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991.
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First-principles study of benzene on noble metal surfaces: Adsorption states and vacuum level shifts
Kenji Toyoda Yosuke Nakano Ikutaro Hamada Kyuho Lee Susumu Yanagisawa Yoshitada Morikawa 《Surface science》2009,603(18):2912-2922
We have studied the interaction of benzene with Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces using density functional theory (DFT) within a generalized gradient approximation (GGA) and the van der Waals density functional [vdW-DF; M. Dion, H. Rydberg, E. Schröder, D.C. Langreth, B.I. Lundqvist, Phys. Rev. Lett. 92 (2004) 246401]. The adsorption energies using vdW-DF are significantly more accurate than those using GGA, while the equilibrium adsorption distances between benzene and metal substrates () calculated by both GGA and vdW-DF are almost identical. The work function changes induced by the adsorption of benzene are significantly underestimated compared with the experimental values, as a result of the overestimation of by both GGA and vdW-DF. Instead of determining the values from first-principles calculations, we deduced the most probable adsorption distances in such a way as to reproduce the experimentally-observed work function changes. The deduced adsorption distance () is shortest on Cu(1 1 1) while it is longest on Ag(1 1 1), reflecting the strength of the interactions between benzene and the metal surfaces. It turns out that the substrate dependence of the work function change is mainly ascribed to the difference in the benzene–metal distance (ZC). Charge transfer and work function changes by the adsorption of benzene were analyzed by means of the induced density of interface states (IDIS) model [H. Vázquez, R. Qszwaldowski, P. Pou, J. Ortega, R. Pérez, F. Flores, A. Kahn, Europhys. Lett. 65 (2004) 802], and compared with the self-consistent GGA calculations. The vacuum level shifts estimated by the IDIS model agree with the GGA results for . On the other hand, the discrepancy between the two methods becomes larger for , where the back donation from the metal substrates to the adsorbate becomes significant. We show that the IDIS model reasonably works well for benzene on Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces because on all surfaces. However, our analysis reveals that the actual charge density redistribution induced by the adsorption of benzene is more complicated than that assumed in the IDIS model. 相似文献
994.
Patrick Nickels Takeji Ueda Zhenghua An Susumu Komiyama 《Infrared Physics & Technology》2009,52(6):438-441
A novel highly sensitive detector for long wavelength infrared radiation, called charge sensitive infrared phototransistor (CSIP), is described, with a stress put on the report of recent improvements in the quantum efficiency. Metallic antenna structure placed on the surface to convert incident radiation has to be optimized. In case of the CSIP, where the absorbing quantum well is very close (~100 nm) to the antenna, near field effects have to be taken into consideration. We consider several patterns based either on a double capacitive (dot) or inductive (hole) grating. We present results of a study comparing four different geometries showing that cross shape hole arrays are most promising candidates reaching efficiencies of almost 8%. Further strategies to optimize essential parameters of antennas by using finite difference time domain (FDTD) simulations are considered. 相似文献
995.
Structural Analysis and Inclusion Mechanism of Native and Permethylated α‐Cyclodextrin‐Based Rotaxanes Containing Alkylene Axles 下载免费PDF全文
Yosuke Akae Dr. Yasuhito Koyama Dr. Hiromitsu Sogawa Dr. Yoshihiro Hayashi Prof. Susumu Kawauchi Prof. Shigeki Kuwata Prof. Toshikazu Takata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5335-5341
Native α‐cyclodextrin‐ (α‐CD) and permethylated α‐CD (PMeCD)‐based rotaxanes with various short alkylene chains as axles can be synthesized through a urea end‐capping method. Native α‐CD tends to form [3]‐ or [5]pseudorotaxanes and not [2]‐ or [4]pseudorotaxanes, which indicates that the coupled CDs act as a single fragment. End‐capping reactions of the pseudorotaxanes with C18 and C24 axle lengths do not occur because the axle termini are covered by the densely stacked CDs. The number of PMeCDs on the pseudorotaxane is flexible and mainly depends on the axle length. Peracetylated α‐CD (PAcCD)‐based rotaxanes are synthesized through O‐acetylation of the α‐CD‐based rotaxanes without any decomposition of the rotaxanated structures. The structures of PMeCD‐based [3]‐ and [4]rotaxanes, and the molecular dynamics calculations on [3]pseudorotaxanes, indicate that the tail face of PMeCDs is regularly directed toward the axle termini. On the basis of the results obtained, it can be concluded that the directions and numbers of CDs in rotaxanes containing short alkylene chains depend on 1) the interactions between CDs, 2) the length of the alkylene axle, and 3) the interactions between the axle end and tail face of the CD. 相似文献
996.
Takahiko Masuda Hideaki Hara Yuki Miyamoto Susumu Kuma Itsuo Nakano Chiaki Ohae Noboru Sasao Minoru Tanaka Satoshi Uetake Akihiro Yoshimi Koji Yoshimura Motohiko Yoshimura 《Hyperfine Interactions》2015,230(1-3):73-77
We recently reported an experiment which focused on demonstrating the macro-coherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 1015 from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect. 相似文献
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We report a new phenomenon of generating X‐rays by fracturing a well‐known material, crystal sugar, in a vacuum. The generated X‐rays had a maximum energy of 250 keV and peak energy of 5 keV. The X‐ray pulses continued for 4 × 10?3 s. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1000.
Kenji Sumida Nirmalya Moitra Julien Reboul Shotaro Fukumoto Kazuki Nakanishi Kazuyoshi Kanamori Shuhei Furukawa Susumu Kitagawa 《Chemical science》2015,6(10):5938-5946
The coordination replication technique is employed for the direct conversion of a macro- and mesoporous Cu(OH)2–polyacrylamide composite to three-dimensional superstructures consisting of the flexible porous coordination polymers, Cu2(bdc)2(MeOH)2 and Cu2(bdc)2(bpy) (bdc2– = 1,4-benzenedicarboxylate, bpy = 4,4′-bipyridine). Detailed characterization of the replicated systems reveals that the structuralization plays an important role in determining the adsorptive properties of the replicated systems, and that the immobilization of the crystals within a higher-order architecture also affects its structural and dynamic properties. The polyacrylamide polymer is also found to be crucial for maintaining the structuralization of the monolithic systems, and in providing the mechanical robustness required for manual handling. In all, the results discussed here demonstrate a significant expansion in the scope of the coordination replication strategy, and further confirms its utility as a highly versatile platform for the preparation of functional three-dimensional superstructures of porous coordination polymers. 相似文献