Synthesis and photoluminescence properties of layered oxides intercalated with Eu3+ ions by electrostatic self-assembly method using oxide nanosheets

Layered oxides intercalated with Eu ions were prepared by self-assembly deposition method based on the electrostatic interaction between negative charged oxide nanosheets and Eu ions. The layered oxides were composed of two-dimensional host nanosheet layer with guest Eu ions and gave Eu emission based on an energy transfer from bandgap excitation of the host oxide nanosheets to the Eu ions. The photoluminescence properties of the Eu ions were influenced by the type of nanosheet and the intercalated water molecules. Relatively-strong emission of Eu was observed from Eu-intercalated titanate layered oxide. The intensity of Eu emission increased with increasing the amount of intercalated water molecules. This indicates that the energy transfer from TiO2-δ nanosheet to Eu is promoted by the intercalated water molecules. In addition, the intensity of Eu emission was stronger at high pH than at low pH. This emission change is presumably due to two phenomena. One is a fine hydration state change of Eu in the interlayer, and the other is a change in energy transfer from the TiO2-δ nanosheet to Eu.