Ultrabright silicon nanoparticles combined with o-phenylenediamine for ratiometric fluorescence and smartphone imaging dual-mode detection of nitrite

Nitrite (NO 2 − ) is widely present in the natural environment and human daily life. Excessive NO 2 − can cause harm to the environment and human health. Herein, silicon nanoparticles (SiNPs) with a fluorescence quantum yield of up to 70 % were synthesised using a one-pot hydrothermal method and combined with the common and inexpensive o -phenylenediamine (OPD) to achieve the detection of NO 2 − . Upon the addition of NO 2 − , the blue fluorescence of the SiNPs was quenched due to static quenching and Förster resonance energy transfer (FRET), while the yellow fluorescence of benzotriazole, the reaction product of OPD and NO 2 − , was enhanced, resulting in the fluorescence color change from blue to yellow. Based on these phenomena, a ratiometric fluorescence sensor integrated with smartphone imaging technology was developed. This sensor is notable for its portability, cost-effectiveness, and satisfactory detection limits (0.016 μM for ratiometric fluorescence and 1.64 μM for smartphone imaging). Importantly, it demonstrates high reliability and practicability in detecting NO 2 − in real water and food samples. This broadens the application of SiNPs in the sensing field and introduces new possibilities for NO 2 − detection in complex sample matrices.