Center for High-Rate Nanomanufacturing and Department of Plastics Engineering, University of Massachusetts, Lowell, Massachusetts 01854, USA.
Langmuir. 2010 Aug 17;26(16):13130-41. doi: 10.1021/la101502e.
A versatile new concept is presented for the synthesis of Janus colloids composed of Laponite nanoclay armored poly(divinylbenzene) with an anisotropic surface potential via a double Pickering emulsion template. First, polystyrene or poly(divinylbenzene) colloids stabilized with Laponite nanoclay are synthesized via a Pickering miniemulsion approach. These nanoparticle-stabilized colloids were then templated at a wax-water interface in a second Pickering emulsion in order to chemically modify one hemisphere of the colloids. Janus modification of the colloids was accomplished by cation exchange of sodium ions, originally present on the surface of the Laponite with various salts of modifying ions (Ca(2+), Fe(2+), and Fe(3+)) in the suspension. The zeta potential of the chemically modified and unmodified colloids was compared. The maximum change in the zeta potential was given by the calcium ions, Ca(2+)-adsorbed modified colloids as compared to unmodified sodium ions, Na(+)-adsorbed colloids. The distribution of charges on the Janus colloids results in a nonuniform zeta potential. XPS and optical microscopy were used to verify the successful chemical modification by the cation exchange of Na(+) for Ca(2+) ions on one hemisphere of the Janus colloids.
提出了一种通用的新概念，用于通过双 Pickering 乳液模板合成由 Laponite 纳米粘土装甲聚（二乙烯基苯）组成的 Janus 胶体，其具有各向异性的表面电势。首先，通过 Pickering 微乳液方法合成了用 Laponite 纳米粘土稳定的聚苯乙烯或聚（二乙烯基苯）胶体。然后，将这些纳米颗粒稳定的胶体在蜡 - 水界面的第二 Pickering 乳液中进行模板化，以化学修饰胶体的一个半球。通过在悬浮液中用各种改性离子（Ca(2+)，Fe(2+)和 Fe(3+)）的盐将原本存在于 Laponite 表面的钠离子进行阳离子交换，实现了胶体的 Janus 改性。比较了化学改性和未改性胶体的 ζ 电位。与未改性的钠离子相比，ζ 电位的最大变化是由吸附在 Ca(2+)上的钙离子，Ca(2+)-吸附的改性胶体引起的。Janus 胶体上的电荷分布导致非均匀的 ζ 电位。XPS 和光学显微镜用于验证通过阳离子交换将 Na(+)成功改性为 Janus 胶体一侧的 Ca(2+)离子。
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