Regulating Plasmonic Properties through Asymmetric Oxidative Etching of Octahedral Au@Ag Core-Shell Nanocrystals with Iridium Chloride.

We present the engineering of plasmonic nanostructures and their optical properties through the asymmetric oxidative etching of octahedral Au@Ag core-shell nanocrystals. This process utilizes iridium chloride to produce Au@Ag-AgCl-IrO products under hydrothermal conditions. This method deviates from conventional techniques that involve the oxidative etching of Ag nanocubes with Au precursors, which typically results in an isotropic and gradual etching process. Our protocol uniquely initiates with the rounding of the octahedral nanocrystals' sharp corners, followed by the selective removal of roughly half of the Ag shell, thus exposing portions of the Au core. Continued etching leads to the creation of yolk-shell structures, where the Au core remains intact while most of the outer shell is converted into silver chloride (AgCl). Comprehensive structural analyses confirm the presence of IrO in the final products, playing a crucial role in directing the observed anisotropic oxidative etching pattern. Additionally, we examined the practical applications of these synthesized materials in plasmonic catalysis, revealing a significant enhancement in the catalytic performance under UV-vis light irradiation. The FDTD simulation confirms the effect of different shell materials and structures on the plasmonic properties and temperature distribution. These findings highlight the potential utility of our approach in the rational design of plasmonic nanostructures.