Presently described are (e.g. brightness enhancing film) optical articles comprising the reaction product of a polymerizable resin and surface modified inorganic nanoparticles, methods of surface modifying inorganic nanoparticles, and surface modified inorganic nanoparticles. The surface treatment comprises at least one monocarboxylic acid having a refractive index of at least 1.50 and/or at least one monocarboxylic acid having a Mn of at least 200 g/mole and an ethylenically unsaturated group and/or at least one dicarboxylic acid.