title: TEM preparation methods and influence of radiation damage on the beam sensitive CaCO3 shell of Emiliania huxleyi.
abstract: The ultrastructure of biologically formed calcium carbonate crystals like the shell of Emiliania huxleyi depends on the environmental conditions such as pH value, temperature and salinity. Therefore, they can be used as indicator for climate changes. However, for this a detailed understanding of their crystal structure and chemical composition is required. High resolution methods like transmission electron microscopy can provide those information on the nanoscale, given that sufficiently thin samples can be prepared. In our study, we developed sample preparation techniques for cross-section and plan-view investigations and studied the sample stability under electron bombardment. In addition to the biological material (Emiliania huxleyi) we also prepared mineralogical samples (Iceland spar) for comparison. High resolution transmission electron microscopy imaging, electron diffraction and electron energy-loss spectroscopy studies revealed that all prepared samples are relatively stable under electron bombardment at an acceleration voltage of 300 kV when using a parallel illumination. Above an accumulated dose of ∼10(5) e/nm2 the material--independent whether its origin is biological or geological--transformed to poly-crystalline calcium oxide.
authors.affiliation: Department of Earth and Environmental Sciences, LMU, 80333 Munich, Germany.
authors.forename: Ramona
authors.initials: R
authors.lastname: Hoffmann
authors.affiliation: Department of Chemistry, LMU, 81377 Munich, Germany.
authors.forename: Angela S
authors.initials: AS
authors.lastname: Wochnik
authors.affiliation: Department of Chemistry, LMU, 81377 Munich, Germany.
authors.forename: Sophia B
authors.initials: SB
authors.lastname: Betzler
authors.affiliation: Walter-Schottky-Institut, TUM, 85748 Garching, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Matich
authors.affiliation: Department of Earth and Environmental Sciences, LMU, 80333 Munich, Germany.
authors.forename: Erika
authors.initials: E
authors.lastname: Griesshaber
authors.affiliation: Department of Earth and Environmental Sciences, LMU, 80333 Munich, Germany.
authors.forename: Wolfgang W
authors.initials: WW
authors.lastname: Schmahl
authors.affiliation: Department of Chemistry, LMU, 81377 Munich, Germany. Electronic address: Christina.scheu@cup.uni-muenchen.de.
authors.forename: Christina
authors.initials: C
authors.lastname: Scheu
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry / Q000528:radiation effects*; D057231:Climate Change; D004583:Electrons / Q000009:adverse effects; D058087:Haptophyta / Q000737:chemistry / Q000528:radiation effects* / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission / Q000379:methods*
chemical_list: D002119:Calcium Carbonate
keywords: Calcium carbonate; Electron energy-loss spectroscopy; Emiliania huxleyi; Radiation damage; Sample preparation; Transmission electron microscopy