Graphene quantum dot-functionalized upconversion nanoparticles for highly sensitive detection of food contaminant azodicarbonamide

Abstract

Excessive consumption of flour products containing excessive azodicarbonamide (ADA) has been associated with some adverse effects in humans. Thus, developing a facile method to monitor the amount of ADA in flour is extremely significant. Herein, a graphene quantum dot (GQD) sensitized upconversion nanoparticles (GQD-UCNPs) was designed to monitor the amount of ADA in flour with high specificity and sensitivity. Surface coating of UCNPs with GQD by coordination interaction significantly enhances the upconversion luminescence (UCL) intensity and the water solubility of UCNPs. Copper ions (Cu²⁺) can quench the UCL intensity of GQD-UCNPs through electron transfer processes. After introduction of glutathione (GSH), the UCL intensity of GQD-UCNPs gradually increases because of the interaction between GSH and Cu²⁺, accompanied by the generation of Cu⁺. The sulfydryl group of GSH can be oxidized to disulfide bond by ADA, which hinders the interaction between GSH and Cu²⁺, preventing the recovery of UCL intensity. Thus, the presence of ADA decreases the UCL intensity of GQD-UCNPs + Cu²⁺ + GSH system, allowing for the quantitative detection of ADA. The nanosensor realized a highly sensitive and specific ADA detection with a high detection limit down to 0.055 μM. Furthermore, excellent recovery rates in spiked real samples were obtained, indicating that the designed method possesses good prospects for practical application. Notably, this method broadens the application prospects of upconversion technology in the field of food safety.