Development of chemical sensors based on redox-dependent receptors. Preparation and characterization of phenanthrenequinone-modified electrodes

The study of phenanthrenequinone(PQ)-modified electrodes, prepared by electropolymerization of a phenanthrenequinone-pyrrole derivative, is described. The surface-confined PQ is shown to behave similarly to PQ in solution, acting as a redox-dependent receptor toward aromatic ureas in aprotic solvents. Large, positive shifts in the E-1/2 of the PQ(0/-) redox couple are observed in the presence of these ureas, due to a strong hydrogen bonding interaction between the PQ radical anion and urea. The effect is fully reversible. Of the substrates examined, only aromatic ureas produce a significant shift. Nonaromatic ureas or other HN and HO containing compounds have little effect on the E-1/2. The magnitude of the shift is also independent of electrode coverage, allowing reproducible measurements to be made despite significant loss in material from the surface.