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Sample records for assembly organic monolayer

  1. Self-Assembled Monolayers of a Multifunctional Organic Radical

    NARCIS (Netherlands)

    Crivillers, Núria; Mas-Torrent, Marta; Perruchas, Sandrine; Roques, Nans; Vidal-Gancedo, José; Veciana, Jaume; Rovira, Concepció; Basabe-Desmonts, Lourdes; Ravoo, Bart Jan; Crego-Calama, Mercedes; Reinhoudt, David N.

    2007-01-01

    A radical switch: Covalent and noncovalent interactions have been used to functionalize silicon oxide surfaces with polychlorotriphenylmethyl radicals, which are electroactive and can be reversibly reduced or oxidized to nonmagnetic and nonfluorescent species. Thus, the self-assembled monolayers beh

  2. Multifunctional Self-Assembled Monolayers for Organic Field-Effect Transistors

    Science.gov (United States)

    Cernetic, Nathan

    Organic field effect transistors (OFETs) have the potential to reach commercialization for a wide variety of applications such as active matrix display circuitry, chemical and biological sensing, radio-frequency identification devices and flexible electronics. In order to be commercially competitive with already at-market amorphous silicon devices, OFETs need to approach similar performance levels. Significant progress has been made in developing high performance organic semiconductors and dielectric materials. Additionally, a common route to improve the performance metric of OFETs is via interface modification at the critical dielectric/semiconductor and electrode/semiconductor interface which often play a significant role in charge transport properties. These metal oxide interfaces are typically modified with rationally designed multifunctional self-assembled monolayers. As means toward improving the performance metrics of OFETs, rationally designed multifunctional self-assembled monolayers are used to explore the relationship between surface energy, SAM order, and SAM dipole on OFET performance. The studies presented within are (1) development of a multifunctional SAM capable of simultaneously modifying dielectric and metal surface while maintaining compatibility with solution processed techniques (2) exploration of the relationship between SAM dipole and anchor group on graphene transistors, and (3) development of self-assembled monolayer field-effect transistor in which the traditional thick organic semiconductor is replaced by a rationally designed self-assembled monolayer semiconductor. The findings presented within represent advancement in the understanding of the influence of self-assembled monolayers on OFETs as well as progress towards rationally designed monolayer transistors.

  3. Photoactive self-assembled monolayers for optically switchable organic thin-film transistors

    OpenAIRE

    Salinas, Michael; Halik, Marcus

    2013-01-01

    We investigate the photoconductive and photovoltaic effects in organic thin-film transistors with thin hybrid dielectrics composed of aluminum oxide and self-assembled monolayers (SAMs). By using SAM molecules with an electro-optical functionality tuning of the photoinduced charge transfer at the interface of semiconductor and SAM upon illumination with laser light can be achieved. Control of the threshold voltage by the SAM composition enables the optical operation of the transistors without...

  4. Organic surfaces exposed by self-assembled organothiol monolayers: Preparation, characterization, and application

    Science.gov (United States)

    Kind, Martin; Wöll, Christof

    2009-07-01

    Organic surfaces play a major role in materials science. Most surfaces that we touch in our daily lives are made from organic materials, e.g., vegetables, fruit, skin, wood, and textiles made from natural fibers. In the context of biology, organic surfaces play a prominent role too, proteins docking onto cell surfaces are a good example. To better understand the characteristics of organic surfaces, including physico-chemical properties like wettability or chemical reactivities and physical properties like friction and lubrication, a structurally well-defined model system that can be investigated with numerous analytical techniques is desirable. In the last two decades, one particular system, self-assembled monolayers or SAMs, have demonstrated their suitability for this purpose. In particular, organothiols consisting of an organic molecule with an attached SH-group are well suited to fabricating structurally well-defined adlayers of monolayer thickness on gold substrates using a simple preparation procedure. These ultrathin monolayers expose an organic surface with properties that can be tailored by varying the type of organothiol employed. After a short introduction into the preparation of SAMs, this article provides an overview of the possibilities and limitations of organic surfaces exposed by Au-thiolate SAMs. Applications are as diverse as the metallization of organic surfaces, a fundamental problem in materials science, and the fabrication of surfaces that resist the adsorption of proteins. In addition to a number of different case studies, we will also discuss the most powerful analytical techniques needed to characterize these important model systems.

  5. Scanning tunneling microscopy study of organic molecules and self-assembled monolayers

    Science.gov (United States)

    Park, Hayn

    In this dissertation I present my findings on alkanethiol self-assembled monolayers (SAM) on Au(111), as well as investigations of the self-assembly and electron transport properties of a custom-synthesized organic molecule (bis-phenyloxazole: BPO) chosen for its interesting physical and electronic structure. Utilizing scanning tunneling microscopy (STM) techniques, we observed unique molecular structures at the boundaries of single-species alkanethiol SAM domains, and propose packing arrangements for the observed structures. We also found evidence for island formation in alkanethiol SAMs; these islands were dynamic and exhibited ordered packing of the adsorbed molecules. For codeposited two-species (dodecanethiol, octanethiol) SAMs, we observed preferential insertion of the longer molecules at domain boundaries, edges, and defect sites, and found that they tended to segregate into separate domains. Scanning tunneling spectroscopy (STS) of the inserted dodecanethiol molecules revealed evidence of conduction resonances within the HOMO-LUMO gap. We explored the charge transport and self-assembly properties of the BPO molecules on a Au(111) surface. The molecules self-assembled into a novel columnar structure after annealing in vacuum. We compare tunneling spectroscopy results to ab initio computations of the molecular orbitals.

  6. Ion-scattering analysis of self-assembled monolayers of silanes on organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, Leszek S., E-mail: leszekw@physics.rutgers.ed [Institute for Advanced Materials and Devices for Nanotechnology, Rutgers University, Piscataway, NJ 08854 (United States); Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States); Katalinic, S.; Lee, B. [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States); Connors, M. [Department of Chemistry, Rutgers University, Piscataway, NJ 08854 (United States); Garfunkel, E. [Institute for Advanced Materials and Devices for Nanotechnology, Rutgers University, Piscataway, NJ 08854 (United States); Department of Chemistry, Rutgers University, Piscataway, NJ 08854 (United States); Feldman, L.C.; Podzorov, V. [Institute for Advanced Materials and Devices for Nanotechnology, Rutgers University, Piscataway, NJ 08854 (United States); Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States)

    2010-06-15

    We describe new Rutherford Backscattering Spectroscopy (RBS) measurements to explore the surface chemistry associated with the growth of self-assembled monolayer (SAM) molecules on conducting organic films. The report includes a description of the optimization of both substrates and RBS scattering parameters to appropriately analyze these novel and damage susceptible structures. Our RBS measurements reveal that the final surface stoichiometry is consistent with a specific model of hydrolyzed and crosslinked trichlorosilanes that form a dense two-dimensional network (a monolayer) at the surface of small-molecule organic semiconductors and a bulk SAM network in the case of conjugated polymer films. Organic semiconductors used in this study are thin films of rubrene (a small molecule semiconductor (C{sub 42}H{sub 28})) and poly(3-hexyl)thiophene (P3HT) (a conjugated polymer (C{sub 10}H{sub 18}S){sub n}). As a substrate we used a thick (1 {mu}m) film of parylene (a non-conjugated polymer (C{sub 8}H{sub 8}){sub n}) deposited on Si (1 0 0) wafers. The SAM molecules used to functionalize the organic semiconductor films are fluoroalkyl trichlorosilane (FTS) (C{sub 8}(H{sub 4}F{sub 13})SiCl{sub 3}) and octyltrichlorosilane (OTS) (C{sub 8}H{sub 17}SiCl{sub 3}). Quantitative detection of medium and small-mass elements, such as O, F, Si, S and residual Cl is demonstrated and used to elucidate the surface chemistry in these novel organic systems.

  7. Room-temperature molecular-resolution characterization of self-assembled organic monolayers on epitaxial graphene.

    Science.gov (United States)

    Wang, Qing Hua; Hersam, Mark C

    2009-06-01

    Graphene, a two-dimensional sheet of carbon atoms, is a promising material for next-generation technology because of its advantageous electronic properties, such as extremely high carrier mobilities. However, chemical functionalization schemes are needed to integrate graphene with the diverse range of materials required for device applications. In this paper, we report self-assembled monolayers of the molecular semiconductor perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) formed on epitaxial graphene grown on the SiC(0001) surface. The molecules possess long-range order with a herringbone arrangement, as shown by ultra-high vacuum scanning tunnelling microscopy at room temperature. The molecular ordering is unperturbed by defects in the epitaxial graphene or atomic steps in the underlying SiC surface. Scanning tunnelling spectra of the PTCDA monolayer show distinct features that are not observed on pristine graphene. The demonstration of robust, uniform organic functionalization of epitaxial graphene presents opportunities for graphene-based molecular electronics and sensors. PMID:21378849

  8. Manipulating the Local Light Emission in Organic Light-Emitting Diodes by using Patterned Self-Assembled Monolayers.

    Science.gov (United States)

    Mathijssen, Simon G J; van Hal, Paul A; van den Biggelaar, Ton J M; Smits, Edsger C P; de Boer, Bert; Kemerink, Martijn; Janssen, René A J; de Leeuw, Dago M

    2008-07-17

    Patterned organic light-emitting diodes are fabricated by using microcontact- printed self-assembled monolayers on a gold anode (see background figure). Molecules with dipole moments in opposite directions result in an increase or a decrease of the local work function (foreground picture), providing a direct handle on charge injection and enabling local modification of the light emission. PMID:25213893

  9. Manipulating the local light emission in organic light-emitting diodes by using patterned self-assembled monolayers

    NARCIS (Netherlands)

    Mathijssen, Simon G. J.; van Hal, Paul A.; van den Biggelaar, Ton J. M.; Smits, Edsger C. P.; de Boer, Bert; Kemerink, Martijn; Janssen, Rene A. J.; de Leeuw, Dago M.

    2008-01-01

    Patterned organic light-emitting diodes are fabricated by using microcontactDrinted self-assembled monolayers on a gold anode (see background figure). Molecules with dipole moments in opposite directions result in an increase or a decrease of the local work function (foreground picture), providing a

  10. Structural investigations of self-assembled monolayers for organic electronics: results from X-ray reflectivity.

    Science.gov (United States)

    Khassanov, Artoem; Steinrück, Hans-Georg; Schmaltz, Thomas; Magerl, Andreas; Halik, Marcus

    2015-07-21

    Self-assembled monolayers (SAMs) have been established as crucial interlayers and electronically active layers in organic electronic devices, such as organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), organic thin film transistors (OTFTs), and nonvolatile memories (NVMs). The use of self-assembling functionalized organic molecules is beneficial due to mainly three advantages compared with common thin film deposition approaches. (1) Molecular self-assembly occurs with surface selectivity, determined by the interaction between the functional anchor group of the organic molecules and the target surface. (2) The film thickness of the resulting layers is perfectly controllable on the angstrom scale, due to the self-terminating film formation to only a single molecular layer. And finally, (3) the wide variability in the chemical structure of such molecules enables different SAM functionalities for devices, ranging from electrical insulation to charge storage to charge transport. The SAM approach can be further expanded by employing several functionalized molecules to create mixed SAMs with consequently mixed properties. The function of SAMs in devices depends not only on the chemical structure of the molecules but also on their final arrangement and orientation on the surface. A reliable and nondestructive in-depth characterization of SAMs on nonconductive oxide surfaces is still challenging because of the very small thickness and the impracticality of methods such as scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In this Account, we illustrate how X-ray reflectivity (XRR) provides analytical access to major questions of SAM composition, morphology, and even formation by means of investigations of pure and mixed SAMs based on phosphonic acids (PAs) of various chain structures on flat alumina (AlOx) surfaces. XRR is an analytical method that provides access to spatially averaged structural depth profiles over a relatively

  11. ADO-phosphonic acid self-assembled monolayer modified dielectrics for organic thin film transistors

    Science.gov (United States)

    Zhefeng, Li; Xianye, Luo

    2014-10-01

    This study explores a strategy of using the phosphonic acid derivative (11-((12-(anthracen-2-yl)dodecyl)oxy)-11-oxoundecyl) phosphonic acid (ADO-phosphonic acid) as self-assembled monolayers (SAMs) on a Si/SiO2 surface to induce the crystallization of rubrene in vacuum deposited thin film transistors, which showed a field-effect mobility as high as 0.18 cm2/(V·s). It is found that ADO-phosphonic acid SAMs play a unique role in modulating the morphology of rubrene to form a crystalline film in the thin-film transistors.

  12. Detection of Volatile Organic Compounds by Self-assembled Monolayer Coated Sensor Array with Concentration-independent Fingerprints

    Science.gov (United States)

    Chang, Ye; Tang, Ning; Qu, Hemi; Liu, Jing; Zhang, Daihua; Zhang, Hao; Pang, Wei; Duan, Xuexin

    2016-04-01

    In this paper, we have modeled and analyzed affinities and kinetics of volatile organic compounds (VOCs) adsorption (and desorption) on various surface chemical groups using multiple self-assembled monolayers (SAMs) functionalized film bulk acoustic resonator (FBAR) array. The high-frequency and micro-scale resonator provides improved sensitivity in the detections of VOCs at trace levels. With the study of affinities and kinetics, three concentration-independent intrinsic parameters (monolayer adsorption capacity, adsorption energy constant and desorption rate) of gas-surface interactions are obtained to contribute to a multi-parameter fingerprint library of VOC analytes. Effects of functional group’s properties on gas-surface interactions are also discussed. The proposed sensor array with concentration-independent fingerprint library shows potential as a portable electronic nose (e-nose) system for VOCs discrimination and gas-sensitive materials selections.

  13. Semiconductor monolayer assemblies with oriented crystal faces

    KAUST Repository

    Ma, Guijun

    2012-01-01

    Fabrication of two-dimensional monolayers of crystalline oxide and oxynitride particles was attempted on glass plate substrates. X-Ray diffraction patterns of the assemblies show only specific crystal facets, indicative of the uniform orientation of the particles on the substrate. The selectivity afforded by this immobilization technique enables the organization of randomly distributed polycrystalline powders in a controlled manner.

  14. Effect of Reactive Self-Assembled Monolayer at the Anode Interface of Organic Light-Emitting Diode.

    Science.gov (United States)

    Ono, Sotaro; Usui, Satoshi; Kim, Seong-Ho; Tanaka, Kuniaki; Advincula, Rigoberto C; Usuil, Hiroaki

    2016-04-01

    Organic light-emitting diodes (OLEDs) were prepared on-indium-tin oxide (ITO) substrates that were modified with various self-assembled monolayers (SAMs) including those which have reactive terminal units. The OLED performance was analyzed in terms of molecular length, dipole moment and HOMO level of SAM molecules estimated by the density functional theory calculation. It was suggested that the current efficiency of OLED is partly improved by controlling the carrier balance, interfacial dipole moment, and electron energy level by SAM modification. More importantly, remarkable improvement in OLED efficiency was achieved by chemically tethering the inorganic/organic interface via benzophenone-terminated SAM. The reactive SAM having benzophenone terminal group can be a promising tool to control the inorganic/organic interface for organic devices. PMID:27451642

  15. Novel self-assembled phosphonic acids monolayers applied in N-channel perylene diimide (PDI) organic field effect transistors

    Science.gov (United States)

    Cheng, Heng; Huai, Jinyue; Cao, Li; Li, Zhefeng

    2016-08-01

    Phosphoric acid (PA) self-assembled monolayers (SAMs) have been developed for applications in organic field-effect transistors (OFETs). This efficient interface modification is helpful for semiconductor layer to form crystal thin film during vapor deposition. Results show that the PDI-i8C based OFETs with PA SAMs exhibit field-effect mobilities up to 0.014 cm2 V-1 s-1 (with ODPA as SAMs), which is over 500 times higher than the device without SAMs. Also, transistors with Naph6PA as SAMs show up to 1.5 × 10-3 cm2 V-1 s-1. By studying the morphology of semiconductor layer and SAMs surface, it is found that ODPA bilayer structure plays a key role in inducing PDI-i8C to form orderly crystal thin film.

  16. Enhancement of fill factor in air-processed inverted organic solar cells using self-assembled monolayer of fullerene catechol

    Science.gov (United States)

    Jeon, Il; Ogumi, Keisuke; Nakagawa, Takafumi; Matsuo, Yutaka

    2016-08-01

    [60]Fullerene catechol self-assembled monolayers were prepared and applied to inverted organic solar cells by an immersion method, and their energy conversion properties were measured. By introducing fullerenes at the surface, we improved the hole-blocking capability of electron-transporting metal oxide, as shown by the fill factor enhancement. The fullerene catechol-treated TiO x -containing device gave a power conversion efficiency (PCE) of 2.81% with a fill factor of 0.56 while the non treated device gave a PCE of 2.46% with a fill factor of 0.49. The solar cell efficiency improved by 13% compared with the non treated reference device.

  17. Seeding Atomic Layer Deposition of High-k Dielectrics on Epitaxial Graphene with Organic Self-assembled Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Alaboson, Justice M. P.; Wang, Qing Hua; Emery, J.D.; Lipson, Albert L; Bedzyk, M.J.; Elam, Jeffrey W.; Pellin, Michael J.; Hersam, Mark C.

    2011-06-28

    The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO₂ and Al₂O₃ on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al₂O₃ and 10 nm HfO₂ dielectric stack show high capacitance values of ~700 nF/cm² and low leakage currents of ~5 × 10{sup –9} A/cm² at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics.

  18. Seeding atomic layer deposition of high-k dielectrics on epitaxial graphene with organic self-assembled monolayers.

    Science.gov (United States)

    Alaboson, Justice M P; Wang, Qing Hua; Emery, Jonathan D; Lipson, Albert L; Bedzyk, Michael J; Elam, Jeffrey W; Pellin, Michael J; Hersam, Mark C

    2011-06-28

    The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO(2) and Al(2)O(3) on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al(2)O(3) and 10 nm HfO(2) dielectric stack show high capacitance values of ∼700 nF/cm(2) and low leakage currents of ∼5 × 10(-9) A/cm(2) at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics. PMID:21553842

  19. Multifunctional self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Zawodzinski, T.; Bar, G.; Rubin, S.; Uribe, F. [Los Alamos National Lab., NM (United States); Ferrais, J. [Texas Univ., Dallas, TX (United States)

    1996-06-01

    This is the final report of at three year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The specific goals of this research project were threefold: to develop multifunctional self-assembled monolayers, to understand the role of monolayer structure on the functioning of such systems, and to apply this knowledge to the development of electrochemical enzyme sensors. An array of molecules that can be used to attach electrochemically active biomolecules to gold surfaces has been synthesized. Several members of a class of electroactive compounds have been characterized and the factors controlling surface modification are beginning to be characterized. Enzymes have been attached to self-assembled molecules arranged on the gold surface, a critical step toward the ultimate goal of this project. Several alternative enzyme attachment strategies to achieve robust enzyme- modified surfaces have been explored. Several means of juxtaposing enzymes and mediators, electroactive compounds through which the enzyme can exchange electrons with the electrode surface, have also been investigated. Finally, the development of sensitive biosensors based on films loaded with nanoscale-supported gold particles that have surface modified with the self-assembled enzyme and mediator have been explored.

  20. Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs)

    OpenAIRE

    Malgorzata Adamkiewicz; David O’Hagan; Georg Hähner

    2014-01-01

    C11-Vinyl-terminated self-assembled monolayers (SAMs) on silica surfaces are successfully modified in C–C bond forming reactions with dihalocarbenes to generate SAMs, terminated with dihalo- (fluoro, chloro, bromo) cyclopropane motifs with about 30% surface coverage.

  1. Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs

    Directory of Open Access Journals (Sweden)

    Malgorzata Adamkiewicz

    2014-12-01

    Full Text Available C11-Vinyl-terminated self-assembled monolayers (SAMs on silica surfaces are successfully modified in C–C bond forming reactions with dihalocarbenes to generate SAMs, terminated with dihalo- (fluoro, chloro, bromo cyclopropane motifs with about 30% surface coverage.

  2. Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs)

    Science.gov (United States)

    Adamkiewicz, Malgorzata

    2014-01-01

    Summary C11-Vinyl-terminated self-assembled monolayers (SAMs) on silica surfaces are successfully modified in C–C bond forming reactions with dihalocarbenes to generate SAMs, terminated with dihalo- (fluoro, chloro, bromo) cyclopropane motifs with about 30% surface coverage. PMID:25550756

  3. Preparation of TiO2 thin film by the LPD method on functionalized organic self-assembled monolayers

    Institute of Scientific and Technical Information of China (English)

    HE ZhongLiang; YU ZhiWei; MIAO HongYan; TAN GuoQiang; LIU Yan

    2009-01-01

    In this paper, uniform titania (TiO2) films have been formed at 50℃ on silanol SAMs by the liquid-phase deposition (LPD) method at a temperature below 100℃. OTS (Octadecyltrichloro-Silane) self-assembled monolayers (SAMs) on glass wafers were used as substrates for the deposition of titanium dioxide thin films. This functionalized organic surface has shown to be effective for promoting the growth of films from titanic aqueous solutions by the LPD method at a low temperature below 10012. The crystal phase composition, microstructure and topography of the as-prepared films were characterized by various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results indicate that the as-prepared thin films are purely crystallized anatase TiO2 constituted by nanorods after being annealed at 500℃. The pH values, concentration of reactants, and deposition temperatures play important roles in the growth of TiO2 thin films.

  4. Improving the Performance of Organic Thin-Film Transistors by Ion Doping of Ethylene-Glycol-Based Self-Assembled Monolayer Hybrid Dielectrics.

    Science.gov (United States)

    Dietrich, Hanno; Scheiner, Simon; Portilla, Luis; Zahn, Dirk; Halik, Marcus

    2015-12-22

    Tuning the electrostatics of ethylene-glycol-based self-assembled monolayers (SAMs) by doping with ions is shown. Molecular dynamics simulations unravel binding mechanisms and predict dipole strengths of the doped layers. Additionally, by applying such layers as dielectrics in organic thin-film transistors, the incorporated ions are proven to enhance device performance by lowering the threshold voltage and increasing conductivity. PMID:26524344

  5. Organic semiconducting thin film growth on an organic substrate: 3,4,9,10-perylenetetracarboxylic dianhydride on a monolayer of decanethiol self-assembled on Au(111)

    International Nuclear Information System (INIS)

    We use surface x-ray diffraction to study the structure of organic-organic heterojunctions grown by organic molecular-beam deposition. In particular, we study films of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) grown on a decanethiol self-assembled monolayer (SAM) on a Au(111) surface. The deposition of several (≅16) monolayers of PTCDA results in unstrained crystalline films whose (012) lattice planes are rotated 21.6 degree sign with respect to the Au azimuthal direction. This alignment, which is different from that of PTCDA on the bare Au(111) surface, is most likely caused by the corrugation of the SAM surface [with the c(4x2) superlattice of the √(3)x√(3)R30 degree sign unit cell]. The SAM structure was found to be unaltered by the presence of the PTCDA overlayer. In addition, the heterogeneous PTCDA/SAM/Au structure, acting as an x-ray interferometer with the SAM as a spacer, allows for the precise determination of the SAM thickness. (c) 2000 The American Physical Society

  6. Self-assembly of amphiphilic janus particles into monolayer capsules for enhanced enzyme catalysis in organic media.

    Science.gov (United States)

    Cao, Wei; Huang, Renliang; Qi, Wei; Su, Rongxin; He, Zhimin

    2015-01-14

    Encapsulation of enzymes during the creation of an emulsion is a simple and efficient route for enhancing enzyme catalysis in organic media. Herein, we report a capsule with a shell comprising a monolayer of silica Janus particles (JPs) (referred to as a monolayer capsule) and a Pickering emulsion for the encapsulation of enzyme molecules for catalysis purposes in organic media using amphiphilic silica JPs as building blocks. We demonstrate that the JP capsules had a monolayer shell consisting of closely packed silica JPs (270 nm). The capsules were on average 5-50 μm in diameter. The stability of the JP capsules (Pickering emulsion) was investigated with the use of homogeneous silica nanoparticles as a control. The results show that the emulsion stabilized via amphiphilic silica JPs presented no obvious changes in physical appearance after 15 days, indicating the high stability of the emulsions and JP capsules. Furthermore, the lipase from Candida sp. was chosen as a model enzyme for encapsulation within the JP capsules during their formation. The catalytic performance of lipase was evaluated according to the esterification of 1-hexanol with hexanoic acid. It was found that the specific activity of the encapsulated enzymes (28.7 U mL(-1)) was more than 5.6 times higher than that of free enzymes in a biphasic system (5.1 U mL(-1)). The enzyme activity was further increased by varying the volume ratio of water to oil and the JPs loadings. The enzyme-loaded capsule also exhibited high stability during the reaction process and good recyclability. In particular, the jellification of agarose in the JP capsules further enhanced their operating stability. We believe that the monolayer structure of the JP capsules, together with their high stability, rendered the capsules to be ideal enzyme carriers and microreactors for enzyme catalysis in organic media because they created a large interfacial area and had low mass transfer resistance through the monolayer shell.

  7. The Self-Assembly of Nano-Objects Code: Applications to supramolecular organic monolayers adsorbed on metal surfaces

    OpenAIRE

    Roussel, Thomas; Vega, Lourdes F.

    2012-01-01

    The Self-Assembly of Nano-Objects (SANO) code we implemented demonstrates the ability to predict the molecular self-assembly of different structural motifs by tuning the molecular building blocks as well as the metallic substrate. It consists in a two-dimensional Grand Canonical Monte-Carlo (GCMC) approach developed to perform atomistic simulations of thousands of large organic molecules self-assembling on metal surfaces. Computing adsorption isotherms at room temperature and spanning over th...

  8. Inside Front Cover: Manipulating the Local Light Emission in Organic Light-Emitting Diodes by using Patterned Self-Assembled Monolayers (Adv. Mater. 14/2008).

    Science.gov (United States)

    Mathijssen, Simon G J; van Hal, Paul A; van den Biggelaar, Ton J M; Smits, Edsger C P; de Boer, Bert; Kemerink, Martijn; Janssen, René A J; de Leeuw, Dago M

    2008-07-17

    The inside cover shows an optical micrograph picture of an organic light-emitting diode with patterned, micro-contact-printed self-assembled monolayers (SAMs) that modify the work function of the anode, reported by Simon Mathijssen, Dago de Leeuw, and co-workers on p. 2703. In this particular light-emitting diode a fluorinated alkanethiol has been used that increases the work function and therefore improves the injection of holes. This results in a higher light emission on the positions where the SAM has been printed, which can be observed as the red pattern. PMID:25213911

  9. Formation of ultrasmooth and highly stable copper surfaces through annealing and self-assembly of organic monolayers.

    Science.gov (United States)

    Platzman, Ilia; Saguy, Cecile; Brener, Reuven; Tannenbaum, Rina; Haick, Hossam

    2010-01-01

    Copper (Cu) has been extensively used as an interconnect material for microelectronic devices because of its high electrical and thermal conductivity and excellent electromigration resistance. However, the formation of relatively rough Cu surfaces ( approximately 5 nm roughness) and Cu-oxide layers upon exposure to air still hinders their reliable application in a wide range of fields. In this article, we show the potential values of highly stable and ultrasmooth polycrystalline bare Cu obtained by simple annealing and chemical modification for a wide range of Cu-based electronic devices. The morphological properties and oxidation behavior of annealed Cu surfaces, before and after coating by self-assembled monolayers of terephthalic acid (TPA), were examined upon exposure to ambient air conditions ( approximately 110 days). Thin films of polycrystalline Cu, deposited on top of an adhesion layer of tantalum nitride (TaN) and annealed for 8 h at 580 degrees C under 2 x 10(-7) Torr, provided ultrasmooth Cu surfaces (R(rms) = 0.15-1.1 nm for fresh samples) and had a stable Cu-oxide layer after 65 days ( approximately 3.5 nm). These observations were perceived to be superior to nonannealed polycrystalline Cu samples. Coating fresh (oxide-free) samples of ultrasmooth Cu with TPA molecules created a closely packed monolayer with a standing-up phase configuration and molecular coverage of approximately 90%. The TPA-coated Cu surface has not shown any detectable oxidation during the first 2 weeks of exposure. The protection efficiency of this layer was found to be superior to those reported earlier on polycrystalline Cu surfaces. The oxidation mechanisms of both annealed and nonannealed Cu surfaces are presented and discussed. PMID:19715329

  10. Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide

    OpenAIRE

    Rabbia, Laurent; Perrut, Vincent; Pons, Patrick; Lellouchi, Djemel

    2009-01-01

    Self-Assembled Monolayers of organic molecules have been successfully deposited onto wafer surface in supercritical carbon dioxide. Deposition method and apparatus are described. The layers are characterized by AFM and water droplet contact angle. Interest of this technique compared to liquid and vapor phase is discussed and studied for surface conversion from hydrophilic to hydrophobic for different materials.

  11. The Self-Assembly of Nano-Objects Code: Applications to supramolecular organic monolayers adsorbed on metal surfaces

    CERN Document Server

    Roussel, Thomas

    2012-01-01

    The Self-Assembly of Nano-Objects (SANO) code we implemented demonstrates the ability to predict the molecular self-assembly of different structural motifs by tuning the molecular building blocks as well as the metallic substrate. It consists in a two-dimensional Grand Canonical Monte-Carlo (GCMC) approach developed to perform atomistic simulations of thousands of large organic molecules self-assembling on metal surfaces. Computing adsorption isotherms at room temperature and spanning over the characteristic sub-micrometric scales, we confront the robustness of the approach with three different well-known systems: ZnPcCl8 on Ag(111), CuPcF16 on Au(111) and PTBC on Ag(111). We retrieve respectively their square, oblique and hexagonal supramolecular tilling. The code incorporates generalized force fields to describe the molecular interactions, which provides transferability and versatility to many organic building blocks and metal surfaces.

  12. Phosphonate self-assembled monolayers as organic linkers in solid-state quantum dot sensetized solar cells

    KAUST Repository

    Ardalan, Pendar

    2010-06-01

    We have employed X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, infrared (IR) spectroscopy, water contact angle (WCA) measurements, ellipsometry, and electrical measurements to study the effects of self-assembled monolayers (SAMs) with phosphonic acid headgroups on the bonding and performance of cadmium sulfide (CdS) solid-state quantum dot sensitized solar cells (QDSSCs). ∼2 to ∼6 nm size CdS quantum dots (QDs) were grown on the SAM-passivated TiO2 surfaces by successive ionic layer adsorption and reaction (SILAR). Our results show differences in the bonding of the CdS QDs at the TiO2 surfaces with a SAM linker. Moreover, our data indicate that presence of a SAM increases the CdS uptake on TiO2 as well as the performance of the resulting devices. Importantly, we observe ∼2 times higher power conversion efficiencies in the devices with a SAM compared to those that lack a SAM. © 2010 IEEE.

  13. Probing the initial stages of molecular organization of oligo(p-phenylenevinylene) assemblies with monolayer protected gold nanoparticles.

    Science.gov (United States)

    Kumar, Vattakattu R Rajeev; Sajini, Vadukumpulli; Sreeprasad, Theruvakkattil S; Praveen, Vakayil K; Ajayaghosh, Ayyappanpillai; Pradeep, Thalappil

    2009-06-01

    Thiol-protected gold nanoparticles (GNPs) have been used to probe the initial stages of the molecular organization of oligo(p-phenylenevinylene) (OPV) gelators. The hybrid materials prepared by the self-assembly of OPVs and GNPs are characterized by optical microscopy, fluorescence microscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. GNPs are located preferentially on the sides of the OPV structures, which implies the presence of alkyl chains at the edges, which makes the assemblies hydrophobic. TEM analyses at the early stages of self-assembly show tapes that have a width of 4 nm, which upon further self-assembly, form fibrils through hydrogen bonding. The experiment was performed with GNPs protected with dodecane and octadecane thiols. The existence of tapes, ribbons, fibrils, and fibers were confirmed by nanoparticle marking. Based on the experimental data, we have proposed a hierarchical model for the self-assembly of OPV molecules. The presence of nanoparticles does not alter the morphology or electronic properties of the OPV structures, as revealed by microscopic and spectroscopic studies. PMID:19462383

  14. Site-selective growth of surface-anchored metal-organic frameworks on self-assembled monolayer patterns prepared by AFM nanografting

    Directory of Open Access Journals (Sweden)

    Tatjana Ladnorg

    2013-10-01

    Full Text Available Surface anchored metal-organic frameworks, SURMOFs, are highly porous materials, which can be grown on modified substrates as highly oriented, crystalline coatings by a quasi-epitaxial layer-by-layer method (liquid-phase epitaxy, or LPE. The chemical termination of the supporting substrate is crucial, because the most convenient method for substrate modification is the formation of a suitable self-assembled monolayer. The choice of a particular SAM also allows for control over the orientation of the SURMOF. Here, we demonstrate for the first time the site-selective growth of the SURMOF HKUST-1 on thiol-based self-assembled monolayers patterned by the nanografting technique, with an atomic force microscope as a structuring tool. Two different approaches were applied: The first one is based on 3-mercaptopropionic acid molecules which are grafted in a 1-decanethiolate SAM, which serves as a matrix for this nanolithography. The second approach uses 16-mercaptohexadecanoic acid, which is grafted in a matrix of an 1-octadecanethiolate SAM. In both cases a site-selective growth of the SURMOF is observed. In the latter case the roughness of the HKUST-1 is found to be significantly higher than for the 1-mercaptopropionic acid. The successful grafting process was verified by time-of-flight secondary ion mass spectrometry and atomic force microscopy. The SURMOF structures grown via LPE were investigated and characterized by atomic force microscopy and Fourier-transform infrared microscopy.

  15. Single photon ionisation of self assembled monolayers

    Science.gov (United States)

    King, B. V.; Savina, M. R.; Tripa, C. E.; Calaway, W. F.; Veryovkin, I. V.; Moore, J. F.; Pellin, M. J.

    2002-05-01

    Self assembled monolayers formed from benzenethiol, diphenylsulphide and diphenyldisulphide have been analysed using secondary ion mass spectrometry (SIMS), sputter neutral mass spectrometry (SNMS) and laser desorption photoionisation mass spectrometry (LDPI). The peak corresponding to the parent ion was much stronger in LDPI than with SIMS or SNMS analysis and fragmentation was lower. A useful yield of order 0.5% was obtained for LDPI from diphenyldisulphide.

  16. Hybrid nanostructures of well-organized arrays of colloidal quantum dots and a self-assembled monolayer of gold nanoparticles for enhanced fluorescence

    Science.gov (United States)

    Liu, Xiaoying; McBride, Sean P.; Jaeger, Heinrich M.; Nealey, Paul F.

    2016-07-01

    Hybrid nanomaterials comprised of well-organized arrays of colloidal semiconductor quantum dots (QDs) in close proximity to metal nanoparticles (NPs) represent an appealing system for high-performance, spectrum-tunable photon sources with controlled photoluminescence. Experimental realization of such materials requires well-defined QD arrays and precisely controlled QD-metal interspacing. This long-standing challenge is tackled through a strategy that synergistically combines lateral confinement and vertical stacking. Lithographically generated nanoscale patterns with tailored surface chemistry confine the QDs into well-organized arrays with high selectivity through chemical pattern directed assembly, while subsequent coating with a monolayer of close-packed Au NPs introduces the plasmonic component for fluorescence enhancement. The results show uniform fluorescence emission in large-area ordered arrays for the fabricated QD structures and demonstrate five-fold fluorescence amplification for red, yellow, and green QDs in the presence of the Au NP monolayer. Encapsulation of QDs with a silica shell is shown to extend the design space for reliable QD/metal coupling with stronger enhancement of 11 times through the tuning of QD-metal spatial separation. This approach provides new opportunities for designing hybrid nanomaterials with tailored array structures and multiple functionalities for applications such as multiplexed optical coding, color display, and quantum transduction.

  17. Hybrid nanostructures of well-organized arrays of colloidal quantum dots and a self-assembled monolayer of gold nanoparticles for enhanced fluorescence

    Science.gov (United States)

    Liu, Xiaoying; McBride, Sean P.; Jaeger, Heinrich M.; Nealey, Paul F.

    2016-07-01

    Hybrid nanomaterials comprised of well-organized arrays of colloidal semiconductor quantum dots (QDs) in close proximity to metal nanoparticles (NPs) represent an appealing system for high-performance, spectrum-tunable photon sources with controlled photoluminescence. Experimental realization of such materials requires well-defined QD arrays and precisely controlled QD–metal interspacing. This long-standing challenge is tackled through a strategy that synergistically combines lateral confinement and vertical stacking. Lithographically generated nanoscale patterns with tailored surface chemistry confine the QDs into well-organized arrays with high selectivity through chemical pattern directed assembly, while subsequent coating with a monolayer of close-packed Au NPs introduces the plasmonic component for fluorescence enhancement. The results show uniform fluorescence emission in large-area ordered arrays for the fabricated QD structures and demonstrate five-fold fluorescence amplification for red, yellow, and green QDs in the presence of the Au NP monolayer. Encapsulation of QDs with a silica shell is shown to extend the design space for reliable QD/metal coupling with stronger enhancement of 11 times through the tuning of QD–metal spatial separation. This approach provides new opportunities for designing hybrid nanomaterials with tailored array structures and multiple functionalities for applications such as multiplexed optical coding, color display, and quantum transduction.

  18. Preparation of TiO2 thin film by the LPD method on functionalized organic self-assembled monolayers

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper, uniform titania (TiO2) films have been formed at 50℃ on silanol SAMs by the liquid-phase deposition (LPD) method at a temperature below 100℃. OTS (Octadecyltrichloro-Silane) selfassembled monolayers (SAMs) on glass wafers were used as substrates for the deposition of titanium dioxide thin films. This functionalized organic surface has shown to be effective for promoting the growth of films from titanic aqueous solutions by the LPD method at a low temperature below 100℃. The crystal phase composition, microstructure and topography of the as-prepared films were characterized by various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results indicate that the as-prepared thin films are purely crystallized anatase TiO2 constituted by nanorods after being annealed at 500℃. The pH values, concentration of reactants, and deposition temperatures play important roles in the growth of TiO2 thin films.

  19. Enhancement of the Luminance Efficiency in Organic Light-Emitting Devices with p-Substituted Phenylphosphonic-Acid Self-Assembled Monolayers.

    Science.gov (United States)

    Kim, Min Sung; Jeon, Young Pyo; Kim, Youngwoo; Noh, Jaegeun; Kim, Tae Whan

    2015-07-01

    Organic light-emitting devices (OLEDs) containing self-assembled monolayers (SAMs) prepared by using p-substituted phenylphosponic acids on indium-tin-oxide electrodes were fabricated and examined to understand the substituent effect of the SAMs on the device performance. OLEDs modified by using (4-methoxyphenyl)phosphonic acid (MOPPA) SAMs or (4-chlorophenyl)phosphonic acid (CPPA) SAMs, both with electron withdrawing groups, had enhanced hole injection, reduced operating voltage, and remarkably increased current density and luminance efficiency compared with those without SAMs. The luminance efficiency which was the ratio of luminous flux to power for OLEDs containing CPPA SAMs and that for the OLEDs containing MOPPA SAMs were enhanced 2.2 and 1.9 times, respectively, in comparison with that of OLEDs without SAMs. CPPA SAMs significantly reduced the operating voltage of OLED by 24.8% compared with OLEDs without SAMs. PMID:26373078

  20. Topographies of Organized Monolayer of α-Amylase Observed by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, a-amylase organized monolayer was assembled on the surface of the PET-CO2- substrate in different conditions. The different topography of the a-amylase/PET monolayer was obtained by AFM in tapping mode.

  1. STM visualisation of counterions and the effect of charges on self-assembled monolayers of macrocycles

    Directory of Open Access Journals (Sweden)

    Tibor Kudernac

    2011-10-01

    Full Text Available Despite their importance in self-assembly processes, the influence of charged counterions on the geometry of self-assembled organic monolayers and their direct localisation within the monolayers has been given little attention. Recently, various examples of self-assembled monolayers composed of charged molecules on surfaces have been reported, but no effort has been made to prove the presence of counterions within the monolayer. Here we show that visualisation and exact localisation of counterions within self-assembled monolayers can be achieved with scanning tunnelling microscopy (STM. The presence of charges on the studied shape-persistent macrocycles is shown to have a profound effect on the self-assembly process at the liquid–solid interface. Furthermore, preferential adsorption was observed for the uncharged analogue of the macrocycle on a surface.

  2. Patterning Self-Assembled Monolayers on Gold: Green Materials Chemistry in the Teaching Laboratory

    Science.gov (United States)

    McFarland, Adam D.; Huffman, Lauren M.; Parent, Kathryn, E.; Hutchison, James E.; Thompson, John E.

    2004-01-01

    An experiment demonstrating self-assembled monolayer (SAM) chemistry, organic thin-film patterning and the use of molecular functionality to control macroscopic properties is described. Several important green chemistry principles are introduced.

  3. Electrochemical stability of self-assembled monolayers on gold

    NARCIS (Netherlands)

    Beulen, Marcel W.J.; Kastenberg, Miryam I.; Veggel, van Frank C.J.M.; Reinhoudt, David N.

    1998-01-01

    Most applications of functionalized self-assembled monolayers (SAMs) are based on changes in electrochemical properties. Such applications require electrochemical stability. This study reveals that there is only a limited potential window from -0.8 to +0.4 VMSE where self-assembled monolayers of sul

  4. Solution processed self-assembled monolayer gate dielectrics for low-voltage organic transistors. : Section Title: Electric Phenomena

    NARCIS (Netherlands)

    Ball, James; Wobkenberg, Paul H.; Colleaux, Florian; Kooistra, Floris B.; Hummelen, Jan C.; Bradley, Donal D. C.; Anthopoulos, Thomas D.

    2008-01-01

    Low-voltage org. transistors are sought for implementation in high vol. low-power portable electronics of the future. Here we assess the suitability of three phosphonic acid based self-assembling mols. for use as ultra-thin gate dielecs. in low-voltage soln. processable org. field-effect transistors

  5. Electronic properties of organic monolayers and molecular devices

    Indian Academy of Sciences (India)

    D Vuillaume; S Lenfant; D Guerin; C Delerue; C Petit; G Salace

    2006-07-01

    We review some of our recent experimental results on charge transport in organic nanostructures such as self-assembled monolayer and monolayers of organic semiconductors. We describe a molecular rectifying junction made from a sequential self-assembly on silicon. These devices exhibit a marked current–voltage rectification behavior due to resonant transport between the Si conduction band and the molecule highest occupied molecular orbital of the molecule. We discuss the role of metal Fermi level pinning in the current–voltage behavior of these molecular junctions. We also discuss some recent insights on the inelastic electron tunneling behavior of Si/alkyl chain/metal junctions.

  6. Manipulating the Local Light Emission in Organic Light-Emitting Diodes by using Patterned Self-Assembled Monolayers

    NARCIS (Netherlands)

    Mathijssen, S.G.J.; Hal, P.A. van; Biggelaar, T.J.M. van den; Smits, E.C.P.; Boer, B. de; Kemerink, M.; Janssen, R.A.J.; Leeuw, D.M. de

    2008-01-01

    In organic light-emitting diodes (OLEDs), interface dipoles play an important role in the process of charge injection from the metallic electrode into the active organic layer.[1,2] An oriented dipole layer changes the effective work function of the electrode because of its internal electric field.

  7. Applications of self-assembled monolayers in materials chemistry

    Indian Academy of Sciences (India)

    Nirmalya K Chaki; M Aslam; Jadab Sharma; K Vijayamohanan

    2001-10-01

    Self-assembly provides a simple route to organise suitable organic molecules on noble metal and selected nanocluster surfaces by using monolayers of long chain organic molecules with various functionalities like -SH, -COOH, -NH2, silanes etc. These surfaces can be effectively used to build-up interesting nano level architectures. Flexibility with respect to the terminal functionalities of the organic molecules allows the control of the hydrophobicity or hydrophilicity of metal surface, while the selection of length scale can be used to tune the distant-dependent electron transfer behaviour. Organo-inorganic materials tailored in this fashion are extremely important in nanotechnology to construct nanoelctronic devices, sensor arrays, supercapacitors, catalysts, rechargeable power sources etc. by virtue of their size and shape-dependent electrical, optical or magnetic properties. The interesting applications of monolayers and monolayer-protected clusters in materials chemistry are discussed using recent examples of size and shape control of the properties of several metallic and semiconducting nanoparticles. The potential benefits of using these nanostructured systems for molecular electronic components are illustrated using Au and Ag nanoclusters with suitable bifunctional SAMs.

  8. Crossbar nanoarchitectonics of the crosslinked self-assembled monolayer

    OpenAIRE

    Hamoudi, Hicham

    2014-01-01

    A bottom-up approach was devised to build a crossbar device using the crosslinked SAM of the 5,5′-bis (mercaptomethyl)-2,2′-bipyridine-Ni2+ (BPD- Ni2+) on a gold surface. To avoid metal diffusion through the organic film, the author used (i) nanoscale bottom electrodes to reduce the probability of defects on the bottom electrodes and (ii) molecular crosslinked technology to avoid metal diffusion through the SAMs. The properties of the crosslinked self-assembled monolayer were determined by XP...

  9. Tunnel magnetoresistance in Self-Assembled Monolayers Based Tunnel Junctions

    Science.gov (United States)

    Mattana, Richard; Barraud, Clément; Tatay, Sergio; Galbiati, Marta; Seneor, Pierre; Bouzehouane, Karim; Jacquet, Eric; Deranlot, Cyrile; Fert, Albert; Petroff, Frédéric

    2012-02-01

    Organic/molecular spintronics is a rising research field at the frontier between spintronics and organic chemistry. Organic molecule and semiconductors were first seen as promising for spintronics devices due to their expected long spin lifetime. But an exciting challenge has also been to find opportunities arising from chemistry to develop new spintronics functionalities. It was shown that the molecular structure and the ferromagnetic metal/molecule hybridization can strongly influence interfacial spin properties going from spin polarization enhancement to its sign control in spintronics devices. In this scenario, while scarcely studied, self-assembled monolayers (SAMs) are expected to become perfect toy barriers to further test these tailoring properties in molecular magnetic tunnel junctions (MTJs). Due to its very high spin polarization and air stability LSMO has positioned itself as the electrode of choice in most of the organic spintronics devices. We will present a missing building block for molecular spintronics tailoring: the grafting and film characterization of organic monofunctionalized long alkane chains over LSMO. We have obtained 35% of magnetoresistance in LSMO/SAMs/Co MTJs. We will discuss the unusual behaviour of the bias voltage dependence of the TMR.

  10. Assembly of citrate gold nanoparticles on hydrophilic monolayers

    Science.gov (United States)

    Vikholm-Lundin, Inger; Rosqvist, Emil; Ihalainen, Petri; Munter, Tony; Honkimaa, Anni; Marjomäki, Varpu; Albers, Willem M.; Peltonen, Jouko

    2016-08-01

    Self-assembled monolayers (SAMs) as model surfaces were linked onto planar gold films thorough lipoic acid or disulfide groups. The molecules used were polyethylene glycol (EG-S-S), N-[tris-(hydroxymethyl)methyl]acrylamide polymers with and without lipoic acid (Lipa-pTHMMAA and pTHMMAA) and a lipoic acid triazine derivative (Lipa-MF). All the layers, but Lipa-MF with a primary amino group were hydroxyl terminated. The layers were characterized by contact angle measurements and atomic force microscopy, AFM. Citrate stabilized nanoparticles, AuNPs in water and phosphate buffer were allowed to assemble on the layers for 10 min and the binding was followed in real-time with surface plasmon resonance, SPR. The SPR resonance curves were observed to shift to higher angles and become increasingly damped, while also the peaks strongly broaden when large nanoparticles assembled on the surface. Both the angular shift and the damping of the curve was largest for nanoparticles assembling on the EG-S-S monolayer. High amounts of particles were also assembled on the pTHMMAA layer without the lipoic acid group, but the damping of the curve was considerably lower with a more even distribution of the particles. Topographical images confirmed that the highest number of particles were assembled on the polyethylene glycol monolayer. By increasing the interaction time more particles could be assembled on the surface.

  11. Tribological properties of OTS self-assembled monolayers

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs)were prepared on the substrates of silicon and glass. The tribological properties were tested with a self-made point-contact pure sliding micro tribometer. The effect of humidity on the tribological properties of both OTS SAMs and the naked substrates were studied. When the substrate is covered by OTS monolayer, the friction coefficient is reduced from 0.5 to 0.1 and the stick-slip phenomenon is weakened. OTS monolayer can keep its friction coefficient steady in a wide range of humidity, because it is highly hydrophobic and thus not sensitive to humidity. In addition, the OTS monolayer has a considerable anti-wear ability.

  12. Template-Directed Self-Assembly of Alkanethiol Monolayers: Selective Growth on Preexisting Monolayer Edges

    NARCIS (Netherlands)

    Sharpe, Ruben B.A.; Burdinski, Dirk; Huskens, Jurriaan; Zandvliet, Harold J.W.; Reinhoudt, David N.; Poelsema, Bene

    2007-01-01

    Self-assembled monolayers were investigated for their suitability as two-dimensional scaffolds for the selective growth of alkanethiol edge structures. Heterostructures with chemical contrast could be grown, whose dimensions were governed by both the initial pattern sizes and the process time. n-Oct

  13. Antifouling Self-assembled Monolayers on Microelectrodes for Patterning Biomolecules

    OpenAIRE

    Noel, John; Teizer, Winfried; Hwang, Wonmuk

    2009-01-01

    We present a procedure for forming a poly(ethylene glycol) (PEG) trimethoxysilane self-assembled monolayer (SAM) on a silicon substrate with gold microelectrodes. The PEG-SAM is formed in a single assembly step and prevents biofouling on silicon and gold surfaces. The SAM is used to coat microelectrodes patterned with standard, positive-tone lithography. Using the microtubule as an example, we apply a DC voltage to induce electrophoretic migration to the SAM-coated electrode in a reversible m...

  14. Actinide sequestration using self-assembled monolayers on mesoporous supports.

    Science.gov (United States)

    Fryxell, Glen E; Lin, Yuehe; Fiskum, Sandy; Birnbaum, Jerome C; Wu, Hong; Kemner, Ken; Kelly, Shelley

    2005-03-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometalate anions, and radionuclides. Details addressing the design, synthesis, and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental cleanup necessary after 40 years of weapons-grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented. PMID:15787373

  15. Microcontact printing of self-assembled monolayers: applications in microfabrication

    Science.gov (United States)

    Wilbur, James L.; Kumar, Amit; Biebuyck, Hans A.; Kim, Enoch; Whitesides, George M.

    1996-12-01

    This paper describes applications in microfabrication using patterned self-assembled monolayers (SAMs) formed by microcontact printing. Microcontact printing 0957-4484/7/4/028/img1 is a flexible new technique that forms patterned SAMs with regions terminated by different chemical functionalities (and thus different physical and chemical properties), in patterns with 0957-4484/7/4/028/img2 dimensions. Patterns of SAM are formed using an alkanethiol as an `ink', and printing the alkanethiol on a metal support with elastomeric `stamp'. We fabricate the stamp by moulding a silicone elastomer using a master prepared by optical or x-ray microlithography or by other techniques. SAMs of long-chain alkanethiolates on gold and other metals can act as nanometer resists by protecting the supporting metal from corrosion by appropriately formulated etchants: the fabrication of microstructures of gold and silicon demonstrates the utility of patterned SAMs (formed by 0957-4484/7/4/028/img3) as nm resists. Patterned SAMs formed by 0957-4484/7/4/028/img3 can also control the wettability of a surface on the 0957-4484/7/4/028/img2 scale. The organization of liquids in patterned arrays with 0957-4484/7/4/028/img2 dimensions, and the patterned deposition of microcrystals and microcrystal arrays illustrate the use of controlled wettability for microfabrication.

  16. Tailoring self-assembled monolayers at the electrochemical interface

    Indian Academy of Sciences (India)

    S Varatharajan; Sheela Berchmans; V Yegnaraman

    2009-09-01

    The main focus of this review is to illustrate the amenability of self-assembled monolayers (SAMs) for functionalisation with different receptors, catalytic materials, biomolecules, enzymes, antigen-antibody, etc for various applications. The review discusses initially about the preparation and characterization of SAMs and tailoring of SAMs by incorporation of suitable recognition elements. A description of how the molecular recognition is achieved through forces like electrostatic, covalent and host-guest interactions is included in the review.

  17. Self Assembled Monolayers for Quartz Crystal Microbalance based Biosensing

    OpenAIRE

    Myrskog, Annica

    2009-01-01

    The work in this thesis has been focused on developing surfaces for use in biosensor systems, especially for quartz crystal microbalances. The surfaces were prepared by adsorption of organosulfur molecules onto gold substrates, so called self assembled monolayers (SAMs). By chemical synthesis these thiols can be specifically tailored to provide surfaces with desired properties. The investigated surfaces were all based on thiols terminated with carboxylic acid groups to render hydrophilic surf...

  18. Comparison of the influence of humidity and D-mannitol on the organization of tetraethylene glycol-terminated self-assembled monolayers and immobilized antimicrobial peptides.

    Science.gov (United States)

    Goel, Mohit; Marsh, E Neil G; Chen, Zhan; Abbott, Nicholas L

    2014-06-24

    We report the use of polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to characterize the effects of relative humidity (RH) and d-mannitol on the conformations of tetraethylene glycol (EG4)-terminated self-assembled monolayers (SAMs) and immobilized antimicrobial peptides (Cecropin P1 and a hybrid of Cecropin A (1-8) and Melittin (1-18)). These results are used to assess the extent to which d-mannitol can substitute for water in promoting conformational states of the SAMs and oligopeptides similar to those induced by hydration. Our measurements reveal a red shift of the COC asymmetric stretching vibration of the EG4-terminated SAMs with increasing humidity, consistent with a transition from a mixed all-trans/helical (7/2 helix) conformation at 0% RH to a predominantly helical conformation at 90% RH. Significantly, under dry conditions, a thin (2 nm in thickness) overlayer of d-mannitol generated the COC spectroscopic signature of the EG4-terminated SAM measured at high humidity. Comparisons of the effects of humidity and d-mannitol on the secondary structure of the two oligopeptides also revealed both to cause the amide I peak positions, which were measured in dry air (and without d-mannitol) to correspond to α-helical conformations, to undergo red-shifts. The magnitudes of the red-shifts, however, were more pronounced for dry d-mannitol than for high RH, with Cecropin P1 and the hybrid peptide exhibiting amide I peak positions under d-mannitol consistent with bulk aqueous solution secondary structures (random and β-sheet, respectively). These results are discussed in the context of prior reports of the tendency of d-mannitol to form glassy states in the absence of water. Overall, the results presented in this paper support the hypothesis that d-mannitol can substitute, in at least some ways, for the influence of water on the conformational states of biologically relevant molecules at interfaces. The results provide guidance for the

  19. Organic Monolayer Protected Topological Surface State.

    Science.gov (United States)

    Yang, Hung-Hsiang; Chu, Yu-Hsun; Lu, Chun-I; Butler, Christopher John; Sankar, Raman; Chou, Fang-Cheng; Lin, Minn-Tsong

    2015-10-14

    Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)/Bi2Se3 and Fe/PTCDA/Bi2Se3 heterointerfaces are investigated using scanning tunneling microscopy and spectroscopy. The close-packed self-assembled PTCDA monolayer possesses big molecular band gap and weak molecule-substrate interactions, which leaves the Bi2Se3 topological surface state intact under PTCDA. Formation of Fe-PTCDA hybrids removes interactions between the Fe dopant and the Bi2Se3 surface, such as doping effects and Coulomb scattering. Our findings reveal the functionality of PTCDA to prevent dopant disturbances in the TSS and provide an effective alternative for interface designs of realistic TI devices. PMID:26393876

  20. Lipid dip-pen nanolithography on self-assembled monolayers

    Science.gov (United States)

    Gavutis, Martynas; Navikas, Vytautas; Rakickas, Tomas; Vaitekonis, Šarūnas; Valiokas, Ramūnas

    2016-02-01

    Dip-pen nanolithography (DPN) with lipids as an ink enables functional micro/nanopatterning on different substrates at high process speeds. However, only a few studies have addressed the influence of the physicochemical properties of the surface on the structure and phase behavior of DPN-printed lipid assemblies. Therefore, by combining the scanning probe and optical imaging techniques in this work we have analyzed lipid microdomain formation on the self-assembled monolayers (SAMs) on gold as well-defined model surfaces that displayed hydrophilic (protein-repellent) or hydrophobic (protein-adhesive) characteristics. We have found that on the tri(ethylene glycol)-terminated SAM the lipid ink transfer was fast (~10-1 μm3 s-1), quasi-linear and it yielded unstable, sparsely packed lipid microspots. Contrary to this, on the methyl-terminated SAM the lipid transfer was ~20 times slower, nonlinear, and the obtained stable dots of ~1 μm in diameter consisted of lipid multilayers. Our comparative analysis indicated that the measured lipid transfer was consistent with the previously reported so-called polymer transfer model (Felts et al 2012, Nanotechnology 23 215301). Further on, by employing the observed distinct contrast in the DPN ink behavior we constructed confined lipid microdomains on pre-patterned SAMs, in which the lipids assembled either into monolayer or multilamellar phases. Such microdomains can be further utilized for lipid membrane mimetics in microarray and lab-on-a-chip device formats.

  1. Self-assembling monolayers of helical oligopeptides with applications in molecular electronics

    International Nuclear Information System (INIS)

    The aim of this project was to develop a generic method of preparing a 'molecular architecture' containing functional groups on a surface at predetermined relative positions several nm apart. This would be of great utility in molecular electronics, chemical sensors and other fields. It was proposed that such an architecture could be prepared on gold using linked, helical oligopeptides that contained the components of interest and sulphur functions able to form monolayers on gold by the self-assembly technique. Towards this ultimate aim Self-Assembled Monolayers (SAMs) of monomeric oligopeptides (13-17 residues) were prepared and characterised. Peptides containing three Met residues spaced in the sequence so that their side-chains lay on the same side of the helix were shown by circular dichroism (CD) to be strongly helical in organic solvents. Their self-assembled films on gold were characterised by Reflection-Absorption Infrared Spectroscopy (RAIRS) which showed the peptides adsorbed with the helix axes parallel to the surface, the orientation expected for self-assembly. However the surface coverage measured by cyclic voltammetry (CV) of the peptides' ferrocenyl derivatives on gold electrodes were less than expected for monolayers. Comparison of the films of ferrocenyl derivatives of Met and Cys showed that the thiolate bound more strongly than the thioether. Accordingly an oligopeptide containing two Cys residues at i, i+3, designed to be 310-helical, was prepared. Transformation of the two (Trt)Cys residues of the resin-bound peptide to the intramolecular disulphide by iodine was achieved in acetonitrile but not in DMF. CD suggested that the conformation of this peptide was a mixture of helix and random coil. Films of the peptide-disulphide and the peptide-dithiol adsorbed from protic solvents were characterised as multilayers by ellipsometry. However CV and ellipsometry showed that a monolayer was successfully prepared from acetonitrile. Future targets for

  2. Self-Assembled Monolayers of CdSe Nanocrystals on Doped GaAs Substrates

    DEFF Research Database (Denmark)

    Marx, E.; Ginger, D.S.; Walzer, Karsten;

    2002-01-01

    This letter reports the self-assembly and analysis of CdSe nanocrystal monolayers on both p- and a-doped GaAs substrates. The self-assembly was performed using a 1,6-hexanedithiol self-assembled monolayer (SAM) to link CdSe nanocrystals to GaAs substrates. Attenuated total reflection Fourier tran...

  3. Strain-relief by single dislocation loops in calcite crystals grown on self-assembled monolayers.

    Science.gov (United States)

    Ihli, Johannes; Clark, Jesse N; Côté, Alexander S; Kim, Yi-Yeoun; Schenk, Anna S; Kulak, Alexander N; Comyn, Timothy P; Chammas, Oliver; Harder, Ross J; Duffy, Dorothy M; Robinson, Ian K; Meldrum, Fiona C

    2016-01-01

    Most of our knowledge of dislocation-mediated stress relaxation during epitaxial crystal growth comes from the study of inorganic heterostructures. Here we use Bragg coherent diffraction imaging to investigate a contrasting system, the epitaxial growth of calcite (CaCO3) crystals on organic self-assembled monolayers, where these are widely used as a model for biomineralization processes. The calcite crystals are imaged to simultaneously visualize the crystal morphology and internal strain fields. Our data reveal that each crystal possesses a single dislocation loop that occupies a common position in every crystal. The loops exhibit entirely different geometries to misfit dislocations generated in conventional epitaxial thin films and are suggested to form in response to the stress field, arising from interfacial defects and the nanoscale roughness of the substrate. This work provides unique insight into how self-assembled monolayers control the growth of inorganic crystals and demonstrates important differences as compared with inorganic substrates. PMID:27302863

  4. Antifouling self-assembled monolayers on microelectrodes for patterning biomolecules.

    Science.gov (United States)

    Noel, John; Teizer, Winfried; Hwang, Wonmuk

    2009-01-01

    We present a procedure for forming a poly(ethylene glycol) (PEG) trimethoxysilane self-assembled monolayer (SAM) on a silicon substrate with gold microelectrodes. The PEG-SAM is formed in a single assembly step and prevents biofouling on silicon and gold surfaces. The SAM is used to coat microelectrodes patterned with standard, positive-tone lithography. Using the microtubule as an example, we apply a DC voltage to induce electrophoretic migration to the SAM-coated electrode in a reversible manner. A flow chamber is used for imaging the electrophoretic migration and microtubule patterning in situ using epifluorescence microscopy. This method is generally applicable to biomolecule patterning, as it employs electrophoresis to immobilize target molecules and thus does not require specific molecular interactions. Further, it avoids problems encountered when attempting to pattern the SAM molecules directly using lithographic techniques. The compatibility with electron beam lithography allows this method to be used to pattern biomolecules at the nanoscale. PMID:19707178

  5. Electrochemical and structural characterization of self-assembled thiol monolayers on gold.

    NARCIS (Netherlands)

    Sondag-Huethorst, J.A.M.

    1994-01-01

    Self-assembled alkanethiol monolayers on gold are used as model systems in a fundamental study of the potential-dependent wetting and of the galvanic metal deposition. For using such monolayers as model systems, well-defined and ordered monolayers are required. In order to control the quality of the

  6. Regulated growth of diatom cells on self-assembled monolayers

    Directory of Open Access Journals (Sweden)

    Kobayashi Koichi

    2007-03-01

    Full Text Available Abstract We succeeded in regulating the growth of diatom cells on chemically modified glass surfaces. Glass surfaces were functionalized with -CF3, -CH3, -COOH, and -NH2 groups using the technique of self-assembled monolayers (SAM, and diatom cells were subsequently cultured on these surfaces. When the samples were rinsed after the adhesion of the diatom cells on the modified surfaces, the diatoms formed two dimensional arrays; this was not possible without the rinsing treatment. Furthermore, we examined the number of cells that grew and their motility by time-lapse imaging in order to clarify the interaction between the cells and SAMs. We hope that our results will be a basis for developing biodevices using living photosynthetic diatom cells.

  7. Nanoscale Nitrogen Doping in Silicon by Self-Assembled Monolayers

    Science.gov (United States)

    Guan, Bin; Siampour, Hamidreza; Fan, Zhao; Wang, Shun; Kong, Xiang Yang; Mesli, Abdelmadjid; Zhang, Jian; Dan, Yaping

    2015-07-01

    This Report presents a nitrogen-doping method by chemically forming self-assembled monolayers on silicon. Van der Pauw technique, secondary-ion mass spectroscopy and low temperature Hall effect measurements are employed to characterize the nitrogen dopants. The experimental data show that the diffusion coefficient of nitrogen dopants is 3.66 × 10-15 cm2 s-1, 2 orders magnitude lower than that of phosphorus dopants in silicon. It is found that less than 1% of nitrogen dopants exhibit electrical activity. The analysis of Hall effect data at low temperatures indicates that the donor energy level for nitrogen dopants is located at 189 meV below the conduction band, consistent with the literature value.

  8. Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

    NARCIS (Netherlands)

    Alonso, Jose Maria; Bielen, Abraham A.M.; Olthuis, Wouter; Kengen, Servé W.M.; Zuilhof, Han; Franssen, Maurice C.R.

    2016-01-01

    Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxy

  9. Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

    NARCIS (Netherlands)

    Aznar Alonso, J.M.; Bielen, A.A.M; Olthuis, W.; Kengen, S.W.M; Zuilhof, H.; Franssen, M.

    2016-01-01

    Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxysuccinimide (N

  10. Special features in self-assembled monolayer revealed by functionalised STM tips

    International Nuclear Information System (INIS)

    Some functional groups in self-assembled monolayers have recently been identified in STM images, due to the chemical modification of gold tips [1]. In those studies, different molecules presenting different functional groups were investigated, resolving several molecular organizations [1-2, 4]. In this paper, we aimed at demonstrating that such chemically modified STM tips can be used to investigate phenomenon routinely observed with standard Pt/Ir tips, such as domain boundary dynamics in hexadecanol SAMs. It also allows transitory features to be identified. Moreover, rarely observed phenomena are also presented below, i.e. bilayers composed of wax esters molecules physisorbed at the phenyloctane/graphite interface

  11. Correlation of Effective Dispersive and Polar Surface Energies in Heterogeneous Self-Assembled Monolayer Coatings

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Hansen, Ole

    2009-01-01

    We show, theoretically, that the measured effective dispersive and polar surface energies of a heterogeneous Surface are correlated; the correlation, however, differs whether a Cassic or an Israelachvili and Gee model is assumed. Fluorocarbon self-assembled monolayers with varying coverage were...... grown oil oxidized (100) silicon Surfaces in a vapor phase process using five different precursors. Experimentally, effective surface energy components of the fluorocarbon self-assembled monolayers were determined from measured contact angles using the Owens-Wendt-Rabel-Kaelble method. We show that the...... correlation between the effective surface energy components of the heterogeneous Surfaces coated with fluorocarbon self-assembled monolayers is in agreement with the Cassie model....

  12. Monolayer coverage and channel length set the mobility in self-assembled monolayer field-effect transistors

    NARCIS (Netherlands)

    Mathijssen, S.G.J.; Smits, E.C.P.; Hal, P.A. van; Wondergem, H.J.; Ponomarenko, S.A.; Moser, A.; Resel, R.; Bobbert, P.A.; Kemerink, M.; Janssen, R.A.J.; Leeuw, D.M. de

    2009-01-01

    The mobility of self-assembled monolayer field-effect transistors (SAMFETs) traditionally decreases dramatically with increasing channel length. Recently, however, SAMFETs using liquid-crystalline molecules have been shown to have bulk-like mobilities that are virtually independent of channel length

  13. Mechanism of UV photoreactivity of alkylsiloxane self-assembled monolayers.

    Science.gov (United States)

    Ye, Tao; McArthur, Eric A; Borguet, Eric

    2005-05-26

    A molecular level understanding of the photoreactivity of self-assembled monolayers (SAMs) becomes increasingly important as the spatial resolution starts to be limited by the size of the resist and the spatial extent of the photochemical reactions in photoresist micropatterning. To this end, a number of surface characterization techniques were combined to understand the reactive agents, reactive sites, kinetics, and reaction pathways in the UV photoreactivity of octadecylsiloxane (ODS) SAMs. Quantitative analysis of our results provides evidence that ground state atomic oxygen is the primary reactive agent for the UV degradation of ODS SAMs. UV degradation, which follows zero-order kinetics, results in the scission of alkyl chains instead of the siloxane headgroups. Our results suggest that the top of the ODS SAMs is the preferential reactive site. Using a novel, highly surface sensitive technique, fluorescence labeling of surface species, we identified the presence of submonolayer quantities chemical functional groups formed by the UV degradation. These groups are intermediates in a proposed mechanism based on hydrogen abstraction. PMID:16852200

  14. Kinetics of self-assembled monolayer formation on individual nanoparticles.

    Science.gov (United States)

    Smith, Jeremy G; Jain, Prashant K

    2016-08-24

    Self-assembled monolayer (SAM) formation of alkanethiols on nanoparticle surfaces is an extensively studied surface reaction. But the nanoscale aspects of the rich microscopic kinetics of this reaction may remain hidden due to ensemble-averaging in colloidal samples, which is why we investigated in real-time how alkanethiol SAMs form on a single Ag nanoparticle. From single-nanoparticle trajectories obtained using in situ optical spectroscopy, the kinetics of SAM formation appears to be limited by the growth of the layer across the nanoparticle surface. A significant spread in the growth kinetics is seen between nanoparticles. The single-nanoparticle rate distributions suggest two distinct modes for SAM growth: spillover of adsorbed thiols from the initial binding sites on the nanoparticle and direct adsorption of thiol from solution. At low concentrations, wherein direct adsorption from solution is not prevalent and growth takes place primarily by adsorbate migration, the SAM formation rate was less variable from one nanoparticle to another. On the other hand, at higher thiol concentrations, when both modes of growth were operative, the population of nanoparticles with inherent variations in surface conditions and/or morphology exhibited a heterogeneous distribution of rates. These new insights into the complex dynamics of SAM formation may inform synthetic strategies for ligand passivation and functionalization of nanoparticles and models of reactive adsorption and catalysis on nanoparticles. PMID:27523488

  15. Investigation of functionalized silicon nanowires by self-assembled monolayer

    Science.gov (United States)

    Hemed, Nofar Mintz; Convertino, Annalisa; Shacham-Diamand, Yosi

    2016-03-01

    The functionalization using self assembled monolayer (SAM) of silicon nanowires (SiNW) fabricated by plasma enhanced chemical vapor deposition (PECVD) is reported here. The SAM is being utilized as the first building block in the functionalization process. The morphology of the SiNW comprises a polycrystalline core wrapped by an hydrogenated amorphous silicon (α-Si:H) shell. Since most of the available methods for SAM verification and characterization are suitable only for flat substrates; therefore, in addition to the SiNW α-Si:H on flat samples were produced in the same system as the SiNWs. First we confirmed the SAM's presence on the flat α-Si:H samples using the following methods: contact angle measurement to determine the change in surface energy; atomic force microscopy (AFM) to determine uniformity and molecular coverage. Spectroscopic ellipsometry and X-ray reflectivity (XRR) were performed to measure SAM layer thickness and density. X-ray photoelectron spectroscopy (XPS) was applied to study the chemical states of the surface. Next, SiNW/SAM were tested by electrochemical impedance spectroscopy (EIS), and the results were compared to α-Si:H/SAM. The SAM electrical coverage on SiNW and α-Si:H was found to be ∼37% and ∼65 ± 3%, respectively. A model, based on transmission line theory for the nanowires is presented to explain the disparity in results between the nanowires and flat surface of the same materials.

  16. A note on the use of ellipsometry for studying the kinetics of formation of self-assembled monolayers

    Indian Academy of Sciences (India)

    Murali Sastry

    2000-06-01

    Ellipsometry is currently one of the most important techniques for characterization of the deposition and growth mode of ultra thin organic films. However, it is well known that for thicknesses normally encountered in organic monolayer films, as would occur for example in self-assembled monolayers, ellipsometry cannot be used to simultaneously determine the thickness and refractive index of the monolayer film. Current practice is to assume a reasonable value for the film refractive index and calculate an effective ‘ellipsometric thickness’. This communication seeks to show that the alternative approach of assuming a thickness for the monolayer (determined by the length of the molecule) and calculating the effective film refractive index lends itself to easier and more meaningful physical interpretation. The Lorentz–Lorenz formula is then used to transform the effective refractive index into a surface coverage and hence to an effective mass coverage. The methodology advanced is applied to the kinetics of formation of a self-assembled monolayer of a well-studied molecule, octadecanethiol on Au.

  17. Studies of Self-assembled Monolayers Formed by Imidazoline on Iron Surface by SEM and SECM

    Institute of Scientific and Technical Information of China (English)

    Xiu Yu LIU; Shen Hao CHEN; Shuai MIAO; Su Xiang WU; Li Xia SHEN; Yuan Xing CAI; Hong Yan ZHAI

    2006-01-01

    The self-assembled monolayers (SAMs) of imidazoline (IM) on the iron surface were characterized by scanning electron microscope (SEM) and scanning electrochemical microscopy(SECM). The results showed that SAMs were an effective inhibition film for iron.

  18. Investigation of Self Assembled Monolayers (SAM) Applied on Si(100) Surfaces by Atomic Force Microscopy

    International Nuclear Information System (INIS)

    Miniaturization of analytical instrumentation in a molecular and nanometer level has technologically significant. The fabrication of nanopatterns with high resolution SPM nanolithograpy may be applied on atomically flat surfaces. Self Assembled-Monolayers (SAMs) are well-ordered two dimensional molecular assemblies formed by a strong adsorption of an active surfactant on a solid surface. In this study, SAM organic thin film method is applied on silicon surfaces. We used various cleaning procedures such as chemical cleaning, ion beam treatment, on p-type Si(1OO) surfaces. SAMs films were produced from bipolar amphiphiles, Octadecylamine ODA-HCl, 1,12-diaminododecane (DAD) and n-tridecylamine (TDA) molecules on Si wafers. Contact mode scanning method and roughness analysis on the scan images were utilized on the SAM coated and uncoated surfaces by Atomic Force Microscopy

  19. Electrochemical Impedance Study of Schiff Base by Means of Self-assembled Monolayer

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this work, the self-assembled monolayer of Schiff base was first investigated using electrochemical impedance spectroscopy (ELS). The complexation of Cu2+ with the Schiff base was also detected with EIS method. The approximate linear relationship between Cu2+ and the reaction resistance (Rr) was observed. All the results suggest that the electrochemical property of Schiff base could be studied conveniently by means of forming self-assembled monolayer.

  20. Characterization and reactivity of organic monolayers on gold and platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chien-Ching

    1995-12-06

    Purpose is to understand how the mobilization, dielectric, orientation, composition, coverage, and structure of self-assembled organic monolayers on metal surfaces affects the surface reactivities and properties of these films in order to facilitate the construction of desired films. Two model systems were used: tiols at Au and aromatic acids at Pt. Surface analysis methods, including contact angle, electrochemistry, ellipsometry, infrared reflection absorption spectroscopy (IRRAS), and x-ray photospectroscopy, were used to study the self-assembled organic monolayers on Au and Pt. IRRAS, contact angle, and electrochemistry were used to determine the surface pK{sub a} of phenylcarboxylic acids and pyridylcarboxylic acids monolayers on Pt. These techniques were also used to determine the orientation of polymethylene chain axis and the carboxylic follow the structural evolution of the chains and end group of the thiolate monolayers during formation. IRRAS was also used to assess the carboxylic acid group in terms of its possible existence as the non-hydrogen-bonded species, the hydrogen-bonded dimeric group, and the hydrogen-bonded polymeric group. These different forms of the end group were also followed vs coverage, as well as the reactivity vs solution pH. IRRAS and contact angle were used to calculate the rate constant of the esterification of carboxylic acid-terminated monolayers on Au.

  1. Self-assembling Process of Alkanethiol Monolayers on Gold Surface via Underpotential Deposition

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    It was demonstrated feasible that underpotential deposition(UPD) of copper on a monolayer-modified gold substrate can be used to determine the gold electrode area. The deposition and stripping of a Cu adlayer can take place reversibly and stably at a bared or a self-assembled monolayer modified gold electrode. The growth kinetics of decanethiol/Au was also investigated via Cu UPD. The difference between the assembling kinetics determined by UPD and that by quartz crystal microbalance measurements reveals the configuration transmutation of the assembled molecules from a disordered arrangement to an ordered arrangement during the self-assembling processes.

  2. Electronic Transport through Self Assembled Thiol Molecules: Effect of Monolayer Order, Dynamics and Temperature

    Science.gov (United States)

    Dholakia, Geetha; Fan, Wendy; Meyyappan, M.

    2005-01-01

    We present the charge transport and tunneling conductance of self assembled organic thiol molecules and discuss the influence of order and dynamics in the monolayer on the transport behavior and the effect of temperature. Conjugated thiol molecular wires and organometals such as terpyridine metal complexes provide a new platform for molecular electronic devices and we study their self assembly on Au(111) substrates by the scanning tunneling microscope. Determining the organization of the molecule and the ability to control the nature of its interface with the substrate is important for reliable performance of the molecular electronic devices. By concurrent scanning tunneling microscopy and spectroscopy studies on SAMs formed from oligo (phenelyne ethynelyne) monolayers with and without molecular order, we show that packing and order determine the response of a self assembled monolayer (SAM) to competing interactions. Molecular resolution STM imaging in vacuum shows that the OPES adopt an imcommensurate SAM structure on Au(111) with a rectangular unit cell. Tunneling spectroscopic measurements were performed on the SAM as a function of junction resistance. STS results show that the I-Vs are non linear and asymmetric due to the inherent asymmetry in the molecular structure, with larger currents at negative sample biases. The asymmetry increases with increasing junction resistance due to the asymmetry in the coupling to the leads. This is brought out clearly in the differential conductance, which also shows a gap at the Fermi level. We also studied the effect of order and dynamics in the monolayer on the charge transport and found that competing forces between the electric field, intermolecular interactions, tip-molecule physisorption and substrate-molecule chemisorption impact the transport measurements and its reliability and that the presence of molecular order is very important for reproducible transport measurements. Thus while developing new electronic platforms

  3. Conformational morphology of polyaniline grown on self-assembled monolayer modified silicon

    Energy Technology Data Exchange (ETDEWEB)

    Sutar, D.S., E-mail: dssutar23@gmail.com [Central Surface Analytical Facility, Indian Institute of Technology Bombay, Mumbai 400076 (India); Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Major, S.S. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Srinivasa, R.S. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Yakhmi, J.V. [Technical Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2011-10-31

    Polyaniline (PANI) films with pyramidal shaped crystallites were prepared by self-organization on self-assembled monolayer (SAM) modified Si substrates. High-resolution atomic force microscopy (HR-AFM) shows that SAM has tridymite structural order and the PANI film has biphasic conformational morphology corresponding to face-on orientation and edge-on orientation. Order parameters obtained from power spectral density analysis of HR-AFM images of SAM and PANI films show that the pyramidal crystallites are in emeraldine salt (ES-I) form and the region between the crystallites is in emeraldine base (EB-II) form. The ordered lattice of PANI crystallites as observed by cross-sectional HR-TEM confirms its single crystalline nature as well as epitaxial growth. The heteroepitaxial growth of PANI is attributed to the structural order of interfacial SAM on Si. - Highlights: > The structural order of self-assembled monolayer (SAM) on Si assists in hetero-epitaxial growth of polyaniline (PANI) films. > The power spectral density (PSD) analysis of the high-resolution AFM images provides the order parameters, which help to elucidate the ordering in SAM and PANI films. > PSD function could be used to analyze the high-resolution AFM images, which hitherto has been used mainly for low-resolution image analysis. > The ordered lattice image and SAED pattern obtained by HR-TEM confirms the single crystalline nature of pyramidal crystallites and their epitaxial growth at the interface.

  4. Self-assembled monolayer-modified block copolymers for chemical surface nanopatterning

    International Nuclear Information System (INIS)

    Research highlights: → Self-organizing PS-b-PMMA creates striped nanostructure scaffolds. → These striped nanostructures can be selectively metalized and modified using light. → Metalized stripes can be decorated with SAMs to create functional substrates. → Nanostructured surfaces thus prepared exhibit controlled wetting and recognition. - Abstract: Thin-film poly(styrene-block-methyl methacrylate) diblock copolymer (PS-b-PMMA) is used to create chemically patterned surfaces via metal deposition combined with self-assembled monolayers (SAMs) and UV exposure. We use this method to produce surfaces that are chemically striped on the scale of a few tens of nanometers. Atomic force and transmission electron microscopies are used to verify the spatially localized organization of materials, and contact angle measurements confirm the chemical tunability of these scaffolds. These surfaces may be used for arraying nanoscale objects, such as nanoparticles or biological species, or for electronic, magnetic memory or photovoltaic applications.

  5. Self-assembling and self-limiting monolayer deposition

    Science.gov (United States)

    Foest, Rüdiger; Schmidt, Martin; Gargouri, Hassan

    2014-02-01

    Effects of spatial ordering of molecules on surfaces are commonly utilized to deposit ultra-thin films with a thickness of a few nm. In this review paper, several methods are discussed, that are distinguished from other thin film deposition processes by exactly these effects that lead to self-assembling and self-limiting layer growth and eventually to coatings with unique and fascinating properties and applications in micro-electronics, optics, chemistry, or biology. Traditional methods for the formation of self-assembled films of ordered organic molecules, such as the Langmuir-Blodgett technique along with thermal atomic layer deposition (ALD) of inorganic molecules are evaluated. The overview is complemented by more recent developments for the deposition of organic or hybrid films by molecular layer deposition. Particular attention is given to plasma assisted techniques, either as a preparative, supplementary step or as inherent part of the deposition as in plasma enhanced ALD or plasma assisted, repeated grafting deposition. The different methods are compared and their film formation mechanisms along with their advantages are presented from the perspective of a plasma scientist. The paper contains lists of established film compounds and a collection of the relevant literature is provided for further reading.

  6. Self-assembly of Carboxyl Functionalized Polystyrene Nanospheres into Close-packed Monolayers via Chemical Adsorption

    Institute of Scientific and Technical Information of China (English)

    LI,Zhi-Wei(李志伟); ZHOU,Jing-Fang(周静芳); ZHANG,Zhi-Jun(张治军); DANG,Hong-Xin(党鸿辛)

    2004-01-01

    The polyacrylic acid functionalized polystyrene nanospheres were synthesized and self-assembled into irregular,densely packed monolayers in non-aqueous media. The polymer nanoparticles were chemically adhered to substrates. The morphologies of the resulting films were investigated. The impact of the volume fraction of alcohol in the mixed solvents on the particle adsorption and fabrication of nanosphere assembled films was examined.

  7. Micro-patterning of Copper Based on Photolithographed Self-assembly Monolayers

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new method has been developed for fabrication of copper micro-pattern by selective chemical copper deposition based on photolithographed (3-mercaptopropyl)-trimethoxysilane (MPTS) self-assembly monolayers (SAMs). As confirmed by scanning electron microscopy (SEM), Cu closely replicated the mask features. The present approach makes this technic to be cheap and may be applicable to assembly of microelectronic circuits.

  8. Electrochemical Studies of Glutathione Monolayer Assembled on A Polycrystalline Gold Electrode

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The glutathione (GSH) monolayer and complex monolayer of GSH-metallic ion on polycrys-talline gold electrode were studied by using K3Fe(CN)6 as the redox probe. As for the GSH monolayer, itwas found that the metallic ions could open the ion-gate in the monolayer dramatically in the order La3+>Pb2+>> Ba2+> Ca2+ whereas Zn2+ ion closed the ion-gate. The complexes of GSH-metallic ions were ca-pable of self-assembling the different kind of monolayer. All the differences were related to the structuralconfiguration of the anchored GSH molecule, which changed with the different metallic ions or pH.

  9. Static and dynamic electronic characterization of organic monolayers grafted on a silicon surface.

    Science.gov (United States)

    Pluchery, O; Zhang, Y; Benbalagh, R; Caillard, L; Gallet, J J; Bournel, F; Lamic-Humblot, A-F; Salmeron, M; Chabal, Y J; Rochet, F

    2016-02-01

    Organic layers chemically grafted on silicon offer excellent interfaces that may open up the way for new organic-inorganic hybrid nanoelectronic devices. However, technological achievements rely on the precise electronic characterization of such organic layers. We have prepared ordered grafted organic monolayers (GOMs) on Si(111), sometimes termed self-assembled monolayers (SAMs), by a hydrosilylation reaction with either a 7-carbon or an 11-carbon alkyl chain, with further modification to obtain amine-terminated surfaces. X-ray photoelectron spectroscopy (XPS) is used to determine the band bending (∼ 0.3 eV), and ultraviolet photoelectron spectroscopy (UPS) to measure the work function (∼ 3.4 eV) and the HOMO edge. Scanning tunneling microscopy (STM) confirms that the GOM surface is clean and smooth. Finally, conductive AFM is used to measure electron transport through the monolayer and to identify transition between the tunneling and the field emission regimes. These organic monolayers offer a promising alternative to silicon dioxide thin films for fabricating metal-insulator-semiconductor (MIS) junctions. We show that gold nanoparticles can be covalently attached to mimic metallic nano-electrodes and that the electrical quality of the GOMs is completely preserved in the process. PMID:26757829

  10. Triazolobithiophene Light Absorbing Self-Assembled Monolayers: Synthesis and Mass Spectrometry Applications

    Directory of Open Access Journals (Sweden)

    Denis Séraphin

    2011-10-01

    Full Text Available The synthesis of five light absorbing triazolobithiophenic thiols, which were utilized for producing self-assembled monolayers (SAMs on gold surfaces, is presented. The monolayer formation was monitored by cyclic voltammetry, indicating excellent surface coverage. The new triazolobithiophenic compounds exhibited an absorption maximum around 340 nm, which is close to the emission wavelength of a standard nitrogen laser. Consequently these compounds could be used to aid ionization in laser desorption mass spectrometry (MS.

  11. Self-assembled monolayers of shape-persistent macrocycles on graphite: interior design and conformational polymorphism.

    Science.gov (United States)

    Vollmeyer, Joscha; Eberhagen, Friederike; Höger, Sigurd; Jester, Stefan-S

    2014-01-01

    Three shape-persistent naphthylene-phenylene-acetylene macrocycles of identical backbone structures and extraannular substitution patterns but different (empty, apolar, polar) nanopore fillings are self-assembled at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Submolecularly resolved images of the resulting two-dimensional (2D) crystalline monolayer patterns are obtained by in situ scanning tunneling microscopy. A concentration-dependent conformational polymorphism is found, and open and more dense packing motifs are observed. For all three compounds alike lattice parameters are found, therefore the intermolecular macrocycle distances are mainly determined by their size and symmetry. This is an excellent example that the graphite acts as a template for the macrocycle organization independent from their specific interior.

  12. Femtosecond-laser processing of nitrobiphenylthiol self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Schröter, Anja; Franzka, Steffen [Fakultät für Chemie, Universität Duisburg-Essen, 45117 Essen (Germany); CENIDE – Center for Nanointegration Duisburg-Essen, 47048 Duisburg (Germany); Koch, Jürgen; Chichkov, Boris N. [LZH – Laser Zentrum Hannover e. V., Hollerithallee 8, 30419 Hannover (Germany); Ostendorf, Andreas [Fakultät für Maschinenbau, Ruhruniversität Bochum, Universitätsstr. 150, 44801 Bochum (Germany); Hartmann, Nils, E-mail: nils.hartmann@uni-due.de [Fakultät für Chemie, Universität Duisburg-Essen, 45117 Essen (Germany); CENIDE – Center for Nanointegration Duisburg-Essen, 47048 Duisburg (Germany)

    2013-08-01

    Single-pulse femtosecond laser patterning of nitrobiphenylthiol monolayers on Au-coated Si substrates at λ = 800 nm, τ < 30 fs and ambient conditions has been investigated. After laser processing wet etching experiments are performed. Laser irradiation reduces the chemical resistance of the coating. In particular, the monolayer acts as a positive-tone resist. Burr-free pattern transfer is feasible at laser pulse fluences between 1 and 2.7 J/cm{sup 2}. Minimum structure sizes at a 1/e laser spot diameter of about 1 μm are close to 300 nm, i.e. sub-wavelength processing is demonstrated. Noteworthy, however, no indications for negative-tone resist properties of processed monolayers are evident, that is, cross-linking of the biphenyl moieties, if at all, is marginal. Also, complementary labeling experiments provide no evidence for chemical transformation of the nitro end groups into amine functionalities. Perspectives of resonant fs-laser processing in exploiting the particular prospects of nitrobiphenylthiol monolayers as negative-tone resists and chemically patternable platforms are discussed.

  13. Fabrication of self-assembled oligophenylethynylenethiol monolayer for electrochemical glucose biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Seul-Ki [Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 121-742 (Korea, Republic of); Namgung, Mi-Ok [Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742 (Korea, Republic of); Oh, Se-Young [Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 121-742 (Korea, Republic of); Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742 (Korea, Republic of); Oh, Byung-Keun, E-mail: bkoh@sogang.ac.kr [Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 121-742 (Korea, Republic of); Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742 (Korea, Republic of)

    2009-07-15

    An electrochemical glucose biosensor was developed using a gold (Au) electrode, which was composed of self-assembled oligophenylethynylenethiol monolayer and glucose oxidase (GOx) structure. Oligophenylethynylenethiol was used as a chemical linker for the immobilization of GOx on Au electrode, which facilitates the transfer of electron produced by enzyme reaction to the Au electrode. The electrical property of self-assembled oligophenylethynylenethiol monolayer was investigated by using cyclic voltammetry (CV). The formation of self-assembled oligophenylethynylenethiol monolayer and GOx layer on Au surface was verified by using atomic force microscopy (AFM) and surface plasmon resonance (SPR). The electrochemical glucose biosensor exhibited a linear relationship between target concentration and oxidation current in the range of 2-30 mM and its detection limit was 2 mM.

  14. The Electrochemical Characteristics of Multilayer Assembly of Hemoglobin and Polystyrene Sulfonate at Self-assembled Monolayer Surface

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A multilayer film of hemoglobin (Hb) molecules and polyelectrolyte sulfonate were fabricated on a thiol self-assembled monolayers (SAMs) by electrostatic force.The Hb maintains electroactive property in the multilayer film, methylene blue (MB) incorporated into the multilayer can enhance the electron transfer rate between the Hb and the electrode surface.

  15. Trapping dynamics of diindenoperylene (DIP) in self-assembled monolayers using molecular simulation

    KAUST Repository

    Kaushik, Ananth P.

    2011-07-01

    All-atom Molecular Dynamics simulation methods employing a well-tested intermolecular potential model, MM3 (Molecular Mechanics 3), demonstrate the propensity for diindenoperylene (DIP) molecules to insert between molecules of a self-assembled monolayer (SAM) during a deposition process intended to grow a thin film of this organic semiconductor molecule onto the surface of self-assembled monolayers. The tendency to insert between SAM molecules is fairly prevalent at normal growth temperatures and conditions, but is most strongly dependent on the density and the nature of the SAM. We posit the existence of an optimal density to favor surface adsorption over insertion for this system. DIP is less likely to insert in fluorinated SAMs, like FOTS (fluorooctatrichlorosilane), than its unfluorinated analog, OTS (octatrichlorosilane). It is also less likely to insert between shorter SAMs (e.g., less insertion in OTS than ODTS (octadecyltrichlorosilane)). Very short length, surface-coating molecules, like HDMS (hexamethyldisilazane), are more likely to scatter energetic incoming DIP molecules with little insertion on first impact (depending on the incident energy of the DIP molecule). Grazing angles of incidence of the depositing molecules generally favor surface adsorption, at least in the limit of low coverage, but are shown to be dependent on the nature of the SAM. The validity of these predictions is confirmed by comparison of the predicted sticking coefficients of DIP at a variety of incident energies on OTS, ODTS, and FOTS SAMs with results obtained experimentally by Desai et al. (2010) [23]. The simulation predictions of the tendency of DIP to insert can be explained, in large part, in terms of binding energies between SAM and DIP molecules. However, we note that entropic and stochastic events play a role in the deposition outcomes. Preliminary studies of multiple deposition events, emulating growth, show an unexpected diffusion of DIP molecules inserted within the

  16. Electric-Field-Assisted Directed Assembly of Transition Metal Dichalcogenide Monolayer Sheets.

    Science.gov (United States)

    Deng, Donna D; Lin, Zhong; Elías, Ana Laura; Perea-Lopez, Nestor; Li, Jie; Zhou, Chanjing; Zhang, Kehao; Feng, Simin; Terrones, Humberto; Mayer, Jeffrey S; Robinson, Joshua A; Terrones, Mauricio; Mayer, Theresa S

    2016-05-24

    Directed assembly of two-dimensional (2D) layered materials, such as transition metal dichalcogenides, holds great promise for large-scale electronic and optoelectronic applications. Here, we demonstrate controlled placement of solution-suspended monolayer tungsten disulfide (WS2) sheets on a substrate using electric-field-assisted assembly. Micrometer-sized triangular WS2 monolayers are selectively positioned on a lithographically defined interdigitated guiding electrode structure using the dielectrophoretic force induced on the sheets in a nonuniform field. Triangular sheets with sizes comparable to the interelectrode gap assemble with an observed preferential orientation where one side of the triangle spans across the electrode gap. This orientation of the sheets relative to the guiding electrode is confirmed to be the lowest energy configuration using semianalytical calculations. Nearly all sheets assemble without observable physical deformation, and postassembly photoluminescence and Raman spectroscopy characterization of the monolayers reveal that they retain their as-grown crystalline quality. These results show that the field-assisted assembly process may be used for large-area bottom-up integration of 2D monolayer materials for nanodevice applications. PMID:27082162

  17. Self-assembly of tetraalkoxydinaphthophenazines in monolayers on HOPG by scanning tunneling microscopy

    Science.gov (United States)

    Jaroch, Tomasz; Maranda-Niedbala, Agnieszka; Kotwica, Kamil; Wamil, Damian; Bujak, Piotr; Pron, Adam; Nowakowski, Robert

    2015-11-01

    2D supramolecular organization in monolayers of tetraalkoxydinaphthophenazines, a new group of solution processable organic semiconductors obtained by simple functionalization of indanthrone (6,15-dihydrodinaphtho[2,3-a:2‧,3‧-h]phenazine-5,9,14,18-tetraone), an old intractable dye, was investigated by scanning tunneling microscopy (STM). Five derivatives with increasing substituent length from butoxy (P-C4) to dodecyloxy (P-C12) were tested. All derivatives show a strong tendency to form ordered monolayers on HOPG graphite via self-assembly which constitute of rows of molecules oriented in one direction. However, local arrangement in this 2D supramolecular organization is strongly dependent on the substituent length. Two tendencies in the structural evolution are observed. For butoxy (P-C4), hexyloxy (P-C6) and octyloxy (P-C8) derivatives increasing substituent length results in the transformation of the structure governed by the conjugated core interactions to the one in which mutual interactions of the alkoxy groups dominate. As a consequence, for P-C8 a very stable 2D structure is obtained with a nearly rectangular 2D unit cell, as a consequence of the alkoxy group interdigitation in two perpendicular directions. With further increase of the substituent length to decyloxy (P-C10) and dodecyloxy (P-C12) a different effect is observed-a directional expansion of the unit cell along the longitudinal axis of the molecules. This is a consequence of structural nonequivalence of the alkoxy groups attached to the same aromatic ring.

  18. Ozone Oxidation of Self-Assembled Monolayers on SiOx-Coated Zinc Selenide Surfaces

    Science.gov (United States)

    McIntire, T. M.; Ryder, O. S.; Finlayson-Pitts, B. J.

    2008-12-01

    Airborne particles are important for visibility, human health, climate, and atmospheric reactions. Atmospheric particles contain a significant fraction of organics and such compounds present on airborne particles are susceptible to oxidation by atmospheric oxidants, such as OH, ozone, halogen atoms, and nitrogen trioxide. Oxidized organics associated with airborne particles are thought to be polar, hygroscopic species with enhanced cloud-nucleating properties. Oxide layers on silicon, or SiO2-coated substrates, act as models of environmentally relevant surfaces such as dust particles upon which organics adsorb. We have shown previously that ozone oxidation of unsaturated self-assembled monolayers (SAMs) on silicon attenuated total reflectance (ATR) crystals leads to the formation of carbonyl groups and micron-sized, hydrophobic organic aggregates surrounded by carbon depleted substrate that do not have increased water uptake as previously assumed. Reported here are further ATR-FTIR studies of the oxidation of alkene SAMs on ZnSe and SiO2-coated ZnSe. These substrates have the advantage that they transmit below 1500 cm-1, allowing detection of additional product species. These experiments show that the loss of C=C and formation of carbonyl groups is also accompanied by formation of a peak at 1110 cm-1, attributed to the secondary ozonide. Details concerning the products and mechanism of ozonolysis of alkene SAMs on surfaces based on these new data are presented and the implications for the oxidation of alkenes on airborne dust particles are discussed.

  19. Self-assembled selenium monolayers: from nanotechnology to materials science and adaptive catalysis.

    Science.gov (United States)

    Romashov, Leonid V; Ananikov, Valentine P

    2013-12-23

    Self-assembled monolayers (SAMs) of selenium have emerged into a rapidly developing field of nanotechnology with several promising opportunities in materials chemistry and catalysis. Comparison between sulfur-based self-assembled monolayers and newly developed selenium-based monolayers reveal outstanding complimentary features on surface chemistry and highlighted the key role of the headgroup element. Diverse structural properties and reactivity of organosulfur and organoselenium groups on the surface provide flexible frameworks to create new generations of materials and adaptive catalysts with unprecedented selectivity. Important practical utility of adaptive catalytic systems deals with development of sustainable technologies and industrial processes based on natural resources. Independent development of nanotechnology, materials science and catalysis has led to the discovery of common fundamental principles of the surface chemistry of chalcogen compounds.

  20. Hybrid plasmonic/semiconductor nanoparticle monolayer assemblies as hyperbolic metamaterials

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Ozel, Tuncay; Mutlugun, Evren;

    2014-01-01

    We show that hybrid nanostructures made of alternating colloidal semiconductor quantum dot and metal nanoparticle monolayers can function as multilayer hyperbolic meta-materials. By choosing the thickness of the spacer between the quantum dot and nanoparticle layers, one can achieve the indefinite...... effective permittivity tensor of the structure. This results in increased photonic density of states and strong enhancement of quantum dot luminescence, in line with recent experimental results. Our findings demonstrate that hyperbolic metamaterials can increase the radiative decay rate of emission centers...

  1. Linear hydrogen adsorbate structures on graphite induced by self-assembled molecular monolayers

    DEFF Research Database (Denmark)

    Nilsson, Louis; Sljivancanin, Zeljko; Balog, Richard;

    2012-01-01

    Combined scanning tunnelling microscopy measurements and density functional theory calculations reveal a method to induce linear structures of hydrogen adsorbates on graphite by covering the surface with a self-assembled molecular monolayer of cyanuric acid and exposing it to atomic hydrogen...

  2. Controlling the stereochemistry and regularity of butanethiol self-assembled monolayers on Au(111)

    DEFF Research Database (Denmark)

    Yan, Jiawei; Ouyang, Runhai; Jensen, Palle Skovhus;

    2014-01-01

    The rich stereochemistry of the self-assembled monolayers (SAMs) of four butanethiols on Au(111) is described, the SAMs containing up to 12 individual C, S, or Au chiral centers per surface unit cell. This is facilitated by synthesis of enantiomerically pure 2-butanethiol (the smallest unsubstitu...

  3. The Effects of Embedded Dipoles in Aromatic Self-Assembled Monolayers

    NARCIS (Netherlands)

    Abu-Husein, Tarek; Schuster, Swen; Egger, David A.; Kind, Martin; Santowski, Tobias; Wiesner, Adrian; Chiechi, Ryan; Zojer, Egbert; Terfort, Andreas; Zharnikov, Michael

    2015-01-01

    Using a representative model system, here electronic and structural properties of aromatic self-assembled monolayers (SAMs) are described that contain an embedded, dipolar group. As polar unit, pyrimidine is used, with its orientation in the molecular backbone and, consequently, the direction of the

  4. Monitoring the hydration of DNA self-assembled monolayers using an extensional nanomechanical resonator

    DEFF Research Database (Denmark)

    Cagliani, Alberto; Kosaka, Priscila; Tamayo, Javier;

    2012-01-01

    We have fabricated an ultrasensitive nanomechanical resonator based on the extensional vibration mode to weigh the adsorbed water on self-assembled monolayers of DNA as a function of the relative humidity. The water adsorption isotherms provide the number of adsorbed water molecules per nucleotide...

  5. On the Hopping Efficiency of Nanoparticles in the Electron Transfer across Self‐Assembled Monolayers

    DEFF Research Database (Denmark)

    Liu, Feng; Khan, Kamran; Liang, Jing‐Hong;

    2013-01-01

    Redox reactions of solvated molecular species at gold‐electrode surfaces modified by electrochemically inactive self‐assembled molecular monolayers (SAMs) are found to be activated by introducing Au nanoparticles (NPs) covalently bound to the SAM to form a reactive Au–alkanedithiol–NP–molecule hy...

  6. Formation of high-quality self-assembled monolayers of conjugated dithiols on gold : Base matters

    NARCIS (Netherlands)

    Valkenier, Hennie; Huisman, Everardus H.; Hal, Paul A. van; de Leeuw, Dagobert; Chiechi, Ryan C.; Hummelen, Jan C.

    2011-01-01

    This Article reports a systematic study on the formation of self-assembled monolayers (SAMs) of conjugated molecules for molecular electronic (ME) devices. We monitored the deprotection reaction of acetyl protected dithiols of oligophenylene ethynylenes (OPEs) in solution using two different bases a

  7. Specific ion effects on the hydrophobic interaction of benzene self-assembled monolayers

    DEFF Research Database (Denmark)

    Dobberschütz, Sören; Pedersen, Morten Rimmen; Hassenkam, Tue;

    2015-01-01

    interaction of benzene self-assembled monolayers. Using the jump to contact phenomenon of an atomic force microscope (AFM) tip as an indicator of attractive forces between the surfaces of a sample and the tip, we discovered lower frequencies in the snap in as well as narrower distributions for the snap...

  8. Self-assembled monolayers of azobenzene functionalized 1,3,5-triazine-4,6-dithiols

    International Nuclear Information System (INIS)

    Two novel azobenzene-functionalized 1,3,5-triazine-4,6-dithiols were synthesized and their ultrathin films were prepared by self-assembling (SA) technique. The switching between trans-and cis-forms was observed by measuring the surface potential using the Kelvin probe technique while alternating irradiation the SA monolayer (SAM) with ultraviolet or visible light

  9. Redox mediation at 11-mercaptoundecanoic acid self-assembled monolayers on gold

    NARCIS (Netherlands)

    Cecchet, F; Marcaccio, M; Margotti, M; Paolucci, F; Rapino, S; Rudolf, P

    2006-01-01

    Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and digital simulation techniques were used to investigate quantitatively the mechanism of electron transfer (ET) through densely packed and well-ordered self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid on gold, eit

  10. Single-Layer Pentacene Field-Effect Transistors Using Electrodes Modified With Self-assembled Monolayers

    NARCIS (Netherlands)

    Asadi, Kamal; Wu, Yu; Gholamrezaie, Fatemeh; Rudolf, Petra; Blom, Paul W. M.

    2009-01-01

    Pentacene field-effect transistor performance can be improved by modifying metal electrodes with self-assembled monolayers. The dominant role in performance is played by pentacene morphology rather than the work function of the modified electrodes. With optimized processing conditions, hysteresis-fr

  11. The lipase monolayer film self-assembly on the negatively charged poly(ethylene terephthalate) substrate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The PET-CO2- film was prepared and the lipase was assembled on the surface of the PET-CO2- substrate. The structure at the surface and activity of lipase/PET monolayer were studied by ATR-FTIR and AFM, and other methods.

  12. Intermixed Adatom and Surface‐Bound Adsorbates in Regular Self‐Assembled Monolayers of Racemic 2‐Butanethiol on Au(111)

    DEFF Research Database (Denmark)

    Ouyang, Runhai; Yan, Jiawei; Jensen, Palle Skovhus;

    2015-01-01

    In situ scanning tunneling microscopy combined with density functional theory molecular dynamics simulations reveal a complex structure for the self‐assembled monolayer (SAM) of racemic 2‐butanethiol on Au(111) in aqueous solution. Six adsorbate molecules occupy a (10×√3)R30° cell organized as tw...

  13. Penetration of surfactin into phospholipid monolayers: nanoscale interfacial organization.

    Science.gov (United States)

    Eeman, M; Berquand, A; Dufrêne, Y F; Paquot, M; Dufour, S; Deleu, M

    2006-12-19

    Atomic force microscopy (AFM) combined with surface pressure-area isotherms were used to probe the interfacial behavior of phospholipid monolayers following penetration of surfactin, a cyclic lipopeptide produced by Bacillus subtilis strains. Prior to penetration experiments, interfacial behavior of different surfactin molecules (cyclic surfactins with three different aliphatic chain lengths--S13, S14, and S15--and a linear surfactin obtained by chemical cleavage of the cycle of the surfactin S15) has been investigated. A more hydrophobic aliphatic chain induces greater surface-active properties of the lipopeptide. The opening of the peptide ring reduces the surface activity. The effect of phospholipid acyl chain length (dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine- (DPPC), and distearoylphosphatidylcholine) and phospholipid polar head (DPPC, dipalmitoylphosphatidylethanolamine and dipalmitoylphosphatidylserine) on monolayer penetration properties of the surfactin S15 has been explored. Results showed that while the lipid monolayer thickness and the presence of electrostatic repulsions from the interfacial film do not significantly influence surfactin insertion, these parameters strongly modulate the ability of the surfactin to alter the nanoscale organization of the lipid films. We also probed the effect of surfactin structure (influence of the aliphatic chain length and of the cyclic structure of the peptide ring) on the behavior of DPPC monolayers. AFM images and isotherms showed that surfactin penetration is promoted by longer lipopeptide chain length and a cyclic polar head. This indicates that hydrophobic interactions are of main importance for the penetration power of surfactin molecules.

  14. Microelectrode array in mixed alkanethiol self-assembled monolayers: Electrochemical studies

    International Nuclear Information System (INIS)

    We report an efficient alternative to obtain recessed microelectrodes device on gold electrode surface, in which mixed self-assembled monolayer of long and short carbon alkanethiol chains was used for this purpose. Development of the modified electrodes included the chemical adsorption of 11-mercaptoundecanoic acid and 2-mercaptoethanol solution, as well as their mixtures, on gold surface, resulting in the final mixed self-assembled monolayer configuration. For comparison, the electrochemical performance of self-assembled monolayer of 11-mercaptoundecanoic acid, 3-mercaptopropionic acid, 4-mercapto-1-butanol and 6-mercapto-1-hexanol modified electrodes was also investigated. It was verified that, in the mixed self-assembled monolayer, the 11-mercaptoundecanoic acid acts as a barrier for electron transfer while the short alkanethiol chair is deposited in an island-like shape through which electrons can be freely transferred to ions in solution, allowing electrochemical reactions to occur. The performance of the modified electrodes toward microelectrode behavior was investigated via cyclic voltammetry and electrochemical impedance spectroscopy measurements using [Fe(CN)6]3−/4− redox couple as a probe. In this case, sigmoidal voltammetric responses were obtained, very similar to those observed for microelectrodes. Such behavior reinforces the proposition of electron transfer through the short alkanethiol chain layer and surface blockage by the long chain one. Electrochemical impedance results allowed calculated the mean radius value of each microelectrode disks of 3.8 μm with about 22 μm interval between them. The microelectrode environment provided by the mixed self-assembled monolayer can be conveniently used to provide an efficient catalytic conversion in biosensing applications.

  15. Crystallization and self-assembly of flowerlike superstructures of calcium carbonate regulated by pepsin Langmuir monolayers

    International Nuclear Information System (INIS)

    Flowerlike superstructures of calcium carbonate were synthesized at air–water interface in the presence of pepsin Langmuir monolayers as the biomimetic template. The phase structure, morphology, and microstructure of the products obtained at various crystallization stages were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy. The structural and morphological evolution processes of the products from monodispersed nanoparticles to nanoparticle aggregates and flowerlike superstructures were investigated. Results indicate that the flowerlike superstructures of calcium carbonate are assembled from amorphous calcium carbonate nanoparticles. The growth and assembly of calcium carbonate minerals are significantly regulated by the pepsin Langmuir monolayers. Namely, the pepsin Langmuir monolayers stabilize amorphous calcium carbonate nanoparticles and direct their transformation to amorphous aggregates via non-oriented aggregation. The present approach presents a feasible way to manipulate the growth of inorganic crystal, which, hopefully, is to help better reveal the role of proteins in mineralization process and understand the mechanism of biomineralization. -- Highlights: ► Pepsin Langmuir monolayer as biomimetic template. ► Flower-like calcite crystals experience a novel assembly and growth process. ► The morphologic evolution and phase transformation were observed. ► The trace of initial nucleation site of CaCO3 at the interface was observed. ► The template directs the crystallization and growth process.

  16. Crystallization and self-assembly of flowerlike superstructures of calcium carbonate regulated by pepsin Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Zhonghui [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China); School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Hu, Binbin; Dai, Shuxi [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China); Du, Zuliang, E-mail: zld@henu.edu.cn [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China)

    2012-10-15

    Flowerlike superstructures of calcium carbonate were synthesized at air-water interface in the presence of pepsin Langmuir monolayers as the biomimetic template. The phase structure, morphology, and microstructure of the products obtained at various crystallization stages were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy. The structural and morphological evolution processes of the products from monodispersed nanoparticles to nanoparticle aggregates and flowerlike superstructures were investigated. Results indicate that the flowerlike superstructures of calcium carbonate are assembled from amorphous calcium carbonate nanoparticles. The growth and assembly of calcium carbonate minerals are significantly regulated by the pepsin Langmuir monolayers. Namely, the pepsin Langmuir monolayers stabilize amorphous calcium carbonate nanoparticles and direct their transformation to amorphous aggregates via non-oriented aggregation. The present approach presents a feasible way to manipulate the growth of inorganic crystal, which, hopefully, is to help better reveal the role of proteins in mineralization process and understand the mechanism of biomineralization. -- Highlights: Black-Right-Pointing-Pointer Pepsin Langmuir monolayer as biomimetic template. Black-Right-Pointing-Pointer Flower-like calcite crystals experience a novel assembly and growth process. Black-Right-Pointing-Pointer The morphologic evolution and phase transformation were observed. Black-Right-Pointing-Pointer The trace of initial nucleation site of CaCO{sub 3} at the interface was observed. Black-Right-Pointing-Pointer The template directs the crystallization and growth process.

  17. Preparation, characterization, and photoelectric properties of a covalently self-assembled monolayer of ferrocenyl hemicyanine.

    Science.gov (United States)

    Li, Lin-Ying; Chen, Xi; Xu, Meng-Yun; Zhang, Qian-Jin; Wang, Ke-Zhi

    2011-11-01

    A monolayer of a ferrocenyl hemicyanine was covalently self-assembled on an indium tin oxide (ITO)-coated glass substrate, and was characterized by UV/Vis absorption and X-ray photoelectron spectroscopy, and cyclic voltammetry. The photoelectrochemical properties and mechanism of photocurrent generation have also been studied. This monolayer film was found to exhibit a large anodic photocurrent density of 0.13 microA/cm2 with the highest photoelectric yield of 3.32% under irradiation of white light (730 nm > lambda > 325 nm) at a bias potential of +0.4 V versus saturated calomel electrode.

  18. Characterization of Formation Kinetics of Self-Assembled Thiol Monolayers on Gold by Electrochemical Impedance Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Self-assembled monolayers of octadecanethiol (ODT) on gold have been studied by electrochemical impedance spectroscopy (EIS). The fractional coverage has been examined as a function of immersion time of Au in ODT deposition solution. The fractional coverage exhibits two distinct adsorption steps: an initial rapid step followed by a slow one. The fractional coverage of ODT monolayer increases sharply from zero to more than 99% of its maximum within the first minute. However, it takes a day for the fractional coverage to approach its final value.

  19. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides.

    Science.gov (United States)

    Zheng, Yu Jie; Huang, Yu Li; Chen, Yifeng; Zhao, Weijie; Eda, Goki; Spataru, Catalin D; Zhang, Wenjing; Chang, Yung-Huang; Li, Lain-Jong; Chi, Dongzhi; Quek, Su Ying; Wee, Andrew Thye Shen

    2016-02-23

    The nature and extent of electronic screening at heterointerfaces and their consequences on energy level alignment are of profound importance in numerous applications, such as solar cells, electronics etc. The increasing availability of two-dimensional (2D) transition metal dichalcogenides (TMDs) brings additional opportunities for them to be used as interlayers in "van der Waals (vdW) heterostructures" and organic/inorganic flexible devices. These innovations raise the question of the extent to which the 2D TMDs participate actively in dielectric screening at the interface. Here we study perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on single-layer tungsten diselenide (WSe2), bare graphite, and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on the electronic screening effects from the substrate. The monolayer WSe2 interlayer provides substantial, but not complete, screening at the organic/inorganic interface. Our results lay a foundation for the exploitation of the complex interfacial properties of hybrid systems based on TMD materials. PMID:26792247

  20. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

    KAUST Repository

    Zheng, Yu Jie

    2016-01-21

    © 2016 American Chemical Society. The nature and extent of electronic screening at heterointerfaces and their consequences on energy level alignment are of profound importance in numerous applications, such as solar cells, electronics etc. The increasing availability of two-dimensional (2D) transition metal dichalcogenides (TMDs) brings additional opportunities for them to be used as interlayers in "van der Waals (vdW) heterostructures" and organic/inorganic flexible devices. These innovations raise the question of the extent to which the 2D TMDs participate actively in dielectric screening at the interface. Here we study perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on single-layer tungsten diselenide (WSe2), bare graphite, and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on the electronic screening effects from the substrate. The monolayer WSe2 interlayer provides substantial, but not complete, screening at the organic/inorganic interface. Our results lay a foundation for the exploitation of the complex interfacial properties of hybrid systems based on TMD materials.

  1. Organization, Structure and Activity of Proteins in Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Boucher,J.; Trudel, E.; Methot, M.; Desmeules, P.; Salesse, C.

    2007-01-01

    Many different processes take place at the cell membrane interface. Indeed, for instance, ligands bind membrane proteins which in turn activate peripheral membrane proteins, some of which are enzymes whose action is also located at the membrane interface. Native cell membranes are difficult to use to gain information on the activity of individual proteins at the membrane interface because of the large number of different proteins involved in membranous processes. Model membrane systems, such as monolayers at the air-water interface, have thus been extensively used during the last 50 years to reconstitute proteins and to gain information on their organization, structure and activity in membranes. In the present paper, we review the recent work we have performed with membrane and peripheral proteins as well as enzymes in monolayers at the air-water interface. We show that the structure and orientation of gramicidin has been determined by combining different methods. Furthermore, we demonstrate that the secondary structure of rhodopsin and bacteriorhodopsin is indistinguishable from that in native membranes when appropriate conditions are used. We also show that the kinetics and extent of monolayer binding of myristoylated recoverin is much faster than that of the nonmyristoylated form and that this binding is highly favored by the presence polyunsaturated phospholipids. Moreover, we show that the use of fragments of RPE65 allow determine which region of this protein is most likely involved in membrane binding. Monomolecular films were also used to further understand the hydrolysis of organized phospholipids by phospholipases A2 and C.

  2. Electrochemical characterization of a 1,8-octanedithiol self-assembled monolayer (ODT-SAM) on a Au(111) single crystal electrode

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Raya, Daniel; Madueno, Rafael; Sevilla, Jose Manuel; Blazquez, Manuel; Pineda, Teresa [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus de Rabanales, Cordoba (Spain)

    2008-11-15

    Recently, it has becoming increasingly important to control the organization of self-assembled monolayers (SAMs) of {omega}-functionalized thiols for its potential applications in the construction of more complex molecular architectures. In this paper, we report on the spontaneous formation of a SAM of octanedithiol (ODT) as a function of the modification time. Electrochemical techniques such as cyclic voltammetry, double layer capacitance and electrochemical impedance spectroscopy are used for the characterization of this monolayer. The increase in modification time brings about changes in the octanedithiol self-assembled monolayer (ODT-SAM) reductive desorption voltammograms that indicate an evolution toward a more ordered and compact monolayer. This trend has also been found by following the changes in the electron transfer processes of the redox probe K{sub 3}Fe(CN){sub 6}. In fact, the ODT-SAM formed at low-modification time does not significantly perturb the electrochemical response as it is typical of either a low coverage or of the presence of large defects in the layer. Upon increasing the modification time, the voltammograms of the redox probe adopt a sigmoidal shape indicating the existence of pinholes in the monolayer distributed as an array of microelectrodes. The surface coverage as well as the size and distribution of these pinholes have been determined by the impedance technique that gives a more reliable evaluation of these monolayer structural parameters. (author)

  3. Electrochemical characterization of a 1,8-octanedithiol self-assembled monolayer (ODT-SAM) on a Au(1 1 1) single crystal electrode

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Raya, Daniel; Madueno, Rafael; Sevilla, Jose Manuel; Blazquez, Manuel [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus de Rabanales, Ed. Marie Curie, E-14071 Cordoba (Spain); Pineda, Teresa [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus de Rabanales, Ed. Marie Curie, E-14071 Cordoba (Spain)], E-mail: tpineda@uco.es

    2008-11-15

    Recently, it has becoming increasingly important to control the organization of self-assembled monolayers (SAMs) of {omega}-functionalized thiols for its potential applications in the construction of more complex molecular architectures. In this paper, we report on the spontaneous formation of a SAM of octanedithiol (ODT) as a function of the modification time. Electrochemical techniques such as cyclic voltammetry, double layer capacitance and electrochemical impedance spectroscopy are used for the characterization of this monolayer. The increase in modification time brings about changes in the octanedithiol self-assembled monolayer (ODT-SAM) reductive desorption voltammograms that indicate an evolution toward a more ordered and compact monolayer. This trend has also been found by following the changes in the electron transfer processes of the redox probe K{sub 3}Fe(CN){sub 6}. In fact, the ODT-SAM formed at low-modification time does not significantly perturb the electrochemical response as it is typical of either a low coverage or of the presence of large defects in the layer. Upon increasing the modification time, the voltammograms of the redox probe adopt a sigmoidal shape indicating the existence of pinholes in the monolayer distributed as an array of microelectrodes. The surface coverage as well as the size and distribution of these pinholes have been determined by the impedance technique that gives a more reliable evaluation of these monolayer structural parameters.

  4. Self-assembly of noble metal monolayers on transition metal carbide nanoparticle catalysts.

    Science.gov (United States)

    Hunt, Sean T; Milina, Maria; Alba-Rubio, Ana C; Hendon, Christopher H; Dumesic, James A; Román-Leshkov, Yuriy

    2016-05-20

    We demonstrated the self-assembly of transition metal carbide nanoparticles coated with atomically thin noble metal monolayers by carburizing mixtures of noble metal salts and transition metal oxides encapsulated in removable silica templates. This approach allows for control of the final core-shell architecture, including particle size, monolayer coverage, and heterometallic composition. Carbon-supported Ti(0.1)W(0.9)C nanoparticles coated with Pt or bimetallic PtRu monolayers exhibited enhanced resistance to sintering and CO poisoning, achieving an order of magnitude increase in specific activity over commercial catalysts for methanol electrooxidation after 10,000 cycles. These core-shell materials provide a new direction to reduce the loading, enhance the activity, and increase the stability of noble metal catalysts.

  5. Distinct self-assembly of dithiol monolayers on Au(1 1 1) in water and hexane

    International Nuclear Information System (INIS)

    Highlights: • The self-assembly of 1,4-benzenedimethanethiol in water and in hexane is studied. • The initial phase of assembly is revealed for each solvent using STM and XPS. • Water stabilizes an ordered lying-down phase. • Hexane coadsorbs with benzenedimethanethiol and promotes standing-up absorption. - Abstract: The self-assembly of 1,4-benzenedimethanethiol on Au(1 1 1), at low concentration in water and in hexane which are respectively polar and non-polar solvent, has been studied by scanning tunneling microscopy (STM). The data reveal that, on clean Au(1 1 1), a complete and ordered self-assembled monolayer (SAM) of lying-down dithiols can form within a few seconds in water. While in hexane the adsorption is initially impeded by the rapid growth of an ordered hexane film that is gradually replaced by disordered domains of dithiol until completion of a saturated monolayer. Complemented by X-ray photoelectron spectroscopy measurements, the STM images resolve the progression of the self-assembly in both these polar and non-polar solvent, and highlight how the self-assembly depends on the trio solvent, dithiol, and substrate

  6. Application of the self-assembled monolayer (SAM) model to dithiophosphate and dithiocarbamate engine wear inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Y.; Jiang, S.; Cagin, T.; Yamaguchi, E.S.; Frazier, R.; Ho, A.; Tang, Y.; Goddard, W.A. III

    2000-03-23

    In previous studies of dithiophosphate [TP=S{sub 2}P(OR){sub 2}] wear inhibitors bound to an oxidized iron surface, it was found that the cohesive energy of the self-assembled monolayers (SAM) for DTP molecules with various organic R groups correlate with the wear inhibition observed in full engine experiments. In this paper the calculations are expanded to consider dynamics at 500 K and the SAM model is used to predict new candidates for wear inhibitors. Using molecular dynamics (MD) simulations show that the SAM has one DTP per two surface Fe sites of iron oxide. At this coverage the cohesive energy of the SAM at 500 K is in the sequence 2-alkyl > 1-alkyl > aryl, which again correlates with wear inhibitor performance in engine wear tests. Dithiocarbamates are selected as the best candidate to supplement DTP.A number of possible alkyl substitutions for DTC were considered. The SAM model suggests that iC{sub 5} and nC{sub 3} are the best candidates, followed closely by iC{sub 3}.

  7. STM observation of sulfur dimerization in alkanethiol self-assembled monolayers on Au{111}

    OpenAIRE

    O'Dwyer, Colm

    2005-01-01

    We present for the first time, direct microscopical observation by STM of sulfur dimer formation on alkanethiol self-assembled monolayers (SAM) on sputtered Au substrates. The sulfur dimers are observed when imaging at a bias where the tip-molecule interaction occurs, and are formed by displacement of sulfur atoms from their normal three-fold hollow site residence of the (4 × 2) superlattice to nearest-neighbor bridge-site residence between two Au atoms. The displacement is ...

  8. Attachment of tyrosinase on mixed self-assembled monolayers for the construction of electrochemical biosensor

    Institute of Scientific and Technical Information of China (English)

    Xue Ping Ji; Xian Rui Li; Na Wang; Rui Xing Ni; Xiao Hong Liu; Hua Ai Xiong

    2010-01-01

    A mixed self-assembled monolayers(SAMs)of thioctic acid(T-COOH)and thioctic acid amide(T-NH2)were used to immobilize tyrosinase for fabricating biosensor.The results showed that the mixed SAMs prepared from solution at the ratio of 1:4provided an excellent microenvironment for enzymatic reaction between tyrosinase and substrate.The biosensor exhibited a fast response and high sensitivity for sensing substrate.

  9. A Solid Ag Film Deposited from Solution on Self-assembled Mercaptopropyltrimethoxysilane (MPTS) Monolayer

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Mercaptopropyltrimethoxysilane (MPTS) bearing mercapto groups was used to form self-assembly monolayers (SAMs) on glass substrates by solution extraction. SEM, XRD and rubbing test analysis illustrated that the Ag film on the SAMs-modified glass was more durable than that on the commonly-modified glass and that the crystallinity of Ag film on the SAMs-modified glass was identical with those of the Ag film on the commonly-modified glass and pure Ag.

  10. Mass spectrometry assisted lithography for the patterning of cell adhesion ligands on self-assembled monolayers.

    Science.gov (United States)

    Kim, Young-Kwan; Ryoo, Soo-Ryoon; Kwack, Sul-Jin; Min, Dal-Hee

    2009-01-01

    Pattern of events: A simple and flexible method has been developed for patterning cell adhesion ligands. Locally erasing self-assembled monolayers with tri(ethyleneglycol) groups on a gold substrate by using a MALDI-TOF MS nitrogen laser and filling the exposed gold surface with an alkanethiol presenting carboxylic acid groups enables subsequent immobilization of maleimide and a cell adhesion peptide, which can then recognize cells (see scheme). PMID:19347909

  11. Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers

    OpenAIRE

    Kruszewski, Kristen M; Nistico, Laura; Mark J Longwell; Hynes, Matthew J; Maurer, Joshua A; Hall-Stoodley, Luanne; Gawalt, Ellen S.

    2013-01-01

    Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with lo...

  12. Self-assembled monolayer as optical transducers using spiropyran photochromic material

    Science.gov (United States)

    Ortiz Ramírez, Alicia; Delgado Macuil, Raúl; Rojas López, Marlon; López Gayou, Valentin; Orduña Díaz, Abdu

    2011-09-01

    The self assembled monolayers (SAM) have become in the most popular strategy for design and generate surfaces characterizing by specific functional organic groups. The aimed of this work is applied this SAM as optical transducer in biosensors. The techniques, Infrared (in ATR mode) and UV/Vis spectroscopy have been used to study the films generated in each step in the self assembled process. The SAM was generated as follow; first silane group was added to the glass substrate. After that, the substrates were immersed in a solution containing carbomiide group (EDC). Finally the spiropyran 1',3'-Dihydro-8-methoxy-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] was attached to functionalized slides. In each process absorbance was analyzed by UV/Vis (270 to 500 nm) and FTIR (650 to 1800 cm-1). In UV, the spectra shows an absorbance band centered at 280 associated to EDC film and a lower intensity band centered at 380 nm associated to spiropyran. In FTIR spectra, the Si-Si and Si-O bond are present below the 1250 cm-1. The EDC film shows very weak bands in the region from 1300 to 1800 cm-1. For the spiropyran film the band associated to the C-N, N-O, C=C, C-H and aromatic ring have a very well defined peaks. Once the transducer bands were detected, it was immersed in glucose solution; the infrared spectral show bands are associated to glucose in the transducer.

  13. Effect of Time and Deposition Method on Quality of Phosphonic Acid Modifier Self-Assembled Monolayers on Indium Zinc Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Lingzi; Knesting, Kristina M.; Bulusu, Anuradha; Sigdel, Ajaya K.; Giordano, Anthony J.; Marder, Seth R.; Berry, Joseph J.; Graham, Samuel; Ginger, David S.; Pemberton, Jeanne E.

    2016-12-15

    Phosphonic acid (PA) self-assembled monolayers (SAMs) are utilized at critical interfaces between transparent conductive oxides (TCO) and organic active layers in organic photovoltaic devices (OPVs). The effects of PA deposition method and time on the formation of close-packed, high-quality monolayers is investigated here for SAMs fabricated by solution deposition, micro-contact printing, and spray coating. The solution deposition isotherm for pentafluorinated benzylphosphonic acid (F5BnPA) on indium-doped zinc oxide (IZO) is studied using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) at room temperature as a model PA/IZO system. Fast surface adsorption occurs within the first min; however, well-oriented high-quality SAMs are reached only after -48 h, presumably through a continual process of molecular adsorption/desorption and monolayer filling accompanied by molecular reorientation. Two other rapid, soak-free deposition techniques, micro-contact printing and spray coating, are also explored. SAM quality is compared for deposition of phenyl phosphonic acid (PPA), F13-octylphosphonic acid (F13OPA), and pentafluorinated benzyl phosphonic acid (F5BnPA) by solution deposition, micro-contact printing and spray coating using PM-IRRAS. In contrast to micro-contact printing and spray coating techniques, 48-168 h solution deposition at both room temperature and 70 degrees C result in contamination- and surface etch-free close-packed monolayers with good reproducibility. SAMs fabricated by micro-contact printing and spray coating are much less well ordered.

  14. Emergence of complex chemistry on an organic monolayer.

    Science.gov (United States)

    Prins, Leonard J

    2015-07-21

    In many origin-of-life scenarios, inorganic materials, such as FeS or mineral clays, play an important role owing to their ability to concentrate and select small organic molecules on their surface and facilitate their chemical transformations into new molecules. However, considering that life is made up of organic matter, at a certain stage during the evolution the role of the inorganic material must have been taken over by organic molecules. How this exactly happened is unclear, and, indeed, a big gap separates the rudimentary level of organization involving inorganic materials and the complex organization of cells, which are the building blocks of life. Over the past years, we have extensively studied the interaction of small molecules with monolayer-protected gold nanoparticles (Au NPs) for the purpose of developing innovative sensing and catalytic systems. During the course of these studies, we realized that the functional role of this system is very similar to that typically attributed to inorganic surfaces in the early stages of life, with the important being difference that the functional properties (molecular recognition, catalysis, signaling, adaptation) originate entirely from the organic monolayer rather than the inorganic support. This led us to the proposition that this system may serve as a model that illustrates how the important role of inorganic surfaces in dictating chemical processes in the early stages of life may have been taken over by organic matter. Here, we reframe our previously obtained results in the context of the origin-of-life question. The following functional roles of Au NPs will be discussed: the ability to concentrate small molecules and create different local populations, the ability to catalyze the chemical transformation of bound molecules, and, finally, the ability to install rudimentary signaling pathways and display primitive adaptive behavior. In particular, we will show that many of the functional properties of the system

  15. Self-assembled monolayers of perfluoroalkylsilane on plasma-hydroxylated silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Lin; Cai, Lu; Liu, Anqi; Wang, Wei; Yuan, Yanhua [College of Textile, Clothing Engineering, Soochow University, Suzhou 215021 (China); National Engineering Laboratory for Modern Silk, Suzhou 215123 (China); Li, Zhanxiong, E-mail: lizhanxiong@suda.edu.cn [College of Textile, Clothing Engineering, Soochow University, Suzhou 215021 (China); State Key Laboratory of Disaster Prevention & Mitigation of Explosion & Impact, Nanjing 210007 (China)

    2015-09-15

    Highlights: • A novel kind of fluoroalkylsilane monomers with different fluoroalkyl chain length was synthesized. • The fluoroalkyl-terminated self-assembled monolayers (SAMs) on silanol-terminated silicon substrates were chemically fabricated using the liquid phase deposition method. • Fluoroalkylsilanes were used for the self-assembly rather than the silane coupling agents and fluorochemicals to fabricate controllable, ordered SAMs. • The angle-dependent XPS study was conducted to investigate the changes of surface structures as well as elemental compositions of the SAMs. • The results indicated that fluoroalkyl groups would migrate from the inner part of the monolayers to the outermost interface after heat treatment, resulting into the microphase separation of the SAMs surface. - Abstract: In this study, a novel kind of fluoroalkylsilane monomers with different fluoroalkyl chain lengths was synthesized via three steps method and characterized by Fourier transform infrared (FT-IR) spectroscopy, {sup 1}H and {sup 19}F nuclear magnetic resonance ({sup 1}H NMR and {sup 19}F NMR), and mass spectra (MS). Fluoroalkyl-terminated self-assembled monolayers (SAMs) on silanol-terminated silicon substrates (O{sub 2} plasma treatment) were chemically fabricated via –Si–O– covalent bonds using the liquid phase deposition method (LPD). The wetabilities of the SAMs were characterized by water contact angles (CA), surface free energies and adhesive force (AF) measurements. 3-(1H,1H,2H,2H-perfluorooctyloxycarbonyl) -propionamidepropyl-triethoxysilane (PFOPT) assembled monolayer was chosen for in-depth investigation as its CA was higher than the others. Attenuated total reflection infrared spectroscopy (ATR-IR) and X-ray photoelectron spectroscopy (XPS) were used to validate the attachment of PFOPT on the silicon substrate, together with the chemical composition and structure of the SAMs. The surface morphologies and roughness of the monolayers were obtained and

  16. Free-Standing Monolayer Two-Dimensional Supramolecular Organic Framework with Good Internal Order.

    Science.gov (United States)

    Pfeffermann, Martin; Dong, Renhao; Graf, Robert; Zajaczkowski, Wojciech; Gorelik, Tatiana; Pisula, Wojciech; Narita, Akimitsu; Müllen, Klaus; Feng, Xinliang

    2015-11-18

    Utilizing dynamic self-assembly and self-sorting to obtain large-area, molecularly precise monolayered structures represents a promising approach toward two-dimensional supramolecular organic frameworks (2D SOF) or 2D supramolecular polymers. So far, related approaches suffer from small domain sizes, fragility and weak long-range internal order. Here we report on the self-assembly of a host-guest enhanced donor-acceptor interaction, consisting of a tris(methoxynaphthyl)-substituted truxene spacer, and a naphthalene diimide substituted with N-methyl viologenyl moieties as donor and acceptor monomers, respectively, in combination with cucurbit[8]uril as host monomer toward monolayers of an unprecedented 2D SOF. Featuring orthogonal solubility, the participating molecules self-assemble at a liquid-liquid interface, yielding exceptionally large-area, insoluble films, which were analyzed by transmission electron microscopy, atomic force microscopy and optical microscopy to be monolayers with a thickness of 1.8 nm, homogeneously covering areas up to 0.25 cm(2), and featuring the ability to be free-standing over holes of 10 μm(2). Characterization with ultraviolet-visible absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, and grazing incidence wide-angle X-ray scattering allowed for confirmation of a successful complexation of all three monomers toward an internal long-range order and gave indications to an expected hexagonal superstructure. Our results extend the existing variety of two-dimensional soft nanomaterials by a versatile supramolecular approach, whereas the possibility of varying the functional monomers is supposed to open adaptability to different applications like membranes, sensors, molecular sieves, and optoelectronics. PMID:26529142

  17. Self-assembled monolayers on mosoporous supports (SAMMS) for RCRA metal removal

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xiangdong; Liu, Jun; Fryxell, G. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-10-01

    The Mixed Waste Focus Area has declared mercury removal and stabilization as the first and fourth priorities among 30 prioritized deficiencies. Resource Conservation and Recovery Act (RCRA) metal and mercury removal has also been identified as a high priority at DOE sites such as Albuquerque, Idaho Falls, Oak Ridge, Hanford, Rocky Flats, and Savannah River. Under this task, a proprietary new technology, Self-Assembled Monolayers on Mesoporous Supports (SAMMS), for RCRA metal ion removal from aqueous wastewater and mercury removal from organic wastes such as vacuum pump oils is being developed at Pacific Northwest National Laboratory (PNNL). The six key features of the SAMMS technology are (1) large surface area (>900 m{sup 2}/g) of the mesoporous oxides (SiO{sub 2}, ZrO{sub 2}, TiO{sub 2}) ensures high capacity for metal loading (more than 1 g Hg/g SAMMS); (2) molecular recognition of the interfacial functional groups ensures the high affinity and selectivity for heavy metals without interference from other abundant cations (such as calcium and iron) in wastewater; (3) suitability for removal of mercury from both aqueous wastes and organic wastes; (4) the Hg-laden SAMMS not only pass TCLP tests, but also have good long-term durability as a waste form because the covalent binding between mercury and SAMMS has good resistance to ion exchange, oxidation, and hydrolysis; (5) the uniform and small pore size (2 to 40 nm) of the mesoporous silica prevents bacteria (>2000 nm) from solubilizing the bound mercury; and (6) SAMMS can also be used for RCRA metal removal from gaseous mercury waste, sludge, sediment, and soil.

  18. Effect of density and structure on dynamics within self-assembled monolayers

    Science.gov (United States)

    Stevens, Derrick; Scott, Mary; Bochinski, Jason; Clarke, Laura

    2009-03-01

    Previously, we have observed interacting dynamics within self-assembled alkylsiloxane monolayers, and characterized this motion via sensitive dielectric spectroscopy (along with more traditional techniques such as ellipsometry, contact angle, and force microscopy). In these monolayers, molecules are covalently bound to the surface and thus cannot spontaneously change density, as in an adsorbate system. We identified this relaxation as akin to the polyethylene-like glass transition observed in polymers with phase-segregated alkyl side chains [1]. As a next step, we deliberately manipulated the physical structure of the monolayers (via different film growth procedures and/or post-deposition heat treating) and the monolayer density (from ˜10% to full coverage), and observed the resultant changes in dynamics. This experimental system may prove a useful model for more complex materials, such as glassy polymers or traditional molecular glasses, where density cannot be explicitly tuned. As density increases, the steepness index increases, indicating a more complex or fragile relaxation. At low densities, the motion has an almost-Arrhenius dependence on temperature. [1] M.C. Scott, D.R. Stevens, J.R. Bochinski, L.I. Clarke, ACS Nano. DOI: 10.1021/nn800543j.

  19. Oxidation protection of copper surfaces using self-assembled monolayers of octadecanethiol

    International Nuclear Information System (INIS)

    Self-assembled monolayers (SAMs) of alkanethiols adsorbed onto clean surfaces of face centred cubic (fcc) metals have been studied extensively for their ability to control the chemical functionality of the surface and as a means of preventing the oxidation and corrosion of the substrate metal. However, in many cases it has been found that on reactive substrates such as copper, it is difficult to prepare SAMs without the incorporation of some oxygen into the structure. In this work, self-assembled monolayers of octadecanethiol (ODT) were formed on copper foil substrates using a series of etching treatments to remove the native oxide layer prior to deposition of the ODT coating from a modified solution. X-ray photoelectron spectroscopy was used to analyse the SAMs and showed that monolayers with no detectable oxygen content could be produced. The effect of exposing the samples to air at different temperatures was monitored to examine the rate of the oxidation process, which was found to vary strongly with temperature. Samples stored at room temperature were found to oxidise relatively quickly, while those kept in a refrigerator were slower. Storing samples in a freezer dramatically reduced the oxidation of the copper, such that samples kept for 10 weeks still did not show any clear evidence of oxygen incorporation

  20. Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solidsa)

    Science.gov (United States)

    Greene, J. E.

    2015-03-01

    The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (˜1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ˜78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese "floating-ink" art (suminagashi) developed ˜1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO2 and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including controlled wetting

  1. Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solids

    Energy Technology Data Exchange (ETDEWEB)

    Greene, J. E. [University of Illinois, Urbana, Illinois 61801 (United States); Linköping University, 581 83 Linköping (Sweden); National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

    2015-03-15

    The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (∼1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ∼78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese “floating-ink” art (suminagashi) developed ∼1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO{sub 2} and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including

  2. Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solids

    International Nuclear Information System (INIS)

    The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (∼1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ∼78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese “floating-ink” art (suminagashi) developed ∼1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO2 and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including

  3. Self-assembly of organic films on a liquid metal

    Science.gov (United States)

    Magnussen, Olaf M.; Ocko, Benjamin M.; Deutsch, Moshe; Regan, Michael J.; Pershan, Peter S.; Abernathy, Douglas; Grübel, Gerhard; Legrand, Jean-François

    1996-11-01

    THE structure and phase behaviour of organic thin films result from the subtle interplay of intermolecular Van der Waals interactions, which promote self-assembly and long-ranged order, and the more complex interactions between the end groups of the organic chains and the substrate. The structure of molecular films of amphiphiles has been extensively studied on subphases of dielectric liquids, notably water (Langmuir mono-layers) and on solid surfaces (self-assembled monolayers, SAMs)1-4. Here we report structural studies, by synchrotron X-ray scattering, of an intermediate case: densely packed alka-nethiol films on the surface of liquid mercury. While, like SAMs, these films form strong chemical bonds to the subphase, this subphase is smooth and unstructured, as in the case of Langmuir monolayers. But unlike either of these1,2,5-7, our films have no in-plane long-range order. We suggest that the strong interaction of the thiol group with the underlying disordered liquid dominates here over the order-promoting interactions of the alkyl chains.

  4. Formation of octadecyltrichlorosilane (OTS) self-assembled monolayers on amorphous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, Sanket S.; Chiavetta, David; Wolden, Colin A., E-mail: cwolden@mines.edu

    2013-10-01

    The kinetics and thermodynamics of octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on vapor deposited alumina were quantified. Ozone cleaning serves to create well-defined hydrophilic surfaces for OTS attachment, and the use of heptane as a solvent enables the formation of high quality SAMs under ambient conditions. The kinetics was characterized as a function of OTS concentration using contact angle goniometry, ellipsometry and Fourier transform infrared (FTIR) spectroscopy. The kinetics of SAM formation and the saturation contact angle (∼100{sup o}) on alumina are comparable to what has been observed for OTS on silicon. The free energy of adsorption with ΔG{sub ads} values ranged from −7.5 to −5.4 kcal/mol, and the SAMs were stable up to 230 {sup o}C. The critical surface tension of the OTS monolayer was found to be 21.4 dyne/cm.

  5. A dielectric model of self-assembled monolayer interfaces by capacitive spectroscopy.

    Science.gov (United States)

    Góes, Márcio S; Rahman, Habibur; Ryall, Joshua; Davis, Jason J; Bueno, Paulo R

    2012-06-26

    The presence of self-assembled monolayers at an electrode introduces capacitance and resistance contributions that can profoundly affect subsequently observed electronic characteristics. Despite the impact of this on any voltammetry, these contributions are not directly resolvable with any clarity by standard electrochemical means. A capacitive analysis of such interfaces (by capacitance spectroscopy), introduced here, enables a clean mapping of these features and additionally presents a means of studying layer polarizability and Cole-Cole relaxation effects. The resolved resistive term contributes directly to an intrinsic monolayer uncompensated resistance that has a linear dependence on the layer thickness. The dielectric model proposed is fully aligned with the classic Helmholtz plate capacitor model and additionally explains the inherently associated resistive features of molecular films.

  6. Electrochemical Study of Biotin-Modified Self-Assembled Monolayers: Recommendations for Robust Preparation

    Directory of Open Access Journals (Sweden)

    Richard J.C. Brown

    2006-01-01

    Full Text Available The development of the underpinning methodology for the production of robust, well-formed, and densely packed biotin-HPDP functionalised gold surfaces, the crucial first step in immobilising bimolecules on surfaces, is described. Self-assembled monolayers (SAMs with biotin end-groups were prepared on polycrystalline gold surfaces according to a published method. The layers formed were studied using cyclic voltammetry to determine the composition of the layer and its quality. Crystal impedance spectroscopy was also applied as a complimentary indicator of the composition of the layer.For the first time, the effect of assembly time on the properties of the layer was studied along with the composition of the layer and the ability of the precursor molecule to self-assemble by oxidative addition.

  7. Preparation and characterization of 3-(triethoxysilyl) propyl isocyanate self-assembled monolayer on surface of chip

    Institute of Scientific and Technical Information of China (English)

    XIE Yao; GENG LiNa; QU Feng; LUO AiQin; QU Feng; DENG YuLin

    2009-01-01

    Monolayer of 3-(triethoxysilyl) propyl isocyanate was prepared on the slide by self-assembled tech-nique. X-ray photoelectron spectroscopy (XPS) was employed to analyze the elementary composition of the film. Contact angle of distilled water was measured to characterize the surface state. It was shown that 3-(triethoxysilyl) propyl isocyanate had been successfully assembled on the slide. The in-crease of contact angle to 80 demonstrated that the hydrophobicity of the surface of chip was in-creased significantly. Moreover, further self-assembly of bovine serum albumin (BSA) on 3-(trietho-xysilyl) propyl isocyanate was also carried out with the advantages such as simple and convenient preparation. Therefore, the potential of broader applications in the modification of micro-channel in the μ-TAS system, the immobilization of protein or peptide and the surface modification of materials are all expectative.

  8. Morphological and Structural Control of Organic Monolayer Colloidal Crystal Based on Plasma Etching and Its Application in Fabrication of Ordered Gold Nanostructured Arrays

    Directory of Open Access Journals (Sweden)

    Guangqiang Liu

    2016-09-01

    Full Text Available The organic monolayer colloidal crystals, which are usually prepared by self-assembling, could be used as templates, due to their interstitial geometry, for the periodically arranged nanostructured arrays, which have important applications in many fields, such as photonic crystals, information storage, super-hydrophobicity, biological and chemical sensing. Obviously, the structures of the obtained arrays mainly depend on those of the templates. However, the self-assembled monolayer colloidal crystal is exclusive in structure and for its hexagonal close-packed colloidal arrangement, leading to the limitation of the monolayer colloidal crystal as the template for the nanostructured arrays. Therefore, structural diversity is important in order for colloidal crystals to be used as the templates for various nanostructured arrays. Recently, there have been some reports on the morphological and structural manipulation of the organic monolayer colloidal crystals. In this review article, we focus on the recent progress in morphological and structural manipulation of polystyrene monolayer colloidal crystals based on plasma etching, and its application in the fabrication of the ordered gold nanostructured arrays with different structures, mainly including close-packed monolayer colloidal crystal and its transferrable property; structural manipulation based on plasma etching; and fabrication of gold nanostructured arrays based on varied monolayer colloidal crystals as template.

  9. Vapor Phase Self-assembled Monolayers for Anti-stiction Applications in MEMS

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Hansen, Ole; Knieling, Thomas;

    2007-01-01

    We have investigated the anti-stiction performance of self-assembled monolayers (SAMs) that were grown in vapor phase from six different organosilane precursors: CF3(CF2)5(CH2)2SiCl3 (FOTS), CF3(CF2)5(CH2)2Si(OC2H5)3 (FOTES), CF3(CF2)5(CH2)2Si(CH3)Cl2 (FOMDS), CF3(CF2)5(CH2)2Si(CH3)2Cl (FOMMS), C...

  10. Towards strain gauges based on a self-assembled nanoparticle monolayer-SAXS study

    International Nuclear Information System (INIS)

    An in situ small-angle x-ray scattering study of the nanoparticle displacement in a self-assembled monolayer as a function of a supporting membrane strain is presented. The average nanoparticle spacing is 6.7 nm in the unstrained state and increases in the applied force direction, following linearly the membrane strain which reaches the maximum value of 11%. The experimental results suggest a continuous mutual shift of the nanoparticles and their gradual separation with the growing stress rather than nanoparticle islands formation. No measurable shift of the nanoparticles was observed in the direction perpendicular to the applied stress.

  11. Crystalline self-assembly into monolayers of folded oligomers at the air-water interface

    DEFF Research Database (Denmark)

    Lederer, K.; Godt, A.; Howes, P.B.;

    2000-01-01

    Insertion of the 115-bis(ethynylene)benzene unit as a rigid spacer into a linear alkyl chain, thus separating the two resulting stems by 9 Angstrom, induces chain folding at the air-water interface. These folded molecules self-assemble into crystalline monolayers at this interface, with the plane...... and position of the hydrophilic groups in the molecule. The molecules form ribbons with a higher crystal coherence in the direction of stacking between the molecular ribbons, and a lower coherence along the ribbon direction. A similar molecule, but with a spacer unit that imposes a 5 Angstrom separation...

  12. Self-assembly of octadecyltrichlorosilane monolayers on silicon-based substrates by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dong Jinping [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, Michigan 48202 (United States); Wang Anfeng [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, Michigan 48202 (United States); Ng, K.Y. Simon [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, Michigan 48202 (United States); Mao Guangzhao [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, Michigan 48202 (United States)]. E-mail: gzmao@eng.wayne.edu

    2006-12-05

    Increasingly, organosilane self-assembled monolayers (SAMs) are used to modify the surfaces of silicon-based sensors and atomic force microscope (AFM) probes. Organosilane SAMs are preferred due to their fast and easy preparation, stability, and applicability to a wide range of substrates. The traditional dip coating method from solution often yields ill-defined particulate aggregates on the two-dimensional SAM. The presence of such three-dimensional aggregates seriously reduces the performance of miniaturized biosensor devices and AFM probes. It is difficult to control the amount of water in solution-based deposition. This paper describes a chemical vapor deposition (CVD) method to deposit octadecyltrichlorosilane (OTS) monolayers on silicon wafers and AFM probes under vacuum condition. OTS coated surfaces with static water contact angle ranging from 20{sup o} to 107{sup o} can be obtained by controlling the deposition conditions. The silicon substrates and AFM probes after CVD are characterized by AFM, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and contact angle goniometry. The OTS monolayer is in a uniform low-density state below 65%. Above 65%, densely packed crystalline-like domains start to form. It takes 24 h to reach the adsorption saturation. The time span in the CVD deposition is much longer than the solution case and thus allowing precise variation of the substrate hydrophobicity for biosensor applications.

  13. Functionalization of SnO₂ crystals with a covalently-assembled porphyrin monolayer.

    Science.gov (United States)

    Cristaldi, Domenico A; Gulino, Antonino

    2013-06-01

    The functionalization of micro- and nano-sized metal-oxide powders offers many advantages because of their large surface areas and, therefore, the large number of functional molecules that can be grafted onto the grain surfaces. Porphyrin molecules on large band-gap semiconducting metal oxides represent key materials for many different optical and electronic applications. Herein, we have proposed a general two-step procedure for the functionalization of metal-oxide crystals with dye-sensitizers. In particular, we functionalized SnO₂ nanoparticles with a monolayer of the bifunctional trichloro[4-(chloromethyl)phenyl]silane. Then, a monolayer of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyne was covalently bound to the silanized SnO₂ grains. IR, UV/Vis, and luminescence measurements were used for optical characterization. The measured footprint of the grafted porphyrin molecules indicated total surface coverage of the grains. The surface electronic characterization was performed by using X-ray photoelectron spectroscopy. Emission measurements revealed two strong bands at 664.1 and 721.0 nm that were attributed to the porphyrin monolayer assembled on the surface of the SnO₂ crystals. PMID:23610085

  14. Long term testing for dropwise condensation using self-assembled monolayer coatings of n-octadecyl mercaptan

    Energy Technology Data Exchange (ETDEWEB)

    Vemuri, S.; Kim, K.J. [Department of Mechanical Engineering, University of Nevada, Reno, NV 89557 (United States); Wood, B.D. [Mechanical and Aerospace Engineering Department, Utah State University, Logan, UT 84322 (United States); Govindaraju, S.; Bell, T.W. [Department of Chemistry, University of Nevada, Reno, NV 89557 (United States)

    2006-03-01

    Two different types of hydrophobic coatings have been analyzed experimentally for their ability to promote dropwise condensation (DWC). For any technique used for promoting dropwise condensation, the longevity of the coating is critical if it is to be used in any further applications. Previous studies using self-assembled monolayers of n-octadecyl mercaptan have not reported any information on the ability for promoting DWC beyond 500h of experimentation. In the current research experiments were carried out using self-assembled monolayers for more than 2600h of experimentation and it showed good dropwise phenomena. Stearic acid solution (SAM-1) and n-octadecyl mercaptan solution (SAM-2) were used to form an ultra-thin organic hydrophobic film on the surface. An oxide layer was initially formed on the substrate surface before coating the surface with monolayers. The oxide layer formed on the substrate surface tends to improve the bonding between the substrate and the monolayers which eventually improves the longevity of the coating. In general, a SAM system with a long-chain, hydrophobic group is nano-resistant, meaning that such a system forms a protective hydrophobic layer with negligible heat transfer resistance but a much stronger bond. When compared to complete filmwise condensation, the SAM-2 (n-octadecyl mercaptan) coating increased the condensation heat transfer coefficient by a factor of approximately 3 after 100h of experimentation and by a factor of approximately 1.8 after 2600h of experimentation for copper alloy surfaces, under vacuum condition (33.86kPa). Lifetime of maintaining dropwise condensation is greatly dependent on the bonding of SAM coating to the condensing surface, form the experimental investigation it was evident that n-octadecyl mercaptan showed good DWC due to its covalent bonding with the substrate surface when compared to that of stearic acid which is bonded to the substrate surface by hydrogen bonding. Contact angles were measured for

  15. A DNA self-assembled monolayer for the specific attachment of unmodified double- or single-stranded DNA.

    OpenAIRE

    Bamdad, C

    1998-01-01

    A novel method for DNA surface immobilization and a paradigm for the attachment of unmodified DNA of any length or sequence are described herein. The development of a DNA self-assembled monolayer (DNA-SAM) that incorporates a DNA-thiol into a monolayer of inert alkane thiolates is reported. This DNA-SAM specifically hybridized complementary oligonucleotides while resisting the nonspecific adsorption of noncomplementary DNA and irrelevant proteins. Duplex DNA, having a single-stranded "capture...

  16. Intermixed adatom and surface-bound adsorbates in regular self-assembled monolayers of racemic 2-butanethiol on Au(111).

    Science.gov (United States)

    Ouyang, Runhai; Yan, Jiawei; Jensen, Palle S; Ascic, Erhad; Gan, Shiyu; Tanner, David; Mao, Bingwei; Niu, Li; Zhang, Jingdong; Tang, Chunguang; Hush, Noel S; Reimers, Jeffrey R; Ulstrup, Jens

    2015-04-01

    In situ scanning tunneling microscopy combined with density functional theory molecular dynamics simulations reveal a complex structure for the self-assembled monolayer (SAM) of racemic 2-butanethiol on Au(111) in aqueous solution. Six adsorbate molecules occupy a (10×√3)R30° cell organized as two RSAuSR adatom-bound motifs plus two RS species bound directly to face-centered-cubic and hexagonally close-packed sites. This is the first time that these competing head-group arrangements have been observed in the same ordered SAM. Such unusual packing is favored as it facilitates SAMs with anomalously high coverage (30%), much larger than that for enantiomerically resolved 2-butanethiol or secondary-branched butanethiol (25%) and near that for linear-chain 1-butanethiol (33%).

  17. High-Efficiency Colloidal Quantum Dot Photovoltaics via Robust Self-Assembled Monolayers

    KAUST Repository

    Kim, Gi-Hwan

    2015-11-11

    © 2015 American Chemical Society. The optoelectronic tunability offered by colloidal quantum dots (CQDs) is attractive for photovoltaic applications but demands proper band alignment at electrodes for efficient charge extraction at minimal cost to voltage. With this goal in mind, self-assembled monolayers (SAMs) can be used to modify interface energy levels locally. However, to be effective SAMs must be made robust to treatment using the various solvents and ligands required for to fabricate high quality CQD solids. We report robust self-assembled monolayers (R-SAMs) that enable us to increase the efficiency of CQD photovoltaics. Only by developing a process for secure anchoring of aromatic SAMs, aided by deposition of the SAMs in a water-free deposition environment, were we able to provide an interface modification that was robust against the ensuing chemical treatments needed in the fabrication of CQD solids. The energy alignment at the rectifying interface was tailored by tuning the R-SAM for optimal alignment relative to the CQD quantum-confined electron energy levels. This resulted in a CQD PV record power conversion efficiency (PCE) of 10.7% with enhanced reproducibility relative to controls.

  18. Understanding the Phase Diagram of Self-Assembled Monolayers of Alkanethiolates on Gold

    Science.gov (United States)

    2016-01-01

    Alkanethiolate monolayers on gold are important both for applications in nanoscience as well as fundamental studies of adsorption and self-assembly at metal surfaces. While considerable experimental effort has been put into understanding the phase diagram of these systems, theoretical work based on density functional theory (DFT) has long been hampered by the inability of conventional exchange-correlation functionals to describe dispersive interactions. In this work, we combine dispersion-corrected DFT calculations using the new vdW-DF-CX functional with the ab initio thermodynamics method to study the stability of dense standing-up and low-coverage lying-down phases on Au(111). We demonstrate that the lying-down phase has a thermodynamic region of stability starting from thiolates with alkyl chains consisting of n ≈ 3 methylene units. This phase emerges as a consequence of a competition between dispersive chain–chain and chain–substrate interactions, where the strength of the latter varies more strongly with n. A phase diagram is derived under ultrahigh-vacuum conditions, detailing the phase transition temperatures of the system as a function of the chain length. The present work illustrates that accurate ab initio modeling of dispersive interactions is both feasible and essential for describing self-assembled monolayers. PMID:27313813

  19. High-Efficiency Colloidal Quantum Dot Photovoltaics via Robust Self-Assembled Monolayers.

    Science.gov (United States)

    Kim, Gi-Hwan; García de Arquer, F Pelayo; Yoon, Yung Jin; Lan, Xinzheng; Liu, Mengxia; Voznyy, Oleksandr; Jagadamma, Lethy Krishnan; Abbas, Abdullah Saud; Yang, Zhenyu; Fan, Fengjia; Ip, Alexander H; Kanjanaboos, Pongsakorn; Hoogland, Sjoerd; Kim, Jin Young; Sargent, Edward H

    2015-11-11

    The optoelectronic tunability offered by colloidal quantum dots (CQDs) is attractive for photovoltaic applications but demands proper band alignment at electrodes for efficient charge extraction at minimal cost to voltage. With this goal in mind, self-assembled monolayers (SAMs) can be used to modify interface energy levels locally. However, to be effective SAMs must be made robust to treatment using the various solvents and ligands required for to fabricate high quality CQD solids. We report robust self-assembled monolayers (R-SAMs) that enable us to increase the efficiency of CQD photovoltaics. Only by developing a process for secure anchoring of aromatic SAMs, aided by deposition of the SAMs in a water-free deposition environment, were we able to provide an interface modification that was robust against the ensuing chemical treatments needed in the fabrication of CQD solids. The energy alignment at the rectifying interface was tailored by tuning the R-SAM for optimal alignment relative to the CQD quantum-confined electron energy levels. This resulted in a CQD PV record power conversion efficiency (PCE) of 10.7% with enhanced reproducibility relative to controls.

  20. Electrochemical and Photoelectrochemical Study of Self-assembled Monolayer of Phytic Acid on Brass

    Institute of Scientific and Technical Information of China (English)

    XU Qun-Jie; WAN Zong-Yue; ZHOU Guo-Ding; YIN Ren-He; CAO Wei-Min; LIN Chang-Jian

    2008-01-01

    Phytic acid is an environment-friendly reagent for processing metals.The anticorrosion and inhibiting mechanism for phytic acid monolayers self-assembled on a brass (HSn70-1) electrode has been investigated by using electrochemical and photocurrent response methods.The electrochemical measurements indicate that phytic acid is liable to form surface complexes on the brass electrode,and the self-assembled monolayers (SAM) change the structure of the electric double-layer and shift the potential of zero charge positively.The photochemical measurement indicates that the brass electrode shows a p-type photoresponse owing to the formation of a Cu2O layer on its surface,and the presence of SAM weakens significantly the photoresponse,suggesting an excellent effect on anticorrosion,which is consistent with the EIS and polarization curve measurements.Adsorption of phytic acid was found to be typical of chemisorption,which can be reasonably described on the basis of the Langmuir isotherm.

  1. Gold electrode modified by self-assembled monolayers of thiols to determine DNA sequences hybridization

    Indian Academy of Sciences (India)

    Mízia M S Silva; Igor T Cavalcanti; M Fátima Barroso; M Goreti F Sales; Rosa Fireman Dutra

    2010-11-01

    The process of immobilization of biological molecules is one of the most important steps in the construction of a biosensor. In the case of DNA, the way it exposes its bases can result in electrochemical signals to acceptable levels. The use of self-assembled monolayer that allows a connection to the gold thiol group and DNA binding to an aldehydic ligand resulted in the possibility of determining DNA hybridization. Immobilized single strand of DNA (ssDNA) from calf thymus pre-formed from alkanethiol film was formed by incubating a solution of 2-aminoethanothiol (Cys) followed by glutaraldehyde (Glu). Cyclic voltammetry (CV) was used to characterize the self-assembled monolayer on the gold electrode and, also, to study the immobilization of ssDNA probe and hybridization with the complementary sequence (target ssDNA). The ssDNA probe presents a well-defined oxidation peak at +0.158 V. When the hybridization occurs, this peak disappears which confirms the efficacy of the annealing and the DNA double helix performing without the presence of electroactive indicators. The use of SAM resulted in a stable immobilization of the ssDNA probe, enabling the hybridization detection without labels. This study represents a promising approach for molecular biosensor with sensible and reproducible results.

  2. Protection of beryllium metal against microbial influenced corrosion using silane self-assembled monolayers

    Science.gov (United States)

    Vaidya, Rajendra U.; Deshpande, Alina; Hersman, Larry; Brozik, Susan M.; Butt, Darryl

    1999-08-01

    The effectiveness of a self-assembled silane monolayer as protection for beryllium against microbiologically influenced corrosion (MIC) was demonstrated. Four-point bend tests on coated and uncoated beryllium samples were conducted after microbiological exposures, and the effectiveness of these coatings as MIC protection was reported through mechanical property evaluations. Application of the silane monolayer to the beryllium surfaces was found to prevent degradation of the failure strength and displacement-to-failure of beryllium in bending. In contrast, the uncoated beryllium samples exhibited a severe reduction in these mechanical properties in the presence of the marine Pseudomonas bacteria. The potentiodynamic measurements showed that both the uncoated and coated samples pitted at the open-circuit potential. However, the size and distribution of the corrosion pits formed on the surface of the beryllium samples were significantly different for the various cases (coated vs uncoated samples exposed to control vs inoculated medium). This study demonstrates the following: (1) the deleterious effects of MIC on the mechanical properties of beryllium and (2) the potential for developing fast, easy, and cost-effective MIC protection for beryllium metal using silane self-assemblies.

  3. Fabrication of a Mono-Domain Alignment Ferroelectric Liquid Crystal Device Using a Polar Self-Assembled Monolayer

    Institute of Scientific and Technical Information of China (English)

    ZOU Zhong-Fei; YAO Li-Shuang; TANG Xian-Zhu; JI Xin-Jian; XUAN Li

    2008-01-01

    A mono-domain ferroelectric liquid crystal device (FLCD) is fabricated using a novel method. The cell used in this method is an asymmetric cell, typically the combination of a polar self-assembled monolayer (SAM) for one substrate and a rubbed polyimide for the other substrate. A defect-free alignment of ferroelectric liquid crystal is fabricated without applying a dc voltage to remove degeneracy in the layer structure. The contact angles of self-assembled monolayer and PI-2942 are measured and the polarity of SAM is higher than the PI alignment. It is found that the polarity of self-assembled monolayer is a key factor in the formation of mono-domain alignment of FLC.

  4. Characterization of perfluorodecanoate self-assembled monolayers on aluminum and comparison of stability with phosphonate and siloxy self-assembled monolayers

    Science.gov (United States)

    DeRose, J. A.; Hoque, E.; Bhushan, B.; Mathieu, H. J.

    2008-04-01

    The long term performance of micro-/nano-electromechanical systems (MEMS/NEMS) depends on their stability to operating conditions, contact friction, adhesion, and wear. Aluminum (Al) substrates have been chemically reacted with perfluorodecanoic acid (PFDA) to form a self-assembled monolayer (SAM) and their surface properties (chemical composition, roughness, friction, and adhesion) characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurement (CAM), and atomic force microscopy (AFM). In addition, stability of the PFDA/Al SAM films have been tested via exposure to corrosive conditions (aqueous solutions of low pH and different temperatures) for various periods of time. The sessile drop static contact angle of pure water demonstrates that PFDA/Al is extremely hydrophobic, giving values typically >125° compared to that of <10° for unmodified Al. A systematic comparison of stability between SAM films formed by reaction of Al with perfluorodecylphosphonic acid (PFDP), octadecylphosphonic acid (ODP), and perfluorodecyldimethylchlorosilane (PFMS) shows PFDA/Al to be less stable than PFDP/Al and ODP/Al, but more stable than PFMS/Al.

  5. Photocatalytic oxidation of the organic monolayers on TiO2 surface investigated by in-situ sum frequency generation spectroscopy

    Directory of Open Access Journals (Sweden)

    Yujin Tong

    2015-10-01

    Full Text Available In-situ vibrational sum frequency generation (SFG spectroscopy has been employed to investigate the photocatalytic oxidation of two types of well-ordered organic monolayers, namely, an arachidic acid (AA monolayer prepared by the Langmuir-Blodgett method and an octadecyltrichlorosilane (OTS monolayer prepared by the self-assembling method, on a TiO2 surface under ultraviolet (UV irradiation. The extremely high sensitivity and unique selectivity of the SFG spectroscopy enabled us to directly probe the structural changes in these monolayers during the surface photocatalytic oxidation and further elucidate their reaction mechanisms at a molecular level. It was revealed that the ordering of the monolayers during the photocatalytic reaction is strongly dependent on their interaction with the substrate; the AA monolayer maintains its ordered conformation until the final oxidation stage, while the OTS monolayer shows a large increase in disordering during the initial oxidation stage, indicating a different photocatalytic reaction mechanism of the two monolayers on the TiO2 surface.

  6. Photocatalytic oxidation of the organic monolayers on TiO{sub 2} surface investigated by in-situ sum frequency generation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Yujin; Peng, Qiling; Ma, Tongsen; Nishida, Takuma; Ye, Shen, E-mail: ye@cat.hokudai.ac.jp [Catalysis Research Center, Hokkaido University, Sapporo 060-0811 (Japan)

    2015-10-01

    In-situ vibrational sum frequency generation (SFG) spectroscopy has been employed to investigate the photocatalytic oxidation of two types of well-ordered organic monolayers, namely, an arachidic acid (AA) monolayer prepared by the Langmuir-Blodgett method and an octadecyltrichlorosilane (OTS) monolayer prepared by the self-assembling method, on a TiO{sub 2} surface under ultraviolet (UV) irradiation. The extremely high sensitivity and unique selectivity of the SFG spectroscopy enabled us to directly probe the structural changes in these monolayers during the surface photocatalytic oxidation and further elucidate their reaction mechanisms at a molecular level. It was revealed that the ordering of the monolayers during the photocatalytic reaction is strongly dependent on their interaction with the substrate; the AA monolayer maintains its ordered conformation until the final oxidation stage, while the OTS monolayer shows a large increase in disordering during the initial oxidation stage, indicating a different photocatalytic reaction mechanism of the two monolayers on the TiO{sub 2} surface.

  7. Studies of the structure and properties of organic monolayers, multilayers and superlattices

    International Nuclear Information System (INIS)

    Organic monolayers and multilayers are both scientifically fascinating and technologically promising; they are, however, both complex systems and relatively inaccessible to experimental probes. In this progress report, we describe our x-ray diffraction studies, which have given us substantial new information about the structures and phase transitions in monolayers on the surface of water; our use of these monolayers as a unique probe of the dynamics of wetting and spreading; and our studies of monolayer mechanical properties using a simple but effective technique available to anyone using the Wilhelmy method to measure surface tension. 20 refs., 11 figs

  8. Patterning of self-assembled monolayers by phase-shifting mask and its applications in large-scale assembly of nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Fan; Zhang, Dakuan; Wang, Jianyu; Sheng, Yun; Wang, Xinran; Chen, Kunji; Zhou, Minmin [Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Yan, Shancheng [Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); School of Geography and Biological Information, Nanjing University of Posts and Telecommunications, Nanjing 210046 (China); Shen, Jiancang; Pan, Lijia; Shi, Yi, E-mail: yshi@nju.edu.cn [Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Micro-structures, Nanjing University, Nanjing 210093 (China)

    2015-01-26

    A nonselective micropatterning method of self-assembled monolayers (SAMs) based on laser and phase-shifting mask (PSM) is demonstrated. Laser beam is spatially modulated by a PSM, and periodic SAM patterns are generated sequentially through thermal desorption. Patterned wettability is achieved with alternating hydrophilic/hydrophobic stripes on octadecyltrichlorosilane monolayers. The substrate is then used to assemble CdS semiconductor nanowires (NWs) from a solution, obtaining well-aligned NWs in one step. Our results show valuably the application potential of this technique in engineering SAMs for integration of functional devices.

  9. Kinetic studies on the interactions between glycolipid biosurfactant assembled monolayers and various classes of immunoglobulins using surface plasmon resonance.

    Science.gov (United States)

    Ito, Seya; Imura, Tomohiro; Fukuoka, Tokuma; Morita, Tomotake; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

    2007-08-01

    Kinetic studies on the interactions between self-assembled monolayers of mannosylerythritol lipids (MELs), which are glycolipid biosurfactants abundantly produced by microorganisms, and various classes of immunoglobulins including human IgG, IgA, and IgM were performed using surface plasmon resonance (SPR). The effect of the MEL structure on the binding behavior of HIgG was examined. Assembled monolayers of MEL-A having two acetyl groups on the headgroup gave a high affinity (K(d)=1.7x10(-6)M) toward HIgG, while those of MEL-B or MEL-C having only one acetyl group at C-6' or C-4' position gave little affinity. Our kinetic analysis revealed that the binding manner of HIgG, HIgA (K(d)=2.4x10(-7)M), and HIgM (K(d)=2.2x10(-7)M) to the assembled monolayers of MEL-A is not the monovalent mode but the bivalent mode, and both the first and second rate association constants (k(a1), k(a2)) increase with an increase in the number of antibody binding sites, while those for dissociation (k(d1), k(d2)) changed little. Moreover, we succeeded in directly observing great amounts of HIgG, HIgA, and HIgM bound to MEL-A monolayers using atomic force microscopy (AFM). Finally, we found that MEL-A assembled monolayer binds toward various IgG derived from mouse, pig, rabbit, horse, goat, rat, and bovine as well as human IgG (HIgG), and the only exception was sheep IgG. These results clearly demonstrate that MEL-A assembled monolayers would be useful as noble affinity ligand system for various immunoglobulins. PMID:17428643

  10. Hematite nanoparticle monolayers on mica preparation by controlled self-assembly.

    Science.gov (United States)

    Oćwieja, Magdalena; Adamczyk, Zbigniew; Morga, Maria; Bielańska, Elżbieta; Węgrzynowicz, Adam

    2012-11-15

    A stable suspension of α-Fe(2)O(3) (hematite) was synthesized according to the method of Matijevic and Scheiner by an acidic hydrolysis of ferric chloride. The average size of the particles was determined by dynamic light scattering (DLS) and atomic force microscopy (AFM) and was 22 nm. The electrophoretic mobility and zeta potential of particles were determined as a function of ionic strength and pH. The zeta potential of the hematite particles was positive for pHAFM and SEM imaging. Particle deposition was diffusion controlled, with the initial rate proportional to the bulk concentration of particles. On the other hand, for long times, the saturation coverage was attained, increasing systematically with ionic strength. The deposition kinetic runs were adequately reflected by the random sequential adsorption (RSA) model. Additionally, particle desorption kinetics, from previously formed monolayers, were studied using the AFM and SEM methods. It was confirmed that hematite particle desorption was practically negligible within the time period of 60 h. Our experimental data proved, therefore, that it is feasible to produce uniform and stable hematite particle monolayers of desired coverage in self-assembly processes controlled by the bulk suspension concentration and the ionic strength. PMID:22909964

  11. Metamaterial Absorbers for Infrared Detection of Molecular Self-Assembled Monolayers

    Science.gov (United States)

    Ishikawa, Atsushi; Tanaka, Takuo

    2015-07-01

    The emerging field of plasmonic metamaterials has introduced new degree of freedom to manipulate optical field from nano to macroscopic scale, offering an attractive platform for sensing applications. So far, metamaterial sensor concepts, however, have focused on hot-spot engineering to improve the near-field enhancement, rather than fully exploiting tailored material properties. Here, we present a novel spectroscopic technique based on the metamaterial infrared (IR) absorber allowing for a low-background detection scheme as well as significant plasmonic enhancement. Specifically, we experimentally demonstrate the resonant coupling of plasmonic modes of a metamaterial absorber and IR vibrational modes of a molecular self-assembled monolayer. The metamaterial consisting of an array of Au/MgF2/Au structures exhibits an anomalous absorption at ~3000 cm-1, which spectrally overlaps with C-H stretching vibrational modes. Symmetric/asymmetric C-H stretching modes of a 16-Mercaptohexadecanoic acid monolayer are clearly observed as Fano-like anti-resonance peaks within a broad plasmonic absorption of the metamaterial. Spectral analysis using Fano line-shape fitting reveals the underlying resonant interference in plasmon-molecular coupled systems. Our metamaterial approach achieves the attomole sensitivity with a large signal-to-noise ratio in the far-field measurement, thus may open up new avenues for realizing ultrasensitive IR inspection technologies.

  12. Self-assembly of human plasma fibrinogens on binary organosilane monolayers with micro domains

    International Nuclear Information System (INIS)

    The adsorption behavior and self-assembly of human plasma fibrinogen (HPF) on binary methyl- and amino-terminated self-assembled monolayers (SAMs) were investigated by atomic force microscopy (AFM). The binary SAMs were fabricated through self-assembly mechanism of organosilane molecules. The height of domains is the domain height is 0.8 ± 0.2 nm from the AFM topographic image. It corresponds to the domain height is 0.8 ± 0.2 nm from the AFM topographic image. It corresponds to the difference between the length of the alkyl chain of octadecyltrichlorosilane (OTS) and that of n-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS). The fibrinogen solution used ultrapure water as the solvent and its pH was adjusted at 3 and 10. From the AFM results at pH 3, HPF only formed network structures on the OTS domains of the binary SAM at early immersion times, and then the network structures expanded and connected between OTS domains through the AHAPS surface at long immersion times. In this case, a few HPFs are discretely adsorbed on the AHAPS surface. However, HPF is uniformly adsorbed on the binary SAM under the other conditions of pH.

  13. Self-Assembly of Protein Monolayers Engineered for Improved Monoclonal Immunoglobulin G Binding

    Directory of Open Access Journals (Sweden)

    Jeremy H. Lakey

    2011-08-01

    Full Text Available Bacterial outer membrane proteins, along with a filling lipid molecule can be modified to form stable self-assembled monolayers on gold. The transmembrane domain of Escherichia coli outer membrane protein A has been engineered to create a scaffold protein to which functional motifs can be fused. In earlier work we described the assembly and structure of an antibody-binding array where the Z domain of Staphylococcus aureus protein A was fused to the scaffold protein. Whilst the binding of rabbit polyclonal immunoglobulin G (IgG to the array is very strong, mouse monoclonal IgG dissociates from the array easily. This is a problem since many immunodiagnostic tests rely upon the use of mouse monoclonal antibodies. Here we describe a strategy to develop an antibody-binding array that will bind mouse monoclonal IgG with lowered dissociation from the array. A novel protein consisting of the scaffold protein fused to two pairs of Z domains separated by a long flexible linker was manufactured. Using surface plasmon resonance the self-assembly of the new protein on gold and the improved binding of mouse monoclonal IgG were demonstrated.

  14. Formation and Characterization of Self-Assembled Phenylboronic Acid Derivative Monolayers toward Developing Monosaccaride Sensing-Interface

    Directory of Open Access Journals (Sweden)

    Kwangnak Koh

    2007-08-01

    Full Text Available We designed and synthesized phenylboronic acid as a molecular recognitionmodel system for saccharide detection. The phenylboronic acid derivatives that haveboronic acid moiety are well known to interact with saccharides in aqueous solution; thus,they can be applied to a functional interface of saccharide sensing through the formation ofself-assembled monolayer (SAM. In this study, self-assembled phenylboronic acidderivative monolayers were formed on Au surface and carefully characterized by atomicforce microscopy (AFM, Fourier transform infrared reflection absorption spectroscopy(FTIR-RAS, surface enhanced Raman spectroscopy (SERS, and surface electrochemicalmeasurements. The saccharide sensing application was investigated using surface plasmonresonance (SPR spectroscopy. The phenylboronic acid monolayers showed goodsensitivity of monosaccharide sensing even at the low concentration range (1.0 × 10-12 M.The SPR angle shift derived from interaction between phenylboronic acid andmonosaccharide was increased with increasing the alkyl spacer length of synthesizedphenylboronic acid derivatives.

  15. Interaction of bovine serum albumin protein with self assembled monolayer of mercaptoundecanoic acid

    Science.gov (United States)

    Poonia, Monika; Agarwal, Hitesh; Manjuladevi, V.; Gupta, R. K.

    2016-05-01

    Detection of proteins and other biomolecules in liquid phase is the essence for the design of a biosensor. The sensitivity of a sensor can be enhanced by the appropriate functionalization of the sensing area so as to establish the molecular specific interaction. In the present work, we have studied the interaction of bovine serum albumin (BSA) protein with a chemically functionalized surface using a quartz crystal microbalance (QCM). The gold-coated quartz crystals (AT-cut/5 MHz) were functionalized by forming self-assembled monolayer (SAM) of 11-Mercaptoundecanoic acid (MUA). The adsorption characteristics of BSA onto SAM of MUA on quartz crystal are reported. BSA showed the highest affinity for SAM of MUA as compared to pure gold surface. The SAM of MUA provides carboxylated surface which enhances not only the adsorption of the BSA protein but also a very stable BSA-MUA complex in the liquid phase.

  16. Electrostatic adsorption of hematite nanoparticles on self-assembled monolayer surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Boris L. T., E-mail: borislau@engin.umass.edu; Huang, Rixiang [Baylor University, Department of Geology (United States); Madden, Andrew S. [University of Oklahoma, School of Geology and Geophysics (United States)

    2013-08-15

    Deposition of nanoparticles (NPs) on different environmental surfaces has important implication on their fate and transport in aquatic systems. This study quantitatively and kinetically analyzed the adsorption of hematite ({alpha}-Fe{sub 2}O{sub 3}) NPs (HNPs) onto self-assembled monolayer modified surfaces using QCM, AFM, and SEM. Experiments were conducted to study the immobilization of two different sizes of HNPs onto gold substrate and surfaces modified with 1-mercapto-11-undecanoic acid and cysteine. It is shown that the extent and rate of HNPs adsorption onto substrate surfaces can be modulated electrostatically. Control over the surface coverage of the adsorbed HNPs has been demonstrated by pH variation. Size-dependent adsorption kinetics was observed, with the 79 nm HNPs adsorbed 2-3 times faster than the 116 nm HNPs.

  17. Multiple-trapping in pentacene field-effect transistors with a nanoparticles self-assembled monolayer

    Directory of Open Access Journals (Sweden)

    Keanchuan Lee

    2012-06-01

    Full Text Available A silver nanoparticles self-assembled monolayer (SAM was incorporated in pentacene field-effect transistor and its effects on the carrier injection and transport were investigated using the current-voltage (I − V and impedance spectroscopy (IS measurements. The I − V results showed that there was a significant negative shift of the threshold voltage, indicating the hole trapping inside the devices with about two orders higher in the contact resistance and an order lower in the effective mobility when a SAM was introduced. The IS measurements with the simulation using a Maxwell-Wagner equivalent circuit model revealed the existence of multiple trapping states for the devices with NPs, while the devices without NPs exhibited only a single trap state.

  18. Suppression of the coffee-ring effect by self-assembling graphene oxide and monolayer titania

    International Nuclear Information System (INIS)

    The in situ self-assembly of two types of typical two-dimensional (2D) nanomaterials (i.e., graphene oxide (GO) and monolayer titania (TO)) is realized using a simple drop-casting method. Within the as-prepared hybrid films, the GO and TO nanosheets arrange alternately into a lamellar structure. Notably, the hybridization of GO and TO suppresses the formation of coffee-rings when drop-cast, which is attributed to the strong interactions between the GO and TO nanosheets. Finally, the mechanism for the in situ hybridization of these two types of nanosheets into heterogeneous lamellar films and the suppression of the coffee-ring effect are discussed. These results demonstrate the potential applications of drop-cast hybrid films for high-quality membrane deposition from liquid phases. (paper)

  19. Interactions of Na+, K+, Mg2+, and Ca 2+ with benzene self-assembled monolayers

    DEFF Research Database (Denmark)

    Pedersen, Morten Rimmen; Matthiesen, Jesper; Bovet, Nicolas Emile;

    2014-01-01

    that are most common in the natural world, namely, Na+, K+, Mg 2+, and Ca2+. Specifically, we investigated how these ions affect the interactions between surfaces covered by self-Assembled monolayers (SAMs) terminated with benzene molecules. We used a flat oxidized silicon substrate and an atomic force...... from X-ray photoelectron spectroscopy (XPS) allowed us to conclude that K+ binds in the benzene layers, creating a positive surface charge on the benzene-covered surfaces, thus leading to lower adhesion in KCl solutions than in pure water. Evidence suggested that Ca2+ does not bind to the surfaces...... measurements. The results of our studies clearly show that even a nonpolar, hydrophobic molecule, such as benzene, has a role to play in the behavior of aqueous solutions and that it interacts differently depending on which ions are present. Even ions from the same column in the periodic table behave...

  20. Creating periodic local strain in monolayer graphene with nanopillars patterned by self-assembled block copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Mi, Hongyi; Mikael, Solomon; Seo, Jung-Hun; Gui, Gui; Ma, Alice L.; Ma, Zhenqiang, E-mail: nealey@uchicago.edu, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States); Liu, Chi-Chun; Nealey, Paul F., E-mail: nealey@uchicago.edu, E-mail: mazq@engr.wisc.edu [Department of Chemical and Biological Engineering, University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States)

    2015-10-05

    A simple and viable method was developed to produce biaxial strain in monolayer graphene on an array of SiO{sub 2} nanopillars. The array of SiO{sub 2} nanopillars (1 cm{sup 2} in area, 80 nm in height, and 40 nm in pitch) was fabricated by employing self-assembled block copolymer through simple dry etching and deposition processes. According to high resolution micro-Raman spectroscopy and atomic force microscopy analyses, 0.9% of maximum biaxial tensile strain and 0.17% of averaged biaxial tensile strain in graphene were created. This technique provides a simple and viable method to form biaxial tensile strain in graphene and offers a practical platform for future studies in graphene strain engineering.

  1. Electroanalysis of dopamine at a gold electrode modified with N-acetylcysteine self-assembled monolayer.

    Science.gov (United States)

    Liu, Ting; Li, Meixian; Li, Qianyuan

    2004-07-01

    Voltammetric behavior of dopamine (DA) on a gold electrode modified with the self-assembled monolayer (SAM) of N-acetylcysteine has been investigated, and one pair of well-defined redox peaks of dopamine is obtained at the SAM modified gold electrode. The oxidation peak current increases linearly with the concentration of dopamine in the range of 1.0x10 (-6)to 2.0x10 (-4)moll(-1). The detection limit is 8.0x10(-7)moll(-1). This method will be applicable to the determination of dopamine in injection of dopamine hydrochloride, and the good recovery of dopamine is obtained. Furthermore, The SAM modified gold electrode can resolve well the voltammetric responses of dopamine and ascorbic acid (AA), so it can also be applied to the determination of dopamine in the presence of ascorbic acid.

  2. Biomimetic synthesis of enamel-like hydroxyapatite on self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Li Hong [Department of Materials Science and Engineering, Jinan University, Guangzhou, 510632 (China); Huang Weiya [Department of Chemistry, Jinan University, Guangzhou, 510632 (China); Zhang Yuanming [Department of Chemistry, Jinan University, Guangzhou, 510632 (China)]. E-mail: tzhangym@jnu.edu.cn; Zhong Mei [Department of Stomatology, Affiliated Hospital of Jinan University, Guangzhou, 510632 (China)

    2007-05-16

    Hydroxyapatite (HAp) crystals mimicking tooth enamel in chemical composition and morphology were formed on sulfonic-terminated self-assembled monolayer (SAM) in 1.5SBF with F{sup -} at 50 {sup o}C for 7 days. F{sup -} ions showed a marked effect on the composition and morphology of deposited HAp crystals. In the absence of F{sup -} ions, HAp containing CO{sub 3} {sup 2-} were formed on SAM, and worm-like crystals of 200-300 nm in length aggregated to form a spherical morphology. When F{sup -} was added, HAp crystals containing both CO{sub 3} {sup 2-} and F{sup -} were formed on SAM. Needle-shaped crystals of high aspect ratio and 1-2 {mu}m in length grew elongated along the c-axial direction. In addition, these needle-shaped crystals grew in bundles, mimicking HAp crystals in tooth enamel. After the process of ripening, the needles in bundle grew to large size of up to 10 {mu}m in length, and still kept no crystal-crystal fusion like enamel HAp crystals. The formation of enamel-like HAp can be attributed to the substitute of F{sup -} for OH{sup -} by disturbing the normal progress of HAp formation on SAM. The results suggest potential applications in preparing a novel dental material by a simple method. -- Graphical abstract: Hydroxyapatite (HAp) crystals mimicking tooth enamel in chemical composition and morphology were formed on self-assembled monolayer (SAM) by a biomimetic process. The needle-shaped crystals grew in bundles, mimicking HAp crystals in tooth enamel. Display Omitted.

  3. Biomimetic synthesis of enamel-like hydroxyapatite on self-assembled monolayers

    International Nuclear Information System (INIS)

    Hydroxyapatite (HAp) crystals mimicking tooth enamel in chemical composition and morphology were formed on sulfonic-terminated self-assembled monolayer (SAM) in 1.5SBF with F- at 50 oC for 7 days. F- ions showed a marked effect on the composition and morphology of deposited HAp crystals. In the absence of F- ions, HAp containing CO32- were formed on SAM, and worm-like crystals of 200-300 nm in length aggregated to form a spherical morphology. When F- was added, HAp crystals containing both CO32- and F- were formed on SAM. Needle-shaped crystals of high aspect ratio and 1-2 μm in length grew elongated along the c-axial direction. In addition, these needle-shaped crystals grew in bundles, mimicking HAp crystals in tooth enamel. After the process of ripening, the needles in bundle grew to large size of up to 10 μm in length, and still kept no crystal-crystal fusion like enamel HAp crystals. The formation of enamel-like HAp can be attributed to the substitute of F- for OH- by disturbing the normal progress of HAp formation on SAM. The results suggest potential applications in preparing a novel dental material by a simple method. -- Graphical abstract: Hydroxyapatite (HAp) crystals mimicking tooth enamel in chemical composition and morphology were formed on self-assembled monolayer (SAM) by a biomimetic process. The needle-shaped crystals grew in bundles, mimicking HAp crystals in tooth enamel. Display Omitted

  4. Scanning Tunneling Microscopic Observation of Adatom-Mediated Motifs on Gold-Thiol Self-assembled Monolayers at High Coverage

    DEFF Research Database (Denmark)

    Wang, Yun; Chi, Qijin; Hush, Noel S.;

    2009-01-01

    Self-assembled monolayers (SAMs) formed by chemisorption of a branched-chain alkanethiol, 2-methyl-1-propanethiol, on Au(111) surfaces were studied by in situ scanning tunneling microscopy (STM) under electrochemical potential control and analyzed using extensive density functional theory (DFT) c...

  5. Self-assembled monolayers of terminal acetylenes as replacements for thiols in bottom-up tunneling junctions

    NARCIS (Netherlands)

    Fracasso, Davide; Kumar, Sumit; Rudolf, Petra; Chiechi, Ryan C.

    2014-01-01

    Why use thiols in Molecular Electronics? They stink, oxidize readily, poison catalysts, and often require nontrivial protection/deprotection chemistry. In this communication we demonstrate the fabrication of tunneling junctions formed by contact of self-assembled monolayers (SAMs) of terminal alkyne

  6. Structural, electrochemical, and photophysical properties of a molecular shuttle attached to an acid-terminated self-assembled monolayer

    NARCIS (Netherlands)

    Cecchet, F; Rudolf, P; Rapino, S; Margotti, M; Paolucci, F; Baggerman, J; Kay, ER; Wong, JKY; Leigh, DA; Kay, Euan R.; Wong, Jenny K.Y.; Brouwer, A.M.

    2004-01-01

    A benzylic amide macrocycle containing a pyridine moiety (macrocycle 2) and a related benzylic amide macrocycle-based molecular shuttle (naphthalimide rotaxane) with two pyridine moieties on the macrocyclic unit were grafted onto a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA

  7. The Molecular Boat: A Hands-On Experiment to Demonstrate the Forces Applied to Self-Assembled Monolayers at Interfaces

    Science.gov (United States)

    Chan, Charlene J.; Salaita, Khalid

    2012-01-01

    Demonstrating how surface chemistry and self-assembled monolayers (SAMs) control the macroscopic properties of materials is challenging as it often necessitates the use of specialized instrumentation. In this hands-on experiment, students directly measure a macroscopic property, the floatation of glass coverslips on water as a function of…

  8. A 3:1 site-differentiated [4Fe-4S] cluster immobilized on a self-assembled monolayer

    NARCIS (Netherlands)

    van der Geer, E.P.L.; van den Brom, C.R.; Arfaoui, I.; Houssiau, L.; Rudolf, P.; van Koten, G.; Klein Gebbink, R.J.M.; Hessen, B.

    2008-01-01

    A 3:1 site-differentiated [4Fe-4S] cluster is immobilized on a thiol-functionalized self-assembled monolayer (SAM) on Au(111) by thiol−thiolate exchange chemistry. Fe 2p signals observed by X-ray photoelectron spectroscopy support the presence of [4Fe-4S] clusters at the SAM surface; further evidenc

  9. Directly Addressable Sub-3 nm Gold Nanogaps Fabricated by Nanoskiving Using Self-Assembled Monolayers as Templates

    NARCIS (Netherlands)

    Pourhossein, Parisa; Chiechi, Ryan C.

    2012-01-01

    This paper describes the fabrication of electrically addressable, high-aspect-ratio (>10000:1) nanowires of gold with square cross sections of 100 nm on each side that are separated by gaps of 1.7-2.2 nm which were defined using self-assembled monolayers (SAMs) as templates. We fabricated these nano

  10. Synthesis of Crown Ether-tethered β-Cyclodextrin and Fabrication of Its Self-assembled Monolayer on Gold Surface

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel β-cyclodextrin derivative 6 bearing a crown ether moiety has been synthesized by a convenient method in 9.4% yield. Its self-assembled monolayer (SAM) was fabricated on the gold surface, which was characterized by using surface-enhanced Raman spectra.

  11. Fast Electron Transfer Exchange at Self-Assembled Monolayers of Organometallic Ruthenium(II) σ-Arylacetylide Complexes.

    Science.gov (United States)

    Mulas, Andrea; Hervault, Yves-Marie; He, Xiaoyan; Di Piazza, Emmanuel; Norel, Lucie; Rigaut, Stéphane; Lagrost, Corinne

    2015-06-30

    A new series of ruthenium organometallic carbon-rich complexes, exhibiting fast electron transfer kinetics combined to a low oxidation potential, was synthesized for self-assembled monolayer (SAM) formation on gold surfaces. The molecules consist of highly conjugated ruthenium(II) mono(σ-arylacetylide) or bis(σ-arylacetylide) complexes functionalized with different bridge units with specific (protected) anchoring groups that possess high affinity for gold, such as thiol, carbodithioate, and isocyanide. Single component and mixed SAMs were prepared and fully characterized by wettability studies, infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and electrochemical analyses. By applying the Laviron's formalism, fast electron transfer kinetics (≈10(4) s(-1)) were found at the derived self-assemblies while no significant effect could have been evidenced with variation of the bridging unit and of the anchoring moiety. Interestingly, a hexyl aliphatic spacer in the bridging unit with a thiol group and dilution with suitable nonelectroactive thiols lead to better SAM organization and packing, in comparison with undiluted complexes with shorter spacers. Such features make these compounds suitable alternatives to the widely used ferrocene center as redox-active building blocks for reversible charge storage devices. PMID:26053314

  12. Ordered Self-assembled Alkane Monolayer on Graphite and Graphene Surface

    Science.gov (United States)

    Su, Yudan; Han, Huiling; Wang, Feng; Cai, Qun; Tian, Chuanshan; Shen, Y. R.

    2015-03-01

    The 2D self-assembly of long chain alkane molecule on graphite and graphene had been studied with phase-sensitive sum-frequency vibrational spectroscopy (PS-SFVS) and scanning tunneling microscopy (STM). The spectrum of Imχs(2) (ωIR) which directly characterizes the surface resonances, shows 10-cm-1 red-shift of the symmetric-stretch frequency of the CH2 groups pointing towards graphite (or graphene) surface indicating Van der Waals interaction in between. The Gibbs adsorption energy of polyethylene (PE, n ~ 140) on graphite from chloroform solution was determined to be -42kJ/mol per molecule or -0.6 kJ/mol per CH2 unit. This large adsorption energy drives the long alkane chain to form an ordered self-assembled monolayer on graphite (or graphene). The sum frequency spectra suggest the orientation of carbon skeleton plane of alkane is predominately perpendicular to the graphite/graphene surface. Our STM result also provides clear evidence for the proposed molecular adsorption model. These results explain the large amount residual of long chain alkane on polystyrene (PS) or poly(methyl methacrylate) (PMMA) transferred graphene, and facilitate a better way to fabricate cleaner large-size graphene.

  13. Self Assembly of Mixed Monolayers of Mercaptoundecylferrocene and Undecanethiol studied by STM

    International Nuclear Information System (INIS)

    Mixed monolayers of mercaptoundecylferrocene and undecanethiol were deposited from solution by coadsorption and by a two-step insertion method, using the alkanethiol monolayer as insulating matrix. The resulting layers were characterized by UHV-STM, showing molecular resolution. For insertion-processed samples, a mesh-like surface structure of ferrocenes was observed, due to the preferential incorporation of molecules along domain boundaries and defect sites of the alkanethiol monolayer. For monolayers in the intermediate coverage regime, a crystalline phase was observed

  14. Molecular Arrangement in Self-Assembled Azobenzene-Containing Thiol Monolayers at the Individual Domain Level Studied through Polarized Near-Field Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    Razvigor Ossikovski

    2011-02-01

    Full Text Available 6-[4-(phenylazophenoxy]hexane-1-thiol self-assembled monolayers deposited on a gold surface form domain-like structures possessing a high degree of order with virtually all the molecules being identically oriented with respect to the surface plane. We show that, by using polarized near-field Raman spectroscopy, it is possible to derive the Raman scattering tensor of the ordered layer and consequently, the in-plane molecular orientation at the individual domain level. More generally, this study extends the application domain of the near-field Raman scattering selection rules from crystals to ordered organic structures.

  15. Modified fabrication process of protein chips using a short-chain self-assembled monolayer.

    Science.gov (United States)

    Jang, Ling-Sheng; Keng, Hao-Kai

    2008-04-01

    In previous work a short chain SAM, 4,4-Dithiodibutyric Acid (DTBA) was found to be a thin monolayer in protein chips. However, obtaining uniform fluorescent intensity remains difficult because water-soluble carbodiimides (EDC) in an aqueous system cause the hydrolysis of N-hydroxysuccinimide ester (NHS esters). The hydrolysis of NHS esters reduces coupling yields and therefore reduces the fluorescent intensity of protein chips. The NHS can increase the stability of active intermediate resulting from the reaction of EDC and NHS, but the ratio of the concentration of EDC to that of NHS strongly affects this stability. The effects of the solvents used in the washing step are studied to solve this problem. The results reveal that PBST (PBS + 5% Tween20) is more effective in reducing the hydrolysis of NHS esters than deionized water. Additionally, the effects of 3:1 and 5:2 EDC/NHS ratios on the chips are examined. The 3:1 EDC/NHS ratio yields a higher fluorescent intensity than the 5:2 ratio. The effects on the chips of dissolving EDC in DI water, DI water + 0.1 M MES and alcohol are also investigated. The results show that alcohol provides higher fluorescent intensity than other solvents and the reaction time of 4 h yields a high fluorescent intensity with 3:1 EDC/NHS ratio. A modified fabrication process of protein chips using 4,4-DTBA is developed. In this work, 160 mM 4,4-DTBA is used as a self-assembled monolayer in the fabrication of protein chips. Experiments to characterize 4,4-DTBA are performed by contact angle goniometry and Fourier transform infrared spectroscopy (FTIR). Furthermore, the immobilized protein A-FITC (fluorescein isothiocyanate) is adopted in fluorescent assays. PMID:17849186

  16. Packing density of HS(CH2)(n)COOH self-assembled monolayers.

    Science.gov (United States)

    Snow, A W; Jernigan, G G; Ancona, M G

    2011-12-01

    Self-assembled monolayers (SAMs) of HS(CH(2))(n)COOH, n = 5, 10, 15 deposited from ethanol solution onto gold are prepared by five approaches, and their packing densities are evaluated by X-ray photoelectron spectroscopy (XPS) measurements. The five approaches are: (1) direct deposition; (2) acetic-acid-assisted deposition; (3) butyl-amine-assisted deposition; (4) displacement of a preformed HS(CH(2))(n)CH(3) (n = 5, 10, 15) SAMs; and (5) co-deposition with HS(CH(2))(n)CH(3) (n = 5, 10, 15). Packing density metrics are calculated from measurements of SAM and substrate photoemission intensities and their attenuations by two methods. In one case the attenuated photoemissions are expressed as a ratio relative to comparable measurements on an experimental HS(CH(2))(n)CH(3) model system. In the other case a new method is introduced where a calculated attenuation based on theoretical random coil and extended chain models is used as the reference to determine a packing density fraction. Packing densities are also correlated with the S2p(Au-bonded):Au4f peak area ratios and with shifts in the C1s binding energies. SAMs prepared by the direct deposition are a partial multilayer where a second molecular layer is physisorbed onto the SAM and not removable by solvent washing. The addition of acetic acid to the deposition solution disrupts dimer associations of HS(CH(2))(n)COOH in solution and at the surface of the monolayer and yields the most ordered monolayer with the highest density of -COOH groups. The addition of butyl amine results in a labile ammonium carbonate ion pair formation but results in a lower packing density in the SAM. The displacement of the preformed HS(CH(2))(n)CH(3) SAM and the co-deposition of HS(CH(2))(n)CH(3) with HS(CH(2))(n)COOH result in SAMs with little incorporation of the -COOH component.

  17. Investigation of cellular and protein interactions with model self-assembled monolayer surfaces

    Science.gov (United States)

    Tegoulia, Vassiliki Apostolou

    Self-assembled monolayers (SAMs) of alkanethiolates on gold have been used to investigate the effect of substrate surface properties on bacterial and blood cell adhesion in the presence and absence of blood proteins. Protein adsorption and binding strength on SAMs as well as complement activation by these model surfaces were also studied. It is hoped that information gained, regarding factors that influence biological processes, will lead to strategies for designing materials and surfaces that specifically inhibit cell adhesion and protein adsorption. Single component SAMs of the general formula HS(CH2) 10X, where X = CH3, CH2OH. COOH and CH2(OCH 2CH2)3OH, and two component mixed SAMs created from binary solutions of HS(CH2), OCH3 and HS(CH 2)10CH2OH, were used. Adhesion was investigated under well-defined flow conditions. Adhesion was found to be higher for the hydrophobic methyl and minimal for the tri(ethyleneoxide) terminated SAM. Preincubation of the SAMs with fibrinogen led to an increase in cell adhesion for bacteria and a decrease for leukocyte adhesion. The effect of surface chemistry on protein adsorption was studied for three blood proteins, fibrinogen, fibronectin and albumin. Adsorption was found to be higher on the hydrophobic CH3 surface and lower but comparable for the other surfaces while proteins adsorbed strongly on all surfaces. SAMs were also used to evaluate complement activation by foreign surfaces. The hydroxyl rich SAMs were found to activate complement more significantly than the anionic carboxyl and the hydrophobic methyl terminated SAMs. A surface modification was introduced to incorporate a zwitterionic phosphorylcholine (PC) group on a hydroxyl monolayer in an effort to create a biomimetic surface that could minimize cell adhesion and protein adsorption. The good antifouling properties of the phosphorylcholine modified surface led to the synthesis of a novel phosphorylcholine functionalized thiol. Single component and two component

  18. Computer organization and assembly language programming

    CERN Document Server

    Peterson, James L

    1978-01-01

    Computer Organization and Assembly Language Programming deals with lower level computer programming-machine or assembly language, and how these are used in the typical computer system. The book explains the operations of the computer at the machine language level. The text reviews basic computer operations, organization, and deals primarily with the MIX computer system. The book describes assembly language programming techniques, such as defining appropriate data structures, determining the information for input or output, and the flow of control within the program. The text explains basic I/O

  19. Electrochemically controlled self-assembled monolayers characterized with molecular and sub-molecular resolution

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Welinder, Anna Christina; Chi, Qijin;

    2011-01-01

    Self-assembled organization of functional molecules on solid surfaces has developed into a powerful and sophisticated tool for surface chemistry and nanotechnology. A number of reviews on the topic have been available since the mid 1990s. This perspective article aims to focus on recent developme...

  20. Effect of processing methods on drug release profiles of anti-restenotic self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Stoebner, Susan E. [Biomedical Engineering Program, University of South Dakota, Sioux Falls, SD 57107 (United States); Mani, Gopinath, E-mail: Gopinath.Mani@usd.edu [Biomedical Engineering Program, University of South Dakota, Sioux Falls, SD 57107 (United States)

    2012-04-01

    The use of anti-restenotic self-assembled monolayers (ARSAMs) has been previously demonstrated for delivering drugs from stents without polymeric carriers. ARSAMs have been prepared by coating an anti-restenotic drug (paclitaxel - PAT) on -COOH terminated phosphonic acid self-assembled monolayers (SAMs) coated Co-Cr alloy specimens. This study investigates the effect of different processing methods on the percentage of drug release from ARSAMs. The different methods that were used in this study to process ARSAMs include room temperature (RT) treatment, heat treatment (HT), cold treatment (CT) and quenching. The changes in polymorphism, chemical structure, morphology, and distribution of PAT on SAMs coated specimens were investigated using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. DSC showed dihydrate, dehydrated dihydrate, semi-crystalline, and mixed (amorphous and dihydrate) forms of PAT for RT, HT, CT, and quenched specimens, respectively. FTIR showed that the chemical structure of PAT was unaltered in all the specimens processed by various methods employed in this study. SEM showed a mixture of spherical, ovoid, and bean-shaped morphologies of PAT on RT, HT, and CT while particle-like and needle-shaped morphologies of PAT were observed on quenched specimens. AFM showed PAT was uniformly distributed on RT, HT and CT specimens while particle-like PAT was well distributed and needle-shaped PAT was sparsely distributed on quenched specimens. CT specimens showed greater density of PAT crystals when compared to other methods. Thus, this study demonstrated that processing methods have significant influence on the polymorphism, morphology, and distribution of PAT on SAMs coated Co-Cr alloy specimens. The in vitro drug elution studies for up to 56 days showed sustained release for all the different groups of specimens. CT showed lesser

  1. Large organized surface domains self-assembled from nonpolar amphiphiles.

    Science.gov (United States)

    Krafft, Marie Pierre

    2012-04-17

    For years, researchers had presumed that Langmuir monolayers of small C(n)F(2n+1)C(m)H(2m+1) (FnHm) diblock molecules (such as F8H16) consisted of continuous, featureless films. Recently we have discovered that they instead form ordered arrays of unusually large (~30-60 nm), discrete self-assembled surface domains or hemimicelles both at the surface of water and on solid substrates. These surface micelles differ in several essential ways from all previously reported or predicted molecular surface aggregates. They self-assemble spontaneously, even at zero surface pressure, depending solely on a critical surface concentration. They are very large (~100 times the length of the diblock) and involve thousands of molecules (orders of magnitude more than classical micelles). At the same time, the surface micelles are highly monodisperse and self-organize in close-packed hexagonal patterns (two-dimensional crystals). Their size is essentially independent from pressure, and they do not coalesce and are unexpectedly sturdy for soft matter (persisting even beyond surface film collapse). We and other researchers have observed large surface micelles for numerous diblocks, using Langmuir-Blodgett (LB) transfer, spin-coating and dip-coating techniques, or expulsion from mixed monolayers, and on diverse supports, establishing that hemimicelle formation and ordering are intrinsic properties of (perfluoroalkyl)alkanes. Notably, they involve "incomplete" surfactants with limited amphiphilic character, which further illustrates the outstanding capacity for perfluoroalkyl chains to promote self-assembly and interfacial film structuring. Using X-ray reflectivity, we determined a perfluoroalkyl-chain-up orientation. Theoretical investigations assigned self-assembly and hemimicelle stability to electrostatic dipole-dipole interactions at the interface between Fn- and Hm-sublayers. Grazing-incidence small-angle X-ray scattering (GISAXS) data collected directly on the surface of water

  2. Surface structure and stereochemical properties of self-assembled monolayer materials. Final Report

    International Nuclear Information System (INIS)

    This document reports the progress the authors have made in support of their proposal to generate well-characterized, well-ordered organic surfaces and to impinge upon the array of oriented organic molecules a well-collimated beam of radical atoms at a well-defined angle of incidence. Using the intensity of helium atom diffraction from the organic surface as a measure of the number of unreacted molecules at the surface, the authors will measure the rate of the reaction. They will then vary the angle of incidence of the reactive atom beam and repeat the measurement. In this manner they plan to map out the reactivity of the molecules on the surface as a function of the angle of incidence of the reactive moiety. To carry out this experiment requires that two fields of research be brought together: (1) molecular beam technology and (2) the science/art of growing well-ordered organic surfaces. The first half of this report describes recent helium diffraction results from molecular beam deposited organic monolayers (structural layer characterization work). The second half reports progress in constructing and characterizing the reactive atom (oxygen) beam source.

  3. Enhanced performance of polymer solar cells with a monolayer of assembled gold nanoparticle films fabricated by Langmuir-Blodgett technique

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiaoqiang; Yang, Xi; Fu, Weifei; Xu, Mingsheng [State Key Lab of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Chen, Hongzheng, E-mail: hzchen@zju.edu.cn [State Key Lab of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2013-01-01

    Highlights: Black-Right-Pointing-Pointer Au NP monolayers are incorporated into ITO/anodic buffer layer by LB method. Black-Right-Pointing-Pointer Au NP monolayers are surface oxidized by UV/O{sub 3} treatment. Black-Right-Pointing-Pointer The effects of packing density and particle size on device performance were investigated. Black-Right-Pointing-Pointer Both short-circuit current and open-circuit voltage are improved with Au NP layer. - Abstract: We reported the enhanced performance of polymer solar cells with the blend of poly (2-methoxy-5(2 Prime -ethylhexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as active layer by incorporation of an assembled gold nanoparticle (Au NP) monolayer. The dense Au NP monolayer has been fabricated by Langmuir-Blodgett (LB) assembly and positioned between the transparent electrode ITO and the anode-modification PEDOT:PSS [poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate)] layer, resulting in the device architecture of ITO/Au/PEDOT:PSS/MEH-PPV:PCBM/Al. We attribute the performance improvement to the localized surface plasmon resonance (LSPR) effect of Au NP films, which could lead to the increased absorption of the active layer. The parameters (nanoparticle size and interparticle distance) that govern this SPR effect have been optimized by selecting various sizes of Au NPs and controlling the LB assembly conditions. We observed {approx}10-20% enhancement in power conversion efficiency for all the devices with the Au NP monolayer.

  4. Controlling the stereochemistry and regularity of butanethiol self-assembled monolayers on au(111).

    Science.gov (United States)

    Yan, Jiawei; Ouyang, Runhai; Jensen, Palle S; Ascic, Erhad; Tanner, David; Mao, Bingwei; Zhang, Jingdong; Tang, Chunguang; Hush, Noel S; Ulstrup, Jens; Reimers, Jeffrey R

    2014-12-10

    The rich stereochemistry of the self-assembled monolayers (SAMs) of four butanethiols on Au(111) is described, the SAMs containing up to 12 individual C, S, or Au chiral centers per surface unit cell. This is facilitated by synthesis of enantiomerically pure 2-butanethiol (the smallest unsubstituted chiral alkanethiol), followed by in situ scanning tunneling microscopy (STM) imaging combined with density functional theory molecular dynamics STM image simulations. Even though butanethiol SAMs manifest strong headgroup interactions, steric interactions are shown to dominate SAM structure and chirality. Indeed, steric interactions are shown to dictate the nature of the headgroup itself, whether it takes on the adatom-bound motif RS(•)Au(0)S(•)R or involves direct binding of RS(•) to face-centered-cubic or hexagonal-close-packed sites. Binding as RS(•) produces large, organizationally chiral domains even when R is achiral, while adatom binding leads to rectangular plane groups that suppress long-range expression of chirality. Binding as RS(•) also inhibits the pitting intrinsically associated with adatom binding, desirably producing more regularly structured SAMs.

  5. Utilizing self-assembled-monolayer-based gate dielectrics to fabricate molybdenum disulfide field-effect transistors

    Science.gov (United States)

    Kawanago, Takamasa; Oda, Shunri

    2016-01-01

    In this study, we apply self-assembled-monolayer (SAM)-based gate dielectrics to the fabrication of molybdenum disulfide (MoS2) field-effect transistors. A simple fabrication process involving the selective formation of a SAM on metal oxides in conjunction with the dry transfer of MoS2 flakes was established. A subthreshold slope (SS) of 69 mV/dec and no hysteresis were demonstrated with the ultrathin SAM-based gate dielectrics accompanied by a low gate leakage current. The small SS and no hysteresis indicate the superior interfacial properties of the MoS2/SAM structure. Cross-sectional transmission electron microscopy revealed a sharp and abrupt interface of the MoS2/SAM structure. The SAM-based gate dielectrics are found to be applicable to the fabrication of low-voltage MoS2 field-effect transistors and can also be extended to various layered semiconductor materials. This study opens up intriguing possibilities of SAM-based gate dielectrics in functional electronic devices.

  6. Direct, Noncovalent Coating of a Gold Surface with Polymeric Self-Assembled Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hojae; Hong, Daewha; Jon, Sangyong; Choi, Insung S. [KAIST, Daejeon (Korea, Republic of)

    2013-12-15

    We demonstrated a simple but rather unexpected method for coating a gold surface with the random copolymer presenting a long alkyl chain. The poly(ethylene glycol) group in the polymer effectively minimized the unwanted adsorption of proteins onto the surface, and the N-hydroxysuccinimide group was utilized for covalent immobilization of the antibody. The successful generation of IgG/anti-IgG showed that the long alkyl chain-mediated coating of the gold surface led to the stable formation of the polymeric self-assembled monolayers at least in water and phosphate-buffered saline. We think that more detailed studies on the stability of the pSAMs on gold are needed for the practical applications of the method described in this work to the bioanalytical analysis, which is our next research thrust. The spatio-selective immobilization of biomolecules, such as DNAs, antibodies, or aptamers, onto a solid surface is required for the development of bioanalytical and biomedical devices that interface the immobilized probe with the target biospecifically.

  7. Long-term stability of self-assembled monolayers on 316L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, C R; Mani, G; Marton, D; Johnson, D M; Agrawal, C M, E-mail: Mauli.Agrawal@utsa.ed [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States)

    2010-04-15

    316L stainless steel (316L SS) has been extensively used for making orthopedic, dental and cardiovascular implants. The use of phosphonic acid self-assembled monolayers (SAMs) on 316L SS has been previously explored for potential biomedical applications. In this study, we have investigated the long-term stability of methyl (-CH{sub 3}) and carboxylic acid (-COOH)-terminated phosphonic acid SAMs on 316L under physiological conditions. The stability of SAMs on mechanically polished and electropolished 316L SS was also investigated as a part of this study. Well-ordered and uniform -CH{sub 3}- and -COOH-terminated SAMs were coated on mechanically polished and electropolished 316L SS surfaces. The long-term stability of SAMs on 316L SS was investigated for up to 28 days in Tris-buffered saline (TBS) at 37 deg. C using x-ray photoelectron spectroscopy, atomic force microscopy and contact angle goniometry. A significant amount of phosphonic acid molecules was desorbed from the 316L SS surfaces within 1 to 7 days of TBS immersion followed by a slow desorption of molecules over the remaining days. The -COOH-terminated SAM was found to be more stable than the -CH{sub 3}-terminated SAM on both mechanically and electropolished surfaces. No significant differences in the desorption behavior of SAMs were observed between mechanically and electropolished 316L SS surfaces.

  8. Direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized on L-glutathione self-assembled monolayers

    Institute of Scientific and Technical Information of China (English)

    Chuan Yin Liu; Ji Ming Hu

    2008-01-01

    A novel hydrogen peroxide biosensor has been fabricated based on covalently linked horseradish peroxidase (HRP) onto Lglutathione self-assembled monolayers (SAMs). The SAMs-based electrode was characterized by electrochemical methods, and direct electrochemistry of HRP can be achieved with formal potential of-0.242 V (vs. saturated Ag/AgCl) in pH7 phosphate buffer solution (PBS), the redox peak current is linear to scan rate and rate constant can be calculated to be 0.042 s-1. The HRP-SAMs-based biosensors show its better electrocatalysis to hydrogen peroxide in the concentration range of 1 × 10-6 mol/L to 1.2 × 10-3 mol/L with a detection limit of 4 × 10-7 mol/L. The apparent Michealis-Menten constant is 3.12 mmol/L. The biosensor can effectively eliminate the interferences of dopamine, ascorbic acid, uric acid, catechol and p-acetaminophen.

  9. Chemical stability of nonwetting, low adhesion self-assembled monolayer films formed by perfluoroalkylsilanization of copper

    Science.gov (United States)

    Hoque, E.; DeRose, J. A.; Hoffmann, P.; Bhushan, B.; Mathieu, H. J.

    2007-03-01

    A self-assembled monolayer (SAM) has been produced by reaction of 1H,1H,2H,2H-perfluorodecyldimethylchlorosilane (PFMS) with an oxidized copper (Cu) substrate and investigated by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), friction force microscopy (FFM), a derivative of AFM, and contact angle measurement. FFM showed a significant reduction in the adhesive force and friction coefficient of PFMS modified Cu (PFMS/Cu) compared to unmodified Cu. The perfluoroalkyl SAM on Cu is found to be extremely hydrophobic, yielding sessile drop static contact angles of more than 130° for pure water and a "surface energy" (which is proportional to the Zisman critical surface tension for a Cu surface with 0rms roughness) of 14.5mJ/m2(nM/m). Treatment by exposure to harsh conditions showed that PFMS/Cu SAM can withstand boiling nitric acid (pH=1.8), boiling water, and warm sodium hydroxide (pH =12, 60°C) solutions for at least 30min. Furthermore, no SAM degradation was observed when PFMS/Cu was exposed to warm nitric acid solution for up to 70min at 60°C or 50min at 80°C. Extremely hydrophobic (low surface energy) and stable PFMS/Cu SAMs could be useful as corrosion inhibitors in micro/nanoelectronic devices and/or as promoters for antiwetting, low adhesion surfaces or dropwise condensation on heat exchange surfaces.

  10. Temperature-responsive self-assembled monolayers of oligo(ethylene glycol): control of biomolecular recognition.

    Science.gov (United States)

    Zareie, Hadi M; Boyer, Cyrille; Bulmus, Volga; Nateghi, Ebrahim; Davis, Thomas P

    2008-04-01

    Self-assembled monolayers (SAMs) of oligo(ethylene glycol) (OEG)-tethered molecules on gold are important for various biorelevant applications ranging from biomaterials to bioanalytical devices, where surface resistance to nonspecific protein adsorption is needed. Incorporation of a stimuli-responsive character to the OEG SAMs enables the creation of nonfouling surfaces with switchable functionality. Here we present an OEG-derived structure that is highly responsive to temperature changes in the vicinity of the physiological temperature, 37 degrees C. The temperature-responsive solution behavior of this new compound was demonstrated by UV-vis and nuclear magnetic resonance spectroscopy. Its chemisorption onto gold(111), and the retention of responsive behavior after chemisorption have been demonstrated by surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS), and atomic force and scanning tunneling microscopy. The OEG-derived SAMs have been shown to reversibly switch the wettability of the surface, as determined by contact angle measurements. More importantly, SPR and AFM studies showed that the OEG SAMs can be utilized to control the affinity binding of streptavidin to the biotin-tethered surface in a temperature-dependent manner while still offering the nonspecific protein-resistance to the surface.

  11. Self-Cleaning Features of Plasma-Treated Surfaces with Self-Assembled Monolayer Coating

    Science.gov (United States)

    Lee, Sang‑Joon; Paik, Bu‑Geun; Kim, Guk‑Bae; Jang, Young‑Gil

    2006-02-01

    A biomimic surface was coated onto a poly(tetrafluoroethylene) (PTFE) substrate. The coated PTFE surface was found to have nanoscale roughness and high hydrophobicity. In the first preparation step, the PTFE surface was modified by plasma etching. A self-assembled monolayer (SAM) of octadecyltrichlorosilane (ODTS) was then deposited onto the modified surface with a thickness of a 2-3 nm. This surface was found to have self-cleaning features similar to those of a lotus leaf. The self-cleaning features were confirmed by comparing the contact and sliding angles of the original PTFE surface, a PTFE surface plasma treated, and a PTFE surface plasma treated and SAM coated. The PTFE surface treated with plasma and SAM coated had an increased contact angle and a decreased sliding angle compared with the other surfaces. It also exhibited increased stability and slow aging. The quantity of oxygen-containing groups that can be greatly influenced by plasma treatment, SAM coating, and aging, seems to play an important role in surface modification.

  12. Surface plasmon resonance immunosensor for human cardiac troponin T based on self-assembled monolayer.

    Science.gov (United States)

    Dutra, Rosa Fireman; Mendes, Renata Kelly; Lins da Silva, Valdinete; Kubota, Lauro Tatsuo

    2007-04-11

    The cardiac troponin T (cTnT) is specific biomarker important for trials of acute myocardial infarctions (AMI). In this paper, a SPR sensor in real time to detect the biomarker was developed on a commercially available surface plasmon resonance AUTOLAB SPIRIT. The cTnT receptor molecule was covalently immobilized on a gold substrate via a self-assembled monolayer (SAM) of thiols by using cysteamine-coupling chemistry. This biosensor presented a linear response range for cTnT between 0.05 and 4.5 ng/mL (r=0.997, p<0.01) with a good reproducibility (CV=4.4%). The effect of the cysteamine (CYS) concentrations on the SAM coated gold sensor was studied as a function of the amount of the immobilized cTnT monoclonal antibodies. Analysis using serum samples undiluted was carried out at room temperature showing a well agreement with the ECLIA methods and the sensor surface could be regenerated by using a solution of 1% (w/v) sodium dodecyl sulphate (SDS) without losing the sensor immunoreactivity. These studies open new perspectives of using SAM to develop regenerable immunosensor with a good reproducibility allowing its use in the clinical applications. PMID:17254730

  13. Utilizing self-assembled-monolayer-based gate dielectrics to fabricate molybdenum disulfide field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Kawanago, Takamasa, E-mail: kawanago.t.ab@m.titech.ac.jp; Oda, Shunri [Quantum Nanoelectronics Research Center (QNERC), Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550 (Japan)

    2016-01-25

    In this study, we apply self-assembled-monolayer (SAM)-based gate dielectrics to the fabrication of molybdenum disulfide (MoS{sub 2}) field-effect transistors. A simple fabrication process involving the selective formation of a SAM on metal oxides in conjunction with the dry transfer of MoS{sub 2} flakes was established. A subthreshold slope (SS) of 69 mV/dec and no hysteresis were demonstrated with the ultrathin SAM-based gate dielectrics accompanied by a low gate leakage current. The small SS and no hysteresis indicate the superior interfacial properties of the MoS{sub 2}/SAM structure. Cross-sectional transmission electron microscopy revealed a sharp and abrupt interface of the MoS{sub 2}/SAM structure. The SAM-based gate dielectrics are found to be applicable to the fabrication of low-voltage MoS{sub 2} field-effect transistors and can also be extended to various layered semiconductor materials. This study opens up intriguing possibilities of SAM-based gate dielectrics in functional electronic devices.

  14. Stabilization of Insulin by Adsorption on a Hydrophobic Silane Self-Assembled Monolayer.

    Science.gov (United States)

    Mauri, Sergio; Volk, Martin; Byard, Stephen; Berchtold, Harald; Arnolds, Heike

    2015-08-18

    The interaction between many proteins and hydrophobic functionalized surfaces is known to induce β-sheet and amyloid fibril formation. In particular, insulin has served as a model peptide to understand such fibrillation, but the early stages of insulin misfolding and the influence of the surface have not been followed in detail under the acidic conditions relevant to the synthesis and purification of insulin. Here we compare the adsorption of human insulin on a hydrophobic (-CH3-terminated) silane self-assembled monolayer to a hydrophilic (-NH3(+)-terminated) layer. We monitor the secondary structure of insulin with Fourier transform infrared attenuated total reflection and side-chain orientation with sum frequency spectroscopy. Adsorbed insulin retains a close-to-native secondary structure on both hydrophobic and hydrophilic surfaces for extended periods at room temperature and converts to a β-sheet-rich structure only at elevated temperature. We propose that the known acid stabilization of human insulin and the protection of the aggregation-prone hydrophobic domains on the insulin monomer by adsorption on the hydrophobic surface work together to inhibit fibril formation at room temperature.

  15. Self-assembled monolayers and titanium dioxide: From surface patterning to potential applications

    Directory of Open Access Journals (Sweden)

    Yaron Paz

    2011-12-01

    Full Text Available The ability to control the properties of self-assembled monolayers (SAMs attached to solid surfaces and the rare photocatalytic properties of titanium dioxide provide a rationale for the study of systems comprising both. Such systems can be realized in the form of SAMs grown on TiO2 or, in a complementary manner, as TiO2 grown on SAMs. Accordingly, the current status of knowledge regarding SAMs on TiO2 is described. Photocatalytic phenomena that are of specific relevance to SAMs, such as remote degradation, and cases where SAMs were used to study photocatalytic phenomena, are discussed as well. Mastering of micro-patterning is a key issue en route to a successful assimilation of a variety of titanium dioxide based devices. Accordingly, particular attention is given to the description of a variety of methods and techniques aimed at utilizing the photocatalytic properties of titanium dioxide for patterning. Reports on a variety of applications are discussed. These examples, representing the areas of photovoltaics, microelectronics, microelectromechanics, photocatalysis, corrosion prevention and even biomedicine should be regarded as appetizers paving the way for further studies to be performed.

  16. Self-assembled monolayers based spintronics: from ferromagnetic surface functionalization to spin-dependent transport

    Science.gov (United States)

    Tatay, Sergio; Galbiati, Marta; Delprat, Sophie; Barraud, Clément; Bouzehouane, Karim; Collin, Sophie; Deranlot, Cyrile; Jacquet, Eric; Seneor, Pierre; Mattana, Richard; Petroff, Frédéric

    2016-03-01

    Chemically functionalized surfaces are studied for a wide range of applications going from medicine to electronics. Whereas non-magnetic surfaces have been widely studied, functionalization of magnetic surfaces is much less common and has almost never been used for spintronics applications. In this article we present the functionalization of La2/3Sr1/3MnO3, a ferromagnetic oxide, with self-assembled monolayers for spintronics. La2/3Sr1/3MnO3 is the prototypical half-metallic manganite used in spintronics studies. First, we show that La2/3Sr1/3MnO3 can be functionalized by alkylphosphonic acid molecules. We then emphasize the use of these functionalized surfaces in spintronics devices such as magnetic tunnel junctions fabricated using a nano-indentation based lithography technique. The observed exponential increase of tunnel resistance as a function of alkyl chain length is a direct proof of the successful connection of molecules to ferromagnetic electrodes. For all alkyl chains studied we obtain stable and robust tunnel magnetoresistance, with effects ranging from a few tens to 10 000%. These results show that functionalized electrodes can be integrated in spintronics devices and open the door to a molecular engineering of spintronics.

  17. An Investigation of the Effects of Self-Assembled Monolayers on Protein Crystallisation

    Directory of Open Access Journals (Sweden)

    Da-Chuan Yin

    2013-06-01

    Full Text Available Most protein crystallisation begins from heterogeneous nucleation; in practice, crystallisation typically occurs in the presence of a solid surface in the solution. The solid surface provides a nucleation site such that the energy barrier for nucleation is lower on the surface than in the bulk solution. Different types of solid surfaces exhibit different surface energies, and the nucleation barriers depend on the characteristics of the solid surfaces. Therefore, treatment of the solid surface may alter the surface properties to increase the chance to obtain protein crystals. In this paper, we propose a method to modify the glass cover slip using a self-assembled monolayer (SAM of functional groups (methyl, sulfydryl and amino, and we investigated the effect of each SAM on protein crystallisation. The results indicated that both crystallisation success rate in a reproducibility study, and crystallisation hits in a crystallisation screening study, were increased using the SAMs, among which, the methyl-modified SAM demonstrated the most significant improvement. These results illustrated that directly modifying the crystallisation plates or glass cover slips to create surfaces that favour heterogeneous nucleation can be potentially useful in practical protein crystallisation, and the utilisation of a SAM containing a functional group can be considered a promising technique for the treatment of the surfaces that will directly contact the crystallisation solution.

  18. Comparative Study of Electroless Copper Film on Different Self-Assembled Monolayers Modified ABS Substrate

    Directory of Open Access Journals (Sweden)

    Jiushuai Xu

    2014-04-01

    Full Text Available Copper films were grown on (3-Mercaptopropyltrimethoxysilane (MPTMS, (3-Aminopropyltriethoxysilane (APTES and 6-(3-(triethoxysilylpropylamino-1,3,5- triazine-2,4-dithiol monosodium (TES self-assembled monolayers (SAMs modified acrylonitrile-butadiene-styrene (ABS substrate via electroless copper plating. The copper films were examined using scanning electron microscopy (SEM and X-ray diffraction (XRD. Their individual deposition rate and contact angle were also investigated to compare the properties of SAMs and electroless copper films. The results indicated that the formation of copper nuclei on the TES-SAMs modified ABS substrate was faster than those on the MPTMS-SAMs and APTES-SAMs modified ABS substrate. SEM images revealed that the copper film on TES-SAM modified ABS substrate was smooth and uniform, and the density of copper nuclei was much higher. Compared with that of TES-SAMs modified resin, the coverage of copper nuclei on MPTMS and APTES modified ABS substrate was very limited and the copper particle size was too big. The adhesion property test demonstrated that all the SAMs enhanced the interfacial interaction between copper plating and ABS substrate. XRD analysis showed that the copper film deposited on SAM-modified ABS substrate had a structure with Cu(111 preferred orientation, and the copper film deposited on TES-SAMs modified ABS substrate is better than that deposited on MPTMS-SAMs or APTES-SAMs modified ABS resins in electromigrtion resistance.

  19. Frictional properties of two alkanethiol self assembled monolayers in sliding contact: Odd-even effects

    Science.gov (United States)

    Ramin, Leyla; Jabbarzadeh, Ahmad

    2012-11-01

    Using molecular dynamics simulation, we have investigated the structural effects on the frictional properties of self assembled monolayers (SAM) of n-alkanethiols [CH3(CH2)n-1SH, n = 12-15] in SAM-SAM contacts attached on Au (111) substrates. We have observed an odd-even effect where friction coefficient for SAM-SAM contacts with n = odd showed consistently higher values than those with n = even. This odd-even effect is independent of the sliding velocity and the relative tilt directions of the SAMs, and persists over a much higher pressure range than that reported before for SAM-Au contacts [L. Ramin and A. Jabbarzadeh, Langmuir 28, 4102-4112 (2012), 10.1021/la204701z]. For odd systems higher gauche defects were shown to be the possible source of high friction coefficient. Under the same load and shear rates (comparable sliding velocities), SAM-SAM contacts show mostly higher friction compared to SAM-Au contacts. For SAM-SAM contacts, a more significant increase of friction occurs at higher shear rates due to a shift in the tilt orientation angle. We show SAM-SAM contacts with misaligned relative tilt orientation angle (˜45°-90°) have considerably lower friction compared with those whose tilt orientation angles are almost aligned in the opposite directions and parallel to the shear.

  20. Passivation of copper surfaces for selective-area ALD using a thiol self-assembled monolayer

    Science.gov (United States)

    Färm, Elina; Vehkamäki, Marko; Ritala, Mikko; Leskelä, Markku

    2012-07-01

    Self-assembled monolayers (SAMs) of 1-dodecanethiol (CH3(CH2)11SH) were prepared from the vapor phase and used as a passivation layer for selective-area ALD. Thiol SAMs have commonly been prepared by immersing the substrates into a solution containing alkyl thiols. Formation of SAMs from the vapor phase, however, has advantages compared to liquid phase preparation. Passivation of surface can be done as a part of the ALD process forming a SAM first and then continuing with the common ALD process. SAMs can also be applied to three-dimensional structures relying on chemical selectivity of the thiol SAM formation. For example in the copper damascene process the thiol SAMs should form only on the copper surface but not on the insulators. In this study, the SAMs were prepared by placing the substrate and the alkylthiol to the reaction chamber and heating the system to the temperature of 73 °C. Preparation time varied from 0.5 to 24 h. Passivation properties of SAMs were tested with ALD iridium and polyimide processes. Iridium was deposited at 250  ° C for 500 cycles and polyimide at 160  ° C for 20 cycles.

  1. Fabrication of a molecularly imprinted polymer sensor by self-assembling monolayer/mediator system

    International Nuclear Information System (INIS)

    Detection of dopamine (DA) by using a molecularly imprinted polymer (MIP) which fabricated by the self-assembling monolayer (SAM)/mediator system was studied. The SAM was made by attaching thioglycolic acid (TGA) on a gold electrode and quercetin (Q) was selected as an electron transfer mediator in this system. Methyl methacrylate (MMA) was polymerized by photopolymerization with the addition of dopamine to form a MIP electrode. The MIP and non-MIP (NMIP) modified electrodes were identified by FTIR and scanning electrochemical microscopy (SECM) approach curves. DA was detected by an amperometric method at a constant potential of 0.45 V and obtained a sensitivity of 0.445 mA cm-2 M-1. The imprinting efficiency approaches infinity due to a non-reactive surface of NMIP. In the interference test, ascorbic acid contributed less than 12% of current response in the coexistence solution with DA and the performance is highly related to the concentration of template added during the fabrication process.

  2. Enhancing the Thermal Conductance of Polymer and Sapphire Interface via Self-Assembled Monolayer.

    Science.gov (United States)

    Zheng, Kun; Sun, Fangyuan; Zhu, Jie; Ma, Yongmei; Li, Xiaobo; Tang, Dawei; Wang, Fosong; Wang, Xiaojia

    2016-08-23

    Interfacial thermal conductance (ITC) receives enormous consideration because of its significance in determining thermal performance of hybrid materials, such as polymer based nanocomposites. In this study, the ITC between sapphire and polystyrene (PS) was systematically investigated by time domain thermoreflectance (TDTR) method. Silane based self-assembled monolayers (SAMs) with varying end groups, -NH2, -Cl, -SH and -H, were introduced into sapphire/PS interface, and their effects on ITC were investigated. The ITC was found to be enhanced up by a factor of 7 through functionalizing the sapphire surface with SAM, which ends with a chloride group (-Cl). The results show that the enhancement of the thermal transport across the SAM-functionalized interface comes from both strong covalent bonding between sapphire and silane-based SAM, and the high compatibility between the SAM and PS. Among the SAMs studied in this work, we found that the ITC almost linearly depends on solubility parameters, which could be the dominant factor influencing on the ITC compared with wettability and adhesion. The SAMs serve as an intermediate layer that bridges the sapphire and PS. Such a feature can be applied to ceramic-polymer immiscible interfaces by functionalizing the ceramic surface with molecules that are miscible with the polymer materials. This research provides guidance on the design of critical-heat transfer materials such as composites and nanofluids for thermal management. PMID:27501117

  3. Utilizing self-assembled-monolayer-based gate dielectrics to fabricate molybdenum disulfide field-effect transistors

    International Nuclear Information System (INIS)

    In this study, we apply self-assembled-monolayer (SAM)-based gate dielectrics to the fabrication of molybdenum disulfide (MoS2) field-effect transistors. A simple fabrication process involving the selective formation of a SAM on metal oxides in conjunction with the dry transfer of MoS2 flakes was established. A subthreshold slope (SS) of 69 mV/dec and no hysteresis were demonstrated with the ultrathin SAM-based gate dielectrics accompanied by a low gate leakage current. The small SS and no hysteresis indicate the superior interfacial properties of the MoS2/SAM structure. Cross-sectional transmission electron microscopy revealed a sharp and abrupt interface of the MoS2/SAM structure. The SAM-based gate dielectrics are found to be applicable to the fabrication of low-voltage MoS2 field-effect transistors and can also be extended to various layered semiconductor materials. This study opens up intriguing possibilities of SAM-based gate dielectrics in functional electronic devices

  4. A priori calculations of the free energy of formation from solution of polymorphic self-assembled monolayers.

    Science.gov (United States)

    Reimers, Jeffrey R; Panduwinata, Dwi; Visser, Johan; Chin, Yiing; Tang, Chunguang; Goerigk, Lars; Ford, Michael J; Sintic, Maxine; Sum, Tze-Jing; Coenen, Michiel J J; Hendriksen, Bas L M; Elemans, Johannes A A W; Hush, Noel S; Crossley, Maxwell J

    2015-11-10

    Modern quantum chemical electronic structure methods typically applied to localized chemical bonding are developed to predict atomic structures and free energies for meso-tetraalkylporphyrin self-assembled monolayer (SAM) polymorph formation from organic solution on highly ordered pyrolytic graphite surfaces. Large polymorph-dependent dispersion-induced substrate-molecule interactions (e.g., -100 kcal mol(-1) to -150 kcal mol(-1) for tetratrisdecylporphyrin) are found to drive SAM formation, opposed nearly completely by large polymorph-dependent dispersion-induced solvent interactions (70-110 kcal mol(-1)) and entropy effects (25-40 kcal mol(-1) at 298 K) favoring dissolution. Dielectric continuum models of the solvent are used, facilitating consideration of many possible SAM polymorphs, along with quantum mechanical/molecular mechanical and dispersion-corrected density functional theory calculations. These predict and interpret newly measured and existing high-resolution scanning tunnelling microscopy images of SAM structure, rationalizing polymorph formation conditions. A wide range of molecular condensed matter properties at room temperature now appear suitable for prediction and analysis using electronic structure calculations.

  5. Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

    Science.gov (United States)

    Alonso, Jose Maria; Bielen, Abraham A. M.; Olthuis, Wouter; Kengen, Servé W. M.; Zuilhof, Han; Franssen, Maurice C. R.

    2016-10-01

    Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxysuccinimide (NHS) ester-derived groups, to provide anchoring points for enzyme immobilization. The functionalized Pt surfaces were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (CA), infrared reflection absorption spectroscopy (IRRAS) and atomic force microscopy (AFM). Glucose oxidase (GOX) was covalently attached to the functionalized Pt electrodes, either with or without additional glutaraldehyde crosslinking. The responses of the acquired sensors to glucose concentrations ranging from 0.5 to 100 mM were monitored by chronoamperometry. Furthermore, lactate oxidase (LOX) and human hydroxyacid oxidase (HAOX) were successfully immobilized onto the PtOx surface platform. The performance of the resulting lactate sensors was investigated for lactate concentrations ranging from 0.05 to 20 mM. The successful attachment of active enzymes (GOX, LOX and HAOX) on Pt electrodes demonstrates that covalently functionalized PtOx surfaces provide a universal platform for the development of oxidase enzyme-based sensors.

  6. Employing X-ray Photoelectron Spectroscopy for Determining Layer Homogeneity in Mixed Polar Self-Assembled Monolayers

    Science.gov (United States)

    2016-01-01

    Self-assembled monolayers (SAMs) containing embedded dipolar groups offer the particular advantage of changing the electronic properties of a surface without affecting the SAM–ambient interface. Here we show that such systems can also be used for continuously tuning metal work functions by growing mixed monolayers consisting of molecules with different orientations of the embedded dipolar groups. To avoid injection hot-spots when using the SAM-modified electrodes in devices, a homogeneous mixing of the two components is crucial. We show that a combination of high-resolution X-ray photoelectron spectroscopy with state-of-the-art simulations is an ideal tool for probing the electrostatic homogeneity of the layers and thus for determining phase separation processes in polar adsorbate assemblies down to inhomogeneities at the molecular level. PMID:27429041

  7. Employing X-ray Photoelectron Spectroscopy for Determining Layer Homogeneity in Mixed Polar Self-Assembled Monolayers.

    Science.gov (United States)

    Hehn, Iris; Schuster, Swen; Wächter, Tobias; Abu-Husein, Tarek; Terfort, Andreas; Zharnikov, Michael; Zojer, Egbert

    2016-08-01

    Self-assembled monolayers (SAMs) containing embedded dipolar groups offer the particular advantage of changing the electronic properties of a surface without affecting the SAM-ambient interface. Here we show that such systems can also be used for continuously tuning metal work functions by growing mixed monolayers consisting of molecules with different orientations of the embedded dipolar groups. To avoid injection hot-spots when using the SAM-modified electrodes in devices, a homogeneous mixing of the two components is crucial. We show that a combination of high-resolution X-ray photoelectron spectroscopy with state-of-the-art simulations is an ideal tool for probing the electrostatic homogeneity of the layers and thus for determining phase separation processes in polar adsorbate assemblies down to inhomogeneities at the molecular level. PMID:27429041

  8. Large work function shift of gold induced by a novel perfluorinated azobenzene-based self-assembled monolayer.

    Science.gov (United States)

    Crivillers, Núria; Osella, Silvio; Van Dyck, Colin; Lazzerini, Giovanni M; Cornil, David; Liscio, Andrea; Di Stasio, Francesco; Mian, Shabbir; Fenwick, Oliver; Reinders, Federica; Neuburger, Markus; Treossi, Emanuele; Mayor, Marcel; Palermo, Vincenzo; Cacialli, Franco; Cornil, Jérôme; Samorì, Paolo

    2013-01-18

    Tune it with light! Self-assembled monolayers on gold based on a chemisorbed novel azobenzene derivative with a perfluorinated terminal phenyl ring are prepared. The modified substrate shows a significant work function increase compared to the bare metal. The photo-conversion between trans and cis isomers chemisorbed on the surface shows great perspectives for being an accessible route to tune the gold properties by means of light.

  9. The structure of thin zirconia films obtained by self-assembled monolayer mediated deposition: TEM and HREM study

    OpenAIRE

    Roddatis, V.; Su, D.; Beckmann, E.; Jentoft, F.; Braun, U.; Kröhnert, J.; Schlögl, R.

    2002-01-01

    Transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS) and energy dispersive X-ray analysis (EDX) have been performed on thin zirconia films produced by means of self-assembled monolayer (SAM) mediated deposition from aqueous zirconium sulphate dispersion at 50°C. As-grown films were found to be amorphous. Electron beam irradiation can induce the crystallization of as-grown amorphous zirconia films to tetragonal polycrystalline ZrO2 films. EELS revealed changes in th...

  10. Self-assembled monolayers of calix[4]arene derivatives on gold

    NARCIS (Netherlands)

    Huisman, Bart-Hendrik; Thoden van Velzen, Eggo U.; Veggel, van Frank C.J.M.; Engbersen, Johan F.J.; Reinhoudt, David N.

    1995-01-01

    Dialkylsulfide substituted calix[4]arenes were synthesized and adsorbed onto gold substrates. Infrared spectroscopy, thickness, and wettability studies revealed that well-ordered monolayers were formed.

  11. Dominant effects of first monolayer energetics at donor/acceptor interfaces on organic photovoltaics.

    Science.gov (United States)

    Izawa, Seiichiro; Nakano, Kyohei; Suzuki, Kaori; Hashimoto, Kazuhito; Tajima, Keisuke

    2015-05-20

    Energy levels of the first monolayer are manipulated at donor/acceptor interfaces in planar heterojunction organic photovoltaics by using molecular self-organization. A "cascade" energy landscape allows thermal-activation-free charge generation by photoirradiation, destabilizes the energy of the interfacial charge-transfer state, and suppresses bimolecular charge recombination, resulting in a higher open-circuit voltage and fill factor.

  12. Self-assembled monolayers of pyridylthio-functionalized carbon nanotubes used as a support to immobilize cytochrome c

    OpenAIRE

    Sun, Qing; Liu, Jiang; Huang, Hong-Xiang; Chen, Meng; Qian, Dong-Jin

    2013-01-01

    Self-assembled monolayers (SAMs) of pyridylthio-functionalized multiwalled carbon nanotubes (pythio-MWNTs) have been constructed on the gold substrate surface, which were used as a support to immobilize cytochrome c (Cyt c). The assembly processes of the SAMs and adsorption of Cyt c were monitored by using quartz crystal microbalance (QCM). Based on the frequency change of the QCM resonator, the surface coverage for the SAMs of pythio-MWNTs was estimated to be about 5.2 μg/cm2, and that of th...

  13. Unprecedented Self-Organized Monolayer of a Ru(II) Complex by Diazonium Electroreduction.

    Science.gov (United States)

    Nguyen, Van Quynh; Sun, Xiaonan; Lafolet, Frédéric; Audibert, Jean-Frédéric; Miomandre, Fabien; Lemercier, Gilles; Loiseau, Frédérique; Lacroix, Jean-Christophe

    2016-08-01

    A new heteroleptic polypyridyle Ru(II) complex was synthesized and deposited on surface by the diazonium electroreduction process. It yields to the covalent grafting of a monolayer. The functionalized surface was characterized by XPS, electrochemistry, AFM, and STM. A precise organization of the molecules within the monolayer is observed with parallel linear stripes separated by a distance of 3.8 nm corresponding to the lateral size of the molecule. Such organization suggests a strong cooperative process in the deposition process. This strategy is an original way to obtain well-controlled and stable functionalized surfaces for potential applications related to the photophysical properties of the grafted chromophore. As an exciting result, it is the first example of a self-organized monolayer (SOM) obtained using diazonium electroreduction. PMID:27430366

  14. Gold nanoparticles modified with self-assembled hybrid monolayer of triblock aptamers as a photoreversible anticoagulant.

    Science.gov (United States)

    Huang, San-Shan; Wei, Shih-Chun; Chang, Huan-Tsung; Lin, Han-Jia; Huang, Chih-Ching

    2016-01-10

    We demonstrated that thrombin-binding aptamer-conjugated gold nanoparticles (TBA-Au NPs), prepared from a self-assembled hybrid monolayer (SAHM) of triblock aptamers on Au NPs (13 nm), can effectively inhibit thrombin activity toward fibrinogen. The first block poly(adenine) at the end of the triblock TBA was used for the self-assembly on Au NP surface. The second block, in the middle of TBA, was composed of oligonucleotides that could hybridize with each other. The third block, containing TBA15 (15-base, binding to the exosite I of thrombin) and TBA29 (29-base, binding to the exosite II of thrombin) provided bivalent interaction with thrombin. The SAHM triblock aptamers have optimal distances between TBA15 and TBA29, aptamer density, and orientation on the Au NP surfaces. These properties strengthen the interactions with thrombin (Kd=1.5 × 10(-11)M), resulting in an extremely high anticoagulant potency. The thrombin clotting time mediated by SAHM TBA15/TBA29-Au NPs was >10 times longer than that of four commercially available drugs (heparin, argatroban, hirudin, or warfarin). In addition, the rat-tail bleeding assay time further demonstrated that the SAHM TBA15/TBA29-Au NPs were superior to heparin. The SAHM TBA15/TBA29-Au NPs exhibited excellent stability in the human plasma (half-life >14 days) and good biocompatibility (low cytotoxicity and hemolysis). Most interestingly, the inhibition by SAHM TBA15/TBA29-Au NPs was controllable by the irradiation of green laser, via heat transfer-induced TBA release from Au NPs. Therefore, these easily prepared (self-assembled), low cost (non-thiolated aptamer), photo-controllable, multivalent TBA15/TBA29-Au NPs (high density of TBA15/TBA29 on Au NPs) show good potential for the treatment of various diseases related to blood-clotting disorders. Our study opens up the possibility of regulation of molecule binding, protein recognition, and enzyme activity using SAHM aptamer-functionalized nanomaterials. PMID:26643617

  15. Self-Assembly of Tetraphenyldibenzoperiflanthene (DBP) Films on Ag(111) in the Monolayer Regime.

    Science.gov (United States)

    Kirchhuebel, Tino; Gruenewald, Marco; Sojka, Falko; Kera, Satoshi; Bussolotti, Fabio; Ueba, Takahiro; Ueno, Nobuo; Rouillé, Gaël; Forker, Roman; Fritz, Torsten

    2016-03-01

    Tetraphenyldibenzoperiflanthene (DBP) is a promising candidate as a component of highly efficient organic photovoltaic cells and organic light-emitting diodes. The structural properties of thin films of this particular lander-type molecule on Ag(111) were investigated by complementary techniques. Highly ordered structures were obtained, and their mutual alignment was characterized by means of low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) images reveal two slightly different arrangements within the first monolayer (ML), both describable as specific herringbone patterns with two molecules per unit cell whose dibenzoperiflanthene framework is parallel to the surface. In contrast, single DBP molecules in the second ML were imaged with much higher intramolecular resolution, resembling the shape of the frontier orbitals in the gas phase as calculated by means of density functional theory (DFT). Further deposition leads to the growth of highly ordered bilayer islands on top of the first ML with identical unit cell dimensions and orientation but slightly inclined molecules. This suggests that the first ML acts as a template for the epitaxial growth of further layers. Simultaneously, a significant number of second-layer molecules mainly located at step edges or scattered over narrow terraces do not form highly ordered aggregates. PMID:26844381

  16. Secondary Structures of Ubiquitin Ions Soft-Landed onto Self-Assembled Monolayer Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qichi; Laskin, Julia

    2016-06-09

    The secondary structures of multiply charged ubiquitin ions soft-landed onto self-assembled monolayer (SAM) surfaces were studied using in situ infrared reflection-absorption spectroscopy (IRRAS). Two charge states of ubiquitin, 5+ and 13+, were mass selected separately from a mixture of different charge states produced by electrospray ionization (ESI). The low 5+ charge state represents a native-like folded state of ubiquitin, while the high 13+ charge state assumes an extended, almost linear conformation. Each of the two charge states was soft-landed onto a CH3- and COOH-terminated SAM of alkylthiols on gold (HSAM and COOH-SAM). HSAM is a hydrophobic surface known to stabilize helical conformations of soft-landed protonated peptides, whereas COOH-SAM is a hydrophilic surface that preferentially stabilizes β-sheet conformations. IRRAS spectra of the soft-landed ubiquitin ions were acquired as a function of time during and after ion soft-landing. Similar to smaller peptide ions, helical conformations of ubiquitin are found to be more abundant on HSAM, while the relative abundance of β-sheet conformations increases on COOH-SAM. The initial charge state of ubiquitin also has a pronounced effect on its conformation on the surface. Specifically, on both surfaces, a higher relative abundance of helical conformations and lower relative abundance of β-sheet conformations is observed for the 13+ charge state compared to the 5+ charge state. Time-resolved experiments indicate that the α-helical band in the spectrum of the 13+ charge state slowly increases with time on the HSAM surface and decreases in the spectrum of the 13+ charge state on COOH-SAM. These results further support the preference of the hydrophobic HSAM surface toward helical conformations and demonstrate that soft-landed protein ions may undergo slow conformational changes during and after deposition.

  17. Unfolding of cytochrome c immobilized on self-assembled monolayers. An electrochemical study

    International Nuclear Information System (INIS)

    Highlights: → Denaturation involves intermediate and partially unfolded forms. → An unfolded species displaying the haem with Fe coordinated by two His is observed. → Under unfolding conditions the nature of the SAM influences conformation of protein. → Concentration of the unfolding agent affects redox properties of immobilized protein. - Abstract: The electron transfer (ET) process of progressively unfolded bovine cytochrome c immobilized on different self-assembled monolayers (SAMs) was investigated. Insight is gained on the role of the SAM surface on the functionality of the partially unfolded and non-native forms of the adsorbed protein. Direct electrochemical measurements were performed on cytochrome c adsorbed on mercaptopyridine (MP) and mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol (MUA/MU) at varying temperature, in the presence of urea as unfolding agent. Under strongly unfolding conditions, a non-native form of cytochrome c, in which the methionine ligand is replaced by a histidine, was observed on both MP and MUA/MU SAMs. The Eo' of the native form, in which the haem is axially coordinated by methionine and histidine, slightly shifts to negative values upon increasing urea concentration. However, the non-native bis-histidinate species shows a much lower Eo' value (by approximately 0.4 V) which is by far enthalpic in origin and largely determined by axial ligand swapping. Analysis of the reduction enthalpies and entropies and of the ET rate constants indicate that the nature of the SAM (hydrophilic or anionic) results in changes in the conformational rearrangement of the cytochrome c under unfolding conditions.

  18. Unfolding of cytochrome c immobilized on self-assembled monolayers. An electrochemical study

    Energy Technology Data Exchange (ETDEWEB)

    Monari, Stefano; Ranieri, Antonio; Bortolotti, Carlo Augusto; Peressini, Silvia [Department of Chemistry, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena (Italy); Tavagnacco, Claudio [Department of Chemistry, University of Trieste, via Giorgieri 1, 34127 Trieste (Italy); Borsari, Marco, E-mail: marco.borsari@unimore.it [Department of Chemistry, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena (Italy)

    2011-08-01

    Highlights: > Denaturation involves intermediate and partially unfolded forms. > An unfolded species displaying the haem with Fe coordinated by two His is observed. > Under unfolding conditions the nature of the SAM influences conformation of protein. > Concentration of the unfolding agent affects redox properties of immobilized protein. - Abstract: The electron transfer (ET) process of progressively unfolded bovine cytochrome c immobilized on different self-assembled monolayers (SAMs) was investigated. Insight is gained on the role of the SAM surface on the functionality of the partially unfolded and non-native forms of the adsorbed protein. Direct electrochemical measurements were performed on cytochrome c adsorbed on mercaptopyridine (MP) and mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol (MUA/MU) at varying temperature, in the presence of urea as unfolding agent. Under strongly unfolding conditions, a non-native form of cytochrome c, in which the methionine ligand is replaced by a histidine, was observed on both MP and MUA/MU SAMs. The E{sup o}' of the native form, in which the haem is axially coordinated by methionine and histidine, slightly shifts to negative values upon increasing urea concentration. However, the non-native bis-histidinate species shows a much lower E{sup o}' value (by approximately 0.4 V) which is by far enthalpic in origin and largely determined by axial ligand swapping. Analysis of the reduction enthalpies and entropies and of the ET rate constants indicate that the nature of the SAM (hydrophilic or anionic) results in changes in the conformational rearrangement of the cytochrome c under unfolding conditions.

  19. n-Octadecanethiol self-assembled monolayer coating with microscopic roughness for dropwise condensation of steam

    Science.gov (United States)

    Chen, Liang; Liang, Shiqiang; Yan, Runsheng; Cheng, Yanjun; Huai, Xiulan; Chen, Shuling

    2009-06-01

    Here we presented a novel technology to achieve a Super-hydrophobic coating with microscopic roughness on copper surface. First, make a layer of verdigris grow on the fresh pure copper surface. Gain it by exposing the copper to air and the mist of acetic acid solution. The green coating is a mixture of basic copper(II) carbonate and copper(II) acetate. Second heat the coating and make it decompose to CuO. Lastly, form an n-octadecanethiol self-assembled monolayers coating on the outermost surface. Contact angle test, scanning electron microscope analysis and electrochemical testing were carried out to characterize the surface, and a heat transfer experiment for dropwise condensation of steam was performed also. Results show that the modified surface bears a few Super-hydrophobic features, the static contact angle is higher than that in literatures, reaching 153.1±1.7°. The microscopic roughness can be seen in SEM images, differing much from H2O2 etched surface and bare copper surface. The condensation of steam on the surface is a typical form of dropwise condensation, in the measured range of temperature difference, under 0.1 MPa, the average convection heat transfer coefficients of the vertical surface are 1.7˜2.1 times for those of film condensation. At the same time, the inhibition efficiency of surface is improved to some extent comparing with the same kind of SAMs, which suggests that the lifetime of maintenance dropwise condensation would have the possibility to surpass the existing record.

  20. n-Octadecanethiol Self-Assembled Monolayer Coating with Microscopic Roughness for Dropwise Condensation of Steam

    Institute of Scientific and Technical Information of China (English)

    Liang CHEN; Shiqiang LIANG; Runsheng YAN; Yanjun CHENG; Xiulan HUAI; Shuling CHEN

    2009-01-01

    Here we presented a novel technology to achieve a Super-hydrophobic coating with microscopic roughness on copper surface. First, make a layer of verdigris grow on the fresh pure copper surface. Gain it by exposing the copper to air and the mist of acetic acid solution. The green coating is a mixture of basic copper(Ⅱ) carbonate and copper(Ⅱ) acetate. Second heat the coating and make it decompose to CuO. Lastly, form an n-octadecanethiol self-assembled monolayers coating on the outermost surface. Contact angle test, scanning electron microscope analysis and electrochemical testing were carried out to characterize the surface, and a heat transfer experiment for dropwise condensation of steam was performed also. Results show that the modified surface bears a few Su-per-hydrophobic features, the static contact angle is higher than that in literatures, reaching 153.1±1.7°. The mi-croscopic roughness can be seen in SEM images, differing much from H2O2 etched surface and bare copper sur-face. The condensation of steam on the surface is a typical form of dropwise condensation, in the measured range of temperature difference, under 0.1 MPa, the average convection heat transfer coefficients of the vertical surface are 1.7-2.1 times for those of film condensation. At the same time, the inhibition efficiency of surface is im-proved to some extent comparing with the same kind of SAMs, which suggests that the lifetime of maintenance dropwise condensation would have the possibility to surpass the existing record.

  1. Self-assembled monolayer cleaning methods: Towards fabrication of clean high-temperature superconductor nanostructures

    International Nuclear Information System (INIS)

    Although extensive amounts of research have been carried out on superconductor-normal metal-superconductor (SNS) electronic devices, the fabrication of superconductor SNS devices still remains difficult. Surface modification of high-temperature superconductors could be a way to control the interface of SNS electronic device fabrication. Here, we developed a cleaning method for thin films of high-temperature superconductor surface based on self-assembled monolayers. High-quality c-axis orientated YBa2Cu3O7-δ (i.e., YBCO) and Y0.6Ca0.4Ba1.6La0.4Cu3O7-δ (i.e., TX-YBCO) thin films were deposited by standard laser ablation methods. YBCO/Au/YBCO and TX-YBCO/Au/TX-YBCO planar type junctions were fabricated by photolithography, focused-ion-beam milling, and ex situ sputter depositions. A 40-50 nm nanotrench was ion milled on the thin film by FIB, and a thin gold layer was deposited by an ex situ method on the nanotrench to connect the two separated high-temperature superconductor electrodes. SEM, AFM, and R vs T resistivity measurements were used to compare the corrosion layer formed in the interface of the SNS junctions with the SAM cleaned SNS junction. Evidence here suggests that the SAM cleaning method can be used to remove the degradation layer on the surface of cuprate superconductors. The obtained contact resistivity value (10-8 Ω cm2) for a SNS junction with SAM treatment is comparable with that of SNS junctions fabricated by the in situ methods

  2. Ultrafast shock compression of self-assembled monolayers: a molecular picture.

    Science.gov (United States)

    Patterson, James E; Dlott, Dana D

    2005-03-24

    Simulations of self-assembled monolayers (SAMs) are performed to interpret experimental measurements of ultrafast approximately 1 GPa (volume compression deltaV approximately 0.1) planar shock compression dynamics probed by vibrational sum-frequency generation (SFG) spectroscopy (Lagutchev, A. S.; Patterson, J. E.; Huang, W.; Dlott, D. D. J. Phys. Chem. B 2005, 109, XXXX). The SAMs investigated are octadecanethiol (ODT) and pentadecanethiol (PDT) on Au(111) and Ag(111) substrates, and benzyl mercaptan (BMT) on Au(111). In the alkane SAMs, SFG is sensitive to the instantaneous orientation of the terminal methyl; in BMT it is sensitive to the phenyl orientation. Computed structures of alkane SAMs are in good agreement with experiment. In alkanes, the energies of gauche defects increase with increasing number and depth below the methyl plane, with the exception of ODT/Au where both single and double gauche defects at the two uppermost dihedrals have similar energies. Simulations of isothermal uniaxial compression of SAM lattices show that chain and methyl tilting is predominant in PDT/Au, ODT/Ag and PDT/Ag, whereas single and double gauche defect formation is predominant in ODT/Au. Time-resolved shock data showing transient SFG signal loss of ODT/Au and PDT/Au are fit by calculations of the terminal group orientations as a function of deltaV and their contributions to the SFG hyperpolarizability. The highly elastic response of PDT/Au results from shock-generated methyl and chain tilting. The viscoelastic response of ODT/Au results from shock generation of single and double gauche defects. Isothermal compression simulations help explain and fit the time dependence of shock spectra but generally underestimate the magnitude of SFG signal loss because they do not include effects of high-strain-rate dynamics and shock front and surface irregularities. PMID:16863164

  3. Charge Retention of Soft-Landed Phosphotungstate Keggin Anions on Self-Assembled Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Gunaratne, Kalupathirannehelage Don D.; Prabhakaran, Venkateshkumar; Andersen, Amity; Johnson, Grant E.; Laskin, Julia

    2016-04-07

    Soft landing of mass-selected ions onto surfaces often results in partial loss of charge that may affect the structure and reactivity of deposited species. In this study, Keggin phosphotungstate anions in two selected charge states, PW12O403- (WPOM3-) and PW12O402- (WPOM2-), were soft-landed onto different self-assembled monolayer (SAM) surfaces and examined using in situ infrared reflection absorption spectroscopy (IRRAS) and density functional theory (DFT) calculations. Partial retention of the 3- charge was observed when WPOM3- was soft-landed onto the fluorinated SAM (FSAM), while the charge state distribution was dominated by the 2- charge after both WPOM3- and WPOM2- were deposited onto a hydrophilic alkylthiol SAM terminated with cationic NH3+ functional groups (NH3+SAM). We found that during the course of the soft landing of WPOM3-, the relative abundance of WPOM3- on FSAM decreased while that of WPOM2- increased. We propose that the higher stability of immobilized WPOM2- in comparison with WPOM3- makes it the preferred charge state of WPOM on both the FSAM and NH3+SAM. We also observe weaker binding of WPOM anions to SAMs in comparison with phosphomolybdate ions (MoPOM) reported previously (J. Phys. Chem. C 2014, 118, 27611–27622). The weaker binding of WPOM to SAMs is attributed to the lower reactivity of WPOM reported in the literature. This study demonstrates that both the charge retention and the reactivity of deposited anionic POM clusters on surfaces are determined by the type of addenda metal atoms in the cluster.

  4. Reducing Staphylococcus aureus biofilm formation on stainless steel 316L using functionalized self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Kruszewski, Kristen M., E-mail: kruszewskik@duq.edu [Duquesne University, Department of Chemistry and Biochemistry, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States); Nistico, Laura, E-mail: lnistico@wpahs.org [Allegheny General Hospital, Center for Genomic Sciences, Allegheny-Singer Research Institute, 320 East North Avenue, 11th floor, South Tower, Pittsburgh, PA 15212 (United States); Longwell, Mark J., E-mail: mlongwel@wpahs.org [Allegheny General Hospital, Center for Genomic Sciences, Allegheny-Singer Research Institute, 320 East North Avenue, 11th floor, South Tower, Pittsburgh, PA 15212 (United States); Hynes, Matthew J., E-mail: mjhynes@go.wustl.edu [Washington University in St. Louis, Department of Chemistry, One Brookings Drive, St. Louis, MO 63130 (United States); Maurer, Joshua A., E-mail: maurer@wustl.edu [Washington University in St. Louis, Department of Chemistry, One Brookings Drive, St. Louis, MO 63130 (United States); Hall-Stoodley, Luanne, E-mail: L.Hall-Stoodley@soton.ac.uk [Southampton Wellcome Trust Clinical Research Facility/NIHR Respiratory BRU, University of Southampton Faculty of Medicine, Southampton General Hospital, Tremona Road, Southampton, Hampshire SO16 6YD (United Kingdom); Gawalt, Ellen S., E-mail: gawalte@duq.edu [Duquesne University, Department of Chemistry and Biochemistry, McGowan Institute for Regenerative Medicine, 600 Forbes Avenue, Pittsburgh, PA 15282 (United States)

    2013-05-01

    Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with long alkyl chains terminated with hydrophobic (− CH{sub 3}) or hydrophilic (oligoethylene glycol) tail groups were used to form coatings and in an orthogonal approach, SAMs were used to immobilize gentamicin or vancomycin on SS316L for the first time to form an “active” antimicrobial coating to inhibit early biofilm development. Modified SS316L surfaces were characterized using surface infrared spectroscopy, contact angles, MALDI-TOF mass spectrometry and atomic force microscopy. The ability of SAM-modified SS316L to retard biofilm development by Staphylococcus aureus was functionally tested using confocal scanning laser microscopy with COMSTAT image analysis, scanning electron microscopy and colony forming unit analysis. Neither hydrophobic nor hydrophilic SAMs reduced biofilm development. However, gentamicin-linked and vancomycin-linked SAMs significantly reduced S. aureus biofilm formation for up to 24 and 48 h, respectively. - Highlights: ► SS316L was modified with glycol terminated SAMs in order to reduce biofilm growth. ► Antibiotics gentamicin and vancomycin were immobilized on SS316L via SAMs. ► Only the antibiotic modifications reduced biofilm development on SS316L.

  5. Structure and dynamics of water near the interface with oligo(ethylene oxide) self-assembled monolayers

    Science.gov (United States)

    Ismail, Ahmed E.; Grest, Gary S.; Stevens, Mark J.

    2007-03-01

    Oligo(ethylene oxide) self-assembled monolayers (OEO SAM's) deposited on Au are the prototypical materials used to study protein resistance. Recently, protein resistance has been shown to vary as a function of surface coverage and to be maximal at about two-thirds coverage, not complete coverage. We use molecular dynamics simulations to study the nature of the interface between water and the OEO SAM for a range of SAM coverages. As SAM coverage decreases, the amount of water within the OEO monolayer increases monotonically; however, the penetration depth of the water shows a maximum near the experimentally-found maximal coverage. As the water content increases, the SAM-water mixture becomes harder to distinguish from bulk water. Since the oxygen atoms of OEO are hydrogen bond acceptors, a hydrogen bond network forms within the SAM-water mixture. The water molecules diffuse freely within the monolayer and exchange with the bulk water. Because the monolayer becomes increasingly like bulk water as the coverage decreases, proteins stay in their bulk soluble conformation and do not adsorb. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract No. DE-AC04-94AL85000.

  6. Reflection and extinction of light by self-assembled monolayers of a quinque-thiophene derivative: A coherent scattering approach

    Science.gov (United States)

    Gholamrezaie, Fatemeh; de Leeuw, Dago M.; Meskers, Stefan C. J.

    2016-06-01

    Scattering matrix theory is used to describe resonant optical properties of molecular monolayers. Three types of coupling are included: exciton-exciton, exciton-photon, and exciton-phonon coupling. We use the K-matrix formalism, developed originally to describe neutron scattering spectra in nuclear physics to compute the scattering of polaritons by phonons. This perturbation approach takes into account the three couplings and allows one to go beyond molecular exciton theory without the need of introducing additional boundary conditions for the polariton. We demonstrate that reflection, absorption, and extinction of light by 2D self-assembled monolayers of molecules containing quinque-thiophene chromophoric groups can be calculated. The extracted coherence length of the Frenkel exciton is discussed.

  7. Influence of Self-Assembled Alkanethiol Monolayers on Stochastic Amperometric On-Chip Detection of Silver Nanoparticles.

    Science.gov (United States)

    Krause, Kay J; Adly, Nouran; Yakushenko, Alexey; Schnitker, Jan; Mayer, Dirk; Offenhäusser, Andreas; Wolfrum, Bernhard

    2016-04-01

    We investigate the influence of self-assembled alkanethiol monolayers at the surface of platinum microelectrode arrays on the stochastic amperometric detection of citrate-stabilized silver nanoparticles in aqueous solutions. The measurements were performed using a microelectrode array featuring 64 individually addressable electrodes that are recorded in parallel with a sampling rate of 10 kHz for each channel. We show that both the functional end group and the total length of the alkanethiol influence the charge transfer. Three different terminal groups, an amino, a hydroxyl, and a carboxyl, were investigated using two different molecule lengths of 6 and 11 carbon atoms. Finally, we show that a monolayer of alkanethiols with a length of 11 carbon atoms and a carboxyl terminal group can efficiently block the charge transfer of free nanoparticles in an aqueous solution.

  8. Application of a gold electrode, modified by a self-assembled monolayer of 2-mercaptodecylhydroquinone, to the electroanalysis of hemoglobin.

    Science.gov (United States)

    Zhang, Jingdong; Seo, Kyoungja; Jeon, Il Cheol

    2003-02-01

    A gold electrode modified by a self-assembled monolayer of 2-mercaptodecylhydroquinone (H(2)Q(CH(2))(10)SH) was applied to investigate the electrochemical response of hemoglobin in aerated buffer solutions. Compared with a bare gold electrode, the monolayer of H(2)Q(CH(2))(10)SH could suppress the reduction wave of dissolved oxygen in the buffer while effectively promoting the rate of electron transfer between hemoglobin and the electrode. Thus, a convenient way for electroanalysis of hemoglobin in air was achieved at the H(2)Q(CH(2))(10)SH/Au electrode. A linear relationship existed between peak current and concentration of hemoglobin in the range 1 x 10(-7)-1 x 10(-6) mol L(-1).

  9. Sub-2 nm Thick Fluoroalkylsilane Self-Assembled Monolayer-Coated High Voltage Spinel Crystals as Promising Cathode Materials for Lithium Ion Batteries

    Science.gov (United States)

    Zettsu, Nobuyuki; Kida, Satoru; Uchida, Shuhei; Teshima, Katsuya

    2016-08-01

    We demonstrate herein that an ultra-thin fluoroalkylsilane self-assembled monolayer coating can be used as a modifying agent at LiNi0.5Mn1.5O4‑δcathode/electrolyte interfaces in 5V-class lithium-ion batteries. Bare LiNi0.5Mn1.5O4‑δ cathode showed substantial capacity fading, with capacity dropping to 79% of the original capacity after 100 cycles at a rate of 1C, which was entirely due to dissolution of Mn3+ from the spinel lattice via oxidative decomposition of the organic electrolyte. Capacity retention was improved to 97% on coating ultra-thin FAS17-SAM onto the LiNi0.5Mn1.5O4 cathode surface. Such surface protection with highly ordered fluoroalkyl chains insulated the cathode from direct contact with the organic electrolyte and led to increased tolerance to HF.

  10. Steering the Self-Assembly of Octadecylamine Monolayers on Mica by Controlled Mechanical Energy Transfer from the AFM Tip

    Energy Technology Data Exchange (ETDEWEB)

    Benitez, J.J.; Heredia-Guerrero, J.A.; Salmeron, M.

    2010-06-24

    We have studied the effect of mechanical energy transfer from the tip of an Atomic Force Microscope on the dynamics of self-assembly of monolayer films of octadecylamine on mica. The formation of the self-assembled film proceeds in two successive stages, the first being a fast adsorption from solution that follows a Langmuir isotherm. The second is a slower process of island growth by aggregation of the molecules dispersed on the surface. We found that the dynamics of aggregation can be altered substantially by the addition of mechanical energy into the system through controlled tip-surface interactions. This leads to either the creation of pinholes in existing islands as a consequence of vacancy concentration, and to the assembly of residual molecules into more compact islands.

  11. Thermal stability and molecular ordering of organic semiconductor monolayers: effect of an anchor group.

    Science.gov (United States)

    Jones, Andrew O F; Knauer, Philipp; Resel, Roland; Ringk, Andreas; Strohriegl, Peter; Werzer, Oliver; Sferrazza, Michele

    2015-06-01

    The thermal stability and molecular order in monolayers of two organic semiconductors, PBI-PA and PBI-alkyl, based on perylene derivatives with an identical molecular structure except for an anchor group for attachment to the substrate in PBI-PA, are reported. In situ X-ray reflectivity measurements are used to follow the stability of these monolayers in terms of order and thickness as temperature is increased. Films have thicknesses corresponding approximately to the length of one molecule; molecules stand upright on the substrate with a defined structure. PBI-PA monolayers have a high degree of order at room temperature and a stable film exists up to 250 °C, but decomposes rapidly above 300 °C. In contrast, stable physisorbed PBI-alkyl monolayers only exist up to 100 °C. Above the bulk melting point at 200 °C no more order exists. The results encourage using anchor groups in monolayers for various applications as it allows enhanced stability at the interface with the substrate.

  12. PM-IRRAS Determination of Molecular Orientation of Phosphonic Acid Self-Assembled Monolayers on Indium Zinc Oxide.

    Science.gov (United States)

    Sang, Lingzi; Mudalige, Anoma; Sigdel, Ajaya K; Giordano, Anthony J; Marder, Seth R; Berry, Joseph J; Pemberton, Jeanne E

    2015-05-26

    Self-assembled monolayers (SAMs) of phosphonic acids (PAs) on transparent conductive oxide (TCO) surfaces can facilitate improvement in TCO/organic semiconductor interface properties. When ordered PA SAMs are formed on oxide substrates, interface dipole and electronic structure are affected by the functional group properties, orientation, and binding modes of the modifiers. Choosing octylphosphonic acid (OPA), F13-octylphosphonic acid (F13OPA), pentafluorophenyl phosphonic acid (F5PPA), benzyl phosphonic acid (BnPA), and pentafluorobenzyl phosphonic acid (F5BnPA) as a representative group of modifiers, we report polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) of binding and molecular orientation on indium-doped zinc oxide (IZO) substrates. Considerable variability in molecular orientation and binding type is observed with changes in PA functional group. OPA exhibits partially disordered alkyl chains but on average the chain axis is tilted ∼57° from the surface normal. F13OPA tilts 26° with mostly tridentate binding. The F5PPA ring is tilted 23° from the surface normal with a mixture of bidentate and tridentate binding; the BnPA ring tilts 31° from normal with a mixture of bidentate and tridentate binding, and the F5BnPA ring tilts 58° from normal with a majority of bidentate with some tridenate binding. These trends are consistent with what has been observed previously for the effects of fluorination on orientation of phosphonic acid modifiers. These results from PM-IRRAS are correlated with recent results on similar systems from near-edge X-ray absorption fine structure (NEXAFS) and density functional theory (DFT) calculations. Overall, these results indicate that both surface binding geometry and intermolecular interactions play important roles in dictating the orientation of PA modifiers on TCO surfaces. This work also establishes PM-IRRAS as a routine method for SAM orientation determination on complex oxide substrates

  13. Molecular dynamics simulations of peptide adsorption on self-assembled monolayers

    Science.gov (United States)

    Xie, Yun; Liu, Meifeng; Zhou, Jian

    2012-08-01

    All-atom molecular dynamics simulations are performed to investigate the neuromedin-B peptide adsorption on the self-assembled monolayers (SAMs) of SH(CH2)10N+(CH3)2CH2CH(OH)CH2SO3- (SBT), SH(CH2)10OH and SH(CH2)10CH3. The force-distance profiles show that the surface resistance to peptide adsorption is mainly generated by the water molecules tightly bound to surfaces via hydrogen bonds (hydration water molecules); but surfaces themselves may also set an energy barrier for the approaching peptide. For the SBT-SAM, the surface first exerts a relatively high repulsive force and then a rather week attractive force on the approaching peptide; meanwhile the hydration water molecules exert a strong repulsive force on the peptide. Therefore, SBT-SAM has an excellent performance on resisting protein adsorption. For the OH-SAM and CH3-SAM, surfaces show low or little energy barrier but strong affinity to the peptide; and the hydration water molecules apply merely a repulsive force within a much narrower range and with lower intensity compared with the case for the SBT-SAM. The analysis of structural and dynamical properties of the peptide, surface and water indicates that possible factors contributing to surface resistance include the hydrogen-bond formation capability of surfaces, mobility of water molecules near surfaces, surface packing density and chain flexibility of SAMs. There are a large number of hydrogen bonds formed between the hydration water molecules and the functional groups of the SBT-SAM, which greatly lowers the mobility of water molecules near the surface. This tightly-bound water layer effectively reduces the direct contact between the surface and the peptide. Furthermore, the SBT-SAM also has a high flexibility and a low surface packing density, which allows water molecules to penetrate into the surface to form tightly-bound networks and therefore reduces the affinity between the peptide and the surface. The results show that the protein

  14. Decaborane thiols as building blocks for self-assembled monolayers on metal surfaces.

    Science.gov (United States)

    Bould, Jonathan; Macháček, Jan; Londesborough, Michael G S; Macías, Ramón; Kennedy, John D; Bastl, Zdeněk; Rupper, Patrick; Baše, Tomáš

    2012-02-01

    Three nido-decaborane thiol cluster compounds, [1-(HS)-nido-B(10)H(13)] 1, [2-(HS)-nido-B(10)H(13)] 2, and [1,2-(HS)(2)-nido-B(10)H(12)] 3 have been characterized using NMR spectroscopy, single-crystal X-ray diffraction analysis, and quantum-chemical calculations. In the solid state, 1, 2, and 3 feature weak intermolecular hydrogen bonding between the sulfur atom and the relatively positive bridging hydrogen atoms on the open face of an adjacent cluster. Density functional theory (DFT) calculations show that the value of the interaction energy is approximately proportional to the number of hydrogen atoms involved in the interaction and that these values are consistent with a related bridging-hydrogen atom interaction calculated for a B(18)H(22)·C(6)H(6) solvate. Self-assembled monolayers (SAMs) of 1, 2, and 3 on gold and silver surfaces have been prepared and characterized using X-ray photoelectron spectroscopy. The variations in the measured sulfur binding energies, as thiolates on the surface, correlate with the (CC2) calculated atomic charge for the relevant boron vertices and for the associated sulfur substituents for the parent B(10)H(13)(SH) compounds. The calculated charges also correlate with the measured and DFT-calculated thiol (1)H chemical shifts. Wetting-angle measurements indicate that the hydrophilic open face of the cluster is directed upward from the substrate surface, allowing the bridging hydrogen atoms to exhibit a similar reactivity to that of the bulk compound. Thus, [PtMe(2)(PMe(2)Ph)(2)] reacts with the exposed and acidic B-H-B bridging hydrogen atoms of a SAM of 1 on a gold substrate, affording the addition of the metal moiety to the cluster. The XPS-derived stoichiometry is very similar to that for a SAM produced directly from the adsorption of [1-(HS)-7,7-(PMe(2)Ph)(2)-nido-7-PtB(10)H(11)] 4. The use of reactive boron hydride SAMs as templates on which further chemistry may be carried out is unprecedented, and the principle may be

  15. Molecular dynamics simulations of peptide adsorption on self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Xie Yun; Liu Meifeng [School of Chemistry and Chemical Engineering, Guangdong Provincial Key Lab for Green Chemical Product Technology, South China University of Technology, Guangzhou, Guangdong Province, 510640 (China); Zhou Jian, E-mail: jianzhou@scut.edu.cn [School of Chemistry and Chemical Engineering, Guangdong Provincial Key Lab for Green Chemical Product Technology, South China University of Technology, Guangzhou, Guangdong Province, 510640 (China)

    2012-08-01

    All-atom molecular dynamics simulations are performed to investigate the neuromedin-B peptide adsorption on the self-assembled monolayers (SAMs) of SH(CH{sub 2}){sub 10}N{sup +}(CH{sub 3}){sub 2}CH{sub 2}CH(OH)CH{sub 2}SO{sub 3}{sup -} (SBT), SH(CH{sub 2}){sub 10}OH and SH(CH{sub 2}){sub 10}CH{sub 3}. The force-distance profiles show that the surface resistance to peptide adsorption is mainly generated by the water molecules tightly bound to surfaces via hydrogen bonds (hydration water molecules); but surfaces themselves may also set an energy barrier for the approaching peptide. For the SBT-SAM, the surface first exerts a relatively high repulsive force and then a rather week attractive force on the approaching peptide; meanwhile the hydration water molecules exert a strong repulsive force on the peptide. Therefore, SBT-SAM has an excellent performance on resisting protein adsorption. For the OH-SAM and CH{sub 3}-SAM, surfaces show low or little energy barrier but strong affinity to the peptide; and the hydration water molecules apply merely a repulsive force within a much narrower range and with lower intensity compared with the case for the SBT-SAM. The analysis of structural and dynamical properties of the peptide, surface and water indicates that possible factors contributing to surface resistance include the hydrogen-bond formation capability of surfaces, mobility of water molecules near surfaces, surface packing density and chain flexibility of SAMs. There are a large number of hydrogen bonds formed between the hydration water molecules and the functional groups of the SBT-SAM, which greatly lowers the mobility of water molecules near the surface. This tightly-bound water layer effectively reduces the direct contact between the surface and the peptide. Furthermore, the SBT-SAM also has a high flexibility and a low surface packing density, which allows water molecules to penetrate into the surface to form tightly-bound networks and therefore reduces the

  16. Effect of substrate composition on atomic layer deposition using self-assembled monolayers as blocking layers

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wenyu; Engstrom, James R., E-mail: jre7@cornell.edu [School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853 (United States)

    2016-01-15

    The authors have examined the effect of two molecules that form self-assembled monolayers (SAMs) on the subsequent growth of TaN{sub x} by atomic layer deposition (ALD) on two substrate surfaces, SiO{sub 2} and Cu. The SAMs that the authors have investigated include two vapor phase deposited, fluorinated alkyl silanes: Cl{sub 3}Si(CH{sub 2}){sub 2}(CF{sub 2}){sub 5}CF{sub 3} (FOTS) and (C{sub 2}H{sub 5}O){sub 3}Si(CH{sub 2}){sub 2}(CF{sub 2}){sub 7}CF{sub 3} (HDFTEOS). Both the SAMs themselves and the TaN{sub x} thin films, grown using Ta[N(CH{sub 3}){sub 2}]{sub 5} and NH{sub 3}, were analyzed ex situ using contact angle, spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), and low energy ion-scattering spectroscopy (LEISS). First, the authors find that both SAMs on SiO{sub 2} are nominally stable at T{sub s} ∼ 300 °C, the substrate temperature used for ALD, while on Cu, the authors find that HDFTEOS thermally desorbs, while FOTS is retained on the surface. The latter result reflects the difference in the head groups of these two molecules. The authors find that both SAMs strongly attenuate the ALD growth of TaN{sub x} on SiO{sub 2}, by about a factor of 10, while on Cu, the SAMs have no effect on ALD growth. Results from LEISS and XPS are decisive in determining the nature of the mechanism of growth of TaN{sub x} on all surfaces. Growth on SiO{sub 2} is 2D and approximately layer-by-layer, while on the surfaces terminated by the SAMs, it nucleates at defect sites, is islanded, and is 3D. In the latter case, our results support growth of the TaN{sub x} thin film over the SAM, with a considerable delay in formation of a continuous thin film. Growth on Cu, with or without the SAMs, is also 3D and islanded, and there is also a delay in the formation of a continuous thin film as compared to growth on SiO{sub 2}. These results highlight the power of coupling measurements from both LEISS and XPS in examinations of ultrathin films formed by ALD.

  17. Surface passivation of (100 GaSb using self-assembled monolayers of long-chain octadecanethiol

    Directory of Open Access Journals (Sweden)

    E. Papis-Polakowska

    2016-05-01

    Full Text Available The passivation of (100 GaSb surface was investigated by means of the long-chain octadecanethiol (ODT self-assembled monolayer (SAM. The properties of ODT SAM on (100 GaSb were characterized by the atomic force microscopy using Kelvin probe force microscopy mode and X-ray photoelectron spectroscopy. The chemical treatment of 10mM ODT-C2H5OH has been applied to the passivation of a type-II superlattice InAs/GaSb photodetector. The electrical measurements indicate that the current density was reduced by one order of magnitude as compared to an unpassivated photodetector.

  18. Self-Spreading of Lipid Bilayer on a Hydrophobic Surface Made by Self-Assembled Monolayer with Short Alkyl Chain.

    Science.gov (United States)

    Omori, Yuya; Sakaue, Hiroyuki; Takahagi, Takayuki; Suzuki, Hitoshi

    2016-04-01

    Behaviors of self-spreading of lipid bilayer membrane on a glass surface modified with self-assembled monolayer (SAM) with short alkyl chain were observed with fluorescence microscopy. Hydrophobic surface made by SAM was found to hamper the self-spreading phenomenon but the lipid bilayer spread on a hydrophilic one where SAM was decomposed by oxidation. On a binary surface having a hydrophobic region and a hydrophilic one, the lipid bilayer spread on the hydrophilic region but it stopped at the boundary of the hydrophobic region.

  19. Capacitance Characterization of the Effect of pH Value on the Self-assembled Monolayers of Octadecanethiol

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In this paper, the membrane capacitance (Cm), which was obtained from the electro- chemical impedance spectroscopy (EIS) method, was used to characterize the effect of pH value on the self-assembled monolayers (SAMs) of octadecanethiol(18SH) for the first time. The results not only strongly proved that inorganic ions could penetrate the SAMs of 18SH, but also ascertained that SAMs of 18SH were not an absolute of free of ion-penetration. Verifying the existence of pin-holes in the octadecanethiol SAMs was the main contribution of this paper, which coincided with the former conjecture very well.

  20. Study of Alkylthiolate Self-assembled Monolayers on Au(111) Using a Semilocal meta-GGA Density Functional

    DEFF Research Database (Denmark)

    Ferrighi, Lara; Pan, Yun-xiang; Grönbeck, Henrik;

    2012-01-01

    We present a density functional theory study of the structure and stability of self-assembled monolayers (SAMs) of alkylthiolate on Au(111) as a function of the alkyl chain length. The most favorable structure of the SAMs involves an RS–Au–SR complex (S being sulfur, R being an alkyl chain) formed...... particular, the use of M06-L yields an increased stability of the SAMs with increasing alkyl chain length and an increased attractive interaction between RS–Au–SR complexes at shorter distances....

  1. Self-assembled monolayer of 3-aminopropyltrimethoxysilane for improved adhesion between aluminum alloy substrate and polyurethane coating

    International Nuclear Information System (INIS)

    A good adhesion between a polymer coating and a metal or metal alloy substrate such as Al 2024-T3 plays a critical role in corrosion protection of metal substrates. In our study, a self-assembled monolayer film of 3-aminopropyltrimethoxysilane was formed on Al 2024-T3 substrate by covalent bonding. The adhesion property of a self-priming polyurethane coating was evaluated by pull-off adhesion test, wet tape test and thermal cycling test. All the testing results indicate that both dry and wet adhesion properties of the polyurethane coating were improved significantly after APS treatment of Al 2024-T3 in polar solvents such as methanol and acetone. In nonpolar solvents such as hexane, the APS treatment led to inconsistent improvement or sometime decreased adhesion of polyurethane coating. X-ray photoelectron spectroscopic study revealed that while a monolayer film was formed on the aluminum alloy surface after treating the substrate with APS in methanol and acetone, a multilayer film was formed on the substrate surface when the treatment was conducted in hexane. The APS monolayer film served as a covalent bond linkage between polymer coating and aluminum alloy substrates, which led to the increased adhesion property of polymer coating and corrosion resistance of the metal alloy substrate

  2. Optical modulation of nano-gap tunnelling junctions comprising self-assembled monolayers of hemicyanine dyes.

    Science.gov (United States)

    Pourhossein, Parisa; Vijayaraghavan, Ratheesh K; Meskers, Stefan C J; Chiechi, Ryan C

    2016-01-01

    Light-driven conductance switching in molecular tunnelling junctions that relies on photoisomerization is constrained by the limitations of kinetic traps and either by the sterics of rearranging atoms in a densely packed monolayer or the small absorbance of individual molecules. Here we demonstrate light-driven conductance gating; devices comprising monolayers of hemicyanine dyes trapped between two metallic nanowires exhibit higher conductance under irradiation than in the dark. The modulation of the tunnelling current occurs faster than the timescale of the measurement (∼1 min). We propose a mechanism in which a fraction of molecules enters an excited state that brings the conjugated portion of the monolayer into resonance with the electrodes. This mechanism is supported by calculations showing the delocalization of molecular orbitals near the Fermi energy in the excited and cationic states, but not the ground state and a reasonable change in conductance with respect to the effective barrier width. PMID:27272394

  3. Chiral hierarchical self-assembly in Langmuir monolayers of diacetylenic lipids

    KAUST Repository

    Basnet, Prem B.

    2013-01-01

    When compressed in the intermediate temperature range below the chain-melting transition yet in the low-pressure liquid phase, Langmuir monolayers made of chiral lipid molecules form hierarchical structures. Using Brewster angle microscopy to reveal this structure, we found that as the liquid monolayer is compressed, an optically anisotropic condensed phase nucleates in the form of long, thin claws. These claws pack closely to form stripes. This appears to be a new mechanism for forming stripes in Langmuir monolayers. In the lower temperature range, these stripes arrange into spirals within overall circular domains, while near the chain-melting transition, the stripes arrange into target patterns. We attributed this transition to a change in boundary conditions at the core of the largest-scale circular domains. © 2013 The Royal Society of Chemistry.

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

    Institute of Scientific and Technical Information of China (English)

    YANG Guangzheng; ZENG Qingdao; WAN Lijun; BAI Chunli

    2003-01-01

    Adsorption of 4-(4-nitrophenylazo)-1-naphthol (NPAN), an azobenzene derivative, on Au(111) has been investigated in aqueous HClO4 solution by using the cyclic voltammetry and scanning tunneling microscopy (STM). The molecule is found to form a stable monolayer on the electrode with a (6×4) structure relative to the underlying Au(111) lattice. Cyclic voltammograms show that the redox reactions occurring on the electrode are retarded by the formation of the monolayer. A structural model is proposed for the two-dimensional adlayer.

  5. Electrochemical assembly of organic molecules by the reduction of iodonium salts

    Science.gov (United States)

    Dirk, Shawn M.; Howell, Stephen W.; Wheeler, David R.

    2009-06-23

    Methods are described for the electrochemical assembly of organic molecules on silicon, or other conducting or semiconducting substrates, using iodonium salt precursors. Iodonium molecules do not assemble on conducting surfaces without a negative bias. Accordingly, the iodonium salts are preferred for patterning applications that rely on direct writing with negative bias. The stability of the iodonium molecule to acidic conditions allows them to be used with standard silicon processing. As a directed assembly process, the use of iodonium salts provides for small features while maintaining the ability to work on a surface and create structures on a wafer level. Therefore, the process is amenable for mass production. Furthermore, the assembled monolayer (or multilayer) is chemically robust, allowing for subsequent chemical manipulations and the introduction of various molecular functionalities for various chemical and biological applications.

  6. Formation of a 1,8-octanedithiol self-assembled monolayer on Au(111) prepared in a lyotropic liquid-crystalline medium.

    Science.gov (United States)

    García Raya, Daniel; Madueño, Rafael; Blázquez, Manuel; Pineda, Teresa

    2010-07-20

    A characterization of the 1,8-octanedithiol (ODT) self-assembled monolayer (SAM) formed from a Triton X-100 lyotropic medium has been conducted by electrochemical techniques. It is found that an ODT layer of standing-up molecules is obtained at short modification time without removing oxygen from the medium. The electrochemical study shows that the ODT layer formed after 15 min of modification time has similar electron-transfer blocking properties to the layers formed from organic solvents at much longer modification times. On the basis of XPS data, it is demonstrated that the inability to bind gold nanoparticles (AuNPs) is due to the presence of extra ODT molecules either interdigited or on top of the layer. Treatment consisting of an acid washing step following the formation of the ODT-Au(111) SAM produces a layer that is able to attach AuNPs as demonstrated by electrochemical techniques and atomic force microscopy (AFM) images.

  7. Self-assembled alkanethiol monolayers on a Zn substrate: Interface studied by XPS

    Science.gov (United States)

    Lang, P.; Nogues, C.

    2008-07-01

    After having presented the organization and self-assembly of alkanethiols on zinc substrates, we focus here on the bond between the thiol sulfur and the metal. The interfacial bond between decanethiol and bulk Zn platelet has been investigated by X-ray photoelectron spectroscopy. In the presence of traces of oxygen, the Zn is oxidized and subsequently the thiolate -Zn(II)-SR is formed whatever the adsorption time tads and ageing conditions. This is attributed to the inability of the thiol to reduce the Zn(II). Results for the Zn substrate are discussed and we put into perspective the behaviour of Zn compared to other metals in the light of its great affinity towards sulfur and its complexing, soft acid and reducing properties.

  8. The structure and dynamics of self-assembling colloidal monolayers in oscillating magnetic fields

    CERN Document Server

    Koser, Alison E; Arratia, Paulo E

    2013-01-01

    Many fascinating phenomena such as large-scale collective flows, enhanced fluid mixing and pattern formation have been observed in so-called active fluids, which are composed of particles that can absorb energy and dissipate it into the fluid medium. For active particles immersed in liquids, fluid-mediated viscous stresses can play an important role on the emergence of collective behavior. Here, we experimentally investigate their role in the dynamics of self-assembling magnetically-driven colloidal particles which can rapidly form organized hexagonal structures. We find that viscous stresses reduce hexagonal ordering, generate smaller clusters, and significantly decrease the rate of cluster formation, all while holding the system at constant number density. Furthermore, we show that time and length scales of cluster formation depend on the Mason number (Mn), or ratio of viscous to magnetic forces, scaling as t / Mn and L / Mn^(1/2). Our results suggest that viscous stresses hinder collective behavior in a se...

  9. Spectroscopic analysis of a nanostructure roughness of plasma-deposited Au films using organic monolayer

    International Nuclear Information System (INIS)

    The morphology and roughness of nanostructure of Au film are discussed using an atomic-force microscope (AFM) and a laser Raman spectroscopy. The Au films are deposited on mica and Si substrate by means of a dc plasma sputtering technique, and a self-assembled monolayer (SAM) of benzene-thiol is formed on the Au films. The cluster size and roughness on the surface increase with substrate annealing during the deposition on mica substrate, while they decrease on Si substrate. Raman spectra show a surface-enhanced Raman scattering (SERS) occurs at the optimum roughness RA∼0.3 of the substrate.

  10. Fabrication of controllable and stable In2O3 nanowire transistors using an octadecylphosphonic acid self-assembled monolayer

    International Nuclear Information System (INIS)

    The controllability and stability of nanowire transistor characteristics are essential for the development of low-noise and fast-switching nano-electronic devices. In this study, the positive shift of threshold voltage and the improvement of interface quality on In2O3 nanowire transistors were simultaneously achieved by using octadecylphosphonic acid (OD-PA) self-assembly. Following the chemical bond of OD-PA molecules on the surface of In2O3 nanowires, the threshold voltage was positively shifted to 2.95 V, and the noise amplitude decreased to approximately 87.5%. The results suggest that an OD-PA self-assembled monolayer can be used to manipulate and stabilize the transistor characteristics of nanowire-based memory and display devices that require high-sensitivity, low-noise, and fast-response. (paper)

  11. Density Functional Theory with Modified Dispersion Correction for Metals Applied to Self-Assembled Monolayers of Thiols on Au(111

    Directory of Open Access Journals (Sweden)

    M. P. Andersson

    2013-01-01

    Full Text Available Using sound physical principles we modify the DFT-D2 atom pairwise semiempirical dispersion correction to density functional theory to work for metallic systems and in particular self-assembled monolayers of thiols on gold surfaces. We test our approximation for two functionals PBE-D and revPBE-D for lattice parameters and cohesive energies for Ni, Pd, Pt, Cu, Ag, and Au, adsorption energies of CO on (111 surfaces of Pd, Pt, Cu, Ag, and Au, and adsorption energy of benzene on Ag(111 and Au(111. Agreement with experimental data is substantially improved. We apply the method to self-assembled monolayers of alkanethiols on Au(111 and find reasonable agreement for PBE-D and revPBE-D for both physisorption of n-alkanethiols as well as dissociative chemisorption of dimethyl disulfide as an Au-adatom-dithiolate complex. By modifying the C6 coefficient for Au, we obtain quantitative agreement for physisorption and chemisorption for both PBE-D and revPBE-D using the same set of parameters. Our results confirm that inclusion of dispersion forces is crucial for any quantitative analysis of the thiol and thiolate bonds to the gold surface using quantum chemical calculations.

  12. Electrical characteristics of conjugated self-assembled monolayers in large-area molecular junctions

    NARCIS (Netherlands)

    Kronemeijer, A.J.; Huisman, E.H.; Akkerman, H.B.; Goossens, A.M.; Katsouras, I.; Hal, P.A. van; Geuns, T.C.T.; Molen, S.J. van der; Blom, P.W.M.; Leeuw, D.M. de

    2010-01-01

    We have studied the electrical characteristics of close-packed monolayers of conjugated para-phenylene oligomers as a function of molecular length in large-area molecular junctions. An exponential increase in resistance with molecular length is observed, Rexp (βL), with β=0.26±0.04 Å-1 and β=0.20±0.

  13. Electrical characteristics of conjugated self-assembled monolayers in large-area molecular junctions

    NARCIS (Netherlands)

    Kronemeijer, A. J.; Huisman, E. H.; Akkerman, H. B.; Goossens, A. M.; Katsouras, I.; van Hal, P. A.; Geuns, T. C. T.; van der Molen, S. J.; Blom, P. W. M.; de Leeuw, D. M.

    2010-01-01

    We have studied the electrical characteristics of close-packed monolayers of conjugated para-phenylene oligomers as a function of molecular length in large-area molecular junctions. An exponential increase in resistance with molecular length is observed, R proportional to exp(beta L), with beta = 0.

  14. On the influence of the aliphatic linker on fabrication of highly ordered and orientated self-assembled monolayers of aromatic selenols on AU(111)

    KAUST Repository

    Azzam, Waleed

    2014-03-06

    Self-assembled monolayers (SAMs) formed by adsorption of 1,2-dibenzyldiselenide (DPMSe) and 1,2-diphenyldiselenide (DBSe) on Au(111) substrates at room temperature have been characterized using scanning tunnelling microscopy, X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and low-energy electron diffraction. Upon adsorption, the Se-Se bonds in DPMSe and DBSe were cleaved on the gold surface to form phenylmethaneselenolate (PMSe) and benzeneselenolate (BSe) species, respectively. Although both PMSe and BSe molecular entities only differ in their structure (an additional methyl group in PMSe), the resulting monolayer films revealed noteworthy dissimilarities regarding their adlayer SAM structure and surface morphology. The molecular adlayer structure and orientation of PMSe and BSe species were found to vary significantly with the immersion time (IT). The resulting PMSe films were poorly organized, and the structure was described by a (4√3 × 2) rectangular unit cell for the SAMs prepared with 24 h of IT. Moreover, the PMSe-SAMs were found to be unstable upon exposure to air for a long time. Our results showed that exposure to air for 48 h results in the formation of small bright ad-islands, which have a height corresponding to that of a single atomic step on the Au(111). Contrary, BSe-SAMs exhibited densely packed and well-ordered monolayers, and two different structural phases were resolved at short and long ITs. The most densely packed structure was obtained for SAMs prepared with very short ITs (10 min). Upon increasing the IT, the SAMs exhibited structural changes to a lower density of molecular packing structure. The spectroscopic data also confirmed this structural transformation by suggesting an upright orientation for BSe-SAMs prepared after short ITs and strongly inclined adsorption geometry for SAMs prepared after long ITs. © 2014 American Chemical Society.

  15. Insights into eisosome assembly and organization

    Indian Academy of Sciences (India)

    Murphy Er; Kim Kt

    2012-06-01

    Eisosomes, large protein complexes that are predominantly composed of BAR-domain-containing proteins Pil1 and its homologs, are situated under the plasma membrane of ascomycetes. A successful targeting of Pil1 onto the future site of eisosome accompanies maturation of eisosome. During or after recruitment, Pil1 undergoes self-assembly into filaments that can serve as scaffolds to induce membrane furrows or invaginations. Although a consequence of the invagination is likely to redistribute particular proteins and lipids to a different location, the precise physiological role of membrane invagination and eisosome assembly awaits further investigation. The present review summarizes recent research findings within the field regarding the detailed structural and functional significance of Pil1 on eisosome organization.

  16. Investigation of Tribological Behavior of Lanthanum-Based Thin Films Deposited on Sulfonated Self-Assembled Monolayer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    3-mercaptopropyl trimethoxysilane (MPTS) was prepared on glass substrate so as to form a two-dimensional self-assembled monolayer (SAM), and the terminal -SH group in the film was in situ oxidized to -SO3H group to confer good chemisorption ability to the film. Thus, lanthanum-based thin films were deposited on oxidized MPTS-SAM, making use of the chemisorption ability of -SO3H group. Atomic force microscopy (AFM) and X-ray photoelectron spectrometry (XPS) and contact angle measurements were used to characterize the thin films. The tribological properties of the as-prepared thin films sliding against a steel ball were evaluated on a friction and wear tester. Tribological experiment shows that the friction coefficient of glass substrate decreases from 0.8 to 0.08 after the rare earth (RE) self-assembled films (SAMs) are formed on its surface. And the RE self-assembled films have longer wear life (500 sliding passes). It is demonstrated that RE self-assembled film exhibits good wear-resistant property. The marked decrease in friction and the longer wear life of RE films are attributed to the excellent adhesion of the film to the substrate and to the special characteristics of the RE elements. The frictional behaviors of RE thin-films-coated silicon surface were sensitive to the applied load and the sliding velocity of the steel ball.

  17. Self-assembling monolayers of helical oligopeptides with applications in molecular electronics

    CERN Document Server

    Strong, A E

    1997-01-01

    prepared. Transformation of the two (Trt)Cys residues of the resin-bound peptide to the intramolecular disulphide by iodine was achieved in acetonitrile but not in DMF. CD suggested that the conformation of this peptide was a mixture of helix and random coil. Films of the peptide-disulphide and the peptide-dithiol adsorbed from protic solvents were characterised as multilayers by ellipsometry. However CV and ellipsometry showed that a monolayer was successfully prepared from acetonitrile. Future targets for improving and extending this method to form monolayers of linked disulphides are presented. The aim of this project was to develop a generic method of preparing a 'molecular architecture' containing functional groups on a surface at predetermined relative positions several nm apart. This would be of great utility in molecular electronics, chemical sensors and other fields. It was proposed that such an architecture could be prepared on gold using linked, helical oligopeptides that contained the components o...

  18. Pit Formation during the Self-Assembly of Dithiol Monolayers on Au(111)

    Science.gov (United States)

    Macdairmid, A. R.; Cappello, M. L.; Keeler, W. J.; Banks, J. T.; Gallagher, M. C.

    2000-03-01

    The formation of pits one gold atom deep during the growth of alkanethiol monolayers on Au(111), has been observed previously by others. Explanations for pit formation include etching of the substrate, or mass transport of gold atom + thiol molecule on the surface, due to changes in surface energy^1. We have investigated the structure of dithiothreitol (DTT) SAMs on Au(111). Ex situ STM measurements indicate similar pitting occurs during formation of the dithiol monolayer. The degree of pitting depends on exposure time, sample temperature during formation, and subsequent annealing of the sample. Pitting is enhanced considerasbly when DTT is coordinated with Ti, in fact DTT/Ti films exhibit considerable pit motion during STM imaging. ^1 F. Teran et al. Electrochimica Acta 44, 1053 (1998).

  19. Direct imaging by atomic force microscopy of surface-localized self-assembled monolayers on a cuprate superconductor and surface X-ray scattering analysis of analogous monolayers on the surface of water

    DEFF Research Database (Denmark)

    Schougaard, Steen B.; Reitzel, Niels; Bjørnholm, Thomas;

    2007-01-01

    A self-assembled monolayer of CF3(CF2)(3)(CH2)(11)NH2 atop the (001) surface of the high-temperature superconductor YBa2Cu3O7-x was imaged by atomic force microscopy (AFM). The AFM images provide direct 2D-structural evidence for the epitaxial 5.5 angstrom square root 2 x root 2R45 degrees unit...... was studied by grazing-incidence X-ray diffraction and specular X-ray reflectivity. Structural differences and similarities between the water-supported and superconductor-localized monolayers are discussed....

  20. Electro- and photochemical switching of dithienylethene self-assembled monolayers on gold electrodes

    DEFF Research Database (Denmark)

    Browne, W.R.; Kudernac, T.; Katsonis, N.;

    2008-01-01

    forms of the dithienylethene SAMs is examined and found to be sensitive to the molecular structure of the switch. For the three dithienylethenes, the electrochemical behavior with respect to electrochemical ring opening/closing is retained in the SAMs. In contrast, a marked dependence on the nature...... are changed markedly compared with those observed in solution. The stability of the monolayers toward desorption following photochemical and electrochemical switching is examined through electrochemistry and X-ray photoelectron spectroscopy....

  1. Single-step DNA immobilization on antifouling self-assembled monolayers covalently bound to silicon (111).

    Science.gov (United States)

    Böcking, Till; Kilian, Kristopher A; Gaus, Katharina; Gooding, J Justin

    2006-04-11

    Hydrosilylation of alkenes with epoxide-terminated tri(ethylene oxide) moieties on Si-H surfaces yields homogeneous monolayers for the efficient coupling of biomolecules. The wetting properties of the epoxide-functionalized surface allow for the spotting of solutions of biomolecules, making the surface amenable to microarraying. Immobilization of thiolated DNA was achieved in a single step to fabricate biorecognition interfaces showing the hybridization of complementary DNA at low concentrations and negligible binding of noncomplementary DNA. PMID:16584219

  2. EXAFS in total reflection (reflEXAFS) for the study of organometallic Pd(II) thiol complexes based self-assembled monolayers on gold

    International Nuclear Information System (INIS)

    Graphical abstract: The molecular structure and organization of organometallic Pd(II) thiolates SAMs and multilayers on Au/Si(1 1 1) were investigated by reflEXAFS. For SAMs, S-Au bond lengths, Pd-S-Au bond angles and molecular orientations were assessed. Research highlights: → Organometallic Pt(II) thiolates deposited as SAMs and multilayers on gold. → Molecular structure and organization of SAMs and multilayers studied by reflEXAFS. → SAMs S-Au bond lengths, Pd-S-Au bond angles and molecular orientations are assessed. - Abstract: The molecular structure and organization of self-assembled monolayers (SAMs) and multilayer films grafted onto Au/Si(1 1 1) surfaces of mononuclear transition metal dialkynyl bridged Pd(II) complexes trans-[HS-Pd(PBu3)2-SH] (1), trans-[HS-Pd(PBu3)2(-C≡C-C6H5)] (2) and of the binuclear complex trans, trans-[HS-Pd(PBu3)2(-C≡C-C6H4-C6H4-C≡C-Pd(PBu3)2-SH] (3), have been investigated by extended X-ray absorption fine structure spectroscopy in total reflection conditions (reflEXAFS). ReflEXAFS analysis of the data lead to determine the local structure around Pd atoms, assessing the square-planar geometry around the transition metal in the multilayers case, preserved in the monolayer regime. The investigation on the SAMs also provided the assessment of the S-Au bond length and Pd-S-Au bond angle and on the molecular orientation on the gold substrate of the complexes, confirmed by quantum chemical calculations.

  3. Motor-mediated cortical versus astral microtubule organization in lipid-monolayered droplets.

    Science.gov (United States)

    Baumann, Hella; Surrey, Thomas

    2014-08-01

    The correct spatial organization of microtubules is of crucial importance for determining the internal architecture of eukaryotic cells. Microtubules are arranged in space by a multitude of biochemical activities and by spatial constraints imposed by the cell boundary. The principles underlying the establishment of distinct intracellular architectures are only poorly understood. Here, we studied the effect of spatial confinement on the self-organization of purified motors and microtubules that are encapsulated in lipid-monolayered droplets in oil, varying in diameter from 5-100 μm, which covers the size range of typical cell bodies. We found that droplet size alone had a major organizing influence. The presence of a microtubule-crosslinking motor protein decreased the number of accessible types of microtubule organizations. Depending on the degree of spatial confinement, the presence of the motor caused either the formation of a cortical array of bent microtubule bundles or the generation of single microtubule asters in the droplets. These are two of the most prominent forms of microtubule arrangements in plant and metazoan cells. Our results provide insights into the combined organizing influence of spatial constraints and cross-linking motor activities determining distinct microtubule architectures in a minimal biomimetic system. In the future, this simple lipid-monolayered droplet system characterized here can be expanded readily to include further biochemical activities or used as the starting point for the investigation of motor-mediated microtubule organization inside liposomes surrounded by a deformable lipid bilayer. PMID:24966327

  4. Self-assembled monolayer and multilayer formation using redox-active Ru complex with phosphonic acids on silicon oxide surface

    International Nuclear Information System (INIS)

    The formation of self-assembled monolayer and multilayer using redox-active Ru complex molecules with phosphonic acids on SiO2 surface has been examined using X-ray photoelectron spectroscopy (XPS), ellipsometry, and time of flight secondary mass-ion spectroscopy (TOF-SIMS). We found that an introduction of a Zr adlayer leads to higher surface molecular density of Ru complex SAMs on the SiO2 surface, compared to that of obtained from the direct adsorption of Ru complex monolayer on the SiO2 surface. We further tried to fabricate a multilayer film using this molecule with Zr(IV) ion acting as a chemical glue by a successive immersion process. The XPS data revealed that the molecular densities of the multilayers were also higher for the immobilization with Zr adlayer between Ru complex and SiO2 surface than those without the Zr adlayer, suggesting that Zr adlayer is effective in forming highly packed molecular layer of phosphonic acids on SiO2 surface. We found the film growth reached a saturation point after 6 layers on the SiO2 surface. The film growth saturation can be explained by a molecular domain boundary effect encountered due to the large tilt angle of the molecular layer.

  5. Formation and dissolution processes of the 6-thioguanine (6TG) self-assembled monolayer. A kinetic study.

    Science.gov (United States)

    Madueño, Rafael; Pineda, Teresa; Sevilla, José Manuel; Blázquez, Manuel

    2005-02-01

    This is a report on the kinetics of the destruction and formation processes of the 6-thioguanine self-assembled monolayer (6TG SAM) on a mercury electrode from acid solutions by chronoamperometry. The destruction of the 6TG SAM that has been previously formed under open circuit potential conditions is carried out by stepping the potential from an initial value where the chemisorbed layer is stable up to potentials where the molecules are no longer chemisorbed. The destruction of the SAM has been described by a model that involves three types of contributions: (i) a Langmuir-type adsorption process, (ii) a 2D nucleation mechanism followed by a growth controlled by surface diffusion, and (iii) a 2D nucleation mechanism followed by a growth at a constant rate. The nonlinear fit of the experimental transients by using this procedure allows the quantitative determination of the individual contributions to the overall process. The kinetics of the formation process is studied under electrochemical conditions. The chronoamperometric experiment allows us to monitor the early stages of 6TG SAM formation. The implications of the physisorbed state at low potentials in the type of monolayer formation and destruction processes as well as the influence of temperature are also discussed. PMID:16851120

  6. Use of Self-Assembling Monolayers to Control Interface Bonding in a Model Study of Interfacial Fracture

    Energy Technology Data Exchange (ETDEWEB)

    Kent, M.S.; Matheson, A.; Reedy, E.D.; Yim, H.

    1999-03-05

    The relationships between the extent of interfacial bonding, energy dissipation mechanisms, and fracture toughness in a glassy adhesive/inorganic solid joint are not well understood. We address this subject with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The extent of interfacial bonding, and the wetting behavior of the epoxy, is varied continuously using self-assembling monolayers (SAMs) of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but forms only a very weak interface with the methylated tails of the ODTS monolayer. We examine the fracture behavior of such joints as a function of the coverage of ODTS in the napkin-ring geometry. Various characterization methods are applied to the ODTS-coated surface before application of the epoxy, and to both surfaces after fracture. The fracture data are discussed with respect to the wetting of the liquid epoxy on the ODTS-coated substrates, the locus of failure, and the energy dissipation mechanisms. Our goal is to understand how energy is dissipated during fracture as a function of interface strength.

  7. Stability of phosphonic self assembled monolayers (SAMs) on cobalt chromium (Co-Cr) alloy under oxidative conditions

    Science.gov (United States)

    Bhure, Rahul; Abdel-Fattah, Tarek M.; Bonner, Carl; Hall, Felicia; Mahapatro, Anil

    2011-04-01

    Cobalt chromium (Co-Cr) alloys have been widely used in the biomedical arena for cardiovascular, orthopedic and dental applications. Surface modification of the alloy allows us to tailor the interfacial properties to address critical challenges of Co-Cr alloy in medical applications. Self assembled monolayers (SAMs) of Octadecylphosphonic acid (ODPA) have been used to form thin films on the oxide layer of the Co-Cr alloy surface by solution deposition technique. The SAMs formed were investigated for their stability to oxidative conditions of ambient laboratory environment over periods of 1, 3, 7 and 14 days. The samples were then characterized for their stability using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and contact angle measurements. Detailed high energy XPS elemental scans confirmed the presence of the phosphonic monolayer after oxidative exposure which suggested that the SAMs were firmly attached to the oxide layer of Co-Cr alloy. AFM images gave topographical data of the surface and showed islands of SAMs on Co-Cr alloy surface, before and after SAM formation and also over the duration of the oxidative exposure. Contact angle measurements confirmed the hydrophobicity of the surface over 14 days. Thus the SAMs were found to be stable for the duration of the study. These SAMs could be subsequently tailored by modifying the terminal functional groups and could be used for various potential biomedical applications such as drug delivery, biocompatibility and tissue integration.

  8. Reversible switching in self-assembled monolayers of azobenzene thiolates on Au (111) probed by threshold photoemission

    International Nuclear Information System (INIS)

    Highlights: ► Photoelectron spectroscopy of liquid phase prepared SAMs of azobenzene derivative. ► Photo-induced reversible switching in densely packed SAM is monitored. ► Maximum density of switched molecules in SAM is derived from photoemission data. ► Switching reaction only enabled at defects sites within the molecular layer. - Abstract: The reversible photo- and thermally activated isomerization of the molecular switch 3-(4-(4-Hexyl-phenylazo)-phenoxy)-propane-1-thiol (ABT, short for AzoBenzeneThiol) deposited by self-assembly from solution on Au (111) was studied using laser-based photoelectron spectroscopy. Differences in the molecular dipole moment characteristic for the trans and the cis isomer of ABT were monitored via changes in the sample work function, accessible by detection of the threshold energy for photoemission. A quantitative analysis of our data shows that the fraction of molecules within the densely packed monolayer that undergoes a switching process is of the order of 1%. This result indicates the relevance of substrate and film defects required to overcome the steric or electronic hindrance of the isomerization reaction in a densely packed monolayer.

  9. Tribological properties of self-assembled monolayers of catecholic imidazolium and the spin-coated films of ionic liquids.

    Science.gov (United States)

    Liu, Jianxi; Li, Jinlong; Yu, Bo; Ma, Baodong; Zhu, Yangwen; Song, Xinwang; Cao, Xulong; Yang, Wu; Zhou, Feng

    2011-09-20

    A novel compound of an imidazolium type of ionic liquid (IL) containing a biomimetic catecholic functional group normally seen in mussel adhesive proteins was synthesized. The IL can be immobilized on a silicon surface and a variety of other engineering material surfaces via the catecholic anchor, allowing the tribological protection of these substrates for engineering applications. The surface wetting and adhesive properties and the tribological property of the synthesized self-assembled monolayers (SAMs) are successfully modulated by altering the counteranions. The chemical composition and wettability of the IL SAMs were characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurements. The adhesive and friction forces were measured with an atomic force microscope (AFM) on the nanometer scale. IL composite films were prepared by spin coating thin IL films on top of the SAMs. The macrotribological properties of these IL composite films were investigated with a pin-on-disk tribometer. The results indicate that the presence of IL SAMs on a surface can improve the wettability of spin-coated ionic liquids and thus the film quality and the tribological properties. These films registered a reduced friction coefficient and a significantly enhanced durability and load-carrying capacity. The tribological properties of the composite films are better than those of pure IL films because the presence of the monolayers improves the adhesion and compatibility of spin-coated IL films with substrates. PMID:21834561

  10. Self-assembly, self-organization and division of labour

    OpenAIRE

    Sendova-Franks, A. B.

    1999-01-01

    The prospect of generic principles of biological organization being uncovered through the increasingly broad use of the concepts of 'self-assembly' and 'self-organization' in biology will only be fulfilled if students of different levels of biological organization use the same terms with the same meanings. We consider the different ways the terms 'self-assembly' and 'self-organization' have been used, from studies of molecules to studies of animal societies. By linking 'self-assembly' and 'se...

  11. Voltammetry of 6,6'-dithiodinicotinic acid on a self-assembled phospholipid monolayer prive

    Science.gov (United States)

    Herrero, R.; Vilariño, T.; Barriada, J. L.; Sastre de Vicente, M. E.; López-Fonseca, J. M.; Moncelli, M. R.

    1999-04-01

    This paper reports a voltammetric study of 6,6'-dithiodinicotinic acid (CPDS) across a biomimetic membrane system consisting of a monolayer of dioleoylphosphatidylcholine, deposited on mercury. Because of the low solubility of this compound and its potential decomposition in alkaline media, estimation of pK values for the carboxyl and amino groups of the pyridine ring of the CPDS entailed using the Hammett equation. UV spectra seem to confirm the presence of the dianionic form of CPDS above pH=3-4. Differential capacity and cyclic voltammetry measurements were made in order to characterize the voltammetric behavior directly on mercury and through a monolayer of dioleoylphosphatidylcholine. Estimation of the CPDS hydrophobicity degree from the partition coefficient in octanol/ water suggests no penetration of the dianion into the monolayer and supports the fact that the named dianion undergoes protonation at the phospholipid/solution interface to give a neutral specie which penetration into the phospholipid region, favored by its higher hydrophobicity, is followed by electrochemical reduction at the mercury surface. Nous avons étudié par voltampérométrie le comportement de l'acide 6,6'-dithiodinicotinique (CPDS) sur l'électrode de mercure couverte par une monocouche de dioleoyl-phosphatidylcholine. La caractérisation électrochimique a été effectuée par des mesures de la capacité différentielle et par voltamétrie cyclique au dessus d'un pH 3-4. Le spectre UV paraît confirmer la présence de la forme dianionique du CPDS. Cependant les données expérimentales associées à une estimation de l'hydrophobicité de la forme dianionique suggèrent que seule la forme neutre du CPDS peut être réduite sur la surface de l'électrode.

  12. Electron-beam patterned self-assembled monolayers as templates for Cu electrodeposition and lift-off

    Directory of Open Access Journals (Sweden)

    Zhe She

    2012-02-01

    Full Text Available Self-assembled monolayers (SAMs of 4'-methylbiphenyl-4-thiol (MBP0 adsorbed on polycrystalline gold substrates served as templates to control electrochemical deposition of Cu structures from acidic solution, and enabled the subsequent lift-off of the metal structures by attachment to epoxy glue. By exploiting the negative-resist behaviour of MBP0, the SAM was patterned by means of electron-beam lithography. For high deposition contrast a two-step procedure was employed involving a nucleation phase around −0.7 V versus Cu2+/Cu and a growth phase at around −0.35 V versus Cu2+/Cu. Structures with features down to 100 nm were deposited and transferred with high fidelity. By using substrates with different surface morphologies, AFM measurements revealed that the roughness of the substrate is a crucial factor but not the only one determining the roughness of the copper surface that is exposed after lift-off.

  13. Support-Free Transfer of Ultrasmooth Graphene Films Facilitated by Self-Assembled Monolayers for Electronic Devices and Patterns.

    Science.gov (United States)

    Wang, Bin; Huang, Ming; Tao, Li; Lee, Sun Hwa; Jang, A-Rang; Li, Bao-Wen; Shin, Hyeon Suk; Akinwande, Deji; Ruoff, Rodney S

    2016-01-26

    We explored a support-free method for transferring large area graphene films grown by chemical vapor deposition to various fluoric self-assembled monolayer (F-SAM) modified substrates including SiO2/Si wafers, polyethylene terephthalate films, and glass. This method yields clean, ultrasmooth, and high-quality graphene films for promising applications such as transparent, conductive, and flexible films due to the absence of residues and limited structural defects such as cracks. The F-SAM introduced in the transfer process can also lead to graphene transistors with enhanced field-effect mobility (up to 10,663 cm(2)/Vs) and resistance modulation (up to 12×) on a standard silicon dioxide dielectric. Clean graphene patterns can be realized by transfer of graphene onto only the F-SAM modified surfaces. PMID:26701198

  14. Self-assembled monolayers of a bis(pyrazol-1-yl)pyridine-substituted thiol on Au(111).

    Science.gov (United States)

    Shen, Cai; Haryono, Marco; Grohmann, Andreas; Buck, Manfred; Weidner, Tobias; Ballav, Nirmalya; Zharnikov, Michael

    2008-11-18

    Self-assembled monolayers (SAMs) of a bis(pyrazol-1-yl)pyridine-substituted thiol (bpp-SH) on Au (111)/mica were studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Using substrates precoated with perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA), preparation at elevated temperatures yields highly ordered layers whose structure is described by a rectangular (5 x radical3) unit cell containing one molecule. The bis(pyrazol-1-yl)pyridine (bpp) units exhibit pi-stacking along the 112 direction, and they are tilted significantly. We conclude the three imine nitrogen atoms in the bpp headgroup adopt a trans,trans arrangement. PMID:18950209

  15. Molecular Dynamics Simulation of the Self-assembled Monolayers of 1-Adamantanethiolate and Its Derivatives on Au(111)Surfaces

    Institute of Scientific and Technical Information of China (English)

    ZHOU, Jun-Hong; ZHU, Rui-Xin; SHI, Liang-Wei; ZHANG, Tao; CHEN, Min-Bo

    2007-01-01

    The self-assembled monolayers (SAMs) of 1-adamantanethiolate and its derivatives on Au(111) surface were investigated. Density functional theory (DFT) calculation indicates that the most stable configuration for absorption is at the face centered cubic (fcc)-bridge site. Canonical ensemble molecular dynamics (MD) simulations were carried out to study the structures and energies of the SAMs. The ordered structures of the SAMs were analyzed by means of radial distribution function and the relative stability of the SAMs was compared. It was concluded by the comparison of various contributions to the SAM formation energy that the formation of the SAMs was determined by the intermolecular nonbonding interaction and the chemical bonding interaction of sulfur and gold.

  16. Cyclic voltammetry on n-alkylphosphonic acid self-assembled monolayer modified large area indium tin oxide electrodes

    International Nuclear Information System (INIS)

    We show stable bonding of n-alkylphosphonic acid self-assembled monolayers (SAMs) to indium tin oxide electrodes and their direct electrical characterization by cyclic voltammetry (CV). The functional coatings were investigated with regards to the addressability and stability of the electrodes, which are related to small changes in molecular layer thickness. The response of a redox active compound in solution to the faradic current is indirectly proportional to the molecular chain length of the SAMs. We observed a decrease of the electrode sensitivity with enhanced surface protection and slow long term degradation of the SAM under electrochemical stress by CV, and therefore conclude a trade-off optimum for molecules with the C10 chain.

  17. A study on oxygen reduction inhibition at pyridine-terminated self assembled monolayer modified Au(111) electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Muglali, Mutlu Iskender; Bashir, Asif; Rohwerder, Michael [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany)

    2010-04-15

    The electroreduction of oxygen on self-assembled monolayers (SAMs) of various pyridinedisulfides and pyridinethiols on Au(111) surfaces has been investigated in alkaline solutions. Electrochemical experiments that were carried out in three-electrode cell reveal a good correlation between the chain-length of thiol molecules and the oxygen reduction inhibition of the resulting adlayer films. The effect of retarded diffusion of oxygen through the protective film has been investigated by forming additional layer of immobilized cytochrome c (cyt.c) metalloprotein on pyridine moiety during linear sweep voltammetry (LSV) scans. At sufficiently negative cathodic potentials the electrochemical reaction rate has been observed to increase together with the density of defects. Morphological changes at different levels of cathodic polarization were investigated by ex situ scanning tunneling microscopy (STM), indicating oxygen reduction reaction (ORR) induced structural defects at the metallorganic interface. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  18. Self-assembled monolayer of designed and synthesized triazinedithiolsilane molecule as interfacial adhesion enhancer for integrated circuit

    Directory of Open Access Journals (Sweden)

    Wang Fang

    2011-01-01

    Full Text Available Abstract Self-assembled monolayer (SAM with tunable surface chemistry and smooth surface provides an approach to adhesion improvement and suppressing deleterious chemical interactions. Here, we demonstrate the SAM comprising of designed and synthesized 6-(3-triethoxysilylpropylamino-1,3,5-triazine-2,4-dithiol molecule, which can enhance interfacial adhesion to inhibit copper diffusion used in device metallization. The formation of the triazinedithiolsilane SAM is confirmed by X-ray photoelectron spectroscopy. The adhesion strength between SAM-coated substrate and electroless deposition copper film was up to 13.8 MPa. The design strategy of triazinedithiolsilane molecule is expected to open up the possibilities for replacing traditional organosilane to be applied in microelectronic industry.

  19. Self-assembled monolayer of designed and synthesized triazinedithiolsilane molecule as interfacial adhesion enhancer for integrated circuit.

    Science.gov (United States)

    Wang, Fang; Li, Yanni; Wang, Yabin; Cao, Zhuo

    2011-08-03

    Self-assembled monolayer (SAM) with tunable surface chemistry and smooth surface provides an approach to adhesion improvement and suppressing deleterious chemical interactions. Here, we demonstrate the SAM comprising of designed and synthesized 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-dithiol molecule, which can enhance interfacial adhesion to inhibit copper diffusion used in device metallization. The formation of the triazinedithiolsilane SAM is confirmed by X-ray photoelectron spectroscopy. The adhesion strength between SAM-coated substrate and electroless deposition copper film was up to 13.8 MPa. The design strategy of triazinedithiolsilane molecule is expected to open up the possibilities for replacing traditional organosilane to be applied in microelectronic industry.

  20. Self-assembled monolayer of designed and synthesized triazinedithiolsilane molecule as interfacial adhesion enhancer for integrated circuit

    Science.gov (United States)

    2011-01-01

    Self-assembled monolayer (SAM) with tunable surface chemistry and smooth surface provides an approach to adhesion improvement and suppressing deleterious chemical interactions. Here, we demonstrate the SAM comprising of designed and synthesized 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-dithiol molecule, which can enhance interfacial adhesion to inhibit copper diffusion used in device metallization. The formation of the triazinedithiolsilane SAM is confirmed by X-ray photoelectron spectroscopy. The adhesion strength between SAM-coated substrate and electroless deposition copper film was up to 13.8 MPa. The design strategy of triazinedithiolsilane molecule is expected to open up the possibilities for replacing traditional organosilane to be applied in microelectronic industry. PMID:21812994

  1. A Rationally Designed Thymidine-Based Self-Assembled Monolayer on a Gold Electrode for Electroanalytical Applications.

    Science.gov (United States)

    Datta, Dhrubajyoti; Bera, Raj Kumar; Jana, Saibal; Manna, Bhaskar; Roy, Debayan; Anoop, Anakuthil; Raj, C Retna; Pathak, Tanmaya

    2015-07-01

    A self-assembled monolayer (SAM) of 1-(3,5-epidithio-2,3,5-trideoxy-β-D-threo-pentofuranosyl)thymine (EFT) on a gold electrode was prepared and characterized by Raman spectral and electrochemical measurements. Voltammetric and electrochemical impedance measurements show that the SAM of EFT on a Au electrode impedes the electron-transfer reaction. The SAM of EFT was successfully used for the voltammetric sensing of urate in neutral solution. The coexisting ascorbate anion does not interfere and therefore the EFT-based electrode was able to quantify urate at the micromolar level in the presence of a large excess amount of ascorbate. To demonstrate the practical applications, the amount of urate in two different human serum samples was quantified by using the EFT-based electrode; the results are in good agreement with those determined by the clinical method. DFT calculations show that both ascorbate and urate have noncovalent interactions including hydrogen-bonding interactions with EFT.

  2. Mechanical and charge transport properties of alkanethiol self-assembled monolayers on Au (111) surface: The Role of Molecular Tilt

    Energy Technology Data Exchange (ETDEWEB)

    Mulleregan, Alice; Qi, Yabing; Ratera, Imma; Park, Jeong Y.; Ashby, Paul D.; Quek, Su Ying; Neaton, J. B.; Salmeron, Miquel

    2007-11-12

    The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAM) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant {beta} = 0.57 {+-} 0.03 {angstrom}{sup -1} was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. This is significantly smaller than the value of {approx} 1 {angstrom}{sup -1} found when the separation is changed by changing the length of the alkanethiol molecules. Calculations indicate that for isolated dithiol molecules S-bonded to hollow sites, the junction conductance does not vary significantly as a function of molecular tilt. The impact of S-Au bonding on SAM conductance is discussed.

  3. Morse potential-based model for contacting composite rough surfaces: Application to self-assembled monolayer junctions

    Science.gov (United States)

    Sierra-Suarez, Jonatan A.; Majumdar, Shubhaditya; McGaughey, Alan J. H.; Malen, Jonathan A.; Higgs, C. Fred

    2016-04-01

    This work formulates a rough surface contact model that accounts for adhesion through a Morse potential and plasticity through the Kogut-Etsion finite element-based approximation. Compared to the commonly used Lennard-Jones (LJ) potential, the Morse potential provides a more accurate and generalized description for modeling covalent materials and surface interactions. An extension of this contact model to describe composite layered surfaces is presented and implemented to study a self-assembled monolayer (SAM) grown on a gold substrate placed in contact with a second gold substrate. Based on a comparison with prior experimental measurements of the thermal conductance of this SAM junction [Majumdar et al., Nano Lett. 15, 2985-2991 (2015)], the more general Morse potential-based contact model provides a better prediction of the percentage contact area than an equivalent LJ potential-based model.

  4. Inhibition of copper corrosion in sodium chloride solution by the self-assembled monolayer of sodium diethyldithiocarbamate

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Q.Q., E-mail: liaoqq1971@yahoo.com.c [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Yue, Z.W.; Yang, D. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Wang, Z.H. [Department of Chemistry, Tongji University, Shanghai 200092 (China); Li, Z.H. [Department of Chemistry, Fudan University, Shanghai 200433 (China); Ge, H.H. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Li, Y.J. [Department of Chemistry, Tongji University, Shanghai 200092 (China)

    2011-05-15

    Research highlights: DDTC is of low toxicity. DDTC SAM had good corrosion inhibition effects on copper in 3% NaCl solution. DDTC SAM was chemisorbed on copper surface by its S atoms. - Abstract: Sodium diethyldithiocarbamate (DDTC) self-assembled monolayer (SAM) on copper surface has been investigated by SERS and EDS and the results show that DDTC SAM is chemisorbed on copper surface by its S atoms with tilted orientation. Corrosion inhibition ability of DDTC SAM was measured in 3% NaCl solution using electrochemical methods. The impedance results indicate that the maximum inhibition efficiency of DDTC SAM can reach 99%. Quantum chemical calculations show that DDTC has relatively small {Delta}E between HOMO and LUMO and large negative charge in its two sulfur atoms, which facilitates the formation of a DDTC SAM on copper surface.

  5. Influence of a self-assembled monolayer on indium-zinc-oxide semiconductor thin-film transistors

    International Nuclear Information System (INIS)

    The fabrication of an active-matrix liquid-crystal display by using printing processes offers the potential to reduce the number of photolithography steps and the manufacturing costs. In this study, we prepare the indium-zinc-oxide (IZO) thin-film transistors (TFTs) by using non-vacuum processes such as inkjet printing. The self-assembled monolayers of hexadecanethiol (HDT) on the surface of the oxide semiconductor prior to the inkjet printing of Ag were employed to modify the electric barrier between the IZO and the printed Ag. The field-effect mobility of the IZO TFTs with 0.5-mM HDT treatments and with the inkjet-printed Ag electrodes that were investigated by using their current-voltage characteristics was approximately 0.36 cm2/Vs.

  6. Optimized modification of gold nanoparticles with a self-assembled monolayer for suppression of nonspecific binding in DNA assays

    Science.gov (United States)

    Esashika, Keiko; Saiki, Toshiharu

    2016-10-01

    Homogeneous DNA assays using gold nanoparticles (AuNPs) require the reduction of nonspecific binding between AuNPs to improve sensitivity in detecting the target molecule. In this study, we employed alkanethiol self-assembled monolayers (SAMs) for modifying the AuNP surface to attain both good dispersability and high hybridization efficiency. The alkanethiol SAMs enhance the repulsive interaction between AuNPs, reducing nonspecific binding and promoting the extension of surface-immobilized ssDNA into the solvent, thus enhancing the hybridization process. Introduction of oligoethylene glycol into the alkanethiol prevented nonspecific binding caused by the entanglement of alkane chains. Finally, the conditions were optimized by controlling the surface charge density through the introduction of a COOH group at the alkanethiol terminus, resulting in the complete blocking of nonspecific binding and the maintenance of high hybridization efficiency.

  7. Self-assembled monolayers of stearic imidazoline on copper electrodes detected using electrochemical measurements, XPS, molecular simulation and FTIR

    Institute of Scientific and Technical Information of China (English)

    LIU XiuYu; MA HouYi; MIAO Shuai; ZHOU Min

    2009-01-01

    A type of imidazoline inhibitor was synthesized using stearic acid and diethylenetriamine (DETA) as raw materials. Self-assembled monolayers (SAMs) of stearic imidazoline (IM) were prepared on copper surface. The copper electrode modified by IM was detected by electrochemical impedance spectros-copy (EIS), Tafel polarization curves, X-ray photoelectron spectroscopy (XPS) and Fourial transform reflection spectroscopy (FTIR). The biggest inhibition efficiency for copper corrosion of IM was 99% in NaCI solution according to EIS results. The XPS results provided evidence that the IM was adsorbed on copper surface. The theoretical calculations of molecular simulation supported the experimental re-sults and showed that the IM molecules were tilted at an angle to the copper surface.

  8. Vascular endothelial growth factor attachment to hydroxyapatite via self-assembled monolayers promotes angiogenic activity of endothelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, Kimberly D., E-mail: solomonk@livemail.uthscsa.edu [Department of Biomedical Engineering, University of Texas at San Antonio, San Antonio, TX (United States); UTSA-UTHSCSA Joint Graduate Program in Biomedical Engineering, San Antonio, TX (United States); Ong, Joo L., E-mail: anson.ong@utsa.edu [Department of Biomedical Engineering, University of Texas at San Antonio, San Antonio, TX (United States); UTSA-UTHSCSA Joint Graduate Program in Biomedical Engineering, San Antonio, TX (United States)

    2013-06-30

    Currently, tissue engineered constructs for critical sized bone defects are non-vascularized. There are many strategies used in order to promote vascularization, including delivery of growth factors such as vascular endothelial growth factor (VEGF). In this study, hydroxyapatite (HA) was coated with self-assembled monolayers (SAMs). The SAMs were in turn used to covalently bind VEGF to the surface of HA. The different SAM chain length ratios (phosphonoundecanoic acid (11-PUDA):16-phosphonohexadecanoic acid (16-PHDA) utilized in this study were 0:100, 25:75, 50:50, 75:25, and 100:0. Surfaces were characterized by contact angle (CA) and atomic force microscopy, and an in vitro VEGF release study was performed. It was observed that CA and root-mean-squared roughness were not significantly affected by the addition of SAMs, but that CA was significantly lowered with the addition of VEGF. VEGF release profiles of bound VEGF groups all demonstrated less initial burst release than adsorbed control, indicating that VEGF was retained on the HA surface when bound by SAMs. An in vitro study using human aortic endothelial cells (HAECs) demonstrated that bound VEGF increased metabolic activity and caused sustained production of angiopoietin-2, an angiogenic marker, over 28 days. In conclusion, SAMs provide a feasible option for growth factor delivery from HA surfaces, enhancing angiogenic activity of HAECs in vitro. - Highlights: • Vascular endothelial growth factor (VEGF) is attached to hydroxyapatite (HA). • Self-assembled monolayers (SAMs) delay the release of VEGF from hydroxyapatite. • SAM chain length ratio affects the total mass of VEGF released. • VEGF on HA up-regulates proliferation and angiogenic activity of endothelial cells.

  9. Preparation of Sm2S3 thin films by liquid phase deposition method with self-assembled monolayers

    International Nuclear Information System (INIS)

    Highlights: ► Sm2S3 thin films with orientation growth along (1 0 3) direction. ► The influence of the precursor solution pH value. ► Liquid phase deposition method on self-assembled monolayers. ► Red photoluminescence properties. - Abstract: Sm2S3 thin films were prepared on Si(1 0 0) substrates using SmCl3 and Na2S2O3 as source material by liquid phase deposition method on self-assembled monolayers. The influence of the precursor solution pH value on the phase composition, surface morphology and optical properties of the as-deposited films were investigated. The as-deposited Sm2S3 thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet–visible (UV–Vis) and photoluminescence spectrum (PL). Results show that it is important to control the solution pH value during the deposition process and monophase Sm2S3 thin films with orientation growth along (1 0 3) direction can be achieved when pH 3.0, using citrate as a template agent. The as-deposited thin films exhibit a dense and crystalline surface morphology. Good transmittance in the visible spectrum and excellent absorbency of ultraviolet light of the thin films are observed, and the band gap of the thin films first decrease and then increase with the increase of the pH value. The as-deposited thin films also exhibit red photoluminescence properties under visible light excitation. With the increase of the solution pH value, the PL properties of Sm2S3 thin films are obviously improved.

  10. Vascular endothelial growth factor attachment to hydroxyapatite via self-assembled monolayers promotes angiogenic activity of endothelial cells

    International Nuclear Information System (INIS)

    Currently, tissue engineered constructs for critical sized bone defects are non-vascularized. There are many strategies used in order to promote vascularization, including delivery of growth factors such as vascular endothelial growth factor (VEGF). In this study, hydroxyapatite (HA) was coated with self-assembled monolayers (SAMs). The SAMs were in turn used to covalently bind VEGF to the surface of HA. The different SAM chain length ratios (phosphonoundecanoic acid (11-PUDA):16-phosphonohexadecanoic acid (16-PHDA) utilized in this study were 0:100, 25:75, 50:50, 75:25, and 100:0. Surfaces were characterized by contact angle (CA) and atomic force microscopy, and an in vitro VEGF release study was performed. It was observed that CA and root-mean-squared roughness were not significantly affected by the addition of SAMs, but that CA was significantly lowered with the addition of VEGF. VEGF release profiles of bound VEGF groups all demonstrated less initial burst release than adsorbed control, indicating that VEGF was retained on the HA surface when bound by SAMs. An in vitro study using human aortic endothelial cells (HAECs) demonstrated that bound VEGF increased metabolic activity and caused sustained production of angiopoietin-2, an angiogenic marker, over 28 days. In conclusion, SAMs provide a feasible option for growth factor delivery from HA surfaces, enhancing angiogenic activity of HAECs in vitro. - Highlights: • Vascular endothelial growth factor (VEGF) is attached to hydroxyapatite (HA). • Self-assembled monolayers (SAMs) delay the release of VEGF from hydroxyapatite. • SAM chain length ratio affects the total mass of VEGF released. • VEGF on HA up-regulates proliferation and angiogenic activity of endothelial cells

  11. Gold Mining by Alkanethiol Radicals: Vacancies and Pits in the Self-Assembled Monolayers of 1-Propanethiol and 1-Butanethiol on Au(111)

    DEFF Research Database (Denmark)

    Wang, Yun; Chi, Qijin; Hush, Noel S.;

    2011-01-01

    Scanning-tunneling microscopy (STM) under electrochemical control (in situ STM) in aqueous solution, combined with a priori density functional theory (DFT) image simulations at room temperature, reveals the atomic nature of the interface between Au(111) and self-assembled monolayers (SAMs) of 1-p...

  12. Building a Low-Cost, Six-Electrode Instrument to Measure Electrical Properties of Self-Assembled Monolayers of Gold Nanoparticles

    Science.gov (United States)

    Gerber, Ralph W.; Oliver-Hoyo, Maria

    2007-01-01

    The development of a new low-cost, six-electrode instrument for measuring the electrical properties of the self-assembled monolayers of gold particles is being described. The system can also be used to measure conductive liquids, except for those that contain aqua region.

  13. Oriented crystalline monolayers and bilayers of 2 x 2 silver(1) grid architectures at the air-solution interface: Their assembly and crystal structure elucidation

    DEFF Research Database (Denmark)

    Weissbuch, J.; Baxter, P.N.W.; Kuzmenko, I.;

    2000-01-01

    Oriented crystalline monolayers, similar to 14 Angstrom thick, of a 2 x 2 Ag+ grid complex, self-assembled at the air-solution interface starting from an water-insoluble ligand 3,6-bis[2-(6-phenylpyridine)]pyridazine spread on silver-ion-containing solutions,were examined by grazing-incidence X...

  14. Self-assembly of mildly reduced graphene oxide monolayer for enhanced Raman scattering

    Science.gov (United States)

    Yin, Fenping; Wu, Shang; Wang, Yanbin; Wu, Lan; Yuan, Peilin; Wang, Xia

    2016-05-01

    Graphene-enhanced Raman scattering (GERS) has attracted much attention recently. In present study, monolayer of chemically reduced graphene oxide (RGO) nanosheets was chemically bonded on Si substrates and their possible applications in Raman scattering were investigated. In comparison with the mechanically exfoliated graphene, mildly reduced graphene oxide (MR-GO) monolayer is a better substrate to quench the fluorescence (FL) signals and simultaneously enhance the Raman signals of adsorbed Rhodamin 6G (R6G) molecules. Raman and X-ray photoelectron spectra indicate that π-π stacking and the residual polarized oxygen groups on MRGO surface, which can produce a strong local electric field under laser excitation, are mainly responsible for the excellent GERS effect of MR-GO substrate, while the charge transfer between R6G and MR-GO has a relatively low contribution for GERS effect. Our results not only provide a new approach to realize sensitive GERS substrate, but also are helpful for improving the fundamental understanding of GERS effect on RGO substrate.

  15. Incorporating bacteria as a living component in supramolecular self-assembled monolayers through dynamic nanoscale interactions

    NARCIS (Netherlands)

    Sankaran, Shrikrishnan; Kiren, Mustafa Can; Jonkheijm, Pascal

    2015-01-01

    Supramolecular assemblies, formed through noncovalent interactions, has become particularly attractive to develop dynamic and responsive architectures to address living systems at the nanoscale. Cucurbit[8]uril (CB[8]), a pumpkin shaped macrocylic host molecule, has been successfully used to constru

  16. Photonic properties of organic molecular assemblies

    Science.gov (United States)

    Huggins, Kevin Edward

    1997-12-01

    This work attempts to characterize various photonic properties of spontaneously created organic molecular objects. A novel diacetylene monomer was synthesized and found to polymerize forming two-dimensional supramolecular assemblies. The two-dimensional structure self assembles when UV light generates polydiacetylene comb polymers. The material forms blue solid thin films which have been characterized by x-ray diffraction, infrared spectroscopy and Raman scattering. The photopolymerization rate of the monomer was followed by Raman scattering and was shown to be of second order. A reaction rate threshold was observed between 300 and 400mW of incident 647.1nm laser radiation where the reaction rate increased substantially. The material generates high third order nonlinear optical signals and have remarkable photochemical stability to 1064nm radiation from a Q-switched Nd:YAG laser. Upon heating to 62oC, the material turns bright red reversibly while maintaining its two-dimensional structure, characterized by differential scanning calorimetry. Heating to 180oC results in an irreversible color change to bright orange characterized by UV-Vis-NIR spectrophotometry. Variable temperature sum frequency generation experiments show that the third harmonic generation signals retain much of their original intensity through the thermochromic transitions. A system of novel rodcoil materials self assembles into mushroom-shaped supramolecular objects. These nanophase separated aggregates form oblique-plane superlattices exhibiting long-range order. The superlattice is composed of isolated crystallized rod domains surrounded by amorphous coil which form from simple solvent casting techniques. Second harmonic generation was used to confirm the polar head-to-tail stacking of the aggregates and to determine the average physical tilt of (5/pm 5)o of the aggregates relative to the film plane. A novel chiral oligomer synthesized in our group gave rise to interesting phase behavior

  17. Characterization of self-assembled monolayers (SAMs) on silicon substrate comparative with polymer substrate for Escherichia coli O157:H7 detection

    Science.gov (United States)

    Moldovan, Carmen; Mihailescu, Carmen; Stan, Dana; Ruta, Lavinia; Iosub, Rodica; Gavrila, Raluca; Purica, Munizer; Vasilica, Schiopu

    2009-08-01

    This article presents the characterization of two substrates, silicon and polymer coated with gold, that are functionalized by mixed self-assembled monolayers (SAMs) in order to efficiently immobilize the anti- Escherichia coli O157:H7 polyclonal purified antibody. A biosurface functionalized by SAMs (self-assembled monolayers) technique has been developed. Immobilization of goat anti- E. coli O157:H7 antibody was performed by covalently bonding of thiolate mixed self-assembled monolayers (SAMs) realized on two substrates: polymer coated with gold and silicon coated with gold. The F(ab') 2 fragments of the antibodies have been used for eliminating nonspecific bindings between the Fc portions of antibodies and the Fc receptor on cells. The properties of the monolayers and the biofilm formatted with attached antibody molecules were analyzed at each step using infrared spectroscopy (FTIR-ATR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV). In our study the gold-coated silicon substrates approach yielded the best results. These experimental results revealed the necessity to investigate each stage of the immobilization process taking into account in the same time the factors that influence the chemistry of the surface and the further interactions as well and also provide a solid basis for further studies aiming at elaborating sensitive and specific immunosensor or a microarray for the detection of E. coli O157:H7.

  18. Characterization of self-assembled monolayers (SAMs) on silicon substrate comparative with polymer substrate for Escherichia coli O157:H7 detection

    Energy Technology Data Exchange (ETDEWEB)

    Moldovan, Carmen, E-mail: carmen.moldovan@imt.ro [National Institute for R and D in Microtechnologies, IMT-Bucharest, 126A Erou Iancu Nicolae, 077190 Bucharest (Romania); Mihailescu, Carmen, E-mail: carmen_mihail28@yahoo.com [University of Bucharest, 90-92 Sos Panduri, Bucharest (Romania); Stan, Dana, E-mail: dana_stan2005@yahoo.com [DDS Diagnostic, 1 Segovia Street, Bucharest (Romania); Ruta, Lavinia, E-mail: laviniacoco@yahoo.com [University of Bucharest, 90-92 Sos Panduri, Bucharest (Romania); Iosub, Rodica, E-mail: rodica.iosub@imt.ro [National Institute for R and D in Microtechnologies, IMT-Bucharest, 126A Erou Iancu Nicolae, 077190 Bucharest (Romania); Gavrila, Raluca, E-mail: raluca.gavrila@imt.ro [National Institute for R and D in Microtechnologies, IMT-Bucharest, 126A Erou Iancu Nicolae, 077190 Bucharest (Romania); Purica, Munizer, E-mail: munizer.purica@imt.ro [National Institute for R and D in Microtechnologies, IMT-Bucharest, 126A Erou Iancu Nicolae, 077190 Bucharest (Romania); Vasilica, Schiopu, E-mail: vasilica.schiopu@imt.ro [National Institute for R and D in Microtechnologies, IMT-Bucharest, 126A Erou Iancu Nicolae, 077190 Bucharest (Romania)

    2009-08-30

    This article presents the characterization of two substrates, silicon and polymer coated with gold, that are functionalized by mixed self-assembled monolayers (SAMs) in order to efficiently immobilize the anti-Escherichia coli O157:H7 polyclonal purified antibody. A biosurface functionalized by SAMs (self-assembled monolayers) technique has been developed. Immobilization of goat anti-E. coli O157:H7 antibody was performed by covalently bonding of thiolate mixed self-assembled monolayers (SAMs) realized on two substrates: polymer coated with gold and silicon coated with gold. The F(ab'){sub 2} fragments of the antibodies have been used for eliminating nonspecific bindings between the Fc portions of antibodies and the Fc receptor on cells. The properties of the monolayers and the biofilm formatted with attached antibody molecules were analyzed at each step using infrared spectroscopy (FTIR-ATR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV). In our study the gold-coated silicon substrates approach yielded the best results. These experimental results revealed the necessity to investigate each stage of the immobilization process taking into account in the same time the factors that influence the chemistry of the surface and the further interactions as well and also provide a solid basis for further studies aiming at elaborating sensitive and specific immunosensor or a microarray for the detection of E. coli O157:H7.

  19. SELFORGANIZING ASSEMBLY MODELING BASED ON RELATIONAL CONSTRAINTS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    On the research of assembly modeling of mechanical products, current CAD systems can only support the design process of componettoassembly. It is difficult to realize the design process of assemblyto component. The theory of selforganizing assembly modeling based on relational constraints is proposed, which implements the product design of assembly to component commencing with conceptual design and supporting abstract design and sepnice refinement design.

  20. Sub-2 nm Thick Fluoroalkylsilane Self-Assembled Monolayer-Coated High Voltage Spinel Crystals as Promising Cathode Materials for Lithium Ion Batteries

    Science.gov (United States)

    Zettsu, Nobuyuki; Kida, Satoru; Uchida, Shuhei; Teshima, Katsuya

    2016-01-01

    We demonstrate herein that an ultra-thin fluoroalkylsilane self-assembled monolayer coating can be used as a modifying agent at LiNi0.5Mn1.5O4−δcathode/electrolyte interfaces in 5V-class lithium-ion batteries. Bare LiNi0.5Mn1.5O4−δ cathode showed substantial capacity fading, with capacity dropping to 79% of the original capacity after 100 cycles at a rate of 1C, which was entirely due to dissolution of Mn3+ from the spinel lattice via oxidative decomposition of the organic electrolyte. Capacity retention was improved to 97% on coating ultra-thin FAS17-SAM onto the LiNi0.5Mn1.5O4 cathode surface. Such surface protection with highly ordered fluoroalkyl chains insulated the cathode from direct contact with the organic electrolyte and led to increased tolerance to HF. PMID:27553901

  1. Impact of chain length, temperature, and humidity on the growth of long alkyltrichlorosilane self-assembled monolayers.

    Science.gov (United States)

    Desbief, Simon; Patrone, Lionel; Goguenheim, Didier; Guérin, David; Vuillaume, Dominique

    2011-02-21

    In this work, we have studied the growth of self-assembled monolayers (SAMs) on silicon dioxide (SiO(2)) made of various long alkyltrichlorosilane chains (16, 18, 20, 24, and 30 carbon atoms in the alkyl chain), at several values of temperature (11 and 20 °C in most cases) and relative humidity (18 and 45% RH). Using atomic force microscopy analysis, thickness measurements by ellipsometry, and contact angle measurements, we have built a model of growth behaviour of SAMs of those molecules according to the deposition conditions and the chain length. Particularly, this work brings not only a better knowledge of the less studied growth of triacontyltrichlorosilane (C(30)H(61)SiCl(3)) SAMs but also new results on SAMs of tetracosyltrichlorosilane (C(24)H(49)SiCl(3)) that have not already been studied to our knowledge. We have shown that the SAM growth behaviour of triacontyltrichlorosilane at 20 °C and 45% RH is similar to that obtained at 11 °C and 45% RH for shorter molecules of hexadecyltrichlorosilane (C(16)H(33)SiCl(3)), octadecyltrichlorosilane (C(18)H(37)SiCl(3)), eicosyltrichlorosilane (C(20)H(41)SiCl(3)) and tetracosyltrichlorosilane (C(24)H(49)SiCl(3)). We have also observed that the monolayers grow faster at 45% than at 18% RH, and surprisingly slower at 20 °C than at 11 °C. Another important result is that the growth time constant decreases with the number of carbon atoms in the alkyl chain except for C(24)H(49)SiCl(3) at 11 °C and 18% RH, and for C(30)H(61)SiCl(3). To our knowledge, such a chain length dependence of the growth time constant has never been reported. The latter and all the other results are interpreted by adapting a diffusion limited aggregation growth model. PMID:21161113

  2. Pd-catalyzed coupling reaction on the organic monolayer: Sonogashira reaction on the silicon (1 1 1) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Qu Mengnan [College of Chemistry and Chemical Engineering, Xi' an University of Science and Technology, Xi' an 710054 (China); State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Zhang Yuan; He Jinmei [State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Cao Xiaoping [State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China)], E-mail: caoxplzu@163.com; Zhang Junyan [State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China)], E-mail: junyanzh@yahoo.com

    2008-12-30

    Iodophenyl-terminated organic monolayers were prepared by thermally induced hydrosilylation on hydrogen-terminated silicon (1 1 1) surfaces. The films were characterized by ellipsometry, contact-angle goniometry, and X-ray photoelectron spectroscopy (XPS). To modify the surface chemistry and the structure of the monolayers, the Sonogashira coupling reaction was performed on the as-prepared monolayers. The iodophenyl groups on the film surfaces reacted with 1-ethynyl-4-fluorobenzene or the 1-chloro-4-ethynylbenzene under the standard Sonogashira reaction conditions for attaching conjugated molecules via the formation of C-C bonds. It is expected that this surface coupling reaction will present a new method to modify the surface chemistry and the structure of monolayers.

  3. Diamondoid monolayers as electron emitters

    Science.gov (United States)

    Yang, Wanli; Fabbri, Jason D.; Melosh, Nicholas A.; Hussain, Zahid; Shen, Zhi-Xun

    2012-04-10

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  4. Electrochemical and surface plasmon resonance characterization of β-cyclodextrin-based self-assembled monolayers and evaluation of their inclusion complexes with glucocorticoids

    International Nuclear Information System (INIS)

    This paper describes the characterization of a self-assembled β-cyclodextrin (β-CD)-derivative monolayer (β-CD-SAM) on a gold surface and the study of their inclusion complexes with glucocorticoids. To this aim the arrangement of a self-assembled β-cyclodextrin-derivative monolayer on a gold surface was monitored in situ by means of surface plasmon resonance (SPR) spectroscopy and double-layer capacitance measurements. Film thickness and dielectric constant were evaluated for a monolayer of β-CD using one-color-approach SPR. The selectivity of the β-CD host surface was verified by using electroactive species permeable and impermeable in the β-CD cavity. The redox probe was selected according to its capacity to permeate the β-CD monolayer and its electrochemical behavior. In order to evaluate the feasibility of an inclusion complex between β-CD-SAM with some steroids such as cortisol and cortisone, voltammetric experiments in the presence of the redox probes as molecules competitive with the steroids have been performed. The formation constant of the surface host-guest by β-CD-SAM and the steroids under study was calculated.

  5. Comparison of Genotoxic Damage in Monolayer Cell and Three-Dimensional Tissue-Like Cell Assemblies

    Science.gov (United States)

    Behravesh, E.; Emami, K.; Wu, H.; Gonda, S.

    Risk assessment for the biological effects of high-energy charged particles, ranging from protons to iron nuclei, encountered in space is essential for the success of long-term space exploration. While prokaryotic and eukaryotic cell models, developed in our lab and others, have advanced our understanding of many aspects of genotoxicity, there is a need for in vitro models to assess the risk to humans from space radiation insults that are representative of the cellular interactions present in tissues and capable of quantifying genotoxic damage. Toward this overall goal, the objective of this study is to examine the effect of the localized microenvironment of cells, either cultured as 2-dimensional monolayers (2D) or 3-dimensional aggregates (3D), on the rate and type of genotoxic damage, and to examine those effects after the normal cell repair processes. Rodent transgenic cell lines containing 50-70 copies of a transgene were utilized to provide the enhanced sensitivity required to enable the identification and quantification of the types of mutational events incurred from exposure to iron charged particles which makes up a significant portion of Space radiation. Although the LacI target of this system is ~1000 bps, each copy of the entire construct is over 45 kbps. The utilization of this system allows for the quantification of mutational frequency and type for the LacI target as well as assessment of DNA damage for the entire 45 kbp construct. The samples were exposed to high-LET iron charged particles at Brookhaven National Laboratory's AGS/NSRL facilities for a total dose of 0, 0.1, 0.25, 0.5, 1.0, and 2.0 Gy and recovered after 0, 1, and 7 days of tissue culture post-irradiation. The mutational frequency was found to be greater for the 3D samples when compared to the 2D samples at all doses. In addition, there was increased mutational frequency with 7 days culture post irradiation when compared to samples analyzed immediately after exposure. DNA sequencing of

  6. Templating gold surfaces with function: a self-assembled dendritic monolayer methodology based on monodisperse polyester scaffolds.

    Science.gov (United States)

    Öberg, Kim; Ropponen, Jarmo; Kelly, Jonathan; Löwenhielm, Peter; Berglin, Mattias; Malkoch, Michael

    2013-01-01

    The antibiotic resistance developed among several pathogenic bacterial strains has spurred interest in understanding bacterial adhesion down to a molecular level. Consequently, analytical methods that rely on bioactive and multivalent sensor surfaces are sought to detect and suppress infections. To deliver functional sensor surfaces with an optimized degree of molecular packaging, we explore a library of compact and monodisperse dendritic scaffolds based on the nontoxic 2,2-bis(methylol)propionic acid (bis-MPA). A self-assembled dendritic monolayer (SADM) methodology to gold surfaces capitalizes on the design of aqueous soluble dendritic structures that bear sulfur-containing core functionalities. The nature of sulfur (either disulfide or thiol), the size of the dendritic framework (generation 1-3), the distance between the sulfur and the dendritic wedge (4 or 14 Å), and the type of functional end group (hydroxyl or mannose) were key structural elements that were identified to affect the packaging densities assembled on the surfaces. Both surface plasmon resonance (SPR) and resonance-enhanced surface impedance (RESI) experiments revealed rapid formation of homogenously covered SADMs on gold surfaces. The array of dendritic structures enabled the fabrication of functional gold surfaces displaying molecular covering densities of 0.33-2.2 molecules·nm(-2) and functional availability of 0.95-5.5 groups·nm(-2). The cell scavenging ability of these sensor surfaces for Escherichia coli MS7fim+ bacteria revealed 2.5 times enhanced recognition for G3-mannosylated surfaces when compared to G3-hydroxylated SADM surfaces. This promising methodology delivers functional gold sensor surfaces and represents a facile route for probing surface interactions between multivalently presented motifs and cells in a controlled surface setting.

  7. Application of Self-Assembled Monolayers to the Electroless Metallization of High Aspect Ratio Vias for Microelectronics

    Science.gov (United States)

    Bernasconi, R.; Molazemhosseini, A.; Cervati, M.; Armini, S.; Magagnin, L.

    2016-07-01

    All-wet electroless metallization of through-silicon vias (TSVs) with a width of 5 μm and a 1:10 aspect ratio was carried out. Immersion in a n-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPTMS) self-assembled monolayer (SAM) was used to enhance the adhesion between the metal film and substrate. Contact angle variation and atomic force microscopy were used to verify the formation of a SAM layer. A PdCl2 solution was later used to activate the silanized substrates, exploiting the affinity of the -NH3 functional group of AEAPTMS to palladium. A nickel-phosphorus-boron electroless bath was employed to deposit the first barrier layer onto silicon. The NiPB growth rate was evaluated on flat silicon wafers, while the structure of the coating obtained was investigated via glow discharge optical emission spectroscopy. Cross-sectional scanning electron microscope observations were carried out on metallized TSVs to characterize the NiPB seed, the Cu seed layer deposited with a second electroless step, and the Cu superfilling obtained with a commercial solution. Complete filling of TSV was achieved.

  8. Seed-mediated growth of gold nanoparticles using self-assembled monolayer of polystyrene microspheres as nanotemplate arrays

    Institute of Scientific and Technical Information of China (English)

    Xiang Yan-Juan; Shen Jun; Zhou Wei-Ya; Zhou Jian-Jun; Wang Chao-Ying; Wang Gang; Wu Xiao-Chun; Liu Dong-Fang; Zhang Zeng-Xing; Song Li; Zhao Xiao-Wei; Liu Li-Feng; Luo Shu-Dong; Ma Wen-Jun

    2006-01-01

    Arrays of noble metal nanoparticles show potential applications in (bio-)sensing, optical storage, surface-enhanced spectroscopy, and waveguides. For all such potential devices, controlling the size, morphology, and interparticle spacing of the nanoparticles is very important. Here, we combine seed-mediated growth with nanosphere lithography to study the controllable growth of gold nanoparticles (Au NPs), in which the self-assembly monolayer of polystyrene (PS)on a silicon surface is used to guide the modification of alkanesilanes and the subsequent adsorption of gold seeds;seed-mediated growth is applied to controlling the morphology and size of Au NPs. The size of adsorption region (determining the number of adsorbed gold seeds) is controlled by etching PS microspheres with oxygen plasma or annealing PS microspheres at the glass transition temperature. The size and morphology of the Au NPs are controlled by changing growth conditions. In such a way, we have achieved the dual control of the obtained Au NPs. Preliminary results show that this strategy holds a great promise. This approach can also be extended to a wide range of materials and substrates.

  9. Atmospheric corrosion of Cu, Zn, and Cu-Zn alloys protected by self-assembled monolayers of alkanethiols

    Science.gov (United States)

    Hosseinpour, Saman; Forslund, Mattias; Johnson, C. Magnus; Pan, Jinshan; Leygraf, Christofer

    2016-06-01

    In this article results from earlier studies have been compiled in order to compare the protection efficiency of self-assembled monolayers (SAM) of alkanethiols for copper, zinc, and copper-zinc alloys exposed to accelerated indoor atmospheric corrosion conditions. The results are based on a combination of surface spectroscopy and microscopy techniques. The protection efficiency of investigated SAMs increases with chain length which is attributed to transport hindrance of the corrosion stimulators in the atmospheric environment, water, oxygen and formic acid, towards the copper surface. The transport hindrance is selective and results in different corrosion products on bare and on protected copper. Initially the molecular structure of SAMs on copper is well ordered, but the ordering is reduced with exposure time. Octadecanethiol (ODT), the longest alkanethiol investigated, protects copper significantly better than zinc, which may be attributed to the higher bond strength of Cu-S than of Zn-S. Despite these differences, the corrosion protection efficiency of ODT for the single phase Cu20Zn brass alloy is equally efficient as for copper, but significantly less for the heterogeneous double phase Cu40Zn brass alloy.

  10. TOF-SIMS structural characterization of self-assembly monolayer of cytochrome b5 onto gold substrate

    CERN Document Server

    Aoyagi, Satoka; Boireau, Wilfrid; 10.1016/j.apsusc.2008.05.086

    2010-01-01

    Orientation and three-dimensional structure of immobilized proteins on bio-devices are very important to assure their high performance. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is able to analyze upper surface of one layer of molecules. Orientation of immobilized proteins can be evaluated based on determination of a partial structure, representing ensemble of amino acids, on the surface part. In this study, a monolayer of cytochrome b5 was reconstituted onto gold substrate and investigated by surface plasmon resonance (SPR). After freeze-drying, the resulted protein self-assembly was evaluated using TOF-SIMS with the bismuth cluster ion source, and then TOF-SIMS spectra were analyzed to select peaks specific to cytochrome b5 and identify their chemical formula and ensembles of amino acids. The results from TOF-SIMS spectra analysis were compared to the amino acid sequence of the modified cytochrome b5 and three-dimensional structure of cytochrome b5 registered in the protein data bank. Finall...

  11. A yeast glycolipid biosurfactant, mannosylerythritol lipid, shows high binding affinity towards lectins on a self-assembled monolayer system.

    Science.gov (United States)

    Konishi, Masaaki; Imura, Tomohiro; Fukuoka, Tokuma; Morita, Tomotake; Kitamoto, Dai

    2007-03-01

    Mannosylerythritol lipids (MEL), which are glycolipid biosurfactants secreted by the Pseudozyma yeasts, show not only excellent surface-active properties but also versatile biochemical actions including antitumor and cell-differentiation activities. In order to address the biochemical actions, interactions between MEL-A, the major component of MEL, and different lectins were investigated using the surface plasmon resonance spectroscopy. The monolayer of MEL-A showed high binding affinity to concanavalin A (ConA) and Maackia amurensis lectin-I (MAL-I). The observed affinity constants for ConA and MAL-I were estimated to be 9.48 +/- 1.31 x 10(6) and 3.13 +/- 0.274 x 10(6) M(-1), respectively; the value was comparable to that of Manalpha1-6(Manalpha1-3)Man, which is one of the most specific probe to ConA. Significantly, alpha-methyl-D-mannopyranoside (1 mM) exhibited no binding inhibition between MEL-A and ConA. MEL-A is thus likely to self-assemble to give a high affinity surface, where ConA binds to the hydrophilic headgroup in a different manner from that generally observed in lectin-saccharide interactions. The binding manner should be related with the biochemical actions of MEL toward mammalian cells via protein-carbohydrate interactions. PMID:17205206

  12. Surface properties of self-assembled monolayer films of tetra-substituted cobalt, iron and manganese alkylthio phthalocyanine complexes

    Energy Technology Data Exchange (ETDEWEB)

    Akinbulu, Isaac Adebayo; Khene, Samson [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.z [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)

    2010-09-30

    Self-assembled monolayer (SAM) films of iron (SAM-1), cobalt (SAM-2) and manganese (SAM-3) phthalocyanine complexes, tetra-substituted with diethylaminoethanethio at the non-peripheral positions, were formed on gold electrode in dimethylformamide (DMF). Electrochemical, impedimentary and surface properties of the SAM films were investigated. Cyclic voltammetry was used to investigate the electrochemical properties of the films. Ability of the films to inhibit common faradaic processes on bare gold surface (gold oxidation, solution redox chemistry of [Fe(H{sub 2}O){sub 6}]{sup 3+}/[Fe(H{sub 2}O){sub 6}]{sup 2+} and underpotential deposition (UDP) of copper) was investigated. Electrochemical impedance spectroscopy (EIS), using [Fe(CN){sub 6}]{sup 3-/4-} redox process as a probe, offered insights into the electrical properties of the films/electrode interfaces. Surface properties of the films were probed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films were employed for the electrocatalytic oxidation of the pesticide, carbofuran. Electrocatalysis was evidenced from enhanced current signal and less positive oxidation potential of the pesticide on each film, relative to that observed on the bare gold electrode. Mechanism of electrocatalytic oxidation of the pesticide was studied using rotating disc electrode voltammetry.

  13. Self-assembled monolayers of alendronate on Ti6Al4V alloy surfaces enhance osteogenesis in mesenchymal stem cells

    Science.gov (United States)

    Rojo, Luis; Gharibi, Borzo; McLister, Robert; Meenan, Brian J.; Deb, Sanjukta

    2016-07-01

    Phosphonates have emerged as an alternative for functionalization of titanium surfaces by the formation of homogeneous self-assembled monolayers (SAMs) via Ti-O-P linkages. This study presents results from an investigation of the modification of Ti6Al4V alloy by chemisorption of osseoinductive alendronate using a simple, effective and clean methodology. The modified surfaces showed a tailored topography and surface chemistry as determined by SEM microscopy and RAMAN spectroscopy. X-ray photoelectron spectroscopy revealed that an effective mode of bonding is created between the metal oxide surface and the phosphate residue of alendronate, leading to formation of homogenous drug distribution along the surface. In-vitro studies showed that alendronate SAMs induce differentiation of hMSC to a bone cell phenotype and promote bone formation on modified surfaces. Here we show that this novel method for the preparation of functional coatings on titanium-based medical devices provides osseoinductive bioactive molecules to promote enhanced integration at the site of implantation.

  14. First Observation of Charge Reduction and Desorption Kinetics of Multiply Protonated Peptides Soft Landed onto Self-Assembled Monolayer Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hadjar, Omar; Futrell, Jean H.; Laskin, Julia

    2007-12-13

    The kinetics of charge reduction and desorption of different species produced by soft-landing of mass-selected ions was studied using in situ secondary ion mass spectrometry (SIMS) in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). The improved SIMS capability described in this work utilizes an in-line 8 keV Cs+ ion gun and allows us to interrogate the surface both during the ion deposition and after the deposition is terminated. As a model system doubly protonated ions of Gramicidin S were deposited onto a fluorinated self-assembled monolayer (FSAM) surface. Our results demonstrate for the first time that various peptide-related peaks in FT-ICR SIMS spectra follow very different kinetics. We obtained unique kinetics signatures for doubly protonated, singly protonated and neutral peptides retained on the surface and followed their evolution as a function of time. The experimental results are in excellent agreement with a kinetic model that takes into account charge reduction and thermal desorption of different species from the surface.

  15. Nano-tribological characteristics of TiO2 films on 3-mercaptopropyl trimethoxysilane sulfonated self-assembled monolayer

    Indian Academy of Sciences (India)

    J Li; X H Sheng

    2009-10-01

    Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was used to prepare twodimensional self-assembled monolayer (SAM) on silicon substrate. The terminal –SH group was in situ oxidized to –SO3H group to endow the film with good chemisorption ability. Then TiO2 thin films were deposited on the oxidized MPTS–SAM to form composite thin films, making use of the chemisorption ability of the –SO3H group. Atomic force microscope (AFM) and contact angle measurements were used to characterize TiO2 films. Adhesive force and friction force of TiO2 thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. Results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. In order to study the effect of capillary force, tests were performed in various relative humidities. Results showed that the adhesive force of silicon substrate increases with relative humidities and the adhesive force of TiO2 thin films only increases slightly with relative humidity. Research showed that surfaces with more hydrophobic property revealed the lower adhesive and friction forces.

  16. Surface plasmon Raman scattering studies of liquid crystal anchoring on liquid-crystal-based self-assembled monolayers.

    Science.gov (United States)

    Critchley, Kevin; Cheadle, Edward M; Zhang, Hao-Li; Baldwin, Kurt J; Liu, Quanying; Cheng, Yaling; Fukushima, Hitoshi; Tamaki, Takashi; Batchelder, David N; Bushby, Richard J; Evans, Stephen D

    2009-11-26

    We studied the anchoring of 6CB on a series of self-assembled monolayers (SAMs) with a functional group that mimics that of the nematic liquid crystal (LC). The SAMs were first characterized by wetting, Fourier-transform infrared spectroscopy, and surface potential measurements. We found that, in two of these SAMs, the end group dipoles were oriented close to the normal of the surface and that these promoted homeotropic anchoring. In the case of the other SAM, the dipole was oriented parallel to the surface, and planar anchoring was obtained. Raman scattering by adsorbates on thin metal films is enhanced by the electromagnetic fields of surface plasmon polaritons (SPPs). Despite the inherent polarization of SPPs, there have been few reports in which SPP Raman scattering has been used to study molecular orientation. We have developed optical instrumentation to provide efficient excitation and collection of SPP Raman scattered light using attenuated total reflection geometry. The Kretschmann prism coupling configuration was used to excite SPPs on thin (500 A) gold films with adsorbed SAMs of alkanethiols in contact with thin films (50 microm) of the nematic liquid crystal 4'-hexylbiphenyl-4-carbonitrile (6CB, Merck). The anchoring and orientational wetting of the LC 6CB at the interface with omega-functionalized SAMs was studied using this arrangement. In agreement with the results of previous studies, a high-energy surface (-COOH) was found to promote planar anchoring, whereas a low-energy surface (-CF(3)) was found to induce homeotropic anchoring. PMID:19921953

  17. Molecular dynamics simulations of water confined between matched pairs of hydrophobic and hydrophilic self-assembled monolayers.

    Energy Technology Data Exchange (ETDEWEB)

    Chandross, Michael Evan; Grest, Gary Stephen; Lane, J. Matthew D.; Lorenz, Christian Douglas (King' s College London, London, UK); Stevens, Mark Jackson

    2008-12-01

    We have conducted a molecular dynamics (MD) simulation study of water confined between methyl-terminated and carboxyl-terminated alkylsilane self-assembled monolayers (SAMs) on amorphous silica substrates. In doing so, we have investigated the dynamic and structural behavior of the water molecules when compressed to loads ranging from 20 to 950 MPa for two different amounts of water (27 and 58 water molecules/nm{sup 2}). Within the studied range of loads, we observe that no water molecules penetrate the hydrophobic region of the carboxyl-terminated SAMs. However, we observe that at loads larger than 150 MPa water molecules penetrate the methyl-terminated SAMs and form hydrogen-bonded chains that connect to the bulk water. The diffusion coefficient of the water molecules decreases as the water film becomes thinner and pressure increases. When compared to bulk diffusion coefficients of water molecules at the various loads, we found that the diffusion coefficients for the systems with 27 water molecules/nm{sup 2} are reduced by a factor of 20 at low loads and by a factor of 40 at high loads, while the diffusion coefficients for the systems with 58 water molecules/nm{sup 2} are reduced by a factor of 25 at all loads.

  18. Near-field photochemical and radiation-induced chemical fabrication of nanopatterns of a self-assembled silane monolayer

    Directory of Open Access Journals (Sweden)

    Ulrich C. Fischer

    2014-09-01

    Full Text Available A general concept for parallel near-field photochemical and radiation-induced chemical processes for the fabrication of nanopatterns of a self-assembled monolayer (SAM of (3-aminopropyltriethoxysilane (APTES is explored with three different processes: 1 a near-field photochemical process by photochemical bleaching of a monomolecular layer of dye molecules chemically bound to an APTES SAM, 2 a chemical process induced by oxygen plasma etching as well as 3 a combined near-field UV-photochemical and ozone-induced chemical process, which is applied directly to an APTES SAM. All approaches employ a sandwich configuration of the surface-supported SAM, and a lithographic mask in form of gold nanostructures fabricated through colloidal sphere lithography (CL, which is either exposed to visible light, oxygen plasma or an UV–ozone atmosphere. The gold mask has the function to inhibit the photochemical reactions by highly localized near-field interactions between metal mask and SAM and to inhibit the radiation-induced chemical reactions by casting a highly localized shadow. The removal of the gold mask reveals the SAM nanopattern.

  19. Effects of Self-Assembled Monolayers on Solid-State CdS Quantum Dot Sensitized Solar Cells

    KAUST Repository

    Ardalan, Pendar

    2011-02-22

    Quantum dot sensitized solar cells (QDSSCs) are of interest for solar energy conversion because of their tunable band gap and promise of stable, low-cost performance. We have investigated the effects of self-assembled monolayers (SAMs) with phosphonic acid headgroups on the bonding and performance of cadmium sulfide (CdS) solid-state QDSSCs. CdS quantum dots ∼2 to ∼6 nm in diameter were grown on SAM-passivated planar or nanostructured TiO 2 surfaces by successive ionic layer adsorption and reaction (SILAR), and photovoltaic devices were fabricated with spiro-OMeTAD as the solid-state hole conductor. X-ray photoelectron spectroscopy, Auger electron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, transmission electron microscopy, water contact angle measurements, ellipsometry, and electrical measurements were employed to characterize the materials and the resulting device performance. The data indicate that the nature of the SAM tailgroup does not significantly affect the uptake of CdS quantum dots on TiO2 nor their optical properties, but the presence of the SAM does have a significant effect on the photovoltaic device performance. Interestingly, we observe up to ∼3 times higher power conversion efficiencies in devices with a SAM compared to those without the SAM. © 2011 American Chemical Society.

  20. Effect of fluorocarbon self-assembled monolayer films on sidewall adhesion and friction of surface micromachines with impacting and sliding contact interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, H.; Komvopoulos, K. [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)

    2013-06-14

    A self-assembled monolayer film consisting of fluoro-octyltrichlorosilane (FOTS) was vapor-phase deposited on Si(100) substrates and polycrystalline silicon (polysilicon) surface micromachines. The hydrophobic behavior and structural composition of the FOTS film deposited on Si(100) were investigated by goniometry and X-ray photoelectron spectroscopy, respectively. The effects of contact pressure, relative humidity, temperature, and impact/sliding cycles on the adhesive and friction behavior of uncoated and FOTS-coated polysilicon micromachines (referred to as the Si and FOTS/Si micromachines, respectively) were investigated under controlled loading and environmental conditions. FOTS/Si micromachines demonstrated much lower and stable adhesion than Si micromachines due to the highly hydrophobic and conformal FOTS film. Contrary to Si micromachines, sidewall adhesion of FOTS/Si micromachines demonstrated a weak dependence on relative humidity, temperature, and impact cycles. In addition, FOTS/Si micromachines showed low and stable adhesion and low static friction for significantly more sliding cycles than Si micromachines. The adhesive and static friction characteristics of Si and FOTS/Si micromachines are interpreted in the context of physicochemical surface changes, resulting in the increase of the real area of contact and a hydrophobic-to-hydrophilic transition of the surface chemical characteristics caused by nanoscale surface smoothening and the removal of the organic residue (Si micromachines) or the FOTS film (FOTS/Si micromachines) during repetitive impact and oscillatory sliding of the sidewall surfaces.

  1. Towards the hybrid organic semiconductor fet (hosfet) : electrical and electrochemical characterization of functionalized and unfunctionalized, covalently bound organic monolayers on silicon surfaces

    OpenAIRE

    Faber, Erik Jouwert

    2006-01-01

    Since their introduction in 1993 the class of covalently bound organic monolayers on oxide free silicon surfaces have found their way to multiple application fields such as passivation layers in solar cells, masking layers in lithographic processing, insulating films in hybrid moleculesilicon electronics, and memory devices. Furthermore, these monolayers can easily be functionalized with a large variety of receptor groups or sensing moieties, thereby forming a new promising material for incor...

  2. Study on surface acid-base property of carboxylic acid-terminated self-assembled monolayers by cyclic voltammetry and electro-chemical impedance spectroscopy

    Institute of Scientific and Technical Information of China (English)

    罗立强; 程志亮; 杨秀荣; 汪尔康

    2000-01-01

    Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the surface acid-base property of carboxylic acid-terminated self-assembled monolayers (SAMs). A carboxylic acid-terminated thiol, such as thioctic acid (1,2-dithiolane-3-pentanoic acid), was self-assembled on gold electrodes. Electron transfer between the bulk solution and the SAM modified electrode was studied at different pH using Fe(CN)63 as a probe. The surface pK. of thioctic acid was determined by cyclic voltammetry and electrochemical impedance spectroscopy to be 5.6±0.1 and 5.8±0.1, respectively. The method is compared with other methods of monolayer pK.measurement.

  3. Citrate-reduced silver hydrosol modified with omega-mercaptoalkanoic acids self-assembled monolayers as a substrate for surface-enhanced resonance Raman scattering. A study with cytochrome c

    NARCIS (Netherlands)

    Bonifacio, A.; Sneppen, van der L.; Gooijer, C.; Zwan, van der G.

    2004-01-01

    A new citrate-reduced silver hydrosol coated with omega-mercaptoalkanoic acids (mercaptopropionic and mercaptoundecanoic acids) self-assembled monolayers was prepared and characterized with surface-enhanced Raman spectroscopy. The structure and the quality of the coating monolayers are discussed and

  4. Hydrogen-plasma-induced magnetocrystalline anisotropy ordering in self-assembled magnetic nanoparticle monolayers

    Directory of Open Access Journals (Sweden)

    Alexander Weddemann

    2013-03-01

    Full Text Available Self-assembled two-dimensional arrays of either 14 nm hcp-Co or 6 nm ε-Co particle components were treated by hydrogen plasma for various exposure times. A change of hysteretic sample behavior depending on the treatment duration is reported, which can be divided in two time scales: oxygen reduction increases the particle magnetization during the first 20 min, which is followed by an alteration of the magnetic response shape. The latter depends on the respective particle species. Based on the Landau–Lifshitz equations for a discrete set of magnetic moments, we propose a model that relates the change of the hysteresis loops to a dipole-driven ordering of the magnetocrystalline easy axes within the particle plane due to the high spatial aspect ratio of the system.

  5. Investigation of Bovine Serum Albumin (BSA) Attachment onto Self-Assembled Monolayers (SAMs) Using Combinatorial Quartz Crystal Microbalance with Dissipation (QCM-D) and Spectroscopic Ellipsometry (SE)

    OpenAIRE

    Phan, Hanh T. M.; Bartelt-Hunt, Shannon; Keith B Rodenhausen; Schubert, Mathias; Bartz, Jason C.

    2015-01-01

    Understanding protein adsorption kinetics to surfaces is of importance for various environmental and biomedical applications. Adsorption of bovine serum albumin to various self-assembled monolayer surfaces including neutral and charged hydrophilic and hydrophobic surfaces was investigated using in-situ combinatorial quartz crystal microbalance with dissipation and spectroscopic ellipsometry. Adsorption of bovine serum albumin varied as a function of surface properties, bovine serum albumin co...

  6. Self-assembly of monolayers of aromatic carboxylic acid molecules on silver and copper modified gold surfaces at the liquid-solid interface

    OpenAIRE

    Aitchison, Hannah

    2015-01-01

    Exploiting coordination bonding of aromatic carboxylic acids at metal surfaces, this thesis explores new directions in the design and application of self-assembled monolayers (SAMs). The SAMs are investigated using a multi-technique approach comprising of a complementary combination of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, the X-ray standing wave technique (XSW) was used to ...

  7. Laterally Mobile, Functionalized Self-Assembled Monolayers at the Fluorous-Aqueous Interface in a Plug-Based Microfluidic System: Characterization and Testing with Membrane Protein Crystallization

    OpenAIRE

    Kreutz, Jason E.; Li, Liang; Roach, L. Spencer; Hatakeyama, Takuji; Ismagilov, Rustem F.

    2009-01-01

    This paper describes a method to generate functionalizable, mobile self-assembled monolayers (SAMs) in plug-based microfluidics. Control of interfaces is advancing studies of biological interfaces, heterogeneous reactions, and nanotechnology. SAMs have been useful for such studies, but they are not laterally mobile. Lipid-based methods, though mobile, are not easily amenable to setting up the hundreds of experiments necessary for crystallization screening. Here we demonstrate a method, comple...

  8. Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Dominik; Schafer, Tobias; Schulz, Philip; Jung, Sebastian; Rittich, Julia; Mokros, Daniel; Segger, Ingolf; Maercks, Franziska; Effertz, Christian; Mazzarello, Riccardo; Wuttig, Matthias

    2016-09-06

    Tuning the work function of the electrode is one of the crucial steps to improve charge extraction in organic electronic devices. Here, we show that N,N-dialkyl dithiocarbamates (DTC) can be effectively employed to produce low work function noble metal electrodes. Work functions between 3.1 and 3.5 eV are observed for all metals investigated (Cu, Ag, and Au). Ultraviolet photoemission spectroscopy (UPS) reveals a maximum decrease in work function by 2.1 eV as compared to the bare metal surface. Electronic structure calculations elucidate how the complex interplay between intrinsic dipoles and dipoles induced by bond formation generates such large work function shifts. Subsequently, we quantify the improvement in contact resistance of organic thin film transistor devices with DTC coated source and drain electrodes. These findings demonstrate that DTC molecules can be employed as universal surface modifiers to produce stable electrodes for electron injection in high performance hybrid organic optoelectronics.

  9. Experimental Investigation Of Microbially Induced Corrosion Of Test Samples And Effect Of Self-assembled Hydrophobic Monolayers. Exposure Of Test Samples To Continuous Microbial Cultures, Chemical Analysis, And Biochemical Studies

    CERN Document Server

    Laurinavichius, K S

    1998-01-01

    Experimental Investigation Of Microbially Induced Corrosion Of Test Samples And Effect Of Self-assembled Hydrophobic Monolayers. Exposure Of Test Samples To Continuous Microbial Cultures, Chemical Analysis, And Biochemical Studies

  10. Controllable growth and field-effect property of monolayer to multilayer microstripes of an organic semiconductor

    OpenAIRE

    Li, Liqiang; Gao, Peng; Schuermann, Klaus C.; Ostendorp, Stefan; Wang, Wenchong; Du, Chuan; Lei, Yong; Fuchs, Harald; DE COLA, Luisa; Müllen, Klaus; Chi, Lifeng

    2011-01-01

    The controllable growth of partially aligned monolayer to multilayer micrometer stripes was demonstrated by adjusting the pulling speed in a dip-coating process. The number of molecular layers decreases with the increasing pulling speed. A lower pulling speed yields mixed multilayers (3−9 monolayers). It is noteworthy that pure monolayer and bilayer microstripes over large areas can be obtained at high pulling speeds. The stripe morphology strongly depends on the pulling speed or the number o...

  11. Direct imaging by atomic force microscopy of surface-localized self-assembled monolayers on a cuprate superconductor and surface X-ray scattering analysis of analogous monolayers on the surface of water

    Energy Technology Data Exchange (ETDEWEB)

    Schougaard, Steen B. [Departement de Chimie, Universite du Quebec a Montreal, Case postale 8888, Succ. Centre-ville, Montreal, Quebec, H3C 3P8 (Canada); Texas Materials Institute, Center for Nano and Molecular Science and Engineering, Department Chemistry and Biochemistry, University of Texas at Austin, Austin, TX, 78722 (United States)], E-mail: schougaard.steen@uqam.ca; Reitzel, Niels; Bjornholm, Thomas [Nano-Science Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark); Kjaer, Kristian [Max-Planck Institute of Colloids and Interfaces, Am Muehlenberg, D-14476 Potsdam (Germany); Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark); Jensen, Torben R. [Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C (Denmark); Shmakova, Olga E.; Colorado, Ramon; Lee, T. Randall [Department of Chemistry, University of Houston, Houston, TX 77204-5003 (United States); Choi, J.-H.; Markert, John T.; Derro, David; Lozanne, Alex de [Department of Physics, University of Texas at Austin, Austin, TX 78712-1081 (United States); McDevitt, John T. [Texas Materials Institute, Center for Nano and Molecular Science and Engineering, Department Chemistry and Biochemistry, University of Texas at Austin, Austin, TX, 78722 (United States)

    2007-09-14

    A self-assembled monolayer of CF{sub 3}(CF{sub 2}){sub 3}(CH{sub 2}){sub 11}NH{sub 2} atop the (001) surface of the high-temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7-x} was imaged by atomic force microscopy (AFM). The AFM images provide direct 2D-structural evidence for the epitaxial 5.5 A square {radical}2 x {radical}2R45{sup o} unit cell previously predicted for alkyl amines by molecular modeling [J.E. Ritchie, C.A. Wells, J.-P. Zhou, J. Zhao, J.T. McDevitt, C.R. Ankrum, L. Jean, D.R. Kanis, J. Am. Chem. Soc. 120 (1998) 2733]. Additionally, the 3D structure of an analogous Langmuir monolayer of CF{sub 3}(CF{sub 2}){sub 9}(CH{sub 2}){sub 11}NH{sub 2} on water was studied by grazing-incidence X-ray diffraction and specular X-ray reflectivity. Structural differences and similarities between the water-supported and superconductor-localized monolayers are discussed.

  12. Controlling coordination reactions and assembly on a Cu(111) supported boron nitride monolayer.

    Science.gov (United States)

    Urgel, José I; Schwarz, Martin; Garnica, Manuela; Stassen, Daphné; Bonifazi, Davide; Ecija, David; Barth, Johannes V; Auwärter, Willi

    2015-02-25

    We report the formation of a metal-organic network on a BN/Cu(111) template by codeposition of carbonitrile-functionalized porphyrin derivatives (2H-TPCN) with Co atoms in an ultrahigh vacuum environment. The resulting metallo-supramolecular structure explored by scanning tunneling microscopy and spectroscopy features a distinct 4-fold coordination motif. Furthermore, we demonstrate an in situ metalation of the tetrapyrrole macrocycles with deposited Co atoms yielding Co-TPCN directly on the BN sheet. Our results provide perspectives for the formation of coordination networks on BN and related systems featuring structural, electronic, and magnetic properties unachievable on metallic supports. PMID:25689599

  13. Synthesis of a Two-Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface.

    Science.gov (United States)

    Dai, Wenyang; Shao, Feng; Szczerbiński, Jacek; McCaffrey, Ryan; Zenobi, Renato; Jin, Yinghua; Schlüter, A Dieter; Zhang, Wei

    2016-01-01

    A two-dimensional covalent organic monolayer was synthesized from simple aromatic triamine and dialdehyde building blocks by dynamic imine chemistry at the air/water interface (Langmuir-Blodgett method). The obtained monolayer was characterized by optical microscopy, scanning electron microscopy, and atomic force microscopy, which unambiguously confirmed the formation of a large (millimeter range), unimolecularly thin aromatic polyimine sheet. The imine-linked chemical structure of the obtained monolayer was characterized by tip-enhanced Raman spectroscopy, and the peak assignment was supported by spectra simulated by density functional theory. Given the modular nature and broad substrate scope of imine formation, the work reported herein opens up many new possibilities for the synthesis of customizable 2D polymers and systematic studies of their structure-property relationships.

  14. Nanodimentional Aggregates In Organic Monolayers Studied With Atomic Force Microscopy (AFM) And Fluorescence Lifetime Imaging Microscopy (FLIM)

    Science.gov (United States)

    Ivanov, George R.; Burov, Julian

    2007-04-01

    Organic monolayers from a fluorescently labeled phospholipid (DPPE-NBD) were deposited on solid supports under special conditions that form stable nanometer wide bilayers cylinders that protrude from the monolayer. This molecule was frequently used in sensor applications due to its sensitivity to environment changes. The proposed configuration should provide both fast response times (ultra thin film) and increased sensitivity (greatly increased surface area). AFM can clearly distinguish between the different phases. The height difference between the solid-expanded and the liquid-expanded phase was measured to be 1.4 nm while the bilayer thickness was 5.6 nm. The solid domains show a 20 % decrease in fluorescence lifetime in comparison to the monolayer as measured by FLIM. This difference in lifetimes is explained in the model of fluorescence self quenching in the solid phase due to the molecules being closer to each other.

  15. Dynamics of Energy Transfer and Soft-Landing in Collisions of Protonated Dialanine with Perfluorinated Self-Assembled Monolayer Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Pratihar, Subha; Kohale, Swapnil C.; Bhakta, Dhruv G.; Laskin, Julia; Hase, William L.

    2014-11-21

    Chemical dynamics simulations are reported which provide atomistic details of collisions of protonated dialanine, ala2-H+, with a perfluorinateted octanethiolate self-assembled monolayer (F-SAM ) surface. The simulations are performed at collisions energy Ei of 5.0, 13.5, 22.5, 30.00, and 70 eV, and incident angles 0o 0 (normal) and grazing 45o. Excellent agreement with experiment (J. Am. Chem. Soc. 2000, 122, 9703-9714) is found for both the average fraction and distribution of the collision energy transferred to the ala2-H+ internal degrees of freedom. The dominant pathway for this energy transfer is to ala2-H+ vibration, but for Ei = 5.0 eV ~20% of the energy transfer is to ala2-H+ rotation. Energy transfer to ala2-H+ rotation decreases with increase in Ei and becomes negligible at high Ei. Three types of collisions are observed in the simulations: i.e. those for which ala2-H+ (1) directly scatters off the F-SAM surface; (2) sticks/physisorbs on//in the surface, but desorbs within the 10 ps numerical integration of the simulations; and (3) remains trapped (i.e. soft-landed) on/in the surface when the simulations are terminated. Penetration of the F-SAM by ala2-H+ is important for the latter two types of events. The trapped trajectories are expected to have relatively long residence times on the surface, since a previous molecular dynamics simulation (J. Phys. Chem. B 2014, 118, 5577-5588) shows that thermally accommodated ala2-H+ ions have an binding energy with the F-SAM surface of at least ~15 kcal/mol.

  16. Effect of chain length on the adhesion behaviour of n-alkanethiol self-assembled monolayers on Au(1 1 1): An atomic force microscopy study

    Indian Academy of Sciences (India)

    S Subramanian; S Sampath

    2005-10-01

    The effect of chain length on the adhesion behaviour of n-alkanethiols CH3(CH2) SH, where = 5, 6, 7, 9, 10, 11, 14 and 15 has been followed by carrying out pull-off force measurement using atomic force microscopy (AFM). The self-assembled monolayers on Au(111) surface has been characterized by reflection absorption infra-red spectroscopy (RAIRS) and contact mode AFM. It is observed that the work of adhesion is independent of thiol chain length though the standard deviation is high for short chain length thiol-based monolayers. This may be attributed to the relatively more deformable nature of the short chain thiol films due to their heterogeneity in the monolayer structure than the long chain ones. This, in turn, increases the contact area/volume between the AFM tip and the monolayer, and hence the force of adhesion. However, in the presence of water, the force of adhesion is lower than that observed in air reflecting the effects of capillary forces/polar components associated with the surface energy.

  17. Silk: molecular organization and control of assembly.

    Science.gov (United States)

    Valluzzi, Regina; Winkler, Stefan; Wilson, Donna; Kaplan, David L

    2002-02-28

    The interface between the science and engineering of biology and materials is an area of growing interest. One of the goals of this field is to utilize biological synthesis and processing of polymers as a route to gain insight into topics such as molecular recognition, self-assembly and the formation of materials with well-defined architectures. The biological processes involved in polymer synthesis and assembly can offer important information on fundamental interactions involved in the formation of complex material architectures, as well as practical knowledge into new and important materials related to biomaterial uses and tissue engineering needs. Classic approaches in biology, including genetic engineering, controlled microbial physiology and enzymatic synthesis, are prototypical methods used to control polymer structure and chemistry, including stereoselectivity and regioselectivity, to degrees unattainable using traditional synthetic chemistry. This type of control can lead to detailed and systematic studies of the formation of the structural hierarchy in materials and the subsequent biological responses to these materials.

  18. Formation of organic monolayers on hydrogen-terminated silicon surfaces via silicon-carbon bond: effect of terminal groups on stability

    International Nuclear Information System (INIS)

    Full text: Functionalization of hydrogen-terminated silicon surfaces with stable and dense aryl-terminated alkyl self-assembled monolayers (SAMs) provides opportunities for the development of low cost organic field effect transistors. In this paper we present results for one such σ-π SAMs, 3-phenylpropyl (C6H5(CH2)3-) SAMs on porous silicon, and compare its stability with octyl (CH3(CH2)7-) SAMs on Si(100). The SAMs were prepared using the Grignard reagent method and characterized using X-ray photoelectron and FT-infrared spectroscopies and contact angle measurements Our results show the 3-phenylpropyl SAMs are not as susceptible to oxidation as the octyl SAMs, and we attribute the increased stability in the former to be due to its more dense structure arising from the π-π stacking of the phenyl rings. Copyright (2005) Australian Institute of Physics

  19. Molecular self-assembly approaches for supramolecular electronic and organic electronic devices

    Science.gov (United States)

    Yip, Hin-Lap

    Molecular self-assembly represents an efficient bottom-up strategy to generate structurally well-defined aggregates of semiconducting pi-conjugated materials. The capability of tuning the chemical structures, intermolecular interactions and nanostructures through molecular engineering and novel materials processing renders it possible to tailor a large number of unprecedented properties such as charge transport, energy transfer and light harvesting. This approach does not only benefit traditional electronic devices based on bulk materials, but also generate a new research area so called "supramolecular electronics" in which electronic devices are built up with individual supramolecular nanostructures with size in the sub-hundred nanometers range. My work combined molecular self-assembly together with several novel materials processing techniques to control the nucleation and growth of organic semiconducting nanostructures from different type of pi-conjugated materials. By tailoring the interactions between the molecules using hydrogen bonds and pi-pi stacking, semiconducting nanoplatelets and nanowires with tunable sizes can be fabricated in solution. These supramolecular nanostructures were further patterned and aligned on solid substrates through printing and chemical templating methods. The capability to control the different hierarchies of organization on surface provides an important platform to study their structural-induced electronic properties. In addition to using molecular self-assembly to create different organic nanostructures, functional self-assembled monolayer (SAM) formed by spontaneous chemisorption on surfaces was used to tune the interfacial property in organic solar cells. Devices showed dramatically improved performance when appropriate SAMs were applied to optimize the contact property for efficiency charge collection.

  20. Assembly of cells and vesicles for organ engineering

    Directory of Open Access Journals (Sweden)

    Tetsushi Taguchi

    2011-01-01

    Full Text Available The development of materials and technologies for the assembly of cells and/or vesicles is a key for the next generation of tissue engineering. Since the introduction of the tissue engineering concept in 1993, various types of scaffolds have been developed for the regeneration of connective tissues in vitro and in vivo. Cartilage, bone and skin have been successfully regenerated in vitro, and these regenerated tissues have been applied clinically. However, organs such as the liver and pancreas constitute numerous cell types, contain small amounts of extracellular matrix, and are highly vascularized. Therefore, organ engineering will require the assembly of cells and/or vesicles. In particular, adhesion between cells/vesicles will be required for regeneration of organs in vitro. This review introduces and discusses the key technologies and materials for the assembly of cells/vesicles for organ regeneration.

  1. Assembly of cells and vesicles for organ engineering

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, Tetsushi, E-mail: taguchi.tetsushi@nims.go.jp [Biofunctional Materials Unit, Nano-Bio Field, Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2011-12-15

    The development of materials and technologies for the assembly of cells and/or vesicles is a key for the next generation of tissue engineering. Since the introduction of the tissue engineering concept in 1993, various types of scaffolds have been developed for the regeneration of connective tissues in vitro and in vivo. Cartilage, bone and skin have been successfully regenerated in vitro, and these regenerated tissues have been applied clinically. However, organs such as the liver and pancreas constitute numerous cell types, contain small amounts of extracellular matrix, and are highly vascularized. Therefore, organ engineering will require the assembly of cells and/or vesicles. In particular, adhesion between cells/vesicles will be required for regeneration of organs in vitro. This review introduces and discusses the key technologies and materials for the assembly of cells/vesicles for organ regeneration. (topical review)

  2. Assembly of cells and vesicles for organ engineering

    Science.gov (United States)

    Taguchi, Tetsushi

    2011-12-01

    The development of materials and technologies for the assembly of cells and/or vesicles is a key for the next generation of tissue engineering. Since the introduction of the tissue engineering concept in 1993, various types of scaffolds have been developed for the regeneration of connective tissues in vitro and in vivo. Cartilage, bone and skin have been successfully regenerated in vitro, and these regenerated tissues have been applied clinically. However, organs such as the liver and pancreas constitute numerous cell types, contain small amounts of extracellular matrix, and are highly vascularized. Therefore, organ engineering will require the assembly of cells and/or vesicles. In particular, adhesion between cells/vesicles will be required for regeneration of organs in vitro. This review introduces and discusses the key technologies and materials for the assembly of cells/vesicles for organ regeneration.

  3. Preparation and electrochemical and photoelectrochemical properties of a covalently self-assembled monolayer film based on a bis-terpyridyl ruthenium(II) complex

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Hao; Dai, Yong-Cheng; Chen, Xi; Huang, Qiu-Ying; Wang, Ke-Zhi, E-mail: kzwang@bnu.edu.cn

    2013-09-02

    A bis-terpyridyl Ru(II) complex of Ru{sup II}(IPTP){sub 2}(ClO{sub 4}){sub 2} (in which IPTP = 4′-(4-(imidazol-1-yl)phenyl)-2,2′:6′,2″-terpyridine) has been synthesized using a microwave irradiation method, and characterized by elementary analysis, and proton nuclear magnetic resonance, and mass spectroscopy. A Ru{sup II}(IPTP){sub 2}(ClO{sub 4}){sub 2} based covalently self-assembled monolayer film was prepared and characterized by UV–Vis spectroscopy and cyclic voltammetry. The cyclic voltammograms demonstrated that Ru{sup II}(IPTP){sub 2}(ClO{sub 4}){sub 2} assembled in the film was redox active with surface-confined characteristics. The photoelectrochemical properties and electron-transfer mechanism of the film were studied. It was found that the Ru{sup II}(IPTP){sub 2}(ClO{sub 4}){sub 2}/ITO electrode film exhibited a large cathodic photocurrent density of 2.72 μA/cm{sup 2} while irradiated with polychromatic light (325 nm < λ < 730 nm) at an applied potential of − 0.4 V versus saturated calomel electrode. The photocurrent action spectrum was in agreement with the metal-to-ligand charge-transfer (MLCT) absorption band of Ru{sup II}(IPTP){sub 2}(ClO{sub 4}){sub 2}, indicating that the photocurrent was generated based on MLCT excitation of the Ru{sup II}(IPTP){sub 2}(ClO{sub 4}){sub 2} in the film. An incident monochromatic photon-to-current conversion efficiency of this monolayer film was calculated to be 1.8% at 500 nm. - Highlights: • Ru complex covalently self-assembled monolayer film. • Reversible electrochemical activity. • Large cathodic photocurrent density of 2.72 μA/cm{sup 2}. • Photoelectric conversion efficiency of 1.8%.

  4. Towards the hybrid organic semiconductor fet (hosfet) : electrical and electrochemical characterization of functionalized and unfunctionalized, covalently bound organic monolayers on silicon surfaces

    NARCIS (Netherlands)

    Faber, Erik Jouwert

    2006-01-01

    Since their introduction in 1993 the class of covalently bound organic monolayers on oxide free silicon surfaces have found their way to multiple application fields such as passivation layers in solar cells, masking layers in lithographic processing, insulating films in hybrid moleculesilicon electr

  5. Simultaneous Determination of Dopamine and Uric Acid at 2-Amino-5-mercapto-[1, 3, 4]triazole Self-assembled Monolayers Gold Electrode

    Institute of Scientific and Technical Information of China (English)

    Chuan Yin LIU; Li Zhu YANG; Feng SONG; Ling Yan JIANG; Guang Han LU

    2005-01-01

    A newly synthesized reagent 2-amino-5-mercapto-[ 1, 3, 4]triazole (MATZ) has been used to fabricate self-assembled monolayers (SAMs) on gold electrode for the first time. The SAMs electrode was characterized by electrochemical methods and scanning electronic microscopy (SEM),the SAMs electrode can be used to determinate dopamine (DA) and uric acid (UA) simultaneously with a detection limit of 8×10-7 mol/L for DA and 1×10-6 mol/L for UA respectively. The SAMs can also be used to detect the contents of DA and UA in synthetic urine sample with satisfactory results.

  6. Molecular organization of antifungal antibiotic amphotericin B in lipid monolayers studied by means of Fluorescence Lifetime Imaging Microscopy

    OpenAIRE

    Gruszecki, Wieslaw I.; Luchowski, Rafał; Gagoś, Mariusz; Arczewska, Marta; Sarkar, Pabak; Hereć, Monika; Myśliwa-Kurdziel, Beata; Strzałka, Kazimierz; Gryczynski, Ignacy; Gryczynski, Zygmunt

    2009-01-01

    Abstract Amphotericin B (AmB) is a life-saving polyene antibiotic used to treat deep-seated mycotic infections. Both the mode of therapeutic action as well as toxic side effects are directly dependent on molecular organization of the drug. Binding of AmB to lipid monolayers formed with dipalmitoylphosphatidylcholine, pure and containing 40 mol% cholesterol or ergosterol, the sterols of human and fungi respectively, has been examined by means of Fluorescence Lifetime Imaging Microsc...

  7. Dopant passivation and work function tuning through attachment of heterogeneous organic monolayers on silicon in ultrahigh vacuum

    Science.gov (United States)

    Cooper, Ashley J.; Keyvanfar, Kian; Deberardinis, Albert; Pu, Lin; Bean, John C.

    2011-05-01

    Electronic structures of silicon-organic interfaces were studied by the scanning Kelvin probe technique. These surfaces were fabricated by covalent bonding of a range of phenylacetylene-based molecules ( p-X-C 6H 4C tbnd CH, where X = CF 3, OCH 3, and H) onto a hydrogen-terminated silicon surface. Organic molecules were bound to the surface under high vacuum conditions by ultraviolet light-induced hydrosilylation. Changes in the electronic structure due to electron-donating ability and dipole moment were analyzed under dark and illuminated conditions. The origin of the silicon band bending was tested to separate the effects of molecular monolayers and unintended dopant passivation. In addition, heterogeneous monolayers were grown by controllably diluting the incoming vapor stream with acetylene during growth. The measured work functions follow a trend linked to dipole moment that can be further tuned by molecular dilution. These results suggest a way to use heterogeneous organic monolayers to tune the electron affinity of silicon and directly alter channel modulation in small semiconductor devices.

  8. Lubrication of Individual Microcontacts by a Self-Assembled Alkyl Phosphonic Acid Monolayer on α-Al2O3(0001).

    Science.gov (United States)

    Paul, Jonas; Meltzer, Christian; Braunschweig, Björn; Peukert, Wolfgang

    2016-08-23

    We report on the tribological behavior of a self-assembled alkyl phosphonic acid monolayer on the microscale using the colloidal probe technique. Friction-load data and adhesion forces were measured with borosilicate glass particles on uncoated and octadecylphosphonic acid (ODPA) coated α-Al2O3(0001) surfaces. A significant decrease in friction force was observed after surface coating, while the adhesion force was only moderately reduced. We assume the lubrication effect of the ODPA self-assembled monolayer (SAM) to be close to the maximum obtainable of alkyl phosphonic acids in the studied system due to the high molecular order which was confirmed by vibrational sum-frequency generation. At small loads, a nonlinear dependence of friction force to load was maintained after surface coating. However, a shift from a contact behavior well described by the DMT model toward the JKR model occurred that is possibly related to the altered elastic properties of the coated surface. With increasing load, a linear friction-load behavior was observed on the coated samples. Molecular plowing and adhesive interactions were identified as responsible mechanisms. In all friction experiments, we could not detect any wear neither of the colloidal probes nor at the surfaces of uncoated and coated samples. This proves the high wear resistivity of the studied ODPA SAM. PMID:27478898

  9. Preparation and optimization of a bienzymic biosensor based on self-assembled monolayer modified gold electrode for alcohol and glucose detection.

    Science.gov (United States)

    Asav, Engin; Akyilmaz, Erol

    2010-01-15

    The aim of this project was to develop a bienzymic biosensor, which was based on co-immobilization of alcohol oxidase and glucose oxidase on the same electrode by formation of self-assembled monolayer (SAM) for selective determination of ethanol and glucose. In the biosensor construction the enzymes and the mediator, tetrathiafulvalene (TTF), were immobilized with cross-linking agents glutaraldehyde and cysteamine by forming a self-assembled monolayer (SAM) on a gold disc electrode. Amounts of ethanol and glucose were amperometrically detected by monitoring current values at reduction potential of TTF(+), 0.1V. Decreases in biosensor responses were linearly related to glucose concentrations between 0.1 and 1.0 mM and ethanol concentrations between 1.0 and 10 mM. Limits of detection of the biosensor for ethanol and glucose were calculated to be 0.75 and 0.03 mM, respectively. In the optimization studies of the biosensor some parameters such as optimum pH, optimum temperature, enzyme amount, effect of TTF concentration and duration of SAM formation were investigated. PMID:19819124

  10. Self-assembled monolayer of ammonium pyrrolidine dithiocarbamate on copper detected using electrochemical methods, surface enhanced Raman scattering and quantum chemistry calculations

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Q.-Q., E-mail: liaoqq1971@yahoo.com.cn [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy-Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Yue, Z.-W.; Yang, D. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy-Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Wang, Z.-H. [Department of Chemistry, Tongji University, Shanghai 200092 (China); Li, Z.-H. [Department of Chemistry, Fudan University, Shanghai 200433 (China); Ge, H.-H. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy-Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Li, Y.-J. [Department of Chemistry, Tongji University, Shanghai 200092 (China)

    2011-07-29

    Ammonium pyrrolidine dithiocarbamate (APDTC) monolayer was self-assembled on fresh copper surface obtained after oxidation-reduction cycle treatment in 0.1 mol L{sup -1} potassium chloride solution at ambient temperature. The APDTC self-assembled monolayer (SAM) on copper surface was investigated by surface enhanced Raman scattering spectroscopy and the results show that APDTC SAM is chemisorbed on copper surface by its sulfur atoms with perpendicular orientation. The optimum immersing period for SAM formation is 4 h at 0.01 mol L{sup -1} concentration of APDTC. The impedance results indicate that APDTC SAM has good corrosion inhibition effects for copper in 0.5 mol L{sup -1} hydrochloric acid solution and its maximum inhibition efficiency could reach 95%. Quantum chemical calculations show that APDTC has relatively small {Delta}E between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and large negative charge in its two sulfur atoms, which facilitate formation of an insulating Cu/APDTC film on copper surface.

  11. Functionalisation of bolaamphiphiles with mononuclear bis(2,2 '-bipyridyl)ruthenium(II) complexes for application in self assembled monolayers

    NARCIS (Netherlands)

    Killeen, JS; Browne, WR; Skupin, M; Fuhrhop, JH; Vos, JG

    2003-01-01

    A novel ruthenium(II) polypyridyl complex connected covalently to a bolaamphiphile, containing amide linkages to provide rigidity via hydrogen bonding in the monolayer, has been prepared. The ruthenium( II) complexes of this ligand and of the intermediates in the synthesis were prepared by modi. cat

  12. Gradients of Rectification: Tuning Molecular Electronic Devices by the Controlled Use of Different-Sized Diluents in Heterogeneous Self-Assembled Monolayers.

    Science.gov (United States)

    Kong, Gyu Don; Kim, Miso; Cho, Soo Jin; Yoon, Hyo Jae

    2016-08-22

    Molecular electronics has received significant attention in the last decades. To hone performance of devices, eliminating structural defects in molecular components inside devices is usually needed. We herein demonstrate this problem can be turned into a strength for modulating the performance of devices. We show the systematic dilution of a monolayer of an organic rectifier (2,2'-bipyridine-terminated n-undecanethiolate) with electronically inactive diluents (n-alkanethiolates of different lengths), gives remarkable gradients of rectification. Rectification is finely tunable in a range of approximately two orders of magnitude, retaining its polarity. Trends of rectification against the length of the diluent indicate the gradient of rectification is extremely sensitive to the molecular structure of the diluent. Further studies reveal that noncovalent intermolecular interactions within monolayers likely leads to gradients of structural defect and rectification. PMID:27443577

  13. Gradients of Rectification: Tuning Molecular Electronic Devices by the Controlled Use of Different-Sized Diluents in Heterogeneous Self-Assembled Monolayers.

    Science.gov (United States)

    Kong, Gyu Don; Kim, Miso; Cho, Soo Jin; Yoon, Hyo Jae

    2016-08-22

    Molecular electronics has received significant attention in the last decades. To hone performance of devices, eliminating structural defects in molecular components inside devices is usually needed. We herein demonstrate this problem can be turned into a strength for modulating the performance of devices. We show the systematic dilution of a monolayer of an organic rectifier (2,2'-bipyridine-terminated n-undecanethiolate) with electronically inactive diluents (n-alkanethiolates of different lengths), gives remarkable gradients of rectification. Rectification is finely tunable in a range of approximately two orders of magnitude, retaining its polarity. Trends of rectification against the length of the diluent indicate the gradient of rectification is extremely sensitive to the molecular structure of the diluent. Further studies reveal that noncovalent intermolecular interactions within monolayers likely leads to gradients of structural defect and rectification.

  14. Si-C Linked Organic Monolayers on Crystalline Silicon Surfaces as Alternative Gate Insulators

    NARCIS (Netherlands)

    Faber, Erik J.; Smet, de Louis C.P.M.; Olthuis, Wouter; Zuilhof, Han; Sudhölter, Ernst J.R.; Bergveld, Piet; Berg, van den Albert

    2005-01-01

    Herein, the influence of silicon surface modification via Si-CnH2n+1 (n=10,12,16,22) monolayer-based devices on p-type (100) and n-type (100) silicon is studied by forming MIS (metal–insulator–semiconductor) diodes using a mercury probe. From current density–voltage (J–V) and capacitance–voltage (C–

  15. Si-C linked organic monolayers on crystalline silicon surfaces as alternative gate insulators

    NARCIS (Netherlands)

    Faber, E.J.; Smet, de L.C.P.M.; Olthuis, W.; Zuilhof, H.; Sudhölter, E.J.R.; Bergveld, P.; Berg, van den A.

    2005-01-01

    Herein, the influence of silicon surface modification via SiCnH2n+1 (n=10,12,16,22) monolayer-based devices on p-type 100 and n-type 100 silicon is studied by forming MIS (metal-insulator-semiconductor) diodes using a mercury probe. From current density-voltage (J-V) and capacitance-voltage (C-V) me

  16. Effects of ambient conditions on adsorbed surfactant and polymer monolayers

    International Nuclear Information System (INIS)

    The physical properties of surfactant-coated and polyelectrolyte-coated surfaces in adhesive contact in air have been studied using the surface forces apparatus technique. Various physisorbed monolayers with different head groups and chains (or polymer segments) were prepared both by adsorption form solution (self-assembly) and by the Langmuir-Blodgett deposition technique. The results show that many monolayer properties depend on the atmospheric conditions such as the relative humidity or presence of organic vapors and that these properties can further change when two monolayer-coated surfaces are brought into contact. These properties include monolayer composition and structure, thickness and compressibility, fluidity and phase state (i.e., whether solid, gel, or liquid), and the adhesion between two monolayer-coated surfaces. In addition, we find that both out-of-plane and in-plane (lateral) phase transitions can be induced in certain adsorbed monolayers when they are subjected to a compressive stress. The results provide new insights into molecular ordering and dynamics in physisorbed monolayers and how monolayers are affected when they are exposed to vapors or when they interact with other surfaces. 18 refs., 13 figs., 4 tabs

  17. Influence of molecular ordering on electrical and friction properties of omega-(trans-4-stilbene)alkylthiol self-assembled monolayers on Au (111)

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Yabing; Liu, Xiaosong; Hendriksen, B.L.M.; Navarro, V.; Park, Jeong Y.; Ratera, Imma; Klopp, J.M.; Edder, C.; Himpsel, Franz J.; Frechet, J.M.J.; Haller, Eugene E.; Salmeron, Miquel

    2010-04-21

    The electrical and friction properties of omega-(trans-4-stilbene)alkylthiol self-assembled monolayers (SAMs) on Au(111) were investigated using atomic force microscopy (AFM) and near edge x-ray absorption fine structure spectroscopy (NEXAFS). The sample surface was uniformly covered with a molecular film consisting of very small grains. Well-ordered and flat monolayer islands were formed after the sample was heated in nitrogen at 120 oC for 1 h. While lattice resolved AFM images revealed a crystalline phase in the islands, the area between islands showed no order. The islands exhibit substantial reduction (50percent) in friction, supporting the existence of good ordering. NEXAFS measurements revealed an average upright molecular orientation in the film, both before and after heating, with a narrower tilt-angle distribution for the heated fim. Conductance-AFM measurements revealed a two orders of magnitude higher conductivity on the ordered islands than on the disordered phase. We propose that the conductance enhancement is a result of a better pi-pi stacking between the trans-stilbene molecular units as a result of improved ordering in islands.

  18. Highly Sensitive Aluminium(III) Ion Sensor Based on a Self-assembled Monolayer on a Gold Nanoparticles Modified Screen-printed Carbon Electrode.

    Science.gov (United States)

    See, Wong Pooi; Heng, Lee Yook; Nathan, Sheila

    2015-01-01

    A new approach for the development of a highly sensitive aluminium(III) ion sensor via the preconcentration of aluminium(III) ion with a self-assembled monolayer on a gold nanoparticles modified screen-printed carbon electrode and current mediation by potassium ferricyanide redox behavior during aluminium(III) ion binding has been attempted. A monolayer of mercaptosuccinic acid served as an effective complexation ligand for the preconcentration of trace aluminium; this led to an enhancement of aluminium(III) ion capture and thus improved the sensitivity of the sensor with a detection limit of down to the ppb level. Under the optimum experimental conditions, the sensor exhibited a wide linear dynamic range from 0.041 to 12.4 μM. The lower detection limit of the developed sensor was 0.037 μM (8.90 ppb) using a 10 min preconcentration time. The sensor showed excellent selectivity towards aluminium(III) ion over other interference ions.

  19. Use of self assembled monolayers at variable coverage to control interface bonding in a model study of interfacial fracture: Pure shear loading

    Energy Technology Data Exchange (ETDEWEB)

    KENT,MICHAEL S.; YIM,HYUN; MATHESON,AARON J.; COGDILL,C.; NELSON,GERALD C.; REEDY JR.,EARL DAVID

    2000-05-16

    The relationships between fundamental interfacial interactions, energy dissipation mechanisms, and fracture stress or fracture toughness in a glassy thermoset/inorganic solid joint are not well understood. This subject is addressed with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The proportions of physical and chemical interactions at the interface, and the in-plane distribution, are varied using self-assembling monolayers of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but forms only a very weak interface with the methylated tails of the ODTS monolayer. The fracture stress is examined as a function of ODTS coverage in the napkin-ring (pure shear) loading geometry. The relationship between fracture stress and ODTS coverage is catastrophic, with a large change in fracture stress occurring over a narrow range of ODTS coverage. This transition in fracture stress does not correspond to a wetting transition of the epoxy. Rather, the transition in fracture stress corresponds to the onset of deformation in the epoxy, or the transition from brittle to ductile fracture. The authors postulate that the transition in fracture stress occurs when the local stress that the interface can support becomes comparable to the yield stress of the epoxy. The fracture results are independent of whether the ODTS deposition occurs by island growth (T{sub dep} = 10 C) or by homogeneous growth (T{sub dep} = 24 C).

  20. Monolayers of Poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) Microparticles Formed by Controlled Self-Assembly with Potential Application as Protein-Repelling Substrates.

    Science.gov (United States)

    Wasilewska, Monika; Adamczyk, Zbigniew; Basinska, Teresa; Gosecka, Monika; Lupa, Dawid

    2016-09-20

    The kinetics of the self-assembly of poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) microparticles on poly(allylamine hydrochloride)-derivatized silicon/silica substrate was determined by direct AFM imaging and streaming potential (SP) measurements. The kinetic runs acquired under diffusion-controlled transport were quantitatively interpreted in terms of the extended random sequential adsorption (RSA) model. This allowed confirmation of a core/shell morphology of the microparticles. The polyglycidol-rich shell of thickness equal to 25 nm exhibited a fuzzy structure that enabled penetration of particles into each other resulting in high coverage inaccessible for ordinary microparticles. The SP measurements interpreted by using the 3D electrokinetic model confirmed this microparticle structure. Additionally, the acid-base characteristics of the microparticle monolayers were determined for a broad pH range. By using the streaming potential measurements, human serum albumin (HSA) adsorption on the microparticle monolayers was investigated under in situ conditions. It was confirmed that the protein adsorption was considerably lower than for the reference case of bare silicon/silica substrate under the same physicochemical conditions. This effect was attributed to the presence of the shell diminishing the protein/microparticle physical interactions.

  1. Etching of Crystalline ZnO Surfaces upon Phosphonic Acid Adsorption: Guidelines for the Realization of Well-Engineered Functional Self-Assembled Monolayers.

    Science.gov (United States)

    Ostapenko, Alexandra; Klöffel, Tobias; Eußner, Jens; Harms, Klaus; Dehnen, Stefanie; Meyer, Bernd; Witte, Gregor

    2016-06-01

    Functionalization of metal oxides by means of covalently bound self-assembled monolayers (SAMs) offers a tailoring of surface electronic properties such as their work function and, in combination with its large charge carrier mobility, renders ZnO a promising conductive oxide for use as transparent electrode material in optoelectronic devices. In this study, we show that the formation of phosphonic acid-anchored SAMs on ZnO competes with an unwanted chemical side reaction, leading to the formation of surface precipitates and severe surface damage at prolonged immersion times of several days. Combining atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal desorption spectroscopy (TDS), the stability and structure of the aggregates formed upon immersion of ZnO single crystal surfaces of different orientations [(0001̅), (0001), and (101̅0)] in phenylphosphonic acid (PPA) solution were studied. By intentionally increasing the immersion time to more than 1 week, large crystalline precipitates are formed, which are identified as zinc phosphonate. Moreover, the energetics and the reaction pathway of this transformation have been evaluated using density functional theory (DFT), showing that zinc phosphonate is thermodynamically more favorable than phosphonic acid SAMs on ZnO. Precipitation is also found for phosphonic acids with fluorinated aromatic backbones, while less precipitation occurs upon formation of SAMs with phenylphosphinic anchoring units. By contrast, no precipitates are formed when PPA monolayer films are prepared by sublimation under vacuum conditions, yielding smooth surfaces without noticeable etching. PMID:27159837

  2. Monolayers of Poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) Microparticles Formed by Controlled Self-Assembly with Potential Application as Protein-Repelling Substrates.

    Science.gov (United States)

    Wasilewska, Monika; Adamczyk, Zbigniew; Basinska, Teresa; Gosecka, Monika; Lupa, Dawid

    2016-09-20

    The kinetics of the self-assembly of poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) microparticles on poly(allylamine hydrochloride)-derivatized silicon/silica substrate was determined by direct AFM imaging and streaming potential (SP) measurements. The kinetic runs acquired under diffusion-controlled transport were quantitatively interpreted in terms of the extended random sequential adsorption (RSA) model. This allowed confirmation of a core/shell morphology of the microparticles. The polyglycidol-rich shell of thickness equal to 25 nm exhibited a fuzzy structure that enabled penetration of particles into each other resulting in high coverage inaccessible for ordinary microparticles. The SP measurements interpreted by using the 3D electrokinetic model confirmed this microparticle structure. Additionally, the acid-base characteristics of the microparticle monolayers were determined for a broad pH range. By using the streaming potential measurements, human serum albumin (HSA) adsorption on the microparticle monolayers was investigated under in situ conditions. It was confirmed that the protein adsorption was considerably lower than for the reference case of bare silicon/silica substrate under the same physicochemical conditions. This effect was attributed to the presence of the shell diminishing the protein/microparticle physical interactions. PMID:27552337

  3. Selective anion sensing by a tris-amide CTV derivative: 1H NMR titration, self-assembled monolayers, and impedance spectroscopy.

    Science.gov (United States)

    Zhang, Sheng; Echegoyen, Luis

    2005-02-16

    A hydrogen-bond forming tris(amide) receptor based on cyclotriveratrylene (CTV) was prepared. Self-assembled monolayers (SAMs) of the receptor were formed on gold surfaces. Desorption experiments show a surface coverage of 2.26 x 10(-10) mol/cm(2). (1)H NMR and UV measurements confirm that the receptor exhibits the highest affinity for acetate ions among the anions studied. Electrochemical impedance was used to investigate anion sensing by the SAMs and proved to be an efficient and convenient technique for detecting anions in aqueous solutions. Upon binding acetate anions, the monolayer-modified gold electrodes show a drastic increase of the R(ct) values when Fe(CN)(6)(3-/4-) is used as the redox probe. When the probe was changed to a positively charged one, Ru(NH3)(6)(3+/2+), the R(ct) values decreased monotonically as the acetate concentration was increased, thus confirming the accumulation of negative surface charge upon anion binding. H(2)PO(4-) shows some interference when sensing AcO-. Other monovalent anions such as Cl-, Br-, NO3(-) and HSO4(-) do not bind to the CTV receptor either in solution or on the surfaces. PMID:15701037

  4. Kinetic studies of attachment and re-orientation of octyltriethoxysilane for formation of self-assembled monolayer on a silica substrate.

    Science.gov (United States)

    Hasan, Abshar; Pandey, Lalit M

    2016-11-01

    The present study deals with kinetic studies of the chemical modification for synthesizing a hydrophobic silica surface. Surface silanization (modification) via formation of Self-Assembled Monolayer (SAM) using a short chain triethoxyoctylsilane (TEOS) was carried out under inert atmosphere at room temperature. Fourier transmission infrared (FTIR) spectroscopy, water contact angle (WCA) and atomic force microscopy (AFM) were employed to investigate surface modification. FTIR analysis in the range from 900-1200cm(-1) and 2850-3000cm(-1) confirmed surface modification and re-orientation of the attached molecules. Kinetic studies of TEOS SAM formation were fitted by Exponential Association function. Kinetic fitting of FTIR data in the range from 900-1200cm(-1) revealed a very fast attachment of TEOS molecules resulting in total surface coverage within 16min whereas re-orientation rate was slow and continued till 512min. Further, change in orientation from lying-down to standing-up state was supported by contact angle analysis. AFM images initially showed small islands of ~20nm, which in-fill with time indicating formation of a smooth monolayer. Our findings indicate that formation of octyl SAM is fast process and completes within 8.5h in contrary to reported 24h in conventional SAM formation protocols. The kinetic fitting data can be explored to design a nanopatterned surface for a specific application. PMID:27524037

  5. Effects of interface modification with self-assembled monolayers on the photovoltaic performance of CdS quantum dots sensitized solar cells

    International Nuclear Information System (INIS)

    We employ 3-PPA, BPA and APPA as self-assembled monolayers (SAMs), who owns the same phosphonic acid headgroup but different tail group, to modify the surface of ZnO nanorods. Their effects on the photovoltaic performance of quantum dots sensitized soar cells are systematically investigated. The results indicate that the deposition of SAMs not only passivates the surface defects of ZnO nanorods, but also tunes their surface work function to adjust the band alignment of solar cells. In particular, the 3-PPA modification exhibits the best passivation effect and makes the surface work function of ZnO decreases by 1.04 eV to realize a better band alignment due to its electron-withdrawing tailgroup, which results in an enhancement in photovoltaic conversion efficiency of solar cells

  6. Enhancement of electron injection into a light-emitting polymer from an aluminum oxide cathode modified by a self-assembled monolayer

    Science.gov (United States)

    Vaynzof, Yana; Dennes, T. Joseph; Schwartz, Jeffrey; Kahn, Antoine

    2008-09-01

    A self-assembled monolayer (SAM) of octylphosphonate was deposited on an AlOx electrode using the tethering by aggregation and growth (T-BAG) procedure. Ultraviolet photoemission spectroscopy (UPS) measurements showed a decrease in the substrate work function from 3.8to3.3eV. Poly[9,9'-dioctylfluorene-co-bis-N ,N'-(4-butylphenyl)-diphenylamine] (TFB) films spin coated on the bare and the SAM-modified oxide surfaces were investigated by UPS. A shift in molecular levels, corresponding to a reduction in the electron injection barrier, was observed for the SAM-modified electrode. This barrier lowering was confirmed by current-voltage measurements showing a corresponding increase in electron current through the TFB/SAM/AlOx device.

  7. Water-COOH Composite Structure with Enhanced Hydrophobicity Formed by Water Molecules Embedded into Carboxyl-Terminated Self-Assembled Monolayers.

    Science.gov (United States)

    Guo, Pan; Tu, Yusong; Yang, Jinrong; Wang, Chunlei; Sheng, Nan; Fang, Haiping

    2015-10-30

    By combining molecular dynamics simulations and quantum mechanics calculations, we show the formation of a composite structure composed of embedded water molecules and the COOH matrix on carboxyl-terminated self-assembled monolayers (COOH SAMs) with appropriate packing densities. This composite structure with an integrated hydrogen bond network inside reduces the hydrogen bonds with the water above. This explains the seeming contradiction on the stability of the surface water on COOH SAMs observed in experiments. The existence of the composite structure at appropriate packing densities results in the two-step distribution of contact angles of water droplets on COOH SAMs, around 0° and 35°, which compares favorably to the experimental measurements of contact angles collected from forty research articles over the past 25 years. These findings provide a molecular-level understanding of water on surfaces (including surfaces on biomolecules) with hydrophilic functional groups.

  8. Improved microstructure and performance of PbS thin films via in-situ thermal decomposition of lead xanthate precursors using self-assembling monolayer

    Science.gov (United States)

    Wang, Jingni; Yao, Kai; Jia, Zhenrong; Wang, Xiaofeng; Li, Fan

    2016-09-01

    Microstructure control is critical to achieve thin film-based devices with high performance. The surface properties of the substrates on which thin films grow are expected to greatly influence the morphology and the resulting performance. Generally, homogeneous, dense and highly crystalline films are required. However, "island" like structures are usually obtained mainly due to the non-uniform nucleation. In this article, the self-assembling monolayer (SAM) strategy was applied to efficiently realize the uniform nucleation and modulate the microstructure of lead sulfide (PbS) thin films, which were fabricated on the modified ZnO-coated substrates with 3-mercaptopropionic acid (MPA) SAM via in-situ thermal decomposition of lead xanthate precursors. The results showed that PbS thin films with reduced pin-holes and uniform crystalline grains were fabricated with the incorporation of MPA SAM. More importantly, PbS thin films modulated by MPA showed better photoelectric response.

  9. Monolayers assembled from a glycolipid biosurfactant from Pseudozyma (Candida) antarctica serve as a high-affinity ligand system for immunoglobulin G and M.

    Science.gov (United States)

    Imura, Tomohiro; Ito, Seya; Azumi, Reiko; Yanagishita, Hiroshi; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

    2007-06-01

    A carbohydrate ligand system has been developed which is composed of self-assembled monolayers (SAMs) of mannosylerythritol lipid-A (MEL-A) from Pseudozyma antarctica, serving for human immunoglobulin G and M (HIgG and HIgM). The estimated binding constants from surface plasmon resonance (SPR) measurement were Ka = 9.4 x 10(6) M(-1) for HIgG and 5.4 x 10(6) M(-1) for HIgM, respectively. The binding site was not in the Fc region of immunoglobulin but in the Fab region. Large amounts of HIgG and HIgM bound to MEL-A SAMs were directly observed by atomic force microscopy. PMID:17342348

  10. Water-COOH Composite Structure with Enhanced Hydrophobicity Formed by Water Molecules Embedded into Carboxyl-Terminated Self-Assembled Monolayers.

    Science.gov (United States)

    Guo, Pan; Tu, Yusong; Yang, Jinrong; Wang, Chunlei; Sheng, Nan; Fang, Haiping

    2015-10-30

    By combining molecular dynamics simulations and quantum mechanics calculations, we show the formation of a composite structure composed of embedded water molecules and the COOH matrix on carboxyl-terminated self-assembled monolayers (COOH SAMs) with appropriate packing densities. This composite structure with an integrated hydrogen bond network inside reduces the hydrogen bonds with the water above. This explains the seeming contradiction on the stability of the surface water on COOH SAMs observed in experiments. The existence of the composite structure at appropriate packing densities results in the two-step distribution of contact angles of water droplets on COOH SAMs, around 0° and 35°, which compares favorably to the experimental measurements of contact angles collected from forty research articles over the past 25 years. These findings provide a molecular-level understanding of water on surfaces (including surfaces on biomolecules) with hydrophilic functional groups. PMID:26565476

  11. Interfacial engineering of self-assembled monolayer modified semi-roll-to-roll planar heterojunction perovskite solar cells on flexible substrates

    DEFF Research Database (Denmark)

    Gu, Zhuowei; Zuo, Lijian; Larsen-Olsen, Thue Trofod;

    2015-01-01

    The morphologies of the perovskite (e.g. CH3NH3PbI3) layer are demonstrated to be critically important for highly efficient perovskite solar cells. This work applies 3-aminopropanoic acid as a self-assembled monolayer (C3-SAM) on a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT......:PSS) hole transport layer (HTL) to modify the crystallinity and coverage of the CH3NH3PbI3 Cl-x(x) film, resulting in a much smoother perovskite surface morphology together with a PCE increase from 9.7% to 11.6%. Since all fabrication steps of these inverted structure devices are carried out under low...

  12. Role of Self-Assembled Monolayers on Improved Electrical Stability of Amorphous In-Ga-Zn-O Thin-Film Transistors

    CERN Document Server

    Du, Xiaosong; Motley, Joshua R; Stickle, William F; Bluhm, Hendrik; Herman, Gregory S

    2014-01-01

    Self-assembled monolayers (SAMs) have been used to improve both the positive and negative bias-stress stability of amorphous indium gallium zinc oxide (IGZO) bottom gate thin film transistors (TFTs). N-hexylphosphonic acid (HPA) and fluorinated hexylphosphonic acid (FPA) SAMs adsorbed on IGZO back channel surfaces were shown to significantly reduce bias stress turn-on voltage shifts compared to IGZO back channel surfaces with no SAMs. FPA was found to have a lower surface energy and lower packing density than HPA, as well as lower bias stress turn-on voltage shifts. The improved stability of IGZO TFTs with SAMs can be primarily attributed to a reduction in molecular adsorption of contaminants on the IGZO back channel surface and minimal trapping states present with phosphonic acid binding to the IGZO surface.

  13. Evaluating the surface density and heterogeneity of a dithiobis (succinimidylpropionate) self-assembled monolayer on gold and its coupling with DNA embedded within a matrix

    International Nuclear Information System (INIS)

    The homogeneity of a self-assembled monolayer (SAM) on a surface is an important parameter which affects the ability of a SAM to fulfill its intended function. As an example, SAMs formed from octanethiols can form an impermeable surface, while SAMs based on a bifunctional coupling reagent can form a surface with uniform reactivity. Exposure of gold nanoparticles or gold surfaces to solutions of dithiobis (succinimidylpropionate) (DSP) gives rise to a surface which can react with DNA. Atomic force microscopy, UV-vis and gel electrophoresis experiments indicate that a self-assembled monolayer of DSP on gold nanoparticles can attenuate aggregation, inhibit the 'lying down' of covalently-bound single-stranded (ss) DNA and promote more efficient hybridization. The determination of the point of aggregation after reacting DSP with colloidal gold yields 2.86 x 10-10 mol/cm2 or 42% of the value determined from molecular modeling. Cyclic voltammetry experiments validate that DSP on a gold quartz crystal (6.3 x 10-10 mol/cm2) forms a fairly uniform SAM that is within 94% of maximum coverage when compared with results obtained from molecular modeling (6.67 x 10-10 mol/cm2). Surface plasmon resonance experiments indicate that the reaction of a DSP coated gold surface with (ss) DNA yields 2.4 x 10-12 mol/cm2 or reaction with about 1% of the available surface area. Subsequent reactions of the DSP surface with the filler, n-boc-1,4-phenylene diamine (n-boc), yield a total surface coverage of 1.8 x 10-11 mol/cm2. The surrounded (ss) DNA yields a surface with 97% hybridization efficiency toward the complement.

  14. Moiré pattern induced by the electronic coupling between 1-octanol self-assembled monolayers and graphite surface

    OpenAIRE

    Silly, Fabien

    2012-01-01

    Two-dimensional self-assembly of 1-octanol molecules on a graphite surface is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. STM images reveal that this molecule self-assembles into a compact hydrogen-bonded herringbone nanoarchitecture. Molecules are preferentially arranged in a head-to-head and tail-to-tail fashion. A Moir'e pattern appears in the STM images when the 1-octanol layer is covering the graphite surface. The large Moir'e stripes are perpend...

  15. DL-valine Self-Assembled Monolayers on Copper Electrode%自组装DL-缬氨酸铜电极的电化学研究

    Institute of Scientific and Technical Information of China (English)

    文泽东

    2011-01-01

    The self-assembly method was used to process DL-valine monolayer modified copper electrode. Compact degree of the DL-Valine film on copper electrode at different times was investigated by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (AC).The results show that spatial conformation of DL-valine in the copper surface has changed. According to the experiment,when the assembly time is 8 h, the packing density is best.%利用自组装的方法制得了DL-缬氨酸修饰铜电极,采用循环伏安法(CV)和交流阻抗谱(AC)探讨了在铜电极上DL-缬氨酸自组装膜在不同组装时间的致密程度.结果表明,DL-缬氨酸在铜表面的空间构象发生变化.并由实验可知,组装时间为8 h时,膜的致密性最好.

  16. Self-assembled monolayers of radical molecules physisorbed on HOPG(0 0 0 1) substrate studied by scanning tunnelling microscopy and electron paramagnetic resonance techniques

    International Nuclear Information System (INIS)

    In this paper, we present a combined STM and EPR study on the adsorption and self-organization of monolayers formed from 2-(14-Carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy (16DS) and 4',4'-Dimethylspiro(5α-cholestane-3,2'-oxazolidin)-3'-yloxy (CSL) adsorbed on a highly oriented pyrolitic graphite HOPG(0 0 0 1) substrate. Both 16DS and CSL molecules are persistent free radicals containing a paramagnetic doxyl group. The STM measurements of 16DS on HOPG(0 0 0 1) were performed at the liquid-solid interface while the studies of CSL on HOPG(0 0 0 1) were carried out under ultrahigh vacuum conditions. It was found that the 16DS molecules on the HOPG(0 0 0 1) surface form a highly-ordered monolayer with a domain structure. The high-resolution STM images show structural details of 16DS molecules on HOPG(0 0 0 1) revealing the paramagnetic doxyl group. In contrast, CSL molecules on HOPG(0 0 0 1) form a well-ordered monolayer without domain structure. The EPR results indicate that both compounds deposited on HOPG(0 0 0 1) substrate are not reduced and retain their paramagnetic character. We believe that the molecular systems described can be used in single spin detection experiments using an electron spin noise-scanning tunnelling microscopy (ESN-STM) technique. In particular, the possibility of obtaining contrast spin signals from the paramagnetic and diamagnetic parts of molecules increases the significance of our results.

  17. Perforated monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Regen, S.L.

    1992-12-01

    Goal of this research program is to create ultrathin organic membranes that possess uniform and adjustable pores ( < 7[angstrom] diameter). Such membranes are expected to possess high permeation selectivity (permselectivity) and high permeability, and to provide the basis for energy-efficient methods of molecular separation. Work carried out has demonstrated feasibility of using perforated monolayer''-based composites as molecular sieve membranes. Specifically, composite membranes derived from Langmuir-Blodgett multilayers of the calix[6]arene-based surfactant shown below plus poly[l-(trimethylsilyl)-l-propyne] (PTMSP) were found to exhibit sieving behavior towards He, N[sub 2] and SF[sub 6]. Results of derivative studies that have also been completed are also described in this report.

  18. Enhanced sensitivity of self-assembled-monolayer-based SPR immunosensor for detection of benzaldehyde using a single-step multi-sandwich immunoassay.

    Science.gov (United States)

    Gobi, K Vengatajalabathy; Matsumoto, Kiyoshi; Toko, Kiyoshi; Ikezaki, Hidekazu; Miura, Norio

    2007-04-01

    This paper describes the fabrication and sensing characteristics of a self-assembled monolayer (SAM)-based surface plasmon resonance (SPR) immunosensor for detection of benzaldehyde (BZ). The functional sensing surface was fabricated by the immobilization of a benzaldehyde-ovalbumin conjugate (BZ-OVA) on Au-thiolate SAMs containing carboxyl end groups. Covalent binding of BZ-OVA on SAM was found to be dependent on the composition of the base SAM, and it is improved very much with the use of a mixed monolayer strategy. Based on SPR angle measurements, the functional sensor surface is established as a compact monolayer of BZ-OVA bound on the mixed SAM. The BZ-OVA-bound sensor surface undergoes immunoaffinity binding with anti-benzaldehyde antibody (BZ-Ab) selectively. An indirect inhibition immunoassay principle has been applied, in which analyte benzaldehyde solution was incubated with an optimal concentration of BZ-Ab for 5 min and injected over the sensor chip. Analyte benzaldehyde undergoes immunoreaction with BZ-Ab and makes it inactive for binding to BZ-OVA on the sensor chip. As a result, the SPR angle response decreases with an increase in the concentration of benzaldehyde. The fabricated immunosensor demonstrates a low detection limit (LDL) of 50 ppt (pg mL(-1)) with a response time of 5 min. Antibodies bound to the sensor chip during an immunoassay could be detached by a brief exposure to acidic pepsin. With this surface regeneration, reusability of the same sensor chip for as many as 30 determination cycles has been established. Sensitivity has been enhanced further with the application of an additional single-step multi-sandwich immunoassay step, in which the BZ-Ab bound to the sensor chip was treated with a mixture of biotin-labeled secondary antibody, streptavidin and biotin-bovine serum albumin (Bio-BSA) conjugate. With this approach, the SPR sensor signal increased by ca. 12 times and the low detection limit improved to 5 ppt with a total response

  19. Metal dependent motif transition in a self-assembled monolayer of bipyridine derivatives via coordination: An STM study

    Science.gov (United States)

    Wang, Yi; Yuan, Qunhui; Xu, Hongbo; Zhu, Xuefeng; Gan, Wei

    2016-07-01

    Low-dimensional molecular motifs with diversity developed via the on-surface chemistry are attracting growing interest for their potential in advanced nanofabrication. In this work, scanning tunneling microscopy was employed to investigate the in situ and ex situ metal coordinations between 4,4'-ditetradecyl-2,2'-bipyridine (bpy) and Zn(ii) or Cu(ii) ions at a highly oriented pyrolytic graphite (HOPG)/1-phenyloctane interface under ambient conditions. The results demonstrate that the bpy adopts a flat-lying orientation with its substituted alkyl chains in a tail-to-tail arrangement in a bpy monolayer. For the in situ coordination, the bpy/Zn(ii) and bpy/Cu(ii) complexes are aligned in edge-on fashions, wherein the bpy stands vertically on the HOPG surface and interdigitates at the alkyl chains. In the two-dimensional arrays of ex situ coordinated complexes, metal dependent motifs have been observed with Zn(ii) and Cu(ii), wherein the bipyridine moieties are parallel to the graphite surface. These results suggest that the desired on-surface coordination architectures may be achieved by the intentional selection of the metal centers.

  20. Ocean warming-acidification synergism undermines dissolved organic matter assembly.

    Science.gov (United States)

    Chen, Chi-Shuo; Anaya, Jesse M; Chen, Eric Y-T; Farr, Erik; Chin, Wei-Chun

    2015-01-01

    Understanding the influence of synergisms on natural processes is a critical step toward determining the full-extent of anthropogenic stressors. As carbon emissions continue unabated, two major stressors--warming and acidification--threaten marine systems on several scales. Here, we report that a moderate temperature increase (from 30°C to 32°C) is sufficient to slow--even hinder--the ability of dissolved organic matter, a major carbon pool, to self-assemble to form marine microgels, which contribute to the particulate organic matter pool. Moreover, acidification lowers the temperature threshold at which we observe our results. These findings carry implications for the marine carbon cycle, as self-assembled marine microgels generate an estimated global seawater budget of ~1016 g C. We used laser scattering spectroscopy to test the influence of temperature and pH on spontaneous marine gel assembly. The results of independent experiments revealed that at a particular point, both pH and temperature block microgel formation (32°C, pH 8.2), and disperse existing gels (35°C). We then tested the hypothesis that temperature and pH have a synergistic influence on marine gel dispersion. We found that the dispersion temperature decreases concurrently with pH: from 32°C at pH 8.2, to 28°C at pH 7.5. If our laboratory observations can be extrapolated to complex marine environments, our results suggest that a warming-acidification synergism can decrease carbon and nutrient fluxes, disturbing marine trophic and trace element cycles, at rates faster than projected.

  1. Molecular Dynamics Simulation of the Binding Interaction between Hormone Glucagon Protein and Self-Assembled Monolayer Molecules

    Institute of Scientific and Technical Information of China (English)

    WANG,Yeng-Tseng; CHENG,Cheng-Lung; SHIH,Yu-Ching; KAN,Heng-Chuan; CHEN,Chang-Hung; HU,Jeu-Jiun; SU,Zhi-Yuan

    2007-01-01

    Restrained molecular dynamics simulations were performed to study the binding affinity of the peptide with alkanethiols of different tail-groups, S(CH2)7CH3, S(CH2)7OH and S(CH2)7COOH, which self-assembled on Au(111)surface in the presence of water molecules. The curves of binding affinity were calculated by fixing the center of mass of the peptide at various distances from the assembling surface. Simulation results show that the binding affinity is in the order as COOH-SAMs>OH-SAMs>CH3-SAMs, while 100% COOH-SAMs>5% COOH-SAMs in concentration. The effects on binding affinity by different tail-groups were also studied. Results show that the binding affinity between COOH-SAMs and the peptide is bigger than those of the others and increasing the acidity of COOH-SAMs will result in stronger attractive power.

  2. Self-assembled hierarchically structured organic-inorganic composite systems.

    Science.gov (United States)

    Tritschler, Ulrich; Cölfen, Helmut

    2016-06-01

    Designing bio-inspired, multifunctional organic-inorganic composite materials is one of the most popular current research objectives. Due to the high complexity of biocomposite structures found in nacre and bone, for example, a one-pot scalable and versatile synthesis approach addressing structural key features of biominerals and affording bio-inspired, multifunctional organic-inorganic composites with advanced physical properties is highly challenging. This article reviews recent progress in synthesizing organic-inorganic composite materials via various self-assembly techniques and in this context highlights a recently developed bio-inspired synthesis concept for the fabrication of hierarchically structured, organic-inorganic composite materials. This one-step self-organization concept based on simultaneous liquid crystal formation of anisotropic inorganic nanoparticles and a functional liquid crystalline polymer turned out to be simple, fast, scalable and versatile, leading to various (multi-)functional composite materials, which exhibit hierarchical structuring over several length scales. Consequently, this synthesis approach is relevant for further progress and scientific breakthrough in the research field of bio-inspired and biomimetic materials. PMID:27175790

  3. Sensing Escherichia coli O157:H7 via frequency shift through a self-assembled monolayer based QCM immunosensor

    Institute of Scientific and Technical Information of China (English)

    Li-jiang WANG; Chun-sheng WU; Zhao-ying HU; Yuan-fan ZHANG; Rong LI; Ping WANG

    2008-01-01

    By means of the specific immuno-recognition and ultra-sensitive mass detection, a quartz crystal microbalance (QCM) biosensor for Escherichia coli O157:H7 detection was developed in this work. As a suitable surfactant, 16-mercaptohexadecanoic acid (MHDA) was introduced onto the Au surface of QCM, and then self-assembled with N-hydroxysuccinimide (NHS) raster as a reactive intermediate to provide an active interface for the specific antibody immobilization. The binding of target bacteria with the immobilized antibodies decreased the sensor's resonant frequency, and the frequency shift was correlated to the bacterial concentration. The stepwise assembly of the immunosensor was characterized by means of the electrochemical techniques. Using the immersion-dry-immersion procedure, this QCM biosensor could detect 2.0×102 colony forming units (CFU)/ml E. coli O157:H7. In order to reduce the fabrication time, a polyelectrolyte layer-by-layer self-assembly (LBL-SA) method was adopted for fast construction. Finally, the reproducibility of this biosensor was discussed.

  4. Thermodynamics of the adsorption of organic molecules on graphitized carbon black modified with a monolayer of 5-hydroxy-6-methyluracil

    Science.gov (United States)

    Gus'kov, V. Yu.; Ivanov, S. P.; Shaikhitdinova, Yu. F.; Kudasheva, F. Kh.

    2016-10-01

    Thermodynamic characteristics of the adsorption of alkanes, alcohols, arenes, and esters on graphitized carbon black with a deposited monolayer (0.17%) of 5-hydroxy-6-methyluracil are studied by means of inverse gas chromatography at infinite dilution. It is established that size effects (violation of the additivity of molar changes in internal energy and the entropy of adsorption for pairs of molecules of one homologous series that differ by one methyl group) are observed when organic molecules are adsorbed on the surface of the resulting adsorbent. The size effects are similar to those observed when 1% 5-hydroxy-6-methyluracil is deposited on graphitized carbon black. It is concluded that the observed violation of additivity is associated with cavities in the supramolecular structure.

  5. Change in surface states of Ag(111) thin films upon adsorption of a monolayer of PTCDA organic molecules

    International Nuclear Information System (INIS)

    The change in the electronic structure of silver thin films of different thicknesses with the Ag( 111) orientation due to the interaction with an adsorbed monolayer of ordered organic molecules of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) has been investigated in terms of density functional theory. It has been shown that one of the two surface states of the pure films transforms into an unocc upied interface state due to the interaction so that all the main features of the initial state are retained. The relation of the resulting state to the unoccupied state experimentally observed in the PTCDA/Ag( 111 ) system by scanning tunneling and two-photon photoemission spectroscopy has been discussed.

  6. Approaching charge balance in organic light-emitting diodes by tuning charge injection barriers with mixed monolayers.

    Science.gov (United States)

    Yu, Szu-Yen; Huang, Ding-Chi; Chen, Yi-Ling; Wu, Kun-Yang; Tao, Yu-Tai

    2012-01-10

    Self-assembled monolayers (SAMs) of binary mixtures of 1-butylphosphonic acid and the trifluoromethyl-terminated analogue (4,4,4-trifluoro-1-butylphosphonic acid) were formed on ITO surfaces to tune the work function of ITO over a range of 5.0 to 5.75 eV by varying the mixing ratio of the two adsorbents. The mixed SAM-modified ITO surfaces were used as the anode in the fabrication of OLED devices with a configuration of ITO/SAM/HTL/Alq3/MX/Al, where HTL was the NPB or BPAPF hole-transporting layer and MX was the LiF or Cs(2)CO(3) injection layer. It was shown that, depending on the HTL or MX used, the maximum device current and the maximum luminance efficiency occurred with anodes of different modifications because of a shift in the point of hole/electron carrier balance. This provides information on the charge balance in the device and points to the direction to improve the performance. PMID:22103763

  7. Interface Engineering of Organic Thin Film Transistors with Self-assembled Organophosphonic Acids

    Science.gov (United States)

    Liu, Danqing

    Organic thin film transistors (OTFTs) are interface devices with their performance highly dependent on the interface between organic semiconductors and gate dielectrics no matter whether the organic semiconductors are processed by vacuum deposition or solution-based methods. Detailed in this thesis are studies of interface engineering for OTFTs with self-assembled organophosphonic acids, which play important roles in tuning the properties of the dielectric surface for high-performance OTFTs. The poor crystallinity of rubrene in conventional vacuum deposited films is a well-known obstacle limiting practical applications of rubrene in thin film transistors. As described in Chapter 2, a template layer of diazapentacene (DAP) is introduced to induce crystallization of rubrene in thin film transistors. This study demonstrates that DAP is a suitable template molecule with negligible contribution to the conduction channel leading to polycrystalline thin films of rubrene with field effect mobility as high as 0.68 cm2 V --1 s--1. This induced-crystallization strategy highly depends on a unique octadecylphosphonic acid (ODPA) bilayer-step surface, which plays important roles in controlling the growth of both DAP and rubrene. In solution-processed OTFTs, one key factor that affects the nucleation and growth of semiconductor molecules during solution-based processing is the wetting behavior of the semiconductor solution on the dielectric surface. Reported in Chapter 3 is a new strategy for preparing solution-processed OTFTs based on enhancing the surface energy of self-assembled monolayers (SAMs) by inserting polar oxygen atoms into the long alkyl chain of phosphonic acids. SAMs of these phosphonic acids on a high-k metal oxide layer of AlOy /TiOx lead to solution-processed n-channel OTFTs with high field effect mobility of up to 2.5 cm2 V--1 s--1 and low operational voltage. Chapter 4 puts forth a new design of SAMs for interface engineering of high-performance OTFTs. This

  8. Long-range order of organized oligonucleotide monolayers on Au(111) electrodes

    DEFF Research Database (Denmark)

    Wackerbarth, Hainer; Grubb, Mikala; Zhang, Jingdong;

    2004-01-01

    Oligonucleotides modified by a hexamethylene linker group adsorb on gold electrodes via Au-S bond formation. We have obtained novel data for adsorption of thiol-modified (HS) single-strand HS-10A and double-stranded HS-10AT oligonucleotides and for analogous thiol-free 10A (A = adenine) and 10T (T......, with electrochemical potential control of both the sample electrode and the tip. All the data are based on single-crystal, atomically planar Au(111)-electrode surfaces. The high sensitivity of such surfaces provides accurate HS-10A and HS-10AT electrode coverages on the basis of the reductive desorption of the Au......-S bond. The coverage is high and in keeping with dense monolayers of adsorbed HS-10A and HS-10AT in an upright or tilted orientation, with the oligonucleotide backbone repelled from the strongly negatively charged electrode surface. Adsorbed thiol-free 10A only gives aAu(111)-reconstruction peak, while...

  9. Additive fabrication of microstructures using self-assembled organic thin-film templates

    Science.gov (United States)

    Jeon, Noo Li

    .5-100 mum) and the selective filling of trenches and vias. To demonstrate the viability of patterning thin oxide layers for applications in integrated microelectronics and optoelectronics, patterned PZT (a capacitor material) and LiNbOsb3 (a waveguide material) thin films were deposited on TiN and sapphire substrates, respectively. Strip waveguides of heteroepitaxial LiNbOsb3 with 4 mum widths were fabricated on sapphire. A simple multilayered device, a ferroelectric capacitor with platinum/PZT/platinum layers, was fabricated using the patterning methods developed in this thesis. This achievement demonstrates the possibility of developing a photolithography-free method for fabricating micron-scale metal-oxide-silicon devices based on printed organic thin films of self-assembled monolayers. With further development, the patterning of metal and ceramic thin films directed by SAMs appears to have a great potential in fabricating the three-dimensional thin film structures needed for advanced device technologies.

  10. Photoelectron spectroscopy of self-assembled monolayers of molecular switches on noble metal surfaces; Photoelektronenspektroskopie selbstorganisierter Adsorbatschichten aus molekularen Schaltern auf Edelmetalloberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, Nils

    2012-09-12

    Self-assembled monolayers (SAMs) of butanethiolate (C4) on single crystalline Au(111) surfaces were prepared by adsorption from solution. The thermally activated desorption behaviour of the C4 molecules from the gold substrate was examined by qualitative thermal desorption measurements (TDM), through this a desorption temperature T{sub Des}=473 K could be determined. With this knowledge, it was possible to produce samples of very good surface quality, by thermal treatment T{sub Sample}assembly from solution on Au(111), was examined using laser-based photoelectron spectroscopy. Differences in the molecular dipole moment characteristic for the trans and the cis isomer of ABT were observed via changes in the sample work function, accessible by detection of the threshold energy for photoemission. A quantitative

  11. Comparison of Genotoxic Damage in Monolayer Cell Cultures and Three-Dimensional Tissue-Like Cell Assemblies

    Science.gov (United States)

    Behravesh, E.; Emami, K.; Wu, H.; Gonda, S.

    2004-01-01

    Assessing the biological risks associated with exposure to the high-energy charged particles encountered in space is essential for the success of long-term space exploration. Although prokaryotic and eukaryotic cell models developed in our laboratory and others have advanced our understanding of many aspects of genotoxicity, in vitro models are needed to assess the risk to humans from space radiation insults. Such models must be representative of the cellular interactions present in tissues and capable of quantifying I genotoxic damage. Toward this overall goal, the objectives of this study were to examine the effect of the localized microenvironment of cells, cultured as either 2-dimensional (2D) monolayers or 3-dimensional (3D) aggregates, on the rate and type of genotoxic damage resulting from exposure to iron charged particles, a significant portion of space radiation. We used rodent transgenic cell lines containing 50-70 copies of a LacI transgene to provide the enhanced sensitivity required to quantify mutational frequency and type in the 1,100-bp LacI target as well as assessment of DNA,damage to the entire 45-kbp construct. Cultured cells were exposed to high-enerir on charged particles at Brookhaven National Laboratory s Alternating Gradient Synchrotron facility for a total dose of 0, 0.1, 0.25,0.5, 1.0, or 2.0 Gy and allowed to recover for 0, 1, or 7 days, after which mutational type and frequency were evaluated. The mutational frequency was found to be higher in 3D samples than in 2D samples at all radiation doses. Mutational frequency also was higher at 7 days after irradiation than immediately after exposure. DNA sequencing of the mutant targets revealed that deletional mutations contributed an increasingly high percentage (up to 27%) of all mutations in cells as the dose was increased from 0.5 to 2 Gy. Several mutants also showed large and complex deletions in multiple locations within the Lac1 target. However, no differences in mutational type were

  12. Atom beam triangulation of organic layers at 100 meV normal energy: self-assembled perylene on Ag(110) at room temperature

    CERN Document Server

    Kalashnyk, Nataliya

    2015-01-01

    The controlled growth of organic layer on surface is still awaiting for an on-line reliable monitoring that would allow improvement of its quality. We show here that the self-assembly of the perylene monolayer deposited on Ag(110) at room temperature can be tracked with low energy atoms in a regime where the energy perpendicular to the layer is less than 0.1 eV preventing damage to the layer. The image processing required for this triangulation technique with atoms is described in details.

  13. Nanostructured materials based on the integration of ferrocenyl-tethered dendrimer and redox proteins on self-assembled monolayers: an efficient biosensor interface

    Energy Technology Data Exchange (ETDEWEB)

    Frasconi, Marco; Deriu, Daniela; Mazzei, Franco [Department of Chemistry and Drug Technologies, Sapienza University of Rome, Piazzale Aldo Moro, 500185 Rome (Italy); D' Annibale, Andrea, E-mail: franco.mazzei@uniroma1.it [Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro, 500185 Rome (Italy)

    2009-12-16

    In this paper we report the use of ferrocenyl-tethered dendrimer (Fc-D) as an electrode modifier supported by a self-assembled monolayer coated gold surface. The pretreatment of electrodes with Fc-D allows the covalent immobilization of glucose oxidase. The resulting integrated hybrid system provides electrical contact between the redox center of the enzyme and the electrode, and improves the overall bioelectrocatalyzed oxidation of glucose. Cyclic voltammetry combined with surface plasmon resonance (SPR) is used to investigate the redox-induced orientation changes of ferrocene-tethered dendrimers and the optimal electrical wiring of the enzyme, depending on the length of the alkyl chain of the ferrocene-tethered groups. The amount of substrate controls the steady-state concentration ratio of Fc/Fc{sup +} in the film composition. Therefore, the SPR spectrum of the film is controlled by the reversible change in the refractive index of the enzyme-integrated redox film. The proposed method demonstrates a new procedure for developing a stable amperometric redox enzyme-based sensor by designing a new nanostructured material that control the biosensing performance.

  14. Nanostructured materials based on the integration of ferrocenyl-tethered dendrimer and redox proteins on self-assembled monolayers: an efficient biosensor interface

    Science.gov (United States)

    Frasconi, Marco; Deriu, Daniela; D'Annibale, Andrea; Mazzei, Franco

    2009-12-01

    In this paper we report the use of ferrocenyl-tethered dendrimer (Fc-D) as an electrode modifier supported by a self-assembled monolayer coated gold surface. The pretreatment of electrodes with Fc-D allows the covalent immobilization of glucose oxidase. The resulting integrated hybrid system provides electrical contact between the redox center of the enzyme and the electrode, and improves the overall bioelectrocatalyzed oxidation of glucose. Cyclic voltammetry combined with surface plasmon resonance (SPR) is used to investigate the redox-induced orientation changes of ferrocene-tethered dendrimers and the optimal electrical wiring of the enzyme, depending on the length of the alkyl chain of the ferrocene-tethered groups. The amount of substrate controls the steady-state concentration ratio of Fc/Fc+ in the film composition. Therefore, the SPR spectrum of the film is controlled by the reversible change in the refractive index of the enzyme-integrated redox film. The proposed method demonstrates a new procedure for developing a stable amperometric redox enzyme-based sensor by designing a new nanostructured material that control the biosensing performance.

  15. A friendly detergent for H2 oxidation by Aquifex aeolicus membrane-bound hydrogenase immobilized on graphite and Self-Assembled-Monolayer-modified gold electrodes

    International Nuclear Information System (INIS)

    Immobilization of membrane bound enzymes onto electrodes is of great interest for studying physiological electron transfer processes and for biotechnological devices. Hydrogenases are the key enzymes for hydrogen metabolism in many microorganisms. Due to the high efficiency and specificity they develop for H2 oxidation, research in the last 5 years has aimed towards their use as biocatalysts for H2/O2 biofuel cells to replace platinum-based bioanodes. We demonstrate in this work that the O2-, CO- and T°-resistant membrane-bound [NiFe] hydrogenase purified from the hyperthermophilic bacterium Aquifex aeolicus can be efficiently immobilized onto electrodes. Both pyrolytic graphite (PG) and hydrophobic Self-Assembled-Monolayers (SAMs) on gold electrodes are used for hydrogenase immobilization. According to the chemistry and structure of the electrochemical interface, a different process for H2 oxidation is observed, from direct to mediated electron transfer process. To gain new insight in the catalytic process, a quantification of the remaining detergent surrounding the membrane protein is performed. Adsorption isotherms of hydrogenase are determined as a function of the electrode material and the amount of detergent. Competitive adsorption of free detergent and hydrogenase is demonstrated coupling electrochemistry and Polarization Modulation Infrared Reflexion Adsorption Spectroscopy (PM-IRRAS). The efficiency of the enzymatic process is then analyzed according to the tiny interaction between the lipophilic redox mediator (methylene blue), the detergent, the enzyme and the electrochemical interface.

  16. Binary self-assembled monolayers of alkanethiols on gold: deposition from solution versus microcontact printing and the study of surface nanobubbles.

    Science.gov (United States)

    Bayat, Haider; Tranchida, Davide; Song, Bo; Walczyk, Wiktoria; Sperotto, Elena; Schönherr, Holger

    2011-02-15

    The coadsorption of alkanethiols on noble metals has been recognized for a long time as a suitable means of affording surfaces with systematically varied wettability and other properties. In this article, we report on a comparative study of the composition of the mixed self-assembled monolayers (SAMs) obtained (i) by the coadsorption of octadecanethiol (ODT) and 16-mercaptohexadecanoic acid (MHDA) from ethanol and chloroform onto gold substrates and (ii) by microcontact printing using poly(dimethyl siloxane) (PDMS) stamps. SAMs prepared by coadsorption from solution showed a preferential adsorption of ODT for both solvents, but this trend was reversed in microcontact-printed SAMs when using chloroform as a solvent, as evidenced by contact angle and Fourier transform infrared (FTIR) spectroscopy measurements. An approximately linear relationship between the static contact angle and the degree of swelling with different solvents was observed, which suggests that the surface composition can be controlled by the interaction of the solvent and the PDMS elastomer. The altered preference is attributed to the different partitioning of the two thiols into solvent-swelled PDMS, as shown by (1)H NMR spectroscopy. Finally, molecularly mixed binary SAMs on ODT and MHDA on template-stripped gold were applied to study the effect of surface nanobubbles on wettability by atomic force microscopy (AFM). With a decreasing macroscopic contact angle measured through water, the nanoscopic contact angle was found to decrease as well. PMID:21117682

  17. Self-assembled monolayers of Aβ peptides on Au electrodes: an artificial platform for probing the reactivity of redox active metals and cofactors relevant to Alzheimer's disease.

    Science.gov (United States)

    Pramanik, Debajyoti; Sengupta, Kushal; Mukherjee, Soumya; Dey, Somdatta Ghosh; Dey, Abhishek

    2012-07-25

    The water-soluble hydrophilic part of human Aβ peptide has been extended to include a C-terminal cysteine residue. Utilizing the thiol functionality of this cysteine residue, self-assembled monolayers (SAM) of these peptides are formed on Au electrodes. Atomic force microscopy imaging confirms formation of small Aβ aggregates on the surface of the electrode. These aggregates bind redox active metals like Cu and cofactors like heme, both of which are proposed to generate toxic partially reduced oxygen species (PROS) and play a vital role in Alzheimer's disease. The spectroscopic and electrochemical properties of these Cu and heme bound Aβ SAM are similar to those reported for the soluble Cu and heme bound Aβ peptide. Experiments performed on these Aβ-SAM electrodes clearly demonstrate that (1) heme bound Aβ is kinetically more competent in reducing O(2) than Cu bound Aβ, (2) under physiological conditions the reduced Cu site produces twice as much PROS (measured in situ) than the reduced heme site, and (3) chelators like clioquinol remove Cu from these aggregates, while drugs like methylene blue inhibit O(2) reactivity of the heme cofactor. This artificial construct provides a very easy platform for investigating potential drugs affecting aggregation of human Aβ peptides and PROS generation by its complexes with redox active metals and cofactors.

  18. First-Principles Surface Stress Calculations and Multiscale Deformation Analysis of a Self-Assembled Monolayer Adsorbed on a Micro-Cantilever

    Directory of Open Access Journals (Sweden)

    Yu-Ching Shih

    2014-04-01

    Full Text Available Micro-cantilever sensors are widely used to detect biomolecules, chemical gases, and ionic species. However, the theoretical descriptions and predictive modeling of these devices are not well developed, and lag behind advances in fabrication and applications. In this paper, we present a novel multiscale simulation framework for nanomechanical sensors. This framework, combining density functional theory (DFT calculations and finite element method (FEM analysis, is capable of analyzing molecular adsorption-induced deformation and stress fields in the sensors from the molecular scale to the device scale. Adsorption of alkanethiolate self-assembled monolayer (SAM on the Au(111 surface of the micro-cantilever sensor is studied in detail to demonstrate the applicability of this framework. DFT calculations are employed to investigate the molecular adsorption-induced surface stress upon the gold surface. The 3D shell elements with initial stresses obtained from the DFT calculations serve as SAM domains in the adsorption layer, while FEM is employed to analyze the deformation and stress of the sensor devices. We find that the micro-cantilever tip deflection has a linear relationship with the coverage of the SAM domains. With full coverage, the tip deflection decreases as the molecular chain length increases. The multiscale simulation framework provides a quantitative analysis of the displacement and stress fields, and can be used to predict the response of nanomechanical sensors subjected to complex molecular adsorption.

  19. Impediment to heterogeneous electron transfer reactions of redox-active species by alkanedithiol self-assembled monolayers with and without an adlayer of Au nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Minli Yang; Zhanjun Zhang [Chinese Academy of Sciences, Beijing (China). Graduate School, Department of Chemistry

    2004-11-01

    The impediment of heterogeneous electron transfer (ET) reactions of several electroactive species by alkanedithiol self-assembled monolayers (SAMs) and those covered with Au nanoparticles was investigated. It was found that, when densely packed 1,6-hexanedithiol and 1,9-nonanedithiol SAMs were formed with and without adsorbed gold nanoparticles, Fe(CN){sub 6}{sup 3-} reduction became extremely sluggish. The attachment of Au nanoparticles does not appear to improve the electronic communication between the solution species and the underlying Au electrode surface. On the other hand, Ru(NH{sub 3}){sub 6}{sup 3+} and ferrocenecarboxylic acid both exhibited quasi-reversible redox waves at these surfaces. The variation of impediment were attributed to the different electron transfer mechanisms for these redox species. The adsorption of Au nanoparticles onto alkanedithiol SAMs was estimated by flow injection quartz crystal microbalance (FI-QCM), showing a rapid adsorption process. Amounts of Au nanoparticles did not vary between the two different alkanedithiols. Finally, we quantified the adsorption of Au nanoparticles at the QCM crystal modified with a 1,9-nonanedithiol SAM in air. A surface coverage of 2.56% was obtained. (author)

  20. Impediment to heterogeneous electron transfer reactions of redox-active species by alkanedithiol self-assembled monolayers with and without an adlayer of Au nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yang Minli [Department of Chemistry, Graduate School, Chinese Academy of Sciences, Beijing 100039 (China); Zhang Zhanjun [Department of Chemistry, Graduate School, Chinese Academy of Sciences, Beijing 100039 (China)]. E-mail: zhangzj@gscas.ac.cn

    2004-11-01

    The impediment of heterogeneous electron transfer (ET) reactions of several electroactive species by alkanedithiol self-assembled monolayers (SAMs) and those covered with Au nanoparticles was investigated. It was found that, when densely packed 1,6-hexanedithiol and 1,9-nonanedithiol SAMs were formed with and without adsorbed gold nanoparticles, Fe(CN){sub 6}{sup 3-} reduction became extremely sluggish. The attachment of Au nanoparticles does not appear to improve the electronic communication between the solution species and the underlying Au electrode surface. On the other hand, Ru(NH{sub 3}){sub 6}{sup 3+} and ferrocenecarboxylic acid both exhibited quasi-reversible redox waves at these surfaces. The variation of impediment were attributed to the different electron transfer mechanisms for these redox species. The adsorption of Au nanoparticles onto alkanedithiol SAMs was estimated by flow injection quartz crystal microbalance (FI-QCM), showing a rapid adsorption process. Amounts of Au nanoparticles did not vary between the two different alkanedithiols. Finally, we quantified the adsorption of Au nanoparticles at the QCM crystal modified with a 1,9-nonanedithiol SAM in air. A surface coverage of 2.56% was obtained.

  1. Laterally Mobile, Functionalized Self-Assembled Monolayers at the Fluorous−Aqueous Interface in a Plug-Based Microfluidic System: Characterization and Testing with Membrane Protein Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Kreutz, Jason E.; Li, Liang; Roach, L. Spencer; Hatakeyama, Takuji; Ismagilov, Rustem F.; (UC)

    2009-11-04

    This paper describes a method to generate functionalizable, mobile self-assembled monolayers (SAMs) in plug-based microfluidics. Control of interfaces is advancing studies of biological interfaces, heterogeneous reactions, and nanotechnology. SAMs have been useful for such studies, but they are not laterally mobile. Lipid-based methods, though mobile, are not easily amenable to setting up the hundreds of experiments necessary for crystallization screening. Here we demonstrate a method, complementary to current SAM and lipid methods, for rapidly generating mobile, functionalized SAMs. This method relies on plugs, droplets surrounded by a fluorous carrier fluid, to rapidly explore chemical space. Specifically, we implemented his-tag binding chemistry to design a new fluorinated amphiphile, RfNTA, using an improved one-step synthesis of RfOEG under Mitsunobu conditions. RfNTA introduces specific binding of protein at the fluorous-aqueous interface, which concentrates and orients proteins at the interface, even in the presence of other surfactants. We then applied this approach to the crystallization of a his-tagged membrane protein, Reaction Center from Rhodobacter sphaeroides, performed 2400 crystallization trials, and showed that this approach can increase the range of crystal-producing conditions, the success rate at a given condition, the rate of nucleation, and the quality of the crystal formed.

  2. A Single-Level Tunnel Model to Account for Electrical Transport through Single Molecule- and Self-Assembled Monolayer-based Junctions

    Science.gov (United States)

    Garrigues, Alvar R.; Yuan, Li; Wang, Lejia; Mucciolo, Eduardo R.; Thompon, Damien; Del Barco, Enrique; Nijhuis, Christian A.

    2016-05-01

    We present a theoretical analysis aimed at understanding electrical conduction in molecular tunnel junctions. We focus on discussing the validity of coherent versus incoherent theoretical formulations for single-level tunneling to explain experimental results obtained under a wide range of experimental conditions, including measurements in individual molecules connecting the leads of electromigrated single-electron transistors and junctions of self-assembled monolayers (SAM) of molecules sandwiched between two macroscopic contacts. We show that the restriction of transport through a single level in solid state junctions (no solvent) makes coherent and incoherent tunneling formalisms indistinguishable when only one level participates in transport. Similar to Marcus relaxation processes in wet electrochemistry, the thermal broadening of the Fermi distribution describing the electronic occupation energies in the electrodes accounts for the exponential dependence of the tunneling current on temperature. We demonstrate that a single-level tunnel model satisfactorily explains experimental results obtained in three different molecular junctions (both single-molecule and SAM-based) formed by ferrocene-based molecules. Among other things, we use the model to map the electrostatic potential profile in EGaIn-based SAM junctions in which the ferrocene unit is placed at different positions within the molecule, and we find that electrical screening gives rise to a strongly non-linear profile across the junction.

  3. Monolayer ice

    NARCIS (Netherlands)

    Zangi, R; Mark, AE

    2003-01-01

    We report results from molecular dynamics simulations of water under confinement and at ambient conditions that predict a first-order freezing transition from a monolayer of liquid water to a monolayer of ice induced by increasing the distance between the confining parallel plates. Since a slab geom

  4. Determination of Parathion and Carbaryl Pesticides in Water and Food Samples Using a Self Assembled Monolayer /Acetylcholinesterase Electrochemical Biosensor

    Directory of Open Access Journals (Sweden)

    Mauro Bertotti

    2008-08-01

    Full Text Available An acetylcholinesterase (AchE based amperometric biosensor was developed by immobilisation of the enzyme onto a self assembled modified gold electrode. Cyclic voltammetric experiments performed with the SAM-AchE biosensor in phosphate buffer solutions (pH = 7.2 containing acetylthiocholine confirmed the formation of thiocholine and its electrochemical oxidation at Ep = 0.28 V vs Ag/AgCl. An indirect methodology involving the inhibition effect of parathion and carbaryl on the enzymatic reaction was developed and employed to measure both pesticides in spiked natural water and food samples without pre-treatment or pre-concentration steps. Values higher than 91-98.0% in recovery experiments indicated the feasibility of the proposed electroanalytical methodology to quantify both pesticides in water or food samples. HPLC measurements were also performed for comparison and confirmed the values measured amperometrically.

  5. Experimental Investigation of Microbially Induced Corrosion of Test Samples and Effect of Self-Assembled Hydrophobic Monolayers. Exposure of Test Samples to Continuous Microbial Cultures, Chemical Analysis, and Biochemical Studies

    Energy Technology Data Exchange (ETDEWEB)

    Laurinavichius, K.S.

    1998-09-30

    The study of biocorrosion of aluminum and beryllium samples were performed under conditions of continuous fermentation of thermophilic anaerobic microorganisms of different groups. This allowed us to examine the effect of various types of metabolic reactions of reduction-oxidation proceeding at different pH and temperatures under highly reduced conditions on aluminum and beryllium corrosion and effect of self-assembled hydrophobic monolayers.

  6. Simple direct formation of self-assembled N-heterocyclic carbene monolayers on gold and their application in biosensing.

    Science.gov (United States)

    Crudden, Cathleen M; Horton, J Hugh; Narouz, Mina R; Li, Zhijun; Smith, Christene A; Munro, Kim; Baddeley, Christopher J; Larrea, Christian R; Drevniok, Benedict; Thanabalasingam, Bheeshmon; McLean, Alastair B; Zenkina, Olena V; Ebralidze, Iraklii I; She, Zhe; Kraatz, Heinz-Bernhard; Mosey, Nicholas J; Saunders, Lisa N; Yagi, Akiko

    2016-01-01

    The formation of organic films on gold employing N-heterocyclic carbenes (NHCs) has been previously shown to be a useful strategy for generating stable organic films. However, NHCs or NHC precursors typically require inert atmosphere and harsh conditions for their generation and use. Herein we describe the use of benzimidazolium hydrogen carbonates as bench stable solid precursors for the preparation of NHC films in solution or by vapour-phase deposition from the solid state. The ability to prepare these films by vapour-phase deposition permitted the analysis of the films by a variety of surface science techniques, resulting in the first measurement of NHC desorption energy (158±10 kJ mol(-1)) and confirmation that the NHC sits upright on the surface. The use of these films in surface plasmon resonance-type biosensing is described, where they provide specific advantages versus traditional thiol-based films. PMID:27585494

  7. Simple direct formation of self-assembled N-heterocyclic carbene monolayers on gold and their application in biosensing

    Science.gov (United States)

    Crudden, Cathleen M.; Horton, J. Hugh; Narouz, Mina R.; Li, Zhijun; Smith, Christene A.; Munro, Kim; Baddeley, Christopher J.; Larrea, Christian R.; Drevniok, Benedict; Thanabalasingam, Bheeshmon; McLean, Alastair B.; Zenkina, Olena V.; Ebralidze, Iraklii I.; She, Zhe; Kraatz, Heinz-Bernhard; Mosey, Nicholas J.; Saunders, Lisa N.; Yagi, Akiko

    2016-09-01

    The formation of organic films on gold employing N-heterocyclic carbenes (NHCs) has been previously shown to be a useful strategy for generating stable organic films. However, NHCs or NHC precursors typically require inert atmosphere and harsh conditions for their generation and use. Herein we describe the use of benzimidazolium hydrogen carbonates as bench stable solid precursors for the preparation of NHC films in solution or by vapour-phase deposition from the solid state. The ability to prepare these films by vapour-phase deposition permitted the analysis of the films by a variety of surface science techniques, resulting in the first measurement of NHC desorption energy (158+/-10 kJ mol-1) and confirmation that the NHC sits upright on the surface. The use of these films in surface plasmon resonance-type biosensing is described, where they provide specific advantages versus traditional thiol-based films.

  8. White organic light-emitting devices based on blue fluorescent dye combined with dual sub-monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Huishan, E-mail: yanghuishan1697@163.com

    2013-10-15

    White organic light-emitting devices have been realized by using highly blue fluorescent dye 4,4′-Bis(2,2-diphenyl-ethen-1-yl)-4,4′-di-(tert-butyl)phenyl(p-TDPVBi) and [2-methyl-6-[2-(2, 3,6,7-tetrahydro-1H, red fluorescent dye 5H-benzo[ij] quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile(DCM2), together with well known green fluorescent dye quinacridone (QAD). The fabrication of multilayer WOLEDs did not involve the hard-to-control doping process. The structure of the device is ITO/m-MTDATA (45 nm)/NPB(8 nm)/p-TDPVBi(15 nm)/DCM2(x nm)/Alq{sub 3} (5 nm)/QAD(y nm)/Alq{sub 3}(55 nm)/LiF(1 nm)/Al, where 4,4′,4′′-tris{N,-(3-methylphenyl)-N-phenylamine}triphenylamine (m-MTDATA) acts as a hole injection layer, N,N′-bis-(1-naphthyl)-N, N′-diphenyl-1, 1′-biph-enyl-4, 4′-diamine (NPB) acts as a hole transport layer, p-TDPVBi acts as a blue emitting layer, DCM2 acts as a red emitting layer, QAD acts as a green emitting layer, tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) acts as an electron transport layer, and WOLEDs of devices A, B, C and D are different in layer thickness of DCM2 and QAD, respectively. To change the thickness of dual sub-monolayer DCM2 and QAD, the WOLEDs were obtained. When x, y=0.05, 0.1, the Commission Internationale de 1’Eclairage (CIE) coordinates of the device change from (0.4458, 0.4589) at 3 V to (0.3137, 0.3455) at 12 V that are well in the white region, and the color temperature and color rendering index were 5348 K and 85 at 8 V, respectively. Its maximum luminance was 35260 cd/m{sup 2} at 12 V, and maximum current efficiency and maximum power efficiency were 13.54 cd/A at 12 V and 6.68 lm/W at 5 V, respectively. Moreover, the current efficiency is largely insensitive to the applied voltage. The electroluminescence intensity of white EL devices varied only little at deferent dual sub-monolayer. Device D exhibited relatively high color rendering index (CRI) in the range of 88–90, which was essentially

  9. Detection of Tetrodotoxins in Puffer Fish by a Self-Assembled Monolayer-Based Immunoassay and Comparison with Surface Plasmon Resonance, LC-MS/MS, and Mouse Bioassay.

    Science.gov (United States)

    Reverté, Laia; de la Iglesia, Pablo; del Río, Vanessa; Campbell, Katrina; Elliott, Christopher T; Kawatsu, Kentaro; Katikou, Panagiota; Diogène, Jorge; Campàs, Mònica

    2015-11-01

    The increasing occurrence of puffer fish containing tetrodotoxin (TTX) in the Mediterranean could represent a major food safety risk for European consumers and threaten the fishing industry. The work presented herein describes the development of a new enzyme linked immunosorbent assay (mELISA) based on the immobilization of TTX through dithiol monolayers self-assembled on maleimide plates, which provides an ordered and oriented antigen immobilization and favors the antigen-antibody affinity interaction. The mELISA was found to have a limit of detection (LOD) of TTX of 0.23 mg/kg of puffer fish matrix. The mELISA and a surface plasmon resonance (SPR) immunosensor previously developed were employed to establish the cross-reactivity factors (CRFs) of 5,6,11-trideoxy-TTX, 5,11-deoxy-TTX, 11-nor-TTX-6-ol, and 5,6,11-trideoxy-4-anhydro-TTX, as well as to determine TTX equivalent contents in puffer fish samples. Results obtained by both immunochemical tools were correlated (R(2) = 0.977). The puffer fish samples were also analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the corresponding CRFs were applied to the individual TTX contents. Results provided by the immunochemical tools, when compared with those obtained by LC-MS/MS, showed a good degree of correlation (R(2) = 0.991 and 0.979 for mELISA and SPR, respectively). The mouse bioassay (MBA) slightly overestimated the CRF adjusted TTX content of samples when compared with the data obtained from the other techniques. The mELISA has been demonstrated to be fit for the purpose for screening samples in monitoring programs and in research activities.

  10. The use of mixed self-assembled monolayers as a strategy to improve the efficiency of carbamate detection in environmental monitoring

    International Nuclear Information System (INIS)

    We report a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which the enzyme acetylcholinesterase (AChE) was immobilized on gold electrodes functionalized with mixed self-assembled monolayer (SAMmix) of 11-mercaptoundecanoic acid (11-MUA) and 2-mercaptoethanol (C2OH). Development of the modified electrodes included the chemical adsorption of SAMmix on gold surface followed by immersion in AChE solution, resulting in the final Au/SAMmix/AChE configuration. For comparison, the electrochemical performance of Au/11-MUA/AChE and Au/C2OH/AChE electrodes were also investigated. The performance of the modified electrodes toward acetylthiocholine hydrolysis was investigated via cyclic voltammetry and chronoamperometric measurements, revealing a fast increase in anodic current with a well-defined peak upon addition of acetylthiocholine iodide to the electrolytic solution. The anodic currents for Au/SAMmix/AChE electrodes were significantly higher than those for Au/11-MUA/AChE and Au/C2OH/AChE electrodes. The Au/SAMmix/AChE architecture provided by the SAMmix surface promoted a high oxidation current of thiocholine at 0.31 V without the need of electron mediators. The chronoamperometric biosensor developed here provided a linear response to carbaryl in the concentration range of 0 to 1.75 μM. The detection limit and quantification values for carbaryl were found to be 3.45 × 10−10 M and 1.15 × 10−9 M, respectively. Michaelis–Menten kinetics, KMapp, of 0.46 mM was obtained, indicating that the electrode architecture employed is advantageous for fabrication of enzymatic devices via physical adsorption process with improvement of the biocatalytic properties.

  11. Comparing the performances of electrochemical sensors using p-aminophenol redox cycling by different reductants on gold electrodes modified with self-assembled monolayers

    International Nuclear Information System (INIS)

    Highlights: • Performances of p-AP redox cycling using different reductants on gold surface are compared. • Background current decreases in order of hydrazine, Na2SO3, NaBH4, NADH, cysteamine, and TCEP. • Chemical reaction rate with QI increases in order of NADH, TCEP, and cysteamine. • NADH, TCEP and cysteamine are suitable for p-AP redox cycling on gold electrode. -- Abstract: p-Aminophenol (p-AP) redox cycling using chemical reductants is one strategy for developing sensitive electrochemical sensors. However, most of the reported reductants are only used on indium-tin oxide (ITO) electrodes but not gold electrodes due to the high background current caused by the oxidation reaction of the reductants on the highly electrocatalytic gold electrodes. Therefore, new strategies and/or reductants are in demand for expanding the application of p-AP redox cycling on gold electrodes. In this work, we compared the performances of several reductants in p-AP redox cycling on self-assembled monolayers (SAMs)-modified gold electrodes. Among the tested reagents, nicotinamide adenine dinucleotide (NADH), tris(2-carboxyethyl)phosphine (TCEP) and cysteamine were demonstrated to be suitable for p-AP redox cycling on the alkanethiol-modified gold electrodes because of their low background current. The rate of chemical reaction between reductants and p-quinone imine (QI, the electrochemically oxidized product of p-AP) increases in the order of NADH −1 was achieved. We believe that our work will be valuable for the development of electrochemical sensors using p-AP redox cycling on gold electrodes

  12. Detection of Tetrodotoxins in Puffer Fish by a Self-Assembled Monolayer-Based Immunoassay and Comparison with Surface Plasmon Resonance, LC-MS/MS, and Mouse Bioassay.

    Science.gov (United States)

    Reverté, Laia; de la Iglesia, Pablo; del Río, Vanessa; Campbell, Katrina; Elliott, Christopher T; Kawatsu, Kentaro; Katikou, Panagiota; Diogène, Jorge; Campàs, Mònica

    2015-11-01

    The increasing occurrence of puffer fish containing tetrodotoxin (TTX) in the Mediterranean could represent a major food safety risk for European consumers and threaten the fishing industry. The work presented herein describes the development of a new enzyme linked immunosorbent assay (mELISA) based on the immobilization of TTX through dithiol monolayers self-assembled on maleimide plates, which provides an ordered and oriented antigen immobilization and favors the antigen-antibody affinity interaction. The mELISA was found to have a limit of detection (LOD) of TTX of 0.23 mg/kg of puffer fish matrix. The mELISA and a surface plasmon resonance (SPR) immunosensor previously developed were employed to establish the cross-reactivity factors (CRFs) of 5,6,11-trideoxy-TTX, 5,11-deoxy-TTX, 11-nor-TTX-6-ol, and 5,6,11-trideoxy-4-anhydro-TTX, as well as to determine TTX equivalent contents in puffer fish samples. Results obtained by both immunochemical tools were correlated (R(2) = 0.977). The puffer fish samples were also analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the corresponding CRFs were applied to the individual TTX contents. Results provided by the immunochemical tools, when compared with those obtained by LC-MS/MS, showed a good degree of correlation (R(2) = 0.991 and 0.979 for mELISA and SPR, respectively). The mouse bioassay (MBA) slightly overestimated the CRF adjusted TTX content of samples when compared with the data obtained from the other techniques. The mELISA has been demonstrated to be fit for the purpose for screening samples in monitoring programs and in research activities. PMID:26424329

  13. Thermodynamic investigations using molecular dynamics simulations with potential of mean force calculations for cardiotoxin protein adsorption on mixed self-assembled monolayers.

    Science.gov (United States)

    Hung, Shih-Wei; Hsiao, Pai-Yi; Lu, Ming-Chang; Chieng, Ching-Chang

    2012-10-25

    Understanding protein adsorption onto solid surfaces is of critical importance in the field of bioengineering, especially for applications such as medical implants, diagnostic biosensors, drug delivery systems, and tissue engineering. This study proposed the use of molecular dynamics simulations with potential of mean force (PMF) calculations to identify and characterize the mechanisms of adsorption of a protein molecule on a designed surface. A set of model systems consisting of a cardiotoxin (CTX) protein and mixed self-assembled monolayer (SAM) surfaces were used as examples. The set of mixed SAM surfaces with varying topographies were created by mixing alkanethiol chains of different lengths. The results revealed that CTX proteins underwent similar conformal changes upon adsorption onto the various mixed SAMs but showed distinctive characteristics in free energy profiles. Enhancement of the adsorption affinity, i.e., the change in free energy of adsorption, for mixed SAMs was demonstrated by using atomic force microscopic measurements. A component analysis conducted to quantify the physical mechanisms that promoted CTX adsorption revealed contributions from both SAMs and the solvent. Further component analyses of thermodynamic properties, such as the free energy, enthalpy, and entropy, indicated that the contribution from SAMs was driven by enthalpy, and the contribution from the solvent was driven by entropy. The results indicated that CTX adsorption was an entropy-driven process, and the entropic component from the solvent, i.e., the hydrophobic interaction, was the major driving force for CTX adsorption onto SAMs. The study also concluded that the surfaces composed of mixtures of SAMs with different chain lengths promoted the adsorption of CTX protein.

  14. Electrically tunable organic-inorganic hybrid polaritons with monolayer WS2

    OpenAIRE

    Flatten, Lucas C.; Coles, David M.; He, Zhengyu; Lidzey, David G.; Taylor, Robert A.; Warner, Jamie H.; Smith, Jason M.

    2016-01-01

    Exciton-polaritons are quasiparticles consisting of a linear superposition of photonic and excitonic states, offering potential for a range of nonlinear optical devices. The excitonic component of the polariton gives rise to nonlinear behaviour, such that the different types of exciton found in organic materials (Frenkel) and inorganic materials (Wannier-Mott) are expected to produce polaritons with different properties. A hybrid polariton state provides a potential technological route toward...

  15. Probing the Orientation and Conformation of alpha-Helix and beta-Strand Model Peptides on Self-Assembled Monolayers Using Sum Frequency Generation and NEXAFS Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weidner, T.; Apte, J; Gamble, L; Castner, D

    2010-01-01

    The structure and orientation of amphiphilic {alpha}-helix and {beta}-strand model peptide films on self-assembled monolayers (SAMs) have been studied with sum frequency generation (SFG) vibrational spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The {alpha}-helix peptide is a 14-mer, and the {beta}-strand is a 15-mer of hydrophilic lysine and hydrophobic leucine residues with hydrophobic periodicities of 3.5 and 2, respectively. These periodicities result in the leucine side chains located on one side of the peptides and the lysine side chains on the other side. The SAMs were prepared from the assembly of either carboxylic acid- or methyl-terminated alkyl thiols onto gold surfaces. For SFG studies, the deuterated analog of the methyl SAM was used. SFG vibrational spectra in the C-H region of air-dried peptides films on both SAMs exhibit strong peaks near 2965, 2940, and 2875 cm{sup -1} related to ordered leucine side chains. The orientation of the leucine side chains was determined from the phase of these features relative to the nonresonant gold background. The relative phase for both the {alpha}-helix and {beta}-strand peptides showed that the leucine side chains were oriented away from the carboxylic acid SAM surface and oriented toward the methyl SAM surface. Amide I peaks observed near 1656 cm{sup -1} for the {alpha}-helix peptide confirm that the secondary structure is preserved on both SAMs. Strong linear dichroism related to the amide {pi}* orbital at 400.8 eV was observed in the nitrogen K-edge NEXAFS spectra for the adsorbed {beta}-strand peptides, suggesting that the peptide backbones are oriented parallel to the SAM surface with the side chains pointing toward or away from the interface. For the {alpha}-helix the dichroism of the amide {pi}* is significantly weaker, probably because of the broad distribution of amide bond orientations in the {alpha}-helix secondary structure.

  16. Assembly and magneto-electrical characterization of hybrid organic-inorganic systems

    OpenAIRE

    Gang, Tian

    2011-01-01

    Organic building blocks are increasingly applied in current nanoelectronics research and development. In this thesis, the assembly and magneto-electrical characterization of several hybrid organic-inorganic magnetically active systems were described. Several molecular approaches were developed to assemble magnetic nanoparticles on various substrates with controllable density. This is considered as a step forward towards nanoparticle based hybrid spintronics devices. An electron interferometer...

  17. Improving Light Extraction of Organic Light-Emitting Devices by Attaching Nanostructures with Self-Assembled Photonic Crystal Patterns

    Directory of Open Access Journals (Sweden)

    Kai-Yu Peng

    2014-01-01

    Full Text Available A single-monolayered hexagonal self-assembled photonic crystal (PC pattern fabricated onto polyethylene terephthalate (PET films by using simple nanosphere lithography (NSL method has been demonstrated in this research work. The patterned nanostructures acted as a scattering medium to extract the trapped photons from substrate mode of optical-electronic device for improving the overall external quantum efficiency of the organic light-emitting diodes (OLEDs. With an optimum latex concentration, the distribution of self-assembled polystyrene (PS nanosphere patterns on PET films can be easily controlled by adjusting the rotation speed of spin-coater. After attaching the PS nanosphere array brightness enhancement film (BEF sheet as a photonic crystal pattern onto the device, the luminous intensity of OLEDs in the normal viewing direction is 161% higher than the one without any BEF attachment. The electroluminescent (EL spectrum of OLEDs with PS patterned BEF attachment also showed minor color offset and superior color stabilization characteristics, and thus it possessed the potential applications in all kinds of display technology and solid-state optical-electronic devices.

  18. Electrical transport measurements on self-assembled organic molecular wires

    NARCIS (Netherlands)

    Durkut, M.; Mas-Torrent, M.; Hadley, P.; Jonkheijm, P.; Schenning, A.P.H.J.; Meijer, E.W.; George, S.; Ajayaghosh, A.

    2006-01-01

    The electrical properties of supermolecular assemblies of oligo(p-phenylene vinylene) were studied. These materials self-assemble into well-defined cylindrical structures in solution with lengths in the range of 100 nm–10 μm and diameters between 5 and 200 nm. Atomic force microscopy showed that by

  19. Controlling nucleation of monolayer WSe2 during metal-organic chemical vapor deposition growth

    Science.gov (United States)

    Eichfeld, Sarah M.; Oliveros Colon, Víctor; Nie, Yifan; Cho, Kyeongjae; Robinson, Joshua A.

    2016-06-01

    Tungsten diselenide (WSe2) is a semiconducting, two-dimensional (2D) material that has gained interest in the device community recently due to its electronic properties. The synthesis of atomically thin WSe2, however, is still in its infancy. In this work we elucidate the requirements for large selenium/tungsten precursor ratios and explain the effect of nucleation temperature on the synthesis of WSe2 via metal-organic chemical vapor deposition (MOCVD). The introduction of a nucleation-step prior to growth demonstrates that increasing nucleation temperature leads to a transition from a Volmer-Weber to Frank-van der Merwe growth mode. Additionally, the nucleation step prior to growth leads to an improvement of WSe2 layer coverage on the substrate. Finally, we note that the development of this two-step technique may allow for improved control and quality of 2D layers grown via CVD and MOCVD processes.

  20. Self-assembled honeycomb lattice in the monolayer of cyclic thiazyl diradical BDTDA (= 4,4‧-bis(1,2,3,5-dithiadiazolyl)) on Cu(111) with a zero-bias tunneling spectra anomaly

    Science.gov (United States)

    Yamamoto, Masayuki; Suizu, Rie; Dutta, Sudipta; Mishra, Puneet; Nakayama, Tomonobu; Sakamoto, Kazuyuki; Wakabayashi, Katsunori; Uchihashi, Takashi; Awaga, Kunio

    2015-12-01

    Scanning tunneling microscopy (STM) observation reveals that a cyclic thiazyl diradical, BDTDA (= 4,4‧-bis(1,2,3,5-dithiadiazolyl)), forms a well-ordered monolayer honeycomb lattice consisting of paramagnetic corners with unpaired electrons on a clean Cu(111) surface. This BDTDA lattice is commensurate with the triangular lattice of Cu(111), with the former being 3 × 3 larger than the latter. The formation of the BDTDA monolayer structure, which is significantly different from its bulk form, is attributed to an interaction with the metal surface as well as the intermolecular assembling forces. STM spectroscopy measurements on the BDTDA molecules indicate the presence of a characteristic zero-bias anomaly centered at the Fermi energy. The origin of this zero-bias anomaly is discussed in terms of the Dirac cones inherent to the honeycomb structure.

  1. From self-organization to self-assembly: a new materialism?

    Science.gov (United States)

    Vincent, Bernadette Bensaude

    2016-09-01

    While self-organization has been an integral part of academic discussions about the distinctive features of living organisms, at least since Immanuel Kant's Critique of Judgement, the term 'self-assembly' has only been used for a few decades as it became a hot research topic with the emergence of nanotechnology. Could it be considered as an attempt at reducing vital organization to a sort of assembly line of molecules? Considering the context of research on self-assembly I argue that the shift of attention from self-organization to self-assembly does not really challenge the boundary between chemistry and biology. Self-assembly was first and foremost investigated in an engineering context as a strategy for manufacturing without human intervention and did not raise new perspectives on the emergence of vital organization itself. However self-assembly implies metaphysical assumptions that this paper tries to disentangle. It first describes the emergence of self-assembly as a research field in the context of materials science and nanotechnology. The second section outlines the metaphysical implications and will emphasize a sharp contrast between the ontology underlying two practices of self-assembly developed under the umbrella of synthetic biology. And unexpectedly, we shall see that chemists are less on the reductionist side than most synthetic biologists. Finally, the third section ventures some reflections on the kind of design involved in self-assembly practices. PMID:27325057

  2. From metal-organic squares to porous zeolite-like supramolecular assemblies

    KAUST Repository

    Wang, Shuang

    2010-12-29

    We report the synthesis, structure, and characterization of two novel porous zeolite-like supramolecular assemblies, ZSA-1 and ZSA-2, having zeolite gis and rho topologies, respectively. The two compounds were assembled from functional metal-organic squares (MOSs) via directional hydrogen-bonding interactions and exhibited permanent microporosity and thermal stability up to 300 °C. © 2010 American Chemical Society.

  3. 铜表面硬脂酸自组装膜的制备及耐腐蚀性能%Preparation and corrosion resistance of self-assembled stearic acid monolayer on copper surface

    Institute of Scientific and Technical Information of China (English)

    余相仁; 李淑英; 范洪强; 钱备; 张琳

    2011-01-01

    A stearic acid (STA) self-assembled monolayer (SAM) was prepared on the surface of Cu(OH)2 nanowire/ hierarchical CuO structure by self-assembly technology. The optimal STA concentration and self-assembly time for SAM formation were studied via electrochemical impedance spectroscopy. The corrosion inhibition performance of stearic acid self-assembled monolayer on copper electrode in a 0.1 mol/L NaCl solution was examined by polarization curve measurement and cyclic voltammetry. The results showed that the stearic acid self-assembled monolayer prepared on CuO/Cu(OH)2 electrode by immersing it in a 8 mmol/L stearic acid solution for 24 h can remarkably improve the corrosion resistance of the copper electrode. Compared with the bare copper electrode, the SAM-CuO/Cu(OH)2 electrode has a corrosion current density decreased by two orders of magnitude, and its inhibition efficiency is up to 98.81%.%应用自组装技术在Cu(OH)2纳米柱/CuO微花阶层结构表面制备硬脂酸自组装膜(SAM),运用电化学阻抗谱探讨了形成自组装膜的较佳浓度和自组装时间,通过极化曲线和循环伏安法考察了硬脂酸自组装膜在0.1 mol/L NaCl溶液中对铜电极的缓蚀性能.结果表明,当CuO/Cu(OH)2电极在8 mmol/L硬脂酸溶液中自组装24 h时,得到的硬脂酸自组装膜能显著提高铜电极的耐蚀性;与裸铜电极相比,SAM-CuO/Cu(OH)2电极的腐蚀电流降低了2个数量级,缓蚀效率达到98.81%.

  4. Strongly Dichroic Organic Films via Controlled Assembly of Modular Aromatic Charge-Transfer Liquid Crystals.

    Science.gov (United States)

    Bé, Ariana Gray; Tran, Cheryl; Sechrist, Riley; Reczek, Joseph J

    2015-10-01

    The formation of highly anisotropic organic thin films based on the designed self-assembly of mixed-stack liquid crystals is reported. A series of alkoxyanthracene donors is combined in a modular fashion with a naphthalenediimide acceptor to generate new charge-transfer columnar liquid crystals. Materials characterization and molecular modeling provides insight into structure-function relationships in these organic materials that lead to the striking bulk dichroic properties of certain molecular assemblies. PMID:26375256

  5. CAPRG: sequence assembling pipeline for next generation sequencing of non-model organisms.

    Directory of Open Access Journals (Sweden)

    Arun Rawat

    Full Text Available Our goal is to introduce and describe the utility of a new pipeline "Contigs Assembly Pipeline using Reference Genome" (CAPRG, which has been developed to assemble "long sequence reads" for non-model organisms by leveraging a reference genome of a closely related phylogenetic relative. To facilitate this effort, we utilized two avian transcriptomic datasets generated using ROCHE/454 technology as test cases for CAPRG assembly. We compared the results of CAPRG assembly using a reference genome with the results of existing methods that utilize de novo strategies such as VELVET, PAVE, and MIRA by employing parameter space comparisons (intra-assembling comparison. CAPRG performed as well or better than the existing assembly methods based on various benchmarks for "gene-hunting." Further, CAPRG completed the assemblies in a fraction of the time required by the existing assembly algorithms. Additional advantages of CAPRG included reduced contig inflation resulting in lower computational resources for annotation, and functional identification for contigs that may be categorized as "unknowns" by de novo methods. In addition to providing evaluation of CAPRG performance, we observed that the different assembly (inter-assembly results could be integrated to enhance the putative gene coverage for any transcriptomics study.

  6. Symmetric organization of self-assembled carbon nitride

    International Nuclear Information System (INIS)

    A scheme for creating 'flower-like' nanostructures of carbon nitride is described that involves the self-assembly of nanocrystals following laser ablation of a solid graphite target immersed in aqueous ammonia solution. The primary nanocrystals possess rod-like symmetry, and then self-assemble upon drying to form nanoleaf or nanopetal shaped structures. Samples were characterized using x-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), x-ray photoelectron microscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The analyses confirmed their composition to be consistent with that of crystalline β-phase carbon nitride. The morphologies of the carbon nitride nanostructures depended strongly on the synthesis conditions and upon the conditions under which the aqueous suspension of ablated particles were dried

  7. A generalized network evolution model and self-organization theory on community assembly

    Directory of Open Access Journals (Sweden)

    WenJun Zhang

    2015-09-01

    Full Text Available Community assembly is the process that species grow and interact to establish a community. In present study, a generalized, rule-based network evolution model, CommAssembly, for community assembly was proposed. The model is based on difference equations with different number of species in different stages of evolution. It consists of pioneer rule, invasion and growth rule, extinction rule, connection (flow rule and termination rule, etc. Species invades, grows in, or quits the community following specific rules. In addition, I proposed the self-organization theory on community assembly. In this theory, I think that community assembly is a self-organization process. In terms of the model proposed, the practical community can spontaneously adjust its A(t, and guarantee itself to evolve in a natural way. Temporal dynamics and species composition of community depend on species composition of species pool, between-species interactions, intrinsic growth of species, environmental capacity (resource availability, and the probability, strength and history of invasions, etc. The invasion, establishment, growth, and extinction of species follow a series of rules. Community assembly can be best described and modeled with self-organization approaches. The model provides the basis to build self-organization models of community assembly.

  8. Hierarchical self-assembly: Self-organized nanostructures in a nematically ordered matrix of self-assembled polymeric chains

    Science.gov (United States)

    Mubeena, Shaikh; Chatterji, Apratim

    2015-03-01

    We report many different nanostructures which are formed when model nanoparticles of different sizes (diameter σn) are allowed to aggregate in a background matrix of semiflexible self-assembled polymeric wormlike micellar chains. The different nanostructures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nanoparticles. The different morphologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nanoparticles in the polymer matrix, and, of course, the ratio of the size of self-assembling nanoparticles and self-avoidance diameter of polymeric chains. We have used a hybrid semi-grand-canonical Monte Carlo simulation scheme to obtain the (nonequilibrium) phase diagram of the self-assembled nanostructures. We observe rodlike structures of nanoparticles which get self-assembled in the gaps between the nematically ordered chains, as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nanoparticles and monomers, in which each crystal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the condition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nanostructures in the laboratory.

  9. Assembly and Folding of Twisted Baskets in Organic Solvents.

    Science.gov (United States)

    Pratumyot, Yaowalak; Chen, Shigui; Hu, Lei; Polen, Shane M; Hadad, Christopher M; Badjić, Jovica D

    2016-09-01

    A synthetic method for obtaining enantiopure and twisted baskets of type (P)-3 is described. These chiral cavitands were found to fold quinoline gates, at the rim of their twisted platform, in acetonitrile and give molecular capsules that assemble into large unilamellar vesicles. In a less polar dichloromethane, however, cup-shaped (P)-3 packed into vesicles but with the quinoline gates in an unfolded orientation. The ability of twisted baskets to form functional nanostructured materials could be of interest for building stereoselective sensors and catalysts. PMID:27513214

  10. Bonus Organisms in High-Throughput Eukaryotic Whole-Genome Shorgun Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Pangilinan, Jasmyn; Shapiro, Harris; Tu, Hank; Platt, Darren

    2006-02-06

    The DOE Joint Genome Institute has sequenced over 50 eukaryotic genomes, ranging in size from 15 MB to 1.6 GB, over a wide range of organism types. In the course of doing so, it has become clear that a substantial fraction of these data sets contains bonus organisms, usually prokaryotes, in addition to the desired genome. While some of these additional organisms are extraneous contamination, they are sometimes symbionts, and so can be of biological interest. Therefore, it is desirable to assemble the bonus organisms along with the main genome. This transforms the problem into one of metagenomic assembly, which is considerably more challenging than traditional whole-genome shotgun (WGS) assembly. The different organisms will usually be present at different sequence depths, which is difficult to handle in most WGS assemblers. In addition, with multiple distinct genomes present, chimerism can produce cross-organism combinations. Finally, there is no guarantee that only a single bonus organism will be present. For example, one JGI project contained at least two different prokaryotic contaminants, plus a 145 KB plasmid of unknown origin. We have developed techniques to routinely identify and handle such bonus organisms in a high-throughput sequencing environment. Approaches include screening and partitioning the unassembled data, and iterative subassemblies. These methods are applicable not only to bonus organisms, but also to desired components such as organelles. These procedures have the additional benefit of identifying, and allowing for the removal of, cloning artifacts such as E.coli and spurious vector inclusions.

  11. Making a Self-feeding Structure by Assembly of Digital Organs

    Science.gov (United States)

    Cussat-Blanc, Sylvain; Luga, Hervé; Duthen, Yves

    In Nature, the intrinsic cooperation between organism's parts is capital. Most living systems are composed of organs, functional units specialized for specific actions. In our last research, we developed an evolutionary model able to generate artificial organs. This paper deals with the assembly of organs. We show, through experimentation, the development of an artificial organism composed of four digital organs able to produce a self-feeding organism. This kind of structure has applications in the mophogenetic-engineering of future nano and bio robots.

  12. Functional metal-organic framework based materials and assemblies

    OpenAIRE

    AMELOOT, Rob

    2011-01-01

    Porous solids, such as zeolites and activated carbons, are strategic materials because of the applications they imply. Recently, metal-organic frameworks (MOFs) were introduced as a novel class of porous and crystalline materials. The crystal lattice of these compounds is constructed by coordination bonds between nodes of metal ions and multidentate organic ligands. Because of the wide range of metal ions and ligands that can be combined as MOF building blocks, a vast variety of crystal struc...

  13. Organic Solvents Mediate Self-assembly of GAV-9 Peptide on Mica Surface

    Institute of Scientific and Technical Information of China (English)

    Hai LI; Feng ZHANG; Yi ZHANG; Jianhua HE; Jun HU

    2007-01-01

    Self-assembly of peptides into fibrils and other morphologies has attracted much attention in many fields, especially in nanofabrication, pathology and biochemistry. In this paper, self-assembly of GAV-9 peptide in organic solvents, ethanol and acetone, was investigated using atomic force microscopy (AFM)and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The results indicated that GAV-9 self- assembled into various nanostructures in both solvents after deposited and evaporated on mica. Fibrils with β-sheet conformation were observed in both solvents when the peptide concentration was higher than 280 μM. However, ordered fibrils with β-sheet conformation were formed in ethanol, but not in acetone, with a peptide concentration ranging from 7 μM to 28 μM. We attribute the formation of various nanostructures to the different physicochemical properties of the polar organic solvents on the self-assembly of GAV-9 peptide.

  14. Influences of hydrophilic and hydrophobic substituents on the organization of supramolecular assemblies of porphyrin derivatives formed at the air/water interface

    International Nuclear Information System (INIS)

    Monolayers and Langmuir-Blodgett (LB) films of several kinds of porphyrin derivatives that have different substituted alkyl chain length, chain numbers and central metals were studied by π-A isotherms, UV-Vis, polarized UV-Vis and fluorescence spectroscopy and low angle X-ray diffractometry (LAXD). The orientation angles of porphyrin rings and alkyl chains were derived from the polarized UV-Vis spectra and LAXD patterns of the monolayers or LB films, respectively. The rings of the freebase porphyrins with different alkyl chain length or number have similar orientation angles in the films due to the same hydrophilic groups on the rings, and those of metal porphyrins have different orientation angles from each other. The orientation of the alkyl chains is related to the special positions of the chains on the rings and the orientation of the rings. The influences of the hydrophilicity of the hydrophilic groups and the alkyl chain number and length on the organization of the supramolecular assemblies of the porphyrin derivatives were discussed

  15. Fundamentals and application of ordered molecular assemblies to affinity biosensing.

    Science.gov (United States)

    Matharu, Zimple; Bandodkar, Amay Jairaj; Gupta, Vinay; Malhotra, Bansi Dhar

    2012-02-01

    Organization of biomolecules in two/three dimensional assemblies has recently aroused much interest in nanobiotechnology. In this context, the development of techniques for controlling spatial arrangement and orientation of the desired molecules to generate highly-ordered nanostructures in the form of a mono/multi layer is considered highly significant. The studies of monolayer films to date have focused on three distinct methods of preparation: (i) the Langmuir-Blodgett (LB) technique, involving the transfer of a monolayer assembled at the gas-liquid interface; (ii) self-assembly at the liquid-solid interface, based on spontaneous adsorption of desired molecules from a solution directly onto a solid surface; and (iii) Layer-by-layer (LBL) self-assembly at a liquid-solid interface, based on inter-layer electrostatic attractions for fabrication of multilayers. A variety of monolayers have been utilized to fabricate biomolecular electronic devices including biosensors. The composition of a monolayer based matrix has been found to influence the activity(ies) of biomolecule(s). We present comprehensive and critical analysis of ordered molecular assemblies formed by LB and self-assembly with potential applications to affinity biosensing. This critical review on fundamentals and application of ordered molecular assemblies to affinity biosensing is likely to benefit researchers working in this as well as related fields of research (401 references). PMID:22105315

  16. An introduction to ultrathin organic films from Langmuir-Blodgett to self-assembly

    CERN Document Server

    Ulman, Abraham

    1991-01-01

    The development of oriented organic monomolecular layers by the Langmuir-Blodgett (LB) and self-assembly (SA) techniques has led researchers toward their goal of assembling individual molecules into highly ordered architectures. Thus the continually growing contribution of LB and SA systems to the chemistry and physics of thin organic films is widely recognized. Equally well-known is the difficulty in keeping up to date with the burgeoning multidisciplinary research in this area. Dr. Ulman provides a massive survey of the available literature. The book begins with a section on analytical tools

  17. Controlled loading of building blocks into temporary self-assembled scaffolds for directed assembly of organic nanostructures.

    Science.gov (United States)

    Banner, L Todd; Danila, Delia C; Sharpe, Katie; Durkin, Melissa; Clayton, Benjamin; Anderson, Ben; Richter, Andrew; Pinkhassik, Eugene

    2008-10-21

    Using temporary self-assembled scaffolds to preorganize building blocks is a potentially powerful method for the synthesis of organic nanostructures with programmed shapes. We examined the underlying phenomena governing the loading of hydrophobic monomers into lipid bilayer interior and demonstrated successful control of the amount and ratio of loaded monomers. When excess styrene derivatives or acrylates were added to the aqueous solution of unilamellar liposomes made from saturated phospholipids, most loading occurs within the first few hours. Dynamic light scattering and transmission electron microscopy revealed no evidence of aggregation caused by monomers. Bilayers appeared to have a certain capacity for accommodating monomers. The total volume of loaded monomers is independent of monomer structure. X-ray scattering showed the increase in bilayer thickness consistent with loading monomers into bilayer interior. Loading kinetics is inversely proportional to the hydrophobicity and size of monomers. Loading and extraction kinetic data suggest that crossing the polar heads region is the rate limiting step. Consideration of loading kinetics and multiple equilibria are important for achieving reproducible monomer loading. The total amount of monomers loaded into the bilayer can be controlled by the loading time or length of hydrophobic lipid tails. The ratio of loaded monomers can be varied by changing the ratio of monomers used for loading or by the time-controlled replacement of a preloaded monomer. Understanding and controlling the loading of monomers into bilayers contributes to the directed assembly of organic nanostructures.

  18. Supramolecular Langmuir monolayers and multilayered vesicles of self-assembling DNA–lipid surface structures and their further implications in polyelectrolyte-based cell transfections

    Energy Technology Data Exchange (ETDEWEB)

    Demirsoy, Fatma Funda Kaya [Ankara University, The Central Laboratory of The Institute of Biotechnology (Turkey); Eruygur, Nuraniye [Gazi University, Department of Pharmacognosy, Faculty of Pharmacy (Turkey); Süleymanoğlu, Erhan, E-mail: erhans@mail.ru [Gazi University, Department of Pharmaceutical Chemistry, Faculty of Pharmacy (Turkey)

    2015-01-15

    The basic interfacial characteristics of DNA–lipid recognitions have been studied. The complex structures of individual unbound DNA molecules and their binary and ternary complexes with zwitterionic lipids and divalent cations were followed by employing lipid monolayers at the air–liquid interfaces, as well as by performing various microscopic, spectroscopic, and thermodynamic measurements with multilayered vesicles. The pressure-area isotherms depicted that Mg{sup 2+}-ions increase the surface pressure of lipid films and thus give rise to electrostatic and hydrophobic lipid–DNA interactions in terms of DNA adsorption, adhesion, and compaction. These features were further approached by using multilamellar vesicles with a mean diameter of 850 nm, where a metal ion-directed nucleic acid compaction and condensation effects were shown. The data obtained show the effectiveness of Langmuir monolayers and lipid multilayers in studying nucleic acid–lipid recognitions. The data provide with further details and support previous reports on mainly structural features of these recognitions. Biomolecular surface recognition events were presented in direct link with spectral and thermodynamic features of lipid vesicle–polynucleotide complex formations. The results serve to build a theoretical model considering the use of neutral lipids in lipoplex designs as a polyelectrolyte alternatives to the currently employed cytotoxic cationic liposomes. The supramolecular structures formed and their possible roles in interfacial electrostatic and hydrophobic mechanisms of endosomal escape in relevant cell transfection assays are particularly emphasized.

  19. Electrophoretic assembly of organic molecules and composites for electrochemical supercapacitors.

    Science.gov (United States)

    Su, Y; Zhitomirsky, I

    2013-02-15

    Electrophoretic deposition (EPD) method has been developed for the fabrication of 1-pyrenebutyric acid (PBH) films from aqueous solutions. The films can be deposited at constant voltage or potentiodynamic conditions. The method allowed the formation of 0.1-2 μm thick films, containing needle-shape PBH particles. The deposition mechanism involved the electrophoresis, pH decrease at the anode surface, charge neutralization and formation of insoluble PBH films. The film morphology and shape of the PBH particles are controlled by the π-π stacking mechanism of the polyaromatic PBH molecules. The important finding was the possibility of controlled EPD of multiwalled carbon nanotubes (MWCNTs) using PBH as a charging, dispersing and film forming agent. It was found that at low voltages or low PBH concentrations the deposits contained mainly MWCNT. The increase in the deposition voltage or/and PBH concentration resulted in co-deposition of MWCNT and needle-shape PBH particles. The new approach to the deposition of MWCNT was used for the fabrication of composite MnO(2)-MWCNT films for electrodes of electrochemical supercapacitors, which showed a specific capacitance of 250 F g(-1). The EPD method developed in this investigation paves the way for the deposition of other small organic molecules and composites and their applications in new materials and devices, utilizing functional properties of the organic molecules, CNT, and other advanced materials. PMID:23141761

  20. Assembly of Human Organs from Stem Cells to Study Liver Disease

    Science.gov (United States)

    Handa, Kan; Matsubara, Kentaro; Fukumitsu, Ken; Guzman-Lepe, Jorge; Watson, Alicia; Soto-Gutierrez, Alejandro

    2015-01-01

    Recently, significant developments in the field of liver tissue engineering have raised new possibilities for the study of complex physiological and pathophysiological processes in vitro, as well as the potential to assemble entire organs for transplantation. Human-induced pluripotent stem cells have been differentiated into relatively functional populations of hepatic cells, and novel techniques to generate whole organ acellular three-dimensional scaffolds have been developed. In this review, we highlight the most recent advances in organ assembly regarding the development of liver tissue in vitro. We emphasize applications that involve multiple types of cells with a biomimetic spatial organization for which three-dimensional configurations could be used for drug development or to explain mechanisms of disease. We also discuss applications of liver organotypic surrogates and the challenges of translating the highly promising new field of tissue engineering into a proven platform for predicting drug metabolism and toxicity. PMID:24333262

  1. Self-Assembly, Guest Capture, and NMR Spectroscopy of a Metal-Organic Cage in Water

    Science.gov (United States)

    Go, Eun Bin; Srisuknimit, Veerasak; Cheng, Stephanie L.; Vosburg, David A.

    2016-01-01

    A green organic-inorganic laboratory experiment has been developed in which students prepare a self-assembling iron cage in D[subscript 2]O at room temperature. The tetrahedral cage captures a small, neutral molecule such as cyclohexane or tetrahydrofuran. [Superscript 1]H NMR analysis distinguishes captured and free guests through diagnostic…

  2. Assembly of Nanoscale Organic Single-Crystal Cross-Wire Circuits

    DEFF Research Database (Denmark)

    Bjørnholm, Thomas

    2009-01-01

    Organic single-crystal transistors and circuits can be assembled by nanomechanical manipulation of nanowires of CuPc, F(16)CuPc, and SnO(2):Sb. The crossed bar devices have low operational voltage, high mobility and are stable in air. They can be combined into circuits, providing varied functions...

  3. Assembly of Human Organs from Stem Cells to Study Liver Disease

    OpenAIRE

    Handa, Kan; Matsubara, Kentaro; Fukumitsu, Ken; Guzman-Lepe, Jorge; Watson, Alicia; Soto-Gutierrez, Alejandro

    2014-01-01

    Recently, significant developments in the field of liver tissue engineering have raised new possibilities for the study of complex physiological and pathophysiological processes in vitro, as well as the potential to assemble entire organs for transplantation. Human-induced pluripotent stem cells have been differentiated into relatively functional populations of hepatic cells, and novel techniques to generate whole organ acellular three-dimensional scaffolds have been developed. In this review...

  4. Reactive self-assembled monolayers on flat and nanoparticle surfaces, and their application in soft and scanning probe lithographic nanofabrication technologies

    NARCIS (Netherlands)

    Li, Xue-Mei; Huskens, Jurriaan; Reinhoudt, David N.

    2004-01-01

    Self-assembly is an interesting process both for its biological relevance and because it provides a novel approach to complex structures having nanometer-scale dimensions. These structures are difficult or impossible to prepare by traditional methods. In this article, a general review on the use of

  5. A new amperometric method for rapid detection of Escherichia coli density using a self-assembled monolayer-based bienzyme biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Tang Hui [Department of Chemistry, East China Normal University, Shanghai 200062 (China); Zhang Wen [Department of Chemistry, East China Normal University, Shanghai 200062 (China)]. E-mail: wenzhang26@163.com; Geng Ping [Department of Chemistry, East China Normal University, Shanghai 200062 (China); Wang Qingjiang [Department of Chemistry, East China Normal University, Shanghai 200062 (China); Jin Litong [Department of Chemistry, East China Normal University, Shanghai 200062 (China)]. E-mail: ltjin@chem.ecnu.edu.cn; Wu Zirong [School of Life Sciences, East China Normal University, Shanghai 200062 (China); Lou Min [School of Life Sciences, East China Normal University, Shanghai 200062 (China)

    2006-03-15

    A new amperometric method was developed for rapid detection of Escherichia coli (E. coli) density using a bienzyme biosensor. The bienzyme biosensor was fabricated based on the covalent immobilization of laccase and horseradish peroxidase (HRP) at indium tin oxide (ITO) electrode by (3-aminopropyl) triethoxysilane (APTES) monolayer. The bienzyme biosensor showed a high sensitivity in determination of the polyphenolic compounds, which was microbially generated from the salicylic acid (SA) added into the culture medium during the course of E. coli metabolism. Since the amount of polyphenolic compounds depends on E. coli density, the bienzyme biosensor was applied for the rapid and high sensitive detection of E. coli density after the E. coli solution was incubated in culture medium with salicylic acid for 2.5 h at 37 deg. C. By chronoamperometry, the amplified response current was obtained at the bienzyme biosensor, due to the substrate recycling of the polyphenolic compounds driven by bienzyme-catalyzed oxidation and electrochemical reduction. The amplified response current at the biosensor was linear with the E. coli density ranging from 1.6 x 10{sup 3} to 1.0 x 10{sup 7} cells/mL. The bienzyme biosensor could detect the E. coli density with a detection limit of 9.7 x 10{sup 2} cells/mL within 3 h.

  6. Biochemical Composition and Assembly of Biosilica-associated Insoluble Organic Matrices from the Diatom Thalassiosira pseudonana.

    Science.gov (United States)

    Kotzsch, Alexander; Pawolski, Damian; Milentyev, Alexander; Shevchenko, Anna; Scheffel, André; Poulsen, Nicole; Shevchenko, Andrej; Kröger, Nils

    2016-03-01

    The nano- and micropatterned biosilica cell walls of diatoms are remarkable examples of biological morphogenesis and possess highly interesting material properties. Only recently has it been demonstrated that biosilica-associated organic structures with specific nanopatterns (termed insoluble organic matrices) are general components of diatom biosilica. The model diatom Thalassiosira pseudonana contains three types of insoluble organic matrices: chitin meshworks, organic microrings, and organic microplates, the latter being described in the present study for the first time. To date, little is known about the molecular composition, intracellular assembly, and biological functions of organic matrices. Here we have performed structural and functional analyses of the organic microrings and organic microplates from T. pseudonana. Proteomics analysis yielded seven proteins of unknown function (termed SiMat proteins) together with five known silica biomineralization proteins (four cingulins and one silaffin). The location of SiMat1-GFP in the insoluble organic microrings and the similarity of tyrosine- and lysine-rich functional domains identifies this protein as a new member of the cingulin protein family. Mass spectrometric analysis indicates that most of the lysine residues of cingulins and the other insoluble organic matrix proteins are post-translationally modified by short polyamine groups, which are known to enhance the silica formation activity of proteins. Studies with recombinant cingulins (rCinY2 and rCinW2) demonstrate that acidic conditions (pH 5.5) trigger the assembly of mixed cingulin aggregates that have silica formation activity. Our results suggest an important role for cingulins in the biogenesis of organic microrings and support the hypothesis that this type of insoluble organic matrix functions in biosilica morphogenesis.

  7. Substituent-Controlled Reversible Switching of Charge Injection Barrier Heights at Metal/Organic Semiconductor Contacts Modified with Disordered Molecular Monolayers.

    Science.gov (United States)

    Nouchi, Ryo; Tanimoto, Takaaki

    2015-07-28

    Electrically stimulated switching of a charge injection barrier at the interface between an organic semiconductor and an electrode modified with a disordered monolayer (DM) is studied by using various benzenethiol derivatives as DM molecules. The switching behavior is induced by a structural change in the DM molecules and is manifested as a reversible inversion of the polarity of DM-modified Au electrode/rubrene/DM-modified Au electrode diodes. The switching direction is found to be dominantly determined by the push-back effect of the thiol bonding group, while the terminal group modulates the switching strength. A device with 1,2-benzenedithiol DMs exhibited the highest switching ratios of 20, 10(2), and 10(3) for the switching voltages of 3, 5, and 7 V, respectively. A variation in the tilt angle of benzenethiol DMs due to the application of 7 V is estimated to be smaller than 23.6° by model calculations. This study offers an understanding for obtaining highly stable operations of organic electronic devices, especially with molecular modification layers. PMID:26161447

  8. Self-assembled hybrid metal oxide base catalysts prepared by simply mixing with organic modifiers

    OpenAIRE

    Tamura, Masazumi; Kishi, Ryota; Nakagawa, Yoshinao; Tomishige, Keiichi

    2015-01-01

    Multidentate materials formed by simply mixing heterogeneous and homogeneous components are promising for construction of versatile active sites on the surface of heterogeneous compounds, however, to the best of our knowledge, there are no reports on such materials. Self-assembly of hetero-hybrid catalytic materials occurs when heterogeneous catalysts having adjacent Lewis acid-Lewis base sites are mixed with an organic modifier that contains at least two Lewis base functional groups. Here we...

  9. Development of Self-Assembled Supramolecular Catalysts and Their Applications to Organic Synthesis

    Institute of Scientific and Technical Information of China (English)

    Shiro IKEGAMI

    2005-01-01

    @@ 1Introduction In modern synthetic organic chemistry, the development of efficient reagent or catalyst recycling systems is regarded as one of the most important topics. We have previously reported a self-assembled process between poly(N-isopropylacrylamide) (PNIPAAm) based polymer ligands and an inorganic species[1]. This process afforded a networked supramolecular complex where the polymers are cross-linked together by the inorganic species. Thus obtained complex was insoluble in water and worked as an efficient triphase catalyst.

  10. First- principle Study of the Self- assembly Monolayer on Silicon (100) Surface%硅(100)表面组装膜的第一性原理研究

    Institute of Scientific and Technical Information of China (English)

    史立秋; 息明东; 张琳; 马清祥

    2012-01-01

    应用基于密度泛函理论的第一原理计算研究硅(100)表面芳香烃重氮盐自组装单层膜的键长、键角和能量的改变.通过模拟计算,可以确定自组装膜的稳定结构和结合能.计算结果显示,单晶硅表面在自组装前后部分键长和键角发生了明显的改变.整个自组装系统减少的能量是-101.95eV,该能量是形成Si-C共价键释放出的结合能,说明芳香烃重氮盐和单晶硅(100)表面很容易形成自组装单层膜.自组装后的系统稳定性很好,证明硅表面的单层膜结合的很牢固.%The first principle calculation based density functional theory was employed to investigate the changes of energy, bonds length and bonds angle of aryldiazonium salt Self - assembly monolayer (SAMs) on silicon (100) surface. The steady structure and binding energy can be determined. It is shown that the partial bonds length and bonds angle have been changed obviously before and after self- assembly. The reduced energy of system is -101.95eV, binding energy, which is emitted energy of Si -C covalent bond coming into being, il- luminates that the SAMs can be fabricated easily between aryldiazonium salt and Si (100) surface. The stability of system can be improved and SAMs can firmly stay on Si (100) surface.

  11. Combined atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) studies of glucose oxidase (GOx) immobilised onto self-assembled monolayer on the gold film

    International Nuclear Information System (INIS)

    In fabrication of biosensors, self-assembled monolayers (SAM) are an attractive method of immobilising enzymes at electrode surface since it allows precise control over the amount and spatial distribution of the immobilized enzyme. The covalent attachment of glucose oxidase (GOx) to a carboxylic terminated SAM chemisorbed onto gold films was achieved via carbodiimide activation of the carboxylic acids to a reactive intermediate susceptible to nucleophilic attack by amines on free lysine chains of the enzyme. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) measurements were used for characterisation of GOx modified gold surfaces. Tapping mode AFM studies have revealed that GOx molecules form slightly disordered arrays of pentagonal or hexagonal clusters. Observed features of immobilised GOx are distributed as a submonolayer on the SAM surface which has allowed visualisation of native and unfolded enzyme structure. The presence of the SAM and enzyme on the gold surface was detected by XPS spectroscopy. Spectra show typical peaks for the C 1s, O 1s and N 1s regions. A kinetic study of the adsorption of GOx onto activated SAM using in-situ QCM allowed determination the amount of immobilised GOx on the layer and consequently the optimal immobilisation conditions. Performance parameters of the biosensor such as sensitivity to glucose concentration as a function of enzyme loading were evaluated amperometrically using the redox mediator p-benzoquinone

  12. The structure of percolating lipid monolayers.

    Science.gov (United States)

    Risović, D; Frka, S; Kozarac, Z

    2012-05-01

    The lattice structure and in plane molecular organization of Langmuir monolayer of amphiphilic material is usually determined from grazing incidence X-ray diffraction (GIXD) or neutron reflectivity. Here we present results of a different approach for determination of monolayer lattice structure based on application of fractal analysis and percolation theory in combination with Brewster angle microscopy. The considerations of compressibility modulus and fractal dimension dynamics provide information on percolation threshold and consequently by application of percolation theory on the lattice structure of a monolayer. We have applied this approach to determine the monolayer lattice structures of single chain and double chain lipids. The compressibility moduli were determined from measured π-A isotherms and fractal dimensions from corresponding BAM images. The monolayer lattice structures of stearic acid, 1-hexadecanol, DPPC and DPPA, obtained in this way conform to the corresponding lattice structures determined previously by other authors using GIXD. PMID:22209411

  13. The supramolecular organization of self-assembling chlorosomal bacteriochlorophyll c, d, or e mimics.

    Science.gov (United States)

    Jochum, Tobias; Reddy, Chilla Malla; Eichhöfer, Andreas; Buth, Gernot; Szmytkowski, Jedrzej; Kalt, Heinz; Moss, David; Balaban, Teodor Silviu

    2008-09-01

    Bacteriochlorophylls (BChls) c, d, and e are the main light-harvesting pigments of green photosynthetic bacteria that self-assemble into nanostructures within the chlorosomes forming the most efficient antennas of photosynthetic organisms. All previous models of the chlorosomal antennae, which are quite controversially discussed because no single crystals could be grown so far from these organelles, involve a strong hydrogen-bonding interaction between the 3(1) hydroxyl group and the 13(1) carbonyl group. We have synthesized different self-assemblies of BChl c mimics having the same functional groups as the natural counterparts, that is, a hydroxyethyl substituent, a carbonyl group and a divalent metal atom ligated by a tetrapyrrole. These artificial BChl mimics have been shown by single crystal x-ray diffraction to form extended stacks that are packed by hydrophobic interactions and in the absence of hydrogen bonding. Time-resolved photoluminescence proves the ordered nature of the self-assembled stacks. FT-IR spectra show that on self-assembly the carbonyl frequency is shifted by approximately 30 cm(-1) to lower wavenumbers. From the FT-IR data we can infer the proximal interactions between the BChls in the chlorosomes consistent with a single crystal x-ray structure that shows a weak electrostatic interaction between carbonyl groups and the central zinc atom. PMID:18755898

  14. Sum-frequency vibrational spectroscopy of a monolayer self-assembled on gold: interference between resonant and nonresonant contributions of nonlinear polarization

    Science.gov (United States)

    Tanaka, Yoshihito; Lin, S.; Aono, M.; Suzuki, T.

    The spectral profiles of sum-frequency signal from CH vibrational modes of octadecanethiol (ODT) self-assembled on gold have been studied for several optical configurations of incident beams. The observed spectra, generally of the shape of dispersion type, have been interpreted by the interference between the resonant contribution from the CH stretching modes of adsorbed molecules and the nonresonant contribution from the gold substrate. We have shown for the first time that the contribution from the zzz component of the resonant nonlinear susceptibility χzzz(R) is dominant in the observed resonant signals, whereas all of the ijk components contribute to the nonresonant signal. The transition frequencies and the relative amplitude of resonant signals are also determined for the CH3 vibrational modes of ODT on gold.

  15. Scaling up self-assembly: bottom-up approaches to macroscopic particle organization.

    Science.gov (United States)

    Lash, M H; Fedorchak, M V; McCarthy, J J; Little, S R

    2015-07-28

    This review presents an overview of recent work in the field of non-Brownian particle self-assembly. Compared to nanoparticles that naturally self-assemble due to Brownian motion, larger, non-Brownian particles (d > 6 μm) are less prone to autonomously organize into crystalline arrays. The tendency for particle systems to experience immobilization and kinetic arrest grows with particle radius. In order to overcome this kinetic limitation, some type of external driver must be applied to act as an artificial "thermalizing force" upon non-Brownian particles, inducing particle motion and subsequent crystallization. Many groups have explored the use of various agitation methods to overcome the natural barriers preventing self-assembly to which non-Brownian particles are susceptible. The ability to create materials from a bottom-up approach with these characteristics would allow for precise control over their pore structure (size and distribution) and surface properties (topography, functionalization and area), resulting in improved regulation of key characteristics such as mechanical strength, diffusive properties, and possibly even photonic properties. This review will highlight these approaches, as well as discuss the potential impact of bottom-up macroscale particle assembly. The applications of such technology range from customizable and autonomously self-assembled niche microenvironments for drug delivery and tissue engineering to new acoustic dampening, battery, and filtration materials, among others. Additionally, crystals made from non-Brownian particles resemble naturally derived materials such as opals, zeolites, and biological tissue (i.e. bone, cartilage and lung), due to their high surface area, pore distribution, and tunable (multilevel) hierarchy. PMID:25947543

  16. Electrochemical Impedance Immunosensor Based on Self-Assembled Monolayers for Rapid Detection of Escherichia coli O157:H7 with Signal Amplification Using Lectin

    Directory of Open Access Journals (Sweden)

    Zhanming Li

    2015-08-01

    Full Text Available Escherichia coli O157:H7 is a predominant foodborne pathogen with severe pathogenicity, leading to increasing attention given to rapid and sensitive detection. Herein, we propose an impedance biosensor using new kinds of screen-printed interdigitated microelectrodes (SPIMs and wheat germ agglutinin (WGA for signal amplification to detect E. coli O157:H7 with high sensitivity and time-efficiency. The SPIMs integrate the high sensitivity and short response time of the interdigitated electrodes and the low cost of the screen-printed electrodes. Self-assembling of bi-functional 3-dithiobis-(sulfosuccinimidyl-propionate (DTSP on the SPIMs was investigated and was proved to be able to improve adsorption quantity and stability of biomaterials. WGA was further adopted to enhance the signal taking advantage of the abundant lectin-binding sites on the bacteria surface. The immunosensor exhibited a detection limit of 102 cfu·mL−1, with a linear detection range from 102 to 107 cfu·mL−1 (r2 = 0.98. The total detection time was less than 1 h, showing its comparable sensitivity and rapid response. Furthermore, the low cost of one SPIM significantly reduced the detection cost of the biosensor. The biosensor may have great promise in food safety analysis and lead to a portable biosensing system for routine monitoring of foodborne pathogens.

  17. Electrochemical Impedance Immunosensor Based on Self-Assembled Monolayers for Rapid Detection of Escherichia coli O157:H7 with Signal Amplification Using Lectin

    Science.gov (United States)

    Li, Zhanming; Fu, Yingchun; Fang, Weihuan; Li, Yanbin

    2015-01-01

    Escherichia coli O157:H7 is a predominant foodborne pathogen with severe pathogenicity, leading to increasing attention given to rapid and sensitive detection. Herein, we propose an impedance biosensor using new kinds of screen-printed interdigitated microelectrodes (SPIMs) and wheat germ agglutinin (WGA) for signal amplification to detect E. coli O157:H7 with high sensitivity and time-efficiency. The SPIMs integrate the high sensitivity and short response time of the interdigitated electrodes and the low cost of the screen-printed electrodes. Self-assembling of bi-functional 3-dithiobis-(sulfosuccinimidyl-propionate) (DTSP) on the SPIMs was investigated and was proved to be able to improve adsorption quantity and stability of biomaterials. WGA was further adopted to enhance the signal taking advantage of the abundant lectin-binding sites on the bacteria surface. The immunosensor exhibited a detection limit of 102 cfu·mL−1, with a linear detection range from 102 to 107 cfu·mL−1 (r2 = 0.98). The total detection time was less than 1 h, showing its comparable sensitivity and rapid response. Furthermore, the low cost of one SPIM significantly reduced the detection cost of the biosensor. The biosensor may have great promise in food safety analysis and lead to a portable biosensing system for routine monitoring of foodborne pathogens. PMID:26251911

  18. Organization of Mitochondrial Gene Expression in Two Distinct Ribosome-Containing Assemblies

    Directory of Open Access Journals (Sweden)

    Kirsten Kehrein

    2015-02-01

    Full Text Available Mitochondria contain their own genetic system that provides subunits of the complexes driving oxidative phosphorylation. A quarter of the mitochondrial proteome participates in gene expression, but how all these factors are orchestrated and spatially organized is currently unknown. Here, we established a method to purify and analyze native and intact complexes of mitochondrial ribosomes. Quantitative mass spectrometry revealed extensive interactions of ribosomes with factors involved in all the steps of posttranscriptional gene expression. These interactions result in large expressosome-like assemblies that we termed mitochondrial organization of gene expression (MIOREX complexes. Superresolution microscopy revealed that most MIOREX complexes are evenly distributed throughout the mitochondrial network, whereas a subset is present as nucleoid-MIOREX complexes that unite the whole spectrum of organellar gene expression. Our work therefore provides a conceptual framework for the spatial organization of mitochondrial protein synthesis that likely developed to facilitate gene expression in the organelle.

  19. Probing the chemical structure of monolayer covalent-organic frameworks grown via Schiff-base condensation reactions.

    Science.gov (United States)

    Hu, Ya; Goodeal, Niall; Chen, Ying; Ganose, Alex M; Palgrave, Robert G; Bronstein, Hugo; Blunt, Matthew O

    2016-08-01

    Two-dimensional covalent-organic frameworks (2D-COFs) on surfaces offer a facile route to new 2D materials. Schiff-base condensation reactions have proven to be an effective fabrication route for such materials. We present scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) studies of porphyrin 2D-COFs grown at a solid-vapour interface. XPS shows that covalent links between porphyrins consist of a mixture of imines and hemiaminals, a non-conjugated intermediate in the Schiff-base condensation reaction. These results demonstrate that environmental conditions during growth can have an important impact on the chemical composition of Schiff-base 2D-COFs. PMID:27436064

  20. Functional-template directed self-assembly (FTDSA) of mesostructured organic-inorganic hybrid materials

    Institute of Scientific and Technical Information of China (English)

    LI LeLe; SUN LingDong; ZHANG YaWen; YAN ChunHua

    2009-01-01

    Since the discovery of a surfactant directed self-assembly approach for the fabrication of mesoporous silica in 1992,increasing attention has been focused on the design and synthesis of mesostructured functional materials.Organic functionalization is becoming a major topic in this research field,since highly ordered mesostructured organic-inorganic hybrids offer novel functionalities and enhanced performance over their individual components.We begin with a brief overview of the three fundamental methods (post-synthetic grafting technique,co-condensation method,and preparation of periodic mesoporous organosilicas) for the preparation of organically functionalized mesostructured silica,and focus on one of the most promising approaches,which herein was named as functional-template directed self-assembly (FTDSA) approach,and in the eyes of the authors it has a special position in the preparation of this class of hybrid materials.A comprehensive overview of the state of research in the area of FTDSA and its potential applications will be given.

  1. Analytical techniques for characterization of organic molecular assemblies in molecular electronics devices

    Energy Technology Data Exchange (ETDEWEB)

    James, Dustin K. [Department of Chemistry and Smalley Institute for Nanoscale Science and Technology, MS 222, Rice University, 6100 Main Street, Houston, TX 77005 (United States)]. E-mail: dustin@rice.edu; Tour, James M. [Department of Chemistry and Smalley Institute for Nanoscale Science and Technology, MS 222, Rice University, 6100 Main Street, Houston, TX 77005 (United States)]. E-mail: tour@rice.edu

    2006-05-24

    The analytical techniques used for the physical characterization of organic molecular electronic-based devices are surveyed and discussed. These protocols include methods that are used to probe molecular assemblies such as single wavelength ellipsometry, water contact angle goniometry, cyclic voltammetry, infrared spectroscopy, and X-ray photoelectron spectroscopy, and methods used to measure charge transport properties of devices such as scanning tunneling microscopy, and inelastic electron tunneling spectroscopy. Examples from our laboratory and the literature are given for each of these analytical techniques.

  2. A study on organized assemblies in the sodium alkylcarboxylate/ fatty alcohol/water systems

    Institute of Scientific and Technical Information of China (English)

    MAO, Mina; FU, Hong-Lanb; ZHU, Bu-Yaoa; HE, Xua; SHI, Hong-Taoa; HUANG, Jian-Bin

    2000-01-01

    The phase behavior and evolution of self-organized assembling sttructures in the sodium allkylcarboxylate/fatty alcohol systems were investigated by TEM. With increasing concentration of fatty alcohd, the micelles transform into lamellar- La phase, sponge L3 phase, multilamellar vesicle, and transform back to lamellar La phase. At higher alcohol concentration, a stable two aqueous phase coexisting region has been observed in this kind of systems after aged two months. Unilamellar vesicles were found both in two separated phases but the vesicle densi ty ofthe upper phase is much higher than that of the bottom phase.

  3. Are Regional Organizations the 'Parties' in the United Nations General Assembly? Comments on a Misconception

    DEFF Research Database (Denmark)

    Burmester, Nicolas; Jankowski, Michael

    In the field of international relations, regional organizations (ROs) are not only assumed to play an important role in the regional context, but also on the international level. A growing number of studies analyze ROs’ voting behavior in the United Nations General Assembly (UNGA) in a similar way...... to the analyses of parties in national parliaments. In this paper, we reflect on the question whether ROs can be treated as ‘political party’-like entities. First, based on literature on political parties and legislative voting, we develop two criteria to evaluate ROs in the UNGA. Second, we analyze UNGA voting...

  4. Self-Assembling Organic Micro-/Nano-Pillars on Gold and Glass Surfaces

    Directory of Open Access Journals (Sweden)

    Hai-Feng Ji

    2014-09-01

    Full Text Available In this work, we report the formation of a family of organic micro-/nano-pillars prepared from surface-assisted self-assembly processes and factors controlling the growth of the pillars. These acids include cyanuric acid (CA, 1,3,5-benzenetricarboxylic acid (TMA, 1,2,4,5-benzenetetracarboxylic acid (TA and 3,4,9,10-perylenetetracarboxylic acid (PTA. Aqueous solutions mixed with acids and melamine (M can be fine-tuned to prepare ordered micro-/nano-pillars on substrates, which can be further optimized for their applications

  5. Research of biosensor and its application based on the mercaptoacetic acid self-assembled monolayer%基于巯基乙酸自组装膜传感器的应用研究

    Institute of Scientific and Technical Information of China (English)

    屈晶; 连靠奇; 康维钧; 牛凌梅

    2013-01-01

    The mercaptoacetic acid self-assemble monolayer modified gold electrode was prepared. The electro-chemical behavior of ferulic acid (FA) at the modified electrode was studied by linear sweep voltammetry. It was found that, in phosphate buffer of pH2.5, the modified electrode showed an excellent electrocatalytic ability to fer-ulic acid and the peak currents were elevated greatly. The peak currents were linearly dependent on the FA concen-trations in the range of 5.0 × 10-6 to 1.0 × 10-4 mol/L , and the detection limit was 1.0 × 10-6 mol/L . This method was applied in the ferulic acid determination in injection with the recovery of 103.7%~104.4%.%  制备了巯基乙酸自组装膜修饰的金电极。利用线性扫描伏安法研究了阿魏酸在此修饰电极上的电化学行为,发现在pH为2.5的磷酸缓冲液中,修饰电极对阿魏酸(FA)表现出良好的电催化能力,能显著地提高阿魏酸的电信号强度。在浓度为5.0×10-6~1.0×10-4 mol/L范围内,阿魏酸的氧化峰电流与其浓度呈线性关系,检出限为1.0×10-6 mol/L。此方法用于注射用阿魏酸钠的检测,回收率在103.7%~104.4%之间。

  6. Electrodeposition of gold nanoparticles onto an etched stainless steel wire followed by a self-assembled monolayer of octanedithiol as a fiber coating for selective solid-phase microextraction.

    Science.gov (United States)

    Yang, Yaoxia; Li, Yi; Liu, Haixia; Wang, Xuemei; Du, Xinzhen

    2014-11-01

    In the present study, a novel approach for rapid electrodeposition on an etched stainless steel (SS) wire followed by self-assembled monolayer (SAM) was proposed for the fabrication of solid-phase microextraction (SPME) fiber. The etched SS wire offers a rough surface structure for subsequent electrochemical deposition of gold nanoparticles (AuNPs). As a result, uniform AuNPs coating was tightly attached to the etched SS wire substrate. After SAM of 1,8-octanedithiol onto AuNPs coating via Au-S bonding, a unique floccular structure with extremely large surface area was obtained for the fabricated fiber. The mercaptooctyl groups modified AuNPs coated etched SS fiber (C8-S-AuNPs/SS) was then assessed for SPME of phthalate esters (PAEs), polychlorinated biphenyls (PCBs), chlorophenols (CPs), ultraviolet (UV) filters, polycyclic aromatic hydrocarbons (PAHs) and substituted anilines coupled to high-performance liquid chromatography with UV detection. This fiber exhibits higher extraction capability and better selectivity for some PCBs, CPs, UV filters and PAHs. Extraction conditions were investigated and optimized for SPME performance of UV filters. Under the optimized conditions, the developed method showed good linearity between 0.10 and 400μgL(-1) with corresponding coefficients in the range of 0.9989-0.9998. The limits of detection ranged from 0.025 to 0.056μgL(-1). The relative standard deviation for fiber-to-fiber reproducibility of five fabricated fibers was less than 9.4%. The developed method was successfully applied to the preconcentration and determination of trace UV filters from environmental water samples. Furthermore the fabrication of the C8-S-AuNPs/SS fiber can be performed in a highly reproducible manner. This fabricated fiber exhibits good stability and long lifetime, and could be a potential alternative for the conventional fused silica fiber. PMID:25465004

  7. Fracton pairing mechanism for unconventional superconductors: Self-assembling organic polymers and copper-oxide compounds

    DEFF Research Database (Denmark)

    Milovanov, A.V.; Juul Rasmussen, J.

    2002-01-01

    Self-assembling organic polymers and copper-oxide compounds are two classes of unconventional superconductors, whose challenging behavior does not comply with the traditional picture of Bardeen-Cooper-Schrieffer (BCS) superconductivity in regular crystals. In this paper, we propose a theoretical...... or holes) exchange fracton excitations, quantum oscillations of fractal lattices that mimic the complex microscopic organization of the unconventional superconductors. For the copper oxides, the superconducting transition temperature T-c as predicted by the fracton mechanism is of the order of similar to......-induced superconducting phase in the electron-doped polymers, we simultaneously find a rather modest transition temperature of similar to2-3 K owing to the limitations imposed by the electron tunneling processes on a fractal geometry. We speculate that the hole-type superconductivity shows a larger onset temperature when...

  8. Molecular and supramolecular control of the work function of an inorganic electrode with self-assembled monolayer of umbrella-shaped fullerene derivatives.

    Science.gov (United States)

    Lacher, Sebastian; Matsuo, Yutaka; Nakamura, Eiichi

    2011-10-26

    The surface properties of inorganic substrates can be altered by coating with organic molecules, which may result in the improvement of the properties suitable for electronic or biological applications. This article reports a systematic experimental study on the influence of the molecular and supramolecular properties of umbrella-shaped penta(organo)[60]fullerene derivatives, and on the work function and the water contact angle of indium-tin oxide (ITO) and gold surfaces. We could relate these macroscopic characteristics to single-molecular level properties, such as ionization potential and molecular dipole. The results led us to conclude that the formation of a SAM of a polar compound generates an electronic field through intermolecular interaction of the molecular charges, and this field makes the overall dipole of the SAM much smaller than the one expected from the simple sum of the dipoles of all molecules in the SAM. This effect, which was called depolarization and previously discussed theoretically, is now quantitatively probed by experiments. The important physical properties in surface science such as work function, ionization potential, and water contact angles have been mutually correlated at the level of molecular structures and molecular orientations on the substrate surface. We also found that the SAMs on ITO and gold operate under the same principle except that the "push-back" effect operates specifically for gold. The study also illustrates the ability of the photoelectron yield spectroscopy technique to rapidly measure the work function of a SAM-covered substrate and the ionization potential value of a molecule on the surface. PMID:21923177

  9. Cold denaturation induces inversion of dipole and spin transfer in chiral peptide monolayers

    Science.gov (United States)

    Eckshtain-Levi, Meital; Capua, Eyal; Refaely-Abramson, Sivan; Sarkar, Soumyajit; Gavrilov, Yulian; Mathew, Shinto P.; Paltiel, Yossi; Levy, Yaakov; Kronik, Leeor; Naaman, Ron

    2016-02-01

    Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers. Here, we use this spin selectivity to probe the organization of self-assembled α-helix peptide monolayers and examine the relation between structural and spin transfer phenomena. We show that the α-helix structure of oligopeptides based on alanine and aminoisobutyric acid is transformed to a more linear one upon cooling. This process is similar to the known cold denaturation in peptides, but here the self-assembled monolayer plays the role of the solvent. The structural change results in a flip in the direction of the electrical dipole moment of the adsorbed molecules. The dipole flip is accompanied by a concomitant change in the spin that is preferred in electron transfer through the molecules, observed via a new solid-state hybrid organic-inorganic device that is based on the Hall effect, but operates with no external magnetic field or magnetic material.

  10. Planar cell polarity proteins differentially regulate extracellular matrix organization and assembly during zebrafish gastrulation.

    Science.gov (United States)

    Dohn, Michael R; Mundell, Nathan A; Sawyer, Leah M; Dunlap, Julie A; Jessen, Jason R

    2013-11-01

    Zebrafish gastrulation cell movements occur in the context of dynamic changes in extracellular matrix (ECM) organization and require the concerted action of planar cell polarity (PCP) proteins that regulate cell elongation and mediolateral alignment. Data obtained using Xenopus laevis gastrulae have shown that integrin-fibronectin interactions underlie the formation of polarized cell protrusions necessary for PCP and have implicated PCP proteins themselves as regulators of ECM. By contrast, the relationship between establishment of PCP and ECM assembly/remodeling during zebrafish gastrulation is unclear. We previously showed that zebrafish embryos carrying a null mutation in the four-pass transmembrane PCP protein vang-like 2 (vangl2) exhibit increased matrix metalloproteinase activity and decreased immunolabeling of fibronectin. These data implicated for the first time a core PCP protein in the regulation of pericellular proteolysis of ECM substrates and raised the question of whether other zebrafish PCP proteins also impact ECM organization. In Drosophila melanogaster, the cytoplasmic PCP protein Prickle binds Van Gogh and regulates its function. Here we report that similar to vangl2, loss of zebrafish prickle1a decreases fibronectin protein levels in gastrula embryos. We further show that Prickle1a physically binds Vangl2 and regulates both the subcellular distribution and total protein level of Vangl2. These data suggest that the ability of Prickle1a to impact fibronectin organization is at least partly due to effects on Vangl2. In contrast to loss of either Vangl2 or Prickle1a function, we find that glypican4 (a Wnt co-receptor) and frizzled7 mutant gastrula embryos with disrupted non-canonical Wnt signaling exhibit the opposite phenotype, namely increased fibronectin assembly. Our data show that glypican4 mutants do not have decreased proteolysis of ECM substrates, but instead have increased cell surface cadherin protein expression and increased intercellular

  11. Self-Assembling Amphiphilic Molecules: A Possible Relationship Between Interstellar Chemistry and Meteoritic Organics

    Science.gov (United States)

    Sandford, Scott A.; Dworkin, Jason P.; Deamer, David W.; Allamandola, Louis J.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    Interstellar gas and dust comprise the primary material from which the solar system formed. Evidence that some of this material was organic in nature and survived incorporation into the protosolar nebula is provided by the presence of deuterium-enriched organics in meteorites and interplanetary dust particles. Once the inner planets had sufficiently cooled, late accretionary infall of meteoroids and cosmic dust must have seeded them with some of these complex organic compounds. Delivery of such extraterrestrial compounds may have contributed to the organic inventory necessary for the origin of life. Interstellar ices, the building blocks of comets, tie up a large fraction of the biogenic elements available in molecular clouds. In our efforts to understand their synthesis, chemical composition, and physical properties, we report here that a complex mixture of molecules is produced by ultraviolet (UV) photolysis of realistic, interstellar ice analogs, and that some of the components have properties relevant to the origin of life, including the ability to self-assemble into vesicular structures.

  12. Self-assembly of ferromagnetic organic-inorganic perovskite-like films.

    Science.gov (United States)

    Akhtar, Naureen; Polyakov, Alexey O; Aqeel, Aisha; Gordiichuk, Pavlo; Blake, Graeme R; Baas, Jacob; Amenitsch, Heinz; Herrmann, Andreas; Rudolf, Petra; Palstra, Thomas T M

    2014-12-10

    Perovskite-based organic-inorganic hybrids hold great potential as active layers in electronics or optoelectronics or as components of biosensors. However, many of these applications require thin films grown with good control over structure and thickness--a major challenge that needs to be addressed. The work presented here is an effort towards this goal and concerns the layer-by-layer deposition at ambient conditions of ferromagnetic organic-inorganic hybrids consisting of alternating CuCl4-octahedra and organic layers. The Langmuir-Blodgett technique used to assemble these structures provides intrinsic control over the molecular organization and film thickness down to the molecular level. Magnetic characterization reveals that the coercive field for these thin films is larger than that for solution-grown layered bulk crystals. The strategy presented here suggests a promising cost effective route to facilitate the excellently controlled growth of sophisticated materials on a wide variety of substrates that have properties relevant for the high density storage media and spintronic devices. PMID:25059565

  13. Mass spectrometric analysis of monolayer protected nanoparticles

    Science.gov (United States)

    Zhu, Zhengjiang

    Monolayer protected nanoparticles (NPs) include an inorganic core and a monolayer of organic ligands. The wide variety of core materials and the tunable surface monolayers make NPs promising materials for numerous applications. Concerns related to unforeseen human health and environmental impacts of NPs have also been raised. In this thesis, new analytical methods based on mass spectrometry are developed to understand the fate, transport, and biodistributions of NPs in the complex biological systems. A laser desorption/ionization mass spectrometry (LDI-MS) method has been developed to characterize the monolayers on NP surface. LDI-MS allows multiple NPs taken up by cells to be measured and quantified in a multiplexed fashion. The correlations between surface properties of NPs and cellular uptake have also been explored. LDI-MS is further coupled with inductively coupled plasma mass spectrometry (ICP-MS) to quantitatively measure monolayer stability of gold NPs (AuNPs) and quantum dots (QDs), respectively, in live cells. This label-free approach allows correlating monolayer structure and particle size with NP stability in various cellular environments. Finally, uptake, distribution, accumulation, and excretion of NPs in higher order organisms, such as fish and plants, have been investigated to understand the environmental impact of nanomaterials. The results indicate that surface chemistry is a primary determinant. NPs with hydrophilic surfaces are substantially less toxic and present a lower degree of bioaccumulation, making these nanomaterials attractive for sustainable nanotechnology.

  14. Effect of phosphonate monolayer adsorbate on the microwave photoresponse of TiO2 nanotube membranes mounted on a planar double ring resonator

    Science.gov (United States)

    Zarifi, Mohammad H.; Farsinezhad, Samira; Wiltshire, Benjamin D.; Abdorrazaghi, Mohammad; Mahdi, Najia; Kar, Piyush; Daneshmand, Mojgan; Shankar, Karthik

    2016-09-01

    In this study, the effects of a phosphonate molecular monolayer adsorbed on the surface of a free-standing self-organized TiO2 nanotube membrane, on the microwave photoresponse of the membrane are presented. This phenomenon is monitored using planar microwave sensors. A double ring resonator is utilized to monitor the permittivity and conductivity variation on the monolayer coated membrane and the sensor environment separately. It is shown that the rise time and subsequent decay of the amplitude (A), resonance frequency (f 0) and quality factor (Q) of the resonator depend on the existence and the type of the monolayer coating the membrane. Three different monolayers of n-decylphosphonic acid (DPA), 1H, 1H‧, 2H, 2H‧-perfluorodecyl phosphonic acid (PFDPA) and 16-phosphonohexadecanoic acid adsorbed on the titania nanotube membrane are investigated while monitoring their microwave properties during the illumination time period and in the relaxation period, which demonstrate different behavior in comparison to each other and to the bare nanotube membrane layer. The effect of humidity on the TiO2 nanotube membrane with and without different monolayers is also studied and the results demonstrate distinguishable microwave responses. While each of the monolayer-coated membranes exhibited an attenuation of the photo-induced change in A, f 0 and Q with respect to the bare membrane, PFDPA-coated membranes showed the smallest relative change in the monitored microwave parameters upon ultraviolet illumination and upon the introduction of different levels of humidity. These effects are explained on the basis of surface trap passivation by the monolayers as well as the hydrophobicity of the monolayers. Our work also shows how the interactions of self-assembled monolayers with charge carriers and surface states on metal oxides may be used to indirectly sense their presence through measurement of the microwave response.

  15. Preconcentration of volatile organics on self-assembled, carbon nanotubes in a microtrap.

    Science.gov (United States)

    Saridara, Chutarat; Brukh, Roman; Iqbal, Zafar; Mitra, Somenath

    2005-02-15

    This paper reports the self-assembly of carbon nanotubes (CNTs) on the inside wall of a steel capillary to fabricate a microtrap for the adsorption/desorption of trace organics. The microtrap functioned as a nanoconcentrator and an injector for gas chromatography (GC). The CNTs were deposited as a thin film by catalytic chemical vapor deposition from either CO or C2H4 as the precursor. The sorbent film synthesized from C2H4-CVD (CVD = chemical vapor deposition) had higher CNT density and thus was a stronger sorbent. In general, the CNT microtraps showed high-capacity adsorption and fast quantitative desorption, and the process showed excellent precision. This study demonstrates that CNT films can be deposited quite easily in a steel capillary for use in different analytical applications, and CNT films can perform as efficiently as packed-bed carbon sorbents. PMID:15859004

  16. Progress in the study of molecular organized assemblies by dielectric relaxation spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Because dielectric spectroscopy covers a great many problems in physical and chemical systems occurring in an extremely wide frequency range, the study of this method plays an important role in physical chemistry. As an effective tool to detect inner properties of substance systems, the dielectric spectroscopy method is widely used in chemical systems and has been dramatically developed in recent decade. This review paper describes the applications of the dielectric spectroscopy in the chemical field, and main concentrations are focused on the micelle, microemulsion and other so-called molecular organized assemblies. Some dielectric principles and models proposed for these systems are introduced. In addition, recent technical developments in dielectric spectroscopy and developing trend of this method in other chemical systems are reviewed.

  17. Fabrication of a molecular-level multilayer film on organic polymer surfaces via chemical bonding assembly.

    Science.gov (United States)

    Zhao, Hongchi; Yang, Peng; Deng, Jianping; Liu, Lianying; Zhu, Jianwu; Sui, Yuan; Lu, Jiaoming; Yang, Wantai

    2007-02-13

    A fresh multilayer film was fabricated on a molecular level and successfully tethered to the surface of a hydroxylated organic substrate via chemical bonding assembly (CBA). Sulfate anion groups (SO4-) were preintroduced onto the surface of biaxially oriented polypropylene (BOPP) films via a reference method. Upon hydrolysis of the SO4- groups, hydroxyl groups (--OH) were formed that subsequently acted as initial reagents for a series of alternate reactions with terephthalyl chloride (TPC) and bisphenol A (BPA). A stable and well-defined multilayer film was thus fabricated via the CBA method. As a result of the nanoscale multilayer fresh film being abundant with reactive groups, it is believed that the film and its fabrication method should provide a fundamental platform for further surface functionalization and direct the design of advanced materials with desired properties.

  18. Ordered organic thin films self-assembled from the vapor phase

    Science.gov (United States)

    Debe, M. K.

    1993-01-01

    Organic films self-assembled from a liquid phase, as in Langmuir-Blodgett or adsorption from solution, have received much attention in the past decade as techniques to achieve highly oriented-ordered polymeric thin films. Many organic compounds including some of the same fatty acids have been vapor deposited as well. However, organic pigments and dyes comprise a major class of important materials which have very low solubilities yet excellent thermal stabilities, making them ideally suited for film deposition from the vapor phase. Surprisingly, such molecular systems exhibit a significant propensity to self order, a high sensitivity to deposition parameters, and a range of microstructural forms that cannot be duplicated by the less energetic mechanisms associated with solution adsorption processes. Molecular solids such as heterocyclic polynuclear aromatics are excellent candidates for film formation by vacuum deposition means. Over the past decade, our work and that of others investigating a wide variety of perylene and phthalocyanine derivatives identified five deposition parameters that can significantly affect film morphology, physical microstructure, and type and extent of ordering developed in vacuum and vapor transport grown films. These parameters are substrate temperature, deposition rate, substrate chemistry and epitaxy, ambient gas convective flows, and post deposition annealing. Examples of how each of these conditions manifest themselves in the film structure and ordering, most frequently revealed by scanning electron microscopy, reflection absorption infrared spectroscopy (RAIR), and grazing incidence x-ray diffraction (GIX), are presented.

  19. Micro-extrusion of organic inks for direct-write assembly

    Science.gov (United States)

    Bruneaux, Julien; Therriault, Daniel; Heuzey, Marie-Claude

    2008-11-01

    Direct-write assembly is a highly versatile microfabrication technique used to create microfluidic networks by the robotic deposition of a fugitive ink onto a moving stage. To optimize the resulting shape of the microchannel, the translational speed of the moving stage has to closely match the linear velocity of the fugitive ink at the micro-nozzle exit. In this work, we have performed a comprehensive characterization of the micro-extrusion process of organic fugitive inks through a nozzle and characterized the rheological properties of petroleum jelly-based organic inks with various microcrystalline wax contents (10 to 40 wt%). The local microcrystal concentration has been probed using polarized optical microscopy and Raman spectroscopy. Small amplitude oscillatory shear tests in a vane geometry have revealed a solid-like structure of the organic inks, and a strong shear-thinning behavior of the complex viscosity. Particle tracking velocimetry (PTV) experiments performed in a glass microchannel have suggested the occurrence of apparent slip, showing a microcrystal depletion layer near the nozzle wall and a plug flow in the remainder of the micro-nozzle. From Raman spectroscopy and polarized microscopy performed on extruded samples, a crystal free layer was observed and estimated to be approximately 10-20 µm thick (or 2-4% of the microcapillary diameter), explaining the strong apparent wall slip behavior.

  20. Molecular Electronics of Self-Assembled Monolayers

    DEFF Research Database (Denmark)

    Wang, Xintai

    providesa brief introduction toself-assembledmonolayers(SAMs), includingits structure, formation, and its role in molecular electronic investigations. Part II is an introduction of different molecular functions, which are interesting for designing real devices. Part III is an introduction of a novel carbon...... material: graphene, and how such material can be incorporated intothe field of molecular electronics.Chapter 3 is a brief introduction of important instruments used in this thesis.Chapter 4, 5 and 6 describe the major experimental work in this thesis. Chapter 4 introduces two novel anchoring...... with voltage triggering functions, includesthe triggering by bias voltage and electrochemical gate. Chapter 6 introduces some method thatcould enhance the reliability of data obtained from different molecular electronic measurement techniques.Chapter 7 gives a brief summary of this thesis and tentatively point...