1. Department of Chemistry; Indian Institute of Technology Guwahati; Guwahati 781039, Assam India
2. Centre for the Environment; Indian Institute of Technology Guwahati; Guwahati 781039, Assam India
3. Department of Chemistry; Presidency University; Kolkata 700073 India
4. Department of Biophysics, Molecular Biology and Bioinformatics; University of Calcutta; Kolkata- 700 009 India