1. Department of Life Sciences, Central University of Technology, Free State, Bloemfontein, South Africa
2. Centre for Nanostructures and Advanced Materials (CeNAM), DSI-CSIR Nanotechnology Innovation Centre, Council for Scientific and Industrial Research, Pretoria, South Africa
3. Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg, South Africa
4. Department of Chemistry and Polymer Science, Stellenbosch University, Stellenbosch, South Africa