Influence of Immersion of Polyethyleneimine Thin Film Modified with Gold Nanoparticles in [Ru(NH3)6]Cl3 Aqueous Solution on Redox Reaction on AuNPs

The influence of immersion in a hexaammineruthenium chloride ([Ru(NH3)6]Cl3) aqueous solution on the redox reaction on a polyethyleneimine (PEI) thin film modified with gold nanoparticles (AuNPs) is investigated for the electrochemical analysis of the conjugated reaction area of electronic and electrochemical conduction. The PEI thin film is electrodeposited on a glassy carbon (GC) electrode in an ethylenediamine acetonitrile solution. AuNPs were prepared by Frens’s method and loaded onto the PEI thin film on the GC (GC/PEI) electrode. The redox reaction of [Ru(NH3)6]3+ on AuNPs loads onto a PEI film on a GC (GC/PEI/AuNPs) electrode is observed by cyclic voltammetry and electrochemical impedance spectroscopy. The apparent electron transfer rate constant at a single AuNP, calculated from the charge transfer resistance and AuNP number density, increases during immersion of GC/PEI/AuNPs in the [Ru(NH3)6]3+ solution. It is suggested that the redox reaction occurs not only at the AuNPs by the tunneling effect, but also at the GC electrode due to the ionic transport of [Ru(NH3)6]3+ during the immersion in the [Ru(NH3)6]3+ solution. Care should be taken that the electrochemical reaction is measured as soon as possible when using PEI films before the electrolyte can penetrate the film completely, because the ionic conduction of the [Ru(NH3)6]3+ solution in the PEI thin film cannot be ignored during immersion in the electrolyte solution.