1. Department of Physics, Sefako Makgatho Health Science University, Medunsa, South Africa
2. Department of Physics, University of the Free State (Qwaqwa Campus), Phuthaditjhaba, South Africa
3. Department of Chemistry, University of Zululand, KwaDlangezwa, South Africa
4. Department of Physics, University of Pretoria, Pretoria, South Africa
5. Department of Physics, Nelson Mandela Metropolitan University (NMMU), Port Elizabeth, South Africa