Tuning Size and Seed Position in Small Silver Nanorods

Although high-quality gold nanorods can be routinely synthesized, within a wide range of sizes and aspect ratios, a similar level of control has not been reached for silver nanorods. Whereas seeded-growth processes have been developed, the reported methods have not met sufficient interest, mainly because of limited quality, particularly when small size (short diameter) and small aspect ratios are targeted. In the surfactant-driven seeded growth of gold nanorods, the success of the synthesis is largely dependent on the quality and stability of the seeds, and thus related methods have been reported for the seeded growth of Ag nanorods, using penta-twinned Au nanorods and bipyramids as seeds. However, Ag nanorods with diameters of >30 nm are consistently obtained, restricting their potential applications. We report the preparation of high-quality silver nanorods, using either small bipyramids or small decahedra as seeds, with special attention to the location of the seeds, either at the center (bipyramids) or at one end (decahedra) of the resulting nanorods.