1. Department of Chemical Sciences, University of Johannesburg, Doornfontein Campus , P. O. Box 17011 , Johannesburg, 2028 , South Africa
2. Department of Science and Innovation (DSI)/National Research Foundation (NRF) South African Research Chair Initiative (SARChI), Nanotechnology for Water, University of Johannesburg , Doornfontein, 2028 , South Africa
3. Department of Science and Innovation (DSI)/Mintek Nanotechnology Innovation Centre, University of Johannesburg , Doornfontein, 2028 , South Africa