Ni-Catalyzed Deoxygenative Borylation of Phenols Via O‑Phenyl-uronium Activation

Herein, we report an efficient method for the Ni-catalyzed deoxygenative borylation of unprotected phenols and also demonstrate that this Ni-catalyzed phenolic C­(sp2)-O transformation is applicable to the Suzuki–Miyaura-type and Heck-type cross-couplings of phenols. Investigations on the reaction intermediate have revealed that the achievement of general, mild deoxygenative cross-coupling reactions of phenols is ascribed to the conversion of phenols into the unusual O-phenyl-uroniums that feature active phenolic C­(sp2)-O bonds. The Ni-complex intermediate resulting from an oxidative addition of a phenolic C­(sp2)-O bond to monophosphine-supported Ni(0) catalyst was characterized and confirmed to be (PCy3)2Ni­(Ar)­(F) complex, offering experimental evidence for the generally proposed C­(sp2)-O oxidative addition step

Comparative Study of Proton Exchange in Tri- and Hexatitanates: Correlations between Stability and Electronic Properties

A hydrothermal method is considered to be convenient and is extensively used in preparing titanate architectures, but the intermediate and final products are complicated and variable. To date, it is accepted that intermediates are tri- and hexatitanates. Here, atomic structures, energetics, and correlations between stability and electronic properties of proton exchange in tri- and hexatitanates, i.e., Na2–xHxTi3O7 and Na2–xHxTi6O13, are investigated by first-principles calculations. We found that the bond length of Na–O bonds plays a significant role in determining the activity of tunnel oxygen atoms, while the proton substitution sites are closely related to the activity of tunnel O atom in titanates. As H+ concentration increases, the formation energy of Na2–xHxTi3O7 and Na2–xHxTi6O13 decreases first and then increases, suggesting that completely protonated titanates, i.e., H2Ti3O7 and H2Ti6O13, are unstable. However, we found that H+ substitution would take place even in an alkaline solution both for Na2Ti3O7 and Na2Ti6O13. With a decrease in the pH, the process of H+ exchange becomes more energetically favorable. Compared to Na2Ti3O7, Na+ ions are more easily exchanged by H+ ions in Na2Ti6O13 at the same pH value. We found that there is a strong correlation between stability and electronic properties during the Na+–H+ exchange process. Finally, hydrogen bonds are observed in H2Ti3O7 and Na2–xHxTi6O13 complexes, which make them more stable than Na2–xHxTi3O7 complexes without H-bonds. All of these findings provide insight into understanding the geometry of possible intermediates in the preparation of titanates and suitable conditions for the synthesis of titanates

Supplementary document for Mechanically stretchable metamaterial with tunable mid-infrared optical properties - 5484924.pdf

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Numerical Simulation and Analysis of Hydraulic Turbines Based on BIM for Sustainable Development

Hydropower is considered to be an important way to achieve the sustainable development goal of human progress. The performance of turbines is very important to the safety and stability of hydropower stations. Most of the hydraulic turbine performance studies only use Computational Fluid Dynamics (CFD) for performance simulation, lacking the integration of Building Information Modeling (BIM) technology and CFD. Therefore, a performance analysis model of a Francis turbine based on BIM was put forward in this paper. The BIM software OpenBuildings Designer CONNECT Edition Update 10 was used to build the hydraulic turbine model, and then the BIM model was transferred to the CFD numerical simulation platform ANSYS through the intermediate format conversion. In the ANSYS environment, the numerical simulation of different working conditions was carried out with the help of Fluent 2021 R1 software. The numerical simulation results show that the fluid velocity gradient in the volute was 2~3 m/s under the three working conditions, which was relatively stable. The water flow could progress the guide vane mechanism at a higher speed, and the drainage effect of the volute was better. There were some negative pressure areas at the back of the runner blades and the inlet of draft tube, and the negative pressure value was as high as −420,000 Pa and −436,842 Pa under maximum head conditions, which were prone to cavitation erosion. It is proven that BIM supported the hydraulic turbine performance analysis and provided a geometric information model for hydraulic turbine CFD numerical simulation, meaning that the performance analysis model based on BIM is feasible. This study can expand the application value of BIM and provide guidance for the study of hydraulic turbine numerical simulation using BIM technology in combination with CFD methods

Numerical Simulation and Application of Radial Steel Gate Structure Based on Building Information Modeling under Different Opening Degrees

The safe and stable operation of the radial gate is highly essential for hydropower stations. As the dynamic load of gate, water flow generally causes the irregular distribution of strength, stiffness, and the stability of the gate structure. Traditional simulation technology is usually used to investigate the impact of water flow on gate structure; however, there is a lack of integration and interaction of building information modeling (BIM) and numerical simulation technology to study this issue. Therefore, this paper proposed a computational framework combing BIM and numerical simulation to calculate and analyze the large complex hydraulic radial steel structure. Firstly, the 3D model of the radial gate was established by MicroStation2020, then, the finite element model was output by using it. Secondly, the change laws of strength, stiffness, and stability of the radial gate were analyzed by Ansys-Workbench2020R2 under different opening degrees. The numerical simulation results show that the maximum equivalent stress value was 142.19 MPa, which occurred at the joint between the lower longitudinal beam and the door blade. The maximum deformation was 3.446 mm, which occurred at two longitudinal beams’ middle in the lower part of the panel. When the opening degree is 0.0 m–9.0 m, the natural vibration frequency increases irregularly with the increase in the opening of the gate. Three main vibration modes of the gate vibration were obtained. It proves that it is feasible to analyze the structural performance of radial gates by using BIM and numerical simulation. Finally, the BIM and numerical simulation information management process was established to make the simulation results more valuable. This study expands the application value of BIM and provides a new research idea for large complex hydraulic steel structural analysis. The information management process described in this research can serve as a guide for gate operation and maintenance management

SnCo Nanoparticles Loaded in Hollow Carbon Spheres Interlinked by N‑Doped Carbon Fibers for High-Performance Sodium-Ion Batteries

The development of Sn-based materials with electrochemically inactive matrices is a novel strategy to alleviate the volume expansion and giant structure strain/stress during the sodiation/desodiation process. In this work, a freestanding membrane based on the unique bean pod-like host composed by nitrogen-doped carbon fibers and hollow carbon spheres (HCSs) encapsulated with SnCo nanoparticles is synthesized by electrospinning (B-SnCo/NCFs). In this unique bean pod-like structure, Sn acts as a host for Na+ storage, while the Co plays the important role of an electrochemically inactive matrix that can not only buffer the volume variations but also inhibit aggregation and particle growth of the Sn phase during the electrochemical Na–Sn alloying process. Meanwhile, the introduction of hollow carbon spheres can not only provide enough sufficient void space to withstand the volume expansion during the (de)sodiation processes but also improve the conductivity of the anode along the carbon fibers. Furthermore, the B-SnCo/NCF freestanding membrane can increase the contact area between the active material and the electrolyte, which can provide more active sites during the cycling process. When used as an anode material for Na-ion batteries, the freestanding B-SnCo/NCF anode exhibits an outstanding rate capacity of 243.5 mA h g–1 at 1.6 A g–1and an excellent specific capacity of 351 mA h g–1 at 0.1 A g–1 for 300 cycles

Mechanically Induced Elastomeric Optical Transmittance Modulator

Optical devices with switchable optical properties have attracted great interest in recent years because of their extensive engineering applications. The dynamic tuning of optical properties can be triggered by various types of external stimuli. In this work, a mechanically induced elastomeric optical transmittance modulator is reported. The design is composed of poly­(dimethylsiloxane), a silicone-based rubber transparent at visible wavelengths, with gold nanofilms deposited on the surface. The influence of geometric parameters on the total transmittance is studied utilizing the Rigorous Coupled Wave Analysis model. Taking advantage of the excellent stretching capacity of the elastomer, reversible modulation of both normal and total transmittance is achieved. A 42% rise in the total transmittance is realized under a strain of 80%. Cycle testing illustrates stable structural integrity and optical performance even after repeated strain cycles. This elastomeric optical transmittance modulator opens avenues for practical applications due to its simple design and facile tunability

Bi@C Nanospheres with the Unique Petaloid Core–Shell Structure Anchored on Porous Graphene Nanosheets as an Anode for Stable Sodium- and Potassium-Ion Batteries

Bismuth (Bi) has emerged as a prospective candidate as Na-ion and potassium-ion battery anodes because of its unique advantages of low cost, high theoretical gravimetric capacity (386 mAh g–1), and superior volumetric capacity (3800 mAh cm–3). However, the low electronic conductivity and the huge volume expansion of Bi during the alloying/dealloying reactions are extremely detrimental to cycling stability, which seriously hinder its practical application. To overcome these issues, we propose a rational design: Bi@C nanospheres with the unique petaloid core–shell structure are synthesized in one step for the first time and then combined with different contents of graphene (GR) nanosheets to form the composites Bi@C@GR. The Bi@C nanospheres with a core–shell structure are beneficial to shortening the transmission path of electrons/ions and reducing the risk from structural rupture of the particles during cycling. In addition, the combination of Bi@C nanospheres and porous GR could greatly improve the conductivity and prevent the aggregation of particles, which is conducive to better cycling stability and rate performance. Consequently, Bi@C@GR-2 presents a superior reversible capacity for sodium storage (300 mAh g–1 over 80 cycles) and potassium storage (200 mAh g–1 over 70 cycles) at 0.1 A g–1. Furthermore, in situ electrochemical impedance spectroscopy and ex situ transmission electron microscopy are carried out to analyze and reflect the kinetic reaction mechanism and the phase change of the Bi@C@GR-2 electrode during the charge/discharge processes

Role of Intrinsic Ion Accumulation in the Photocurrent and Photocapacitive Responses of MAPbBr₃ Photodetectors

We studied steady state and transient photocurrents in thin film and single-crystal devices of MAPbBr₃, a prototype organic–inorganic hybrid perovskite. We found that the devices’ capacitance is abnormally large, which originates from accumulation of large densities of Pb²⁺ and Br^– in the active perovskite layer. Under applied bias, these ions are driven toward the opposite electrodes leading to space-charge fields close to the metal/perovskite interfaces. The ion accumulation, in turn, causes photocurrent reversal polarity that depends on the history of the applied bias and excitation photon energy with respect to the optical gap. Furthermore, the large capacitive response dominates the transient photocurrent and, therefore, obscures the weaker contribution from the photocarriers’ drift. We show that these properties depend on the ambient conditions in which the measurements are performed. Understanding these phenomena may lead to better control over the stability of perovskite photodetectors for visible light

Artificial Cytochrome c Mimics: Graphene Oxide–Fe(III) Complex-Coated Molecularly Imprinted Colloidosomes for Selective Photoreduction of Highly Toxic Pollutants

Our previous works showed that the molecularly imprinted TiO2 photocatalyst has been one of the most efficient materials for selective photooxidation of highly toxic organic pollutants (HTOPs) from complicated wastewater. However, some highly toxic pollutants (e.g., heavy metals) are very stable under the oxidizing environment. Therefore, the design of enzyme-like catalysts to selectively reduce highly toxic pollutants is extremely needed. In this work, inspired by the bioreduction ability of cytochrome c (cyt c, a heme containing metalloprotein), we presented a simple and efficient way to generate an artificial cyt c mimic (ACM) using graphene oxide (GO)–Fe­(III) complex-coated molecularly imprinted colloidosomes. Prior to loading of Fe­(III) centers to GO for constructing ACMs, GO-coated molecularly imprinted colloidosomes were synthesized via Pickering emulsion polymerization. Similar to a nature cyt c, the ACM contained both the molecular recognition element (molecularly imprinted cavity) and the non-heme electron sink (GO–Fe­(III) complex), which resulted in the ACMs having good selectivity toward the enzyme-like reduction of the highly toxic target Cr­(VI). Moreover, by using HepG2 cells as model cells, the Cr­(VI) solution after treating by ACMs was proved to be safe and nontoxic. To confirm that the present method was universal for constructing ACMs, various GO–Fe­(III) complex-coated molecularly imprinted colloidosomes, which could selectively photoreduce other highly toxic inorganic ions and organic pollutants, were also investigated. The ACMs described herein will act as a vector that encourages the design of more functional non-heme enzymes in sensing, environmental separation, clinical diagnose, and delivery of therapeutic agents