1. School of Chemistry & Physics; University of KwaZulu-Natal, Pietermaritzburg Campus; Private Bag X01 Scottsville 3209 South Africa
2. Department of Physics & Engineering Physics; Obafemi Awolowo University; Ile-Ife Nigeria
3. UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology Laboratories, College of Graduate Studies; University of South Africa (UNISA), Muckleneuk Ridge; PO Box 392 Pretoria South Africa
4. Nanosciences African network (NANOAFNET); Materials Research Group (MRG), iThemba LABS-National Research Foundation (NRF), 1 Old Faure Road; 7129 PO Box 722, Somerset West, Western Cape Province South Africa
5. National Center for Physics; Quaid-i-Azam University; Islamabad 44000 Pakistan