Sensing of halogenated aromatic hydrocarbons in water with a cavitand coated piezoelectric device

A study leading to the development of a piezoelectric sensing device for environmental monitoring of aromatic micropollutants in water is reported. A Piezoelectric Quartz Crystal (PQC) was functionalized through electropolymerization of a quinoxaline cavitand, known to possess remarkable capabilities in selectively trapping aromatic compounds through multiple pi-pi and CH-pi interactions. The obtained film was characterized via X-ray Photoelectron spectroscopy (XPS) to elucidate its chemical composition. The design and synthesis of the new quinoxaline cavitand functionalized at the upper rim with a bithiophene moiety suitable for electropolymerization is described. The molecular structure of the new receptor was elucidated via X-ray diffraction analysis. The performance of the obtained sensor towards selected chlorinated and not chlorinated hydrocarbons in water was tested. Excellent limit of detection (0.17 ppm), below the present stringent Italian value, was achieved for 1,2,4-trichlorobenzene, outperforming conventional systems. The frequencymetric sensor showed high reproducibility from independent functionalized PQCs, with RSD values lower than 5%.