<title>Surface phenomena with organic coatings for chemical sensing</title>

Abstract

The surface modification of SAW (surface acoustic wave)-and QCM (quartz crystal microbalance)-devices proves very important in chemical sensing. Silanes on one hand are very useful for hydrophobizing of quartz-surfaces whereas on the other hand thiols are used to adsorb on gold. In this way the influence of humidity on the transducers, which originates in the hydrophilicity of the quartz is decreased. These monolayers not only reduce the cross-sensitivity to water but also enhance the sensor effects of solvent vapors. In order to obtain better selectivity molecular hollows, like calix[n]arenes can be attached to the spacers. Another way to improve the selectivity was found in the treatment of the device with mixtures of silanes and thiols, respectively. In this way cavities are produced in which analytes are incorporated and thus are detected in the lower ppm range. The surface of mass-sensitive devices was also modified in order to detect analytes in the nano-to micrometer range. Here a stamping process with cells yields patterns on polymer surfaces which favor the reinclusion of these microorganisms. These effects are due to geometrical effects and chemical interactions via an adapted polarity and hydrogen bonds of the chosen polymer. The sensor responses proved highly selective to the bacteria in respect to nutrient liquid and other microorganisms.

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

“…42,[1243][1244][1245][1246][1247] The use of polyurethane to imprint larger chemical/biochemical entities has been detailed by the group, using combinations of QCM analyses with atomic force microscopy to examine cell/polyurethane 'impression' interactions. [1248][1249][1250] By creating an imprinted polymer layer bound to the surface of silica beads, Hirayama and co-workers 763 succeeded in creating a QCM sensor with specificity for the enzyme lysozyme, again demonstrating the applicability of this technology to larger chemical species than the smaller organic molecules typically used in imprinting protocols. 764 Smaller biochemicals, however, such as AMP, 703 peptides 1251 and amino acids, 1252 are more typical templates.…”