Rational Synthesis of Cylindrical Silver Single-crystalline Nanowires via Poly(vinyl pyrrolidone) Reduction of AgCl

We presented a simple yet convenient hydrothermal approach for the large-scale synthesis of uniform cylindrical silver (Ag) single-crystalline nanowires with diameters of about 25 nm and lengths of 1-4 μm. Poly(vinyl pyrrolidone) (PVP) was used as a reducing agent, and AgCl was used as a precursor to deliberately control [Ag^+] at a low degree in the overall reaction process through its dynamic equilibrium by directly reducing AgCl with PVP at a quasi-equilibrium growth condition. The as-obtained products were characterized by powder X-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), infrared spectra (IR) and Raman spectra. Factors such as [PVP], reaction temperature, time, and species of reducing agents and precursors were investigated to have strong influences on the morphologies and structures of the resultant Ag nanostructures. The wire diameter can conveniently be adjusted between 25 and 50 nm by simply adjusting [PVP], reaction temperature and reducing agent species. The as-synthesized silver nanowires can be self-assembled into perfect order arrays after being dried on tin foil due to the PVP coating on the surface, the circular cross-section and the uniform diameter of the Ag nanowires. These special silver nanowires with a core-shell structure as well as their spontaneous self-assembly of order arrays are expected to provide potential applications in flexible conductors, dielectric materials, electromagnetic shielding materials and nano-devices.