Disclosed herein are compositions of metal oxide nanoparticles having regular polyhedral nanocavities, where the metal oxide can be titania, and where the nanoparticles be nanorods. Also disclosed are titania nanoparticles with nanocavities that are doped with dopants. Methods of making metal oxide nanoparticles with nanocavities are also disclosed. Also disclosed are ultraviolet-blocking compositions including metal oxide nanoparticles with nanocavities, as well as methods of enhancing ultraviolet absorbance efficiency of an ultraviolet blocking composition. Additional uses of metal oxide nanoparticles with nanocavities include solar energy conversion systems and lithium-ion batteries.
STATEMENT OF GOVERNMENT LICENSE RIGHTS
 The present invention was made with government support under contract number DE-AC02-98CH10886 awarded by the U.S. Department of Energy. The United States government has certain rights in the invention.