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      https://www.ias.ac.in/article/fulltext/jcsc/127/01/0061-0070

    • Keywords

       

      Mixed solvent systems; electrolyte solutions; dynamic fluorescence measurements; theory.

    • Abstract

       

      In this manuscriptwe explore electrolyte-induced modification of preferential solvation of a dipolar solute dissolved in a binary mixture of polar solvents. Composition dependence of solvation characteristics at a fixed electrolyte concentration has been followed. Binary mixtures of two different polarities have been employed to understand the competition between solute-ion and solute-solvent interactions. Time-resolved fluorescence Stokes shift and anisotropy have been measured for coumarin 153 (C153) in moderately polar (ethyl acetate + 1-propanol) and strongly polar (acetonitrile + propylene carbonate) binary mixtures at various mixture compositions, and in the corresponding 1.0M solutions of LiClO4. Both the mixtures show red shifts in C153 absorption and fluorescence emission upon increase of mole fraction of the less polar solvent component in presence of the electrolyte. In addition, measured average solvation times become slower and rotation times faster for the above change in the mixture composition. A semi-molecular theory based on solution density fluctuations has been developed and found to successfully capture the essential features of the measured Stokes shift dynamics of these complex multi-component mixtures. Dynamic anisotropy results have been analyzed by using both Stokes-Einstein-Debye (SED) and Dote-Kivelson-Schwartz (DKS) theories. The importance of local solvent structure around the dissolved solute has been stressed.

    • Author Affiliations

       

      Harun Al Rasidgazi1 Hemant K Kashyap2 Ranjit Biswas3

      1. Department of Chemistry, Aliah University, Kolkata 700 064, India
      2. Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, Delhi 110 016, India
      3. Department of Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata 700 098,West Bengal, India
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    • Supplementary Material

       
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