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Mossbauer
57Fe Mossbauer was conducted at 298 K on samples
prepared with and without DHP in the gel. In the case of sample prepared
with DHP, we found 3 species necessary to adequately fit the acquired
spectrum. These include superparamagnetic hematite,
Additionally, there appears to only be Fe3+ species
present. There is no resonance indicating the presence of six-line
magnetic SS such as large-grain Fe2O3.
The isomer shifts are all consistent with the presence of only
Fe3+ due to absence of resonance indicating the
presence of Fe2+ (significantly higher isomer shifts
and quadrupole splittings). The very low Fe content sample sprepared
without DHP exhibit low relative counts as expected. The presence of any
signal may indicate Fe sites due to binding directly to the mesoporous
silica. Only the amorphous phase was detected by XRD but any Fe phases
are likely below the detection limit.