Hydrophobic coatings for mass‐sensitive sensor devices, which yield a negligible water cross sensitivity, are the aim of the reported research. Molecular modeling was used to gain an understanding of the binding mechanism of some solvent molecules with a tetraazaparacyclophane containing alkyl substituents at the amino bridgeheads (CPO44VAL)— the figure shows the calculated geometry of the benzene complex of CPO44VAL. The theoretical results were then compared with the actual performance of CPO44VAL in devices.

Chemical sensors based on highly mass sensitive QCM or SAW devices, coated with sensitive layers, are especially suited for the trace analysis of organic solvent vapors, such as halogenated or aromatic hydrocarbons. The paracyclophanes B44TOS and CP44 were used as sensitive coatings, employing the principles of host-guest chemistry. The application of the BET model to the incorporation of chloroform in the sensitive coatings proves intracavitative complexation according to a 1:1 stoichiometry. Beyond the mass-sensitive detection, the complexation was studied by FT-IR spectroscopy. The exhibited saturation behavior of the characteristic CDCl 3 bands confirms the results of the mass-sensitive measurements. The lowering of the C-D stretching frequency was compared with the shifts caused by several model compounds, such as N-butylaniline. All results described indicate the formation of host-guest complexes between chloroform and paracyclophanes.

Sensors for a huge variety of detection tasks can be made by combining chemically sensitive materials with microstructured physical devices. How individual analyte species can be recognized using host–guest binding schemes (the Figure shows a paracyclophane host molecule) and how categories of compounds can be identified using sensors that respond to different functionalities are reviewed.

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