Design Principle of a Water-Dispersed Photocatalytic Perovskite through Ligand Deconstruction

Strategically designed surface modifiers that produce stable perovskite nanocrystals (NCs) and allow efficient charge extraction in polar solvents are critical for perovskite photocatalysis. We designed a multifunctional bolaamphiphilic ligand (NKE-12) with multidentate ionic groups at both ends, which significantly increases the colloidal stability of CsPbBr3 NCs in an aqueous medium without affecting their structural integrity and catalytic attributes. Ligand deconstruction via K and E fragmented ligands revealed synergistic actions of the cationic and anionic functionalities in surface passivation, phase separation, and water localization away from the surface of NKE-12-modified CsPbBr3 NCs. Multidimensional nuclear magnetic resonance experiments and contact angle measurements further suggested surface interactions and improved hydrophilicity via ionic terminal groups that account for water stability. Photogenerated hole-transfer dynamics of CsPbBr3/NKE-12 NCs to a probe molecule 6,7-dihydroxycoumarin was studied using transient absorption spectroscopy. Overall, this study paves the way for ligand design principles for surface engineering to develop water-stable perovskite photocatalysts.