Tuning the band gap of ferritin nanoparticles by co-depositing iron with halides or oxo-anionsElectronic supplementary information (ESI) available: TEM images with accompanying EDX spectra of NaBr, NaI, MnO42−, and WO42− co-deposited ferritin, are shown as ESI Fig. 1-4, respectively. Also, ESI Table 1 shows the iron content and band gap measurements of ferritin samples ranging from 200-2100 iron/ferritin. See DOI: 10.1039/c4ta04588b

Iron-containing ferritin has been used for light harvesting and as a photocatalyst. In this study, we test the hypothesis that changing the iron mineral core composition can alter the light harvesting and photocatalytic properties of ferritin, by co-depositing iron in the presence of halides or oxo-anions. This caused the anions to be incorporated into the iron mineral. We report that some of these new iron minerals possess different band gaps than the original ferrihydrite within ferritin. We found an increase in band gap of up to 0.288 eV or a decrease by as much as 0.104 eV, depending on the type of anion and amount of anions incorporated into the ferrihydrite mineral. The substitution of alternate anions into the iron core of ferritin alters the mineral and changes the band gap of the resulting materials.