Characterization and Surface Reactivity of Ferrihydrite Nanoparticles Assembled in Ferritin

• Published in: Langmuir Vol. 22; no. 22; pp. 9313 - 9321
• Main Authors: Liu, Gang, Debnath, Sudeep, Paul, Kristian W, Han, Weiqiang, Hausner, Douglas B, Hosein, Hazel-Ann, Michel, F. Marc, Parise, John B, Sparks, Donald L, Strongin, Daniel R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 24.10.2006
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; Ferric Compounds - chemistry; Ferritins - chemistry; Ferritins - ultrastructure; General and physical chemistry; Microscopy, Atomic Force; Microscopy, Electron, Transmission; Models, Molecular; Molecular Conformation; Nanoparticles - chemistry; Nanoparticles - ultrastructure; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Spectrophotometry, Infrared; Sulfur Dioxide - chemistry; Surface Properties; Vibration; X-Ray Diffraction; Molecular orbital; Atomic force microscopy; Particle size; High resolution; Nanoparticle; Ferritin; Iron; Characterization; Particle; Scanning tunneling microscopy; Calculation; Chemical reactivity; Crystalline phase; Transition metal; Crystallinity; Protein; Functional theory; Infrared spectrometry; Electronic structure; Density functional; Transmission electron microscopy; Storage; Morphology; Frequency; Reflectance
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la0602214

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 SO3 2- surface species. The concentration of SO3 2- appeared to be dependent on the ferrihydrite particle size (or differences in structural properties).