Electrochemical and optical evaluation of noble metal– and carbon–ITO hybrid optically transparent electrodes

Optically transparent hybrid electrodes were constructed by sputtering or thermally evaporating layers of varying thickness of Au, Pd, Pt, or C onto an existing conductive indium–tin oxide (ITO) layer on glass. These electrodes were characterized using UV–Vis spectroscopy and cyclic voltammetry; redox probes examined were potassium ferricyanide, tris-(2,2′-bipyridyl)ruthenium(II) chloride, hydroquinone, and para-aminophenol (PAP). Each type of hybrid was evaluated and compared with other hybrids, as well as with bare ITO electrodes and commercially available Au, Pt, and glassy carbon disk electrodes. Our results indicate that these hybrid electrodes are reasonably robust, easy to prepare, and extend the capabilities of bare ITO surfaces with respect to the electrochemical response (especially for organic redox probes), while giving up little in the way of optical transparency. Because of these characteristics, hybrid electrodes should be especially suited to many spectroelectrochemical applications.