[1] Univ Dschang, Fac Sci, Dept Chem, POB 67, Dschang, Cameroon
[2] Univ Kashan, Fac Chem, Dept Phys Chem, Kashan, Iran
[3] Univ Yaounde I, Fac Sci, Dept Inorgan Chem, POB 812, Yaounde, Cameroon
[4] Univ Ngaoundere, Univ Inst Technol, POB 455, Ngaoundere, Cameroon
[5] Univ Freiburg, Inst Microsyst Engn IMTEK, Lab Sensors, Georges Koelher Allee 103, D-79110 Freiburg, Germany
[6] Tech Univ Berlin, Dept Chem, Str 17 Juni 124, D-10623 Berlin, Germany