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991.
Test‐Strip‐Based Fluorometric Detection of Fluoride in Aqueous Media with a BODIPY‐Linked Hydrogen‐Bonding Receptor
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Dr. Pichandi Ashokkumar Dr. Hardy Weißhoff Dr. Werner Kraus Dr. Knut Rurack 《Angewandte Chemie (International ed. in English)》2014,53(8):2225-2229
The measurement of biologically relevant anions, such as fluoride, is an important task in analytical chemistry, in particular, for dental health and osteoporosis. Although a large number of fluoride probes are known, the applicability under relevant conditions is limited to a few examples. To improve this situation, BODIPY‐amidothiourea dyes with varying hydrogen‐bond donating strengths were developed, the most H‐acidic of which ( 1 c ) could detect F? from an inorganic source (NaF) in 50 % aqueous solution (DMSO/water 1:1, v/v) with 0.01 ppm sensitivity through selective fluorescence quenching by a photoinduced electron‐transfer (PET) process. Use of the probe and a reference dye with a test‐strip assay and a portable and rapidly recording lateral‐flow fluorescence reader made determination of F? in neat aqueous solutions, such as spiked water samples and toothpaste extracts, possible in a self‐referenced manner, achieving a detection limit of 0.2 ppm. 相似文献
992.
The Direct Synthesis of Hydrogen Peroxide Using Platinum‐Promoted Gold–Palladium Catalysts
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Dr. Jennifer K. Edwards James Pritchard Li Lu Marco Piccinini Greg Shaw Dr. Albert F. Carley David J. Morgan Prof. Christopher J. Kiely Prof. Graham J. Hutchings 《Angewandte Chemie (International ed. in English)》2014,53(9):2381-2384
The direct synthesis of hydrogen peroxide offers a potentially green route to the production of this important commodity chemical. Early studies showed that Pd is a suitable catalyst, but recent work indicated that the addition of Au enhances the activity and selectivity significantly. The addition of a third metal using impregnation as a facile preparation method was thus investigated. The addition of a small amount of Pt to a CeO2‐supported AuPd (weight ratio of 1:1) catalyst significantly enhanced the activity in the direct synthesis of H2O2 and decreased the non‐desired over‐hydrogenation and decomposition reactions. The addition of Pt to the AuPd nanoparticles influenced the surface composition, thus leading to the marked effects that were observed on the catalytic formation of hydrogen peroxide. In addition, an experimental approach that can help to identify the optimal nominal ternary alloy compositions for this reaction is demonstrated. 相似文献
993.
An Efficient RuII–RhIII–RuII Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution
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Dr. Thibaut Stoll Dr. Marcello Gennari Dr. Jérôme Fortage Dr. Carmen E. Castillo Dr. Mateusz Rebarz Dr. Michel Sliwa Dr. Olivier Poizat Dr. Fabrice Odobel Dr. Alain Deronzier Dr. Marie‐Noëlle Collomb 《Angewandte Chemie (International ed. in English)》2014,53(6):1654-1658
The development of multicomponent molecular systems for the photocatalytic reduction of water to hydrogen has experienced considerable growth since the end of the 1970s. Recently, with the aim of improving the efficiency of the catalysis, single‐component photocatalysts have been developed in which the photosensitizer is chemically coupled to the hydrogen‐evolving catalyst in the same molecule through a bridging ligand. Until now, none of these photocatalysts has operated efficiently in pure aqueous solution: a highly desirable medium for energy‐conversion applications. Herein, we introduce a new ruthenium–rhodium polypyridyl complex as the first efficient homogeneous photocatalyst for H2 production in water with turnover numbers of several hundred. This study also demonstrates unambiguously that the catalytic performance of such systems linked through a nonconjugated bridge is significantly improved as compared to that of a mixture of the separate components. 相似文献
994.
Direct Spectroscopic Detection of the Orientation of Free OH Groups in Methyl Lactate–(Water)1,2 Clusters: Hydration of a Chiral Hydroxy Ester
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Javix Thomas Dr. Oleksandr Sukhorukov Prof. Dr. Wolfgang Jäger Prof. Dr. Yunjie Xu 《Angewandte Chemie (International ed. in English)》2014,53(4):1156-1159
Hydration of chiral molecules is a subject of significant current interest in light of recent experimental observations of chirality transfer from chiral solutes to water in solution and the important roles which water plays in biological events. Using a broadband chirped pulse and a cavity based microwave spectrometer, we detected spectroscopic signatures of the mono‐ and dihydrates of methyl lactate, a chiral hydroxy ester. Surprisingly, these small hydration clusters show highly specific binding preferences. Not only do they strongly prefer the insertion H‐bonding topology, but they also favor specific pointing direction(s) for their non‐H‐bonded hydroxy group(s). We observed that the particular dihydrate conformer identified is not the most stable one predicted. This work highlights the superior capability of high‐resolution spectroscopy to identify specific water binding topologies, and provides quantitative data to test state‐of‐the‐art theory. 相似文献
995.
Activation and Retention: A Magnetic Resonance Probe for the Detection of Acute Thrombosis
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Galen S. Loving Prof. Peter Caravan 《Angewandte Chemie (International ed. in English)》2014,53(4):1140-1143
Blood‐clot formation that results in the complete occlusion of a blood vessel (thrombosis) often leads to serious life‐threatening events, such as strokes and heart attacks. As the composition of a thrombus changes as it matures, new imaging methods that are capable of distinguishing new clots from old clots may yield important diagnostic and prognostic information. To address this need, an activatable magnetic resonance (MR) probe that is responsive to a key biochemical process associated with recently formed clots has been developed. 相似文献
996.
Cobalt‐Embedded Nitrogen‐Rich Carbon Nanotubes Efficiently Catalyze Hydrogen Evolution Reaction at All pH Values
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Dr. Xiaoxin Zou Xiaoxi Huang Dr. Anandarup Goswami Dr. Rafael Silva Dr. Bhaskar R. Sathe Eliška Mikmeková Prof. Tewodros Asefa 《Angewandte Chemie (International ed. in English)》2014,53(17):4372-4376
Despite being technically possible, splitting water to generate hydrogen is still practically unfeasible due mainly to the lack of sustainable and efficient catalysts for the half reactions involved. Herein we report the synthesis of cobalt‐embedded nitrogen‐rich carbon nanotubes (NRCNTs) that 1) can efficiently electrocatalyze the hydrogen evolution reaction (HER) with activities close to that of Pt and 2) function well under acidic, neutral or basic media alike, allowing them to be coupled with the best available oxygen‐evolving catalysts—which also play crucial roles in the overall water‐splitting reaction. The materials are synthesized by a simple, easily scalable synthetic route involving thermal treatment of Co2+‐embedded graphitic carbon nitride derived from inexpensive starting materials (dicyandiamide and CoCl2). The materials’ efficient catalytic activity is mainly attributed to their nitrogen dopants and concomitant structural defects. 相似文献
997.
Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles
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Eric J. Popczun Carlos G. Read Christopher W. Roske Prof. Nathan S. Lewis Prof. Raymond E. Schaak 《Angewandte Chemie (International ed. in English)》2014,53(21):5427-5430
Nanoparticles of cobalt phosphide, CoP, have been prepared and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) under strongly acidic conditions (0.50 M H2SO4, pH 0.3). Uniform, multi‐faceted CoP nanoparticles were synthesized by reacting Co nanoparticles with trioctylphosphine. Electrodes comprised of CoP nanoparticles on a Ti support (2 mg cm?2 mass loading) produced a cathodic current density of 20 mA cm?2 at an overpotential of ?85 mV. The CoP/Ti electrodes were stable over 24 h of sustained hydrogen production in 0.50 M H2SO4. The activity was essentially unchanged after 400 cyclic voltammetric sweeps, suggesting long‐term viability under operating conditions. CoP is therefore amongst the most active, acid‐stable, earth‐abundant HER electrocatalysts reported to date. 相似文献
998.
Enzymetically Regulating the Self‐Healing of Protein Hydrogels with High Healing Efficiency
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Dr. Yuzhou Gao Prof. Quan Luo Shanpeng Qiao Liang Wang Prof. Zeyuan Dong Jiayun Xu Prof. Junqiu Liu 《Angewandte Chemie (International ed. in English)》2014,53(35):9343-9346
Enzyme‐mediated self‐healing of dynamic covalent bond‐driven protein hydrogels was realized by the synergy of two enzymes, glucose oxidase (GOX) and catalase (CAT). The reversible covalent attachment of glutaraldehyde to lysine residues of GOX, CAT, and bovine serum albumin (BSA) led to the formation and functionalization of the self‐healing protein hydrogel system. The enzyme‐mediated protein hydrogels exhibit excellent self‐healing properties with 100 % recovery. The self‐healing process was reversible and effective with an external glucose stimulus at room temperature. 相似文献
999.
Back Cover: Surface Polarization Matters: Enhancing the Hydrogen‐Evolution Reaction by Shrinking Pt Shells in Pt–Pd–Graphene Stack Structures (Angew. Chem. Int. Ed. 45/2014)
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1000.
Noble Metals Can Have Different Effects on Photocatalysis Over Metal–Organic Frameworks (MOFs): A Case Study on M/NH2‐MIL‐125(Ti) (M=Pt and Au)
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Dengrong Sun Wenjun Liu Dr. Yanghe Fu Zhenxing Fang Fangxiang Sun Prof. Dr. Xianzhi Fu Prof. Dr. Yongfan Zhang Prof. Dr. Zhaohui Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(16):4780-4788
M‐doped NH2‐MIL‐125(Ti) (M=Pt and Au) were prepared by using the wetness impregnation method followed by a treatment with H2 flow. The resultant samples were characterized by powder X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), X‐ray absorption fine structure (XAFS) analyses, N2‐sorption BET surface area, and UV/Vis diffuse reflectance spectroscopy (DRS). The photocatalytic reaction carried out in saturated CO2 with triethanolamine (TEOA) as sacrificial agent under visible‐light irradiations showed that the noble metal‐doping on NH2‐MIL‐125(Ti) promoted the photocatalytic hydrogen evolution. Unlike that over pure NH2‐MIL‐125(Ti), in which only formate was produced, both hydrogen and formate were formed over Pt‐ and Au‐loaded NH2‐MIL‐125(Ti). However, Pt and Au have different effects on the photocatalytic performance for formate production. Compared with pure NH2‐MIL‐125(Ti), Pt/NH2‐MIL‐125(Ti) showed an enhanced activity for photocatalytic formate formation, whereas Au has a negative effect on this reaction. To elucidate the origin of the different photocatalytic performance, electron spin resonance (ESR) analyses and density functional theory (DFT) calculations were carried out over M/NH2‐MIL‐125(Ti).The photocatalytic mechanisms over M/NH2‐MIL‐125(Ti) (M=Pt and Au) were proposed. For the first time, the hydrogen spillover from the noble metal Pt to the framework of NH2‐MIL‐125(Ti) and its promoting effect on the photocatalytic CO2 reduction is revealed. The elucidation of the mechanism on the photocatalysis over M/NH2‐MIL‐125(Ti) can provide some guidance in the development of new photocatalysts based on MOF materials. This study also demonstrates the potential of using noble metal‐doped MOFs in photocatalytic reactions involving hydrogen as a reactant, like hydrogenation reactions. 相似文献