Preparation of silica nanoparticles in reversed micellar sysytems

Abstract

When surfactants are in apolar media, they form reverse micelles by encapsulating a water droplet inside their hydrophilic head groups. The hydrophilic core of the water droplet which is dispersed in the oily apolar environment can solubilize water-soluble species and can be used as a microreactor for a number of reactions. The aim of this study is to use these hydrophilic cores of reverse micelles as a microreactor to synthesize fluorescent dye-doped silica nanoparticles. Both anionic and nonionic surfactants have been used to prepare reverse micelles. Silica nanoparticles were prepared inside the droplet cores and the effects of changing the surfactant, as well as the size of the dispersed droplets, on the particle size were investigated. Since the fluorescence dye-doped silica nanoparticles can be used as labeling agents for biomolecules, these nanoparticles were then doped with three different types of fluorescent dyes while forming inside the dispersed droplets and their optical properties were investigated. It has been observed that the silica nanoparticle size can be controlled by changing the water-to-surfactant molar ratio, i.e. the droplet size. The fluorescent emission spectrum results have shown that the doping with inorganic hydrophilic dye Ru(bipy)3 was highly successful. When the dye was changed to amphiphilic Rhodamine 101 and more hydrophobic Bodipy, structural dye-modification seemed to be necessary to achieve doping.