Hematite and goethite are two common iron oxides important for environmental processes. In the presence of aqueous iron (II), iron oxide nanoparticles reduce oxidized environmental pollutants; Fe(II) in solution is oxidized to Fe(III) and incorporated into the bulk crystal. The new iron oxide layer may be of a different form than the original nanoparticle; goethite has been shown to grow on hematite nanoparticles, altering the reactivity of the nanoparticle. Previous work in the Penn group found that Natural Organic Matter (NOM) hinders the reduction of nitrobenzenes. To simplify the many functional groups in NOM, this study replaces NOM with catechol as surrogate organic matter (1,2-dihydroxybenzene). For the concentrations conducted in these experiments, roughly 15% of the catechol in solution binds to the nanoparticle surface. We have found that catechol in concentrations as low as 2uM decreases the reaction rate of hematite nanoparticles. XRD analysis is being performed to assess the effect of catechol on the phase identity of oxidative growth. Catechol concentrations of 20, 50, and 100 uM have been shown to slow the reaction rate of goethite nanoparticles. Particle measurements were performed using TEM to assess the location of oxidative growth. The observation of slowed reaction rates in both particles due to catechol suggests that catechol inhibits reactive sites on the nanoparticle surfaces.

Investigating the reactivity and growth of iron oxide nanoparticles using catechol

2019 Spring National Meeting

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