[1] Indian Inst Technol, Indian Sch Mines, Dept Appl Phys, Opt Mat & Bioimaging Res Lab, Dhanbad 826004, Bihar, India
[2] Univ Porto, Fac Sci, Ctr Res Chem CIQ UP, P-4169007 Porto, Portugal
[3] Univ Free State, Dept Phys, ZA-9300 Bloemfontein, South Africa