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Band gap variations in ferritin-templated nanocrystals

Band gap variations in ferritin-templated nanocrystals. John S. Colton Physics Department Brigham Young University. Collaborators: Stephen Erickson (next talk) Dr. Richard Watt (BYU Chemistry) Trevor Smith (BYU Chemistry). Talk for APS March Meeting Mar 5, 2014.

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Band gap variations in ferritin-templated nanocrystals

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  1. Band gap variations in ferritin-templated nanocrystals John S. Colton Physics Department Brigham Young University Collaborators: Stephen Erickson (next talk) Dr. Richard Watt (BYU Chemistry) Trevor Smith (BYU Chemistry) Talk for APS March Meeting Mar 5, 2014 Reference for some of this: Colton et al., Nanotech. 25 (2014) 135703

  2. What is ferritin? “3-fold channel”

  3. 1. Nanocrystal Why is ferritin interesting? • Template for nanocrystals • Photo-oxidation catalyst • Self healing against photo corrosion From Watt, Petrucci, and Smith, Catl. Sci. Technol. 2013

  4. Why is ferritin interesting? (cont.) • Surface bonding

  5. Nanocrystals grown with ferritin • From Watt, Petrucci, and Smith, Catl. Sci. Technol. 2013

  6. Examples of our samples Non-native samples • Take iron out: dithionite dialysis, 0.050 M TRIS-base buffer at pH 7.4 carefully titrated with NaNO3. • Putting iron (for example) back in: 10 mM ferrous ammonium sulfate added at a rate of 200 irons per ferritin every 10 minutes Manganese replacing iron Native

  7. Ferrihydrite basics • (Fe3+)2O3 • 0.5H2O • Nanomaterial • Found in soils • Found in organisms • Contains defects image: Wikipedia Lopez-Castro et al., Dalton Trans. 2012

  8. Nanocrystals grown with ferritin • From Watt, Petrucci, and Smith, Catl. Sci. Technol. 2013 1.0 – 3.5 eV

  9. (1967) (1955) Absorption to measure band gaps • Figures from Yu and Cardona, Fundamentals of Semiconductors (2010)

  10. Band structure of ferrihydrite in native ferritin • Figure from Colton et al, Nanotechnology (2014) • Compare table value: 2.5-3.5 eV, More details: next talk • ~1100 iron atoms per ferritin

  11. Reconstituted ferritin: 1500 Fe atoms/ferritin • band gap vs. day • Tris buffer native ferritin

  12. Band gap vs. day • 1500 Fe atoms/ferritin • characteristic 1/e time in Tris: 10.9 days TRIS buffer, two-line Imidizole buffer, six-line

  13. Band gap vs. day, cont. TRIS buffer 10.9 days two-line Imidizole buffer Instantaneous six-line TEM studies: coming soon

  14. Nanocrystals grown with ferritin • From Watt, Petrucci, and Smith, Catl. Sci. Technol. 2013

  15. Band gap of other metal oxides • Imidizole buffer • Compare: “CoOOH 1.4-1.8 eV” from table • Size dependent effects: next talk

  16. 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) 135703

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