Isa Lucio, Amstad Esther, Textor Marcus, Reimhult Erik
Laboratory for Surface Science and Technology, Eidgenössische Technische Hochschule Zürich, Wolfgang-Pauli-Strasse 10, HCI G543, CH-8093 Zürich.
Chimia (Aarau). 2010;64(3):145-9. doi: 10.2533/chimia.2010.145.
Nanoparticles (NPs) play an increasingly important role in the fabrication of functional advanced materials. Two major steps need to be carried out in order to achieve control of the material properties. First of all, the properties of the single NPs have to be under control, especially in relation to colloidal stability; aggregation and corrosion negate all the benefits associated to the nanoscopic dimensions. Secondly, the assembly process has to be controlled to achieve a material with the desired properties. We propose here to use stabilized ceramic NPs consisting of a magnetite core, coated by a poly(ethylene glycol) (PEG) shell and study their assembly at polar/ non-polar liquid interfaces, en route to fabricating functional NP membranes. These NPs show extraordinary stability in aqueous solutions achieved by anchoring linear PEG chains through an end-terminating nitroDOPA group to their surface. Furthermore, the core and shell sizes of these NPs can be independently varied with ease. We first describe the details of the NP synthesis and stabilization in bulk solutions, discussing the PEG molecular weight needed to achieve bulk stability. Subsequently, we demonstrate self-assembly of these particles at liquid-liquid interfaces (SALI) into monolayers of stable properties. SALI has been chosen as path for the assembly given its suitability for fabricating two-dimensional materials. We report here results from pendant drop tensiometry which illustrate the kinetics of NP adsorption at the liquid-liquid interface and highlight the role played by the molecular weight of the PEG shell in the interfacial assembly. In particular we show that the requisites to ensure particle stability at a liquid interface are more stringent compared to the bulk case.
纳米颗粒（NPs）在功能性先进材料的制备中发挥着越来越重要的作用。为了实现对材料性能的控制，需要进行两个主要步骤。首先，单个纳米颗粒的性能必须得到控制，特别是与胶体稳定性相关的性能；聚集和腐蚀会抵消与纳米尺寸相关的所有益处。其次，必须控制组装过程以获得具有所需性能的材料。我们在此提议使用由磁铁矿核心组成、包覆有聚乙二醇（PEG）外壳的稳定化陶瓷纳米颗粒，并研究它们在极性/非极性液体界面的组装情况，以制备功能性纳米颗粒膜。这些纳米颗粒在水溶液中表现出非凡的稳定性，这是通过将线性PEG链通过末端硝基多巴胺基团锚定在其表面实现的。此外，这些纳米颗粒的核心和外壳尺寸可以轻松独立变化。我们首先描述纳米颗粒在本体溶液中的合成和稳定化细节，讨论实现本体稳定性所需的PEG分子量。随后，我们展示了这些颗粒在液-液界面（SALI）自组装成具有稳定性能的单层。鉴于SALI适用于制造二维材料，我们选择它作为组装途径。我们在此报告悬滴张力测量的结果，这些结果说明了纳米颗粒在液-液界面吸附的动力学，并突出了PEG外壳分子量在界面组装中所起的作用。特别是，我们表明与本体情况相比，确保颗粒在液体界面稳定的要求更为严格。
