(286h) The Influence of Sequenced Peptoids in Controlling Five-Fold Twinned Au Nanostar Formation
- Conference: AIChE Annual Meeting
- Year: 2020
- Proceeding: 2020 Virtual AIChE Annual Meeting
- Group: Computational Molecular Science and Engineering Forum
- Time: Tuesday, November 17, 2020 - 9:30am-9:45am
We use all-atom molecular dynamics (MD) simulations, together with enhanced sampling methods, such as Parallel Bias metadynamics (PBMetaD) and umbrella sampling, to study the adsorption of peptoid Nce3Ncp6 at the Au-water interface and unravel how surface adsorption can affect shape revolution. Using PBMetaD, we find that Nce3Ncp6 strongly prefers Au(111) over Au(100), and the origin of this binding preference can be dissected into two aspects. First, while water forms layers near both surfaces, the packing of the first-layer water molecules is much more ordered on Au(100) than Au(111), which protects the Au(100) facet from molecular adsorptions. Second, aromatic rings significantly favor Au(111) surface due to surface electron density distribution, and their energetic preference is the major contribution to the energetic selectivity of Nce3Ncp6. The carboxyl side chains on the peptoid, however, bind weakly and non-selectively to either facet. As a result, the adsorption of Nce3Ncp6 can largely passivate the Au(111) facet thermodynamically, counterbalance the energy associated with the twin and stabilize the five-fold twinned structure. Due to the amphiphilic and facet-selectivity nature of the peptoid, its packing on surfaces can influence the deposition of solution-phase atoms towards different facets. Using umbrella sampling, we investigated the steric effect from the peptoids adsorbed on Au(100) and Au(111). Weak adsorption results in loosely packed peptoids on Au(100), allowing a higher deposition flux towards Au(100), and thus grows the vertices on the nanostars. In sum, the formation of five-fold Au nanostar is regulated both thermodynamically and kinetically by the strongly selective binding of peptoid Nce3Ncp6 on Au surfaces.