Ethanol and hydrogen sensors based on ZnO nanoparticles and nanowires.

Hydrogen sensing characteristics of thick films of nanoparticles of ZnO and 3% Mn or Co doped ZnO with and without impregnation of 1% Pt have been investigated over a wide concentration range. The sensor characteristics of the Pt impregnated ZnO and 3% Mn or Co-doped ZnO nanoparticles are found to be excellent with the sensitivity reaching values in the 1000-1500 range for 1000 ppm of H2 at 125 degrees C or lower. The sensitivity is quite high even for 10 ppm of H2. The response and recovery times are generally less than 10 s in the region of high sensitivity. These films exhibit very good sensing characteristics for ethanol, the sensitivity being well above 2000 at 50 degrees C for 1000 ppm of vapour. Nanowires of Pt-impregnated ZnO also exhibit satisfactory sensing characteristics, but the values of the sensitivity are somewhat lower. Humidity has negligible effect on the performance of these sensors.