Effect of nano Ag on gas sensing performance of ZnOThick films

Thick films of AR grade ZnO were prepared by screen-printing technique. The gas sensing performance of thick films were tested for various gases. It showed maximum sensitivity to CO gas at 100degC for 100 ppm gas concentration. To improve the sensitivity and selectivity of the film towards a particular gas, ZnO thick films were surface modified by dipping them in a solution of nano silver for different intervals of time. These surface modified ZnO films showed larger sensitivity to H2S gas (100 ppm) than pure ZnO film at 300degC. Nano silver on the surface of the film shifts the reactivity of film from CO to H2S gas. A systematic study, of sensing performance of the sensor, indicates the key role-played by the nano silver species on the surface. The sensitivity, selectivity, response and recovery time of the sensor were measured and presented.