One-step green synthesis of fluorescent bimetallic Au/Ag nanoclusters for temperature sensing and in vitro detection of Fe3+

Herein, we demonstrate a facile, straightforward and green method for synthesis of highly red-emitting fluorescent bimetallic Au/Ag nanoclusters (NCs) employing lipoic acid as both a reducing agent and a protecting agent. The as-prepared Au/Ag NCs exhibited bright red emission with a strong peak centered at 630   nm (quantum yield measured as 6.4%), and showed excellent stability and remarkable temperature-dependent fluorescent property. The fluorescence responses were reversible and linear to the environment temperature from 20 to 65   °C with a resolution as high as 1.34   °C, which allows its potential application as a fluorescent nanothermometer. Moreover, Au/Ag NCs were also explored for selective and sensitive determination of Fe 3+ based on the specific quenching of the fluorescence by Fe 3+ , and explored for fluorescence imaging Fe 3+ in living HeLa cells thanks to their very low cytotoxicity.