Preparation of biomass water‐soluble carbon quantum dots and their application in Cr (VI) ions detection

Abstract To quickly and quantitatively detect the concentration of harmful Cr 6+ in food and packaging, biomass nitrogen‐doped blue fluorescent carbon quantum dots (CQDs) were synthesized by a one‐step hydrothermal method using longan peel. The synthesized biomass CQDs are spherical, and the particle size is distributed between 1 and 6 nm. There are functional groups such as carboxyl, hydroxyl and amino groups on the surface of the CQDs, which promotes the excellent water dispersibility of the CQDs. CQDs have good fluorescence stability in salt solutions, different pH environments and long‐term storage. A fluorescence sensor for detecting Cr 6+ was constructed, based on the specific quenching effect of Cr 6+ on the fluorescence of CQDs. There is a good linear relationship between the fluorescence quenching rate of the fluorescence sensor and the Cr 6+ concentration of the detected sample. The sensor has a linear range of 20–200 μM and a detection limit of 1.4 μM. In addition, the CQDs fluorescence sensor has an ideal recovery rate in the actual water sample spiked with Cr 6+ . This research innovatively combined longan and hydrothermal method to prepare a quantitative, fast and wide detection limit Cr 6+ sensor.