SUPRAMOLECULAR DETECTION OF SOLVENT VAPORS WITH QMB AND SAW DEVICES

The principles of supramolecular host-guest chemistry can be applied f or the design of chemically sensitive layers. Using molecular cavities , such as modified cyclodextrines, surface acoustic wave (SAW) devices yield a detection limit of a few ppm for tetrachloroethylene even wit h monomolecular films. Paracyclophanes have the advantage that chemica l modifications can tune the cavity parameters in a wide range. Thus, systems with a graduated sensitivity for benzene, chloroform and tetra chloroethylene, for example, are obtained. The results of molecular mo delling simulations provide a suitable basis for predicting the sensit ivity of a given system. Channel structures in crystalline solids are also applicable. They strictly exclude too-bulky molecules. The sensit ivity depends on the molecular weight and on the vapour pressure of th e analyte. Thus, branched and unbranched isomers, e.g., n- and i-octan e, can be differentiated.