Structural Model of Ultrathin Gold Nanorods Based on High-Resolution Transmission Electron Microscopy: Twinned 1D Oligomers of Cuboctahedrons

Abstract

Recently, we have developed a synthetic method of ultrathin gold nanorods (AuUNRs) with a fixed diameter of ∼1.8 nm and variable lengths in the range of 6–400 nm. It was reported that these AuUNRs exhibited intense IR absorption assigned to the longitudinal mode of localized surface plasmon resonance and broke up into spheres owing to Rayleigh-like instability at reduced surfactant concentration and at elevated temperatures. In order to understand the structure–property correlation of AuUNRs, their atomic structures were examined in this work using aberration-corrected high-resolution transmission electron microscopy. Statistical analysis revealed that the most abundant structure observed in the AuUNRs (diameter ≈ 1.8; length ≈ 18 nm) was a multiply twinned crystal, with a periodicity of ∼1.4 nm in length. We propose that the AuUNRs are composed of cuboctahedral Au₁₄₇ units, which are connected one-dimensionally through twin defects