The synthesis of gold nanoclusters with high stability and their application in fluorometric detection for Hg2+ and cell imaging

Sensing Hg2+ 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 syn-thesized by optimizing the reactive parameters with high quantum yield of 34.7%. Main components of Au4L were confirmed by MALDI-TOF, and the electron-rich residues of FA shell enabled FA-AuNCs excellent photo-stability. FA-AuNCs exhibited sensitive response behavior to Hg2+ with a minimum detectability of 1.3 nM, and presented extreme effect to the detection of Hg2+ in real water. Notably, the cellular imaging and in-situ detection of Hg2+ in cells can be achieved visually. The high selectivity was attributed to the chemical bond formed between Au+ (4f145d10) and Hg2+ (4f145d10). 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 Hg2+ from environmental and biological samples.