Advanced Materials: TechConnect Briefs 2015Advanced Materials TechConnect Briefs 2015

Informatics, Modeling & Simulation Chapter 2

Synthesis of {111}-faceted Au Nanocrystals Mediated by Polyvinylpyrrolidone: Insights from Density-Functional Theory and Molecular Dynamics

S.-H. Liu, W.A. Saidi, Y. Zhou, K.A. Fichthorn
The Pennsylvania State University, United States

pp. 91 - 94

Keywords: polyvinylpyrrolidone, adsorption, surface energy, nanostructure, reconstruction, density-functional theory, molecular dynamics

We use dispersion-corrected density-functional theory (DFT) and classical molecular-dynamics (MD) to resolve the role of polyvinylpyrrolidone (PVP), a widely used structure-directing agent, in the shape-selective synthesis of {111}-faceted Au nanostructures. First by DFT, we consider the interaction of 2-pyrrolidone (2P) with Au(111), Au(100), and (5 X 1) Au(100)-hex surface. We find that the 2P-covered Au(111) surface is thermodynamically favored because it has the lowest surface energy. Also, by comparing 2P binding energies and their spatial distribution across the three surfaces, we suggest that PVP may exhibit a comparable or greater binding affinity for Au(111) than for (5 X 1) Au(100)-hex. Further by MD, atactic PVP icosamers are considered because of the typical atacticity of PVP. We conclude that PVP has a comparable binding affinity for Au(111) with for (5 X 1) Au(100)-hex, and we find that this PVP-covered Au(111) surface still has lower surface energy than (5 X 1) Au(100)-hex. In addition, by examining the oxygen density profile, it is likely that Au(111) grows more rapidly than (5 X 1) Au(100)-hex. Based on both thermodynamic and kinetic points of view from DFT and MD, we predict that {111}-faceted Au nanocrystals are preferred in PVP-mediated synthesis, consistent with experiment.