1. Laboratory of Porous Materials for Sensors and Energy, Faculty of Science, University of Yaounde 1, P. O. Box 812, Yaoundé, Cameroon
2. Laboratoire d’Electrochimie et de Génie des Materiaux, Faculté des Science, B. P 812, Yaoundé, Cameroon
3. Department of Chemistry, University of Pretoria, Private Bag, X20 Hatfield, 0028, South Africa
4. Department of Chemistry, Maseno University, P. O. Box, 333-40105, Maseno, Kenya
5. Nanotechnology Research and Application Center (SUNUM), Sabanci University, Istanbul, 34956, Turkey
6. School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK