Carbon dots based dual-emission silica nanoparticles as ratiometric fluorescent probe for chromium speciation analysis in water samples

A simple and effective strategy for designing a ratiometric fluorescent nanosensor was described. A carbon dots (CDs) based dual-emission nanosensor for chromium speciation analysis was developed by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of the resulting dual-emission silica nanoparticles was quenched in acetic acid through potassium bromate (KBrO3) oxidation. Cr(VI) was able to catalyze KBrO3 oxidation, resulting in ratiometric fluorescence accelerated quenching response of the dual-emission silica nanoparticles. Several important parameters affecting the nanosensor performance, including acid type, concentrations of KBrO3, and reaction temperature and time were examined. Under the optimized conditions, the detection limit of the nanosensor towards Cr(VI) reached 1.3 ng mL−1, and pretty good linearity was obtained between 20 to 500 ng mL−1. More importantly, the sensor was found suitable for speciation analysis of both Cr(III) and Cr(VI) in different water samples with satisfactory results.