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Title: Oxygen K-Edge Emission and Absorption Spectroscopy of Iron Oxyhydroxide Nanoparticles

Abstract

Transition metal oxide and oxyhydroxide nanoparticles are the focus of considerable current interest in geochemistry. Much progress has been made in understanding the structure and phase relationships in mineral nanoparticles, but the effects of small size and modified surface structure on reactivity remains an outstanding problem. Common environmental nanoparticles have been shown to exhibit enhanced chemical reactivity relative to bulk mineral surfaces, but the origin of this behavior is not well established. We studied the electronic structure component of mineral reactivity by comparing soft x-ray absorption and emission spectra of bulk goethite ({alpha}-FeOOH) with spectra obtained from {approx} 6 nm FeOOH nanoparticles and larger FeOOH nanoparticles obtained by hydrothermal coarsening. The semiconductor band gap is reduced in the FeOOH nanoparticles, mainly due to the presence of additional states in the upper valence band. We performed ab initio simulation of the electronic structure of oxygen sites at the 010 surface of goethite, and observe that oxygen sites with reduced metal coordination contribute to the O 2p DOS at higher binding energy. Hence we conclude that FeOOH nanoparticle surfaces are more disordered than the surfaces of goethite, and that this structural component is likely the dominant cause of enhanced rates of reductivemore » dissolution.« less

Authors:
;  [1];  [2]; ;  [3];  [4]
  1. Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
  2. Department of Physical Sciences, Chapman University, Orange, CA 92866 (United States)
  3. Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
  4. Chemical Sciences, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
21054729
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644643; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; BINDING ENERGY; ELECTRONIC STRUCTURE; EMISSION SPECTRA; GOETHITE; IRON; IRON HYDROXIDES; NANOSTRUCTURES; OXYGEN; PARTICLE SIZE; PARTICLES; REACTIVITY; SEMICONDUCTOR MATERIALS; SOFT X RADIATION; SURFACES; VALENCE; X-RAY SPECTRA

Citation Formats

Gilbert, Benjamin, Nico, Peter S., Kim, Christopher S., Dong, Chung-Li, Guo, Jinghua, and Shuh, David K. Oxygen K-Edge Emission and Absorption Spectroscopy of Iron Oxyhydroxide Nanoparticles. United States: N. p., 2007. Web. doi:10.1063/1.2644643.
Gilbert, Benjamin, Nico, Peter S., Kim, Christopher S., Dong, Chung-Li, Guo, Jinghua, & Shuh, David K. Oxygen K-Edge Emission and Absorption Spectroscopy of Iron Oxyhydroxide Nanoparticles. United States. doi:10.1063/1.2644643.
Gilbert, Benjamin, Nico, Peter S., Kim, Christopher S., Dong, Chung-Li, Guo, Jinghua, and Shuh, David K. Fri . "Oxygen K-Edge Emission and Absorption Spectroscopy of Iron Oxyhydroxide Nanoparticles". United States. doi:10.1063/1.2644643.
@article{osti_21054729,
title = {Oxygen K-Edge Emission and Absorption Spectroscopy of Iron Oxyhydroxide Nanoparticles},
author = {Gilbert, Benjamin and Nico, Peter S. and Kim, Christopher S. and Dong, Chung-Li and Guo, Jinghua and Shuh, David K.},
abstractNote = {Transition metal oxide and oxyhydroxide nanoparticles are the focus of considerable current interest in geochemistry. Much progress has been made in understanding the structure and phase relationships in mineral nanoparticles, but the effects of small size and modified surface structure on reactivity remains an outstanding problem. Common environmental nanoparticles have been shown to exhibit enhanced chemical reactivity relative to bulk mineral surfaces, but the origin of this behavior is not well established. We studied the electronic structure component of mineral reactivity by comparing soft x-ray absorption and emission spectra of bulk goethite ({alpha}-FeOOH) with spectra obtained from {approx} 6 nm FeOOH nanoparticles and larger FeOOH nanoparticles obtained by hydrothermal coarsening. The semiconductor band gap is reduced in the FeOOH nanoparticles, mainly due to the presence of additional states in the upper valence band. We performed ab initio simulation of the electronic structure of oxygen sites at the 010 surface of goethite, and observe that oxygen sites with reduced metal coordination contribute to the O 2p DOS at higher binding energy. Hence we conclude that FeOOH nanoparticle surfaces are more disordered than the surfaces of goethite, and that this structural component is likely the dominant cause of enhanced rates of reductive dissolution.},
doi = {10.1063/1.2644643},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}