Research Institute of Materials Science, South China University of Technology, Guangzhou 510641, China.
Langmuir. 2013 Apr 30;29(17):5138-44. doi: 10.1021/la400053g. Epub 2013 Apr 16.
This work presents a facile approach to produce a novel type of Janus microspheres with dual anisotropy of porosity and magnetism based on Pickering-type double emulsion templates. A stable aqueous Fe3O4 dispersion-in-oil-in-water (WF/O/W) double Pickering emulsion is first generated by using hydrophobic silica and hydrophilic mesoporous silica particles as stabilizers. Janus microspheres with multihollow structure possessing magnetite nanoparticles concentrated on one side of the microspheres are obtained after polymerization of the middle oil phase of the double emulsion under a magnetic field. The resultant Janus microspheres are characterized by optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX). Moreover, we have systematically investigated the influences of Fe3O4 particle concentration, hydrophobic silica particle content, and volume ratio of the inner water phase to middle oil phase (WF/O) on the double emulsion formation and consequently on the structure of the resulting Janus microspheres. Our results show that the distribution of the multihollow structures within the prepared microspheres can be accurately tailored by adjusting the ratio of WF/O. In addition, the obtained Janus microsphere can be fairly orientated under a magnetic field, making them a potential candidate for synthesizing Janus membrane.
本工作提出了一种简便的方法，基于 Pickering 型双乳液模板，制备出具有孔隙率和磁性双重各向异性的新型 Janus 微球。首先，使用疏水二氧化硅和亲水介孔硅粒子作为稳定剂，制备出稳定的油包水型 Fe3O4 分散体（WF/O/W）双 Pickering 乳液。然后，在外加磁场作用下，对双乳液的中间油相进行聚合，得到具有多中空结构的 Janus 微球，其一侧富集有磁铁矿纳米粒子。通过光学显微镜、扫描电子显微镜（SEM）和能谱分析（EDX）对所得 Janus 微球进行了表征。此外，我们系统地研究了 Fe3O4 粒子浓度、疏水二氧化硅粒子含量以及内水相和中间油相（WF/O）的体积比对双乳液形成的影响，进而对所得 Janus 微球的结构产生影响。研究结果表明，通过调节 WF/O 的比例，可以精确控制多中空结构在制备的微球中的分布。此外，所得 Janus 微球在外磁场下可以很好地定向，使其成为合成 Janus 膜的潜在候选材料。
