Oxide thin films (ZnO, TeO2, SnO2, and TiO2) based surface acoustic wave (SAW) E-nose for the detection of chemical warfare agents

Chemical warfare agents (CWA) are deadly chemicals even at low levels of concentration. In the present work, an electronic-nose (E-nose) comprising of an array of four surface acoustic wave (SAW) sensors having different chemical sensitive coatings of ZnO, TeO2, SnO2 and TiO2 is prepared for the detection of CWA. The oxide thin films are coated on the surface of SAW devices by rf sputtering technique. ZnO and SnO2 thin films are poly-crystalline with fine surface morphology whereas TeO2 and TiO2 thin films are amorphous. The E-nose shows good sensitivity toward the four simulants (dimethyl methylphosphonate (DMMP), dibutyl sulfide (DBS), chloroethyl phenyl sulfide (CEPS) and diethyl chlorophosphate (DECP)) of CWA allowing sub ppm level detection possible. Different simulants give distinct characteristic pattern when passed through the surface of E-nose. Using principal component analysis (PCA), the four different simulants of CWA are well separated from each other. Even with the incorporation of interferants (petrol, diesel, kerosene, VOCs and water vapors) in the PCA study, all four simulants are well separated showing the capability of the prepared SAW E-nose to classify simulants of chemical warfare agents efficiently.