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Spatially Resolved Energy Electron Loss Spectroscopy Studies of Iron Oxide Nanoparticles

Published online by Cambridge University Press:  23 August 2006

Jacek Jasinski ,
Kent E. Pinkerton ,
I.M. Kennedy  and
Valerie J. Leppert
Jacek Jasinski
Affiliation:
School of Engineering, University of California, Merced, CA 95344, USA
Kent E. Pinkerton
Affiliation:
Center for Health and the Environment, University of California, Davis, CA 95616, USA
I.M. Kennedy
Affiliation:
Department of Mechanical and Aeronautical Engineering, University of California, Davis, CA 95616, USA
Valerie J. Leppert
Affiliation:
School of Engineering, University of California, Merced, CA 95344, USA
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Abstract

The oxidation state of iron oxide nanoparticles co-generated with soot during a combustion process was studied using electron energy-loss spectroscopy (EELS). Spatially resolved EELS spectra in the scanning transmission electron microscopy mode were collected to detect changes in the oxidation state between the cores and surfaces of the particles. Quantification of the intensity ratio of the white lines of the iron L-ionization edge was used to measure the iron oxidation state. Quantitative results obtained from Pearson's method, which can be directly compared with the literature data, indicated that the L3 /L2-intensity ratio for these particles changes from 5.5 ± 0.3 in the particles' cores to 4.4 ± 0.3 at their surfaces. This change can be directly related to the reduction of the iron oxidation state at the surface of the particles. Experimental results indicate that the cores of the particles are composed of γ-Fe2O3, which seems to be reduced to FeO at their surfaces. These results were also supported by the fine structure of the oxygen K-edge and by the significant chemical shift of the iron L-edge.

Keywords

EELSSTEMnanoprobenanoparticlesiron oxideionization edgeswhite linesoxidation state
Type
MICROANALYSIS
Information
Microscopy and Microanalysis , Volume 12 , Issue 5 , October 2006 , pp. 424 - 431
Copyright
© 2006 Microscopy Society of America

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