XPS Study of the reduction of cerium dioxide

Roméo, M.; Bak, K.; Fallah, Jaâfar El; Normand, F. Le; Hilaire, L.

doi:10.1002/sia.740200604

Cited by 590 publications

(386 citation statements)

References 26 publications

(3 reference statements)

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“…Thermodynamic calculations were used to explain the significant loss of oxygen occurs during ablation of various transition-metal oxides [28,29], that were consistent with the formation of sub-stoichiometric metal oxides reported by Sol and Tilley. They noted color modifications of the surface when stoichiometric metal oxides were irradiated at 308 nm with laser irradiance in the 3.2 ϫ 10 5 Ϫ 1.4 ϫ 10 8 W/cm 2 range [30].…”

Section: Modification Of Surface Chemistry Under Photon Irradiationsupporting

confidence: 53%

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

Aubriet

Müller

2008

J. Am. Soc. Mass Spectrom.

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Laser ablation of transition-metal oxides have been investigated to better understand the formation processes of inorganic cluster ions. The study of binary oxide mixtures and the relative distribution of the ions produced suggest three salient mechanisms that occur after laser/matter interaction, that function to produce the observed ensemble of ionic species. Molecular recombination reactions, unimolecular dissociation processes, emission of small neutrals, including molecular oxygen from transition-metal oxide samples, or from species expelled in gas phase appear to be a significant mechanism, especially under high laser irradiance conditions. These processes are used to propose a set of pathways to rationalize the envelope of ionic clusters formed under photon bombardment. T he study of ion formation processes by mass spectrometry during inorganic compound laser ablation is not yet fully understood. However, several models have been proposed to describe and explain the laser ablation of inorganic compounds [1][2][3][4][5][6][7]. The interaction of a laser beam with a non-metallic solid induces different processes, leading to ejection of neutral and ionized species into the gas phase. Haglund proposed a qualitative description of these processes [7], which begins with the assumption that laser sputtering could be decomposed into four phases: (1) the absorption of laser energy by one or multiple-photon processes; (2) the conversion of the incident energy through radiative and non-radiative relaxation processes; (3) the ejection of species-atoms, molecules, neutrals, ions, excited species-from the irradiated surface; and (4) the formation and the expansion of a more or less dense plume of neutrals and ions. Two lasermatter interaction regimes have to be considered: the laser desorption (LD) and the laser ablation (LA). It is generally reported that LD results in emission of ions, atoms, and molecules without any substantial disturbance in the surrounding surface. LA implies a largescale disruption of surface and near-surface geometrical and electronic structure. These substantial qualitative differences allowed Haglung to identify desorption with a microscopic, and ablation with a mesoscopic view point. LD and LA have to be viewed as the extremes of a continuum, which ranges from the emission of isolated neutrals or ions in the case of LD to the massive removal of material resulting from the collective effects of multiple photons irradiating the same spatial locale in the case of LA. The phenomenology of LA is thought of in terms of formation of a plume of ejected species, which follows the laws of plasma and gas dynamics, and produces a large number of ionized species. Collisions of ions with neutrals occurring in the gas-phase plume after LA lead to ion-molecule condensation reactions. On the other hand, ions and neutrals possess a significant amount of energy, which can result in dissociation reactions. The length scale associated with laser ablation is on the order of d Х laser ϫv s , where laser is the dur...

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Section: Modification Of Surface Chemistry Under Photon Irradiationsupporting

confidence: 53%

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

Aubriet

Müller

2008

J. Am. Soc. Mass Spectrom.

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“…The spectra were decomposed to calculate Ce 3+ contribution. [12] Therefore, Ce 3+ percentage was calculated to be about 28% for P20C/Al 2 O 3 -La and 29% for P20C/Al 2 O 3 -Si. Lanthana-modified sample reduced at 800 • C and passivated with O 2 /He as described in the experimental section was also analyzed.…”

Section: Resultsmentioning

confidence: 96%

Origin of the redox deactivation phenomena in modified alumina‐supported Ce/Pr mixed oxide

Aboussaïd

Bernal

Blanco

et al. 2008

Surface & Interface Analysis

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However, at 900 • C, there is a decrease of OSC, which is moderate for silica-modified sample, while for lanthana-modified catalyst, the OSC is almost negligible. XPS analysis of the fresh samples shows that the redox state of cerium cations close to the surface is mainly +4, while praseodymium appears always as Pr 3+ . Samples reduced at different temperatures were also investigated by XPS. In the case of silica-modified alumina reduced at 900 • C, significant amounts of Ce 4+ can still be detected, which is in good agreement with the OSC value observed at that temperature. However, lanthana-modified sample reduced at 800 • C shows an important amount of Ce 3+ , being the only oxidation state observed for cerium after reduction at 900 • C. This is in good agreement with the strong drop in OSC observed for this latter sample, which can be thus attributable to the trapping of trivalent cations by the alumina, forming a stable perovskite-like aluminate, LnAlO 3 , as confirmed by X-Ray Diffraction (XRD).

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“…The binding energy of the Au (4f7/2) at 84.0±0.1 eV was used to calibrate the binding energy scale of the spectrometer, and ratios of Ce 3 þ and Ce 4 þ in the samples were determined. 62,63 Statistics. Results were collected from three or more independent experiments and are expressed as mean ± S.D.…”

Section: Methodsmentioning

confidence: 99%

Cerium oxide nanoparticles protect against Aβ-induced mitochondrial fragmentation and neuronal cell death

et al. 2014

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Evidence indicates that nitrosative stress and mitochondrial dysfunction participate in the pathogenesis of Alzheimer's disease (AD). Amyloid beta (Ab) and peroxynitrite induce mitochondrial fragmentation and neuronal cell death by abnormal activation of dynamin-related protein 1 (DRP1), a large GTPase that regulates mitochondrial fission. The exact mechanisms of mitochondrial fragmentation and DRP1 overactivation in AD remain unknown; however, DRP1 serine 616 (S616) phosphorylation is likely involved. Although it is clear that nitrosative stress caused by peroxynitrite has a role in AD, effective antioxidant therapies are lacking. Cerium oxide nanoparticles, or nanoceria, switch between their Ce 3 þ and Ce 4 þ states and are able to scavenge superoxide anions, hydrogen peroxide and peroxynitrite. Therefore, nanoceria might protect against neurodegeneration. Here we report that nanoceria are internalized by neurons and accumulate at the mitochondrial outer membrane and plasma membrane. Furthermore, nanoceria reduce levels of reactive nitrogen species and protein tyrosine nitration in neurons exposed to peroxynitrite. Importantly, nanoceria reduce endogenous peroxynitrite and Ab-induced mitochondrial fragmentation, DRP1 S616 hyperphosphorylation and neuronal cell death.

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XPS Study of the reduction of cerium dioxide

Cited by 590 publications

References 26 publications

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

Origin of the redox deactivation phenomena in modified alumina‐supported Ce/Pr mixed oxide

Cerium oxide nanoparticles protect against Aβ-induced mitochondrial fragmentation and neuronal cell death

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