Direct stöber synthesis of monodisperse silica particles functionalized with mercapto-, vinyl- and aminopropylsilanes in alcohol–water mixed solvents

In this study we explore the preparation of 3-mercaptopropyl-, vinyl- and 3-aminopropyl-functionalized silica monodisperse nanoparticles by direct synthesis (`one-pot synthesisʹ) in alcohol–water mixed solvents. These functionalized monodisperse silicas are denoted as MP-silica, V-silica and AP-silica, respectively. Monodisperse particles with diameters ranging from several tens to one hundred nanometers were successfully prepared, and dispersion was confirmed by dynamic light scattering. The synthetic conditions that were required to achieve monodispersion differed considerably among the different types of organic functional groups. The change in particle size were mainly influenced by the concentration of ammonia, by the mixing ratio of organosilica against TEOS and by the solvent composition for MP-silica, V-silica and AP-silica, respectively. The shapes of the monodisperse nanoparticles were revealed as being spherical by SEM observations. The organic functional groups were analysed by IR and Raman vibrational spectroscopies. We show experimental evidence for the formation of SS bonds in MP-silica, and a considerable blue shift of the NH2 scissor vibration in AP-silica.