Compartmentalized Hollow Silica Nanospheres Templated from Nanoemulsions

Nanoemulsions with very high stability can be created by ultrasonication using a rich variety of surfactants, oils, and solution conditions. Multicompartments within a nanoemulsion droplet can also be created via a carefully chosen surfactant system. We will show in this paper that silica templating of a nanoemulsion system results in compartmentalized hollow silica nanospheres (HSN) of sub-100 nm size under neutral pH conditions. The system consists of water, cetyltrimethylammonium bromide (CTAB), tetraethyl orthosilicate, n-hexadecane, n-octane, and n-hexanol. Two types of HSN can be obtained by manipulating the formulation; one is named single-compartment HSN (SC-HSN), where the HSN encapsulate a single water-in-oil droplet; the other is multiple-compartment HSN (MC-HSN), where the HSN encapsulate multiple smaller HSN. Using a high concentration of CTAB, we obtained a transparent solution of narrow size-distributed ultrasmall HSN (US-HSN) with a diameter of 12 nm. Parameters involved in the nanoemulsio...