PNNL

Abstract

A new type of spectroelectrochemical sensor that embodies two modes of instrumental selectivity (electrochemical and spectroscopic) in addition to selective partitioning into an appllied film barrier is described. The sensor consists of a planar optical substrate/electrode coated with a chemically-selective film. Sensing is based on the change in the attenuation of light passing through the guided wave optic which accompanies a chemical reaction of an analyte induced by eletromodulation. Threefold selectivity for a chosen analyte relative to other environmental components is obtained by the cloice of coating material, the electrolysis potential, and the wavelength for optical monitoring. The sensor concept is demonstrated with an indium tin oxide coated glass guided wave device that has been over-coated with a sol-gel derived charge-selective thin film. This device is then shown to be able to sense ferrocyanide in Hanford waste tank simulant solution. The ongoing development of a small portable sensor unit including a virtual interface, control electronics and optics is also described.