School of Chemical and Biological Engineering, and Institute of Chemical Processes, Seoul National University, Seoul 08826, Republic of Korea.
Center for Nanoparticle Research, Institute of Basic Science (IBS), Seoul 08826, Republic of Korea.
Nano Lett. 2020 Dec 9;20(12):8704-8710. doi: 10.1021/acs.nanolett.0c03517. Epub 2020 Nov 13.
The formation mechanism of colloidal nanoparticles is complex because significant nonclassical pathways coexist with the conventional nucleation and growth processes. Particularly, the coalescence of the growing clusters determines the final morphology and crystallinity of the synthesized nanoparticles. However, the experimental investigation of the coalescence mechanism is a challenge because the process is highly kinetic and correlates with surface ligands that dynamically modify the surface energy and the interparticle interactions of nanoparticles. Here, we employ quantitative TEM with multichamber graphene liquid cell to observe the coalescence processes occurring in the synthesis of gold nanoparticles in different ligand systems, thus affording us an insight into their ligand-dependent coalescence kinetics. The analyses of numerous liquid-phase TEM trajectories of the coalescence and MD simulations of the ligand shells demonstrate that enhanced ligand mobility, employing a heterogeneous ligand mixture, results in the rapid nanoparticle pairing approach and a fast post-merging structural relaxation.
胶体纳米粒子的形成机制很复杂，因为显著的非经典途径与传统的成核和生长过程并存。特别是，生长簇的合并决定了合成纳米粒子的最终形态和结晶度。然而，由于该过程具有高度的动力学特性，并与动态改变纳米粒子表面能和粒子间相互作用的表面配体相关联，因此实验研究合并机制是一个挑战。在这里，我们采用带有多腔石墨烯液体池的定量 TEM 来观察在不同配体体系中合成金纳米粒子时发生的合并过程，从而深入了解它们与配体相关的合并动力学。对大量液相 TEM 轨迹的分析以及配体壳的 MD 模拟表明，增强配体的迁移率，采用非均相配体混合物，导致纳米粒子快速配对并快速进行合并后的结构弛豫。
