Fluorescent sensor based on bimetallic Au/Os nanoclusters: Enabling rapid and on-site detection of amaranth in food

Food colorants are ubiquitous in the food industry. However, their excessive use can degrade food quality and also pose significant health risks to consumers. Accordingly, it is crucial to develop efficient analytical methods for the rapid and on-site detection of colorants in food. Here, we presented an innovative fluorescent sensor based on a unique polyethyleneimine-capped Au/Os bimetallic nanoclusters (PEI-capped Au/Os NCs) for the rapid and on-site detection of amaranth, a prevalent synthetic red food colorant. The synthesized PEI-capped Au/Os NCs exhibit robust fluorescence emission at 465 nm (Φ_f = 51.5 %), which is significantly quenched upon interaction with amaranth. The sensor demonstrates exceptional specificity and sensitivity, with a linear detection range of 0.03–20.00 μM and a detection limit as low as 18.00 nM. Notably, the PEI-capped Au/Os NCs sensor was integrated onto paper strips, allowing for visual capture and recording of fluorescence changes using a smartphone with a built-in camera. This approach was successfully applied for rapid and on-site detection of amaranth in grape juice beverages and candies. This work pioneers the use of fluorescent bimetallic NCs in the rapid and on-site detection of food colorants, providing a convenient and powerful tool for the surveillance of food safety.