A label-free yellow-emissive carbon dot-based nanosensor for sensitive and selective ratiometric detection of chromium (VI) in environmental water samples

Measurement of Cr (VI) in environmental water samples is essential for monitoring drinking water quality and the risks of industrial waste. In this study, we report the first use of a new type of label-free carbon dot-based nanosensor for ratiometric fluorescence detection of Cr (VI) in environmental water samples. By using a simple one-pot method based on the solvothermal treatment of o-phenylenediamine, bright-yellow-emissive carbon dots (Y-CDs) were synthesized, exhibiting two emission bands centered at 430 and 560 nm under a singlewavelength excitation at 345 nm. Fluorescence intensities of the two emission bands of the as-synthesized Y-CDs were found to be simultaneously Cr (VI)-sensitive. The ratio of intensity (I-560 (nm)/I-430 nm) was linear against Cr (VI) concentrations from 0.01 to 4.5 mu M at pH 6.0, and the detection limit (S/N = 3: 1) was 2.3 nM, therefore having a propensity to be a suitable ratiometric probe for sensing Cr (VI). Furthermore, the nanosensor was successfully applied to quantitatively detect Cr (VI) in environmental water samples. Compared with the majority of current ratiometric Cr (VI) sensors, this label-free CD-based ratiometric probe has low toxicity, a simple synthesis route, and excellent photostability.