Improved Synthesis,Structure, and Solution Characterization of the Cyclic 48-Tungsto-8-Arsenate(V), [H4As8W48O184]36−

We report on an improved synthesis and structural characterization of the cyclic 48-tungsto–8-arsenate(V) [H₄As₈W₄₈O₁₈₄]^36? (1). The mixed lithium–potassium salt of this polyanion, K_26.5Li_9.5[H₄As₈W₄₈O₁₈₄]·90H₂O (KLi-1), has been studied in the solid state by IR, single-crystal X-ray diffraction, and elemental analysis, and in solution by ¹⁸³W NMR spectroscopy.     

Effects of AC‐Electrolysis on the Enzymatic Activity of Glucose Oxidase

The change in the activity of glucose oxidase subjected to an asymmetrical alternating current (AC) electric field is investigated via horseradish peroxidase (HRP)‐coupled bioassay. The effect of the amplitude, frequency and enzyme concentration have been shown to affect the enzyme activity towards glucose oxidation. The decrease in the enzyme activity is directly related to the change in pH and temperature of the GOx solution during AC electrolysis. The enzyme activity reduces with increasing amplitude, enzyme concentration and decreasing frequency. Results from UV‐vis, FT‐IR and UV CD spectroscopy showed that the AC treated GOx samples undergo structural modifications.     

Performance of SLS/MWCNTs/PANI capacitor electrodes in a physiological electrolyte and in serum

We report a stainless steel/multi walled carbon nanotubes/polyaniline (SLS/MWCNTs/PANI) capacitor electrode capable of operating in a physiological electrolyte and in serum. The specific capacitance of SLS/MWCNTs/PANI reaches 401 F g(-1) in the physiological electrolyte and 326 F g(-1) in serum. The capacity loss at 6.4 μA mm(-2) over 2000 cycles is 10% in the physiological electrolyte and 21% in serum.     

Hybrid material based on 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and Dawson polyoxoanion [P2Mo18O62]6−. Part II: further characterizations and catalytic oxidation of the NADH coenzyme

In this account, [BMIM]₆P₂Mo₁₈O₆₂ hybrid material was further characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. XRD illustrated that compared to the parent K₆P₂Mo₁₈O₆₂·nH₂O, where 92 % of the structure is crystalline, 84 % of the structure of [BMIM]₆P₂Mo₁₈O₆₂ hybrid material is fine-grain amorphous and only 16 % is crystalline. This was attributed to the replacement of most of the protons and constitution water molecules in K₆P₂Mo₁₈O₆₂·nH₂O by [BMIM]⁺ cations. TEM showed that K₆P₂Mo₁₈O₆₂·nH₂O has uniform and spherical nanoparticles with an average diameter of ~100 nm. However, the hybrid material displayed less uniform morphology with spherical and variously shaped nanoparticles with diameters varying from ~10 to 100 nm. Raman spectroscopy of [BMIM]₆P₂Mo₁₈O₆₂ illustrated that peaks of the Dawson [P₂Mo₁₈O₆₂]^6? unit in [BMIM]₆P₂Mo₁₈O₆₂ hybrid material are not obvious due to the overlap with the peaks of [BMIM]⁺. The latter was related to the large number of [BMIM]⁺ cations surrounding the Dawson unit in the hybrid material. [BMIM]₆P₂Mo₁₈O₆₂ was immobilized on glassy carbon electrode and studied by electrochemistry. Linear sweep voltammetry illustrated that unlike the parent polyoxoanion [P₂Mo₁₈O₆₂]^6? which showed no particular catalytic activity towards the oxidation of the NADH coenzyme, the hybrid material [BMIM]₆P₂Mo₁₈O₆₂ is found to efficiently catalyze the oxidation of the NADH coenzyme at low overpotentials. Amperometry revealed high sensitivities (~1.97 μA?mM^?1?mm^?2) and extended linearity (~9.1 mM) of [BMIM]₆P₂Mo₁₈O₆₂/GC electrode towards the oxidation of the NADH coenzyme.     

Facile synthesis of Cu-LDH with different Cu/Al molar ratios: application as antibacterial inhibitors

Research on Chemical Intermediates - A range of Cu-LDHs has been synthesized by co-precipitation using metal nitrate precursors and sodium carbonate under varying molar ratios Cu/Al...     

Neighboring pyrrolidine amide participation in thioether oxidation. Methionine as a "hopping" site

Methionine residues have been shown to function as efficient "hopping" sites in long-range electron transfer in model polyprolyl peptides. We suggest that a key to this ability of methionine is stabilization of the transient sulfur radical cation by neighboring proline amide participation. That is, in a model system a neighboring pyrrolidine amide lowers the oxidation potential of the thioether by over 0.5 V by formation of a two-center three-electron SO bond.     

Cyclic Voltammetry Study of the Mn‐Substituted Polyoxoanions [MnII4(H2O)2(H4AsW15O56)2]18− and [((MnIIOH2)MnII2PW9O34)2(PW6O26)]17−: Electrodeposition of Manganese Oxides Electrocatalysts for Dioxygen Reduction

The electrochemical behavior of two manganese (Mn)‐substituted polyoxoanions, the dissymmetrical Dawson sandwich‐type [Mn^II₄(H₂O)₂(H₄AsW₁₅O₅₆)₂]^18? and the Keggin sandwich banana‐shaped [((Mn^IIOH₂)Mn^II₂PW₉O₃₄)₂(PW₆O₂₆)]^17? is investigated. At pH 5, the oxidation of the Mn^II‐centers results in one oxidation wave for [Mn^II₄(H₂O)₂(H₄AsW₁₅O₅₆)₂]^18? and two oxidation waves for [((Mn^IIOH₂)Mn^II₂PW₉O₃₄)₂(PW₆O₂₆)]^17?. To the best of our knowledge, presence of the second Mn‐based wave is rarely observed in the electrochemistry of Mn‐containing polyoxometalates. Deposition of Mn‐oxides electrocatalysts for dioxygen reduction is noticed by cyclic voltammetry, which can be distinguished by the significant positive shift in potentials of the dioxygen reduction reaction.     

Nitrite sensor based on multilayer film of Dawson-type tungstophosphate α-K7[H4PW18O62]·18H2O immobilized on glassy carbon

A nitrite sensor based on immobilized Dawson-type tungstophosphate α-K₇[H₄PW₁₈O₆₂]·18H₂O (PW₁₈) in multilayers of charged polyelectrolyte poly(allylamine hydrochloride) (PAH) on a glassy carbon electrode is described. A nitrite sensor manufactured with 10 layers has a sensitivity of ∼4 nA/μM nitrite, fast response time (<6 s), low detection limit (∼0.1 μM), high selectivity towards endogenous interferences such as nitrate and molecular oxygen, a linear range from 0.1 μM to at least 20 mM nitrite and was stable for at least 2 months. In addition, such nitrite sensors can operate in a pH range from 1 to 9, and the sensitivity can be increased by increasing the number of layers at the expense of increasing the response time.