Electron Energy-Loss Safe-Dose Limits for Manganese Valence Measurements in Environmentally Relevant Manganese Oxides

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• 作者：Kenneth J. T. Livi ; Brandon Lafferty ; Mengqiang Zhu ; Shouliang Zhang ; Anne-Claire Gaillot ; Donald L. Sparks
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：January 17, 2012
• 年：2012
• 卷：46
• 期：2
• 页码：970-976
• 全文大小：359K
• 年卷期：v.46,no.2(January 17, 2012)
• ISSN：1520-5851

文摘

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 鈥渟afe dose鈥?of electrons. Time series analyses determined the safe dose fluence (electrons/nm²) for todorokite (10⁶ e/nm²), acid birnessite (10⁵), triclinic birnessite (10⁴), randomly stacked birnessite (10³), and 未-MnO₂ (<10³) at 200 kV. The results show that meaningful estimates of the mean Mn valence can be acquired by EELS if proper care is taken.