Indian Association for the Cultivation of Science

About: Indian Association for the Cultivation of Science is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Excited state & Catalysis. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Properties of Mixed Micelles of Binary Surfactant Combinations

Abstract: The behavior of binary mixtures of aqueous solutions of surfactants has been analyzed in the light of (a) Rubingh's approach based on regular solution theory, (b) the method of excess thermodynamic quantities of Motomura et al., and (c) the molecular thermodynamic theory of Sarmoria et al. and Puvvada et al. The binary combinations of anionic−nonionic, anionic−cationic, anionic−anionic, cationic−cationic, and nonionic−nonionic surfactant systems including a number of bile salts and several synthetic ionic and nonionic surfactants have been tested. The theoretical approaches are found to be most successful in describing the mixed micellar properties of anionic−nonionic surfactant solutions. The anionic−cationic combinations of bile salts and cetyltrimethylammonium bromide exhibit striking behaviors. The scope and limitations of the treatments in describing and also predicting the behaviors of different types of mixed micellar entities have been discussed.

Photoluminescence phenomena prevailing in c-axis oriented intrinsic ZnO thin films prepared by RF magnetron sputtering

Abstract: Substantial c-axis orientation of the hexagonal ZnO crystals with wurtzite structure demonstrates only those two preferred peaks in the first-order spectra which are permitted by the Raman scattering selection rule viz., the Ehigh2 and A1 (LO) modes, that identify the improved structural quality of the undoped ZnO film grown by magnetron sputtering in Ar ambient at an RF power of P = 200 W. The presence of a substantial amount of hydroxyl groups attached to the Zn lattice has been correlated to the dominant c-axis orientation of the ZnO crystals which exhibited a distinct UV luminescence band that arises due to the typical exciton emission or near-band-edge emission. At higher applied powers, disorder-activated Raman scattering introduces a well resolved Bhigh1 mode and gradually growing second order Raman peaks, (Ehigh2 − Elow2) and (Bhigh1 − Blow1), which are caused by the breakdown of translational symmetry of the lattice by defects or impurities and lead to deviation from preferred c-axis orientation with I002/I103 < 1. Out diffusion of oxygen from the network creates increasing oxygen vacancy states and in addition, various other defects e.g., Zn interstitial , doubly ionized Zn vacancy and oxygen antisite (OZn) as the dynamic acceptor defects, act as the origins of different visible photoluminescence components classified in the UV-violet, violet, violet-blue, blue and green regions.