Fluorescent nitrogen-doped Ti3C2 MXene quantum dots as a unique “on-off-on” nanoprobe for chrominum (VI) and ascorbic acid based on inner filter effect

Abstract The MXene quantum dots (MQDs) derived from two-dimensional MXene nanosheets is a kind of rising-star nanomaterial recently, exhibiting important applications in many fields, while the investigation of element-doping MQDs with better performances for chem/biosensing is jut beginning. In this work, by cutting Ti3C2 MXene nanosheets with a simple method, we synthesized firstly nitrogen-doping Ti3C2 MQDs (N-Ti3C2 MQDs) which displays remarkable excitation-dependent photoluminescence and photobleaching resistance. Interestingly, the fluorescence of N-Ti3C2 MQDs can be quenched by chromium (VI) (Cr(VI)) owing to the existence of Inner filter effect and static quenching, triggering a fluorescent “on-off” signal; on account of the oxidation-reduction reaction between ascorbic acid (AA) and Cr(VI), the related fluorescence of N-Ti3C2 MQDs can be further recovered in the presence of AA, inducing an “off-on” fluorescence response. Thus, N-Ti3C2 MQDs was then used as nanoprobe for the fluorescent detection of Cr(VI) and AA, and the developed sensing method was verified to possess great sensitivity with the wide linear ranges from 0.1–500.0 μM toward both Cr(VI) and AA as well as low detection limits of 0.012 μM for Cr(VI) and 0.02 μM for AA. Furthermore, the investigation about the selectivity and practical application demonstrated N-Ti3C2 MQDs has important actual values for Cr(VI) and AA sensing.