Among various NG-based active sensors, ZnO nano/micro-wires are popular building blocks because of their semiconducting and piezoelectric coupling properties. Also, ZnO one-dimensional nanostructures are extremely sensitive and fast-responding materials for gas sensing due to their large surface-to-volume ratio and surface adsorption activity.

The output of a piezoelectric nanogenerator (NG) fabricated using ZnO nanowire arrays is influenced by the density of the surface charge carriers at the nanowire surfaces. Adsorption of gas molecules modifies the surface carrier density through a screening effect, and thus, the output of the NG is sensitive to the gas concentration.

In the work, the piezoelectric output voltage of a test device was measured in dry air, pure oxygen, water vapor (85 RH%) and H2S (1000 ppm in air). Here, the voltage response of the device in different gases was 0.45 V, 0.7 V, 0.35 V and 0.198 V, respectively.

The piezoelectric output voltage of the NGs decreased as the concentration of H2S increased. Upon exposure to 100, 250, 400, 550, 700, 850 and 1000 ppm H2S, the piezoelectric output voltage of NGs under a constant applied strain (0.012%, 0.4 Hz) is about 0.398, 0.360, 0.289, 0.251, 0.203, 0.202 and 0.198 V, respectively. The sensitivity S against 100, 250, 400, 550, 700, 850 and 1000 ppm H2S is about 13.1, 25.5, 55.7, 79.3, 121.7, 122.8 and 127.3 %, respectively

Full details can be found in the journal Nanotechnology.