1. Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar, Guntur 522510, India
2. Department of Geology, Acharya Nagarjuna University, Nagarjuna Nagar, Guntur 522510, India
3. Department of Chemical Science, Faculty of Science, Universiti Tunku Abdul Rahman, Jalan Universiti, Bandar Barat, 31900 Kampar, Malaysia