A controlled formation of cage-like nanoporous hollow silica microspheres

Abstract

Cage-like hollow silica microspheres composed of mesoporous silica nanoparticles and macroporous interparticle voids were fabricated via the latex–surfactant dual templates route, simply by controlling the surfactant additions below its critical micelle concentration. The surface area, pore volume increase, and both the mesopore and macropore sizes decrease with the increase in surfactant amount. The surfactant cations preferentially assemble with negatively charged silica species generated by the hydrolysis and condensation of tetraethyl orthosilicate to form composite silica–surfactant nanoparticles. The electrostatic repulsion between the silica–surfactant composite nanoparticles and negatively charged polystyrene (PS) beads is smaller than that between surfactant–free silica and PS, favoring the deposition of composite nanoparticles on the surface of PS template. In the meantime, the deposited nanoparticles also have reduced repulsion from their neighbors, favoring their bridging to form silica shells. The more the surfactant is used, the less the repulsion exists among the composite particles and the smaller the interparticle macroporous voids are.