Using ESR spectroscopy to study radical intermediates in proton-exchange membranes exposed to oxygen radicals

Using ESR spectroscopy to study radical intermediates in proton-exchange membranes exposed to... Direct ESR and spin-trapping experiments were used to study the behavior of Nafion, a perfluorinated ionomer membrane used in fuel cells, when exposed in the laboratory to oxygen radicals produced by Fenton and photo-Fenton reactions. DMPO (5,5-dimethyl-1-pyroline) was used as the spin trap. The results suggest that the two ESR methods provide complementary information on Nafion fragmentation. The presence of membrane-derived fragments was suggested indirectly by the presence of a broad signal (line width ≈ 84 G) after prolonged exposure of the membrane to the Fenton reagent based on Ti(III), and by the DMPO adduct of a carbon-centered radical in the spin-trapping experiments. The most convincing proof for the presence of perfluorinated radicals was obtained in Nafion membranes partially neutralized by Cu(II), Fe(II) and Fe(III) upon exposure to UV-irradiation in the presence or absence of H2O2 (photo-Fenton treatment). Identification of the chain-end radical RCF2CF 2 • with magnetic parameters different to those determined for the chain-end detected in γ-irradiated Teflon, was taken as evidence for the attack of reactive oxygen radicals on the side-chain of the membrane. Additional support for this suggestion was the detection of the “quartet” ESR signal assigned to the CF3C•O radical, and of the “quintet” ESR signal assigned to the radical centered at the intersection of the main and side chains. The limitations and advantages of each approach are discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Research on Chemical Intermediates Springer Journals

Using ESR spectroscopy to study radical intermediates in proton-exchange membranes exposed to oxygen radicals

Loading next page...
 
/lp/springer_journal/using-esr-spectroscopy-to-study-radical-intermediates-in-proton-aClKH1EgsI
Publisher
Springer Journals
Copyright
Copyright © 2007 by VSP
Subject
Chemistry; Catalysis; Physical Chemistry; Inorganic Chemistry
ISSN
0922-6168
eISSN
1568-5675
D.O.I.
10.1163/156856707782169372
Publisher site
See Article on Publisher Site

Abstract

Direct ESR and spin-trapping experiments were used to study the behavior of Nafion, a perfluorinated ionomer membrane used in fuel cells, when exposed in the laboratory to oxygen radicals produced by Fenton and photo-Fenton reactions. DMPO (5,5-dimethyl-1-pyroline) was used as the spin trap. The results suggest that the two ESR methods provide complementary information on Nafion fragmentation. The presence of membrane-derived fragments was suggested indirectly by the presence of a broad signal (line width ≈ 84 G) after prolonged exposure of the membrane to the Fenton reagent based on Ti(III), and by the DMPO adduct of a carbon-centered radical in the spin-trapping experiments. The most convincing proof for the presence of perfluorinated radicals was obtained in Nafion membranes partially neutralized by Cu(II), Fe(II) and Fe(III) upon exposure to UV-irradiation in the presence or absence of H2O2 (photo-Fenton treatment). Identification of the chain-end radical RCF2CF 2 • with magnetic parameters different to those determined for the chain-end detected in γ-irradiated Teflon, was taken as evidence for the attack of reactive oxygen radicals on the side-chain of the membrane. Additional support for this suggestion was the detection of the “quartet” ESR signal assigned to the CF3C•O radical, and of the “quintet” ESR signal assigned to the radical centered at the intersection of the main and side chains. The limitations and advantages of each approach are discussed.

Journal

Research on Chemical IntermediatesSpringer Journals

Published: Jan 1, 2007

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off