We study the assembly kinetics of surfactant-stabilized gold nanoparticles in the presence of sulfate ions. The reaction proceeds in two steps: very rapid (a few minutes) formation of amorphous aggregates, followed by slow reordering (over several hours). The latter process is the only one detectable via absorbance spectroscopy and results in the formation of intimate contacts between the objects, with interparticle distances below the thickness of a surfactant bilayer. The rate-limiting step of the reaction could be related to surfactant expulsion from the initial aggregates, which allows the particles to come in close contact and form chains. There are marked differences in reaction yield and rate constant between spheres, rods and bipyramids, highlighting the role of surface curvature in contact formation. Once formed, the assemblies are very sturdy and stable under centrifugation and dialysis. The contact interaction is strong and highly directional, as shown by liquid-cell transmission electron microscopy.

中文翻译：

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金纳米粒子的两步组装动力学

我们研究了表面活性剂稳定的金纳米粒子在硫酸根离子存在下的组装动力学。反应分两步进行：非常快速（几分钟）形成无定形聚集体，然后缓慢重新排序（数小时）。后一种过程是唯一可通过以下途径检测到的过程吸收光谱法并导致物体之间形成紧密接触，且粒子间距离低于表面活性剂双层的厚度。反应的限速步骤可能与表面活性剂从初始聚集体中排出有关，这使颗粒紧密接触并形成链。球体，棒体和双锥体之间的反应产率和速率常数存在显着差异，突出了表面曲率在接触形成中的作用。一旦形成，组件在离心和透析下非常坚固且稳定。如液体细胞透射电子显微镜所示，接触相互作用强且方向性强。