Mass-Sensitive Detection of Solvent Vapors. Mechanistic Studies on Host−Guest Sensor Principles by FT-IR Spectroscopy and BET Adsorption Analysis

Abstract

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 CDCl3 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.