Hierarchical synthesis of silver nanoparticles and wires by copolymer templates and visible light

Self-assembled silver wires in micro-meter scale were obtained from aqueous silver nitrate solution in the presence of a comb-like copolymer as the sole organic component. The requisite copolymer was easily prepared by the grafting poly(oxyethylene)-monoamine (POE-amine) onto poly(styrene-co-maleic anhydride) (SMA). Upon storage at ambient temperature with exposure to daylight, the aqueous AgNO3/SMA–POE solution gradually underwent a color changed from transparent pale-yellow to dark-violet over a period of hours, and after several months a solid precipitate was deposited. The formation process was monitored by ultraviolet–visible spectrometer, particle size analysis, scanning electron microscope, and transmission electron microscope. Silver wires were hierarchically formed by progressive transformation from the initial appearance of silver nanoparticles (ca. 10 nm in diameter), followed by the intermediate rectangles (0.6–1.0 μm in width and 0.4 μm in length) in solution and ultimately the precipitates in micro-scale of silver wires at 1.6–6.4 μm in diameter and 100–370 μm in length. The progressive formation of the precipitated silver wires was accelerated by the exposure of visible light as a photo-reducing energy source. The micron-scale wires have a silver content over 97.4 wt.% and a sheet resistance of 5.5 × 101 Ω/square.

The silver nitrate/copolymer aqueous solution slowly changed its color from pale-yellow to dark-violet under visible light (top) and self-assembly into silver wires with a string of rectangle units (bottom).Figure optionsDownload high-quality image (59 K)Download as PowerPoint slideResearch highlights
► AgNO3/SMA–POE aqueous solution.
► Color variation from pale-yellow to dark-violet under visible light.
► Self-assembly and precipitation.
► Silver wires with a string of rectangle units.