Abstract In this paper, a redox and magnetic dual responsive toluene-in-water Pickering emulsion was stabilized by negatively charged Fe3O4 nanoparticles hydrophobically modified by positively charged oxidized ferrocene azine (Fc+A) via electrostatic interaction. The results showed that the adsorbed amount was 0.24 mmol/g and the molecular area was 0.27 nm2 for Fc+A at the Fe3O4 particles surface, which was higher than that at air-water interface (0.21 nm2), implying the adsorption process was typical monolayer adsorption. Because of the adsorption and desorption of Fc+A on the Fe3O4 particles surface, the Pickering emulsion prepared by Fc+A modified Fe3O4 nanoparticles could be reversibly switched between stable and unstable states by alternately adding reducing agent N2H4·H2O and oxidant H2O2. And approximately 80% of particles adsorbed at oil-water interface were returned to water phase after adding N2H4·H2O into the emulsion. At the same time, the emulsion droplets could be close to each other by applying an external magnetic field without demulsification due to the super paramagnetic properties of Fe3O4 nanoparticles, indicating the high stability and magnetic responsiveness of emulsion. Moreover, by applying an external magnetic field, Fc+A modified Fe3O4 nanoparticles stabilized Pickering emulsion was a good extraction system for purifying the aqueous solution contaminated by rhodamine B (RhB).The extraction efficiency (about 97.5 %) was attributed to the hydrophobicity, non-covalent interaction between RhB and Fc+A modified Fe3O4 nanoparticles, and the high specific surface area of emulsion droplets. After the adsorption, the emulsion droplets could be restored to the original emulsion by washing using magnetic field, which can be used to extract contaminated water again. That is to say, the redox and magnetic field dual-responsive Pickering emulsions can not only achieve demulsification/emulsification cycles by redox regulation, but also respond to magnetic field, which provides a promising way to construct functional Pickering emulsion in situ to adsorb dye molecules from aqueous solution.

中文翻译：

---

由电化学活性分子原位疏水化的 Fe3O4 纳米颗粒稳定的双响应 Pickering 乳液

摘要 在本文中，通过带正电荷的氧化二茂铁吖嗪 (Fc+A) 通过静电相互作用疏水改性的带负电荷的 Fe3O4 纳米粒子稳定了氧化还原和磁性双重响应的水包甲苯 Pickering 乳液。结果表明，Fe3O4颗粒表面对Fc+A的吸附量为0.24 mmol/g，分子面积为0.27 nm2，高于气水界面（0.21 nm2），表明吸附过程是典型的单层吸附。由于Fc+A在Fe3O4颗粒表面的吸附和解吸作用，通过交替加入还原剂N2H4·H2O和氧化剂H2O2，Fc+A改性Fe3O4纳米颗粒制备的Pickering乳液可以在稳定和不稳定状态之间可逆地转换。在乳液中加入N2H4·H2O后，吸附在油水界面上的颗粒约有80%返回水相。同时，由于Fe3O4纳米粒子的超顺磁特性，通过施加外部磁场可以使乳液液滴彼此靠近而不会破乳，表明乳液具有高稳定性和磁响应性。此外，通过施加外部磁场，Fc+A 修饰的 Fe3O4 纳米粒子稳定的 Pickering 乳液是一种很好的提取体系，用于净化被罗丹明 B（RhB）污染的水溶液。提取效率（约 97.5%）归因于疏水性， RhB 和 Fc+A 修饰的 Fe3O4 纳米粒子之间的非共价相互作用，以及乳液液滴的高比表面积。吸附后，通过磁场洗涤，乳液液滴可以恢复到原来的乳液状态，可以再次提取污染水。也就是说，氧化还原和磁场双响应的Pickering乳液不仅可以通过氧化还原调节实现破乳/乳化循环，而且还可以响应磁场，这为原位构建功能性Pickering乳液以吸附染料分子提供了一种有前景的方法从水溶液。