Accurately Tunable AuNC-ZIF Content Architecture Based on Coordination-Dissociation Mechanism Enables Highly Brightness Dual-Site Fluorescent Biosensor.

The quantum yield and fluorescence intensity of gold nanocluster (AuNC) nanocarriers are critical parameters for developing ultrasensitive biosensors. In this study, AuNCs-zeolitic-imidazolate-framework (Au-ZIF) nanocomposites are systematically constructed by impregnating AuNCs onto the ZIF-8 surface through a coordination-dissociation mechanism, resulting in a dual-site fluorescence-loaded structure. In this configuration, AuNCs are anchored to the external surface while the integrity of the inner cavity remains intact. The surface of ZIF-8 induces a confinement effect on the configuration and electrons of AuNCs, significantly enhancing luminescence (18-fold increase). The quantum yield of AuNCs exhibits an increase of more than 13-fold, from 2.80% to 38.1%. This approach demonstrates broad applicability and maintains strong fluorescence across different ZIFs. Additionally, a novel nanocomposite, Au-ZIF@carbon-dots (CDs), is synthesized by encapsulating CDs into the inner cavity of Au-ZIF. A ratiometric fluorescence detection platform is subsequently developed and incorporated into hydrogels for the quantitative detection of the pesticide triazophos. By employing an image-processing algorithm, quantitative detection is achieved with a detection limit of 0.07 ng mL⁻. The findings provide crucial insights into the relationship between the assembly and performance of AuNCs and ZIFs, offering guidance for designing ultrasensitive multifunctional biosensors applicable in the field of biosensing.