Room-Temperature Acetone Sensing by Sulfonated Copper Phthalocyanine (TsCuPc)-Modified ZnO Films

Sulfonated copper phthalocyanine (TsCuPc) surface-modified zinc oxide (ZnO) films were synthesized, and their structural as well as room-temperature acetone sensing characteristics were investigated. x-Ray diffraction analysis showed that modification by TsCuPc leads to preferential c-axis orientation of pure ZnO films. Field-emission scanning electron microscopy of pure and surface-modified ZnO films indicated freely distributed needle-like crystallites and agglomerated grains, respectively. Measurement of electrical properties of modified ZnO films also shows an increase in resistance as compared with pure ZnO films. It has been demonstrated that these films were more sensitive to acetone compared with pure ZnO films. The response for 50 ppm acetone reached -162% for ZnO films modified by 1 M TsCuPc. The negative value of the response was attributed to the p-type character of the ZnO films resulting from the p-type TsCuPc. However, for concentrations>100 ppm, the response saturated.