1. Department of Applied Chemistry, School of Applied Natural Science, Adama Science and Technology University, P.O. Box 1888, Adama 251, Ethiopia
2. Department of Prosthodontics, Saveetha Dental College & Hospital, Saveetha Institute of Medical and Technical Science (SIMATS), Saveetha University, Chennai 600077, Tamil Nadu, India
3. Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa
4. Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9310, South Africa
5. Department of Chemistry, University of Botswana, P.bag UB 00704 Gaborone, Botswana