Web Release Date: September 29,
Characterization and Surface Reactivity of Ferrihydrite Nanoparticles Assembled in Ferritin
and
Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware 19716, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, and Center for Environmental Molecular Science, The State University of New York at Stony Brook, Stony Brook, New York 11794
Received January 23, 2006
In Final Form: August 21, 2006
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 SO32- surface species. The concentration of SO32- appeared to be dependent on the ferrihydrite particle size (or differences in structural properties).
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