As an antioxidant and preservative agent, nitrite (NO2−) plays an essential role in the food industry to maintain freshness or inhibit microbial growth. However, excessive addition of NO2− is detrimental to health, so accurate and portable detection of NO2− is critical for food quality control. Notably, the selectivity of most carbon dots (CDs)-based fluorescence sensors was not enough due to the nonspecific interaction mechanism of hydrogen bond, electrostatic interaction and inner filter effect etc. Herein, a novel fluorescence/UV–vis absorption (FL/UV–vis) dual-mode sensor was developed on basis of mC-CDs, which were prepared by simple solvothermal treatment of m-Phenylenediamine (m-PDA) and cyanidin cation (CC). The fluorescence of these mC-CDs could be selectively responded by NO2− through the specific diazo coupling reaction between NO2− and amino groups on the surface of mC-CDs, thus effectively improving the selectivity of NO2− detection. The CDs-based fluorescence sensor possessed a low detection limit of 0.091 μM and 0.143 μM for FL and UV–vis methods and the excellent linear range of 0.0–60.0 μM. Furthermore, the mC-CDs sensor was employed to detect NO2− in real samples with a recovery rate of 97.11 %–104.15 % for quantitative addition. Moreover, the smartphone-assisted fluorescence sensing platform developed could identify the subtle color changes that could not be distinguished by the naked eye, and had the advantages of fast detection speed and intelligence. More importantly, the portable solid phase sensor based on mC-CDs had been successfully applied to the specific fluorescence identification and concentration monitoring of NO2−. Accordingly, the designed sensor provided a new strategy for the highly selective and convenient sensing of NO2− in food substrates, and paved the way for the wide application of CDs-based nanomaterials in the detection of food safety.

中文翻译：

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基于碳点的双模式传感器，用于通过重氮偶联反应高选择性检测食品底物中的亚硝酸盐


作为一种抗氧化剂和防腐剂，亚硝酸盐 （NO2−） 在食品工业中起着至关重要的作用，可以保持新鲜度或抑制微生物生长。然而，过量添加 NO2− 对健康有害，因此准确、便携地检测 NO2− 对于食品质量控制至关重要。值得注意的是，由于氢键的非特异性相互作用机制、静电相互作用和内部过滤效应等，大多数基于碳点 （CDs） 的荧光传感器的选择性不够。在此，在 mC-CDs 的基础上开发了一种新型荧光/紫外-可见吸收 （FL/UV-vis） 双模式传感器，其是通过对 m-苯二胺 （m-PDA） 和矢车菊胺阳离子 （CC） 进行简单的溶剂热处理制备的。这些 mC-CDs 的荧光可以通过 mC-CDs 表面 NO2− 与氨基之间的特异性重氮偶联反应被 NO2− 选择性响应，从而有效提高 NO2− 检测的选择性。基于 CDs 的荧光传感器在 FL 和 UV-Vis 方法中具有 0.091 μM 和 0.143 μM 的低检测限，以及 0.0–60.0 μM 的出色线性范围。此外，采用 mC-CDs 传感器检测实际样品中的 NO2−，定量添加回收率为 97.11 %–104.15 %。此外，开发的智能手机辅助荧光传感平台可以识别肉眼无法区分的细微颜色变化，具有检测速度快、智能化等优点。更重要的是，基于 mC-CDs 的便携式固相传感器已成功应用于 NO2− 的特异性荧光识别和浓度监测。 因此，所设计的传感器为食品基材中 NO2− 的高选择性和便捷传感提供了一种新策略，并为基于 CDs 的纳米材料在食品安全检测中的广泛应用铺平了道路。