Physical Aspects of Radiation-Induced Processes on SiO2, γ-Al2O3, Zeolites, and Clays

Thomas, Jayakar

doi:10.1021/cr020378a

Cited by 96 publications

(79 citation statements)

References 273 publications

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“…7 However no absorption assignable to the radical cation transient was detected between 300 nm and 800 nm, probably due to the low absorption in this spectral range and/or to its fast reaction, 20,41 in a time-range which is not detectable in our set-up. In all three solids under study, we were not able to confirm this pathway for the OH adduct formation.…”

Section: Reaction Pathwaysmentioning

confidence: 62%

Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces

Ferreira¹,

Machado²,

Silva

et al. 2006

Photochem Photobiol Sci

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This work reports the use of benzophenone, a very well characterized probe, to study new hosts: two reversed-phase silicas. Laser-induced room temperature luminescence of argon purged solid powdered samples of benzophenone adsorbed onto the two different reversed-phase silicas, RP-18 and RP-8, revealed the existence of a low energy emission band in contrast with the benzophenone adsorbed on 60 Å pore silica, where only triplet benzophenone emits. This low energy emission band was identified as the fluorescence of the ketyl radical of benzophenone, which is formed as the result of a hydrogen atom abstraction reaction of the triplet excited benzophenone from the alkyl groups of the surface of the reversed silicas. Such emission does not exist for benzophenone adsorbed onto 60 Å pore silica. Room temperature phosphorescence was obtained in argon purged samples for all the surfaces under use. The decay times of the benzophenone emission vary greatly with the alkylation of the silica surface when compared with "normal" silica surface. A lifetime distributions analysis has shown that the shortest lifetimes for the benzophenone emission exist in the former case. Triplet-triplet absorption of benzophenone was detected in all cases and is the predominant absorption in the case of 60 Å pore silica, while benzophenone ketyl radical formation occurs in the case of the reversed silicas. Diffuse reflectance laser flash photolysis and gas chromatography-mass spectrometry techniques provided complementary information, the former about transient species and the latter regarding the final products formed after laser irradiation, both at 266 nm or 355 nm. Product analysis and identification show that the degradation photoproducts are dependent on the excitation wavelength, the photochemistry being much more rich and complex in the 266 nm excitation case, where an a-cleavage reaction occurs. A detailed mechanistic analysis is proposed.

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Section: Reaction Pathwaysmentioning

confidence: 62%

Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces

Ferreira¹,

Machado²,

Silva

et al. 2006

Photochem Photobiol Sci

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“…Contrary to silica for which mostly excitonic chemistry is reported, both zeolites and -alumina (Al 2 O 3 ) exhibit an ionic surface chemistry [84]. In the case of zeolites, a very efficient charge separation takes place due to the presence of Na + and water clusters which are electron-trapping sites [85].…”

Section: Ste Excitonmentioning

confidence: 99%

Water Radiolysis: Influence of Oxide Surfaces on H2 Production under Ionizing Radiation

Caër

2011

Water

489

309

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Abstract:The radiolysis of water due to ionizing radiation results in the production of electrons, H  atoms,  OH radicals, H 3 O + ions and molecules (dihydrogen H 2 and hydrogen peroxide H 2 O 2 ). A brief history of the development of the understanding of water radiolysis is presented, with a focus on the H 2 production. This H 2 production is strongly modified at oxide surfaces. Different parameters accounting for this behavior are presented.

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“…The interface effect can thus hide the hypothetical generic confinement effect or finite size effect. This is typically what happens when the reactivity of a solvated electron in water is studied in a zeolite [6][7][8]. Zeolites are crystalline aluminosilicate nanoporous materials that are widely used as selective catalysts and adsorbents [9].…”

Section: Introductionmentioning

confidence: 99%

Confinement effect on the hydrated electron behaviour

Coudert

Boutin

2006

Chemical Physics Letters

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We report the first direct simulation of an excess hydrated electron confined in a zeolite nanopore by means of mixed quantum-classical molecular dynamics. The experimental dependence of the hydrated electron absorption spectrum maximum upon water loading in faujasites is reproduced. The diffusion of the confined hydrated electron is also studied and a prediction of the diffusion coefficient is provided.

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Physical Aspects of Radiation-Induced Processes on SiO₂, γ-Al₂O₃, Zeolites, and Clays

Cited by 96 publications

References 273 publications

Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces

Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces

Water Radiolysis: Influence of Oxide Surfaces on H2 Production under Ionizing Radiation

Confinement effect on the hydrated electron behaviour

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