Electrochemical behavior of inorganic–organic hybrid polyoxometalate ((Cys)3[PW12O40]) nanostructure self-assembled monolayer on polycrystalline gold electrode surfaces

Abstract

The electrochemistry of polyoxometalates (POMs) is very rich, as many of them can transfer multiple electrons without their structure being changed. In this study, an inorganic–organic hybrid compound, building from H₃[PW₁₂O₄₀] (HPW) and L-cysteine (Cys), was prepared by a solvent free reaction and structurally characterized by routine methods. The results showed that HPW preserved its parent structure after functionalization by Cys. Then, (Cys)PW was assembled on a cleaned polycrystalline gold (poly Au) electrode for the first time. The electrochemical behavior of the poly Au-(Cys)PW SAMs-modified electrode was then investigated in detail using cyclic voltammetry (CV). Experimental results showed that the poly Au-(Cys)PW SAMs-modified electrode not only had a higher electrochemical activity than a poly Au-HPW SAMs-modified electrode, but also showed remarkable stability due to greater insolubility of the hybrid POM nanoparticles than the parent POM and a strong covalent bond poly Au–S, which is important for practical applications. Moreover, surface coverage of the different monolayers was determined from linear sweep voltammetry (LSV) data. Cys and (Cys)PW solutions prepared in 0.1 M HClO₄ provided coverages of 1.9 ± 0.2 and 2.1 ± 0.2 nmol cm⁻² on the poly Au surface, respectively as evaluated from their reductive desorption peaks. The significance of our research is to provide a kind of gold surface modified with the (Cys)PW nanostructure with a higher electrochemical activity and stability and was applied in an electrode modification.