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71.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献
72.
Polly L. Arnold Micha S. Dutkiewicz Markus Zegke Olaf Walter Christos Apostolidis Emmalina Hollis Anne‐Frderique Pcharman Nicola Magnani Jean‐Christophe Griveau Eric Colineau Roberto Caciuffo Xiaobin Zhang Georg Schreckenbach Jason B. Love 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(41):12989-12993
A dramatic difference in the ability of the reducing AnIII center in AnCp3 (An=U, Np, Pu; Cp=C5H5) to oxo‐bind and reduce the uranyl(VI) dication in the complex [(UO2)(THF)(H2L)] (L=“Pacman” Schiff‐base polypyrrolic macrocycle), is found and explained. These are the first selective functionalizations of the uranyl oxo by another actinide cation. At‐first contradictory electronic structural data are explained by combining theory and experiment. Complete one‐electron transfer from Cp3U forms the UIV‐uranyl(V) compound that behaves as a UV‐localized single molecule magnet below 4 K. The extent of reduction by the Cp3Np group upon oxo‐coordination is much less, with a NpIII‐uranyl(VI) dative bond assigned. Solution NMR and NIR spectroscopy suggest NpIVUV but single‐crystal X‐ray diffraction and SQUID magnetometry suggest a NpIII‐UVI assignment. DFT‐calculated Hirshfeld charge and spin density analyses suggest half an electron has transferred, and these explain the strongly shifted NMR spectra by spin density contributions at the hydrogen nuclei. The PuIII–UVI interaction is too weak to be observed in THF solvent, in agreement with calculated predictions. 相似文献
73.
Fungisai Matemadombo Sophie Griveau Fethi Bedioui Tebello Nyokong 《Electroanalysis》2008,20(17):1863-1872
Manganese phthalocyanine MnPc(SPh)4 has been synthesized and used to form self assembled monolayers on gold electrodes. The well packed SAM monolayer was characterized by analyzing the blocking of a number of Faradic processes by cyclic voltammetry, evaluating the electrical characteristics of the modified electrode by electrochemical impedance and imaging the modified surface by electrochemical scanning microscopy. Finally, MnPc(SPh)4‐SAM modified electrode displayed an electrocatalytic behavior toward the oxidation of nitrite. 相似文献
74.
Bedioui F Griveau S Nyokong T Appleby AJ Caro CA Gulppi M Ochoa G Zagal JH 《Physical chemistry chemical physics : PCCP》2007,9(26):3383-3396
In this work we discuss different approaches for achieving electrodes modified with N(4) macrocyclic complexes for the catalysis of the electrochemical oxidation of thiols. These approaches involve adsorption, electropolymerization and molecular anchoring using self assembled monolayers. We also discuss the parameters that determine the reactivity of these complexes. Catalytic activity is associated with the nature of the central metal, redox potentials and Hammett parameters of substituents on the ligand. Correlations between catalytic activity (log i at constant E) and the redox potential of catalysts for complexes of Cr, Mn, Fe, Co, Ni and Cu are linear with an increase of activity for more positive redox potentials. For a great variety complexes bearing the same metal center (Co) correlations between log i and E(o') of the Co(II)/Co(I) couple have the shape of an unsymmetric volcano. This indicates that the potential of the Co(II)/Co(I) couple can be tuned using the appropriate ligand to achieve maximum catalytic activity. Maximum activity probably corresponds to a DeltaG of adsorption of the thiol on the Co center equal to zero, and to a coverage of active sites by the thiol equal to 0.5. 相似文献
75.
José H. Zagal Sophie Griveau J. Francisco Silva Tebello Nyokong Fethi Bedioui 《Coordination chemistry reviews》2010,254(23-24):2755-2791
Metallophthalocyanines confined on the surface of electrodes are active catalysts for a large variety of electrochemical reactions and electrode surfaces modified by these complexes can be obtained by simple adsorption on graphite and carbon. However, more stable electrodes can be achieved by coating their surfaces with electropolymerized layers of the complexes, that show similar activity than their monomer counterparts. In all cases, fundamental studies carried out with adsorbed layers of these complexes have shown that the redox potential is a very good reactivity index for predicting the catalytic activity of the complexes. Volcano-shaped correlations have been found between the electrocatalytic activity (as log I at constant E) versus the Co(II)/(I) formal potential (E°′) of Co-macrocyclics for the oxidation of several thiols, hydrazine and glucose. For the electroreduction of O2 only linear correlations between the electrocatalytic activity versus the M(III)/M(II) formal potential have been found using Cr, Mn, Fe and Co phthalocyanines but it is likely that these correlations are “incomplete volcano” correlations. The volcano correlations strongly suggest that E°′, the formal potential of the complex needs to be in a rather narrow potential window for achieving maximum activity, probably corresponding to surface coverages of an M-molecule adduct equal to 0.5 and to standard free energies of adsorption of the reacting molecule on the complex active site equal to zero. These results indicate that the catalytic activity of metallophthalocyanines for the oxidation of several molecules can be “tuned” by manipulating the E°′ formal potential, using proper groups on the macrocyclic ligand. This review emphasizes once more that metallophthalocyanines are extremely versatile materials with many applications in electrocatalysis, electroanalysis, just to mention a few, and they provide very good models for testing their catalytic activity for several reactions. Even though the earlier applications of these complexes were focused on providing active materials for electroreduction of O2, for making active cathodes for fuel cells, the main trend in the literature nowadays is to use these complexes for making active electrodes for electrochemical sensors. 相似文献
76.
Ferrocene was covalently bonded to a layer of adsorbed single‐walled carbon nanotubes on a glassy carbon electrode surface using electrochemical grafting and click chemistry. Grafting of the 4‐azidobenzenediazonium salt onto the surface was accomplished by electrochemical reduction. The surface‐bound azide groups, with the use of a copper(I) catalyst, were reacted with ethynylferrocene to form covalent 1,2,3‐triazole bonds by click chemistry. This layer by layer construction of the electrode surface results in stable electrodes by combining good electrical conductivity and increased surface area of the nanotubes with the versatility of the Sharpless click reaction. 相似文献
77.
Park HS Blewitt G Cortez BG Foster GW Gajewski W Haines TJ Kielczewska D LoSecco JM Bionta RM Bratton CB Casper D Chrysicopoulou P Claus R Errede S Ganezer KS Goldhaber M Jones TW Kropp WR Learned JG Lehmann E Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak LR Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(1):22-25
78.
Seidel S Bionta RM Blewitt G Bratton CB Casper D Ciocio A Claus R Dye ST Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG LoSecco JM Matthews J Park HS Price L Reines F Schultz J Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R Thornton G van der Velde JC Wuest C 《Physical review letters》1988,61(22):2522-2525
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