Spectroscopic studies of electron trapping by sodium cationic clusters in zeolites

Iu, Kai Kong; Liu, Xinsheng; Thomas, J. K.

doi:10.1021/j100133a009

Cited by 44 publications

(25 citation statements)

References 2 publications

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“…These bands are almost identical with the reference spectra of trapped electrons which are stabilized as Na 4 3+ , Na 3 2+ , or Na 2 + in zeolites. 3,23,24 It is reported that the bands around 550 nm and above 750 nm are ascribed to Na 4 3+ and Na 2 + , respectively. 3,23,24 Furthermore, it is known that Na 3 2+ has an absorption peak at about 680 nm.…”

Section: Resultsmentioning

confidence: 99%

“…3,23,24 It is reported that the bands around 550 nm and above 750 nm are ascribed to Na 4 3+ and Na 2 + , respectively. 3,23,24 Furthermore, it is known that Na 3 2+ has an absorption peak at about 680 nm. Therefore, the main species of NaX/300 °C and NaA/300 °C excited by 248 nm laser differ and the long wavelength component of NaX/300 °C may be related to the main species of NaA/300 °C.…”

Section: Resultsmentioning

confidence: 99%

“…[11][12][13][14][15][16][17][18][19] Radiation effects upon zeolites without adsorbates have also recieved much attention in photochemistry and radiation chemistry, since they are expected to provide useful information on the catalytic nature of zeolites and also may contribute to improve their properties. Of these, radiation-and photoinduced generation of trapped electrons is a representative process studied by many research groups, [20][21][22][23][24][25][26] because this is one of the important processes to understand dynamic behavior occurring in zeolites. Production of trapped electrons means that the effective polarity inside zeolites is high.…”

Section: Introductionmentioning

confidence: 99%

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Nanosecond Electron Transfer Dynamics between Traps in Zeolites Studied by Double-Pulse Excitation Diffuse Reflectance Spectroscopy

et al. 1997

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The 248 nm excitation of zeolites results in the formation of trapped electrons which are very sensitive to photoexcitation and the amount of water contained in zeolites. Na 4 3+ , Na 3 2+ , and Na 2 + , which are prepared by 248 nm single-photon excitation, are directly confirmed as electron trapping states by nanosecond diffuse reflectance spectroscopy. Their stability decreases in the order of Na 4 3+> Na 3 2+ < Na 2 + in terms of the observed lifetimes of these trapped species. Water accelerates recombination between trapped electrons and the electron-ejected sites in the zeolite frameworks. Photoinduced conversion processes between these ion clusters were measured directly by double-pulse excitation experiments.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nanosecond Electron Transfer Dynamics between Traps in Zeolites Studied by Double-Pulse Excitation Diffuse Reflectance Spectroscopy

et al. 1997

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“…Previous studies dealing with the radiolysis of zeolites with adsorbed water agree to the point that irradiation of the solid matrices of the zeolites induces decomposition of water in the pores resulting in H 2 production. − The energy/charge transfer from the zeolites was confirmed by pulse radiolysis studies of excess electrons in hydrated zeolites. − The pulse radiolysis studies concluded that generation of excess electrons hydrated in the zeolite pores occurred at yields greater than hydrated electron (e – aq ) during the radiolysis of bulk water. The high yields of e – aq would qualitatively explain the H 2 production by the irradiation of hydrated zeolites because e – aq is a main precursor of H 2 in water radiolysis. , However, understanding radiation-induced reactions in zeolites is not sufficient to estimate the yield of H 2 because the reaction scheme of H 2 production is not well-defined .…”

Section: Introductionmentioning

confidence: 74%

Hydrogen Production by γ-Ray Irradiation from Different Types of Zeolites in Aqueous Solution

et al. 2017

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Dihydrogen (H 2 ) production via irradiation of zeolite−water mixtures was studied to investigate the effect of zeolites on the reaction process for H 2 production. Four types of zeolites were comparatively examined under anoxic and aerated conditions. High yields of H 2 were observed for the zeolites with high aluminum contents, A-type and X-type zeolites, compared to the Y-type and mordenite-type zeolites. The difference in the H 2 yields was considerable at weight fractions of water below 50 wt % under anoxic conditions. The experimental results demonstrated a reaction pathway for H 2 production that has different yields between the four zeolites. The H 2 yields were compared with chemical analyses of the zeolites, and the comparison suggested that the extraframework aluminum species in the zeolites are involved in the reaction pathway for H 2 production. On the other hand, under aerated conditions, the H 2 yields from the zeolites were lower than under anoxic conditions probably due to the H 2 O 2 that was produced by water radiolysis. Moreover, the difference between the zeolites in H 2 yields was suppressed at water fractions above 50 wt %. The comparable H 2 yields suggested yet another reaction pathway for H 2 production that is less affected by the structure and composition of the zeolites.

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“…The broad absorption band from 550 to 700 nm was assigned to Na 4 3+ . This species is formed when cationic sodium clusters, which are present within the cage as charge‐balancing counterions, trap an electron (37). The observation of Na 4 3+ is further evidence for the formation of the phenoxyl radical via photoejection of an electron.…”

Section: Resultsmentioning

confidence: 99%

Reducing Adverse Effects from UV Sunscreens by Zeolite Encapsulation: Comparison of Oxybenzone in Solution and in Zeolites

Chrétien

Heafey

Scaiano

2010

Photochem & Photobiology

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Oxybenzone (OXB) is one of the most widely employed sunscreen ingredients, yet its allowed load is limited to a maximum of 6% reflecting the frequency with which adverse effects are reported. From a spectroscopic point of view, OXB has excellent absorption properties in both the UVB and UVA regions. We propose that zeolite encapsulation can lead to a sunscreen composite ingredient, that we describe as a supramolecular sunscreen, that will retain the excellent spectroscopic properties of OXB, while preventing contact between the skin and the active ingredient. OXB is very photostable, with the only photodegradative pathway observed being the monophotonic photoejection of electrons that leads to trace yields of phenoxyl radicals; this trace reaction is so minor that it cannot be detected from the recovery of unreacted OXB following UV exposure. Solution, as well as powder and in vitro studies of the supramolecular sunscreen, demonstrate that the protective properties of OXB are totally preserved when encapsulated in zeolite NaY.

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Spectroscopic studies of electron trapping by sodium cationic clusters in zeolites

Cited by 44 publications

References 2 publications

Nanosecond Electron Transfer Dynamics between Traps in Zeolites Studied by Double-Pulse Excitation Diffuse Reflectance Spectroscopy

Nanosecond Electron Transfer Dynamics between Traps in Zeolites Studied by Double-Pulse Excitation Diffuse Reflectance Spectroscopy

Hydrogen Production by γ-Ray Irradiation from Different Types of Zeolites in Aqueous Solution

Reducing Adverse Effects from UV Sunscreens by Zeolite Encapsulation: Comparison of Oxybenzone in Solution and in Zeolites

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