Lateral flow assay with dual-emission nitrogen-doped carbon dots for ratiometric fluorescent determination of nitrite in food

Nitrite ion (NO 2 – ), renowned for its potent antiseptic properties and color-preserving abilities, potentially leads to carcinogenesis and hypertension if consumed excessively. Herein, a ratiometric fluorescent probe exhibits specific response to NO 2 – using nitrogen-doped carbon dots (N-CDs) with a low detection limit (LOD) as low as 52 nM and a low quantification limit (LOQ) of 173 nM. Initially, the emission peaks at 495 nm and 415 nm decrease as result of the internal filtration effect (IFE). With further increasing NO 2 – concentration, the reaction between NO 2 – and N-CDs forms an azoic compound (N-CDs@NO 2 – ), which promotes the instant quenching of the emission peak at 415 nm through fluorescence resonance energy transfer (FRET). Moreover, portable N-CDs/LFASs devices with smartphone are successfully applied to visually identify NO 2 – with the exceptional LOD, achieving excellent recoveries and high precision in real sample. Therefore, this newly N-CDs/LFASs offers a reliable means for the NO 2 – detection, showcasing potential applications.