Disclosed are metal phosphate sols made by mixing at least one metal oxide, at least one phosphate precursor, at least one organosilane, and a liquid. Also disclosed are nanocomposites containing the metal phosphate sols and at least one of metal nanoparticle and metal-chalcogenide nanoparticle. The nanocomposites containing metal nanoparticles may be chalcogenized to provide nanocomposites containing metal-chalcogenide nanoparticles. Also disclosed are composites containing a dielectric material such as a polymer and at least one of the metal phosphate sol and the nanocomposite.