Enhancement of the near-infrared emission in novel quantum cutting SiO_2:Tb^3+, Yb^3+ thin films by Ag species

Abstract

The SiO2: Tb, Yb thin films (or inverse opals) including Ag nanoparticles (NPs) were successfully synthesized by using the sol-gel method. The influence of Ag species on the photoluminescence (PL) property of SiO2: Tb, Yb, Ag material was investigated. Under 250 nm excitation, the visible-infrared (NIR) quantum cutting (QC) emission from Tb3+ and Yb3+ are greatly enhanced with formation of Ag NPs in SiO2 thin films. Meanwhile, an interesting broad excitation band which may be attributed to Ag nanoclusters of (Ag4)2+ tetramers is obtained by monitoring 977 nm emission of Yb3+. It is supposed that the (Ag4)2+ can pass energy to Yb3+ directly, where the energy transfer (ET) between (Ag4)2+ to the Yb3+ is suggested in a QC process. Moreover, we demonstrated that the Tb ions are required for the formation of the (Ag4)2+ in SiO2 glass hosts. In the SiO2: Tb, Yb, Ag inverse opals thin films, the QC emission intensity of Yb3+ is considerably improved by inhibiting the blue and green emission of Tb3+. The results demonstrated that the ET between Tb3+ and Yb3+ is enhanced. In addition, we not only observed the existence of (Ag4)2+, but also obtained ET from silver aggregates of (Ag2)+ to Tb3+ in the inverse opals under 377 nm excitation. The mechanism of visible-NIR QC emission of the SiO2: Tb, Yb, Ag films with inverse opal structure are discussed.