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[Er0.5K0.5(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.