1. Inorganic Chemistry Department, Faculty of Science, University of Yaoundé I, PO. Box 812, Yaoundé, Cameroon
2. Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, SE-106 91 Sweden
3. Laboratoire des Multimatériaux et Interfaces (UMR 5615), Université Claude Bernard de Lyon 1, Campus de la Doua, 69622 Villeurbanne, France
4. Chemistry and Biochemistry, Dept. of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296 Göteborg, Sweden