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: Catalysis & Excited state. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Charge Carrier Relaxation in Different Plasticized PEO/PVDF-HFP Blend Solid Polymer Electrolytes.

Abstract: In this article, we report first the effect of concentration of ethylene carbonate plasticizer on conduction and relaxation of charge carriers in PEO/PVDF-HFP–LiClO4 blend electrolytes. Second, the results for different plasticizers, such as ethylene carbonate, propylene carbonate, and dimethyle carbonate, on the conductivity and relaxation in these blend electrolytes are compared. We have followed a new approach for the analysis of the conductivity data. The frequency dependent conductivity is analyzed using random free-energy barrier model, taking into consideration the low frequency polarization effect. The temperature dependences of the ionic conductivity and the relaxation time obtained from the model exhibit Vogel–Tammann–Fulcher behavior. Using the scaling of the ac conductivity spectra it is observed that the relaxation dynamics of charge carriers in blend electrolytes are independent of temperature but depend on the nature of plasticizers. The electric modulus is studied using Havriliak–Negami fu...

A Mechanistic Approach on the Self-Organization of the Two-Component Thermoreversible Hydrogel of Riboflavin and Melamine

Abstract: The riboflavin (R) and melamine (M) supramolecular complex in the mole ratio of 3:1 (RM31) produces a thermoreversible gel in aqueous medium. The gelation mechanism has been elucidated from morphological investigations using optical, electron, and atomic force microscopy together with time-dependent circular dichroism (CD) and photoluminescence (PL) spectroscopy. Optical microscopy indicates spherulitic morphology at lower gelation temperature (≤25 °C), but at higher temperature fibrillar network morphology develops. Electron and atomic force microscopy indicate the presence of left handed helical structures in the fibrils. Kinetic study of gel formation using circular dichroism (CD) and photoluminescence (PL) spectra indicates that there are three steps: (1) RM complex formation, (2) conformational ordering, and (3) π−π-stacking of ordered conformers. The first step of RM complex formation is already established from Fourier transform infrared (FTIR) spectroscopy (Manna, S.; Saha, A.; Nandi, A. K. Chem....

Cocrystallization Behavior of Poly(3-alkylthiophenes): Influence of Alkyl Chain Length and Head to Tail Regioregularity

Abstract: The cocrystallization behavior of poly(3-alkylthiophene)s (P3ATs) of varying regioregularity and alkyl chain length was explored via differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) studies. For the regioregular samples both DSC and WAXS studies revealed that cocrystallization was limited to the difference of the alkyl chain length by two carbon atoms. On the other hand, P3AT samples with the same alkyl chain length but different regioregularities cocrystallized with a difference of 17 mol % head to tail (H−T) regularity studied here. P3AT samples with varying regioregularity and alkyl chain length by two carbon atoms showed cocrystallization for a regioregularity difference of 7 mol %. The WAXS study indicated that cocrystals had crystallized within the same interchain lamella and noncocrystals had crystallized within the independent interchain lamella of the components. It also indicated the formation of type 1 P3AT crystals with a noninterdigited side chain during the cocr...

Photophysical Processes of Ethidium Bromide in Micelles and Reverse Micelles

Abstract: Photophysical processes of ethidium bromide (EB) in homogeneous solutions, micelles, and reverse micelles have been investigated. In acetonitrile, the fluorescence intensity and lifetime of EB are 6.3 ± 0.3 times those in water and 1.25 ± 0.1 times those in acetone. This is attributed to the weaker hydrogen-bond acceptor property of acetonitrile, compared to water and acetone. Addition of water to acetonitrile leads to a marked quenching of the EB emission, with a quenching constant of (1.7 ± 0.3) × 107 M-1 s-1. In aqueous solution, hydroxyl ion quenches EB emission more dramatically with a quenching constant of (4.4 ± 0.4) × 1010 M-1 s-1. This is ascribed to the abstraction of the amino proton of the excited ethidium ion by the hydroxyl ion. Emission properties of EB are found to be good monitors for the micellization of an anionic micelle, sodium dodecyl sulfate (SDS). In AOT microemulsion, EB exhibits nearly (1.8 ± 0.1)-fold emission enhancement relative to water. The emission properties of EB are foun...