Aggregation-induced emission and absorption enhancement of mixed-valent rhenium oxide quantum dots by triethylamine: Implications for food safety monitoring

Abstract

Food freshness monitoring and volatile amine detection are key to food safety. In this study, we demonstrated the applicability of mixed-valence rhenium oxide quantum dots (MV-ReOQDs), synthesized via the hydrothermal reaction of α-cyclodextrin and rhenium ion precursors, in triethylamine (TEA) sensing. Spectroscopic correlation techniques showed that the developed MV-ReOQDs possessed mixed-valent rhenium, α-cyclodextrin as capped ligand, partially carbonized surface, and amorphous phase structure. The multiple oxidation states in the MV-ReOQDs facilitated electron precipitation, contributing to increased excitation-dependent emission, broadened absorption band, and extended luminescence lifetime with increasing emission wavelength. TEA was found to trigger aggregation-induced emission enhancement (AIEE) in the MV-ReOQDs owing to hydrophobic inclusions and hydrogen bonding. Moreover, TEA engaged in charge-transfer interactions with the MV-ReOQDs, amplifying their visible absorption. The MV-ReOQDs afford a limit of detection (signal-to-noise ratio of 3) for TEA at 5 µM (0.5 ppm) for colorimetric detection and 700 nM (0.071 ppm) in luminescent detection modes. Embedding the MV-ReOQDs onto a filter paper yielded a straightforward tool for the real-time detection of TEA vapors released during shrimp spoilage. This MV-ReOQD-coated filter paper provides a convenient solution for monitoring food freshness and facilitates safer food handling and quality control practices.