One-dimensional copper (Cu) nanowires have been used widely for transparent electrode, high-efficiency catalysts and for heat dissipation. Solution-based hydrothermal syntheses are the most common methods to make Cu nanowires. As-prepared nanowires are almost inevitably accompanied by a large quantity of nanoparticles.
Nanowires and nanoparticles are generated together and have similar physical and chemical properties, and thus are very difficult to separate. Current nanowire and nanoparticle separation methods are based on their morphology and density. Such methods include using hollow-fiber membrane, multiple filtration, and rate-zone centrifuge. These procedures are laborious, use complicated solutions, bulky instruments, resulting in poor separations and/or limitations in up-scaling.
LLNL researchers have developed a new method of separating copper nanowires from copper nanoparticles in a two-phase liquid system, within one step, within a few minutes and with excellent separation results.
LLNL's new method of separation is based on the unique observation that copper nanowires can cross the interface between water and a wide range of hydrophobic organic solvent (e.g. chloroform, hexane, toluene), while copper nanoparticles cannot.
Using Livermore's approach, copper nanowires and nanoparticles can be separated with nearly 100% purity quickly and economically by simply adding organic solvent.
Copper nanowires show promise for replacing ITO in optoelectronics applications such as consumer electronics touchscreens, solar cells and OLEDs. Besides their conductivity, they are relatively easy to synthesize.
Livermore's cross-phase separation method for copper nanowires was originally developed for LLNL's NIF laser targets. Other potential applications envisioned are transparent electrodes, ultralight copper aerogels, heat dissipators, liquid fuel generation, sensors, solar cells, data storage.
LLNL has filed a patent application for this invention.