A surfactant-free microemulsion consisting of water, ethanol, and dichloromethane and its template effect for silica synthesis.

A new type of surfactant-free microemulsion (SFME) containing water/ethanol/dichloromethane was constructed, and three microregions water-in-dichloromethane (W/O), bicontinuous (B.C.) and dichloromethane-in-water (O/W) regions were identified. The polarity environment of the SFME was investigated. Solid silica nanoparticle (SSN) was selected as a model nanomaterial to investigate the feasibility of the water/ethanol/dichloromethane SFME for the preparation of nanomaterials. In the O/W SFME region of the microemulsions, uniform spherical solid silica nanoparticles (SSNs) were synthesized. Under the same experimental conditions, they are of smaller particle size and have narrower range of diameter distribution, than the SSNs synthesized from ethanol and water mixture. The effects of tetraethylorthosilicate concentration (CTEOS), ammonia hydroxide concentration ( [Formula: see text] ) and dichloromethane content on the size and morphology of the SSNs were investigated. The average diameters of the SSNs increased with increasing CTEOS and [Formula: see text] . However, the effect of increasing [Formula: see text] on the particle size is more significant. The time evolution of the morphology and diameter of the SSNs were also investigated to elucidate the growth mechanism for the SSNs synthesized in the O/W SFMEs.