1. School of Physics and DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa
2. DST/NRF Centre of Excellence in Strong Materials, School of Physics University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa
3. School of Chemical and Metallurgical Engineering, University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa
4. Advanced Materials Division; Mintek; Randburg South Africa
5. Raman and Luminescence Laboratory, School of Physics, University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa