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 AgNO 3 (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:AgNO 3 ratio because of the rapid heating process and the presence of O 2 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 O 2 /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 Ag 0 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 O 2 conditions, leading to significant potential for the large-scale fabrication of Ag nanowires using this simple approach.