Influence of nitrogen-boron-sulfur triple-doping on the fluorescence emission of carbon dots and their sensing detection of copper ions

Abstract

This study used a one-step hydrothermal approach to synthesize three doped carbon dots, Cdots-1 (N-doped), Cdots-2 (N, S co-doped), and Cdots-3 (N, S, B co-doped), using aspartic acid, cysteine, and boric acid as raw ingredients. We employed XRD, TEM, Uv-Vis, XPS, FTIR, and PL techniques to characterize the morphology, elemental composition, and optical properties of samples. We found that doping is an effective way to control the core structure and emission properties of carbon dots. Among the three carbon dots, Cdots-3 has the highest fluorescence intensity and emits strong blue fluorescence. In addition, we found that Cdots-3 is highly responsive to Cu^2 + with a linear equation of y = 955.02–1.68976x, which makes it a fluorescent probe that can detect Cu²⁺ rapidly. The fluorescence lifetime of Cdots-3 was shortened from 3.76 ns to 3.33 ns after adding Cu²⁺. The analysis shows that the fluorescence quenching of Cdots-3 is mainly a dynamic quenching mechanism accompanied by a standard static quenching process. Moreover, to verify the detection accuracy of the experiment, we used the linear regression model, random forest regression model, support vector machine regression model, and decision tree regression model to predict the detection model, respectively. Among them, the random forest model has the best prediction effect. The coefficient of determination reaches 0.9996, and the mean square error is 0.0167. It is suggested that Cdots can be used as fluorescent probes to detect the reliability of Cu²⁺.