1. Department of Chemical and Physical Sciences, Walter Sisulu University (Mthatha Campus), P.O. Box Private Bag X-1, Mthatha 5117, South Africa
2. Department of Physics, College of Natural and Computational Science, Dambi Dollo University, Dambi Dollo 260, Ethiopia
3. Department of Physics, The University of the West Indies, St. Augustine 330912, Trinidad and Tobago
4. Department of Chemistry, College of Natural and Computational Science, Dambi Dollo University, Dambi Dollo 260, Ethiopia