基于生物基质碳点构建荧光探针用于腌腊肉制品中亚硝酸盐的检测

为建立一种快速检测食品中亚硝酸盐含量的方法，以生物基质鸡爪外皮为碳源，采用一步水热法合成绿色碳量子点（carbon quantum dots, CQDs）。通过高分辨率透射电子显微镜、紫外可见吸收光谱、傅里叶变换红外光谱仪、X射线光电子能谱、荧光光谱仪对其形貌、结构及光学性质进行表征。结果表明:所制备的鸡爪外皮CQDs尺寸均匀，分散性良好，表面富含羟基、羧基、羰基等多种官能团；在365 nm紫外光照射下发射出蓝色荧光，荧光激发峰与发射峰呈现狭窄对称特征，具有良好的发光特性。在酸性溶液中，亚硝酸盐（NO₂?）具有很强的氧化性，能将Fe2+转化为Fe3+，Fe3+可与CQDs表面的含氧官能团形成配位键从而导致CQDs荧光信号被猝灭，从而可实现NO₂?的间接检测。基于此原理构建CQDs-Fe2+荧光探针，对CQDs的激发波长、缓冲液pH、反应时间进行优化。在实验优化条件下，CQDs-Fe2+体系荧光猝灭值与NO₂?浓度在1~500 μmol/L范围内呈现良好的线性关系（R2=0.9979），检出限为0.61 μmol/L，且具备良好的抗干扰能力。将该方法应用于三种不同腌腊肉制品中亚硝酸盐的测定，结果显示回收率为98.61%~100.95%，与离子色谱检测所得的结果相接近，表明制备的CQDs-Fe2+荧光探针可用于实际样品中NO₂?的检测。综上所述，基于生物基质碳点构建的荧光探针绿色安全，制备简单，可实现对腌腊肉制品中亚硝酸盐含量的检测，具有良好的实际应用前景。

A Fluorescent Probe Based on Biological Matrix Carbon Dots for the Detection of Nitrite in Cured Meat Products

In order to establish a rapid method for detecting the content of nitrite in food, green carbon quantum dots (CQDs) originating from chicken paw skin were synthesized by the one-step hydrothermal method. The morphology, structure and optical properties of CQDs were characterized systematically by high resolution transmission electron microscopy (HRTEM), UV-Vis absorption spectroscopy (UV-Vis), Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy (FS) technologies. The prepared CQDs were distributed uniformly with a regular size, and the surface of the CQDs was rich in functional groups including hydroxyl, carboxyl, and carbonyl, et al. In addition, the CQDs emitted intense blue fluorescence under the excitation of a 365 nm UV light lamp. And the excitation spectrum and emission spectrum of CQDs were narrow and symmetrical, indicating CQDs had good luminescence properties. In the presence of Fe3+, the fluorescence of CQDs was quenched due to the formation of coordination bonds between Fe3+ and the oxygen-containing functional groups on the surface of CQDs. Based on that, a simple fluorescent probe was designed to detect indirectly nitrite (NO₂?) by CQDs for nitrite possesses strong oxidation in acidic solution and was capable to transform iron (II) into iron (III) ions. The parameters including the excitation wavelength of CQDs, buffer pH value and reaction time were studied. Under the optimized conditions, the fluorescence quenching intensity of CQDs-Fe2+ fluorescent probe increased linearly with the NO₂? concentration in the range of 1~500 μmol/L (R2=0.9979) with a low detection limit of 0.61 μmol/L, and the probe had a good anti-interference ability. The method was applied to the determination of NO₂? in three marinate meat and satisfactory recoveries of 98.61%~100.95% and consistent data compared with ion chromatography were obtained. The results indicated that the CQDs-Fe2+ fluorescent probe could be used for the detection of NO₂? in real samples. In summary, the fluorescent probe constructed based on the carbon dots of the biological matrix is green and safe, simple to prepare, can detect the content of nitrite in cured meat products, indicating a good practical application prospect.