Blue luminescent amino-functionalized graphene quantum dots as a responsive material for potential detection of metal ions and malathion

Large amounts of hazardous and toxic substances in the environment require non-toxic, cheap, easy, rapid, and sensitive methods for their detection. Blue luminescent graphene quantum dots (GQDs) were produced by electrochemical cleavage of graphite electrodes followed by gamma irradiation in the presence of ethylenediamine (EDA). Modified dots were able to detect metal ions (Co2+, Pd2+, Fe3+) due to photoluminescence quenching. The highest sensitivity was detected for the sample irradiated at a dose of 25 kGy. The limits of detection (LODs) were 1.79, 2.55, and 0.66 μmol L−1 for Co2+, Fe3+, and Pd2+, respectively. It was observed that GQDs irradiated at 200 kGy act as an ultra-sensitive turn-on probe for Malathion detection with LOD of 94 nmol L−1. Atomic force microscopy images proved the aggregation of GQDs in the presence of the investigated metal ions. Results obtained by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and LIVE/DEAD cytotoxicity test indicated that GQDs irradiated with EDA are not toxic towards MRC-5 cells, which makes them a promising, eco-friendly and safe material for sensing application.