J.S. Colton, Band-gaps in ferritin-templated nanocrystals Band gap variations in ferritin- templated nanocrystals Talk for APS March Meeting Mar 5, 2014 John S. Colton Physics Department Brigham Young University Collaborators: Stephen Erickson (next talk) Dr. Richard Watt (BYU Chemistry) Trevor Smith (BYU Chemistry) Reference for some of this: Colton et al., Nanotech. 25 (2014) J.S. Colton, Band-gaps in ferritin-templated nanocrystals What is ferritin? 3-fold channel J.S. Colton, Band-gaps in ferritin-templated nanocrystals Why is ferritin interesting? Template for nanocrystals Photo-oxidation catalyst Self healing against photo corrosion 1. Nanocrystal From Watt, Petrucci, and Smith, Catl. Sci. Technol. 2013 J.S. Colton, Band-gaps in ferritin-templated nanocrystals Why is ferritin interesting? (cont.) Surface bonding J.S. Colton, Band-gaps in ferritin-templated nanocrystals Nanocrystals grown with ferritin From Watt, Petrucci, and Smith, Catl. Sci. Technol. 2013 J.S. Colton, Band-gaps in ferritin-templated nanocrystals Examples of our samples Non-native samples Take iron out: dithionite dialysis, M TRIS-base buffer at pH 7.4 carefully titrated with NaNO 3. Putting iron (for example) back in: 10 mM ferrous ammonium sulfate added at a rate of 200 irons per ferritin every 10 minutes Native Manganese replacing iron J.S. Colton, Band-gaps in ferritin-templated nanocrystals Ferrihydrite basics (Fe 3+ ) 2 O 3 0.5H 2 O Nanomaterial image: Wikipedia Found in soils Found in organisms Contains defects Lopez-Castro et al., Dalton Trans. 2012 J.S. Colton, Band-gaps in ferritin-templated nanocrystals Nanocrystals grown with ferritin From Watt, Petrucci, and Smith, Catl. Sci. Technol 3.5 eV J.S. Colton, Band-gaps in ferritin-templated nanocrystals Absorption to measure band gaps Figures from Yu and Cardona, Fundamentals of Semiconductors (2010) (1967) (1955) J.S. Colton, Band-gaps in ferritin-templated nanocrystals Band structure of ferrihydrite in native ferritin Figure from Colton et al, Nanotechnology (2014) Compare table value: eV, More details: next talk ~1100 iron atoms per ferritin J.S. Colton, Band-gaps in ferritin-templated nanocrystals Reconstituted ferritin: 1500 Fe atoms/ferritin band gap vs. day Tris buffer native ferritin J.S. Colton, Band-gaps in ferritin-templated nanocrystals Band gap vs. day 1500 Fe atoms/ferritin characteristic 1/e time in Tris: 10.9 days TRIS buffer, two-lineImidizole buffer, six-line J.S. Colton, Band-gaps in ferritin-templated nanocrystals Band gap vs. day, cont. TRIS buffer 10.9 days two-line Imidizole buffer Instantaneous six-line TEM studies: coming soon J.S. Colton, Band-gaps in ferritin-templated nanocrystals Nanocrystals grown with ferritin From Watt, Petrucci, and Smith, Catl. Sci. Technol. 2013 J.S. Colton, Band-gaps in ferritin-templated nanocrystals Band gap of other metal oxides Imidizole buffer Compare: CoOOH eV from table Size dependent effects: next talk J.S. Colton, Band-gaps in ferritin-templated nanocrystals Conclusions Ferritin: template for nanocrystal growth with many other desirable properties Indirect band gap / direct transition FeOOH: 1.92 eV / 3.05 eV CoOOH: 1.59 eV / 2.74 eV MnOOH: 1.54 eV / 2.59 eV Mineralization 10.9 days (in Tris) nearly immediate (in imidizole) Reference for some of this: Colton et al., Nanotech. 25 (2014)