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71.
The optical absorption resulting from pulse radiolysis of ice has been studied with subnanosecond resolution. The half-time for electron solvation is ≈ 400 ps at ?5°C. A species with a spectrum similar to that of the “solvated” electron is formed within the 30 ps time resolution of the measurements and decays over several hundred picoseconds. 相似文献
72.
Austin G. Wardrip Amir Mazaheripour Dr. Nina Hüsken Jonah‐Micah Jocson Andrew Bartlett Robert C. Lopez Nathan Frey Cade B. Markegard Dr. Gregor Kladnik Dr. Albano Cossaro Dr. Luca Floreano Dr. Alberto Verdini Dr. Anthony M. Burke Mary N. Dickson Prof. Ioannis Kymissis Prof. Dean Cvetko Prof. Alberto Morgante Prof. Sahar Sharifzadeh Prof. Hung D. Nguyen Prof. Alon A. Gorodetsky 《Angewandte Chemie (International ed. in English)》2016,55(46):14267-14271
Advanced molecular electronic components remain vital for the next generation of miniaturized integrated circuits. Thus, much research effort has been devoted to the discovery of lossless molecular wires, for which the charge transport rate or conductivity is not attenuated with length in the tunneling regime. Herein, we report the synthesis and electrochemical interrogation of DNA‐like molecular wires. We determine that the rate of electron transfer through these constructs is independent of their length and propose a plausible mechanism to explain our findings. The reported approach holds relevance for the development of high‐performance molecular electronic components and the fundamental study of charge transport phenomena in organic semiconductors. 相似文献
73.
Inside Back Cover: Stretch‐Induced Drug Delivery from Superhydrophobic Polymer Composites: Use of Crack Propagation Failure Modes for Controlling Release Rates (Angew. Chem. Int. Ed. 8/2016)
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74.
75.
Recombination of the hydrated electron at high temperature and pressure in hydrogenated alkaline water 总被引:1,自引:0,他引:1
Marin TW Takahashi K Jonah CD Chemerisov SD Bartels DM 《The journal of physical chemistry. A》2007,111(45):11540-11551
Pulse radiolysis experiments were performed on hydrogenated, alkaline water at high temperatures and pressures to obtain rate constants for the reaction of hydrated electrons with hydrogen atoms (H* + e-(aq) --> H(2) + OH-, reaction 1) and the bimolecular reaction of two hydrated electrons (e-(aq) + e-(aq) --> H(2) + 2 OH-, reaction 2). Values for the reaction 1 rate constant, k(1), were obtained from 100 - 325 degrees C, and those for the reaction 2 rate constant, k(2), were obtained from 100 - 250 degrees C, both in increments of 25 degrees C. Both k(1) and k(2) show non-Arrhenius behavior over the entire temperature range studied. k(1) shows a rapid increase with increasing temperature, where k(1) = 9.3 x 10(10) M(-1) s(-1) at 100 degrees C and 1.2 x 10(12) M(-1) s(-1) at 325 degrees C. This behavior is interpreted in terms of a long-range electron-transfer model, and we conclude that e-aq diffusion has a very high activation energy above 150 degrees C. The behavior of k(2) is similar to that previously reported, reaching a maximum value of 5.9 x 10(10) M(-1) s(-1) at 150 degrees C in the presence of 1.5 x 10(-3) m hydroxide. At higher temperatures, the value of k(2) decreases rapidly and above 250 degrees C is too small to measure reliably. We suggest that reaction 2 is a two-step reaction, where the first step is a proton transfer stimulated by the proximity of two hydrated electrons, followed immediately by reaction 1. 相似文献
76.
Jonah W. Jurss Rony S. Khnayzer Julien A. Panetier Karim A. El Roz Eva M. Nichols Martin Head-Gordon Jeffrey R. Long Felix N. Castellano Christopher J. Chang 《Chemical science》2015,6(8):4954-4972
Mononuclear metalloenzymes in nature can function in cooperation with precisely positioned redox-active organic cofactors in order to carry out multielectron catalysis. Inspired by the finely tuned redox management of these bioinorganic systems, we present the design, synthesis, and experimental and theoretical characterization of a homologous series of cobalt complexes bearing redox-active pyrazines. These donor moieties are locked into key positions within a pentadentate ligand scaffold in order to evaluate the effects of positioning redox non-innocent ligands on hydrogen evolution catalysis. Both metal- and ligand-centered redox features are observed in organic as well as aqueous solutions over a range of pH values, and comparison with analogs bearing redox-inactive zinc(ii) allows for assignments of ligand-based redox events. Varying the geometric placement of redox non-innocent pyrazine donors on isostructural pentadentate ligand platforms results in marked effects on observed cobalt-catalyzed proton reduction activity. Electrocatalytic hydrogen evolution from weak acids in acetonitrile solution, under diffusion-limited conditions, reveals that the pyrazine donor of axial isomer 1-Co behaves as an unproductive electron sink, resulting in high overpotentials for proton reduction, whereas the equatorial pyrazine isomer complex 2-Co is significantly more active for hydrogen generation at lower voltages. Addition of a second equatorial pyrazine in complex 3-Co further minimizes overpotentials required for catalysis. The equatorial derivative 2-Co is also superior to its axial 1-Co congener for electrocatalytic and visible-light photocatalytic hydrogen generation in biologically relevant, neutral pH aqueous media. Density functional theory calculations (B3LYP-D2) indicate that the first reduction of catalyst isomers 1-Co, 2-Co, and 3-Co is largely metal-centered while the second reduction occurs at pyrazine. Taken together, the data establish that proper positioning of non-innocent pyrazine ligands on a single cobalt center is indeed critical for promoting efficient hydrogen catalysis in aqueous media, akin to optimally positioned redox-active cofactors in metalloenzymes. In a broader sense, these findings highlight the significance of electronic structure considerations in the design of effective electron–hole reservoirs for multielectron transformations. 相似文献
77.
The thermal neutron moderation analysis facility at the Institute of Experimental Physics, Debrecen, Hungary has been used
to determine the weight percent of total hydrogen content in Nigerian palm oil. The facility utilizes the fast neutron moderation
technique in which the intensity of reflected thermalized neutrons is proportional to the hydrogen content of the sample exposed
to fast neutrons. Using a 100 cm3 sample the total hydrogen content in the oven-dry palm oil sample was found to be 12.0±0.1% within a measuring time of 5
minutes. The method is fast and can be used in plant quality control where the hydrogen content must be determined within
specific limits. 相似文献
78.
Investigation of nanoparticulate silicon as printed layers using scanning electron microscopy,transmission electron microscopy,X‐ray absorption spectroscopy and X‐ray photoelectron spectroscopy
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David M. Unuigbe Margit Harting Emmanuel O. Jonah David T. Britton Dennis Nordlund 《Journal of synchrotron radiation》2017,24(5):1017-1023
The presence of native oxide on the surface of silicon nanoparticles is known to inhibit charge transport on the surfaces. Scanning electron microscopy (SEM) studies reveal that the particles in the printed silicon network have a wide range of sizes and shapes. High‐resolution transmission electron microscopy reveals that the particle surfaces have mainly the (111)‐ and (100)‐oriented planes which stabilizes against further oxidation of the particles. X‐ray absorption spectroscopy (XANES) and X‐ray photoelectron spectroscopy (XPS) measurements at the O 1s‐edge have been utilized to study the oxidation and local atomic structure of printed layers of silicon nanoparticles which were milled for different times. XANES results reveal the presence of the +4 (SiO2) oxidation state which tends towards the +2 (SiO) state for higher milling times. Si 2p XPS results indicate that the surfaces of the silicon nanoparticles in the printed layers are only partially oxidized and that all three sub‐oxide, +1 (Si2O), +2 (SiO) and +3 (Si2O3), states are present. The analysis of the change in the sub‐oxide peaks of the silicon nanoparticles shows the dominance of the +4 state only for lower milling times. 相似文献
79.
Guangping Dong Iredia D. Iyamu Jonah Z. Vilseck Dongxing Chen Rong Huang 《Molecules (Basel, Switzerland)》2022,27(4)
Protein N-terminal methyltransferase 1 (NTMT1) recognizes a unique N-terminal X-P-K/R motif (X represents any amino acid other than D/E) and transfers 1–3 methyl groups to the N-terminal region of its substrates. Guided by the co-crystal structures of NTMT1 in complex with the previously reported peptidomimetic inhibitor DC113, we designed and synthesized a series of new peptidomimetic inhibitors. Through a focused optimization of DC113, we discovered a new cell-potent peptidomimetic inhibitor GD562 (IC50 = 0.93 ± 0.04 µM). GD562 exhibited improved inhibition of the cellular N-terminal methylation levels of both the regulator of chromosome condensation 1 and the oncoprotein SET with an IC50 value of ~50 µM in human colorectal cancer HCT116 cells. Notably, the inhibitory activity of GD562 for the SET protein increased over 6-fold compared with the previously reported cell-potent inhibitor DC541. Furthermore, GD562 also exhibited over 100-fold selectivity for NTMT1 against several other methyltransferases. Thus, this study provides a valuable probe to investigate the biological functions of NTMT1. 相似文献
80.