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

Nitrite (NO) is an inorganic contaminant that exists widely in the environment including water and food products, excessive amounts of NO would threaten humans and aquatic life. Developing a rapid and convenient sensing method for NO remains a great challenge. Herein, a colorimetric and near-infrared fluorescent probe (TBM) was synthesized and applied for sensitively and selectively detecting NO in water, food samples and Escherichia coli (E. coli). With the addition of NO, 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 NO quantitatively with a detection limit of 85 nM based on a 3σ/slope. Under optimum conditions, TBM has been successfully used to detect NO in real-world environmental and dietary samples, with positive results. Besides, paper strips loaded with TBM have been used to visually determine NO levels. Most importantly, TBM has also been proven to be able to discriminate from different concentrations of NO in E. coli by fluorescence imaging. In summary, the probe TBM was successfully developed for the accurate quantification, naked eyes detection and bioimaging of NO 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.