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141.
142.
In this short letter, we describe the effects of low temperature on the Metal-Enhanced Fluorescence (MEF) phenomenon. Fluorophores
close to Silver Island Films (SiFs) show on average two- to ten-fold enhancements in their fluorescence signatures at room
temperature. However, at 77 K, we have observed that MEF is even more pronounced as compared to an identical glass control
sample. We also demonstrate that the further enhancements in MEF occur at low temperature over a range of visible wavelengths
for different fluorophores, for both SiFs and 20 nm surface deposited gold colloids. 相似文献
143.
Luke Gordon Joel B. Varley John L. Lyons Anderson Janotti Chris G. Van de Walle 《固体物理学:研究快报》2015,9(8):462-465
Achieving high levels of n‐type conductivity in AlN and high Al‐content nitride alloys is a long standing problem; significant decreases in conductivity are observed as the Al content is increased, a phenomenon that has been attributed to donors such as oxygen or silicon forming DX centers. We address this problem through a comprehensive first‐principles hybrid density functional study of potential n‐type dopants, identifying SN and SeN as two elements which are potential shallow donors because they do not undergo a DX transition. In particular, SN is highly promising as an n‐type dopant because it also has a low formation energy and hence a high solubility. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
144.
Mapping of the Photoinduced Electron Traps in TiO2 by Picosecond X‐ray Absorption Spectroscopy
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Dr. M. Hannelore Rittmann‐Frank Dr. Chris J. Milne Dr. Jochen Rittmann Dr. Marco Reinhard Dr. Thomas J. Penfold Prof. Majed Chergui 《Angewandte Chemie (International ed. in English)》2014,53(23):5858-5862
Titanium dioxide (TiO2) is the most popular material for applications in solar‐energy conversion and photocatalysis, both of which rely on the creation, transport, and trapping of charges (holes and electrons). The nature and lifetime of electron traps at room temperature have so far not been elucidated. Herein, we use picosecond X‐ray absorption spectroscopy at the Ti K‐edge and the Ru L3‐edge to address this issue for photoexcited bare and N719‐dye‐sensitized anatase and amorphous TiO2 nanoparticles. Our results show that 100 ps after photoexcitation, the electrons are trapped deep in the defect‐rich surface shell in the case of anatase TiO2, whereas they are inside the bulk in the case of amorphous TiO2. In the case of dye‐sensitized anatase or amorphous TiO2, the electrons are trapped at the outer surface. Only two traps were identified in all cases, with lifetimes in the range of nanoseconds to tens of nanoseconds. 相似文献
145.
Facile Synthesis of Phosphaamidines and Phosphaamidinates using Nitrilium Ions as an Imine Synthon
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Tom van Dijk Dr. Sebastian Burck Mark K. Rong Amos J. Rosenthal Dr. Martin Nieger Dr. J. Chris Slootweg Prof. Dr. Koop Lammertsma 《Angewandte Chemie (International ed. in English)》2014,53(34):9068-9071
Readily accessible nitrilium triflates are convenient imine building blocks for the expedient synthesis of a novel class of 1,3‐P,N ligands as demonstrated for the reaction with primary phosphanes. This procedure allows variation of all substituents. X‐ray crystal structures are reported for nitrilium ions, phosphaamidines, and three phosphaamidinate complexes. The lithium phosphaamidinate is N coordinated and its reaction with [AuCl(tht)] (tht=tetrahydrothiophene) gives a unique P‐bridged gold trimer, while a P,N‐bidentate complex results from [{RhCl(cod)}2]. The nitrilium ion methodology allows extension of the 1,3‐P,N motive to bis(imino)phosphanes, which are the neutral phosphorus analogues of the valuable β‐diketiminate ligand. 相似文献
146.
147.
Willem Jespers Dr. Grégory Verdon Dr. Jhonny Azuaje Dr. Maria Majellaro Dr. Henrik Keränen Prof. Xerardo García-Mera Dr. Miles Congreve Dr. Francesca Deflorian Dr. Chris de Graaf Dr. Andrei Zhukov Dr. Andrew S. Doré Dr. Jonathan S. Mason Prof. Johan Åqvist Dr. Robert M. Cooke Prof. Eddy Sotelo Dr. Hugo Gutiérrez-de-Terán 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16679-16686
We present a robust protocol based on iterations of free energy perturbation (FEP) calculations, chemical synthesis, biophysical mapping and X-ray crystallography to reveal the binding mode of an antagonist series to the A2A adenosine receptor (AR). Eight A2AAR binding site mutations from biophysical mapping experiments were initially analyzed with sidechain FEP simulations, performed on alternate binding modes. The results distinctively supported one binding mode, which was subsequently used to design new chromone derivatives. Their affinities for the A2AAR were experimentally determined and investigated through a cycle of ligand-FEP calculations, validating the binding orientation of the different chemical substituents proposed. Subsequent X-ray crystallography of the A2AAR with a low and a high affinity chromone derivative confirmed the predicted binding orientation. The new molecules and structures here reported were driven by free energy calculations, and provide new insights on antagonist binding to the A2AAR, an emerging target in immuno-oncology. 相似文献
148.
149.
Alan R. Katritzky Dai Cheng Peter Leeming Ion Ghiviriga Chris M. Hartshorn Peter J. Steel 《Journal of heterocyclic chemistry》1996,33(6):1935-1941
N,N-Dimethylaminobenzotriazolylcarbene ( 5 ) reacted with phenyl isocyanate in a [1+2+2] cycloaddition and then with nucleophiles to generate various hydantoins 10 in a one-pot procedure. It was also found that this novel carbene reacted with trans-dibenzoylethylene ( 11 ) in a [1+4] cycloaddition, generating 2-dimethylamino-3-benzoyl-5-phenylfuran ( 13 ) and 2-phenyl-3-[benzotriazol-1-yl]-4-benzoylfuran ( 14 ) whose structures were confirmed by 1H-13C long range correlations as well as the structure of furan 14 being confirmed by X-ray crystallography. 相似文献
150.
Chris Umminger 《电子产品世界》2006,(10):69-71
许多电子系统必须保证不间断的、连续的工作.因此技术员们必须在不关闭电源的情况下向这些"高可用性的"系统中添加新的板卡,或者更换其中报废的及受损的板卡.不过,将板卡从通电的底板抽出,或者插入底板,都会带来问题.底板从本质上来说,往往等效于在板卡边缘连接器和电源的大容量电容间的大电感.如果通电的板卡与周围断开时,底板中会出现环振和高压尖峰.例如,在一个-48V的分布式系统中,拔走一块带电板卡会产生足以损伤连接器接触点的电弧.更糟糕的是,当插入新板卡、电压线刚一接触时,对板卡的大容量电容进行充电的、极大的底板电流会在周围电路上产生有害的瞬态浪涌. 相似文献