Laser pyrolysis method is one of the synthesis methods that the Swihart research group is interested due to its ability to deliver rapid heating and rapid cooling of vapors, enabling the system to synthesize nanoparticles of diverse materials.
Nanoparticle synthesis, the production of particles from 1 to 100 nm in characteristic size, is a key component of nanotechnology. Vapor-phase nanoparticle synthesis has advantages including high throughput continuous operation, scalability, and product purity that have given it a dominant role in the commercial production of nanomaterials. Laser pyrolysis is one of the important vapor phase nanoparticle synthesis methods. In laser pyrolysis, a laser beam is used to selectively heat a gas stream containing nanoparticle precursors, such that they decompose, inducing nucleation of nanoparticles. One of the most important advantages of laser pyrolysis is its flexibility to synthesize nanoparticles of diverse materials using appropriate precursors. A key advantage of laser pyrolysis compared to furnace-based methods is that only the gas, which has small heat capacity, is heated and, moreover, only that part of the gas that absorbs the laser energy is heated. As a result, the gas benefits from very rapid heating and rapid cooling by mixing of the heated gas with unheated gas. Gaseous, liquid, or solid precursors can be used in this method. Although gaseous precursors have most often been used in laser pyrolysis synthesis, solid or liquid precursors would be preferable in many cases, due to issues of safety and precursor cost and availability. These precursors can be delivered to the reaction zone as small droplets that rapidly evaporate upon laser heating. Precursors with sufficiently high vapor pressure could also be delivered as vapors from a bubbler. However, for some metals, no sufficiently volatile precursor is available. Accordingly, spray-based precursor delivery is the most general approach to delivering precursors for the synthesis of nanoparticles by laser pyrolysis.