Europium‐Doped Mesoporous Titania Thin Films: Rare‐Earth Locations and Emission Fluctuations under Illumination

Abstract

Herein, Eu(III)-doped 3D mesoscopically ordered arrays of mesoporous and nanocrystalline titania are prepared and studied. The rare-earth-doped titania thin films-synthesized via evaporation-induced self-assembly (EISA)-are characterized by using environmental ellipsoporosimetry, electronic microscopy (i.e. high-resolution scanning electron microscopy, HR-SEM, and transmission electron microscopy, HR-TEM), X-ray diffraction, and luminescence spectroscopy. Structural characterizations show that high europium-ion loadings can be incorporated into the titanium-dioxide walls without destroying the mesoporous arrangement. The luminescence properties of Eu(III) are investigated by using steady-state and time-resolved spectroscopy via excitation of the Eu(III) ions through the titania host. Using Eu(III) luminescence as a probe, the europium-ion sites can be addressed with at least two different environments within the mesoporous framework, namely, a nanocrystalline environment and a glasslike one. Emission fluctuations ((5)D(0)-->(7)F(2)) are observed upon continuous UV excitation in the host matrix. These fluctuations are attributed to charge trapping and appear to be strongly dependent on the amount of europium and the level of crystallinity.

Synthesis and characterization of Eu3+, Ti4+@ ZnO organosols and nanocrystalline c-ZnTiO3thin films aiming at high transparency and luminescence

“…In these films, the ratio is about 6-8 (see figure 8). This is similar to the reported values (6)(7)(8)(9)(10)(11)(12) [39], indicating that Eu 3+ ions are located at a low-symmetry site lacking the inversion center, whether they are in the well-crystallized phase, in amorphous phase or in a site characteristic of small nanoparticles. The low site symmetry is confirmed also by the three peaks in the region of the 5 D 0 → 7 F 1 transition, indicating that the symmetry around the Eu 3+ ions is lower than, e.g.…”

Luminescence properties of europium titanate thin films grown by atomic layer deposition

“…Very similarly shaped PL spectra have also been observed before and been described as typical for a Eu 3+ doped disordered system. 10 Leroy et al 13 observed very similar spectra for PL from Eu 3+ doped mesoporous titania with the same gradual spectrum change accompanying the change from anatase to amorphous phase. Comparing the AFM images, XRD data, and PL spectra, there is a clear correlation between the amount of crystallites, the XRD peak intensities, and ratio between the two overlapping PL spectra.…”

“…The PL from the inlet strip of 10Eu also has a shape that is consistent with Eu 3+ doped anatase. 13,18 The PL from 80Eu has smeared out peaks which one can imagine arise from the continuous slight variation in the coordination environment for a cation in an amorphous oxide where the bond angles are varying. Very similarly shaped PL spectra have also been observed before and been described as typical for a Eu 3+ doped disordered system.…”

Sol–gel technique for the generation of europium-doped mesoporous and dense thin films: A luminescent study

“…Such systems developed by different groups [9][10][11][12][13][14] are very attractive materials for multiple domains of applications. Recently, we evidenced the locations adopted by the rare-earth ion within titania mesoporous thin films [15]. We have shown that rare-earth ions are well dispersed into two distinct phases of the titania pore wall structure framework.…”