A coating composition is provided comprising a) an aqueous dispersion, having a pH of less than 7.5, of silica nanoparticles having average particle diameters of 40 nanometers or less, b) an alkoxysilane oligomer; c) a silane coupling agent, and d) optionally a metal β-diketone complexing agent. The compositions may be used to prepare coated articles wherein the coating is substantially uniform in thickness, durably adheres to the substrate, and provides hydrophilic and/or antireflection surface properties to the substrate.