Effect of functional groups on condensation and properties of sol-gel silica nanoparticles prepared by direct synthesis from organoalkoxysilanes

Silsesquioxane nanoparticles were synthesized from organotrialkoxysilanes in ethanol/water medium by a two-step hydrolysis–condensation process. Regular shaped spheres functionalized by vinyl, methyl, ethyl, phenyl, amyl, octyl, 3-aminopropyl groups were obtained, with sizes in the range 100–400 nm. The integrity of the organic functional groups and the condensation degree of the silsesquioxane networks were detected by multinuclear solid state Nuclear Magnetic Resonance (NMR). The nanoparticles thermal behavior was studied by thermogravimetric analyses, and N2 sorption was used to measure the particles porosity. Coatings were obtained from particles suspensions by spin coating technique and the surface properties were studied by contact angle measurements. The emission of Rhodamine 6G doped nanoparticles was analyzed in the visible light region. The fluorescence experiments highlight the influence of the different matrices on amount of dye retained into the network and fluorescence intensity.