Molecular Mechanism of Specific Recognition of Cubic Pt Nanocrystals by Peptides and of the Concentration‐Dependent Formation from Seed Crystals

Abstract

Metal nanocrystals enable new functionality in sensors, biomarkers, and catalysts while mechanisms of shape‐control in synthesis remain incompletely understood. This study explains mechanisms of biomolecule recognition and ligand‐directed growth of cubic platinum nanocrystals in atomic detail using molecular dynamics simulation (MD), synthesis, and characterization. Peptide T7 is shown to selectively recognize {100} bounded nanocubes through preferential adsorption near the edges as opposed to facet centers. Spatial preferences in peptide binding are related to differences in the binding of water molecules and conformational matching of polarizable atoms in the peptide to {100} epitaxial sites. Changes in peptide concentration also have profound impact on attraction versus repulsion on a given surface. As an example, the selective synthesis of cubes in the presence of peptide T7 demonstrates that only intermediate T7 concentration leads to high yield. High‐resolution transmission electron microscopy (HRTEM) shows concentration‐dependent changes in crystal shape, yield, and size. Large‐scale MD simulations explain associated differences in facet coverage and in adsorption energies of T7 peptides on cuboctahedral seed crystals, supporting a growth mechanism of adatom deposition. A similar analysis using a different peptide S7 is presented as well. Emerging computational opportunities to predict ligand binding to metal nanocrystals and rationalize growth preferences are summarized.

CHARMM-GUI Nanomaterial Modeler for Modeling and Simulation of Nanomaterial Systems

“…At low concentration (<20 μg/mL), the binding of the T7 peptides to the Pt nanoparticle preferentially occurs near edges as opposed to the inner portions of the (100) facets. This is due to the substantially reduced binding of water at the edges, which is consistent with previously reported data . These simulations provide insight into the mechanisms of nanocrystal growth and the spatial distribution of facet-specific ligands as a function of concentration.…”

Insight into induced charges at metal surfaces and biointerfaces using a polarizable Lennard–Jones potential

“…In instances where solvents and solutes are neutral, the nonpolarizable model can be used 10 . The results reported here support the validity of earlier computational studies of ligands with no or few charged groups in contact with fcc metals in solution using the nonpolarizable model and the good agreement with experiment that has been demonstrated 5 , 13 , 17 – 22 . Nevertheless, the (hkl) surfaces, edges, and corners of metal nanocrystals are often covered by layers of chloride, bromide, or iodide ions from ionic surfactants (CTAB, CTAC) that induce substantial polarization effects with estimated contributions to binding up to 40% 21 , 64 , 69 .…”

Accurate and Ultrafast Simulation of Molecular Recognition and Assembly on Metal Surfaces in Four Dimensions

“…Similar soft epitaxial binding has been earlier discovered for amino acids, surfactants, and saturated hydrocarbons on Pt and other metal surfaces by IFF MD simulations . The binding mechanism is supported by LEED data, relative binding affinities, spectroscopic measurements, and preferences in crystal growth. ,,,− The strength of binding of a single benzene molecule to a Pt(111) surface is ∼189 kJ/mol in experiments, remains steady up to medium coverage, and then decreases toward higher coverage (Figure a, b). Hereby, SCAC measurements were limited up to a monolayer thickness.…”