Covalently anchored supramolecular monolayers on quartz surfaces for use in SAW sensors

Anchoring alkyl silane monolayers on quartz surfaces and consecutive derivatization steps, e.g. the addition of silanes and the immobilisation of calix[n]arenes, were studied by FTIR–HATR-spectroscopy and atomic force microscopy. The entire technique of this two-dimensional chemistry was adapted to meet the favourable sensitivity of mass-sensitive SAW-devices based on ST-cut quartz substrates and gold interdigital electrodes working at 417 MHz. It leads to the successful detection of vapours, aromatic and halogenated hydrocarbons such as xylenes, toluene and tetrachloroethylene with the immobilised calix[4]- and calix[6]arenes. The sensors react to analyte changes within a few seconds and show a noise level that allows detection limits as low as a few part per million for xylenes.