Hollow silica nanoparticles can have well defined non-porous shells with low shell fragmentation and good dispersability. These well defined hollow particles can be formed through the controlled oxidation of silicon nanoparticles in an organic solvent. The hollow nanoparticles can have a submicron secondary particle sizes. The hollow silica nanoparticles can be incorporated into polymer composites, such as low index-of-refraction composites, for appropriate applications.