Web Release Date: January 30,
Shape Adjustment between Multiply Twinned and Single-Crystalline Polyhedral Gold Nanocrystals: Decahedra, Icosahedra, and Truncated Tetrahedra
and
Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea, BioNanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-333, Korea, and Department of Chemistry, Kyung Hee University, Seoul 130-701, Korea
Received: November 16, 2007
Abstract:
Polyhedral gold nanocrystals with decahedral, icosahedral, and truncated tetrahedral shapes are synthesized by a simple one-pot polyol process in the prescence of poly(vinyl pyrrolidone) (PVP). High PVP concentration up to 360 equiv of the gold precursor, HAuCl4, effectively stabilizes decahedral seeds to yield uniform decahedra with various edge sizes. Decreased PVP concentration subsequently leads to selective formation of icosahedra and truncated tetrahedra. This results from a combination between the relative energy difference of the polyhedral structures and the oxidative etching rate of the seeds by Cl-/O2 during the reaction. The distinct morphologies of gold nanocrystals exhibit characteristic extinction patterns in the UV-vis-NIR ranges, and these properties are successfully analyzed by the discrete dipole approximation (DDA) calculation. Most extinctions stem from the polar and azimuthal dipolar excitations, and azimuthal quardrupole resonance appears between two dipolar bands in the 88-nm decahedra. Given these shape- and size-dependent optical properties, gold nanocrystals hold considerable promise for biomedical and photonic applications.
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