Silver nanowires with five-fold symmetric cross-section

Abstract

Uniform silver (Ag) nanowires with an average length of 6 μm and diameter of 70 nm have been synthesized via PVP-assisted (polyvinylpyrrolidone, PVP-K30) polyol reduction. The structure of thus-obtained Ag nanowires has been investigated thoroughly through scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Combined with the previous results, it is concluded that the Ag nanowires possess five-fold twinned crystal structure with [1 1 0] growth direction, bounded by five [1 0 0] planes and capped by ten [1 1 1] planes. The SAED of the pentagonal cross-section gives direct evidence of the five-fold symmetry of the Ag nanowires. The high-resolution TEM image clearly shows the five twinning boundaries with various defects. UV–visible absorption spectra, which are related to the well-defined structure of the Ag nanowires, exhibit unique transversal modes of the Ag nanowries. IR spectra of the Ag nanowires, compared with the pure PVP, indicate that the Ag atoms on the surface of the Ag nanowires are coordinated with oxygen atoms in the carbonyl group of the PVP. It has been proposed that the PVP main chain might lie on the surface of the Ag nanowires with the pyrrolidone ring tilted on them.