Simulation of yolk-shell nanostructures optical properties

Abstract. A yolk-shell structure is a double-layer hollow nanostructure, which is composed of a shell, a cavity, and a core. The yolk-shell structures have fascinating properties because of their attractive localized surface plasmon resonance (LSPR) feature, which arouses considerable interest in both optically active nanostructures and practical applications. Compared with the single metal nanostructure, a yolk shell has a more controlled degree of freedom, superior optical properties, and potential applications in photocatalysis and solar cell. However, the preparation of yolk shells often requires multiple steps, making it difficult to control the geometric parameters accurately, which leads to uncontrollability of the experimental results. Therefore, it is necessary to study how the size and composition of a yolk shell affect LSPR properties to further guide and optimize the experimental process. Based on the discrete dipole approximation (DDA) method, the absorption spectra, near-field enhancement, and sensing properties of yolk-shell nanoparticles were analyzed. By adjusting the diameters of cavities, cores, shells, and the materials of the shells, we study the influence of yolk-shell structures on the LSPR properties. In detail, the thicknesses of the shells are set from 5 to 20 nm, the diameters of the cavities being set from 50 to 70 nm and the diameters of the yolks are set from 20 to 40 nm. The materials of the shells are set to be dielectric TiO2 and metallic Au, and both of them have Au cores. It is found that Au@Au yolk shells with large cavities or thick shells have better absorption efficiency, but Au  @  TiO2 yolk shells are just the opposite. For near-field intensity, Au@Au yolk shells are higher than Au  @  TiO2. A yolk-shell structure with larger cavity has smaller full width at half maximum. These results can effectively guide the design of yolk-shell structures for sensing and optoelectronic applications based on LSPR.