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I. Popov T. Kunze S. Gemming G. Seifert 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):439-446
The preferred adsorption sites and the propensity for a self-organised growth of the molybdenum sulfide cluster Mo6S8 on the Au(111) surface are investigated by density-functional band-structure calculations with pseudopotentials and a plane
wave basis set. The quasi-cubic cluster preferentially adsorbs via a face and remains structurally intact.
It experiences a strong, mostly non-ionic attraction to the surface
at several quasi-isoenergetic adsorption positions. A scan of the potential energy surface exhibits only small barriers between
adjacent strong adsorption sites. Hence, the cluster may move in a potential well with degenerate local energy minima at room
temperature. The analysis of the electronic structure reveals a negligible
electron transfer and S-Au hybridised states, which indicate that the cluster-surface
interaction is dominated by S-Au bonds, with minor contributions from
the Mo atom in the surface vicinity. All results indicate that Mo6S8 clusters
on the Au(111) surface can undergo a template-mediated self-assembly to an ordered inorganic monolayer, which is still redox
active and may be employed as surface-active agent in the integration of noble metal and ionic or biological components within
nano-devices.
Therefore, a classical potential model was developed on the basis of the DFT data,
which allows to study larger cluster assemblies on the Au(111). 相似文献
35.
Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster 下载免费PDF全文
Nathan A. Seifert Dr. Daniel P. Zaleski Dr. Cristóbal Pérez Dr. Justin L. Neill Prof. Brooks H. Pate Montserrat Vallejo‐López Prof. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Fernando Castaño Prof. Isabelle Kleiner 《Angewandte Chemie (International ed. in English)》2014,53(12):3210-3213
Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. 相似文献
36.
Hydrogen Bond Cooperativity and the Three‐Dimensional Structures of Water Nonamers and Decamers 下载免费PDF全文
Dr. Cristóbal Pérez Dr. Daniel P. Zaleski Nathan A. Seifert Dr. Berhane Temelso Prof. George C. Shields Prof. Zbigniew Kisiel Prof. Brooks H. Pate 《Angewandte Chemie (International ed. in English)》2014,53(52):14368-14372
Broadband rotational spectroscopy of water clusters produced in a pulsed molecular jet expansion has been used to determine the oxygen atom geometry in three isomers of the nonamer and two isomers of the decamer. The isomers for each cluster size have the same nominal geometry but differ in the arrangement of their hydrogen bond networks. The nearest neighbor O? O distances show a characteristic pattern for each hydrogen bond network isomer that is caused by three‐body effects that produce cooperative hydrogen bonding. The observed structures are the lowest energy cluster geometries identified by quantum chemistry and the experimental and theoretical O? O distances are in good agreement. The cooperativity effects revealed by the hydrogen bond O? O distance variations are shown to be consistent with a simple model for hydrogen bonding in water that takes into account the cooperative and anticooperative bonding effects of nearby water molecules. 相似文献
37.
Tamar Shamai Yamin Hagit Prihed Moran Madmon Merav Blanca Avi Weissberg 《Journal of mass spectrometry : JMS》2020,55(10)
V‐nerve agents present information‐poor spectra, both in GC‐EI‐MS and LC‐ESI‐MS/MS, with dominant fragments/product ions corresponding to the amine‐containing residue. Hence, derivatives/isomers with the same amine residue exhibit similar mass spectral patterns, leading to ambiguity in the phosphonate structure. We present a simple approach for their structural elucidation based on two complementary experiments: ESI‐MS/MS of the original compound, which provides information about the amine moiety, and ESI‐MS/MS of the phosphonic acid hydrolysis products generated by N‐iodosuccinimide, which provides ions' characteristic of the phosphonate structure. This approach enables the structural elucidation of the original V‐agents with a higher degree of certainty. 相似文献
38.
Fan Xie Nathan A. Seifert Wolfgang Jger Yunjie Xu 《Angewandte Chemie (International ed. in English)》2020,59(36):15703-15710
Chirality recognition in dimers of tetrahydro‐2‐furoic acid (THFA) was studied in a conformer‐specific manner using rotational spectroscopy and theoretical approaches. THFA shows a strong preference for the trans‐ over the cis‐COOH configuration. Two drastically different scenarios are possible for the detectable (THFA)2: a kinetically preferred dimer bound by feeble interactions between two trans THFAs or a thermodynamically favored dimer with a double hydrogen‐bonded ring structure between two cis subunits. To identify the conformers responsible for the extremely dense rotational spectra observed, it was essential not only to locate several hundred homo/heterochiral (THFA)2 minima in ab initio calculations but also to evaluate the energetic connectivities among the minima. The study further reveals an interesting chirality dependent structure–energy ordering relationship. A method for enantiomeric excess (ee) determination of THFA is presented using a recently proposed chiral self‐tag approach. 相似文献
39.
Growth experiments with GaN in the system Ga/HCl/NH3/He or H2 were carried out in a reactor with two deposition zones. The extent of the reaction in the first zone, called the predeposition zone, is controlled by the NH3 flow rate. In the second zone GaN is deposited epitaxially onto sapphire substrates. The variation of the carrier concentration of these epilayers indicates the dominating effect of impurities especially oxygen in opposition to the widely accepted vacancy model. Due to the high incorporation ratio of donor impurities into the solid a predeposition reduces the impurity content in the vapour phase. A reduction of the free carrier concentration in the epitaxial layers could be achieved. Different behaviour in the two carrier gas systems could be established. 相似文献
40.
The fundamentals of the method are described. From applications of this measuring method the following results were obtained: The determination of the diffusion length on glass-plate bevels with evaporated Schottky contacts is frequently quite difficult and sometimes even impossible. Besides a reduction of the diffusion length with increasing microdefect density surprisingly also the opposite behaviour can be found. Comparative PEM and EBIC investigations yield differences between both diffusion lengths (LEBIC < < LPEM) depending on the sample pre-history. 相似文献