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@ARTICLE{berrck:859820,
      author       = {Überrück, Till and Neudert, Oliver and Kreuer,
                      Klaus-Dieter and Blümich, Bernhard and Granwehr, Josef and
                      Stapf, Siegfried and Han, Songi},
      title        = {{E}ffect of nitroxide spin probes on the transport
                      properties of {N}afion membranes},
      journal      = {Physical chemistry, chemical physics},
      volume       = {20},
      number       = {41},
      issn         = {1463-9084},
      address      = {Cambridge},
      publisher    = {RSC Publ.66479},
      reportid     = {FZJ-2019-00651},
      pages        = {26660 - 26674},
      year         = {2018},
      abstract     = {Nafion is the most common material used as a proton
                      exchange membrane in fuel cells. Yet, details of the
                      transport pathways for protons and water in the inner
                      membrane are still under debate. Overhauser Dynamic Nuclear
                      Polarization (ODNP) has proven to be a useful tool for
                      probing hydration dynamics and interactions within 5–8 Å
                      of protein and soft material surfaces. Recently it was
                      suggested that ODNP can also be applied to analyze surface
                      water dynamics along Nafion's inner membrane. Here we
                      interrogate the viability of this method for Nafion by
                      carrying out a series of measurements relying on 1H nuclear
                      magnetic resonance (NMR) relaxometry and diffusometry
                      experiments with and without ODNP hyperpolarization,
                      accompanied by other complementary characterization methods
                      including small angle X-ray scattering (SAXS), thermal
                      gravimetric analysis (TGA) of hydration, and proton
                      conductivity by AC impedance spectroscopy. Our comprehensive
                      study shows that commonly used paramagnetic spin
                      probes—here, stable nitroxide radicals—for ODNP, as well
                      as their diamagnetic analogues, reduce the inner membrane
                      surface hydrophilicity, depending on the location and
                      concentration of the spin probe. This heavily reduces the
                      hydration of Nafion, hence increases the tortuosity of the
                      inner membrane morphology and/or increases the activiation
                      barrier for water transport, and consequently impedes water
                      diffusion, transport, and proton conductivity.},
      cin          = {IEK-9},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IEK-9-20110218},
      pnm          = {135 - Fuel Cells (POF3-135)},
      pid          = {G:(DE-HGF)POF3-135},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:30320331},
      UT           = {WOS:000448665900063},
      doi          = {10.1039/C8CP04607G},
      url          = {https://juser.fz-juelich.de/record/859820},
}