[1] Tshwane Univ Technol, Inst Nanoengn Res INER, Fac Engn & Built Environm, ZA-0183 Pretoria, South Africa
[2] Tshwane Univ Technol, Fac Engn & Built Environm, Dept Chem Met & Mat Engn, ZA-0183 Pretoria, South Africa
[3] Tshwane Univ Technol, Fac Engn & Built Environm, Dept Elect Engn, ZA-0183 Pretoria, South Africa
[4] Ecole Super Ingenieurs Electrotechn & Electron, F-93160 Paris, France
[5] DSI CSIR Nanotechnol Innovat Ctr, Ctr Nanostruct & Adv Mat, Council Sci & Ind Res, CSIR, ZA-0001 Pretoria, South Africa
[6] Univ Johannesburg, Dept Chem Sci, ZA-2028 Johannesburg, South Africa