(236c) Facile Synthesis of Organosilica Nanoparticles Having Hollow Interiors and Porous Shells in Buffer Solution Using Colloidal Silica As Templates

Hollow nanoporous silica nanoparticles possess hollow interiors with nanoporous shells. They have become of particular interest for numerous potential applications including in catalysis, bio-sensing, drug delivery and anti-reflection (AR) coatings. Hollow structures can provide large cavities in nanometer-scale that can be accessed through nanoporous shells. Instead of silica, bridged silsesquioxanes (hereafter denoted organosilica), prepared by hydrolysis and polycondensation of precursors with the general formula (R’O)₃Si–R–Si(OR’)₃(R = organic bridge; R’ = alkoxyl groups), have several advantages as shell components, including facile functionalization and potential to modify mechanical and physical properties of the particles. A general method for preparing hollow organosilica nanoparticles requires the use of soft-templates such as block copolymer micelles.

Herein, we report a facile method for preparing monodisperse, hollow organosilica nanoparticles using silica nanospheres as hard templates [1]. A shell having tiny particles of organosilica was successfully formed on hard templates by stirring a biphasic mixture of bridged alkoxysilane precursors and an aqueous dispersion of hard templates, yielding silica-organosilica core-shell nanoparticles. The internal silica cores were selectively removed by treating the core-shell nanoparticles in a basic solution at elevated pH owing to the difference in hydrolytic stability between silica and organosilica, yielding the nanoporous organosilica nanoparticles with hollow interiors. Our newly developed method can be performed in a one-pot fashion and is applicable to bridged silanes with different organic functional group.

[1] N. Koike, T. Ikuno, T. Okubo, A. Shimojima, Chem. Commun. 2013, 49, 4998–5000.