An optical sensing platform for the detection of an important mycotoxin, aflatoxin B1 (AFB1), in the absence of a bioactive environment is explored. In this work, a fluorescence-based sensing technique was designed by combining graphene quantum dots (GQDs) and AFB1 via fluorescence quenching, where AFB1 acts as the quencher of GQD fluorescence. GQDs were synthesized through a single-step hydrothermal reaction from the leaves of "curry tree" (Murraya Koenigii) at 200 °C. The fluorescent GQDs were quenched by AFB1 (quencher), which itself is detecting the analyte. Hence, this study reports the direct sensing of the mycotoxin AFB1 without the involvement of inhibitors or biological entities. The possible mode of quenching is the nonradiative resonance energy transfer between the GQDs and the AFB1 molecules. This innovative sensor could detect AFB1 in the range from 5 to 800 ng mL-1 with a detection limit of 0.158 ng mL-1. The interferent study was also carried out in the presence of different mycotoxins and carbohydrates (d-fructose, cellulose, and starch), which demonstrated the high selectivity and robustness of the sensor in the complex sample matrix. The recovery percentage of the spiked samples was also calculated to be up to 106.8%. Thus, this study reports the first GQD based optical sensor for AFB1.
Keywords: Murraya Koenigii; aflatoxin B1; fluorescence quenching; graphene quantum dots; hydrothermal reaction.