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ORIGINAL RESEARCH

Full Atomistic Simulation of Cross‑Linked Gold Nanoparticle Assemblies Kai‑Chih Yeh1 · Yuan Chiang1 · Shu‑Wei Chang1  Received: 30 March 2020 / Revised: 25 August 2020 / Accepted: 3 October 2020 © Korean Multi-Scale Mechanics (KMSM) 2020

Abstract Nanoparticles (NPs) comprised of noble metal cores and organic ligands have been widely used in many engineering applications in the recent years due to their exceptional material properties. Numerous studies have explored the tunability of the elastic and electronic transport properties of nano-scale thin films made of gold nanoparticles. However, the nanoscale mechanisms, such as the conformation of ligands, cross-linking behavior, are still not well understood. In this study, we developed a full atomistic modeling approach to construct full atomistic cross-linked gold nanoparticle thin films to explore the nanoscale features and molecular configurations of cross-linked gold nanoparticle assemblies at the nano-scale. Keywords  Nanoparticle · Gold Nanoparticles (GNPs) · Organic-Inorganic System · Molecular Dynamics · Membrane

Introduction Nanoparticles (NPs) comprised of noble metal cores and organic ligands attracted much attention over 20 years [1–4]. Due to their tunable electronic and optical properties, they have been applied for a variety of applications, including strain gauge [5, 6], touch sensor [7] and vapor sensor [8]. Recently, the thin films formed by cross-linked or ligand-stabilized NPs have been studied in experiments [9–11]. Important chemical and physical properties for applications, including mechanical stiffness and conductivity, were measured in experiments [11–13]. Moreover, these studies showed that these properties can be controlled by the chemical nature and length of ligand, and the size of the NPs [14, 15]. However, the nanoscale mechanisms, such as the conformation of ligands, cross-linking behavior, are still not well understood. Experimentally, there have been several ways to fabricate nanoparticle thin films, including using evaporation-induced ordering [2], DNA-programmable NPs [16], and layer-bylayer spin-coating [4]. Some thin films were cross-linked with short alkanedithiol (ADT) chains or single-stranded DNA (ssDNA), while some thin films were aggregated by * Shu‑Wei Chang [email protected] 1



Department of Civil Engineering, National Taiwan University, Taipei 10617, Taiwan

the van der Waals interaction between the alkanethiol chains coating on NPs. The Young’s moduli of these thin film were measured on the order of 1–10 GPa. And it is found that the interparticle spacing can affect the film’s conductivity because the charge transport proceeds via thermally activated tunneling. There have been a number of molecular dynamics (MD) simulation studies in the properties of the single NP or NPs assembly. Earlier, Luedtke et al. examined the equilibrium structure and thermodynamic properties of the single gold nanoparticle (GNP) coated with alkanethiol chains [17, 18]. Recently, the conformation of the self-assembled