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Longitudinal and Transversal Directed Overgrowth of Pentatwinned Silver Nanorods with Tunable Optica


Silver nanorods (AgNRs) with a controllable aspect ratio can be formed by templated growth from pentatwinned seeds. However, it is challenging to control the volume of the AgNRs and their aspect ratio independently because of the selective protection against growth of the lateral facets by halides. Here we demonstrate the preparation of AgNRs with tunable width via the addition of dimethyl sulfoxide (DMSO). AgNRs with custom dimensions were produced by separating the longitudinal and transverse growth in a two-step procedure. In the first step, the length is tuned by directing the overgrowth on the {111} tips of the AgNRs. In the second step, the width is adjusted by directing the overgrowth on the {100} lateral facets in the presence of DMSO. AgNRs of varying dimensions were obtained and characterized by a combination of techniques including scanning transmission electron microscopy, electron energy loss spectroscopy, and cathodoluminescence, which are, respectively, sensitive to the extinction and scattering component of the AgNRs’ response. This method allows tuning the plasmon energies, but also the ratio of the scattering and absorption contributions.