A paper-based ratiometric fluorescent sensor for NH detection in gaseous phase: Real-time monitoring of chilled chicken freshness.

A ratiometric fluorescence sensor platform with easy-to-use and accurate is nanoengineered for NH quantitative detection and visual real-time monitoring of chicken freshness using smartphones. The ratiometric fluorescent probe formed by combining the zinc ion complex and carbon dots has a double-emitted fluorescence peak. The fluorescence intensity of the complex changed can be clearly observed with the increase of the concentration of ammonia solution under 365 nm wavelength excitation. In order to detect NH concentration in gaseous phase, a portable paper-based sensor was designed. The sensor had a good linear relationship with NH concentration ranging from 10.0 to 90.0 μmol/L and the LOD value was 288 nM. This fluorescent paper-based sensor was used to check the freshness of chicken breast refrigerated at 4 °C, revealed observable shifts from blue to green. The fluorescent paper-based sensor can detect NH concentration in real time and simplify the monitoring process of meat freshness while ensuring accuracy and stability.