(264b) Ultrasonic Spray Delivery of Precursors for Laser Pyrolysis Synthesis of Nanoparticles

Laser pyrolysis is a useful approach for aerosol (vapor-phase) production of nanoparticles (NPs). In vapor-phase methods, precursors must be delivered as a vapor or as small droplets or particles that can be vaporized within the process. In laser pyrolysis, a laser beam is employed to selectively heat a gas stream containing NP precursors, such that they decompose, including nucleation of NPs. Laser pyrolysis provides advantages of extremely high heating and cooling rate, which increases throughput, and flexibility in tuning particle size and composition. Gaseous, liquid or solid precursors can be used in this method. Due to issues of safety and precursor cost and limited availability of gaseous precursors, solid or liquid precursors would be preferable in many cases. The 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, no sufficiently volatile precursor is available for some metals. Accordingly, spray-based precursor delivery is the most general approach to delivering precursors for the synthesis of NPs by laser pyrolysis. We have designed a low-cost atomizer to deliver small droplets of a precursor solution to the reaction zone in this method. Indeed, any stable precursor solution can be used to synthesize various NPs by using this atomizer to spray it to the reaction zone as small droplets. However, when the goal is production of small particles by gas to particle conversion, then using a precursor with relatively high vapor pressure is desirable. Employing this atomizer to spray a precursor solution mixture of zinc acetate and thioacetamide enabled us to synthesize zinc sulfide nanocrystalline particles with an average size below 10 nm, which makes them potentially useful for optoelectronic applications.