Drying-induced photoluminescence enhancement of gold nanoclusters for ultrafast and highly sensitive lateral flow assay detection of food contaminants.

Abstract

Metal nanoclusters (MNCs) hold great promise as photoluminescent probes but often suffer from low emission efficiency in aqueous media. Herein, we report a simple yet powerful strategy to enhance and regulate the photoluminescence (PL) of 6-aza-2-thiothymine-protected Au nanoclusters (ATT-AuNCs) through drying-induced emission enhancement (DIEE). A series of experimental results reveal that intra-cluster hydrogen bonding rigidifies the surface ligands and promotes ligand-to-core charge transfer, thereby suppressing non-radiative decay and inducing red-shifted emission. This phenomenon is universal to AuNCs stabilized by N-heterocycles with conjugated carbonyl groups. Harnessing this unique property, ATT-AuNCs enables advanced applications in lateral flow assay (LFA) platform for quantitative analysis of dimethomorph (DMM) and zearalenone (ZEN), typical food contaminants. The resulting AuNCs-LFA achieved outstanding sensitivity and ultrafast detection (no more than 6 min), with detection limits 15-20-fold lower than those of conventional colorimetric AuNPs-LFAs for DMM and ZEN. This work establishes direct drying regulation as an efficient photoluminescence control strategy and demonstrates its utility in developing cost-effective and highly sensitive point-of-care platforms for food safety monitoring.