Optical properties of Prussian-Blue-modified gold and platinum single-crystal electrodes

Abstract

Prussian Blue (PB) is a polynuclear mixed-valent iron cyanide complex which is zeolitic in nature and has a face-centred cubic structure with a lattice constant of about 10 A [l]. PB-modified electrode surfaces have been the subject of intense study in recent years because of their potential for application in areas such as electrochromism [2,3], electrocatalysis [4,5], photosensing devices [61, charge storage [7,8], ion-selective sensors [9] and semiconducting films [lo-121. Modification of electrodes such as polycrystalline Pt, Au and glassy carbon (GC) with thin PB films using different chemical and electrochemical procedures have been described in the literature [2,7,8,12]. A cyclic polarization procedure for the modification of GC with PB in a neutral medium has been reported in earlier communications [lO,ll]. The PB overlayer has been characterized by in-situ Mijssbauer spectroscopy [13] in order to identify the low spin Fen and the high spin Fe”’ species present in the PB skeleton. In-situ optical absorption spectra on PB-modified SnO, have also been reported in the 400-800 nm region [14]. However, it is desirable to characterize the optical properties of the material over as wide a wavelength range as possible. In the following we present the results of an optical study of PB-modified single-crystal Au and Pt electrodes with special emphasis on the (111) faces of Au and Pt, where the surface redox processes are seen particularly clearly.