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