New strategies for enhancing the fluorescence emission of metal nanoclusters (MNCs) are very crucial for the highly sensitive sensing of food hazards. In this work, we prepared MNC supraparticles (Sc-CB/AuNCs) by simultaneously introducing cucurbit[7]uril (CB[7]) and Sc3+ ions into ATT-AuNCs for the first time. The obtained supraparticles exhibited strong emission enhancement due to synergistic aggregation-induced emission enhancement and restriction of intramolecular motion effects. Notably, the fluorescence of ATT-AuNCs was enhanced by 24-fold due to the combination of CB[7] and Sc3+ ions, and the quantum yield reached 69.1%. Moreover, we found that tetracycline (TC) could bind to the Sc-CB/AuNCs through simultaneous host-guest recognition and ionic complexation, which effectively quenched the Sc-CB/AuNCs through the synergy of photoinduced electron transfer and inner filter effect. Based on the above multiple interactions between TC and Sc-CB/AuNCs, an ultrasensitive sensing method for TC was constructed with an LOD of 0.3 nM. Furthermore, a portable fluorescent gel sensor was constructed and successfully used for TC detection in honey samples. The test took only 2 min. This work not only provided a simple and effective fluorescence enhancement strategy for MNCs but also offered a novel sensing strategy, which may largely extend the potential of host-guest recognition-based sensors for food and environmental hazards.
Keywords: dual recognition; fluorescence enhancement; metal nanoclusters; supraparticles; tetracycline.