Carbon Dots Derived from the Maillard Reaction for pH Sensors and Cr (VI) Detection

The Maillard reaction involves a series of complex reactions; fluorescent compounds have been considered as vital intermediate products of the reaction. In this article, carbon dots (CDs) based on the Maillard reaction (MR-CDs) were prepared with L-tryptophan and D-glucose, and they had excellent photoluminescence stability. MR-CDs showed stable pH-dependence behavior and exhibited an excellent linear response to pH in the range of 4.0–7.5 and 7.5–13.0, respectively. Under the masking effect of sodium fluoride for Fe(III), MR-CDs showed excellent selectivity and sensitivity for Cr (VI). The linear range of Cr(VI) was 0.2–50 μM and the limit of detection was 20 nM. (S/N ≥ 3). Furthermore, MR-CDs were used to detect Cr(VI) in tap water samples. The recoveries were between 95.8% and 98.94%, and RSDs were less than 3.17%.