Photostable <i>o</i> -Carborane-DAPA Hybrids for On-Site Nitrite Screening: Dual-Mode Detection Achieving Sub-100 nM Sensitivity in Complex Food Matrices

Nitrite is widely used in food processing; however, excessive intake can lead to severe carcinogenic and toxic effects, highlighting the urgent need for sensitive and reliable detection methods. Herein, we report the design of an <i>o</i>-carborane-modified fluorophore, DAPA-1CB, which integrates nitrite-specific recognition motifs with enhanced photophysical properties. Incorporation of the <i>o</i>-carborane unit markedly improves photostability and expands the Stokes shift, enabling dual-mode (fluorescence and colorimetric) detection with sub-100 nM sensitivity. DAPA-1CB exhibits outstanding selectivity and sensitivity, distinguishing nitrite from diverse potential interferents even at low concentrations. Notably, the probe achieves accurate recovery rates (92-106%) in complex food matrices such as pickles, bacon, and smoked fish. These findings establish DAPA-1CB as a robust and practical tool for nitrite monitoring and present a promising design strategy for high-performance fluorescent probes in food safety applications.