1. Department of Physics and Astronomy University of Nigeria Nsukka 410001 Enugu State Nigeria
2. National Center for Physics Islamabad 44000 Pakistan
3. NPU-NCP Joint International Research Center on Advanced Nanomaterials and Defects Engineering Northwestern Polytechnical University Xi'an 710072 China
4. Nanosciences African Network (NANOAFNET) iThemba LABS-National Research Foundation 1 Old Faure Road Cape Town, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province South Africa.
5. UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology College of Graduate Studies University of South Africa (UNISA) Muckleneuk Ridge, P.O. Box 392 Pretoria South Africa
6. School of Materials Science & Engineering Northwestern Polytechnical University Xi'an 710072 China
7. Department of Pure and Industrial Chemistry University of Nigeria Nsukka 410001 Enugu State Nigeria