Silica nanoparticles are widely applied as fillers in silica-polymer nanocomposites. The most commonly used route for
synthesizing silica nanoparticles is sol-gel method due to its ability to produce monodispersed with narrow-size distribution
nanoparticles at mild conditions. However, a critical challenge in the preparation of nanocomposites is the homogeneity
in the mixing between the filler and organic components. This can be achieved through surface modification of silica by using silane-coupling agents. Other than applications covered in this paper, surface modification makes the possibility to graft or conjugate the nanostructured silica with polymers or proteins for future applications in biotechnology andmedicine such as dental filling composites, cancer treatment, and drug delivery.