Accurate quantification, naked eyes detection and bioimaging of nitrite using a colorimetric and near-infrared fluorescent probe in food samples and Escherichia coli

Nitrite (NO2−) is an inorganic contaminant that exists widely in the environment including water and food products, excessive amounts of NO2− would threaten humans and aquatic life. Developing a rapid and convenient sensing method for NO2− remains a great challenge. Herein, a colorimetric and near-infrared fluorescent probe (TBM) was synthesized and applied for sensitively and selectively detecting NO2− in water, food samples and Escherichia coli (E. coli). With the addition of NO2−, the probe TBM solution has a distinct visual color changed from red to colorless and fluorescence intensity at 620 nm quickly decreased. The probe TBM could detect NO2− quantitatively with a detection limit of 85 nM based on a 3σ/slope. Under optimum conditions, TBM has been successfully used to detect NO2− in real-world environmental and dietary samples, with positive results. Besides, paper strips loaded with TBM have been used to visually determine NO2− levels. Most importantly, TBM has also been proven to be able to discriminate from different concentrations of NO2− in E. coli by fluorescence imaging. In summary, the probe TBM was successfully developed for the accurate quantification, naked eyes detection and bioimaging of NO2− in water, food samples and E. coli, which provides a useful tool to better guarantee the quality and safety of daily life and food industry.