The synthesis of gold nanoclusters with high stability and their application in fluorometric detection for Hg and cell imaging.

Sensing Hg is significant to protecting human health and environmental ecosystems, for its toxicity and genotoxicity. Here, highly stable fluorescent folic acid (FA)-protected Au nanoclusters (FA-AuNCs) were synthesized by optimizing the reactive parameters with high quantum yield of 34.7%. Main components of AuL were confirmed by MALDI-TOF, and the electron-rich residues of FA shell enabled FA-AuNCs excellent photostability. FA-AuNCs exhibited sensitive response behavior to Hg with a minimum detectability of 1.3 nM, and presented extreme effect to the detection of Hg in real water. Notably, the cellular imaging and in-situ detection of Hg in cells can be achieved visually. The high selectivity was attributed to the chemical bond formed between Au (4f5d) and Hg (4f5d). And the internal filter effect and static quenching effect were proved triggering the quenching of FA-AuNCs. The ultra-stable FA-AuNCs provide a potential promising opportunity for the in-situ tracing Hg from environmental and biological samples.