title: Characterization and surface reactivity of ferrihydrite nanoparticles assembled in ferritin.
abstract: Ferrihydrite nanoparticles with nominal sizes of 3 and 6 nm were assembled within ferritin, an iron storage protein. The crystallinity and structure of the nanoparticles (after removal of the protein shell) were evaluated by high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). HRTEM showed that amorphous and crystalline nanoparticles were copresent, and the degree of crystallinity improved with increasing size of the particles. The dominant phase of the crystalline nanoparticles was ferrihydrite. Morphology and electronic structure of the nanoparticles were characterized by AFM and STM. Scanning tunneling spectroscopy (STS) measurements suggested that the band gap associated with the 6 nm particles was larger than the band gap associated with the 3 nm particles. Interaction of SO2(g) with the nanoparticles was investigated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and results were interpreted with the aid of molecular orbital/density functional theory (MO/DFT) frequency calculations. Reaction of SO2(g) with the nanoparticles resulted primarily in SO(3)2- surface species. The concentration of SO3(2-) appeared to be dependent on the ferrihydrite particle size (or differences in structural properties).
authors.affiliation: Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.forename: Sudeep
authors.initials: S
authors.lastname: Debnath
authors.forename: Kristian W
authors.initials: KW
authors.lastname: Paul
authors.forename: Weiqiang
authors.initials: W
authors.lastname: Han
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Hausner
authors.forename: Hazel-Ann
authors.initials: HA
authors.lastname: Hosein
authors.forename: F Marc
authors.initials: FM
authors.lastname: Michel
authors.forename: John B
authors.initials: JB
authors.lastname: Parise
authors.forename: Donald L
authors.initials: DL
authors.lastname: Sparks
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Strongin
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D005293:Ferritins / Q000737:chemistry* / Q000648:ultrastructure*; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D013055:Spectrophotometry, Infrared; D013458:Sulfur Dioxide / Q000737:chemistry; D013499:Surface Properties; D014732:Vibration; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D013458:Sulfur Dioxide; C092844:ferric oxyhydroxide; D005293:Ferritins