Spectroscopy Study on the Location and Distribution of Eu³⁺ Ions in TiO₂ Nanoparticles

Abstract

Eu 3þ -and non-doped TiO 2 nanoparticles were synthesized by the sol-gel method at sintering temperatures of 500 or 900 C. The photoluminescence spectra of these nanoparticles have been investigated at various temperatures between 290 and 12 K. Two kinds of Eu 3þ photoluminescence spectra were observed. One spectrum consists of sharp lines; the other consists of broad bands. The former was obtained by indirect excitation into Eu 3þ with light of wavelengths shorter than 330 nm, while the latter was obtained by direct excitation into Eu 3þ with light of wavelengths longer than 380 nm which correspond to the Eu 3þ absorption bands. In the latter case, different spectra were obtained depending on the excitation wavelength even in the same absorption band. It is suggested that the sharp line spectrum is caused by Eu 3þ ions substituted for Ti 4þ but with some distortion around the Eu 3þ ions in the matrix of TiO 2 due to the large difference in ionic radius between the Ti 4þ and Eu 3þ ions, which are mainly present in the interior region of the nanoparticle. The broad band spectrum is caused by the disordered Eu 3þ ions with Eu-O-Ti bonds which are predominantly present in the near surface region.

Narrow-linewidth red-emission Eu3+-doped TiO2 spheres for light-emitting diodes

“…Compared to the reported TiO 2 crystals, [41][42][43] the TiO 2 spheres synthesized in this work yield a larger band gap, which is consistent with the results from Pan and coworkers. 44 The larger band gap observed in our study is attributed to the amorphous phase of the TiO 2 particles, 45 as indicated in the XRD patterns. Thus, the 270 nm broad band absorption most possibly originates from the undoped TiO 2 spheres.…”

Hydrothermal Synthesis of Nb‐ and Eu‐ Co‐Substituted Nanocrystalline Anatase: EuxTi1–2xNbxO2 with Photoluminescence and Photocatalytic Activity: Compositional Dependence of Multifunctional Properties

“…On the other hand, substitution of TiO 2 with rare earth elements has recently attracted much attention . Some more studies on the photoluminescent materials based on TiO 2 nanocrystals have been reported as follows.…”

“…23 On the other hand, substitution of TiO 2 with rare earth elements has recently attracted much attention. [25][26][27][28][29] Some more studies on the photoluminescent materials based on TiO 2 nanocrystals have been reported as follows. Europium (Eu(III))-doped TiO 2 nanocrystals, which were synthesized via Ar/O 2 thermal plasma oxidizing mists of liquid precursors mists of Ti tetra-n-butoxide and Eu(III) nitrate, consisting of mixtures of the anatase (30-36 nm) and rutile (64-83 nm) polymorphs, showed bright red emissions either by exciting the TiO 2 host with UV light shorter than 405 nm or by directly exciting Eu(III) at a wavelength beyond the absorption edge (405 nm) of TiO 2 .…”

Emission-photoactivity cross-processing of mesoporous interfacial charge transfer in Eu3+ doped titania

“…Earlier studies have demonstrated that the Eu 3+ dopant is really incorporated within the sub-surface of the titania nanocrystallites. 8,[14][15][16][17][18][19][20] It thus could be used as a probe of the effects of interfacial charge transfer processes at semiconductor interfaces.…”