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Gold catalysis

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https://www.readbyqxmd.com/read/29328339/reduced-sintering-of-mass-selected-au-clusters-on-sio2-by-alloying-with-ti-an-aberration-corrected-stem-and-computational-study
#1
Yubiao Niu, Philomena Schlexer, Bela Sebok, Ib Chorkendorff, Gianfranco Pacchioni, Richard E Palmer
Au nanoparticles represent the most remarkable example of a size effect in heterogeneous catalysis. However, a major issue hindering the use of Au nanoparticles in technological applications is their rapid sintering. We explore the potential of stabilizing Au nanoclusters on SiO2 by alloying them with a reactive metal, Ti. Mass-selected Au/Ti clusters (400 000 amu) and Au2057 clusters (405 229 amu) were produced with a magnetron sputtering, gas condensation cluster beam source in conjunction with a lateral time-of-flight mass filter, deposited onto a silica support and characterised by XPS and LEIS...
January 12, 2018: Nanoscale
https://www.readbyqxmd.com/read/29323447/solvation-induced-changes-of-the-mechanism-of-alcohol-oxidation-at-aqueous-versus-gas-phase-au-tio%C3%A2-nanocatalysts
#2
Daniel Muñoz-Santiburcio, Matteo Farnesi Camellone, Dominik Marx
Gold/titania catalysts are widely used for key reactions, notably including the selective oxidation of alcohols in the liquid phase. Our large-scale ab initio simulations disclose that the liquid-phase reaction mechanism is distinctly different from that in the gas phase due to active participation of water molecules. While concerted charge transfers related to O₂ splitting and abstraction of both, protonic and hydridic hydrogens are enforced under dry conditions, stepwise charge transfer is preferred in the condensed phase...
January 11, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29319082/%C3%AF-holes-and-%C3%AF-lumps-direct-the-lewis-basic-and-acidic-interactions-of-noble-metal-nanoparticles-introducing-regium-bonds
#3
Joakim Halldin Stenlid, Adam Johannes Johansson, Tore Brinck
Using local DFT-based probes for electrostatic as well as charge transfer/polarization interactions, we are able to characterize Lewis basic and acidic sites on copper, silver and gold nanoparticles. The predictions obtained using the DFT-probes are compared to the interaction energies of the electron donating (CO, H2O, NH3 and H2S) and the electron accepting (BH3, BF3, HCl [H-down] and Na+) compounds. The probes include the local electron attachment energy [E(r)], the average local ionization energy [Ī(r)], and the electrostatic potential [V(r)] and are evaluated on isodensity surfaces located at distances corresponding to typical interaction distances...
January 10, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29318878/ultrasensitive-enzyme-free-biosensor-by-coupling-cyclodextrin-functionalized-au-nanoparticles-and-high-performance-au-paper-electrode
#4
Xiaoxiao Zheng, Li Li, Kang Cui, Yan Zhang, Lina Zhang, Shenguang Ge, Jinghua Yu
Microfluidic paper-based analytical device (μPAD), originally developed for improving healthcare in developing countries, presents a simple yet powerful platform for performing low-cost and portable diagnostic devices. Here, we reported an enzyme-free μPAD for the detection of two tumor markers. Firstly, a porous structure of gold nanoparticles (AuNPs) modified paper working electrode (Au-PWE), with a feature of all-around conductivity and plenty of active sites favoring for the biological ligands attachment, was firstly fabricated as a sensor substrate...
January 10, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29316786/controlled-growth-and-grafting-of-high-density-au-nanoparticles-on-zinc-oxide-thin-films-by-photo-deposition
#5
Jeremy Cure, Hala Assi, Kévin Cocq, Lorena Marín, Katia Fajerwerg, Pierre Fau, Eric Beche, Yves J Chabal, Alain Esteve, Carole Rossi
The integration of high-purity nano-objects on substrates remains a great challenge for addressing scaling-up issues in nanotechnology. For instance, grafting gold nanoparticles (NPs) on zinc oxide films, a major step process for catalysis or photovoltaic applications, still remains difficult to master. We report a modified photo-deposition (P-D) approach that achieves tight control of the NPs size (7.5 ± 3 nm), shape (spherical), purity, and high areal density (3500 ± 10 NPs/m2) on ZnO films. This deposition method is also compatible with large ZnO surface areas...
January 9, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29314298/chiral-phosphine-phosphite-ligands-in-asymmetric-gold-catalysis-highly-enantioselective-synthesis-of-furo-3-4-d-tetrahydropyridazine-derivatives-through-3-3-cycloaddition
#6
Qingwei Du, Jörg-Martin Neudörfl, Hans-Günther Schmalz
The Au(I)-catalyzed reaction of 2-(1-alkynyl)-2-alken-1-ones with azomethine imines regio- and diastereoselectively affords furo[3,4-d]tetrahydropyridazines in a tandem cyclization/intermolecular [3+3]-cycloaddition process under mild conditions. By employing a chiral gold catalyst (prepared in-situ from a Taddol-derived phosphine-phosphite ligand, Me2SAuCl, and AgOTf) high yields and enantioselectivities (up to 94% yield, up to 96% ee) are obtained. The method provides an efficient modular route to substituted hetero-tricyclic furan derivatives and can be easily scaled up (using catalyst loads of only 0...
January 4, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29313532/a-label-free-versatile-and-low-background-chemiluminescence-aptasensing-strategy-based-on-gold-nanocluster-catalysis-combined-with-the-separation-of-magnetic-beads
#7
Yueyue Yao, Xiuzhong Wang, Wenna Duan, Feng Li
A label-free, versatile and low-background chemiluminescence (CL) sensing strategy based on gold nanocluster catalysis combined with the separation of magnetic beads (MBs) was developed. Kanamycin was selected as the target analyte to exhibit the analytical performance of this platform. Two single-stranded DNA (named DNA1 and DNA2) are ingeniously designed. DNA1, containing an aptamer sequence of the targets, was firstly immobilized on the MBs which were modified with many amino groups by amidation reaction...
January 9, 2018: Analyst
https://www.readbyqxmd.com/read/29297680/gold-i-catalyzed-glycosylation-with-glycosyl-o-alkynylbenzoates-as-donors
#8
Biao Yu
Naturally occurring glycans and glycoconjugates have extremely diverse structures and biological functions. Syntheses of these molecules and their artificial mimics, which have attracted the interest of those developing new therapeutic agents, rely on glycosylation methodologies to construct the various glycosidic linkages. In this regard, a wide array of glycosylation methods have been developed, and they mainly involve the substitution of a leaving group on the anomeric carbon of a glycosyl donor with an acceptor (a nucleophile) under the action of a particular promoter (usually a stoichiometric electrophile)...
January 3, 2018: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29276382/a-facile-and-sensitive-peptide-modulating-graphene-oxide-nanoribbon-catalytic-nanoplasmon-analytical-platform-for-human-chorionic-gonadotropin
#9
Aihui Liang, Chongning Li, Dan Li, Yanghe Luo, Guiqing Wen, Zhiliang Jiang
The nanogold reaction between HAuCl4 and citrate is very slow, and the catalyst graphene oxide nanoribbon (GONR) enhanced the nanoreaction greatly to produce gold nanoparticles (AuNPs) that exhibited strong surface plasmon resonance (SPR) absorption (Abs) at 550 nm and resonance Rayleigh scattering (RRS) at 550 nm. Upon addition of the peptide of human chorionic gonadotropin (hCG), the peptide could adsorb on the GONR surface, which inhibited the catalysis. When hCG was added, peptides were separated from the GONR surface due to the formation of stable peptide-hCG complex, which led to the activation of GONR catalytic effect...
2017: International Journal of Nanomedicine
https://www.readbyqxmd.com/read/29239136/composite-polymer-colloids-for-sers-based-applications
#10
REVIEW
Malte S Strozyk, Dorleta Jimenez de Aberasturi, Luis M Liz-Marzán
Polymers and nanoparticles can be combined into different materials with applications in various fields like catalysis, biotechnology, or drug delivery, to cite just a few. Colloidal composites may vary significantly, ranging from a single nanoparticle stabilized by a polymer shell through a polymeric carrier decorated with hundreds of particles. We review here composite colloids comprising gold nanoparticles, with an emphasis in systems with potential application in surface enhanced Raman scattering (SERS)...
December 14, 2017: Chemical Record: An Official Publication of the Chemical Society of Japan ... [et Al.]
https://www.readbyqxmd.com/read/29234757/water-facilitates-oxygen-migration-on-gold-surfaces
#11
Fang Xu, Ioanna Fampiou, Christopher R O'Connor, Stavros Karakalos, Fanny Hiebel, Efthimios Kaxiras, Robert J Madix, Cynthia M Friend
The water-oxygen-gold interface is important in many surface processes and has potential influence on heterogeneous catalysis. Herein, it is shown that water facilitates the migration of atomic oxygen on Au(110), demonstrating the dynamic nature of surface adsorption. We demonstrate this effect for the first time, using in situ scanning tunnelling microscopy (STM), temperature-programmed reaction spectroscopy (TPRS) and first-principles theoretical calculations. The dynamic interaction of water with adsorbed O maintains a high dispersion of O on the surface, potentially creating reactive transient species...
December 13, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29218812/gold-catalyzed-divergent-ring-closing-modes-of-indole-tethered-amino-allenynes
#12
Pedro Almendros, Benito Alcaide, Israel Fernández, Fernando Herrera, Amparo Luna
Indole-tethered amino allenynes were chemodivergently cyclized for the controlled preparation of fused polycyclic indoles using gold catalysis. Double cyclization of terminal allenynes afforded hexacyclic 15H-indolo[1,2,3-de]quinolino[3,2,1-ij]quinoxalines, where allenynes bearing a substituted alkyne at the terminal end generated 12,13-dihydro-7H-indolo[3,2-c]acridines, which are 5-membered cyclized adducts. Density Functional Theory calculations were performed to shed light on this difference in reactivity...
December 8, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29205746/well-defined-chiral-gold-iii-complexes-new-opportunities-in-asymmetric-catalysis
#13
Jessica Rodriguez, Didier Bourissou
Square way to heaven: As a result of their square-planar geometry, the reactive site of gold(III) complexes is much closer to the ancillary ligands. This offers new perspectives in asymmetric catalysis, as recently evidenced by the groups of Wong and Toste with well-defined chiral complexes.
December 5, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29191908/selective-increase-in-co2-electroreduction-activity-at-grain-boundary-surface-terminations
#14
Ruperto G Mariano, Kim McKelvey, Henry S White, Matthew W Kanan
Altering a material's catalytic properties requires identifying structural features that give rise to active surfaces. Grain boundaries create strained regions in polycrystalline materials by stabilizing dislocations and may provide a way to create high-energy surfaces for catalysis that are kinetically trapped. Although grain-boundary density has previously been correlated with catalytic activity for some reactions, direct evidence that grain boundaries create surfaces with enhanced activity is lacking. We used a combination of bulk electrochemical measurements and scanning electrochemical cell microscopy with submicrometer resolution to show that grain-boundary surface terminations in gold electrodes are more active than grain surfaces for electrochemical carbon dioxide (CO2) reduction to carbon monoxide (CO) but not for the competing hydrogen (H2) evolution reaction...
December 1, 2017: Science
https://www.readbyqxmd.com/read/29185732/efficient-energy-transfer-from-near-infrared-emitting-gold-nanoparticles-to-pendant-ytterbium-iii
#15
Scott E Crawford, Christopher M Andolina, Derrick C Kaseman, Bo Hyung Ryoo, Ashley M Smith, Kathryn A Johnston, Jill E Millstone
Here, we demonstrate efficient energy transfer from near-infrared-emitting ortho-mercaptobenzoic acid-capped gold nanoparticles (AuNPs) to pendant ytterbium(III) cations. These functional materials combine the high molar absorptivity (1.21 × 106 M-1 cm-1) and broad excitation features (throughout the UV and visible regions) of AuNPs with the narrow emissive properties of lanthanides. Interaction between the AuNP ligand shell and ytterbium is determined using both nuclear magnetic resonance and electron microscopy measurements...
November 29, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29182183/dendrimer-encapsulated-nanoparticle-core-micelles-as-a-modular-strategy-for-particle-in-a-box-in-a-box-nanostructures
#16
J B Ten Hove, J Wang, F W B van Leeuwen, A H Velders
The hierarchically controlled synthesis and characterization of self-assembling macromolecules and particles are key to explore and exploit new nanomaterials. Here we present a versatile strategy for constructing particle-in-a-box-in-a-box systems by assembling dendrimer-encapsulated gold nanoparticles (DENs) into dendrimicelles. This is realized by combining positively charged PAMAM dendrimers with a negative-neutral block copolymer. The number of particles per dendrimicelle can be controlled by mixing DENs with empty PAMAM dendrimers...
November 28, 2017: Nanoscale
https://www.readbyqxmd.com/read/29175215/pdpt-nanoparticles-anchored-on-the-n-g-with-the-integration-of-pani-nanohybrids-as-novel-redox-probe-and-catalyst-for-the-detection-of-rs1801177
#17
Jing Wu, Junlin He, Chengli Zhang, Jun Chen, Yazhen Niu, Qiqi Yuan, Chao Yu
Single nucleotide polymorphism (SNP) in lipoprotein lipase (LPL) gene (rs1801177) is strongly associated with the increased progression of atherosclerosis, threatening global public health. In this work, a relatively simple, specific and ultrasensitive electrochemical DNA biosensor was constructed to detect rs1801177 for the first time. A glass carbon electrode was modified with fullerene (C60)/polyamidoamine (PAMAM)/gold (Au) nanoparticles nanocomposites film. In addition the nitrogen-doped graphene (N-G)/palladium platinum (PdPt) bimetallic nanoparticle/ polyaniline (PANI) nanohybrids were synthesised and used to label the signal probes...
November 21, 2017: Biosensors & Bioelectronics
https://www.readbyqxmd.com/read/29172479/enamine-dienamine-and-br%C3%A3-nsted-acid-catalysis-elusive-intermediates-reaction-mechanisms-and-stereoinduction-modes-based-on-in-situ-nmr-spectroscopy-and-computational-studies
#18
Polyssena Renzi, Johnny Hioe, Ruth M Gschwind
Over the years, the field of enantioselective organocatalysis has seen unparalleled growth in the development of novel synthetic applications with respect to mechanistic investigations. Reaction optimization appeared to be rather empirical than rational. This offset between synthetic development and mechanistic understanding was and is generally due to the difficulties in detecting reactive intermediates and the inability to experimentally evaluate transition states. Thus, the first key point for mechanistic studies is detecting elusive intermediates and characterizing them in terms of their structure, stability, formation pathways, and kinetic properties...
November 27, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29168491/structure-and-reactivity-of-a-mononuclear-gold-ii-complex
#19
Sebastian Preiß, Christoph Förster, Sven Otto, Matthias Bauer, Patrick Müller, Dariush Hinderberger, Haleh Hashemi Haeri, Luca Carella, Katja Heinze
Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn-Teller distortion enabled by the relativistically lowered 6s orbital of gold...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29162805/the-key-role-of-au-substrate-interactions-in-catalytic-gold-subnanoclusters
#20
Jesús Cordón, Gonzalo Jiménez-Osés, José M López-de-Luzuriaga, Miguel Monge
The development of gold catalysis has allowed significant levels of activity and complexity in organic synthesis. Recently, the use of very active small gold subnanoclusters (Au n , n < 10) has been reported. The stabilization of such nanocatalysts to prevent self-aggregation represents a true challenge that has been partially remediated, for instance, by their immobilization in polymer matrices. Here, we describe the transient stabilization of very small gold subnanoclusters (Au n , n < 5) by alkyl chains or aromatic groups appended to the reactive π bond of simple alkynes...
November 21, 2017: Nature Communications
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