Electrochemical reaction of Fe (CN)(6)(3-)/(4-) on gold electrodes analyzed by surface plasmon resonance

Surface plasmon resonance (SPR) measurements were combined with cyclic volt ammetry (CV) to analyze the electrochemical reactions of Fe(CN)(6)(3-/4-) o n gold electrodes in the phosphate electrolyte. The time differential of th e SPR signal was correlated with the current. When a low concentration of F e(CN)(6)(3-/4-) was introduced, the replacement of adsorbed phosphate ions with Fe(CN)(6)(3-/4-) was observed in SPR. At higher concentrations, the SP R signal reflected the refractive index difference of the redox state of Fe (CN)(6)(3-/4-). After continuous potential scanning, the potential dependen ce of the SPR signal changed completely. However, the cyclic voltammogram w as almost identical to that for the first cycle. The change in the SPR sign al reflected the formation of a surface film, but electrochemical data show ed that this film did not affect the electron transfer reaction in the expe rimental time window. (C) 1999 Elsevier Science B.V. All rights reserved.