Synthesis and characterization of the Fe3O4@SiO2 nanoparticles

ABSTRACT In this work the synthesis and characterization of the magnetic nanoparticles of magnetite (Fe3O4) from the methodology via co-precipitation and its subsequent functionalization by silica (SiO2), carried out via sol-gel methodology were studied. The characterization of the nanoparticles was performed by X-ray diffractometry (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and zeta potential variation as a function of pH. The results showed that the synthesis of the Fe3O4 and Fe3O4@SiO2 nanoparticles was successful, with a high homogeneity of shape and size, according to the results of the analysis of the images obtained by MET, including the formation of shell structures for the Fe3O4@SiO2 nanoparticles. The functionalization of the magnetite surface was confirmed by the FTIR data and the zeta potential measurements. Surface functionalization by silica causes an increase in nanoparticle size due to the introduction of an inorganic shell around magnetite nanoparticles. The zeta potential curves showed that with the addition of silica, the colloidal stability increases in relation to the magnetite and this increase is related to the functionalized silica that should be minimizing the surface energies around the magnetic nanoparticles.

摘要 本研究针对采用共沉淀法制备四氧化三铁（Fe₃O₄）磁性纳米颗粒，并通过溶胶-凝胶法对其进行二氧化硅（SiO₂）表面功能化的相关过程展开了系统探究。研究采用X射线衍射（X-ray diffractometry, XRD）、透射电子显微镜（transmission electron microscopy, TEM）、傅里叶变换红外光谱（Fourier transform infrared spectroscopy, FTIR）以及zeta电位（zeta potential）随pH变化曲线对所制备的纳米颗粒进行了全面表征。结果表明，Fe₃O₄与Fe₃O₄@SiO₂纳米颗粒的合成均取得成功；透射电镜图像分析显示，两类纳米颗粒均具备优异的形貌与尺寸均一性，其中Fe₃O₄@SiO₂纳米颗粒成功形成了清晰的核壳结构。傅里叶变换红外光谱数据与zeta电位测试结果证实了四氧化三铁表面的二氧化硅功能化修饰。由于在四氧化三铁纳米颗粒表面包覆了无机壳层，二氧化硅功能化修饰会导致纳米颗粒粒径有所增大。zeta电位曲线结果显示，相较于纯四氧化三铁纳米颗粒，经二氧化硅修饰后的纳米颗粒胶体稳定性显著提升，这一现象与功能化二氧化硅壳层降低磁性纳米颗粒表面能的作用密切相关。