Anomalous Tb3+ luminous spectrum in the TiO2 nanocrystals

In order to get Tb3+ luminescence in the TiO2 nanocrystals, nanoaggregate of terbium oxide in the TiO2 nanocrystal has been produced using a reverse micelles and solvothermal method in toluene solution. Transmission electron microscopy and X-ray diffraction measurements have identified particles with average size of 6.7-10.2 nm in the anatase phase corresponding to the sintering temperature. The time-resolved spectroscopic technique has been used for the measurement of luminescence spectra and decay curves. No emission from Tb3+ ions was observed from the sample with Tb3+ ions dispersed in TiO2. However, from the sample that terbium oxide is formed a colony of aggregates in the TiO2 solution strong emissions from 5D4 levels of Tb3+ ions were observed. The PL spectrum was very anomalous, extraordinarily it has a very strong emission band due to the transition of 5D4 → 7F2. It was proposed to describe anomalous spectrum that two kinds of energy migrations (5D4-7F6 and 5D4-7F2) are occurred among Tb3+ ions, and quenching centers located at the boundary of titanium oxide powerfully operate to higher energy.