Strain-Induced Modulation of Localized Surface Plasmon Resonance in Ultrathin Hexagonal Gold Nanoplates.

Anisotropic gold nanoplates (NPLs) have raised the interesting possibility that their reduced geometrical symmetry allows fine tuning of their optical properties associated with the excitation of localized surface plasmon resonances (LSPRs). Recent developments have greatly improved LSPR tunability by utilizing the spatial distribution of LSPR modes. However, the nanoscale interplay between defect-induced mechanical strain and the spatial variation of LSPR modes remains poorly understood. In this work, the combination of high spatial- and spectral-resolution mapping of LSPR modes and nanoscale strain mapping using aberration-corrected transmission electron microscopy are applied to investigate the nanoscale distribution of LSPR modes in an ultrathin single hexagonal gold NPL and the effect of defect-induced strains on its LSPR properties. The electron energy-loss spectral maps reveal four distinct LSPR components and intensity distributions of all LSPR modes in a hexagonal gold NPL. Furthermore, the strain maps provide experimental evidence that the tensile strain field induced by a Z-shaped faulted dipole is responsible for the asymmetric distribution of LSPR intensity in a hexagonal gold NPL.