1. Laboratoire de Chimie Analytique, Faculté des Sciences; Université de Yaoundé 1; B.P. 812 Yaoundé Cameroun
2. Department of Chemistry and Biomolecular Sciences, and Centre for Catalysis Research and Innovation; University of Ottawa; Ontario K1N 6N5 Canada
3. Electrochemistry and Chemistry of Materials, Department of Chemistry, Faculty of Science; University of Dschang; P.O. Box 67 Dschang Cameroon