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Facet Selectivity of Ligands on Silver Nanoplates: Molecular Mechanics Study

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journal contribution
posted on 18.09.2014, 00:00 by Zhiye Tang, Qiao Zhang, Yadong Yin, Chia-en A. Chang
Colloidal nanomaterials with well-defined shapes have wide applications in many fields. However, the exact role of capping ligands, which often dictates the shape of products in colloidal syntheses, is often unclear. Here we use a classical molecular-mechanics force-field method, mining minima (M2), to compute the binding free energy of the ligands such as citrate, monocarboxylates, dicarboxylates, and tricarboxylates to both (111) and (100) facets of silver and to investigate the mechanisms of the anisotropic growth of silver nanoplates. The distribution of partial charges on a ligand, the geometry complementation in the complex, and the entropic penalty on binding played crucial roles in discriminating the two facets and determining a good or poor ligand. Our finding allows rational design of capping ligands that may perform as well as citrate in promoting the anisotropic growth of nanoplates; however, designing a compound that outperforms citrate is found to be challenging.