Controlling the Growth Kinetics of Nanocrystals via Galvanic Replacement: Synthesis of Au Tetrapods and Star-Shaped Decahedra

By controlling the kinetics of nanocrystal growth via a galvanic replacement process, branched Au nanocrystals, including Au tetrapods and star-shaped decahedra, have been synthesized in high yield. Such control is achieved by the establishment of a Pt(II)/Pt redox couple during nanocrystal formation, which provides locally high concentrations of Au adatoms via galvanic replacement. These remarkable structures have been extensively characterized by microscopy techniques, which illustrate that the internal twin features of the nanocrystals provide a break in the symmetry of the face centered cubic lattice of the Au particles and account for the specific branching patterns observed. Significantly, this study validates a new class of redox couples for use in nanosyntheses and will enable the preparation of other nanocrystals as kinetic products.