Controllable synthesis of selenolate ligand-costabilized water-soluble near-infrared fluorescent gold nanoclusters for cell imaging

Selenolate ligands are expected to endow fluorescent gold nanoclusters (AuNCs) with better stability and more bioactivity than thiolate ligands, making them promising in the biological field. However, there are few studies on the synthesis of water-soluble selenolate-protected AuNCs, and the impact of selenolate ligands on the optical properties of AuNCs is still unclear. In this study, we synthesized selenolate-costabilized water-soluble, near-infrared fluorescent AuNCs with four different amounts of benzeneselenol (PhSeH), and systematically investigated the role of PhSeH on their optical properties. It is discovered that an appropriate PhSeH content is favorable for the fluorescence enhancement of AuNCs due to the ligand to metal charge transfer effect. Moreover, AuNCs co-stabilized by selenolate ligands exhibit better photostability and long-term stability compared with AuNCs stabilized by thiolate ligands, owing to the introduction of Au-Se bond on their surfaces. Further cellular experiments revealed that selenolate ligands can also affect the cellular uptake efficiency of AuNCs and their imaging property. These results provide important knowledges for further development of new, robust selenolate-stabilized metal NCs for biological application.