title: Electron energy-loss safe-dose limits for manganese valence measurements in environmentally relevant manganese oxides.
abstract: Manganese (Mn) oxides are among the strongest mineral oxidants in the environment and impose significant influence on mobility and bioavailability of redox-active substances, such as arsenic, chromium, and pharmaceutical products, through oxidation processes. Oxidizing potentials of Mn oxides are determined by Mn valence states (2+, 3+, 4+). In this study, the effects of beam damage during electron energy-loss spectroscopy (EELS) in the transmission electron microscope have been investigated to determine the "safe dose" of electrons. Time series analyses determined the safe dose fluence (electrons/nm(2)) for todorokite (10(6) e/nm(2)), acid birnessite (10(5)), triclinic birnessite (10(4)), randomly stacked birnessite (10(3)), and δ-MnO(2) (<10(3)) at 200 kV. The results show that meaningful estimates of the mean Mn valence can be acquired by EELS if proper care is taken.
authors.affiliation: The High-Resolution Analytical Electron Microbeam Facility of the Integrated Imaging Center Departments of Earth and Planetary Sciences and Biology, Johns Hopkins University, Baltimore, Maryland 21218, United States. klivi@jhu.edu
authors.forename: Kenneth J T
authors.initials: KJ
authors.lastname: Livi
authors.forename: Brandon
authors.initials: B
authors.lastname: Lafferty
authors.forename: Mengqiang
authors.initials: M
authors.lastname: Zhu
authors.forename: Shouliang
authors.initials: S
authors.lastname: Zhang
authors.forename: Anne-Claire
authors.initials: AC
authors.lastname: Gaillot
authors.forename: Donald L
authors.initials: DL
authors.lastname: Sparks
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D017895:Manganese Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D046590:Spectroscopy, Electron Energy-Loss / Q000379:methods*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide