Site selective excitation in La2O3:Eu3+ nanoparticles

Eu3+ is a favorite fluorescence probe for studying local structure in solids. In this report, Eu3+ ions in La2O3 nanoparticles were selectively excited; variation of the Eu emission spectra with the excitation wavelengths was observed. It was found that emission spectrum of the Eu ions near the center of the nanocrystals was similar to that of the bulk, where the Eu ions locate at the C3v symmetry site. By tuning the excitation wavelength, Eu ions in the vicinity of the particle surface may be selectively excited. A gradual variation in emission line positions was observed. Moreover, surface provided an additional non-radiative transition route for the rare-earth fluorescence, shortening the 5D0 lifetime from 1.25 to 0.87 ms