1. Department of Chemistry, Faculty of Sciences, University of Maroua, Maroua P.O. Box 55, Cameroon
2. National Advanced School of Engineering, University of Maroua, P.O. Box. 46, Maroua, Cameroon
3. Advanced School of Agriculture, Forestry, Water and Environment, University of Ebolowa, P.O. Box 786, Ebolowa, Cameroon
4. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China