The Deposition Of Continuous SiO₂and Gold Shells On Tween-20Modified Fe₃O₄Superparticles

Superparamagnetic iron oxide nanoparticles have attracted considerable interests dueto their application potentials in biotechnology. But usually the naked iron oxidenanoparticles are readily to undergo aggregation and oxidization, which limit theirpractical applications. A general strategy to protect the iron oxide particles is todeposit inert shells on their surface. SiO₂and Au are considered to be the idealcoating layers due to their excellent chemical stability and biocompatibility. Both ofFe₃O₄/SiO₂and Fe₃O₄/Au have very important applications in biotechnology. So theobjective of researching is to prepare the composite particles with good dispersibility,controlled particles′sizes and magnetic content, and good response ability.In the second chapter, Tween-20-modified Fe₃O₄superparticles were obtained by theemulsion droplet solvent evaporation method. And then analysis the effects of theconcentration of Fe₃O₄nanoparticles in oil phase and the volume ratio of oil phaseagainst water phase on the size of Fe₃O₄superparticles. At last the superparticleswere directly transferred into a pre-hydrolyzed St ber system to carry out silicacoating. The Size and the thickness of silica coating layer of Fe₃O₄/SiO₂particleswere tunable. Then, we developed a facile approach to deposit continuous Au shell on Fe₃O₄colloidal superparticles （SPs）. In this new approach, first the Fe₃O₄nanoparticlessynthesized by the typical Massart’s method were modified with oleic acid, and thenTween-20-modified Fe₃O₄SPs were obtained by the emulsion droplet solventevaporation method. After the addition of HAuCl4and30min incubation, reductionof Au³⁺by ascorbic acid resulted in the deposition of continuous Au shell on theFe₃O₄SPs. The as-prepared Fe₃O₄/Au core-shell particles showed good chemicalstability and efficient photo-thermal conversion performance under the irradiation ofnear infrared laser. The thickness of Au shell and the absorbance peak were tunableby changing the changing the concentration of HAuCl4in the growth solution. Theobtained Fe₃O₄/Au core-shell particles have a lot of advantages, such as excellentchemical stability, superparamagnetic properties and efficient photothermalconversion performance under laser irradiation at808nm, and were expected to be auseful material for biodetection and cancer therapy. This approach could also beextended for the deposition of continuous Ag shells on the Tween-20modified Fe₃O₄SPs. The resulting Fe₃O₄/Ag core–shell particles showed extensive absorbance in theNIR region attributed to the plasmon peaks of the Ag shells.