A selective SAW-based organophosphonate chemical sensor employing a self-assembled, composite monolayer: a new paradigm for sensor design

Abstract

The device described in this report derives its selectivity, reversibility, and durability from a simple, self-assembled monolayer and its sensitivity from a mass-sensitive surface acoustic wave (SAW) device. The coating design takes advantage of the interaction between organophosphonate nerve-agent simulants and a composite monolayer, consisting of Cu[sup 2+] tethered to the SAW device by an ordered, carboxylate-terminated n-alkanethiol monolayer. The rationale for this design is that Cu[sup 2+] and some of its chelates are hydrolysis catalysts for certain nerve agents. Thus, a surface layer of coordinatively unsaturated Cu[sup 2+] might be expected to provide selective and reversible binding sites for organophosphonates. The authors have demonstrated that this simple fabrication procedure incorporates all of the essential features of an ideal sensor: (1) it is selective for organophosphonates; (2) it is sensitive to 100 ppb of an important nerve-gas simulant; (3) it provides a reversible and proportional response to target analytes; (4) it is durable for periods of months. 19 refs., 3 figs.