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| - Preparation of Uniform Magnetic Microspheres through Hydrothermal Reduction of Iron Hydroxide Nanoparticles Embedded in a Polymeric Matrix
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| Abstract
| - A novel method is described for the preparation of nearly monodispersed and highly magnetic responsive microspheres with magnetite nanocrystals formed in a polymeric matrix by hydrothermal reduction. The method is based on the formation of iron hydroxide/polymer composite microspheres by acid-catalyzed condensation polymerization of urea and formaldehyde in the presence of colloidal iron hydroxide. The iron hydroxide colloids entrapped in the polymer matrix are then in situ converted to magnetite nanocrystals by reaction with sodium borohydride under hydrothermal conditions. Characterization of the resulting microspheres with electron microscopy and vibrating sample magnetometry confirmed that these particles possessed a uniform spherical morphology, narrow particle size distribution, and high magnetic susceptibility. More interestingly, the magnetic nanoparticles embedded in the polymer matrix are of cubic shape and highly crystalline structure. While the growth of uniform composite microspheres is accounted for by the well-known LaMer model, the formation of the cubic magnetite nanocrystals appears to involve a dissolution−recrystallization process. After being coated with silica by the sol−gel approach, the magnetic particles were used as adsorbents for isolation of genomic DNA from biological samples, with results comparable to those obtained by magnetic silica microspheres. Incorporation of iron hydroxide colloids into polymer microspheres coupled with chemically induced phase transformation represents a new cost-effective approach to the preparation of uniform magnetic microspheres that is more controllable with respect to particle properties and more amenable to large-scale production.
- Uniform magnetic microspheres were prepared by a method involving formation of iron hydroxide/polymer composite microspheres and subsequent in situ conversion of the iron hydroxide to magnetite by hydrothermal reduction.
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| - Preparation of Uniform Magnetic Microspheres
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