Reaction Mechanism for the Dual Gold‐Catalyzed Synthesis of Dibenzopentalene: A DFT Study

A wide range of gold‐catalyzed reactions based on a dual activation mechanism has recently been reported in the literature. Herein, we present a computational investigation of the mechanism for the formation of dibenzopentalenes from 1‐ethynyl‐2‐(phenylethynyl)benzene. Transition states have been found, which substantiate the dual activation mechanism previously published and furthermore point towards a continuous presence of two gold moieties throughout the mechanistic cycle, an observation of high importance for all reactions in the field of dual activation. The initial activation of the diyne has been shown to proceed via an intermolecular transfer of a cationic gold catalyst from the thermodynamically preferred geminal‐σ,π‐acetylide complex to the active non‐geminal analogue. Furthermore, the regioselectivity of a 5‐endo versus a 6‐endo cyclization has been addressed, and the 5‐endo cyclization was found to be most favorable both thermodynamically and with regard to the activation barrier.     

Surface chemical approach to single-step measurement of antibody in human serum using localized surface plasmon resonance biosensor on microtiter plate system

In clinical settings, serum antibody levels serve as markers of pathology. For example, antibodies related to autoimmune diseases are among the conventional targets in laboratory tests. Simple clinical tests can improve the efficacy of laboratory practice. This study describes a single-step, wash-free technique for optically detecting antibodies in human serum through the localized surface plasmon resonance (LSPR) of gold nanoparticles. As a proof-of-concept experiment, the amount of antibiotin dissolved in human serum was measured with a LSPR-based biosensor in a wash-free manner using a conventional 96-well microtiter plate and a plate reader. For an efficient surface modification of biosensors, zwitterionic copolymer was used as a scaffold on the gold nanoparticle surface to immobilize antigen and blocking reagent. Single-step, wash-free measurement of antibiotin in human serum was successfully achieved. In addition, nonspecific responses from serum contents were significantly reduced because both the copolymer and hydrophilic antigen reagent that we employed were composed of poly(ethylene oxide) spacer. Comparative experiments of the antigen-antibody reaction in serum to that in buffered solution revealed that serum is a favorable environment for the biological reaction. In conclusion, our gold-nanoparticle-based LSPR method may provide a rapid and simple way to measure the amount of antibody in serum quantitatively in clinical practice.

Literatur

Ohne Zusammenfassung     

Literatur

Ohne Zusammenfassung     

Dispersion und Absorption transversaler Schallwellen im Magnetfeld

The propagation velocity and absorption of transverse ultrasonic waves have bsen measured in a polycristalline metallic probe as functions of a magnetic field parallel to the direction of propagation. In agreement with the macroscopic theory, these measurements showed, that the propagation velocity was increased by the magnetic field for frequencies below a transition frequency characteristic for the medium. In case of high frequencies the magnetic field causes an absorption. In the dispersion region characterized by the transition frequency, the magnetohydrodynamic Reynolds number is of order one and the magnetically induced changes in propagation velocity and absorption are strongly frequency dependent.     

Effect of ion-exchange nanofiber fabrics on water splitting in bipolar membrane

In the present study, the effect of ion-exchange fiber fabric made by electrospray deposition (ESD) on water splitting in a composite bipolar membrane (CBM) was investigated. Cation- and anion-exchange fiber (CEF and AEF) fabrics, which were composed of very thin fibers, were prepared by ESD and postdeposition chemical modification and then used as the intermediate layer of a CBM. The current-voltage characteristics under reverse bias conditions showed that the AEF fabrics enhanced water splitting. The water dissociation is accelerated by the AEF fabric, which contains both tertiary pyridyl groups and quaternary pyridinium groups and has a high specific surface area. On the other hand, the CEF fabric, which contains sulfonic acid groups and has an insufficient specific surface area, reduced water splitting. These results indicate that fiber fabric with catalytic activity and a high surface area obtained by ESD can improve the performance of a CBM.     

Domino Heck-C-H activation reaction of unsymmetrically substituted [3]cumulene

The Heck reaction of an unsymmetrically substituted [3]cumulene has been investigated. Although a carbonyl conjugated alkene is present, the arylpalladium species selectively inserts into the C3-4 double bond, and a subsequent C-H activation reaction with a neighboring phenyl group gives the indene derivatives with a tetrasubstituted olefin moiety.     

Microgravimetric corrosion study of magnetron-sputtered Co-Cr-Mo and Ni-Cr-Mo alloys in an oxygen-containing atmosphere

A quartz crystal microbalance (QCM) has been used for in situ corrosion studies of magnetron-sputtered Co-Cr-Mo and Ni-Cr-Mo alloys, which are of great importance in various technical and medical applications. The corrosion monitoring has been performed in an oxygen-containing atmosphere and in NaCl solution. The alloys were deposited on quartz substrates by means of DC magnetron sputtering. X-ray photoelectron spectroscopy analysis showed that the composition of the deposits was similar to that of the magnetron-sputtering targets. X-ray diffraction revealed an amorphous structure of the sputtered deposits, while the casting alloys had a crystalline structure. The polarization resistance of sputtered alloys in NaCl solution was higher than the activity of conventional alloys, which implied a superior corrosion resistance of the sputtered deposits. Corrosion was initiated by supplying oxygen gas into a wet argon atmosphere and the QCM detected corrosion with nanogram resolution as the increase in mass. Corrosion currents were calculated from the mass versus time curves. The QCM appeared to be an effective tool for corrosive characterization of sputtered alloys in gaseous environments. A corrosion current calculation in solution was complicated by metal transfer to the liquid phase. Electronic Publication