Double Direct Templated Hollow ZnS Microspheres Formed on Chemically Modified Silica Colloids

Abstract

The effect of surface chemistry of SiO2 colloids dispersed in a nonionic surfactant based lyotropic liquid crystal (LLC) on the double direct templating of hollow mesostructured ZnS capsules was investigated. In double direct templating, a LLC templates the mineralization of ZnS on the surface of a colloidal particle. Removal of the colloid results in a periodically mesostructured hollow capsule. After ZnS mineralization and a subsequent etching of the sacrificial SiO2 core, the ZnS mesostructure was imaged using transmission electron microscopy (TEM). The highest quality mesostructure was observed for poly(acrylic acid) (PAA) functionalized colloids, while other surface chemistries, including bare silica, poly(ethylene glycol), amine, and thiol surface chemistries yielded much less favorable results. In the PAA system, the order of the hexagonally arranged 3 nm mesopores in the ZnS shell closely matched that of the lyotropic liquid crystal template. Detailed TEM revealed the presence of regions where the mesopores lay parallel to the colloidal surface and others where they were perpendicularly arranged. We suspect the PAA functionalization favored both the nucleation of ZnS and organization of the LLC template responsible for templating mesostructured ZnS shell around the colloidal particle.