Application of EPR spectroscopy for elucidation of vanadium speciation in VO x /ZrO2 catalysts subject to redox treatment

Adamski, Andrzej; Spałek, Tomasz; Sojka, Zbigniew

doi:10.1163/156856703322601807

Cited by 67 publications

(56 citation statements)

References 23 publications

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“…A sample of PTFE with 100% reflectance was used as reference. Electron Paramagnetic Resonance (EPR) spectra, recorded at 60 room temperature and at liquid nitrogen temperature, were run on a X-band CW-EPR Bruker EMX spectrometer equipped with a cylindrical cavity operating at 100 kHz field modulation and computer simulation of the spectra were obtained using the SIM32 programme developed by Prof. Sojka (Jagellonian University, Cracow, Poland 42 ). The XPS measurements were carried out in an ultrahigh vacuum system equipped with a VG MkII Escalab electron analyzer, working at a base pressure of 10 -10 mbar.…”

Section: Characterization Of Samplesmentioning

confidence: 99%

The interaction of oxygen with the surface of CeO₂–TiO₂mixed systems: an example of fully reversible surface-to-molecule electron transfer

Gionco

Giamello

Mino

et al. 2014

Phys. Chem. Chem. Phys.

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Mixed CeO 2 -TiO 2 systems have been synthesized using the sol-gel technique in a symmetric range of 5 nominal compositions (0.1, 0.5, 0.9 CeO 2 molar fraction respectively). The solid materials have been characterised using a variety of diffractometric and spectroscopic techniques. The intimate contact between the two components during the synthesis leads to heterogeneous systems which are based on the presence, beside the two individual oxide phases, of a mixed phase of a cerium titanate (Ce 2 Ti 2 O 7 , pyrochlore structure) which contains Ce 3+ ions imparting particular optical properties to the solid 10 (pronounced red shift with respect to the band gap transition of the two oxides). Ce 3+ ions are present at the surface of the systems together with tetravalent Ce and Ti ions. The mixed solids can be reduced by annealing under vacuum and, upon reoxidation in mild conditions with O 2 , form superoxide species adsorbed on Ce 4+ which have, as already reported for low loading CeO 2 -TiO 2 systems, peculiar spectroscopic properties with respect to superoxide adsorbed on bare cerium dioxide.

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Section: Characterization Of Samplesmentioning

confidence: 99%

The interaction of oxygen with the surface of CeO₂–TiO₂mixed systems: an example of fully reversible surface-to-molecule electron transfer

Gionco

Giamello

Mino

et al. 2014

Phys. Chem. Chem. Phys.

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“…Nuclear hyperfine coupling constants (HCCs) were confirmed following computer simulation using SimEPR32 software [22]. The relative concentrations of PBN adducts (expressed in arbitrary units), as opposed to absolute concentrations according to a calibration curve, were determined by measuring the mean signal intensity of each spectral peak-to-trough line height.…”

Section: Analysesmentioning

confidence: 99%

Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trial

et al. 2008

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Aims/hypothesis Patients with type 1 diabetes mellitus are more susceptible than healthy individuals to exercise-induced oxidative stress and vascular endothelial dysfunction, which has important implications for the progression of disease. Thus, in the present study, we designed a randomised doubleblind, placebo-controlled trial to test the original hypothesis that oral prophylaxis with vitamin C attenuates rest and exercise-induced free radical-mediated lipid peroxidation in type 1 diabetes mellitus. Methods All data were collected from hospitalised diabetic patients. The electron paramagnetic resonance spectroscopic detection of spin-trapped α-phenyl-tert-butylnitrone (PBN) adducts was combined with the use of supporting markers of lipid peroxidation and non-enzymatic antioxidants to assess exercise-induced oxidative stress in male patients with type 1 diabetes (HbA 1c 7.9±1%, n=12) and healthy controls (HbA 1c 4.6±0.5%, n=14). Following participant randomisation using numbers in a sealed envelope, venous blood samples were obtained at rest, after a maximal exercise challenge and before and 2 h after oral ingestion of 1 g ascorbate or placebo. Participants and lead investigators were blinded to the administration of either placebo or ascorbate treatments. Primary outcome was the difference in changes in free radicals following ascorbate ingestion. Results Six diabetic patients and seven healthy control participants were randomised to each of the placebo and ascorbate groups. Diabetic patients (n=12) exhibited an elevated concentration of PBN adducts (p<0.05 vs healthy, n=14), which were confirmed as secondary, lipid-derived oxygen-centred alkoxyl (RO·) radicals (a nitrogen =1.37 mT and aβ hydrogen =0.18 mT). Lipid hydroperoxides were also selectively elevated and associated with a depression of retinol and lycopene (p<0.05 vs healthy). Vitamin C supplementation increased plasma vitamin C concentration to a similar degree in both groups (p<0.05 vs presupplementation) and attenuated the exercise-induced oxidative stress response (p<0.05 vs healthy).There were no selective treatment differences between groups in the primary outcome variable. Conclusions/interpretation These findings are the first to suggest that oral vitamin C supplementation provides an Diabetologia

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“…Spectra simulations and fits were performed using the SIM 32 program. 47 ' RESULTS AND DISCUSSION Structural and Morphological Characterization. Figure 1 summarizes the TEM investigation performed on the anatase shape-controlled nanoparticles.…”

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confidence: 99%

Photogenerated Defects in Shape-Controlled TiO₂ Anatase Nanocrystals: A Probe To Evaluate the Role of Crystal Facets in Photocatalytic Processes

et al. 2011

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The promising properties of anatase TiO2 nanocrystals exposing specific surfaces have been investigated in depth both theoretically and experimentally. However, a clear assessment of the role of the crystal faces in photocatalytic processes is still under debate. In order to clarify this issue, we have comprehensively explored the properties of the photogenerated defects and in particular their dependence on the exposed crystal faces in shape-controlled anatase. Nanocrystals were synthesized by solvothermal reaction of titanium butoxide in the presence of oleic acid and oleylamine as morphology-directing agents, and their photocatalytic performances were evaluated in the phenol mineralization in aqueous media, using O2 as the oxidizing agent. The charge-trapping centers, Ti3+, O–, and O2 –, formed by UV irradiation of the catalyst were detected by electron spin resonance, and their abundance and reactivity were related to the exposed crystal faces and to the photoefficiency of the nanocrystals. In vacuum conditions, the concentration of trapped holes (O– centers) increases with increasing {001} surface area and photoactivity, while the amount of Ti3+ centers increases with the specific surface area of {101} facets, and the highest value occurs for the sample with the worst photooxidative efficacy. These results suggest that {001} surfaces can be considered essentially as oxidation sites with a key role in the photoxidation, while {101} surfaces provide reductive sites which do not directly assist the oxidative processes. Photoexcitation experiments in O2 atmosphere led to the formation of Ti4+–O2 – oxidant species mainly located on {101} faces, confirming the indirect contribution of these surfaces to the photooxidative processes. Although this work focuses on the properties of TiO2, we expect that the presented quantitative investigation may provide a new methodological tool for a more effective evaluation of the role of metal oxide crystal faces in photocatalytic processes.

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Application of EPR spectroscopy for elucidation of vanadium speciation in VO x /ZrO2 catalysts subject to redox treatment

Cited by 67 publications

References 23 publications

The interaction of oxygen with the surface of CeO₂–TiO₂mixed systems: an example of fully reversible surface-to-molecule electron transfer

The interaction of oxygen with the surface of CeO₂–TiO₂mixed systems: an example of fully reversible surface-to-molecule electron transfer

Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trial

Photogenerated Defects in Shape-Controlled TiO₂ Anatase Nanocrystals: A Probe To Evaluate the Role of Crystal Facets in Photocatalytic Processes

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Application of EPR spectroscopy for elucidation of vanadium speciation in VO x /ZrO2 catalysts subject to redox treatment

Cited by 67 publications

References 23 publications

The interaction of oxygen with the surface of CeO2–TiO2mixed systems: an example of fully reversible surface-to-molecule electron transfer

The interaction of oxygen with the surface of CeO2–TiO2mixed systems: an example of fully reversible surface-to-molecule electron transfer

Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trial

Photogenerated Defects in Shape-Controlled TiO2 Anatase Nanocrystals: A Probe To Evaluate the Role of Crystal Facets in Photocatalytic Processes

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The interaction of oxygen with the surface of CeO₂–TiO₂mixed systems: an example of fully reversible surface-to-molecule electron transfer

The interaction of oxygen with the surface of CeO₂–TiO₂mixed systems: an example of fully reversible surface-to-molecule electron transfer

Photogenerated Defects in Shape-Controlled TiO₂ Anatase Nanocrystals: A Probe To Evaluate the Role of Crystal Facets in Photocatalytic Processes