Synthesis and grafting of a thiourea-based chelating agent on SH-SAW transducers for the preparation of thin films sensitive to heavy metals

The surface functionalization of guided SH-SAW (Shear Horizontal — Surface Acoustic Wave) transducers was carried out to prepare layers sensitive to heavy metals. To this purpose, a thiourea molecule acting as a chelating agent was grafted on the top-layer of the transducer. This covalent immobilization was obtained by amide bonds through primary amine groups immobilized on the device by the chemisorption of the 3-aminopropyltriethoxysilane (APTES). The physico-chemical characterizations of the multi-layer systems were done by ellipsometry, wettability studies, UV–visible spectroscopy and XPS and shown that the grafting of the molecule is achieved through the preparation of nanometric films. The acoustic properties of the devices were mainly related to the nanometric thickness of the layers, which proved chemisorption of APTES was an efficient method to prepare a chemical acoustic sensor. The possibility to use such a functionalized layer in a microfluidic analysis system was shown by first attempts of sensitivity in liquid media.