Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 4. Sensing with poly(vinyl alcohol)-polyelectrolyte blend modified optically transparent electrodes

The feasibility of using polymer blend thin films covalently attached to indium tin oxide-glass, via the silane coupling agent (3-aminopropyl)triethoxysilane, for performing spectroelectrochemical modulation is demonstrated in aqueous solutions, The polymer blends were formulated by entrapping three polyetectrolytes-poly(vinylbenzyltrimethylammonium chloride) (PVTAC), poly(acrylic acid), and Nafion-in cross-linked poly(vinyl alcohol) (PVA) matrix for the purpose of selectively incorporating solution-phase anions and cations. Ru(BiPy)(3)(2+) (BiPy = 2,2'-bipyridine), Ru(CN)(6)(4-) and Fe(CN)(6)(3-) were chosen as I the analytes for their suitable optical and electrochemical properties. Peak current enhancements, compared with the bare electrode under the same conditions, ranging from 2 to 7 were observed for these systems with the largest being for Fe(CN)(6)(3-) at an electrode coated with PVA-PVTAC blend. The optical absorbance change under attenuated total reflection during cyclic voltammetry (spectroelectrochemical modulation) was observed for all systems. The effects of potential window, electrochemical reversibility of the analyte, and potential scan rate on the resulting absorbance-time plot for modulation by cyclic voltammetry are reported for the different analyte-polymer blend systems. The modulation transfer ratios of analyte-polymer systems were studied. Modulation at 450 nm resulting from oxidation/reduction of the Ru(BiPy)(3)(2+/3+) couple at 1.30 and 0.90 V vs Ag/AgCl with varying concentrations was used to construct analytical working curves for the spectroelectrochemical sensor.