PROBLEMS ASSOCIATED WITH THE THIN-FILM AG AGCL REFERENCE ELECTRODE AND A NOVEL STRUCTURE WITH IMPROVED DURABILITY/

We have developed a novel thin-film Ag/AgCl reference electrode which shows dramatic improvement in its durability. To make the electrode re sistant to heat treatment in its fabrication, a metal adhesive layer i n the currently used thin-film Ag/AgCl electrodes was replaced by a po lyimide layer, and a gold backbone structure was employed. Unlike the currently used structure, the entire surface of the silver layer was c overed with a polyimide layer and AgCl was grown from the periphery of the pattern. The structure was resistant to baking at 300 degrees C. Whereas the currently used Ag/AgCl electrode has a very short lifespan in concentrated KCl solutions, the novel electrode showed surprising resistance in these solutions. In a KCl and AgCl saturated solution, t he novel electrode gave a stable potential for approximately 8 h, whil e the currently used electrode functioned for only 1.5 min. A dramatic difference was also observed in the resistance to interfering materia ls. Although 1 mM Kl or K2S was enough to break the currently used ele ctrode, the novel electrode was resistant to these materials and showe d much smaller potential shift. In the novel Ag/AgCl structure, the ra te of AgCl formation was significantly delayed and the spread of the A gCl layer was visualized. Therefore, any of the electrochemical and ch emical methods of AgCl formation could be easily applied. (C) 1998 Els evier Science S.A. All rights reserved.