Physico- and Electrochemical Properties of First-Row Transition-Metal-Substituted Sandwich Polyoxometalates.

The physico- and electrochemical behaviors of a series of [WZn(HO)(ZnWO)] (Zn-WZn) and its first-row transition-metal-substituted analogues [WZn(TM)(HO)(ZnWO)] (Zn-WZn(TM); TM = Mn, Co, Fe, Ni and Cu) are reported. Various spectroscopic studies, including Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, electrospray ionization (ESI)-mass spectrometry, and Raman spectroscopy, show similar spectral patterns in all sandwich polyoxometalates (POMs) because of their isostructural geometry and constancy of the overall negative charge (-12). However, the electronic properties highly depend on the transition metals at the "sandwich core" and correlate well with the density functional theory (DFT) study.

PVIM-CoPOM/MNC composite as a flexible electrode for the ultrasensitive and highly selective non-enzymatic electrochemical detection of cholesterol.

To address the issues allied with cardiovascular diseases and the increased prevalence of hypertension, a novel electrochemical sensor was developed based on poly(ionic liquid) [PVIM]-cobalt polyoxometalate (Co5POM) supported on carbonaceous materials (MNCs) for the highly selective and ultrasensitive non-enzymatic detection of cholesterol. The novel composite exhibits excellent selectivity and sensitivity towards the non-enzymatic electrochemical detection of cholesterol with a low detection limit of 1 fM (1 × 10-15 M), a response time of ∼5 s, and a wide detection range of 1 fM-5 mM with two linear ranges of 1 fM-200 nM and 0.5 μM-5 mM with sensitivities of 210 and 64 μA μM-1 cm-2, respectively, even in the presence of ascorbic acid, glucose and uric acid.

Ultrasensitive and Highly Selective Electrochemical Detection of Dopamine Using Poly(ionic liquids)-Cobalt Polyoxometalate/CNT Composite.

A novel sandwich polyoxometalate (POM) Na[WCo(HO)(CoWO)] and poly(vinylimidazolium) cation [PVIM] in combination with nitrogen-doped carbon nanotubes (NCNTs) was developed for a highly selective and ultrasensitive detection of dopamine. Conductively efficient heterogenization of CoPOM catalyst by PVIM over NCNTs provides the synergy between PVIM-POM catalyst and NCNTs as a conductive support which enhances the electron transport at the electrode/electrolyte interface and eliminates the interference of ascorbic acid (AA) at physiological pH (7.4).