Engineering the internal structure of magnetic silica nanoparticles by thermal control
Type
ArticleKAUST Department
Advanced Membranes and Porous Materials Research CenterBiological and Environmental Sciences and Engineering (BESE) Division
Chemical Science Program
Physical Science and Engineering (PSE) Division
Smart Hybrid Materials (SHMs) lab
Date
2014-09-30Online Publication Date
2014-09-30Print Publication Date
2015-03Permanent link to this record
http://hdl.handle.net/10754/563766
Metadata
Show full item recordAbstract
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.201400118Sponsors
The authors gratefully acknowledge support from King Abdullah University of Science and Technology (KAUST) and the NSF grant DBI-1266377.Publisher
Wileyae974a485f413a2113503eed53cd6c53
10.1002/ppsc.201400118