Neutron Scattering Reveals a Dynamic Surface Equilibrium on l-α-Lecithin Functionalized CsPbBr₃ Nanocrystals

Cesium lead bromide perovskite nanocrystals (NCs) covered with lecithin ligands in liquid toluene suspensions were investigated with a range of complementary scattering techniques and nuclear magnetic resonance to reveal their surface chemistry, solution structure, and diffusive dynamics. Distinct self-diffusion coefficients were determined and analyzed, namely the center-of-mass diffusion of the NCs and of coexisting ligand micelles, as well as the lateral diffusion of the l-α-lecithin ligand relative to the NC surface and within the micelles. We find a dynamic surface equilibrium, represented by a tunable lateral diffusion coefficient dependent on the ligand surface density. This phenomenon can be rationalized by the extraordinary binding of this zwitterionic ligand and its ability to bind via two different binding sites. These results highlight the dynamic nature of the ligand binding to lead halide perovskite NCs.