Incorporation of planar waveguide technology into a spectroelectrochemical sensor is described. In this sensor design, a potassium ion-exchanged BK7 glass waveguide was over-coated with a thin film of indium tin oxide (ITO) that served as an optically transparent electrode. A chemically selective film was spin-coated on top of the ITO film. The sensor supported five optical modes at 442 nm and three at 633 nm. Investigations on the impact of the ITO film on the optical properties of the waveguide and on the spectroelectrochemical performance of the sensor are reported. Sensing was based on the change in attenuation of light propagated through the waveguide resulting from an optically absorbing analyte. By applying either a triangular or square wave excitation potential waveform, electromodulation of the optical signal has been demonstrated with Fe(CN)6(3-/4-) as a model electroactive couple that partitions into a PDMDAAC-SiO2 film [where PDMDAAC = poly(dimethyldiallylammonium chloride)] and absorbs at 442 nm.

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The detailed kinetics and associated optical waveforms of the spectroelectrochemical sensor in competitive binary mixtures of analytes are presented. The extension of the sensor concept to planar waveguide structures is described. Two different planar waveguide designs have been made and evaluated. One design was an asymmetric slab waveguide with the waveguide layer sandwiched between a silica substrate and a chemically-selective film. The other design was a channel waveguide, which consisted of an ion-exchanged channel between two gold electrodes in a "bus bar" configuration. These new designs are described in detail and evaluation of them with respect to operation of the sensor in the near ultraviolet region is discussed. Results with the devices in demonstration of the novel spectroelectrochemical concept with three modes of selectivity are given. Instrumentation developed specifically for operation of the sensors and acquisition of sensor data is described.

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