• Nilmoni Sarkar

      Articles written in Journal of Chemical Sciences

    • Solvent relaxation of a room-temperature ionic liquid [bmim][PF6] confined in a ternary microemulsion

      Debabrata Seth Palash Setua Anjan Chakraborty Nilmoni Sarkar

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      In this paper we have reported the solvent and rotational relaxation of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) confined in tween 20/([bmim][PF6]/water microemulsion using coumarin 153 (C-153) as probe. The most interesting feature of our experiment was that we observed an increase in solvent relaxation time with increase in 𝑅 (𝑅 = tween 20-to-[bmim][PF6] molar ratio). This is due to the fact that with increase in [bmim][PF6] content of the microemulsions, the microviscosity of the pool of the microemulsions increases, and motion of ions of [bmim][PF6] is hindered in the pool of microemulsions. Since motion of ions is responsible for solvation in room-temperature ionic liquids (RTILs), solvent-relaxation time increases with increase in 𝑅.

    • Modification of fatty acid vesicle using an imidazolium-based surface active ionic liquid: a detailed study on its modified properties using spectroscopy and microscopy techniques

      SHREYA ROY SARTHAK MANDAL PAVEL BANERJEE NILMONI SARKAR

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      Fatty acid vesicles have attracted views as model protocell membranes in understanding the emergence of life, but their properties can be further modified in the presence of some external molecules. In this work, we have investigated the spontaneous formation of large unilamellar vesicles (LUVs) of oleic acidin aqueous medium in presence of a popular imidazolium-based cationic surface active ionic liquid (SAIL) [C16mim] Cl and studied the micelle–vesicle transition of aqueous [C16mim] Cl solution in presence of different molar fractions ( f ) of oleic acid. This newly formed oleic acid [C16mim] Cl vesicles exhibit some modifiedproperties compared to the pure fatty acid vesicles. Unlike pure fatty acid vesicles, these vesicles are stable in the pH range of 2 to 11.2. We have observed the fusion process of these oleic acid/SAIL vesicles to form giantunilamellar vesicles (GUVs) in presence of low concentration of NaCl solution. To investigate the dynamics of different oleic acid/[16] Cl self-assemblies, we have used fluorescence correlation spectroscopy (FCS). The translational diffusion behavior of three different dyes, Rhodamine 6G, DCM and Pyrromethene 597, which are non-covalently bound to the different regions of the oleic acid/SAIL self-assemblies, have been determined using FCS during the micelle–vesicle transition and upon varying the pH of the vesicular solution.

    • A review on recent application of proton transfer photophysics of bipyridine-3,3'-diol in organized assemblies

      SOURAV NANDI NILMONI SARKAR

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      The rich photophysics of the excited-state intramolecular proton transfer (ESIPT) process in 2,2'-Bipyridine-3,3'-diol (BP(OH)2) system has interested a lot of researchers from both the experimental and the theoretical sides. The resemblance of BP(OH)2 with Watson-Crick canonical base pairs of DNA has led tosome interesting spectroscopic investigation. Several efforts have been made to arrive at a detailed mechanism of the ESIPT process that generates the ‘‘stepwise or concerted?’’ question, which has been a controversy for years. This controversy led to an enlightening discussion on excited state symmetry and symmetry conservation during the ESIPT process. Under this context, the time has ripened to make a concise view of the fundamental photophysics of this molecule in various organized media, like, micelles, vesicles, fibrils, etc. Moreover, the recent application of this molecule as a fluorescent marker is seen in many self-assembled aggregates formed by various biomolecules, which needs to be highlighted to let the researchers acknowledge it. With this aim, the review, however, by all means, is not an exhaustive article information collection that covers all aspects of ESIPPT, rather, it will mostly focus on the recent application of this probe in many organized assemblies.

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