Epitaxial growth of one-dimensional different-diameter silver nanowires

With the increasing demand for higher-level functional nanodevices, there is a strong requirement for the fabrication of high-crystallinity composite nanowires, e.g., one-dimensional end-to-end different-diameter silver nanowires. However, these nanowires have been mostly assembled by end-to-end physicomechanical coupling, which causes gap junctions or loose connections between the nanowires, limiting their extensive application. In this study, one-dimensional different-diameter silver nanowires with well-controlled shapes and high yields were synthesized. This type of nanowire comprises a thick nanowire and a thin nanowire of uniform diameters. The thin nanowire epitaxially grows on the end surface of the thick nanowire. The connection between the thick and thin nanowires shows high-crystallinity with Ag{100} facets. With temperature approaching 150 degrees C, the cross-linking reaction of the PVP chains is gradually intensified. As a result, the cross-linked PVP chains, which are adsorbed on the side surface (Ag{100}) near the end of the nanowire, extend over the edge of the end, forming Ag{100} facets. This reduces the effective area of the Ag {111} facets on the end surfaces of the nanowires. Consequently, a thin nanowire grows from the remaining Ag{111} facets at the end of the existing nanowire, forming different-diameter silver nanowires. Moreover, the surface plasmon propagation along this nanowire shows distinctive performance compared with that of the conventional end-to-end mechanically coupled nanowires, indicating that these different-diameter nanowires have unique properties, which can lead to more significant applications.