Detection of herbicides in food samples using hybrid carbon dot sensors and test kit fabrication via paper-based analytical devices

In this study, hybrid carbon dots were prepared via surface modification of carbazole (Car@CD) and anthracene (Ant@CD) and applied for fluorometric determination of benfluralin, aclonifen, and pendimethalin herbicides in food samples. The characterizations of hybrid carbon dots were performed using different spectroscopic, thermal, and microscopic techniques. The optimal detection conditions and analytical parameters (LOD, LOQ, RSD%, etc.) were determined for the presented fluorometric methods. According to the results, the surface fluorophore groups increased the number of interaction points with analytes, and fluorescence responses were observed owing to PET processes between herbicides and nanosensors. The detection limits were calculated to be 6.00–9.40 nM, with a wide linear working range. The presented fluorometric techniques were applied to quantify benfluralin, aclonifen, and pendimethalin in food samples, and the novel methods were validated using GC–MS analyses and spike/recovery tests. Finally, the fluorescence-quenching responses of Car@CD and Ant@CD were used for RGB analysis with a smartphone via fabricated paper-based test kits. The fluorometric responses of Car@CD and Ant@CD demonstrated accurate and reliable detection due to their high selectivity and sensitivity to herbicides. Additionally, the colorimetric readout, accessible via a smartphone, enabled a convenient and portable assessment. This study introduces carbazole- and anthracene-modified carbon dots that integrate π-π stacking and hydrogen-bonding functionalities, thereby enhancing herbicide recognition. Considering that fluorescence-based detection of benfluralin and aclonifen is still almost absent and studies on pendimethalin remain scarce, the presented approach offers one of the first comprehensive strategies that combines high sensitivity, real-sample validation, and a portable smartphone-assisted paper kit for practical food safety monitoring.