Highly sensitive and ratiometric detection of nitrite in food based on upconversion-carbon dots nanosensor

Nitrite (NO2-) is extensively found in the daily dietary environment. However, consuming too much NO2- can pose serious health risks. Thus, we designed a NO2--activated ratiometric upconversion luminescence (UCL) nanosensor which could realize NO2- detection via the inner filter effect (IFE) between NO2--sensitive carbon dots (CDs) and upconversion nanoparticles (UCNPs). Due to the exceptional optical properties of UCNPs and the remarkable selectivity of CDs, the UCL nanosensor exhibited a good response to NO2-. By taking advantage of NIR excitation and ratiometric detection signal, the UCL nanosensor could eliminate the autofluorescence thereby increasing the detection accuracy effectively. Additionally, the UCL nanosensor proved successful in detecting NO2- quantitatively in actual samples. The UCL nanosensor provides a simple as well as sensitive sensing strategy for NO2- detection and analysis, which is anticipated to extend the utilization of upconversion detection in food safety.