High Quantum Yield Fluorescent Chitosan-Based Carbon Dots for the Turn-On-Off-On Detection of Cr(VI) and H2O2

One-pot hydrothermal carbonization approach was employed to synthesize the blue-emission carbon dots derived from chitosan (Cs) and o-phenylenediamine (OPD). The Cs-based carbon dots (Cs–CDs) possessed a certain high quantum yield of 58% and exhibited excellent solubility, stability and fluorescence response in aqueous solutions. The Cs–CDs were designed as a sensor for Cr(VI) and H 2 O 2 determination. The sensing strategy of Cr(VI) was based on the inner filter effect (IFE) and static quenching effect (SQE), showing a good linear correlation ranging from 1 to 130[Formula: see text][Formula: see text]M with a detection limit (LOD) of 0.91[Formula: see text][Formula: see text]M. In addition, the determination for H 2 O 2 was attributed to the elimination of IFE (EIFE) due to the reduction reaction and the detection for H 2 O 2 was in the linear range from 1.0 to 200.0[Formula: see text][Formula: see text]M with LOD of 0.51[Formula: see text][Formula: see text]M. Finally, the proposed designed sensor could be simply applied for detection of Cr(VI) and H 2 O 2 in real samples.