Direct observation of monomer film structure of bacteriochlorophyll <Emphasis Type="Italic">c</Emphasis>

The adsorption and assembling of bacteriochlorophyll c (BChl c) on a highly oriented pyrolytic graphite (HOPG) surface have been investigated by the scanning tunneling microscopy (STM). BChl c molecules are found to self-organize a well-defined adlayer on HOPG surface with a monomeric structure different from the dimer association seen on adlayers of Chls a, c and BChlide c, d. A structural model is proposed for the adlayer.     

First-principles studies of the adsorption of O2 on Al （001）

Oxidationisaubiquitousphenomenonofnature.Theeconomiclossduetooxidationisverylargeeveryyear.Theinvestigationoftheadsorptionofoxygenonthesur-facesofmetalsisofgreatimportanceforbetterunder-standingoftheoxidationmechanismbecauseitistheverybeginningstageofoxidationofmetals.Itisgenerallybe-lievedthattheprocessofO2adsorptiononmetalsisinanorderofO2?O?O-?O2-,andthefollowingstagesareoxidenucleation,growthandtheoxidefilmformation.Astheprocessofadsorptionistooquicktobeobservedbyexperiments,atheoreticals…     

Angular dependent NEXAFS study of the molecular orientation of PTCDA multilayers on Au （111） surface

The molecular orientation of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) multilayers adsorbed on Au (111) surface has been investigated using angular dependent O K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The significant angular dependence of important resonant structures (π* and σ*) reveals that PTCDA molecules adopt an ordered geometry on the substrate surface. The average tilt angle of the PTCDA molecular planes is 27°±10° from the Au (111) surface.     

A Ti–Zr–Cu–Ni–Co–Fe–Al–Sn amorphous filler metal for improving the strength of Ti–6Al–4V alloy brazing joint

Ti_(50)Zr_(27)Cu_8Ni_4Co_3Fe_2Al_3Sn_3(at%) amorphous filler metal with low Cu and Ni contents in a melt-spun ribbon form was developed for improving mechanical properties of Ti–6Al–4V alloy brazing joint through decreasing brittle intermetallics in the braze zone. Investigation on the crystallization behavior of the multicomponent Ti–Zr–Cu–Ni–Co–Fe–Al–Sn amorphous alloy indicates the high stability of the supercooled liquid against crystallization that favors the formation of amorphous structure. The Ti–6Al–4V joint brazed with this Ti-based amorphous filler metal with low total content of Cu and Ni at 1203K for 900s mainly consists of α-Ti, β-Ti,minor Ti–Zr-rich phase and only a small amount of Ti_3Cu intermetallics, leading to the high shear strength of the joint of about 460 MPa. Multicomponent composition design of amorphous alloys is an effective way of tailoring filler metals for improving the joint strength.     

4,5-二氨基-2-硫脲嘧啶膜氯化钠溶液中对铜缓蚀性能的研究

通过自组装方法将4,5-二氨基-2-硫脲嘧啶(MPD)分子吸附在铜(Cu)表面,应用电化学极化、电化学阻抗谱(EIS)和拉曼光谱方法,研究其在质量分数为3.5%的氯化钠(NaCl)溶液中的缓蚀能力.在最佳装配条件下,MPD膜的最大缓蚀效率达到98.1%.拉曼光谱研究表明:MPD分子通过N_9-H_(10)和S_7-H_8吸附在Cu表面上.     

BLim1/2+(m=6、7)团簇的结构及储氢性能的研究

为开发新型储氢材料提供更为丰富的理论基础,采用B3LYP泛函在6-311++G(d,p)基组水平上对BLi₆⁺超碱团簇和BLi₇²⁺超碱土团簇的稳定性结构、电荷分布等方面进行理论研究,进而研究团簇的储氢性能。结果表明：两个离子团簇均比它们所对应的中性团簇均具有较高的动力学稳定性。两个离子团簇中的每个Li原子同时有效吸附2个氢分子,BLi₆⁺团簇中氢分子在团簇表面平均吸附能为0.969~2.162kCal/mol,储氢质量分数达31.56wt%。而BLi₇⁺团簇中氢分子在团簇表面平均吸附能为1.764~3.714kCal/mol,储氢质量分数达32.21wt%。它们的储氢性能表明BLi₆⁺团簇和BLi₇²⁺团簇均有望成为良好的储氢媒介。     

水环境下甲烷在不同润湿性石英表面吸附行为的分子动力学模拟

采用分子动力学模拟方法研究水环境下石英表面润湿性对甲烷在石英狭缝中吸附行为的影响。结果表明:对于亲水性较强的石英表面,水分子优先吸附于石英表面,甲烷分子在狭缝中心发生团聚;而疏水性较强的石英表面,甲烷分子优先吸附于石英表面,水分子在狭缝中心发生团聚;当石英表面为中性润湿时,石英表面对这两种分子没有表现出优先选择性吸附。水、甲烷与不同润湿性石英表面的相互作用能表明,水/固相互作用是水环境下甲烷在石英狭缝中吸附构型改变的主要驱动力。     

Self-assembly of N-3-γ-pyridyl Aza[60]fulleroid on Au(111)

Self-assembled monolayers of novel C₆₀ derivative, N-3-γ-pyridyl Aza[60]fulleroid (C₆₀Py), on Au(111) were studied by a scanning tunneling microscope under ultrahigh vacuum (UHV). C₆₀Py molecules were assembled on Au (111) via pyridyl nitrogen-Au interaction. The sole assembly of C₆₀Py molecules on Au (111) only exhibited randoml aggregation of C₆₀Py even the films were annealed at 50 and 105°C. By co-assembling with benzyl mercaptan (BM), the C₆₀PyBM films showed highly dense aggregation, but C₆₀Py assemblies still had disordered structure. After the co-assembled C₆₀Py-BM films were annealed at 50°C, BM molecules were partially desorbed, but the assembly of C₆₀Py remained without obvious change. After the co-assembled C₆₀Py-BM films were further annealed at 105°C, the C₆₀Py monolayers with ordered structure were obtained, while the BM molecules were nearly thoroughly desorbed from the surface. Here, the BM molecules play a key role as a surfactant in the formation of the ordered C₆₀Py monolayer.     

Structural and magnetic properties of ZnFe2O4 films deposited by low sputtering power

To validate the correctness of the Hartman-Perdok Theory (HPT), which indicates that the {111} planes have the lowest surface energy in spinel ferrites, the {111} plane orientated ZnFe₂O₄ thin films on Si(100), Si(111), and SiO₂(500 nm)/Si(111) substrates were obtained through a radio frequency (RF) magnetron sputtering method with a low sputtering power of 80 W. All of the experiments prove that the atom energy determined by sputtering power plays an important role in the orientated growth of the ZnFe₂O₄ thin films, and it matches well with HPT. The ZnFe₂O₄ thin films exhibit ferromagnetism with a magnetization of 84.25 kJ/mol at room temperature, which is different from the bulk counterpart (antiferromagnetic as usual). The ZnFe₂O₄ thin films can be used as high-quality oriented inducing buffer layers for other spinel (Ni, Mn)Zn ferrite thin films and may have high potential in magnetic thin films-based devices.     

Li3O+超碱团簇的结构及储氢性能的理论研究

采用杂化密度泛函理论(DFT)的B3LYP方法,在6-311++G (d, p)基组水平上对Li₃O ^{0, +}超碱团簇的几何结构和稳定性进行理论计算,并研究了Li₃O⁺团簇的储氢性能。结果表明,Li₃O⁺团簇结构相比中性Li₃O团簇结构的动力学稳定性要高。氢分子在Li₃O⁺团簇表面能以介于物理吸附与化学吸附之间的形式吸附,每个Li原子最多可以有效吸附三个H₂,储氢质量分数可达33.01 wt%。H₂分子在Li₃O⁺团簇表面的平均吸附能范围为1.959~3.591 kCal/mol,该吸附能满足在近室温条件下可逆吸放氢反应的热力学要求。     

Self-assembly of 4-（amyloxy） cinnamic acid on HOPG and its photoinduced transformation： An STM study

With the development of the nanoscience and nanotechnology, scientists try to use single molecule to fabricate electronic device, and the so-called “bot- tom-up” technology was considered to be one of the effective methods, which constructs molecular el…     

Direct observation of monomer film structure of bacteriochlorophyll c

The adsorption and assembling of bacteriochlorophyll c (BChl c) on a highly oriented pyrolytic graphite (HOPG) surface have been investigated by the scanning tunneling microscopy (STM). BChl c molecules are found to self-organize a well-defined adlayer on HOPG surface with a monomeric structure different from the dimer association seen on adlayers of Chls a, c and BChlide c, d. A structural model is proposed for the adlayer.     

H2在催化剂上的吸附行为

研究了氢气在金属体Ni(111)表面的top,bridge,hcp,fcc这4个不同位置吸附能以及4个吸附位中H原子距离下层Ni原子层的垂直距离,可知hcp和fcc这2种空洞位的吸附要稳定些,bridge吸附位是非常不稳定的,容易走向hcp位吸附.各吸附位的吸附能分别是E_ad-top=－11.622 kJ·mol^-1,E_ad-bridge=－12.036 kJ·mol^-1,E_ad-hcp=－12.047 kJ·mol^-1,E_ad-fcc=－12.078 kJ·mol^-1,表明H₂在表面Ni(111)的4种吸附属于化学吸附.表面Pt(111),Rh(111),Ru(111)对具有H₂相似的吸附行为有待进一步的研究.     

Domain structures and copper vacancies in natural low-djurleite (CU1.93S)

Based on HRTEM studies, the domain structure and the copper vacancy model of Dongxiang low-djurleite are discussed. The HRTEM images show: (ⅰ) The domain structures are the intergrowth between djurleit (dj) and digenite (dg) on nm scale. Although there is a transition area which appears as hexagonal-chalcocite-like structure between them, they still follow orientation relationship of (100)_dj//(111)_dg. (ⅱ) 1.56%—3.12% vacancies of Cu are present in low-djurleite. There are 1—2 Cu vacancies averagely in every b₀ /2 of the unit cell. This ratio is coincident to the composition of djurleite (Cu_1.93-1.97S).     

二氧化硅胶体聚合体吸附铀的研究

采用自制的二氧化硅胶体聚合体,进行了pH值、接触时间和铀初始浓度对二氧化硅胶体聚合体吸附铀效果影响试验,结果表明,溶液的pH对二氧化硅胶体聚合体吸附铀的效果影响较大,并且在pH为4时吸附铀的效果达到最佳;二氧化硅胶体聚合体吸附铀的速度快,30 min即可达到吸附平衡;该材料去除铀的效率高,当溶液中铀初始浓度低于10 mg/L时,该材料对铀的去除率大于98%;随着初始铀浓度增加,吸附容量增加,铀的去除率降低;扫描电镜分析结果表明,二氧化硅胶体聚合体表面形貌吸附铀前后变化不大;能谱分析结果表明,1 g吸附剂所吸附铀的质量分数为4.32%,与二氧化硅胶体聚合体从溶液中吸附铀43.0 mg相吻合.     

Structure of self-assembled monolayer of NPAN on Au(111) electrode

Recently, much attention has been paid to the self-assembled monolayers (SAMs) or Langmuir-Blodgett films (LB films) of molecules bearing azobenzene group on the surface. Azobenzene derivatives are attractive ow-ing to their interesting photoresoponsive behavior[1—5]. Azobenzene and its derivatives take both trans (E) and cis (Z) structures with respect to the azo linkage and normally exist in the more stable trans form[6]. Being irradiated with appropriate light, organic molecules and po…     

Microstructural evolutions of Cu(Ni)/AuSn/Ni joints during reflow

Interfacial reactions of the Ni/AuSn/Ni and Cu/AuSn/Ni joints are experimentally studied at 330℃for various reflow times.The microstructures and mechanical properties of the as-solidified solder joints are examined.The as-solidified solder matrix of Ni/AuSn/Ni presents a typical eutecticξ-(Au,Ni)_5Sn+δ-(Au,Ni)Sn lamellar microstructure after reflow at 330℃for 30 s.After reflow for 60 s,a thin and flat(Ni,Au)_3Sn_2 intermetallic compound(IMC) layer is formed,and some needle-like(Ni,Au)_3Sn_2 phases grow f...     

Synthesis of novel chiral bisoxazoline ligands with a spiro[4,4]-1,6-nonadiene skeleton

A new type of chiral bisoxazoline ligands 1 based on spiro[4,4]-1,6-nonadiene backbone was easily prepared in six steps from racemic spiro[4,4]-nonane-1,6-dione, with the Pd-catalyzed coupling of the enol triflates with CO and amino alcohols as the key steps for the construction of the oxazoline moiety. The structure of the ligand (R,S,S)-1b was unambiguously established by X-ray crystallographic analysis. The chiral Cu(II) complex generated in situ from the combination of spiro bisoxazoline ligand (S,S,S)- 1c and Cu(OTf)₂ was effective in the catalysis of asymmetric chlorination of the β-ketoester, methyl 1-oxo-2,3-dihydro-1H- in-dene-2-carboxylate, affording the corresponding chlorinated derivative in 99% yield with 17% ee.     

Growth mechanism of liquid Hg/solid β-HgS metal-semiconductor heterostructures

Density functional theory (DFT) was utilized to simulate the reactions occurred in the mixture solution of cysteine and Hg(II) ions with the ratio < 2. Simulation result shows that Hg ions will coordinate to cysteine by the thiol groups with the form of S–Hg₂ and S–Hg₃, and moreover, the content of free Hg ions can only be reduced by these two forms. OH^? plays an important role in the growth of β-HgS, because its nucleophilic substitution reaction supplies plenty of Hg–S–Hg radicals, which will be adsorbed onto the surface of liquid mercury ball and form the precursor of β-HgS(111) plane. Three valent bonds adsorption of Hg–S–Hg radicals onto the surface of Hg ball has more adsorption energy (?32.768 kcal mol^?1) than that of two valent bond adsorption (?20.882 kcal mol^?1). Hg balls will stop growing after completely covered with Hg–S–Hg radicals and their size will be limited. The growth direction of β-HgS is parallel to the “repelling” force, that is [111] direction in β-HgS lattice. The calculated results are in good agreement with the experimental observations, demonstrating that the DFT method can be taken as a very useful tool to interpret the solution reactions that cannot be solved by conventional methods.     

The influence of the nonmagnetic metal spacer Bi, Ag and Cu on the properties of the multilayer films

When a ferromagnetic (FM)/antiferromagnetic (AFM) bilayer is field-cooled below the Neel temperature (TN) of the AF layer, a unidirectional anisotropy is induced in the FM. Exchange bias is one of the phenomena as- sociated with the exchange anisotorpy cr…