Application Note: Synthesis of Silver Nanowires

Uniform Ag nanowires can be readily synthesized using a modified polyol process. A typical synthesis involves ethylene glycol (EG) (Prod. No. 324558) as both the solvent and the reducing agent, with AgNO₃ (Prod. No. 204390) and poly(vinvlpyrrolidone) (PVP, MW=55000) (Prod. No. 856568) as the Ag precursor and the polymeric capping agent, respectively. In this synthesis, CuCl₂ (Prod. No. 203149) species can be added to facilitate the anisotropic growth of Ag nanowires. In a typical synthesis, 5 mL of EG was added to a disposable glass vial with a Teflon stir bar in it; the vial was then suspended in an oil bath (temperature = 151.5 oC) and heated for 1 h under magnetic stirring (260 rpm). At 1 h, 40 μL of a 4 mM CuCl2 solution in EG was injected into the heated EG. The solution was heated for an additional 15 min. 1.5 mL of a 0.147 M PVP solution in EG (concentration calculated in terms of the repeating unit) was then injected into the heated EG, followed by the addition of 1.5 mL of a 0.094 M AgNO₃ solution in EG. The color of the reaction solution changed as follows: initially clear and colorless to yellow (within 1 min), to red-orange (within 3 min), to green, beginning cloudiness (within 5 min), to cloudiness, with a gradual shift from green to brown-red (within 30 min), and finally to opaque gray with wispiness indicating the formation of long nanowires (within 1 to 1.5 h). Upon formation of Ag nanowires, the reaction was quenched by cooling the reaction vial in a room temperature water bath. The products were washed with acetone once and water three times to remove excess EG and PVP prior to characterization.