Experiments have been performed to characterize the electrical propert
ies and functionality of a poly(3-hexylthiophene)-coated platinum elec
trode developed as a sensor for immunoassay read-out. Admittance measu
rements were performed on the coated electrodes as a function of frequ
ency. The admittance spectra obtained show that the sensor is capaciti
ve in nature. A circuit model is presented for comparison to other con
ducting polymer systems. Dynamic sensor response is characterized by o
xidizing the polymer via a hydrogen peroxide-iodide pathway. Hydrogen
peroxide is introduced either by direct injection or through a glucose
-glucose oxidase reaction to determine electrode functionality and sen
sitivity. Sensor response to chemical oxidation is measured as a funct
ion of frequency and applied signal amplitude. System response is line
ar in frequency from 1 Hz to 70 Hz and in excitation amplitude up to a
pproximately 600 mV. System sensitivity is analyzed based on oxidant g
eneration from the enzyme-initiated pathway, sensor baseline drift, an
d the noise band on the quiescent sensor current. (C) 1998 Elsevier Sc
ience S.A. Published by Elsevier Science S.A.