Structural investigations of copper nanorods by high-resolution TEM

Abstract

Well-defined long Cu rods having a length of the order of 1 μm and diameters of several nanometers were prepared by reduction of copper compounds. After deposition on amorphous carbon films, high-resolution transmission electron microscopy and electron diffraction were performed in order to explain the structure of the rods. By applying computer simulations with multislice calculations, the particle structure was obtained. The rods were held to be truncated decahedra with a fivefold symmetry. It could be shown that most particles were oriented in the [001] direction with respect to the substrate for one of the five deformed tetrahedral subunits, i.e., the fivefold axis very often was parallel to the surface of the substrate. It was also proven that the Cu fcc bulk structure containing stacking faults had to be excluded as a possible structural model. Also, truncated icosahedral structures or icosahedra with additional intermediate planes did not serve to explain the experimental process. Icosahedra are often observed together with decahedral structures for particles with a spherical-like morphology. Due to the presence of surfactant, only growth in the direction of the fivefold axis of decahedra was possible, resulting in long needlelike rods.