Cu/Au Bimetallic Nanobranched Structures and Nanocubes: Their Synthesis and Mechanistic Studies

Yonglin Liu and A. R. Hight Walker

Optical Technology Division, Physics Laboratory

The galvanic replacement reaction has been applied to produce hollow-interior nanostructures (nanocages) using pre-synthesized nanoparticles as templates.  These unique nanomaterials have potential applications in the fields of catalysis, chemical and biological sensors, and surface-enhanced Raman scattering spectroscopy.  In the first synthesis, we demonstrate that a replacement reaction can be used to obtain branched Cu/Au nanostructures attached to hollow nanocrystals using surface-modified Cu nanoparticles as sacrifice templates.  In the presence of 1-dodecanethiol, we found that CuS layers grow unevenly on the surfaces of pre-synthesized Cu nanoparticles (50 nm-200 nm) with various shapes such as pyramids, cubes, and polygons.  Then, a galvanic replacement reaction between HAuCl₄ and surface-modified Cu nanoparticles produces branched Cu/Au bimetallic nanostructures attached to nanocages.  The as prepared nanostructures are characterized using TEM, HR-TEM, XRD, and UV-visible spectroscopy.  The mechanistic aspects of branched particles will also be presented.

In the second synthesis to be presented, we report, for the first time, a one-step polyol synthesis method for single-crystalline Cu/Au nanocubes in the presence of amine and acid as capping agents.  The Cu/Au nanocubes are synthesized by the reduction of a gold precursor with 1,2-hexadecanediol in the surfactant solution using diphenyl ether as a solvent.  By simply changing the reaction parameters such as the concentrations of starting materials, nearly monodispersive Au nanocubes with controllable average edge sizes of 8 nm, 25 nm, 50 nm, and 100 nm can be obtained. The formation mechanism of these Au nanocubes will be presented.  The size-dependent surface plasmon resonance properties of the as-synthesized nanocubes have also been investigated.

Author Information:

Name:  Yonglin Liu

Mentor’s name: Angela R. Hight Walker

Division: Optical Technology, 844

Laboratory: Physics

Building/Room: 216/B219

Mail Stop: 8443

Telephone #: 301-975-8568

Fax #: 301-976-6991

Email:  yonglin.liu@nist.gov

Sigma Xi:  member

Category: Physics