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Gold catalysis

Qu Chen, Kuang He, Alex W Robertson, Angus I Kirkland, Jamie H Warner
The atomic level dynamics of gold on graphene is studied at temperatures up to 800 °C using an in situ heating holder within an aberration-corrected transmission electron microscope. At this high temperature, individual gold atoms and nanoclusters are mobile across the surface of graphene and attach to defect sites and migrate along the edges of holes in graphene. Gold nanoclusters on clean graphene show crystallinity at temperatures above their predicted melting point for equivalent sized clusters due to strong epitaxial interactions with the underlying graphene lattice...
November 22, 2016: ACS Nano
Weiwei Qin, Tianhuan Peng, Yanjing Gao, Fei Wang, Xiaocai Hu, Kun Wang, Jiye Shi, Di Li, Jicun Ren, Chunhai Fan
It is highly demanding to design active nanomotors that can move in response to specific signals with controllable rate and direction. A catalysis-driven nanomotor was constructed by designing catalytically and plasmonically active Janus gold nanoparticles (Au NPs), which generate an asymmetric temperature gradient of local solvent surrounding NPs in catalytic reactions. The self-thermophoresis behavior of the Janus nanomotor is monitored from its inherent plasmonic response. The diffusion coefficient of the self-thermophoresis motion is linearly dependent on chemical reaction rate, as described by a stochastic model...
December 6, 2016: Angewandte Chemie
Judith Schöbel, Matthias Burgard, Christian Hils, Roland Dersch, Martin Dulle, Kirsten Volk, Matthias Karg, Andreas Greiner, Holger Schmalz
Heterogeneous catalysis with supported nanoparticles (NPs) is a highly active field of research. However, the efficient stabilization of NPs without deteriorating their catalytic activity is challenging. By combining top-down (coaxial electrospinning) and bottom-up (crystallization-driven self-assembly) approaches, we prepared patchy nonwovens with functional, nanometer-sized patches on the surface. These patches can selectively bind and efficiently stabilize gold nanoparticles (AuNPs). The use of these AuNP-loaded patchy nonwovens in the alcoholysis of dimethylphenylsilane led to full conversion under comparably mild conditions and in short reaction times...
December 6, 2016: Angewandte Chemie
Pradip N Bagle, Manoj V Mane, K Vanka, Dinesh R Shinde, Samir R Shaikh, Rajesh G Gonnade, Nitin T Patil
A co-operative Au(i)/Ag(i) catalyst system has been developed to utilize N-allenamides as nucleophilic enal equivalents for the interceptive capturing of incipient carbocations generated through π-acid-triggered imino-alkyne cyclization. The salient features include the in situ generation of silver-bound carbocations (from iminoalkynes), α-gold(i) enals (from N-allenamides) and union of these two species to form indolizines with the regeneration of Au and Ag catalysts.
November 30, 2016: Chemical Communications: Chem Comm
Massimo Rigo, Lara Hettmanczyk, Frank J L Heutz, Stephan Hohloch, Martin Lutz, Biprajit Sarkar, Christian Müller
Gold(i) complexes based on a 2,4,6-triarylphosphinine and a mesoionic carbene derivative have been prepared and characterized crystallographically. Although structurally related, both heterocycles differ significantly in their donor/acceptor properties. These opposed electronic characteristics have been exploited in Au(i)-catalyzed cycloisomerization reactions. For the conversion of the standard substrate dimethyl 2-(3-methylbut-2-enyl)-2-(prop-2-ynyl)malonate the results obtained for both Au-catalysts were found to be very similar and comparable to the ones reported in the literature for other carbene- or phosphorus(iii)-based Au(i)-complexes...
November 29, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Chuanhua Qu, Songlin Zhang, Hongbin Du, Chengjian Zhu
A new method for the synthesis of 3-arylindoles has been developed by visible light mediated dual gold/photoredox catalysis. This transformation has many features such as cascade catalysis, high efficiency, redox-neutral reaction conditions and good functional group tolerance. The reaction proceeds through the photoredox-promoted formation of an electrophilic arylgold(iii) intermediate that undergoes coupling with the arylamine nucleophile.
November 28, 2016: Chemical Communications: Chem Comm
Samir A Belhout, Ji Yoon Kim, David T Hinds, Natalie J Owen, Jonathan A Coulter, Susan J Quinn
The preparation of a family of composite particles comprising gold nanoparticles (AuNP) assembled at a polystyrene (PS) surface is reported. Tunable loading is demonstrated for AuNP sizes (4.5-26 nm). The robust composites are stable to multiple centrifugation and dispersion cycles and to conditions of high ionic strength, physiological buffer and cell culture media. These properties provide potential for a variety of applications from cellular studies to catalysis.
November 28, 2016: Chemical Communications: Chem Comm
Alper Kinaci, Badri Narayanan, Fatih G Sen, Michael J Davis, Stephen K Gray, Subramanian K R S Sankaranarayanan, Maria K Y Chan
Au nanoclusters are of technological relevance for catalysis, photonics, sensors, and of fundamental scientific interest owing to planar to globular structural transformation at an anomalously high number of atoms i.e. in the range 12-14. The nature and causes of this transition remain a mystery. In order to unravel this conundrum, high throughput density functional theory (DFT) calculations, coupled with a global structural optimization scheme based on a modified genetic algorithm (GA) are conducted. More than 20,000 Au12, Au13, and Au14 nanoclusters are evaluated...
November 28, 2016: Scientific Reports
Daichi Yoshii, Xiongjie Jin, Takafumi Yatabe, Jun-Ya Hasegawa, Kazuya Yamaguchi, Noritaka Mizuno
In the presence of Au nanoparticles supported on manganese oxide OMS-2 (Au/OMS-2), various kinds of β-heteroatom-substituted α,β-unsaturated ketones (heteroatom = N, O, S) can be synthesized through α,β-dehydrogenation of the corresponding saturated ketones using O2 (in air) as the oxidant. The catalysis of Au/OMS-2 is truly heterogeneous, and the catalyst can be reused.
December 6, 2016: Chemical Communications: Chem Comm
Carmela Saturnino, Ines Barone, Domenico Iacopetta, Annaluisa Mariconda, Maria Stefania Sinicropi, Camillo Rosano, Antonella Campana, Stefania Catalano, Pasquale Longo, Sebastiano Andò
AIM: Metal carbenic complexes have received considerable attention in both the catalysis and biological fields for their potential applications in cancer and antimicrobial therapies. RESULTS: A small series of new silver and gold N-heterocyclic carbene complexes has been designed and synthesized. Among the tested complexes, one compound was particularly active in inhibiting anchorage-dependent and -independent breast cancer proliferation, and inducing cell apoptosis via a mitochondria-related process...
November 22, 2016: Future Medicinal Chemistry
Yanhu Wang, Chaomin Gao, Shenguang Ge, Lina Zhang, Jinghua Yu, Mei Yan
By incorporating the Prussian Blue (PB) electrochromic display as cathode, a solar-driven photoelectrochemical (PEC) cell was constructed through combining sandwich-structured graphite-like carbon nitride (g-C3N4)-Au-branched-titanium dioxide (B-TiO2) nanorods as photoanode for self-powered hydrogen peroxide (H2O2) sensing, which exhibits both direct photoelectrochemical and electrochromic response. The gold nanoparticles (Au NPs) sandwiched between the B-TiO2 nanorods and the g-C3N4 layer served as electron relay as well as plasmonic photosensitizer to enhance the solar-to-chemical energy conversion efficiency...
November 11, 2016: Biosensors & Bioelectronics
Xiaokun Li, Youlin Zhang, Yulei Chang, Bin Xue, Xianggui Kong, Wei Chen
In view of the high biotoxicity and trace concentration of mercury (Hg) in environmental water, developing simple, ultra-sensitive and highly selective method capable of simultaneous determination of various Hg species has attracted wide attention. Here, we present a novel catalysis-reduction strategy for sensing inorganic and organic mercury in aqueous solution through the cooperative effect of AuNP-catalyzed properties and the formation of gold amalgam. For the first time, a new AuNP-catalyzed-organic reaction has been discovered and directly used for sensing Hg(2+), Hg2(2+) and CH3Hg(+) according to the change of the amount of the catalytic product induced by the deposition of Hg atoms on the surface of AuNPs...
November 5, 2016: Biosensors & Bioelectronics
Jun Chen, Chao Yu, Yilin Zhao, Yazhen Niu, Lei Zhang, Yujie Yu, Jing Wu, Junlin He
The small amount of cell-free fetal DNA (cffDNA) can be a useful biomarker for early non-invasive prenatal diagnosis (NIPD) of achondroplasia. In this study, a novel non-invasive electrochemical DNA sensor for ultrasensitive detecting FGFR3 mutation gene, a pathogenic gene of achondroplasia, based on biocatalytic signal materials and the biotin-streptavidin system are presented. Notably encapsulation of hemin in metal-organic frameworks-based materials (hemin-MOFs) and platinum nanoparticles (PtNPs) were used to prepare hemin-MOFs/PtNPs composites via a one-beaker-one-step reduction...
November 1, 2016: Biosensors & Bioelectronics
Ling Zhang, Yangzhong Wang, Qianqian Tian, Yang Liu, Jinghong Li
A novel ECL biosensor for cytosensing and cell surface carbohydrate expression evaluation was developed, by the integration of the peptide modified interface for highly specific carbohydrate recognition and sodium alginate loaded glucose oxidase as the signal probe with high signal amplification efficiency. A cysteine-terminated peptide self-assembled on the electrode through Au-S bond to construct a functional interface for cell capture, with decent biocompatibility and high affinity for the human breast cancer cell MCF-7...
October 19, 2016: Biosensors & Bioelectronics
Zhiyang Zhang, Zhaopeng Chen, Fangbin Cheng, Yaowen Zhang, Lingxin Chen
Based on enzymatic-like reaction mediated etching of gold nanorods (GNRs), an ultrasensitive visual method was developed for on-site detection of urine glucose. With the catalysis of MoO4(2)(-), GNRs were efficiently etched by H2O2 which was generated by glucose-glucose oxidase enzymatic reaction. The etching of GNRs lead to a blue-shift of logitudinal localized surface plasmon resonance of GNRs, accompanied by an obvious color change from blue to red. The peak-shift and the color change can be used for detection of glucose by the spectrophotometer and the naked eyes...
September 26, 2016: Biosensors & Bioelectronics
Lara Hettmanczyk, Lisa Suntrup, Sinja Klenk, Carolin Hoyer, Biprajit Sarkar
Mesoionic carbenes (MICs) are currently hugely popular as ligands and triazolylidenes are arguably the most prominent classes of such MICs. We present here mesoionic carbenes with ferrocenyl substituents that can act as metalloligands for the generation of heteromultimetallic iridium(I) and gold(I) complexes. The ferrocenyl substituents allow for reversible oxidation of these heteromultimetallic complexes and these oxidation steps have a strong influence on the donor properties of the MICs. Tolman electronic parameters (TEP) determined from analysis of the iridium-carbonyl complexes show that the neutral ferrocenyl-MIC ligands are stronger donors than the imidazolylidene based carbenes, the one-electron oxidized ferrocenyl MICs are in the range of the tricyclohexyl phosphines and the two-electron oxidized forms which are electron-poor lie in the range of triphenyl phosphines...
November 3, 2016: Chemistry: a European Journal
Stephen M Budy, Desmond J Hamilton, Yuheng Cai, Michelle K Knowles, Scott M Reed
Gold nanoparticles (GNPs) have a wide range of properties with potential applications in electronics, optics, catalysis, and sensing. In order to demonstrate that dense, stable, and portable samples could be created for these applications, multiple layers of GNPs were assembled via drop casting on glass substrates by layer-by-layer (LBL) techniques. Two cationic polyelectrolytes, poly(diallyldimethylammonium chloride) and polyethyleneimine, one anionic polyelectrolyte, poly(sodium 4-styrene sulfonate), and one neutral polymer, polyvinylpyrrolidone, were combined with four different shapes of GNPs (spherical, rod, triangular prismatic, and octahedral) to prepare thin films...
February 1, 2017: Journal of Colloid and Interface Science
Rosaria Ciriminna, Valerica Pandarus, Riccardo Delisi, Antonino Scurria, Maria Pia Casaletto, Francesco Giordano, François Béland, Mario Pagliaro
BACKGROUND: The introduction of an heterogeneously catalyzed gold-based alcohol oxidation process of broad applicability using a clean primary oxidant would be highly desirable. Gold is non toxic and carbonyl and carboxyl compounds are widely used to produce medicines, plastics, colorants, paints, detergents, fragrances, flavors, and other valued functional products. RESULTS: The sol-gel entrapment of gold nanoparticles in hybrid silica improves gold-based oxidation catalysis applied to the selective oxidation of alcohols with aqueous hydrogen peroxide as eco-friendly primary oxidant...
2016: Chemistry Central Journal
Stavros Karakalos, Yun-Fei Xu, Fairoja Cheenicode Kabeer, Wei Chen, Juan Carlos F Rodriguez-Reyes, Alexandre Tkatchenko, Efthimios Kaxiras, Robert J Madix, Cynthia M Friend
Enhancing the selectivity of catalytic processes has potential for substantially increasing the sustainability of chemical production. Herein, we establish relationships between reaction selectivity and molecular structure for a homologous series of key intermediates for oxidative coupling of alcohols on gold using a combination of experiment and theory. We establish a scale of binding for molecules with different alkyl structures and chain lengths and thereby demonstrate the critical nature of non-covalent van der Waals interactions in determining the selectivity by modulating the stability of key reaction intermediates bound to the surface...
October 24, 2016: Journal of the American Chemical Society
Zhenglong Zhang, Yurui Fang, Wenhui Wang, Li Chen, Mengtao Sun
Plasmonics is a well-established field, exploiting the interaction of light and metals at the nanoscale; with the help of surface plasmon polaritons, remote-excitation can also be observed by using silver or gold plasmonic waveguides. Recently, plasmonic catalysis was established as a new exciting platform for heterogeneous catalytic reactions. Recent reports present remote-excitation surface catalytic reactions as a route to enhance the rate of chemical reactions, and offer a pathway to control surface catalytic reactions...
January 2016: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
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