1. Department of Physics, Catholicate College, Pathanamthitta, Kerala 689 645, India
2. School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam, Kerala 686560, India
3. International and Interuniversity Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala 686560, India
4. Department of Periodontics, Pushpagiri Institute of Medical Sciences, Thiruvalla, Kerala 689101, India