Construction Of Magnetic Microspheres Based On Urea Formaldehyde Template

Magnetic microspheres and nanocrystals are of great interest for researchers from a wide range of hot research field including biotechnology/biomedicine, catalysis, magnetic resonance imaging, data storage, and environmental remediation.Although a number of suitable methods have been developed for the synthesis of magnetic nanoparticles of various different compositions, few of them are capable of producing high quality magnetic microspheres with large quantity. Therefore, it's of great urgency to develop methods for large scale production of these materials to meet growing demands from the above fields.Our research is focused on the development of methods for preparation of magnetic microspheres based on the urea-formaldehyde templates and production of a series of novel functional magnetic microspheres. Those novel magnetic microspheres fully characterized by SEM, TEM, VSM, XRD, BET, TGA, FTIR, DLS have been successfully applied to the DNA extraction and arsenic removal. The results are list as follows:1) Development of novel method for one pot preparation of magnetic microspheres at room temperature. By this method, magnetic nano particles were embedded by UF to form the microspheres with sphereical like morphology and 8 emu/g magnetic saturation. The microspheres were applied to extraction of DNA from human blood. Also, the fluorescent compounds can be added during the polymerization to form the bi-functional microspheres. The mechanism of UF microspheres were studied systematically.2) Development of novel method for two-step preparation of magnetic microspheres. The method is based on the formation of iron hydroxide/polymer composite microspheres followed by in situ conversion to strong magnetizable them to magnetite nanocrystals by reaction with sodium borohydride under hydrothermal conditions. The obtained magnetic crystals embedded in the polymer matrix are of cubic shape and highly crystalline structure. 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.3) Development of a novel method for three-step preparation of porous magnetite microspheres. As for two-step method, the ironhydroxide/UF microspheres were stablized by condensation polymerization and then subjected to heating treatment to remove polymer template. The porous iron-oxide was transferred into magnetite by thermal reduction. The porous magnetite microspheres were proved be an effective adsorbent for removal of arsenic from the water.4) Investigation on high temperature reduction of magnetic precursors embedded in UF matrix at H2 atmospheres in attempt to preparation of carbon coated magnetic microspheres. The reduction of hydroxide/UF microspheres by H2 produces the magnetite nano tubes along with magnetic microspheres. A CVD procedure applied for hydroxide/UF produces magnetic microspheres and carbon fiber, and for iron coated microspheres produced the highly uniform graphite nanospheres with magnetic 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.The above results confirm that the novel system of magnetic microspheres preparation based on urea formaldehyde polymerization is facile, cost-effective, environmentally benign, and readily scaled up for mass production.