Synthesis of ZnO Tetrapods by Atmospheric Pressure Microwave Plasma Jet and Their Enhanced Photocatalytic Performance

Among various metal oxide semiconductors, ZnO has an excellent electrical, optical properties with n-type conductivity, and a sensitive bandgap of 3.4 eV in the UV region. It is highly likely to be applied as a photocatalytic material due to its high absorption rate along with physical and chemical stability to UV light.

In this study, we report the synthesis of ZnO using an atmospheric pressure microwave plasma (APMP) jet system and enhanced photocatalytic property. A commercial micro-sized Zn powder was continuously introduced in the plume of the APMP jet ignited with mixture gases of oxygen and nitrogen. The effect of plasma power and collection sites on ZnO nanostructure was investigated. After the plasma discharge for 10 min, the produced materials deposited inside the 60-cm-long quartz tube were collected with respect to the distance from the plume. According to the SEM analysis, all the synthesized nanoparticles were found to be ZnO tetrapods ranging from 100 to 500-nm-diameter depending on both operation conditions and collection sites. To evaluate the photocatalytic properties, 1 mg of ZnO powder was dispersed in methylene blue dissolved (10 ppm) deionized water and UV light was exposured in a dark room. The photocatalytic efficiency was confirmed through UV-vis spectroscopy. As a result of checking the photocatalytic properties, we found that the rate of decomposition of methylene blue solutions increases with the (100), (101) crystal plane ratio of ZnO.