1. Nanomaterials and Sensors Research Laboratory, Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow 226025, U.P., India
2. Advanced Nanomaterials Research Laboratory, U. G. C. Centre of Advanced Studies, Department of Physics, University of Allahabad, Prayagraj 211002, India
3. Department of Physics, Lal Bahadur Shastri Smarak Post Graduate College, Maharajganj 273161, U.P., India