[1] Tshwane Univ Technol, Fac Engn & Built Environm, Inst NanoEngn Res INER, Dept Chem, ZA-0183 Pretoria, South Africa
[2] CSIR, DSI CSIR Nanotechnol Innovat Ctr, Ctr Nanostruct & Adv Mat, ZA-0001 Pretoria, South Africa
[3] Tshwane Univ Technol, Dept Elect Engn, Fac Engn & Built Environm, ZA-0183 Pretoria, South Africa
[4] Ecole Super Ingenieurs Electrotech & Elect, Cite Descartes, 2 Blvd Blaise Pascal, F-93160 Paris, France
[5] Univ Johannesburg, Dept Chem Sci, ZA-2028 Johannesburg, South Africa