1. UNESCO-UNISA Africa Chair in Nanoscience and-Nanotechnology, Muckleneuk Ridge, College of Graduate Studies, University of South Africa, P.O. Box 392, Pretoria 0002, South Africa
2. Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, P.O. Box 722, Somerset West 7129, South Africa
3. Department of Chemistry, Debre Berhan University, P.O. Box 445, Debrebirhan 1000, Ethiopia
4. Department of Physics, Adigrat University, P.O. Box 50, Adigrat 7040, Ethiopia
5. iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West 7129, South Africa
6. Department of Chemistry, University of South Africa, P.O. Box 392, Florida 1709, South Africa