Functional faceted silver nano-hexapods: Synthesis, structure characterizations, and optical properties

We report a new application of the polyol process to produce silver nanohexapods (AgNHs) with a well-defined concave shape and a unique crystal structure. The structure was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), selected-area electron diffraction (SAED), and high-resolution electron microscopy (HREM). The experimental results were compared with simulations. The AgNHs are single crystals with a face-centered-cubic (FCC) lattice with a lattice constant of 9.6193 angstrom, larger than the 4.0862 angstrom of bulk FCC-Ag. Each AgNH has six branches along the (100) directions. Each of these branches terminates with a square-pyramidal tip of four {111} faces. The faceted AgNHs have a skeleton of Ag-6 octahedra stabilized by organic capping molecules. The AgNHs are metastable and decay under electron beam irradiation to FCC-Ag polycrystalline nanoparticles with abundant stacking faults. The AgNHs were found to be a good substrate for chemical sensing using the surface-enhanced Raman scattering (SERS) method.