Suspended CoPP-ZnO nanorods integrated with micro-heaters for highly sensitive VOC detection

Suspended nanomaterials including nanowires and nanorods have attracted great interest as promising candidates for gas sensing materials because they can perform sensitive gas detection without being affected by the substrate. However, the suspended nanomaterial-based gas sensors reported so far have been developed in the absence of a heater, and given the fact that most sensors require high operating temperature, integration with the heater is essential for practical use of the sensor. This work demonstrates a suspended ZnO nanorod-based sensor integrated with a heater, based on a batch process. Depending on the degree of heating from the integrated heater, the suspended ZnO nanorods exhibited various sensitivities and the highest response was obtained when heated to 5.2 V. To further increase the response to volatile organic compounds (VOCs), the ZnO nanorods were functionalized with cobalt porphyrin and the functionalized ZnO nanorods exhibited response that was 2.6 times higher than that of the pristine one at 10 ppm toluene. The functionalized ZnO nanorods detected 2 ppb of toluene, which is lower than the concentration detectable by any of the previously reported chemoresistive VOC sensors.