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@ARTICLE{Wang:18219,
      author       = {Wang, W. and Dong, H. and Pacheco, V. and Willbold, D. and
                      Zhang, Y. and Offenhäusser, A. and Hartmann, R. and
                      Weirich, T. and Ma, P. and Krause, H. J. and Gu, Z.},
      title        = {{R}elaxation behavior study of ultra-small
                      superparamagnetic iron oxide nanoparticles at ultra-low and
                      ultra-high magnetic fields},
      journal      = {The journal of physical chemistry / B},
      volume       = {115},
      issn         = {1520-6106},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {PreJuSER-18219},
      pages        = {14789 - 14793},
      year         = {2011},
      note         = {We would like to thank F. Dorn for TEM imaging, J.
                      Bachhausen for IR measurements, and H. Lippert for the
                      ICP-OES measurements. This work is supported by the Research
                      Center Juelich, the China Scholarship Council (CSC), and the
                      German Helmholtz Association.},
      abstract     = {Ultrasmall superparamagnetic iron oxide nanoparticles
                      (USPIOs) have attracted attention because of their current
                      and potential usefulness as contrast agents for magnetic
                      resonance imaging (MRI) and nuclear magnetic resonance
                      (NMR). USPIOs are usually used for their significant
                      capacity to produce predominant proton relaxation effects,
                      which result in signal reduction. However, most previous
                      studies that utilized USPIOs have been focused on the
                      relaxation behavior at commonly used magnetic fields of
                      clinical MRI systems (typically 1-3 T). In this paper,
                      magnetic relaxation processes of protons in water
                      surrounding the USPIOs are studied at ultralow (≤10 mT)
                      and ultrahigh magnetic fields (14.1 T). USPIOs used in our
                      experiments were synthesized with a core size of 6 nm, and
                      transferred from organic to water by ligand exchange. The
                      proton spin-lattice relaxation time (T(1)) and spin-spin
                      relaxation time (T(2)) were investigated at ultralow (212
                      μT for T(2) and 10 mT for T(1)) and at 14.1 T with
                      different iron concentrations. At all of the fields, there
                      is a linear relationship between the inverse of relaxation
                      times and the iron concentration. The spin-spin relaxivity
                      (r(2)) at 14.1 T is much larger than that value of the
                      ultralow field. At ultralow field, however, the spin-lattice
                      relaxivity (r(1)) is larger than the r(1) at ultrahigh
                      field. The results provide a perspective on potential in
                      vivo and in vitro applications of USPIOs in ultralow and
                      ultrahigh field NMR and MRI.},
      keywords     = {Contrast Media: chemistry / Ferric Compounds: chemistry /
                      Magnetic Fields / Magnetite Nanoparticles: chemistry /
                      Solubility / Water: chemistry / Contrast Media (NLM
                      Chemicals) / Ferric Compounds (NLM Chemicals) / Magnetite
                      Nanoparticles (NLM Chemicals) / ferric oxide (NLM Chemicals)
                      / Water (NLM Chemicals) / J (WoSType)},
      cin          = {ICS-6 / PGI-8 / ICS-8},
      ddc          = {530},
      cid          = {I:(DE-Juel1)ICS-6-20110106 / I:(DE-Juel1)PGI-8-20110106 /
                      I:(DE-Juel1)ICS-8-20110106},
      pnm          = {Funktion und Dysfunktion des Nervensystems / Grundlagen
                      für zukünftige Informationstechnologien / BioSoft:
                      Makromolekulare Systeme und biologische
                      Informationsverarbeitung},
      pid          = {G:(DE-Juel1)FUEK409 / G:(DE-Juel1)FUEK412 /
                      G:(DE-Juel1)FUEK505},
      shelfmark    = {Chemistry, Physical},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:21972868},
      UT           = {WOS:000297608600051},
      doi          = {10.1021/jp2066138},
      url          = {https://juser.fz-juelich.de/record/18219},
}