2D‐ and 3D‐Photoluminescence Imaging of Eu ( III ) Embedded in CeO ₂ Nanomatrix

Abstract

2D‐ and 3D‐photoluminescence characteristics of Eu ( III ) doped in CeO 2 nanoparticles were fully imaged for the first time. Their fundamental natures were also examined by scanning electron microscopy ( SEM ), X‐ray diffraction ( XRD ) crystallography, and UV –visible absorption spectroscopy. The magnetic dipole 5 D 0 → 7F 1 transition was dominated by an indirect transition associated with a O 2− – Ce 4+ charge‐transfer band of CeO 2 . The electric dipole 5 D 0 → 7 F 2 transition was dominated by a direct transition of Eu ( III ), indicating that Eu ( III ) replaces Ce ( IV ) at octahedral sites (O h and O) with and without an inversion center. Upon annealing, the photoluminescence intensity caused by direct transition was dramatically decreased, whereas that induced by indirect transition was greatly enhanced. These findings indicate that charge transfer to the Eu ( III ) at the octahedral (O h ) site with the inversion center is more efficient than that to the Eu ( III ) site without an inversion center. The absolute quantum yield for the 10 mol% Eu ( III )– CeO 2 was found to be ϕ = 0.007 at an excitation wavelength of 350 nm. The photoluminescence of Tb ‐doped CeO 2 was briefly discussed for comparison.