10.1021/jp3113057.s001
David
S. Jordan
David
S.
Jordan
Christopher J. Hull
Christopher J.
Hull
Julianne M. Troiano
Julianne M.
Troiano
Shannon C. Riha
Shannon C.
Riha
Alex B. F. Martinson
Alex
B. F. Martinson
Kevin M. Rosso
Kevin M.
Rosso
Franz M. Geiger
Franz M.
Geiger
Second Harmonic Generation
Studies of Fe(II) Interactions
with Hematite (α-Fe<sub>2</sub>O<sub>3</sub>)
American Chemical Society
2013
4 times
pH 4
2O
transformation pathway
ferrous iron ions
spectroscopic techniques
iron oxide surfaces
electron transfer
1 mM NaCl
Fe
ALD
Second Harmonic Generation Studies
pH values
surface sites
electron conduction
layer deposition
square centimeter
surface charge densities
2013-02-28 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Second_Harmonic_Generation_Studies_of_Fe_II_Interactions_with_Hematite_Fe_sub_2_sub_O_sub_3_sub_/2439487
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<sub>2</sub>O<sub>3</sub> were
analyzed using the Eisenthal χ<sup>(3)</sup> 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).