Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device. 8. Selectivity at Poly(vinyl alcohol)-Polyelectrolyte Blend Modified Optically Transparent Electrodes

Abstract

Poly(vinyl alcohol) (PVA)-based polymer blends show potential utility as polymer films for a newly designed spectroelectrochemical sensor to achieve three modes of selectivity: charge-selective partitioning, electrolysis potential, and spectral absorption wavelength. The polymer blends were formulated by entrapping two polyelectrolytes, poly(vinylbenzyltrimethylammonium chloride) (PVTAC) and poly(acrylic acid) (PAA) into a cross-linked PVA matrix, which was covalently coated onto the surface of ITO glass. Sensing of the analyte is based on the change in attenuation of the light guiding through an optical substrate resulting from an electrochemical reaction of the analyte induced by electromodulation. The signal of the analyte in a competitive binary system is isolated by careful choice of polymer modifying film, potential window and monitoring wavelength. A 10−4 M equimolar binary solution of Ru(BiPy)32+ and Fe(CN)63– was used to study the selectivity of charge-selective partitioning. Cyclic voltammograms clearly demonstrated the exclusion of same charged ions from the selective layer with polymer blend modified sensors. 10−4 M equimolar Ru(CN)64– and Fe(CN)64– was chosen to demonstrate the selectivities of electrolysis potential and spectral absorbance wavelength. The detailed kinetics and associated electrochemical and optical waveforms from the spectroelectrochemical sensors in competitive binary mixtures of analytes are presented.