High-Resolution Spectroscopy of Europium-Doped Ceria as a Tool To Correlate Structure and Catalytic Activity

Abstract

Site-selective emission spectra of Eu 3+ -doped CeO 2 nanoparticles up to the 5 D 0 − 7 F 5 transition were recorded under cryogenic conditions to identify the local structure around the Eu 3+ dopants in ceria. It is found that pretreatment conditions are crucial for the redistribution of dopants from a broad variety of environments to six well-defined lattice sites. The influence of the dopant and the host structure on the catalytic activity was investigated. A relationship between structure and reactivity is discussed. It is shown that oxygen transport is most efficient in particles with a pronounced amorphous character.

Tracking the Motion of Lanthanide Ions within Core–Shell–Shell NaYF4 Nanocrystals via Resonance Energy Transfer

“…High-resolution luminescence experiments were performed using Eu 3+ as an optical probe in order to complement the XRD data. , Especially for the low dopant concentrations of Eu 3+ , the detection of slight differences in the lattice (or the formation of a separate phase) can be demanding and the use of high-resolution luminescence data at ultralow temperature yields additional structural information related to the location of the Eu 3+ ions in the lattice. ,, A typical total luminescence spectrum recorded at T = 4 K is shown in Figure together with selected spectral traces for emission (top) and excitation spectra (right), respectively. The respective luminescence bands resulting from the 5 D 0 → 7 F j transition ( j = 0, 1, 2) and the 5 D 1 → 7 F 3 are shown.…”

Europium-Doped Ceria–Gadolinium Mixed Oxides: PARAFAC Analysis and High-Resolution Emission Spectroscopy under Cryogenic Conditions for Structural Analysis

“…In the former case, there is excitation of one of the many f–f absorption bands Eu 3+ exhibits in the UV–vis spectral range, for example, the 7 F 0 – 5 D 2 transition around 464 nm (we used this transition in our room temperature measurements) and 7 F 0 – 5 D 0 transition around 580 nm, which is used for site-selective excitation with a narrow-bandwidth laser source (we used this transition in our ultralow temperature measurements, vide infra). Indirect excitation of Eu 3+ -doped ceria via the Ce 4+ –O 2– charge transfer (CT) band (λ ex = 280–375 nm) results in a sensitization of Eu 3+ dopants by ceria …”

“…Upon doping ceria with lanthanide ions, the site preference of oxygen vacancies as the nearest neighbor (NN) or next-nearest neighbor (NNN) to the dopant ion is determined by the strength and nature of their interaction, both of which rely on dopant ion size. Thus, lanthanides with ionic radii greater than Gd 3+ , such as Eu 3+ (0.1066 nm), , favor the oxygen vacancy in the NNN position, while those smaller than Gd 3+ favor the NN position. ,, …”

“…Thus, lanthanides with ionic radii greater than Gd 3+ , such as Eu 3+ (0.1066 nm), 16,17 favor the oxygen vacancy in the NNN position, 18 while those smaller than Gd 3+ favor the NN position. 14,19,20 Doping is often used to tailor the properties of ceria for different applications, such as the introduction of luminescence properties. Sorbello et al 20 studied the structural variation of Ce−Gd−Eu 3+ oxide phosphors at a fixed Eu 3+ doping of 5 mol % with respect to the application as a bioprobe and concluded that up to a molar fraction of 20% Gd 3+ in the host lattice, a cubic structure was found to be stable (space group Fm3̅ m).…”

Enhancing the dual magnetic and optical properties of co-doped cerium oxide nanostructures

“…The intensity ratio between I( 5 D 0 -7 F 2 )/I( 5 D 0 -7 F 1 ) known as asymmetry ratio (R) is sensitive to the local symmetry environment around Eu 3+oxygen coordination and have low value for high local symmetry around Eu 3+ ion. 35,36 The calculated R value was 0.9 and 0.76 for EFC9 on excitation at 330 and 466 nm, respectively. Relatively low value of R than that reported in the literature indicated the presence of Eu 3+ in high symmetry with inversion centre.…”