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1.
Munkhshur Myekhlai Dr. Tania M. Benedetti Dr. Lucy Gloag Agus R. Poerwoprajitno Dr. Soshan Cheong Prof. Dr. Wolfgang Schuhmann Prof. Dr. J. Justin Gooding Prof. Dr. Richard D. Tilley 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15501-15504
Producing stable but active materials is one of the enduring challenges in electrocatalysis and other types of catalysis. Producing branched nanoparticles is one potential solution. Controlling the number of branches and branch size of faceted branched nanoparticles is one of the major synthetic challenges to achieve highly active and stable nanocatalysts. Herein, we use a cubic-core hexagonal-branch mechanism to synthesize branched Ru nanoparticles with control over the size and number of branches. This structural control is the key to achieving high exposure of active {10–11} facets and optimum number of Ru branches that enables improved catalytic activity for oxygen evolution reaction while maintaining high stability. 相似文献
2.
Facile synthesis of multi‐branched gold nanostructures by using the tetrabutyl ammonium bromide (TBAB) as a capping agent is described. The reaction is carried out in a one‐step process at mild temperature. Gold nanostructures with more than six sharp branches ranging from 70 to 130 nm in length are synthesized in high yield. It is proposed that the relative weak adsorption capacity of TBAB leads to the incompletely covered gold surface and the growth of nanoparticles occurs on the uncovered gold surface, and therefore short branches appear consequently. Then positively charged TBAB layers on the gold surfaces prevent the branches from aggregating with each other which stimulates the branch growth. The prepared branched gold nanoparticles show efficient surface‐enhanced Raman scattering (SERS) properties. Low temperature (4°C) is unfavorable to the formation of multi‐branched gold nanostructures, and only thin small irregular plate‐like nanoparticles are produced. The addition of SDS in TBAB aqueous solution results in forming SDS micelles at much lower concentration of SDS (0.4 mmol/L) as compared to that in pure water, and short branched gold nanoparticles are obtained in the SDS‐TBAB system. 相似文献
3.
Multi-branched gold nanoparticles were synthesized in high-yield through the reduction of HAuCl(4) by using hydrazine as a reducing agent. Practically 100% of the particles have numerous branches. The high reduction capability of hydrazine is found to be crucial for the formation of these branched gold nanoparticles. Their size can be controlled from 20 to 130 nm by varying the amounts of hydrazine. The prepared nanoparticles exhibit efficient surface-enhanced Raman scattering (SERS) properties and the SERS activity of the particles depends on the aspect ratio of their branches, which are most likely related to a great increase in the localized electromagnetic field enhancement from their unique sharp surface features arising from the branches. 相似文献
4.
Three‐Dimensional Branched and Faceted Gold–Ruthenium Nanoparticles: Using Nanostructure to Improve Stability in Oxygen Evolution Electrocatalysis 下载免费PDF全文
Dr. Lucy Gloag Dr. Tania M. Benedetti Dr. Soshan Cheong Dr. Yibing Li Dr. Xuan‐Hao Chan Prof. Lise‐Marie Lacroix Prof. Shery L. Y. Chang Dr. Raul Arenal Dr. Ileana Florea Dr. Hector Barron Dr. Amanda S. Barnard Dr. Anna M. Henning Prof. Chuan Zhao Prof. Wolfgang Schuhmann Prof. J. Justin Gooding Prof. Richard D. Tilley 《Angewandte Chemie (International ed. in English)》2018,57(32):10241-10245
Achieving stability with highly active Ru nanoparticles for electrocatalysis is a major challenge for the oxygen evolution reaction. As improved stability of Ru catalysts has been shown for bulk surfaces with low‐index facets, there is an opportunity to incorporate these stable facets into Ru nanoparticles. Now, a new solution synthesis is presented in which hexagonal close‐packed structured Ru is grown on Au to form nanoparticles with 3D branches. Exposing low‐index facets on these 3D branches creates stable reaction kinetics to achieve high activity and the highest stability observed for Ru nanoparticle oxygen evolution reaction catalysts. These design principles provide a synthetic strategy to achieve stable and active electrocatalysts. 相似文献
5.
Kittichote Musikabhumma Thomas P. Spaniol Jun Okuda 《Journal of polymer science. Part A, Polymer chemistry》2003,41(4):528-544
The synthesis of branched polyethylenes by ethylene polymerization with new tandem catalyst systems consisting of methylaluminoxane‐preactivated linked cyclopentadienyl‐amido titanium catalysts [Ti(η5:η1‐C5Me4SiMe2NR)Cl2 (R = Me or tBu)] supported on pyridylethylsilane‐modified silica (PySTiNMe and PySTiNtBu) and homogeneous dibromo nickel catalyst having a pyridyl‐2,6‐diisopropylphenylimine ligand (PyminNiBr2) in the presence of modified methylaluminoxane was investigated. Ethylene polymerization with only PyminNiBr2 yielded a mixture of 1‐ and 2‐olefin oligomers with methyl branches [weight‐average molecular weight (Mw) ~ 460)] with a ratio of about 1:7. By the combination of this nickel catalyst with PySTiNtBu, polyethylenes with long‐chain branches (Mw = 15,000–50,000) were produced. No incorporation of 2‐olefin oligomers was observed in the 13C NMR spectra. Unexpectedly, the combination of the nickel catalyst with PySTiNMe produced lower molecular weight polyethylenes with only methyl branches. The molecular weight distributions of branched polyethylenes obtained with both PySTiNMe and PySTiNtBu combined with the nickel catalyst were broad (weight‐average molecular weight/number‐average molecular weight < 9). Bimodal gel permeation chromatography (GPC) curves were clearly observed in the PySTiNMe system, whereas GPC curves with small shoulders in low molecular weight areas were observed for PySTiNtBu. The synthesis of branched polyethylenes with tandem catalyst systems of corresponding homogeneous titanium catalysts and the nickel catalyst was also investigated for comparison. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 528–544, 2003 相似文献
6.
Kim M Park JC Kim A Park KH Song H 《Langmuir : the ACS journal of surfaces and colloids》2012,28(15):6441-6447
The surface of Pd@SiO(2) core-shell nanoparticles (1) was simply modified by the formation of nickel phyllosilicate. The addition of nickel salts formed branched nickel phyllosilicates and generated pores in the silica shells, yielding Pd@SiO(2)-Niphy nanoparticles (Niphy = nickel phyllosilicate; 2, 3). By removal of the silica residue, Pd@Niphy yolk-shell nanoparticles (4) was uniformly obtained. The four distinct nanostructures (1-4) were employed as catalysts for Suzuki coupling reactions with aryl bromide and phenylboronic acid, and the conversion yields were in the order of 1 < 2 < 3 < 4 as the pore volume and surface area of the catalysts increased. The reaction rates were strongly correlated with shell porosity and surface exposure of the metal cores. The chemical inertness of nickel phyllosilicate under the basic conditions rendered the catalysts reusable for more than five times without loss of activity. 相似文献
7.
Noriyuki Suzuki Jian Yu Yuji Masubuchi Akira Horiuchi Yasuo Wakatsuki 《Journal of polymer science. Part A, Polymer chemistry》2003,41(2):293-302
The polymerization of 1‐hexene under high pressures (100–750 MPa) was investigated with nickel–α‐diimine complex/methylaluminoxane and palladium–α‐diimine complex/methylaluminoxane as catalyst systems. The catalytic activity of both the nickel and palladium complexes monotonously increased as pressure rose and became two to four times higher than that observed at atmospheric pressure. Palladium catalysts gave poly(1‐hexene)s with higher molecular weights under high pressure, whereas nickel‐catalyzed high‐pressure polymerizations gave polymers with higher molecular weights only at rather low monomer concentrations. The living‐like character in the palladium‐catalyzed polymerizations was somewhat enhanced under higher pressures, whereas the nickel‐catalyzed polymerizations under high pressures were not living. More branches were found in the polymers produced by nickel catalysts at higher pressures. The chain‐transfer reaction seemed to be accelerated by the high pressure in the nickel‐catalyzed reactions, although this was not apparent in the palladium‐catalyzed reactions. Dimers formed and were accompanied by high molecular weight polymers when nickel catalysts were used under high pressures and at high monomer concentrations. The possibility that very congested five‐coordinated species act as key intermediates for the dimerization is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 293–302, 2003 相似文献
8.
Synthesis of ultra‐small branched star poly(ε‐caprolactone)s and their high end group concentration effects on crystallization 下载免费PDF全文
Woohyuk Choi Jae Woo Chung Seung‐Yeop Kwak 《Journal of polymer science. Part A, Polymer chemistry》2015,53(9):1134-1142
We successfully synthesize the three‐ and six‐branched star poly(ε‐caprolactone)s with extremely small branched segments (USB‐SPCLs) using a facile pseudo‐one‐pot process in a pilot scale and investigate the effect of ultra‐small branches on their crystallization behaviors. The number of branched segments and the individual branched segment lengths for USB‐SPCLs are precisely controlled via manipulating monomer‐to‐core ratio, adjusting monomer‐to‐polymer conversion, end‐capping the terminal hydroxyl groups, and vacuum purification, which results in USB‐SPCLs having the branched segments below five degree of polymerization with a high yield exceeding 93%. The molecular weights obtained from 1H NMR spectroscopy are consistent with that obtained from MALDI‐TOF‐MS and the molecular weight distributions are narrow with Mw/Mn ≤ 1.2, indicating that USB‐SPCLs have mono‐dispersed branches. USB‐SPCLs have low melting temperatures and broad double‐melting peaks attributed to their extremely small branches, and the crystallization behaviors for USB‐SPCLs depend on the end group concentration. On the other hand, the glass transitions for USB‐SPCLs depend on the total molecular weights, regardless of the number and length of branched segments. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1134–1142 相似文献
9.
Nickel‐Catalyzed Mizoroki–Heck Reaction of Aryl Sulfonates and Chlorides with Electronically Unbiased Terminal Olefins: High Selectivity for Branched Products 下载免费PDF全文
Sarah Z. Tasker Dr. Alicia C. Gutierrez Prof. Timothy F. Jamison 《Angewandte Chemie (International ed. in English)》2014,53(7):1858-1861
Achieving high selectivity in the Heck reaction of electronically unbiased alkenes has been a longstanding challenge. Using a nickel‐catalyzed cationic Heck reaction, we were able to achieve excellent selectivity for branched products (≥19:1 in all cases) over a wide range of aryl electrophiles and aliphatic olefins. A bidentate ligand with a suitable bite angle and steric profile was key to obtaining high branched/linear selectivity, whereas the appropriate base suppressed alkene isomerization of the product. Although aryl triflates are traditionally used to access the cationic Heck pathway, we have shown that, by using triethylsilyl trifluoromethanesulfonate, we can effect a counterion exchange of the catalytic nickel complex, such that cheaper and more stable aryl chlorides, mesylates, tosylates, and sulfamates can be used to yield the same branched products with high selectivity. 相似文献
10.
NiAl nanoparticles are of considerable importance because of interest in examining the effects of size, surface area, and composition on their physical and catalytic properties. Recently, a new method for the ‘bottom up’ wet chemical preparation of nickel aluminides has been reported. The ability to leach the aluminum from this system provides an entrance to the preparation of skeletal‐type metal catalysts similar to those produced in Raney‐type systems. Furthermore, it is believed that these nanoparticulate catalysts should provide high surface areas and high activities, while the presence of aluminum within the bulk of these catalysts provides additional stability. Here, we present the results of studies conducted on this system which compare their properties and behavior with traditional bulk Raney nickel systems. Additionally, we show that we are able to alter the properties of these nanoparticles by changing the stoichiometric ratio of nickel and aluminum. The properties of all systems have been analyzed through the use of nitrogen adsorption, X‐ray diffraction, and elemental analysis. Finally, the catalysts generated have been compared for their activity in the hydrogenation of butyronitrile. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
11.
Carbon nanotubes are synthesized by catalytic pyrolysis method with a kind of new type catalyst--nickel-zinc-alumina catalyst prepared from Feitknecht compound. Tubular carbon nanotubes, bamboo-shaped carbon naotubes, herringbone carbon nanotubues and branched carbon nanotubes are all found formed at moderate temperature. It is important for the formation of quasi-liquid state of the metal nanoparticles at the tip of carbon naotubes during the growth of carbon nanotubes to lead to different kinds of carbon nanotubes. It is likely that the addition of zinc make the activity of nickel catalyst after calcinations and reduction changed strangely. 相似文献
12.
Michael J. Rachita R. Leigh Huff Jordan L. Bennett Maurice Brookhart 《Journal of polymer science. Part A, Polymer chemistry》2000,38(Z1):4627-4640
A series of neutral phosphinosulfonamide complexes of nickel(II) were synthesized that catalyzed the oligomerization of ethylene to branched oligomers with average degrees of polymerization between 10 and 35. Branching numbers varied from 17 to 80 branches per 1000 carbons, depending on the catalyst structure and reaction conditions. The catalysts were active in a variety of solvents, including toluene, CH2Cl2, tetrahydrofuran, ethyl acetate, and methanol, but showed decreasing activity at temperatures higher than 40 °C. Electron‐rich phosphinosulfonamides produced the highest catalyst activities in a series of structure–reactivity studies. The mechanism of oligomer formation was investigated with 1H NMR spectroscopy, which indicated that branching arose from the isomerization of the nickel alkyl species during propagation rather than the reincorporation of α‐olefin products. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4627–4640, 2000 相似文献
13.
14.
Bis(1,5‐cyclooctadiene) nickel [Ni(COD)2] was employed as a nickel precursor to prepare nickel oxide nanoparticles upon high‐surface‐area mesoporous silica. Under protection of argon, Ni(COD)2 was dissolved in tetrahydrofuran (THF) to react with surface silanols of mesoporous silica SBA‐15, which formed a black powder after completion of the surface reaction. Calcination of the powder produced ultrafine NiO inside the mesoporous silica matrix, which was evidenced by X‐ray diffraction, N2 adsorption–desorption, transmission electron microscopy and thermogravimetric analysis. The thermogravimetric analysis suggests that NiO formation is a result of surface nickel species calcination, whereas structural characterization clearly show that NiO nanoparticles of <5 nm are evenly distributed inside the silica SBA‐15 matrix and mesoporosity is well preserved upon calcinations and NiO formation. The surface reaction between Ni(COD)2 and surface silanols was found for the first time, and the method used here may be extended conveniently to prepare other metal oxide nanoparticles upon high‐surface‐area supports as well. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
15.
Weiqiang Zhou Wei Liang Teo Dongdong Wang Gancheng Zuo Deblin Jana Cheng Qian Hou Wang Jiawei Liu Yanli Zhao 《化学:亚洲杂志》2020,15(16):2513-2519
Development of heterogeneous catalysts has attracted increasing attention, owing to their remarkable catalytic performance and recyclability. Herein, we report well‐developed heterogeneous catalysts with a three‐dimensional ordered hierarchical structure, constructed from nickel or cobalt nanoparticles embedded in porous carbon. The obtained catalysts were fully characterized by several techniques. On account of the uniform distribution of metal nanoparticles in the porous carbon matrix and large diffusion channels that allow for effective mass transport, the catalysts exhibited superior catalytic performance for styrene epoxidation reaction. In particular, the catalysts showed good catalytic activity, high selectivity and excellent recyclability toward the styrene epoxidation. Thus, this facile approach developed allows for fabricating advanced heterogeneous catalysts with high catalytic activities for useful practical applications. 相似文献
16.
Tailoring polymers through interplay of ligands within precatalysts: 8‐(Nitro/benzhydryl‐arylimino)‐7,7‐dimethyl‐5,6‐dihydroquinolylnickel halides in ethylene polymerization 下载免费PDF全文
Chuanbing Huang Yanning Zeng Zygmunt Flisak Zhijuan Zhao Tongling Liang Wen‐Hua Sun 《Journal of polymer science. Part A, Polymer chemistry》2017,55(12):2071-2083
A series of 8‐(nitro/benzhydryl‐substituted arylimino)‐7,7‐dimethyl‐5,6‐dihydroquinolines and the corresponding nickel halide complexes were synthesized and characterized. Molecular structures of representative nickel complexes were determined by single crystal X‐ray diffraction, showing the dinuclear dimers with distorted square‐pyramidal geometry around the nickel center. The binding energies determined by X‐ray photoelectron spectroscopy (XPS) indicate the effective coordination between the sp2‐nitrogen and nickel atoms as well as the influence of both the halogen ligands and the substituents within dihydroquinolines on the strength of the Ni? N bond. Ethylene polymerization with the nickel precatalysts in presence of either methylaluminoxane or diethylaluminum chloride was explored in detail. For the complexes containing the nitro substituent within the organic ligand, the catalytic activity is inversely proportional to the electron density around the nickel core determined by XPS; such phenomenon is consistent with the conclusion of the computational study stating that the activity of precatalysts is correlated with the net charge on the metal center. In the polymerization process, unimodal and branched polyethylenes containing vinyl or vinylene groups were obtained. The nickel precatalysts bearing bulky benzhydryl within the organic ligand as well as bromide rather than chloride attached to the nickel atom produce polymers with relatively large amount of vinylene groups. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2071–2083 相似文献
17.
Supported nickel nanoparticles with high dispersion have been prepared by partial reduction of NiAl‐layered double hydroxide (NiAl‐LDH) precursors, which exhibit significant electrocatalytic behavior towards glucose. XRD and XPS results confirm that the nickel nanoparticles are successfully synthesized. TEM images reveal that the nickel nanoparticles are highly dispersed in the NiAl‐LDH matrix with a size of 6±0.3 nm. The resulting nanocomposite modified electrode displays significant electrocatalytic performance to glucose with a broad linear response range (8.0×10?5–2.0×10?3 M), low detection limit (3.6 µM), high sensitivity (339.2 µA/mM), selectivity and excellent reproducibility as well as repeatability. 相似文献
18.
Fengshou Liu Haiyang Gao Zhilong Hu Haibin Hu Fangming Zhu Qing Wu 《Journal of polymer science. Part A, Polymer chemistry》2012,50(18):3859-3866
1‐Hexene polymerizations catalyzed by α‐diimine nickel complexes after activation with modified methylaluminoxane were performed at various reaction temperatures. Effects of catalyst structure and polymerization temperature on activity and polymer microstructure were evaluated in detail. Bulky catalyst 1b with camphyl backbone exhibited good control ability and greatly enhanced thermal stability to be capable of polymerizing 1‐hexene at 80°C. The poly(1‐hexene)s with long methylene sequences and dominate branches (methyl and butyl) were synthesized using catalyst 1b . Differential scanning calorimetry analysis further confirmed that long polymethylene block (? (CH2)n? , n > 20) was formed in the poly(1‐hexene)s with melting point of 64°C obtained by catalyst 1b on the basis of initial branched model polyethylene. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
19.
Xiaoyan Wang Dr. Dong Zhao Dr. Chao Wang Dr. Yonggao Xia Wenshuai Jiang Senlin Xia Shanshan Yin Dr. Xiuxia Zuo Dr. Ezzeldin Metwalli Ying Xiao Prof. Dr. Zaicheng Sun Prof. Dr. Jin Zhu Prof. Dr. Peter Müller‐Buschbaum Prof. Dr. Ya‐Jun Cheng 《化学:亚洲杂志》2019,14(9):1557-1569
Super‐small sized TiO2 nanoparticles are in situ co‐composited with carbon and nickel nanoparticles in a facile scalable way, using difunctional methacrylate monomers as solvent and carbon source. Good control over crystallinity, morphology, and dispersion of the nanohybrid is achieved because of the thermosetting nature of the resin polymer. The effects of the nickel nanoparticle on the composition, crystallographic phase, structure, morphology, tap density, specific surface area, and electrochemical performance as both lithium‐ion and sodium‐ion battery anodes are systematically investigated. It is found that the incorporation of the in situ formed nickel nanoparticles with certain content effectively enhances the electrochemical performance including reversible capacities, cyclic stability and rate performance as both lithium‐ion and sodium‐ion battery anodes. The experimental I‐V profiles at different temperatures and theoretical calculations reveal that the charge carriers are accumulated in the amorphous carbon regions, which act as scattering centers to the carriers and lower the carrier mobility for the composite. With increasing nickel content, the mobility of the charge carriers is significantly increased, while the number of the charge carriers maintains almost constant. The nickel nanoparticles provide extra pathways for the accumulated charge, leading to reduced scatterings among the charge carriers and enhanced charge‐carrier transportation. 相似文献
20.
Shota Tanaka Daiki Tanaka Go Tatsuta Kohei Murakami Shunsuke Tamba Dr. Atsushi Sugie Prof. Dr. Atsunori Mori 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1658-1665
The synthesis of linear and branched oligothiophenes of well‐defined structures is performed with regioselective deprotonation of 3‐substituted thiophenes and nickel‐catalyzed cross‐coupling of the thus formed metalated species with a bromothiophene. The reaction of 3‐hexylthiophene with EtMgCl and 2,2,6,6‐tetramethylpiperidine (TMP‐H, 10 mol %) induces the metalation selectively at the 5‐position by use of the catalytically generated hindered magnesium amide (TMPMgCl) and the subsequent reaction of a 2‐halo‐3‐hexylthiophene (bromide or chloride) in the presence of a nickel catalyst affords a head‐to‐tail (HT)‐type dimer. By repeating the same sequence, the linear oligothiophene up to a 4‐mer is synthesized in good yield. The reaction of 3‐hexylthiophene with 2,3‐dibromothiophene also takes place to afford a branched oligothiophene 3‐mer in quantitative yield. The obtained 3‐mer is also metalated at the sterically less‐hindered position in a regioselective manner furnishing a 7‐mer in >99 % yield after a further coupling reaction with 2,3‐dibromothiophene. These dendrimers react with several multifunctionalized organic electrophiles, leading to a variety of branched oligothiophenes. 相似文献