Morphological Control in the Synthesis of Silver Nanostructures: Role of Polyvinylpyrrolidone*

Solution-phase syntheses are useful for assembling metallic nanostructures with desired morphologies. For example, a wide variety of silver nanostructures have been synthesized in the polyol process [1], including nanowires, nanoplates, cubes, etc. Polyvinylpyrrolidone (PVP) plays a key role in controlling nanostructure morphologies in these fabrication processes. Based on experimental observations, the interaction strength between PVP chains and Ag atoms in different crystallographic facets is expected to vary significantly and this shape selectivity is expected to play a key role in directing the formation of various nanostructures. Using first-principles calculations based on density-functional theory including van der Waals interactions, we compute the interactions of the basic elements of a repeat unit in PVP (2-pyrollidone and ethane) with various crystal faces of Ag. Our results indicate that PVP does exhibit the expected structure sensitivity and that this arises from an interesting balance between van der Waals interactions and direct chemical bonding. We discuss the ramifications of our calculations for the assembly of Ag nanostructures. \\[4pt] [1] B. Wiley et al., Chem. Eur. J. 11, 454 (2005).