Fabrication and Characterization of a Hydroquinone-Functionalized Polypyrrole Thin-Film pH Sensor

Abstract

The physical and chemical properties of polypyrrole (PPy) derivatized at the 3-position with dimethoxybenzyl and dihydroxybenzyl functionalities via a novel high-yield pathway were evaluated for pH response. The monomers were electrochemically polymerized with perchlorate dopant in a propylene carbonate electrolyte solution. The potentiometric characteristics of the resulting films show a sub-Nernstian response of 46.0 mV pH-1 (25 °C); a detection limit of 1 × 10-10 mol dm-1; potential drift of ±1.9 mV and a low hysteresis with Δslope = ±1.9 mV pH-1. X-ray photoelectron spectroscopy (XPS) shows a reduction in the carbon 1s and chlorine 2p photoelectron peaks widths for functionalized PPy in comparison with the PPy indicating presence of β-carbon substituents. Time-of-flight secondary positive ion mass spectra showed peaks at m/z values of 107 and 109, indicating the presence of hydroquinone species at the outermost film surface of the functionalized PPy. The structure of the functionalized monomers was co...