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从第一性原理出发,利用密度泛函理论研究了SH-C8H16-SH分子和金表面的相互作用,并利用分子前线轨道理论和微扰理论定量地确定了该相互作用能常数,然后,利用弹性散射格林函数方法研究了该分子与金表面形成的分子线的伏-安特性.研究结果表明,当含有硫氢官能团的有机分子化学吸附于金表面时,硫原子将与金原子形成以共价键为主的混和键,此时,扩展的分子轨道使分子线的电导呈现出欧姆特性,而对于局域的分子轨道,电子的输运只能通过隧道效应来实现.对分子线伏-安特性的计算结果显示,在零偏压附近,存在一个电流禁区,随着偏压的增加,分子线的电导呈现出平台特征. 相似文献
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利用密度泛函理论(DFT)总能计算研究了Ni(110)-p2mg(2×1)-CO表面的原子结构和电子态. 计算结果表明: CO分子吸附于该表面的短桥位附近, 分子吸附能为1.753 eV, CO分子的键长dC—O为0.117 nm, 分子与表面竖直方向的夹角为20.0°, 碳原子和短桥位中点的连线与竖直方向的夹角为20.9°; 吸附的CO分子内原子间的伸缩振动频率为1876和1803 cm-1. 态密度研究结果表明吸附作用主要来自CO分子π、σ轨道与衬底d轨道间的杂化作用. CO分子σ轨道和衬底表面镍原子dxz轨道杂化形成的表面电子态主要位于费米能以下-10.4 至-8.8 eV和-7.4至-5.1 eV 范围内. σ和dxz轨道间的杂化作用可能是形成p2mg表面对称性的重要因素之一. 相似文献
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应用带有分子碎片相互作用、分子轨道分析等功能的量子化学程序MOAN及分子动力学模拟软件Materials Studio计算了矿物表面的电子结构及其与巯基类浮选剂的相互作用.确定了矿物相的最可几计算模型,提出了合理的吸附作用模型及浮选剂在矿物表面的吸附排列方式,对其吸附作用机理及吸附剂与矿物表面之间的多种电子转移形式作了合理解释,发现巯基苯并类浮选剂的p-π共轭结构对浮选作用有重要的影响,从理论上确定的矿物表面单位面积内单层饱和吸附分子数与实验值接近.讨论了三种不同共轭效应、诱导效应的官能团取代浮选剂的苯环氢原子,对浮选剂的活性及选择性的影响.本研究将对理解浮选的高捕收性和选择性有着重要的意义,直接指导定向合成新型高效浮选剂,浮选试验结果与理论计算基本一致. 相似文献
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双氰胺是氰胺的二聚体,具有亚氨式和氨式两种互变异构体.将表面增强拉曼光谱(SERS)与密度泛函理论(DFT)结合,研究了互变异构的双氰胺分子在金表面的吸附行为.通过理论计算获得了亚氨式和氨式双氰胺分子的能量、分子轨道和光谱信息,以及双氰胺分子吸附在金簇表面的SERS响应.计算结果表明两种异构化的双氰胺分子都与Au3簇形成较稳定的复合物,并且双氰胺分子中N2原子优先吸附在金簇表面.拉曼实验结果与计算结果较为吻合,进一步说明具有互变异构的双氰胺分子在金基底中共存,并通过N2原子垂直吸附到金表面,符合SERS电磁场增强机制. 相似文献
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硅衬底是很有应用前景的表面。这是因为硅衬底在机械上和化学上的适应性能够抵御水环境和有机环境带来的影响。除此之外,优良的电学性质也是它们成为具有应用前景的表面的原因。目前有许多方法来进行硅表面的巯基化,很多情况下是将具有―SH末端的分子接枝到硅衬底上。但这些方法存在反应时间长的问题。在这篇报导中,我们发展了一种新的硅表面巯基化方法。这种方法可以实现将巯基直接接枝到硅片表面。新方法需要对硅衬底进行氯化和巯基化反应,所需的反应时间缩短。X射线光电子能谱(XPS)和接触角测量被用于研究反应中每个步骤的表面表征。 相似文献
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Britton AJ Weston M Taylor JB Rienzo A Mayor LC O'Shea JN 《The Journal of chemical physics》2011,135(16):164702
The interaction of the dye molecule, N3 (cis-bis(isothiocyanato)bis(2,2(')-bipyridyl-4,4(')-dicarboxylato)-ruthenium(II)), and related ligand molecules with a Au(111) surface has been studied using synchrotron radiation-based electron spectroscopy. Resonant photoemission spectroscopy (RPES) and autoionization of the adsorbed molecules have been used to probe the coupling between the molecules and the substrate. Evidence of charge transfer from the states near the Fermi level of the gold substrate into the lowest unoccupied molecular orbital (LUMO) of the molecules is found in the monolayer RPES spectra of both isonicotinic acid and bi-isonicotinic acid (a ligand of N3), but not for the N3 molecule itself. Calibrated x-ray absorption spectroscopy and valence band spectra of the monolayers reveals that the LUMO crosses the Fermi level of the surface in all cases, showing that charge transfer is energetically possible both from and to the molecule. A core-hole clock analysis of the resonant photoemission reveals a charge transfer time of around 4 fs from the LUMO of the N3 dye molecule to the surface. The lack of charge transfer in the opposite direction is understood in terms of the lack of spatial overlap between the π?-orbitals in the aromatic rings of the bi-isonicotinic acid ligands of N3 and the gold surface. 相似文献
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The geometric and electronic structural properties of symmetric and asymmetric metal cluster-molecule-cluster' complexes have been explored. The metals include Au, Ag, Pd, and Al, and both benzenedithiol and the three isometric forms of dicyanobenzene are included as bridging molecules. Calculated properties such as cluster-molecule interface geometry, electronic state, degree of metal --> molecule charge transfer, metal-molecule mixing in the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy region, the HOMO-LUMO gap, cluster --> cluster' charge transfer as a function of external field strength and direction, and the form of the potential profile across such complexes have been examined. Attempts are made to correlate charge transport with the characteristics of the cluster-complex systems. Indications of rectification in complexes that are asymmetric in the molecule, clusters, and molecule-cluster interfaces are discussed. The results obtained here are only suggestive because of the limitations of the cluster-complex model as it relates to charge transport. 相似文献
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Molecular crystals from thiophene molecules can be doped with TCNQ-F4 molecules for use in all-organic optoelectronic and semiconductor devices. The charge transfer and the molecular orbital energy level formation in between these two organic molecules are investigated here by density functional theory calculations. The isolated molecules are calculated nonbonded and bonded together, forming a charge transfer complex (CTC). The relaxed structure of the complex shows essentially coplanar and centered molecules with the alpha-sexithiophene rings tilted alternatingly by 4.8 degrees. The bond formation of these molecules results in a charge transfer of approximately 0.4 e from the alpha-sexithiophene to the TCNQ-F4 molecule. The highest occupied molecular orbital-lowest unoccupied molecular orbital gap width is reduced as compared to the isolated molecules due to the newly formed orbitals in the CTC. Upon adsorption on a Au(111) surface, electrons are transferred onto the molecule complex, thereby causing the molecular levels to align asymmetric with respect to the charge neutrality level. The theoretical results for the single molecule and CTC layer are compared to experimental photoemission and scanning tunneling spectroscopy results. 相似文献
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Arivazhagan M Prabhakaran S Gayathri R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,82(1):332-339
In this work, the experimental and theoretical vibrational spectra of P-Iodobenzene sulfonyl chloride (P-IBSC) were studied. P-IBSC and its derivatives present in many biologically active compounds. Because of their spectroscopic properties and chemical significance in particular, sulfonyl chloride and its derivatives have been studied extensively by spectroscopic (FTIR and FT-Raman spectra) and theoretical methods. The infrared spectra of these compounds were recorded in condensed states, while the Raman spectra were measured without polarization using both parallel and perpendicular polarizations of scattered light. The molecular geometry, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), first order hyperpolarizability and thermodynamic properties of P-IBSC have been computed with the help of density functional theory (B3LYP) and ab initio (HF) methods with the LanL2DZ basis set. The HOMO and LUMO energy gap explains the charge transfer interactions taking place within the molecule. NBO study explains charge delocalization of the molecule. The contributions of the different modes to each wave number were determined using potential energy distributions (PEDs). The experimental and calculated results were consistent with each other. 相似文献
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Recent efforts to understand the interaction of large aromatic molecules with metal surfaces are discussed. We focus exclusively on work involving the model molecule 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) and the noble metal surfaces of Cu, Ag, and Au. Using this material system as an example, salient features of the (chemical) bond between an extended π-conjugated electron system and a metallic substrate are illustrated. Interface structures are a valuable indicator of the metal–molecule interaction strength. Consistent with the trend observed for small molecule adsorption, they indicate that the interaction strength of PTCDA with the metal substrate decreases in the order Cu–Ag–Au. The interfaces of PTCDA with the Au(1 1 1) and Ag(1 1 1) surfaces have been studied in particular detail. The interaction of Au(1 1 1) with PTCDA is weak, leading to point-on-line coincidence between the lattices of the substrate and the molecular overlayer. Experimental results on this surface are generally consistent with a predominantly physisorptive bonding of PTCDA. The situation is different on Ag surfaces, and in particular on Ag(1 1 1), where clear signs of PTCDA chemisorption are observed in many ensemble averaging and single molecule spectroscopies. Issues of electronic and geometric structure as well as electron–vibron interaction, and their relation to the chemical molecule–substrate interaction, are discussed in detail. 相似文献
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We have studied zinc phthalocyanine (ZnPc) and iron phthalocyanine (FePc) thick films and monolayers on Au(111) using photoelectron spectroscopy and x-ray absorption spectroscopy. Both molecules are adsorbed flat on the surface at monolayer. ZnPc keeps this orientation in all investigated coverages, whereas FePc molecules stand up in the thick film. The stronger inter-molecular interaction of FePc molecules leads to change of orientation, as well as higher conductivity in FePc layer in comparison with ZnPc, which is reflected in thickness-dependent differences in core-level shifts. Work function changes indicate that both molecules donate charge to Au; through the π-system. However, the Fe3d derived lowest unoccupied molecular orbital receives charge from the substrate when forming an interface state at the Fermi level. Thus, the central atom plays an important role in mediating the charge, but the charge transfer as a whole is a balance between the two different charge transfer channels; π-system and the central atom. 相似文献
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Beerbom MM Gargagliano R Schlaf R 《Langmuir : the ACS journal of surfaces and colloids》2005,21(8):3551-3558
The electronic and chemical structure of the interface between the amino acid L-cysteine and Au was determined by photoemission spectroscopy (PES). L-cysteine was deposited by repeatedly dipping Au substrates into solutions of L-cysteine in methanol with various concentrations. To enable repeat deposition without significant contamination, the dipping procedure was performed in a glovebox directly connected to the ultrahigh vacuum (UHV) chamber in a N2 atmosphere. X-ray photoemission spectroscopy (XPS) measurements between deposition steps allowed to characterize the chemical interaction at the interface to be characterized. Ultraviolet photoemission spectroscopy (UPS) measurements yielded the orbital line-up at the interface as well as the highest occupied molecular orbital (HOMO) structure of L-cysteine. The charge injection barrier between the L-cysteine HOMO and the Au Fermi level was found to be 3.0 eV. The interface dipole between the Au substrate and the L-cysteine overlayer was determined to be 1.03 eV. The results also indicate the formation of an interface state approximately 1.5 eV above the HOMO of the L-cysteine. 相似文献
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Nanofriction properties of molecular deposition films 总被引:15,自引:0,他引:15
The nanofriction properties of Au substrate and monolayer molecular deposition film and multilayer molecular deposition films on Au substrate and the molecular deposition films modified with alkyl-terminal molecule have been investigated by using an atomic force microscope. It is concluded that ( i ) the deposition of molecular deposition films on Au substrate and the modification of alkyl-terminal molecule to the molecular deposition films can reduce the frictional force; (ii) the molecular deposition films with the same terminal exhibit similar nanofriction properties, which has nothing to do with the molecular chain-length and the layer number; (iii) the unstable nanofriction properties of molecular deposition films are contributed to the active terminal of the molecular deposition film, which can be eliminated by decorating the active molecular deposition film with alkyl-terminal molecule, moreover, the decoration of alkyl-terminal molecule can lower the frictional force conspicuously; (iv) the relat 相似文献
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Meyer J Wadewitz A Lokamani Toher C Gresser R Leo K Riede M Moresco F Cuniberti G 《Physical chemistry chemical physics : PCCP》2011,13(32):14421-14426
The electronic and geometrical structure of single difluoro-bora-1,3,5,7-tetraphenyl-aza-dipyrromethene (aza-BODIPY) molecules adsorbed on the Au(111) surface is investigated by low temperature scanning tunneling microscopy and spectroscopy in conjunction with ab initio density functional theory simulations of the density of states and of the interaction with the substrate. Our DFT calculations indicate that the aza-bodipy molecule forms a chemical bond with the Au(111) substrate, with distortion of the molecular geometry and significant charge transfer between the molecule and the substrate. Nevertheless, most likely due to the low corrugation of the Au(111) surface, diffusion of the molecule is observed for applied bias in excess of 1 V. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(45):14333-14336
We report that the single‐molecule junction conductance of thiol‐terminated silanes with Ag electrodes are higher than the conductance of those formed with Au electrodes. These results are in contrast to the trends in the metal work function Φ(Ag)<Φ(Au). As such, a better alignment of the Au Fermi level to the molecular orbital of silane that mediates charge transport would be expected. This conductance trend is reversed when we replace the thiols with amines, highlighting the impact of metal–S covalent and metal–NH2 dative bonds in controlling the molecular conductance. Density functional theory calculations elucidate the crucial role of the chemical linkers in determining the level alignment when molecules are attached to different metal contacts. We also demonstrate that conductance of thiol‐terminated silanes with Pt electrodes is lower than the ones formed with Au and Ag electrodes, again in contrast to the trends in the metal work‐functions. 相似文献