Convenient, Rapid Synthesis of Ag Nanowires

Abstract

The rapid, microwave-assisted aerobic synthesis of silver nanowires based on the polyol method is described. Benchtop dissolution of NaCl and AgNO3 (ratio 1:6 to 1:3) in ethylene glycol and subsequent heating using microwave irradiation (300 W) in the presence of polyvinylpyrrolidone generates Ag nanowires in ∼80% yield in 3.5 min. Upon purification, microscopy (TEM, SEM) and powder X-ray diffraction reveal a uniform set of crystalline Ag nanowires with dimensions of 45 nm × 4−12 μm. Wire formation is highly dependent upon the microwave heating power, time, and NaCl:AgNO3 ratio because of the rapid heating process and the presence of O2 as an etching coreagent. Extended microwave heating causes the wires to fuse if in proximity or degrade to shorter wires presumably via the etching reaction. In the absence of O2/Cl-, the wires melt upon extended microwave heating (>4 min), suggesting that nanowire melting may contribute to the observed morphology under etching conditions. Compared to existing wet-chemical methods using traditional heating techniques, microwave irradiation not only rapidly heats, but dielectric heating of the growing wires also occurs, resulting in accelerated deposition of Ag0 at the wire ends. Furthermore, this high yielding preparation does not require any external seed crystals, precursors, or mechanical stirring and is conducted under ambient O2 conditions, leading to significant potential for the large-scale fabrication of Ag nanowires using this simple approach.