Highly Sensitive Ethanol Gas Sensor Using Pyramid-Shaped ZnO Particles with (0001) Basal Plane

For monitoring of air quality and medical diagnosis, metal-oxide-semiconductor particles with high sensitivity to detect small amount of gases are desirable. Herein, we report the fabrication of ZnO pyramid-shaped particles with remarkably high sensitivity to ethanol gas. The ZnO pyramid-shaped particles were synthesized solvothermally under agitation from the solution of zinc acetate anhydride, hexamethylenetetramine, ethylene glycol, and water. Gas sensing response was evaluated as the ratio of electrical resistance of the ZnO particulate layer in air to that in ethanol. The agitation during the solvothermal process resulted in dispersion of the pyramid-shaped particles rather than spherical aggregates. TEM studies revealed that the base of the pyramid-shaped particles is the (0001) plane and that the six side surfaces are the {101̅1̅} plane. The highest gas sensing response value to 50 ppm ethanol gas was about 10 000, which is remarkably higher than that of previously reported ZnO particles. The influence of the crystal facets and the polarity is discussed.