1. Functional Nanomaterials Research Laboratory (FNRL), Department of Physics and Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India
2. CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India
3. Analytical Techniques Division, CSIR-CSIO, Chandigarh 160030, India