Selective attachment of 1,4-benzenedimethanethiol on the copper mediated Si(111)-(7 x 7) surface through S-Cu linkage

The well-defined and patterned copper clusters formed on the Si(111)-(7 x 7) surface have been employed as a template for selective binding of 1,4-benzenedimethanethiol (HS-CH2-C6H4-CH2-SH, 1,4-BDMT), to form ordered molecular nanostructures. Scanning tunneling microscopic (STM) studies showed that each 1,4-BDMT molecule preferentially binds to two neighboring copper atoms within one copper cluster through the S-Cu interaction with its molecular plane parallel to the surface, whereas some 1,4-BDMT bond to individually adsorbed copper atoms, resulting in an upright configuration. Large-scale two-dimensional molecular nanostructures can be obtained using this patterned assembly technique. Our experiments demonstrate the feasibility for controllable growth of ordered molecular nanostructures on the Si(111)-(7 x 7) surface.     

Growth of palladium nanoparticles on nanostructured highly ordered pyrolytic graphite

We report on the growth of palladium nanoparticles on the basal plane of as‐cleaved highly oriented pyrolytic graphite (HOPG) samples, and on CO₂ ion sputtered nanostructured HOPG surfaces. The morphology of Pd nanostructures grown at room temperature is investigated by scanning tunneling microscopy (STM). The STM observations indicate that the morphology of the Pd films is strongly dependent on the HOPG surface. Stabilized Pd particles only form on the sputtered surface, while ramified Pd particles decorate the clean HOPG terraces. The prestructuring of HOPG surface leads to a selective location of particles at the rim of the nanopits generated by the CO₂ ion sputtering and annealing of the surface. The correlation between size, form, density, spatial distribution of the Pd nanoparticles and the quantity of metal added on surface is discussed. We also describe trench channeling of graphite or graphene basal planes by means of Pd nanoparticles in an ambient environment. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of gold nanorod/single-wall carbon nanotube heterojunctions directly on surfaces

This contribution describes the synthesis of gold nanorod (Au NR)/single-wall carbon nanotube (SWCNT) heterojunctions assembled directly on Si/SiOx substrates. SWCNTs are attached to amine-functionalized Si/SiOx substrates, and Au monolayer-protected clusters (MPCs) are adsorbed to the surface of SWCNTs through hydrophobic interactions. Seed-mediated reduction of HAuCl4 with ascorbic acid in the presence of cetyltrimethylammonium bromide (CTAB) onto the Au MPCs leads to the growth of larger Au nanostructures directly on the SWCNTs. Au NRs account for 19% of the nanostructures, some of which are attached directly to the sidewall and some at the ends of the SWCNTs. Raman spectroscopic measurements of SWCNTs before and after growth of the Au nanostructures reveal that the presence of Au leads to an approximately 50-fold enhancement of the Raman scattering signal. Combining 1D nanostructures of different materials (Au and carbon in this example) is of fundamental interest and may find use in nanoelectronics, chemical sensing, electrochemical, and spectroscopy applications.     

Anisotropic polymerization of a long-chain diacetylene derivative Langmuir-Blodgett film on a step-bunched SiO2/Si surface

Alternating facet/terrace nanostructures were fabricated on a SiO2 surface by step-bunching and thermal oxidation of a vicinal Si(111) substrate, and their influence upon the polymerization direction of a long-chain diacetylene derivative monolayer film was investigated by angle-dependent polarized near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. It was found that the peak intensity of the C 1s-pi transition was stronger when the electric vector plane of the incident X-ray was parallel to the direction of the periodic facet/terrace structures rather than perpendicular to them. On the contrary, a polymer film fabricated on a flat SiO2 surface showed no in-plane anisotropy of the peak intensity. These results indicate that the diacetylene groups in the diacetylene derivative monolayer are preferentially photopolymerized in the direction not across but along the periodic one-dimensional structures on the step-bunched and thermally oxidized SiO2/Si(111) surface.     

Surface analysis and electrochemical characterization of palladium–cobalt nanoring formation from molecular precursor, [Et3NH]2[CoPd2(μ‐4‐I‐3,5‐Me2pz)4Cl4], on highly ordered pyrolytic graphite

A Pd₂Co precursor, [Et₃NH]₂[CoPd₂(μ‐4‐I‐3,5‐Me₂pz)₄Cl₄], was used to synthesize palladium–cobalt nanorings and nanoparticles on highly ordered pyrolytic graphite (HOPG) surface. Different types of nanostructures were formed on HOPG surfaces and were controlled by relative humidity (%RH). These structures included Pd₂Co nanorings on HOPG surface by self‐assembly with humidity control. The %RH affects the size and dispersion of the self‐formation of the Pd₂Co rings on HOPG surfaces. The modified HOPG surface with Pd₂Co precursor at 80%RH has rings of similar sizes, while modification at 76%RH gives well‐formed rings and 70%RH with smaller diameters. After thermal reduction of the Pd₂Co precursor on HOPG, bimetallic nanostructures were formed. X‐ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy with energy‐dispersive X‐ray fluorescence spectroscopy techniques were employed to study the composition and morphology of the nanostructures formations on the HOPG surface. Electrochemical characterization of the Pd₂Co nanostructures was performed. Moreover, the bimetallic catalyst has electrocatalytic activity for the oxygen reduction reaction. Copyright © 2013 John Wiley & Sons, Ltd.     

Morphology and modulus evolution of graphite anode in lithium ion battery: An in situ AFM investigation

We investigated the interfacial electrochemical processes on graphite anode of lithium ion battery by using highly oriented pyrolytic graphite(HOPG)as a model system.In situ electrochemical atomic force microscopy experiments were performed in 1M lithium bis(trifluoromethanesulfonyl)imide/ethylene carbonate/diethyl carbonate to reveal the formation process of solid electrolyte interphase(SEI)on HOPG basal plane during potential variation.At 1.45 V,the initial deposition of SEI began at the defects of HOPG surface.After that,direct solvent decomposition took place at about 1.3 V,and the whole surface was covered with SEI.The thickness of SEI was 10.4±0.2 nm after one cycle,and increased to 13.8±0.2 nm in the second cycle,which is due to the insufficient electron blocking ability of the surface film.The Young’s modulus of SEI was measured by a peak force quantitative nanomechanical mapping(QNM).The Young’s modulus of SEI is inhomogeneous.The statistic value is 45±22 MPa,which is in agreement with the organic property of SEI on basal plane of HOPG.     

Adsorption characteristic of self‐assembled corrole dimers on HOPG

Our study first focus on two types of corrole dimers oxidized and reduced forms on highly oriented pyrolytic graphite (HOPG) surface. Scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and contact angle measurement (CAM) were used to investigate the self‐assembled monolayers of corrole dimers adsorbed on HOPG surfaces at room temperature in air. XPS and CAM results have confirmed both two molecules adsorbed on an HOPG surface and formed self‐assembled films, and STM experiments found that the corrole dimers adsorbed on HOPG surfaces form similar lobes. The different stable space structure of the oxidized form molecule (OFM) and reduced form molecule (RFM), led to the diversity of the tetramer structural dimensions. The occurrence of molecular aggregations and assembly was controlled by the interactions between molecular–molecular and molecule–substrate. The electrostatic interactions between the molecules control the geometrical sizes and molecule–substrate interactions determine topographical shapes of the self‐assembled corrole dimers on HOPG surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Optical emission from C60-molecule-coupled Si nanocrystallites

Using C60 molecule as a kind of surface-passivated agent to modify the electronic structure of Si nanocrystallites in porous silicon, we disclose that this kind of C60/nanocrystalline Si coupling system can show a strong blue emission at approximately 460 nm when stored in air for more than one year. After a full characterization of the photoluminescence properties, we propose a luminescent center in the SiOx layer at the surface of a Si nanocrystallite. It is a pair consisting of an oxygen vacancy and an interstitial oxygen. The interstitial oxygen also forms a peroxy linkage with a neighboring lattice oxygen. Radiative recombination of carriers photogenerated from Si nanocrystallite cores in the luminescent centers results in the observed blue photoluminescence. Neutron irradiation experiments support our assignment of the blue emission mechanism. This work improves the understanding of the origin of blue emission from silicon/oxygen-related nanostructured materials.     

硅杂苯与亲二烯体的Diels-Alder反应

采用密度泛函理论(DFT)在B3LYP/6-311G(d,p)水平上研究了硅杂苯与一些亲二烯体的两类可能的Diels-Alder反应的微观机理、势能剖面、取代基效应和溶剂化效应. 计算结果表明, 所研究反应均以协同的方式进行. 亲二烯体分子碳原子上的苯基取代基对两个新键形成的非同步性和反应的活化能垒的影响取决于苯基在产物中的相对位置, 而硅杂苯分子中硅原子上的CCl3取代基有利于杂Diels-Alder反应的进行. 形成一个C—Si键的杂Diels-Alder反应在热力学和动力学上均远比相应的全碳Diels-Alder反应容易进行, 实验观察到的杂Diels-Alder反应中的区域选择性由动力学因素所控制. 硅杂苯与烯烃的反应比与相应炔烃的反应在动力学上容易进行一些, 但在热力学上后者远比前者容易进行. 苯溶剂对所研究反应的势能剖面影响较小.     

Host-guest supramolecular chemistry at solid-liquid interface: An important strategy for preparing two-dimensional functional nanostructures

Supramolecular self-assembly,an important strategy in nanotechnology,has been widely studied in the past two decades.In this review,we have introduced the recent progress on construction of two-dimensional(2D)nanostructures by host-guest supramolecular chemistry at solid-liquid interface,and the interactions between the host assembly and the guest molecules are the major concerns.At first,the hydrogen bonds connected hybrid structures are discussed.And then we have paid a close attention on the surface-confined condensation reactions that has flourished recently in direct preparing novel nanostructures with increasing structural complexity.In the end,the cavity confinement of the 2D supramolecular host-guest architectures has been studied.On the basis of the above-mentioned interactions,a group of functional hybrid structures have been prepared.Notably,scanning tunneling microscopy(STM),a unique technique to probe the surface morphology and information at the single molecule level,has been used to probe the formed structures on highly oriented pyrolytic graphite(HOPG)surface.     

Influence of ultrathin poly-(3,4-ethylenedioxythiophene) (PEDOT) film supports on the electrodeposition and electrocatalytic activity of discrete platinum nanoparticles

Coating a carbon electrode surface, specifically highly oriented pyrolytic graphite (HOPG) with an ultrathin film of poly-(3,4-ethylenedioxythiophene), PEDOT, provides a support on which a high density of uniformly dispersed Pt nanoparticles (NPs) can readily be formed by electrodeposition. The NPs tend to be much smaller, have a higher surface coverage, better dispersion and show a much lower tendency to aggregate, than Pt NPs produced under identical electrochemical conditions on HOPG alone. The electrocatalytic activity of the NPs was investigated for methanol (MeOH) and formic acid (HCOOH) oxidation. Significantly, for similarly prepared particles, Pt NP-PEDOT arrays exhibited higher catalytic activity (in terms of current density, based on the Pt area), towards MeOH oxidation, by an order of magnitude, and towards HCOOH oxidation at high potentials, than Pt NPs supported on native HOPG. These findings can be rationalised in terms of the enhanced oxidation of adsorbed CO, a key reaction intermediate and a catalyst poison. This research provides strong evidence that employing conducting polymers, such as PEDOT, as a support substrate, can greatly improve particular catalytic reactions, allowing for better catalyst utilisation in fuel cell technology.     

Chemoselective On‐surface Homocoupling of Terminal Alkynes Catalyzed by Exogenous Cupric Ions

The on‐surface coupling reactions of terminal alkynes catalyzed by exogenous cupric ions on chemically inert highly oriented pyrolytic graphite (HOPG) surface have been investigated by scanning tunnelling microscopy. In the presence of exogenous cupric ions, diyne‐linked nanostructures generated via homocoupling of terminal alkynes are the exclusive products, whereas no coupling reaction occurs for the terminal alkynes on the surface in the absence of the cupric ions, suggesting that exogenous cupric ions are efficient to catalyze the highly chemoselective on‐surface reaction of terminal alkynes. The HOPG surface displays a template effect to the growth and alignment of the products on the surface. As a result, 2D arrays of diyne‐linked zigzag polymers and 2D diyne‐linked porous polymers are fabricated from ditopic monomer 3,6‐diethynylcarbazole and tritopic monomer 1,3,5‐tris‐(4‐ethynylphenyl) benzene, respectively. This synthetic strategy combining the high selectivity of cupric ion catalyst as well as the template effect of on‐surface synthesis approach could be a general strategy to fabricate diyne‐linked nanostructures and nanomaterials on solid surfaces.     

Influence of ultrathin poly-(3,4-ethylenedioxythiophene) (PEDOT) film supports on the electrodeposition and electrocatalytic activity of discrete platinum nanoparticles

Coating a carbon electrode surface, specifically highly oriented pyrolytic graphite (HOPG) with an ultrathin film of poly-(3,4-ethylenedioxythiophene), PEDOT, provides a support on which a high density of uniformly dispersed Pt nanoparticles (NPs) can readily be formed by electrodeposition. The NPs tend to be much smaller, have a higher surface coverage, better dispersion and show a much lower tendency to aggregate, than Pt NPs produced under identical electrochemical conditions on HOPG alone. The electrocatalytic activity of the NPs was investigated for methanol (MeOH) and formic acid (HCOOH) oxidation. Significantly, for similarly prepared particles, Pt NP-PEDOT arrays exhibited higher catalytic activity (in terms of current density, based on the Pt area), towards MeOH oxidation, by an order of magnitude, and towards HCOOH oxidation at high potentials, than Pt NPs supported on native HOPG. These findings can be rationalised in terms of the enhanced oxidation of adsorbed CO, a key reaction intermediate and a catalyst poison. This research provides strong evidence that employing conducting polymers, such as PEDOT, as a support substrate, can greatly improve particular catalytic reactions, allowing for better catalyst utilisation in fuel cell technology.

     

STM study of the conformation and reaction of long-chain haloalkanes at Si(111)-7 x 7

Scanning tunneling microscopy (STM) has been used to study the adsorption of 1-fluoro-, 1-chloro-, and 1-bromo-substituted C(12) alkanes at the Si(111)-7 x 7 surface, at temperatures from 300 to 500 K. We report self-assembly of these physisorbed adsorbates, C(12)H(25)X, to form approximately circular corrals, (C(12)H(25)X)(2), with charge transfer to a corralled adatom in each case (cf. Dobrin et al. Surf. Sci. 2006, 600, L43). The corrals comprised pairs of semicircular horizontal long-chain molecules stable to approximately 100 degrees C. At > or =150 degrees C, the corrals desorbed or reacted locally to imprint a halogen atom, X-Si, and an adjacent alkane residue, R-Si. The corral height profiles, together with the location of the imprinted X-Si resulting from thermal or electron-induced surface reaction, led to a picture of the molecular configurations in these haloalkane corrals, (C(12)H(25)X)(2), X = F, Cl, Br, and the dichloro corrals, 1,12-dichlorododecane, (ClC(12)H(24)Cl)(2).     

枝状分子表面组装结构的形成与结构转变

本文是对近期有关枝状分子在石墨表面吸附组装研究的综述.利用扫描隧道显微技术,系统研究了5-甲氧基间苯二酸类枝状分子在石墨表面组装结构的形成及结构转变,发现虽然该类枝状分子大都可以在石墨表面自发有序组装,但是最终形成的组装结构不仅与分子本身结构例如烷基链的数目有关,与分子浓度有关,还与所用溶剂有关.分子浓度和溶剂的变化,影响组装体系内的相互作用力如分子与基底间的作用力、分子间氢键的作用力等,影响分子迁移和结构转变的动力学过程,从而影响枝状分子组装的最终结构.研究揭示了特定体系中枝状分子组装结构与分子浓度、所用溶剂的定量和定性关系.研究结果有助于认识和掌握枝状分子组装规律,进而可以通过改变相关技术参数,调控得到不同的枝状分子表面组装体,为实现可控构筑分子表面组装结构提供了新的思路.     

Decoration of Graphitic Surfaces with Sn Nanoparticles through Surface Functionalization Using Diazonium Chemistry

Composites of tin nanoparticles (Sn NP) and graphene are candidate materials for high capacity and mechanically stable negative electrodes in rechargeable Li ion batteries. A uniform dispersion of Sn NP with controlled size is necessary to obtain high electrochemical performance. We show that the nucleation of Sn particles on highly ordered pyrolitic graphite (HOPG) from solution can be controlled by functionalizing the HOPG surface by aryl groups prior to Sn deposition. On the contrary, we observe heterogeneous deposition of micrometer sized Sn islands on HOPG subjected to oxidation prior to deposition in the same conditions. We demonstrate that functional groups act as nucleation sites for Sn NP nucleation, and that homogeneous nucleation of small particles can be achieved by combining surface functionalization with diazonium chemistry and appropriate stabilizers in solution.     

The chemisorption of coronene on Si(001)-2 x 1

Coronene (C24H12) adsorption on the clean Si(001)-2 x 1 surface was investigated by scanning tunneling microscopy and by density-functional calculations. The coronene adsorbed randomly at 25 degrees C on the surface and did not form two-dimensional islands. The scanning tunneling microscopy measurements revealed three adsorption sites for the coronene molecule on the Si(001) surface at low coverage. The major adsorption configuration involves coronene bonding to four underlying Si atoms spaced two lattice spacings apart in a dimer row. The two minor adsorption configurations involve asymmetrical bonding of a coronene molecule between Si dimer rows and form surface species with a mirror plane symmetry to their chiral neighbor species. The two minor bonding arrangements are stabilized by a type-C defect on the Si(001) surface.     

Molybdenum disulfide nanowires and nanoribbons by electrochemical/chemical synthesis

Molybdenum disulfide nanowires and nanoribbons have been synthesized by a two-step, electrochemical/chemical synthetic method. In the first step, MoO(x) wires (a mixture of MoO(2) and MoO(3)) were electrodeposited size-selectively by electrochemical step-edge decoration on a highly oriented pyrolytic graphite (HOPG) surface. Then, MoO(x) precursor wires were converted to MoS(2) by exposure to H(2)S either at 500-700 degrees C, producing "low-temperature" or LT MoS(2) nanowires that were predominantly 2H phase, or above 800 degrees C producing "high-temperature" or HT MoS(2) ribbons that were predominantly 3R phase. The majority of these MoS(2) wires and ribbons were more than 50 microm in length and were organized into parallel arrays containing hundreds of wires or ribbons. MoS(2) nanostructures were characterized by X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, selected area electron diffraction, X-ray diffraction, UV-visible absorption spectrometry, and Raman spectroscopy. HT and LT MoS(2) nanowires were structurally distinct: LT MoS(2) wires were hemicylindrical in shape and nearly identical in diameter to the MoO(x) precursor wires from which they were derived. LT MoS(2) wires were polycrystalline, and the internal structure consisted of many interwoven, multilayer strands of MoS(2); HT MoS(2) ribbons were 50-800 nm in width and 3-100 nm thick, composed of planar crystallites of 3R-MoS(2). These layers grew in van der Waals contact with the HOPG surface so that the c-axis of the 3R-MoS(2) unit cell was oriented perpendicular to the plane of the graphite surface. Arrays of MoS(2) wires and ribbons could be cleanly separated from the HOPG surface and transferred to glass for electrical and optical characterization. Optical absorption measurements of HT MoS(2) nanoribbons reveal a direct gap near 1.95 eV and two exciton peaks, A1 and B1, characteristic of 3R-MoS(2). These exciton peaks shifted to higher energy by up to 80 meV as the wire thickness was decreased to 7 nm (eleven MoS(2) layers). The energy shifts were proportional to 1/ L( parallel)(2), and the effective masses were calculated. Current versus voltage curves for both LT and HT MoS(2) nanostructures were probed as a function of temperature from -33 degrees C to 47 degrees C. Conduction was ohmic and mainly governed by the grain boundaries residing along the wires. The thermal activation barrier was found to be related to the degree of order of the crystallites and can be tuned from 126 meV for LT nanowires to 26 meV for HT nanoribbons.     

基于表面起皱法的梯度图案的可控制备

报道了基于非刻蚀法的表面起皱机制来实现高分子薄膜表面的周期性梯度图案的简单可控制备.即对于处于机械拉伸状态的聚二甲基硅氧烷(PDMS)弹性基底,在其底部垫入"积木",而后对其进行紫外-臭氧(UVO)和氧等离子体(OP)的联合表面处理."积木"的加入引起了表面处理后表面硅氧层(SiOx)梯度厚度的形成,进而当释放拉伸应变后,诱导产生了梯度皱纹图案.结果表明:当UVO与OP联用处理时,不仅实现了较小拉伸应变下梯度皱纹形貌的制备,而且扩大了UVO单独使用时梯度皱纹周期的变化范围.通过OP与UVO的处理顺序和处理时间等因素的简单调节,进一步实现了不同梯度皱纹微结构的精细构筑.     

C60的产生与石墨晶面的关联（I）

Ｃ_（６０）的产生与石墨晶面的关联（Ｉ）谢兆雄，刘朝阳，林逢辰，王春儒，郑兰荪（厦门大学化学系固体表面物理化学国家重点实验室厦门，３６１００５）关键词Ｃ_（６０），激光溅射，石墨晶面Ｓｍａｌｌａｙ等［１］曾以激光在超声分子束喷口的喉道处蒸发石墨得到了Ｃ...