1. Department of Physics and Nanotechnology SRM Institute of Science and Technology Kattankulathur 603203 TN India
2. Department of Medical Physics Anna University Chennai 600 025 TN India
3. Department of Physics Ethiraj College for Women Chennai 600 008 TN India
4. National Centre for Nanoscience and Nanotechnology University of Madras Chennai 600 025 TN India