Ordered Si/Si–O nanowire array and its optical properties

Glancing angle deposition (GLAD) has been employed to fabricate the Si/Si–O nanowires (NWs). The perpendicular NW on silicon substrate shows the amorphous nature. The visible light emission from the NWs was observed from the Si/Si–O nanoparticles. High light absorption inside the Si/Si–O NW structure was recorded.     

TrocCl Mediated Efficient Synthesis of Nitriles from Primary Amides

In order to establish a rapid conversion method of primary amides to nitriles, various types of carboxamides were treated with 2,2,2-trichloroethyl chloroformate and Et₃N, as a dehydrating agent to obtain the desired nitriles in 82–95% yields.     

Role of alkyl substituent in room temperature ionic liquid on the electrochemical behavior of uranium ion and its local environment

A systematic study was carried out to understand the effect of structural modification of C_nmim⁺ moiety of C_nmimBr (n = 6, 8 or 10) on the electrochemical behavior of uranium. The cyclic voltammetric study of the above room-temperature ionic liquids (RTIL) media revealed that with increase in the chain length the electrochemical window extended more towards the negative potential. This resulted in the possibility of conversion of U(VI) to U(III) or even possibly to, U metal via U(IV) (as UO₂) when n ≥ 10. The diffusion coefficient of U(VI) was found to decrease from n = 6 to 8 to 10 due to the increasing order of viscosity of the RTIL. As a consequence, the activation energy was found to follow reverse order i.e. E _act(C₆mimBr) < E _act(C₈mimBr) < E _act(C₁₀mimBr). The conversion of UO₂ ²⁺ to UO₂ was found to be quasi reversible and also exothermic while the entropy was found to decrease due to the reduction reaction. An UV–Vis spectroscopic study was also carried out to understand the local environment around uranium in aqueous and RTIL media. Among several cationic and anionic species, the predominance of UO₂Cl₄ ^2? in 7 M HCl with D_4h coordination symmetry was observed. The decrease in symmetric stretching frequency of UO₂ ²⁺ in RTILs in comparison with aqueous system indicates that the bond strength of UO₂ ²⁺ in aqueous is less than that of UO₂ ²⁺ in RTILs.     

A comparative study of the complexation of Am(III) and Eu(III) with TODGA in room temperature ionic liquid

On the growing awareness of the environmental impact associated with the use of volatile organic diluents, room temperature ionic liquid gained world-wild acceptance as environmentally benign diluents for actinide partitioning. The observed unusual behavior of less extraction efficiency of Eu with TODGA in RTIL in comparison with that of Am-TODGA was addressed in this paper. The stoichiometry of Am-TODGA complex was found to be 1:2 while that of Eu-TODGA was 1:1. More the ligand molecules associated in the metal ligand complex, the organophilicity of the complex will be more and the solubility of the metal–ligand complex in RTIL will be more which reflects in the higher distribution ratio for Am. In RTIL both Am and Eu showed slower kinetics of extraction with TODGA which can be attributed to the high viscosity coefficient of RTIL compared to the molecular diluents. The observed slower kinetics of extraction was quantified and found to follow first order kinetics with the rate constant of 5.5 × 10^?4 s^?1. The formation constant of Am-TODGA complex was found to be more (4.18 × 10⁸ M^?1) than Eu-TODGA complex (3.31 × 10⁸ M^?1) in RTIL. The parameters viz. diffusion coefficient, activation energy for Eu(III)/Eu(II) were determined and found to be 3.08 × 10^?8/cm² s^?1 (at 303 K) and 39.34 kJ mol^?1 respectively. The thermodynamic parameters ΔG, ΔH and ΔS for the reaction were evaluated using the linear regression of the plot of E ^0* versus T. The redox reaction was found to be exothermic with decrease in entropy value.     

Spectral interference study of uranium on other analytes by using CCD based ICP-AES

Due to the multi-electronic nature, uranium is having line rich emission spectra and is expected to interfere during the determination of analytes at the trace level in uranium matrix. Therefore, chemical separation of uranium followed by the determination of trace metallic impurities in the raffinate by ICP-AES is generally adopted procedure in nuclear industries. There is restriction on choosing alternate analytical lines of elements by photomultiplier tube based ICP-AES associated with the polychromator while monochromator needs significant time to scan different analytical lines of all the elements. Since charged coupled detector (CCD) consists of array of pixels, it is having more option in choosing alternative analytical lines of the analytes. Therefore, an attempt was made to study the spectral interference of uranium on different analytical lines of analytes viz. Al, Ga, In, Si, Li, Ti, Mg, Sr, K, Ce, Nd, Lu, Sc, V, Er, Y, Ba, Bi, Pb, W, La, Tl, Sn, Yb, Mo, Sb, Pr and Zr; and the correction factors were evaluated (where ever necessary) using CCD based ICP-AES technique. The sensitivity and the detection limits of the analytical channels of the elements in presence of uranium matrix were calculated. The present study also deals with the identification of suitable analytical lines of uranium and its detection limits.     

Broadband dielectric relaxation study on a diluted solution of a ferroelectric liquid crystal by time domain reflectometry

Abstract

In this work, complex permittivity measurements on a diluted solution of the ferroelectric liquid crystal, 4-[(S,S)-2,3-epoxyhexyloxy]-phenyl 4-(decyloxy)-benzoate, which shows ferroelectric smectic C phase (S*_C), have been performed. Using time domain reflectometry, at frequencies between 10 MHz and 10 GHz, in the temperature range from 50°C down to 10°C for every 10°C, at 5, 10 and 30 wt.% in benzene we observe two independent relaxation processes around 150 MHz and 2 GHz. It is shown that the high frequency process is due to the internal molecular reorientations while the low frequency one is due to molecular orientation around the long molecular axis. It is concluded that the reorientation around the long axis is hindered and leads to a resultant macroscopic polarization.     

Highly Efficient Diglycolamide‐Based Task‐Specific Ionic Liquids: Synthesis,Unusual Extraction Behaviour,Irradiation, and Fluorescence Studies

Two new diglycolamide‐based task‐specific ionic liquids (DGA? TSILs) were evaluated for the extraction of actinides and lanthanides from acidic feed solutions. These DGA? TSILs were capable of exceptionally high extraction of trivalent actinide ions, such as Am³⁺, and even higher extraction of the lanthanide ion, Eu³⁺ (about 5–10 fold). Dilution of the DGA? TSILs in an ionic liquid, C₄mim⁺ ? NTf₂^?, afforded reasonably high extraction ability, faster mass transfer, and more efficient stripping of the metal ion. The nature of the extracted species was studied by slope analysis, which showed that the extracted species contained one NO₃^? anion, along with the participation of two DGA? TSIL molecules. Time‐resolved laser fluorescence spectroscopy (TRLFS) analysis showed a strong complexation with no inner‐sphere water molecule in the Eu^III? DGA? TSIL complexes in the presence and absence of C₄mim⁺ ? NTf₂^? as the diluent. The very high radiolytic stability of DGA? TSIL 6 makes it one of the most‐efficient solvent systems for the extraction of actinides under acidic feed conditions.