ARTICLE | doi:10.20944/preprints202107.0222.v1
Subject: Materials Science, Biomaterials Keywords: Graphene oxide; Quantum Dots; TD-DFT; Absorption; Quenching effect; Concentration; Optical Response
Online: 9 July 2021 (13:22:41 CEST)
In this work, we investigate by ab initio calculations and optical experiments the sensitiv- ity of graphene quantum dots in their use as devices to measure the presence, and concentration, of heavy metals in water. We demonstrate that the quenching or enhancement in the optical response (absorption, emission) depends on the metallic ion considered. In particular, two test cases of opposite behaviour are considered: Cd 2+ , where we observe an increase in the optical response for increasing concentration, and Pb 2 whose emission spectra are quenched along the concentration rise. We envisage that quantum dots of graphene may be routinely used as cheap detectors to measure the degree of poisoning ions in water
ARTICLE | doi:10.20944/preprints201710.0026.v1
Subject: Materials Science, Nanotechnology Keywords: carbon materials; heavy metals; optical sensors; spectroscopy; photoluminescence; quenching
Online: 4 October 2017 (16:55:37 CEST)
A novel type of graphene-like quantum dots, synthesized by oxidation and cage-opening of C60 buckminsterfullerene, has been studied as a fluorescent and absorptive probe for heavy-metal ions. The lattice structure of such unfolded fullerene quantum dots (UFQDs) is distinct from that of graphene since it includes both carbon hexagons and pentagons. The basic optical properties, however, are similar to those of regular graphene oxide quantum dots. On the other hand, UFQDs behave quite differently in the presence of heavy-metal ions, in that multiple sensitivity to Cu2+, Pb2+ and As(III) was observed through comparable quenching of the fluorescent emission and different variations of the transmittance spectrum. By dynamic light scattering measurements we confirmed, for the first time in metal sensing, that this response is due to multiple complexation and subsequent aggregation of UFQDs. Nonetheless, the explanation of the distinct behaviour of transmittance in the presence of As(III) and the formation of precipitate with Pb2+ require further studies. These differences, however, also make it possible to discriminate between the three metal ions in view of the implementation of a selective multiple sensor.