Layer‐by‐Layer Construction of Hybrid Film Based on PEI Polymer and Preyssler‐Type Polyoxometalates: Its Electrochemical and Quartz Crystal Microbalance Measurement

Abstract

In this work, Preyssler‐type POM (NH4)14[NaP5W30O110].44H2O (NH4P5W30), has been synthesised and its electrochemical behaviour in solution was examined at the surface of glassy carbon (GC) and gold electrodes. Furthermore, multilayer assemblies of NH4P5W30 POM were constructed onto the surfaces of GCE, gold electrode, and gold quartz electrode via the electrostatic Layer‐by‐Layer (LBL) technique employing polyethyleneimine as the cationic layer and POM as an anionic layer. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and electrochemical quartz crystal microbalance measurements (EQCM) were used to monitor the LBL assembly as the NH4P5W30 POM layer was being built. These techniques revealed significant differences in film growth. The multilayer film exhibited well‐defined redox couples associated with POM's tungsten‐oxo framework and showed surface‐confined behaviour up to 100 mVs−1 on both the GC and gold electrodes. The pH dependency and stability of the film were investigated. EIS demonstrated that when the POM layer was the outer layer, the layers were less conductive, and resistance increased as the number of layers increased. In addition, the charge transfer resistance values (Rct) for the layers were calculated. The solvation of ions into the film associated with POM redox activity was studied employing an in‐situ EQCM.