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Gold catalysis

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https://www.readbyqxmd.com/read/28817146/controlled-deposition-of-palladium-nanodendrites-on-the-tips-of-gold-nanorods-and-their-enhanced-catalytic-activity
#1
Gaoxing Su, Huaqiao Jiang, Hongyan Zhu, Jing-Jing Lv, Guohai Yang, Bing Yan, Jun-Jie Zhu
Plasmonic Au-Pd nanostructures have drawn significant attention for use in heterogeneous catalysis. In this study, palladium nanodendrite-tipped gold nanorods (PdND-T-AuNRs) were subjected to a facile fabrication under mild reaction conditions. The palladium amounts on the two tips were tunable. In the preparation of PdND-T-AuNRs, dense capped AuNRs, a low reaction temperature, and suitable stabilizing agents were identified as critical reaction parameters for controlling palladium nanodendrites deposited on both ends of AuNRs...
August 17, 2017: Nanoscale
https://www.readbyqxmd.com/read/28813601/platinum-decorated-gold-nanoparticles-with-dual-functionalities-for-ultrasensitive-colorimetric-in-vitro-diagnostics
#2
Zhuangqiang Gao, Haihang Ye, Dianyong Tang, Jing Tao, Sanaz Habibi, Adrienne Minerick, Dianping Tang, Xiaohu Xia
Au nanoparticles (AuNPs) as signal reporters have been utilized in colorimetric in vitro diagnostics (IVDs) for decades. Nevertheless, it remains a grand challenge to substantially enhance the detection sensitivity of AuNP-based IVDs as confined by the inherent plasmonics of AuNPs. In this work, we circumvent this confinement by developing unique dual-functional AuNPs that were engineered by coating conventional AuNPs with ultrathin Pt skins of sub-10 atomic layers (i.e., Au@Pt NPs). The Au@Pt NPs retain the plasmonic activity of initial AuNPs while possessing ultrahigh catalytic activity enabled by Pt skins...
August 18, 2017: Nano Letters
https://www.readbyqxmd.com/read/28812891/catalytic-alkynylation-of-cyclic-acetals-and-ketals-enabled-by-synergistic-gold-i-trimethylsilyl-catalysis
#3
Matheo Berthet, Olivier Songis, Catherine Taillier, Vincent Dalla
A completely regioselective and challenging gold(I)-catalyzed ring-opening of cyclic 1,3-dioxolanes and dioxanes by trimethylsilyl alkynes to set diol-derived propargyl trimethylsilyl bis-ethers is reported. This unprecedented and not trivial transformation does not operate with the catalytic methodologies recently reported for catalytic alkynylation of acyclic acetals/ketals, and is uniquely enabled by the application of a recently introduced synergistic gold(I)-silicon catalysis concept capable of producing simultaneously catalytic amounts of two key players, a silicon-based Lewis superacid and a nucleophilic gold acetylide...
August 16, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28809497/a-chlorinating-reagent-yields-vinyl-chlorides-with-high-regioselectivity-under-heterogeneous-gold-catalysis
#4
Shengzong Liang, Rene Ebule, Gerald B Hammond, Bo Xu
A novel chlorinating reagent with a high concentration of HCl has enabled the highly regioselective hydrochlorination of unactivated alkynes using a commercial nanogold catalyst. No overchlorination or hydration products were formed, and various functional groups were tolerated. This hydrochlorination method could be conducted under open air.
August 15, 2017: Organic Letters
https://www.readbyqxmd.com/read/28804992/gold-catalyzed-4-2-annulation-cyclization-cascades-of-benzisoxazoles-with-propiolate-derivatives-to-access-highly-oxygenated-tetrahydroquinolines
#5
Rajkumar Lalji Sahani, Rai-Shung Liu
This work describes gold-catalyzed annulations of electron-deficient alkynes with benzisoxazoles to yield quinoline oxides chemoselectively. Chemical functionalizations of these resulting azacyclic compounds afforded various oxygenated tetrahydroquinolines that are present as the cores of many bioactive molecules. With the same reactants, a new relay catalysis using gold and Zn(II) catalysts affords highly oxygenated tetrahydroquinoline derivatives stereoselectively.
August 13, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28800505/electrochemical-aptasensor-for-thrombin-using-co-catalysis-of-hemin-g-quadruplex-dnazyme-and-octahedral-cu2o-au-nanocomposites-for-signal-amplification
#6
Shuai Chen, Pin Liu, Kewen Su, Xuan Li, Zhen Qin, Wei Xu, Jun Chen, Chaorui Li, Jingfu Qiu
In this work, novel octahedral Cu2O-Au nanocomposites were synthesized and first applied in an electrochemical aptasensor to detect thrombin (TB) with the aid of a DNAzyme for signal amplification. The octahedral Cu2O-Au nanocomposites have not only simultaneously served as signal amplifying molecules but have also been utilized as an ideal loading platform to immobilize a large number of electroactive substances and recognition probes. Gold nanoparticles (AuNPs) were grown directly on the surface of the octahedral Cu2O nanocrystals, and the Cu2O-Au nanocomposites obtained had the advantages of large surface areas and excellent biocompatibilities...
August 5, 2017: Biosensors & Bioelectronics
https://www.readbyqxmd.com/read/28775270/a-sustainable-nanocomposite-au-salen-cc-for-catalytic-degradation-of-eosin-y-and-chromotrope-2r-dyes
#7
Vishal J Mayani, Suranjana V Mayani, Sang Wook Kim
Up to now, a very few catalysts have been developed approaching the heterogeneous catalytic degradation of Eosin Y and Chromotrope 2R dyes (Acid Red 29). The present study provides a complete perspective of recyclable nanocomposite Au(Salen)@CC for catalytic degradation of hazardous water pollutant dyes viz., Eosin Y & Chromotrope 2R using mild reaction conditions. New gold Salen complex doped carbon nanocomposite Au(Salen)@CC was developed by easy methodology using nano carbon cage (CC) prepared from low-priced Pyrolysis fuel oil (PFO) residue based Pitch...
August 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28773196/surface-plasmon-resonance-or-biocompatibility-key-properties-for-determining-the-applicability-of-noble-metal-nanoparticles
#8
REVIEW
Ana Maria Craciun, Monica Focsan, Klara Magyari, Adriana Vulpoi, Zsolt Pap
Metal and in particular noble metal nanoparticles represent a very special class of materials which can be applied as prepared or as composite materials. In most of the cases, two main properties are exploited in a vast number of publications: biocompatibility and surface plasmon resonance (SPR). For instance, these two important properties are exploitable in plasmonic diagnostics, bioactive glasses/glass ceramics and catalysis. The most frequently applied noble metal nanoparticle that is universally applicable in all the previously mentioned research areas is gold, although in the case of bioactive glasses/glass ceramics, silver and copper nanoparticles are more frequently applied...
July 21, 2017: Materials
https://www.readbyqxmd.com/read/28771334/well-defined-chiral-gold-iii-complex-catalyzed-direct-enantioconvergent-kinetic-resolution-of-1-5-enynes
#9
Patrick T Bohan, F Dean Toste
The development of a gold(III) catalyzed direct enantioconvergent 1,5-enyne cycloisomerization and kinetic resolution reaction is described. The transformation results in highly enantioenriched bicyclo[3.1.0]hexenes at all levels of conversion, with no racemization or symmetrization taking place during the course of the reaction, and simultaneously affords optically enriched 1,5-enynes. This report marks the first highly enantioselective transformation catalyzed by a well-defined cationic gold(III) catalyst and demonstrates the unique potential of gold(III) complexes in enantioselective catalysis...
August 16, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28771322/characterization-of-ligand-shell-for-mixed-ligand-coated-gold-nanoparticles
#10
Quy Ong, Zhi Luo, Francesco Stellacci
Gold nanoparticles owe a large number of their properties to their ligand shell. Indeed, many researchers routinely use mixtures of ligand molecules for their nanoparticles to impart complex property sets. It has been shown that the morphology of ligand shells (e.g., Janus, random, stripelike) leads to specific properties. Examples include wettability, solubility, protein nonspecific adsorption, cell penetration, catalysis, and cation-capturing abilities. Yet, it remains a great challenge to evaluate such morphologies in even the most fundamental terms such as dimension and shape...
August 3, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28771319/preparation-and-self-assembly-of-dendronized-janus-fe3o4-pt-and-fe3o4-au-heterodimers
#11
Davit Jishkariani, Yaoting Wu, Da Wang, Yang Liu, Alfons van Blaaderen, Christopher B Murray
Janus nanoparticles (NPs) often referred to as nanosized analogs of molecular surfactants are amphiphilic structures with potential applications in materials science, biomedicine, and catalysis, and their synthesis and self-assembly into complex architectures remain challenging. Here, we demonstrate the preparation of Janus heterodimers via asymmetric functionalization of Fe3O4-Pt and Fe3O4-Au heterodimeric NPs. The hydrophobic and hydrophilic dendritic ligands that carry phosphonic acid and disulfide surface binding groups selectively coat the iron oxide and platinum (or gold) parts of the heterodimer, respectively...
August 11, 2017: ACS Nano
https://www.readbyqxmd.com/read/28770602/extending-the-%C3%AF-hole-concept-to-metals-an-electrostatic-interpretation-of-the-effects-of-nanostructure-in-gold-and-platinum-catalysis
#12
Joakim Halldin Stenlid, Tore Brinck
Crystalline surfaces of gold are chemically inert, whereas nanoparticles of gold are excellent catalysts for many reactions. The catalytic properties of nanostructured gold have been connected to increased binding affinities of reactant molecules for low-coordinated Au atoms. Here we show that the high reactivity at these sites is a consequence of the formation of σ-holes, i.e., maxima in the surface electrostatic potential (VS,max), due to the overlap of mainly the valence s-orbitals when forming the bonding σ-orbitals...
August 16, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28752308/green-synthesis-of-gold-nanoparticles-using-fungus-mariannaea-sp-hj-and-their-catalysis-in-reduction-of-4-nitrophenol
#13
Xiaofang Pei, Yuanyuan Qu, Wenli Shen, Huijie Li, Xuwang Zhang, Shuzhen Li, Zhaojing Zhang, Xuanying Li
In the present study, biosynthesis of gold nanoparticles (AuNPs) by the cells (cells-AuNPs) and cell-free extracts (extracts-AuNPs) of a new fungus Mariannaea sp. HJ was reported. The as-synthesized particles were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The effects of different parameters on AuNP biosynthesis were investigated, and initial gold ion concentration of 2 mM, pH 7, was demonstrated to be suitable for both cells-AuNP and extracts-AuNP syntheses...
July 27, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28752169/intramolecular-ipso-arylative-cyclization-of-aryl-alkynoates-and-n-arylpropiolamides-with-aryldiazonium-salts-through-merged-gold-visible-light-photoredox-catalysis
#14
Avinash H Bansode, Samir R Shaikh, Rajesh G Gonnade, Nitin T Patil
A visible-light-promoted merged gold/photoredox catalyzed ipso-arylative cyclization has been reported. For instance, the reaction of aryl-alkynoates and N-arylpropiolamides with aryldiazonium salts in the presence of catalytic amounts of [(4-OCH3)C6H4]3PAuCl and Ru(bpy)3(PF6)2 under irradiation using a 32 W CFL bulb gave arylated spirocarbocycles in moderate to good yields.
July 28, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28745479/visualizing-local-morphology-and-conductivity-switching-in-interface-assembled-nanoporous-c60-thin-films
#15
Jean-Nicolas Tisserant, Tino Wagner, Patrick A Reissner, Hannes Beyer, Yuriy Fedoryshyn, Andreas Stemmer
Carbon materials promise a revolution in optoelectronics, medical applications, and sensing provided that their morphology can be controlled down to the nanometer scale. Nanoporous materials are particularly appealing as they offer a drastically enlarged interfacial area compared to the corresponding planar materials. Entire fields such as organic solar cells, catalysis, or sensing may profit from an enlarged interface and facilitated molecular interaction between a carbon material and the environment. Nanoporous fullerene thin films obtained by the deposition of suspended nanoclusters of fullerene were already reported but suffered from the limitation of the size of these particles to over 100 nm...
August 16, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28745360/investigating-synergistic-interactions-of-group-4-5-and-6-metals-with-gold-nanoparticles-for-the-catalysis-of-the-electrochemical-hydrogen-evolution-reaction
#16
Ubisha Joshi, Souradip Malkhandi, Boon Siang Yeo
An investigation of the catalysis of the electrochemical hydrogen evolution reaction (HER, 2H(+) + 2e(-) → H2) in aqueous 0.5 M H2SO4 electrolyte using composites consisting of gold nanoparticles (AuNP), carbon (Black Pearl 2000) and group 4, 5, and 6 metals is presented. This study is a continuation of our earlier work (Phys. Chem. Chem. Phys., 2016, 18, 21548-21553) on molybdenum and AuNP, which we found to interact synergistically to enhance the HER. We demonstrate here that tungsten not only also showed synergy with AuNP, but the extent of synergy is even larger than that of the Mo-AuNP composite...
August 9, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28739132/colorimetric-sensing-of-selenocystine-using-gold-nanoparticles
#17
Liyang Liu, Xia Wang, Juan Yang, Yan Bai
We present a highly selective and sensitive colorimetric method for the detection of selenocystine (SeCys) coexisting with other amino acids, especially cysteine (Cys) using the gold nanoparticles (AuNPs). Firstly, Cys was oxidized to cystine (Cys-Cys) by dissolved oxygen under Cu(2+) catalysis in the pre-reaction, which eliminated the interference of Cys in the SeCys sensing process. Then SeCys induced the rapid aggregation of AuNPs through Au-Se bond and complex formation of Cu(2+)-SeCys in the colorimetric reaction, in which the color change of AuNPs from red to blue or purple with the naked eye detection or with a UV-vis spectrophotometric determination...
July 21, 2017: Analytical Biochemistry
https://www.readbyqxmd.com/read/28731109/the-preference-for-dual-gold-i-catalysis-in-the-hydro-alkoxylation-vs-phenoxylation-of-alkynes
#18
Èric Casals-Cruañas, Oscar F González-Belman, Pau Besalú-Sala, David J Nelson, Albert Poater
Dinuclear gold complexes and their use in catalysis have received significant recent attention, but there are few critical comparisons of mono- versus dual gold-catalysed pathways. Herein we study the hydroalkoxylation and hydrophenoxylation of alkynes using density functional theory calculations, and compare two possible mechanisms that have been proposed previously on the basis of theoretical and experimental studies, which unravel different preferences because of both the nature of the alkyne and alcohol and the non-innocent role of the counter-anion of a dual gold based catalyst...
August 2, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28723090/transformative-heterointerface-evolution-and-plasmonic-tuning-of-anisotropic-trimetallic-nanoparticles
#19
Mouhong Lin, Gyeong-Hwan Kim, Jae-Ho Kim, Jeong-Wook Oh, Jwa-Min Nam
Multicomponent nanoparticles that incorporate multiple nanocrystal domains into a single particle represent an important class of material with highly tailorable structures and properties. The controlled synthesis of multicomponent NPs with 3 or more components in the desired structure, particularly anisotropic structure, and property is, however, challenging. Here, we developed a polymer and galvanic replacement reaction-based transformative heterointerface evolution (THE) method to form and tune gold-copper-silver multimetallic anisotropic nanoparticles (MAPs) with well-defined configurations, including structural order, particle and junction geometry, giving rise to extraordinarily high tunability in the structural design, synthesis and optical property of trimetallic plasmonic nanoantenna structures...
July 25, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28712944/a-fe3o4-au-basedpseudo-homogeneous-electrochemical-immunosensor-for-afp-measurement-using-afp-antibody-gnps-hrp-as-detection-probe
#20
Yulin Yuan, Shanshan Li, Yewei Xue, Jintao Liang, Lijie Cui, Qingbo Li, Sufang Zhou, Yong Huang, Guiyin Li, Yongxiang Zhao
In this study, a Fe3O4@Au-based pseudo-homogeneous electrochemical immunosensor was prepared for detection of alpha fetoprotein (AFP), a well-known hepatocellular carcinoma biomarker. The primary antibody (Ab1) was immobilized on Fe3O4@Au NPs as the capture probe. Horseradish peroxidase (HRP) and secondary antibody (Ab2) were conjugated on gold nanoparticles (GNPs) through electrostatic adsorption to form signal-amplifying labels. In the presence of AFP, a sandwich immunocomplex was formed via specific recognition of antigen-antibody in a Fe3O4@Au-basedpseudo-homogeneousreaction system...
July 13, 2017: Analytical Biochemistry
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