| In recent years, with the strengthening emphasis on environmental monitoring and human security, the studies on detection of toxic and flammable volatile organic compounds (VOCs) have drawn considerable attentions. Nanostructured copper oxide (CuO), as a nontoxic and low-cost p-type semiconductor, owns wide commercial applications because of its large surface-to-volume ratio and size effect and exhibits outstanding sensing properties when used as sensing materials.In this paper, 0-dimensional (0-D) CuO nanopaticles,1-dimensional (1-D) CuO nanowires and two-dimensional (2-D) CuO nanosheets are synthesized by using facile and low-cost solution methods. The three CuO nanostructured sensors are fabricated by manual coating of the as-prepared materials on the cylindrical substrate. All of the three CuO based sensors exhibit excellent and reliable sensing performances, fast response, and baseline stability toward different common VOCs, and all show the best response and consistent selectivity to acetone, ethanol and methanol upon exposure to 9-11 kinds of VOCs while the CuO nansheets exhibits higer sensing response than CuO nanoparticles toward detecting gases. The optimized operating temperature of the three sensors is confirmed as 300℃ while the CuO nanowires sensor can exhibit steady sensing responses at 200℃. The CuO nanosheets based sensor has higher sensitivity than that of CuO nanoparticles sensor toward all detectingVOCs. No matter at high operating temperature 320℃ or low temperature 170℃, the CuO nanosheets sensor shows substantially superior response to the one-dimensional CuO nanoparticles toward acetone, ethanol and methanol. The sensitivities of different sensors toward 10-1000ppm ethanol vapor at 300℃ in descending order are CuO nanowires sensor, CuO nanosheets sensor, CuO nanoparticles sensor and commercial SnO2 sensor.The integrated CuO nanoparticles based sensor is fabricated by using magnetron sputtering technique with subsequent thermal oxidation in order to overcome the problems caused by the rough conventional coating procedure. The effects of sputtering current and sputtering time to the conductivity of the Cu film are investigated, and the optimized sputtering conditions are confirmed. The results of the sensing measurements show that the integrated sputtered CuO nanoparticles based sensor exhibits good response sensitivity, sensing performances, recovery ability and baseline stability, and also shows good selectivity to ethanol, methanol and acetone upon exposure to 11 kinds of VOCs. The integrated sputtered CuO sensor exhibits the highest and fastest response with response time of 4-10 s and recovery time of 4-8 s toward 20-500ppm ethanol at 200℃ compared to the other two well-coated CuO nanoparticles and CuO nanowires based cylindrical sensors. When exposed to 500 ppm CCl4 vapor, the as-deposited CuO nanoparticles sensor exhibits completely contrarily sensing response and resistance change comparably to that upon exposure to other chlorinated volatile organic compounds (CVOCs) (1,2-dichloroethane, 1,1,2-trichloroethane, and dichloromethane).The sensing properties of the CuO nanostructured sensors with different morphologies fabricated by the same manual coating procedure are compared and the integrated CuO sensor with superior sensing properties are prepared by sputtering technology which guarantees a good adhesion between sensitive films and substrate and provides stable and reliable Ohmic contacts. All of the works will significantly help to choose the sensing application area of CuO materials, improve the utilization efficiency and fabricate new sensing devices with high sensing properties. |
PDF Full Text Request