1. Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
2. Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
3. Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94107-5605, United States
4. School of Health Science and Technology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India