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Rational design of carbon dot nanozymes for ratiometric dual-signal and smartphone-assisted visual detection of nitrite in food matrices

Hao Y, Wang Z, Wang H, Dong W, Liu Y, Hu Q, Shuang S, Dong C et al.

Journal of hazardous materials, 2024

Abstract

Developing reliable nitrite (NO2-) sensors is essential for food safety and reducing health risks from NO2- exposure. In this study, we strategically designed nitrogen-doped carbon dot (N-CD) nanozymes to establish an accessible dual-signal ratiometric sensing system for detecting NO2- in food matrices. This system utilizes the photoluminescence and enzyme-like properties of N-CD nanozymes combined with NO2--triggered diazotization reactions of substrates such as o-phenylenediamine (OPD) or 3,3',5,5'-tetramethylbenzidine (TMB). The resulting N-CD/OPD and N-CD/TMB composites provide dual-mode detection-fluorescence and colorimetric-with high selectivity for NO2- and excellent resistance to interference. These sensors exhibit clear color changes under both ultraviolet and visible light, and can be combined with smartphones for visual, on-site detection of NO2-. By incorporating a ratiometric strategy, dual-signal output, and smartphone compatibility, our system achieved a low detection limit (≤ 1.92 μM) and satisfactory recovery rates (85.6-115 %) in environmental water and food samples. This highlights the potential of smartphone-assisted sensors for environmental monitoring and food safety applications. Our carbon dot-based platform offers a practical and effective solution for on-site NO2- detection, contributing valuable insights to the field.

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