Functionalization of SiO2 Nanoparticles and Their Superhydrophobic Surface Coating

Silica (SiO2) nanoparticles synthesized from the gas phase in a microwave plasma reactor were dispersed in organic solvents and subsequently chemically modified with silane coupling agents (SCAs) to reduce agglomeration. A transparent and stable dispersion of silica nanoparticles in toluene could be achieved after functionalization with octyltriethoxysilane (OTES). FTIR measurements indicated that the concentration of free hydroxyl groups on the nanoparticle surface was notably decreased. Nanodispersions of functionalized silica particles with several SCAs were prepared and coated onto glass substrates. The resulting highly hydrophilic/hydrophobic glass substrates were investigated by water contact angle measurements. As a result, the hydrophobically OTES-functionalized silica nanoparticles in toluene showed an average diameter of 28 nm and remained for more than eight weeks.