In this talk, we will elucidate the role of surface diffusion in controlling the evolution of Ag nanocrystal seeds into new shapes or morphologies. When citrate-free Ag nanoplates was employed as the seeds, the newly formed Ag atoms were preferentially deposited on the top and bottom {111} facets, followed by two growth pathways determined by surface diffusion. We discovered that the nanoplates were transformed into bipyramids through vertical growth when surface diffusion was less significant in moving the deposited atoms to side faces at a high injection rate for AgNO3 or at a low reaction temperature of 0 oC. In contrast, larger hexagonal plates were formed through lateral growth when surface diffusion was in dominance at room temperature with a slow injection rate for AgNO3. We will also validate the role of facet capping of {111} on the shape evolution of nanoplates by titrating different amounts of citrate into the reaction solution. As long as citrate had limited coverage on {111} facets, the Ag atoms would be preferentially deposited on {111} rather than {100} facets, leading to the formation of bipyramids when the growth was dominated by atom deposition over surface diffusion.  However, in the presence of adequate citrate, atom deposition occurred on the {100} side facets, leading to the formation of larger triangular plates. We believe that a comprehensive understanding on the role of surface diffusion represents a leap towards the rational design of seeded growth with exquisite controls to generate nanocrystals with new morphologies.

Understanding the role of surface diffusion in controlling the growth pathway of citrate-free silver nanoplates

247th National Meeting (2014)

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