Hydrothermal synthesis of biomass waste derived graphene quantum dots with high ion detection ability

Abstract

Graphene quantum dots (GQDs) hold extensive application prospects in ion detection owing to their high sensitivity, excellent water solubility, strong fluorescence stability and great biocompatibility. In here, GQDs were synthesized via hydrothermal method, utilizing biomass waste bean dregs and coffee grounds as raw materials, respectively. The optimum conditions for the preparation of GQDs were explored, and their structure, morphology and optical properties were characterized. The results show that the particle size of GQDs-B derived from bean dregs is about 1.6 nm and exhibits a more uniform distribution than that of GQDs-C obtained from coffee grounds. Additionally, the GQDs-B displays good aqueous solubility, higher degree of graphitization and abundant surface functional groups, with the fluorescence quantum yield of 21.32 %. When GQDs-B was employed as a fluorescent probe for the detection of Fe³⁺ and Ce⁴⁺, a favorable linear relationship was observed between fluorescence intensity and the concentrations of Fe³⁺ and Ce⁴⁺, with the fitting factor is 0.993 and 0.911, and the limit of detection (LOD) is 0.0019 mM and 0.0025 mM, respectively. Moreover, the Ce⁴⁺@GQDs-B fluorescence probe was fabricated, and the fitting factor between the fluorescence intensity and the concentration of PO₄^3- is 0.971. This study provides a green and environmentally friendly approach for the preparation of high-performance GQDs, and the synthesized GQDs demonstrate great potential for sensing application in water environment, thereby contributing to the development of advanced materials for environmental monitoring and analysis.