• Camargo, Pedro
• Silva, Anderson G. M. Da
• Vara, Madeline
• Nguyen, Quynh N.
• Chen, Ruhui
• Xia, Younan

Abstract

<p>The rational synthesis of nanostructured materials with desired properties calls for a thorough understanding of the growth mechanism. Here we report a mechanistic case study of Pd nanostructures synthesized by reducing a Pd(II) precursor with hydroquinone in the presence of KBr. As the reaction temperature was decreased from 100 to 20 degrees C, sub-10 nm cubes, concave nanocubes, and cube-like aggregates of much smaller particles were sequentially obtained. Our time-lapse experiments and a set of controls indicated that primary particles of 1-4 nm in size were formed during the initial stage of the synthesis, followed by their aggregation into cube-like structures through an attachment process. In addition to the influence of surface capping, the reaction temperature played a vital role in determining the exact shape or morphology of the final products by affecting the reduction kinetics, fusion of the attached particles, and surface diffusion of atoms. At 100 degrees C, corresponding to a quick depletion of the Pd(II) precursor, the primary particles in each aggregate could easily fuse together to form nanocubes with flat faces owing to adequate surface diffusion. At 60 degrees C, the constituent particles also fused into cubes and then evolved into concave cubes through atomic deposition at the corners. At 20 degrees C, although fusion did not occur due to the substantially decreased diffusion rate, the primary particles in each aggregate still grew through atomic deposition for the formation of larger, cube-like aggregates. Explicating the growth mechanism, this work offers a mechanistic understanding of the nonclassical growth mode involved in the formation of various metal nanostructures.</p>

Topics

• Deposition
• morphology
• surface
• experiment