Modeling of ionic diffusion by space charge depolarization

For the study of transport properties of a nano-composite material, an open circuit condition of current is considered, where the sum of diffusion current density, displacement current density, ohmic current density, and excess charge current density is vanished. Including the effects of drift and trapping of ions, drift and trapping diffusion coefficients are modeled respectively and the significance of the type of ionic motion in the study of ionic diffusion is discussed.     

Phase matching,X-Ray topography,optical and thermal analysis of L-alanine cadmium chloride monohydrate: a nonlinear optical material

A potential semiorganic nonlinear optical material, L-alanine cadmium chloride monohydrate has been successfully synthesised and single crystals have been grown by slow evaporation solution growth technique at room temperature by using double distilled water as the solvent. The lattice dimensions of the grown crystal have been analysed by adopting powder X-ray diffraction technique and found that it crystallised in monoclinic system with space group C2. The crystalline perfection of the as-grown crystal has been assessed by high resolution X-ray diffraction and X-ray topography techniques and observed that the quality of the grown specimen is reasonably good. Its optical properties were examined by UV–Vis and photoluminescence techniques and found that there is no absorption in the entire visible range. Its functional groups were identified from FT-Raman and observed that there is no incorporation of other impurities during crystallisation. Its relative second harmonic generation efficiency has been tested with different particle size by Kurtz powder technique and found that within the coherence length the title compound is phase matchable. Its various thermal properties like thermal conductivity, specific heat, thermal effusivity, etc. have been evaluated by photopyroelectric technique and compared with other organic and inorganic materials. To confirm its piezoelectric response, its piezoelectric charge coefficient was measured using piezometer and found low. Its optical homogeneity as well as birefringence measurement of the grown specimen has been carried out by interferometric technique. The surface defects of the grown LACCM single crystal were analysed with etching at room temperature using water as an etchant.     

High frequency and static dielectric constants of zinc blende structured solids

A correlation is presented for the high frequency ε_∞ and static ε_o dielectric constants of A^IIB^{V I} and A^IIIB^V semiconductors with the zinc blende structure. The high frequency ε_∞ and static ε_o dielectric constants can be represented by an empirical linear relation that is a simple function of melting temperature T_m, atomic volume Ω and product of ionic charges (Z₁Z₂). Values of high frequency ε_∞ and static ε_o dielectric constants of A^IIB^{V I} and A^IIIB^V zinc blende semiconductors exhibit a linear relationship when plotted against the k_BT_m/Ω (k_B=Boltzmann’s constant), but fall on two straight lines according to the product of ionic charges of the compounds. The calculated results are compared with available experimental data and previous calculations based on phenomenological models.     

Modeling of Ag<Superscript>+</Superscript> mobility in AgI by space charge depolarization process

A mathematical modeling of mobility of Ag⁺ ion in AgI is presented. In the model, regime is space charge polarized initially by applying a fixed d.c. field of ∼0.5 V across the sample, sandwiched between two electronically conducting graphite electrodes. The depolarization potential is recorded at various isothermal conditions in the temperature range 300–535 K. By considering open-circuit condition (where the sum of all current densities, i.e., drift current density, trapped current density, and displacement current density, is vanished), ionic drift- and trap-modulated mobilities are modeled. Result obtained through this model is compared with the ionic mobility, measured by conventional transient ionic current technique in the same temperature range.     

Determination of crystalline perfection,optical indicatrix,birefringence and refractive-index homogeneity of ZTS crystals

Single crystals of the semi-organic non-linear optical material zinc tris (thiourea) sulphate (ZTS) were grown by slow evaporation solution growth technique. The crystals were characterized for crystalline perfection and optical homogeneity using high-resolution X-ray diffraction (HRXRD) and optical interferometric techniques. The FWHM of 6 arc sec in HRXRD rocking curve shows the good crystalline quality. Transmittance of ∼75% shows that the crystal is free from volume defects. Conoscopy was used to assess the optical quality and investigate the optical indicatrix of the grown crystal. Birefringence values of the crystal along the three principal crystallographic axes were measured using birefringence interferometry. Mach–Zehnder interferograms exhibit good refractive-index homogeneity of the grown crystal.     

Synthesis of 5-iodopyrrolo[1,2-a]quinolines and indolo[1,2-a]quinolines via iodine-mediated electrophilic and regioselective 6-endo-dig ring closure

The endo-cyclic ring closure of 1-(2-(substituted ethynyl)phenyl)-1H-pyrroles 3a-t and 1-(2-(substituted ethynyl)phenyl)-H-indole 4a-o mediated by Lewis acid (I(2)) under mild conditions afforded substituted 5-iodopyrrolo[1,2-a]quinolines 5a-t and 5-iodoindolo[1,2-a]quinolines 6a-o in good to excellent yields. The reaction shows selective C-C bond formation on the more electrophilic alkynyl carbon, resulting in the regioselective 6-endo-dig-cyclized product. Iodo derivatives of pyrrolo- and indoloquinolines allow functional group diversification on the quinoline nucleus, which proves to be highly advantageous for structural and biological activity assessments.     

Solid-phase extraction combined with headspace single-drop microextraction of chlorophenols as their methyl ethers and analysis by high-performance liquid chromatography-diode array detection

Solid-phase extraction (SPE) of phenol and chlorophenols, their derivatization to methyl ethers, headspace single-drop microextraction (HS-SDME) of methyl ethers using 1-butanol as extraction solvent, and direct transfer of the drop into the injector for high performance liquid chromatography with diode array detection (HPLC-DAD) have been reported. A flanged-end polytetrafluoroethylene sleeve, 3 mm × 0.5 mm, placed at the tip of the syringe needle, allowed the use of 10 μL solvent drop for extraction. The procedure has been optimized for variables involved in SPE and HS-SDME. A rectilinear relationship was obtained between the amount of chlorophenols and peak area ratio of their methyl ethers/internal standard (4-methoxyacetophenone) in the range 0.01-10 mg L⁻¹, correlation coefficient in the range 0.9956-0.9996, and limit of detection in the range 1.5-3.9 μg L⁻¹ when HS-SDME alone was used for sample preparation. When using coupled SPE and HS-SDME, the linear range obtained was 0.1-500 μg L⁻¹, correlation coefficient in the range 0.9974-0.9998, and the limit of detection in the range 0.04-0.08 μg L⁻¹. Spiked real samples have been analyzed with adequate accuracy, and application of the method has been demonstrated for the analysis of chlorophenols formed upon bamboo pulp bleaching.     

Comparison of conventional hollow fiber based liquid phase microextraction and electromembrane extraction efficiencies for the extraction of ephedrine from biological fluids

In the present study, hollow fiber liquid phase microextraction (HF-LPME) based on pH gradient and electromembrane extraction (EME) coupled with high-performance liquid chromatography (HPLC) was compared for the extraction of ephedrine from biological samples. The influences of fundamental parameters affecting the extraction efficiency of ephedrine were studied and optimized for both methods. Under the optimized conditions, preconcentration factors of 120 and 35 for urine and 51 and 8 for human plasma were obtained using EME and HF-LPME, respectively. The calibration curves showed good linearity for urine and plasma samples by both methods with the coefficient of estimations higher than 0.98. The limits of detection were obtained 5 and 10 ng mL(-1) using EME and 60 and 200 ng mL(-1) by HF-LPME for urine and plasma samples respectively. The relative standard deviations of the analysis were found in the range of 5.2-8.6% (n=3). The results showed that in comparison with HF-LPME based on pH gradient, EME is a much more effective transport process, providing high extraction efficiencies in very short time.     

Solvothermally synthesized europium-doped CdS nanorods: applications as phosphors

To exploit the photoluminescent behavior of CdS at nanoscale with different doping concentration of europium—a rare earth element, we report the synthesis of Eu-doped CdS nanorods by using low temperature solvothermal process by using ethylenediamine. The outcomes can have future applications as phosphors, photovoltaic cells, lasers, light emitting diodes, bio-imaging, and sensors. The doping was confirmed by electron dispersive spectroscopy supported by X-ray diffraction. From scanning electron microscopy and transmission electron microscopy analysis it was observed that the average diameter of the Cd_1−x Eu _x S nanorods is about 10–12 nm having lengths in the range of 50–100 nm. UV–Visible spectroscopy study was carried out to determine the band gap of the nanorods and the absorbance peaks showed blue shift with respect to the bulk CdS. The blue shift was also observed as the doping concentration of Eu increases. From photoluminescence (PL) studies at λ_ex = 450 nm, peaks at 528 and 540 nm were observed due to CdS, peak at 570 nm is due to defects related transitions, while the peak at 613 nm is due to Eu. As the doping concentration of Eu is increased the intensity of the luminescent peak at 613 nm is increased. Thermogravimetric analysis showed the nanorods are thermally stable up to 300 °C. The traces of impurities adsorbed on the nanorods were confirmed by Fourier transform infrared spectroscopy.