The Vibrational and Photoluminescence Properties of TiO$_2$ Nanoparticles Reacted with Eu$^{3+}$ Ions under Hydrothermal Conditions

TiO$_{2}$ has been shown to be an effective material for environmental purification and photocatalysis. The catalytic activity of TiO$_{2}$ nanoparticles (NPs) is enhanced due to the increase in the ratio of surface area to volume at the nano-scale. The enhancement of catalytic activity is further increased by the modification of the surface due to the adsorption of transition-metal ions on TiO$_{2}$ NPs. The reactivity of Eu$^{3+}$ ions with anatase TiO$_{2}$ nanoparticles under various pH and pressure-temperature (P-T) conditions in aqueous fluids has been investigated. A hydrothermal reactor was used to modify the surface of the TiO$_{2}$ nanoparticles with Eu$^{3+}$ ions in aqueous fluids at high P-T conditions. The Eu-reacted and untreated TiO$_{2}$ NPs were examined using XRD, SEM, and Raman and photoluminescence spectroscopy. The modifications of the vibrational and photoluminescence properties of the TiO$_{2}$ NPs due to the surface-adsorption of Eu$^{3+}$ ions are discussed.