Formation of luminescent centers in CeO2 nanocrystals

The nature of luminescence centers in CeO2 nanocrystals with varied oxygen stoichiometry has been investigated. It was shown that the luminescence of CeO2 is caused by the radiative relaxation in two different optical centers: the first one is Ce4+-O2− charge transfer state and the second one is Ce3+ ions. The ratio of Ce4+/Ce3+ centers depends on the amount of oxygen vacancies, therefore the variation of ceria stoichiometry allows changing the concentration of Ce4+-O2− and Ce3+ luminescence centers. Analysis of splitting of the excitation bands of Ce3+ luminescence has shown that oxygen vacancies in CeO2 nanocrystals are formed at the nearest-neighbor position to the cerium ion.