1. Department of Chemistry, University of Fort Hare, Alice, South Africa;
2. Department of Pharmacology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa;
3. Department of Chemistry, Auckland Park Campus, University of Johannesburg, Johannesburg, South Africa;
4. DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria, South Africa;
5. Polymer and Composites, CSIR Materials Science and Manufacturing, Pretoria, South Africa