| Surface characterization of poly(3,4-ethylenedioxythiophene) (PEDOT) based polymers utilizing sum frequency generation (SFG) vibrational spectroscopy and X-ray photoelectron spectroscopy (XPS) were carried out to determine the surface phenyl functional group orientation as well as to investigate PEDOT counter-ion affinity and the driving force determining counter-ion incorporation during electrochemical polymerization. The characterization culminated into the fabrication and characterization of PEDOT enzyme based biosensors.;SFG was used to investigate the surface phenyl ring orientation differences between polystyrene, poly (sodium 4-styrenesulfonate) (PSSNa), and the PSSNa found in the PEDOT: PSSNa suspension, Baytron P. The variety of counter-ions probed during the XPS study included the poly-anions, PSSNa and poly (acrylic acid) (PAA), and small anions such as citrates (C6H5O 73-), carbonates (CO32- ), thiosulfate (S2O32-), phosphates (H2PO4- and HPO 42-), acetate (C2H3O 2-), chloride (Cl-), bromides (Br-), perchlorates (ClO4-), and sodium p-toluenesulfonate (TosNa).;In mixtures containing PSS with other counter-ions, PSS was found to be the dominant PEDOT counter-ion due to its polymeric nature over TosNa, ClO4-, and Cl-anions, though Br- was found to act as a PEDOT. The general qualitative trend of PEDOT counter-ion affinity amongst small anions (from strongest to weakest) follows: S2O32->COO- (citrate), Br-, ClO4->Cl -, COO- (acetate), CO3 2->NO3->H 2PO4-/HPO42- . These results did not follow the Hofmeister Series rigidly, but some general trends such as the dominance of Br- and ClO4- in all mixtures not containing S 2O32- were observed. Thiosulfate was found to be the dominating counter-ion in every mixture it was present in regardless of the anionic charge, cation, or anionic hydration.;Functional PEDOT-based glucose biosensors were fabricated using physical immobilization of the enzymes glucose oxidase (GOx), l-lactate dehydrodenase (LDH), Tyrosinase, and glutamate oxidase (GLOD) within a PEDOT counter-ion matrix. The counter-ions used were either PSS, heparin, or the enzyme itself. XPS was used to verify enzyme entrapment, while electrochemical impedance spectroscopy, cyclic voltammetry, and chrono-amperometry were used to characterize the films. The minimum glucose concentration that was detected for GOx based sensors was found to be ∼5x10-4 M. Further enzyme entrapment was also proven with LDH, Tyrosinase, and chemically immobilized GLOD; however biosensor functionality could not be proven at this time. |
