1. Department of Physics, University of Free State, Bloemfontein 9300, South Africa
2. Department of Applied Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad 826004, India
3. Department of Physics, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India
4. Université Clermont Auvergne, CNRS, SIGMA Clermont, Institut de Chimie de Clermont-Ferrand (ICCF), 63000 Clermont-Ferrand, France
5. Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi 110016, India
6. Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France