1. Electrochemistry and Chemistry of Materials, Department of Chemistry, University of Dschang, P.O. Box 67, 00237 Dschang, Cameroon
2. Institut für Anorganische Chemie, Heinrich-Heine-Universität Düsseldorf, D-40204 Düsseldorf, Germany
3. Hoffmann Institute of Advanced Materials, Shenzhen Polytechnic, 7098 Liuxian Blvd, Nanshan District, 518055 Shenzhen, China