Document Detail


Spontaneous charge separation induced by phenothiazine sorption within acidic H(n)ZSM-5.
MedLine Citation:
PMID:  19458831     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
In situ diffuse reflectance UV-visible, Raman scattering and EPR experiments, carried out as a function of time after phenothiazine (PTZ) direct exposure to thermally activated acid H(n)ZSM-5 zeolite without any solvent, provide evidence of phenothiazine sorption and simultaneous spontaneous ionization. For comparison, phenothiazine behavior was investigated within non acidic zeolite and showed that most of the phenothiazine molecules were occluded as intact molecules and that ionization was very weak. The multivariate curve resolution analysis of the diffuse reflectance UV-visible spectra set recorded during the sorption process resolve the absorption spectra and respective concentrations of individual species involved in the sorption course. When PTZ entered through the acidic zeolite channels, PTZ (+)@H(n)ZSM-5 (-) radical pair is generated by the polarization energy. Subsequent PTZ(2+) formation was fast but only partial. After months, equilibrium including PTZ (+), PTZ(2+) and occluded PTZ was reached within acid H(n)ZSM-5 but depends on the Si/Al ratio: the higher the Al content, the easier the spontaneous ionization. The close match between PTZ and the pore size of zeolites combined with efficient polarizing effect of proton and aluminium electron trapping sites appear to be the most important factors responsible for the stabilization of PTZ (+) and PTZ(2+) and hinder efficiently the charge recombination. No evidence of Brønsted acid sites of H(n)ZSM-5 was found during the sorption of phenothiazine through generation of protonated species.
Authors:
A Moissette; F Luchez; C Brémard; H Vezin; M Hureau
Publication Detail:
Type:  Journal Article     Date:  2009-04-16
Journal Detail:
Title:  Physical chemistry chemical physics : PCCP     Volume:  11     ISSN:  1463-9076     ISO Abbreviation:  Phys Chem Chem Phys     Publication Date:  2009 Jun 
Date Detail:
Created Date:  2009-05-21     Completed Date:  2009-07-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100888160     Medline TA:  Phys Chem Chem Phys     Country:  England    
Other Details:
Languages:  eng     Pagination:  4286-97     Citation Subset:  IM    
Affiliation:
Laboratoire de Spectrochimie Infrarouge et Raman UMR-CNRS 8516, Centre d' Etudes et de Recherches Lasers et Applications, FR-CNRS 2416, Bât. C5 Université des Sciences et Technologies de Lille, 59655, Villeneuve d'Ascq cedex, France.
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MeSH Terms
Descriptor/Qualifier:
Absorption
Diffusion
Electron Spin Resonance Spectroscopy
Electrons
Hydrogen-Ion Concentration
Models, Molecular
Molecular Conformation
Phenothiazines / chemistry*
Porosity
Spectrophotometry, Ultraviolet
Spectrum Analysis, Raman
Water / chemistry
Zeolites / chemistry*
Chemical
Reg. No./Substance:
0/Phenothiazines; 1318-02-1/Zeolites; 7732-18-5/Water; 92-84-2/phenothiazine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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