Building Nanostructured Porous Silica Materials Directed by Surfactants

Abstract

Silica nanomaterials have found prevailing use in biomedical applications due to their biocompatibility and non-toxicity. The use of a structure-directing agent in silica sol-gel synthesis enables us to direct the formation of silica nanostructures into forms that are otherwise difficult to obtain, allowing the exertion of a fine degree of control over the morphology, dimensions and architecture of the nanostructures. Single-tailed surfactants have been used extensively as soft templates to produce mesoporous silica materials. This study investigates the use of a double-tailed surfactant, a didodecyldimethylammonium phosphate surfactant (DDAH2PO4) as a structure-directing agent in the sol-gel synthesis of silica at ambient conditions in aqueous solution. The effects of varying reaction parameters such as surfactant concentration and solution temperature on resulting silica morphology are presented. Morphological transitions from nanobeads to hexagonal plates and toroidal concave particles are observed with increasing surfactant concentrations, as well as a gradual loss in templating ability at elevated solution temperatures (up to 25 °C). This allows us to access different morphologies and dimensions of nanostructures within the same synthesis scheme templated with DDAH2PO4.