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51.
Julia Rebholz Peter Bonanati Udo Weimar Nicolae Barsan 《Analytical and bioanalytical chemistry》2014,406(16):3977-3983
A model for sensing with semiconducting metal oxide (SMOX)-based gas sensors was developed which takes the effect of the shape of the grains in the sensing layers into account. Its validity is limited to materials in which the grains of the SMOX sensing layer are large enough to have an undepleted bulk region (large grains). This means that in all experimental conditions, the SMOX properties ensure that the influence of surface phenomena is not extended to the whole grain. The model takes the surface chemistry and its impact on the electrical properties of the sensing material into consideration. In this way, it relates the sensor signal—defined as the relative change of the sensor’s conductance—directly to the concentration of the target gas and also exhibits meaningful chemical parameters, such as the type of reactive oxygen species, the reaction constants, and the concentration of adsorption sites. The validity of the model is confirmed experimentally by applying it to data gathered by measuring homemade sensors in relevant conditions. 相似文献
52.
Dr. Gordon Jacob Boehlich Hannes Sterzel Prof. Dr. Julia Rehbein Ass. Prof. Dr. Nina Schützenmeister 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202619
Due to their high stability towards enzymatic hydrolysis C-acyl glycosidic compounds are useful synthetic intermediates for potential candidates in drug discovery. Syntheses for C-acyl mannosides have remained scarce and usually employ donors obtained from lengthy syntheses. Furthermore, syntheses of unprotected C-acyl mannosides have not been reported so far, due to the incapability of the C-acyl mannoside motif with deprotection conditions for protective groups commonly used in carbohydrate chemistry. Herein, we report an efficient and highly α-selective four-step one-pot method for the synthesis of C-acyl α-d -manno-, l -rhamno- and d -lyxopyranosides from easily accessible persilylated monosaccharides and dithianes requiring only trace amounts of a copper source as catalyst and explain the crucial role of the catalyst by mechanistic studies. Furthermore, the C-acyl α-glycosides were easily isomerized to give rapid access to their β-anomers. 相似文献
53.
If the baryon asymmetry of the Universe is produced by leptogenesis, CP violation is required in the lepton sector. In the seesaw extension of the standard model with three hierarchical right-handed neutrinos, we show that the baryon asymmetry is insensitive to the Pontecorvo-Maki-Nagakawa-Sakata phases: thermal leptogenesis can work for any value of the observable phases. This result was well known when there were no flavor effects in leptogenesis; we show that it remains true when flavor effects are included. 相似文献
54.
Julia Beerhues Maren Neubrand Dr. Sebastian Sobottka Dr. Nicolás I. Neuman Hannes Aberhan Shubhadeep Chandra Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6557-6568
Carbene-based radicals are important for both fundamental and applied chemical research. Herein, extensive electrochemical investigations of nine different 1,2,3-triazolylidene selenium adducts are reported. It is found that the half-wave potentials of the first reduction of the selones correlate with their calculated LUMO levels and the LUMO levels of the corresponding triazolylidene-based mesoionic carbenes (MICs). Furthermore, unexpected quasi-reversibility of the reduction of two triazoline selones, exhibiting comparable reduction potentials, was discovered. Through UV/Vis/NIR and EPR spectroelectrochemical investigations supported by DFT calculations, the radical anion was unambiguously assigned to be triazoline centered. This electrochemical behavior was transferred to a triazolylidene-type MIC-gold phenyl complex resulting in a MIC-radical coordinated AuI species. Apart from UV-Vis-NIR and EPR spectroelectrochemical investigations of the reduction, the reduced gold-coordinated MIC radical complex was also formed in situ in the bulk through chemical reduction. This is the first report of a monodentate triazolylidene-based MIC ligand that can be reduced to its anion radical in a metal complex. The results presented here provide design principles for stabilizing radicals based on MICs. 相似文献
55.
Parajuli Prakash Acharya Sanjit Shamshina Julia L. Abidi Noureddine 《Cellulose (London, England)》2021,28(12):7559-7577
Cellulose - In this study, alkali and alkaline earth metal chlorides with different cationic radii (LiCl, NaCl, and KCl, MgCl2, and CaCl2) were used to gain insight into the behavior of cellulose... 相似文献
56.
Anna Rabe Julia Büker Dr. Soma Salamon Adarsh Koul Dr. Ulrich Hagemann Dr. Joachim Landers Dr. Klaus Friedel Ortega Dr. Baoxiang Peng Prof. Dr. Martin Muhler Prof. Dr. Heiko Wende Prof. Dr. Wolfgang Schuhmann Prof. Dr. Malte Behrens 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17038-17048
By using the crystalline precursor decomposition approach and direct co-precipitation the composition and mesostructure of cobalt-based spinels can be controlled. A systematic substitution of cobalt with redox-active iron and redox-inactive magnesium and aluminum in a cobalt spinel with anisotropic particle morphology with a preferred 111 surface termination is presented, resulting in a substitution series including Co3O4, MgCo2O4, Co2FeO4, Co2AlO4 and CoFe2O4. The role of redox pairs in the spinels is investigated in chemical water oxidation by using ceric ammonium nitrate (CAN test), electrochemical oxygen evolution reaction (OER) and H2O2 decomposition. Studying the effect of dominant surface termination, isotropic Co3O4 and CoFe2O4 catalysts with more or less spherical particles are compared to their anisotropic analogues. For CAN-test and OER, Co3+ plays the major role for high activity. In H2O2 decomposition, Co2+ reveals itself to be of major importance. Redox active cations in the structure enhance the catalytic activity in all reactions. A benefit of a predominant 111 surface termination depends on the cobalt oxidation state in the as-prepared catalysts and the investigated reaction. 相似文献
57.
Corrigendum: Combined Two‐Photon Excitation and d→f Energy Transfer in a Water‐Soluble IrIII/EuIII Dyad: Two Luminescence Components from One Molecule for Cellular Imaging 下载免费PDF全文
58.
1,10‐Phenanthroline and Non‐Symmetrical 1,3,5‐Triazine Dipicolinamide‐Based Ligands For Group Actinide Extraction 下载免费PDF全文
Dr. Julia Bisson Dr. Jérémy Dehaudt Dr. Marie‐Christine Charbonnel Dr. Denis Guillaneux Dr. Manuel Miguirditchian Dr. Cécile Marie Nathalie Boubals Guy Dutech Dr. Muriel Pipelier Dr. Virginie Blot Prof. Didier Dubreuil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7819-7829
The synthesis and evaluation of new extractants for spent nuclear fuel reprocessing are described. New bitopic ligands constituted of phenanthroline and 1,3,5‐triazine cores functionalized by picolinamide groups were designed. Synthetic routes were investigated and optimized to obtain twelve new polyaza‐heterocyclic ligands. In particular, an efficient and versatile methodology was developed to access non‐symmetric 2‐substituted‐4,6‐di(6‐picolin‐2‐yl)‐1,3,5‐triazines from the 1,3,5‐triazapentadiene precursor in the presence of anhydride reagents. Extraction studies showed the ability of both ligand series to extract and separate actinides selectively at different oxidation states (UVI, NpV,VI, AmIII, CmIII, and PuIV) from an acidic solution (3 M HNO3). Phenanthroline‐based ligands show the most promising efficiency for use in the group actinide extraction (GANEX) process due to a higher number of donor nitrogen atoms and a suitable pre‐organization of the dipicolinamide‐1,10‐phenanthroline architecture. 相似文献
59.
Yuwei Gu Julia Zhao Jeremiah A. Johnson 《Angewandte Chemie (International ed. in English)》2020,59(13):5022-5049
Polymer networks, which are materials composed of many smaller components—referred to as “junctions” and “strands”—connected together via covalent or non‐covalent/supramolecular interactions, are arguably the most versatile, widely studied, broadly used, and important materials known. From the first commercial polymers through the plastics revolution of the 20th century to today, there are almost no aspects of modern life that are not impacted by polymer networks. Nevertheless, there are still many challenges that must be addressed to enable a complete understanding of these materials and facilitate their development for emerging applications ranging from sustainability and energy harvesting/storage to tissue engineering and additive manufacturing. Here, we provide a unifying overview of the fundamentals of polymer network synthesis, structure, and properties, tying together recent trends in the field that are not always associated with classical polymer networks, such as the advent of crystalline “framework” materials. We also highlight recent advances in using molecular design and control of topology to showcase how a deep understanding of structure–property relationships can lead to advanced networks with exceptional properties. 相似文献
60.
The effect of shear flow on the phase behaviour of partially miscible blends exhibiting a lower critical solution temperature behaviour has been investigated. Miscibility limits were detected, with and without the application of flow, as changes from optical clarity to turbidity using light scattering and as the appearance of double glass transition temperatures. Light scattering data were collected on a rheo-optical device that was designed to monitor phase changes in polymer blends undergoing shear flow between parallel glass plates in a temperature controlled environment. Glass transition temperatures of some quenched sheared blends were measured using a differential scanning calorimeter in order to confirm the conclusions from the light scattering data. It was found that shear induced demixing and shear induced mixing may be observed within the same blend depending on the magnitude of the applied flow. Miscibility gaps and closed miscibility loops may appear in the phase diagrams. At certain temperatures and shear rates unusual scattering patterns were observed and these were associated with a “ripple” morphology when directly viewed through the microscope. 相似文献