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https://www.readbyqxmd.com/read/28738598/green-and-efficient-sample-preparation-method-for-the-determination-of-catalyst-residues-in-margarine-by-icp-ms
#1
Carla Andrade Hartwig, Rodrigo Mendes Pereira, Diogo La Rosa Novo, Dirce Taina Teixeira Oliveira, Marcia Foster Mesko
Responding to the need for green and efficient methods to determine catalyst residues with suitable precision and accuracy in samples with high fat content, the present work evaluates a microwave-assisted ultraviolet digestion (MW-UV) system for margarines and subsequent determination of Ni, Pd and Pt using inductively coupled plasma mass spectrometry (ICP-MS). It was possible to digest up to 500mg of margarine using only 10mL of 4molL(-1) HNO3 with a digestion efficiency higher than 98%. This allowed the determination of catalyst residues using the ICP-MS and free of interferences...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28738278/well-dispersed-rhenium-nanoparticles-on-three-dimensional-carbon-nanostructures-efficient-catalysts-for-the-reduction-of-aromatic-nitro-compounds
#2
Pitchaimani Veerakumar, Pounraj Thanasekaran, King-Chuen Lin, Shang-Bin Liu
Rhenium nanoparticles (ReNPs) supported on ordered mesoporous carbon (OMC) as a catalyst (Re/OMC) through a solvent-evaporation induced self-assembly (ELSA) method were prepared. The synthesized heterogonous catalyst was fully characterized using X-ray diffraction, field emission transmission electron microscopy, N2 sorption, metal dispersion, thermogravimetric analysis, Raman, Fourier-transform infrared, and X-ray photon spectroscopies. In addition, the catalyst was applied to reduce the aromatic nitro compounds (ANCs) for the first time in aqueous media and the reactions were monitored by following the intensity changes in the UV-vis absorption spectra with respect to time...
July 18, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28737944/in-situ-generated-glycinyl-chloroaminals-for-a-one-pot-synthesis-of-non-proteinogenic-%C3%AE-amino-esters
#3
Shyam S Samanta, Stephane P Roche
An acetyl chloride-mediated cascade transformation involving a primary carbamate, ethyl glyoxylate and various types of nucleophiles is reported for the synthesis of orthogonally protected α-amino esters. These reactions proceeded rapidly to afford the pivotal α-chloroglycine intermediate in excellent yields which can be directly functionalized in situ with various types of nucleophiles. A mild and unique AcOH(cat.)/AcCl system was found to promote an autocatalytic-like condensation and facilitate the multicomponent assembly of non-proteinogenic α-amino esters...
July 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28737820/effect-of-substrate-concentrations-on-the-aggregation-behavior-and-dynamic-oscillatory-properties-of-self-oscillating-block-copolymers
#4
Ryota Tamate, Takeshi Ueki, Mitsuhiro Shibayama, Ryo Yoshida
We developed a novel type of block copolymer, named the self-oscillating block copolymer, which exhibits autonomous assembly and disassembly driven by the dissipative structures formed by the oscillatory Belousov-Zhabotinsky (BZ) reaction. In a catalyst-free BZ solution, this polymer undergoes autonomous structural changes following the periodic redox changes of a metal catalyst incorporated into the polymer side chain. However, until now, a detailed study of the relationship between the dynamic structural changes and polymer solution conditions has not been conducted...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28737813/the-synthesis-of-cuymnzal1-zox-mixed-oxide-as-a-low-temperature-nh3-scr-catalyst-with-enhanced-catalytic-performance
#5
Qinghua Yan, Sining Chen, Lei Qiu, Yanshan Gao, Dermot O'Hare, Qiang Wang
A new type of low-temperature selective catalytic reduction (SCR) catalyst, CuyMnzAl1-zOx, derived from layered double hydroxides is presented in this contribution. By tuning the Cu/Mn/Al ratio, the optimal catalyst Cu2Mn0.5Al0.5Ox resulted in a NOx conversion of 91.2% at 150 °C, which is much higher than that of all other control catalysts, Cu2AlOx (71.1%), Cu-Mn/γ-Al2O3 (65.23%), and Mn/γ-Al2O3 (59.32%). All samples were characterized in detail using various physico-chemical techniques including XRD, BET, FTIR, TEM, H2-TPR, NH3-TPD, and XPS analyses, and the results revealed that the superior catalytic performance of the Cu2Mn0...
July 24, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28737812/a-dft-mechanistic-study-of-the-organocatalytic-asymmetric-reaction-of-aldehydes-and-homophthalic-anhydride
#6
Cristina Trujillo, Isabel Rozas, Astrid Botte, Stephen J Connon
The first DFT study of the cycloaddition of benzaldehyde with homophthalic anhydride under the influence of a bifunctional organocatalyst is reported. The catalyst first binds and then deprotonates the anhydride, leading to a squaramide-bound enolate, which then adds to the aldehyde with activation of the electrophile by the catalyst's ammonium ion.
July 24, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28737811/extremely-low-catalyst-loading-for-electroless-deposition-on-a-non-conductive-surface-by-a-treatment-for-reduced-graphene-oxide
#7
Jing Zhan, Desmond C L Tan, Swaek Prakitritanon, Ming Lin, Hirotaka Sato
Enhancement of electroless deposition using reduced-graphene-oxide (rGO) coating for a conductive surface on the non-conductive substrate is proposed and demonstrated. We confirmed that the rGO treatment enhanced the Pd catalytic activity and achieved a sufficient rate in electroless deposition with extremely low Pd loading (3.94 × 10(-2) μg cm(-2)).
July 24, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28737794/heterogeneous-enantioselective-synthesis-of-chromans-via-the-oxa-michael-michael-cascade-reaction-synergically-catalyzed-by-grafted-chiral-bases-and-inherent-hydroxyls-on-mesoporous-silica-surface
#8
Shanshan Wang, Jing He, Zhe An
A heterogeneous enantioselective oxa-Michael-Michael reaction for the synthesis of chromans has been developed on a heterogeneous acid-base synergic catalyst with inherent silica as acidic sites and immobilized chiral amines as basic sites. Final products were afforded in selectivity of up to 98% and ee of 97% from 2-nitrovinyl phenol and 3-methyl-2-butenal. The heterogeneous synergistic catalytic mechanism has also been studied.
July 24, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28737405/enhanced-gas-sensitivity-and-sensing-mechanism-of-network-structures-assembled-from-%C3%AE-fe2o3-nanosheets-with-exposed-104-facets
#9
Yong Ma, Juan Yang, Yukun Yuan, Hua Zhao, Qian Shi, Fangjuan Zhang, Cuijin Pei, Bin Liu, Heqing Yang
Network structures assembled from -Fe2O3 nanosheets with exposed {104} facets were successfully prepared by heating Fe(NO3)3 solution containing polyvinyl pyrrolidone (PVP) in air. The -Fe2O3 nanosheets based network structures demonstrate significantly higher response to ethanol and triethylamine than -Fe2O3 sea urchin-like nanostructures and commercial powders. The response to 200 ppb of C2H5OH and 90 ppb of N(C2H5)3 is 1.27 and 1.12, respectively. The excellent sensing performances can be ascribed to the exposed (104) facet terminated with Fe atoms...
July 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28737172/selective-production-of-arenes-via-direct-lignin-upgrading-over-a-niobium-based-catalyst
#10
Yi Shao, Qineng Xia, Lin Dong, Xiaohui Liu, Xue Han, Stewart F Parker, Yongqiang Cheng, Luke L Daemen, Anibal J Ramirez-Cuesta, Sihai Yang, Yanqin Wang
Lignin is the only large-volume renewable source of aromatic chemicals. Efficient depolymerization and deoxygenation of lignin while retaining the aromatic functionality are attractive but extremely challenging. Here we report the selective production of arenes via direct hydrodeoxygenation of organosolv lignin over a porous Ru/Nb2O5 catalyst that enabled the complete removal of the oxygen content from lignin. The conversion of birch lignin to monomer C7-C9 hydrocarbons is nearly quantitative based on its monomer content, with a total mass yield of 35...
July 24, 2017: Nature Communications
https://www.readbyqxmd.com/read/28737170/high-performance-platinum-single-atom-electrocatalyst-for-oxygen-reduction-reaction
#11
Jing Liu, Menggai Jiao, Lanlu Lu, Heather M Barkholtz, Yuping Li, Ying Wang, Luhua Jiang, Zhijian Wu, Di-Jia Liu, Lin Zhuang, Chao Ma, Jie Zeng, Bingsen Zhang, Dangsheng Su, Ping Song, Wei Xing, Weilin Xu, Ying Wang, Zheng Jiang, Gongquan Sun
For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm(-2) at 80 °C with a low platinum loading of 0...
July 24, 2017: Nature Communications
https://www.readbyqxmd.com/read/28737161/linbo-sub-3-sub-surfaces-from-a-microscopic-perspective
#12
Simone Sanna, Wolf Gero Schmidt
A large number of oxides has been investigated in the last twenty years as possible new materials for various applications ranging from opto-electronics to heterogeneous catalysis. In this context, ferroelectric oxides are particularly promising. The electric polarization plays a crucial role at many oxide surfaces, and it largely determines their physical and chemical properties. Ferroelectrics offer in addition the possibility to control/switch the electric polarization and hence the surface chemistry, allowing for the realization of domain-engineered nanoscale devices such as molecular detectors or highly efficient catalysts...
July 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28737030/enantioselective-palladium-catalyzed-conjugate-additions-of-arylboronic-acids-to-form-bis-benzylic-quaternary-stereocenters
#13
Abhishek A Kadam, Arkady Ellern, Levi M Stanley
We report enantioselective, palladium-catalyzed conjugate additions of arylboronic acids to β-aryl, β,β-disubstituted enones to generate ketones containing bis-benzylic quaternary stereocenters. A catalyst generated from palladium trifluoroacetate and (S)-4-tert-butyl-2-(2-pyridyl)oxazoline ligand ((S)-t-BuPyOx) promotes conjugate additions of a wide range of arylboronic acids to a variety of β-aryl, β,β-disubstituted enones. Iterative addition of the arylboronic acid to minimize undesired protodeboronation pathways leads to efficient formation of the corresponding ketones containing bis-benzylic quaternary stereocenters in up to 92% yield and up to 93% enantioselectivity...
July 24, 2017: Organic Letters
https://www.readbyqxmd.com/read/28737023/monodispersed-bioactive-glass-nanoclusters-with-ultralarge-pores-and-intrinsic-exceptionally-high-mirna-loading-for-efficiently-enhancing-bone-regeneration
#14
Yumeng Xue, Yi Guo, Meng Yu, Min Wang, Peter X Ma, Bo Lei
Bioactive glass nanoparticles (BGNs) have attracted much attention in drug delivery and bone tissue regeneration, due to the advantages including biodegradation, high bone-bonding bioactivity, and facile large-scale fabrication. However, the wide biomedical applications of BGNs such as efficient gene delivery are limited due to their poor pore structure and easy aggregation. Herein, for the first time, this study reports novel monodispersed bioactive glass nanoclusters (BGNCs) with ultralarge mesopores (10-30 nm) and excellent miRNA delivery for accelerating critical-sized bone regeneration...
July 24, 2017: Advanced Healthcare Materials
https://www.readbyqxmd.com/read/28737005/atomically-precise-gold-nanoclusters-accelerate-hydrogen-evolution-over-mos2-nanosheets-the-dual-interfacial-effect
#15
Shuo Zhao, Renxi Jin, Yongbo Song, Hui Zhang, Stephen D House, Judith C Yang, Rongchao Jin
Hydrogen generation via electrocatalytic water splitting holds great promise for future energy revolution. It is desirable to design abundant and efficient catalysts and achieve mechanistic understanding of hydrogen evolution reaction (HER). Here, this paper reports a strategy for improving HER performance of molybdenum disulfide (MoS2 ) via introducing gold nanoclusters as a cocatalyst. Compared to plain MoS2 nanosheets, the Au25 (SR)18 /MoS2 nanocomposite exhibits enhanced HER activity with a small onset potential of -0...
July 24, 2017: Small
https://www.readbyqxmd.com/read/28736951/component-customizable-porous-rare-earth-based-colloidal-spheres-towards-highly-effective-catalysts-and-bioimaging-applications
#16
Cheng Chao Li, Xianhong Rui, Weifeng Wei, Libao Chen
Multicomponent porous colloidal spheres are of interest because they not only show a combination of the properties associated with all different components, but also usually present synergy effect. However, combination of different components in a single porous sphere is still greatly challenged due to different precipitation behaviors of each component. In this work, we have developed a general synthetic route to prepare several categories of porous monodisperse RE-based colloidal spheres with customizable elemental compositions and uniform element distribution...
July 23, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28736879/synthesis-of-benzofurans-and-indoles-from-terminal-alkynes-and-iodoaromatics-catalyzed-by-recyclable-palladium-nanoparticles-immobilized-on-siliceous-mesocellular-foam
#17
Jan-E Bäckvall, Alexandre Bruneau, Karl Gustafson, Ning Yuan, Ingmar Persson, Xiaodong Zou, Cheuk-Wai Tai
Herein, we report on the utilization of a heterogeneous catalyst, consisting of Pd nanoparticles supported on a siliceous mesocellular foam (Pd0-AmP-MCF), for the synthesis of heterocycles. Reaction of o-iodophenols and protected o-iodoanilines with acetylenes in the presence of a Pd nanocatalyst produced 2-subsituted benzofurans and indoles, respectively. In general, the catalytic protocol afforded the desired products in good to excellent yields under mild reaction conditions without the addition of ligands...
July 23, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28736581/the-remarkable-amphoteric-nature-of-defective-uio-66-in-catalytic-reactions
#18
Julianna Hajek, Bart Bueken, Michel Waroquier, Dirk De Vos, Veronique Van Speybroeck
One of the major requirements in solid acid and base catalyzed reactions is that the reactants, intermediates or activated complexes cooperate with several functions of catalyst support. In this work the remarkable bifunctional behavior of the defective UiO-66(Zr) metal organic framework is shown for acid-base pair catalysis. The active site relies on the presence of coordinatively unsaturated zirconium sites, which may be tuned by removing framework linkers and by removal of water from the inorganic bricks using a dehydration treatment...
June 22, 2017: ChemCatChem
https://www.readbyqxmd.com/read/28735194/deposition-precipitation-preparation-of-ag-ag3po4-wo3-nanocomposites-for-efficient-visible-light-degradation-of-rhodamine-b-under-strongly-acidic-alkaline-conditions
#19
Qingyong Li, Fulei Wang, Yuxiang Hua, Yuting Luo, Xiaoheng Liu, Guorong Duan, Xujie Yang
A series of novel visible-light-driven Ag/Ag3PO4/WO3 (AAPW) Z-scheme heterostructures were fabricated using a facile deposition-precipitation method followed by photo-reduction without adding any surfactant. To explore more deeply about the photocatalytic activity of AAPW nanocomposites under neutral and strongly acidic/alkaline conditions, we investigated their photocatalytic rhodamine B (RhB) efficiency at different pH value that was controlled by adding HNO3 or NaOH aqueous solution. It was found that as-prepared AAPW photocatalysts showed enhanced photocatalytic RhB efficiency under neutral and even strongly acidic/alkaline environment...
July 6, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28735193/fabrication-of-in2s3-zn2geo4-composite-photocatalyst-for-degradation-of-acetaminophen-under-visible-light
#20
Tao Yan, Tingting Wu, Yaru Zhang, Meng Sun, Xiaodong Wang, Qin Wei, Bin Du
A novel indium trisulfide/zinc germinate (In2S3/Zn2GeO4) composite was developed via a co-precipitation hydrothermal method. The as-prepared composite was characterized in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectroscopy (DRS). Zn2GeO4 nanorods work as the main photocatalyst while In2S3 nanoparticles deposited on them acts as the photosensitizer. The resulting In2S3/Zn2GeO4 heterogeneous photocatalyst not only has enhanced visible light absorption, but also improved photo-generated charge transfer efficiency with remarkably high efficiency in decomposing acetaminophen (APAP)...
June 23, 2017: Journal of Colloid and Interface Science
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