与传统量子点相比, 碳量子点作为一种新型的荧光碳纳米材料, 由于其良好的生物相容性、 易于表面功能化、 低毒性等优点受到了广泛关注。 采用柠檬酸为碳源, 氨水为氮源, 热解法制备出水溶性好的氮掺杂碳量子点(NCDs)。 透射电镜(TEM)观察NCDs的粒径在3 nm左右; X射线光电子能谱(XPS)和傅里叶红外光谱(FIIR)证明NCDs的表面被羧基、 氨基、 羟基、 羰基等官能团功能化, 说明NCDs有很好的水溶性。 研究还发现Hg2+对NCDs的荧光有良好的猝灭作用, 可作为荧光探针检测水中Hg2+含量。 在PBS缓冲液中(0.1 mol·L-1 pH 7.0), NCDs的荧光猝灭率(F/F0)与汞离子浓度在0.001～0.1 μmol·L-1之间存在良好的线性关系, 检出限为2.1 nmol·L-1。 该方法灵敏度高、 选择性好、 方法简便, 可应用于Hg2+快速、 灵敏的检测。

Compared with traditional quantum dots, carbon quantum dots (CQDs) have aroused tremendous research interest among scientists as new fluorescent carbon nanomaterials due to their unique properties (easy surface functionalization, good biocompatibility, and low toxicity). The nitrogen-doped carbon quantum dots (NCDs) was synthesized with one-step hydrothermal treatment with citric acid as carbon source, and ammonia as nitrogen source. The obtained NCDs exhibited excellent water-solubility and high stability. High-resolution Transmission electron microscopy (HRTEM) image showed that the diameter of particles was about 3nm. Fourier transform infrared (FIIR) and X-ray photoelectron spectroscopy (XPS) spectra analysis demonstrated that the NCDs are functionalized with hydroxyl, amino, carbonyl, and carboxylic acid groups, which indicated NCDs has better water-solubility. It was further demonstrated that such NCDs can serve as effective fluorescent sensing platform for Hg2+ ions detection with sensitivity and selectivity. In a PBS butter solution (0.1 mol·L-1 pH 7.0), the fluorescence quenching ratio (F/F0) indicated linear responses with Hg2+ concentration ranging from 0.001 to 0.1 μmol·L-1, with the detection limit of 2.1 nmol·L-1. The fluorescence technique was superior in terms of sensitivity, selectivity and simplicity. It was successfully applied to determination of Hg2+ in samples.