How Nanotechnology Scientists Grow Nanoparticles
Producing nanoparticles involves breaking up a bulk material into atoms or ions and then allowing them to condense into nanoparticles. In nature, a campfire produces a small quantity of carbon nanotubes. In the lab, equipment designed to produce nanoparticles makes the process more efficient by breaking down more of the raw material to the atomic level under controlled conditions to condense atoms together and form nanoparticles.
Several types of systems are used to produce nanoparticles. A description of a few commonly used systems follows.
Plasma source system: In a plasma source system, an inert gas, such as argon, flows into a chamber. This gas carries macroscopic particles of the material from which you want to produce nanoparticles. A high-power radio frequency signal applied to the carrier gas produces plasma, which then flows into a cooled chamber. The ions then condense into nanoparticles. This method is often used for volume production of metallic nanoparticles.Using a plasma source to produce nanoparticles.
Spark system: If you’re interested in growing only small quantities of nanoparticles, try a spark system. This system uses a high-voltage pulse to create a spark between two electrodes. The electrodes are made from the material from which you want to create nanoparticles. The spark causes atoms to evaporate from the electrodes, and the atoms then move into the flow of the argon carrier gas to the condensation chamber.Using a spark source to produce nanoparticles.
Laser ablation system: In the laser ablation system, you focus a laser beam on a target that has been preheated in a furnace. The target is made of the same material from which you want to create nanoparticles. The laser vaporizes atoms off the target and a flow of argon gas sweeps the atoms downstream to the condensation chamber.Vaporizing atoms with a laser ablation system.
Plasma-enhanced chemical vapor deposition system: If you want to grow carbon nanotubes, you might also try a plasma-enhanced chemical vapor deposition system. This type of system uses a gaseous source instead of a solid target or powder, as in other systems we’ve discussed.
A gas, such as methane, flows between two electrodes to which you’ve applied a high-power radio frequency signal. This procedure generates a plasma, breaking up the methane or other source gas into atoms. A substrate is mounted on one of the electrodes.A substrate mounted on electrodes to grow carbon nanotubes.
Particles on the surface of the substrate act like seed crystals because carbon naturally bonds to them. Additional carbon atoms bond to the carbon atoms already in place until — voilá — you’ve grown a carbon nanotube.