Second harmonic generation studies of Fe(II) interactions with hematite (α-Fe2O3)

David S. Jordan, Christopher J. Hull, Julianne M. Troiano, Shannon C. Riha, Alex B.F. Martinson, Kevin M. Rosso, Franz M. Geiger*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Iron oxides are a ubiquitous class of compounds that are involved in many biological, geological, and technological processes, and the Fe(III)/Fe(II) redox couple is a fundamental transformation pathway; however, the study of iron oxide surfaces in aqueous solution by powerful spectroscopic techniques has been limited due to "strong absorber problem". In this work, atomic layer deposition (ALD) thin films of polycrystalline α-Fe 2O3 were analyzed using the Eisenthal χ(3) technique, a variant of second harmonic generation that reports on interfacial potentials. By determining the surface charge densities at multiple pH values, the point of zero charge was found to be 5.5 ± 0.3. The interaction of aqueous Fe(II) at pH 4 and in 1 mM NaCl with ALD-prepared hematite was found to be fully reversible and to lead to about 4 times more ferrous iron ions adsorbed per square centimeter than on fused-silica surfaces under the same conditions. The data are consistent with a recently proposed conceptual model for net Fe(II) uptake or release that is underlain by a dynamic equilibrium between Fe(II) adsorbed onto hematite, electron transfer into favorable surface sites with attendant Fe(III) deposition, and electron conduction to favorable remote sites that release and replenish aqueous Fe(II).

Original languageEnglish (US)
Pages (from-to)4040-4047
Number of pages8
JournalJournal of Physical Chemistry C
Issue number8
StatePublished - Feb 28 2013

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films


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