1. Electrochemistry and Chemistry of Materials, Department of Chemistry, Faculty of Sciences, University of Dschang, P.O. Box 67, Dschang, Cameroon
2. Department of Pharmaceutical Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 2701, Douala, Cameroon
3. Institute of Chemistry, Faculty of Process and Systems Engineering, Universitätsplatz 2, Magdeburg 39106, Germany