A new [Co21(H2O)4(OH)12]30+ unit-incorporating polyoxotungstate for sensitive detection of dichlorvos

A new [Co21(H2O)4(OH)12]30+ unit-incorporating polyoxotungstate, Na18[Co(H2O)6]2{[Na(H2O)4]2[Na(H2O)2]2[Co(H2O)3]2[Co21(H2O)4(OH)12](SiW10O37)6}·24H2O (denoted as Co25Si6W60), has been hydrothermally synthesized and fully characterized via elemental analyses, thermogravimetric analysis, bond valence sum (BVS) calculations, IR spectrum, UV-vis spectrum, diffuse reflectance spectrum, powder X-ray diffraction and single-crystal structural analysis. The most remarkable feature is that the gigantic [Co21(H2O)4(OH)12(SiW10O37)6]30− core in Co25Si6W60 is composed of a square-like [Co21(H2O)4(OH)12]30+ nanosheet encapsulated by six dilacunary Keggin [α-SiW10O37]10− moieties in a staggered fashion, resulting in a remarkable sandwich-type assembly. Furthermore, the unique Co25Si6W60-based biosensing system, as a simple, rapid, and highly sensitive electrochemical platform, offers an environmentally friendly route for detecting dichlorvos in the field of both food safety and environmental pollution.