Iron oxide nanoparticles offer many beneficial photocatalytic properties. To both stabilize iron oxide in the presence of light and to harness a greater portion of the solar spectrum in regards to its photo-excitation we have utilized a synthetic protocol to decorate the iron oxide-storage protein, ferritin, with plasmonic gold nanoparticles (NPs).  We illustrate that these iron-gold ferritin proteins offer the photocatalytic benefits of iron oxide nanoparticles but are sensitized to visible light excitation via the presence of the plasmon associated with gold NPs. Apoferritin was loaded with different iron concentrations and, via photochemical synthesis, Au NPs were grown on the protein in the presence of aqueous sodium citrate. Transmission electron microscopy (TEM) and size exclusion chromatography (SEC) indicate that ~8-10 nm AuNPs were present exclusively on the exterior of the protein cage. The effect of AuNPs on the photochemistry of ferritin was investigated by quantifying iron release as a function of incident light wavelength. When exposed to full spectrum of simulated solar radiation (Xenon lamp) Ferritin and Au/Ferritin released 29 and 62% of their total Fe, respectively, for a similar exposure time. Importantly, when exposed to visible light (≥ 450 nm, via band pass filters) Fe release was 3.9 and 34%, respectively, indicating effective sensitization of the iron core. We also demonstrate that the Au/Ferritin photocatalyst was able to facilitate the environmentally important reduction of Cr(VI) when activated with visible light, while Au-free Ferritin was inactive under these conditions.

Photochemistry of gold Nanoparticle sensitized ferritin protein

254th National Meeting (2017)

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