Nitrogen-doped graphene quantum dots prepared by electrolysis of nitrogen-doped nanomesh graphene for the fluorometric determination of ferric ions

Abstract

Nitrogen-doped graphene quantum dots (N-GQDs) were synthesized by direct electrolysis of a carbon cloth electrode coated with nitrogen-doped nanomesh graphene (NG) in high yield (~ 25%). The N-GQDs emit intense blue fluorescence with a quantum yield (QY) of 10% ± 3%. Meanwhile, the N-GQDs are rich in hydroxyl, carboxyl, basic pyridinic nitrogen, and nitro groups, which are conducive to strengthen the interaction between N-GQDs and Fe³⁺ for highly sensitive determination of Fe³⁺ ions. Specifically, the determination for Fe³⁺ was conducted at different concentrations of N-GQD solution with a wide linear range of 10–1000 μM (150 μg·mL⁻¹) and a low detection limit of 0.19 μM (10 μg·mL⁻¹). Moreover, the fluorescence quenching mechanism illustrated that the functional groups generated by electrochemical oxidation enhanced the interaction of N-GQDs and Fe³⁺, and the narrow band gap (2.83 eV) of N-GQDs accomplished electron transfer from N-GQDs to Fe³⁺ easily. A highly conductive carbon cloth electrode coated with nitrogen-doped nanomesh graphene (NG) was developed to prepared nitrogen-doped graphene quantum dots (N-GQDs) which was endowed with a wide linear range from 10 to 1000 μM (150 μg/mL) and a low detection limit of 0.19 μM (10 μg/mL) in the determination of Fe³⁺.