Discrimination effects in zeolite modified metal oxide semiconductor gas sensors

The use of zeolites to enhance the response and discriminating power of solid state metal oxide semiconductor gas sensors is demonstrated. Thick film sensors were prepared by screen printing layers of chromium titanium oxide (CTO) with various zeolites as over-layers. The sensors gas response was tested against two similar gases; ethanol and isopropyl alcohol. The modified sensors effectively discriminated between the two gases. An understanding of this discriminating behaviour is elucidated through computer modelling of diffusion and reaction processes occurring in the zeolite transformation layer and sensor element. Our analysis suggests that the discriminating behaviour is the result of a size and shape selective catalysis.