1. Electrochemistry and chemistry of materials Department of Chemistry Faculty of Science University of Dschang Dschang Cameroon
2. Institute of Microsystems Engineering IMTEK Laboratory for Bioinspired Materials -BMBT University of Freiburg 79110 Freiburg Germany
3. Institute of Inorganic Chemistry Christian-Albrechts-Universität zu Kiel Max-Eyth-Straie 2 24118 Kiel Germany