Fluorescence sensing and adsorption kinetics of Gd-doped AgInS2 I-III-VI quantum dots – A case study of Ag+ ions interactions
Bambesiwe M. May,
Olayemi J. Fakayode,
Mokae F. Bambo,
Ajay K. Mishra,
Edward N. Nxumalo
Affiliations
Bambesiwe M. May
Institute for Nanotechnology and Water Sustainability (iNanoWS), College of Science, Engineering, and Technology, University of South Africa, Florida Campus, 28 Pioneer Avenue, Roodepoort, 1709, Johannesburg, South Africa; DSI/Mintek Nanotechnology Innovation Centre, Advanced Materials Division, Mintek, 200 Malibongwe Drive, Randburg, Johannesburg, South Africa
Olayemi J. Fakayode
Institute for Nanotechnology and Water Sustainability (iNanoWS), College of Science, Engineering, and Technology, University of South Africa, Florida Campus, 28 Pioneer Avenue, Roodepoort, 1709, Johannesburg, South Africa
Mokae F. Bambo
DSI/Mintek Nanotechnology Innovation Centre, Advanced Materials Division, Mintek, 200 Malibongwe Drive, Randburg, Johannesburg, South Africa
Ajay K. Mishra
Department of Chemistry, Durban University of Technology, Steve Biko Road, Durban, 400, South Africa; Department of Chemical and Metallurgical, Vanderbijlpark Campus, Vaal University of Technology, Private Bag X021, Vanderbijlpark, South Africa
Edward N. Nxumalo
Institute for Nanotechnology and Water Sustainability (iNanoWS), College of Science, Engineering, and Technology, University of South Africa, Florida Campus, 28 Pioneer Avenue, Roodepoort, 1709, Johannesburg, South Africa; Corresponding author.
The poor fluorescence properties of magneto-fluorescent paramagnetic-ion (Gd, Mn, or Co) doped I-III-VI quantum dots (QDs) at higher paramagnetic-ion doping concentrations have limited their use in magnetic-driven water-based applications. This work presents, for the first time, the use of stable magneto-fluorescent Gd-doped AgInS2 QDs at high Gd mole ratios of 16, 20, and 30 for the fluorescence detection and adsorption of Ag+ ions in water environments. The effect of pH, initial concentration, contact time, and adsorbent dosage were systematically evaluated. The AgInS2 QDs with the least Gd mole ratio (16) exhibited the best fluorescence characteristics (LOD = 0.88, R2 = 0.9549) while all materials showed good adsorption properties under optimized conditions (pH of 2, initial concentration of 30 ppm, contact time of 10 min and adsorbent dosage of 0.02 g) and a pseudo 2nd order reaction was followed. The adsorption mechanism was proposed to be a combination of ion-exchange, electrostatic interaction, complexation, and diffusion processes. Application in environmental wastewater samples revealed complete removal of Ag + ions alongside Ti2+ Pb2+, Ni2+, Cr3+, and Zn2+ ions.
