Atomic Structure\nand 3D Shape of a Multibranched Plasmonic\nNanostar from a Single Spatially Resolved Electron Diffraction Map

Despite the interest in improving the sensitivity of\noptical sensors\nusing plasmonic nanoparticles (NPs) (rods, wires, and stars), the\nfull structural characterization of complex shape nanostructures is\nchallenging. Here, we derive from a single scanning transmission electron\nmicroscope diffraction map (4D-STEM) a detailed determination of both\nthe 3D shape and atomic arrangement of an individual 6-branched AuAg\nnanostar (NS) with high-aspect-ratio legs. The NS core displays an\nicosahedral structure, and legs are decahedral rods attached along\nthe 5-fold axes at the core apexes. The NS legs show an anomalous\nanisotropic spatial distribution (all close to a plane) due to an\ninterplay between the icosahedral symmetry and the unzipping of the\nsurfactant layer on the core. The results significantly improve our\nunderstanding of the star growth mechanism. This low dose diffraction\nmapping is promising for the atomic structure study of individual\nmultidomain, multibranched, or multiphase NPs, even when constituted\nof beam-sensitive materials.