Self-powered Active Gas Sensor Based On ZnO Nanowire Arrays

With study of the nanogenerator technology, people try to integrate nanogenerators and nanodevices to form self-powered nanosystems. In self-powered nanosystems, the energy created by nanogenerators can drive nanodevices directly. In this paper, concept and theoretical model of the self-powered active gas sensor are put forward firstly, which can integrate nanogenerators and gas sensors in a single device to achieve the piezoelectric power generation and gas sensing processes simultaneously. This pioneering work has been selected in IOP select because greatly promoted the development of the next generation of gas sensors. Through further researching the piezoelectric gas sensing properties of ZnO and its composite nanostructures, the performances of self-powered active gas sensors are improved greatly. Specific studies are as follows:(1) Based on the piezoelectric and gas sensing coupling characteristics of ZnO, the working mechanism of self-powered active gas sensors is put forward. ZnO nanowire arrays are prepared on Ti substrate using hydrothermal method. The gas sensing properties of self-powered active gas sensors using ZnO nanowire arrays as nano-generation materials and gas sensing materials are tested. The test results show that output voltages of the self-powered active gas sensor in pure oxygen rise to 0.7 V from 0.45 V (in dry air) and down to 0.198 V in 1000 ppm H2S. The sensitivity against 1000 ppm H2S is 127.3 and the detection limit for H2S reaches 100 ppm.(2) The CuO/ZnO PN-junction nanowire arrays are synthesized via a two-step method. Gas sensing properties of the self-powered active gas sensors using CuO/ZnO PN-junction nanowire arrays acting as the nano-generation materials and gas sensing materials are tested and the mechanism is further discussed. CuO nanoparticles on the surface of ZnO NWs are converted to CuS when exposed to hydrogen sulfide gas, and metallic CuS can offer electrons for n-type ZnO to improve the screen effect in ZnO nanowires. Test results show that the sensitivity of self-powered active gas sensor fabricated with CuO/ZnO PN-junction NW arrays against 200,400,600 and 800 ppm H2S are 60.4,153.4,604.5 and 629.8, respectively.(3) The ZnSnO3/ZnO heterojunction nanowire arrays are synthesized via a wet chemical method. The self-powered active gas sensor is maked with ZnSnO3/ZnO heterojunction nanowire arrays acting as the nano-generation materials and gas sensing materials to realize the room temperature sensing of alcohol gas. The mechanism is further discussed which may attribute to the excellent alcohol sensing properties of ZnSnO3 nanoparticles. The test results show that the sensitivity of self-powered active gas sensor fabricated with ZnSnO3/ZnO heterojunction NW arrays against 250,500, 750,1000 and 1250 ppm alcohol gas are 61.7,126.1,190.3,300.9 and 307.7, respectively.