[1] Univ Limpopo Turfloop, Sch Phys & Mineral Sci, Dept Chem, Nanotechnol Res Grp, ZA-0727 Polokwane, South Africa
[2] Tshwane Univ Technol, Fac Sci, Dept Chem, Arcadia Campus, ZA-0001 Pretoria, South Africa
[3] Univ Witwatersrand, DSI NRF Ctr excellence Strong Mat, Private Bag X3, Wits, ZA-2050 Johannesburg, South Africa
[4] Univ Witwatersrand, Mol Sci Inst, Sch Chem, Private Bag X3, Wits, ZA-2050 Johannesburg, South Africa
[5] Univ Witwatersrand, Microscopy & Microanal Unit, Private Bag 3, ZA-2050 Johannesburg, South Africa
[6] Yeungnam Univ, Coll Nat Sci, Dept Chem, 280 Daehak Ro, Gyeongbuk 38541, Gyeongsan, South Korea