Effect of surface treatment of magnetic particles on the preparation of magnetic polymer microspheres by miniemulsion polymerization

Surface treated magnetic particles were used to prepare well encapsulated submicron polystyrene/magnetic (PS/Fe₃O₄) composite microspheres via miniemulsion polymerization. The effects of the different surface treatment agents Disperbyk-106, Disperbyk-111, KH550, sodium dodecyl sulfate (SDS) and oleic acid were investigated on the encapsulation of polymer via miniemulsion polymerization. The interface interactions between magnetic particles, dispersants and coupling agents were analyzed from their IR spectra. It was found that Disperbyk-106 was the best dispersant in terms of preparing magnetic polymer microspheres with high encapsulation efficiency. The effect of wet or dry magnetic particles on encapsulation was also discussed.     

Preparation of low density TiO2/poly (methyl methacrylate) composite particles by emulsifier-free emulsion polymerization

Based on the 3-(trimethoxysilyl) propylmethacrylate (MPS) modified TiO₂ particles, the TiO₂/poly (methyl methacrylate) (PMMA) composite particles have been prepared successfully via emulsifier-free emulsion polymerization in water. A facile floating-sinking method is proposed to roughly evaluate the composite particles’ density. Chemical component of obtained composite particles was identified by Fourier transform infrared spectra (FTIR). The morphology and grain size of the composite particles were investigated by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Thermal analysis of the composite particles was measured by differential thermal analysis-thermo gravimetric analysis (DTA-TGA). The zeta potential and electrophoretic mobility of composite particles with suitable density in water was measured by dynamic light scattering (DLS).     

Preparation of Co3O4 nanoparticles by nonhydrolytic thermolysis of [Co(Pht)(H2O)]n polymers

Benzenedicarboxylate complexes, especially phthalate ones, can be significant precursors for the preparation of nano-sized metal and metal oxides. The injection of organic surfactants such as oleic acid (OA) and triphenylphosphine into molecular precursors has yielded samples with size control, narrow size distributions and crystallinity of individual nanocrystals. Fourier transform infrared and X-ray photoelectron spectroscopy revealed that the OA molecules were adsorbed on the ferromagnetic nanoparticles by chemisorption. The temperature-dependent magnetization curve in zero-field-cooled and field-cooled exhibit weak ferromagnetism of the Co₃O₄ nanoparticles. At 300 K the remanent magnetization is 0.02 emu/g, the coercive field is 441 Oe and the magnetization at saturation is 1.05 emu/g.     

Re-examination of characteristic FTIR spectrum of secondary layer in bilayer oleic acid-coated Fe3O4 nanoparticles

Bilayer oleic acid-coated Fe₃O₄ nanoparticles can be applied in more areas than single layer oleic acid-coated ones because they can be well dispersed not only in nonpolar carrier liquids but also in polar carrier liquids, while the single layer oleic acid-coated ones can be dispersed only in nonpolar carrier liquids. Therefore, it is of significance to characterize the surface structure of bilayer and single layer oleic acid-coated Fe₃O₄ nanoparticles. However, there existed a discrepancy in the characteristic FTIR spectrum of the secondary layer in bilayer oleic acid-coated Fe₃O₄ nanoparticles. The goal of this paper was to resolve the discrepancy through using FTIR and TGA together with dispersibility to characterize the surface structure of bilayer and single layer oleic acid-coated Fe₃O₄ nanoparticles. The results showed that the band at 1710 cm⁻¹ was the characteristic band of the secondary layer in bilayer oleic acid-coated Fe₃O₄ nanoparticles. It can be used to distinguish whether the oleic acid-coated Fe₃O₄ nanoparticles are bilayer or not.     

Preparation and photocatalytic properties of magnetically reusable Fe3O4@ZnO core/shell nanoparticles

Fe₃O₄@ZnO binary nanoparticles were synthesized by a simple two-step chemical method and characterized using various analytical instruments. TEM result proved the binary nanoparticles have core/shell structures and average particle size is 60 nm. Photocatalytic investigation of Fe₃O₄@ZnO core/shell nanoparticles was carried out using rhodamine B (RhB) solution under UV light. Fe₃O₄@ZnO core/shell nanoparticles showed enhanced photocatalytic performance in comparison with the as prepared ZnO nanoparticles. The enhanced photocatalytic activity for Fe₃O₄@ZnO might be resulting from the higher concentration of surface oxygen vacancies and the suppressing effect of the Fe³⁺ ions on the recombination of photoinduced electron–hole pairs. Magnetization saturation value (5.96 emu/g) of Fe₃O₄@ZnO core/shell nanoparticles is high enough to be magnetically removed by applying a magnetic field. The core/shell photocatalyst can be easily separated by using a commercial magnet and almost no decrease in photocatalytic efficiency was observed even after recycling six times.     

Relationship between surface structure and morphology of Fe3O4/silica composite nanospheres and nucleic acid extraction

Fe₃O₄/silica composite nanospheres with different surface structure and morphology were synthesized by changing reaction conditions. As-synthesized nanospheres were characterized by high performance particle sizer (HPPS), transmission electron microscopy (TEM), nitrogen adsorption and thermogravimetry (TGA). Besides thoroughly characterization, the particles were used for DNA extraction. We found that the particle surface structure and morphology affected the nucleic acid extraction efficiency. When comparing different samples with the same silanol density (10¹⁸), the one with a surface area of 60.37 m²/g extracted DNA most effectively. Also, with increasing silanol density per surface area, DNA extraction efficiency increased.