Eu3+-Doped In2O3 Nanophosphors: Electronic Structure and Optical Characterization

Rare-earth ion-doped semiconducting nanocrystals have attracted extensive attention due to the ability to tailor their optical properties via size control and to achieve efficient luminescence through the host sensitization. A new type of nanophosphor based on Eu3+-ion-doped In2O3 nanocrystals, synthesized via a facile solvothermal method, shows intense and well-resolved intra4f emissions of Eu3+ upon bandgap excitation. Optical properties of Eu3+ occupying two crystallographic sites (C-2 and S-6) are systematically investigated by means of high-resolution emission and excitation spectra at 10-300 K. The crystal-field (CF) analysis and Judd-Ofelt (JO) intensity calculation of Eu3+ at C-2 site yield relatively large CF strength and JO intensity parameters, indicating the good optical performance of this nanophosphor. Due to a small filling factor (0.43) of the In2O3 nanocrystals, the radiative lifetime of D-5(0) of Eu3+ is found to be significantly affected by the surrounding media with various refractive indices, which is about 3 times longer than that in the submicrometer counterparts. Furthermore, as compared to the subrnicrometer counterparts, an enhanced host-to-Eu3+ energy transfer with higher quenching temperature is observed due to more effective photon-induced carrier localization and trapping around Eu3+ in nanocrystals.