The present disclosure relates to surface-modified zirconia nanoparticles, methods for making and using the same, and high index of refraction films made therefrom. The provided zirconia nanoparticles are surface modified with ligands that include N-hydroxyurea functionalities. The provided ligands also can contain compatibilizing groups that allow the provided surface-modified zirconia nanoparticles to be incorporated into an organic matrix. High index of refraction films can be made using these organic matrices.