Ligand modification strategy enhancing highly sensitive smart copper nanoclusters fluorescent tag for visual monitoring of aquatic products freshness

The exploration of cost-effective methods for monitoring aquatic products freshness is significant. Metal nanoclusters (MNCs) show considerable potential in detecting food spoilage. A ligand modification strategy has been proposed as an effective approach for preparing high-performance MNCs. In this study, polyvinylpyrrolidone (PVP) and methylthioxanthine (MTU)-capped copper nanoclusters (PVP-MTU-CuNCs) with high quantum yield (43.76 %) were synthesized using an eco-friendly one-pot method. PVP improved the electron transfer and restricted the motion of MTU, enhancing photoluminescence, while its long-chain formed a physical barrier, effectively improving dispersibility and stability. PVP-MTU-CuNCs exhibited a satisfactory responsiveness to volatile basic nitrogens (VBNs), with detection limits of 0.34, 0.36, 0.33, 3.23, and 3.45 ppm for spermine, spermidine, histamine, cadaverine, and ammonia, respectively. An intelligent fluorescent label was developed for ammonia sensing and achieved visual semi-quantification and real-time tracking of the freshness of sea bass and shrimp, demonstrating its practical potential in assessing aquatic products freshness