Coal-derived nitrogen, phosphorus and sulfur co-doped graphene quantum dots: A promising ion fluorescent probe

Abstract

N, P, S co-doped graphene quantum dots (NPS-GQDs) were prepared via a one-step wet chemical plus dialysis method directly using anthracite coal as raw material. This facile oxidation process simultaneously synthesized graphene quantum dots (GQDs) and doped N, P and S atoms on edges or forming functional groups of GQDS. X-ray photoelectron spectroscopy (XPS) proved that the involved heteroatoms were successfully doped on GQDs. The local doping of N, P and S on GQDs can reach high levels as 5.6%, 3.7% and 3.7% (by atomic) during XPS detection, respectively. Raman spectra showed that the amount of defects or disorders of prepared GQDs increased during the transition of the coal hunk toward the nano-GQDs. The effect of graphitizing degree of applied coals (varied coal ranks) on the formation of GQDs implied that raw coals with too high or too low graphitizing degree were not optimizing for the formation of high-quality GQDs. The prepared NPS-GQDs showed excellent properties on the excitation-dependent fluorescence and the quench by some trace metals. Thus, the NPS-GQDs were applied to detect of Pb2+ in both a DI water and a multi-elements analysis matrix, exhibited wide linear detection range (1–20 μM) and a detection limit of 0.75 μM.