41: Synthesis of Cyclic Ethers Using Phase Transfer Catalysis

The reaction of (1) and (2) uith (3a)² 2nd (3b)³ under liquid-liquid (L-L) and solid-liquid (3-L) phase transfer (PT) conditions furnish the corresponding (4) and (6) respectively and the reaction of (2) with (5) gives dioxolane derivative (7)     

Assessment of natural radioactivity in soil samples and comparison of direct and indirect measurement of environmental air kerma rate

This study presents the high purity germanium (HPGe) gamma spectrometric measurement of natural radioactivity mainly due to ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples collected in Ferozepur and Faridkot district of Punjab, India. ²²⁶Ra activity varied from 28.6 to 51.1 Bq kg⁻¹ with the mean of 39.7 Bq kg⁻¹. The range and mean activity of ²³²Th were 42.9–73.2 and 58.2 Bq kg⁻¹, respectively. ⁴⁰K activity was in the range of 470.9–754.9 Bq kg⁻¹ with the mean of 595.2 Bq kg⁻¹. The air kerma rate (AKR) at 1 m height from the ground was also measured using gamma survey meter in all the sampling locations, which was ranging from 92.1 to 122.8 nGy h⁻¹ with the mean of 110.6 nGy h⁻¹. The radiological parameters such as Ra_eq and activity index of the soil samples were also evaluated, which are the tools to assess the external radiation hazard due to building materials. The mean and range of the Ra_eq values were 168.7 and 132.9–210.4 Bq kg⁻¹, respectively, whereas the activity index varied from 0.5 to 0.8 with the mean value of 0.62. These indices show that the indoor external dose due to natural radioactivity in the soil used for the construction will not exceed the dose criteria. The AKR was also evaluated from soil activity concentration and altitude correction of cosmic radiation contribution. The statistical tests such as Pearson correlation, spearman rank correlation, box and whisker plot, the Wilcoxon/Mann–Whitney test and chi-square test, were used to compare the measured AKR with evaluated AKR, which indicates good correlation.     

Detection-theoretic analysis of the observer-based psychophysical procedure

The observer-based procedure, used in research applications to measure the hearing sensitivity of young infants, is analyzed within the framework of a two-stage (infant-judge) detection model involving a minimum number of assumptions. The model is taken to develop convergence theorems useful for estimating the number of judges and/or trials required to achieve a desired level of accuracy using the procedure. The model is also used to consider ways in which bias in estimates, known to be associated with the procedure, might be evaluated and reduced. Finally, a method is proposed by which the results of the analysis and different procedural variations designed to improve estimates can be evaluated empirically.     

Dynamic correlation effects on drag resistivity of a symmetric electron–electron bilayer

We have studied the effect of dynamic electron correlations on Coulomb drag in a low density symmetric electron–electron bilayer. The drag resistivity is calculated considering the contribution from direct e–e scattering processes using the semi-classical Boltzmann approach, with the effective inter-layer interaction W₁₂(q, ω; T) determined within the ?wierkowski, Szyman?ki, and Gortel model, generalized to include the dynamics of electron correlations through the frequency-dependent intra- and inter-layer local-field correction (LFC) factors. In turn, the LFCs are obtained by extending the quantum Singwi, Tosi, Land, and Sjölander (qSTLS) approach to finite temperatures. At low temperatures (T ? 2 K), the calculated drag resistivity is found to agree nicely with the measurements by Kellogg et al., while it is somewhat overestimated at higher temperatures. The overestimation is seen to increase with decreasing density of electrons. However, there is found to be a marked improvement over the predictions of the conventional (i.e., static) STLS and random-phase approximation (RPA). It turns out that the inclusion of exchange-correlations in the RPA causes a red-shift in the bilayer plasmons which leads to an enhancement of drag resistivity. Our study demonstrates clearly the importance of including the dynamical nature of correlations to have a reasonable account of measured drag resistivity.     

A Mössbauer and electrochemical study of mononuclear iron(III) complexes with benzimidazole-based flexible bidentate ligands

A series of FeIII complexes of stoichiometry [FeLX3].nH2O have been synthesized, where X=Cl–, HCO–2 and L is a flexible bidentate ligand, 1,3(bis-benzimidazolyl) propane and 1,4(bis-benzimidazolyl)butane. Mössbauer data reveals that the isomer shift values lie in the range typically observed for high spin FeIII complexes, while the slightly large quadrupole splitting parameter indicates a rhombically distorted FeIII centre. Cyclic voltammetric studies reveal that the E1/2 for the FeIII/FeII couple for the formate complex shifts more cathodically than for the chloride complex; implying that HCO–2 is more effective at lowering the Lewis acidity of the FeIII centre.     

Cell theory and equation‐of‐state of chain molecular systems: Application to polymer solids

We use the Lennard‐Jones and Devonshire cell theory without any ad hoc simplification of the cell potential to obtain the equation‐of‐state (EOS) for chain molecular systems. The interactions of the central segment with second and third shells of neighbors are taken into account. Numerical values of the cell integrals are given in tabular form along with interpolation expressions that cover the range of PVT variables appropriate to polymers. Results of comparison with EOS based on square‐well form are also discussed. Application of the theory to polymer glasses of diverse structures is found to be quite successful in explaining the PVT behavior over a wide range of temperatures both at atmospheric and elevated pressures. Further, scaled volume at the glass‐transition temperature is discovered to be a corresponding state property. Turning to crystals, the theory is generally in good accordance with the PVT data of three well‐studied polymers both at atmospheric and elevated pressures. For linear polyethylene the agreement is good up to 42 kbar for the room‐temperature isotherm. On the other hand, at higher temperatures where the data are limited to 5 kbar, the agreement is determined to be satisfactory for the three polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 515–530, 2001     

Growth and properties of calcium tungstate

CaWO₄ single crystals have been grown and compared by three different high temperature solution methods, viz. the normal flux-cooling procedure, the indirect flux-reaction technique and the isothermal flux-evaporation method. The typical as-grown bipyramidal crystals obtained by these methods have been found to be mostly large and perfect with varying degree of transparency. The crystals are characterised by using EDAX, X-ray diffraction, electrical conduction, micromechanical tests and chemical etching. The assessment of various characteristics of the grown crystals is likely to show enormous usefulness of the flux grown crystals.     

Etching and Dissolution Mechanism of Cadmium Oxalate Trihydrate Crystals

Dislocation etching and dissolution of gel-grown cadmium oxalate trihydrate crystals are carried out using different etchants. The study revealed the existence of dislocation network in the body of the crystal and shallow dislocation loops in the substructure. Faster dissolution of the crystal at elevated temperatures revealed that the rate of dissolution in the initial part of the dissolution time is much lesser, which increases fast to attain a steady value. This observation is related to the available specific surface area of the crystal.     

Study of Raman spectrum of uranium using a surface‐enhanced Raman scattering technique

Raman spectroscopic investigation on weak scatterers such as metals is a challenging scientific problem. Technologically important actinide metals such as uranium and plutonium have not been investigated using Raman spectroscopy possibly due to poor signal intensities. We report the first Raman spectrum of uranium metal using a surface‐enhanced Raman scattering‐like geometry where a thin gold overlayer is deposited on uranium. Raman spectra are detected from the pits and scratches on the sample and not from the smooth polished surface. The 514.5‐ and 785‐nm laser excitations resulted in the Raman spectra of uranium metal whereas 325‐nm excitation did not give rise to such spectra. Temperature dependence of the B_3g mode at 126 cm⁻¹ is also investigated. Copyright © 2011 John Wiley & Sons, Ltd.