Techniques to identify processes related to the biogeochemistry of iron

Theme 4

MagnetosomesFor assessing the functions of iron minerals in biogeochemical processes it is important to identify the mineral species and to understand its physical and chemical properties. Several iron oxide and oxyhydroxide, as well as sulfide species have similar structures and little compositional differences. In addition, these minerals are typically nanocrystalline, making their proper characterization difficult.

Several microscopic and spectroscopic techniques are available for characterizing iron mineralogy and morphology.

  • Atomic force microscopy may be used for observing structural changes of individual iron crystals during Fe redox reactions.
  • Synchrotron based spectroscopic techniques (e.g., XAFS, XANES) potentially offer highly resolved mineralogy information.
  • Electron microscopy (SEM and TEM) provides imaging capabilities for evaluating changes in particle morphology and estimating particle sizes.
  • Transmission electron microscopy is uniquely suitable for studying the properties of nanocrystalline iron minerals, since it includes a combination of imaging, diffraction, and spectroscopic techniques.
  • In combination with high-resolution images, electron diffraction can be used for identifying the structures of the iron minerals.
  • Energy-dispersive X-ray spectrometry and electron energy-loss spectroscopy are used for quantitative analyses of individual nanoparticles.
  • Advanced TEM techniques include off-axis electron holography that can be used to quantitatively measure the magnetic moments and to study the magnetic microstructures of both individual particles and their assemblages.

Research Theme 4 supports activities aimed at disseminating existing knowledge on how to identify and characterize nanocrystalline iron minerals.

In addition, we aim at developing new procedures and applying advanced TEM techniques for the study of magnetic properties and atomic-scale compositional and structural features of iron minerals.

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last modified 2010-03-05