Abstract
Deprotonation-induced conductivity shift of poly(3,4-ethylenedixoythiophene)s (PEDOTs) in aqueous solutions is a promising platform for chemical or biological sensor due to its large signal output and minimum effect from material morphology. Carboxylic acid group functionalized poly(Cn-EDOT-COOH)s are synthesized and electrodeposited on microelectrodes. The microelectrodes are utilized to study the effect of carboxylic acid side-chain length on the conductivity curve profiles in aqueous buffer with different pH. The conductivity shifts due to the buffer pH are effected by the length of the carboxylic acid side-chains. The shifts can be explained by the carboxylic acid dissociation property (pKa) at the solid–liquid interface, self-doping effect, and effective conjugation length. Conductivity profiles of poly(EDOT-OH-co-C2-EDOT-COOH) copolymers are also studied. The shifts show linear relationship with the feed monomer composition used in electrochemical polymerization.
Highlights
Nowadays, human health and environmental monitoring has become a critical issue due to ever-growing diseases and pollution concerns
As reported by our group, poly(EDOT-COOH) polymer film is biocompatible, has low intrinsic cytotoxicity, and no inflammatory response for implantation, and we suggested that it is an ideal polymer for the preparation of biosensors [17]
Poly(C4 -EDOT-COOH), the latter showed a larger horizontal shift toward more positive potential in the drain current onset potential when pH of an aqueous buffer changed from pH 4 to pH 10 [27]
Summary
Human health and environmental monitoring has become a critical issue due to ever-growing diseases and pollution concerns. A study by Xu’s group reported electrochemical polymerization of poly(C4 -EDOT-COOH) films and preparation of electrochemical chemical-/bio-sensors by covalent linkage of the polymer carboxyl group with biomolecules and layer-by-layer assembly with inorganic materials for fast and sensitive determination of catechol, ascorbic acid, Cd2+ , acetaminophen, quercetin, epinephrine, and tryptophan via different electrochemical methods [14]. Poly(C4 -EDOT-COOH), the latter showed a larger horizontal shift toward more positive potential in the drain current onset potential when pH of an aqueous buffer changed from pH 4 to pH 10 [27] These initial results inspired us to further explore and understand on the length effect of the carboxylic acid side chains toward PEDOT conductivity profile. Such system can be used to detect any analyte (proton, biomolecules, or other cations) that can interact with the polymer with in a particular concentration and cause a negative charge gradient surrounding the polymer backbone
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