Atomic-scale theory and simulations for colloidal metal nanocrystal growth

A significant challenge in the development of functional nanomaterials is understanding the growth of colloidal nanocrystals. Although it is presently possible to achieve the shape-selective growth of colloidal nanocrystals, the process is not well understood and not generally scalable to a manufacturing environment. Advances in our fundamental understanding are hampered by the complexity of the colloidal environment, which makes it difficult to experimentally interrogate the liquid-solid interface of a growing nanocrystal. Theory can be beneficial, but because of the lack of quantitative experimental data, theoretical efforts should be based on first-principles to ensure sufficient accuracy. I review our studies with first-principles, density-functional theory of how polyvinylpyrrolidone (PVP), a widely used structure-directing agent (SDA) in the synthesis of Ag nanocrystals, might function effectively as an SDA. These studies indicate that the beneficial characteristics of PVP are not present in poly(ethylene oxide) (PEO), which is experimentally determined to be less effective as an SDA. I discuss our recently developed force field to characterize the interaction of PVP, PEO, and ethylene glycol solvent with Ag surfaces. The availability of a reliable force field will enable future studies using classical molecular dynamics simulations to probe various aspects of nanocrystal growth.