CERAMICS INTERNATIONAL
·
2025
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IF 5.6
Yanlei Li,Haibo Ouyang,Cuiyan Li,Bohan Sun,Tianzhan Shen,Qianqian Chen
Hafnium carbide (HfC) nanomaterials hold significant potential for enhancing the performance of ultra-high temperature ceramic matrix composites. However, achieving the synergistic optimization of their mechanical and ablation resistance properties through controllable synthesis remains a challenge. To address this issue, this study employed a nickel-catalyzed pyrolysis method using hafnium tetrachloride (HfCl 4 ) and furfuryl alcohol as precursors. By precisely controlling the catalyst concentration within a carbon/carbon (C/C) preform, the controlled synthesis of HfC nanowires (HfC NWs ) with two distinct diameters (500 nm and 1000 nm) was successfully achieved. Subsequently, corresponding C/C-HfC-SiC composites (denoted as HS-1 and HS-2) were fabricated via the polymer impregnation and pyrolysis (PIP) process. The results demonstrate that the HS-1 composite modified with 500 nm HfC NWs exhibits the most superior performance: its flexural strength was significantly increased by 51.84 % compared to the unmodified sample, and it displayed the best ablation resistance after 60 s of exposure to an oxyacetylene flame. In-depth characterization revealed that this enhancement originates from the dense three-dimensional network formed by the finer nanowires, which effectively traps ceramic particles and facilitates the formation of a denser, more protective oxide layer. This work elucidates the critical role of nanowire diameter control and provides valuable insights for designing high-performance composites for extreme environments.
研究领域:
材料科学
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陶瓷基复合材料
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纳米材料
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高温材料工程
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JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
·
2019
·
IF 3.202
Xu Zhao,Jing Chen,Weiying Zhang,Chengdui Yang,Xiaoxiao Ma,Sichun Zhang,Xinrong Zhang
Lipids exert substantial influences on vertebrate embryogenesis, but their metabolic dynamics at detailed structural levels remains elusive, primarily owing to the lack of a tool capable of resolving their huge structural diversity. Herein, we present the first large-scale and spatiotemporal monitoring of unsaturated lipids with C=C specificity in single developing zebrafish embryos enabled by photochemical derivatization and tandem mass spectrometry (MS). The lipid isomer composition was found extremely stable in yolk throughout embryogenesis, while notable differences in ratios of C=C location (e.g., PC 16:0_16:1 (7) vs. 16:0_16:1 (9)) and fatty acyl composition isomers (e.g., PC 16:1_18:1 vs. 16:0_18:2) were unveiled between blastomeres and yolk from zygote to 4 h post fertilization (hpf). From 24 hpf onwards, lipid isomer compositions in embryo head and tail evolved distinctively with development, suggesting a meticulously regulated lipid remodeling essential for cell division and differentiation. This work has laid the foundation for functional studies of structurally defined lipids in vertebrate embryology.
研究领域:
生物化学
·
发育生物学
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Journal of the American Chemical Society
·
2020
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IF 14.612
Hai-Fang Li,Wenbo Cao,Xiaoxiao Ma,Xiaobo Xie,Yu Xia,Zheng Ouyang
The [2 + 2] photocycloaddition of alkenes and carbonyls is of fundamental interest and practical importance, as this process is extensively involved in oxetane-ring constructions. Although individual carbonyl group or alkene moiety has been utilized as photoactive species for oxetane formations upon ultraviolet photoexcitation, direct excitation of the entire noncovalent complex involving alkene and carbonyl substrates to achieve [2 + 2] photocycloadditions is rarely addressed. Herein, complexes with noncovalent interactions between benzophenone and C═C bonds in unsaturated lipids have been successfully characterized, and for the first time a [2 + 2] cycloaddition leading to the formation of oxetanes has been identified under visible-light irradiation. The mechanism of this reaction is distinctly different from the well-studied Paternò–Büchi reaction. The entire complexes characterized as dimeric proton-bonded alkene and carbonyl substrates can be excited under visible light, leading to electron transfer from the alkene moiety in fatty acyls to the carbonyl group within the complex. These results provide new insight into utilizing noncovalent complexes for the synthesis of oxetanes in which the excitation wavelength becomes independent of each individual substrate.
研究领域:
有机化学
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光化学
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材料科学
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高影响因子
iScience
·
2023
·
IF 5.8
Cheng Wang,Zirui Qiao,Yulan Tian,Haijun Yang,Huaqiang Cao,Anthony K. Cheetham
Imines are important intermediates for synthesizing various fine chemicals, with the disadvantage of requiring the use of expensive metal-containing catalysts. We report that the dehydrogenative cross-coupling of phenylmethanol and benzylamine (or aniline) directly forms the corresponding imine with a yield of up to 98%, and water as the sole by-product, in the presence of a stoichiometric base, using carbon nanostructures as the “green” metal-free carbon catalysts with high spin concentrations, which is synthesized by C(sp 2 )-C(sp 3 ) free radical coupling reactions. The catalytic mechanism is attributed to the unpaired electrons of carbon catalysts to reduce O 2 to O 2 ·− , which triggers the oxidative coupling reaction to form imines, whereas the holes in the carbon catalysts receive electrons from the amine to restore the spin states. This is supported by density functional theory calculations. This work will open up an avenue for synthesizing carbon catalysts and offer great potential for industrial applications.
研究领域:
化学
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材料科学
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催化反应
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Nature Communications
·
2026
·
IF 18.1
Li Xiancheng,Xia Yuangu,Ma Yanchao,Liu Jiaxuan,Ma Yue,Wang Shuizhong,Lu Qiang,Song Guoyong
C-lignin, a natural biopolymer of caffeyl alcohol subunits linked by benzodioxane motifs, is an ideal feedstock for direct catechol production. However, its hydrogenolysis is hindered by the high bond dissociation energies and steric congestion of vicinal C–O bonds in benzodioxane structures. Here, we report a low-loaded Co–Zn dual single-atom catalyst (Co SA –Zn SA @NC) that enables efficient C-lignin hydrogenolysis, achieving 84.6% catechol yield, 82% selectivity toward 4-propylcatechol, and a turnover number five times higher than precious Ru/C, attributing to the synergistic effect of the dual atomic sites. The major product, 4-propylcatechol, can be readily purified and upgraded into diverse value-added molecules. Mechanistic investigations reveal that the Zn and Co species, acting as the directing and active centers, respectively, synergistically drive the quasi-concerted cleavage of the vicinal C–O bonds. This work presents an atomically dispersed non-precious metal catalyst for C-lignin hydrogenolysis, providing a sustainable route to well-defined aromatics.
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CERAMICS INTERNATIONAL
·
2026
·
IF 6
Xiao-Dong Kang,Guo-Hua Zhang
To address the challenge of balancing hardness, toughness, and strength in Ti(C, N)-based cermets, existing research predominantly focused on composition design and sintering optimization, while comparatively less attention was paid to the critical role of initial Ti(C, N) powder characteristics in determining properties. In this study, high-quality Ti(C, N) powders with varying C/N ratios were synthesized via carbothermal reduction-nitridation (CRN) coupled with Ca treatment, followed by the fabrication of Ti(C, N)-20WC-5Mo-5Ni-5Co (wt%) cermets using vacuum pre-sintering assisted spark plasma sintering (SPS). The prepared powders were characterized by the absence of free carbon, low oxygen content, uniform morphology, superior crystallinity, and excellent dispersibility. After sintering, all samples achieved high densification, comprising the (Ti, W, Mo)(C, N) hard phase, (Co, Ni) binder phase, and trace residual WC. The ceramic grains mainly displayed black core-gray rim, black core-rimless, and white core-gray rim structures, characterized by overall thin rims. As the C/N ratio decreased, the dissolution-precipitation process during sintering was inhibited. Accordingly, hardness exhibited an initial decline followed by an increase, whereas the fracture toughness ( K IC ) showed an opposite trend. Transverse rupture strength (TRS) peaked at an intermediate C/N ratio. Cermet derived from Ti(C 0.44 , N 0.56 ) powder achieved an optimal combination of properties, with hardness, K IC , and TRS values of 1867 ± 12 HV 30 , 9.13 ± 0.21 MPa m 1/2 , and 1748 ± 75 MPa, respectively. The synthesized high-quality Ti(C, N) powders provided a crucial foundation for microstructural control and improved overall properties of cermets, and adjusting the C/N ratio served to further optimize the balance among hardness, toughness, and strength.
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ADVANCED MATERIALS
·
2026
·
IF 29.1
Chao Peng,Xiong Wang,Lang Chen,Shuang-Feng Yin
Selective photocatalytic upgrading of glycerol to glycolaldehyde is intrinsically challenging because, under a conventional C–C cleavage scenario, the carbon-based selectivity of a C2 product is, in principle, capped at 66.67%. Here, a size-regulated Pd on TiO 2 platform as an efficient photocatalyst realized selective oxidation of glycerol into glycolaldehyde with selectivity up to 87.54%. As the Pd size increases from single atoms to nanoparticles, both glycerol conversion and glycolaldehyde selectivity increase monotonically, reaching 36.52% conversion and a glycolaldehyde formation rate of 12.05 mmol g ‒1 h ‒1 . Combined in situ spectroscopy, isotope-labeling experiments, and density functional theory calculations reveal that increasing Pd size switches glycerol adsorption from a symmetric terminal–terminal mode to an asymmetric terminal–secondary mode, thereby promoting C–C activation and enabling a radical-mediated cleavage-recoupling route toward glycolaldehyde. Isotopic liquid chromatography-mass spectrometry verifies C–C recombination after bond cleavage, which accounts for the glycolaldehyde selectivity exceeding the conventional 66.67% carbon limit, water as a direct contributor to •OH generation, and oxygen incorporation into the products. This work establishes a mechanistic framework in which metal size alters the interfacial adsorption geometry and reaction energy, thereby providing a general strategy for the selective photocatalytic valorization of polyol biomass molecules.
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LANGMUIR
·
2026
·
IF 4.4
Honglin Li,Yingqi Duan,Qingwen Feng,Linjiao Wei,Jingbin Zeng,Ziyue Chen,Qingtong Zhang,Yanpeng Chen,Zifeng Yan
Ag–Cu tandem catalysis provides an effective strategy to enhance C2+ selectivity in the electrochemical CO2 reduction reaction (CO2RR) by integrating CO generation and utilization for C–C coupling. Here, we report a series of Ag@Cu2O, Ag@CuO, and Ag@CuO-BDC core–shell catalysts designed to regulate the CO generation, Cu-oxidation states, and surface structures. The Ag@Cu2O catalysts exhibit pronounced tandem effects, suppressing CH4 formation while enhancing the C–C coupling on the Cu sites. Notably, Ag@Cu2O-30 achieves a high C2H4/CH4 Faradaic efficiency ratio of 6.5 at −1.8 V (vs RHE) with an increased C2H4 partial current density of 12.3 mA cm–2. Oxidation to Ag@CuO further modifies the Cu species distribution, facilitating CO and CO2 diffusion while reducing H2 formation. Moreover, constructing Cu-BDC-MOF followed by electrochemical reconstruction generates additional oxygen vacancies and stabilizes Cu+ species, enhancing C2H4 selectivity and stability but with increased CH4 formation and reduced current density. This study highlights Ag–Cu tandem catalysis and structural regulation of Cu as effective strategies for achieving selective reduction of CO2 toward C2H4.
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ORGANIC & BIOMOLECULAR CHEMISTRY
·
2022
·Vol. 20
·期 28
·5535-5542
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IF 3.89
Na Li,Xiao Liu,Mingliang Zhang,Zekun Zhang,Beibei Zhang,Xiaohui Wang,Juan Wang,Pengfei Tu,Yong Jiang,She-po Shi
Prenyltransferases (PTs) play important roles in the biosynthesis and structural diversification of natural products. In the present study, two new PTs were characterized from a medicinal plant Murraya exotica. MePT1 unprecedentedly catalyses the formation of two C-geranylated products 8/6-C-geranylumbelliferone together with a trace product 7-O-geranylumbelliferone from umbelliferone. MePT2 regio-specifically catalyses the formation of C-3 dimethylallylated products from quinolone alkaloids. This is the first report that a plant PT catalyses the simultaneous formation of C- and O-prenylated products, and a plant PT specifically utilizes quinolone alkaloids as prenyl acceptors. The results not only provide important insight into the functional diversity of plant PTs and the biosynthesis of the prenylated coumarins, quinolone and carbazole alkaloids in Murraya plants, but also pave the way for the overproduction of the prenylated coumarins and alkaloids using metabolic engineering approaches.
研究领域:
生物化学
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植物生物技术
·
生药学
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BIOMACROMOLECULES
·
2020
·
IF 6.092
Caicai Jiao,Lilong Gao,Hui Zhang,Bing Yu,Hailin Cong,Youqing Shen
Hydrogels have a wide range of applications in the fields of biomedicine, flexible electronics, and bionics. In this study, injectable and self-healable hydrogels were first prepared based on a dynamic covalent C═C bond formed via the Knoevenagel condensation reaction between poly(ethylene glycol) dicyanoacetate and water-soluble poly(vanillin acrylate). Three kinds of catalysts (phosphate buffer, zeolitic imidazolate framework-8, and tertiary amine) were used in Knoevenagel condensation for preparing hydrogels. All hydrogels in this study could be formed in situ, and their gelation time ranged from seconds to minutes. The properties and application of hydrogels could be customized according to the type of catalyst employed. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) results indicated that all the components and hydrogels exhibited low toxicity, and the hydrogels could be used as 3D cell culture scaffolds. Because of the dynamic covalent C═C bond formed by Knoevenagel condensation, the resultant hydrogels were found to be dynamic and showed good self-healing properties. This work presents a new dynamic covalent chemistry for the preparation of self-healable materials.
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Journal of Energy Chemistry
·
2020
·
IF 7.216
Da Pang,Wei Weng,Jing Zhou,Dong Gu,Wei Xiao
Direct conversion of biomass to functional materials is an ideal solution to relieve challenges in environmental and energy sustainability. We herein demonstrate a molten salt thermoelectrolysis of rice husks (RHs) mainly consisting of organic mass and biosilica to achieve high-efficiency and upgraded utilization of both Si and C in RHs. By coupling pyrolysis of organic mass with electrochemical reduction of silica in molten salts, the thermoelectrolysis of RHs in molten CaCl 2 –NaCl at 800 °C refines the RHs and acid-leached RHs to SiC nanowire/C (SiC-NW/C) and Si nanoparticle/C (Si-NP/C), respectively. The present study highlights the molten salt thermoelectrolysis for reclamation of biomass wastes in an affordable and controllable manner.
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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
·
2023
·Vol. 120
·期 44
·e2307320120
·
IF 11.1
Yangyang Yu,Ye He,Ping Yan,Shengyao Wang,Fan Dong
The selective photocatalytic conversion of CO2 and H2O to high value-added C2H4 remains a great challenge, mainly attributed to the difficulties in C–C coupling of reaction intermediates and desorption of C2H4* intermediates from the catalyst surface. These two key issues can be simultaneously overcome by alloying Ag with Cu which gives enhanced activity to both reactions. Herein, we developed a facile stepwise photodeposition strategy to load Cu–Ag alloy sub-nanoclusters (ASNCs) on TiO2 for CO2 photoreduction to produce C2H4. The optimized catalyst exhibits a record-high C2H4 formation rate (1110.6 ± 82.5 μmol g−1 h−1) with selectivity of 49.1 ± 1.9%, which is an order-of-magnitude enhancement relative to current work for C2H4 photosynthesis. The in situ FT-IR spectra combined with DFT calculations reveal the synergistic effect of Cu and Ag in Cu–Ag ASNCs, which enable an excellent C–C coupling capability like Ag and promoted C2H4* desorption property like Cu, thus advancing the selective and efficient production of C2H4. The present work provides a deeper understanding on cluster chemistry and C–C coupling mechanism for CO2 reduction on ASNCs and develops a feasible strategy for photoreduction CO2 to C2 fuels or industrial feedstocks.
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