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Abstract: A novel diperoxovanadate complex NH4[OV(O2)2{2-(2′-pyridyl)-imidazole}]·4H2O was synthesized in aqueous solution under physiological conditions. The solution structure of the complex was characterized by multinuclear (1H, 13C, 14N, and 51V) as well as multi-dimensional (DOSY and C-H COSY) NMR techniques in the interaction system of NH4VO3/H2O2/2-(2′-pyridyl)-imidazole at room temperature. The crystal structure of the complex was determined at 173K by single-crystal X-ray diffraction method. It belongs to the monoclinic space group P21/c with a =13.048(4), b =6.984(2), c =17.814(5) Å, β =104.695(5), V =1570.3(8) Å3 and Z =4. The crystal is composed of ammonium ions, {2-(2′-pyridyl)-imidazole}oxodiperoxovanadate(V) ions, and water molecules, which are held together by ionic and hydrogen bond forces. The metal atom in the complex is seven-coordinated with a distorted pentagonal bipyramidal geometry. It is the first mononuclear diperoxovanadate complex with a N, N′-chelating biheteroaromatic ligand and its 51V chemical shift is at the highest field among the known mononuclear diperoxovanadate(V) complexes. [Copyright &y& Elsevier]

The 19F NMR chemical shieldings of MF2 (M=Zn, Cd, Pb), MF3 (M=Al, Ga, In), and SnF4 were studied by the GIAO-B3LYP method. The aug-cc-pVTZ basis set was used for the inspected fluorine atom, and LanL2DZ for the remaining fluorine atoms. The 3-21G(2d) basis set was utilized for the Al atom, and CRENBL and/or DZVP for the other metal atoms. When appropriate cluster models were employed, the theoretical shieldings agree well with experimental ones. The relativistic and electron correlation effects have greater influence on the calculated results of fluorides containing heavy or transition metal atoms. [Copyright &y& Elsevier]

[Display omitted] • Co-fueling increases the current densities of C 3 -alcohols maximally by 9.9 times. • Product evolutions are recorded with in situ NMR monitoring. • Charge distributions are quantitatively analyzed with EC-NMR technique. • Co-fueling enhances the adsorption of –OH and the cleavage of C-C-C bonds. C 3 -alcohols can theoretically provide high current efficiencies in direct fuel cell applications because of their intrinsically large energy densities. However, during realistic reactions, molecular multiple carbon–carbon (C C C) bonds are hardly broken, severely reducing current efficiencies. Herein, directly with commercial Pt/C as the catalyst, the operation of co-fueling with formic acid significantly enhances the current efficiencies of two types of C 3 -alcohols, namely, isopropanol and 1,2-propanediol. Compared with the current densities of pure C 3 -alcohols, those of co-fueled C 3 -alcohols increase maximally by 9.9 times. The reason lies in the fact that the co-fueling design facilitates the breaking of C C C bonds, as elucidated by charge distributions that are obtained via electrochemical nuclear magnetic resonance analyses. Density-functional-theory computational results indicate that the generation of OH groups adsorbed on Pt surfaces is promoted in co-fueling experiments, reducing energy barriers for breaking progress. The co-fueling strategy is capable of optimizing C 3 -alcohol electrooxidations in direct fuel cells and deserves extensive study. [ABSTRACT FROM AUTHOR]

In this work, we report a facile, sensitive, selective, and reproducible DNA impedimetric sensor device. We demonstrate that, combined with exonuclease III, the easily prepared electrochemically reduced graphene oxide (rGO) could be a desirable platform to amplify signals in electrochemical impedance spectroscopy for ultrasensitive DNA detection. Guided by enzyme assisted target recycling, efficient interfacial tuning can be obtained, from the situation with high impedance caused by single-stranded DNA probes directly adsorbed onto rGO to the one with low impedance due to the continuous desorption of target–probe DNA hybrids and the consequent digestion of DNA probes. Just a few DNA targets can specifically trigger the enzymatic digestion of a large number of DNA probes. It is the excellent electrical conductivity of rGO that further enlarges the changes of electron transfer resistance after the removal of DNA probes. As a result of synergistically combining both enzymatic and electrical amplification, the enlarged changes of impedimetric signals can be measured to sensitively report DNA targets. The specificity has been guaranteed by the intrinsic recognition of hybrids through both rGO and exonuclease III. A limit of detection as low as 10 aM target DNA in the matrix of cell culture medium, as well as a wide linear range and good discrimination of mismatched sequences even at the one-base level, suggests its great application prospect in biosensing and biomedical analysis. It also has other advantages including easy operation, low cost, and convenient regeneration, with more competitive performance in developing impedimetric biosensors. [ABSTRACT FROM AUTHOR]

Lately, polymers as electrochemical catalysts have attracted intense interest. As two promising candidates, herein, electrochemically deposited polyaniline and poly(aspartic acid) thin film materials have been fabricated on glassy carbon electrodes. Through multiple characterizations, including attenuated total reflection Fourier transform infrared spectrophotometry, cyclic voltammetry, electrochemical impedance spectroscopy, and proton nuclear magnetic resonance, essential properties of these two electro-synthesized polymers, especially the capacity in electrochemically catalyzing the oxidation of electro-active isomers of hydroquinone and catechol, have been investigated. The polymer-modified electrodes present improved conductivity, and diffusion-dominated redox behaviors of hydroquinone and catechol at both modified glassy carbon electrodes are observed. In addition, quantitative proton nuclear magnetic resonance spectra provide the evident information on the electrochemically induced molecular transformation, which confirms the better electrochemical activity of poly(aspartic acid). [ABSTRACT FROM AUTHOR]

In this paper, we developed a direct way for the study of hydroquinone oxidation through in situ electrochemistry-combined nuclear magnetic resonance (EC-NMR). Electro-polymerization-induced nano-polyaniline film was utilized as the catalyst in the process of electrochemical oxidation of hydroquinone. In situ EC-NMR provides a powerful tool to probe products distribution and reaction rate, which could be useful to investigate electro-catalytic mechanism and evaluate the electro-catalytic capacity. To study the influence of both protic and aprotic media in the electrocatalytic process, we mixed water and dimethylsulfoxide to mimic possible real-life electrochemical environments. The proposed in situ EC-NMR is capable of quantitatively monitoring the generation of products under varied solvent composition and pH values. A positive effect to electro-catalysis capacity is observed when the concentration of DMSO or water is increased from the volume equivalent point, implying that there should be a competition between protic and aprotic media, which can be characterized by EC-NMR technique. [ABSTRACT FROM AUTHOR]

In many ultrafast imaging applications, the reduced field-of-view (rFOV) technique is often used to enhance the spatial resolution and field inhomogeneity immunity of the images. The stationary-phase characteristic of the spatiotemporally-encoded (SPEN) method offers an inherent applicability to rFOV imaging. In this study, a flexible rFOV imaging method is presented and the superiority of the SPEN approach in rFOV imaging is demonstrated. The proposed method is validated with phantom and in vivo rat experiments, including cardiac imaging and contrast-enhanced perfusion imaging. For comparison, the echo planar imaging (EPI) experiments with orthogonal RF excitation are also performed. The results show that the signal-to-noise ratios of the images acquired by the proposed method can be higher than those obtained with the rFOV EPI. Moreover, the proposed method shows better performance in the cardiac imaging and perfusion imaging of rat kidney, and it can scan one or more regions of interest (ROIs) with high spatial resolution in a single shot. It might be a favorable solution to ultrafast imaging applications in cases with severe susceptibility heterogeneities, such as cardiac imaging and perfusion imaging. Furthermore, it might be promising in applications with separate ROIs, such as mammary and limb imaging. [ABSTRACT FROM AUTHOR]