Surface chemistry regulates the optical properties and cellular interactions of ultrasmall MoS₂quantum dots for biomedical applications

Molybdenum disulfide quantum dots (MoS₂QDs) have drawn increasing attention owing to their distinct optical properties and potential applications in many fields such as biosensing, photocatalysis and cell imaging. Elucidating the relationship between the surface chemistry of MoS₂QDs and their optical properties as well as biological behaviors is critical for their practical applications, which remain largely unclear. Herein, by adopting a sulfur vacancy modification strategy, a toolbox of MoS₂QDs functionalized with different thiolate ligands was prepared. The effect of surface chemistry on the optical properties of MoS₂QDs was systematically explored by various spectroscopic techniques, revealing the important role of surface ligands in defining their absorption band gap and luminescence quantum yield. Furthermore, cellular experiments showed that the cytotoxicity and intracellular fate (i.e., lysosomal accumulation) of MoS₂QDs are closely related to the properties of surface ligands. Our results underscore the important roles of surface ligands in regulating the properties and biological interactions of these QDs, which will facilitate the future development of MoS₂-based materials with precisely controlled functions for biomedical applications.