Metal phosphonate-based quartz crystal microbalance sensors for amines and ammonia

Microporous solids such as zeolites and layered metal phosphates are interesting materials on which to base chemical sensors, because sorption of molecules into their internal volume shows size and shape selectivity. Recently, zeolites have been interfaced to quartz crystal microbalance (QCM) and surface acoustic wave (SAW) devices, permitting piezoelectric transduction of chemical intercalation events. In parallel work, we and Clearfield and co-workers have shown that intercalation of amines and ammonia occurs with a high degree of shape selectivity in layered metal phosphonates of formula Zn(O3PR) (R=CH3, C6H5). In this paper we describe chemical sensors based on these intercalation reactions, using QCM devices for signal transduction.