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 elect ropolymerization of a phenanthrenequinone-pyrrole derivative, is described. The surface-confined PQ is shown to behave similarly to PQ in solution, ac ting as a redox-dependent receptor toward aromatic ureas in aprotic solvent s. Large, positive shifts in the E-1/2 of the PQ(0/-) redox couple are obse rved in the presence of these ureas, due to a strong hydrogen bonding inter action between the PQ radical anion and urea. The effect is fully reversibl e. Of the substrates examined, only aromatic ureas produce a significant sh ift. 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 elec trode coverage, allowing reproducible measurements to be made despite signi ficant loss in material from the surface.