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Synergistic Effects of a Combination of Cr2O3-Functionalization and UV-Irradiation Techniques on the Ethanol Gas Sensing Performance of ZnO Nanorod Gas Sensors

Park, Sunghoon, Sun, Gun-Joo, Jin, Changhyun, Kim, Hyoun Woo, Lee, Sangmin, Lee, Chongmu
ACS applied materials 2016 v.8 no.4 pp. 2805-2811
adsorption, ambient temperature, ethanol, evaporation, graphene, nanoparticles, nanorods, oxidation, powders, ultraviolet radiation, zinc oxide
There have been very few studies on the effects of combining two or more techniques on the sensing performance of nanostructured sensors. Cr₂O₃-functionalized ZnO nanorods were synthesized using carbothermal synthesis involving the thermal evaporation of a mixture of ZnO and graphite powders followed by a solvothermal process for Cr₂O₃-functionalization. The ethanol gas-sensing properties of multinetworked pristine and Cr₂O₃-functionalized ZnO nanorod sensors under UV illumination were examined to determine the effects of combining Cr₂O₃–ZnO heterostructure formation and UV irradiation on the gas-sensing properties of ZnO nanorods. The responses of the pristine and Cr₂O₃-functionalized ZnO nanorod sensors to 200 ppm of ethanol at room temperature by UV illumination at 2.2 mW/cm² were increased by 3.8 and 7.7 times, respectively. The Cr₂O₃-functionalized ZnO nanorod sensor also showed faster response/recovery and better selectivity than those of the pristine ZnO nanorod sensor at the same ethanol concentration. This result suggests that a combination heterostructure formation and UV irradiation had a synergistic effect on the gas-sensing properties of the sensor. The synergistic effect might be attributed to the catalytic activity of Cr₂O₃ for ethanol oxidation as well as to the increased change in conduction channel width accompanying adsorption and desorption of ethanol under UV illumination due to the presence of Cr₂O₃ nanoparticles in the Cr₂O₃-functionalized ZnO nanorod sensor.