Metal nanocrystals have gained tremendous attention due to their superior performance in various applications, ranging from selective catalysis to electronic devices to plasmonic applications, such as photovoltaics and sensing. The properties of nanocrystals are highly sensitive to their size and shape. To this end, solution-phase synthetic protocols have been highly successful at producing a variety of nanocrystal structures. However, great challenges remain in achieving high selectivity to particular nanostructures. A significant difficulty lies in understanding and controlling shape evolution in these systems. A deep, fundamental understanding of the phenomena that promote selective growth in these syntheses would enable tight control of nanostructure morphologies in next-generation techniques.<br/><br/>A common adage is that solution-phase additives, such as capping molecules, can direct the shapes of colloidal nanocrystals by adsorbing selectively to certain facets. Though our first-principles-based studies indicate that capping molecules alone can direct the formation of nanocrystal shapes in certain systems, experiments demonstrate that more robust syntheses can be achieved in the co-presence of halide additives. We use DFT-based <i>ab initio</i> thermodynamics calculations to probe the influence of chloride on Ag nanoshapes. Consistent with experiment, these calculations indicate that chloride adsorption alone can lead to truncated Ag cubes. We find that adsorbed chlorine works synergistically with PVP, a common capping agent for Ag, to enhance the tendency for Ag cubes.  These results are consistent with experiment. We also show how adsorbed Cl works synergistically with HDA capping molecules to facilitate the growth of Cu nanowires - consistent with experiment. These studies indicate that halides and various capping molecules can be a powerful combination to create selective nanoshapes in solution-phase syntheses.

How solution-phase additives control the shapes of metal nanocrystals in solution

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.