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Gold catalysis

Piotr Piotrowski, Joanna Pawłowska, Jarosław Grzegorz Sadło, Renata Bilewicz, Andrzej Kaim
C60TEMPO10 catalytic system linked to a microspherical gold support through a covalent S-Au bond was developed. The C60TEMPO10@Au composite catalyst had a particle size of 0.5-0.8 μm and was covered with the fullerenes derivative of 2.3 nm diameter bearing ten nitroxyl groups; the organic film showed up to 50 nm thickness. The catalytic composite allowed for the oxidation under mild conditions of various primary and secondary alcohols to the corresponding aldehyde and ketone analogues with efficiencies as high as 79-98%, thus giving values typical for homogeneous catalysis, while retaining at the same time all the advantages of heterogeneous catalysis, e...
2017: Journal of Nanoparticle Research: An Interdisciplinary Forum for Nanoscale Science and Technology
Huixiang Ouyang, Chongning Li, Qingye Liu, Guiqing Wen, Aihui Liang, Zhiliang Jiang
Mercury (Hg) is a heavy metal pollutant, there is an urgent need to develop simple and sensitive methods for Hg(II) in water. In this article, a simple and sensitive resonance Rayleigh scattering (RRS) method was developed for determination of 0.008-1.33 µmol/L Hg, with a detection limit of 0.003 μmol/L, based on the Hg(II) regulation of gold nanoenzyme catalysis on the HAuCl₄-H₂O₂ to form gold nanoparticles (AuNPs) with an RRS peak at 370 nm. Upon addition of molecular probes of Victoria blue B (VBB), the surface-enhanced Raman scattering (SERS) peak linearly decreased at 1612 cm(-1) with the Hg(II) concentration increasing in the range of 0...
May 17, 2017: Nanomaterials
Rui Gao, Yao Lin, Yi-Lun Ying, Xiao-Yuan Liu, Xin Shi, Yong-Xu Hu, Yi-Tao Long, He Tian
The self-assembly of nanoparticles is a challenging process for organizing precise structures with complicated and ingenious structures. In the past decades, a simple, high-efficiency, and reproducible self-assembly method from nanoscale to microscale has been pursued because of the promising and extensive application prospects in bioanalysis, catalysis, photonics, and energy storage. However, microscale self-assembly still faces big challenges including improving the stability and homogeneity as well as pursuing new assembly methods and templates for the uniform self-assembly...
May 16, 2017: Small
Kento Taniguchi, Xiongjie Jin, Kazuya Yamaguchi, Kyoko Nozaki, Noritaka Mizuno
Diarylamines are an important class of widely utilized chemicals, and development of diverse procedures for their synthesis is of great importance. Herein, we have successfully developed novel versatile catalytic procedures for the synthesis of diarylamines through acceptorless dehydrogenative aromatization. In the presence of a gold-palladium alloy nanoparticle catalyst (Au-Pd/TiO2), various symmetrically substituted diarylamines could be synthesized starting from cyclohexylamines. The observed catalysis of Au-Pd/TiO2 was heterogeneous in nature and Au-Pd/TiO2 could be reused several times without severe loss of catalytic performance...
March 1, 2017: Chemical Science
Eric H Hill, Christoph Hanske, Alexander Johnson, Luis Yate, Hans Jelitto, Gerold A Schneider, Luis M Liz-Marzán
Recent studies have shown that layered silicate clays can be used to form a nacre-like bioinspired layered structure with various polymer fillers, leading to composite films with good material strength, gas barrier properties, and high loading capacity. We go one step farther by in situ growing metal nanoparticles in nacre-like layered films based on layered silicate clays, which can be used for applications in plasmonic sensing and catalysis. The degree of anisotropy of the nanoparticles grown in the film can be controlled by adjusting the ratio of clay to polymer, gold to clay, and reducing agent concentration, as well as silver overgrowth, which greatly enhances the surface-enhanced Raman scattering activity of the composite...
May 13, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Matthew J Barrett, Ghulam F Khan, Paul W Davies, Richard S Grainger
Alkynyl sulfoxides are shown to act as α-sulfinyl metallocarbene synthons under oxidative gold catalysis, enabling reactions that are not available from diazo-precursors. This strategy is exemplified in the synthesis of fused α-sulfinyl cyclopropanes.
May 11, 2017: Chemical Communications: Chem Comm
Laurynas Pukenas, Panida Prompinit, Boda Nishitha, Daniel J Tate, N D Pradeep Singh, Christoph Wälti, Stephen D Evans, Richard J Bushby
Under a layer of 0.1 M HCl in isopropanol, soft ultraviolet (UV) (365 nm) photolysis of the thiol-on-gold self-assembled monolayer (SAM) derived from the lipoic acid ester of α-hydroxy-1-acetylpyrene results in the expected removal of the acetylpyrene protecting group. When photolyzing through a mask, this can be used to produce a patterned surface and, at a controlled electrochemical potential, it is then possible to selectively and reversibly electrodeposit copper on the photolyzed regions. Rather surprisingly, under these photolysis conditions, there is not only the expected photodeprotection of the ester but also partial removal of the lipoic acid layer which has been formed...
May 19, 2017: ACS Applied Materials & Interfaces
Man Liang, Shuai Zhang, Jiong Jia, Chen-Ho Tung, Jianwu Wang, Zhenghu Xu
An ultrafast synthesis of spiroketals by synergistic gold(I) and Sc(III) catalysis has been reported. Diverse 5,6-benzannulated spiroketals were rapidly constructed by the diastereoselective [4 + 2] cycloaddition between gold-generated enol ether and Sc(III)-catalyzed o-quinone methide intermediates. Ultrafast reaction rate, ambient reaction temperature, general scope, high yields, excellent diastereoselectivity, and good scalability are attractive features of this method.
May 5, 2017: Organic Letters
Irene Vassalini, Laura Borgese, Michele Mariz, Stefano Polizzi, Giuliana Aquilanti, Paolo Ghigna, Andrea Sartorel, Vincenzo Amendola, Ivano Alessandri
Oxygen evolution reaction (OER) is the most critical step in water splitting, still limiting the development of efficient alkaline water electrolyzers. Here we investigate the OER activity of Au-Fe nanoalloys obtained by laser-ablation synthesis in solution. This method allows a high amount of iron (up to 11 at %) to be incorporated into the gold lattice, which is not possible in Au-Fe alloys synthesized by other routes, due to thermodynamic constraints. The Au0.89 Fe0.11 nanoalloys exhibit strongly enhanced OER in comparison to the individual pure metal nanoparticles, lowering the onset of OER and increasing up to 20 times the current density in alkaline aqueous solutions...
May 2, 2017: Angewandte Chemie
Gustavo Salinas, Wei Gao, Yang Wang, Mariana Bonilla, Long Yu, Andrei Novikov, Veridiana G Virginio, Henrique Ferreira, Marisol Vieites, Vadim N Gladyshev, Dinorah Gambino, Shaodong Dai
AIMS: New drugs are needed to treat flatworm infections that cause severe human diseases such as schistosomiasis. The unique flatworm enzyme thioredoxin glutathione reductase (TGR), structurally different from the human enzyme, is a key drug target. Structural studies of the flatworm Echinococcus granulosus TGR, free and complexed with AuI-MPO, a novel gold inhibitor, together with inhibition assays were performed. RESULTS: AuI-MPO is a potent TGR inhibitor that achieves 75% inhibition at a 1:1 TGR:Au ratio and efficiently kills E...
May 2, 2017: Antioxidants & Redox Signaling
Svetlana Tšupova, Matthias Rudolph, Frank Rominger, A Stephen K Hashmi
Various tetrayne systems were converted under dual gold catalyzed conditions. For symmetric tetraalkynyl-substituted thiophenes bearing two alkyl-substituted alkynes and two terminal alkyne units, bidirectional cyclisations led to the efficient formation of dibenzothiophene systems. In all cases, selective CH-activation of the CH-bond of the alkyl substituent was observed leading to cyclopentane moieties annelated to the newly formed aromatic cores. If two thiophene moieties were tethered over the attached non-terminal alkynes, depending on the length of the connecting alkyl tether, either bidirectional processes or tandem processes can be addressed leading to interesting molecular structures such as spiro compounds or isolated benzothiophenes connected by a CC-bond...
May 2, 2017: Chemistry: a European Journal
Ben Liu, Ting Jiang, Haoquan Zheng, Shanka Dissanayke, Wenqiao Song, Anthony Federico, Steven L Suib, Jie He
Loading catalytically active, aggregation-free and thermally stable metal nanoparticles (NPs) on a high surface area support represents a major interest in heterogeneous catalysis. Current synthetic approaches to these hybrid catalysts, however, still lack controllability in the thermal stability of metal NPs, particularly at high temperatures in the absence of organic ligands. We herein report a facile "co-assembly" methodology to prepare aggregation-free, ligand-free and thermally stable mesoporous hybrid nanocatalysts of metal-oxides and metal-carbons...
May 18, 2017: Nanoscale
Dong Ding, Tao Mou, Jiahui Xue, Xuefeng Jiang
A chemo- and regio-selectively controllable approach for construction of diverse benzo-heterocycles is established. A new strategy for using the ligand effect in gold catalysis to control the regioselectivity in the cyclization of o-alkynyl-N-methoxyl-benzamide is successfully achieved. Meanwhile, the chemoselectivity between nitrogen and oxygen nucleophiles is precisely switched by gold and platinum catalysts.
May 9, 2017: Chemical Communications: Chem Comm
Peng Peng, Richard R Schmidt
Inverting glycosyltransferases enforce in the active site an intramolecular, acid-base catalyzed glycosidation that, due to proximity of the donor anomeric carbon and the acceptor hydroxyl group, follows an SN2-type reaction. Spacers, tethering donor and acceptor via nonreacting functional groups, led in intramolecular glycosidations to excellent yields and, independent of the donor anomeric configuration, to either the α- or the β-anomer. The requirement of a demanding protecting group pattern confines the application of this efficient method...
April 25, 2017: Accounts of Chemical Research
Shouting Zhang, Zhuoyue Zhang, Tiansheng Wang, Dongxu Zhang, Xuemei Li, Zhonghua Xue, Duoliang Shan, Xiaoquan Lu
Herein, we present a catalysis-based, label-free, and efficient strategy for a rapid, high-throughput, highly selective and ultrasensitive naked-eye colorimetric assay of Au(3+) in aqueous solutions, based on the gold amalgam-stimulated peroxidase mimetic activity.
April 21, 2017: Chemical Communications: Chem Comm
Yuxiang Pan, Zijian Wan, Longjie Zhong, Xueqin Li, Qi Wu, Jun Wang, Ping Wang
Okadaic acid (OA) is a marine toxin ingested by shellfish. In this work, a simple, sensitive and label-free gap-based electrical competitive bioassay has been developed for this biotoxin detection. The gap-electrical biosensor is constructed by modifying interdigitated microelectrodes with gold nanoparticles (AuNPs) and using the self-catalytic growth of AuNPs as conductive bridges. In this development, the AuNPs growth is realized in the solution of glucose and chloroauric acid, with glucose oxidation used as the catalysis for growth of the AuNPs...
June 2017: Biomedical Microdevices
Vincenzo Amendola, Roberto Pilot, Marco Frasconi, Onofrio M Maragò, Maria Antonia Iatì
In the last two decades, plasmon resonance in gold nanoparticles (Au NPs) has been the subject of intense research efforts. Plasmon physics is intriguing and its precise modelling proved to be challenging. In fact, plasmons are highly responsive to a multitude of factors, either intrinsic to the Au NPs or from the environment, and recently the need emerged for the correction of standard electromagnetic approaches with quantum effects. Applications related to plasmon absorption and scattering in Au NPs are impressively numerous, ranging from sensing to photothermal effects to cell imaging...
May 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yu-Chen Karen Chen-Wiegart, Ross Harder, David C Dunand, Ian McNulty
We studied the evolution of dealloying-induced strain along the {111} in a Ag-Au nano-crystal in situ, during formation of nanoporous gold at the initial stage of dealloying using Bragg coherent X-ray diffractive imaging. The strain magnitude with maximum probability in the crystal doubled in 10 s of dealloying. Although formation of nano-pores just began at the surface, the greatest strain is located 60-80 nm deep within the crystal. Dealloying induced a compressive strain in this region, indicating volume shrinkage occurred during pore formation...
May 4, 2017: Nanoscale
Jin-Cheng Liu, Yang-Gang Wang, Jun Li
We have constructed a general thermodynamic model of chemical potentials and applied ab initio electronic structure and molecular dynamics simulations, as well as kinetic Monte Carlo analysis, to probe the dynamical, reactive, and kinetic aspects of metal single-atom catalysts (SACs) on oxide support. We choose Au single atoms (SAs) supported on ceria as a typical example to demonstrate how our model can guide the rational design of highly stable and reactive SACs. It is shown that, under realistic conditions, various factors such as temperature, pressure, particle size, and the reducibility of the support can strongly affect both the stability and the reactivity of SACs by altering the relative chemical potentials between SAs and metal nanoparticles (NPs)...
April 25, 2017: Journal of the American Chemical Society
Cristina E Stere, James A Anderson, Sarayute Chansai, Juan Jose Delgado, Alexandre Goguet, Willam G Graham, C Hardacre, S F Rebecca Taylor, Xin Tu, Ziyun Wang, Hui Yang
Non-thermal plasma activation has been used to enable low-temperature water-gas shift over a Au/CeZrO4 catalyst. The activity obtained was comparable with that attained by heating the catalyst to 180 °C providing an opportunity for the hydrogen production to be obtained under conditions where the thermodynamic limitations are minimal. Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), structural changes associated with the gold nanoparticles in the catalyst have been observed which are not found under thermal activation indicating a weakening of the Au-CO bond and a change in the mechanism of deactivation...
May 8, 2017: Angewandte Chemie
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