Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands.
Physics of Fluids, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands.
Nanoscale. 2017 Jan 26;9(4):1670-1675. doi: 10.1039/c6nr09245d.
A critical complication in handling nanoparticles is the formation of large aggregates when particles are dried e.g. when they need to be transferred from one liquid to another. The particles in these aggregates need to disperse into the destined liquid medium, which has been proven difficult due to the relatively large interfacial interaction forces between nanoparticles. We present a simple method to capture, move and release nanoparticles without the formation of large aggregates. To do so, we employ the co-non-solvency effect of poly(N-isopropylacrylamide) (PNIPAM) brushes in water-ethanol mixtures. In pure water or ethanol, the densely end-anchored macromolecules in the PNIPAM brush stretch and absorb the solvent. We show that under these conditions, the adherence between the PNIPAM brush and a silicon oxide, gold, polystyrene or poly(methyl methacrylate) colloid attached to an atomic force microscopy cantilever is low. In contrast, when the PNIPAM brushes are in a collapsed state in a 30-70 vol% ethanol-water mixture, the adhesion between the brush and the different counter surfaces is high. For potential application, we demonstrate that this difference in adhesion can be utilized to pick up, move and release 900 silicon oxide nanoparticles of diameter 80 nm using only 10 × 10 μm PNIPAM brush.
处理纳米颗粒的一个关键问题是当颗粒干燥时（例如，当需要将它们从一种液体转移到另一种液体时）会形成大的聚集体。这些聚集体中的颗粒需要分散到预定的液体介质中，但由于纳米颗粒之间相对较大的界面相互作用力，这已经被证明是困难的。我们提出了一种简单的方法来捕获、移动和释放纳米颗粒而不会形成大的聚集体。为此，我们利用聚（N-异丙基丙烯酰胺）（PNIPAM）刷在水-乙醇混合物中的共非溶剂效应。在纯水中或乙醇中，PNIPAM 刷中的致密端锚定的大分子伸展并吸收溶剂。我们表明，在这些条件下，PNIPAM 刷与附着在原子力显微镜悬臂上的氧化硅、金、聚苯乙烯或聚甲基丙烯酸甲酯胶体之间的粘附力很低。相比之下，当 PNIPAM 刷在 30-70vol%乙醇-水混合物中处于塌陷状态时，刷与不同对表面之间的粘附力很高。为了潜在的应用，我们证明，这种粘附力的差异可用于仅使用 10×10μm 的 PNIPAM 刷拾取、移动和释放 900 个直径为 80nm 的氧化硅纳米颗粒。
