Recent progress and challenges in carboxylation with CO2

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Low spin ferric hemoglobin complexes

A caloulation has been made of the energy eigenfunotions and eigenvalues of low spin ferric ion in complexes with a strong cubic crystal field including the effects of tetragonal and rhombic distortions and of spin-orbit coupling among the ground state components and with excited states. Using the resultant, spin-orbit coupled eigenfunotions as a basis set, the magnetic susceptibility, the components of magnetic field energy, and the lattice and valence contributions to an electric field gradient at the iron nucleus were all calculated as a function of rhombic, tetragonal, and spin-orbit coupling strength used as parameters: R, u and . All of the calculated results agree reasonable well with experiment for the values of parameters R=1000 cm^–1, u=2000 cm^–1 and the free ion value (=420 cm^–1. These values of parameters were selected for the excellent fit they gave of the calculated values of g _x, g_y and g _z compared with the experimental ones obtained from single crystal electron spin resonance of ferrihemoglobin azide. With them, a value of 2.29 Bohr magnetons was calculated for the effective magnetic moment compared to the experimental value of 2.35. The total field gradient calculated under the same conditions, predicts a nuclear quadrupole moment Q in the range of. 107 –127. Barns, which is smaller than the range predicted from the high spin ferric ion results. Reasons for this discrepancy are discussed.

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Zusammenfassung Ausgehend von einem starken kubischen Ligandenfeld und unter Berücksichtigung tetragonaler (R) und rhombischer (u) Verzerrung sowie der Spin-Bahn-Kopplung () werden Eigenfunktionen und Energien fur Low-Spin-Ferrihämoglobinkomplexe berechnet. Mit den Parametern R=1000 cm^–1, u=2000 cm^–1, =420 cm^–1 erhält man für Suszeptibilität, elektrischen Feldgradienten am Fe und g-Werte gute Übereinstimmung mit experimentellen Daten. Aus dem berechneten Feldgradienten folgt ein Quadrupolmoment des Fe⁵⁷ von 0.107–0.127 Barn, im Gegensatz zu den viel höheren Resultaten bei High-Spin-Fe(III)-Verbindungen; diese Diskrepanz wird diskutiert.

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Résumé Les fonctions propres et les énergies du complexe Ferrihémoglobine «low spin» sont calculées pour un fort champ de ligandes à symétrie cubique, en tenant compte des distortions tétragonale (R) et rhomboédrique (u), ainsi que du couplage spin-orbite (). Avec les parametres R=1000 cm^–1, u=2000 cm^–1, =420 cm^–1, on trouve pour la susceptibilité, le gradient du champ électrique à l'emplacement de Fe et le facteur g des valeurs en bon accord avec les données expérimentales. On déduit du gradient de champ calculé un moment quadrupolaire de Fe⁵⁷ de 0,107 à 0,127 Barn, en désaccord avec les résultats beaucoup plus élevés obtenus à partir des associations Fe (III) «high spin». Ce désaccord fait l'objet d'une discussion.

     

Morphologie und Wachstumskinetik von Crazes in amorphen Polymeren

Zusammenfassung Im vorfibrillaren Stadium besitzt die Crazematerie eine in Verformungsrichtung deformierte Netzwerkstruktur, die sich bei Polystyrol und Styrol-Acrylnitril-Copolymerisat elektronenoptisch an Oberflächenabdrücken sauerstoffionengeätzter Proben nachweisen läßt. Während die durchschnittlichen Globulitverformungen zumeist deutlich unterhalb von 50% liegen, werden partiell Spitzenwerte von bis zu 300% erreicht. Am Beispiel des Polystyrols verdeutlichen quantitative Strukturvergleiche mit warmgerecktem Material, daß die molekulare Beweglichkeit während des Crazewachstums und der Schulter-Hals-Verstreckung derjenigen entspricht, die für thermisch aktiviertes Material oberhalb der Glastemperatur charakteristisch ist.Mit 7 Abbildungen und 2 Tabellen     

钽硫原子簇的形成及激光裂解的初步研究

报导用激光直接溅射的方法产生了大量的钽硫原子团簇离子Ta_nS_m~+(n≤9, m≤30),并用串级飞行时间质谱仪研究了所产生团簇离子的组成及紫外激光裂解规律。实验发现, 最稳定的团簇正离子往往具有Ta_nS_(2n+7)~+(n=1,2,…9)的组成, 相应的负离子具有, Ta_nS_(2n+3)~-(n=1,2,…9)的组成。各种团簇正离子的激光裂解的主要通道是连续的S_2消除过程, 且对于n=3,4,5的团簇, 主要光解产物还有Ta_3S_4~+或Ta_4S_6~+离子。据此推测出Ta_nS_m~+团簇离子的可能结构为在Ta原子周围有6个左右的S原子配位。Ta原子之间不存在直接的化学键,而较大团簇可能是以Ta_3S_4或Ta_4S_6为核心的结构。     

Langmuir Aggregation of Thionin on Sodium Dodecyl Sulfate and Its Application

The microphase adsorption–spectral correction (MPASC) technique was applied to the interaction of thioin (TN) with sodium dodecyl sulfate (SDS) at pH 4.56. The synergism mechanism of SDS in solution was analyzed and discussed. The great electrostatic aggregation of TN on SDS obeys Langmuir monolayer adsorption. The property constants of the aggregate were determined and the quantitative determination of the anionic surfactant (AS) in samples was made in the presence of EDTA. Results showed that the large micellar aggregate is (TN–SDS₂)₃₁, the adsorption constant of the monomer aggregate is 1.85 × 10⁵ (18°C), and its molar absorptivity is 4.45 × 10⁶ L mol^–1 cm^–1. For analysis of samples, the recovery is between 94.5 and 111% and the RSD is less than 7.62%.     

A dimer of α‐ and β‐dihydro­arte­misinin: bis­(3,6,9‐trimethyl‐3,12‐epidioxy‐3,4,5,5a,6,7,8,8a,9,10‐deca­hydro‐12H‐pyrano[4,3‐j][1,2]­benzo­dioxepin‐10‐yl) ether

The title compound, C₃₀H₄₆O₉, prepared from a mixture of α‐ and β‐dihydro­artemisinin, has α‐ and β‐arteether moieties linked via an –O– bridge, so that the mol­ecule is asymmetric about the bridge. The endoperoxide bridges of the parent compounds have been retained in each half of the ether‐bridged dimer. The rings exhibit chair and twist–boat conformations.     

Influence of Light Scattering by Residual Alumina Nanoparticles on the Analysis of Surfactants Adsorption Using Spectroscopy

The adsorption of a surfactant mixture, based on an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS) and a nonionic surfactant (Triton X-100, or TX100), on alumina nanoparticles was determined by solution depletion method combined with spectrometric measurement. It is shown that the light scattering, originated from the residual adsorbent alumina particles in the supernatant after centrifugation separation, interferes with the measurements of absorbance of the surfactant molecules, and therefore constitutes an error source for determination of the surfactant concentration in the supernatant by spectrometric means. The intensity of this light scattering, namely the influence of the residual alumina nanoparticles upon the surfactant adsorption, was related to the surfactant adsorption and its equilibrium concentration and varied among a batch. In this paper we report a Kalman filter method in order to eliminate the variational scattering background caused by non-separated residual alumina nanoparticles in each supernatant. This method is of interest as it is simple, easy to carry out and of high precision.     

A multiple coupling approach to produce high-performance SERS substrates

In this work, large area gold-nanoparticle-cluster pillar array with a gold mirror as high-performance SERS substrate was facilely fabricated by combined use of nanosphere lithography and self-assembly approach.     

In situ friction study of Ag Underpotential deposition (UPD) on Au(111) in aqueous electrolyte

The electrodeposition of silver on Au(111) was investigated using lateral force microscopy (LFM) in Ag⁺ containing sulfuric acid. Friction force images show that adsorbed sulfate forms structure ( on Au(111) prior to Ag underpotential deposition (UPD) and structure ( ) on a complete monolayer or bilayer of Ag. Variation of friction with normal load shows a non-monotonous dependence, which is caused by increasing penetration of the tip into the sulfate adlayer. In addition, the friction force is influenced by the varying coverage and mobility of Ag atoms on the surface. Before Ag coverage reaches the critical value, the deposited silver atoms may be mobile enough to be dragged by the movement of AFM tip. Possible penetration of the tip into the UPD layer at very high loads is discussed as a model for self-healing wear. However, when the coverage of Ag is close to 1, the deposited Ag atoms are tight enough to resist the influence of the AFM tip and the tip penetrates only into the sulfate adlayer.     

The atomic-level structure of bandgap engineered double perovskite alloys Cs2AgIn1−xFexCl6

Although lead-free halide double perovskites are considered as promising alternatives to lead halide perovskites for optoelectronic applications, state-of-the-art double perovskites are limited by their large bandgap. The doping/alloying strategy, key to bandgap engineering in traditional semiconductors, has also been employed to tune the bandgap of halide double perovskites. However, this strategy has yet to generate new double perovskites with suitable bandgaps for practical applications, partially due to the lack of fundamental understanding of how the doping/alloying affects the atomic-level structure. Here, we take the benchmark double perovskite Cs₂AgInCl₆ as an example to reveal the atomic-level structure of double perovskite alloys (DPAs) Cs₂AgIn_1−xFe_xCl₆ (x = 0–1) by employing solid-state nuclear magnetic resonance (ssNMR). The presence of paramagnetic alloying ions (e.g. Fe³⁺ in this case) in double perovskites makes it possible to investigate the nuclear relaxation times, providing a straightforward approach to understand the distribution of paramagnetic alloying ions. Our results indicate that paramagnetic Fe³⁺ replaces diamagnetic In³⁺ in the Cs₂AgInCl₆ lattice with the formation of [FeCl₆]³⁻·[AgCl₆]⁵⁻ domains, which show different sizes and distribution modes in different alloying ratios. This work provides new insights into the atomic-level structure of bandgap engineered DPAs, which is of critical significance in developing efficient optoelectronic/spintronic devices.

Through Fe³⁺-alloying, the bandgap of benchmark double perovskite Cs₂AgInCl₆ can be tuned from 2.8 eV to 1.6 eV. The atomic-level structure of Cs₂AgIn_1−xFe_xCl₆ was revealed by solid-state nuclear magnetic resonance (ssNMR).