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Gold catalysis

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...
April 20, 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 atom 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 single atoms and metal nanoparticles...
April 13, 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...
April 12, 2017: Angewandte Chemie
Fang Sun, Daniel D Galvan, Priyesh Jain, Qiuming Yu
Surface-enhanced Raman spectroscopy (SERS) has been recognized as one of the most sensitive sensing technologies and has been used for a variety of chemical, biological and medical applications. Compared to traditional direct SERS detection using a bare metal SERS-active substrate, surface chemistries and surface modifications on SERS-active substrates are becoming more and more important to achieve the detection of target analytes with a small surface affinity or weak Raman activity. As one special class of surface chemistries and modifications for SERS-active substrates, the thiophenol-based molecules offer new functions, increased sensitivity, and improved specificity to SERS-based sensing...
April 20, 2017: Chemical Communications: Chem Comm
Matthew A Wall, Stefan Harmsen, Soumik Pal, Lihua Zhang, Gianluca Arianna, John R Lombardi, Charles Michael Drain, Moritz F Kircher
Gold nanoparticles have unique properties that are highly dependent on their shape and size. Synthetic methods that enable precise control over nanoparticle morphology currently require shape-directing agents such as surfactants or polymers that force growth in a particular direction by adsorbing to specific crystal facets. These auxiliary reagents passivate the nanoparticles' surface, and thus decrease their performance in applications like catalysis and surface-enhanced Raman scattering. Here, a surfactant- and polymer-free approach to achieving high-performance gold nanoparticles is reported...
April 4, 2017: Advanced Materials
Patrick M Barbour, Wei Wang, Le Chang, Kasey L Pickard, Rana Rais, Barbara S Slusher, Xiang Wang
Antibiotic resistance is a worldwide public health threat that needs to be addressed by improved antibiotic stewardship and continuing development of new chemical entities to treat resistant bacterial infections. Compounds that work alongside known antibiotics as combination therapies offer an efficient and sustainable approach to counteract antibiotic resistance in bacteria. Guided by property-based analysis, a series of aza-tricyclic indolines (ATIs) were synthesized to optimize their physiochemical properties as novel combination therapies with β-lactams to treat methicillin-resistant S...
April 28, 2016: Advanced Synthesis & Catalysis
Grazia Malta, Simon A Kondrat, Simon J Freakley, Catherine J Davies, Li Lu, Simon Dawson, Adam Thetford, Emma K Gibson, David J Morgan, Wilm Jones, Peter P Wells, Peter Johnston, C Richard A Catlow, Christopher J Kiely, Graham J Hutchings
There remains considerable debate over the active form of gold under operating conditions of a recently validated gold catalyst for acetylene hydrochlorination. We have performed an in situ x-ray absorption fine structure study of gold/carbon (Au/C) catalysts under acetylene hydrochlorination reaction conditions and show that highly active catalysts comprise single-site cationic Au entities whose activity correlates with the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalysts are supported analogs of single-site homogeneous Au catalysts and propose a mechanism, supported by computational modeling, based on a redox couple of Au(I)-Au(III) species...
March 31, 2017: Science
Jian Liu, Nan Jian, Isabel Ornelas, Alexander J Pattison, Tanja Lahtinen, Kirsi Salorinne, Hannu Häkkinen, Richard E Palmer
Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au144(SCH2CH2Ph)60 provided by two different research groups...
November 22, 2016: Ultramicroscopy
Rachelle Quach, Daniel P Furkert, Margaret A Brimble
In the last decade the use of homogenous gold catalysts has rapidly grown and become a valuable tool for complex natural product synthesis. Spiroketal natural products are valuable targets for total synthesis and medicinal chemistry applications. The use of gold catalysts has emerged as a useful tool to synthesise these privileged scaffolds. This review summarises the application of gold catalysis for the syntheses of spiro, bridged and fused ketal natural products.
April 11, 2017: Organic & Biomolecular Chemistry
Chenyang Sun, Xiao Yuan, Yan Li, Xiaoxiao Li, Zhigang Zhao
A N(1)-selective alkenylation of 1-sulfonyl-1,2,3-triazoles with alkynes via gold catalysis is reported. N(1)-Vinyl substituted 1,2,3-triazoles were selectively prepared in up to 92% yield through the sulfonyl group of 1,2,3-triazole derivatives transformed to alkenyl groups in a "one-pot two steps" manner. This method provided a new method for the synthesis of potentially biological-active vinyl-triazole building blocks.
March 10, 2017: Organic & Biomolecular Chemistry
Kyuju Kwak, Woojun Choi, Qing Tang, Minseok Kim, Yongjin Lee, De-En Jiang, Dongil Lee
The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. Here, we report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanocluster...
March 10, 2017: Nature Communications
Subin Choi, Vunnam Srinivasulu, Sujin Ha, Cheol-Min Park
An efficient synthetic method for carbazoles has been developed employing diazo anilinoalkynes as substrates. Sequential activation of the orthogonal functional groups embedded in diazo anilinoalkyne substrates by tandem gold-copper catalysis leads to the formation of highly substituted carbazoles. Substrate scope reveals a broad tolerability toward the substitution on aryl groups.
March 9, 2017: Chemical Communications: Chem Comm
Romain Poupart, Antoine Benlahoues, Benjamin Le Droumaguet, Daniel Grande
Original nanoporous catalytic supports can be engineered via an effective and straightforward synthetic route to polystyrene-block-poly(D,L-lactide) diblock copolymer precursors displaying an acid-cleavable acetal junction between both blocks. To this purpose, an acetal-containing hetero-difunctional initiator was synthesized, thus enabling to combine two different polymerization methods, i.e. first Atom Transfer Radical Polymerization (ATRP) of styrene, and then Ring-Opening Polymerization (ROP) of D,L-lactide...
March 7, 2017: ACS Applied Materials & Interfaces
Debdip Bhandary, Vasumathi Valechi, Maria Natália D S Cordeiro, Jayant K Singh
Janus particles provide an asymmetry in structure, which can impart diverse functionalities leading to immense importance in various applications, ranging from targeted delivery to interfacial phenomena, including catalysis, electronics, and optics. In this work, we present results of a molecular dynamics study of the growth mechanism of coating on gold nanoparticles (AuNPs) from droplets of n-alkyl thiols with different chain lengths (C5 and C11) and terminal groups (CH3 and COOH). The effect of chain lengths and functional groups on the formation of a monolayer of alkyl thiols on AuNPs is investigated...
March 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ghibom Bhak, Junghee Lee, Chang-Hyun Kim, Dong Young Chung, Jin Hyoun Kang, Soojung Oh, Jungsup Lee, Jin Soo Kang, Ji Mun Yoo, Jee Eun Yang, Kun Yil Rhoo, Sunghak Park, Somin Lee, Ki Tae Nam, Noo Li Jeon, Jyongsik Jang, Byung Hee Hong, Yung-Eun Sung, Myung-Han Yoon, Seung R Paik
Functional graffiti of nanoparticles onto target surface is an important issue in the development of nanodevices. A general strategy has been introduced here to decorate chemically diverse substrates with gold nanoparticles (AuNPs) in the form of a close-packed single layer by using an omni-adhesive protein of α-synuclein (αS) as conjugated with the particles. Since the adsorption was highly sensitive to pH, the amino acid sequence of αS exposed from the conjugates and its conformationally disordered state capable of exhibiting structural plasticity are considered to be responsible for the single-layer coating over diverse surfaces...
March 1, 2017: ACS Applied Materials & Interfaces
Zhengnan Shen, Hani Mobarak, Wei Li, Göran Widmalm, Biao Yu
The β-(1→2)-linked 6-deoxy-l-altropyranose di- to pentasaccharides 2-5, relevant to the O-antigen of the infectious Yersinia enterocolitica O:3, were synthesized for the first time. The challenging 1,2-cis-altropyranosyl linkage was assembled effectively via glycosylation with 2-O-benzyl-3,4-di-O-benzoyl-6-deoxy-l-altropyranosyl ortho-hexynylbenzoate (7) under the catalysis of PPh3AuNTf2. NMR and molecular modeling studies showed that the pentasaccharide (5) adopted a left-handed helical conformation.
March 2, 2017: Journal of Organic Chemistry
Kasper P Kepp
Gold plays a major role in nanochemistry, catalysis, and electrochemistry. Accordingly, hundreds of studies apply density functionals to study chemical bonding with gold, yet there is no systematic attempt to assess the accuracy of these methods applied to gold. This paper reports a benchmark against 51 experimental bond enthalpies of AuX systems and seven additional polyatomic and cationic molecules. Twelve density functionals were tested, covering meta functionals, hybrids with variable HF exchange, double-hybrid, dispersion-corrected, and nonhybrid GGA functionals...
February 24, 2017: Journal of Physical Chemistry. A
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