Formation of silica nanocapsules from nanoemulsions obtained by the phase inversion temperature method

A method for preparation of silica nanocapsules is described, by interfacial polymerisation of nanoemulsions which are prepared by the phase inversion temperature (PIT) method. This is a low-energy emulsification technique which does not require any special equipment, such as high-pressure homogenisers. The nanoemulsions were prepared with decane as the oil phase, in which tetraethoxysilane (TEOS) was dissolved with an ethoxylated alcohol as the surfactant. The hydrolysis and polymerisation of the TEOS was performed under acidic and basic conditions using HCl and ammonia, respectively. The obtained nanocapsules with an average size between 100 and 300 nm, which were comprised of an oil core (decane) and silica shell, were characterised using dynamic light scattering, fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM) and by fluorescence of an encapsulated solvatochromic dye. The capsules could be positively or negatively charged by adsorption of ionic surfactants after they were formed.