• Aniruddha Paul

      Articles written in Journal of Chemical Sciences

    • Optical absorption and fluorescence studies on imidazolium ionic liquids comprising thebis(trifluoromethanesulphonyl)imide anion

      Aniruddha Paul Anunay Samanta

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      Optical absorption and fluorescence behaviour of two rigorously purified imidazolium ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)imide are studied in the neat condition and in solution. Non-negligible absorption in the UV region with a long tail extending into the visible region is the main feature of the absorption. Excitation wavelength-dependent two-component fluorescence characterizes the emission behaviour of these liquids. That ion association gives rise to the long absorption tail and shifting fluorescence maximum, which appears to be common to most of the imidazolium ionic liquids, is evident from the effect of the conventional solvents

    • Excited state dynamics of 9,9'-bianthryl in room temperature ionic liquids as revealed by picosecond time-resolved fluorescence study

      Dinesh Chandra Khara Aniruddha Paul Kotni Santhosh Anunay Samanta

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      Picosecond time-resolved fluorescence measurements have been carried out on 9,9'-bianthryl in three imidazolium ionic liquids to probe the excited state dynamics. In the early time-scale, the fluorescence spectra of bianthryl have been found to consist of emission from both locally excited (LE) and charge transfer (CT) states. The LE → CT relaxation time, as estimated from the decay of the fluorescence intensity of the LE emission, is found to vary between 230 and 390 ps, while the average solvent relaxation time, as estimated from the analysis of time-dependent fluorescence Stokes shift, is found to vary between 620 ps and 1840 ps, depending on the viscosity of the ionic liquids. The results confirm that while in conventional less viscous solvents the CT formation kinetics of bianthryl occurs simultaneously with the solvation dynamics, in ionic liquids the two processes mostly occur in different time scales.

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