Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device. 9. Incorporation of Planar Waveguide Technology

Abstract

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.

Three-component spectroelectrochemical sensor module for the detection of pertechnetate (TcO4-)

“…For the last several years, our research group has been developing a spectroelectrochemical sensor that combines the functional components of (a) selective partitioning, (b) electrochemistry and (c) optical spectroscopy into a single device ( Shi et al 1997a, b , Gao et al 1999, Gao et al 2001, Slaterbeck et al 2000, Slaterbeck et al 1999, DiVirgilio-Thomas et al 2000, Maizels et al 2000, Maizels et al 2002, Ross et al 2000, Richardson et al 2002, Kaval et al 2003, Stegemiller et al 2003. This sensor is based on a novel device that incorporates multiple internal reflection (MIR) spectroscopy in an optically transparent electrode (OTE) coated with a selective film ( Kaval et al 2003 ).…”

Characterization of Charge-Transfer Kinetics at Organic/Electrode Interfaces Using Potential-modulated Attenuated Total Reflectance (PM-ATR) Spectroscopy

“…Subsequent reports by our group [7][8][9] and others [10][11][12] described spectroelectrochemical ATR systems implemented in multi-mode and single-mode waveguide configurations, providing broadband spectral information, sensitivity to submonolayer electroactive films, and chemical selectivity. Potential-modulated attenuated total reflectance (PM-ATR) spectroscopy 13 is a unique form of waveguide-based spectroelectrochemistry that utilizes the electroreflectance (ER) spectroscopic approach developed largely by Niki, Sagara, and coworkers.…”

Planar Integrated Optical Waveguide Spectroscopy

“…This discrimination power can provide selectivity in chemical sensing applications, particularly when the ITO is overcoated with a chemically selective adsorption layer (22).…”