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971.
Jing-Yu Li Chang-Long Tan Ming-Yu Qi Prof. Dr. Zi-Rong Tang Prof. Dr. Yi-Jun Xu 《Angewandte Chemie (International ed. in English)》2023,62(22):e202303054
Photocatalytic epoxide alcoholysis through C−O bond cleavage and formation has emerged as an alternative to synthesizing anti-tumoral pharmaceuticals and fine chemicals. However, the lack of crucial evidence to interpret the interaction between reactants and photocatalyst surface makes it challenging for photocatalytic epoxide alcoholysis with both high activity and regioselectivity. In this work, we report the hierarchical ZnIn2S4@CdS photocatalyst for epoxide alcoholysis with high regioselectivity nearly 100 %. Mechanistic studies unveil that the precise activation switch on exposed Zn acid sites for C−O bond polarization and cleavage has a critical significance for achieving efficient photocatalytic performance. Furthermore, the establishment of Z-scheme heterojunction facilitates the interface charge separation and transfer. Remarkably, the underlying regioselective photocatalytic reaction pathway has been distinctly revealed. 相似文献
972.
Guo-Dong Zhang Min Yang Yinnian He 《Numerical Methods for Partial Differential Equations》2023,39(1):501-522
In this article, we develop the first and second order unconditionally energy stable schemes for magnetohydrodynamics (MHD) equations and design robust preconditioners for these schemes. Inspired by operator preconditioning ideas, appropriate parameter-dependent norms on function spaces are subtly defined to uniformly bound the bilinear and trilinear terms, which implies the uniform well-posedness of the schemes under the newly defined norms. Then robust block preconditioners are constructed using the Riesz operators. We prove that, if time step size , the proposed preconditioners are uniformly robust with respect to physical parameters and discrete parameters. Various numerical experiments, including energy stability tests, Kelvin–Helmholtz instability and magnetic driven cavity physical benchmark problems, are presented to manifest unconditional energy stability of the schemes and robustness of our preconditioners. 相似文献
973.
This article proposes a structure-preserving quaternion full orthogonalization method (QFOM) for solving quaternion linear systems arising from color image restoration. The method is based on the quaternion Arnoldi procedure preserving the quaternion Hessenberg form. Combining with the preconditioning techniques, we further derive a variant of the QFOM for solving the linear systems, which can greatly improve the rate of convergence of QFOM. Numerical experiments on randomly generated data and color image restoration problems illustrate the effectiveness of the proposed algorithms in comparison with some existing methods. 相似文献
974.
Panpan Sun Zelong Qiao Prof. Shitao Wang Danyang Li Xuerui Liu Prof. Qinghua Zhang Prof. Lirong Zheng Prof. Zhongbin Zhuang Prof. Dapeng Cao 《Angewandte Chemie (International ed. in English)》2023,62(6):e202216041
To achieve practical application of fuel cell, it is vital to develop highly efficient and durable Pt-free catalysts. Herein, we prepare atomically dispersed ZnNC catalysts with Zn-Pyrrolic-N4 moieties and abundant mesoporous structure. The ZnNC-based anion-exchange membrane fuel cell (AEMFC) presents an ultrahigh peak power density of 1.63 and 0.83 W cm−2 in H2-O2 and H2-air (CO2-free), and also exhibits long-term stability with more than 120 and 100 h for H2-air (CO2-free) and H2-O2, respectively. Density functional calculations further unveil that the Zn-Pyrrolic-N4 structure is the origin of high activity of as-synthesized ZnNC catalyst, while the Zn-Pyridinic-N4 moiety is inactive for oxygen reduction reaction (ORR), which successfully explain the puzzle why most Zn-metal-organic framework -derived ZnNC catalysts in previous reports did not present good ORR activity because of their Zn-Pyridinic-N4 moieties. This work offers a new route for speeding up development of AEMFCs. 相似文献
975.
Qixia Bai Yu-Ming Guan Tun Wu Ying Liu Zirui Zhai Qingwu Long Zhiyuan Jiang Peiyang Su Ting-Zheng Xie Pingshan Wang Zhe Zhang 《Angewandte Chemie (International ed. in English)》2023,62(39):e202309027
The precise control over hierarchical self-assembly of superstructures relying on the elaboration of multiple noncovalent interactions between basic building blocks is both elusive and highly desirable. We herein report a terpyridine-based metallo-cage T with a tetrahedral motif and utilized it as an efficient building block for the controlled hierarchical self-assembly of superstructures in response to different halide ions. Initially, the hierarchical superstructure of metallo-cage T adopted a hexagonal close-packed structure. By adding Cl−/Br− or I−, drastically different hierarchical superstructures with highly-tight hexagonal packing or graphite-like packing arrangements, respectively, have been achieved. These unusual halide-ion-triggered hierarchical structural changes resulted in quite distinct intermolecular channels, which provided new insights into the mechanism of three-dimensional supramolecular aggregation and crystal growth based on macromolecular construction. In addition, the chiral induction of the metallo-cage T can be realized with the addition of chiral anions, which stereoselectively generated either PPPP- or MMMM-type enantiomers. 相似文献
976.
Xiuxing Liu Dr. Qiuyan Liao Dr. Jie Yang Prof. Zhen Li Prof. Qianqian Li 《Angewandte Chemie (International ed. in English)》2023,62(24):e202302792
Phosphorescence of organic materials is highly dependent on intermolecular interactions, for the sensitive triplet excitons toward environment and aggregated structures. However, until now, relationship between phosphorescence and intermolecular interactions is still unclear for complicated influence factors and uncontrollable aggregated behaviors. Herein, taking temperature as the controlled variable, the afterglow can continuously change from blue to green, then to yellow, even achieve the white emission with deuteration process. It is mainly due to the hierarchical architectures of molecular aggregates with rational distribution of intermolecular interactions, as well as gradually unlocking process of interactions with different energies. Accordingly, the one-to-one correspondence between the determinate interactions and excited triplet states have been established, guiding accurate design of desirable phosphorescence materials by hierarchical control of aggregated structures. 相似文献
977.
Zheng-Fei Liu Dr. Jiahuan Ren Dr. Pan Li Prof. Li-Ya Niu Prof. Qing Liao Prof. Shaodong Zhang Prof. Qing-Zheng Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202214211
Without external chiral intervention, it is a challenge to form homochirality from achiral molecules with conformational flexibility. We here report on a rational strategy that uses multivalent noncovalent interactions to clamp the molecular conformations of achiral D-A molecules. These interactions overcome the otherwise dominant dipole-dipole interactions and thus disfavor their symmetric antiparallel stacking. It in turn facilitates parallel packing, leading to spontaneous symmetry breaking during crystallization and thus the formation of homochiral conglomerates. When this emergent homochirality is coupled with optical gain characteristics of the molecules, the homochiral crystals are explored as excellent circularly polarized micro-lasers with low lasing threshold (16.4 μJ cm−2) and high dissymmetry factor glum (0.9). This study therefore provides a facile design strategy for supramolecular chiral materials and active laser ones without the necessity of intrinsic chiral element. 相似文献
978.
An Algebraic Multigrid-Based Physical Factorization Preconditioner for the Multi-Group Radiation Diffusion Equations in Three Dimensions 下载免费PDF全文
The paper investigates the robustness and parallel scaling properties of
a novel physical factorization preconditioner with algebraic multigrid subsolves in
the iterative solution of a cell-centered finite volume discretization of the three-dimensional multi-group radiation diffusion equations. The key idea is to take advantage of a particular kind of block factorization of the resulting system matrix and
approximate the left-hand block matrix selectively spurred by parallel processing
considerations. The spectral property of the preconditioned matrix is then analyzed.
The practical strategy is considered sequentially and in parallel. Finally, numerical results illustrate the numerical robustness, computational efficiency and parallel
strong and weak scalabilities over the real-world structured and unstructured coupled problems, showing its competitiveness with many existing block preconditioners. 相似文献
979.
Lei Tan Dr. Nianming Jiao Xinrui Bai Dr. Hongyan Wang Prof. Jun Wang Prof. Hui Wang Prof. Xiangping Zhang 《欧洲无机化学杂志》2023,26(24):e202300314
Zeolites are widely used in petrochemical processes and refineries due to their well-ordered microporous network and large surface area. However, the diffusion of reactants and products is hampered by the narrow microporous channels, causing limitations. To overcome this challenge, modifying the pore structure is crucial, and the chemical etching technique is a powerful tool that introduces mesopores and macropores, consequently enhancing mass transfer and accessibility. Diverse chemical etching methods have been invented, including exposure to both acids (organic/inorganic acids), alkali (organic/inorganic alkali), and neutral etchants (e. g., ammonium fluoride). This review summarizes and assesses the chemical etching methods and their relevance to catalytic cracking reactions, methanol to hydrocarbons (MTH), and biomass conversion. The potential of zeolites with modified pore structures has motivated researchers to develop novel methods to tackle the practical challenges associated with their applications. 相似文献
980.
《Arabian Journal of Chemistry》2023,16(3):104521
The continuous development of resistance to antibiotic drugs by microorganisms causes high mortality and morbidity. Pathogens with distinct features and biochemical abilities make them destructive to human health. Therefore, early identification of the pathogen is of substantial importance for quick ailments and healthcare outcomes. Several phenotype methods are used for the identification and resistance determination but most of the conventional procedures are time-consuming, costly, and give qualitative results. Recently, great focus has been made on the utilization of advanced techniques for microbial identification. This review is focused on the research studies performed in the last five years for the identification of microorganisms particularly, bacteria using advanced spectroscopic techniques including mass spectrometry (MS), infrared (IR) spectroscopy, Raman spectroscopy (RS), and nuclear magnetic resonance (NMR) spectroscopy. Among all the techniques, MS techniques, particularly MALDI-TOF/MS have been widely utilized for microbial identification. A total of 44 bacteria i.e., 6 Staphylococcus spp., 3 Enterococcus spp., 6 Bacillus spp., 4 Streptococcus spp., 6 Salmonella spp., and one from each genus including Escherichia, Acinetobacter, Pseudomonas, Proteus, Clostridioides, Candida, Brucella, Burkholderia, Francisella, Yersinia, Moraxella, Vibrio, Shigella, Serratia, Citrobacter, and Haemophilus (spp.) were discussed in the review for their identification using the above-mentioned techniques. Among all the identified microorganisms, 21% of studies have been conducted for the identification of E. coli, 14% for S. aureus followed by 37% for other microorganisms. 相似文献