Fabrication and Properties of Redox Ion Doped Few Monolayer Thick Polyelectrolyte Film for Electrochemical Biosensors at High Sensitivity and Specificity

Redox ions are deposited on a polyelectrolyte-coated gold electrode by an electric field to fabricate an ion-selective thin film electrode. The Fe(CN)${{{4- \hfill \atop 6\hfill}}}$ ions are deposited on a few monolayer-coated polyelectrolyte gold electrode by a slow periodic potential cycle. The deposition process and electrode properties are quantitatively and simultaneously monitored by cyclic voltammetry and a novel technique, using a Scanning Electrometer for Electrical Double-layers (SEED). No redox properties are obtained without the electric-field-deposition. Owing to the redox mediation and net charge due to the redox ion, the electrode is ion-selective. We demonstrate the principle to detect 1 mu M of dopamine in a mixture with 1mM of ascorbic acid.