A novel biological active multilayer film based on polyoxometalate with pendant support-ligand

A novel nanosized biological active multilayer film composed of polyoxometalate (POM) anion α-[SiW11O39Co(H2PO4)]7−(abbr. SiW11Co–PO4) and poly(diallyldi methylammonium chloride) (abbr. PDDA) was fabricated by layer-by-layer self-assembly (LBL). The composition and growth processes of the films have been determined by X-ray photoelectron spectra (XPS) and ultraviolet-visible absorption spectra (UV). The composite film was formed by the alternate adsorption of SiW11Co–PO4 and PDDA, and the deposition process was quantitative and highly reproducible from layer to layer. The morphology of the film was studied by atomic force microscopy (AFM), which showed that the film was relatively uniform and smooth, and POM anions aggregated into nanoclusters distributing on the surface uniformly. The film exhibited favorable electrochemical behavior of POM indicated by cyclic voltammetry (CV). The film can immobilize the DNA molecules via Mg2+-bridging medium.