Optical and Dynamical Properties of Chemically Synthesized Gold Nanoplates

Single crystal, micrometer-sized nanoplates were formed by reducing Au(III) in the presence of surfactants using a modified polyol protocol. The shapes of the plates range from triangular to hexagonal. The nanoplates have {111} surfaces with an average edge length of 5 ± 2 μm and an average width of 107 ± 30 nm. Scanning electron microscopy (SEM) images reveal that the plates grow through a re-entrant groove created by twinning. The optical properties of the plates were studied by scattered light and transient absorption experiments. The scattered light measurements show that propagating surface plasmon polariton (SPP) modes of the Au nanoplates can be excited when a laser beam is focused at the edge of the nanoplate. We also demonstrate that the direction of propagation of the SPP modes can be controlled through the polarization of the laser beam. The transient absorption traces for single suspended nanoplates show oscillations, which are assigned to thickness vibrations of the plates. The quality factors for the oscillations are smaller than those recently measured for suspended gold nanowires, indicating possible contributions to the vibrational damping from surface bound molecules or from the crystal structure.