An unprecedented dumbbell-shaped pentadeca-nuclear W–Er heterometal cluster stabilizing nanoscale hexameric arsenotungstate aggregate and electrochemical sensing properties of its conductive hybrid film-modified electrode

Cluster-based functional materials have made remarkable progress owing to their wonderful structures and distinctive physicochemical performances, one of on-going advancements of which is basically driven by synthetic chemistry of exploring and constructing novel nanosized gigantic polyoxometalate (POM) aggregates. In this article, an unprecedented nanoscale hexameric arsenotungstate aggregate Na₉K₁₆H₄[Er_0.5K_0.5(H₂O)₇][Er₅W₁₀O₂₆(H₂O)₁₄][B-α-AsW₉O₃₃]₆·102H₂O (1) has been synthesized by the combined synthetic strategy of simultaneously using the arsenotungstate precursor and simple tungstate material in a highly acidic aqueous solution. The {[Er₅W₁₀O₂₆(H₂O)₁₄][B-α-AsW₉O₃₃]₆}³¹⁻ polyanion in 1 consists of an intriguing dumbbell-shaped pentadeca-nuclear W–Er heterometal {Er₅W₁₀O₂₆(H₂O)₁₄}²³⁺ cluster connecting six trilacunary [B-α-AsW₉O₃₃]⁹⁻ moieties, which has never been seen previously. Furthermore, through electropolymerization of 1 and pyrrole on the conductive substrate, a thickness-controllable and robust 1–PPY (PPY = polypyrrole) hybrid film was successfully prepared, which represents the first POM–PPY film assembled from high-nuclear lanthanide (Ln) encapsulated POM and PPY hitherto. The 1–PPY film-based electrochemical biosensor exhibits a favorable recognition performance for ochratoxin A in multiple media. This work not only provides a feasible combined synthetic strategy of the POM precursor and simple tungstate material for constructing complicated multi-Ln-inserted POM aggregates, but also offers a promising electrochemical platform constructed from POM-based conductive films for identifying trace biomolecules in complex environments.