1. Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
2. Department of Electronics and Electrical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
3. Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India