Controlled Self-Assembly of Silica-Coated Nanocrystal Networks through Ligand-Depletion-Induced Gelation

Nanocrystal (NC) aerogels are porous network structures assembled from NC building blocks, enabling the formation of macroscopic architectures that preserve their nanoscale properties. Although silica has been incorporated into NC aerogels as a stabilizer or interparticle spacer, its use for the precise control of assembly and quantitative structural analysis has not been reported. Here, we present a ligand-depletion-mediated gelation strategy in which the gradual consumption of CTAB during the growth of a mesoporous silica (mSiO₂) shell destabilizes the NC surfaces and induces self-assembly into three-dimensional networks. Network assembly was induced during the growth of mSiO₂ shells using gold nanorods as a model system. After freeze-drying, the assembled network retained its porous structure, exhibiting pores of approximately 45 nm. Machine learning-based image analysis confirmed that the interparticle spacing could be tuned between 10 and 30 nm. Furthermore, the assembly orientation was controlled by modulating the kinetics of CTAB removal. These structural variations enabled precise tuning of the plasmonic properties. Importantly, this approach was extended to other types of NCs, including spherical gold nanoparticles, magnetic nanoparticles, and quantum dots, thereby enabling the fabrication of multifunctional aerogels that preserve their intrinsic optical and magnetic properties.