N/S-GQDs/KMnO4 hybrid as a colorimetric and fluorescent dual-signal readout probe for sensitive and selective detection of ascorbic acid

Abstract

A nitrogen and sulfur co-doped graphene quantum dots (N/S-GQDs) and permanganate was employed to prepare a N/S-GQDs/KMnO4 dual-signal readout colorimetric and fluorescent probe for sensitive detection of ascorbic acid (AA). In the detection system, the addition of KMnO4 quenched significantly the fluorescence (FL) of N/S-GQDs, meanwhile, the transparent aqueous dispersion of N/S-GQDs changed into yellow–brown with new absorption peak (maximum absorption at 338 nm). Interestingly, introduction of AA into the N/S-GQDs/KMnO4 system could recover the quenched fluorescence and result in a decrease in the absorbance (at 338 nm) of the test solution in a concentration dependent manner, and hence demonstrated the potential practical use of the sensing system for AA detection. Based on various spectroscopic studies, it has been concluded that the static as well as inner filter effect was the main quenching mechanisms in the detection system. The dual-response sensor showed linear response in the concentration range between 0.01 and 30 µM with the limit of detection (LOD) of 8.3 nM and 100 nM, respectively, for the fluorescent and colorimetric detections. In addition, the proposed detection system has been successfully applied to the detection of AA in vitamin C tablets. Moreover, the proposed detection strategy is convenient and fast, prevents complex and tedious probe preparation procedure, and capable of visual detection of AA.