Damage-Free Silica Coating for Colloidal Nanocrystals Through a Proactively Water-Generating Amidation Reaction at High Temperature.

Silica is a promising shell coating material for colloidal nanoparticles due to its excellent chemical inertness and optical transparency. To encapsulate high-quality colloidal nanocrystals with silica shells, the silane coupling hydrolysis is currently the most effective approach. However, this reaction requires water, which often adversely affects the intrinsic physicochemical properties of nanocrystals. Achieving a damage-free silica encapsulation process to nanocrystals by hydrolysis is a huge challenge. Here, a novel strategy is developed to coat colloidal nanocrystals with a denser silica shell via a proactively water-generating reaction at high temperature. In this work, water molecules are continuously and proactively released into the reaction system through the amidation reaction, followed by in situ hydrolysis of silane, completely avoiding the impacts of water on nanocrystals during the silica coating process. In this work, water sensitive perovskite nanocrystals (CsPbBr) are selected as the typical colloidal nanocrystals for silica coating. Notably, this high-temperature in situ encapsulation technology greatly improves the optical properties of nanocrystals, and the silica shells exhibit a denser structure, providing nanocrystals with better protection. This method overcomes the challenge of the influence of water on nanocrystals during the hydrolysis process, and provides an important reference for the non-destructive encapsulation of colloidal nanocrystals.