(354e) Size- and Morphology-Controlled Synthesis of Zinc Oxide Nanoparticles in a Two-Phase Millifluidic Reactor

We present a novel technique for the continuous synthesis of nanoparticles using a two-phase millifluidic reactor. Conducting the synthesis reaction inside droplets of controlled size offers several advantages such as eliminating temperature and concentration gradients inside the reactor as well as preventing reactor fouling. Additionally, by locating the synthesis reagents initially in separate phases the rate of reagent addition can be controlled and the need for having a reliable means of droplet merging in order to combine the synthesis reagents is eliminated. The technique is demonstrated by synthesizing zinc oxide nanoparticles inside aqueous droplets that initially contain zinc acetate. Sodium hydroxide then diffuses into the droplet phase in a controlled manner, producing zinc oxide nanoparticles with a narrow particle size distribution as compared to a batch reactor. Spherical as well as plate-like shapes of zinc oxide nanoparticles are seen for the ranges of parameters studied. The size and morphology of the nanoparticles is shown to be easily controlled by varying the droplet size, reagent concentrations, reaction temperature, and residence time. The effect of adding surfactants to either the bulk or droplet phase on the zinc oxide size and shape is also presented.