[1] Tshwane Univ Technol, Inst Nanoengn Res INER, Fac Engn & Built Environm, Dept Chem Met & Mat Engn, Pretoria, South Africa
[2] Univ Johannesburg, Dept Chem Sci, ZA-2028 Johannesburg, South Africa
[3] Tshwane Univ Technol, French South African Inst Technol FSATI, Dept Elect Engn, ZA-0001 Pretoria, South Africa
[4] CSIR, Ctr Nanostruct & Adv Mat, CSIR Nanotechnol Innovat Ctr, DSI,CSIR, ZA-0001 Pretoria, South Africa
[5] Ecole Super Ingenieurs & Electrotech & Elect, Cite Descartes,2 Blvd Blaise Pascal, F-93160 Paris, France