Structure and photoluminescent properties of TiO$_2$:Eu$^{3+}$ nanoparticles synthesized under hydro and solvothermal conditions from different precursors

Crystalline phosphors of Eu$^{3+}$-doped titania (TiO$_2$:Eu$^{3+}$) were prepared by hydro and solvothermal synthesis with luminescent ion concentration of 2 mol.%. The structure and shape of the synthesized nanoparticles were characterized using X-ray powder diffraction, transmission electron microscopy, and Raman spectroscopy. Changes in the emission, excitation spectra, and the intensity decay of the photoluminescence for TiO$_2$:Eu$^{3+}$ nanoparticles were analyzed their phase composition. The photoluminescence of synthesized TiO$_2$:Eu$^{3+}$ crystalline phosphors depends on whether the said nanophosphors are formed from organometallic or inorganic precursors under hydro- and solvothermal conditions. Indeed, photoluminescence excitation at wavelengths ranging from 350–550 nm leads to splitting of electron dipole transitions into Stark components according to the symmetry of the Eu$^{3+}$ surroundings. Also, both nanoparticles with the anatase structure and phosphors predominantly containing rutile showed very short photoluminescence lifetimes.