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    Engineering the internal structure of magnetic silica nanoparticles by thermal control

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    Type
    Article
    Authors
    Song, Hyon Min
    Zink, Jeffrey I.
    Khashab, Niveen M. cc
    KAUST Department
    Advanced Membranes and Porous Materials Research Center
    Biological and Environmental Sciences and Engineering (BESE) Division
    Chemical Science Program
    Physical Science and Engineering (PSE) Division
    Smart Hybrid Materials (SHMs) lab
    Date
    2014-09-30
    Online Publication Date
    2014-09-30
    Print Publication Date
    2015-03
    Permanent link to this record
    http://hdl.handle.net/10754/563766
    
    Metadata
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    Abstract
    Calcination of hydrated iron salts in the pores of both spherical and rod-shaped mesoporous silica nanoparticles (NPs) changes the internal structure from an ordered 2D hexagonal structure into a smaller number of large voids in the particles with sizes ranging from large hollow cores down to ten nanometer voids. The voids only form when the heating rate is rapid at a rate of 30 °C min-1. The sizes of the voids are controlled reproducibly by the final calcination temperature; as the temperature is decreased the number of voids decreases as their size increases. The phase of the iron oxide NPs is α-Fe2O3 when annealed at 500 °C, and Fe3O4 when annealed at lower temperatures. The water molecules in the hydrated iron (III) chloride precursor salts appear to play important roles by hydrolyzing Si-O-Si bonding, and the resulting silanol is mobile enough to affect the reconstruction into the framed hollow structures at high temperature. Along with hexahydrates, trivalent Fe3+ ions are assumed to contribute to the structure disruption of mesoporous silica by replacing tetrahedral Si4+ ions and making Fe-O-Si bonding. Volume fraction tomography images generated from transmission electron microscopy (TEM) images enable precise visualization of the structures. These results provide a controllable method of engineering the internal shapes in silica matrices containing superparamagnetic NPs.
    Citation
    Song, H. M., Zink, J. I., & Khashab, N. M. (2014). Engineering the Internal Structure of Magnetic Silica Nanoparticles by Thermal Control. Particle & Particle Systems Characterization, 32(3), 307–312. doi:10.1002/ppsc.201400118
    Sponsors
    The authors gratefully acknowledge support from King Abdullah University of Science and Technology (KAUST) and the NSF grant DBI-1266377.
    Publisher
    Wiley
    Journal
    Particle and Particle Systems Characterization
    DOI
    10.1002/ppsc.201400118
    10.1002/ppsc.201570008
    ae974a485f413a2113503eed53cd6c53
    10.1002/ppsc.201400118
    Scopus Count
    Collections
    Articles; Biological and Environmental Sciences and Engineering (BESE) Division; Advanced Membranes and Porous Materials Research Center; Physical Science and Engineering (PSE) Division; Controlled Release and Delivery Laboratory; Chemical Science Program

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