Cathodoluminescence Spectroscopy of Complex Dendritic Au Architectures for Application in Plasmon-Mediated Photocatalysis and as SERS Substrates

Complex 3D metallic nanostructures with large surface areas and broadband absorption are attractive candidates for efficient photocatalysis and spectroscopy. Here, hierarchical Au dendrites are self-assembled over centimeter-scales by electrodeposition and the plasmon modes are locally mapped using cathodoluminescence spectroscopy. A correlation between the spatial and spectral distribution of the plasmonic "hot-spots" and the morphology of these structures are demonstrated. Electrodynamic simulations show that the spectra of the plasmon modes are determined by the local geometry of sharp features. Their performance as both surface-enhanced Raman scattering (SERS) substrates and as photocatalysts for the N-demethylation reaction of methylene blue is investigated. High hot-spot densities result in larger SERS enhancement, while the sample with the lowest hot-spot density has a reaction yield 136% larger than the sample with the highest density. These findings indicate that maximizing the hot-spot density is not sufficient to optimize plasmonic substrates for all applications. The spectral and spatial distribution of the plasmon resonances will modify the hot electron generation efficiency and need to be considered for plasmon-enhanced photocatalysis. This work extends the understanding of light-matter interactions in complex 3D structures and provides direction for the rational design of plasmonic architectures for different applications.