1. Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
2. Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
3. Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg 412 96, Sweden