Rapid and high-yield synthesis of silver nanowires using air-assisted polyol method with chloride ions

Effects of gas bubbling were studied for synthesis of silver nanostructures from a mixture of AgNO3/NaCl/poly(vinylpyrrolidone) (PVP) in ethylene glycol (EG). Monodispersed silver nanowires were synthesized under oil-bath heating in high yield (>90% without isolation) using bubbling of air through a reagent solution from ca. 20 °C to the boiling point of EG (198 °C) for 20 min. On the other hand, mixtures of cubes, bipyramids, and wires were prepared under bubbling of N2. The Ag nanostructures’ growth mechanism was studied by observing ultraviolet–visible (UV–vis) spectra and transmission electron microscope (TEM) images at various temperatures. Results show that the formation process of Ag nanostructures under gas bubbling is separable into two stages: a low temperature range of 20–180 °C at 0–17 min, where mixtures of variously shaped Ag seeds are produced independent of the bubbling gas; and a high temperature range of 180–198 °C at 17–20 min, where rapid growth of nanowires and oxidative etching of cubes and bipyramids by Cl−/O2 occur simultaneously in bubbling of air, thereby producing long nanowires in high yield. Because the etching process is absent during processing by bubbling of N2, mixtures of shorter nanowires, cubes, and bipyramids are produced.