Photochemistry of ferritin decorated with plasmonic gold nanoparticles

The photochemistry of a plasmonic biomaterial that consisted of gold nanoparticles (AuNP) on the exterior of the iron sequestration protein, ferritin (Ftn), was investigated. The light driven photochemistry of the hybrid system was studied mechanistically and for the reduction of the high priority pollutant, chromate, Cr(VI) as CrO42-. In the absence of aqueous Cr(VI), but in the presence of a sacrificial electron donor, the Fe(III) oxyhydroxide semiconducting core of Ftn underwent a photoreaction to release Fe(II) when exposed to light having wavelengths, lambda < 475 nm. AuNP grown on the exterior of the Ftn produced plasmonic heterostructures (Au/Ftn) that allowed similar photochemistry to occur at longer wavelengths of light (i.e., lambda > 475 nm). Au/Ftn also facilitated the reduction of Cr(VI) to Cr(III) in the presence of visible light (lambda > 475 nm), a reaction that was not observed if AuNP were not attached to the Ftn cage. Results also indicated that AuNP need to be intimately bound to Ftn to extend the photochemistry of Au/Ftn to longer light wavelengths, relative to Au-free Ftn.