Synthesis of Janus-Like Gold Nanoparticles with Hydrophilic/Hydrophobic Faces by Surface Ligand Exchange and Their Self-Assemblies in Water
Synthesis of Janus-Like Gold Nanoparticles with Hydrophilic/Hydrophobic Faces by Surface Ligand Exchange and Their Self-Assemblies in Water
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DOI：
10.1021/la504647z
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发表时间：
2015-04-14
期刊：
影响因子：
3.9
通讯作者：
Ijiro, Kuniharu
中科院分区：
文献类型：
--
作者：
Iida, Ryo;Kawamura, Hitoshi;Ijiro, Kuniharu
本研究旨在通过简单的配体交换反应在均相体系中合成具有亲疏水面的Janus金纳米粒子（Janus GNPs），并阐明Janus GNPs在水中的自组装结构。作为亲水性表面配体，我们合成了具有C3、C7或C11烷基链的六甘醇（E6）端巯基配体，分别称为E6C3、E6C7和E6C11。作为疏水配体，合成了在E6C11末端引入C4烷基的丁基头硫酸酯配体C4-E6C11。采用基质辅助激光解吸/电离时间-质谱（MALDI-TOF MS）分析了两种配体在直径为5 nm的GNPs上的偏析程度。我们发现，固定方法的选择，一步或两步添加到GNP溶液中的两种配体，对分离程度有重要影响。亲水配体（E6C3）和疏水配体（C4-E6C11）的两步加成在GNPs上产生了很大程度的分离，提供了类似janus的GNPs。当这些Janus-like GNPs分散在水中时，形成直径约为160 nm的组装体，而当NPs表面亲疏水配体的摩尔比接近1:1时，两个配体在表面形成部分结构域的Domain GNPs也会析出。利用x射线自由电子激光器，通过脉冲相干x射线溶液散射直接观察了水中Janus-like GNPs的组装结构，揭示了表面不均匀的不规则球形结构。
This study aims at the synthesis of Janus gold nanoparticles (Janus GNPs) with hydrophilic/hydrophobic faces by a simple ligand exchange reaction in an homogeneous system and at the elucidation of the self-assembled structures of the Janus GNPs in water. As hydrophilic surface ligands, we synthesized hexaethylene glycol (E6)-terminated thiolate ligands with C3, C7, or C11 alkyl chains, referred to as E6C3, E6C7, and E6C11, respectively. As a hydrophobic ligand, a butyl-headed thiolate ligand C4-E6C11, in which a C4 alkyl was introduced on the E6C11 terminus, was synthesized. The degree of segregation between the two ligands on the GNPs (5 nm in diameter) was examined by matrix-assisted laser desorption/ionization time-of fright mass spectrometry (MALDI-TOF MS) analysis. We found that the choice of immobilization methods, one-step or two-step addition of the two ligands to the GNP solution, crucially affects the degree of segregation. The two-step addition of a hydrophilic ligand (E6C3) followed by a hydrophobic ligand (C4-E6C11) produced a large degree of segregation on the GNPs, providing Janus-like GNPs. When dispersed in water, these Janus-like GNPs formed assemblies of similar to 160 nm in diameter, whereas Domain GNPs, in which the two ligands formed partial domains on the surface, were precipitated even when the molar ratio of the hydrophilic ligand and the hydrophobic ligand on the surface of the NPs was almost 1:1. The assembled structure of the Janus-like GNPs in water was directly observed by pulsed coherent X-ray solution scattering using an X-ray free-electron laser, revealing irregular spherical structures with uneven surfaces.