借助于多巴胺在Fe₃O₄纳米颗粒表面自聚合形成聚多巴胺薄膜制备出Fe₃O₄/聚多巴胺(Fe₃O₄/PD)复合纳米颗粒,利用扫描电子显微镜、透射电子显微镜、X射线衍射仪对样品的形貌、结构及成分进行分析.所制备的颗粒经1H,1H,2H,2H-全氟癸基三氯硅烷化学修饰后表现出超疏水性.有趣的是,超疏水性的Fe₃O₄/PD纳米颗粒包裹在水滴表面能形成磁性液珠,该液珠(4 μL)在亲水性玻璃表面上的接触角高达164°、滚动角为8°.这些磁性液珠具有良好的机械稳定性和强度,同时研究了外部磁场驱动液珠在平面、曲面、油相中运动.结果表明,磁性液珠能够有效应用于操作微流体装置中的液体输送.水滴在Fe₃O₄/PD纳米颗粒构成表面的接触角超过150°,而油滴则接近0°,因此,在磁场存在下,这些颗粒能用于吸收油水混合物中的油滴而实现油水分离.此外,回收的Fe₃O₄/PD纳米颗粒保持着超疏水性且能再次利用. 

We report a simple approach to creating bifunctional Fe₃O₄/polydopamine (Fe₃O₄/PD) composite nanoparticles (NPs) with both superparamagnetic and superhydrophobic properties. The Fe₃O₄/PD NPs were prepared by virtue of dopamine self-polymerization under mild conditions. Their morphology, structure and composition of nanocomposites were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), respectively. The Fe₃O₄/PD NPs have uniform sizes in a narrow range of 100 similar to 300 nm. Magnetic measurement reveals the Fe₃O₄/PD NPs are superparamagnetic with saturation magnetization of 73.40 emu/g. The as-prepared particles showed superhydrophobicity after being modified by 1H,1H,2H,2H-perfluorodecyltrichlorosilane. The Fe₃O₄ particles were also modified by fluoroalkylsilane, and surface composed of the particles present a water contact angle (CA) of 117°. This result indicated that plenty of phenolic hydroxyl groups in polydopamine may promote the modification of fluorosilane for the surface of Fe₃O₄. In this study, the magnetic liquid marble was obtained by coating some superhydrophobic Fe₃O₄/PD NPs on a water droplet. The CA of a liquid marble (4 μL) on the hydrophilic slide glass is 164°, and the sliding angle is 8°. Meanwhile, the mechanical strength and robustness of the liquid marbles were demonstrated. The liquid marbles are facilely controlled to move on various surfaces, such as flat surfaces, on curved surfaces, in oil phase under an external magnetic field control. These results indicate that the magnetic liquid marbles are effective application for manipulation of liquid transport in microfluidic devices. The Fe₃O₄/PD NPs composed surface has a water CA more than 150°, while the CA of oil is nearly 0°. Therefore, these particles can be used to oil/water separation and the separated oil can be easily transported in the water with an external magnetic field. Impotrantly, the particles could be simply retrieved on the basis of their superparamagnetic properties. Moreover, the reclaimed Fe₃O₄/PD NPs after washed and dried can still be superhydrophobicity and can be reused.