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Molecularly imprinted polyurethanes are presented as sensitive coatings for the detection of polycyclic aromatic hydrocarbons in water. These sensor layers were combined with fluorescence and mass-sensitive transducers. Imprinting based on van der Waals interactions allows detection of these analytes even without any pronounced functionality. The geometry of the imprint molecule determines the selectivity of the sensor layer. In varying the size of template molecules from anthracene up to 1,12benzoperylene, selectivity is tuned to a distinct analyte. The enrichment factor of up to approximately 10 7 renders detection down to the ppt range possible with hardly any matrix effect by humic acids.

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Surface acoustic wave (SAW) resonators represent some of the most prominent acoustic devices for chemical sensing applications. As their frequency ranges from several hundred MHz to GHz, therefore they can record remarkably diminutive frequency shifts resulting from exceptionally small mass loadings. Their miniaturized design, high thermal stability and possibility of wireless integration make these devices highly competitive. Owing to these special characteristics, they are widely accepted as smart transducers that can be combined with a variety of recognition layers based on host-guest interactions, metal oxide coatings, carbon nanotubes, graphene sheets, functional polymers and biological receptors. As a result of this, there is a broad spectrum of SAW sensors, i.e., having sensing applications ranging from small gas molecules to large bio-analytes or even whole cell structures. This review shall cover from the fundamentals to modern design developments in SAW devices with respect to interfacial receptor coatings for exemplary sensor applications. The related problems and their possible solutions shall also be covered, with a focus on emerging trends and future opportunities for making SAW as established sensing technology.