1. Department of Physics University of Kerala Kariavattom Thiruvananthapuram Kerala 695581 India
2. Chemical Sciences and Technology Division CSIR-National Institute of Interdisciplinary Science and Technology (CSIR-NIIST) Thiruvananthapuram Kerala 695019 India
3. Materials Science and Technology Division CSIR- National Institute of Interdisciplinary Science and Technology (CSIR-NIIST) Thiruvananthapuram Kerala 695019 India