Zeolites sensing mechanism

In contrast to equilibrium-based sensing such as described above, it is also possible to use the zeolite film as a membrane controlling molecular access to an appropriate transduction mechanism. In this case, Pd-doped semiconductor gas sensors were used as a fairly non-selective sensor platform. After coating these sensors with a thin film of MFI-type or LTA-type zeolites, they were examined with respect to gas phase sensing of different analytes such as methane, propane and ethanol, at different humidity levels (Fig. 14).[121] The response of a zeolite-coated sensor towards the paraffins was strongly reduced compared to the non-coatcd sensor device, thus resulting in an increase of the sensor selectivity towards ethanol. 

In parallel to developments in the field of electronics, nanostmctured materials have been developed by materials scientists and chemists also. The concept of nanocrystalline structures emerged in the field of materials science, and polycrystals with ultrafine grain sizes in the nanometer range have been produced. These nanophase materials have been shown to have significant modifications of their mechanical properties compared with the coarse-grain equivalent materials. The huge surface area of nanoporous materials has attracted much attention for applications in chemistry such as molecular sieves, catalysis, and gas sensing. This has motivated intense research aimed at the fabrication of materials with a well-controlled composition and nanoscale stracture, such as synthetic zeolites. 

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