Highly sensitive isoprene gas sensor using Au-loaded pyramid-shaped ZnO particles

Highly sensitive sensors to detect small amounts of gases are expected to be used for monitoring air quality and analyzing breath for medical diagnosis. We report a highly sensitive isoprene gas sensor using Au-loaded pyramid-shaped ZnO particles. The pyramid-shaped ZnO particles with (0001) base and {10 1¯1¯} six side surfaces were synthesized solvothermally. Loading of 0.5 % Au nanoparticles successfully increased the sensor response. The response value (the resistivity ratio in air and isoprene gas) to 50 ppb isoprene gas was 42 at 350 °C in dry air, which is remarkably higher than that of previously reported sensors of metal-oxide semiconductors. Under 80 % relative humidity, the response value to 50 ppb was 4.8. The isoprene concentration dependence of the sensor response implied that 10 ppb can be detected with a response value of 1.4 and that diagnosis of liver diseases and sleep state is possible. Enhanced selectivity compared to acetone, ethanol and hydrogen was confirmed in Au-doped samples.