Carbon dots derived from Poria cocos polysaccharide as an effective 'on-off' fluorescence sensor for chromium (VI) detection

Chromium is a harmful contaminant showing mutagenicity and carcinogenicity. Therefore, detection of chromium requires the development of low-cost and high-sensitivity sensors. Herein, blue-fluorescent carbon quantum dots were synthesized by one-step hydrothermal method from alkali-soluble Poria cocos polysaccharide, which is green source, cheap and easy to obtain, and has no pharmacological activity due to low water solubility. These carbon quantum dots exhibit good fluorescence stability, water solubility, anti-interference and low cytotoxicity, and can be specifically combined with the detection of Cr(VI) to form a non-fluorescent complex that causes fluorescence quenching, so they can be used as a label-free nanosensor. High-sensitivity detection of Cr(VI) is achieved through internal filtering and static quenching effects. The fluorescence quenching degree of CDs fluorescent probe showed a good linear relationship with Cr(VI) concentration in the range of 1–100 μM. The linear equation was F0/F = 0.9942 + 0.01472[Cr(VI)] (R2 = 0.9922), and the detection limit can be as low as 0.25 μM (S/N = 3), which has been successfully applied to Cr(VI) detection in actual water samples herein.