Reflectance infrared spectroscopy on operating surface acoustic wave chemical sensors during exposure to gas-phase analytes

Instrumentation, software, and a specialized device were developed to combi ne surface acoustic wave (SAW) sensor measurements with direct, in situ Fou rier transform infrared external-reflectance spectroscopy (FT-IR-ERS). Prob ing surface-confined sensing films with molecularly specific IR spectroscop y during analyte exposure characterizes in unprecedented detail the interac tions between sorptive SAW coatings and gaseous analytes. The unique device and measurement system are described. The power of the combined measuremen ts is demonstrated by SAW/FT-IR-ERS responses to several organic analytes i nteracting with a conventional organic polymer, a transition-metal-coordina ting self-assembled alkanethiol monolayer, and a "molecular cage" film base d on a cyclodextrin.