Carbon dots-based stimuli-responsive hydrogel for in-situ detection of thiram on fruits and vegetables

Stimuli-responsive hydrogel possesses a strong loading capacity to embed luminescent indicators for constructing food safety sensors, which are suitable for field application. In this work, a fluorescent hydrogel sensor was fabricated by incorporating Ag⁺-modified carbon dots (CDs-Ag⁺) into a sodium alginate (SA) hydrogel for in-situ detection of thiram. The fluorescence of CDs was quenched due to the combined effects of electrostatic adsorption and electron transfer between Ag⁺ and CDs. The formation of an AgS bond between thiram and Ag⁺ facilitates the release of CDs, causing subsequently fluorescence recovery. Combined with smartphone and analysis software, the fluorescence color change of the hydrogel sensor was converted into data information for quantitative detection of thiram. Such a sample-to-result step is completed within 10 min. Notably, the in-situ detection experiment of thiram in fruit and vegetable samples confirmed the practical application of the hydrogel sensor. Therefore, the hydrogel sensor provides a new research direction for the in-situ detection of pesticide residues in the monitoring of food safety.