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Long-lived electron–hole pair formation through photoionization of diphenylacetylene occluded in medium pores of aluminum rich M6.6ZSM-5 zeolite (M = Li+, Na+, K+, Rb+, Cs+): Influence of the counterbalancing cations on the recombination rate

Paper ID Volume ID Publish Year Pages File Format Full-Text
27829 44044 2009 10 PDF Available
Title
Long-lived electron–hole pair formation through photoionization of diphenylacetylene occluded in medium pores of aluminum rich M6.6ZSM-5 zeolite (M = Li+, Na+, K+, Rb+, Cs+): Influence of the counterbalancing cations on the recombination rate
Abstract

Diffuse reflectance UV–vis and Raman spectroscopies show complete sorption of neutral diphenylacetylene (DPA) in the void space of M6.6ZSM-5 zeolites (M = Li+, Na+, K+, Rb+, Cs+) after several months of exposure of solid DPA to empty zeolite at room temperature. After a long organization period, the laser photolysis of DPA occluded in M6.6ZSM-5 generates long-lived DPA+ radical cation as primary phenomenon. Charge recombination occurs mainly through electron transfer and DPA@M6.6ZSM-5−+ electron–hole pair formation. This subsequent electron transfer takes place between the electron deficient radical cation DPA+ and the electron donor oxygen atom of zeolite framework. The multivariate curve resolution analysis of the DRUVv spectra recorded during the reaction sequence including charge separation, electron transfer and charge recombination provide the specific absorption spectra and respective spectral concentrations of all species as function of time. The DRUVv spectrum assigned to the long-lived DPA@M6.6ZSM-5−+ electron–hole pair exhibits broad bands between 450 and 550 nm. The electron–hole pair recombination depends on M+ and appears to be in relation with the electron donor properties of the framework. The charge recombination rate decreases in the order Cs+ > Rb+ ∼ K+ > Na+ > Li+. The electron–hole pair lifetime exceeds several hours at room temperature. The stabilization of DPA+-electron pair and DPA@M6.6ZSM-5−+ electron–hole pair depends on the combined effects of confinement which dramatically reduces the DPA mobility in the zeolite void space and on the intrazeolithe electrostatic field of DPA@MnZSM-5 (M = Li+, Na+, K+, Rb+, Cs+).

Keywords
ZSM-5; Diphenylacetylene; Charge separation; Photoionization; Diffuse reflectance UV–vis spectrometry; Kinetic
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Long-lived electron–hole pair formation through photoionization of diphenylacetylene occluded in medium pores of aluminum rich M6.6ZSM-5 zeolite (M = Li+, Na+, K+, Rb+, Cs+): Influence of the counterbalancing cations on the recombination rate
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 208, Issues 2–3, 15 December 2009, Pages 203–212
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
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