Strain mapping in symmetrical core-shell gold nanorods from HRTEM images

Strain distribution, interface type and the causes of strain in gold core-shell nanorods were studied by employing high-resolution electron transmission microscope (HRTEM) and Geometric Phase Analysis (GPA). Anisotropic Strain distributions in gold core-shell nanorods were affected by L-cysteine (Cys) concentration and AA/Au3+ ratio which determines shell growth kinetics. Strain circles were generated at the core-shell interfaces of gold nanorods. The {002} strain distributions of gold nanorods were very sensitive to the increase of Cys concentration and AA/Au3+ ratio. Strain distributions with high strain values on {111} planes were more significant than that on {002} planes. This state was related to the preferential adsorption of thiols on {111} planes. The core-shell interface of gold nanorods was determined to be a mix of distorted coherent interface and semicoherent interface, which was mainly produced via the slip of {111} planes along < 110 > slip direction. The gold shell covered the whole core at the growth conditions of different Cys concentrations and AA/Au3+ ratios provided in this work via seed-mediated symmetric epitaxial growth. The strain at the core-shell interface was mainly generated by Au-S bonds and lattice distortion.