邻苯二胺修饰碳量子点的制备及其对茶叶中痕量铜的分析应用

Determination of Copper in Tea Samples by Phenylenediamine Modified Carbon Dots

摘要: 以柠檬酸为碳源，通过水热法制备了碳量子点(CDs)；然后通过-NH₂与-COOH之间的偶联反应，将邻苯二胺(OPD)修饰到CDs表面，得到了邻苯二胺修饰荧光碳点(CDs-OPD)。采用UV-vis，FT-IR和荧光光谱对所制备的CDs-OPD进行光学性质表征。结果表明，与未经OPD修饰的CDs相比，当激发波长为260 nm时，CDs-OPD出现了新的荧光发射峰(295 nm，440 nm和580 nm)。Cu²⁺能够与CDs-OPD表面的基团作用，使得CDs-OPD在295 nm处荧光峰产生明显猝灭，且荧光猝灭程度与加入Cu²⁺的浓度呈线性关系。据此建立了基于CDs-OPD的荧光猝灭分析Cu²⁺的新方法，方法检测限(3σ)为1.4ng mL⁻¹，相对标准偏差(RSD)为5.0% (C = 100 ng mL⁻¹, n = 11)，线性范围为10~500 ng mL⁻¹，所建立的分析方法成功应用于茶叶样品中痕量Cu²⁺的测定，结果满意。

Abstract: CDs was prepared by hydrothermal method using citric acid as a carbon source. By coupling reac-tion between -NH₂ and -COOH, the o-phenylenediamine (OPD) was grafted to the surface of CDs, and the phthalic two amine modified fluorescent carbon dots (CDs-OPD) was obtained. The optical properties of the prepared CDs-OPD were characterized by UV-vis, FT-IR and fluorescence spec-troscopy. The results show that CDs-OPD has a three fluorescence emission peaks (295 nm, 440 nm and 580 nm) with an excitation wavelength of 260 nm, compared with the CDs without OPD modification. The effects of metal ions on the fluorescence properties of CDs-OPD were investigated. The results showed that Cu²⁺ could selectively quencher the fluorescence of CDs-OPD, and other metal ions did not produce obvious fluorescence quenching. Cu²⁺ can interact with the groups on the surface of CDs-OPD, which makes the fluorescence peak (295 nm) of CDs-OPD obviously quenched, and the degree of fluorescence quenching is linear with the concentration of Cu²⁺. A new analytical method for Cu²⁺ based on CDs-OPD was established. The detection limit (3σ) was 1.4 ng mL⁻¹, the relative standard deviation (RSD) was 5% (C = 100 ng mL⁻¹, n = 11), and the linear range was 10 - 500 ng mL⁻¹. The developed method was successfully applied to the determination of trace amounts in tea samples. The results were satisfactory.