Raman study ofCeO2: Second-order scattering, lattice dynamics, and particle-size effects

Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

“…The Raman spectrum of the ceria support, presented in Figure 2, shows a characteristic single, broad and intense band located at 465 cm −1 . This peak is assigned to the F 2g phonon mode of cubic fluorite CeO 2 [40,41]. This band was also detected in the Raman spectra for the ceria-supported cobalt spinel catalysts with the [42,43,44].…”

Influence of the nanoparticles agglomeration state in the quantum-confinement effects: Experimental evidences

“…The CeO 2 microparticles present a single active mode related to the symmetry F 2g at 464.5 cm-1 in good agreement with previously published data. 14 As can be seen in the figure 2(a), the Raman mode of the as received nanoparticles is located at 459 cm −1 and at 462.5 cm −1 for the dry dispersed nanoparticles. Both measurements present a clear shift in respect to the result obtained for microparticles, probably indicating that Raman quantization effect is taking place.…”

“…4 These new available vibration modes produce a strongly particle-size dependent displacement and broadening of the Raman spectrum, as previously described by H. Richter et al 6 The above mentioned quantum effects has been proposed as a tool to determine particles size by different analytical methods. 4,5 Nonetheless, there are many examples in the literature presenting a bad agreement between the particle size estimated from these calculations and the actual particle size measured by other methods. 5 One possible source of error that has not been thoroughly studied up to know (to the best of our knowledge) is the agglomeration state of the nanoparticles, which can produce an alteration of their properties due to the interparticles interactions and/or to surface modifications.…”

“…4,5 Nonetheless, there are many examples in the literature presenting a bad agreement between the particle size estimated from these calculations and the actual particle size measured by other methods. 5 One possible source of error that has not been thoroughly studied up to know (to the best of our knowledge) is the agglomeration state of the nanoparticles, which can produce an alteration of their properties due to the interparticles interactions and/or to surface modifications. In this work, we will study the effect of the agglomeration of nanoparticles in the quantum effect given in the Raman vibrational modes.…”

Techniques for the Study of the Structural Properties

“…600 cm -1 that can be related to a second-order phonon or a local mode centered on the vacancy positions. 63,75,78 The presence of second order peaks associated to nanostructured configurations has been also reported for ZrO 2 . 79 Observation of acoustic modes.…”