AuNCs@Ce-MOFs/CdTe@SiO₂: Preparation and application of a novel ratiometric fluorescent composite for the detection of Hg²+

The development of a sensitive and accurate method for detecting Hg²⁺ is essential to ensuring the safety of the water environment and protecting human health. Although fluorescence sensing methods based on gold nanoclusters (AuNCs) can selectively detect Hg²⁺ via specific Au-Hg recognition, their sensitivity and accuracy require enhancement due to the low luminescence efficiency of AuNCs and the susceptibility of single-method detection to environmental interference. Herein, AuNCs were encapsulated within the pores of cerium metal-organic frameworks (Ce-MOFs) featuring a large pore size and porous architecture via a one-step in-situ self-assembly approach, yielding a AuNCs@Ce-MOFs composite that exhibited superior luminescence performances and enhanced stability. Studies have unequivocally demonstrated that the remarkable luminescence properties of AuNCs@Ce-MOFs are primarily ascribed to two pivotal mechanisms: the restriction of intramolecular motion (RIM) effect, which arises from the coordination between the AuNCs surface ligand 6-aza-2-thiothymine and the cerium ions within Ce-MOFs, and the intrinsic aggregation-induced emission (AIE) effect characteristic of AuNCs. On this basis, in conjunction with a secondary fluorescent probe, namely CdTe@SiO₂, where the SiO₂ coating serves to suppress the photoinduced electron transfer process between CdTe quantum dots (QDs) and AuNCs@Ce-MOFs, a reference-type ratiometric fluorescence sensing platform that enables sensitive, selective, and accurate detection of Hg²⁺ in water was developed.