The Use of Reactive Thin Films for an IR-Based Detection of Toxic Compounds in Water

We are currently developing a detection system based on the principles of infrared (IR) spectroscopy that operates in heterogeneous aqueous environments and provides fast detection (<10 min) and high sensitivity/selectivity to nonvolatile toxic materials with minimal false alarms. The key enablers to using IR spectroscopy for aqueous-based detection are the development of selective and robust sampling protocols. In this paper, we describe a new sampling approach based on the use of reactive thin films sublimed onto an IR amenable support. The films chemically react with a predefined class of compounds and identification of the specific chemical is provided by IR spectral analysis. Proof of concept of this approach is demonstrated for the detection of cyanide in water. Specifically, CuI has been vacuum sublimed on silicon wafers, and upon exposure to solutions of NaCN, CuCN is formed producing a single sharp band at 2173 cm^-1. The intensity of this band varies linearly with NaCN concentration, and it is shown that a detection limit below 100 ppb (parts per billion) is achievable.