(346t) Simulation-Guided Tuning of Sequenced Peptoids Towards Achieving Shape-Controlled Au Nanocrystal Growth

Metal nanocrystals have remarkably advanced cutting-edge technologies owing to their unique plasmonic, electronic and catalytic properties, which are highly dependent on their shapes and sizes. A broad spectrum of nanostructures has been synthesized in solution with chemical additives. These chemical additives often show facet selectivity and can impart shape-controlled growth thermodynamically, kinetically, or both. The identification of these chemical additives, however, is still based on a “trial and error” process experimentally and only a small library of effective structure-directing chemical additives has been found so far. Thus, a less expensive and theory-based selection of such chemical additives is urgently in demand.

Peptoids are synthetic polymers that have similar backbone structure as peptides, with side chains connected to the backbone nitrogen atoms instead of the -carbons. Some peptoids have been shown to effectively assist shape-controlled metal nanocrystal formation. Because peptoid sides chains come in a variety of chemical structures and their sequence is tunable, they can serve as excellent templates to be engineered towards chemical additives for shape-controlled nanocrystal growth. We use molecular dynamics simulations and enhanced sampling methods to obtain adsorption free energies of several side chain analogs and understand their adsorption mechanisms. Based on theoretical findings from previous studies on how facet selectivity can influence nanocrystal growth, we program peptoid sequences to achieve a facet selectivity that may bring a desired outcome. We verify the energetic facet selectivity of peptoids by calculating their adsorption free energies using Parallel Bias metadynamics. These peptoids have effectively guided the experiments to realize desired nanostructures.