10.1021/acs.nanolett.8b03139.s003 Biao Jin Biao Jin Maria L. Sushko Maria L. Sushko Zhaoming Liu Zhaoming Liu Chuanhong Jin Chuanhong Jin Ruikang Tang Ruikang Tang In Situ Liquid Cell TEM Reveals Bridge-Induced Contact and Fusion of Au Nanocrystals in Aqueous Solution American Chemical Society 2018 multistep process advances surface diffusion solution dehydration Classical density nanoparticle coalescence mechanism nanobridge structure theory calculations nanocrystal liquid-cell transmission electron microscopy nanobridge forms auric ions nanoparticle coalescence hydration layers ab initio grain boundary migration Aqueous Solution coalescence process dynamics simulations contact Situ Liquid Cell TEM Bridge-Induced Contact 2018-09-06 00:00:00 Media https://acs.figshare.com/articles/media/In_Situ_Liquid_Cell_TEM_Reveals_Bridge-Induced_Contact_and_Fusion_of_Au_Nanocrystals_in_Aqueous_Solution/7059167 During nanoparticle coalescence in aqueous solution, dehydration and initial contact of particles are critically important but poorly understood processes. In this work, we used in situ liquid-cell transmission electron microscopy to directly visualize the coalescence process of Au nanocrystals. It is found that the Au atomic nanobridge forms between adjacent nanocrystals that are separated by a ∼0.5 nm hydration layer. The nanobridge structure first induces initial contact of Au nanocrystals over their hydration layers and then surface diffusion and grain boundary migration to rearrange into a single nanocrystal. Classical density functional theory calculations and ab initio molecular dynamics simulations suggest that the formation of the nanobridge can be attributed to the accumulation of auric ions and a higher local supersaturation in the gap, which can promote dehydration, contact, and fusion of Au nanocrystals. The discovery of this multistep process advances our understanding of the nanoparticle coalescence mechanism in aqueous solutions.