Nano Ag-Doped In 2 O 3 Thick Film: A Low-Temperature H 2 S Gas Sensor

Thick films of AR grade In 2 O 3 were prepared by standard screen-printing technique. The gas sensing performances of thick films were tested for various gases. It showed maximum sensitivity to ethanol vapour at 350 ° C for 80 ppm concentration. To improve the sensitivity and selectivity of the film towards a particular gas, In 2 O 3 sensors were surface-modified by dipping them in a solution of 2% nanosilver for different intervals of time. Obtained results indicated that spherical nano-Ag grains are highly dispersed on the surface of In 2 O 3 sensor. The surface area of the nano-Ag/ In 2 O 3 sensor is several times larger than that of pure In 2 O 3 sensor. In comparison with pure In 2 O 3 sensor, all of the nano-Ag-doped sensors showed better sensing performance in respect of response, selectivity, and optimum operating temperature. The surface-modified (30 min) In 2 O 3 sensor showed larger sensitivity to H 2 S gas (10 ppm) at 100 ° C. Nano silver on the surface of the film shifts the reactivity of film from ethanol vapour to H 2 S gas. A systematic study of gas 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.