Article révisé par les pairs
Résumé : The modification of gold electrodes by a short thiolated hepta(ethylene glycol) self-assembled monolayer(SAM) significantly inhibits the electron transfer kinetics of the [Fe(CN)6]3-/4- couple. By contrast, otherredox species such as Fc(CH2OH)2, Fc+, [Ru(NH3)6]3+ and methylene blue are barely affected by thepresence of the SAM. Considering the properties of the hydrated monolayer and the documentedpeculiarities of the [Fe(CN)6]3-/4- electron transfer kinetics, hydration is hypothesized to be a key factorto explain the particular behaviour of the ferri/ferrocyanide system. Further support to the role ofhydration is provided through the effect of “water structure breakers” ions, whose presence in solutionpromotes a gradual concentration-dependent recovery of the electron transfer. Taking advantage of thefacile kinetics displayed by other redox species, these are used at micromolar concentrations asmediators to catalytically amplify the electron transfer of the ferri-ferrocyanide couple at the SAM. Thevoltammetric behaviours recorded in the presence of these redox species are in very good agreementwith the theoretical framework of homogeneous redox catalysis of electrochemical processes. The libraryof available redox mediators enables one to tune the electrochemistry of [Fe(CN)6]3-/4- in a desiredpotential range.