H2S gas sensing performance and mechanisms using CuO-Al2O3 composite films based on both surface acoustic wave and chemiresistor techniques.

• CuO in mesoporous film can selectively adsorb and react with H 2 S gas molecules. • The adsorbed H 2 S changes both the film's mass and conductivity. • The SAW sensor has better performance because of the mass sensitive mechanism. • The SAW sensor can precisely detect H 2 S gas ranging from 5 ppb to100 ppm. Surface acoustic wave and chemiresistor based gas sensors integrated with a sensing layer of sol-gel CuO-Al 2 O 3 composite film were fabricated and their performance and mechanisms for H 2 S sensing were characterized and compared. In the composite film, CuO nanoparticles provide active sites for adsorption and reaction of H 2 S molecules while Al 2 O 3 nanoparticles help to form a uniform and mesoporous film structure, both of which enhance the sensitivity of the sensors by providing numerous active CuO surfaces. Through the comparative studies, the SAW based H 2 S sensor operated at room temperature showed a lower detection limit, higher sensitivity, better linearity and good selectivity to H 2 S gas with its concentration ranging from 5 ppb to 100 ppm, compared with those of the chemiresistor sensor, which are mainly attributed to the effective mass sensing properties of the SAW sensor, because a minor change in the mass of the film caused by adsorbed H 2 S molecules would lead to a significant and monotonous change of the resonant frequency of the SAW devices. [ABSTRACT FROM AUTHOR]