Photoluminescent Ag nanoclusters for reversible temperature and pH nanosenors in aqueous solution.

A facile, straightforward, and green method was reported for the preparation of water-soluble and highly luminescent silver nanoclusters (AgNCs) using captopril (Capt) as a stabilizing agent. The as-prepared Capt@AgNCs exhibited bright red emission with a strong peak centered at 637 nm and showed low toxicity and good stability. Interestingly, the AgNCs displayed temperature sensitivity based on obvious temperature dependence of the fluorescence emission intensity. Furthermore, the AgNCs showed a good reversible and linear response to the environment temperature over the range from 10 °C to 45 °C with a high resolution and activation energy, which allowed its potential application as a fluorescent nanothermometer. In addition, the AgNCs were prepared to monitor pH via the fluorescence intensity of AgNCs responding sensitively to pH fluctuating within a wide range from 2.08 to 6.06. The study provides promising applications as a convenient and eco-friendly fluorescent temperature and pH nanosenser in environmental and biological fields. Graphical abstract Novel silver nanocluster-based fluorescent nanosensors have been successfully constructed for temperature detection. The nanosensors showed a good reversible and linear response to the environment temperature over the range from 10 °C to 45 °C. In addition, the AgNCs described here are employed as pH sensors by virtue of the fluorescence intensity of their sensitive response to fluctuating pH in a linear range of 2.08-6.06.