Room-temperature self-powered ethanol sensing of a Pd/ZnO nanoarray nanogenerator driven by human finger movement.

A flexible room-temperature self-powered active ethanol sensor has been realized from a Pd/ZnO nanoarray nanogenerator. Pd nanoparticles are uniformly loaded on the whole surface of the ZnO nanowire arrays by a simple hydrothermal method. The piezoelectric output of the Pd/ZnO nanowire arrays can act as both the power source of the device and the room-temperature ethanol sensing signal. Upon exposure to 800 ppm ethanol gas at room temperature, the piezoelectric output voltage decreased from 0.52 V (in air) to 0.25 V. Such a room-temperature self-powered ethanol sensing behavior can be attributed to the catalytic effect of Pd, the Schottky barrier at the Pd/ZnO interface, and the piezotronics effect of the ZnO nanowires. Moreover, this flexible device can be driven by tiny mechanic energy in the environment, such as human finger movement. The present results can stimulate a research trend on designing new material systems and device structures in self-powered ethanol sensing at room temperature.