IFE and Dynamic Quenching mediated fluorescent sensing of Cr(Ⅵ) based on nitrogen-doped biomass carbon dots

In recent years, carbon dots (CDs) have received much attention as a new type of nanomaterials. CDs have good water solubility, stability and fluorescence properties, and thus are widely used in the fields of bioimaging, sensors and photocatalysis. While CDs face interference from other metal ions when used as sensors for detecting iron ions, this study demonstrates that the prepared biomass carbon dots (BCDs) exhibit selective detection of Cr(Ⅵ). In this study, nitrogen-doped biomass carbon dots (N-BCDs) were successfully prepared by microwave-assisted method using hawthorn branch as the carbon source and urea as the nitrogen source, and their morphological structures and optical properties were characterised. The results showed that the synthesized N-BCDs had an average size of 3.3 nm and exhibited bright blue fluorescence under UV illumination. The excitation wavelength is located at 307 nm, and the optimal emission wavelength is 372 nm, with a quantum yield of 16.08 % and good fluorescence stability. The mixture of N-BCDs with Cr(Ⅵ) causes obvious fluorescence quenching, which was used as fluorescence probe for Cr(Ⅵ). The method had good linear correlation in the range of 20-100 μM for Cr(Ⅵ), and the limit of detection is as low as 0.84 μM. The fluorescence quenching of N-BCDs by Cr(Ⅵ) is a combination of dynamic quenching and internal filtration effects. The fluorescent probe has high selectivity and sensitivity for Cr(Ⅵ), providing a promising fluorescent probe for Cr(Ⅵ).