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)${{{4- hfill atop 6hfill}}}$ 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 µM of dopamine in a mixture with 1 mM of ascorbic acid.