The impact of dendrite morphology on the optical properties of sunflower mimic plasmonic metasurfaces

Dendritic nanostructures are commonly observed in nanomaterials and thin films synthesized using electrochemical methods. The dendritic morphology has a unique fractal structure consisting of several closely spaced tips and gaps. This article investigates the impact of variations in the morphology of sunflower mimic metasurfaces on their plasmonic activity using experimental studies and finite difference time domain (FDTD) simulations. Different types of gold sunflower arrays with gold dendrites of varying shapes, aspect ratios and packing densities were first synthesized by selective electrodeposition on the lateral surfaces of Au-SiO2 disc arrays. Elementary model structures were then designed for FDTD simulations based on the structure of experimentally fabricated gold sunflower arrays. The distributions of enhanced electric field and hot spots were mapped with variations in the morphological features. The experimentally observed optical properties of gold sunflower arrays such as optical reflectance, surface-enhanced Raman scattering and photocatalytic activities were rationalized based on the fundamental understanding developed from FDTD simulations.