Luminescent phosphate sensor based on upconverting graphene quantum dots

In this paper, we have presented a novel graphene quantum dots based upconversion fluorescent sensor for detection of phosphate. The upconversion fluorescence of graphene quantum dots with emission wavelength at 407nm was quenched by rare earth ion, Eu3+ in proper concentration. The quenching constant is calculated from Stern-Volmer equation. Importantly, quenched fluorescence of graphene quantum dots-Eu3+ could be recovered with the addition of phosphate based on a competition mechanism, which provides a turn-on sensing strategy for phosphate assay. The recovered fluorescence is proportional to the concentration of phosphate. The linear range for the detection of phosphate was 1 to 12 mu M with a detection limit of 100 nM. The proposed sensing system has been successfully used for the assay of phosphate in real river water samples, indicating the practical potential.