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Scanning Electrometer for Electrical Double-layer (SEED) : The direct measurement of ion dynamics for biosensor

Seung-Woo Lee, University of Nebraska - Lincoln


As a working electrode (WE) comes in contact with an electrolyte, an electrical double layer (EDL) forms. EDL is the ion accumulation at the surface of the WE. Typically, the thickness of EDL is ~2nm. All electrochemical phenomena, i.e. redox reaction, which take place at the electrode surface, depend on the structure and the dynamics of the ions at the EDL. Thus, the direct measurement of the ion dynamics in the EDL will finger print the redox reaction. The novel optical measurement technique based on the phase differential interferometry is developed to probe the electrochemical reaction. The method is called Scanning Electrometer for Electrical Double-layer (SEED). As the optical signal measured by SEED is linearly proportional to the maximum redox current obtained by CV, the optical signal quantitatively maps the local redox current density distribution. To demonstrate the scanning capability, the local redox behavior on a "V-shaped" electrode is performed by scanning the laser beam over the electrode. SEED measures the change in local charge state of the EDL that abruptly changes due redox reaction. By immobilizing multiple enzymes on the electrode, SEED detects multi-analyte by quantitatively probing selective immunospecific binding to each enzyme-spot. SEED does not require an array of multiple pairs of sensing and reference electrodes. Three different enzymes on a monolith electrode are patterned in a microfluidics device to demonstrate the principle of quantitatively detecting multiple analyte by SEED at high specificity. SEED monitors the deposition process of the redox ions on the WE. 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) 64- ions are deposited on a polyelectrolyte coated gold electrode by a slow periodic potential cycle. The inclusion of redox ions makes the film ion-selective and enhances the sensitivity to measure analyte in micromolar concentrations. The redox film modification of gold (Au) electrode allows detection of 1µM of dopamine (DA) in 1mM of ascorbic acid (AA).

Subject Area

Physical chemistry|Chemical engineering

Recommended Citation

Lee, Seung-Woo, "Scanning Electrometer for Electrical Double-layer (SEED) : The direct measurement of ion dynamics for biosensor" (2013). ETD collection for University of Nebraska - Lincoln. AAI3558859.