Cross-Reactive Fluorescence Fingerprinting: Discrimination of Alkylresorcinol Homologues Using a Graphene Quantum Dot Sensor Array

Alkylresorcinols (ARs) are biomarkers of whole-grain intake and food authenticity, but simultaneous discrimination of AR homologues remains challenging due to structural similarity and co-occurrence in complex food matrices. Herein, a three-channel fluorescent sensor array based on graphene quantum dots (GQDs) was developed to discriminate and quantify five AR homologues (C17:0, C19:0, C21:0, C23:0, and C25:0). Noncovalent interactions between GQDs and ARs, with distinct surface chemistries, induce differential interfacial charge redistribution and excited-state relaxation, generating cross-reactive fluorescence patterns. Using principal component analysis and hierarchical cluster analysis, the array yields unique fingerprints separating low, medium, and high concentrations. Linear correlation between PC1 scores and AR concentrations (0–60 μg·mL–1) enabled quantification, with detection limits down to 1.1 ng·mL–1. Validation using commercial whole-wheat products distinguished all five ARs, with recoveries of 96.10–108.40% and relative standard deviations below 3.76%. This robust, low-cost, high-throughput platform shows potential for food authenticity evaluation and biosensing.