Search

Developing portable membrane sensors to accurately detect the biomolecule ascorbic acid (AA) is extremely important for food safety and human health. Herein, we successfully design and synthesize a novel cationic metal organic framework (Eu-pbmc, Hpbmc = 2-(pyridine-2-yl)-1H-benzimidazole-5-carboxylic acid) and assemble polyacrylonitrile/Eu-pbmc membrane (PEM) by an in-situ growth strategy. Benefiting from the appreciable loading of Eu-pbmc nanoparticles and high water permeation flux, PEM possesses effective detection for MnO4− with a limit of detection (LOD) of 17 nM. Utilizing the cationic porous framework, we load MnO4− into PEM and construct a “on-off-on” system for effective AA detection. The oxidative MnO4− can be reduced by AA and the resulting turn-on luminescence can reflect the concentration of AA. Compared with pure Eu-pbmc crystals, PEM exhibits improved AA detection performance with LOD of 48 nM and detection time of 1 min via a concise detection operation. The stable membrane sensor realizes an accurate detection in real biological samples, meeting the practical requirement. Moreover, an IMP logic gate is helpful to analyze MnO4− and AA in water. The proposed novel luminescence platform as well as reasonable “on-off-on” luminescence mode provide a promising method for AA detection.

A pair of redox flow batteries containing polyoxometalates was tested as part of an ongoing program in stationary energy storage. The iron-containing dimer, (SiFe3W9(OH)3O34)2(OH)311−, cycled between (SiFe3W9(OH)3O34)2(OH)311−/(SiFe3W9(OH)3O34)2(OH)314−and (SiFe3W9(OH)3O34)2(OH)317−/(SiFe3W9(OH)3O34)2(OH)314− for the positive and negative electrode, respectively. This compound demonstrated a coulombic efficiency of 83% after 20 cycles with an electrochemical yield (measured discharge capacity as a percentage of theoretical capacity) of 55%. Cyclic voltammetry on the Lindqvist ion, cis-V2W4O194−, showed quasi-reversible vanadium electrochemistry, but tungsten reduction was mostly irreversible. In a flow cell configuration, cis-V2W4O194−had a coulombic efficiency of 45% (for a two-electron process) and an electrochemical yield of 16% after 20 cycles. The poor performance of cis-V2W4O194−was attributed primarily to its higher charge density. Collectively, the results showed that both polyoxometalate size and charge density are both important parameters to consider in battery material performance.

Flow batteries including an electrolyte of a polyoxometalate material are disclosed herein. In a general embodiment, the flow battery includes an electrochemical cell including an anode portion, a cathode portion and a separator disposed between the anode portion and the cathode portion. Each of the anode portion and the cathode portion comprises a polyoxometalate material. The flow battery further includes an anode electrode disposed in the anode portion and a cathode electrode disposed in the cathode portion.

The colorless crystals of the novel dimeric polyoxometalate Na 12 H 4 [A-β-PW 9 O 34 Na(H 2 O)] 2 ·38H 2 O were obtained by recrystallization of the precursor Na 9 [A-PW 9 O 34 ]·19H 2 O in acidic solution. The crystal is triclinic, space group P 1 , with lattice constants a=12.6134(4) A , b=13.146(6) A , c=18.243(4) A , α =88.373(3)°, β =69.92(2)°, γ =63.23(3)°, V=2507.4(14) A 3 and Z =1. The crystal structure confirms the dimeric anhydride is formed by Na–O–Na bridges linking two A-β-PW 9 O 34 Keggin units. One of the Na + ions is linked with the inner oxygen atom [O a (1)] forming a dimeric anion, while the coordination of polyoxoanions with Na + ions and water molecules results in a two-dimension network structure.