Branched noble metal nanostructures are interesting architectures with sharp tips and crevices which, upon excitation, generate regions of concentrated electromagnetic field. These �hot spots� amplify Raman signals of adsorbed molecules, useful for sensing applications. Many branched nanoparticle syntheses yield non-uniform, asymmetric nanostructures, making systematic studies difficult and optical property measurements irreproducible. Homogeneity achieved through seed-mediated synthesis is accomplished by growing smaller seeds followed by additional metal deposition. Previously, we demonstrated Au/Pd octopod synthesis by seed-mediated co-reduction. Here, we show how seed shape directs bimetallic overgrowth to branched nanocrystals (e.g. octopods and tetradecapods). The seed is a modifiable platform, selectively controlling the number of symmetric branches. This study was achieved with Pd seeds and Au/Pd overgrowth conditions which provide high contrast between the seed and overgrowth phases through scanning transmission electron microscopy coupled with energy-dispersive electron microscopy (STEM-EDX) imaging. These results provide significant insight into the co-reduction method and seed-mediated synthesis.

Core controls: Influence of Pd seed structure on Au/Pd overgrowth for the synthesis of symmetrically branched nanocrystals

244th National Meeting (2012)

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