Reaction-Induced Microsyneresis in Oxide-Based Gels: The Assembly of Hierarchical Microsphere Networks

Rigid and stable networks composed of litchi-shaped microspheres were formed via hierarchical self-assembly (SA) of oxide-based nanoparticles (NPs). The phenomenon of the apparent changes from NPs networks to microspheres networks after the gelation was similar to normal microsyneresis. However, in-situ composition evolution results indicate that the SA is driven by interparticle dehydration, but not affinity difference between the network for itself and for the solvent. In-situ small-angle X-ray scattering (SAXS), UV–vis–NIR, and electric conductivity were used to study the microsyneresis process. To further demonstrate the mechanism, extra complexant was added and successfully restrained the NPs–microsphere transition by inactivating the surface hydroxyl of the NPs. Considering the structural similarity, this work may provide a new approach to control the assemblies of diverse oxide-based NPs.