Preparation of Metal Nanocluster Supraparticles for\nUltrasensitive Sensing of Tetracycline Based on Multiple Interactions\nbetween a Target and Sensor

New strategies for enhancing the\nfluorescence emission of metal\nnanoclusters (MNCs) are very crucial for the highly sensitive sensing\nof food hazards. In this work, we prepared MNC supraparticles (Sc-CB/AuNCs)\nby simultaneously introducing cucurbit[7]uril (CB[7]) and Sc<sup>3+</sup> ions into ATT-AuNCs for the first time. The obtained supraparticles\nexhibited strong emission enhancement due to synergistic aggregation-induced\nemission enhancement and restriction of intramolecular motion effects.\nNotably, the fluorescence of ATT-AuNCs was enhanced by 24-fold due\nto the combination of CB[7] and Sc<sup>3+</sup> ions, and the quantum\nyield reached 69.1%. Moreover, we found that tetracycline (TC) could\nbind to the Sc-CB/AuNCs through simultaneous host–guest recognition\nand ionic complexation, which effectively quenched the Sc-CB/AuNCs\nthrough the synergy of photoinduced electron transfer and inner filter\neffect. Based on the above multiple interactions between TC and Sc-CB/AuNCs,\nan ultrasensitive sensing method for TC was constructed with an LOD\nof 0.3 nM. Furthermore, a portable fluorescent gel sensor was constructed\nand successfully used for TC detection in honey samples. The test\ntook only 2 min. This work not only provided a simple and effective\nfluorescence enhancement strategy for MNCs but also offered a novel\nsensing strategy, which may largely extend the potential of host–guest\nrecognition-based sensors for food and environmental hazards.