Correlation between the surface state and optical properties of S6 site and C2 site in nanocrystalline Eu3+:Y2O3

Eu3+ doped Y2O3 nanocrystals are synthesized via precipitation and hydrothermal methods. With the increase of hydrothermal temperature, the number of surface states decreases when nanorods are formed. The decrease of surface states induces the increase in the ratio of S6 site to C2 site, and meanwhile results in the spectral red-shift of charge transfer band as well as the enhancement of red emission. The results indicate that the surface states and optical properties have close correlations.

Research highlightsAs the main red emitting materials in commercial application on fluorescent lighting and displaying, trivalent europium-doped Y2O3 (Eu3+:Y2O3) has attracted much attention. It is well known that there exist two types of crystallographic sites in cubic Y2O3, S6 site and C2 site and it has been reported in several publications that the two sites have a close relationship. However, the correlation between the surface states and the optical properties of the two sites is still unclear. In this study, we prepared Eu3+ doped Y2O3 NCs with different crystallinity and surface states under different hydrothermal conditions followed by annealing. After studying the luminescent properties, including the charge transfer band (CTB) and red emission, we correlated the luminescent properties with the surface states of the NCs. This study provides a strong insightful explanation to the observed phenomena, and the results can shed light on the investigation of the influence of the surface states on the luminescence property of NCs.