Abstract
In this review, we describe in detail the methods to produce various nanoparticles using ultrasonic spray pyrolysis. In general, droplets generated by an ultrasonic nebulizer have a size of approximately 5 micrometers so that submicrometer particles are typically produced by the conventional spray pyrolysis (CSP). In order to produce nanoparticles, modifications in technique such as adding salts or polymers to precursor solutions are necessary. However, salt assisted-SP requires an additional treatment of washing to dissolve and remove residual material from the produced nanoparticles. The addition of polymers does not require washing process because they are decomposed and volatilized during the pyrolysis. Both methods produce isolated nanocrystals. In flame spray pyrolysis, the formation of nanoparticles is dominated by the evaporation-condensation route, and therefore the flame temperature controls the formation of nanoparticles. This review concludes that ultrasonic nebulization with subsequent pyrolysis is one of the effective methods to produce nanoparticles.
