Fuzzy gold electrodes for lowering impedance and improving adhesion with electrodeposited conducting polymer films

For sensor and actuator devices where conducting polymers are electrochemically deposited on the surface of electrodes, the adhesion between the deposited polymer film and substrate metal electrode is crucial for maintaining the long-term performance. Electroplating gold on sputtered gold microelectrode sites was studied as a means to provide a fuzzy, roughened surface for electrodeposited conducting polymers to adhere. It was found that concentration of Au(CN)(2)(-) solution and current density played important roles in controlling the morphology of the deposits. Impedance spectroscopy was used to quantitatively compare the surface area of sputtered gold and electrodeposited gold obtained by different current densities. By examining the impedance response in the limit of low frequencies, we found that the electroplated gold layer deposited at 125 nA out of a 4.5 mM Au(CN)(2)(-) solution for 8 min (deposition charge density of 4.8 C/cm(2)) gives an electrodeposited gold layer having eight times larger effective surface area compared to a sputtered gold layer. This increase in surface area leads to improved adhesion of the subsequently deposited electropolymerized conducting polymers. Conducting polymer PPy/PSS deposited on the electrodes that were preprocessed with a fuzzy electroplated gold layer showed electrochemical properties and morphologies similar to those deposited on smooth sputtered gold electrodes. A significant improvement on adhesion of these polymer films on the fuzzy gold substrate was demonstrated. (C) 2002 Elsevier Science B.V. All rights reserved.