Shape-directional growth of Pt and Pd nanoparticlesElectronic supplementary information (ESI) available: TEM images of platinum nanoparticles synthesized in the presence of different directing agents. See DOI: 10.1039/c4nr02755h

The design and synthesis of shape-directed nanoscale noble metal particles have attracted much attention due to their enhanced catalytic properties and the opportunities to study fundamental aspects of nanoscale systems. As such, numerous methods have been developed to synthesize crystals with tunable shapes, sizes, and facets by adding foreign species that promote or restrict growth on specific sites. Many hypotheses regarding how and why certain species direct growth have been put forward, however there has been no consensus on a unifying mechanism of nanocrystal growth. Herein, we develop and demonstrate the capabilities of a mathematical growth model for predicting metal nanoparticle shapes by studying a well known procedure that employs AgNO 3 to produce {111} faceted Pt nanocrystals. The insight gained about the role of auxiliary species is then utilized to predict the shape of Pd nanocrystals and to corroborate other shape-directing syntheses reported in literature. The fundamental understanding obtained herein by combining modeling with experimentation is a step toward computationally guided syntheses and, in principle, applicable to predictive design of the growth of crystalline solids at all length scales (nano to bulk). The convergence of experimentation with modeling of shaped platinum nanoparticle synthesis directed by silver concentration enables materials design of other systems: modeling of facet selective growth predicted shaped palladium nanoparticles synthesized by silver limiting the growth of {111} surface facets.