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Sample records for monolayer sam surface

  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; O'Hagan, David; Hähner, Georg

    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.

  3. 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

  4. Drug delivery from therapeutic self-assembled monolayers (T-SAMs) on 316L stainless steel.

    Science.gov (United States)

    Mahapatro, Anil; Johnson, Dave M; Patel, Devang N; Feldman, Marc D; Ayon, Arturo A; Agrawal, C Mauli

    2008-01-01

    Delivery of therapeutic agents from self-assembled monolayers (SAMs) on 316L stainless steel (SS) has been demonstrated as a viable method to deliver drugs for localized coronary artery stent application. SAMs are highly-ordered, nano-sized molecular coatings, adding 1-10 nm thickness to a surface. Hydroxyl terminated alkanethiol SAMs of 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS with 48 hr immersion in ethanolic solutions. Attachment of ibuprofen (a model drug) to the functional SAMs was carried out in toluene for 5 hrs at 60 degrees C using Novozume-435 as a biocatalyst. SAM formation and subsequent attachment of ibuprofen was characterized collectively using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle (CA) measure-ments. The quantitative in vitro release of ibuprofen into a "physiological" buffer solution was characterized using reverse phase HPLC. Drug release kinetics showed that 14.1 microg of ibuprofen eluted over a period of 35 days with 2.7microg being eluted in the first day and the remaining being eluted over a period of 35 days. The drug release kinetics showed an increase in ibuprofen elution that occurred during first 14 days (2.7microg in 1 day to 9.5 microg in 14 days), following which there was a decrease in the rate of elution. Thus, functional SAMs on 316L SS could be used as tethers for drug attachment and could serve as a drug delivery mechanism from stainless steel implants such as coronary artery stents.

  5. 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.

  6. Formation and Stability of Phenylphosphonic Acid Monolayers on ZnO: Comparison of In Situ and Ex Situ SAM Preparation.

    Science.gov (United States)

    Ostapenko, Alexandra; Klöffel, Tobias; Meyer, Bernd; Witte, Gregor

    2016-05-24

    Self-assembled monolayers (SAMs) enable an electronic interface tailoring of conductive metal oxides and offer an alternative to common transparent electrodes in optoelectronic devices. Here, the influence of surface orientation and pretreatment on the formation and stability of SAMs has been studied for the case of phenylphosphonic acid (PPA) on ZnO single crystals. Using thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS), near-edge X-ray adsorption fine structure spectroscopy (NEXAFS) and density-functional theory (DFT) calculations, the thermal stability and orientational ordering of PPA-SAMs on the polar and mixed-terminated ZnO surfaces were analyzed. On all surfaces, PPA-SAMs remain stable up to 550 K, while at higher temperatures a C-P bond cleavage and dissociative desorption takes place yielding two distinct desorption peaks. Based on DFT calculations, these desorption channels are attributed to protonated and deprotonated chemisorbed PPA molecules, which can be related to tri- and bidentate species, hence allowing to determine their relative abundance from the intensity ratio. Beside immersion, an alternative monolayer preparation based on vacuum deposition in combination with controlled desorption of excess multilayers is demonstrated. This enables a SAM preparation on bare ZnO surfaces without any precoating due to exposure to ambient air, which is further compared with SAM formation on intentionally hydroxylated substrates. Corresponding TDS data indicate that initial hydroxylation favors the formation of tridentate and deprotonated bidentate, while the OMBD preparation on bare surfaces yields a larger fraction of protonated bidentate species. The orientation of PPA molecules adopted in the SAMs was determined from the dichroism of K-edge NEXAFS measurements and reveals an almost upright orientation for the deprotonated species, while a slight tilting is obtained for monolayer films with a large fraction of protonated

  7. Influence of chain ordering on frictional properties of self-assembled monolayers (SAMs) in nano-lubrication.

    Science.gov (United States)

    Cheng, Hefa; Hu, Yuanan

    2012-01-01

    Adhesion of organic films to substrates is important in applications that involve solid surfaces in sliding contact. Although the thickness of self-assembled monolayers (SAMs) is only a few nanometers, they can drastically modify the frictional properties of the underlying substrate, and thus have great potential for serving as boundary lubricants on micro- and nano-scales. This review focuses on the relationship between the structural and compositional properties of SAMs and their frictional response. Adhesion of SAMs to the substrate surface usually occurs through chemisorption of the head groups on the constituent molecules, with molecular interactions such as van der Waals interactions playing important roles in organizing the molecules into surface films, and in controlling their tribological behavior. The durability and wear resistance of SAMs depend on the nature and strength of the binding forces between the head groups and the substrate surfaces, while the adhesion and friction forces are strongly influenced by the interactions of the terminal groups with the counterfaces. Results from both experimental measurements and molecular dynamics simulations consistently indicate that structural ordering of alkyl chains in SAMs reduces their frictional response, and that SAMs formed by molecules with alkyl chains longer than 8 to 10 methylene units are well organized, exhibiting low levels of friction. Less densely packed or more disordered monolayers inherently possess greater numbers of conformational defects at room temperature and present lower barriers to defect creation under the action of a contacting surface, and thus exhibit higher friction. Cross-linking of the spacer chains can reduce the frictional response of disordered films by increasing the chain ordering, but has little impact on SAMs that are already well ordered. On the other hand, introduction of sterically demanding terminal groups and dissimilar molecules reduces molecular ordering in SAMs

  8. Regioselective patterning of multiple SAMs and applications in surface-guided smart microfluidics.

    Science.gov (United States)

    Chen, Chuanzhao; Xu, Pengcheng; Li, Xinxin

    2014-12-24

    A top-down nanofabrication technology is developed to integrate multiple SAMs (self-assembled monolayers) into regioselective patterns. With ultraviolet light exposure through regioselectively hollowed hard mask, an existing SAM at designated microregions can be removed and a dissimilar kind of SAM can be regrown there. By repeating the photolithography-like process cycle, diverse kinds of SAM building blocks can be laid out as a desired pattern in one microfluidic channel. In order to ensure high quality of the surface modifications, the SAMs are vapor-phase deposited before the channel is closed by a bonding process. For the first time the technique makes it possible to integrate three or more kinds of SAMs in one microchannel. The technique is very useful for multiplex surface functionalization of microfluidic chips where different segments of a microfluidic channel need to be individually modified with different SAMs or into arrayed pattern for surface-guided fluidic properties like hydrophobicity/philicity and/or oleophobicity/philicity, etc. The technique has been well validated by experimental demonstration of various surface-directed flow-guiding functions. By modifying a microchannel surface into an arrayed pattern of multi-SAM "two-tone" stripe array, surface-guiding-induced 3D swirling flow is generated in a microfluidic channel that experimentally exhibits quick oil/water mixing and high-efficiency oil-to-water chemical extraction.

  9. 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)

  10. 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.

  11. Mixed carboranethiol self-assembled monolayers on gold surfaces

    Science.gov (United States)

    Yavuz, Adem; Sohrabnia, Nima; Yilmaz, Ayşen; Danışman, M. Fatih

    2017-08-01

    Carboranethiol self-assembled monolayers on metal surfaces have been shown to be very convenient systems for surface engineering. Here we have studied pure and mixed self-assembled monolayers (SAMs) of three different carboranethiol (CT) isomers on gold surfaces. The isomers were chosen with dipole moments pointing parallel to (m-1-carboranethiol, M1), out of (m-9-carboranethiol, M9) and into (o-1-carboranethiol, O1) the surface plane, in order to investigate the effect of dipole moment orientation on the film properties. In addition, influence of the substrate surface morphology on the film properties was also studied by using flame annealed (FA) and template stripped (TS) gold surfaces. Contact angle measurements indicate that in M1/M9 and M1/O1 mixed SAMs, M1 is the dominant species on the surface even for low M1 ratio in the growth solution. Whereas for O1/M9 mixed SAMs no clear evidence could be observed indicating dominance of one of the species over the other one. Though contact angle values were lower and hysteresis values were higher for SAMs grown on TS gold surfaces, the trends in the behavior of the contact angles with changing mixing ratio were identical for SAMs grown on both substrates. Atomic force microscopy images of the SAMs on TS gold surfaces indicate that the films have similar morphological properties regardless of mixing ratio.

  12. Chemical analyses of hydroxyapatite formation on SAM surfaces modified with COOH, NH(2), CH(3), and OH functions.

    Science.gov (United States)

    Hirata, Isao; Akamatsu, Mai; Fujii, Eri; Poolthong, Suchit; Okazaki, Masayuki

    2010-08-01

    Hydroxyapatite formation was examined at the surface of self-assembled monolayers (SAMs) modified with four functional groups, -COOH, -NH(2), -CH(3), and -OH. For COOH-SAM and NH(2)-SAM, scanning electron spectroscopic observation showed that flake-like sheet crystals covered the whole wafer and small broccoli-like crystals were observed occasionally on the flake-like crystal base layer. For CH(3)-SAM and OH-SAM, no flake-like sheet crystals were observed; broccoli-like crystals were observed in a dispersed manner for CH(3)-SAM, but in localized spots for OH-SAM. X-ray diffraction patterns showed a strong apatite pattern oriented toward the c-axis direction for COOH-SAM. ESCA analysis revealed distinct Ca, P, O peaks for COOH-, NH(2)-, CH(3)-, and OH-SAM. Surface plasmon resonance (SPR) analysis indicated that during the supply of supersaturated calcium phosphate solution, the deposition of precipitates increased monotonically with time for COOH-SAM, increased slightly for NH(2)-SAM, but little increase in deposition was detected for CH(3)-SAM and OH-SAM.

  13. Fabrication and tribological properties of self-assembled monolayer of n-alkyltrimethoxysilane on silicon: Effect of SAM alkyl chain length

    Science.gov (United States)

    Huo, Lixia; Du, Pengcheng; Zhou, Hui; Zhang, Kaifeng; Liu, Peng

    2017-02-01

    It is well known that the self-assembled organic molecules on a solid surface exhibit the friction-reducing performance. However, the effect of the molecular size of the self-assembled organic molecules has not been established. In the present work, self-assembled monolayers (SAMs) of n-alkyltrimethoxysilanes with different alkyl chain lengths (C6, C12, or C18) were fabricated on silicon substrate. The water contact angles of the SAMs increased from 26.8° of the hydroxylated silicon substrate to near 60° after self-assembly. The atomic force microscopy (AFM) analysis results showed that the mean roughness (Ra) of the SAMs decreased with increasing the alkyl chain length. The tribological properties of the SAMs sliding against Al2O3 ball were evaluated on an UMT-2 tribometer, and the worn surfaces of the samples were analyzed by means of Nano Scratch Tester and surface profilometry. It was found that lowest friction coefficient and smallest width of wear were achieved with the SAMs of C12 alkyl chain (C12-SAM). The superior friction reduction and wear resistance of the SAMs in comparison with the bare silicon substrate are attributed to good adhesion of the self-assembled films to the substrate, especially the C12-SAM with desirable alkyl chain length.

  14. A simulation study on the thermal and wetting behavior of alkane thiol SAM on gold (111) surface

    Institute of Scientific and Technical Information of China (English)

    J. Meena Devi

    2014-01-01

    Molecular dynamics simulations have been performed to investigate the structural, thermal and wetting properties of self-assembled monolayer (SAM) of alkane thiol on gold surface. The specific heat capacity of the gold SAM surface was found to linearly increase with the temperature in the range 100-300 K. It was found to drop down at 400 K and this decrease might be attributed to the disorder of the SAM chains. Hydration of gold SAM surface for two different terminal groups, namely methyl (hydrophobic), and hydroxy (hydrophilic) was studied at room temperature. The difference in their wetting behavior and the structure of their interfacial water were examined from the estimation of the z density profile, radial distribution function, hydrogen bonds and orientation of water dipoles in the interfacial region. The present simulation results suggest that the wetting behavior of the gold SAM surface can be modified by altering the terminal functional group of the SAM chains.

  15. Reactive monolayers for surface gradients and biomolecular patterned interfaces

    NARCIS (Netherlands)

    Nicosia, C.

    2013-01-01

    Self-assembled monolayers (SAMs) are an excellent platform to implement and develop interfacial reactions for the preparation of versatile materials of pivotal importance for the fabrication of, among others, biochips, sensors, catalysts, smart surfaces and electronic devices. The development of met

  16. Friction Properties of OTS SAMs and Silicon Surface under Water Lubrication

    Institute of Scientific and Technical Information of China (English)

    WANG Xin; ZHANG Xiangjun; AHMED Imad; LIU Ying; WEN Shizhu

    2009-01-01

    The friction and wear properties of silicon surface covered with octadecyltrichloro-silane (OTS) self-assembled monolayers (SAMs) were investigated by a UMT-2 microtribometer with and without water as lubricant, and then compared with that of bare silicon surface. Dry friction measurement results show that OTS SAMs have a very low friction coefficient compared to bare silicon surface under lower sliding velocity and normal contact load. However, heavy wear occurs on OTS SAMs under higher contact stress and sliding velocity. Under water lubrication, OTS SAMs can prevent wear obviously and meanwhile present low coefficient of friction even under high velocities.The improved frictional and anti-wear property on OTS SAMs surface is attributed to the hydrophobic property of OTS and hydrodynamic effect of water. Furthermore, a wear critical phase diagram for OTS SAMs with and without water was proposed, which indicates that OTS SAMs working under water lubrication owns a wider range of available load and velocity to reduce friction and prevent wear.

  17. AFM-assisted fabrication of thiol SAM pattern with alternating quantified surface potential

    Directory of Open Access Journals (Sweden)

    Simons Janet

    2011-01-01

    Full Text Available Abstract Thiol self-assembled monolayers (SAMs are widely used in many nano- and bio-technology applications. We report a new approach to create and characterize a thiol SAMs micropattern with alternating charges on a flat gold-coated substrate using atomic force microscopy (AFM and Kelvin probe force microscopy (KPFM. We produced SAMs-patterns made of alternating positively charged, negatively charged, and hydrophobic-terminated thiols by an automated AFM-assisted manipulation, or nanografting. We show that these thiol patterns possess only small topographical differences as revealed by AFM, and distinguished differences in surface potential (20-50 mV, revealed by KPFM. The pattern can be helpful in the development of biosensor technologies, specifically for selective binding of biomolecules based on charge and hydrophobicity, and serve as a model for creating surfaces with quantified alternating surface potential distribution.

  18. Surface engineering and adhesion modification of SAM surfaces of 1-hexanethiol and 1-decanethiol: confining Staphylococcus aureus

    Science.gov (United States)

    Olsen, Morgan; Amroski, Alicia; Calabrese, Joseph; Senevirathne, Reshani; Senevirathne, Indrajith

    2012-02-01

    Engineering surfaces for adhesion and confinement of bacteria is interesting towards development of respective biosensors, and bio machine interfacing. Investigation was focused towards modification of surfaces towards confinement and entrapment of the nonpathogenic strain Staphylococcus aureus or similar pathogenic strains and to study surface engineering. Clean, flat Au(111) on mica surfaces were used for self assembly for Self Assembled Monolayers (SAM). 1-hexanethiol, and 1-decanethiol were used at total 5 mM solutions in varying ratios, in 200 proof Ethanol solution. Resulting SAM layers were investigated for surface corrugation, morphology and structure variation at different thiol ratios. Observations will be discussed, quantitatively and qualitatively. Eventual mixture ratios were so selected towards optimum conditions for confining Staphylococcus aureus as a model system. SAM surfaces were investigated using intermittent contact, noncontact, lateral force and contact modes of Atomic Force Microscopy (AFM).

  19. Fabrication and Surface Properties of Composite Films of SAM/Pt/ZnO/SiO 2

    KAUST Repository

    Yao, Ke Xin

    2008-12-16

    Through synthetic architecture and functionalization with self-assembled monolayers (SAMs), complex nanocomposite films of SAM/Pt/ZnO/SiO2 have been facilely prepared in this work. The nanostructured films are highly uniform and porous, showing a wide range of tunable wettabilities from superhydrophilicity to superhydrophobicity (water contact angles: 0° to 170°). Our approach offers synthetic flexibility in controlling film architecture, surface topography, coating texture, crystallite size, and chemical composition of modifiers (e.g., SAMs derived from alkanethiols). For example, wettability properties of the nanocomposite films can be finely tuned with both inorganic phase (i.e., ZnO/SiO2 and Pt/ZnO/SiO2) and organic phase (i.e., SAMs on Pt/ZnO/SiO2). Due to the presence of catalytic components Pt/ZnO within the nanocomposites, surface reactions of the organic modifiers can further take place at room temperature and elevated temperatures, which provides a means for SAM formation and elimination. Because the Pt/ZnO forms an excellent pair of metal-semiconductors for photocatalysis, the anchored SAMs can also be modified or depleted by UV irradiation (i.e., the films possess self-cleaning ability). Potential applications of these nanocomposite films have been addressed. Our durability tests also confirm that the films are thermally stable and structurally robust in modification- regeneration cycles. © 2008 American Chemical Society.

  20. 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.

  1. 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.

  2. Colloidal silicon quantum dots: from preparation to the modification of self-assembled monolayers (SAMs) for bio-applications.

    Science.gov (United States)

    Cheng, Xiaoyu; Lowe, Stuart B; Reece, Peter J; Gooding, J Justin

    2014-04-21

    Concerns over possible toxicities of conventional metal-containing quantum dots have inspired growing research interests in colloidal silicon nanocrystals (SiNCs), or silicon quantum dots (SiQDs). This is related to their potential applications in a number of fields such as solar cells, optoelectronic devices and fluorescent bio-labelling agents. The past decade has seen significant progress in the understanding of fundamental physics and surface properties of silicon nanocrystals. Such understanding is based on the advances in the preparation and characterization of surface passivated colloidal silicon nanocrystals. In this critical review, we summarize recent advances in the methods of preparing high quality silicon nanocrystals and strategies for forming self-assembled monolayers (SAMs), with a focus on their bio-applications. We highlight some of the major challenges that remain, as well as lessons learnt when working with silicon nanocrystals (239 references).

  3. Donor/Acceptor Mixed Self-Assembled Monolayers for Realising a Multi-Redox-State Surface.

    Science.gov (United States)

    Casado-Montenegro, Javier; Marchante, Elena; Crivillers, Núria; Rovira, Concepció; Mas-Torrent, Marta

    2016-06-17

    Mixed molecular self-assembled monolayers (SAMs) on gold, based on two types of electroactive molecules, that is, electron-donor (ferrocene) and electron-acceptor (anthraquinone) molecules, are prepared as an approach to realise surfaces exhibiting multiple accessible redox states. The SAMs are investigated in different electrolyte media. The nature of these media has a strong impact on the types of redox processes that take place and on the redox potentials. Under optimised conditions, surfaces with three redox states are achieved. Such states are accessible in a relatively narrow potential window in which the SAMs on gold are stable. This communication elucidates the key challenges in fabricating bicomponent SAMs as electrochemical switches.

  4. Method for selective immobilization of macromolecules on self assembled monolayer surfaces

    Science.gov (United States)

    Laskin, Julia [Richland, WA; Wang, Peng [Billerica, MA

    2011-11-29

    Disclosed is a method for selective chemical binding and immobilization of macromolecules on solid supports in conjunction with self-assembled monolayer (SAM) surfaces. Immobilization involves selective binding of peptides and other macromolecules to SAM surfaces using reactive landing (RL) of mass-selected, gas phase ions. SAM surfaces provide a simple and convenient platform for tailoring chemical properties of a variety of substrates. The invention finds applications in biochemistry ranging from characterization of molecular recognition events at the amino acid level and identification of biologically active motifs in proteins, to development of novel biosensors and substrates for stimulated protein and cell adhesion.

  5. Study of Fused Thiophene Based Organic Semiconductors and Interfacial Self-Assembled Monolayer (SAM) for Thin-Film Transistor (TFT) Application

    Science.gov (United States)

    Youn, Jangdae

    In this thesis, the molecular packing motifs of our newly designed fused thiophenes, benzo[d,d]thieno[3,2-b;4,5-b]dithiophene (BTDT) derivatives, were studied by utilizing grazing incidence wide angle X-ray scattering (GIWAXS). Considering the potential of fused thiophene molecules as an environmentally stable, high performance semiconductor building block, it must be an important groundwork to investigate their thin film structures in relation to molecular structures, single crystal structures, and organic thin-film transistors (OTFT) performances. OTFT device performance is not only determined by semiconductor materials, but also influenced by the interfacial properties. Since there are three major components in TFT structures---electrodes, semiconductors, and dielectrics, two types of major interfaces exist. One is the semiconductor-electrode interface, and the other is the semiconductor-dielectric interface. Both of these interfaces have critical roles for TFT operation. For example, the semiconductor-electrode interface determines the charge injection barrier. Before charge carriers go through the electrode (source)-semiconductor-electrode (drain) pathways, the energy gaps between the work function of the electrodes and the HOMO energy of the semiconductor materials must be overcome for hole injection, or the energy gap between the metal work function of the electrodes and the LUMO energy of the semiconductor materials must be overcome for electron injection. These charge injection barriers are largely determined by the energetic structure of the semiconductor material and work function of the electrode. However, the size of energy gap can be modified by introducing an organic self-assembled monolayer (SAM) on the surface of metal electrode. In addition, the structure of semiconductor films, especially within several monolayers right above the electrode, is greatly influenced by the SAM, and it changes charge injection property of OTFT devices. In this thesis

  6. Functionalization of Organic Semiconductors and Other Carbon-based Materials by Self-Assembled Monolayers (SAMs) and Charge Transport in Organic Field-effect Transistors (OFETs)

    Science.gov (United States)

    Lee, Bumsu

    In the first part of the thesis, studies of the charge carrier transport in organic semiconductors performed using organic field-effect transistors (OFETs) with polymeric gate dielectric (parylene) are presented. By combining OFET and ultraviolet photoelectron spectroscopy (UPS) studies, the effect of bias-stress instability at the semiconductor/insulator interface have been investigated and understood. The effect is understood in terms of the transfer of holes from an accumulation channel of the semiconductor to localized states of the insulator that depends on energetic overlap between HOMO band tails of the semiconductor and the insulator. Second, surface functionalization of various materials such as organic single crystals, conjugated semiconductor polymers, graphene and carbon nanotubes (CNTs) with Self-Assembled Monolayers (SAMs) is described. In most cases, an enhanced surface conductivity is observed as a result of SAM treatment. Especially, fluorinated alkyl-silane (FTS) SAM induces the highest density of p-type charge carriers (in excess of an order of 1013cm-2), which leads to a strong surface hole-doping of these materials. In this thesis, (1) the mechanism of SAM nucleation, growth process and doping effect at the surface of organic single crystals and graphene is revealed. SAM nucleation occurs predominantly at molecular step edges or defect sites present at the surface and a consecutive lateral growth proceeds by cross-linking between SAM molecules. The strong hole-doping is explained by an interfacial charge transfer that during SAM formation. In addition, conductive atomic force microscopy (C-AFM) confirms that conducting paths along the step edges are formed by FTS nucleation at the early stage of FTS growth on rubrene. (2) it is reported that conductivity of solution-deposited thin film of conjugated polymers increases by up to six orders of magnitude, reaching (1.1 ± 0.1) × 103 Scm-1 for poly (2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b

  7. Interactions of doxorubicin with self-assembled monolayer-modified electrodes: electrochemical, surface plasmon resonance (SPR), and gravimetric studies.

    Science.gov (United States)

    Nieciecka, Dorota; Krysinski, Pawel

    2011-02-01

    We present the results on the partitioning of doxorubicin (DOX), a potent anticancer drug, through the model membrane system, self-assembled monolayers (SAMs) on gold electrodes. The monolayers were formed from alkanethiols of comparable length with different ω-terminal groups facing the aqueous electrolyte: the hydrophobic -CH(3) groups for the case of dodecanethiol SAMs or hydrophilic -OH groups of mercaptoundecanol SAMs. The electrochemical experiments combined with the surface plasmon resonance (SPR) and gravimetric studies show that doxorubicin is likely adsorbed onto the surface of hydrophilic monolayer, while for the case of the hydrophobic one the drug mostly penetrates the monolayer moiety. The adsorption of the drug hinders further penetration of doxorubicin into the monolayer moiety.

  8. Preparation of surface-tethered polymer layer on inorganic substrates by photoreactive self-assembled monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong-Ho; Ohtsuka, Hanae [Tokyo University of Agriculture and Technology, Department of Organic and Polymer Materials Chemistry, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Tria, Maria Celeste R. [University of Houston, Department of Chemistry, 136 Fleming Building, Houston, TX 77204-5008 (United States); Tanaka, Kuniaki [Tokyo University of Agriculture and Technology, Department of Organic and Polymer Materials Chemistry, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Advincula, Rigoberto C. [Case Western Reserve University, Department of Macromolecular Science and Engineering, 2100 Adelbert Road, Cleveland, OH 44106 (United States); Usui, Hiroaki, E-mail: h_usui@cc.tuat.ac.jp [Tokyo University of Agriculture and Technology, Department of Organic and Polymer Materials Chemistry, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)

    2014-03-03

    A self-assembled monolayer (SAM) that has benzophenone (BP) terminal group was prepared on Si and indium–tin oxide (ITO) substrates, on which poly(9-vinyl carbazol) (PVK) was spin-coated and then irradiated with ultraviolet (UV) light. Upon UV irradiation, the BP unit reacted with the PVK backbone, yielding a crosslinked PVK layer that was covalently tethered to the substrate surface. Using this procedure, a patterned thin film of PVK was obtained by irradiating UV light through a photomask and then rinsing in chloroform. When polystylene (PSt) was spin-coated on the BP-SAM, only a thin interfacial layer was tethered by UV irradiation because PSt does not crosslink upon UV irradiation. The BP-SAM improved the adhesion strength between the PVK layer and ITO substrate without reducing the carrier injection from ITO to PVK. The photoreactive BP-SAM appeared to be an effective method to improve the interface between an inorganic electrode and a polymer layer deposited on its surface. - Highlights: • Polyvinylcarbazole (PVK) was tethered to substrate by self-assembled monolayer (SAM). • The photoreactive SAM was effective in improving adhesion strength of the films. • This process was applied for photopatterning of PVK layer. • The photoreactive SAM did not impede carrier injection from electrode to PVK.

  9. 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

  10. Self-assembled alkanethiol monolayers on gold surfaces: resolving the complex structure at the interface by STM.

    Science.gov (United States)

    Guo, Quanmin; Li, Fangsen

    2014-09-28

    The surface properties of metals and metal oxides can be modified by adding a single layer of organic molecules. A most popular route for depositing such a molecular layer is via the formation of self-assembled monolayers (SAMs). The molecules that form SAMs have a functionality which binds to the surface and the adsorption is self-regulated to terminate at exactly one single molecular layer. The very first example, which has become the most widely studied system, of SAMs on metal surfaces consists of chemisorbed alkylthiolate on gold. Despite the simplicity in the preparation of alkanethiol SAMs and the seemingly straightforward structure of such SAMs, the detailed bonding between the sulfur head group and gold is still subject to debate. Experimental and theoretical effort in the last six years has led to a much improved understanding of this classical system of SAMs. In this review, we will highlight the most recent progress in the study of the interfacial structure of alkanethiol SAMs on gold. We focus on the important phenomenon of phase transition that occurs from n-propanethiol to n-butanethiol, and propose a unified structural model to explain how the (3 × 4) phase for short chain alkanethiol monolayers (methyl-, ethyl- and propylthiolate monolayers) changes into the (3 × 2√3)-rect./c(4 × 2) phase for long chain molecular monolayers.

  11. Binary functionalization of H:Si(111) surfaces by alkyl monolayers with different linker atoms enhances monolayer stability and packing.

    Science.gov (United States)

    Arefi, Hadi H; Nolan, Michael; Fagas, Giorgos

    2016-05-14

    Alkyl monolayer modified Si forms a class of inorganic-organic hybrid materials with applications across many technologies such as thin-films, fuel/solar-cells and biosensors. Previous studies have shown that the linker atom, through which the monolayer binds to the Si substrate, and any tail group in the alkyl chain, can tune the monolayer stability and electronic properties. In this paper we study the H:Si(111) surface functionalized with binary SAMs: these are composed of alkyl chains that are linked to the surface by two different linker groups. Aiming to enhance SAM stability and increase coverage over singly functionalized Si, we examine with density functional theory simulations that incorporate vdW interactions, a range of linker groups which we denote as -X-(alkyl) with X = CH2, O(H), S(H) or NH(2) (alkyl = C6 and C12 chains). We show how the stability of the SAM can be enhanced by adsorbing alkyl chains with two different linkers, e.g. Si-[C, NH]-alkyl, through which the adsorption energy is increased compared to functionalization with the individual -X-alkyl chains. Our results show that it is possible to improve stability and optimum coverage of alkyl functionalized SAMs linked through a direct Si-C bond by incorporating alkyl chains linked to Si through a different linker group, while preserving the interface electronic structure that determines key electronic properties. This is important since any enhancement in stability and coverage to give more densely packed monolayers will result in fewer defects. We also show that the work function can be tuned within the interval of 3.65-4.94 eV (4.55 eV for bare H:Si(111)).

  12. Absence of molecular slip on ultraclean and SAM-coated surfaces

    Science.gov (United States)

    Pye, Justin; Wood, Clay; Burton, Justin

    2016-11-01

    The liquid/solid boundary condition is a complex problem that is becoming increasingly important for the development of nanoscale fluidic devices. Many groups have now measured slip near an interface at nanoscale dimensions using a variety of experimental techniques. In simple systems, large slip lengths are generally measured for non-wetting liquid/solid combinations, but many conflicting measurements and interpretations remain. We have developed a novel pseudo-differential technique using a quartz crystal microbalance (QCM) to measure slip lengths on various surfaces. A drop of one liquid is grown on the QCM in the presence of a second, ambient liquid. We have isolated any anomalous boundary effects such as interfacial slip by choosing two liquids which have identical bulk effects on the QCM frequency and dissipation in the presence of no-slip. Slip lengths are -less than 2 nm- for water (relative to undecane) on all surfaces measured, including plasma cleaned gold, SiO2, and two different self assembled monolayers (SAMs), regardless of contact angle. We also find that surface cleanliness is crucial to accurately measure slip lengths. Additionally, clean glass substrates appear to have a significant adsorbed water layer and SAM surfaces show excess dissipation, possibly associated with contact line motion. In addition to investigating other liquid pairs, future work will include extending this technique to surfaces with independently controllable chemistry and roughness, both of which are known to strongly affect interfacial hydrodynamics.

  13. 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.

  14. 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.

  15. Chemically sensitive surface plasmon devices employing a self-assembled monolayer composite film

    Science.gov (United States)

    DePriest, J. C.; Meriaudeau, Fabrice; Oden, Patrick I.; Downey, Todd R.; Passian, A.; Wig, A. G.; Ferrell, Trinidad L.

    1998-12-01

    In this paper the results of detecting volatile organic compounds (VOC) employing surface plasmon-based sensors are presented. The initial step in preparing the sensing elements herein requires depositing Au degree(s) on a quartz slide. The sensing elements are based on either (1) freshly deposited Au degree(s) or (2) growth of a self assembled monolayer composite film (SAM) on to a freshly deposited Au degree(s) surface. The desired SAM is either (1) acid terminated using (omega) -mercaptoundecanoic acid (MUA-COOH) or (2) Cu2+ metal ion terminated yielding (omega) - mercaptoundecanoic acid-Cu2+ (MUA-Cu2+). The experimental apparatus shown here measures the reflectivity of the Au degree(s) surface as a function of time at a given angle. The response of this surface plasmon device to various VOC's is correlated to the composition of the SAM film.

  16. Microfluidic lithography of SAMs on gold to create dynamic surfaces for directed cell migration and contiguous cell cocultures.

    Science.gov (United States)

    Lamb, Brian M; Barrett, Devin G; Westcott, Nathan P; Yousaf, Muhammad N

    2008-08-19

    A straightforward, flexible, and inexpensive method to create patterned self-assembled monolayers (SAMs) on gold using microfluidics-microfluidic lithography-has been developed. Using a microfluidic cassette, alkanethiols were rapidly patterned on gold surfaces to generate monolayers and mixed monolayers. The patterning methodology is flexible and, by controlling the solvent conditions and thiol concentration, permeation of alkanethiols into the surrounding PDMS microfluidic cassette can be advantageously used to create different patterned feature sizes and to generate well-defined SAM surface gradients with a single microfluidic chip. To demonstrate the utility of microfluidic lithography, multiple cell experiments were conducted. By patterning cell adhesive regions in an inert background, a combination of selective masking of the surface and centrifugation achieved spatial and temporal control of patterned cells, enabling the design of both dynamic surfaces for directed cell migration and contiguous cocultures. Cellular division and motility resulted in directed, dynamic migration, while the centrifugation-aided seeding of a second cell line produced contiguous cocultures with multiple sites for heterogeneous cell-cell interactions.

  17. Determination of Surface pKa of Pure Mercaptoacetic Acid and 2- Mercaptobenzothiazole Mixed Monolayers by Impedance Titration

    Institute of Scientific and Technical Information of China (English)

    Guang Han LU; Chuan Yin LIU; Hong Yan ZHAO; Wei LIU; Li Ping JIANG; Ling Yan JIANG

    2004-01-01

    Interfacial proton transfer reactions of pure mercaptoacetic acid (MA) and 2-mercaptobenzothiazole (Mbz) mixed self-assembled monolayers (SAMs) have been studied using a.c. impedance titration method. The charge-transfer resistance (Rct) is measured with the monolayer composition and the ionic strength of pH solution. The surface pKa can be obtained by the plots of Rct and pH, the reasons of shifts of surface pKa are also explained.

  18. Effect of surface chemical composition on the work function of silicon substrates modified by binary self-assembled monolayers.

    Science.gov (United States)

    Kuo, Che-Hung; Liu, Chi-Ping; Lee, Szu-Hsian; Chang, Hsun-Yun; Lin, Wei-Chun; You, Yun-Wen; Liao, Hua-Yang; Shyue, Jing-Jong

    2011-09-07

    It has been shown that the application of self-assembled monolayers (SAMs) to semiconductors or metals may enhance the efficiency of optoelectronic devices by changing the surface properties and tuning the work functions at their interfaces. In this work, binary SAMs with various ratios of 3-aminopropyltrimethoxysilane (APTMS) and 3-mercaptopropyltrimethoxysilane (MPTMS) were used to modify the surface of Si to fine-tune the work function of Si to an arbitrary energy level. As an electron-donor, amine SAM (from APTMS) produced outward dipole moments, which led to a lower work function. Conversely, electron-accepting thiol SAM (from MPTMS) increased the work function. It was found that the work function of Si changed linearly with the chemical composition and increased with the concentration of thiol SAMs. Because dipoles of opposite directions cancelled each other out, homogeneously mixing them leads to a net dipole moment (hence the additional surface potential) between the extremes defined by each dipole and changes linearly with the chemical composition. As a result, the work function changed linearly with the chemical composition. Furthermore, the amine SAM possessed a stronger dipole than the thiol SAM. Therefore, the SAMs modified with APTMS showed a greater work function shift than did the SAMs modified with MPTMS.

  19. 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.

  20. A Thermodynamics Model for the Emergence of a Stripe-like Binary SAM on a Nanoparticle Surface.

    Science.gov (United States)

    Ge, Xinwei; Ke, Pu Chun; Davis, Thomas P; Ding, Feng

    2015-10-01

    It has been under debate if a self-assembled monolayer (SAM) with two immiscible ligands of different chain lengths and/or bulkiness can form a stripe-like pattern on a nanoparticle (NP) surface. The entropic gain upon such pattern formation due to difference in chain lengths and/or bulkiness has been proposed as the driving force in literature. Using atomistic discrete molecular dynamics simulations it is shown that stripe-like pattern could indeed emerge, but only for a subset of binary SAM systems. In addition to entropic contributions, the formation of a striped pattern also strongly depends upon interligand interactions governed by the physicochemical properties of the ligand constituents. Due to the interplay between entropy and enthalpy, a binary SAM system can be categorized into three different types depending on whether and under what condition a striped pattern can emerge. The results help clarify the ongoing debate and our proposed principle can aid in the engineering of novel binary SAMs on a NP surface.

  1. 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.

  2. Applications of Self-Assembled Monolayers in Surface-Enhanced Raman Scattering

    Directory of Open Access Journals (Sweden)

    Charles K. Klutse

    2012-01-01

    Full Text Available The increasing applications of surface-enhanced Raman scattering (SERS has led to the development of various SERS-active platforms (SERS substrates for SERS measurement. This work reviews the current optimization techniques available for improving the performance of some of these SERS substrates. The work particularly identifies self-assembled-monolayer- (SAM- based substrate modification for optimum SERS activity and wider applications. An overview of SERS, SAM, and studies involving SAM-modified substrates is highlighted. The focus of the paper then shifts to the use of SAMs to improve analytical applications of SERS substrates by addressing issues including long-term stability, selectivity, reproducibility, and functionalization, and so forth. The paper elaborates on the use of SAMs to achieve optimum SERS enhancement. Specific examples are based on novel multilayered SERS substrates developed in the author’s laboratory where SAMs have been demonstrated as excellent dielectric spacers for improving SERS enhancement more than 20-fold relative to conventional single layer SERS substrates. Such substrate optimization can significantly improve the sensitivity of the SERS method for analyte detection.

  3. 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.

  4. BSA adsorption on aliphatic and aromatic acid SAMs: investigating the effect of residual surface charge and sublayer nature.

    Science.gov (United States)

    Vallée, Anne; Humblot, Vincent; Al Housseiny, Rana; Boujday, Souhir; Pradier, Claire-Marie

    2013-09-01

    In this work, the influence of surface charge and layer rigidity on Bovin Serum Albumin (BSA) adsorption has been investigated. To this aim, Self Assembled Monolayers (SAMs) bearing terminal COOH or COO(-) groups were built on gold surfaces. The rigidity of the acid terminated SAMs was modified using either an aliphatic, mercaptoundecanoic acid (MUA), or an aromatic, mercaptobenzoic acid (MBA) thiol. X-Ray Photoelectron Spectroscopy (XPS), Polarization Modulation Reflection Absorption Infrared Spectroscopy (PM-RAIRS) and contact angle measurements, were used to deeply characterize the so-built layers. The surface charge was successfully modified by varying the pH of the rinsing solution. Indeed, COOH were the dominating species upon rinsing at pH 2 and COO(-) species dominated upon rinsing at pH 11. Rinsing at an intermediate pH, 5.5, led to the coexistence of both carboxylic and carboxylate moieties. The hydrophilic character of the surface was also found to depend on the rinsing pH, with a minimum after rinsing at intermediate pH. Using aromatic or aliphatic thiols did not affect the speciation but led to considerable differences in the hydrophilic character of these surfaces. Eventually, the adsorption of BSA on the acidic layers was investigated using PM-RAIRS. The results showed interesting differences between the charged layers. Thus, for both MUA and MBA -based SAMs, the amount of adsorbed proteins decreased when the amount of COO(-) on the surface increased. Interestingly, these effects were totally annihilated when the adsorption was carried out in PBS buffer. Moreover, for similar surface charges, the aromatic layers were able to bind higher amounts of proteins than the aliphatic ones. This work points out the key role of both surface charge and rigidity on protein adsorption. The influence of additional parameters, such as hydrophilicity and SAMs' rigidity is also established.

  5. High-Quality Alkyl Monolayers on Silicon Surfaces

    NARCIS (Netherlands)

    Sieval, A.B.; Linke, R.; Zuilhof, H.; Sudh"lter, E.J.R.

    2000-01-01

    Covalent attachment of functionalized monolayers onto silicon surfaces (see Figure for examples) is presented here as a strategy for surface modification. The preparation and structure of both unfunctionalized and functionalized alkyl-based monolayers are described, as are potential applications,

  6. Simulation and Modeling of Self-Assembled Monolayers of Carboxylic Acid Thiols on Flat and Nanoparticle Gold Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Techane, Sirnegeda D.; Baer, Donald R.; Castner, David G.

    2011-09-01

    Quantitative analysis of the 16-mercaptohexadecanoic acid self-assembled monolayer (C16 COOH-SAM) layer thickness on gold nanoparticles (AuNPs) was performed using simulation of electron spectra for surface analysis (SESSA) and x-ray photoelectron spectroscopy (XPS). XPS measurements of C16 COOH SAMs on flat gold surfaces were made at 9 different photoelectron take-off angles (5o to 85o in 5o increments), corrected using geometric weighting factors and then summed together to approximate spherical AuNPs. The SAM thickness and relative surface roughness (RSA) in SESSA were optimized to determine the best agreement between simulated and experimental surface composition. Based on the glancing angle results, it was found that inclusion of a hydrocarbon contamination layer on top the C16 COOH-SAM was necessary to improve the agreement between the SESSA and XPS results. For the 16 COOH-SAMs on flat Au surfaces, using a SAM thickness of 1.1Å/CH2 group, an RSA of 1.05 and a 1.5Å CH2-contamination overlayer (total film thickness = 21.5Å) for the SESSA calculations provided the best agreement with the experimental XPS data. After applying the appropriate geometric corrections and summing the SESSA flat surface compositions, the best fit results for the 16 COOH-SAM thickness and surface roughness on the AuNPs were determined to be 0.9Å/CH2 group and 1.06 RSA with a 1.5Å CH2-contamination overlayer (total film thickness = 18.5Å). The three angstrom difference in SAM thickness between the flat Au and AuNP surfaces suggests the alkyl chains of the SAM are slightly more tilted or disordered on the AuNP surfaces.

  7. 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.

  8. The protonation state of thiols in self-assembled monolayers on roughened Ag/Au surfaces and nanoparticles.

    Science.gov (United States)

    Bandyopadhyay, Sabyasachi; Chattopadhyay, Samir; Dey, Abhishek

    2015-10-14

    The protonation state of thiols in self-assembled monolayers (SAMs) on Ag and Au surfaces and nanoparticles (NPs) has been an issue of contestation. It has been recently demonstrated that deuterating the thiol proton produces ostentatious changes in the Raman spectra of thiols and can be used to detect the presence of the thiol functional group. Surface enhanced Raman spectroscopy (SERS) of H/D substituted aliphatic thiols on Ag surfaces clearly shows the presence of S-H vibration between 2150-2200 cm(-1) which shifts by 400 cm(-1) upon deuteration and a simultaneous >20 cm(-1) shift in the C-S vibration of thiol deuteration. Large shifts (>15 cm(-1)) in the C-S vibration are also observed for alkyl thiol SAMs on Au surfaces. Alternatively, neither the S-H vibration nor the H/D isotope effect on the C-S vibration is observed for alkyl thiol SAMs on Ag/Au NPs. XPS data on Ag/Au surfaces bearing aliphatic thiol SAMs show the presence of both protonated and deprotonated thiols while on Ag/Au NPs only deprotonated thiols are detected. These data suggest that aliphatic thiol SAMs on Au/Ag surfaces are partially protonated whereas they are totally deprotonated on Au/Ag NPs. Aromatic PhSH SAMs on Ag/Au surfaces and Ag/Au NPs do not show these vibrations or H/D shifts as well indicating that the thiols are deprotonated at these interfaces.

  9. Preparation and Characterization of Covalently Binding of Rat Anti-human IgG Monolayer on Thiol-Modified Gold Surface

    Directory of Open Access Journals (Sweden)

    Lv Zhengjian

    2009-01-01

    Full Text Available Abstract The 16-mercaptohexadecanoic acid (MHA film and rat anti-human IgG protein monolayer were fabricated on gold substrates using self-assembled monolayer (SAM method. The surface properties of the bare gold substrate, the MHA film and the protein monolayer were characterized by contact angle measurements, atomic force microscopy (AFM, grazing incidence X-ray diffraction (GIXRD method and X-ray photoelectron spectroscopy, respectively. The contact angles of the MHA film and the protein monolayer were 18° and 12°, respectively, all being hydrophilic. AFM images show dissimilar topographic nanostructures between different surfaces, and the thickness of the MHA film and the protein monolayer was estimated to be 1.51 and 5.53 nm, respectively. The GIXRD 2θ degrees of the MHA film and the protein monolayer ranged from 0° to 15°, significantly smaller than that of the bare gold surface, but the MHA film and the protein monolayer displayed very different profiles and distributions of their diffraction peaks. Moreover, the spectra of binding energy measured from these different surfaces could be well fitted with either Au4f, S2p or N1s, respectively. Taken together, these results indicate that MHA film and protein monolayer were successfully formed with homogeneous surfaces, and thus demonstrate that the SAM method is a reliable technique for fabricating protein monolayer.

  10. 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.

  11. Water-repellent coating: formation of polymeric self-assembled monolayers on nanostructured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Woo Kyung [Department of Chemistry and School of Molecular Science (BK21), Center for Molecular Design and Synthesis, KAIST, Daejeon 305-701 (Korea, Republic of); Park, Sangjin [Research Center for Biomolecular Nanotechnology, Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Jon, Sangyong [Research Center for Biomolecular Nanotechnology, Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Choi, Insung S [Department of Chemistry and School of Molecular Science (BK21), Center for Molecular Design and Synthesis, KAIST, Daejeon 305-701 (Korea, Republic of)

    2007-10-03

    In this paper, we suggest a facile and effective method for water-repellent coating of oxide surfaces. As a coating material, we synthesized a new random copolymer, referred to as poly(TMSMA-r-fluoroMA), by the radical polymerization of 3-(trimethoxysilyl)propyl methacrylate (TMSMA) and a fluoromonomer'' (registered) bearing methacrylate moiety (fluoroMA). The random copolymer was designed to consist of a 'surface-reactive part' (trimethoxysilyl group) for anchoring onto oxide-based surfaces and a 'functional part' (perfluoro group) for water repellency. The polymeric self-assembled monolayers (pSAMs) of poly(TMSMA-r-fluoroMA) were constructed on three different aluminum oxide substrates, such as flat, concave-textured, and nanoporous plates, and the static water contact angle of each surface before and after the formation of pSAMs was measured. The formation of pSAMs resulted in significantly enhanced hydrophobicity compared with the corresponding bare surfaces. In particular, among three poly(TMSMA-r-fluoroMA)-coated surfaces, the nanoporous plate showed the highest water-repellent property, with a static contact angle of {approx}163 deg., which is indicative of superhydrophobic surfaces.

  12. Water-repellent coating: formation of polymeric self-assembled monolayers on nanostructured surfaces

    Science.gov (United States)

    Cho, Woo Kyung; Park, Sangjin; Jon, Sangyong; Choi, Insung S.

    2007-10-01

    In this paper, we suggest a facile and effective method for water-repellent coating of oxide surfaces. As a coating material, we synthesized a new random copolymer, referred to as poly(TMSMA-r-fluoroMA), by the radical polymerization of 3-(trimethoxysilyl)propyl methacrylate (TMSMA) and a fluoromonomer® bearing methacrylate moiety (fluoroMA). The random copolymer was designed to consist of a 'surface-reactive part' (trimethoxysilyl group) for anchoring onto oxide-based surfaces and a 'functional part' (perfluoro group) for water repellency. The polymeric self-assembled monolayers (pSAMs) of poly(TMSMA-r-fluoroMA) were constructed on three different aluminum oxide substrates, such as flat, concave-textured, and nanoporous plates, and the static water contact angle of each surface before and after the formation of pSAMs was measured. The formation of pSAMs resulted in significantly enhanced hydrophobicity compared with the corresponding bare surfaces. In particular, among three poly(TMSMA-r-fluoroMA)-coated surfaces, the nanoporous plate showed the highest water-repellent property, with a static contact angle of ~163°, which is indicative of superhydrophobic surfaces.

  13. One-pot reaction for the preparation of biofunctionalized self-assembled monolayers on gold surfaces

    Science.gov (United States)

    Raigoza, Annette F.; Fies, Whitney; Lim, Amber; Onyirioha, Kristeen; Webb, Lauren J.

    2017-02-01

    The Huisgen cycloaddition reaction (;click; chemistry) has been used extensively to functionalize surfaces with macromolecules in a straightforward manner. We have previously developed a procedure using the copper(I)-catalyzed click reaction to tether synthetic α-helical peptides carrying two alkyne groups to a well-ordered azide-terminated alkanethiol self-assembled monolayer (SAM) on a Au(111) surface. While convenient, click-based strategies potentially pose significant problems from reagents, solvents, and reaction temperatures that may irreversibly damage some molecules or substrates. Tuning click chemistry conditions would allow individual optimization of reaction conditions for a wide variety of biomolecules and substrate materials. Here, we explore the utility of simultaneous SAM formation and peptide-attachment chemistry in a one-pot reaction. We demonstrate that a formerly multistep reaction can be successfully carried out concurrently by mixing azide-terminated alkanethiols, CuCl, and a propargylglycine-containing peptide over a bare gold surface in ethanol and reacting at 70 °C. X-ray photoelectron spectroscopy (XPS), surface infrared spectroscopy, surface circular dichroic (CD) spectroscopy, and scanning tunneling microscopy (STM) were used to determine that this one-pot reaction strategy resulted in a high density of surface-bound α-helices without aggregation. This work demonstrates the simplicity and versatility of a SAM-plus-click chemistry strategy for functionalizing Au surfaces with structured biomolecules.

  14. Surface dilatational viscosity of Langmuir monolayers

    Science.gov (United States)

    Lopez, Juan; Vogel, Michael; Hirsa, Amir

    2003-11-01

    With increased interest in microfluidic systems, interfacial phenomena is receiving more attention. As the length scales of fluid problems decrease, the surface to volume ratio increases and the coupling between interfacial flow and bulk flow becomes increasingly dominated by effects due to intrinsic surface viscosities (shear and dilatational), in comparison to elastic effects (due to surface tension gradients). The surface shear viscosity is well-characterized, as cm-scale laboratory experiments are able to isolate its effects from other interfacial processes (e.g., in the deep-channel viscometer). The same is not true for the dilatational viscosity, because it acts in the direction of surface tension gradients. Their relative strength scale with the capillary number, and for cm-scale laboratory flows, surface tension effects tend to dominate. In microfluidic scale flows, the scaling favors viscosity. We have devised an experimental apparatus which is capable of isolating and enhancing the effects of dilatational viscosity at the cm scales by driving the interface harmonically in time, while keeping the interface flat. In this talk, we shall present both the theory for how this works as well as experimental measurements of surface velocity from which we deduce the dilatational viscosity of several monolayers on the air-water interface over a substantial range of surface concentrations. Anomalous behavior over some range of concentration, which superficially indicates negative viscosity, maybe explained in terms of compositional effects due to large spatial and temporal variations in concentration and corresponding viscosity.

  15. Reactive Landing of Gramicidin S and Ubiquitin Ions onto Activated Self-Assembled Monolayer Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Laskin, Julia; Hu, Qichi

    2017-03-13

    Using mass-selected ion deposition combined with in situ infrared reflection absorption spectroscopy (IRRAS), we examined the reactive landing of gramicidin S and ubiquitin ions onto activated self-assembled monolayer (SAM) surfaces terminated with N-hydroxysuccinimidyl ester (NHS-SAM) and acyl fluoride (COF-SAM) groups. Doubly protonated gramicidin S, [GS+2H]2+, and two charge states of ubiquitin, [U+5H]5+ and [U+13H]13+, were used as model systems, allowing us to explore the effect of the number of free amino groups and the secondary structure on the efficiency of covalent bond formation between the projectile ion and the surface. For all projectile ions, ion deposition resulted in the depletion of IRRAS bands corresponding to the terminal groups on the SAM and the appearance of several new bands not associated with the deposited species. These new bands were assigned to the C=O stretching vibrations of COOH and COO- groups formed on the surface as a result of ion deposition. The presence of these bands was attributed to an alternative reactive landing pathway that competes with covalent bond formation. This pathway with similar yields for both gramicidin S and ubiquitin ions is analogous to the hydrolysis of the NHS ester bond in solution. The covalent bond formation efficiency increased linearly with the number of free amino groups and was found to be lower for the more compact conformation of ubiquitin compared with the fully unfolded conformation. This observation was attributed to the limited availability of amino groups on the surface of the folded conformation. Our results have provided new insights on the efficiency and mechanism of reactive landing of peptides and proteins onto activated SAMs

  16. Reactive Landing of Gramicidin S and Ubiquitin Ions onto Activated Self-Assembled Monolayer Surfaces

    Science.gov (United States)

    Laskin, Julia; Hu, Qichi

    2017-03-01

    Using mass-selected ion deposition combined with in situ infrared reflection absorption spectroscopy (IRRAS), we examined the reactive landing of gramicidin S and ubiquitin ions onto activated self-assembled monolayer (SAM) surfaces terminated with N-hydroxysuccinimidyl ester (NHS-SAM) and acyl fluoride (COF-SAM) groups. Doubly protonated gramicidin S, [GS + 2H]2+, and two charge states of ubiquitin, [U + 5H]5+ and [U + 13H]13+, were used as model systems, allowing us to explore the effect of the number of free amino groups and the secondary structure on the efficiency of covalent bond formation between the projectile ion and the surface. For all projectile ions, ion deposition resulted in the depletion of IRRAS bands corresponding to the terminal groups on the SAM and the appearance of several new bands not associated with the deposited species. These new bands were assigned to the C=O stretching vibrations of COOH and COO- groups formed on the surface as a result of ion deposition. The presence of these bands was attributed to an alternative reactive landing pathway that competes with covalent bond formation. This pathway with similar yields for both gramicidin S and ubiquitin ions is analogous to the hydrolysis of the NHS ester bond in solution. The covalent bond formation efficiency increased linearly with the number of free amino groups and was found to be lower for the more compact conformation of ubiquitin compared with the fully unfolded conformation. This observation was attributed to the limited availability of amino groups on the surface of the folded conformation. Our results have provided new insights on the efficiency and mechanism of reactive landing of peptides and proteins onto activated SAMs.

  17. Reactive Landing of Gramicidin S and Ubiquitin Ions onto Activated Self-Assembled Monolayer Surfaces

    Science.gov (United States)

    Laskin, Julia; Hu, Qichi

    2017-07-01

    Using mass-selected ion deposition combined with in situ infrared reflection absorption spectroscopy (IRRAS), we examined the reactive landing of gramicidin S and ubiquitin ions onto activated self-assembled monolayer (SAM) surfaces terminated with N-hydroxysuccinimidyl ester (NHS-SAM) and acyl fluoride (COF-SAM) groups. Doubly protonated gramicidin S, [GS + 2H]2+, and two charge states of ubiquitin, [U + 5H]5+ and [U + 13H]13+, were used as model systems, allowing us to explore the effect of the number of free amino groups and the secondary structure on the efficiency of covalent bond formation between the projectile ion and the surface. For all projectile ions, ion deposition resulted in the depletion of IRRAS bands corresponding to the terminal groups on the SAM and the appearance of several new bands not associated with the deposited species. These new bands were assigned to the C=O stretching vibrations of COOH and COO- groups formed on the surface as a result of ion deposition. The presence of these bands was attributed to an alternative reactive landing pathway that competes with covalent bond formation. This pathway with similar yields for both gramicidin S and ubiquitin ions is analogous to the hydrolysis of the NHS ester bond in solution. The covalent bond formation efficiency increased linearly with the number of free amino groups and was found to be lower for the more compact conformation of ubiquitin compared with the fully unfolded conformation. This observation was attributed to the limited availability of amino groups on the surface of the folded conformation. Our results have provided new insights on the efficiency and mechanism of reactive landing of peptides and proteins onto activated SAMs.

  18. Fast and slow responses of Southern Ocean sea surface temperature to SAM in coupled climate models

    Science.gov (United States)

    Kostov, Yavor; Marshall, John; Hausmann, Ute; Armour, Kyle C.; Ferreira, David; Holland, Marika M.

    2017-03-01

    We investigate how sea surface temperatures (SSTs) around Antarctica respond to the Southern Annular Mode (SAM) on multiple timescales. To that end we examine the relationship between SAM and SST within unperturbed preindustrial control simulations of coupled general circulation models (GCMs) included in the Climate Modeling Intercomparison Project phase 5 (CMIP5). We develop a technique to extract the response of the Southern Ocean SST (55°S-70°S) to a hypothetical step increase in the SAM index. We demonstrate that in many GCMs, the expected SST step response function is nonmonotonic in time. Following a shift to a positive SAM anomaly, an initial cooling regime can transition into surface warming around Antarctica. However, there are large differences across the CMIP5 ensemble. In some models the step response function never changes sign and cooling persists, while in other GCMs the SST anomaly crosses over from negative to positive values only 3 years after a step increase in the SAM. This intermodel diversity can be related to differences in the models' climatological thermal ocean stratification in the region of seasonal sea ice around Antarctica. Exploiting this relationship, we use observational data for the time-mean meridional and vertical temperature gradients to constrain the real Southern Ocean response to SAM on fast and slow timescales.

  19. A nano-patterned self assembled monolayer (SAM) rutile titania cancer chip for rapid, low cost, highly sensitive, direct cancer analysis in MALDI-MS.

    Science.gov (United States)

    Manikandan, M; Gopal, Judy; Hasan, Nazim; Wu, Hui-Fen

    2014-12-01

    We developed a cancer chip by nano-patterning a highly sensitive SAM titanium surface capable of capturing and sensing concentrations as low as 10 cancer cells/mL from the environment by Matrix Assisted Laser Desorption and Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS). The current approach evades any form of pretreatment and sample preparation processes; it is time saving and does not require the (expensive) conventional MALDI target plate. The home made aluminium (Al) target holder cost, on which we loaded the cancer chips for MALDI-TOF MS analysis, is about 60 USD. While the conventional stainless steel MALDI target plate is more than 700 USD. The SAM surface was an effective platform leading to on-chip direct MALDI-MS detection of cancer cells. We compared the functionality of this chip with the unmodified titanium surfaces and thermally oxidized (TO) titanium surfaces. The lowest detectable concentration of the TO chip was 10(3) cells/mL, while the lowest detectable concentration of the control or unmodified titanium chips was 10(6) cells/mL. Compared to the control surface, the SAM cancer chip showed 100,000 times of enhanced sensitivity and compared with the TO chip, 1000 times of increased sensitivity. The high sensitivity of the SAM surfaces is attributed to the presence of the rutile SAM, surface roughness and surface wettability as confirmed by AFM, XRD, contact angle microscope and FE-SEM. This study opens a new avenue for the potent application of the SAM cancer chip for direct cancer diagnosis by MALDI-TOF MS in the near future.

  20. Self-assembly of organic monolayers as protective and conductive bridges for nanometric surface-mount applications.

    Science.gov (United States)

    Platzman, Ilia; Haick, Hossam; Tannenbaum, Rina

    2010-09-01

    In this work, we present a novel surface-mount placement process that could potentially overcome the inadequacies of the currently used stencil-printing technology, when applied to devices in which either their lateral and/or their horizontal dimensions approach the nanometric scale. Our novel process is based on the "bottom-up" design of an adhesive layer, operative in the molecular/nanoscale level, through the use of self-assembled monolayers (SAMs) that could form protective and conductive bridges between pads and components. On the basis of previous results, 1,4-phenylene diisocyanide (PDI) and terephthalic acid (TPA) were chosen to serve as the best candidates for the achievement of this goal. The quality and stability of these SAMs on annealed Cu surfaces (Rrms=0.15-1.1 nm) were examined in detail. Measurements showed that the SAMs of TPA and PDI molecules formed on top of Cu substrates created thermally stable organic monolayers with high surface coverage (∼90%), in which the molecules were closely packed and well-ordered. Moreover, the molecules assumed a standing-up phase conformation, in which the molecules bonded to the Cu substrate through one terminal functional group, with the other terminal group residing away from the substrate. To examine the ability of these monolayers to serve as "molecular wires," i.e., the capability to provide electrical conductivity, we developed a novel fabrication method of a parallel plate junction (PPJ) in order to create symmetric Cu-SAM-Cu electrical junctions. The current-bias measurements of these junctions indicated high tunneling efficiency. These achievements imply that the SAMs used in this study can serve as conductive molecular bridges that can potentially bind circuital pads/components.

  1. Adsorption of biopolymers human serum albumin and human gamma globulin to well-defined surfaces of self-assembled monolayers

    Science.gov (United States)

    Cregger, Tricia Ann

    The tenacity with which the blood proteins Human Serum Albumin (HSA) and Human Gamma Globulin (HGG) adsorb to a surface modified with a monomolecular coating varies with the packing of the alkyl chains in the coating. The adsorption of proteins onto well-defined surfaces of self-assembled monolayers (SAMs) was studied with X-ray reflectometry (XR), neutron reflectometry (NR), optical reflectometry, and total internal reflection fluorescence (TIRF). NR and XR was used to study adsorption in the absence of flow, while optical reflectometry and TIRF were used to probe the adsorption under flow conditions. In particular, competitive adsorption measurements of binary solutions of HSA, HGG and Fibrinogen (FIB) were performed with TIRE The properties of the surface were varied by altering the alkyl chains' packing density and the chain end functionality of the SAMs. The depth profiles of protein concentration near the adsorbing surface measured by NR were dependent upon the chain packing density in the case of HSA. The concentration depth profile of HGG was unaltered by varying chain packing density. Measurements performed under flow using optical reflectometry showed a different behavior: the surface excess of adsorbed HSA was relatively independent of the surface packing, while the surface excess of HGG depended on the packing density of the SAM. The tenacity with which the proteins adsorbed to different functionalized surfaces was determined by attempting to remove the protein using a strong surfactant, sodium dodecyl sulfate (SDS). Ex situ XR measurements suggested that both HSA and HGG adsorb more tenaciously to a less densely-packed monolayer, almost independent of surface functionality. Two exceptions were a less densely-packed vinyl-terminated monolayer and a less densely-packed bromine-terminated monolayer, from which HSA could not be removed at all.

  2. Surface effects of monolayer-protected gold nanoparticles on the redox reactions between ferricyanide and thiosulfate

    Institute of Scientific and Technical Information of China (English)

    LI Di; SUN Chunyan; HUANG Yunjie; LI Jinghong; CHEN Shaowei

    2005-01-01

    Electron transfer through the self-assembled monolayers (SAMs) on gold nanoparticles is investigated by using the monolayer protected gold nanoclusters (MPCs) as electron-transfer mediators. 3-Mercaptopropionic acid (MPA) and 11-meraptoundecanoic acid (MUA) MPCs were employed to catalyze the redox reaction between potassium ferricyanide and sodium thiosulfate. The catalytic mechanism was proposed that the MPCs act as diffusing electron-mediators and electron transfers to and from the MPCs surface. Therefore the electron transfer rate through the capping layers would be proportional to the MPCs catalyzed reaction rate, which was monitored by the UV absorbance of ferricyanide. The calculated apparent rate constant was orders of magnitude smaller than that of the maximum of tunneling current, which was attributed to the splited energy level of the nanoscale particles.

  3. 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.

  4. 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

    2016-02-07

    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.

  5. Modelling Organic Surfaces with Self-Assembled Monolayers

    Science.gov (United States)

    1989-05-01

    reactive organic liquids. Fluorinated thiols form monolayers that are more water and oil-repellent than Teflon. The hydrophobicity and oleophobicity of...and are both hydrophobic and oleophobic . The surface of a monolayer containing an approximately equal mixture of the two components 13 resembles a

  6. Influence of surface structure on single or mixed component self-assembled monolayers via in situ spectroelectrochemical fluorescence imaging of the complete stereographic triangle on a single crystal Au bead electrode.

    Science.gov (United States)

    Yu, Zhinan Landis; Casanova-Moreno, Jannu; Guryanov, Ivan; Maran, Flavio; Bizzotto, Dan

    2015-01-14

    The use of a single crystal gold bead electrode is demonstrated for characterization of self-assembled monolayers (SAM)s formed on the bead surface expressing a complete set of face centered cubic (fcc) surface structures represented by a stereographic projection. Simultaneous analysis of many crystallographic orientations was accomplished through the use of an in situ fluorescence microscopic imaging technique coupled with electrochemical measurements. SAMs were prepared from different classes of molecules, which were modified with a fluorescent tag enabling characterization of the influence of electrical potential and a direct comparison of the influence of surface structure on SAMs adsorbed onto low index, vicinal and chiral surfaces. The assembly of alkylthiol, Aib peptide and DNA SAMs are studied as a function of the electrical potential of the interface revealing how the organization of these SAMs depend on the surface crystallographic orientation, all in one measurement. This approach allows for a simultaneous determination of SAMs assembled onto an electrode surface onto which the whole fcc stereographic triangle can be mapped, revealing the influence of intermolecular interactions as well as the atomic arrangement of the substrate. Moreover, this method enables study of the influence of the Au surface atom arrangement on SAMs that were created and analyzed, both under identical conditions, something that can be challenging for the typical studies of this kind using individual gold single crystal electrodes. Also demonstrated is the analysis of a SAM containing two components prepared using thiol exchange. The two component SAM shows remarkable differences in the surface coverage, which strongly depends on the surface crystallography enabling estimates of the thiol exchange energetics. In addition, these electrode surfaces enable studies of molecular adsorption onto the symmetry related chiral surfaces since more than one stereographic triangle can be

  7. Nanoseeding via dual surface modification of alkyl monolayer for site-controlled electroless metallization.

    Science.gov (United States)

    Chen, Sung-Te; Chen, Giin-Shan

    2011-10-04

    In this work, an attempt to fabricate nanostructured metallization patterns on SiO(2) dielectric layers is made by using plasma-patterned self-assembled monolayers (SAMs), in conjunction with a novel aqueous seeding and electroless process. Taking octadecyltrichlorosilane (OTS) as a test material, the authors demonstrate that optimizing the N(2)-H(2) plasma conditions leads to the successive conversion of the topmost aliphatic chains of alkyl SAMs to carboxyl (COOH) and hydroxyl (C-OH) functional groups, which was previously found in alkyl SAMs only by exposure to "oxygen-based" plasma. Further modifying the plasma-exposed (either COOH or C-OH terminated) regions with an aqueous solution (SC-1) creates surface functionalities that are viable for site-controlled metallic seeding (e.g., Co or Ni) with an adsorption selectivity of greater than 1000:1. Neither the combination of costly PdCl(2) and complex additives nor the demerits of the associated aqueous chemistry (e.g., seed agglomeration and seed sparseness) are involved. Therefore, the seed particles are only 3 nm in size. Simultaneously, there are sufficient particle densities previously unattainable for electroless deposition to trigger highly resolved Cu metallization patterns with a film thickness of less than 10 nm. The formation of the seed-adsorbing sites is discussed, based on a plasma-dissociated, water-mediated chemical oxidation route.

  8. Depth profiling of APTES self-assembled monolayers using surface-enhanced confocal Raman microspectroscopy

    Science.gov (United States)

    Sun, Yingying; Yanagisawa, Masahiro; Kunimoto, Masahiro; Nakamura, Masatoshi; Homma, Takayuki

    2017-09-01

    The internal structure of self-assembled monolayers (SAMs) such as 3-aminopropyltriethoxysilane (APTES) fabricated on a glass substrate is difficult to characterize and analyze at nanometer level. In this study, we employed surface-enhanced Raman spectroscopy (SERS) to study the internal molecular structure of APTES SAMs. The sample APTES SAMs were deposited with Ag nanoparticles to enhance the Raman signal and to obtain subtler structure information, which were supported by density functional theory calculations. In addition, in order to carry out high-resolution analysis, especially for vertical direction, a fine piezo electric positioner was used to control the depth scanning with a step of 0.1 nm. We measured and distinguished the vertical Raman intensity variations of specific groups in APTES, such as Ag/NH2, CH2, and Sisbnd O, with high resolution. The interfacial bond at the two interfaces of Ag-APTES and APTES-SiO2 was identified. Moreover, APTES molecule orientation was demonstrated to be inhomogeneous from frequency shift.

  9. Low adhesion, non-wetting phosphonate self-assembled monolayer films formed on copper oxide surfaces.

    Science.gov (United States)

    Hoque, E; DeRose, J A; Bhushan, B; Hipps, K W

    2009-07-01

    Self-assembled monolayer (SAM) films have been formed on oxidized copper (Cu) substrates by reaction with 1H,1H,2H,2H-perfluorodecylphosphonic acid (PFDP), octadecylphosphonic acid (ODP), decylphosphonic acid (DP), and octylphosphonic acid (OP) and then investigated by X-ray photoelectron spectroscopy (XPS), contact angle measurement (CAM), and atomic force microscopy (AFM). The presence of alkyl phosphonate molecules, PFDP, ODP, DP, and OP, on Cu were confirmed by CAM and XPS analysis. No alkyl phosphonate molecules were seen by XPS on unmodified Cu as a control. The PFDP/Cu and ODP/Cu SAMs were found to be very hydrophobic having water sessile drop static contact angles of more than 140 degrees , while DP/Cu and OP/Cu have contact angles of 119 degrees and 76 degrees , respectively. PFDP/Cu, ODP/Cu, DP/Cu, and OP/Cu SAMs were studied by friction force microscopy, a derivative of AFM, to better understand their micro/nanotribological properties. PFDP/Cu, ODP/Cu, and DP/Cu had comparable adhesive force, which is much lower than that for unmodified Cu. ODP/Cu had the lowest friction coefficient followed by PFDP/Cu, DP/Cu, and OP/Cu while unmodified Cu had the highest. XPS data gives some indication that a bidentate bond forms between the alkyl phosphonate molecules and the oxidized Cu surface. Hydrophobic phosphonate SAMs could be useful as corrosion inhibitors in micro/nanoelectronic devices and/or as promoters for anti-wetting, low adhesion surfaces.

  10. Surface Modification of TiO2 Photoanodes with Fluorinated Self-Assembled Monolayers for Highly Efficient Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Wooh, Sanghyuk; Kim, Tea-Yon; Song, Donghoon; Lee, Yong-Gun; Lee, Tae Kyung; Bergmann, Victor W; Weber, Stefan A L; Bisquert, Juan; Kang, Yong Soo; Char, Kookheon

    2015-11-25

    Dye aggregation and electron recombination in TiO2 photoanodes are the two major phenomena lowering the energy conversion efficiency of dye-sensitized solar cells (DSCs). Herein, we introduce a novel surface modification strategy of TiO2 photoanodes by the fluorinated self-assembled monolayer (F-SAM) formation with 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFTS), blocking the vacant sites of the TiO2 surface after dye adsorption. The F-SAM helps to efficiently lower the surface tension, resulting in efficient repelling ions, e.g., I3(-), in the electrolyte to decrease the electron recombination rate, and the role of F-SAM is characterized in detail by impedance spectroscopy using a diffusion-recombination model. In addition, the dye aggregates on the TiO2 surface are relaxed by the F-SAM with large conformational perturbation (i.e., helix structure) seemingly because of steric hindrance developed during the SAM formation. Such multifunctional effects suppress the electron recombination as well as the intermolecular interactions of dye aggregates without the loss of adsorbed dyes, enhancing both the photocurrent density (11.9 → 13.5 mA cm(-2)) and open-circuit voltage (0.67 → 0.72 V). Moreover, the combined surface modification with the F-SAM and the classical coadsorbent further improves the photovoltaic performance in DSCs.

  11. Interface electronic structures of reversible double-docking self-assembled monolayers on an Au(111) surface.

    Science.gov (United States)

    Zhang, Tian; Ma, Zhongyun; Wang, Linjun; Xi, Jinyang; Shuai, Zhigang

    2014-04-13

    Double-docking self-assembled monolayers (DDSAMs), namely self-assembled monolayers (SAMs) formed by molecules possessing two docking groups, provide great flexibility to tune the work function of metal electrodes and the tunnelling barrier between metal electrodes and the SAMs, and thus offer promising applications in both organic and molecular electronics. Based on the dispersion-corrected density functional theory (DFT) in comparison with conventional DFT, we carry out a systematic investigation on the dual configurations of a series of DDSAMs on an Au(111) surface. Through analysing the interface electronic structures, we obtain the relationship between single molecular properties and the SAM-induced work-function modification as well as the level alignment between the metal Fermi level and molecular frontier states. The two possible conformations of one type of DDSAM on a metal surface reveal a strong difference in the work-function modification and the electron/hole tunnelling barriers. Fermi-level pinning is found to be a key factor to understand the interface electronic properties.

  12. Biological Activation of Inert Ceramics: Recent Advances Using Tailored Self-Assembled Monolayers on Implant Ceramic Surfaces

    Directory of Open Access Journals (Sweden)

    Frederik Böke

    2014-06-01

    Full Text Available High-strength ceramics as materials for medical implants have a long, research-intensive history. Yet, especially on applications where the ceramic components are in direct contact with the surrounding tissue, an unresolved issue is its inherent property of biological inertness. To combat this, several strategies have been investigated over the last couple of years. One promising approach investigates the technique of Self-Assembled Monolayers (SAM and subsequent chemical functionalization to create a biologically active tissue-facing surface layer. Implementation of this would have a beneficial impact on several fields in modern implant medicine such as hip and knee arthroplasty, dental applications and related fields. This review aims to give a summarizing overview of the latest advances in this recently emerging field, along with thorough introductions of the underlying mechanism of SAMs and surface cell attachment mechanics on the cell side.

  13. Molecular simulation of alkyl monolayers on the Si(111)surface

    Institute of Scientific and Technical Information of China (English)

    YUAN; Shiling; (苑世领); CAI; Zhengting; (蔡政亭); XIAO; Li; (肖莉); XU; Guiying; (徐桂英); LIU; Yongjun; (刘永军)

    2003-01-01

    The structure of twelve-carbon monolayers on the H-terminated Si(111) surface is investigated by molecular simulation method. The best substitution percent on Si(111) surface obtained via molecular mechanics calculation is equal to 50%, and the (8×8) simulated cell can be used to depict the structure of alkyl monolayer on Si surface. After two-dimensional cell containing alkyl chains and four-layer Si(111) crystal at the substitution 50% is constructed, the densely packed and well-ordered monolayer on Si(111) surface can be shown through energy minimization in the suitable-size simulation cell. These simulation results are in good agreement with the experiments. These conclusions show that molecular simulation can provide otherwise inaccessible mesoscopic information at the molecular level, and can be considered as an adjunct to experiments.

  14. Preparation and biocompatibility of BSA monolayer on silicon surface.

    Science.gov (United States)

    Tao, Caihong; Zhang, Junyan; Yang, Shengrong

    2011-06-01

    This paper describes a general strategy for grafting protein molecules on silicon surface by using dopamine as adhesive layer. With this method, silicon surface had been successfully modified by BSA monolayer. Fourier transform infrared spectra, X-ray photoelectron spectroscopy, contact angle analysis and atomic force microscopy confirmed the sequential grafting of initiator and protein molecules. Cell adhesion experiments with PC-12 cells showed that the obtained monolayer exhibits good biocompatibility. The corrosion resistance behavior of the polydopamine and BSA modified silicon wafers was investigated by potentiodynamic test, which indicated that the modified surfaces exhibited a better anti-corrosion capability than silicon surface. All these results must be valuable for the application of protein monolayer in biological and biomedical technology.

  15. 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.

  16. 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.

  17. Vibrations on Cu surfaces covered with Ni monolayer

    Science.gov (United States)

    Sklyadneva, I. Yu.; Rusina, G. G.; Chulkov, E. V.

    1999-08-01

    Vibrational modes on the Cu(100) and Cu(111) surfaces covered with a Ni monolayer have been calculated using the embedded-atom method. A detailed discussion of the dispersion relations and polarizations of adsorbate modes and surface phonons is presented. The dispersion of the Rayleigh phonon is in good agreement with the experimental EELS data. The changes in interatomic force constants are discussed.

  18. 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.

  19. Tuning of metal work functions with self-assembled monolayers

    NARCIS (Netherlands)

    de Boer, B; Hadipour, A; Foekema, R; van Woudenbergh, T; Mandoc, MM; Mihailetchi, VD; Blom, PWM; Heremans, PL; Muccini, M; Hofstraat, H

    2004-01-01

    Tuning the work functions of metals was demonstrated by chemically modifying the metal surface through the formation of chemisorbed self-assembled monolayers (SAMs) derived from 1H,1H,2H,2H-perfluorinated alkanethiols and hexadecanethiol. The ordering inherent in the SAMs creates an effective, molec

  20. Self-assembled monolayers on metal oxides : applications in nanotechnology

    NARCIS (Netherlands)

    Yildirim, O.

    2010-01-01

    The thesis describes the use of phosph(on)ate-based self-assembled monolayers (SAMs) to modify and pattern metal oxides. Metal oxides have interesting electronic and magnetic properties such as insulating, semiconducting, metallic, ferromagnetic etc. and SAMs can tailor the surface properties. FePt

  1. ELECTROCATALYSIS ON SURFACES MODIFIED BY METAL MONOLAYERS DEPOSITED AT UNDERPOTENTIALS.

    Energy Technology Data Exchange (ETDEWEB)

    ADZIC,R.

    2000-12-01

    The remarkable catalytic properties of electrode surfaces modified by monolayer amounts of metal adatoms obtained by underpotential deposition (UPD) have been the subject of a large number of studies during the last couple of decades. This interest stems from the possibility of implementing strictly surface modifications of electrocatalysts in an elegant, well-controlled way, and these bi-metallic surfaces can serve as models for the design of new catalysts. In addition, some of these systems may have potential for practical applications. The UPD of metals, which in general involves the deposition of up to a monolayer of metal on a foreign substrate at potentials positive to the reversible thermodynamic potential, facilitates this type of surface modification, which can be performed repeatedly by potential control. Recent studies of these surfaces and their catalytic properties by new in situ surface structure sensitive techniques have greatly improved the understanding of these systems.

  2. Immobilization of rhodium complexes at thiolate monolayers on gold surfaces : Catalytic and structural studies

    NARCIS (Netherlands)

    Belser, T; Stöhr, Meike; Pfaltz, A

    2005-01-01

    Chiral rhodium-diphosphine complexes have been incorporated into self-assembled thiolate monolayers (SAMS) on gold colloids. Catalysts of this type are of interest because they combine properties of homogeneous and heterogeneous systems. In addition, it should be possible to influence the catalytic

  3. Ellipsometry of clean surfaces, submonolayer and monolayer films

    NARCIS (Netherlands)

    Habraken, F.H.P.M.; Gijzeman, O.L.J.; Bootsma, G.A.

    1980-01-01

    The geometric and electronic structure of the surface region of a crystal is often different from the bulk structure and therefore the optical properties differ in principle also. Theories for the optical properties of (sub)monolayer films are compared, with special attention to anisotropic layers.

  4. Oxygen adsorption on palladium monolayer as a surface catalyst

    Science.gov (United States)

    Shah, Janki; Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh

    2017-09-01

    In the recent work, we study on the structural and electronic properties of the graphene like Pd monolayer with the adsorption of oxygen adatoms by using first-principles calculations. The electronic band structure and projected density of states investigate that Pd-surface with oxygen molecule adsorption gives metallic behaviour. We found that the behaviour changed at M-point in the electronic band structure as adding oxygen atoms. The oxygen adsorption was dissociative until the Pd surface immersed with oxygen atoms. The electron charge density increases as the number of oxygen atoms on Pd-surface increases. The noticeable observation is that by adding 7th oxygen atom, they started to ripple from fixed Pd-surface without making a bond due to oxygen coverage increases. The results show that Pd monolayer has different applications as a oxygen catalyst and it can be utilized as the pellet, surface, and film materials to safeguard sustenance from oxidation.

  5. 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

  6. 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.

  7. Hexadecadienyl Monolayers on Hydrogen-Terminated Si(III): Faster Monolayer Formation and Improved Surface Coverage Using the Enyne Moiety

    NARCIS (Netherlands)

    Rijksen, B.M.G.; Pujari, S.P.; Scheres, L.M.W.; Rijn, van C.J.M.; Baio, J.E.; Weidner, T.; Zuilhof, H.

    2012-01-01

    To further improve the coverage of organic monolayers on hydrogen-terminated silicon (H–Si) surfaces with respect to the hitherto best agents (1-alkynes), it was hypothesized that enynes (H–C=C–HC-CH–R) would be even better reagents for dense monolayer formation. To investigate whether the increased

  8. Dynamic pattern formation of liquid crystals using binary self-assembled monolayers on an ITO surface under DC voltage.

    Science.gov (United States)

    Ishida, Takao; Oyama, Makiko; Terada, Kei-ichi; Haga, Masa-aki

    2014-12-07

    There have been numerous studies of liquid crystal (LC) convection using sandwich-type LC cells under AC voltage. In contrast to previous LC convection studies under AC voltage, we propose the use of a binary self-assembled monolayer (SAM) with a redox-active Ru complex and insulating octadecyl phosphonic acid (C18) molecules on an indium tin oxide (ITO) surface as the electrode of sandwich-type LC cells under DC bias voltage. This is because the functionalized molecules immobilized on the ITO surface are expected to control the LC orientation and electrical conduction of LC cells, under an exact DC bias voltage. We successfully achieved LC pattern formation using ITO electrodes with binary SAMs in LC cells. Moreover, we confirmed that the LC pattern size was increased by increasing the coverage of the Ru complex in binary SAMs. We consider that a combination of three factors, electrical conduction change, controlling of LC orientation in the initial stage and redox-activity of the Ru-complex, is the reason for LC convection although we cannot fully explain the distribution of these three factors. We believe that our LC pattern formation is promising for new type devices e.g., artificial compound eyes using the LC device technology.

  9. Dynamics of SAMs in Boundary Lubrication

    Directory of Open Access Journals (Sweden)

    J. Manojlović

    2013-09-01

    Full Text Available Surfactant molecules have some properties responsible for a number ofremarkable phenomena, such as oriented adsorption of surfactants at surfaces and interfaces. The capability to self -assemble into well- defined structures is often seen as being more important than their surface activity. When a surfactant solution is in contact with a solid surface, the surfactant molecules adsorb onto the surface, ideally forming an adsorbed layer of a high order, termed as a self- assembled monolayer (SAM. Many surface properties are influenced bysuch a film, and therefore, SAMs offer the capability to form ordered organic surface coatings, suitable for various applications, such as wetting or corrosion protection. Due to the flexibility in choosing the molecular architecture, organic molecules have many interesting applications, such as biosensors, in Photoelectronics, in controlling water adsorption or boundary lubricant coating. This paper Focuses on cationic surfactants (quaternary ammonium surfactants with some unique properties that are not present in other surfactants.

  10. Mechanic studies of monolayer formation on H-Si(111) surfaces

    NARCIS (Netherlands)

    Rijksen, B.M.G.

    2012-01-01

    Covalently attached organic monolayers on silicon surfaces form thermally and chemically stable platforms for (bio)functionalization of the surface. Recent advances in monolayer formation – yielding increases in monolayer quality and the complete exclusion of oxygen at modified surfaces &ndash

  11. Structure of adsorbed monolayers. The surface chemical bond

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, G.A.; Bent, B.E.

    1984-06-01

    This paper attempts to provide a summary of what has been learned about the structure of adsorbed monolayers and about the surface chemical bond from molecular surface science. While the surface chemical bond is less well understood than bonding of molecules in the gas phase or in the solid state, our knowledge of its properties is rapidly accumulating. The information obtained also has great impact on many surface science based technologies, including heterogeneous catalysis and electronic devices. It is hoped that much of the information obtained from studies at solid-gas interfaces can be correlated with molecular behavior at solid-liquid interfaces. 31 references, 42 figures, 1 table.

  12. Fabrication of molecular nanopatterns at aluminium oxide surfaces by nanoshaving of self-assembled monolayers of alkylphosphonates.

    Science.gov (United States)

    El Zubir, Osama; Barlow, Iain; Leggett, Graham J; Williams, Nicholas H

    2013-11-21

    Nanoshaving, by tracing an atomic force microscope probe across a surface at elevated load, has been used to fabricate nanostructures in self-assembled monolayers of alkylphosphonates adsorbed at aluminium oxide surfaces. The simple process is implemented under ambient conditions. Because of the strong bond between the alkylphosphonates and the oxide surface, loads in excess of 400 nN are required to pattern the monolayer. Following patterning of octadecylphosphonate SAMs, adsorption of aminobutyl phosphonate yielded features as small as 39 nm. Shaving of monolayers of aryl azide-terminated alkylphosphonates, followed by attachment of polyethylene glycol to unmodified regions in a photochemical coupling reaction, yielded 102 nm trenches into which NeutrAvidin coated, dye-labelled, polymer nanospheres could be deposited, yielding bright fluorescence with little evidence of non-specific adsorption to other regions of the surface. Structures formed in alkylphosphonate films by nanoshaving were used to etch structures into the underlying metal. Because of the isotropic nature of the etch process, and the large grain size, some broadening was observed, but features 25-35 nm deep and 180 nm wide were fabricated.

  13. Formation of self-assembled monolayer of curcuminoid molecules on gold surfaces

    Science.gov (United States)

    Berlanga, Isadora; Etcheverry-Berríos, Álvaro; Mella, Andy; Jullian, Domingo; Gómez, Victoria Alejandra; Aliaga-Alcalde, Núria; Fuenzalida, Victor; Flores, Marcos; Soler, Monica

    2017-01-01

    We investigated the formation of self-assembled monolayers of two thiophene curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), on polycrystalline gold substrates prepared by immersion of the surfaces in a solution of the molecules during 24 h. The functionalized surfaces were studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Despite the fact that both molecules have the same composition and almost the same structure, these molecules exhibit different behavior on the gold surface, which can be explained by the different positions of the sulfur atoms in the terminal aromatic rings. In the case of molecule 1, the complete formation of a SAM can be observed after 24 h of immersion. In the case of molecule 2, the transition from flat-lying to upright configuration on the surface is still in process after 24 h of immersion. This is attributed to the fact that molecule 2 have the sulfur atoms more exposed than molecule 1.

  14. 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.

  15. Poly(ethylene glycol) monolayer formation and stability on gold and silicon nitride substrates.

    Science.gov (United States)

    Cerruti, Marta; Fissolo, Stefano; Carraro, Carlo; Ricciardi, Carlo; Majumdar, Arun; Maboudian, Roya

    2008-10-07

    Poly(ethylene glycol) (PEG) self-assembled monolayers (SAMs) are extensively used to modify substrates to prevent nonspecific protein adsorption and to increase hydrophilicity. X-ray photoelectron spectroscopy analysis, complemented by water contact angle measurements, is employed to investigate the formation and stability upon aging and heating of PEG monolayers formed on gold and silicon nitride substrates. In particular, thiolated PEG monolayers on gold, with and without the addition of an undecylic spacer chain, and PEG monolayers formed with oxysilane precursors on silicon nitride have been probed. It is found that PEG-thiol SAMs are degraded after less than two weeks of exposure to air and when heated at temperatures as low as 120 degrees C. On the contrary, PEG-silane SAMs are stable for more than two weeks, and fewer molecules are desorbed even after two months of aging, compared to those desorbed in two weeks from the PEG-thiol SAMs. A strongly bound hydration layer is found on PEG-silane SAMs aged for two months. Heating PEG-silane SAMs to temperatures as high as 160 degrees C improves the quality of the monolayer, desorbing weakly bound contaminants. The differences in stability between PEG-thiol SAMs and PEG-silane SAMs are ascribed to the different types of bonding to the surface and to the fact that the thiol-Au bond can be easily oxidized, thus causing desorption of PEG molecules from the surface.

  16. Protein-induced surface structuring in myelin membrane monolayers.

    Science.gov (United States)

    Rosetti, Carla M; Maggio, Bruno

    2007-12-15

    Monolayers prepared from myelin conserve all the compositional complexity of the natural membrane when spread at the air-water interface. They show a complex pressure-dependent surface pattern that, on compression, changes from the coexistence of two liquid phases to a viscous fractal phase embedded in a liquid phase. We dissected the role of major myelin protein components, myelin basic protein (MBP), and Folch-Lees proteolipid protein (PLP) as crucial factors determining the structural dynamics of the interface. By analyzing mixtures of a single protein with the myelin lipids we found that MBP and PLP have different surface pressure-dependent behaviors. MBP stabilizes the segregation of two liquid phases at low pressures and becomes excluded from the film under compression, remaining adjacent to the interface. PLP, on the contrary, organizes a fractal-like pattern at all surface pressures when included in a monolayer of the protein-free myelin lipids but it remains mixed in the MBP-induced liquid phase. The resultant surface topography and dynamics is regulated by combined near to equilibrium and out-of-equilibrium effects. PLP appears to act as a surface skeleton for the whole components whereas MBP couples the structuring to surface pressure-dependent extrusion and adsorption processes.

  17. Surface analysis of gold nanoparticles functionalized with thiol-modified glucose SAMs for biosensor applications.

    Directory of Open Access Journals (Sweden)

    Valentina eSpampinato

    2016-02-01

    Full Text Available In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS, Principal Component Analysis (PCA and X-ray Photoelectron Spectroscopy (XPS have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP.The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules.Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behaviour of the glucose-modified particles in presence of the maltose binding protein.

  18. Response of sea surface fugacity of CO2 to the SAM shift south of Tasmania: Regional differences

    Science.gov (United States)

    Xue, Liang; Gao, Libao; Cai, Wei-Jun; Yu, Weidong; Wei, Meng

    2015-05-01

    Using observational data collected south of Tasmania during 14 austral summer cruises during 1993-2011, we examined the response of sea surface fugacity of carbon dioxide (fCO2) to the Southern Annular Mode (SAM) shift, which occurred around 2000. In the southern part of the Southern Ocean (SO) or the Polar Zone (PZ) and the Polar Frontal Zone (PFZ), fCO2 increased faster at the sea surface than in the atmosphere before the SAM shift, but not after the shift. In the northern part of the SO or the Subantarctic Zone (SAZ), however, surface fCO2 increased faster than atmospheric fCO2 both before and after the shift. The SAM shift had an important influence on the surface fCO2 trend in the PZ and PFZ but not in the SAZ, which we attribute to differences in regional oceanographic processes (upwelling versus nonupwelling). The SAM shift may have reversed the negative trend of SO CO2 uptake.

  19. "Click" Patterning of Self-Assembled Monolayers on Hydrogen-Terminated Silicon Surfaces and Their Characterization Using Light-Addressable Potentiometric Sensors.

    Science.gov (United States)

    Wang, Jian; Wu, Fan; Watkinson, Michael; Zhu, Jingyuan; Krause, Steffi

    2015-09-08

    Two potential strategies for chemically patterning alkyne-terminated self-assembled monolayers (SAMs) on oxide-free silicon or silicon-on-sapphire (SOS) substrates were investigated and compared. The patterned surfaces were validated using a light-addressable potentiometric sensor (LAPS) for the first time. The first strategy involved an integration of photolithography with "click" chemistry. Detailed surface characterization (i.e. water contact angle, ellipsometry, AFM, and XPS) and LAPS measurements showed that photoresist processing not only decreases the coverage of organic monolayers but also introduces chemically bonded contaminants on the surfaces, thus significantly reducing the quality of the SAMs and the utility of "click" surface modification. The formation of chemical contaminants in photolithography was also observed on carboxylic acid- and alkyl-terminated monolayers using LAPS. In contrast, a second approach combined microcontact printing (μCP) with "click" chemistry; that is azide (azido-oligo(ethylene glycol) (OEG)-NH2) inks were printed on alkyne-terminated SAMs on silicon or SOS through PDMS stamps. The surface characterization results for the sample printed with a flat featureless PDMS stamp demonstrated a nondestructive and efficient method of μCP to perform "click" reactions on alkyne-terminated, oxide-free silicon surfaces for the first time. For the sample printed with a featured PDMS stamp, LAPS imaging showed a good agreement with the pattern of the PDMS stamp, indicating the successful chemical patterning on non-oxidized silicon and SOS substrates and the capability of LAPS to image the molecular patterns with high sensitivity.

  20. 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...

  1. Preparation of metal-SAM-dendrimer-SAM-metal junctions by supramolecular metal transfer printing

    NARCIS (Netherlands)

    Nijhuis, Christian A.; ter Maat, Jurjen; Bisri, Satria Z.; Weusthof, Marcel H. H.; Salm, Cora; Schmitz, Jurriaan; Ravoo, Bart Jan; Huskensa, Jurriaan; Reinhoudt, David N.

    2008-01-01

    Metal-self-assembled monolayer (SAM)-dendrimer-SAM-metal junctions were prepared by a new type of metal transfer printing (mTP) that uses multiple beta-cyclodextrin (beta CD) host-guest interactions between a metal-coated stamp decorated with a monolayer of host molecules and a substrate which is fu

  2. Preparation of metal-SAM-dendrimer-SAM-metal junctions by supramolecular metal transfer printing

    NARCIS (Netherlands)

    Nijhuis, Christian A.; Maat, ter Jurjen; Bisri, Satria Z.; Weusthof, Marcel H.H.; Salm, Cora; Schmitz, Jurriaan; Ravoo, Bart Jan; Huskens, Jurriaan; Reinhoudt, David N.

    2008-01-01

    Metal-self-assembled monolayer (SAM)-dendrimer-SAM-metal junctions were prepared by a new type of metal transfer printing (mTP) that uses multiple ß-cyclodextrin (ßCD) host-guest interactions between a metal-coated stamp decorated with a monolayer of host molecules and a substrate which is functiona

  3. Increasing the Fill Factor of Inverted P3HT:PCBM Solar Cells Through Surface Modification of Al-Doped ZnO via Phosphonic Acid-Anchored C60 SAMs

    DEFF Research Database (Denmark)

    Stubhan, Tobias; Salinas, Michael; Ebel, Alexander

    2012-01-01

    The influence of aluminum-doped zinc oxide (AZO) electron extraction layers modified with self-assembled monolayers (SAMs) on inverted polymer solar cells is investigated. It is found that AZO modification with phosphonic acid-anchored Fullerene–SAMs leads to a reduction of the series resistance...

  4. Detection of C-reactive protein on a functional poly(thiophene) self-assembled monolayer using surface plasmon resonance

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun-Chul; Lee, Soo-Keun; Jeon, Won Bae; Lyu, Hong-Kun [Division of Nano-Bio Technology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 704-230 (Korea, Republic of); Lee, Seung Woo [School of Display and Chemical Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Jeong, Sang Won [Division of Nano-Bio Technology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 704-230 (Korea, Republic of)], E-mail: sjeong@dgist.ac.kr

    2008-09-15

    The preparation of a new poly(thiophene) with pendant N-hydroxysuccinimide ester groups and its application to immobilization of biomolecules are reported. A thiophene derivative of N-hydroxysuccinimide ester was polymerized with FeCl{sub 3} in chloroform and the resulting poly(thiophene) was characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), and gel permeation chromatography (GPC). This polymer reacts with amine-bearing molecules to yield new poly(thiophene) derivatives and the specific interactions at the side groups could be detected. Thus, a self-assembled monolayer (SAM) using the polymer was formed on a gold-coated quartz cell and anti-C-reactive protein (anti-CRP) was immobilized. The binding behavior of CRP on the surface was monitored by use of a surface plasmon resonance (SPR) sensor system.

  5. Characterization of Functionalized Self-Assembled Monolayers and Surface-Attached Interlocking Molecules Using Near-Edge X-ray Absorption Fine Structure Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Willey, Trevor M. [Univ. of California, Davis, CA (United States)

    2004-04-01

    Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively characterized, and preparation conditions that lead to desired films are outlined. A dithiol is often insufficient to form a molecular species bound at each end to the substrate, while a structurally related disulfide-containing polymer yields surface-attached loops. Similarly, spectroscopic techniques show the successful production of a simple, surface-attached rotaxane that requires a ''molecular riveting'' step to hold the

  6. 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.

    Directory of Open Access Journals (Sweden)

    Hanh T M Phan

    Full Text Available 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 concentration and pH value. Charged surfaces exhibited a greater quantity of bovine serum albumin adsorption, a larger bovine serum albumin layer thickness, and increased density of bovine serum albumin protein compared to neutral surfaces at neutral pH value. The quantity of adsorbed bovine serum albumin protein increased with increasing bovine serum albumin concentration. After equilibrium sorption was reached at pH 7.0, desorption of bovine serum albumin occurred when pH was lowered to 2.0, which is below the isoelectric point of bovine serum albumin. Our data provide further evidence that combinatorial quartz crystal microbalance with dissipation and spectroscopic ellipsometry is a sensitive analytical tool to evaluate attachment and detachment of adsorbed proteins in systems with environmental implications.

  7. Hexadecadienyl monolayers on hydrogen-terminated Si(111): faster monolayer formation and improved surface coverage using the enyne moiety.

    Science.gov (United States)

    Rijksen, Bart; Pujari, Sidharam P; Scheres, Luc; van Rijn, Cees J M; Baio, J E; Weidner, Tobias; Zuilhof, Han

    2012-04-24

    To further improve the coverage of organic monolayers on hydrogen-terminated silicon (H-Si) surfaces with respect to the hitherto best agents (1-alkynes), it was hypothesized that enynes (H-C≡C-HC═CH-R) would be even better reagents for dense monolayer formation. To investigate whether the increased delocalization of β-carbon radicals by the enyne functionality indeed lowers the activation barrier, the kinetics of monolayer formation by hexadec-3-en-1-yne and 1-hexadecyne on H-Si(111) were followed by studying partially incomplete monolayers. Ellipsometry and static contact angle measurements indeed showed a faster increase of layer thickness and hydrophobicity for the hexadec-3-en-1-yne-derived monolayers. This more rapid monolayer formation was supported by IRRAS and XPS measurements that for the enyne show a faster increase of the CH2 stretching bands and the amount of carbon at the surface (C/Si ratio), respectively. Monolayer formation at room temperature yielded plateau values for hexadec-3-en-1-yne and 1-hexadecyne after 8 and 16 h, respectively. Additional experiments were performed for 16 h at 80° to ensure full completion of the layers, which allows comparison of the quality of both layers. Ellipsometry thicknesses (2.0 nm) and contact angles (111-112°) indicated a high quality of both layers. XPS, in combination with DFT calculations, revealed terminal attachment of hexadec-3-en-1-yne to the H-Si surface, leading to dienyl monolayers. Moreover, analysis of the Si2p region showed no surface oxidation. Quantitative XPS measurements, obtained via rotating Si samples, showed a higher surface coverage for C16 dienyl layers than for C16 alkenyl layers (63% vs 59%). The dense packing of the layers was confirmed by IRRAS and NEXAFS results. Molecular mechanics simulations were undertaken to understand the differences in reactivity and surface coverage. Alkenyl layers show more favorable packing energies for surface coverages up to 50-55%. At higher

  8. 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.

  9. Preparation of organothiol self-assembled monolayers for use in templated crystallization.

    Science.gov (United States)

    Nielsen, Michael H; Lee, Jonathan R I

    2013-01-01

    Organothiol self-assembled monolayers (SAMs) have garnered much interest as templates for oriented crystallization of biominerals. While, on the surface, SAM preparation appears to be straightforward, there are many subtleties that may yield films that lack the desired effect on the mineral component in subsequent use for templated mineralization. Herein, we discuss literature that uses organothiol SAMs to understand various principles in biomineralization, to motivate the following discussion of preparation procedures and pitfalls that may arise while working with SAMs. We provide a range of parameters for each element of a SAM-forming process, which have been shown in the literature to produce monolayers suitable for mineralization experiments, and close with a step-by-step procedure, based on findings in the cited literature, that yields functional SAMs with very high fidelity.

  10. Surface sealing using self-assembled monolayers and its effect on metal diffusion in porous low-k dielectrics studied using monoenergetic positron beams

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira, E-mail: uedono.akira.gb@u.tsukuba.ac.jp [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Armini, Silvia; Zhang, Yu [IMEC, Kapeldreef 75, B-3001 Heverlee, Leuven (Belgium); Kakizaki, Takeaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Krause-Rehberg, Reinhard [Department of Physics, Martin Luther University Halle, 06099 Halle (Germany); Anwand, Wolfgang; Wagner, Andreas [Institute for Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany)

    2016-04-15

    Graphical abstract: - Highlights: • Pores with cubic pore side lengths of 1.1 and 3.1 nm coexisted in the low-k film. • For the sample without the SAM sealing process, metal atoms diffused from the top Cu/MnN layer into the OSG film and were trapped by the pores. Almost all pore interiors were covered by those metals. • For the sample damaged by a plasma etch treatment before the SAM sealing process, self-assembled molecules diffused into the OSG film, and they were preferentially trapped by larger pores. - Abstract: Surface sealing effects on the diffusion of metal atoms in porous organosilicate glass (OSG) films were studied by monoenergetic positron beams. For a Cu(5 nm)/MnN(3 nm)/OSG(130 nm) sample fabricated with pore stuffing, C{sub 4}F{sub 8} plasma etch, unstuffing, and a self-assembled monolayer (SAM) sealing process, it was found that pores with cubic pore side lengths of 1.1 and 3.1 nm coexisted in the OSG film. For the sample without the SAM sealing process, metal (Cu and Mn) atoms diffused from the top Cu/MnN layer into the OSG film and were trapped by the pores. As a result, almost all pore interiors were covered with those metals. For the sample damaged by an Ar/C{sub 4}F{sub 8} plasma etch treatment before the SAM sealing process, SAMs diffused into the OSG film, and they were preferentially trapped by larger pores. The cubic pore side length in these pores containing self-assembled molecules was estimated to be 0.7 nm. Through this work, we have demonstrated that monoenergetic positron beams are a powerful tool for characterizing capped porous films and the trapping of atoms and molecules by pores.

  11. Collapse of Langmuir monolayer at lower surface pressure: Effect of hydrophobic chain length

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kaushik, E-mail: kaushikdas2089@gmail.com; Kundu, Sarathi [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Vigyan Path, Paschim Boragaon, Garchuk, Guwahati, Assam 781035 (India)

    2016-05-23

    Long chain fatty acid molecules (e.g., stearic and behenic acids) form a monolayer on water surface in the presence of Ba{sup 2+} ions at low subphase pH (≈ 5.5) and remain as a monolayer before collapse generally occurs at higher surface pressure (π{sub c} > 50 mN/m). Monolayer formation is verified from the surface pressure vs. area per molecule (π-A) isotherms and also from the atomic force microscopy (AFM) analysis of the films deposited by single upstroke of hydrophilic Si (001) substrate through the monolayer covered water surface. At high subphase pH (≈ 9.5), barium stearate molecules form multilayer structure at lower surface pressure which is verified from the π-A isotherms and AFM analysis of the film deposited at 25 mN/m. Such monolayer to multilayer structure formation or monolayer collapse at lower surface pressure is unusual as at this surface pressure generally fatty acid salt molecules form a monolayer on the water surface. Formation of bidentate chelate coordination in the metal containing headgroups is the reason for such monolayer to multilayer transition. However, for longer chain barium behenate molecules only monolayer structure is maintained at that high subphase pH (≈ 9.5) due to the presence of relatively more tail-tail hydrophobic interaction.

  12. Corrosion protection ability of self-assembled monolayer of 3-amino-5-mercapto-1,2,4-triazole on copper electrode

    Energy Technology Data Exchange (ETDEWEB)

    Rajkumar, Ganesan; Sethuraman, Mathur Gopalakrishnan, E-mail: mgsethu@rediffmail.com

    2014-07-01

    The self-assembled monolayer (SAM) of 3-amino-5-mercapto-1,2,4-triazole (AMTa) was formed on a copper surface and characterized using cyclic voltammetry, Fourier Transform Infra-red spectroscopy and scanning electron microscopy. Quantum chemical calculations suggested the stronger interaction between AMTa and copper. The protection ability of SAM has been evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The formed monolayer showed significant protection ability in 1% NaCl medium. The enhanced corrosion protection ability could be due to the compact film structure which blocks the electron transfer from the solution to AMTa monolayer modified copper substrate. - Highlights: • Self-assembled monolayer (SAM) of AMTa has been achieved on copper surface. • Monolayer formed has been duly characterized. • SAM of AMTa has been shown to offer significant protection to copper in NaCl medium.

  13. Molecular Simulation study of Alkyl Monolayers on Si(III) Surface

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The structure of eight-carbon monolayers on the H-terminated Si(III) surface was investigated by molecular simulation method. The best substitution percent 50% for octene or octyne-derived monolayer can be obtained using molecular mechanics calculation. And the densely packed, well-ordered monolayer on Si(III) surface can be shown through energy minimization in the suitable-size simulation cell.

  14. Grafted silane monolayers: reconsideration of growth mechanisms

    Science.gov (United States)

    Ivanov, D. A.; Nysten, B.; Jonas, A. M.; Legras, R.

    1998-03-01

    Chemical force microscopy is a new technique devised to image chemical heterogeneities on surfaces. It requires the chemical modification of Atomic Force Microscopy (AFM) tips in order to create chemical probes. In this respect, self-assembled monolayers (SAM) of alkylchlorosilanes are particularly interesting as modifying agents for AFM tips. We report here our results on the kinetics of silanization and on the structure of such SAM's grafted on model surfaces (hydroxylated Si(100) wafers). AFM, contact angle measurements, X-ray reflectivity and X-ray photoelectron spectroscopy were used to characterize SAM's of octadecyltrichlorosilane (OTS) and octadecyldimethylchlorosilane (ODMS) grown from hexadecane and toluene solutions. The mechanism of grafting of OTS follows two stages. The first rapid stage corresponds to the nucleation and growth of island-like monolayer domains. The second slower stage is related to the densification of the monolayer. SAM's of ODMS were found to form thinner layers as compared to OTS, due to their lower grafting density probably resulting in a more disordered state of grafted alkyl chains. We also address the problems concerning the relationships between the quality of final SAM structures and the water content as well as the nature of the solvent used for silanization.

  15. Reactions between monolayer Fe and Si(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, M.; Kobayashi, N.; Hayashi, N. [Electrotechnical Lab., Tsukuba, Ibaraki (Japan)

    1997-03-01

    Reactions between 1.5 monolayer(ML) Fe deposited on Si(001)-2x1 and -dihydride surfaces were studied in situ by reflection high-energy electron diffraction and time-of-flight ion scattering spectrometry with the use of 25 keV H ions. The reactions between Fe and Si which were successively deposited on Si(001)-dihydride surface were also studied. After the room temperature deposition Fe reacted with Si(001)-2x1 substrate resulting in the formation of polycrystalline Fe5Si3. By annealing to 560-650degC composite heteroepitaxial layer of both type A and type B {beta}-FeSi2 was formed. On the dihydride surface polycrystalline Fe was observed after 1.5ML Fe deposition at room temperature, and reaction between Fe and Si(001)-dihydride surface is not likely at room temperature. We observed 3D rough surface when we deposited only Fe layer on the dihydride surface and annealed above 700degC. The hydrogen termination of Si(001) surface prevents the deposited Fe from diffusing into the substrate below 500degC, however the annealing above 710degC leads to the diffusion. We obtained 2D ordered surface, which showed 3x3 RHEED pattern as referenced to the primitive unreconstructed Si(001) surface net, when we deposited 2.5ML Fe and 5.8ML Si successively onto Si(001)-dihydride surface and annealed to 470degC. (author)

  16. 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.

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

    NARCIS (Netherlands)

    Geer, Erwin P.L. van der; Brom, Coenraad R. van den; Arfaoui, Imad; Houssiau, Laurent; Rudolf, Petra; Koten, Gerard van; Klein Gebbink, Robertus J.M.; Hessen, Bart

    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

  18. Interface chemistry and molecular bonding of functional ethoxysilane-based self-assembled monolayers on magnesium surfaces.

    Science.gov (United States)

    Killian, Manuela S; Seiler, Steffen; Wagener, Victoria; Hahn, Robert; Ebensperger, Christina; Meyer, Bernd; Schmuki, Patrik

    2015-05-06

    The modification of magnesium implants with functional organic molecules is important for increasing the biological acceptance and for reducing the corrosion rate of the implant. In this work, we evaluated by a combined experimental and theoretical approach the adsorption strength and geometry of a functional self-assembled monolayer (SAM) of hydrolyzed (3-aminopropyl)triethoxysilane (APTES) molecules on a model magnesium implant surface. In time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS), only a minor amount of reverse attachment was observed. Substrate-O-Si signals could be detected, as well as other characteristic APTES fragments. The stability of the SAM upon heating in UHV was investigated additionally. Density-functional theory (DFT) calculations were used to explore the preferred binding mode and the most favorable binding configuration of the hydrolyzed APTES molecules on the hydroxylated magnesium substrate. Attachment of the molecules via hydrogen bonding or covalent bond formation via single or multiple condensation reactions were considered. The impact of the experimental conditions and the water concentration in the solvent on the thermodynamic stability of possible APTES binding modes is analyzed as a function of the water chemical potential of the environment. Finally, the influence of van der Waals contributions to the adsorption energy will be discussed.

  19. Improving the dielectric properties of ethylene-glycol alkanethiol self-assembled monolayers.

    Science.gov (United States)

    Zaccari, Irene; Catchpole, Benjamin G; Laurenson, Sophie X; Davies, A Giles; Wälti, Christoph

    2014-02-11

    Self-assembled monolayers (SAMs) can be formed at the interface between solids and fluids, and are often used to modify the surface properties of the solid. One of the most widely employed SAM systems is exploiting thiol-gold chemistry, which, together with alkane-chain-based molecules, provides a reliable way of SAM formation to modify the surface properties of electrodes. Oligo ethylene-glycol (OEG) terminated alkanethiol monolayers have shown excellent antifouling properties and have been used extensively for the coating of biosensor electrodes to minimize nonspecific binding. Here, we report the investigation of the dielectric properties of COOH-capped OEG monolayers and demonstrate a strategy to improve the dielectric properties significantly by mixing the OEG SAM with small concentrations of 11-mercaptoundecanol (MUD). The monolayer properties and composition were characterized by means of impedance spectroscopy, water contact angle, ellipsometry and X-ray photoelectron spectroscopy. An equivalent circuit model is proposed to interpret the EIS data and to determine the conductivity of the monolayer. We find that for increasing MUD concentrations up to about 5% the resistivity of the SAM steadily increases, which together with a considerable decrease of the phase of the impedance, demonstrates significantly improved dielectric properties of the monolayer. Such monolayers will find widespread use in applications which depend critically on good dielectric properties such as capacitive biosensor.

  20. Self-Assembled Monolayers Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols.

    Science.gov (United States)

    Chinwangso, Pawilai; Lee, Han Ju; Lee, T Randall

    2015-12-15

    Self-assembled monolayers (SAMs) were prepared on gold substrates from an unsymmetrical partially fluorinated spiroalkanedithiol adsorbate with the specific structure of [CH3(CH2)7][CF3(CF2)7(CH2)8]C[CH2SH]2 (SADT) and compared to SAMs formed from the semifluorinated monothiol F8H10SH [CF3(CF2)7(CH2)10SH] of analogous chain length and n-octadecanethiol. The adsorbate with two alkyl chains, one terminally fluorinated and the other nonfluorinated, was designed to form monolayers in which the bulky helical fluorocarbon segments assemble on top of an underlying layer of well-packed trans-extended alkyl chains. Different combinations of deposition solvents and temperatures were used to produce the bidentate SAMs. Characterization of the resulting monolayers revealed that SAMs formed in DMF at room temperature allow complete binding of the sulfur headgroups to the surface and exhibit higher conformational order than those produced using alternative solvent/temperature combinations. The reduced film thicknesses and enhanced wettability of the SADT SAMs, as compared to the SAMs generated from F8H10SH, suggest loose packing and an increase in the tilt of the terminal fluorocarbon chain segments. Nevertheless, the density of the underlying hydrocarbon chains of the SADT SAMs was higher than that of the F8H10SH SAMs, owing to the double-chained structure of the new adsorbate. The conformational orders of the SAM systems were observed to decrease as follows: C18SH > F8H10SH > SADT. However, the SAMs formed from this new double-chained bidentate adsorbate in DMF expose a fluorinated interface with a relatively low surface roughness, as determined by contact-angle hysteresis.

  1. A self-assembled monolayer-assisted surface microfabrication and release technique

    NARCIS (Netherlands)

    Kim, B.J.; Liebau, M.; Huskens, J.; Reinhoudt, D.N.; Brugger, J.P.

    2001-01-01

    This paper describes a method of thin film and MEMS processing which uses self-assembled monolayers as ultra-thin organic surface coating to enable a simple removal of microfabricated devices off the surface without wet chemical etching. A 1.5-nm thick self-assembled monolayer of dodecyltrichlorosil

  2. 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....

  3. Tuning Oleophobicity of Silicon Oxide Surfaces with Mixed Monolayers of Aliphatic and Fluorinated Alcohols.

    Science.gov (United States)

    Lee, Austin W H; Gates, Byron D

    2016-12-13

    We demonstrate the formation of mixed monolayers derived from a microwave-assisted reaction of alcohols with silicon oxide surfaces in order to tune their surface oleophobicity. This simple, rapid method provides an opportunity to precisely tune the constituents of the monolayers. As a demonstration, we sought fluorinated alcohols and aliphatic alcohols as reagents to form monolayers from two distinct constituents for tuning the surface oleophobicity. The first aspect of this study sought to identify a fluorinated alcohol that formed monolayers with a relatively high surface coverage. It was determined that 1H,1H,2H,2H-perfluoro-1-octanol yielded high quality monolayers with a water contact angle (WCA) value of ∼110° and contact angle values of ∼80° with toluene and hexadecane exhibiting both an excellent hydrophobicity and oleophobicity. Tuning of the oleophobicity of the modified silicon oxide surfaces was achieved by controlling the molar ratio of 1H,1H,2H,2H-perfluoro-1-octanol within the reaction mixtures. Surface oleophobicity progressively decreased with a decrease in the fluorinated alcohol content while the monolayers maintained their hydrophobicity with WCA values of ∼110°. The simple and reliable approach to preparing monolayers of a tuned composition that is described in this article can be utilized to control the fluorocarbon content of the hydrophobic monolayers on silicon oxide surfaces.

  4. 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.

  5. Surface Equation of State for Pure Phospholipid Monolayer at the Air/Water Interface

    Institute of Scientific and Technical Information of China (English)

    曾作祥; 陈琼; 薛为岚; 聂飞

    2004-01-01

    A surface equation of state, applicable to liquid-expanded (LE) monolayers, was derived by analyzing the Helmholtz free energy of the LE monolayers. Based on this equation, a general equation was obtained to describe all states of single-component phospholipid monolayers during comprassion. To verify the applicability of the equation, π-A isotherms of 1,2-dipalmitoylphosphatidylcholine (DPPC), 1,2-dipalmitoylphosphatidylglycerol (DPPG), and 1,2-dimyristoyphosphatildylcholine (DMPC) were measured. The comparison between model and experimental values indicates that the equation can describe the behavior of pure phospholipid monolayers.

  6. Self-Assembled Monolayer of Mixed Gold and Nickel Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Yanni Jie; Huiqing Fan; Wei You

    2012-01-01

    Forming a monolayer of mixed nickel and gold nanoparticles through self-assembly via simple solu-tion processing constitutes an important step toward inexpensive nanoparticle-based carbon nanofiber growth. In this work, mixed gold and nickel nanoparticles were anchored on the silicon wafer using self-assembled monolayers (SAMs) as a template. SAMs of 3-mercaptopropyl trimethoxysilane (MPTS-SAMs) were formed on silicon wafer, with the exposed thiol functionality providing ligand exchange sites to form the mixed mono-layer of nickel and gold nanoparticles via a two-step sequential soaking approach. The densities of the nickel and gold nanoparticles on the surface can be varied by adjusting the soaking sequence.

  7. Preparation of Carbazole Polymer Thin Films Chemically Bound to Substrate Surface by Physical Vapor Deposition Combined with Self-Assembled Monolayer

    Science.gov (United States)

    Katsuki, Kiyoi; Bekku, Hiroshi; Kawakami, Akira; Locklin, Jason; Patton, Derek; Tanaka, Kuniaki; Advincula, Rigoberto; Usui, Hiroaki

    2005-01-01

    Vinyl polymer thin films having carbazole units were prepared by a new method combining physical vapor deposition and self-assembled monolayer (SAM) techniques. 3-(N-carbazolyl)propyl acrylate monomer was evaporated onto a gold substrate that had a VAZO 56 (DuPont) initiator attached as a SAM. The VAZO initiator was activated by irradiating ultraviolet light after depositing the monomer. Although the polymerization reaction can proceed even without the surface initiator, the SAM was effective in improving the surface smoothness, thermal stability, and film-substrate adhesion as a consequence of the formation of covalent chemical bonds between the film and the substrate. Thermal activation of the initiator was examined for the deposition polymerization of 9-H-carbazole-9-ethylmethacryrate. Substrate heating during the evaporation was not effective for accumulating thin films. On the other hand, performing postdeposition annealing on the film after deposition at room temperature resulted in the formation of a polymer thin film chemically bound to the substrate.

  8. Theoretical and experimental study of the vibrational excitations in ethane monolayers adsorbed on graphite (0001) surfaces

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Taub, H.

    1987-01-01

    The collective vibrational excitations of two different crystalline monolayer phases of ethane (C2H6) adsorbed on the graphite (0001) surface have been investigated theoretically and experimentally. The monolayer phases studied are the commensurate 7/8 ×4 structure in which the ethane molecules lie...

  9. Surface viscoelastic properties of spread ferroelectric liquid crystal monolayer on air-water interface

    Science.gov (United States)

    Kaur, Ramneek; Bhullar, Gurpreet Kaur; Raina, K. K.

    2013-06-01

    Ferroelectric Liquid crystal having Smectic C* phase at room temperature was capable of forming Langmuir monolayer due to presence of both hydrophilic and hydrophobic groups in it. Surface viscoelasticity properties of FLC monolayer spread on water surface had been determined by dynamic oscillation method and discussed as a function of surface pressure. Dynamic viscoelastic properties such as G (Elastic modulus), G' (storage (elastic) modulus), G' (Loss (viscous) modulus) and phase change with sinusoidal oscillation had been measured at phase changing surface pressure values. As monolayer was becoming condensed, increasing trend was observed in G' values while G' was decreasing. At higher frequencies, viscous modulus G' had negative values. This relaxation phenomenon was probably caused by conformational rearrangements that acted to fluidize monolayer. Phase change tan θ was positive, response in surface pressure was ahead of the de-formation in area and the monolayer had positive dilatational viscosity. Phase change tan θ was negative, response in surface pressure was hysteretic to the deformation in area, and negative dilatational viscosity had been observed. Studies of monolayer in barrier oscillating mode provided us the surface pressure which was most suitable for Langmuir Blodgett monolayer deposition.

  10. Ultralow effective work function surfaces using diamondoid monolayers.

    Science.gov (United States)

    Narasimha, Karthik Thimmavajjula; Ge, Chenhao; Fabbri, Jason D; Clay, William; Tkachenko, Boryslav A; Fokin, Andrey A; Schreiner, Peter R; Dahl, Jeremy E; Carlson, Robert M K; Shen, Z X; Melosh, Nicholas A

    2016-03-01

    Electron emission is critical for a host of modern fabrication and analysis applications including mass spectrometry, electron imaging and nanopatterning. Here, we report that monolayers of diamondoids effectively confer dramatically enhanced field emission properties to metal surfaces. We attribute the improved emission to a significant reduction of the work function rather than a geometric enhancement. This effect depends on the particular diamondoid isomer, with [121]tetramantane-2-thiol reducing gold's work function from ∼ 5.1 eV to 1.60 ± 0.3 eV, corresponding to an increase in current by a factor of over 13,000. This reduction in work function is the largest reported for any organic species and also the largest for any air-stable compound. This effect was not observed for sp(3)-hybridized alkanes, nor for smaller diamondoid molecules. The magnitude of the enhancement, molecule specificity and elimination of gold metal rearrangement precludes geometric factors as the dominant contribution. Instead, we attribute this effect to the stable radical cation of diamondoids. Our computed enhancement due to a positively charged radical cation was in agreement with the measured work functions to within ± 0.3 eV, suggesting a new paradigm for low-work-function coatings based on the design of nanoparticles with stable radical cations.

  11. Cation-induced monolayer collapse at lower surface pressure follows specific headgroup percolation

    Science.gov (United States)

    Das, Kaushik; Sah, Bijay Kumar; Kundu, Sarathi

    2017-02-01

    A Langmuir monolayer can be considered as a two-dimensional (2D) sheet at higher surface pressure which structurally deform with mechanical compression depending upon the elastic nature of the monolayer. The deformed structures formed after a certain elastic limit are called collapsed structures. To explore monolayer collapses at lower surface pressure and to see the effect of ions on such monolayer collapses, out-of-plane structures and in-plane morphologies of stearic acid Langmuir monolayers have been studied both at lower (≈6.8) and higher (≈9.5) subphase p H in the presence of M g2 +,C a2 +,Z n2 +,C d2 + , and B a2 + ions. At lower subphase p H and in the presence of all cations, the stearic acid monolayer remains as a monolayer before collapse, which generally takes place at higher surface pressure (πc>50 mN /m ). However, at higher subphase p H , structural changes of stearic acid monolayers occur at relatively lower surface pressure depending upon the specific dissolved ions. Among the same group elements of M g2 +,C a2 + , and B a2 + , only for B a2 + ions does monolayer to multilayer transition take place from a much lower surface pressure of the monolayer, remaining, however, as a monolayer for M g2 + and C a2 + ions. For another same group elements of Z n2 + and C d2 + ions, a less covered bilayer structure forms on top of the monolayer structure at lower surface pressure, which is evidenced from both x-ray reflectometry and atomic force microscopy. Fourier transform infrared spectroscopy confirms the presence of two coexisting conformations formed by the two different metal-headgroup coordinations and the monolayer to trilayer or multilayer transformation takes place when the coverage ratio of the two molecular conformations changes from the critical value (pc) of ≈0.66 . Such ion-specific monolayer collapses are correlated with the 2D lattice percolation model.

  12. Controlling charge injection by self-assembled monolayers in bottom-gate and top-gate organic field-effect transistors

    NARCIS (Netherlands)

    Gholamrezaie, F.; Asadi, K.; Kicken, R.A.H.J.; Langeveld-Voss, B.M.W.; Leeuw, D.M. de; Blom, P.W.M.

    2011-01-01

    We investigate the modulation of the charge injection in organic field-effect transistors with self-assembled monolayers (SAMs) using both a bottom-gate and a top-gate geometry. The current modulation by using SAMs is more pronounced in the top-gate geometry due to the better defined upper surface o

  13. Beauty is Skin Deep: A Surface Monolayer Perspective on Nanoparticle Interactions with Cells and Biomacromolecules**

    OpenAIRE

    Saha, Krishnendu; Bajaj, Avinash; Duncan, Bradley; Rotello, Vincent M.

    2011-01-01

    Surface recognition of biosystems is a critical component in the development of novel biosensors, delivery vehicles and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with biomacromolecules and cells. Through engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-biomacrom...

  14. Increasing the fill factor of inverted P3HT:PCBM solar cells through surface modification of Al-doped ZnO via phosphonic acid-anchored C60 SAMs

    Energy Technology Data Exchange (ETDEWEB)

    Stubhan, Tobias [Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University, Erlangen-Nuremberg, Erlangen (Germany); Salinas, Michael; Halik, Marcus [Organic Materials and Devices (OMD)-Institute of Polymer Materials, University Erlangen-Nuremberg, Erlangen (Germany); Ebel, Alexander; Hirsch, Andreas [Institute for Organic Chemistry II, Friedrich-Alexander-University, Erlangen-Nuremberg, Erlangen (Germany); Krebs, Frederick C. [Risoe National Laboratory for Sustainable Energy, Technical University of Denmark, Roskilde (Denmark); Brabec, Christoph J. [Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University, Erlangen-Nuremberg, Erlangen (Germany); Bavarian Center for Applied Energy Research (ZAE Bayern), Erlangen (Germany)

    2012-05-15

    The influence of aluminum-doped zinc oxide (AZO) electron extraction layers modified with self-assembled monolayers (SAMs) on inverted polymer solar cells is investigated. It is found that AZO modification with phosphonic acid-anchored Fullerene-SAMs leads to a reduction of the series resistance, while increasing the parallel resistance. This results in an increased efficiency from 2.9 to 3.3%. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. AFM Study of Surface Nanobubbles on Binary Self-Assembled Monolayers on Ultraflat Gold with Identical Macroscopic Static Water Contact Angles and Different Terminal Functional Groups.

    Science.gov (United States)

    Song, Bo; Chen, Kun; Schmittel, Michael; Schönherr, Holger

    2016-11-01

    All experimental findings related to surface nanobubbles, such as their pronounced stability and the striking differences of macroscopic and apparent nanoscopic contact angles, need to be addressed in any theory or model of surface nanobubbles. In this work we critically test a recent explanation of surface nanobubble stability and their consequences and contrast this with previously proposed models. In particular, we elucidated the effect of surface chemical composition of well-controlled solid-aqueous interfaces of identical roughness and defect density on the apparent nanoscopic contact angles. Expanding on a previous atomic force microscopy (AFM) study on the systematic variation of the macroscopic wettability using binary self-assembled monolayers (SAMs) on ultraflat template stripped gold (TSG), we assessed here the effect of different surface chemical composition for macroscopically identical static water contact angles. SAMs on TSG with a constant macroscopic water contact angle of 81 ± 2° were obtained by coadsorption of a methyl-terminated thiol and a second thiol with different terminal functional groups, including hydroxy, amino, and carboxylic acid groups. In addition, surface nanobubbles formed by entrainment of air on SAMs of a bromoisobutyrate-terminated thiol were analyzed by AFM. Despite the widely differing surface potentials and different functionality, such as hydrogen bond acceptor or donor, and different dipole moments and polarizability, the nanoscopic contact angles (measured through the condensed phase and corrected for AFM tip broadening effects) were found to be 145 ± 10° for all surfaces. Hence, different chemical functionalities at identical macroscopic static water contact angle do not noticeably influence the apparent nanoscopic contact angle of surface nanobubbles. This universal contact angle is in agreement with recent models that rely on contact line pinning and the equilibrium of gas outflux due to the Laplace pressure and

  16. Sandwich Sam

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    SAM, a 28-year-old Canadian, has a nice family name: Goodman. Four years ago, he came to China and now he owns two cafes. Sam is not tall. To match his loose black sweater, he wears a pair of jeans which are so long that the trouser legs are wrinkled over his sneakers. Why did he think of running a cafe in Beijing? "After graduating from college, I went to Hong Kong to be a fitness coach for half a year. Then, I went to South Korea. While sightseeing, I taught English to make a living.

  17. Mono-Fluorinated Alkyne-Derived SAMs on Oxide-Free Si(III) Surfaces: Preparation, Characterization and Tuning of the Si Workfunction

    NARCIS (Netherlands)

    Pujari, S.P.; Andel, van E.; Yaffe, O.; Cahen, D.; Weidner, T.; Rijn, van C.J.M.; Zuilhof, H.

    2013-01-01

    Organic monolayers derived from ¿-fluoro-1-alkynes of varying carbon chain lengths (C(10)-C(18)) were prepared on Si(111) surfaces, resulting in changes of the physical and electronic properties of the surface. Analysis of the monolayers using XPS, Infrared Reflection Absorption Spectroscopy, ellips

  18. Increased monolayer domain size and patterned growth of tungsten disulfide through controlling surface energy of substrates

    Science.gov (United States)

    Godin, Kyle; Kang, Kyungnam; Fu, Shichen; Yang, Eui-Hyeok

    2016-08-01

    We report a surface energy-controlled low-pressure chemical vapor deposition growth of WS2 monolayers on SiO2 using pre-growth oxygen plasma treatment of substrates, facilitating increased monolayer surface coverage and patterned growth without lithography. Oxygen plasma treatment of the substrate caused an increase in the average domain size of WS2 monolayers by 78%  ±  2% while having a slight reduction in nucleation density, which translates to increased monolayer surface coverage. This substrate effect on growth was exploited to grow patterned WS2 monolayers by patterned plasma treatment on patterned substrates and by patterned source material with resolutions less than 10 µm. Contact angle-based surface energy measurements revealed a dramatic increase in polar surface energy. A growth model was proposed with lowered activation energies for growth and increased surface diffusion length consistent with the range of results observed. WS2 samples grown with and without oxygen plasma were similar high quality monolayers verified through transmission electron microscopy, selected area electron diffraction, atomic force microscopy, Raman, and photoluminescence measurements. This technique enables the production of large-grain size, patterned WS2 without a post-growth lithography process, thereby providing clean surfaces for device applications.

  19. Atomic-level elucidation of the initial stages of self-assembled monolayer metallization and nanoparticle formation.

    Science.gov (United States)

    Keith, John A; Jacob, Timo

    2010-11-02

    The development of high-performance molecular electronics and nanotech applications requires deep understanding of atomic level structural, electronic, and magnetic properties of electrode/molecular interfaces. Recent electrochemical experiments on self-assembled monolayers (SAMs) have identified highly practical means to generate nanoparticles and metal monolayers suspended above substrate surfaces through SAM metallizations. A rational basis why this process is even possible is not yet well-understood. To clarify the initial stages of interface formation during SAM metallization, we used first-principles spin-polarized density functional theory (DFT) calculations to study Pd diffusion on top of 4-mercaptopyridine (4MP) SAMs on Au(111). After distinguishing potential-energy surfaces (PESs) for different spin configurations for transition metal atoms on the SAM, we find adatom diffusion is not possible over the clean 4MP-SAM surface. Pre-adsorption of transition-metal atoms, however, facilitates atomic diffusion that appears to explain multiple reports on experimentally observed island and monolayer formation on top of SAMs. Furthermore, these diffusions most likely occur by moving across low-lying and intersecting PESs of different spin states, opening the possibility of magnetic control over these systems. Vertical diffusion processes were also investigated, and the electrolyte was found to play a key role in preventing metal permeation through the SAM to the substrate.

  20. 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.

  1. Fluorescent self-assembled monolayers as new sensing materials

    NARCIS (Netherlands)

    Basabe Desmonts, Lourdes

    2006-01-01

    Fluorescent self-assembled monolayers (SAMs) on glass surfaces have been studied as a new material for chemical sensing. The new sensing system presented in this thesis is a label-free sensing approach suitable for metal ion and inorganic anions sensing in both organic solvents and aqueous solution.

  2. 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......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 hybrid entity. The NP appears to relay long‐range electron transfer (ET) so that the rate of the redox reaction may be as efficient as directly on a bare Au electrode, even though the ET distance is increased by several nanometers. In this study, we have employed a fast redox reaction of surface...

  3. Role of SAM Chain Length in Enhancing the Sensitivity of Nanopillar Modified Electrodes for Glucose Detection

    Directory of Open Access Journals (Sweden)

    2009-02-01

    Full Text Available In this report, alkanethiol self assembled monolayers (SAM with two different chain lengths were used to immobilize the functionalizing enzyme (glucose oxidase onto gold nanopillar modified electrodes and the electrochemical processes of these functionalized electrodes in glucose detection were investigated. First, the formation of these SAMs on the nanopillar modified electrodes was characterized by the cyclic voltammetry and electrochemical impedance spectroscopy techniques, and then the detection sensitivity of these functionalized electrodes to glucose was evaluated by the amperometry technique. Results showed that the SAM of alkanethiols with a longer chain length resulted in a higher degree of surface coverage with less defect and a higher electron transfer resistance, whereas the SAM of alkanethiols with a shorter chain length gave rise to a higher detection sensitivity to glucose. This study sheds some new insight into how to enhance the sensing performance of nanopillar modified electrodes.

  4. Nanopatterning of mobile lipid monolayers on electron-beam-sculpted Teflon AF surfaces.

    Science.gov (United States)

    Shaali, Mehrnaz; Lara-Avila, Samuel; Dommersnes, Paul; Ainla, Alar; Kubatkin, Sergey; Jesorka, Aldo

    2015-02-24

    Direct electron-beam lithography is used to fabricate nanostructured Teflon AF surfaces, which are utilized to pattern surface-supported monolayer phospholipid films with 50 nm lateral feature size. In comparison with unexposed Teflon AF coatings, e-beam-irradiated areas show reduced surface tension and surface potential. For phospholipid monolayer spreading experiments, these areas can be designed to function as barriers that enclose unexposed areas of nanometer dimensions and confine the lipid film within. We show that the effectiveness of the barrier is defined by pattern geometry and radiation dose. This surface preparation technique represents an efficient, yet simple, nanopatterning strategy supporting studies of lipid monolayer behavior in ultraconfined spaces. The generated structures are useful for imaging studies of biomimetic membranes and other specialized surface applications requiring spatially controlled formation of self-assembled, molecularly thin films on optically transparent patterned polymer surfaces with very low autofluorescence.

  5. Chiral and herringbone symmetry breaking in water-surface monolayers

    DEFF Research Database (Denmark)

    Peterson, I.R.; Kenn, R.M.; Goudot, A.

    1996-01-01

    We report the observation from monolayers of eicosanoic acid in the L(2)' phase of three distinct out-of-plane first-order diffraction peaks, indicating molecular tilt in a nonsymmetry direction and hence the absence of mirror symmetry. At lower pressures the molecules tilt in the direction of th...

  6. Characterization of self-assembled monolayers of thiols on Au(111)

    Institute of Scientific and Technical Information of China (English)

    邓文礼; 杨大本; 方晔; 白春礼

    1996-01-01

    Self-assembled monolayers (SAMs) of n-butanethiol, n-dodecanethiol and their equimolar mixture on Au(111) were prepared and characterized by ellipsometry, contact angle measurement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results revealed that these SAMs are oriented ultrathin films with the thickness of nanometer scale, and the SAMs were influenced by the molecular chain length, the lattice orientation and cleanliness of the substrates. The surface of the longer chain SAM is hydrophobic. The thicknesses of three SAMs of n-butanethiol, n-dodecanethiol and their mixture revealed by ellipsometry and XPS are about 0.59 - 0.67nm, 1.60- 1.69 nm and 1.23 - 1.32nm, respectively. AFM images further demonstrated that the SAM formed by the mixture has some microdomains with two different thicknesses.

  7. 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

    2015-04-07

    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%).

  8. Work function shifts of a zinc oxide surface upon deposition of self-assembled monolayers: a theoretical insight.

    Science.gov (United States)

    Cornil, D; Van Regemorter, T; Beljonne, D; Cornil, J

    2014-10-14

    We have investigated at the theoretical Density Functional Theory level the way the work function of zinc oxide layers is affected upon deposition of self-assembled monolayers (SAMs). 4-tert-Butylpyridine (4TBP) and various benzoic acids (BA) were adsorbed on the apolar (101[combining macron]0) ZnO and used as probe systems to assess the influence of several molecular parameters. For the benzoid acids, we have investigated the impact of changing the nature of the terminal group (H, CN, OCH3) and the binding mode of the carboxylic acid (monodentate versus bidentate) on the apolar (101[combining macron]0) surface. For each system, we have quantified the contribution from the molecular core and the anchoring group as well as of the degree of surface reconstruction on the work function shift. For the benzoic acids, the structural reorganization of the surface induces a negative shift of the work function by about 0.3 ± 0.15 eV depending on the nature of the binding mode, irrespective of the nature of the terminal function. The bond-dipole potential strongly contributes to the modification of the work function, with values in the range +1.2 to +2.0 eV. In the case of 4TBP, we further characterized the influence of the degree of coverage and of co-adsorbed species (H, OH, and water molecules) on the ZnO/SAM electronic properties as well as the influence of the ZnO surface polarity by considering several models of the polar (0001) ZnO surface. The introduction of water molecules in the (un)dissociated form at full coverage on the non-polar surface only reduces the work function by 0.3-0.4 eV compared to a reference system without co-adsorbed species. Regarding the polar surface, the work function is also significantly reduced upon deposition of a single 4BTP molecule (from -1.44 eV to -1.73 eV for our model structures), with a shift similar in direction and magnitude compared to the non-polar surfaces.

  9. Comparative Study of Protein Immobilization Properties on Calixarene Monolayers

    Directory of Open Access Journals (Sweden)

    Kwangnak Koh

    2007-06-01

    Full Text Available Three calix[4]arene (Cal-4 derivatives of which contain ethylester (1,carboxylic acid (2, and crownether (3 at the lower rim with a common reactive thiol at theupper rim were synthesized and constructed to self-assembled monolayers (SAMs on Aufilms. After spectroscopic characterization of monolayers, the interaction between Cal-4and surface confined bovine serum albumin (BSA in the SAMs was analyzed by surfaceplasmon resonance (SPR. The estimated surface concentration of BSA on the Cal-4 SAMwith crownether group was the highest among the three Cal-4 derivatives. Anti-hIgG andhIgG pair was employed for the investigation of protein-protein interaction. Molecularinteraction between anti-hIgG and hIgG can be detected in a concentration range of 10pg/mL to 200 pg/mL on the Cal-4 derivative 3 SAM modified SPR chip.

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

    Science.gov (United States)

    Kelkar, Sanket S.; Chiavetta, David; Wolden, Colin A.

    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 (∼100̊) on alumina are comparable to what has been observed for OTS on silicon. The free energy of adsorption with ΔGads values ranged from -7.5 to -5.4 kcal/mol, and the SAMs were stable up to 230 ̊C. The critical surface tension of the OTS monolayer was found to be 21.4 dyne/cm.

  11. 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.

  12. Preparation of metal-SAM-dendrimer-SAM-metal junctions by supramolecular metal transfer printing

    NARCIS (Netherlands)

    Nijhuis, C.A.; Maat, ter J.; Bisri, S.Z.; Weusthof, M.H.H.; Salm, C.; Schmitz, J.; Ravoo, B.J.; Huskens, J.; Reinhoudt, D.N.

    2008-01-01

    Metal–self-assembled monolayer (SAM)–dendrimer–SAM–metal junctions were prepared by a new type of metal transfer printing (mTP) that uses multiple -cyclodextrin (CD) host–guest interactions between a metal-coated stamp decorated with a monolayer of host molecules and a substrate which is functionali

  13. Anti-fouling chemistry of chiral monolayers: enhancing biofilm resistance on racemic surface.

    Science.gov (United States)

    Bandyopadhyay, Debjyoti; Prashar, Deepali; Luk, Yan-Yeung

    2011-05-17

    This work reports the resistance to protein adsorption and bacterial biofilm formation by chiral monolayers of polyol-terminated alkanethiols surrounding micrometer-sized patterns of methyl-terminated alkanethiols on gold films. We discover that patterned surfaces surrounded by chiral polyol monolayers can distinguish different stages of biofilm formation. After inoculation on the surfaces, bacteria first reversibly attached on the chiral polyol monolayers. Over time, the bacteria detached from the polyol surfaces, and attached on the hydrophobic micropatterns to form biofilms. Interestingly, while both enantiomers of gulitol- and mannonamide-terminated monolayer resisted adsorption of proteins (bovine serum albumin, lysozyme, and fibrinogen) and confined biofilms formed on the micropatterns, the monolayers formed by the racemic mixture of either pair of enantiomers exhibited stronger antifouling chemistry against both protein adsorption and biofilm formation than monolayers formed by one enantiomer alone. These results reveal the different chemistries that separate the different stages of biofilm formation, and the stereochemical influence on resisting biofoulings at a molecular-level.

  14. Surface chemistry of lipid raft and amyloid Aβ (1-40) Langmuir monolayer.

    Science.gov (United States)

    Thakur, Garima; Pao, Christine; Micic, Miodrag; Johnson, Sheba; Leblanc, Roger M

    2011-10-15

    Lipid rafts being rich in cholesterol and sphingolipids are considered to provide ordered lipid environment in the neuronal membranes, where it is hypothesized that the cleavage of amyloid precursor protein (APP) to Aβ (1-40) and Aβ (1-42) takes place. It is highly likely that the interaction of lipid raft components like cholesterol, sphingomylein or GM1 leads to nucleation of Aβ and results in aggregation or accumulation of amyloid plaques. One has investigated surface pressure-area isotherms of the lipid raft and Aβ (1-40) Langmuir monolayer. The compression-decompression cycles and the stability of the lipid raft Langmuir monolayer are crucial parameters for the investigation of interaction of Aβ (1-40) with the lipid raft Langmuir monolayer. It was revealed that GM1 provides instability to the lipid raft Langmuir monolayer. Adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing neutral (POPC) or negatively charged phospholipid (DPPG) was examined. The adsorption isotherms revealed that the concentration of cholesterol was important for adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing POPC whereas for the lipid raft Langmuir monolayer containing DPPG:cholesterol or GM1 did not play any role. In situ UV-vis absorption spectroscopy supported the interpretation of results for the adsorption isotherms.

  15. Antifouling properties of oligo(lactose)-based self-assembled monolayers.

    Science.gov (United States)

    Nugraha, Roni; Finlay, John A; Hill, Sophie; Fyrner, Timmy; Yandi, Wetra; Callow, Maureen E; Callow, James A; Ederth, Thomas

    2015-01-01

    The antifouling (AF) properties of oligo(lactose)-based self-assembled monolayers (SAMs), using four different proteins, zoospores of the green alga Ulva linza and cells of the diatom Navicula incerta, were investigated. The SAM-forming alkylthiols, which contained 1, 2 or 3 lactose units, showed significant variation in AF properties, with no differences in wettability. Non-specific adsorption of albumin and pepsin was low on all surfaces. Adsorption of lysozyme and fibrinogen decreased with increasing number of lactose units in the SAM, in agreement with the generally observed phenomenon that thicker hydrated layers provide higher barriers to protein adsorption. Settlement of spores of U. linza followed an opposite trend, being greater on the bulkier, more hydrated SAMs. These SAMs are more ordered for the larger saccharide units, and it is therefore hypothesized that the degree of order, and differences in crystallinity or stiffness between the surfaces, is an important parameter regulating spore settlement on these surfaces.

  16. Inhibition of copper corrosion by the formation of Schiff base self-assembled monolayers

    Science.gov (United States)

    Zhang, Jing; Liu, Zheng; Han, Guo-Cheng; Chen, Shi-Liang; Chen, Zhencheng

    2016-12-01

    Self-assembled monolayers (SAMs) of 4-((2-thiophenecarboxylic acid hydrazide) methylene) benzoic acid (HD2) (denoted as HD2-SAMs) were formed on copper surface. The SAMs were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Polarization curve and weight loss methods indicated that the highest inhibition efficiency was 93.9% for CO2-saturated simulative oilfield water at a self-assembled time of 3 h. Potential-time curve, electrochemical impedance tests showed that HD2-SAMs on copper surface exhibited excellent inhibition effect at 30 °C. The adsorption behavior of HD2-SAMs on the copper surface followed the Langmuir adsorption isotherm, which was indicative of typically chemical adsorption. Quantum chemistry calculation showed that O and N atoms can interact with Cu atoms by coordination bonds which were the mainly active area of the adsorption of HD2 molecules.

  17. Fabrication of dynamic self-assembled monolayers for cell migration and adhesion studies.

    Science.gov (United States)

    Westcott, Nathan P; Yousaf, Muhammad N

    2011-01-01

    How cells interact with the extracellular matrix (ECM) is important for a number of fundamental -processes in cell biology. However, the ECM is highly complex and in order to simplify the matrix for cell biological studies, it has been modeled with self-assembled monolayers (SAMs) of alkanethiolates on gold substrates. In this chapter, we outline procedures to create dynamic surfaces by functionalizing SAMs. SAMs based on quinone, oxyamine, and alcohol-terminated thiols were used to immobilize cell adhesive peptides with spatial control. Cells were seeded to these surfaces to provide cell co-culture -patterns suitable for biological studies.

  18. 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.

  19. Tuning the self-assembled monolayer formation on nanoparticle surfaces with different curvatures: investigations on spherical silica particles and plane-crystal-shaped zirconia particles.

    Science.gov (United States)

    Feichtenschlager, Bernhard; Lomoschitz, Christoph J; Kickelbick, Guido

    2011-08-01

    The ordering of dodecyl-chain self-assembled monolayers (SAM) on different nanoscopic surfaces was investigated by FT-IR studies. As model systems plane-crystal-shaped ZrO(2) nanoparticles and spherical SiO(2) nanoparticles were examined. The type of capping agent was chosen dependent on the substrate, therefore dodecylphosphonic acid and octadecylphosphonic acid were used for ZrO(2) and dodecyltrimethoxysilane for SiO(2) samples. The plane ZrO(2) nanocrystals yielded more ordered alkyl-chain structures whereas spherical SiO(2) nanoparticles showed significantly lower alkyl-chain ordering. Submicron-sized silica spheres revealed a significantly higher alkyl chain ordering, comparable to an analogously prepared SAM on a non-curved plane oxidized Si-wafer. In the case of ZrO(2) nanocrystals an intense alkyl-chain alignment could be disturbed by decreasing the grafting density from the maximum of 2.1 molecules/nm(2) through the variation of coupling agent concentration to lower values. Furthermore, the co-adsorption of a different coupling agent, such as phenylphosphonic acid for ZrO(2) and phenyltrimethoxysilane for SiO(2), resulted in a significantly lower alkyl-chain ordering for ZrO(2) plane crystals and for large SiO(2) spherical particles at high grafting density. An increasing amount of order-disturbing molecules leads to a gradual decrease in alkyl-chain alignment on the surface of the inorganic nanoparticles. In the case of the ZrO(2) nanoparticle system it is shown via dynamic light scattering (DLS) that the mixed monolayer formation on the particle surface impacts the dispersion quality in organic solvents such as n-hexane.

  20. 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.

  1. Self-assembled monolayers of cyclohexyl-terminated phosphonic acids as a general dielectric surface for high-performance organic thin-film transistors.

    Science.gov (United States)

    Liu, Danqing; He, Zikai; Su, Yaorong; Diao, Ying; Mannsfeld, Stefan C B; Bao, Zhenan; Xu, Jianbin; Miao, Qian

    2014-11-12

    A novel self-assembled monolayer (SAM) on AlOy /TiOx is terminated with cyclohexyl groups, an unprecedented terminal group for all kinds of SAMs. The SAM-modified AlOy /TiOx functions as a general dielectric, enabling organic thin-film transistors with a field-effect mobility higher than 5 cm(2) V(-1) s(-1) for both holes and electrons, good air stability with low operating voltage, and general applicability to solution-processed and vacuum-deposited n-type and p-type organic semiconductors.

  2. A Trimeric Surfactant: Surface Micelles, Hydration-Lubrication, and Formation of a Stable, Charged Hydrophobic Monolayer.

    Science.gov (United States)

    Kampf, Nir; Wu, Chunxian; Wang, Yilin; Klein, Jacob

    2016-11-15

    The surface structure of the trimeric surfactant tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD) on mica and the interactions between two such DTAD-coated surfaces were determined using atomic force microscopy and a surface force balance. In an aqueous solution of 3 mM, 5 times the critical aggregation concentration (CAC), the surfaces are coated with wormlike micelles or hemimicelles and larger (∼80 nm) bilayer vesicles. Repulsive normal interactions between the surfaces indicate a net surface charge and a solution concentration of ions close to that expected from the CAC. Moreover, this surface coating is strongly lubricating up to some tens of atmospheres, attributed to the hydration-lubrication mechanism acting at the exposed, highly hydrated surfactant headgroups. Upon replacement of the DTAD solution with surfactant-free water, the surface structures have changed on the DTAD monolayers, which then jump into adhesive contact on approach, both in water and following addition of 0.1 M NaNO3. This trimeric surfactant monolayer, which is highly hydrophobic, is found to be positively charged, which is evident from the attraction between the DTAD monolayer and negatively charged bare mica across water. These monolayers are stable over days even under a salt solution. The stability is attributed to the several stabilization pathways available to DTAD on the mica surface.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chien-Ching [Iowa State Univ., Ames, IA (United States)

    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 pKa 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.

  4. Covalently bound organic monolayers on silicon surfaces : visible light attachment, charaterization, and electrical properties

    NARCIS (Netherlands)

    Smet, de L.C.P.M.

    2006-01-01

    The full control over surface properties is a 'Holy Grail' in material science. A significant step forward in this area includes the modification of silicon surfaces, by the covalent attachment of organic monolayers. In this way receptors than can specifically bind with ions or molecules be attached

  5. Optimizing the quality of monoreactive perfluoroalkylsilane-based self-assembled monolayers.

    Science.gov (United States)

    Gong, Yuanyuan; Wang, Michael C P; Zhang, Xin; Ng, Him Wai; Gates, Byron D

    2012-08-14

    Self-assembled monolayers (or SAMs) created from monoreactive perfluoroalkylsilanes by deposition from a toluene solution are investigated for the dependence of their quality on processing conditions. Surface-sensitive spectroscopic techniques are used to provide feedback on the processing conditions in which solution temperature, silane concentration, and reaction time are optimized to improve the quality of these SAMs. For these analyses, monolayers are formed at 20, 40, 60, or 80 °C from solutions containing between 0.5 and 5 mM perfluoroalkylsilane over a period of up to 5 h. Physically adsorbed molecules are removed from these surfaces by extraction to determine the quality of the covalently bound monolayer. Water contact angle measurements, spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), respectively, are used in combination to assess the uniformity of the surface hydrophobicity, monolayer thickness, composition of the assembled perfluoroalkylsilane molecules, and topography of these monolayers. A comparison is also presented for two approaches to fill defects within these solvent extracted monolayers with more perfluoroalkylsilane molecules, aiming to improve the quality of these SAMs. A detailed XPS analysis is used to assess both the relative changes in density and average tilt of molecules within the monolayers as the process temperature is increased in increments from 20 to 80 °C. The observed differences in quality of the SAMs are attributed to temperature- and time-dependent organization and reactivity of the silane molecules. Although the assembly of these monoreactive perfluoroalkylsilanes is driven by thermodynamics, the quality of the monolayer is ultimately limited by the kinetics and mass transport during this assembly process. Lessons from these studies can be exploited for improving the quality of monolayers composed of other alkylsilane molecules that are covalently bound to the surfaces

  6. UV/Vis and NIR Light-Responsive Spiropyran Self-Assembled Monolayers

    NARCIS (Netherlands)

    Ivashenko, Oleksii; Herpt, Jochem T. van; Feringa, Ben L.; Rudolf, Petra; Browne, Wesley R.

    2013-01-01

    Self-assembled monolayers of a 6-nitro BIPS spiropyran (SP) modified with a disulfide-terminated aliphatic chain were prepared on polycrystalline gold surfaces and characterized by UV/vis absorption, surface-enhanced Raman scattering (SEAS), and X-ray photoelectron spectroscopies (XPS). The SAMs

  7. UV/Vis and NIR Light-Responsive Spiropyran Self-Assembled Monolayers

    NARCIS (Netherlands)

    Ivashenko, Oleksii; Herpt, Jochem T. van; Feringa, Ben L.; Rudolf, Petra; Browne, Wesley R.

    2013-01-01

    Self-assembled monolayers of a 6-nitro BIPS spiropyran (SP) modified with a disulfide-terminated aliphatic chain were prepared on polycrystalline gold surfaces and characterized by UV/vis absorption, surface-enhanced Raman scattering (SEAS), and X-ray photoelectron spectroscopies (XPS). The SAMs obt

  8. STM study of short chain hydrophobic thiol SAMs on HOPG and Au capped HOPG under ambient conditions

    Science.gov (United States)

    Bowers, Alexis; Maurer, Mackenzie; Senevirathne, Indrajith

    2015-03-01

    Self-assembled monolayer(SAM) surfaces provide common architecture in many device applications including sensor engineering. The conductivity characteristics and surface molecular structure and orientation of these SAM are important as physiochemical properties are dependent on the surface arrangement. SAMs used in this study are short chain -R terminated (hydrophobic) 1-Butanethiol on Highly Oriented Pyrolytic Graphite (HOPG) surface and on thermally annealed Au thin film capped on HOPG. Scanning Tunneling Microscopy (STM), contact angle measurements and reflective spectroscopy are used to assess the SAM layered surfaces. Solutions of 1-Butanethiol, dissolved in 200 proof Ethanol with 5mM concentration were prepared for the self-assembly process. These solutions were used in developing SAMs on purchased, freshly cleaved HOPG substrates. Au thin layers were sputter deposited on HOPG and subsequently annealed. Initial data shows low Au deposition yields rougher inconsistent surfaces. Ambient conditions under which data was obtained impose fresh surfaces for each investigation. Tentative surface structure, consistency and thiol molecular arrangement of the SAM layer on HOPG and Au capped HOPG will be discussed. National Science Foundation.

  9. Self assembled monolayers on silicon for molecular electronics.

    Science.gov (United States)

    Aswal, D K; Lenfant, S; Guerin, D; Yakhmi, J V; Vuillaume, D

    2006-05-24

    We present an overview of various aspects of the self-assembly of organic monolayers on silicon substrates for molecular electronics applications. Different chemical strategies employed for grafting the self-assembled monolayers (SAMs) of alkanes having different chain lengths on native oxide of Si or on bare Si have been reviewed. The utility of different characterization techniques in determination of the thickness, molecular ordering and orientation, surface coverage, growth kinetics and chemical composition of the SAMs has been discussed by choosing appropriate examples. The metal counterelectrodes are an integral part of SAMs for measuring their electrical properties as well as using them for molecular electronic devices. A brief discussion on the variety of options available for the deposition of metal counterelectrodes, that is, soft metal contacts, vapor deposition and soft lithography, has been presented. Various theoretical models, namely, tunneling (direct and Fowler-Nordheim), thermionic emission, Poole-Frenkel emission and hopping conduction, used for explaining the electronic transport in dielectric SAMs have been outlined and, some experimental data on alkane SAMs have been analyzed using these models. It has been found that short alkyl chains show excellent agreement with tunneling models; while more experimental data on long alkyl chains are required to understand their transport mechanism(s). Finally, the concepts and realization of various molecular electronic components, that is, diodes, resonant tunnel diodes, memories and transistors, based on appropriate architecture of SAMs comprising of alkyl chains (sigma- molecule) and conjugated molecules (pi-molecule) have been presented.

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

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, Jose Maria; Bielen, Abraham A.M. [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB, Wageningen (Netherlands); Olthuis, Wouter [BIOS Lab on a Chip Group, MESA+ and MIRA Institutes, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Kengen, Servé W.M. [Laboratory of Microbiology, Wageningen University, 6703HB Wageningen (Netherlands); Zuilhof, Han, E-mail: han.zuilhof@wur.nl [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB, Wageningen (Netherlands); Department of Chemical and Materials Engineering, King Abdulaziz University, Jeddah 22254 (Saudi Arabia); Franssen, Maurice C.R., E-mail: maurice.franssen@wur.nl [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB, Wageningen (Netherlands)

    2016-10-15

    Highlights: • Three different oxidases are covalently attached to alkene based SAMs on PtOx. • Attached enzymes remain active and their activity is assessed by chronoamperometry. • Functionalized PtOx allows electron mediator free chronoamperometry measurements. • The thus formed enzyme electrodes are useful as biosensors for glucose and lactate. • Immobilization of human HAOX foresees in vivo lactate monitoring in humans. - Abstract: 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. NH{sub 2}-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.

  11. 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.

  12. Self-assembled Monolayers of n-Hexadecanoic Acid and α-Hydroxyl n-Hexadecanoic Acid on Titanium Surfaces

    Institute of Scientific and Technical Information of China (English)

    CHEN,Hai-Gang(陈海刚); WU,Xue-Dong(乌学东); YU,Qin-Qin(虞勤琴); YANG,Sheng-Rong(杨生荣); WANG,Da-Pu(王大璞); SHEN,Wen-Zhong(沈文忠)

    2002-01-01

    n-Hexadecanoic acid (HA) and a.hydroxyl n-hexadecanoic acid ( HHA ) are shown to spontaneously assemble on Si-supported titanium surfaces. Contact angle measurements, reflection absorbance IR, AFM and XPS characterizatiions are performed to examine the physical and chenical states of attached monolayers. The results show that the two amphiphiles tend to form disordered monolayers on titanium surfaces. The HHA headgroups are believed to form polydentate coordination with Ti, which is more chemically stable than the bidentate coordination of HA. All the facts of characterization indicate that HHA monolayer has more surface coverage than HA monolayer.

  13. Ionic Strength, Surface Charge, and Packing Density Effects on the Properties of Peptide Self-Assembled Monolayers.

    Science.gov (United States)

    Leo, Norman; Liu, Juan; Archbold, Ian; Tang, Yongan; Zeng, Xiangqun

    2017-02-28

    The various environmental parameters of packing density, ionic strength, and solution charge were examined for their effects on the properties of the immobilized peptide mimotope CH19 (CGSGSGSQLGPYELWELSH) that binds with the therapeutic antibody Trastuzumab (Herceptin) on a gold substrate. The immobilization of CH19 onto gold was examined with a quartz crystal microbalance (QCM). The QCM data showed the presence of intermolecular interactions resulting in the increase of viscoelastic properties of the peptide self-assembled monolayer (SAM). The CH19 SAM was diluted with CS7 (CGSGSGS) to decrease the packing density as CH19/CS7. The packing density and ionic strength parameters were evaluated by atomic force microscopy (AFM), ellipsometry, and QCM. AFM and ellipsometry showed a distinct conformational difference between CH19 and CH19/CS7, indicating a relationship between packing density and conformational state of the immobilized peptide. The CH19 SAM thickness was 40 Å with a rough topology, while the CH19/CS7 SAM thickness was 20 Å with a smooth topology. The affinity studies showed that the affinity of CH19 and CH19/CS7 to Trastuzumab were both on the order of 10(7) M(-1) in undiluted PBS buffer, while the dilution of the buffer by 1000× increased both SAMs affinities to Trastuzumab to the order of 10(15) M(-2) and changed the binding behavior from noncooperative to cooperative binding. This indicated that ionic strength had a more pronounced effect on binding properties of the CH19 SAM than packing density. Electrochemical impedance spectroscopy (EIS) was conducted on the CH19/CS7 SAM, which showed an increase in impedance after each EIS measurement cycle. Cyclic voltammetry on the CH19/CS7 SAM decreased impedance to near initial values. The impact of the packing density, buffer ionic strength, and local charge perturbation of the peptide SAM properties was interpreted based on the titratable sites in CH19 that could participate in the proton transfer and

  14. Triptycene-terminated thiolate and selenolate monolayers on Au(111

    Directory of Open Access Journals (Sweden)

    Jinxuan Liu

    2017-04-01

    Full Text Available To study the implications of highly space-demanding organic moieties on the properties of self-assembled monolayers (SAMs, triptycyl thiolates and selenolates with and without methylene spacers on Au(111 surfaces were comprehensively studied using ultra-high vacuum infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy and thermal desorption spectroscopy. Due to packing effects, the molecules in all monolayers are substantially tilted. In the presence of a methylene spacer the tilt is slightly less pronounced. The selenolate monolayers exhibit smaller defect densities and therefore are more densely packed than their thiolate analogues. The Se–Au binding energy in the investigated SAMs was found to be higher than the S–Au binding energy.

  15. Triptycene-terminated thiolate and selenolate monolayers on Au(111).

    Science.gov (United States)

    Liu, Jinxuan; Kind, Martin; Schüpbach, Björn; Käfer, Daniel; Winkler, Stefanie; Zhang, Wenhua; Terfort, Andreas; Wöll, Christof

    2017-01-01

    To study the implications of highly space-demanding organic moieties on the properties of self-assembled monolayers (SAMs), triptycyl thiolates and selenolates with and without methylene spacers on Au(111) surfaces were comprehensively studied using ultra-high vacuum infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy and thermal desorption spectroscopy. Due to packing effects, the molecules in all monolayers are substantially tilted. In the presence of a methylene spacer the tilt is slightly less pronounced. The selenolate monolayers exhibit smaller defect densities and therefore are more densely packed than their thiolate analogues. The Se-Au binding energy in the investigated SAMs was found to be higher than the S-Au binding energy.

  16. Characterization of self-assembled monolayers of porphyrins bearing multiple-thiol and photoelectric response

    Institute of Scientific and Technical Information of China (English)

    Jian Dong Yang; Xiao Quan Lu

    2012-01-01

    Self-assembled monolayers (SAMs) of thiol-derivatized porphyrin molecules on Au substrate have attracted extensively interest for use in sensing,optoelectronic devices and molecular electronics.In this paper,tetra-[p-(3-mercaptopropyloxy)-phenyl]-porphyrin was synthesized and self-assembled with thiol on Au substrate for porphyrin SAMs (PPS4).The electrochemical results demonstrated that PPS4 could form excellent SAMs on gold surface.Self-assembled nanojunctions of PPS4 were fabricated by using gold nanogap electrodes (gap width:ca.100 nm).With the light on/off,the nanojunctions showed current high/low as nanometer scaled photo switch.

  17. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. I. Structure

    Science.gov (United States)

    Enevoldsen, A. D.; Hansen, F. Y.; Diama, A.; Criswell, L.; Taub, H.

    2007-03-01

    The structure of a monolayer film of the branched alkane squalane (C30H62) adsorbed on graphite has been studied by neutron diffraction and molecular dynamics (MD) simulations and compared with a similar study of the n-alkane tetracosane (n-C24H52). Both molecules have 24 carbon atoms along their backbone and squalane has, in addition, six methyl side groups. Upon adsorption, there are significant differences as well as similarities in the behavior of these molecular films. Both molecules form ordered structures at low temperatures; however, while the melting point of the two-dimensional (2D) tetracosane film is roughly the same as the bulk melting point, the surface strongly stabilizes the 2D squalane film such that its melting point is 91K above its value in bulk. Therefore, squalane, like tetracosane, will be a poor lubricant in those nanoscale devices that require a fluid lubricant at room temperature. The neutron diffraction data show that the translational order in the squalane monolayer is significantly less than in the tetracosane monolayer. The authors' MD simulations suggest that this is caused by a distortion of the squalane molecules upon adsorption on the graphite surface. When the molecules are allowed to relax on the surface, they distort such that all six methyl groups point away from the surface. This results in a reduction in the monolayer's translational order characterized by a decrease in its coherence length and hence a broadening of the diffraction peaks. The MD simulations also show that the melting mechanism in the squalane monolayer is the same footprint reduction mechanism found in the tetracosane monolayer, where a chain melting drives the lattice melting.

  18. Tribology of monolayer films: comparison between n-alkanethiols on gold and n-alkyl trichlorosilanes on silicon.

    Science.gov (United States)

    Booth, Brandon D; Vilt, Steven G; McCabe, Clare; Jennings, G Kane

    2009-09-01

    This Article presents a quantitative comparison of the frictional performance for monolayers derived from n-alkanethiolates on gold and n-alkyl trichlorosilanes on silicon. Monolayers were characterized by pin-on-disk tribometry, contact angle analysis, ellipsometry, and electrochemical impedance spectroscopy (EIS). Pin-on-disk microtribometry provided frictional analysis at applied normal loads from 10 to 1000 mN at a speed of 0.1 mm/s. At low loads (10 mN), methyl-terminated n-alkanethiolate self-assembled monolayers (SAMs) exhibited a 3-fold improvement in coefficient of friction over SAMs with hydroxyl- or carboxylic-acid-terminated surfaces. For monolayers prepared from both n-alkanethiols on gold and n-alkyl trichlorosilanes on silicon, a critical chain length of at least eight carbons is required for beneficial tribological performance at an applied load of 9.8 mN. Evidence for disruption of chemisorbed alkanethiolate SAMs with chain lengths n tribology wear tracks. The direct comparison between the tribological stability of alkanethiolate and silane monolayers shows that monolayers prepared from n-octadecyl dimethylchlorosilane and n-octadecyl trichlorosilane withstood normal loads at least 30 times larger than those that damaged octadecanethiolate SAMs. Collectively, our results show that the tribological properties of monolayer films are dependent on their internal stabilities, which are influenced by cohesive chain interactions (van der Waals) and the adsorbate-substrate bond.

  19. Applied electrochemical biosensor based on covalently self assembled monolayer at gold surface for determination of epinephrine in the presence of Ascorbic acid

    Directory of Open Access Journals (Sweden)

    Moghadam Zohreh

    2017-02-01

    Full Text Available In this paper, a new electrochemical sensor for the determination of epinephrine (Epi in the presence of ascorbic acid (AA is described. The characterization of Au TMBH self-assembled monolayer modified electrode (TMBH SAM-ME was investigated by cyclic voltammetry (CV using the [Fe(CN6]−3/−4 redox couple. The mediated oxidation of Epi at the modified electrode was investigated by voltammetric methods and the values of transfer coefficient (α, the ionic exchanging current density (io, catalytic rate constant (kh and diffusion coefficient (D were calculated. By double potential step chronoamperometric experiments (DPCHA at the modified electrode was obtained two linear segments of 1.7–24.9 μM and 24.9–91.7 μM by a detection limit (3σ of 0.19 ± 0.01 μM for Epi. The advantages of this modified electrode were reproducibility and repeatability, stability and anti fouling effect against oxidation products of Epi at the surface of TMBH SAM-ME. Finally, the modified electrode was shown agreeable responses to recovery of Epi from real sample solutions by standard addition method.

  20. Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations.

    Science.gov (United States)

    Yan, Chang; Yuan, Rongfeng; Pfalzgraff, William C; Nishida, Jun; Wang, Lu; Markland, Thomas E; Fayer, Michael D

    2016-05-03

    Functionalized self-assembled monolayers (SAMs) are the focus of ongoing investigations because they can be chemically tuned to control their structure and dynamics for a wide variety of applications, including electrochemistry, catalysis, and as models of biological interfaces. Here we combine reflection 2D infrared vibrational echo spectroscopy (R-2D IR) and molecular dynamics simulations to determine the relationship between the structures of functionalized alkanethiol SAMs on gold surfaces and their underlying molecular motions on timescales of tens to hundreds of picoseconds. We find that at higher head group density, the monolayers have more disorder in the alkyl chain packing and faster dynamics. The dynamics of alkanethiol SAMs on gold are much slower than the dynamics of alkylsiloxane SAMs on silica. Using the simulations, we assess how the different molecular motions of the alkyl chain monolayers give rise to the dynamics observed in the experiments.

  1. The use of alkanethiol self-assembled monolayers on 316L stainless steel for coronary artery stent nanomedicine applications: an oxidative and in vitro stability study.

    Science.gov (United States)

    Mahapatro, Anil; Johnson, Dave M; Patel, Devang N; Feldman, Marc D; Ayon, Arturo A; Agrawal, C Mauli

    2006-09-01

    The use of self-assembled monolayers (SAMs) on medical devices offers a methodology for the incorporation of nanotechnology into medicine. SAMs are highly ordered nanosized molecular coatings, adding 1 to 10 nm thickness to a surface. This work is part of an overall goal to deliver therapeutic drugs from the surface of metal coronary stents using SAMs. In this study the oxidative and in vitro stability of functional alkylthiol SAMs on 316L stainless steel (SS) has been demonstrated. SAMs of 11-mercaptoundecanoic acid (-COOH SAM) and 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle (CA) measurements collectively confirmed the formation of functional alkylthiol SAMs on 316L SS. Well-formed SAMs (CA: 82 deg +/- 9 deg) were achieved within 48 hours of immersion in ethanolic solutions, after which no significant improvement in CA was observed. The ratio of the thiolate peak (163.5 eV) to the oxidized sulfur (sulfonates) peak (166.5 eV) gives us an indication of the percentage SAMs that would bind to the metal and serve as a drug reservoir in vivo; which in turn represents the stability and viability of these SAMs, keeping in mind the cardiovascular application under consideration. Oxidative and in vitro stability studies showed that alkanethiol SAMs oxidized completely within 14 days. The SAMs tend to desorb and leave the metal surface after longer time periods (21 days) in phosphate-buffered saline (PBS) immersion, whereas for oxidative exposure the SAMs continue to remain on the metal surface in the form of sulfonates. Although the chemistry of bonding of alkylthiol with the 316L SS is not well understood, the nanosized alkylthiol SAMs demonstrate sufficient stability to justify further study on these systems for potential in vivo drug delivery in the chosen coronary artery stent applications.

  2. Electrochemical immobilization of biomolecules on gold surface modified with monolayered L-cysteine

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Mitsunori, E-mail: honda.mitsunori@jaea.go.jp; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

    2014-04-01

    Immobilization of organic molecules on the top of a metal surface is not easy because of lattice mismatch between organic and metal crystals. Gold atoms bind to thiol groups through strong chemical bonds, and a self-assembled monolayer of sulfur-terminated organic molecules is formed on the gold surface. Herein, we suggested that a monolayer of L-cysteine deposited on a gold surface can act as a buffer layer to immobilize biomolecules on the metal surface. We selected lactic acid as the immobilized biomolecule because it is one of the simplest carboxyl-containing biomolecules. The immobilization of lactic acid on the metal surface was carried out by an electrochemical method in an aqueous environment under the potential range varying from − 0.6 to + 0.8 V. The surface chemical states before and after the electrochemical reaction were characterized using X-ray photoelectron spectroscopy (XPS). The N 1s and C 1s XPS spectra showed that the L-cysteine-modified gold surface can immobilize lactic acid via peptide bonds. This technique might enable the immobilization of large organic molecules and biomolecules. - Highlights: • Monolayer l-cysteine deposited on Au surface as a buffer layer to immobilize biomolecules. • Lactic acid as the immobilized biomolecule as it is simple carboxyl-containing biomolecule. • X-ray photoelectron spectroscopy (XPS) of surface chemical states, before and after. • L-cysteine-modified Au surface can immobilize lactic acid via peptide bonds.

  3. Controlled Oxidation, Biofunctionalization, and Patterning of Alkyl Monolayers on Silicon and Silicon Nitride Surfaces using Plasma Treatment

    NARCIS (Netherlands)

    Rosso, M.; Giesbers, M.; Schroën, C.G.P.H.; Zuilhof, H.

    2010-01-01

    A new method is presented for the fast and reproducible functionalization of silicon and silicon nitride surfaces coated with covalently attached alkyl monolayers. After formation of a methyl-terminated 1-hexadecyl monolayer on H-terminated Si(100) and Si(111) surfaces, short plasma treatments (1-3

  4. Surface Modification through Chemically Adsorbed Monolayer of Thiophene Molecules

    Science.gov (United States)

    Yamamoto, Shin-ichi; Ogawa, Kazufumi

    2008-07-01

    Using a time-averaged dielectrophoretic force from an applied electric field, we have observed the assembly of a chemically adsorbed monomolecular layer (CAM) on microwires and connections and the formation of an electric path between a lithographically patterned array of two platinum (Pt) electrodes. A Pt electrode/monolayer/Pt electrode junction was fabricated by the self-assembly of a rigid monomolecular layer, namely 3-{6-[11-(trichlorosilyl)undecanoyl]hexyl} thiophene (TEN) with thiophene groups in the lateral direction between the Pt electrodes. Conductive probe AFM (CP-AFM) was used to investigate the forward bias conduction properties of a TEN film grown by a wet deposition process on a glass substrate. The self-assembly depends on the ideal rigidity of the CAM and the strong affinity of the thiophene end groups of the CAM for the Pt electrode. The current-voltage (I-V) characteristics of the conjugated thiophene junction exhibited stepwise features at room temperature. The I-V characteristics can be explained by electron transport through the junction. From the results of experiments carried out under ambient conditions, the conductivity of the laterally conjugated polythiophene groups was calculated to be 5.0 ×104 S/cm. Understanding and using these effects will allow the controlled fabrication and positioning of microwires or connections at densities much greater than those now achievable.

  5. Effect of Alkyl Chain Length on Carboxylic Acid SAMs on Ti-6Al-4V

    Directory of Open Access Journals (Sweden)

    Gavin A. Buckholtz

    2012-07-01

    Full Text Available The formation of methyl-terminated carboxylic acid self-assembled monolayers (SAMs with even numbers of carbons, from eighteen to thirty, was investigated on the oxide surface of Ti-6Al-4V and component metal oxides. Modified surfaces were characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT, matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS and contact angle analysis. Infrared spectroscopy indicated that using aerosol spray deposition techniques, stable, all-trans SAMs of octacosanoic (28 carbons and triacontanoic (30 carbons acids were formed on the alloy. Films were similarly formed on titanium and aluminum oxide. The surface of vanadium oxide exhibited limited reactivity. MALDI-TOF MS confirmed that formed films were monolayers, without multilayers or aggregates present. Water contact angles are indicative of the presence of hydrophobic methyl groups at the interface. This stable carboxylic acid SAM formation could be a useful alternative to phosphonic acid SAMs for corrosion and other applications.

  6. Cross-Reactive Sensor Array for Metal Ion Sensing Based on Fluorescent SAMs

    Directory of Open Access Journals (Sweden)

    Mercedes Crego-Calama

    2007-09-01

    Full Text Available Fluorescent self assembled monolayers (SAMs on glass were previouslydeveloped in our group as new sensing materials for metal ions. These fluorescent SAMs arecomprised by fluorophores and small molecules sequentially deposited on a monolayer onglass. The preorganization provided by the surface avoids the need for complex receptordesign, allowing for a combinatorial approach to sensing systems based on small molecules.Now we show the fabrication of an effective microarray for the screening of metal ions andthe properties of the sensing SAMs. A collection of fluorescent sensing SAMs wasgenerated by combinatorial methods and immobilized on the glass surfaces of a custom-made 140 well microtiter-plate. The resulting libraries are easily measured and show variedresponses to a series cations such as Cu2+ , Co2+ , Pb2+ , Ca2+ and Zn2+ . These surfaces are notdesigned to complex selectively a unique analyte but rather they are intended to producefingerprint type responses to a range of analytes by less specific interactions. The unselectiveresponses of the library to the presence of different cations generate a characteristic patternfor each analyte, a “finger print” response.

  7. Cross-Reactive Sensor Array for Metal Ion Sensing Based on Fluorescent SAMs

    Science.gov (United States)

    Basabe-Desmonts, Lourdes; van der Baan, Frederieke; Zimmerman, Rebecca S.; Reinhoudt, David N.; Crego-Calama, Mercedes

    2007-01-01

    Fluorescent self assembled monolayers (SAMs) on glass were previously developed in our group as new sensing materials for metal ions. These fluorescent SAMs are comprised by fluorophores and small molecules sequentially deposited on a monolayer on glass. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on small molecules. Now we show the fabrication of an effective microarray for the screening of metal ions and the properties of the sensing SAMs. A collection of fluorescent sensing SAMs was generated by combinatorial methods and immobilized on the glass surfaces of a custom-made 140 well microtiter-plate. The resulting libraries are easily measured and show varied responses to a series cations such as Cu2+, Co2+, Pb2+, Ca2+ and Zn2+. These surfaces are not designed to complex selectively a unique analyte but rather they are intended to produce fingerprint type responses to a range of analytes by less specific interactions. The unselective responses of the library to the presence of different cations generate a characteristic pattern for each analyte, a “finger print” response.

  8. Formation of carboxy- and amide-terminated alkyl monolayers on silicon(111) investigated by ATR-FTIR, XPS, and X-ray scattering: Construction of photoswitchable surfaces

    DEFF Research Database (Denmark)

    Rück-Braun, Karola; Petersen, Michael Åxman; Michalik, Fabian

    2013-01-01

    We have prepared high-quality, densely packed, self-assembled monolayers (SAMs) of carboxy-terminated alkyl chains on Si(111). The samples were made by thermal grafting of methyl undec-10-enoate under an inert atmosphere and subsequent cleavage of the ester functionality to disclose the carboxyli...

  9. "Living" free radical photopolymerization initiated from surface-grafted iniferter monolayers

    NARCIS (Netherlands)

    de Boer, B.; Simon, H.K.; Werts, M.P L; van der Vegte, E.W.; Hadziioannou, G

    2000-01-01

    A method for chemically modifying a surface with grafted monolayers of initiator groups, which can be used for a "living" free radical photopolymerization, is described. By using "living" free radical polymerizations, we were able to control the length of the grafted polymer chains and therefore the

  10. First-Principle Calculation for Scanning-Tunneling-Microscopic Images of a Monolayer Graphite Surface

    Institute of Scientific and Technical Information of China (English)

    陈向荣; 押山淳; 岡田晋; 芶清泉

    2003-01-01

    We have applied first-principle total-energy electronic structure calculations in the local density approximation to calculate the scanning tunnelling microscopy images of a monolayer graphite surface near the Fermi level. The results obtained agree well with the observation, which has not been interpreted before.

  11. 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–

  12. Growing extremely thin bulklike metal film on a semiconductor surface: Monolayer Al(111) on Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Ying; Kim, Yong-Hyun; Zhang, S. B.; Ebert, Philipp; Yang, Shenyuan; Tang, Zhe; Wu, Kehui; Wang, E. G.

    2007-10-29

    We report combined scanning tunneling microscopy, x-ray photoelectron emission spectroscopy, electron energy loss spectroscopy, and theoretical study of the growth of ultrathin Al film on the Si(111) substrate. We show that by (i) a modification of the substrate reconstruction with a √3×√3 surface and (ii) a choice of materials with commensurate lattices, atomically flat film can be obtained even at the ultimate one monolayer limit, while maintaining a bulklike atomic structure. Detailed analysis shows that this monolayer Al(111)-1×1Al(111)-1×1 film is electronically decoupled from the Si substrate, and it shows metallic characteristics.

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

    Science.gov (United States)

    Kaufmann, C R; Mani, G; Marton, D; Johnson, D M; Agrawal, C M

    2010-04-01

    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(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(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 degrees 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(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.

  14. Stability of silanols and grafted alkylsilane monolayers on plasma-activated mica surfaces.

    Science.gov (United States)

    Liberelle, Benoît; Banquy, Xavier; Giasson, Suzanne

    2008-04-01

    We investigated the effect of physical and chemical modifications of mica surfaces induced by water vapor-based plasma treatments on the stability of silanols and grafted alkylsilane monolayers. The plasma-activated substrates were characterized using XPS, TOF-SIMS, and contact angle measurements. They revealed a large surface coverage of silanol groups (Si-OH) and a loss of aluminum atoms compared to freshly cleaved mica surfaces. The stability of plasma-induced silanol groups was investigated by contact angle measurements using ethylene glycol as a probe liquid. The Si-OH surface coverage decreased rapidly under vacuum or thermal treatment to give rise to hydrophobic dehydrated surfaces. The stability of end-grafted monofunctionalized n-alkylsilanes was investigated in different solvents and at different pH using water contact angle measurements. The degrafting of alkylsilanes from the activated mica was promoted in acidic aqueous solutions. This detachment was associated with the hydrolysis of covalent bonds between the alkylsilanes and the mica surface. The monolayer stability was enhanced by increasing the length of the alkyl chains that probably act as a hydrophobic protective layer against hydrolysis reactions. Stable alkylsilane monolayers in water with pH greater than 5.5 were obtained on mica surfaces activated at low plasma pressure. We attributed this stability to the loss of surface Al atoms induced by the plasma treatment.

  15. The additional phase transition of DPPC monolayers at high surface pressure confirmed by GIXD study

    DEFF Research Database (Denmark)

    Shen, Chen; Serna, Jorge B. de la; Struth, Bernd

    Pulmonary surfactant forms the alveolar monolayer at the air/aqueous interface within the lung. During the breathing process, the surface pressure periodically varies from ~40mN/m up to ~70mN/m. The film is mechanically stable during this rapid and reversible expansion. The monolayer consists...... of ~90% of lipid with 10% integrated proteins. Among its lipid compounds, di- palmitoyl-phosphatidylcholine (DPPC) dominates (~45wt%). No other lipid but DPPC was so far reported to be compressible to very high surface pressure (~70mN/m) before its monolayer collapsed. Its liquid......-expanded/liquid-condensed (LE/LC) phase transition at ~10mN/m is well known. Here we present results from Langmuir isotherm measurements that evidence a so far not documented second phase transition at elevated surface pressure Π (~50mN/m). The varying lateral structures of the monolayer at 8mN/m, 20mN/m, 30mN/m, 40mN/m, 50m...

  16. Hyperthermal Carbon Dioxide Interactions with Self-Assembled Monolayer Surfaces

    Science.gov (United States)

    2013-09-08

    from squalane and PFPE surfaces,[8,13] indicating a localized collision with a region of the surface with a finite effective mass. Nesbitt and co...distributions. Average final energies may also be obtained from the translational energy distributions. It was suggested by Nesbitt and co...In their work on CO2 molecules scattering from PFPE surfaces, Nesbitt and co-workers presented a two temperature (or “two-Boltzmann”) model for

  17. Molecular Understanding on the Underwater Oleophobicity of Self-Assembled Monolayers: Zwitterionic versus Nonionic.

    Science.gov (United States)

    Cheng, Gang; Liao, Mingrui; Zhao, Daohui; Zhou, Jian

    2017-02-21

    Molecular dynamics simulations are conducted to investigate the underwater oleophobicity of self-assembled monolayers (SAMs) with different head groups. Simulation results show that the order of underwater oleophobicity of SAMs is methyl oleophobicity have better antifouling performance. Further study on the effect of different alkyl ammonium ions on mixed-charged SAMs reveals that the underwater OCAs are >143.6° for all SAMs; mixed-charged SAMs containing primary alkyl ammonium ion are likely to possess the best underwater oleophobicity for its strong hydration capacity. It seems that alkyl sulfonate anion (SO3(-)) is more hydrophilic than alkyl trimethylammonium ion (NC3(+)) for the hydrophobic methyl groups on nitrogen atoms and that the hydration of SO3(-) in mixed-charged SAMs can be seriously blocked by NC3(+). The monomer of SO3(-) should be slightly longer than that of NC3(+) to obtain better underwater oleophobicity in NC3(+)-/SO3(-)-SAMs. In addition, the underwater oleophobicity of SAMs might become worse at low grafting densities. This work systematically proves that a zwitterionic surface is more underwater oleophobic than a nonionic surface. These results will help for the design and development of superoleophobic surfaces.

  18. Self-assembled monolayers on gold of ferrocene-terminated thiols and hydroxyalkanethiols

    NARCIS (Netherlands)

    Auletta, T.; van Veggel, F.C.J.M.; Reinhoudt, David

    2002-01-01

    this paper, a study on the adsorption of mixed self-assembled monolayers (SAMs) for two different combinations of thiols (Fc(CH2)6SH/HO(CH2)2SH and Fc(CH2)16SH/HO(CH2)11SH (Fc = ferrocene)) is presented, to obtain surfaces with single isolated ferrocenylalkanethiols embedded in shorter

  19. Dipole Formation at Interfaces of Alkanethiolate Self-assembled Monolayers and Ag(111)

    NARCIS (Netherlands)

    Rusu, Paul C.; Giovannetti, Gianluca; Brocks, Geert

    2007-01-01

    The formation of interface dipoles in self-assembled monolayers (SAMs) of −CH3 and −CF3 terminated short-chain alkanethiolates on Ag(111) is studied by means of density functional theory calculations. The interface dipoles are characterized by monitoring the change in the surface work function upon

  20. 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

  1. Tuning the hydrophobic properties of silica particles by surface silanization using mixed self-assembled monolayers.

    Science.gov (United States)

    Kulkarni, Sneha A; Ogale, Satishchandra B; Vijayamohanan, Kunjukrishanan P

    2008-02-15

    Here we describe a novel method of preparing hydrophobic silica particles (100-150 nm; water contact angle of dropcasted film ranging from 60 degrees to 168 degrees) by surface functionalization using different alkyltrichlorosilanes. During their preparation, the molecular surface roughness is also concurrently engineered facilitating a change in both the surface chemical composition and the geometrical microstructure to generate hierarchical structures. The water contact angle has been measured on drop-cast film surface. The enhancement in the water contact angle on 3D (curved) SAMs in comparison to that on 2D (planar) surface is discussed using the Cassie-Baxter equation. These silica particles can be utilized for many potential applications including selective adsorbents and catalysts, chromatographic supports and separators in microfluidic devices.

  2. Tunable doping in PbS nanocrystal field-effect transistors using surface molecular dipoles

    Science.gov (United States)

    Nugraha, Mohamad I.; Matsui, Hiroyuki; Bisri, Satria Z.; Sytnyk, Mykhailo; Heiss, Wolfgang; Loi, Maria A.; Takeya, Jun

    2016-11-01

    We study the effect of self-assembled monolayer (SAM) treatment of the SiO2 dielectric on the electrical characteristics of PbS transistors. Using SAMs, we observe threshold voltage shifts in the electron transport, allowing us to tune the electrical properties of the devices depending on the SAM molecule used. Moreover, the use of a specific SAM improves the charge carrier mobility in the devices by a factor of three, which is attributed to the reduced interface traps due to passivated silanol on the SiO2 surface. These reduced traps confirm that the voltage shifts are not caused by the trap states induced by the SAMs.

  3. Ripple-Free Graphene Sheets on Alkanethiol Self-Assembled Monolayers Provided from Unzipped Multi-Walled Carbon Nanotubes.

    Science.gov (United States)

    Koo, Hyunmo; Lee, Nam-Suk; Shin, Hoon-Kyu; Noh, Jaegeun; Majima, Yutaka; Cho, Gyoujin

    2015-02-01

    Octanethiol (C8S, CH3(CH2)7SH) self-assembled monolayers/Au(111) were utilized as an inert surface to provide ripple-free graphene oxide layers provided from chemically unzipped multi-walled carbon nanotubes (MWCNTs). The resulting graphene oxide monolayers were characterized with atomic resolution by UHV-STM. The honeycomb structure for the graphene monolayer and "three-for-six" triangular pattern for the multi-layer graphene sheets on C8S SAMs were clearly observed without ripples by the high-resolution UHV-STM. These results provide new insight into the preparation of ripple-free graphene monolayers.

  4. An Improved Method for the Preparation of Organic Monolayers of 1-Alkenes on Hydrogen-Terminated Silicon Surfaces

    NARCIS (Netherlands)

    Sieval, A.B.; Vleeming, V.; Zuilhof, H.; Sudhölter, E.J.R.

    1999-01-01

    The possibility to use dilute alkene solutions for the formation of alkene monolayers with 1-hexadecene on a hydrogen-terminated silicon(100) surface has been investigated for a variety of solvents. The resulting monolayers were analyzed by water contact angles. Anisole, n-butylbenzene, and n-decane

  5. Simple method for coating Si (1 0 0) surfaces with ferritin monolayers-Iron oxide quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Papadopoulos, Georgios, E-mail: geopap@bio.uth.gr [University of Thessaly, Department of Biochemistry and Biotechnology, Ploutonos 26 and Aeolou, 41221 Larisa (Greece); Anetakis, Constantine, E-mail: kanetaki@physics.auth.gr [Aristotle University of Thessaloniki, Department of Physics, Laboratory for Thin Films - Nanosystems and Nanometrology and Laboratory of Electronic Microscopy, 54124 Thessaloniki (Greece); Gravalidis, Christoforos, E-mail: cgrava@physics.auth.gr [Aristotle University of Thessaloniki, Department of Physics, Laboratory for Thin Films - Nanosystems and Nanometrology and Laboratory of Electronic Microscopy, 54124 Thessaloniki (Greece); Kassavetis, Spiros, E-mail: skasa@physics.auth.gr [Aristotle University of Thessaloniki, Department of Physics, Laboratory for Thin Films - Nanosystems and Nanometrology and Laboratory of Electronic Microscopy, 54124 Thessaloniki (Greece); Vouroutzis, Nikolaos, E-mail: nikosv@auth.gr [Aristotle University of Thessaloniki, Department of Physics, Laboratory for Thin Films - Nanosystems and Nanometrology and Laboratory of Electronic Microscopy, 54124 Thessaloniki (Greece); Frangis, Nikolaos, E-mail: frangis@auth.gr [Aristotle University of Thessaloniki, Department of Physics, Laboratory for Thin Films - Nanosystems and Nanometrology and Laboratory of Electronic Microscopy, 54124 Thessaloniki (Greece); Logothetidis, Stergios, E-mail: logot@auth.gr [Aristotle University of Thessaloniki, Department of Physics, Laboratory for Thin Films - Nanosystems and Nanometrology and Laboratory of Electronic Microscopy, 54124 Thessaloniki (Greece)

    2011-04-15

    With the goal to develop iron oxide quantum dots we developed a simple method to spread horse spleen ferritin monolayers on a Si (1 0 0) surface. Application of atomic force microscopy and spectroscopic ellipsometry showed the existence of regions with dense ferritin monolayers. Application of transmission electron microscopy identified the core of the spread ferritin as FeO nanocrystals.

  6. Study of the ability of self-assembled N-vinylcarbazole monolayers to protect copper against corrosion

    Directory of Open Access Journals (Sweden)

    NAI-XING WANG

    2002-10-01

    Full Text Available N-Vinylcarbazole (NVC monolayers were self-assembled on copper surfaces. The electrochemical properties of the copper surfaces modified by NVC self-assembled monolayers (SAMs were investigated using polarization and electrochemical impedance spectroscopic (EIS methods. The polarization measurements indicated that the NVC SAMs could reduce the rates of the anodic and cathodic reaction on the surface of copper electrodes in 0.5 mol dm-3 NaCl solution. The EIS results showed the NVC formed a closely packed film that was able to inhibit copper corrosion. X-Ray photoelectron spectroscopy (XPS analysis of the copper samples and atomic adsorption analysis of the solution showed that the copper surfaces were covered by NVC SAMs, and the adsorption of NVC on the copper surfaces was accompanied with dissolution of Cu into the solution.

  7. 金属表面席夫碱缓蚀剂自组装膜的制备及性能研究现状%Research Status of Preparation and Properties of Self-assembled Monolayers of Schiff Base on Metal Surface

    Institute of Scientific and Technical Information of China (English)

    陈世亮; 刘峥; 张小鸽

    2011-01-01

    席夫碱是由伯胺与活性羰基缩合而成的含有甲亚胺活性基团-RC=N-的一类有机化合物,能在金属表面发生化学吸附反应而形成结构稳定、排列紧密有序的自组装膜(SAMs);SAMs是一种有缓蚀性能的单分子膜,对基底金属有良好的防腐蚀作用.本文综述了近年来席夫碱类自组装膜的制备方法及自组装膜的表征技术,进一步概述了分子模拟及拓扑结构在腐蚀防护研究中的应用现状,展望了自组装膜的应用前景.%Shiff bases are a class of organic compounds containing azomethine active groups-RC=N-, synthesized by the condensation of primary amine and active carbonyl. Shiff bases could form self-assembled monolayers (SAMs) through chemical adsorption on metal surface, stable and compactly arranged. SAMs are corrosion inhibition molecular films and have good corrosion resistance for the metal substrate. The methods of preparation and characterization of self-assembled monolayers (SAMs) are reviewed, the application status of the molecular modeling and topological structure in the corrosion protection are outlined, and the prospect of self-assembled monolayers (SAMs)are outlooked.

  8. Effects of surface pressure on the properties of Langmuir monolayers and interfacial water at the air-water interface.

    Science.gov (United States)

    Lin, Wei; Clark, Anthony J; Paesani, Francesco

    2015-02-24

    The effects of surface pressure on the physical properties of Langmuir monolayers of palmitic acid (PA) and dipalmitoylphosphatidic acid (DPPA) at the air/water interface are investigated through molecular dynamics simulations with atomistic force fields. The structure and dynamics of both monolayers and interfacial water are compared across the range of surface pressures at which stable monolayers can form. For PA monolayers at T = 300 K, the untilted condensed phase with a hexagonal lattice structure is found at high surface pressure, while the uniformly tilted condensed phase with a centered rectangular lattice structure is observed at low surface pressure, in agreement with the available experimental data. A state with uniform chain tilt but no periodic spatial ordering is observed for DPPA monolayers on a Na(+)/water subphase at both high and low surface pressures. The hydrophobic acyl chains of both monolayers pack efficiently at all surface pressures, resulting in a very small number of gauche defects. The analysis of the hydrogen-bonding structure/dynamics at the monolayer/water interface indicates that water molecules hydrogen-bonded to the DPPA head groups reorient more slowly than those hydrogen-bonded to the PA head groups, with the orientational dynamics becoming significantly slower at high surface pressure. Possible implications for physicochemical processes taking place on marine aerosols in the atmosphere are discussed.

  9. 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.

  10. Influence of the molecular-scale structures of 1-dodecanethiol and 4-methylbenzenethiol self-assembled monolayers on gold nanoparticles adsorption pattern.

    Science.gov (United States)

    Mamun, Abdulla Hel Al; Yoon, Sangwoon; Hahn, Jae Ryang

    2014-07-01

    In an effort to understand the effects of the molecular structures of self-assembled monolayers on the patterns formed by immobilized Au nanoparticles (AuNPs), we characterized and compared the morphologies and properties of AuNPs adsorbed onto self-assembled monolayers formed by 1-dodecanethiol (DDT-SAM) or 4-methylbenzenethiol (MBT-SAM) assembled on Au(111) surfaces. The AuNP adsorption pattern on the MBT-SAM surface was well-dispersed and characterized by a low degree of corrugation. By contrast, an aggregated and highly corrugated AuNP pattern was observed on the surface of the DDT-SAM. This difference was attributed to the retention or removal of citrate anions present on the AuNPs during adsorption onto the SAM surface. Direct interactions between the AuNPs and the highly corrugated hydrophobic surfaces of the DDT-SAMs could strip the citrate layers from the AuNP surfaces, leading to aggregated adsorption. The water molecules appeared to mediate the adsorption of the AuNPs by reducing the hydrophobicity of the MBT-SAM surface and promoting a more dispersed adsorption configuration.

  11. Sum-frequency generation analyses of the structure of water at amphoteric SAM-liquid water interfaces.

    Science.gov (United States)

    Nomura, Kouji; Nakaji-Hirabayashi, Tadashi; Gemmei-Ide, Makoto; Kitano, Hiromi; Noguchi, Hidenori; Uosaki, Kohei

    2014-09-01

    Surfaces of both a cover glass and the flat plane of a semi-cylindrical quartz prism were modified with a mixture of positively and negatively charged silane coupling reagents (3-aminopropyltriethoxysilane (APTES) and 3-(trihydroxysilyl)propylmethylphosphonate (THPMP), respectively). The glass surface modified with a self-assembled monolayer (SAM) prepared at a mixing ratio of APTES:THPMP=4:6 was electrically almost neutral and was resistant to non-specific adsorption of proteins, whereas fibroblasts gradually adhered to an amphoteric (mixed) SAM surface probably due to its stiffness, though the number of adhered cells was relatively small. Sum frequency generation (SFG) spectra indicated that total intensity of the OH stretching region (3000-3600cm(-1)) for the amphoteric SAM-modified quartz immersed in liquid water was smaller than those for the positively and negatively charged SAM-modified quartz prisms and a bare quartz prism in contact with liquid water. These results suggested that water molecules at the interface of water and an amphoteric SAM-modified quartz prism are not strongly oriented in comparison with those at the interface of a lopsidedly charged SAM-modified quartz prism and bare quartz. The importance of charge neutralization for the anti-biofouling properties of solid materials was strongly suggested.

  12. Effects of smooth random surface on fluid monolayer thermodynamics

    Science.gov (United States)

    Khlyupin, A. N.

    2016-11-01

    We consider the lattice gas approach to statistical mechanics of fluid adsorbed on random surfaces with fluid-fluid and fluid-surface potentials. It was shown that effective Hamiltonian contains quenched random interactions and random site fields. Their statistical features combine the properties of random geometry and fluid-fluid pair interaction potential. The high-temperature expansion leads to infinite-ranged random field model and Sherrington-Kirkpatrick spin-glass model. Thermodynamic properties are evaluated using replica theory procedure widely used to analyze quenched disorder systems. On the other hand we consider the random field model in random graph with finite connectivity instead of previous “infinite-ranged” approximations. This model has been investigated using finite connectivity technique. The replica symmetry ansatz for the order function is expressed in terms of an effective-field distribution. Analysis of random geometry effects on thermodynamic properties in such approach was done for the first time.

  13. The role of surface Pt on the coadsorption of hydrogen and CO on Pt monolayer film modified Ru(0001) surfaces

    Science.gov (United States)

    Diemant, T.; Hartmann, H.; Bansmann, J.; Behm, R. J.

    2016-10-01

    We have investigated the impact and role of the Pt surface modification on the coadsorption of hydrogen and CO on structurally well defined bimetallic Pt monolayer island/film modified Ru(0001) surfaces with Pt contents up to a complete Pt layer, employing temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS). Kinetic limitations in the surface diffusion are shown to play an important role for adsorption at 90 K, and lead to profound effects of the dosing sequence on the adsorption and desorption characteristics. Furthermore, they are responsible for spill-over effects during the TPD measurements, where COad becomes mobile and can spill-over from weakly bonding Pt monolayer areas to strongly bonding Pt-free Ru(0001) areas, which displaces Dad from these surface areas. The present findings are discussed in comparison with previous results on related metallic and bimetallic adsorption and coadsorption systems.

  14. 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

  15. 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

  16. Oligo(ethylene glycol)-terminated monolayers on silicon surfaces and their nanopatterning with a conductive atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Functionalization of silicon substrate surfaces with a stable monolayer for resisting non-specific adsorption of proteins has attracted great interest,since it is directly relevant to the development of miniature,silicon-based biosensors and implantable microdevices,such as silicon-neuron interfaces.This brief review summarizes our contribution to the development of robust monolayers grown by surface hydrosilylation on atomically flat,hydrogen-terminated silicon surfaces.The review also outlines our strategy and progress on the fabrication of single molecule patterns on such monolayer platforms.

  17. Highly wear-resistant ultra-thin per-fluorinated organic monolayers on silicon(1 1 1) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Pujari, Sidharam P. [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen (Netherlands); Zuilhof, Han, E-mail: Han.Zuilhof@wur.nl [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen (Netherlands); Department of Chemical and Materials Engineering, King Abdulaziz University, Jeddah (Saudi Arabia)

    2013-12-15

    This study reports on fluorine-containing alkyne-derived monolayers onto Si(1 1 1) substrates to obtain densely packed, highly wear-resistant surfaces. The nano-wear properties were measured using atomic force microscopy (AFM). The presence of the fluorinated monolayers was found to enhance the wear properties of the silicon surfaces, with a decrease of the depth of wear scratches of up to 120 times as compared to the unmodified surface. Ultimately, the scratch depth was only 6 nm for a heptadecafluoro-alkyl based monolayer for scratching normal forces as high as 38 μN.

  18. Adsorption behavior of Fe atoms on a naphthalocyanine monolayer on Ag(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Linghao; Wu, Rongting; Bao, Deliang; Ren, Junhai; Zhang, Yanfang; Zhang, Haigang; Huang, Li; Wang, Yeliang; Du, Shixuan; Huan, Qing; Gao, Hong-Jun

    2015-05-29

    Adsorption behavior of Fe atoms on a metal-free naphthalocyanine (H2Nc) monolayer on Ag(111) surface at room temperature has been investigated using scanning tunneling microscopy combined with density functional theory (DFT) based calculations. We found that the Fe atoms adsorbed at the centers of H2Nc molecules and formed Fe-H2Nc complexes at low coverage. DFT calculations show that the configuration of Fe at the center of a molecule is the most stable site, in good agreement with the experimental observations. After an Fe-H2Nc complex monolayer was formed, the extra Fe atoms self-assembled to Fe clusters of uniform size and adsorbed dispersively at the interstitial positions of Fe-H2Nc complex monolayer. Furthermore, the H2Nc monolayer grown on Ag(111) could be a good template to grow dispersed magnetic metal atoms and clusters at room temperature for further investigation of their magnetism-related properties.

  19. Phosphonate-anchored monolayers for antibody binding to magnetic nanoparticles.

    Science.gov (United States)

    Benbenishty-Shamir, Helly; Gilert, Roni; Gotman, Irena; Gutmanas, Elazar Y; Sukenik, Chaim N

    2011-10-04

    Targeted delivery of magnetic iron oxide nanoparticles (IONPs) to a specific tissue can be achieved by conjugation with particular biological ligands on an appropriately functionalized IONP surface. To take best advantage of the unique magnetic properties of IONPs and to maximize their blood half-life, thin, strongly bonded, functionalized coatings are required. The work reported herein demonstrates the successful application of phosphonate-anchored self-assembled monolayers (SAMs) as ultrathin coatings for such particles. It also describes a new chemical approach to the anchoring of antibodies on the surface of SAM-coated IONPs (using nucleophilic aromatic substitution). This anchoring strategy results in stable, nonhydrolyzable, covalent attachment and allows the reactivity of the particles toward antibody binding to be activated in situ, such that prior to the activation the modified surface is stable for long-term storage. While the SAMs do not have the well-packed crystallinity of other such monolayers, their structure was studied using smooth model substrates based on an iron oxide layer on a double-side polished silicon wafer. In this way, atomic force microscopy, ellipsometry, and contact angle goniometry (tools that could not be applied to the nanoparticles' surfaces) could contribute to the determination of their monomolecular thickness and uniformity. Finally, the successful conjugation of IgG antibodies to the SAM-coated IONPs such that the antibodies retain their biological activity is verified by their complexation to a secondary fluorescent antibody.

  20. 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

  1. 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)

  2. 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

  3. Study of two grafting methods for obtaining a 3-aminopropyltriethoxysilane monolayer on silica surface.

    Science.gov (United States)

    Simon, A; Cohen-Bouhacina, T; Porté, M C; Aimé, J P; Baquey, C

    2002-07-15

    In order to establish a 3-aminopropyltriethoxysilane (APTES) grafting procedure with limited number of APTESs noncovalently linked to the silica surface, two different methods of grafting (in acid-aqueous solution and in anhydrous solution) were compared. The grafted surface state was investigated by atomic force microscopy (AFM). The stability of the grafting was checked at different temperatures by AFM. Continuous and plane APTES grafted surfaces were successfully prepared using both grafting preparations. The grafting in an anhydrous solution behaves homogeneously and stably compared to the grafting in an acid-aqueous solution. Moreover, with anhydrous solution, results showed that a unique monolayer of APTES was grafted.

  4. Ternary surface monolayers for ultrasensitive (zeptomole) amperometric detection of nucleic acid hybridization without signal amplification.

    Science.gov (United States)

    Wu, Jie; Campuzano, Susana; Halford, Colin; Haake, David A; Wang, Joseph

    2010-11-01

    A ternary surface monolayer, consisting of coassembled thiolated capture probe, mercaptohexanol and dithiothreitol, is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers. Remarkably low detection limits down to 40 zmol (in 4 μL samples) as well as only 1 CFU Escherichia coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3',5,5'-tetramethylbenzidine system. Such dramatic improvements in the detection limits (compared to those of common binary alkanethiol interfaces and to those of most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to nonspecific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration "backfillers" that leads to a remarkably low background noise even in the presence of complex sample matrixes. A wide range of surface compositions have been investigated, and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety, and forensic analysis.

  5. Vibrational Stark Effect of the Electric-Field Reporter 4-Mercaptobenzonitrile as a Tool for Investigating Electrostatics at Electrode/SAM/Solution Interfaces

    Directory of Open Access Journals (Sweden)

    Peter Hildebrandt

    2012-06-01

    Full Text Available 4-mercaptobenzonitrile (MBN in self-assembled monolayers (SAMs on Au and Ag electrodes was studied by surface enhanced infrared absorption and Raman spectroscopy, to correlate the nitrile stretching frequency with the local electric field exploiting the vibrational Stark effect (VSE. Using MBN SAMs in different metal/SAM interfaces, we sorted out the main factors controlling the nitrile stretching frequency, which comprise, in addition to external electric fields, the metal-MBN bond, the surface potential, and hydrogen bond interactions. On the basis of the linear relationships between the nitrile stretching and the electrode potential, an electrostatic description of the interfacial potential distribution is presented that allows for determining the electric field strengths on the SAM surface, as well as the effective potential of zero-charge of the SAM-coated metal. Comparing this latter quantity with calculated values derived from literature data, we note a very good agreement for Au/MBN but distinct deviations for Ag/MBN which may reflect either the approximations and simplifications of the model or the uncertainty in reported structural parameters for Ag/MBN. The present electrostatic model consistently explains the electric field strengths for MBN SAMs on Ag and Au as well as for thiophenol and mercaptohexanoic acid SAMs with MBN incorporated as a VSE reporter.

  6. Self-Assembled Monolayers Exposed by Metastable Helium for Nano-Patterning: Octanethiol and Dodecanethiol

    Institute of Scientific and Technical Information of China (English)

    巨新; 仓桥光纪; 铃木拓; 山内泰

    2003-01-01

    A large-area gold pattern with nanoscale edge on muscovite mica was fabricated by using a metastable helium beam and octanethiol(OT)and dodecanethiol(DDT)self-assembled monolayers(SAM),in which the width of edge was typically ~70nm for the OT SAM and ~90nm for the DDT SAM,respectively.The mask was reproduced with high fidelity.Combined the analysis of roughness with grain size,more flat surface and sharper edge of patterns were obtained by using the shorter chain molecules such as the OT.All the information indicated that the OT SAMs on atomically flat surfaces can be used as a resist for exposure to metastable atom beams.

  7. Characterization of Self-assembled Monolayers on Gold Electrode Using Electrochemical Quartz Crystal Microbalance

    Institute of Scientific and Technical Information of China (English)

    Yonggui Dong

    2006-01-01

    The electrochemical quartz crystal microbatance (EQCM) is used to investigate the characteristics of the thiolated self-assembled monolayer(SAM) on gold surface. A 5MHz QCM element serves as both the mass-sensitive sensor and the working electrode of the electrochemical system. The 6-mecapto-1-hexanol and and the 16-mer oligonucleotide with a mercaptohexyl group at the 5'-phosphate end are utilized to form the SAM on the gold electrode. The frequency response of the QCM during cyclic voltammetry (CV) scanning and chronoamperometry are recorded together with the electrochemical current. The experimental results indicates that the frequency response is more sensitive to the surface coverage. Therefore, the response of the EQCM reveals more details of the SAM on gold electrode. It is especially useful for analysing the immobilization quality, such as probe orientation and coverage, of the SAM.

  8. Underpotential deposition of a copper monolayer on a gold film sensed by integrated optical surface plasmon resonance

    OpenAIRE

    Abanulo, J.C.; Harris, R.D.; Bartlett, P.N.; Wilkinson, J.S.

    2000-01-01

    An integrated optical surface plasmon resonance sensor combined with electrochemical control is used to monitor the underpotential deposition of a copper monolayer onto a gold film from 1 mM Cu2+ in 0.1 M perchloric acid.

  9. Surface-enhanced infrared absorption spectroscopy (SEIRAS) to probe monolayers of membrane proteins.

    Science.gov (United States)

    Ataka, Kenichi; Stripp, Sven Timo; Heberle, Joachim

    2013-10-01

    Surface-enhanced infrared absorption spectroscopy (SEIRAS) represents a variation of conventional infrared spectroscopy and exploits the signal enhancement exerted by the plasmon resonance of nano-structured metal thin films. The surface enhancement decays in about 10nm with the distance from the surface and is, thus, perfectly suited to selectively probe monolayers of biomembranes. Peculiar to membrane proteins is their vectorial functionality, the probing of which requires proper orientation within the membrane. To this end, the metal surface used in SEIRAS is chemically modified to generate an oriented membrane protein film. Monolayers of uniformly oriented membrane proteins are formed by tethering His-tagged proteins to a nickel nitrilo-triacetic acid (Ni-NTA) modified gold surface and SEIRAS commands molecular sensitivity to probe each step of surface modification. The solid surface used as plasmonic substrate for SEIRAS, can also be employed as an electrode to investigate systems where electron transfer reactions are relevant, like e.g. cytochrome c oxidase or plant-type photosystems. Furthermore, the interaction of these membrane proteins with water-soluble proteins, like cytochrome c or hydrogenase, is studied on the molecular level by SEIRAS. The impact of the membrane potential on protein functionality is verified by monitoring light-dark difference spectra of a monolayer of sensory rhodopsin (SRII) at different applied potentials. It is demonstrated that the interpretations of all of these experiments critically depend on the orientation of the solid-supported membrane protein. Finally, future directions of SEIRAS including cellular systems are discussed. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.

  10. Hydration in Lipid Monolayers: Correlation of Water Activity and Surface Pressure.

    Science.gov (United States)

    Disalvo, E Anibal; Hollmann, Axel; Martini, M Florencia

    2015-01-01

    In order to give a physical meaning to each region of the membrane we define the interphase as the region in a lipid membrane corresponding to the polar head groups imbibed in water with net different properties than the hydrocarbon region and the water phase. The interphase region is analyzed under the scope of thermodynamics of surface and solutions based on the definition of Defay-Prigogine of an interphase and the derivation that it has in the understanding of membrane processeses in the context of biological response. In the view of this approach, the complete monolayer is considered as the lipid layer one molecule thick plus the bidimensional solution of the polar head groups inherent to it (the interphase region). Surface water activity appears as a common factor for the interaction of several aqueous soluble and surface active proteins with lipid membranes of different composition. Protein perturbation can be measured by changes in the surface pressure of lipid monolayers at different initial water surface activities. As predicted by solution chemistry, the increase of surface pressure is independent of the particle nature that dissolves. Therefore, membranes give a similar response in terms of the determined surface states given by water activity independent of the protein or peptide.

  11. N-Hydroxysuccinimide-terminated self-assembled monolayers on gold for biomolecules immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Cabrita, J.F. [Laboratorio de SPM, Faculdade de Ciencias da Universidade de Lisboa, Ed. ICAT, Campo Grande, 1749-016 Lisbon (Portugal); CQB, Departamento de Quimica e Bioquimica da Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisbon (Portugal); Abrantes, L.M. [Laboratorio de SPM, Faculdade de Ciencias da Universidade de Lisboa, Ed. ICAT, Campo Grande, 1749-016 Lisbon (Portugal); CQB, Departamento de Quimica e Bioquimica da Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisbon (Portugal); Viana, A.S. [Laboratorio de SPM, Faculdade de Ciencias da Universidade de Lisboa, Ed. ICAT, Campo Grande, 1749-016 Lisbon (Portugal)]. E-mail: anaviana@icat.fc.ul.pt

    2005-03-15

    Pure and mixed N-hydroxysuccinimide-terminated and butanethiol monolayers were prepared on flat gold (1 1 1) surfaces with the intent of developing suitable platforms for the direct biomolecules immobilisation. The self-assembled monolayers (SAMs) were characterised by electrochemical reductive desorption of the thiolate from the gold surface. The data have shown that certain solution proportions of the two compounds yield modified electrodes exhibiting intermediate electrochemical behaviour of the corresponding pure SAMs. The reactivity of the terminal N-hydroxysuccinimide (NHS) towards amine functionalities has been tested for the covalent attachment of Dopamine. The cyclic voltammetric responses of the investigated monolayers, after contacting with a Dopamine solution, have confirmed the chemical coupling of the amine as well as the formation of mixed SAMs. The Dopamine surface coverage increased with the amount of surface NHS. Laccase was also successfully immobilised onto this modified electrodes. The electrochemical behaviour of the modified SAMs with Laccase indicates direct electron transfer between the immobilised enzyme and the gold surface. Evidence for Laccase immobilisation was also provided by atomic force microscopic measurements.

  12. pH-regulated release of dopamine from well-ordered self-assembled monolayers: electrochemical studies.

    Science.gov (United States)

    Kazemi, Sayed Habib; Alizadeh, Abdolhamid; Mohamadi, Rahim; Khodaei, Mohammad Mahdi; Kordestani, Davood

    2013-12-01

    In the present work, gold electrode modified with novel aldehyde-terminated self-assembled monolayers (SAMs) was used for controllable load and release of dopamine molecules by pH triggering. Electrochemical techniques including cyclic voltammetry (CV) and electrochemcial impedance spectroscopy (EIS) were employed to investigate the SAMs characteristic on the gold electrode surface. The electrochemical experiments indicated Faradaic behavior for the electrode surface after its modification with dopamine. Notably, it was observed that decreasing the conditioning pH, results in a decrease of peak currents, presumably due to the hydrolysis of the terminal imine bonds and releasing the dopamine moiety into the solution. Moreover, the preliminary kinetics studies were done for dopamine release from the SAMs surface as a model to design future drug delivery systems. Finally, the rate constant of dopamine release from the SAMs modified surface estimated to be 0.167 day(-1) at pH=3.

  13. Electrochemically driven organic monolayer formation on silicon surfaces using alkylammonium and alkylphosphonium reagents

    Science.gov (United States)

    Wang, Dong; Buriak, Jillian M.

    2005-10-01

    The functionalization of silicon surfaces with organic monolayers, bound through Si-C bonds, is an area of wide interest due to the technological promise of organosilicon hybrid devices, but also to investigate fundamental surface reactivity. In this paper, the use of alkylammonium and alkylphosphonium cations as sources of organic moieties to bind to hydrogen-terminated flat and porous silicon is demonstrated. Tetraalkylammonium, tetraalkyl/arylphosphonium reagents, and alkyl pyridinium salts can be utilized, but trialkylammonium salts cannot as they yield substantial surface oxidation. Under electrochemical conditions, either potentiostatic or galvanostatic modes, alkyl groups derived from the ammonium or phosphonium salts are grafted to the silicon surface and are bound through Si-C bonds. Covalent attachment of the organic monolayers to the surface was demonstrated by XPS, AFM scribing, and FTIR. The mechanism may proceed via reduction of the ammonium salt yielding alkyl radicals, R rad , which may be reduced to R - and attack surface Si-Si bonds, leading to Si-C bonds, or the formation of silyl anions (≡Si -) under the cathodic conditions followed by nucleophilic attack on the trialkylammonium cation.

  14. 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....

  15. Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment

    Science.gov (United States)

    Ito, Takashi; Perera, D. M. Neluni T.; Nagasaka, Shinobu

    2008-01-01

    This article describes an undergraduate electrochemistry laboratory experiment in which the students measure the L-ascorbic acid content of a real sample. Gold electrodes modified with self-assembled monolayers (SAMs) of thioctic acid and cysteamine are prepared to study the effects of surface modification on the electrode reaction of L-ascorbic…

  16. 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...

  17. 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…

  18. 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}SAMs of an other alkanethiol on Au(111) in a densely packed phase. Furthermore the 2PPE data indicated that the high quality of the ex situ prepared SAMs supported the formation of image potential states. The reversible photo- and thermally activated isomerization of the molecular switch 3-(4-(4-Hexyl-phenylazo)-phenoxy)-propane-1-thiol (ABT), deposited by self-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

  19. Variation of Surface Adhesion Force During the Formation of OTS Self-assembled Monolayer Investigated by AFM

    Institute of Scientific and Technical Information of China (English)

    徐国华; HigashitaniKo

    1999-01-01

    Variation of the surface adhesion force during the formation of octadecyl trichlororilane (OTS) .self-assembled monolayer on a glass substrate surface was investigated hy atomic force microscope (AFM). The research shows that the hydrophobicity and the adbeslon force of the sample surface increases gradualy while the substrate surface is covered by OTS molecules as the reaction proceeds. After 15 min reaction, a cloee-pac.ked and smooth OTS self-assembled monolayer could from on the glass subetrate surface with an advancing contact angle of 105° and an interfaeial energy of 55.79 mJ.m-2.

  20. Enhanced vertical carrier mobility in poly(3-alkylthiophene) thin films sandwiched between self-assembled monolayers and surface-segregated layers.

    Science.gov (United States)

    Ma, Jusha; Hashimoto, Kazuhito; Koganezawa, Tomoyuki; Tajima, Keisuke

    2014-04-07

    End-functionalized poly(3-butylthiophene) with a thiol group (P3BT-S) was synthesized and used to form a self-assembled monolayer (SAM). It can induce the end-on orientation in the thin film which has the potential to further enhance hole mobility up to 1.1 × 10(-2) cm(2) V(-1) s(-1) in the vertical direction.

  1. Electrical resistivity of nanoporous gold modified with thiol self-assembled monolayers

    Science.gov (United States)

    Hakamada, Masataka; Kato, Naoki; Mabuchi, Mamoru

    2016-11-01

    The electrical resistivity of nanoporous gold (NPG) modified with thiol self-assembled monolayers (SAMs) has been measured at 298 K using a four-probe method. We found that the adsorption of thiol SAMs increases the electrical resistivity of NPG by up to 22.2%. Dependence of the electrical resistivity on the atmosphere (air or water) was also observed in SAMs-modified NPG, suggesting that the electronic states of the tail groups affect the electrons of the binding sulfur and adjacent surface gold atoms. The present results suggest that adsorption of thiol molecules can influence the behavior of the conducting electrons in NPG and that modification of NPG with SAMs may be useful for environmental sensing.

  2. Toward the Control of the Creation of Mixed Monolayers on Glassy Carbon Surfaces by Amine Oxidation.

    Science.gov (United States)

    Groppi, Jessica; Bartlett, Philip N; Kilburn, Jeremy D

    2016-01-18

    A versatile and simple methodology for the creation of mixed monolayers on glassy carbon (GC) surfaces was developed, using an osmium-bipyridyl complex and anthraquinone as model redox probes. The work consisted in the electrochemical grafting on GC of a mixture of mono-protected diamine linkers in varying ratios which, after attachment to the surface, allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to remove one of the protecting groups selectively, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the resulting surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution.

  3. Adjusting the surface areal density of click-reactive azide groups by kinetic control of the azide substitution reaction on bromine-functional SAMs.

    Science.gov (United States)

    Zhang, Shuo; Maidenberg, Yanir; Luo, Kai; Koberstein, Jeffrey T

    2014-06-03

    Azide-alkyne click chemistry has emerged as an important and versatile means for tethering a wide variety of guest molecules to virtually any substrate. In many of these applications, it is important to exercise control over the areal density of surface functional groups to achieve a desired areal density of the tethered guest molecule of interest. We demonstrate herein that the areal density of surface azide groups on flat germanium surfaces and nanoparticle substrates (silica and iron oxide) can be controlled kinetically by appropriately timed quenching of the S(N)2 substitution reaction of bromo-alkane-silane monolayers induced by the addition of sodium azide. The kinetics of the azide substitution reaction on monolayers formed on flat Ge substrates, determined by attenuated total reflection infrared spectroscopy (ATR-IR), are found to be identical to those for monolayers formed on both silica and iron oxide nanoparticles, the latter determined by transmission infrared spectroscopy. To validate the method, the percentages of surface bromine groups converted to azide groups after various reaction times were measured by quenching the S(N)2 reaction followed by analysis with ATR-IR (for Ge) and thermogravimetric analysis (after a subsequent click reaction with an alkyne-terminal polymer) for the nanoparticle substrates. The conversions found after quenching agree well with those expected from the standard kinetic curves. The latter result suggests that the kinetic method for the control of azide group areal density is a versatile means for functionalizing substrates with a prescribed areal density of azide groups for subsequent click reactions, and that the method is universal for any substrate, flat or nanoparticle, that can be modified with bromo-alkane-silane monolayers. Regardless of the surface geometry, we find that the azide substitution reaction is complete within 2-3 h, in sharp contrast to previous reports that indicate times of 48-60 h required for

  4. Electronic Structure of Single-Crystal Monolayer Graphene on Hydrogen-Terminated Germanium Surface

    Science.gov (United States)

    Ahn, Sung Joon; Lee, Jae-Hyun; Ahn, Joung Real; Whang, Dongmok

    2015-03-01

    Graphene, atomically flat 2-Dimensional layered nano material, has a lot of interesting characteristics from its unusual electronic structure. Almost properties of graphene are influenced by its crystallinity, therefore the uniform growth of single crystal graphene and layer control over the wafer scale areas remains a challenge in the fields of electronic, photonic and other devices based on graphene. Here, we report the method to make wafer scale single crystal monolayer graphene on hydrogen terminated germanium(110) surface and properties and electronic band structure of the graphene by using the tool of scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, electron transport measurement, electron diffraction and angle-resolved photoemission spectroscopy.

  5. Surface properties and morphology of mixed POSS-DPPC monolayers at the air/water interface.

    Science.gov (United States)

    Rojewska, Monika; Skrzypiec, Marta; Prochaska, Krystyna

    2017-02-01

    From the point of view of the possible medical applications of POSS (polyhedral oligomeric silsesquioxanes), it is crucial to analyse interactions occurring between POSS and model biological membrane at molecular level. Knowledge of the interaction between POSS and DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) allows prediction of the impact of POSS contained in biomaterials or cosmetics on a living organism. In the study presented, the surface properties and morphology of Langmuir monolayers formed by mixtures of POSS and the phospholipid (DPPC) at the air/water surface are examined. We selected two POSS derivatives, with completely different chemical structure of substituents attached to the corner of the silicon open cage, which allowed the analysis of the impact of the character of organic moieties (strongly hydrophobic or clearly hydrophilic) on the order of POSS molecules and their tendency to form self-aggregates at the air/water surface. POSS derivatives significantly changed the profile of the π-A isotherms obtained for DPPC but in different ways. On the basis of the regular solution theory, the miscibility and stability of the two components in the monolayer were analysed in terms of compression modulus (Cs(-1)), excess Gibbs free energy (ΔGexc), activity coefficients (γ) and interaction parameter (ξ). The results obtained indicate the existence of two different interaction mechanisms between DPPC and POSS which depend on the chemical character of moieties present in POSS molecules.

  6. Surface Coverage and Structure of Mixed DNA/Alkylthiol Monolayers on Gold: Characterization by XPS, NEXAFS, and Fluorescence Intensity Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lee,C.; Gong, P.; Harbers, G.; Grainger, D.; Castner, D.; Gamble, L.

    2006-01-01

    Self-assembly of thiol-terminated single-stranded DNA (HS-ssDNA) on gold has served as an important model system for DNA immobilization at surfaces. Here, we report a detailed study of the surface composition and structure of mixed self-assembled DNA monolayers containing a short alkylthiol surface diluent [11-mercapto-1-undecanol (MCU)] on gold supports. These mixed DNA monolayers were studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and fluorescence intensity measurements. XPS results on sequentially adsorbed DNA/MCU monolayers on gold indicated that adsorbed MCU molecules first incorporate into the HS-ssDNA monolayer and, upon longer MCU exposures, displace adsorbed HS-ssDNA molecules from the surface. Thus, HS-ssDNA surface coverage steadily decreased with MCU exposure time. Polarization-dependent NEXAFS and fluorescence results both show changes in signals consistent with changes in DNA orientation after only 30 min of MCU exposure. NEXAFS polarization dependence (followed by monitoring the N 1s{yields}{pi}* transition) of the mixed DNA monolayers indicated that the DNA nucleotide base ring structures are oriented more parallel to the gold surface compared to DNA bases in pure HS-ssDNA monolayers. This indicates that HS-ssDNA oligomers reorient toward a more-upright position upon MCU incorporation. Fluorescence intensity results using end-labeled DNA probes on gold show little observable fluorescence on pure HS-ssDNA monolayers, likely due to substrate quenching effects between the fluorophore and the gold. MCU diluent incorporation into HS-ssDNA monolayers initially increases DNA fluorescence signal by densifying the chemisorbed monolayer, prompting an upright orientation of the DNA, and moving the terminal fluorophore away from the substrate. Immobilized DNA probe density and DNA target hybridization in these mixed DNA monolayers, as well as effects of MCU diluent on DNA hybridization in

  7. Surface Coverage and Structure of Mixed DNA/Alkylthiol Monolayers on Gold: Characterization by XPS, NEXAFS, and Fluorescence Intensity Measurements

    Science.gov (United States)

    Lee, Chi-Ying; Gong, Ping; Harbers, Gregory M.; Grainger, David W.; Castner, David G.; Gamble, Lara J.

    2006-01-01

    Self-assembly of thiol-terminated single-stranded DNA (HS-ssDNA) on gold has served as an important model system for DNA immobilization at surfaces. Here, we report a detailed study of the surface composition and structure of mixed self-assembled DNA monolayers containing a short alkylthiol surface diluent [11-mercapto-1-undecanol (MCU)] on gold supports. These mixed DNA monolayers were studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and fluorescence intensity measurements. XPS results on sequentially adsorbed DNA/MCU monolayers on gold indicated that adsorbed MCU molecules first incorporate into the HS-ssDNA monolayer and, upon longer MCU exposures, displace adsorbed HS-ssDNA molecules from the surface. Thus, HS-ssDNA surface coverage steadily decreased with MCU exposure time. Polarization-dependent NEXAFS and fluorescence results both show changes in signals consistent with changes in DNA orientation after only 30 min of MCU exposure. NEXAFS polarization dependence (followed by monitoring the N 1s → π* transition) of the mixed DNA monolayers indicated that the DNA nucleotide base ring structures are oriented more parallel to the gold surface compared to DNA bases in pure HS-ssDNA monolayers. This indicates that HS-ssDNA oligomers reorient toward a more-upright position upon MCU incorporation. Fluorescence intensity results using end-labeled DNA probes on gold show little observable fluorescence on pure HS-ssDNA monolayers, likely due to substrate quenching effects between the fluorophore and the gold. MCU diluent incorporation into HS-ssDNA monolayers initially increases DNA fluorescence signal by densifying the chemisorbed monolayer, prompting an upright orientation of the DNA, and moving the terminal fluorophore away from the substrate. Immobilized DNA probe density and DNA target hybridization in these mixed DNA monolayers, as well as effects of MCU diluent on DNA hybridization in complex

  8. Surface coverage and structure of mixed DNA/alkylthiol monolayers on gold: characterization by XPS, NEXAFS, and fluorescence intensity measurements.

    Science.gov (United States)

    Lee, Chi-Ying; Gong, Ping; Harbers, Gregory M; Grainger, David W; Castner, David G; Gamble, Lara J

    2006-05-15

    Self-assembly of thiol-terminated single-stranded DNA (HS-ssDNA) on gold has served as an important model system for DNA immobilization at surfaces. Here, we report a detailed study of the surface composition and structure of mixed self-assembled DNA monolayers containing a short alkylthiol surface diluent [11-mercapto-1-undecanol (MCU)] on gold supports. These mixed DNA monolayers were studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and fluorescence intensity measurements. XPS results on sequentially adsorbed DNA/MCU monolayers on gold indicated that adsorbed MCU molecules first incorporate into the HS-ssDNA monolayer and, upon longer MCU exposures, displace adsorbed HS-ssDNA molecules from the surface. Thus, HS-ssDNA surface coverage steadily decreased with MCU exposure time. Polarization-dependent NEXAFS and fluorescence results both show changes in signals consistent with changes in DNA orientation after only 30 min of MCU exposure. NEXAFS polarization dependence (followed by monitoring the N 1s --> pi* transition) of the mixed DNA monolayers indicated that the DNA nucleotide base ring structures are oriented more parallel to the gold surface compared to DNA bases in pure HS-ssDNA monolayers. This indicates that HS-ssDNA oligomers reorient toward a more-upright position upon MCU incorporation. Fluorescence intensity results using end-labeled DNA probes on gold show little observable fluorescence on pure HS-ssDNA monolayers, likely due to substrate quenching effects between the fluorophore and the gold. MCU diluent incorporation into HS-ssDNA monolayers initially increases DNA fluorescence signal by densifying the chemisorbed monolayer, prompting an upright orientation of the DNA, and moving the terminal fluorophore away from the substrate. Immobilized DNA probe density and DNA target hybridization in these mixed DNA monolayers, as well as effects of MCU diluent on DNA hybridization in complex

  9. 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.

  10. 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.

  11. 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.

  12. Interaction of hydrocarbon monolayer surfaces across n-alkanes: A steric repulsion

    Science.gov (United States)

    Herder, Christina E.; Ninham, Barry W.; Christenson, Hugo K.

    1989-05-01

    We present results of force measurements between hydrocarbon monolayer surfaces across n-alkanes (hexane, decane, and tetradecane). The interaction is qualitatively different from that of any previously studied system and, in particular, bears no resemblance to an oscillatory solvation force. Instead, the force is repulsive from about 2.5 nm, with the exception of a shallow minimum just outside a force maximum at 0.8-0.9 nm. At smaller separations the force becomes attractive and there is a weak adhesion at contact. We suggest that the force law is due to a steric effect—a repulsive interaction originating in restrictions on chain conformations of the alkanes at small surface separations. This interaction is accessible via simple mean-field theories. The similarity of the liquid-liquid and liquid-surface interactions allows this to dominate over solvation effects. The results are of significance for interaggregate interactions in lamellar liquid crystals, microemulsions, and surfactant-stabilized dispersions.

  13. Infrared beam-steering using acoustically modulated surface plasmons over a graphene monolayer

    KAUST Repository

    Chen, Paiyen

    2014-09-01

    We model and design a graphene-based infrared beamformer based on the concept of leaky-wave (fast traveling wave) antennas. The excitation of infrared surface plasmon polaritons (SPPs) over a \\'one-atom-thick\\' graphene monolayer is typically associated with intrinsically \\'slow light\\'. By modulating the graphene with elastic vibrations based on flexural waves, a dynamic diffraction grating can be formed on the graphene surface, converting propagating SPPs into fast surface waves, able to radiate directive infrared beams into the background medium. This scheme allows fast on-off switching of infrared emission and dynamic tuning of its radiation pattern, beam angle and frequency of operation, by simply varying the acoustic frequency that controls the effective grating period. We envision that this graphene beamformer may be integrated into reconfigurable transmitter/receiver modules, switches and detectors for THz and infrared wireless communication, sensing, imaging and actuation systems.

  14. 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.

  15. Photopatterning of self-assembled alkanethiolate monolayers on gold. A simple monolayer photoresist utilizing aqueous chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Huang, J.; Hemminger, J.C. (Univ. of California, Irvine, CA (United States)); Dahlgren, D.A. (Photometrics, Huntington Beach, CA (United States))

    1994-03-01

    In this paper we demonstrate that self-assembled monolayers (SAMs) of alkanethiols on gold can be used as effective photoresists. UV photolysis of an alkanethiol SAM generates the corresponding sulfonate in the monolayer film. The sulfonate is easily rinsed off of the surface with water, exposing a clean gold substrate, which can then be modified with subsequent chemistry. We describe here experiments in which an alkanethiol SAM on a gold film on silicon is irradiated through a mask, followed by immersion of the sample in an aqueous acid etching solution (HCI:HNO[sub 3]:H[sub 2]O = 3:1:4). The gold is etched away from the areas which have been exposed to UV radiation leaving a pattern which reproduces the original mask. The spatial resolution in the present experiments is limited by the mask which is a 6-[mu]m wire grid. Scanning electron microscopy images of patterned samples show sharp edges to the features suggesting that spatial patterning on the 1-[mu]m scale should be attainable with this simple chemistry. 11 refs., 4 figs.

  16. Fluorescence detection and imaging of amino-functionalized organic monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Shirahata, Naoto [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)], E-mail: SHIRAHATA.naoto@nims.go.jp; Furumi, Seiichi [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Masuda, Yoshitake; Hozumi, Atsushi [National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Shimo-shidami, Moriyama, Nagoya 463-8560 (Japan); Sakka, Yoshio [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2008-03-03

    Amino-terminated organic monolayer formed on silicon covered with native oxide (SiO{sub 2}/Si) was directly visualized under observation with fluorescent microscopy. This successful fluorescence visualization was achieved by a combination of fluorescamine method and photopatterning of the amino-terminated surface. As a typical example, an amino-terminated self-assembled monolayer (SAM) was formed on SiO{sub 2}/Si substrate in a vapor of 12.5 vol.% solution of N-(6-aminohexyl)-3-aminopropyltrimethoxysilane [H{sub 2}N(CH{sub 2}){sub 6}NH(CH{sub 2}){sub 3}Si(OCH{sub 3}){sub 3}, AHAPS] diluted with absolute toluene. A micropattern of AHAPS-SAM was photolithographycally prepared using 172 nm vacuum ultraviolet (VUV) light under a reduced pressure of 10 Pa for 30 min through a photomask. The resultant micropattern composed of AHAPS- and SiOH-covered regions was provided to fluorescamine method. Due to a nonluminescence of fluorescamine itself under UV/visible irradiation, a fluorescent emission could not be observed on SiOH regions of the micropattern. In contrast, fluorescamine reacted with the outermost amino group of the AHAPS-SAM to give a fluorescent emission. A comprehensible fluorescence method for verifying formation of an amino-terminated organic monolayer has been developed.

  17. 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.

  18. 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.

  19. 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

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

    Science.gov (United States)

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

    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 (-CH3) 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.

  1. 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

  2. Molecular simulations of mixed self-assembled monolayer coated gold nanoparticles in water.

    Science.gov (United States)

    J, Meena Devi

    2015-06-01

    Molecular dynamics simulations have been employed to study the hydration of a series of nanoparticles, each of which was coated with a mixed self-assembled monolayer (SAM) comprising methyl- and hydroxy-terminated alkane thiol chains. The mixing ratio of those chains are different for each nanoparticle. The simulations focused on the wetting behavior of the SAM-coated gold nanoparticles and the distribution and structure of their interfacial water molecules. The interactions of the mixed SAM-coated gold nanoparticles with water were analyzed by evaluating the radial distribution function, hydrogen bonds, the dipole orientations of the water molecules, and the water residence time in the interfacial region. The wettability of the mixed SAM-coated gold nanoparticles improved as the concentration of terminal hydroxy moieties was increased. The distribution and dynamics of the interfacial water molecules were found to be influenced by the mixing ratio of the terminal moieties of the SAM chains. The results of our simulations suggest that the surface interactions of the mixed SAM-coated gold nanoparticles with the aqueous medium can be modulated by systematically altering the mixing ratio of the terminal methyl and hydroxy moieties. This work may lead to new biological and technological applications and inspire the development of novel biomimetic materials. Graphical Abstract Mixed SAM-coated gold nanoparticles.

  3. 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.

  4. Enantiopure chiral poly(glycerol methacrylate) self-assembled monolayers knock down protein adsorption and cell adhesion.

    Science.gov (United States)

    Li, Zheng; Köwitsch, Alexander; Zhou, Guoying; Groth, Thomas; Fuhrmann, Bodo; Niepel, Marcus; Amado, Elkin; Kressler, Jörg

    2013-10-01

    Chirality plays a fundamental role not only in biological systems, but also in synthetic materials intended for bio-applications. Self-assembled monolayers (SAMs) are prepared on gold surfaces through a "grafting to" method from racemic or enantiopure chiral poly(glycerol methacrylate)s (PGMA(rac), PGMA(R), and PGMA(S)), having a thiol endgroup. Such SAMs constitute a chemically and structurally well-defined model substrate for studying protein adsorption and cell adhesion as a function of the polymer chirality. Surface plasmon resonance measurements reveal that PGMA SAMs greatly reduce the adsorption of bovine serum albumin (BSA) compared to bare gold surfaces. Interestingly, enantiopure SAMs based on PGMA(R) or PGMA(S) show a significantly larger reduction in BSA adsorption than PGMA(rac)-covered surfaces. Studies with the monocytic cell line THP-1 show a similar relationship between enantiopurity of PGMA SAMs and the extent of cell adhesion. Ellipsometry and Raman spectroscopy measurements indicate that SAMs formed by PGMA(rac) have a higher grafting density compared to SAMs of PGMA(R) and PGMA(S). This seems to be due to the ability of PGMA(rac) to form more intermolecular hydrogen bonds among polymer chains compared to the enantiopure PGMAs. Circular dichroism spectroscopy provide evidence that enantiopure polymers adopt a chiral ordered conformation, most likely helical, in aqueous solutions. It is concluded that a higher water content of SAMs formed by enantiopure PGMA(S) and PGMA(R) SAMs arises from the macromolecular chiral conformation adopted by their enantiopure PGMA chains, and it is the decisive reason for the reduced BSA adsorption and cell adhesion as compared to PGMA(rac) SAMs.

  5. Preparation and characterization of alkylphosphonic acid self-assembled monolayers on titanium alloy by chemisorption and electrochemical deposition.

    Science.gov (United States)

    Metoki, Noah; Liu, Liang; Beilis, Edith; Eliaz, Noam; Mandler, Daniel

    2014-06-17

    Ti-6Al-4V alloy is the most commonly used alloy for dental and orthopedic implants. In order to improve osseointegration, different surface modification methods are usually employed, including self-assembled monolayers (SAMs). This study presents an investigation of both active (electroassisted) and passive (adsorption) approaches for the modification of Ti-6Al-4V using alkylphosphonic acid. The monolayers were characterized by cyclic voltammetry, double-layer capacitance, contact angle measurements, X-ray photoelectron spectroscopy, polarization modulation infrared reflection adsorption spectroscopy, electrochemical impedance spectroscopy, and corrosion potentiodynamic polarization measurements. It is shown that the electrochemically assisted monolayers, which are assembled faster, exhibit better control over surface properties, a superior degree of order, and a somewhat higher packing density. The electrosorbed SAMs also exhibit better blockage of electron transfer across the interface and thus have better corrosion resistance.

  6. Highly Polymer-Repellent yet Atomically Flat Surfaces Based on Organic Monolayers with a Single Fluorine Atom

    NARCIS (Netherlands)

    Wang, Zhanhua; Pujari, S.P.; Lagen, van B.; Smulders, M.M.J.; Zuilhof, H.

    2016-01-01

    Organic monolayers or polymer brushes, often in combination with surface structuring, are widely used to prevent nonspecific adsorption of polymeric or biological material on sensor and microfluidic surfaces. Here it is demonstrated for the first time how robust, covalently attached alkyne-derived m

  7. Sub-monolayer film growth of a volatile lanthanide complex on metallic surfaces

    Science.gov (United States)

    Chen, Jinjie; Edelmann, Kevin; Wulfhekel, Wulf

    2015-01-01

    Summary We deposited a volatile lanthanide complex, tris(2,2,6,6-tetramethyl-3,5-heptanedionato)terbium(III), onto metal surfaces of Cu(111), Ag(111) and Au(111) in vacuum and observed well-ordered sub-monolayer films with low temperature (5 K) scanning tunneling microscopy. The films show a distorted three-fold symmetry with a commensurate structure. Scanning tunneling spectroscopy reveals molecular orbitals delocalized on the ligands of the molecule. Our results imply that this complex can be transferred onto the metal substrates without molecular decomposition or contamination of the surface. This new rare-earth-based class of molecules broadens the choice of molecular magnets to study with scanning tunneling microscopy. PMID:26733215

  8. Sub-monolayer film growth of a volatile lanthanide complex on metallic surfaces

    Directory of Open Access Journals (Sweden)

    Hironari Isshiki

    2015-12-01

    Full Text Available We deposited a volatile lanthanide complex, tris(2,2,6,6-tetramethyl-3,5-heptanedionatoterbium(III, onto metal surfaces of Cu(111, Ag(111 and Au(111 in vacuum and observed well-ordered sub-monolayer films with low temperature (5 K scanning tunneling microscopy. The films show a distorted three-fold symmetry with a commensurate structure. Scanning tunneling spectroscopy reveals molecular orbitals delocalized on the ligands of the molecule. Our results imply that this complex can be transferred onto the metal substrates without molecular decomposition or contamination of the surface. This new rare-earth-based class of molecules broadens the choice of molecular magnets to study with scanning tunneling microscopy.

  9. 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

    2016-08-04

    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.

  10. SAM in a Nutshell.

    Science.gov (United States)

    Givens, Larry R.

    2000-01-01

    Explains what the Association of Higher Education Facilities Officers' Strategic Assessment Model (SAM) is and how to use it to achieve organizational excellence through continuous improvement. Showing features of both the Malcolm Baldrige programs and the Balanced Scorecard, the SAM components are described along with an explanation of the four…

  11. Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

    OpenAIRE

    Guus Rijnders; Jurriaan Huskens; van der Wiel, Wilfred G.; Blank, Dave H. A.; Reinhoudt, David N.; Sachin Kinge; Tian Gang; Oktay Yildirim

    2010-01-01

    FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP) or phosphonoundecanoic acid (PNDA) SAMs or with poly(ethyleneimine) (PEI) as a reference. FePt NPs assem...

  12. Modification of degenerative photoluminescence in aged monolayer WSsub>2sub> by PCsub>61sub>BM surface processing.

    Science.gov (United States)

    Liu, Yu; Zheng, Xin; Li, Han; Xu, Zhongjie; Jiang, Tian

    2017-02-01

    Owing to their unique physical properties, monolayer transition metal dichalcogenides (TMDCs) have been widely used in applications of light-emitting diodes (LEDs). However, monolayers of TMDCs undergo dramatic aging effects, including intense degradation in optical behavior, extensive cracking, and severe quenching of the direct gap photoluminescence (PL), seriously limiting the device performance. In this work, we show that monolayer WSsub>2sub> stored for three months even in the glovebox exhibits obvious degenerative PL with changed peak position that can be attributed to the presence of a large number of trions induced by the aging effect. PCsub>61sub>BM surface processing was used to modify the surface of the aged monolayer WSsub>2sub>. As expected, higher uniformity in the PL spectrum was obtained. Besides, the PL peak wavelength was modified to be the same as that of the nonaged one and did not change even at higher excitation power. This strategy is shown to successfully suppress the formation of the trion by transferring the excess electrons from WSsub>2sub> to PCsub>61sub>BM. The results demonstrate the feasibility of applying PCsub>61sub>BM surface modification to improve the performance of the LED based on monolayer WSsub>2sub>.

  13. The influence of the surface composition of mixed monolayer films on the evaporation coefficient of water.

    Science.gov (United States)

    Miles, Rachael E H; Davies, James F; Reid, Jonathan P

    2016-07-20

    We explore the dependence of the evaporation coefficient of water from aqueous droplets on the composition of a surface film, considering in particular the influence of monolayer mixed component films on the evaporative mass flux. Measurements with binary component films formed from long chain alcohols, specifically tridecanol (C13H27OH) and pentadecanol (C15H31OH), and tetradecanol (C14H29OH) and hexadecanol (C16H33OH), show that the evaporation coefficient is dependent on the mole fractions of the two components forming the monolayer film. Immediately at the point of film formation and commensurate reduction in droplet evaporation rate, the evaporation coefficient is equal to a mole fraction weighted average of the evaporation coefficients through the equivalent single component films. As a droplet continues to diminish in surface area with continued loss of water, the more-soluble, shorter alkyl chain component preferentially partitions into the droplet bulk with the evaporation coefficient tending towards that through a single component film formed simply from the less-soluble, longer chain alcohol. We also show that the addition of a long chain alcohol to an aqueous-sucrose droplet can facilitate control over the degree of dehydration achieved during evaporation. After undergoing rapid gas-phase diffusion limited water evaporation, binary aqueous-sucrose droplets show a continued slow evaporative flux that is limited by slow diffusional mass transport within the particle bulk due to the rapidly increasing particle viscosity and strong concentration gradients that are established. The addition of a long chain alcohol to the droplet is shown to slow the initial rate of water loss, leading to a droplet composition that remains more homogeneous for a longer period of time. When the sucrose concentration has achieved a sufficiently high value, and the diffusion constant of water has decreased accordingly so that bulk phase diffusion arrest occurs in the monolayer

  14. The Tunable Hybrid Surface Phonon and Plasmon Polariton Modes in Boron Nitride Nanotube and Graphene Monolayer Heterostructures

    CERN Document Server

    Sun, Yu; Cheng, Jiangtao; Liu, Jiansheng

    2014-01-01

    The hybrid modes incorporating surface phonon polariton (SPhP) modes in boron nitride nanotubes (BNNTs) and surface plasmon polariton (SPP) modes in graphene monolayers are theoretically studied. The combination of the 1D BNNTs and 2D graphene monolayer further improves the modal characteristics with electrical tunability. Superior to the graphene monolayers, the proposed heterostructures supports single mode transmission with lateral optical confinement. The modal characteristics can be shifted from SPP-like toward SPhP-like. Both the figure of merit and field enhancement of hybrid modes are improved over 3 times than those of BNNT SPhP modes, which may further enable sub-wavelength mid-infrared applications.

  15. Chemisorption and catalytic reactivity of cobalt and sulfur monolayers on ordered molybdenum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Knight, C.C.

    1992-03-01

    Complex Co/Mo sulfide catalysts are modelled by the chemisorption of layers on Mo single crystal surfaces. Growth and structure of overlayers on flat, stepped and kinked surfaces were investigated. Growth of Co overlayers on clean and S covered Mo surfaces was studied using AES and CO chemisorption; results reveal that Co grows as a flat monolayer on clean Mo surfaces. Co multilayers then form 3-D islands. When Co is deposited on S covered surfaces, the S overlayer migrates to the top; this topmost overlayer reduces CO adsorption capacity. While growth mode of Co overlayers are similar on flat and stepped surfaces, the number and type of ordered Co and S structures on flat and stepped surfaces are different. In the case of Co, an ordered (3 {times} 1) structure is formed on Mo(910) and (28,4,1) surfaces; this structure does not develop on clean (100) surface. Only one of two possible (3 {times} 1) Co domains are formed on Mo(910) and Mo(28,4,1) surfaces. These domains have one side of (3 {times} 1) unit cell parallel to the step edges, suggesting that Co adsorbs at the step edges. The (3 {times} 1) structure does not form on Mo(911) surface, indicating that step orientation can restrict formation of ordered overlayers. For chemisorbed S, only a subset of ordered overlayers on flat (100) surface nucleate on (910) and (911) and (28,4,1) surfaces. Ordered S overlayers also form domains that maximize the number of sulfur-step atom bonds. The adsorption and ordering of S overlayers on stepped and kinked Mo surfaces lead to doubling of step height and terrace width. Thiophene hydrodesulfurization (HDS) reactions were performed over Mo crystal surfaces modified by chemisorption of S, Co, C, and S + Co. The stepped and kinked Mo surfaces have reactivities greater than low Miller index (100) surface. Chemisorption of adsorbates decreased the thiophene HDS reactivity. Deposition of Co on Mo single crystal surfaces did not lead to increased HDS activity.

  16. Giant perpendicular magnetic anisotropy of an Ir monolayer on a NiAl(001) surface

    Science.gov (United States)

    Kim, Dongyoo; Yang, Jeonghwa; Hong, Jisang

    2009-08-01

    Using the state-of-the-art full potential linearized augmented plane-wave method, we have investigated the magnetic properties of Os and Ir monolayer (ML) film on NiAl(001) surface. It has been found that the one ML of Os and Ir film can have ferromagnetic ground state with magnetic moment of 0.35 and 0.64μB on Ni terminated surface, whereas both films display no sign of magnetic state on Al terminated surface. In addition, the surface Ni atom has an induced magnetic moment of 0.26μB in Ir/NiAl(001), while only 0.09μB is observed in Os/NiAl(001). We attribute the existence of magnetism to the interaction between 5d of adlayer and 3d of surface Ni. Moreover, we have obtained that the Os/NiAl(001) and Ir/NiAl(001) films show a perpendicular magnetic anisotropy (PMA). Surprisingly, it appears that the Ir/NiAl(001) has a giant PMA energy of 7.18 meV.

  17. Immunophenotypic analysis of human articular chondrocytes: changes in surface markers associated with cell expansion in monolayer culture.

    Science.gov (United States)

    Diaz-Romero, Jose; Gaillard, Jean Philippe; Grogan, Shawn Patrick; Nesic, Dobrila; Trub, Thomas; Mainil-Varlet, Pierre

    2005-03-01

    Cartilage tissue engineering relies on in vitro expansion of primary chondrocytes. Monolayer is the chosen culture model for chondrocyte expansion because in this system the proliferative capacity of chondrocytes is substantially higher compared to non-adherent systems. However, human articular chondrocytes (HACs) cultured as monolayers undergo changes in phenotype and gene expression known as "dedifferentiation." To gain a better understanding of the cellular mechanisms involved in the dedifferentiation process, our research focused on the characterization of the surface molecule phenotype of HACs in monolayer culture. Adult HACs were isolated by enzymatic digestion of cartilage samples obtained post-mortem. HACs cultured in monolayer for different time periods were analyzed by flow cytometry for the expression of cell surface markers with a panel of 52 antibodies. Our results show that HACs express surface molecules belonging to different categories: integrins and other adhesion molecules (CD49a, CD49b, CD49c, CD49e, CD49f, CD51/61, CD54, CD106, CD166, CD58, CD44), tetraspanins (CD9, CD63, CD81, CD82, CD151), receptors (CD105, CD119, CD130, CD140a, CD221, CD95, CD120a, CD71, CD14), ectoenzymes (CD10, CD26), and other surface molecules (CD90, CD99). Moreover, differential expression of certain markers in monolayer culture was identified. Up-regulation of markers on HACs regarded as distinctive for mesenchymal stem cells (CD10, CD90, CD105, CD166) during monolayer culture suggested that dedifferentiation leads to reversion to a primitive phenotype. This study contributes to the definition of HAC phenotype, and provides new potential markers to characterize chondrocyte differentiation stage in the context of tissue engineering applications. 2004 Wiley-Liss, Inc.

  18. Polystyrene sphere monolayer assisted electrochemical deposition of ZnO nanorods with controlable surface density

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, D., E-mail: daniel.ramirez@ucv.c [Laboratorio de Electroquimica, Pontificia Universidad Catolica de Valparaiso, Valparaiso (Chile); Gomez, H. [Laboratorio de Electroquimica, Pontificia Universidad Catolica de Valparaiso, Valparaiso (Chile); Lincot, D. [Institute de Recherche et Developpement sur l' Energie Photovoltaique-IRDEP, 6 Quai Watier 78401, Chatou Cedex (France)

    2010-02-15

    In this paper we report the zinc oxide nanorods (ZnO NRs) growth by electrochemical deposition onto polycrystalline gold electrodes modified with assemblies of polystyrene sphere monolayers (PSSMs). Growth occurs through the interstitial spaces between the hexagonally close packed spheres. ZnO NRs nucleate in the region where three adjacent spheres leave a space, being able to grow and projected over the PSSMs. The nanorod surface density (N{sub NR}) shows a linear dependence with respect to a PS sphere diameter selected. XRD analysis shows these ZnO NRs are highly oriented along the (0 0 2) plane (c-axis). This open the possibility to have electronic devices with mechanically supported nanometric materials.

  19. Surface polaritons of one-dimensional photonic crystals containing graphene monolayers

    Science.gov (United States)

    Madani, Amir; Roshan Entezar, Samad

    2014-11-01

    We investigated theoretically the existence of surface polaritons (SPs) at the interface of a one-dimensional photonic crystal containing graphene monolayers. It is shown that the structure has a new type of the photonic band gap in the THz region which is strictly omnidirectional for the TM-polarization and can support the SPs for both TM-polarization and TE-polarization. The results show that the characteristics of the SPs depends on the optical properties of the graphene sheets which can be controlled by a gate voltage. We plotted the electromagnetic field profiles of the SPs at the frequency range of the graphene induced band gap and a conventional Bragg gap of the structure. It is found that the SPs at the graphene induced band gap are more localized than the SPs at the Bragg gaps.

  20. Band structure and Fermi surface of electron-doped C60 monolayers.

    Science.gov (United States)

    Yang, W L; Brouet, V; Zhou, X J; Choi, Hyoung J; Louie, Steven G; Cohen, Marvin L; Kellar, S A; Bogdanov, P V; Lanzara, A; Goldoni, A; Parmigiani, F; Hussain, Z; Shen, Z-X

    2003-04-11

    C60 fullerides are challenging systems because both the electron-phonon and electron-electron interactions are large on the energy scale of the expected narrow band width. We report angle-resolved photoemission data on the band dispersion for an alkali-doped C60 monolayer and a detailed comparison with theory. Compared to the maximum bare theoretical band width of 170 meV, the observed 100-meV dispersion is within the range of renormalization by electron-phonon coupling. This dispersion is only a fraction of the integrated peak width, revealing the importance of many-body effects. Additionally, measurements on the Fermi surface indicate the robustness of the Luttinger theorem even for materials with strong interactions.

  1. Influence of surface properties of mix-monolayers on lipolytic hydrolysis

    DEFF Research Database (Denmark)

    Peters, Günther H. J.; Dahmen, U.; Brezesinski, G.

    2000-01-01

    Fluorescence microscopy, surface potential, and activity measurements were used to investigate the influence of fatty acids and fatty alcohols on the lipolytic activity of several lipases. We have determined the lateral lipid distribution and interfacial properties of Langmuir mixed monolayers...... correlates with the isoelectric point (pI) of the enzymes. A simpler mechanism is observed by the addition of fatty alcohol. Within the concentration range studied, 1-octadecanol is immiscible in the diacylglyceride matrix, forming liquid-condensed domains. The inhibitory effect is related to the reduction...... composed of 1,2-didecanoylglycerol/eicosanoic acid or 1,2-didecanoylglycerol/1-octadecanol molecules and have measured lipase activities toward these films. Enzymatic activities are remarkably influenced by the addition of fatty acid. Activity decreases continuously up to a mole fraction of ≈ 0.1 fatty...

  2. Controlled modulation of electronic properties of graphene by self-assembled monolayers on SiO2 substrates.

    Science.gov (United States)

    Yan, Zheng; Sun, Zhengzong; Lu, Wei; Yao, Jun; Zhu, Yu; Tour, James M

    2011-02-22

    In this study, with self-assembled monolayers (SAMs) of aminopropyl-, ammoniumpropyl-, butyl-, and 1H,1H,2H,2H-perfluorooctyltriethoxysilanes deposited in-between graphene and the SiO(2) substrate, a controlled doping of graphene was realized with a threshold voltage ranging from -18 to 30 V. In addition, the SAMs are covalently bonded to the SiO(2) surface rather than the graphene surface, thereby producing minimal effects on the mobility of the graphene. Finally, it is more stable than conventional noncovalent dopants.

  3. 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.

  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. 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

    2016-03-09

    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.

  6. Covalently attached organic monolayers on SiC and SixN4 surfaces: Formation using UV light at room temperature

    NARCIS (Netherlands)

    Rosso, M.; Giesbers, M.; Arafat, A.; Schroën, C.G.P.H.; Zuilhof, H.

    2009-01-01

    We describe the formation of alkyl monolayers on silicon carbide (SiC) and silicon-rich silicon nitride (SixN4) surfaces, using UV irradiation in the presence of alkenes. Both the surface preparation and the monolayer attachment were carried out under ambient conditions. The stable coatings obtained

  7. 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.

  8. Morphology of self assembled monolayers using liquid phase reaction on silica and their effect on the morphology of adsorbed insulin

    Science.gov (United States)

    Sharma, Indu; Pattanayek, Sudip K.; Aggarwal, Varsha; Ghosh, Subhasis

    2017-05-01

    The effect of roughness of two different categories of self-assembled monolayers (SAMs) with propyl amine and propyl groups respectively on the morphology of adsorbed insulin is observed. SAMs are obtained by liquid phase reaction of silica with organo silane coupling agents (SCA). The influence of the morphology and physical characteristics of the SAMs on the reaction time and concentration of the modifiers are explored. We have tested three SCA containing propyl amine with varying groups linked to Si present on it. In addition, we have used a silane coupling agent to prepare SAM of methyl head group. The approach of these molecules towards the surface depends on the head group and the groups linked to Si of the SCA. The morphology of the surfaces is analysed using power spectral density distribution (PSD), skewness, ellipsometry thickness and surface energy. Both chemical nature and physical morphology of the adsorbent influence the morphology of the adsorbed insulin. In general, a low number of aggregates of big size are formed on the surfaces obtained from low concentration of SAMs, while a higher number but of smaller size of aggregates are formed over surfaces obtained from 1% concentration of SAMs modifiers. The peak to valley ratio of the aggregates of insulin is strongly influenced by the size of grains of SCA over the adsorbent.

  9. Molecular dynamics studies of the melting of butane and hexane monolayers adsorbed on the basal-plane surface of graphite

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Newton, J. C.; Taub, H.

    1993-01-01

    The effect of molecular steric properties on the melting of quasi-two-dimensional solids is investigated by comparing results of molecular dynamics simulations of the melting of butane and hexane monolayers adsorbed on the basal-plane surface of graphite. These molecules differ only in their leng...

  10. Selective in situ potential-assisted SAM formation on multi electrode arrays

    Science.gov (United States)

    Haag, Ann-Lauriene; Toader, Violeta; Lennox, R. Bruce; Grutter, Peter

    2016-11-01

    The selective modification of individual components in a biosensor array is challenging. To address this challenge, we present a generalizable approach to selectively modify and characterize individual gold surfaces in an array, in an in situ manner. This is achieved by taking advantage of the potential dependent adsorption/desorption of surface-modified organic molecules. Control of the applied potential of the individual sensors in an array where each acts as a working electrode provides differential derivatization of the sensor surfaces. To demonstrate this concept, two different self-assembled monolayer (SAM)-forming electrochemically addressable ω-ferrocenyl alkanethiols (C11) are chemisorbed onto independent but spatially adjacent gold electrodes. The ferrocene alkanethiol does not chemisorb onto the surface when the applied potential is cathodic relative to the adsorption potential and the electrode remains underivatized. However, applying potentials that are modestly positive relative to the adsorption potential leads to extensive coverage within 10 min. The resulting SAM remains in a stable state while held at potentials <200 mV above the adsorption potential. In this state, the chemisorbed SAM does not significantly desorb nor do new ferrocenylalkythiols adsorb. Using three set applied potentials provides for controlled submonolayer alkylthiol marker coverage of each independent gold electrode. These three applied potentials are dependent upon the specifics of the respective adsorbate. Characterization of the ferrocene-modified electrodes via cyclic voltammetry demonstrates that each specific ferrocene marker is exclusively adsorbed to the desired target electrode.

  11. STM and XPS study on the self-assembled films of Schiff base on copper surface

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    SAMs (self-assembled monolayers) of Schiff base were prepared on the copper surface, and characterized by the modern technique of surface analysis. The results demonstrated that the well-ordered and densely packed SAMs of N-2-hydroxyphenyl-(3-methoxy-salicylidenimine), designated as V-bso, were formed on the Cu(111) surface. And two benzene rings in the V-bso molecule were not flat on the copper surface, but tilted at a certain angle. The development of this new system of self-assembly would be of significance to the application of the SAMs in the field of metal corrosion and protection.

  12. Electrochemistry of 2-dimethylaminoethanethiol SAM on gold electrode: Interaction with SWCNT-poly(m-aminobenzene sulphonic acid), electric field-induced protonation-deprotonation, and surface pKa

    CSIR Research Space (South Africa)

    Pillay, J

    2009-06-01

    Full Text Available -called electric field induced protonation-deprotonation process, hitherto observed for the -COOH terminated SAMs, is also observed for the -N(H)+(CH3)2 terminated. The surface pKa of DMAET was estimated as 7.6, smaller than its solution pKa of 10.8. It is also...

  13. SAM Photovoltaic Model Technical Reference

    Energy Technology Data Exchange (ETDEWEB)

    Gilman, P. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2015-05-27

    This manual describes the photovoltaic performance model in the System Advisor Model (SAM). The U.S. Department of Energy’s National Renewable Energy Laboratory maintains and distributes SAM, which is available as a free download from https://sam.nrel.gov. These descriptions are based on SAM 2015.1.30 (SSC 41).

  14. Adsorption and dissociation of H2S on monometallic and monolayer bimetallic Ni/Pd(111) surfaces: A first-principles study

    Science.gov (United States)

    Li, Yi; Huang, Pan; Tao, Dandan; Wu, Juan; Qiu, Mei; Huang, Xin; Ding, Kaining; Chen, Wenkai; Su, Wenyue; Zhang, Yongfan

    2016-11-01

    Periodic density functional theory calculations have been performed to investigate the adsorption structures and dissociative reaction pathways for H2S molecule on Ni(111), Pd(111) and Ni/Pd(111) monolayer bimetallic surfaces with surface monolayer and subsurface monolayer structures. Our results indicate that, for the molecular adsorption mode, the introducing Pd atoms on Ni(111) can enhance the binding strength between H2S and the surface, while an opposite effect is achieved when the Ni monolayer is formed on Pd(111) surface. The decompositions of H2S molecule on all Ni/Pd(111) surfaces are exothermic, especially for the surfaces that the top layer is composed of Ni atoms. According to the predicted minimum energy paths that connect the molecular and dissociative states, two elementary steps are found for all Ni/Pd(111) metal surfaces, and the breaking of the first Hsbnd S bond is the rate-determining step for the H2S dissociation. Our results reveal that in most cases, the decomposition of H2S molecule on the monometallic and Ni/Pd(111) monolayer bimetallic surfaces is easy to happen. However, on the monolayer Ni-Pd(111) surface, there is a competition between the trapping-desorption channel and activated dissociation channel, which implies that depositing one monolayer Ni on a Pd(111) surface may help reducing sulfur poisoning by hindering the dissociation of H2S molecule.

  15. Anti-tarnish Characteristics and Formation Mechanism of Self-Assembled Monolayers on Surface of Silver Coins%银币表面自组装膜抗变色性能及成膜机理

    Institute of Scientific and Technical Information of China (English)

    梁成浩; 杨长江; 黄乃宝; 金光明

    2013-01-01

    Octadecanethiol (C18SH) self-assembled monolayers (SAM) were prepared on the silver coin surface.The anti-tarnish characteristics of C18SH SAMs were investigated in 0.5 mol/L NaCl+0.01 mol/L Na2S solution by an electrochemical technique.The results indicate that silver's corrosion potential moves by 30 mV to positive direction after forming SAMs.C18SH SAMs could inhibit oxygen depolarization and silver sulfuration.The inhibition effect for cathode process is better than that for anode.After SAMs is formed on the surface of silver,the silver coin's charge-transfer resistance increases and double layer capacitance decreases.The formation of SAMs on silver is in accordance with a two-phase model.In the initial stage,the adsorption obeys two grade Langmuir equation,which is θ(t)=1.706ct/1+1.706ct.In the latter stage,the adsorption is the process of reforming and recrystallization,and is in accordance with onegrade Langmuir equation,which is θ (t) =1-e-0.547ct.The relationship between rate constant and temperature is ln(k)=5826/T+26.5 during absorption.The apparent activation energy of self-assembled process is 48.4 kJ/mol and the self-assembled process is controlled by chemical adsorption.%利用化学方法在银币表面制备了十八烷基硫醇组装膜(C18SH SAMs),并通过电化学技术研究了其在0.5 mol/LNaCl+0.01 mol/L Na2S溶液中的抗变色性能.结果表明:银表面形成SAMs后腐蚀电位正移30 mV;阴极氧去极化和阳极银的硫化过程均受到抑制,对阴极极化过程的阻滞作用较阳极极化过程明显;银表面成膜后,容抗弧、电荷传递系数Rt增大,双电层电容Cd降低.有效提高银币的抗变色性能.银表面C18SH SAMs的形成过程符合两阶段模型.膜初始吸附阶段(Ⅰ)为2级Langmuir吸附,重整结晶阶段(Ⅱ)为l级Langmuir吸附,动力学公式分别为,Ⅰ阶段:θ(t)=1.706ct/1+1.706ct,Ⅱ阶段:θ(t)=1-e-0.547ct.速率常数与温度的关系为ln(k)=-5826/T+26.5,自

  16. Chemoselective ligand patterning of electroactive surfaces using microfluidics.

    Science.gov (United States)

    Westcott, Nathan P; Yousaf, Muhammad N

    2009-10-01

    To generate model substrates for cell adhesion, we have developed two different biocompatible strategies based on self-assembled monolayers (SAMs) of alkanethiolates on gold terminated with latent ketones and aldehydes. Under spatial control, the hydroquinone and alcohol-terminated SAMs can be oxidized to allow for oxyamine ligand patterning on the surface with microfluidic cassettes. These immobilization strategies were characterized by electrochemistry, fluorescence, and utilizing a cell adhesive peptide, cell patterns were generated.

  17. Self-assembled monolayer-functionalized half-metallic manganite for molecular spintronics.

    Science.gov (United States)

    Tatay, Sergio; Barraud, Clément; Galbiati, Marta; Seneor, Pierre; Mattana, Richard; Bouzehouane, Karim; Deranlot, Cyrile; Jacquet, Eric; Forment-Aliaga, Alicia; Jegou, Pascale; Fert, Albert; Petroff, Frédéric

    2012-10-23

    (La,Sr)MnO(3) manganite (LSMO) has emerged as the standard ferromagnetic electrode in organic spintronic devices due to its highly spin-polarized character and air stability. Whereas organic semiconductors and polymers have been mainly envisaged to propagate spin information, self-assembled monolayers (SAMs) have been overlooked and should be considered as promising materials for molecular engineering of spintronic devices. Surprisingly, up to now the first key step of SAM grafting protocols over LSMO surface thin films is still missing. We report the grafting of dodecyl (C12P) and octadecyl (C18P) phosphonic acids over the LSMO half-metallic oxide. Alkylphosphonic acids form ordered self-assembled monolayers, with the phosphonic group coordinated to the surface and alkyl chains tilted from the surface vertical by 43° (C12P) and 27° (C18P). We have electrically characterized these SAMs in nanodevices and found that they act as tunnel barriers, opening the door toward the integration of alkylphosphonic acid//LSMO SAMs into future molecular/organic spintronic devices such as spin OLEDs.

  18. Fabrication of Calix[4]arene Derivative Monolayers to Control Orientation of Antibody Immobilization

    Directory of Open Access Journals (Sweden)

    Hongxia Chen

    2014-03-01

    Full Text Available Three calix[4]arene (Cal-4 derivatives which separately contain ethylester (1, carboxylic acid (2, and crownether (3 at the lower rim with a common reactive thiol at the upper rim were synthesized and constructed to self-assembled monolayers (SAMs on Au films. After spectroscopic characterization of the monolayers, surface coverage and orientation of antibody immobilized on the Cal-4 derivative SAMs were studied by surface plasmon resonance (SPR technique. Experimental results revealed that the antibody could be immobilized on the Cal-4 derivatives spontaneously. The orientation of absorbed antibody on the Cal-4 derivative SAMs is related to the SAM’s dipole moment. The possible orientations of the antibody immobilized on the Cal-4 derivative 1 SAM are lying-on or side-on, while on the Cal-4 derivative 2 and Cal-4 derivative 3 head-on and end-on respectively. These experimental results demonstrate the surface dipole moment of Cal-4 derivative appears to be an important factor to antibody orientation. Cal-4 derivatives are useful in developing site direct protein chips.

  19. Comparative protective abilities of organothiols SAM coatings applied to copper dissolution in aqueous environments

    Energy Technology Data Exchange (ETDEWEB)

    Sinapi, F. [Fonds pour la Formation a la Recherche dans l' Industrie et dans l' Agriculture, Rue d' Egmont 5, B-1000 Bruxelles (Belgium); Lejeune, I. [Laboratoire de Chimie et d' Electrochimie des Surfaces, Facultes Universitaires Notre-Dame de la Paix, Rue de Bruxelles 61, B-5000 Namur (Belgium); Delhalle, J. [Laboratoire de Chimie et d' Electrochimie des Surfaces, Facultes Universitaires Notre-Dame de la Paix, Rue de Bruxelles 61, B-5000 Namur (Belgium); Mekhalif, Z. [Laboratoire de Chimie et d' Electrochimie des Surfaces, Facultes Universitaires Notre-Dame de la Paix, Rue de Bruxelles 61, B-5000 Namur (Belgium)]. E-mail: zineb.mekhalif@fundp.ac.be

    2007-04-30

    Self-assembled monolayers (SAMs) obtained by adsorption of n-organothiols molecules have been formed onto polycrystalline copper surfaces in order to build up barrier films protecting copper from oxidation. In this context, formation of n-dodecanethiol (DT), (3-mercaptopropyl)trimethoxysilane (MPTS) and 11-perfluorobutylundecanethiol (F{sub 4}H{sub 11}) monolayers has been elaborated on copper and evaluated by X-ray photoelectron spectroscopy while polarization and cyclic voltammetry curves were used to compare the inhibition efficiency of the three organic coatings. Furthermore, atomic absorption spectrometry measurements were carried out in domestic water and in NaCl 0.5 M solutions in order to evaluate and quantify the dissolution of copper electrodes before and after protection. Results showed evidences that, among the three organic compounds assessed, F{sub 4}H{sub 11} is the most suitable candidate to slow down the copper oxidation process.

  20. Investigation of the mechanism of electroless deposition of copper on functionalized alkanethiolate self-assembled monolayers adsorbed on gold.

    Science.gov (United States)

    Lu, Peng; Walker, Amy V

    2007-12-04

    We have investigated the reaction pathways involved in the unseeded electroless deposition of copper on self-assembled monolayers (SAMs) adsorbed on Au, using time-of-flight secondary ion mass spectrometry, optical microscopy, and scanning electron microscopy. At 22 degrees C copper deposits on both -CH3 and -COOH terminated SAMs. No copper deposition is observed on -OH terminated SAMs because the hydroxyl terminal groups react with formaldehyde in the plating solution, forming an acetal which prevents Cu deposition. At higher deposition temperatures (45 degrees C), no Cu is observed to deposit on -CH3 terminated SAMs because Cu2+ ions are not stabilized on the SAM surface. Copper complexes are still able to form with the -COOH terminal group at 45 degrees C, and so copper continues to be deposited on -COOH terminated SAMs. Copper also penetrates through -CH3 and -COOH terminated SAMs to the Au/S interface, suggesting that soft deposition techniques do not prevent the penetration of low-to-moderate reactivity metals through organic films.

  1. Surface Shear Viscosity and Phase Transitions of Monolayers at the Air-Water Interface

    Science.gov (United States)

    Relini, A.; Ciuchi, F.; Rolandi, R.

    1995-08-01

    The canal method has been employed to measure the in-plane steady shear viscosity of monolayers of bolaform lipids extracted from the membrane of the thermophilic microorganism Sulfolobus solfataricus. Monolayers were formed with the polar lipid extract (PLE), which is a mixture of several bolaform lipids, each one endowed with two nonequivalent polar headgroups. Viscosities were obtained from the measured flows by using the equation introduced by Joly; this equation contains a semiempirical parameter A, which takes into account the monolayer-subphase mechanical coupling. Measuring the flows for two different substances (PLE and oleic acid) and channel widths, the monolayer viscosities and the parameter A were determined at the same time. The analysis of the viscosity data according to the free area model shows evidences of the molecular conformational changes matching monolayer phase transitions.

  2. Photosystem I in Langmuir-Blodgett and Langmuir-Schaefer monolayers.

    Science.gov (United States)

    Yan, Xun; Faulkner, Christopher J; Jennings, G Kane; Cliffel, David E

    2012-10-23

    Photosystem I (PSI) is a membrane protein complex that generates photoinduced electrons and transfers them across the thylakoid membrane during photosynthesis. The PSI complex, separated from spinach leaves, was spread onto the air-water interface as a monolayer and transferred onto a gold electrode surface that was precoated with a self-assembled monolayer (SAM). The electrochemical properties of the transferred PSI monolayer, including cyclic voltammetry and photoinduced chronoamperometry, were measured. The results showed that PSI retained its bioactivity after the manipulation. Its capability of converting photoenergy into electrical potential was demonstrated by its reducing an electron acceptor, dichloroindophenol (DCIP), and by oxidizing an electron donor, sodium ascorbate (ASC). We have shown that the protein has two possible orientations at the water interface. The orientation distribution was determined by comparing the controlled reductive and oxidative photocurrents generated from Langmuir-Blodgett and Langmuir-Schaefer monolayers.

  3. Surface-enhanced Raman scattering-active gold nanoparticles modified with a monolayer of silver film.

    Science.gov (United States)

    Chang, Chun-Chao; Yang, Kuang-Hsuan; Liu, Yu-Chuan; Yu, Chung-Chin; Wu, Yi-Hao

    2012-11-07

    As shown in the literature, electrochemical underpotential deposition (UPD) offers the ability to deposit up to a monolayer of one metal onto a more noble metal with a flat surface. In this work, we develop an electrochemical pathway to prepare more surface-enhanced Raman scattering (SERS)-active substrates with Ag UPD-modified Au nanoparticles (NPs) by using sonoelectrochemical deposition-dissolution cycles (SEDDCs). Encouragingly, the SERS of Rhodamine 6G (R6G) adsorbed on these Ag UPD-modified Au NPs exhibits a higher intensity by ca. 12-fold magnitude, as compared with that of R6G adsorbed on unmodified Au NPs. The prepared SERS-active substrate demonstrates a large Raman scattering enhancement for R6G with a detection limit of 2 × 10(-14) M and an enhancement factor of 5.0 × 10(8). Also, the strategy proposed in this work to improve the SERS effects by using UPD Ag based on SEDDCs has an effect on the smaller probe molecules of 2,2'-bipyridine (BPy).

  4. Determination of low levels of cadmium ions by the under potential deposition on a self-assembled monolayer on gold electrode

    Energy Technology Data Exchange (ETDEWEB)

    Noyhouzer, Tomer [Institute of Chemistry, Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Mandler, Daniel, E-mail: mandler@vms.huji.ac.il [Institute of Chemistry, Hebrew University of Jerusalem, Jerusalem 91904 (Israel)

    2011-01-17

    The electrochemical determination of low levels of Cd using a self-assembled monolayer (SAM) modified Au electrode is reported. Determination was based on the stripping of Cd, which was deposited by under potential deposition (UPD). A series of short alkanethiol SAMs bearing different end groups, i.e., sulfonate, carboxylate and ammonium, were examined. Lowest level of detection (ca. 50 ng L{sup -1}) was achieved with a 3-mercaptopropionic acid (MPA) monolayer using subtractive anodic square wave voltammetry (SASV). Additional surface methods, namely, reductive desorption and X-ray photoelectron spectroscopy, were applied to determine the interfacial structure of the electrodeposited Cd on the modified electrodes. We conclude that the deposited Cd forms a monoatomic layer, which bridges between the gold surface and the alkanethiol monolayer associating with both the gold and the sulfur atoms.

  5. Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics.

    Science.gov (United States)

    Hutchins, Daniel O; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E; Castner, David G; Ma, Hong; Jen, Alex K-Y

    2012-11-15

    Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlOx (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10(-8) A cm(-2) and capacitance density of 0.62 µF cm(-2) at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm(2) V(-1) s(-1).

  6. Thiol-yne adsorbates for stable, low-density, self-assembled monolayers on gold.

    Science.gov (United States)

    Stevens, Christopher A; Safazadeh, Leila; Berron, Brad J

    2014-03-04

    We present a novel approach toward carboxylate-terminated, low-density monolayers on gold, which provides exceptional adsorbate stability and conformational freedom of interfacial functional groups. Adsorbates are synthesized through the thiol-yne addition of two thiol-containing head groups to an alkyne-containing tail group. The resulting monolayers have two distinct phases: a highly crystalline head phase adjacent to the gold substrate, and a reduced density tail phase, which is in contact with the environment. The ellipsometric thickness of 27 Å is consistent with the proposed structure, where a densely packed decanedithiol monolayer is capped with an 11 carbon long, second layer at 50% lateral chain density. The Fourier transform infrared peak at 1710 cm(-1) supports the presence of the carbonyl group. Further, the peaks associated with asymmetric and symmetric methylene stretching are shifted toward higher wavenumbers compared to those of well-packed self-assembled monolayers (SAMs), which shows a lower average crystallinity of the thiol-yne monolayers compared to a typical monolayer. Contact angle measurements indicate an intermediate surface energy for the thiol-yne monolayer surface, owing to the contribution of exposed methylene functionality at the surface in addition to the carbonyl terminal group. The conformational freedom at the surface was demonstrated through remodeling the thiol-yne surface under an applied potential. Changes in the receding contact angle in response to an external potential support the capacity for reorientation of the surface presenting groups. Despite the low packing at the solution interface, thiol-yne monolayers are resistant to water and ion transport (R(f) ~ 10(5)), supporting the presence of a densely structured layer at the gold surface. Further, the electrochemical stability of the thiol-yne adsorbates exceeded that of well-packed SAMs, requiring a more reductive potential to desorb the thiol-yne monolayers from the

  7. Calculation of the molecular exchanging energy of binary surfactants system on the surface monolayer of aqueous solution

    Institute of Scientific and Technical Information of China (English)

    WANG ZhengWu; YI XiZhang

    2007-01-01

    By using the binary anionic/cationic surfactants system CH3(CH2)nOSO-3/CH3(CH2)nN+(CH3)3 as an example, the molecular exchanging energy (ε) of adsorption on the surface monolayer of aqueous solution has been studied. εcan be obtained with two methods. One is from the relationship between εand the molecule interaction parameter (β). This relationship is founded by considering that the adsorption of mixed surfactants on the surface monolayer of solution satisfies the dimensional crystal model condition under which β can be obtained by testing the surface tension of solution. The other is directly from the molecular structure of surfactants with the Lennard-Jones formula. The results for the studied system show that these two methods coincide well.

  8. Calculation of the molecular exchanging energy of binary surfactants system on the surface monolayer of aqueous solution

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    By using the binary anionic/cationic surfactants system CH3(CH2)nOSO3/CH3(CH2)nN+(CH3)3 as an ex-ample, the molecular exchanging energy (ε) of adsorption on the surface monolayer of aqueous solu-tion has been studied. ε can be obtained with two methods. One is from the relationship between ε and the molecule interaction parameter (β). This relationship is founded by considering that the adsorption of mixed surfactants on the surface monolayer of solution satisfies the dimensional crystal model condition under which β can be obtained by testing the surface tension of solution. The other is directly from the molecular structure of surfactants with the Lennard-Jones formula. The results for the studied system show that these two methods coincide well.

  9. Study on Behavior of Docecanethiol SAMs on Pure Copper Surface%硫醇分子自组装膜在铜表面的作用行为研究

    Institute of Scientific and Technical Information of China (English)

    陈振宇; 黄礼平; 黄玲; 李玲杰

    2012-01-01

    采用动电位扫描、电化学阻抗谱、循环伏安法,研究了十二烷基硫醇分子在纯铜电极表面的自组装行为以及形成的自组装膜对铜的缓蚀作用.电化学测试结果显示:十二烷基硫醇自组装膜通过阻碍电子穿过电极/溶液界面,以及阻挡腐蚀介质与铜基底的接触,有效地抑制了铜的腐蚀;随着组装时间的延长,自组装膜更为完整,对铜的腐蚀抑制效率更高.%The assembling behavior and corrosion inhibition of docecanethiol SAMs on pure copper surface were investigated by potentiodynamic polarization, impedance spectroscopy and cyclic voltametry. The results show that dode-canethiol SAMs prevent electrons pass through electrode/solution interface and block the contact between corrosion ions and metal surface, the SAMs have obvious inhibition effect on pure copper; The SAMs are more complete, and it's inhibition efficiency increases with assembling time.

  10. Specific binding of avidin to biotin containing lipid lamella surfaces studied with monolayers and liposomes.

    Science.gov (United States)

    Liu, Z; Qin, H; Xiao, C; Wen, C; Wang, S; Sui, S F

    1995-01-01

    The interaction of avidin (from egg white) with phospholipid (monolayer and bilayer) model membranes containing biotin-conjugated phospholipids has been studied. In the first part, using surface sensitive techniques (ellipsometry and surface plasmon resonance) we demonstrated that the nonspecific adsorption of avidin to phospholipid lamella could be abolished by adding an amount of Ca2+, Mg2+ or Ba2+ that led to an electrostatic interaction. The specific binding of avidin to lipid mixtures containing biotin-conjugated phospholipids was obviously composition dependent. The ratio 1:12 of a B-DPPE/DPPE mixture was found to be the optimum molar ratio. When we compared the results from the surface sensitive techniques with those from the electron micrographs of a two dimensional crystal of avidin (obtained in our laboratory), the optimum ratio was found to be determined by the effect of lateral steric hindrance. In the second part, we observed the pattern of the layers of fluorescently labeled phospholipid and adsorbed proteins with a home-made micro fluorescence film balance. The fluorescence images showed that avidin was preferentially bound to the receptors that were in the fluid domains. Further, with a sensitive fluorescence assay method, the effect of the phase behavior of liposomes on the specific binding of avidin was measured. This showed that avidin interacted with biotinlipid more weakly in the gel state liposome than in the liquid state liposome. The major conclusion was that the binding of avidin to a membrane bound model receptor was significantly restricted by two factors: one was the lateral steric hindrance and the other was the fluidity of the model membrane.

  11. Effect of time and deposition method on quality of phosphonic acid modifier self-assembled monolayers on indium zinc oxide

    Science.gov (United States)

    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.

    2016-12-01

    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 °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.

  12. 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.

  13. Pattern formation in fatty acid-nanoparticle and lipid-nanoparticle mixed monolayers at water surface

    Science.gov (United States)

    Choudhuri, M.; Datta, A.; Iyengar, A. N. Sekar; Janaki, M. S.

    2015-06-01

    Dodecanethiol-capped gold nanoparticles (AuNPs) are self-organized in two different amphiphilic monolayers one of which is a single-tailed fatty acid Stearic acid (StA) and the other a double-tailed lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). In the StA-AuNP film the AuNPs self-organize to form an interconnected network of nanoclusters on compression while in the DMPC-AuNP film the AuNPs aggregate to form random, isolated clusters in the film. The long time evolution of the films at constant surface pressure reveals ring structures in the former and diffusion limited aggregates in the latter that with time evolve into an irregular porous maze of AuNPs in the DMPC film. The difference in structure of the AuNP patterns in the two films can be attributed to a difference in the lipophilic interactions between the NPs and the amphiphilic molecules. The mean square intensity fluctuations f(ln) calculated along a typical line for the 2D structures in both the films at initial and final stages of long time evolution reflect the structural changes in the films over time.

  14. SAM Theory Manual

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Rui [Argonne National Lab. (ANL), Argonne, IL (United States)

    2017-03-01

    The System Analysis Module (SAM) is an advanced and modern system analysis tool being developed at Argonne National Laboratory under the U.S. DOE Office of Nuclear Energy’s Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. SAM development aims for advances in physical modeling, numerical methods, and software engineering to enhance its user experience and usability for reactor transient analyses. To facilitate the code development, SAM utilizes an object-oriented application framework (MOOSE), and its underlying meshing and finite-element library (libMesh) and linear and non-linear solvers (PETSc), to leverage modern advanced software environments and numerical methods. SAM focuses on modeling advanced reactor concepts such as SFRs (sodium fast reactors), LFRs (lead-cooled fast reactors), and FHRs (fluoride-salt-cooled high temperature reactors) or MSRs (molten salt reactors). These advanced concepts are distinguished from light-water reactors in their use of single-phase, low-pressure, high-temperature, and low Prandtl number (sodium and lead) coolants. As a new code development, the initial effort has been focused on modeling and simulation capabilities of heat transfer and single-phase fluid dynamics responses in Sodium-cooled Fast Reactor (SFR) systems. The system-level simulation capabilities of fluid flow and heat transfer in general engineering systems and typical SFRs have been verified and validated. This document provides the theoretical and technical basis of the code to help users understand the underlying physical models (such as governing equations, closure models, and component models), system modeling approaches, numerical discretization and solution methods, and the overall capabilities in SAM. As the code is still under ongoing development, this SAM Theory Manual will be updated periodically to keep it consistent with the state of the development.

  15. 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.

  16. 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.

  17. Phosphatidylcholine Monolayer Formation at a Liquid:Liquid Interface as Monitored by the Dynamic Surface Tension

    Science.gov (United States)

    2007-11-02

    concentration, while liquid crystalline vesicles form tightly packed monolayers at bulk PC concentrations above 2 ^Molar. Resolving this paradigm ...regardless of lipid bilayer phase. Initially, vesicle rupture probably represents an entropically driven process. The system will become increasingly

  18. Copper Contamination of Self-Assembled Organic Monolayer Modified Silicon Surfaces Following a "Click" Reaction Characterized with LAPS and SPIM.

    Science.gov (United States)

    Wu, Fan; Zhang, De-Wen; Wang, Jian; Watkinson, Michael; Krause, Steffi

    2017-04-04

    A copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) reaction combined with microcontact printing was used successfully to pattern alkyne-terminated self-assembled organic monolayer-modified silicon surfaces. Despite the absence of a copper peak in X-ray photoelectron spectra, copper contamination was found and visualized using light-addressable potentiometric sensors (LAPS) and scanning photo-induced impedance microscopy (SPIM) after the "click"-modified silicon surfaces were rinsed with hydrochloric acid (HCl) solution, which was frequently used to remove copper residues in the past. Even cleaning with an ethylenediaminetetraacetic acid (EDTA) solution did not remove the copper residue completely. Different strategies for avoiding copper contamination, including the use of bulky chelators for the copper(I) catalyst and rinsing with different reagents, were tested. Only cleaning of the silicon surfaces with an EDTA solution containing trifluoroacetic acid (TFA) after the click modification proved to be an effective method as confirmed by LAPS and SPIM results, which showed the expected potential shift due to the surface charge introduced by functional groups in the monolayer and allowed, for the first time, imaging the impedance of an organic monolayer.

  19. 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.

  20. 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.

  1. Work-Function Engineering of Graphene Electrodes by Self-Assembled Monolayers for High-Performance Organic Field-Effect Transistors.

    Science.gov (United States)

    Park, Jaesung; Lee, Wi Hyoung; Huh, Sung; Sim, Sung Hyun; Kim, Seung Bin; Cho, Kilwon; Hong, Byung Hee; Kim, Kwang S

    2011-04-21

    We have devised a method to optimize the performance of organic field-effect transistors (OFETs) by controlling the work functions of graphene electrodes by functionalizing the surface of SiO2 substrates with self-assembled monolayers (SAMs). The electron-donating NH2-terminated SAMs induce strong n-doping in graphene, whereas the CH3-terminated SAMs neutralize the p-doping induced by SiO2 substrates, resulting in considerable changes in the work functions of graphene electrodes. This approach was successfully utilized to optimize electrical properties of graphene field-effect transistors and organic electronic devices using graphene electrodes. Considering the patternability and robustness of SAMs, this method would find numerous applications in graphene-based organic electronics and optoelectronic devices such as organic light-emitting diodes and organic photovoltaic devices.

  2. Structure and dynamics of monolayer films of squalane molecules adsorbed on a solid surface

    Science.gov (United States)

    D. T Enevoldsen, A.; Hansen, F. Y.; Diama, A.; Taub, H.

    2003-03-01

    Squalane is a branched alkane (C_30H_62). It consists of a straight chain with 24 carbon atoms, as in tetracosane (C_24H_50), and has six methyl side groups. Branched polymers such as squalane are thought to be better lubricants than n-alkanes. At low temperature, our molecular dynamics (MD) simulations show that the molecules form an ordered monolayer which melts at approximately 325 K compared to the tetracosane monolayer melting point of ˜ 340 K. Our MD simulations indicate the same melting mechanism in the squalane monolayer that was found previously for tetracosane (F. Y. Hansen and H. Taub, Phys. Rev. Lett. 69, 652 (1992).) They also show that the adsorbed molecules are distorted from an all-trans carbon backbone in contrast to what was found for tetracosane. This may explain why the Bragg diffraction peaks were observed to be broader for the squalane monolayer than for tetracosane (D. Fuhrmann, A. P. Graham, L. Criswell, H. Mo, B. Matthies, K. W. Herwig, and H. Taub, Surf. Sci. 482-485, 77 (2001).). The diffusive motion in a squalane monolayer has been investigated by both quasielastic neutron scattering and MD simulations and compared to the dynamics in tetracosane monolayers. Focus will be on differences in the dynamics.

  3. Assembly of citrate gold nanoparticles on hydrophilic monolayers

    OpenAIRE

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

    2016-01-01

    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 mi...

  4. Noncovalent Self-Assembled Monolayers on Graphene as a Highly Stable Platform for Molecular Tunnel Junctions.

    Science.gov (United States)

    Song, Peng; Sangeeth, C S Suchand; Thompson, Damien; Du, Wei; Loh, Kian Ping; Nijhuis, Christian A

    2016-01-27

    Monolayer graphene is used as the bottom electrode to fabricate stable and high-quality self-assembled monolayer (SAM)-based tunnel junctions. The SAMs are formed on graphene via noncovalent bonds without altering the structure of the graphene. This work paves the way to new types of molecular electronic junctions based on 2D materials.

  5. Nanoscale patterning of self-assembled monolayers using DNA nanostructure templates.

    Science.gov (United States)

    Surwade, S P; Zhou, F; Li, Z; Powell, A; O'Donnell, C; Liu, H

    2016-01-28

    We describe a method to pattern arbitrary-shaped silane self-assembled monolayers (SAMs) with nm scale resolution using DNA nanostructures as templates. The DNA nanostructures assembled on a silicon substrate act as a soft-mask to negatively pattern SAMs. Mixed SAMs can be prepared by back filling the negative tone patterns with a different silane.

  6. Chemical conversion of self-assembled hexadecyl monolayers with active oxygen species generated by vacuum ultraviolet irradiation in an atmospheric environment.

    Science.gov (United States)

    Soliman, Ahmed I A; Ichii, Takashi; Utsunomiya, Toru; Sugimura, Hiroyuki

    2015-07-28

    Vacuum ultraviolet (VUV, λ = 172 nm) irradiation of alkyl self-assembled monolayers (SAMs) in the presence of dry air alters their surface properties. In this work, UV photochemically prepared hexadecyl (HD)-SAMs on hydrogen-terminated silicon substrates were irradiated by VUV light in dry air, which generated active oxygen species upon excitation of the atmospheric oxygen molecules. These active oxygen species converted the terminal methyl groups of the SAMs to polar functional groups, which were examined quantitatively by X-ray photoelectron spectroscopy (XPS) and chemical labeling. At the first stage of VUV irradiation, the surface of SAMs was functionalized, and the ratios of the generated polar functional groups markedly increased. With the elongation of the irradiation period, the SAMs gradually degraded, and the total polar group percentages gradually decreased. The difference between the oxygenated carbon components derived by the deconvolution of the XPS carbon (C1s) spectrum and the chemical labeling of polar groups revealed enormous quantities of ethereal and ester groups that cannot react with the labeling reagents but are included in the C1s spectral envelope. These modifications were reflected on morphological structures of SAMs, which were gradually distorted until a complete amorphous structure was obtained after the complete elimination of HD-SAMs.

  7. Surface diffusion of CO on Ni(111) studied by diffraction of optical second-harmonic generation off a monolayer grating

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, X.D.; Rasing, T.; Shen, Y.R.

    1988-12-19

    Diffraction of optical second-harmonic generation from a monolayer grating created by laser desorption of adsorbates can be used to study surface diffusion of molecules on substrates. Application of this novel technique to CO on Ni(111) yields a diffusion activation energy of 6.9 kcal/mol and a preexponential factor of approx. =1.2 x 10/sup -5/ cm/sup 2/s/sup -1/.

  8. Membrane protein resistance of oligo(ethylene oxide) self-assembled monolayers.

    Science.gov (United States)

    Vaish, Amit; Vanderah, David J; Vierling, Ryan; Crawshaw, Fay; Gallagher, D Travis; Walker, Marlon L

    2014-10-01

    As part of an effort to develop biointerfaces for structure-function studies of integral membrane proteins (IMPs) a series of oligo(ethylene oxide) self-assembled monolayers (OEO-SAMs) were evaluated for their resistance to protein adsorption (RPA) of IMPs on Au and Pt. Spectroscopic ellipsometry (SE) was used to determine SAM thicknesses and compare the RPA of HS(CH2)3O(CH2CH2O)6CH3 (1), HS(CH2)3O(CH2CH2O)6H (2), [HS(CH2)3]2CHO(CH2CH2O)6CH3 (3) and [HS(CH2)3]2CHO(CH2CH2O)6H (4), assembled from water. For both substrates, SAM thicknesses for 1 to 4 were found to be comparable indicating SAMs with similar surface coverages and OEO chain order and packing densities. Fibrinogen (Fb), a soluble plasma protein, and rhodopsin (Rd), an integral membrane G-protein coupled receptor, adsorbed to the SAMs of 1, as expected from previous reports, but not to the hydroxy-terminated SAMs of 2 and 4. The methoxy-terminated SAMs of 3 were resistant to Fb but, surprisingly, not to Rd. The stark difference between the adsorption of Rd to the SAMs of 3 and 4 clearly indicate that a hydroxy-terminus of the OEO chain is essential for high RPA of IMPs. The similar thicknesses and high RPA of the SAMs of 2 and 4 show the conditions of protein resistance (screening the underlying substrate, packing densities, SAM order, and conformational mobility of the OEO chains) defined from previous studies on Au are applicable to Pt. In addition, the SAMs of 4, exhibiting the highest resistance to Fb and Rd, were placed in contact with undiluted fetal bovine serum for 2h. Low protein adsorption (≈12.4ng/cm(2)), obtained under these more challenging conditions, denote a high potential of the SAMs of 4 for various applications requiring the suppression of non-specific protein adsorption.

  9. 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.

  10. Use of enzyme label for quantitative evaluation of liposome adhesion on cell surface: studies with J774 macrophage monolayers.

    Science.gov (United States)

    Trubetskoy, V S; Dormeneva, E V; Tsibulsky, V P; Repin, V S; Torchilin, V P

    1988-07-01

    A method for quantitation of cell surface-bound liposomes utilizing J774 macrophage monolayers is developed. Surface-bound biotinyl-containing and 125I-labeled liposomes were quantified with avidin-peroxidase in an ELISA-like assay. Peroxidase substrate absorbance values were recalculated into the absolute amount of liposomal lipid using a special calibration plot. Total liposome uptake by macrophages was determined following the binding of 125I radioactivity. The approach suggested allows quantitative evaluation of the changes in the content of surface-adhered liposomes during their interaction with cells in vitro.

  11. Lubrication of polysilicon micromechanisms with self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, U.; Foster, J.D.; Habib, U.; Howe, R.T.; Maboudian, R. [Berkeley Sensor and Actuator Center, CA (United States); Senft, D.C.; Dugger, M.T. [Sandia National Labs., Albuquerque, NM (United States)

    1998-06-01

    Here, the authors report on the lubricating effects of self-assembled monolayers (SAMs) on MEMS by measuring static and dynamic friction with two polysilicon surface- micromachined devices. The first test structure is used to study friction between laterally sliding surfaces and with the second, friction between vertical sidewalls can be investigated. Both devices are SAM-coated following the sacrificial oxide etch and the microstructures emerge released and dry from the final water rinse. The coefficient of static friction, {mu}{sub s} was found to decrease from 2.1 {+-} 0.8 for the SiO{sub 2} coating to 0.11 {+-} 0.01 and 0.10 {+-} 0.01 for films derived from octadecyltrichloro-silane (OTS) and 1H,1H,2H,2H-perfluorodecyl-trichlorosilane (FDTS). Both OTS and FDTS SAM-coated structures exhibit dynamic coefficients of friction, {mu}{sub d} of 0.08 {+-} 0.01. These values were found to be independent of the apparent contact area, and remain unchanged after 1 million impacts at 5.6 {micro}N (17 kPa), indicating that these SAMs continue to act as boundary lubricants despite repeated impacts. Measurements during sliding friction from the sidewall friction testing structure give comparable initial {mu}{sub d} values of 0.02 at a contact pressure of 84 MPa. After 15 million wear cycles, {mu}{sub d} was found to rise to 0.27. Wear of the contacting surfaces was examined by SEM. Standard deviations in the {mu} data for SAM treatments indicate uniform coating coverage.

  12. Detection of submonolayer oxygen-18 on a gold surface by nuclear reaction analysis

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L.S.; Kenny, M.J.; Wieczorek, L. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics

    1993-12-31

    A gold substrate is the preferred solid surface for formation of an organic self-assembled monolayer ( SAM ). Device fabrication process may require the gold film to be exposed to photolithographic processing and plasma treatment prior to molecular assembly. It has been observed that oxygen plasma treatment prevents the formation of SAMs; however, subsequent treatment with an argon plasma allows assembly of the organic monolayers. To understand the mechanisms involved, a plasma containing 98% {sup 18}O was used and the film surface was analysed using the {sup 18}O (p,{alpha}){sup 15}N nuclear reaction. 5 refs., 1 tab., 3 figs.

  13. Anodic passivation of tin by alkanethiol self-assembled monolayers examined by cyclic voltammetry and coulometry.

    Science.gov (United States)

    Worley, Barrett C; Ricks, William A; Prendergast, Michael P; Gregory, Brian W; Collins, Ross; Cassimus, John J; Thompson, Raymond G

    2013-10-22

    The self-assembly of medium chain length alkanethiol monolayers on polycrystalline Sn electrodes has been investigated by cyclic voltammetry and coulometry. These studies have been performed in order to ascertain the conditions under which their oxidative deposition can be achieved directly on the oxide-free Sn surface, and the extent to which these electrochemically prepared self-assembled monolayers (SAMs) act as barriers to surface oxide growth. This work has shown that the potentials for their oxidative deposition are more cathodic (by 100-200 mV) than those for Sn surface oxidation and that the passivating abilities of these SAMs improve with increasing film thickness (or chain length). Oxidative desorption potentials for these films have been observed to shift more positively, and in a highly linear fashion, with increasing film thickness (~75 mV/CH2). Although reductive desorption potentials for the SAMs are in close proximity to those for reduction of the surface oxide (SnOx), little or no SnOx formation occurs unless the potential is made sufficiently anodic that the monolayers start to be removed oxidatively. Our coulometric data indicate that the charge involved with alkanethiol reductive desorption or oxidative deposition is consistent with the formation of a close-packed monolayer, given uncertainties attributable to surface roughness and heterogeneity phenomena. These experiments also reveal that the quantity of charge passed during oxidative desorption is significantly larger than what would be predicted for simple alkylsulfinate or alkylsulfonate formation, suggesting that oxidative removal involves a more complex oxidation mechanism. Analogous chronocoulometric experiments for short-chain alkanethiols on polycrystalline Au electrodes have evidenced similar oxidative charge densities. This implies that the mechanism for oxidative desorption on both surfaces may be very similar, despite the significant differences in the inherent dissolution

  14. Charge retention of soft-landed phosphotungstate Keggin anions on self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-01-01

    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.

  15. Micro-patterning of self-assembled organic monolayers by using tunable ultrafast laser pulses

    Science.gov (United States)

    Maragkaki, Stella; Aumann, Andreas; Schulz, Florian; Schröter, Anja; Schöps, Benjamin; Franzka, Steffen; Hartmann, Nils; Ostendorf, Andreas

    2014-03-01

    We study the application of tunable ultrafast laser pulses in micropatterning self- assembled organic monolayer (SAMs) employing non collinear optical parametric amplification (NOPA). SAMs are ultrathin organic monolayers, which can be used in a variety of ways to assemble functionalized surface structures. In our study, we investigate the characteristics of SAMs as monomolecular resists during etching of gold. NOPA is a versatile method which provides the generation of ultrafast laser pulses, with a tunable wavelength in the visible and near infrared range. Due to the noncollinear geometry, a broadened spectral range can be amplified. The NOPA delivers wavelengths in the range of 480 nm to 950 nm at laser pulse lengths in the sub- 30 femtosecond range using a prism compressor after the nonlinear conversion. The ultrashort laser technology together with the advantages of the NOPA system guarantee high precision and allows us to determine the optimum conditions of sub-wavelength patterning by studying the effects of the fluence and the wavelength. At the same time, single-pulse processing allows us to selectively remove the ultrathin organic coating, while it ensures short processing time. In our study we used thiol-based SAMs as ultrathin layers on gold-coated glass substrates with a film thickness of 1-2 nm and 40 nm respectively.

  16. Modulation of electrochemical hydrogen evolution rate by araliphatic thiol monolayers on gold

    Science.gov (United States)

    Muglali, Mutlu I.; Erbe, Andreas; Chen, Ying; Barth, Christoph; Koelsch, Patrick; Rohwerder, Michael

    2013-01-01

    Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum–frequency–generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which di er between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two–dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre–orientation of water present in the nanometer–sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER. PMID:24235778

  17. Modulation of electrochemical hydrogen evolution rate by araliphatic thiol monolayers on gold.

    Science.gov (United States)

    Muglali, Mutlu I; Erbe, Andreas; Chen, Ying; Barth, Christoph; Koelsch, Patrick; Rohwerder, Michael

    2013-02-15

    Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum-frequency-generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which di er between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two-dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre-orientation of water present in the nanometer-sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER.

  18. 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.

  19. Optical imaging beyond the diffraction limit by SNEM: Effects of AFM tip modifications with thiol monolayers on imaging quality

    Energy Technology Data Exchange (ETDEWEB)

    Cumurcu, Aysegul [Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, Enschede NL-7500 (Netherlands); Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX, Eindhoven (Netherlands); Diaz, Jordi [Scientific and Technological Centers of the University of Barcelona, C/ Lluís Solé i Sabaris, 1-3, 08028 Barcelona (Spain); Lindsay, Ian D. [Nanophysics and Soft Matter Group, H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Beer, Sissi de; Duvigneau, Joost [Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, Enschede NL-7500 (Netherlands); Schön, Peter [Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, Enschede NL-7500 (Netherlands); NanoBioInterface, Research Center Design and Technology, Saxion University of Applied Sciences, 7500 KB Enschede (Netherlands); Julius Vancso, G., E-mail: g.j.vancso@utwente.nl [Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, Enschede NL-7500 (Netherlands)

    2015-03-15

    Tip-enhanced nanoscale optical imaging techniques such as apertureless scanning near-field optical microscopy (a-SNOM) and scanning near-field ellipsometric microscopy (SNEM) applications can suffer from a steady degradation in performance due to adhesion of atmospheric contaminants to the metal coated tip. Here, we demonstrate that a self-assembled monolayer (SAM) of ethanethiol (EtSH) is an effective means of protecting gold-coated atomic force microscopy (AFM) probe tips from accumulation of surface contaminants during prolonged exposure to ambient air. The period over which they yield consistent and reproducible results for scanning near-field ellipsometric microscopy (SNEM) imaging is thus extended. SNEM optical images of a microphase separated polystyrene-block-poly (methylmethacrylate) (PS-b-PMMA) diblock copolymer film, which were captured with bare and SAM-protected gold-coated AFM probes, both immediately after coating and following five days of storage in ambient air, were compared. During this period the intensity of the optical signals from the untreated gold tip fell by 66%, while those from the SAM protected tip fell by 14%. Additionally, gold coated AFM probe tips were modified with various lengths of alkanethiols to measure the change in intensity variation in the optical images with SAM layer thickness. The experimental results were compared to point dipole model calculations. While a SAM of 1-dodecanethiol (DoSH) was found to strongly suppress field enhancement we find that it can be locally removed from the tip apex by deforming the molecules under load, restoring SNEM image contrast. - Highlights: • SAM of ethanethiol is used to prevent contamination of gold coated tips. • Functionalizing gold coated tips with a SAM lead to reproducible SNEM imaging. • Point dipole model agreed with the experimental results of the SNEM images. • SAM of 1-dodecanethiol was found to strongly suppress field enhancement in SNEM. • SAM of 1-dodecanethiol

  20. 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.

  1. 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.

  2. 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 development...... in the investigations of electronic structures and assembling dynamics of electrochemically controlled self-assembled monolayers (SAMs) of thiol containing molecules on gold surfaces. A brief introduction is first given and particularly illustrated by a Table summarizing the molecules studied, the surface lattice...

  3. On the lipid head group hydration of floating surface monolayers bound to self-assembled molecular protein layers

    DEFF Research Database (Denmark)

    Lösche, M.; Erdelen, C.; Rump, E.

    1994-01-01

    with molecular resolution. Emphasis here is placed on the hydration of the lipid head groups in the bound state. For three functionalized lipids with spacers of different lengths between the biotin and their chains it was observed that the head groups were dehydrated in monolayers of the pure lipids, which were...... kept at low surface pressure before protein adsorption. The introduction of dipole moments at the interface by the admixture of phospholipids or the application of lateral pressure on the lipid monolayer before protein adsorption were found to impose an extension of the spacer moieties. The biotin...... groups were thus presented further away from the interface, and a hydration layer between the protein and the functionalized interface was observed in the self-assembled supramolecular structures....

  4. Reaction kinetics of metal deposition via surface limited red-ox replacement of underpotentially deposited metal monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Gokcen, Dincer; Bae, Sang-Eun [Electrical and Computer Engineering, University of Houston, Houston, TX 772004-4005 (United States); Brankovic, Stanko R., E-mail: Stanko.Brankovic@mail.uh.edu [Electrical and Computer Engineering, University of Houston, Houston, TX 772004-4005 (United States); Chemical and Biomolecular Engineering, University of Houston, Houston, TX 772004-4005 (United States); Chemistry Department, University of Houston, Houston, TX 772004-4005 (United States)

    2011-06-30

    The study of the kinetics of metal deposition via surface limited red-ox replacement of underpotentially deposited metal monolayers is presented. The model system was Pt submonolayer deposition on Au(1 1 1) via red-ox replacement of Pb and Cu UPD monolayers on Au(1 1 1). The kinetics of a single replacement reaction was studied using the formalism of the comprehensive analytical model developed to fit the open circuit potential transients from deposition experiments. The practical reaction kinetics parameters like reaction half life, reaction order and reaction rate constant are determined and discussed with their relevance to design and control of deposition experiments. The effects of transport limitation and the role of the anions/electrolyte on deposition kinetics are investigated and their significance to design of effective deposition process is discussed.

  5. 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

  6. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. II. Dynamics

    Science.gov (United States)

    Enevoldsen, A. D.; Hansen, F. Y.; Diama, A.; Taub, H.; Dimeo, R. M.; Neumann, D. A.; Copley, J. R. D.

    2007-03-01

    The dynamics of monolayer films of the n-alkane tetracosane (n-C24H52) and the branched alkane squalane (C30H62) adsorbed on graphite have been studied by quasielastic and inelastic neutron scattering and molecular dynamics (MD) simulations. Both molecules have 24 carbon atoms along their carbon backbone, and squalane has an additional six methyl side groups symmetrically placed along its length. The authors' principal objective has been to determine the influence of the side groups on the dynamics of the squalane monolayer and thereby assess its potential as a nanoscale lubricant. To investigate the dynamics of these monolayers they used both the disk chopper spectrometer (DCS) and the high flux backscattering spectrometer (HFBS) at the National Institute of Standards and Technology. These instruments made it possible to study dynamical processes such as molecular diffusive motions and vibrations on very different time scales: 1-40ps (DCS) and 0.1-4ns (HFBS). The MD simulations were done on corresponding time scales and were used to interpret the neutron spectra. The authors found that the dynamics of the two monolayers are qualitatively similar on the respective time scales and that there are only small quantitative differences that can be understood in terms of the different masses and moments of inertia of the two molecules. In the course of this study, the authors developed a procedure to separate out the low-frequency vibrational modes in the spectra, thereby facilitating an analysis of the quasielastic scattering. They conclude that there are no major differences in the monolayer dynamics caused by intramolecular branching. It remains to be seen whether this similarity in monolayer dynamics also holds for the lubricating properties of these molecules in confined geometries.

  7. 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.

  8. Surface modification of cobalt-chromium-tungsten-nickel alloy using octadecyltrichlorosilanes

    Energy Technology Data Exchange (ETDEWEB)

    Mani, Gopinath [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Feldman, Marc D. [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Division of Cardiology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229 (United States); The Department of Veteran Affairs South Texas Health Care System, 7400 Merton Minter Blvd., San Antonio, TX 78229 (United States); Oh, Sunho [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Agrawal, C. Mauli [Department of Biomedical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States)], E-mail: Mauli.Agrawal@utsa.edu

    2009-03-15

    Cobalt-chromium (Co-Cr) alloys have been extensively used for medical implants because of their excellent mechanical properties, corrosion resistance, and biocompatibility. This first time study reports the formation and stability of self-assembled monolayers (SAMs) on a Co-Cr-W-Ni alloy. SAMs of octadecyltrichlorosilanes (OTS) were coated on sputtered Co-Cr-W-Ni alloy thin film and bulk Co-Cr-W-Ni alloy. OTS SAM coated alloy specimens were characterized using contact angle goniometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Contact angle analysis and FTIR suggested that ordered monolayers were coated on both sputtered and bulk alloy. XPS suggested the selective dissolution of cobalt from the alloy during the formation of OTS SAM. The bonding between the alloy and the OTS SAM was mainly attributed to Si-O-Cr and Si-O-W covalent bonds and a smaller contribution from Si-O-Co bonds. AFM images showed the distribution of islands of monolayers coated on the alloy. The height of monolayers in majority of the islands was closer to the theoretical length of fully extended OTS molecules oriented perpendicular to the surface. The stability of OTS SAM was investigated in tris-buffered saline at 37 {sup o}C for up to 7 days. Contact angle, FTIR, and XPS collectively confirmed that the monolayers remain ordered and bound to the alloy surface under this condition. This study shows that Co-Cr alloys can be surface modified using SAMs for potential biomedical applications.

  9. 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.

  10. 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.

  11. 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.

  12. Heterogeneous nanotribological response of polymorphic self-assembled monolayers arising from domain and phase dependent friction.

    Science.gov (United States)

    Paradinas, Markos; Munuera, Carmen; Silien, Christophe; Buck, Manfred; Ocal, Carmen

    2013-01-28

    Micro-/nanoelectromechanical systems demand robust ultrathin films for lubrication. As they can drastically modify the frictional properties of surfaces, few nanometers thick self-assembled monolayers (SAMs) constitute accepted candidates as boundary lubricants. Their high stability and easy preparation make them attractive also for low cost applications. Given their high order, organosulfur SAMs have been archetypal systems for structural investigations, but few efforts have been devoted to analyze the influence of lateral inhomogeneities on their surface properties. The impact on the frictional response of the surface due to the existence of crystalline domains with lateral dimension in the sub-micrometer range is considered here. To this end, two polymorphic structures of self-assembled monolayers of ω-(4'-methylbiphenyl-4-yl) butane-1-thiol coexisting on Au(111) are investigated by scanning tunneling and force microscopy. Described by rectangular 5√5 × 3 (α-phase) and oblique 6√3 × 2√3 (β-phase) unit cells, they exhibit pronouncedly different frictional responses. The lateral nano-tribological heterogeneity of the surface is further influenced by the azimuthal orientation dependence of friction for each phase. In particular, this phenomenon is exploited in the less densely packed β-phase for which the separate analysis of forward and backward lateral force scans is used to differentiate domains rotated 180°. The results demonstrate the level of structural control required in the design of SAMs for nano-tribology applications.

  13. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. I. Structure

    DEFF Research Database (Denmark)

    Enevoldsen, Ann Dorrit; Hansen, Flemming Yssing; Diama, A.

    2007-01-01

    The structure of a monolayer film of the branched alkane squalane (C30H62) adsorbed on graphite has been studied by neutron diffraction and molecular dynamics (MD) simulations and compared with a similar study of the n-alkane tetracosane (n-C24H52). Both molecules have 24 carbon atoms along their...

  14. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. II. Dynamics

    DEFF Research Database (Denmark)

    Enevoldsen, Ann Dorrit; Hansen, Flemming Yssing; Diama, A.;

    2007-01-01

    The dynamics of monolayer films of the n-alkane tetracosane (n-C24H52) and the branched alkane squalane (C30H62) adsorbed on graphite have been studied by quasielastic and inelastic neutron scattering and molecular dynamics (MD) simulations. Both molecules have 24 carbon atoms along their carbon...

  15. pH sensitivity of Si-C linked organic monolayers on crystalline silicon surfaces

    NARCIS (Netherlands)

    Faber, Erik Jouwert; Sparreboom, Wouter; Groeneveld, Wilrike; de Smet, Louis C.P.M.; Bomer, Johan G.; Olthuis, Wouter; Zuilhof, Han; Sudholter, Ernst; Sudhölter, Ernst J.R.; Bergveld, Piet; van den Berg, Albert

    2007-01-01

    The electrochemical behaviour of Si-C linked organic monolayers is studied in electrolyte-insulator-Si devices, under conditions normally encountered in potentiomeric biosensors, to gain fundamental knowledge on the behaviour of such Si electrodes under practical conditions. This is done via

  16. Self-assembled monolayers applications for the development of electrochemical sensors

    OpenAIRE

    Renato S. Freire; Pessoa, Christiana A.; Lauro T. Kubota

    2003-01-01

    Self-assembled monolayers (SAMs) modified electrodes exhibit unique behavior that can greatly benefit electrochemical sensing. This brief review highlights the applications of SAM modified electrodes in electroanalytical chemistry. After a general introduction, which includes the approaches for SAM development, different electrochemical systems for detecting inorganic and organic species are described and discussed. Special attention to the coupling of biological sensing element to the SAM is...

  17. Photoswitching of azobenzene-containing self-assembled monolayers as a tool for control over silicon surface electronic properties

    Science.gov (United States)

    Malyar, Ivan V.; Titov, Evgenii; Lomadze, Nino; Saalfrank, Peter; Santer, Svetlana

    2017-03-01

    We report on photoinduced remote control of work function and surface potential of a silicon surface modified with a photosensitive self-assembled monolayer consisting of chemisorbed azobenzene molecules (4-nitroazobenzene). It was found that the attachment of the organic monolayer increases the work function by hundreds of meV due to the increase in the electron affinity of silicon substrates. The change in the work function on UV light illumination is more pronounced for the azobenzene jacketed silicon substrate (ca. 250 meV) in comparison to 50 meV for the unmodified surface. Moreover, the photoisomerization of azobenzene results in complex kinetics of the work function change: immediate decrease due to light-driven processes in the silicon surface followed by slower recovery to the initial state due to azobenzene isomerization. This behavior could be of interest for electronic devices where the reaction on irradiation should be more pronounced at small time scales but the overall surface potential should stay constant over time independent of the irradiation conditions.

  18. Rotational superstructure in van der Waals heterostructure of self-assembled C60 monolayer on the WSe2 surface

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Elton J.G.; Sullion, Declan; Chu, Ximo S.; Li, Duo O.; Guisinger, Nathan P.; Wang, Qing Hua

    2017-09-21

    Hybrid van der Waals (vdW) heterostructures composed of two-dimensional (2D) layered materials and self-assembled organic molecules are promising systems for electronic and optoelectronic applications with enhanced properties and performance. Control of molecular assembly is therefore paramount to fundamentally understand the nucleation, ordering, alignment, and electronic interaction of organic molecules with 2D materials. Here, we report the formation and detailed study of highly ordered, crystalline monolayers of C60 molecules self-assembled on the surface of WSe2 in well-ordered arrays with large grain sizes (∼5 μm). Using high-resolution scanning tunneling microscopy (STM), we observe a periodic 2 × 2 superstructure in the C60 monolayer and identify four distinct molecular appearances. Using vdW-corrected ab initio density functional theory (DFT) simulations, we determine that the interplay between vdW and Coulomb interactions as well as adsorbate–adsorbate and adsorbate–substrate interactions results in specific rotational arrangements of the molecules forming the superstructure. The orbital ordering through the relative positions of bonds in adjacent molecules creates a charge redistribution that links the molecule units in a long-range network. This rotational superstructure extends throughout the self-assembled monolayer and opens a pathway towards engineering aligned hybrid organic/inorganic vdW heterostructures with 2D layered materials in a precise and controlled way.

  19. Cobalt monolayer islands on Ag(111) for ORR catalysis.

    Science.gov (United States)

    Loglio, Francesca; Lastraioli, Elisa; Bianchini, Claudio; Fontanesi, Claudio; Innocenti, Massimo; Lavacchi, Alessandro; Vizza, Francesco; Foresti, Maria Luisa

    2011-08-22

    The design of a catalyst for one of the most important electrocatalytic reactions, the oxygen reduction reaction (ORR), was done following the most recent guidelines of theoretical studies on this topic. Aim of this work was to achieve a synergic effect of two different metals acting on different steps of the ORR. The catalytic activity of Ag, already known and characterized, was enhanced by the presence of a monolayer of cobalt subdivided into nanosized islands. To obtain such a controlled nanostructure, a novel method utilizing self-assembled monolayers (SAMs) as templates was employed. In a recent study, we were able to perform a confined electrodeposition of cobalt onto Ag(111) in a template formed by selectively desorbing a short-chain thiol (3-mercaptopropionic acid, MPA) from binary SAMs using 1-dodecanthiols (DDT). This method allows for an excellent control of the morphology of the deposit by varying the molar ratio of the two thiols. Because cobalt does not deposit on silver at an underpotential, the alternative approach of surface limited redox replacement (SLRR) was used. This method, recently developed by Adžić et al., consists of the use of a monolayer of a third metal, which can be deposited at an underpotential, as a template for the spontaneous deposition of a more noble metal. Herein, we choose zinc as template for the deposition of cobalt. Ag(111) crystals were covered by monolayer islands consisting of cobalt, with the surface atomic ratios ranging from 12 to 39% for cobalt. The catalytic activity of such samples towards ORR was evaluated and the best improvement in activity was found to be that of the sample with a cobalt percentage of approximately 30% with respect to the bare silver, which is in good agreement with theoretical hypotheses.

  20. Electron transfer behavior at polyoxometalate-adsorbed alkanethiol self-assembled monolayers

    Science.gov (United States)

    Chu, Yeonyi; Kim, Jandee; Choi, Suhee; Rhee, Choong Kyun; Kim, Jongwon

    2011-09-01

    The interaction between polyoxometalate (POM) anions, SiMo 12O 404-, and a self-assembled monolayer (SAM) of dodecanethiol (DT) on Au surfaces was investigated using electrochemical methods, X-ray photoelectron spectroscopy, and scanning probe microscopy. The SiMo 12O 404- ions adsorb on the SAM of DT on Au to form a composite organic-inorganic hybrid layer. The adsorbed SiMo 12O 404- ion on the SAM layer shows its characteristic redox waves with an electron transfer rate slower than that on a bare Au electrode. The electron transfer behavior at DT-SAM could be regulated by the adsorption of SiMo 12O 404- depending on the charge of the investigated electroactive species: a significant increase toward a positively charged Ru(NH 3) 63+ ion, a moderate increase toward a neutral 1,1'-ferrocenedimethanol molecule and a slight decrease toward a negatively charged Fe(CN) 63- ion. The effect of the chain length of alkanethiols on the adsorption of SiMo 12O 404- ion was also investigated: as the chain length decreases, the amount of the adsorbed POM increases and the electron transfer rate through the composite layers increases. The nature of SiMo 12O 404- ions adsorbed on the SAMs of alkanethiols on Au is discussed in detail.

  1. 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.

  2. A New Organofunctional Ethoxysilane Self-Assembly Monolayer for Promoting Adhesion of Rubber to Aluminum

    Directory of Open Access Journals (Sweden)

    Qian Wang

    2009-10-01

    Full Text Available Practical adhesion of rubber to aluminum is measured for various aluminum silanization treatments. In this study, 6-(3-triethoxysilylpropylamino-1,3,5-triazine-2,4-dithiol (TES was used as the coupling agent for preparing self-assembly monolayers (SAMs on an aluminum surface. The structure and chemical composition of the SAMs were analyzed using Fourier transform infra-red spectroscopy (FT-IR and X-ray photoelectron spectroscopy (XPS. The changes in the surface features of the aluminum surface due to TES treatment were investigated by atomic force microscopy (AFM. The adhesive properties of the silanized aluminum surface and EPDM rubber have been evaluated by a T-peel strength test. The results suggested that the Si-O-Al bonding at aluminum TES interface existed and a TES self-assembly monolayer was formed on the aluminum surface. More than 6.0 KN/m adhesion strength is obtained when the aluminum is silanized with 2.5 mmol/dm3 TES, cured at 160 °C and vulcanized with EPDM rubber at 160 °C for 30 min. It is suggested that the TES self-assembly monolayer is bound to aluminum through its ethoxysilyl functional group, and the thiol function group is strongly crosslinked to EPDM rubber, respectively.

  3. Laser desorption ionization-time-of-flight mass analysis of perfluoropolyether monolayer directly from hard disk medium surface.

    Science.gov (United States)

    Kudo, Toshiji; Macht, Marcus; Kuroda, Masami

    2011-07-15

    Modern life is dependent on computer technology, and because the volume of digital data in the world is increasing rapidly, the importance of data storage devices is also increasing rapidly. Among them, demands for magnetic disk drive well-known as hard disk drives is quite huge and information recording density on the disk media is continuing to grow dramatically. For the research and development of the magnetic disk media, it is critical to investigate and characterize the lubricant layer formed on the disk media surface. However, it is difficult because the layer is only a monolayer which has only approximately 1 nm thickness in many cases. Although matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) measurements of monolayers have already been reported (Su, J.; Mrksich, M. Langmuir, 2003, 19, 4867-4870), lubricants used here are (co)polymers which have molecular weight distributions and are mixtures of various degrees of polymerization. This can reduce the sensitivity of MS measurement because the number (or density) of distinct single molecular species is lower than for homogeneous samples. In this report, direct measurement and characterization of lubricant monolayers using the LDI-TOF-MS instrument is performed to gain insight into detailed information like average molecular weight, polymer distribution, and two-dimensional mapping directly from magnetic disk monolayers. To our knowledge, this is the first time such information was acquired directly from hard disk media. The technique reported here might open up new possibilities also for investigations of various electronic devices other than magnetic hard disks.

  4. Adsorption and dissociation of H{sub 2}S on monometallic and monolayer bimetallic Ni/Pd(111) surfaces: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yi, E-mail: liy99@fzu.edu.cn [College of Chemistry, Fuzhou University, Fuzhou, Fujian, 350116 (China); Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen, Fujian, 361005 (China); Huang, Pan; Tao, Dandan; Wu, Juan; Qiu, Mei; Huang, Xin; Ding, Kaining; Chen, Wenkai [College of Chemistry, Fuzhou University, Fuzhou, Fujian, 350116 (China); Su, Wenyue [State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou, Fujian, 350002 (China); Zhang, Yongfan, E-mail: zhangyf@fzu.edu.cn [College of Chemistry, Fuzhou University, Fuzhou, Fujian, 350116 (China); State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou, Fujian, 350002 (China)

    2016-11-30

    Highlights: • For the molecular adsorption, the introducing Ni monolayer on Pd(111) can reduce the binding strength between H{sub 2}S and the surface. • The decompositions of H{sub 2}S molecule on all Ni/Pd(111) surfaces are exothermic, especially for the surfaces that the top layer is composed of Ni atoms. • Monolayer Ni-Pd(111) surface may exhibit a good sulfur resistance performance because there is a competition between the desorption and decomposition of H{sub 2}S molecule. - Abstract: Periodic density functional theory calculations have been performed to investigate the adsorption structures and dissociative reaction pathways for H{sub 2}S molecule on Ni(111), Pd(111) and Ni/Pd(111) monolayer bimetallic surfaces with surface monolayer and subsurface monolayer structures. Our results indicate that, for the molecular adsorption mode, the introducing Pd atoms on Ni(111) can enhance the binding strength between H{sub 2}S and the surface, while an opposite effect is achieved when the Ni monolayer is formed on Pd(111) surface. The decompositions of H{sub 2}S molecule on all Ni/Pd(111) surfaces are exothermic, especially for the surfaces that the top layer is composed of Ni atoms. According to the predicted minimum energy paths that connect the molecular and dissociative states, two elementary steps are found for all Ni/Pd(111) metal surfaces, and the breaking of the first H−S bond is the rate-determining step for the H{sub 2}S dissociation. Our results reveal that in most cases, the decomposition of H{sub 2}S molecule on the monometallic and Ni/Pd(111) monolayer bimetallic surfaces is easy to happen. However, on the monolayer Ni-Pd(111) surface, there is a competition between the trapping-desorption channel and activated dissociation channel, which implies that depositing one monolayer Ni on a Pd(111) surface may help reducing sulfur poisoning by hindering the dissociation of H{sub 2}S molecule.

  5. 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.

  6. 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

    2015-10-01

    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.

  7. 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.

  8. Hydrophobicity of fluoroalkylsilane and alkylsilane-grafted surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Farzaneh, M.; Kulinich, S.A.; Volat, C. [Quebec Univ., Chicoutimi, PQ (Canada). Industrial Chair on Atmospheric Icing of Power Network Equipment

    2005-07-01

    The microstructure and surface chemistry of self-assembled monolayers (SAMs) were investigated with reference to their hydrophobic and snow and ice-repellent properties. This paper presented a comparative analysis of wetting behaviour of both flat and rough surfaces covered with common fluoroalkylsiloxane (FAS-17 and FAS 13) and octadecylsiloxane (ODS) monolayers. In addition, the study aimed to show the importance of self-assembly order as an important factor governing hydrophobicity of SAM-coated surfaces. Both static and dynamic hydrophobicities were theoretically modelled as functions of self-assembly order/disorder degree and area fraction of air entrapped into the rough hydrophobic surfaces. The model was used to describe the wetting behaviour of SAM-grafted surfaces as a function of assembly degree of organic molecules and amount of air trapped between water and solid. The model was applied to compare wetting surfaces fully coated with FAS-17 and FAS-13 monolayers. The contact angle of a sessile water droplet was shown to be approximately 10 degrees larger on smooth fluoroalkylsilane-coated surfaces and to gradually increase with the assembly order. However, the difference decreased when rough substrates with air inclusion were used. The modelling results predicted very close values of contact angles on surfaces coated with perfluorodecylsiloxane and perfluorooctylsiloxane monolayers but demonstrated little difference at low self-assembly degree, when organic molecules were spread on the surface. ODS coatings showed lower values of contact angle. It was concluded that both static and dynamic hydrophobicity of SAM coated surfaces are strongly affected by the degree of self-assembly of organic molecules, and by water coverage of a rough composite surface, which can trap air. It was concluded that increasing the assembly order of SAM molecules in combination with properly designed roughness leads to considerably enhanced water repellency of the surface. 34 refs

  9. Formation of Self-Assembled Monolayer on Cerium Conversion Coated AZ31 Mg Alloy

    Science.gov (United States)

    Salman, S. A.; Akira, N.; Kuroda, K.; Okido, M.

    Magnesium alloys are recognized as alternatives to Al alloys and steel to reduce the weight of structural materials. However, a major obstacle to the widespread use of magnesium alloys is its poor corrosion resistance. Therefore, further surface treatment of magnesium and its alloy is important in meeting several industrial specifications. In a previous research, we investigated the surface treatment of AZ31 magnesium alloy using cerium conversion coating. The anticorrosion properties could be improved with the cerium treatment. In this present research, self-assembled monolayer (SAM) was adsorbed on the surface of cerium conversion coated AZ31 magnesium alloy. The SAM thin film was deposited using (Tridecafluoro-1, 1, 2, 2-tetrahydrooctyl) trimethoxysilane (FAS13) and Tetrakis(trimethylsiloxy)titanium (TTMS) as a catalyst. The corrosion resistance of cerium conversion coated AZ31 Mg alloy was improved with SAM post treatment. Furthermore, the contact angle increases from 13 deg. to 169 deg. indicating to production of super hydrophobic surface with SAM post treatment.

  10. Binary self-assembled monolayers modified Au nanoparticles as carriers in biological applications.

    Science.gov (United States)

    Chang, Hsun-Yun; You, Yun-Wen; Liao, Hua-Yang; Shyue, Jing-Jong

    2014-12-01

    Gold nanoparticles (AuNPs) are good nonviral carriers because of their ease of synthesis and conjugation in biochemistry, and self-assembled monolayers (SAMs) provide a tunable system to change their interfacial properties. Using homogeneously mixed carboxylic acid and amine functional groups, a series of surface potentials and isoelectric points (IEPs) could be obtained and allow systematic study of the effect of surface potential. In this work, the result of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay revealed that binary-SAM modified AuNPs have high biocompatibility with HEK293T cells. The amount of AuNPs ingested by the cells was found to increase with increasing surface potential and the difference was also confirmed with a scanning transmission electron microscope. The ability of binary-SAM modified AuNPs as carriers was examined, and the plasmid deoxyribose nucleic acid (DNA)-containing eGFP reporter gene was used as the model cargo. Fluorescence imaging revealed that the transfection efficiency generally increased with increasing surface potential. More importantly, when the IEP of the AuNPs was higher than that of the environment of the endosome but lower than that of the cytoplasm, the plasmid DNA can be protected better and released more easily during the endocytosis process hence higher efficiency is obtained with 60% NH2 and 40% COOH in the binary-SAM.

  11. Effects of interface roughness on cohesive strength of self-assembled monolayers

    Science.gov (United States)

    Zhang, Chen; Awasthi, Amnaya P.; Geubelle, Philippe H.; Grady, Martha E.; Sottos, Nancy R.

    2017-03-01

    Self-assembled monolayers (SAMs) are aggregates of small molecular chains that have the property to form highly ordered assemblies. The choice of terminal groups on the chains makes them excellent contenders of molecular-level tailoring. Molecular dynamics (MD) simulations and experimental observations of spallation of two SAM-enhanced gold-film/silicon-substrate interfaces have shown that the cohesive strength of SAM-enriched transfer-printed interfaces is strongly dependent on the choice of terminal groups. Though the MD results of perfectly ordered atomistic surfaces show the same qualitative trend as the experiments, they over-predict the interfacial cohesive strengths by a factor of about 50. Results from AFM studies have revealed that the roughness of these interfaces is of the same order (∼1 nm) as the range of atomistic interactions. Hence, surface roughness is a key contributor in significantly reducing interfacial cohesive strength in these systems. In this manuscript, a continuum-level study is performed to investigate the influence of surface roughness on the cohesive strength of the interface between a Si/SAM substrate and a transfer-printed gold film. We approximate the film as a deformable continuum interacting with a rough substrate of SAMs represented by a harmonic function. Using a cohesive law derived from MD, spallation is simulated to evaluate the effective traction-separation characteristics for the rough SAM-gold interface. Our analysis shows that incorporating roughness may reduce the interfacial cohesive strength by an order of magnitude depending on the film properties and the surface roughness. Additionally, we observe that the gold film adopts unique separation attributes based on roughness parameters and material properties.

  12. Characterization of benzenethiolate self-assembled monolayer on Cu(1 0 0) by XPS and NEXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Beccari, Marco [Dipartimento di Chimica, Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, I-00185 Roma (Italy)], E-mail: Marco.Beccari@uniroma1.it; Kanjilal, Aloke [INFM-CNR Center on nanoStructures and bioSystems at Surfaces (S3), Via G. Campi 231/A, I-41100 Modena (Italy); Betti, Maria Grazia; Mariani, Carlo [Dipartimento di Fisica, CNISM, CNIS, Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, I-00185 Roma (Italy); Floreano, Luca; Cossaro, Albano [Laboratorio TASC-INFM, Basovizza SS14 Km 163.5, I-34012 Trieste (Italy); Di Castro, Valeria [Dipartimento di Chimica, Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, I-00185 Roma (Italy)

    2009-05-15

    The composition, electronic structure and molecular orientation of a self-assembled monolayer (SAM) of benzenethiolate on the Cu(1 0 0) surface have been investigated by means of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS). An ordered benzenethiolate SAM with c(2 x 6) superstructure has been obtained by the reaction of diphenyldisulfide with the Cu(1 0 0) surface at room temperature. S 2p and C 1s XP spectra show S-Cu bond formation without significant thiolate decomposition. The strong dichroic signal of C K-edge NEXAFS upon varying polarization angle indicates upstanding of the adsorbed molecules with the benzene ring tilted by 20 deg. from the surface normal.

  13. From monomer to monolayer: a global optimisation study of (ZnO)n nanoclusters on the Ag surface.

    Science.gov (United States)

    Demiroglu, Ilker; Woodley, Scott M; Sokol, Alexey A; Bromley, Stefan T

    2014-12-21

    We employ global optimisation to investigate how oxide nanoclusters of increasing size can best adapt their structure to lower the system energy when interacting with a realistic extended metal support. Specifically, we focus on the (ZnO)@Ag(111) system where experiment has shown that the infinite Ag(111)-supported ZnO monolayer limit corresponds to an epitaxially 7 : 8 matched graphene-like (Zn(3)O(3))-based hexagonal sheet. Using a two-stage search method based on classical interatomic potentials and then on more accurate density functional theory, we report global minina candidate structures for Ag-supported (ZnO)n cluster with sizes ranging from n = 1-24. Comparison with the respective global minina structure of free space (ZnO)n clusters reveals that the surface interaction plays a decisive role in determining the lowest energy Ag-supported (ZnO)n cluster structures. Whereas free space (ZnO)n clusters tend to adopt cage-like bubble structures as they grow larger, Ag-supported (ZnO)n clusters of increasing size become progressively more like planar cuts from the infinite graphene-like ZnO single monolayer. This energetic favourability for planar hexagonal Ag-supported clusters over their 3D counterparts can be partly rationalised by the ZnO-Ag(111) epitaxial matching and the increased number of close interactions with the Ag surface. Detailed analysis shows that this tendency can also be attributed to the capacity of 2D clusters to distort to improve their interaction with the Ag surface relative to more rigid 3D bubble cluster isomers. For the larger sized clusters we find that the adsorption energies and most stable structural types appear to be rather converged confirming that our study makes a bridge between the Ag-supported ZnO monomer and the infinite Ag-supported ZnO monolayer.

  14. Critical role of wettability in assembly of zirconia nanoparticles on a self-assembled monolayer-patterned substrate

    Science.gov (United States)

    Yang, Mi-Sun; Lee, Seung-Hoon; Moon, Byung Kee; Yoo, Seung Ryul; Hwang, Seongpil; Jang, Jae-Won

    2016-08-01

    This study investigated which factors decisively influence colloidal nanoparticle (NP) assembly on a self-assembled monolayer (SAM)-patterned substrate. Zirconia (ZrO2) NP assembly on a poly(dimethylsiloxane) (PDMS)-stamped SAM-patterned Au substrate was carried out while the size and surface charge state of the NPs and the substrate wettability were altered. ZrO2 particles with diameters of 350 nm, 560 nm, and 1100 nm were employed to examine the effect of NP size on the assembly. Bare ZrO2 NPs with a negatively charged surface and ZrO2 NPs with a positively charged surface through 3-aminopropyltriethoxysilane encapsulation were prepared for the NP assembly. Moreover, the substrate wettability effect on the NP assembly was evaluated by comparing the assembly on substrates with the PDMS-patterned SAMs of thiols with polar and non-polar functional groups. From the characterization of the number of NPs in a pattern and the effective area of assembled NPs (Aeff), positively charged ZrO2 NP assembly on negatively charged patterns showed the highest number density of particles in a pattern compared with the other combinations in both 350-nm and 560-nm ZrO2 NPs. This observation can be attributed to negatively charged 16-mercaptohexadecanoic acid SAMs having greater polarity (more polar groups) than positively charged 11-amino-1-undecanethiol SAMs within the condition of the colloidal ZrO2 NP assembly.

  15. X-ray diffraction studies of organic monolayers on the surface of water

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, P.; Peng, J.B.; Lin, B.; Ketterson, J.B.; Prakash, M.; Georgopoulos, P.; Ehrlich, S.

    1987-05-25

    We have used synchrotron radiation to study organic monolayers on water (''Langmuir films''). At high monolayer pressures, lead stearate (Pb(C/sub 17/H/sub 35/COO)/sub 2/) shows a powder peak at 1.60 A/sup -1/, implying an area per unit cell of 17.8 A/sup 2/ if the lattice is triangular. The correlation length is about 250 A. Lignoceric acid (C/sub 23/H/sub 47/COOH) shows a similar peak even though no heavy ions are attached. When the pressure is reduced, the peak in lead stearate does not observably move or broaden; below the ''knee'' in the isotherm, however, the peak height decreases slowly with increasing area, implying a first-order melting transition.

  16. Electrochemical fabrication of surface chemical gradients in thiol self-assembled monolayers with tailored work-functions.

    Science.gov (United States)

    Fioravanti, Giulia; Lugli, Francesca; Gentili, Denis; Mucciante, Vittoria; Leonardi, Francesca; Pasquali, Luca; Liscio, Andrea; Murgia, Mauro; Zerbetto, Francesco; Cavallini, Massimiliano

    2014-10-01

    The studies on surface chemical gradients are constantly gaining interest both for fundamental studies and for technological implications in materials science, nanofluidics, dewetting, and biological systems. Here we report on a new approach that is very simple and very efficient, to fabricate surface chemical gradients of alkanethiols, which combines electrochemical desorption/partial readsorption, with the withdrawal of the surface from the solution. The gradient is then stabilized by adding a complementary thiol terminated with a hydroxyl group with a chain length comparable to desorbed thiols. This procedure allows us to fabricate a chemical gradient of the wetting properties and the substrate work-function along a few centimeters with a gradient slope higher than 5°/cm. Samples were characterized by cyclic voltammetry during desorption, static contact angle, XPS analysis, and Kelvin probe. Computer simulations based on the Dissipative Particle Dynamics methods were carried out considering a water droplet on a mixed SAM surface. The results help to rationalize the composition of the chemical gradient at different position on the Au surface.

  17. Organic Monolayers by B(C6F5)3-Catalyzed Siloxanation of Oxidized Silicon Surfaces

    Science.gov (United States)

    2017-01-01

    Inspired by the homogeneous catalyst tris(pentafluorophenyl) borane [B(C6F5)3], which acts as a promotor of Si–H bond activation, we developed and studied a method of modifying silicon oxide surfaces using hydrosilanes with B(C6F5)3 as the catalyst. This dedihydrosiloxanation reaction yields complete surface coverage within 10 min at room temperature. Organic monolayers derived from hydrosilanes with varying carbon chain lengths (C8–C18) were prepared on oxidized Si(111) surfaces, and the thermal and hydrolytic stabilities of the obtained monolayers were investigated in acidic (pH 3) medium, basic (pH 11) medium, phosphate-buffered saline (PBS), and deionized water (neutral conditions) for up to 30 days. DFT calculations were carried out to gain insight into the mechanism, and the computational results support a mechanism involving silane activation with B(C6F5)3. This catalyzed reaction path proceeds through a low-barrier-height transition state compared to the noncatalyzed reaction path. PMID:28230381

  18. Cyclodextrin-based surface acoustic wave chemical microsensors

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.Q.; Shi, J.X.; Springer, K.; Swanson, B.I.

    1996-07-01

    Cyclodextrin thin films were fabricated using either self-assembled monolayer (SAM) or solgel techniques. The resulting host receptor thin films on the substrates of surface acoustic wave (SAW) resonators were studied as method of tracking organic toxins in vapor phase. The mass loading of surface-attached host monolayers on SAW resonators gave frequency shifts corresponding to typical monolayer surface coverages for SAM methods and ``multilayer`` coverages for sol-gel techniques. Subsequent exposure of the coated SAW resonators to organic vapors at various concentrations, typically 5,000 parts per millions (ppm) down to 100 parts per billions (ppb) by mole, gave responses indicating middle-ppb-sensitivity ({approximately}50 ppb) for those sensor-host-receptors and organic-toxin pairs with optimum mutual matching of polarity, size, and structural properties.

  19. Improved aging performance of vapor phase deposited hydrophobic self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Gnanappa, Arun Kumar, E-mail: arun@imel.demokritos.gr [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland); Institute of Microelectronics, NCSR Demokritos, Athens (Greece); O' Murchu, Cian; Slattery, Orla; Peters, Frank [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland); O' Hara, Tony [Memsstar Technology (registered) , Starlaw Park, Starlaw Road, Livingston (United Kingdom); Aszalos-Kiss, Balazs; Tofail, Syed A.M. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland)

    2011-02-15

    A hydrophobic self-assembled monolayer (SAM) of fluoro-octyl-trichloro-silane (FOTS) was deposited on silicon using a vapor phase technique. The aging of the hydrophobic layer was examined using water contact angle measurements. It has been found that while such monolayer films suffer from a loss of hydrophobicity with time, pre-immersion nitrogen annealing can significantly improve the aging characteristics of these monolayers. The effect of nitrogen annealing on the improved aging properties of SAM coatings has been investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The hydrolytic stability and the effect of nitrogen annealing were studied by morphological evolution during immersion. A spontaneous formation of silane mounds on the surface of the monolayers was found by AFM. These mounds have been irreversibly transformed from initially uniform hydrophobic surface layers. It is highly probable that the compliance of these mounds can reasonably allow hydrophilic sites to be located around the mounds. Interestingly, the density of these mounds formation is very less on the annealed samples. XPS reveals a higher level of coverage by the N{sub 2}-annealed film due to agglomeration. A relative abundance of CF{sub 3} and CF{sub 2} moieties in the annealed film may explain the enhancement of the hydrophobicity as revealed by higher level of water contact angle. This hydrophobicity was found to be significantly stable in water. This novel finding explains the improved hydrophobic stability of FOTS monolayers as primarily a morpho-chemical effect that originates from the densification of the monolayers upon annealing.

  20. 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.

  1. Optimisation and Characterisation of Anti-Fouling Ternary SAM Layers for Impedance-Based Aptasensors

    Directory of Open Access Journals (Sweden)

    Anna Miodek

    2015-09-01

    Full Text Available An aptasensor with enhanced anti-fouling properties has been developed. As a case study, the aptasensor was designed with specificity for human thrombin. The sensing platform was developed on screen printed electrodes and is composed of a self-assembled monolayer made from a ternary mixture of 15-base thiolated DNA aptamers specific for human thrombin co-immobilised with 1,6-hexanedithiol (HDT and further passivated with 1-mercapto-6-hexanol (MCH. HDT binds to the surface by two of its thiol groups forming alkyl chain bridges and this architecture protects from non-specific attachment of molecules to the electrode surface. Using Electrochemical Impedance Spectroscopy (EIS, the aptasensor is able to detect human thrombin as variations in charge transfer resistance (Rct upon protein binding. After exposure to a high concentration of non-specific Bovine Serum Albumin (BSA solution, no changes in the Rct value were observed, highlighting the bio-fouling resistance of the surface generated. In this paper, we present the optimisation and characterisation of the aptasensor based on the ternary self-assembled monolayer (SAM layer. We show that anti-fouling properties depend on the type of gold surface used for biosensor construction, which was also confirmed by contact angle measurements. We further studied the ratio between aptamers and HDT, which can determine the specificity and selectivity of the sensing layer. We also report the influence of buffer pH and temperature used for incubation of electrodes with proteins on detection and anti-fouling properties. Finally, the stability of the aptasensor was studied by storage of modified electrodes for up to 28 days in different buffers and atmospheric conditions. Aptasensors based on ternary SAM layers are highly promising for clinical applications for detection of a range of proteins in real biological samples.

  2. Optimisation and Characterisation of Anti-Fouling Ternary SAM Layers for Impedance-Based Aptasensors.

    Science.gov (United States)

    Miodek, Anna; Regan, Edward M; Bhalla, Nikhil; Hopkins, Neal A E; Goodchild, Sarah A; Estrela, Pedro

    2015-09-29

    An aptasensor with enhanced anti-fouling properties has been developed. As a case study, the aptasensor was designed with specificity for human thrombin. The sensing platform was developed on screen printed electrodes and is composed of a self-assembled monolayer made from a ternary mixture of 15-base thiolated DNA aptamers specific for human thrombin co-immobilised with 1,6-hexanedithiol (HDT) and further passivated with 1-mercapto-6-hexanol (MCH). HDT binds to the surface by two of its thiol groups forming alkyl chain bridges and this architecture protects from non-specific attachment of molecules to the electrode surface. Using Electrochemical Impedance Spectroscopy (EIS), the aptasensor is able to detect human thrombin as variations in charge transfer resistance (Rct) upon protein binding. After exposure to a high concentration of non-specific Bovine Serum Albumin (BSA) solution, no changes in the Rct value were observed, highlighting the bio-fouling resistance of the surface generated. In this paper, we present the optimisation and characterisation of the aptasensor based on the ternary self-assembled monolayer (SAM) layer. We show that anti-fouling properties depend on the type of gold surface used for biosensor construction, which was also confirmed by contact angle measurements. We further studied the ratio between aptamers and HDT, which can determine the specificity and selectivity of the sensing layer. We also report the influence of buffer pH and temperature used for incubation of electrodes with proteins on detection and anti-fouling properties. Finally, the stability of the aptasensor was studied by storage of modified electrodes for up to 28 days in different buffers and atmospheric conditions. Aptasensors based on ternary SAM layers are highly promising for clinical applications for detection of a range of proteins in real biological samples.

  3. Origin of the contact angle hysteresis of water on chemisorbed and physisorbed self-assembled monolayers.

    Science.gov (United States)

    Belman, Nataly; Jin, Kejia; Golan, Yuval; Israelachvili, Jacob N; Pesika, Noshir S

    2012-10-16

    Self-assembled monolayers (SAMs) are known to form on a variety of substrates either via chemisorption (i.e., through chemical interactions such as a covalent bond) or physisorption (i.e., through physical interactions such as van der Waals forces or "ionic" bonds). We have studied the behavior and effects of water on the structures and surface energies of both chemisorbed octadecanethiol and physisorbed octadecylamine SAMs on GaAs using a number of complementary techniques including "dynamic" contact angle measurements (with important time and rate-dependent effects), AFM, and electron microscopy. We conclude that both molecular overturning and submolecular structural changes occur over different time scales when such SAMs are exposed to water. These results provide new insights into the time-dependent interactions between surfaces and colloids functionalized with SAMs when synthesized in or exposed to high humidity or bulk water or wetted by water. The study has implications for a wide array of phenomena and applications such as adhesion, friction/lubrication and wear (tribology), surfactant-solid surface interactions, the organization of surfactant-coated nanoparticles, etc.

  4. 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.

  5. Directed immobilization of reduced antibody fragments onto a novel SAM on gold for myoglobin impedance immunosensing.

    Science.gov (United States)

    Billah, Md Morsaline; Hodges, Christopher S; Hays, Henry C W; Millner, P A

    2010-11-01

    The successful construction of an immunosensor depends on having an effective procedure for immobilising the bio-recognition element to the transducer surface. In the present study, an amino-terminated 4-aminothiophenol (ATP) self-assembled monolayer (SAM) was modified with heterobifunctional crosslinker sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate to couple reduced anti-myoglobin half-antibody fragments. The disulphide groups present in the hinge region of IgG molecules were selectively cleaved by 2-mercaptoethylamine to produce reduced half-antibody fragments with free sulphydryl groups. The maleimide terminated 4-ATP SAM modified surface was coupled to these reduced antibody fragments to produce highly oriented immobilization of the half-antibody via its Fc domain and to allow free access to the Fv bindings sites. This represents an improvement by comparison with biotin/avidin mediated IgG attachment which is essentially randomly oriented. Functional immunosensors were able to detect myoglobin in both phosphate buffered saline and whole serum over the range of concentrations from 10(-13)M to 10(-6)M, and order of magnitude better than avidin/biotin linked immunosensors. In addition, atomic force microscopy (AFM) was carried out to elucidate the nanotopology of the immunosensor surface at different stages of fabrication; the images demonstrate that half antibodies bind as described and show structural changes on subsequent antigen binding.

  6. Interface control between an indium–tin-oxide electrode and a hole-transport polymer via reactive self-assembled monolayers

    Science.gov (United States)

    Ono, Sotaro; Usui, Satoshi; Tanaka, Kuniaki; Usui, Hiroaki

    2017-04-01

    The indium–tin-oxide (ITO) surface was modified with self-assembled monolayers (SAMs) having different terminal groups including methyl, vinyl, benzophenone, and azo units. A hole-transport layer of fluorene-phenoxazine copolymer was spin-coated on the surface and then irradiated with UV light to induce photochemical reaction at the interface between the SAMs and the polymer. It was observed that the SAMs having the benzophenone and azo terminal groups can tether the spin-coated polymer after UV irradiation. The photochemical tethering was effective in improving charge injection from the ITO anode to the hole-transport polymer as well as in improving the adhesion strength of the polymer to the substrate. It is considered that the covalent tethering can be an important factor for improving the interfacial characteristics of organic/inorganic junctions.

  7. Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold

    Energy Technology Data Exchange (ETDEWEB)

    Willey, T M; Fabbri, J; Lee, J I; Schreiner, P; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J; Carlson, B; Vance, A L; Yang, W; Terminello, L J; van Buuren, T; Melosh, N

    2007-11-27

    Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.

  8. Characteristics of localized surface plasmons excited on mixed monolayers composed of self-assembled Ag and Au nanoparticles.

    Science.gov (United States)

    Tanaka, Daisuke; Imazu, Keisuke; Sung, Jinwoo; Park, Cheolmin; Okamoto, Koichi; Tamada, Kaoru

    2015-10-07

    The fundamental characteristics of localized surface plasmon resonance (LSPR) excited on mixed monolayers composed of self-assembled Ag and Au nanoparticles (AgNPs and AuNPs, respectively) were investigated. Mixed monolayered films were fabricated at the air-water interface at different mixing ratios. The films retained their phase-segregated morphologies in which AuNPs formed several 10 to 100 nm island domains in a homogeneous AgNP matrix phase. The LSPR bands originating from the self-assembled domains shifted to longer wavelengths as the domain size increased, as predicted by a finite-difference time-domain (FDTD) simulation. The FDTD simulation also revealed that even an alternating-lattice-structured two-dimensional (2D) AgNP/AuNP film retained two isolated LSPR bands, revealing that the plasmon resonances excited on each particle did not couple even in a continuous 2D sheet, unlike in the homologous NP system. The fluorescence quenching test of Cy3 and Cy5 dyes confirmed that the independent functions of AuNPs and AgNPs remained in the mixed films, whereas the AuNPs exhibited significantly higher quenching efficiency for the Cy3 dye compared with AgNPs due to the overlap of the excitation/emission bands of the dyes with the AuNP LSPR band. Various applications can be considered using this nanoheterostructured plasmonic assembly to excite spatially designed, high-density LSPR on macroscopic surfaces.

  9. Modification of structure and pattern of lipid monolayer on water and solid surfaces in presence of globular protein

    Science.gov (United States)

    Sah, Bijay Kumar; Kundu, Sarathi

    2017-05-01

    Langmuir monolayers of phospholipids at the air-water interface are well-established model systems for mimicking biological membranes and hence are useful for studying lipid-protein interactions. In the present work, phases and phase transformations occurring in the lipid (DMPA) monolayer in the presence of globular protein (BSA) at neutral subphase pH (≈7.0) are highlighted and the corresponding in-plane pattern and morphology are explored from the surface pressure (π) - specific molecular area (A) isotherm, Brewster angle microscopy (BAM) and atomic force microscopy (AFM) both at air-water and air-solid interfaces. Films of pure lipid and lipid-protein complexes are deposited on solid surfaces by Langmuir-Blodgett method. Due to the presence of BSA molecules, phases and domain pattern changes in comparison with that of the pure DMPA. Moreover, accumulations of globular proteins in between lipid domains are also visible through BAM. AFM shows that the mixed film has relatively bigger globular-like morphology in comparison with that of pure DMPA domains. Combination of electrostatic and hydrophobic interactions between protein and lipid are responsible for such modifications.

  10. Partial ion yield and NEXAFS of 2-(perfluorooctyl)ethanethiol self-assembled monolayer: Comparison with PTFE results

    CERN Document Server

    Setoyama, H; Murase, T; Imamura, M; Mase, K; Okudaira, K K; Hara, M; Ueno, N

    2003-01-01

    Partial-ion-yield (PIY) spectra using ion time-of-flight (TOF) method and near-edge absorption fine structure (NEXAFS) spectra were measured for 2-(perfluorooctyl)ethanethiol [CF sub 3 (CF sub 2) sub 7 (CH sub 2) sub 2 SH] self-assembled monolayer (F8-SAM) on Au(1 1 1) near carbon K-edge. The PIY spectra of the F8-SAM at the magic angle, where -CF sub 3 groups exist at the surface were compared with those of the rubbed polytetrafluoroethylene (PTFE) thin film. The F sup + intensity from the F8-SAM at the photon energy of the sharp peak of the NEXAFS, which originates from the excitation of C1s electron to sigma sup * (C-F) states at -CF sub 2 - chain, was extremely smaller than that from the rubbed PTFE film. This result clearly indicates that the ions observed by PIY do not originate from the film inside but from the surface. This was confirmed by changes in ion-TOF mass spectra during soft X-ray induced etching of the F8-SAM. The NEXAFS peaks of the F8-SAM were also assigned by considering PIY results.

  11. Energy-Level Engineering at ZnO/Oligophenylene Interfaces with Phosphonate-Based Self-Assembled Monolayers.

    Science.gov (United States)

    Timpel, Melanie; Nardi, Marco V; Ligorio, Giovanni; Wegner, Berthold; Pätzel, Michael; Kobin, Björn; Hecht, Stefan; Koch, Norbert

    2015-06-10

    We used aromatic phosphonates with substituted phenyl rings with different molecular dipole moments to form self-assembled monolayers (SAMs) on the Zn-terminated ZnO(0001) surface in order to engineer the energy-level alignment at hybrid inorganic/organic semiconductor interfaces, with an oligophenylene as organic component. The work function of ZnO was tuned over a wide range of more than 1.7 eV by different SAMs. The difference in the morphology and polarity of the SAM-modified ZnO surfaces led to different oligophenylene orientation, which resulted in an orientation-dependent ionization energy that varied by 0.7 eV. The interplay of SAM-induced work function modification and oligophenylene orientation changes allowed tuning of the offsets between the molecular frontier energy levels and the semiconductor band edges over a wide range. Our results demonstrate the versatile use of appropriate SAMs to tune the energy levels of ZnO-based hybrid semiconductor heterojunctions, which is important to optimize its function, e.g., targeting either interfacial energy- or charge-transfer.

  12. Scattering properties of gas molecules on self-assembled monolayers using molecular dynamics simulation

    Science.gov (United States)

    Takeuchi, Hideki

    2016-11-01

    The scattering properties of argon gas molecules on the SAM (self-assembled monolayer) surface which consists of 1-propanethiol molecules chemically adsorbed on a gold surface have been investigated by using the molecular dynamics method. The trapping probability, the angular distribution and the angular scattering distribution for the gas molecule have been obtained for various incident energies and angles. It is shown that the trapping probability decreases with increasing the incident energy. The angular distribution for small incident angle is almost close to the cosine distribution. In addition, the partial accommodation coefficients of tangential momentum and energy for gas molecules are discussed.

  13. 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.

  14. Immobilisation of a thrombopoietin peptidic mimic by self-assembled monolayers for culture of CD34+ cells.

    Science.gov (United States)

    Lee, Eun-Ju; Be, Cheang Ly; Vinson, Andrew R; Riches, Andrew G; Fehr, Friederike; Gardiner, James; Gengenbach, Thomas R; Winkler, David A; Haylock, David

    2015-01-01

    Compared to soluble cytokines, surface-tethered ligands can deliver biological signalling with precise control of spatial positioning and concentration. A strategy that immobilises ligand molecules on a surface in a uniform orientation using non-cleavable linkages under physiological conditions would enhance the specific and systemic delivery of signalling in the local environment. We used mixed self-assembled monolayers (SAMs) of oxyamine- and oligo(ethylene glycol)-terminated thiols on gold to covalently install aldehyde- or ketone-functionalised ligands via oxime conjugation. Characterisation by electrochemistry and X-ray photoelectron spectroscopy showed quantitative immobilisation of the ligands on SAM surfaces. The thrombopoietin mimetic peptide, RILL, was immobilised on SAMs and the bioactivity of the substrate was demonstrated by culturing factor-dependent cells. We also optimised the immobilisation and wash conditions so that the peptide was not released into the culture medium and the immobilised RILL could be re-used for consecutive cell cultures. The surface also supported the growth of haematopoietic CD34+ cells comparable to the standard thrombopoietin-supplemented culture. Furthermore, the RILL-immobilised SAM surface was as effective in expanding uncommitted CD34+ cells as standard culture. The stimulatory effect of surface-tethered ligands in haematopoietic stem cell expansion supports the use of ligand immobilisation strategies to replicate the haematopoietic stem cell niche.

  15. Study on the formation of self-assembled monolayers on sol-gel processed hafnium oxide as dielectric layers.

    Science.gov (United States)

    Ting, Guy G; Acton, Orb; Ma, Hong; Ka, Jae Won; Jen, Alex K-Y

    2009-02-17

    High dielectric constant (k) metal oxides such as hafnium oxide (HfO2) have gained significant interest due to their applications in microelectronics. In order to study and control the surface properties of hafnium oxide, self-assembled monolayers (SAMs) of four different long aliphatic molecules with binding groups of phosphonic acid, carboxylic acid, and catechol were formed and characterized. Surface modification was performed to improve the interface between metal oxide and top deposited materials as well as to create suitable dielectric properties, that is, leakage current and capacitance densities, which are important in organic thin film transistors. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle goniometry, atomic force microscopy (AFM), and simple metal-HfO2-SAM-metal devices were used to characterize the surfaces before and after SAM modification on sol-gel processed hafnium oxide. The alkylphosphonic acid provided the best monolayer formation on sol-gel processed hafnium oxide to generate a well-packed, ultrathin dielectric exhibiting a low leakage current density of 2x10(-8) A/cm2 at an applied voltage of -2.0 V and high capacitance density of 0.55 microF/cm2 at 10 kHz. Dialkylcatechol showed similar characteristics and the potential for using the catechol SAMs to modify HfO2 surfaces. In addition, the integration of this alkylphosphonic acid SAM/hafnium oxide hybrid dielectric into pentacene-based thin film transistors yields low-voltage operation within 1.5 V and improved performance over bare hafnium oxide.

  16. Modification of gold surface by grafting of poly(ethylene glycol) for reduction in protein adsorption and platelet adhesion.

    Science.gov (United States)

    Zhang, F; Kang, E T; Neoh, K G; Huang, W

    2001-01-01

    Gold surfaces were first treated in an alkanethiol solution to form self-assembled monolayers (SAMs). The thiolated Au surface was then subjected to Ar plasma pretreatment, followed by air exposure and UV-induced graft polymerization of poly(ethylene glycol) methacrylate (PEGMA) macromonomer. In comparison with the 3-mercaptopropionic acid-2-ethylhexyl ester (MPAEE) SAM, the (3-mercaptoproply)trimethoxysilane (MPTMS) SAM on Au exhibited higher stability under the conditions of Ar plasma pretreatment. The graft concentration of the PEGMA polymer on SAM-modified Au surface increased with increasing PEGMA macromonomer concentration and UV-graft polymerization time. The modified-Au surfaces were characterized by X-ray spectroscopy (XPS), atomic force microscopy (AFM), and water contact angle measurement. The Au surface with a high concentration of grafted PEGMA polymer could completely repel protein adsorption and platelet adhesion.

  17. Assembly of citrate gold nanoparticles on hydrophilic monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Vikholm-Lundin, Inger, E-mail: inger.vikholm-lundin@uta.fi [University of Tampere, BioMediTech, Tampere (Finland); Fimlab Laboratories Ltd., Tampere (Finland); Rosqvist, Emil; Ihalainen, Petri [Abo Akademi University, Center for Functional Materials, Laboratory of Physical Chemistry (Finland); Munter, Tony [VTT Technical Research Centre of Finland, Process Chemistry end Environmental Engineering, Tampere (Finland); Honkimaa, Anni [University of Tampere, Department of Virology, School of Medicine, Tampere (Finland); Marjomäki, Varpu [University of Jyväskylä, Department of Biological and Environmental Science, Nanoscience Center, Jyväskylä (Finland); Albers, Willem M. [BioNavis Oy Ltd., Ylöjärvi, Tampere (Finland); Peltonen, Jouko [Abo Akademi University, Center for Functional Materials, Laboratory of Physical Chemistry (Finland)

    2016-08-15

    Highlights: • The self-assembled layers were all hydrophilic with Lipa-pTHMMAA exhibiting close to full wetting. • The polyacrylamide layers smoothen the gold surface to a higher extent than the polyethylene glycol and lipoic acid terminated with an amino group. • SPR resonance curves shift to higher angles and become increasingly damped when large nanoparticles assembled on the surface. • 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. - Abstract: 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

  18. CareSam

    DEFF Research Database (Denmark)

    Liveng, Anne; Christensen, Jonas

    2016-01-01

    negative cultural perceptions of help-needing elderly and the people who support them in everyday life? In answering these questions and thereby reflecting on our own work process we apply a caring, a learning and a political perspective. Hereby the article wishes to formulate a methodological point......This article presents findings and discussions generated on the basis of the Danish-Swedish development project CareSam. The article will on the one hand focus on how work in groups consisting of representatives from different levels in the elderly care sector at one time served as learning spaces...... in the project-groups this paper will ask whether it is possible to represent care work for elderly people with all the ambiguities it holds: How can we as researchers represent both meaningfulness and straining dimensions of care work? Can we avoid either supporting Florence Nightingale-ideals or cementing...

  19. Surface dynamics of organic layers explored by scanning probe microscopy techniques

    NARCIS (Netherlands)

    Wu, Hairong

    2015-01-01

    Organic thin layers, especially self-assembled monolayers (SAMs), on well-defined solid surfaces have attracted tremendous attention owing to their interesting physical and chemical behavior as well as potential applications. The aim of this PhD thesis was to study the structural properties, electro

  20. 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.

  1. Self-Assembled Monolayers of Perfluoroanthracenylaminoalkane Thiolates on Gold as Potential Electron Injection Layers.

    Science.gov (United States)

    Zhang, Zibin; Wächter, Tobias; Kind, Martin; Schuster, Swen; Bats, Jan W; Nefedov, Alexei; Zharnikov, Michael; Terfort, Andreas

    2016-03-23

    As a material with relatively small band gap and low lying valence orbitals, perfluoroanthracene (PFA) is of interest for the modification of electrode surfaces, for example, as charge injection layers for n-type organic semiconductors. To covalently attach PFA in the form of self-assembled monolayers (SAMs), we developed a synthesis of derivatives with a sulfur termination, linked to the 2-position of the PFA moieties by an -NH- group and a short alkane chain with two and three methylene groups, respectively. Spectroscopic characterization of the SAMs reveals that the molecules adopt an almost upright orientation on the gold surface, with the packing density mostly determined by the steric demands of the PFA units. The number of the methylene groups in the -NH-alkyl linker has only a minor impact on the SAM structure because of the nonsymmetric attachment of the PFA units, which permits the compensation of the orientational constraints imposed by the bending potential. The investigated SAMs alter the work function of gold by +(0.59-0.64) eV, suggesting comparably strong depolarization effects, affecting the extent of the work function modification.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.H. [Faculty of Engineering, Shinshu Universuty, 4-17-1 Wakasato, Nagano 380 8553 (Japan); Saito, N., E-mail: hiro@eco-t.esi.nagoya-u.ac.jp [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464 8603 (Japan); Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464 8603 (Japan); Takai, O. [EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa, Nagoya 464 8603 (Japan)

    2009-06-30

    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.

  3. Comparative electrochemical scanning tunneling microscopy study of nonionic fluorosurfactant zonyl FSN self-assembled monolayers on Au(111) and Au(100): a potential-induced structural transition.

    Science.gov (United States)

    Tang, Yongan; Yan, Jiawei; Zhu, Feng; Sun, Chunfeng; Mao, Bingwei

    2011-02-01

    We investigate the structure of nonionic fluorosurfactant zonyl FSN self-assembled monolayers on Au(111) and Au(100) in 0.05 M H(2)SO(4) as a function of the electrode potential by electrochemical scanning tunneling microscopy (ECSTM). On Au(111), a (3(1/2) × 3(1/2))R30° arrangement of the FSN SAMs is observed, which remains unchanged in the potential range where the redox reaction of FSN molecules does not occur. On Au(100), some parallel corrugations of the FSN SAMs are observed, which originate from the smaller distance and the repulsive interaction between FSN molecules to make the FSN molecules deviate from the bridging sites, and ECSTM reveals a potential-induced structural transition of the FSN SAMs. The experimental observations are rationalized by the effect of the intermolecular interaction. The smaller distance between molecules on Au(100) results in the repulsive force, which increases the probability of structural change induced by external factors (i.e., the electrode potential). The appropriate distance and interactions of FSN molecules account for the stable structure of FSN SAMs on Au(111). Surface crystallography may influence the intermolecular interaction through changing the molecular arrangements of the SAMs. The results benefit the molecular-scale understanding of the behavior of the FSN SAMs under electrochemical potential control.

  4. Molecular dynamics analysis of reflected gas molecules on self-assembled monolayers

    Science.gov (United States)

    Takeuchi, Hideki

    2015-11-01

    In order to investigate the gas flow of high Knudsen number, it is necessary to specify the boundary condition for the reflected gas molecules at a solid surface. In most cases of the analysis, the diffuse reflection is generally assumed, but there are many cases for which this reflection cannot be applied. The characteristics of the reflected gas molecules depend on the state of the solid surface as well as the gas-surface interaction. The present author analyzed the scattering properties of monoatomic and diatomic gases on various solid surfaces based on the molecular dynamics (MD) method and proposed the boundary condition of reflected gas molecule (Phys. Fluids 18, 046103, 2006). Recently, self-assembled monolayers (SAMs) for the functionalization of the solid surface have been used in the development of micro/nano devices such as microarray and nanosensor. Therefore, it is interesting to study the scattering behavior of the reflected gas molecules on the SAM surface and make the scattering model of gases for the boundary condition. In this study, the angular distribution and the trapping probability for gas molecule on the SAM surface are observed by using MD simulation. The scattering probability at different incident energies is also discussed. JSPS KAKENHI Grant Number 26870813.

  5. Sub-micron scale patterning using femtosecond laser and self-assembled monolayers interaction

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Wonseok [Nanoprocess Group, Korea Institute of Machinery and Materials, 171 Jang-dong, Yusong-gu, Daejeon 305-343 (Korea, Republic of)]. E-mail: paul@kimm.re.kr; Choi, Moojin [Nanoprocess Group, Korea Institute of Machinery and Materials, 171 Jang-dong, Yusong-gu, Daejeon 305-343 (Korea, Republic of); Kim, Jaegu [Nanoprocess Group, Korea Institute of Machinery and Materials, 171 Jang-dong, Yusong-gu, Daejeon 305-343 (Korea, Republic of); Cho, Sunghak [Nanoprocess Group, Korea Institute of Machinery and Materials, 171 Jang-dong, Yusong-gu, Daejeon 305-343 (Korea, Republic of); Whang, Kyunghyun [Nanoprocess Group, Korea Institute of Machinery and Materials, 171 Jang-dong, Yusong-gu, Daejeon 305-343 (Korea, Republic of)

    2005-02-15

    Standard positive photoresist techniques were adapted to generate sub-micron scale patterns of gold substrate using self-assembled monolayers (SAMs) and femtosecond laser. Self-assembled monolayers formed by the adsorption of alkanethiols onto gold substrate are employed as very thin photoresists. The process underlying photopatterning of SAMs on gold is well-known at the phenomenological level. Alkanethiolates formed by the adsorption of alkanethiols are oxidized on exposure to UV light in the presence of air to alkylsulfonates. Specifically, it is known that deep UV light of wavelength less than 200 nm is necessary for oxidation to occur. In this study, solid state femtosecond laser of wavelength 800 nm is applied for photolithography. The results show that ultrafast laser of near infrared (NIR) range wavelength can replace deep UV laser source for photopatterning using thin organic films. The essential basis of our approach is the photochemical excitation of specific reactions in a particular functional group (in this case a thiolate sulfur atom) distributed with monolayer coverage on a solid surface. Femtosecond laser photolithography could be applied to fabricate the patterning of surface chemical structure and the creation of three-dimensional nanostructures by combination with suitable etching methods.

  6. Crystalline structures of alkylamide monolayers adsorbed on the surface of graphite.

    Science.gov (United States)

    Bhinde, Tej; Clarke, Stuart M; Phillips, Tamsin K; Arnold, Thomas; Parker, Julia E

    2010-06-01

    Synchrotron X-ray and neutron diffraction have been used to determine the two-dimensional crystalline structures of alkylamides adsorbed on graphite at submonolayer coverage. The calculated structures show that the plane of the carbon backbone of the amide molecules is parallel to the graphite substrate. The molecules form hydrogen-bonded dimers, and adjacent dimers form additional hydrogen bonds yielding extended chains. By presenting data from a number of members of the homologous series, we have identified that these chains pack in different arrangements depending on the number of carbons in the amide molecule. The amide monolayers are found to be very stable relative to other closely related alkyl species, a feature which is attributed to the extensive hydrogen bonding present in these systems. The characteristics of the hydrogen bonds have been determined and are found to be in close agreement with those present in the bulk materials.

  7. Functionalizing Arrays of Transferred Monolayer Graphene on Insulating Surfaces by Bipolar Electrochemistry

    DEFF Research Database (Denmark)

    Koefoed, Line; Pedersen, Emil Bjerglund; Thyssen, Lena

    2016-01-01

    graphene sheets supported on SiO2. Using this technique, transferred graphene can be electrochemically functionalized without the need of a metal support or the deposition of physical contacts. X-ray photoelectron spectroscopy and Raman spectroscopy are used to map the chemical changes and modifications....... Furthermore, it is shown that it is possible to simultaneously modify an array of many small graphene electrodes (1 × 1 mm2) on SiO2.......Development of versatile methods for graphene functionalization is necessary before use in applications such as composites or as catalyst support. In this study, bipolar electrochemistry is used as a wireless functionalization method to graft 4-bromobenzenediazonium on large (10 × 10 mm2) monolayer...

  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. Hotspot-engineered quasi-3D metallic network for surface-enhanced Raman scattering based on colloid monolayer templating

    Science.gov (United States)

    Du, Wei; Liu, Long; Gu, Ping; Hu, Jingguo; Zhan, Peng; Liu, Fanxin; Wang, Zhenlin

    2016-09-01

    A hotspot-engineered quasi-3D metallic network with controllable nanogaps is purposed as a high-quality surface-enhanced Raman scattering (SERS) substrate, which is prepared by a combination of non-close-packed colloid monolayer templating and metal physical deposition. The significant SERS effect arises from a strongly enhanced local electric field originating from the ultra-small-gaps between neighboring metal-caps and tiny interstices and between the metal-caps and the metal-bumps on the base, which is recognized by the numerical simulation. A remarkable average SERS enhancement factor of up to 1.5 × 108 and a SERS intensity relative standard deviation (RSD) of 10.5% are achieved by optimizing the nanogap size to sub-10 nm scale, leading to an excellent capability for Raman detection, which is represented by the clearly identified SERS signal of the Rhodamine 6G solution with a fairly low concentration of 1 nM.

  10. The effect of vanadium-carbon monolayer on the adsorption of tungsten and carbon atoms on tungsten-carbide (0001 surface

    Directory of Open Access Journals (Sweden)

    Moitra A.

    2011-01-01

    Full Text Available We report a first-principles calculations to study the effect of a vanadium-carbon (VC monolayer on the adsorption process of tungsten (W and carbon (C atoms onto tungsten-carbide (WC (0001 surface. The essential configuration for the study is a supercell of hexagonal WC with a (0001 surface. When adding the VC monolayer, we employed the lowest energy configuration by examining various configurations. The total energy of the system is computed as a function of the W or C adatoms’ height from the surface. The adsorption of a W and C adatom on a clean WC (0001 surface is compared with that of a W and C adatom on a WC (0001 surface with VC monolayer. The calculations show that the adsorption energy increased for both W and C adatoms in presence of the VC monolayer. Our results provide a fundamental understanding that can explain the experimentally observed phenomena of inhibited grain growth during sintering of WC or WC-Co powders in presence of VC.

  11. Study of PEGylated lipid layers as a model for PEGylated liposome surfaces: molecular dynamics simulation and Langmuir monolayer studies.

    Science.gov (United States)

    Stepniewski, Michał; Pasenkiewicz-Gierula, Marta; Róg, Tomasz; Danne, Reinis; Orlowski, Adam; Karttunen, Mikko; Urtti, Arto; Yliperttula, Marjo; Vuorimaa, Elina; Bunker, Alex

    2011-06-21

    We have combined Langmuir monolayer film experiments and all-atom molecular dynamics (MD) simulation of a bilayer to study the surface structure of a PEGylated liposome and its interaction with the ionic environment present under physiological conditions. Lipids that form both gel and liquid-crystalline membranes have been used in our study. By varying the salt concentration in the Langmuir film experiment and including salt at the physiological level in the simulation, we have studied the effect of salt ions present in the blood plasma on the structure of the poly(ethylene glycol) (PEG) layer. We have also studied the interaction between the PEG layer and the lipid bilayer in both the liquid-crystalline and gel states. The MD simulation shows two clear results: (a) The Na(+) ions form close interactions with the PEG oxygens, with the PEG chains forming loops around them and (b) PEG penetrates the lipid core of the membrane for the case of a liquid-crystalline membrane but is excluded from the tighter structure of the gel membrane. The Langmuir monolayer results indicate that the salt concentration affects the PEGylated lipid system, and these results can be interpreted in a fashion that is in agreement with the results of our MD simulation. We conclude that the currently accepted picture of the PEG surface layer acting as a generic neutral hydrophilic polymer entirely outside the membrane, with its effect explained through steric interactions, is not sufficient. The phenomena we have observed may affect both the interaction between the liposome and bloodstream proteins and the liquid-crystalline-gel transition and is thus relevant to nanotechnological drug delivery device design.

  12. Electron transfer kinetics of cytochrome c immobilized on a phenolic terminated thiol self assembled monolayer determined by scanning electrochemical microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, Vali [Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Mousavi, Mir Fazlollah, E-mail: mousavim@modares.ac.ir [Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Mehrgardi, Masoud Ayatollahi [Department of Chemistry, University of Isfahan, Isfahan (Iran, Islamic Republic of); Kazemi, Sayed Habib [Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan (Iran, Islamic Republic of); Sharghi, Hashem [Department of Chemistry, Shiraz University, Shiraz (Iran, Islamic Republic of)

    2011-07-01

    Highlights: > Preparing a thiolated phenolic self-assembled monolayer surface (SAM). > Application of this SAM to immobilize cytochrome C. > Scanning electrochemical microscopy used for these studies. > Determination of both tunneling electron transfer and bimolecular rate constants between the immobilized protein-substrate and probe. - Abstract: In the present manuscript, the electrochemical behavior of cytochrome c (cyt-c) immobilized onto a phenolic terminated self assembled monolayer (SAM) on a gold electrode is investigated using cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The tunneling electron transfer (ET) rate constant between the immobilized protein and the underlying electrode surface, and also the bimolecular ET rate constant between the immobilized protein and a probe has been obtained using approach curves that were obtained by SECM. The approach curves were recorded at different substrate overpotentials in the presence of various concentrations of ferrocyanide as a probe and various surface concentrations of cyt-c; then the standard tunneling ET and bimolecular rate constants are obtained as 3.4 {+-} 0.3 s{sup -1} and (2.0 {+-} 0.5) x 10{sup 7} cm{sup 3} mol{sup -1} s{sup -1}, respectively.

  13. 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.

  14. Atomic stick-slip friction between commensurate self-assembled monolayers

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The classical molecular dynamics simulations have been used to examine the compression and friction between commensurate self-assembled monolayers (SAMs) on Au (111). The friction force changes in a period corresponding to the geometric structure of sliding surfaces. The simulations reveal an ordered atomic stick-slip motion and discontinuous movements of diverse monomers, mainly head and tail groups. All of the head groups of the static film have 2~3 metastable positions (MPs). They oscillate around one of the MPs in stick phases and jump simultaneously to a new MP in slip phases. The tail groups of the sliding film are pulled forward together with opposite ones while sticking and jump forward half of the lattice constant relative to opposite ones while slipping. A complete vision of the motion of SAM chains is thereby built up and compared with the molecule behavior predicted by the Tomlinson model.

  15. Characterization of monolayer formation on aluminum-doped zinc oxide thin films.

    Science.gov (United States)

    Rhodes, Crissy L; Lappi, Simon; Fischer, Daniel; Sambasivan, Sharadha; Genzer, Jan; Franzen, Stefan

    2008-01-15

    The optical and electronic properties of aluminum-doped zinc oxide (AZO) thin films on a glass substrate are investigated experimentally and theoretically. Optical studies with coupling in the Kretschmann configuration reveal an angle-dependent plasma frequency in the mid-IR for p-polarized radiation, suggestive of the detection of a Drude plasma frequency. These studies are complemented by oxygen depletion density functional theory studies for the calculation of the charge carrier concentration and plasma frequency for bulk AZO. In addition, we report on the optical and physical properties of thin film adlayers of n-hexadecanethiol (HDT) and n-octadecanethiol (ODT) self-assembled monolayers (SAMs) on AZO surfaces using reflectance FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Our characterization of the SAM deposition onto the AZO thin film reveals a range of possible applications for this conducting metal oxide.

  16. The Effect of Ring Substitution Position on the Structural Conformation of Mercaptobenzoic Acid Self-Assembled Monolayers on Au(111)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J; Willey, T; Nilsson, J; Terminello, L; De Yoreo, J; van Buuren, T

    2006-04-12

    Near edge X-ray absorption fine structure (NEX-AFS) spectroscopy, photoemission spectroscopy (PES) and contact angle measurements have been used to examine the structure and bonding of self-assembled monolayers (SAMs) prepared on Au(111) from the positional isomers of mercaptobenzoic acid (MBA). The isomer of MBA and solvent chosen in SAM preparation has considerable bearing upon film morphology. Carbon K-edge NEXAFS measurements indicate that the monomers of 2-, 3- and 4-MBA have well-defined orientations within their respective SAMs. Monomers of 3- and 4-MBA assume an upright orientation on the Au substrates in monolayers prepared using an acetic acid in ethanol solvent. The aryl ring and carboxyl group of these molecules are tilted from the surface normal by a colatitudal angle of {approx} 30{sup o}. Preparation of 4-MBA SAMs using pure ethanol solvent, a more traditional means of synthesis, had no appreciable effect upon the monomer orientation. Nonetheless, S(2p) PES measurements illustrate that it results in extensive bilayer formation via carboxyl group hydrogen-bonding between 4-MBA monomers. In 2-MBA monolayers prepared using acetic acid/ethanol solvent, the monomers adopt a more prostrate orientation on the Au substrates, in which the aryl ring and carboxyl group of the molecules are tilted {approx} 50{sup o} from the surface normal. This configuration is consistent with an interaction between both the mercaptan sulfur and carboxyl group of 2-MBA with the underlying substrate. S(2p) and C(1s) PES experiments provide supporting evidence for a bidentate interaction between 2-MBA and Au(111).

  17. Change of the surface electronic structure of Au(111) by a monolayer MgO(001) film

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Yi; Nilius, Niklas; Freund, Hans-Joachim [Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin (Germany); Benedetti, Stefania [CNR, Istituto Nanoscienze, Centro S3, Via G. Campi 213/a, 41100 Modena (Italy)

    2011-07-01

    Monolayer films of MgO(001) have been prepared on an Au(111) surface and explored with scanning tunneling microscopy and spectroscopy. The symmetry mismatch between the hexagonal substrate and the squared over-layer results in the formation of a (6 x 1) super-lattice, as revealed from the distinct stripe pattern observed in the STM. The presence of the oxide film modifies the potential situation at the interface, which induces a substantial up-shift of the Shockley-type surface band on Au(111). The resulting MgO/Au interface band is also characterized by a pseudo-gap at around 0.5 eV that opens at the position of the new Brillouin zone of the enlarged (6 x 1) cell. In addition, the oxide layer gives rise to a drastic decrease of the Au(111) work function, as deduced from the energy position of field-emission resonance on the bare and MgO-covered surface. The work function drop is explained by an interfacial charge transfer from the oxide film into the electro-negative gold surface.

  18. 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.

  19. 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).

  20. 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.

  1. Superhydrophobic SAM Modified Electrodes for Enhanced Current Limiting Properties in Intrinsic Conducting Polymer Surge Protection Devices.

    Science.gov (United States)

    Jabarullah, Noor H; Verrelli, Emanuele; Mauldin, Clayton; Navarro, Luis A; Golden, Josh H; Madianos, Leonidas M; Kemp, Neil T

    2015-06-09

    Surface interface engineering using superhydrophobic gold electrodes made with 1-dodecanethiol self-assembled monolayer (SAM) has been used to enhance the current limiting properties of novel surge protection devices based on the intrinsic conducting polymer, polyaniline doped with methanesulfonic acid. The resulting devices show significantly enhanced current limiting characteristics, including current saturation, foldback, and negative differential effects. We show how SAM modification changes the morphology of the polymer film directly adjacent to the electrodes, leading to the formation of an interfacial compact thin film that lowers the contact resistance at the Au-polymer interface. We attribute the enhanced current limiting properties of the devices to a combination of lower contact resistance and increased Joule heating within this interface region which during a current surge produces a current blocking resistive barrier due to a thermally induced dedoping effect caused by the rapid diffusion of moisture away from this region. The effect is exacerbated at higher applied voltages as the higher temperature leads to stronger depletion of charge carriers in this region, resulting in a negative differential resistance effect.

  2. 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

  3. 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

  4. 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

  5. Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles.

    Science.gov (United States)

    Song, Bo; Zhou, Yi; Schönherr, Holger

    2016-11-01

    The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired in situ on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili-Gee model suggests that the binary SAMs do not segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8-10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties.

  6. Molecular modeling of alkyl monolayers on the Si (100)-2 x 1 surface

    NARCIS (Netherlands)

    Lee, M.V.; Guo, D.; Linford, M.R.; Zuilhof, H.

    2004-01-01

    Molecular modeling was used to simulate various surfaces derived from the addition of 1-alkenes and 1-alkynes to Si=Si dimers on the Si(100)-2 × 1 surface. The primary aim was to better understand the interactions between adsorbates on the surface and distortions of the underlying silicon crystal du

  7. 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

    The photochemical and electrochemical properties of self-assembled monolayers (SAM) of three structurally distinct hexahydro- and hexafluoro-dithienylcyclopentene-based photochromic switches on gold electrodes are reported. The photochemical and electrochemical switching between the open and closed...

  8. 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.

  9. Improving performance, stability, and processability of OFETs with printed Ag electrodes by means of a novel, multipurpose self-assembled monolayer (Conference Presentation)

    Science.gov (United States)

    Alt, Milan; Jesper, Malte; Schinke, Janusz; Hillebrandt, Sabina; Reiser, Patrick; Rödlmeier, Tobias; Angelova, Iva; Hamburger, Manuel; Lemmer, Ulrich; Hernandez-Sosa, Gerardo; Lovrincic, Robert

    2016-11-01

    We present a novel SAM-forming molecule bisjulolidyldisulfide that reduces the WF of metal surfaces by 1.2 eV and can lower the barrier for electron injection to organic semiconductors. Applied to Au and Ag surfaces, including inkjet-printed Ag on PET, we characterized bisjulolidyldisulfide monolayers by means of photoelectron spectroscopy (PES) and sessile drop technique, as well as their influence on the performance of n-type OFETs. Next a strong reduction of the contact resistance by two orders of magnitude, we found that this SAM treatment extends the shelf lifetime of ambient-stored OFET devices. Also, it improves the wettability and thereby facilitates solution processing of a subsequent layer with respect to the untreated surface. The full electrical functionality of bisjulolidyldisulfide SAMs was found to become manifest with only one minute of immersion in ethanol solution. PES measurements suggests that the surface coverage is thorough on Au, but only fractional on Ag, especially on printed Ag. However, the quality of SAM-treated bottom contacts in n-type OFETs is very similar for all three investigated metal surfaces (Au and Ag evaporated and printed Ag). This is especially important for printed Ag-electrodes, as their surface was found to be significantly worse for device performance in comparison to their evaporated Ag counterpart. Using this surface treatment we realized integrated unipolar n-type ring oscillators with inkjet printed Ag electrodes.

  10. Self-assembled monolayers of cholesterol and cholesteryl esters on graphite.

    Science.gov (United States)

    Hibino, Masahiro; Tsuchiya, Hiroshi

    2014-06-17

    The molecular arrangements of self-assembled monolayers (SAMs) of cholesterol, cholesteryl laurate, and cholesteryl stearate adsorbed on a graphite surface were studied using scanning tunneling microscopy (STM) at the liquid-solid interface. The STM images of the SAMs showed two-dimensional periodic arrays of bright regions that corresponded to the sterol rings. However, individual sterol rings could not be observed in the bright regions in the STM images of the cholesterol monolayers. Nevertheless, by comparing the STM images and the crystallographic data, it is concluded that the cholesterol molecules are arranged in pairs oriented head-to-head owing to the hydrogen bonds between the hydroxyl groups. These dimers, in turn, are oriented parallel to each other, owing to the interactions between the sterol rings. The STM images of cholesteryl ester monolayers had molecular resolution and showed pairs of cholesteryl ester molecules oriented in an antiparallel manner, with their fatty acid chains located in the central regions. Furthermore, the fatty acid chains of cholesteryl stearate were observed to be oriented in the (1120) zigzag direction of the graphite lattice, whereas those of cholesteryl laurate were oriented in the (1010) armchair direction. These observations reveal that the interactions between the fatty acid chains affect the structure of the SAMs. The molecular arrangements also depend on the lengths of the fatty acid chains of the cholesterol esters and hence on the interactions between the alkyl chains and the graphite surface. The self-assembly at the liquid-solid interface is therefore controlled by the interactions between sterol rings, between alkyl chains, and between alkyl chains and the substrate.

  11. Surface-water interface induces conformational changes critical for protein adsorption: Implications for monolayer formation of EAS hydrophobin

    Directory of Open Access Journals (Sweden)

    Kamron eLey

    2015-11-01

    Full Text Available The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth. These proteins have attracted increasing attention for industrial and biomedical applications, with the aim of designing surfaces that have the potential to maintain their clean state by resisting non-specific protein binding. To gain a better understanding of this process, we have employed all-atom molecular dynamics to study initial stages of the spontaneous adsorption of monomeric EAS hydrophobin on fully hydroxylated silica, a commonly used industrial and biomedical substrate. Particular interest has been paid to the Cys3-Cys4 loop, which has been shown to exhibit disruptive behavior in solution, and the Cys7-Cys8 loop, which is believed to be involved in the aggregation of EAS hydrophobin at interfaces. Specific and water mediated interactions with the surface were also analyzed. We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution. We have also identified intermittent interactions with water which mediate the protein adsorption to the surface, as well as longer lasting interactions which control the diffusion of water around the adsorption site. These results have shown that EAS behaves in a similar way at the air-water and surface-water interfaces, and have also highlighted the need for hydrophilic ligand functionalization of the silica surface in order to prevent the adsorption of EAS hydrophobin.

  12. Molecular junctions based on SAMs of cruciform oligo(phenylene ethynylene)s

    DEFF Research Database (Denmark)

    Wei, Zhongming; Li, Tao; Jennum, Karsten Stein

    2012-01-01

    Cruciform oligo(phenylene ethynylene)s (OPEs) with an extended tetrathiafulvalene (TTF) donor moiety (OPE5-TTF and OPE3-TTF) and their simple analogues (OPE5-S and OPE3) without conjugated substituents were used to form high quality self-assembled monolayers (SAMs) on ultra-flat gold substrates...

  13. Electrochemical surface modification technique to impede mild steel corrosion using perfluorooctanoic acid

    Directory of Open Access Journals (Sweden)

    Shubha H Natarj

    2016-02-01

    Full Text Available The present work demonstrated that corrosion inhibition efficiency of electrochemically generated organic coat is remarkably effective than self-assembled monolayer (SAM generated by dip coating technique. Perfluorooctanoic Acid (PFOA is used to modify mild steel surface for effective protection. Infrared reflection absorption spectroscopy and contact angle measurements substantiate the modification of mild steel surface and its effect on surface hydrophobicity. A comparison between electrochemical properties of PFOA SAM generated by dip coat method (DC-PFOA and PFOA coat generated by electrochemical method (EC-PFOA is presented. Electrochemical measurements reveal that the corrosion protection efficiency of EC-PFOA (91% is much superior to DC-PFOA (28%.

  14. Surface interactions, thermodynamics and topography of binary monolayers of Insulin with dipalmitoylphosphatidylcholine and 1-palmitoyl-2-oleoylphosphatidylcholine at the air/water interface.

    Science.gov (United States)

    Grasso, E J; Oliveira, R G; Maggio, B

    2016-02-15

    The molecular packing, thermodynamics and surface topography of binary Langmuir monolayers of Insulin and DPPC (dipalmitoylphosphatidylcholine) or POCP (1-palmitoyl-2-oleoylphosphatidylcholine) at the air/water interface on Zn(2+) containing solutions were studied. Miscibility and interactions were ascertained by the variation of surface pressure-mean molecular area isotherms, surface compressional modulus and surface (dipole) potential with the film composition. Brewster Angle Microscopy was used to visualize the surface topography of the monolayers. Below 20mN/m Insulin forms stable homogenous films with DPPC and POPC at all mole fractions studied (except for films with XINS=0.05 at 10mN/m where domain coexistence was observed). Above 20mN/m, a segregation process between mixed phases occurred in all monolayers without squeezing out of individual components. Under compression the films exhibit formation of a viscoelastic or kinetically trapped organization leading to considerable composition-dependent hysteresis under expansion that occurs with entropic-enthalpic compensation. The spontaneously unfavorable interactions of Insulin with DPPC are driven by favorable enthalpy that is overcome by unfavorable entropic ordering; in films with POPC both the enthalpic and entropic effects are unfavorable. The surface topography reveals domain coexistence at relatively high pressure showing a striped appearance. The interactions of Insulin with two major membrane phospholipids induces composition-dependent and long-range changes of the surface organization that ought to be considered in the context of the information-transducing capabilities of the hormone for cell functioning.

  15. 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.

  16. Multicolor, large-area fluorescence sensing through oligothiophene-self-assembled monolayers.

    Science.gov (United States)

    Melucci, Manuela; Zambianchi, Massimo; Favaretto, Laura; Palermo, Vincenzo; Treossi, Emanuele; Montalti, Marco; Bonacchi, Sara; Cavallini, Massimiliano

    2011-02-14

    We present a new strategy to realize self-assembled monolayers (SAMs) on quartz and silicon with a multicolour fluorescence pattern starting from a single, proton sensitive oligothiophene dye exposed at a defined pH. Fine tuning of the SAMs emission color over the entire visible range, including white, is demonstrated. Finally, integration of SAMs in patterned thin layer cells (TLCs) is exploited to demonstrate cation sensing potential in real devices.

  17. Unveiling self-assembled monolayers' potential for molecular spintronics: spin transport at high voltage.

    Science.gov (United States)

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

    2012-12-18

    Molecular magnetic tunnel junctions using self-assembled monolayers (SAMs) as tunnel barriers show stable and efficient spin transport properties. Large tunnel magnetoresistance with a flat bias voltage dependence of the magnetoresistance is observed in La(2/3) Sr(1/3) MnO(3) /dodecylphosphonic acid SAM/Co nanocontacts. This opens the door to spintronic tailoring though SAM engineering and could also lead to new venues for spin injection in organic devices.

  18. Atomic force microscopy reveals two phases in single stranded DNA self-assembled monolayers

    Science.gov (United States)

    Kosaka, Priscila M.; González, Sheila; Domínguez, Carmen M.; Cebollada, Alfonso; San Paulo, Alvaro; Calleja, Montserrat; Tamayo, Javier

    2013-07-01

    We have investigated the structure of single-stranded (ss) DNA self-assembled monolayers (SAMs) on gold by combining peak force tapping, Kelvin probe and phase contrast atomic force microscopy (AFM) techniques. The adhesion, surface potential and phase shift signals show heterogeneities in the DNA film structure at two levels: microscale and nanoscale; which cannot be clearly discerned in the topography. Firstly, there is multilayer aggregation covering less than 5% of the surface. The DNA multilayers seem to be ordered phases and their existence suggests that DNA end-to-end interaction can play a role in the self-assembly process. Secondly, we find the formation of two phases in the DNA monolayer, which differ both in surface energy and surface potential. We relate the two domains to differences in the packing density and in the ssDNA conformation. The discovered heterogeneities in ssDNA SAMs provide a new scenario in our vision of these relevant films that have direct consequences on their biological, chemical and physical properties.

  19. Ion-induced erosion of organic self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Cyganik, P. E-mail: cyganik@castor.if.uj.edu.pl; Postawa, Z.; Meserole, C.A.; Vandeweert, E.; Winograd, N

    1999-01-02

    Laser post-ionization mass spectrometry combined with Scanning Tunneling Microscopy (STM) has been used to investigate processes of ion-stimulated erosion of self-assembled monolayers (SAM) of phenethyl mercaptan C{sub 6}H{sub 5}CH{sub 2}CH{sub 2}S (PEM) deposited on gold. Results indicate that only PEM fragments are emitted from the surface. Most of the PEM fragments (predominantly C{sub 6}H{sub 5}CH{sub 2}CH{sub 3} with m/z=106) are emitted with thermal kinetic energies. STM images collected on 8 keV H{sup +}{sub 2}-irradiated surfaces with a system tuned to probe electronic states of sulfur atoms show no additional damage induced by irradiation. This indicates that sulfur atoms are not removed from the surface during hydrogen bombardment. It is proposed that the emission of SAM molecules is initiated by chemical reactions which gently break C-S bonds.

  20. Deposition of metal Islands, metal clusters and metal containing single molecules on self-assembled monolayers

    NARCIS (Netherlands)

    Speets, Emiel Adrianus

    2005-01-01

    The central topic of this thesis is the deposition of metals on Self-Assembled Monolayers (SAMs). Metals are deposited in the form of submicron scale islands, nanometer scale clusters, and as supramolecular, organometallic coordination cages. Several SAMs on various substrates were prepared and anal

  1. Surface symmetry of monolayer titanium oxide on Mo(1 1 2) studied via fast atom diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, J., E-mail: jan.seifert@physik.hu-berlin.de; Winter, H.

    2013-11-15

    In studies on titanium oxide thin films we demonstrate the potential of Fast Atom Diffraction (FAD) and triangulation methods to derive the surface unit cell with enhanced surface sensitivity. Helium atoms with energies of 1–2 keV are scattered from the surface along low indexed surface directions under grazing angles of incidence. From the observed diffraction patterns, the lateral periodicity of the surface structures is derived. For low TiO{sub x} coverages a well-ordered c(2 × 4) superstructure and for higher coverage a p(8 × 2) film is observed. Based on FAD and triangulation methods for azimuthal rotation of the target the arrangement of topmost atoms in smaller sub-unit cells is revealed.

  2. 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.

  3. Surface Analysis of 4-Aminothiophenol Adsorption at Polycrystalline Platinum Electrodes

    Science.gov (United States)

    Rosario-Castro, Belinda I.; Fachini, Estevao R.; Contes, Enid J.; Perez-Davis, Marla E.; Cabrera, Carlos R.

    2008-01-01

    Formation of self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) on polycrystalline platinum electrodes has been studied by surface analysis and electrochemistry techniques. The 4-ATP monolayer was characterized by cyclic voltammetry (CV), Raman spectroscopy, reflection absorption infrared (RAIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) experiments give an idea about the packing quality of the monolayer. RAIR and Raman spectra for 4-ATP modified platinum electrodes showed the characteristic adsorption bands for neat 4-ATP indicating the adsorption of 4-ATP molecules on platinum surface. The adsorption on platinum was also evidenced by the presence of sulfur and nitrogen peaks by XPS survey spectra of the modified platinum electrodes. High resolution XPS studies and RAIR spectrum for platinum electrodes modified with 4-ATP indicate that molecules are sulfur-bonded to the platinum surface. The formation of S-Pt bond suggests that ATP adsorption gives up an amino terminated SAM. Thickness of the monolayer was evaluated via angle-resolved XPS (AR-XPS) analyses. Derivatization of 4-ATP SAM was performed using 16-Br hexadecanoic acid.

  4. Comparison of two different plasma surface-modification techniques for the covalent immobilization of protein monolayers.

    Science.gov (United States)

    Cifuentes, Anna; Borrós, Salvador

    2013-06-04

    The immobilization of biologically active species is crucial for the fabrication of smart bioactive surfaces. For this purpose, plasma polymerization is frequently used to modify the surface nature without affecting the bulk properties of the material. Thus, it is possible to create materials with surface functional groups that can promote the anchoring of all kinds of biomolecules. Different methodologies in protein immobilization have been developed in recent years, although some drawbacks are still not solved, such as the difficulties that some procedures involve and/or the denaturalization of the protein due to the immobilization process. In this work, two different strategies to covalently attach bovine serum albumin (BSA) protein are developed. Both techniques are compared in order to understand how the nature of the surface modification affects the conformation of the protein upon immobilization.

  5. Surface Equation of State for Pure Phospholipid Monolayer at the Air/Water Interface%空气/水界面上的纯组分磷酯单分子膜的表面状态方程

    Institute of Scientific and Technical Information of China (English)

    曾作祥; 陈琼; 薛为岚; 聂飞

    2004-01-01

    A surface equation of state, applicable to liquid-expanded (LE) monolayers, was derived by analyzing the Helmholtz free energy of the LE monolayers. Based on this equation, a general equation was obtained to describe all states of single-component phospholipid monolayers during comprassion. To verify the applicability of the equation,r-A isotherms of 1,2-dipalmitoylphosphatidylcholine (DPPC),1,2-dipalmitoylphosphatidylglycerol (DPPG),and 1,2-dimyristoyphosphatildylcholine (DMPC) were measured. The comparison between model and experimental values indicates that the equation can describe the behavior of pure phospholipid monolayers.

  6. 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.

  7. Two step formation of metal aggregates by surface X-ray radiolysis under Langmuir monolayers: 2D followed by 3D growth

    Directory of Open Access Journals (Sweden)

    Smita Mukherjee

    2015-12-01

    Full Text Available In order to form a nanostructured metallic layer below a Langmuir monolayer, radiolysis synthesis was carried out in an adapted geometry that we call surface X-ray radiolysis. In this procedure, an X-ray beam produced by a synchrotron beamline intercepts the surface of an aqueous metal-ion solution covered by a Langmuir monolayer at an angle of incidence below the critical angle for total internal reflection. Underneath the organic layer, the X-ray beam induces the radiolytic synthesis of a nanostructured metal–organic layer whose ultrathin thickness is defined by the vertical X-ray penetration depth. We have shown that increasing the X-ray flux on the surface, which considerably enhances the kinetics of the silver layer formation, results in a second growth regime of silver nanocrystals. Here the formation of the oriented thin layer is followed by the appearance of a 3D powder of silver clusters.

  8. Thermal desorption characteristics of CO, O2 and CO2 on non-porous water, crystalline water and silicate surfaces at sub-monolayer and multilayer coverages

    CERN Document Server

    Noble, J A; Dulieu, F; Fraser, H J

    2011-01-01

    The desorption characteristics of molecules on interstellar dust grains are important for modelling the behaviour of molecules in icy mantles and, critically, in describing the solid-gas interface. In this study, a series of laboratory experiments exploring the desorption of three small molecules from three astrophysically relevant surfaces are presented. The desorption of CO, O2 and CO2 at both sub-monolayer and multilayer coverages was investigated from non-porous water, crystalline water and silicate surfaces. Experimental data was modelled using the Polanyi-Wigner equation to produce a mathematical description of the desorption of each molecular species from each type of surface, uniquely describing both the monolayer and multilayer desorption in a single combined model. The implications of desorption behaviour over astrophysically relevant timescales are discussed.

  9. Sub-monolayer growth of Ag on flat and nanorippled SiO2 surfaces

    Science.gov (United States)

    Bhatnagar, Mukul; Ranjan, Mukesh; Jolley, Kenny; Smith, Roger; Mukherjee, Subroto

    2016-05-01

    In-situ Rutherford Backscattering Spectrometry (RBS) and Molecular Dynamics (MD) simulations have been used to investigate the growth dynamics of silver on a flat and the rippled silica surface. The calculated sticking coefficient of silver over a range of incidence angles shows a similar behaviour to the experimental results for an average surface binding energy of a silver adatom of 0.2 eV. This value was used to parameterise the MD model of the cumulative deposition of silver in order to understand the growth mechanisms. Both the model and the RBS results show marginal difference between the atomic concentration of silver on the flat and the rippled silica surface, for the same growth conditions. For oblique incidence, cluster growth occurs mainly on the leading edge of the rippled structure.

  10. Poly(glycidyl ether)-Based Monolayers on Gold Surfaces: Control of Grafting Density and Chain Conformation by Grafting Procedure, Surface Anchor, and Molecular Weight.

    Science.gov (United States)

    Heinen, Silke; Weinhart, Marie

    2017-03-07

    For a meaningful correlation of surface coatings with their respective biological response reproducible coating procedures, well-defined surface coatings, and thorough surface characterization with respect to layer thickness and grafting density are indispensable. The same applies to polymeric monolayer coatings which are intended to be used for, e.g., fundamental studies on the volume phase transition of surface end-tethered thermoresponsive polymer chains. Planar gold surfaces are frequently used as model substrates, since they allow a variety of straightforward surface characterization methods. Herein we present reproducible grafting-to procedures performed with thermoresponsive poly(glycidyl ether) copolymers composed of glycidyl methyl ether (GME) and ethyl glycidyl ether (EGE). The copolymers feature different molecular weights (2 kDa, 9 kDa, 24 kDa) and are equipped with varying sulfur-containing anchor groups in order to achieve adjustable grafting densities on gold surfaces and hence control the tethered polymers' chain conformation. We determined "wet" and "dry" thicknesses of these coatings by QCM-D and ellipsometry measurements and deduced anchor distances and degrees of chain overlap of the polymer chains assembled on gold. Grafting under cloud point conditions allowed for higher degrees of chain overlap compared to grafting from a good solvent like ethanol, independent of the used sulfur-containing anchor group for polymers with low (2 kDa) and medium (9 kDa) molecular weights. By contrast, the achieved grafting densities and thus chain overlaps of surface-tethered polymers with high (24 kDa) molecular weights were identical for both grafting methods. Monolayers prepared from an ethanolic solution of poly(glycidyl ether)s equipped with sterically demanding disulfide-containing anchors revealed the lowest degrees of chain overlap. The ratio of the radius of gyration to the anchor distance (2 Rg/l) of the latter coating was found to be lower than 1

  11. Emprego de monocamadas auto-organizadas no desenvolvimento de sensores eletroquímicos Self-assembled monolayers applications for the development of electrochemical sensors

    Directory of Open Access Journals (Sweden)

    Renato S. Freire

    2003-05-01

    Full Text Available Self-assembled monolayers (SAMs modified electrodes exhibit unique behavior that can greatly benefit electrochemical sensing. This brief review highlights the applications of SAM modified electrodes in electroanalytical chemistry. After a general introduction, which includes the approaches for SAM development, different electrochemical systems for detecting inorganic and organic species are described and discussed. Special attention to the coupling of biological sensing element to the SAM is given, which can selectively recognize the analyte. Future prospects are also evaluated.

  12. Functional monolayers on oxide-free silicon surfaces via thiol-ene click chemistry

    NARCIS (Netherlands)

    Caipa Campos, M.A.; Paulusse, J.M.J.; Zuilhof, H.

    2010-01-01

    Thiol–ene click chemistry was used for the attachment of a variety of functional molecules onto oxide-free Si(111) surfaces using very mild conditions; the efficient nature of this coupling strategy allowed for successful light-induced micropatterning and thus provides a novel route towards biofunct

  13. Surface pK(sub a) of Self-Assembled Monolayers

    Science.gov (United States)

    Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.

    2005-01-01

    The difference between solution and surface properties such as pK(sub a) is illustrated enabling students to understand the differences between nanoscale and macroscopic systems. Details regarding the usage of electrochemical instrumentation, such as a potentiostat, and of the technique such as cyclic voltammetry are given.

  14. Syntheses of alkenylated carbohydrate derivatives toward the preparation of monolayers on silicon surfaces

    NARCIS (Netherlands)

    Smet, de L.C.P.M.; Pukin, A.V.; Stork, G.A.; Vos, de C.H.; Visser, G.M.; Zuilhof, H.; Sudhölter, E.J.R.

    2004-01-01

    This note describes the synthesis of different alkenylated carbohydrate derivatives suitable for direct attachment to hydrogen-terminated silicon surfaces. The derivatives were alkenylated at the C-1 position, while the remaining hydroxyl groups were protected. The development of such new carbohydra

  15. Functional monolayers on oxide-free silicon surfaces via thiol–ene click chemistry

    NARCIS (Netherlands)

    Caipa Campos, Mabel A.; Paulusse, Jos Marie Johannes; Zuilhof, Han

    2010-01-01

    Thiol–ene click chemistry was used for the attachment of a variety of functional molecules onto oxide-free Si(111) surfaces using very mild conditions; the efficient nature of this coupling strategy allowed for successful light-induced micropatterning and thus provides a novel route towards biofunct

  16. Functional monolayers on oxide-free silicon surfaces via thiol–ene click chemistry

    NARCIS (Netherlands)

    Caipa Campos, Mabel A.; Paulusse, Jos M.J.; Zuilhof, Han

    2010-01-01

    Thiol–ene click chemistry was used for the attachment of a variety of functional molecules onto oxide-free Si(111) surfaces using very mild conditions; the efficient nature of this coupling strategy allowed for successful light-induced micropatterning and thus provides a novel route towards biofunct

  17. Molecular modeling of alkyl monolayers on the Si(100)-2 x 1 surface.

    Science.gov (United States)

    Lee, Michael V; Guo, Dawei; Linford, Matthew R; Zuilhof, Han

    2004-10-12

    Molecular modeling was used to simulate various surfaces derived from the addition of 1-alkenes and 1-alkynes to Si=Si dimers on the Si(100)-2 x 1 surface. The primary aim was to better understand the interactions between adsorbates on the surface and distortions of the underlying silicon crystal due to functionalization. Random addition of ethylene and acetylene was used to determine how the addition of an adduct molecule affects subsequent additions for coverages up to one molecule per silicon dimer, that is, 100% coverage. Randomization subdues the effect that the relative positions of the adsorbates have on the enthalpy of the system. For ethylene and acetylene, the enthalpy of reaction changes less than 3 and 5 kcal/mol, respectively, from the first reacted species up to 100% coverage. As a result, a (near-)complete coverage is predicted, which is in line with experimental data. When 1-alkenes and 1-alkynes add by [2 + 2] addition, the hydrocarbon chains interact differently depending on the direction they project from the surface. These effects were investigated for four-carbon chains: 1-butene and 1-butyne. As expected, the chains that would otherwise intersect bend to avoid each other, raising the enthalpy of the system. For alkyl chains longer than four carbons, the chains are able to reorient themselves in a favorable manner, thus, resulting in a steady reduction in reaction enthalpy of about 2 kcal/mol for each additional methylene unit.

  18. Symmetry Control of Polymer Colloidal Monolayers and Crystals by Electrophoretic Deposition on Patterned Surfaces

    NARCIS (Netherlands)

    Dziomkina, Nina V.; Hempenius, Mark A.; Vancso, G. Julius

    2005-01-01

    Colloidal crystals with body-centered cubic packing (see Figure) can be fabricated by electrophoretic deposition of charged latex particles onto patterned surfaces. Laser-interference lithography produces SiO2 layers patterned with controlled symmetry that can then be used to control the orientation

  19. Bell-shaped superhydrophilic-superhydrophobic-superhydrophilic double transformation on a pH-responsive smart surface.

    Science.gov (United States)

    Cheng, Mengjiao; Liu, Qian; Ju, Guannan; Zhang, Yajun; Jiang, Lei; Shi, Feng

    2014-01-15

    Superhydrophobic to neutral water droplets, superhydrophilic to acidic or basic. This double transition of surface wettability in response to a single stimulus - pH - is demonstrated for the first time. The smart surface is composed of a rough gold surface modified with a self-assembled monolayer (SAM) containing three thiols, HS(CH2 )11 CH3 , HS(CH2 )10 COOH, and HS(CH2 )11 NH2 . A ternary diagram is generated that describes wettability as a function of the SAM composition and the pH of the surrounding solution. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Adsorption geometry and electronic properties of flat-lying monolayers of tetracene on the Ag(111) surface

    Science.gov (United States)

    Zaitsev, N. L.; Nechaev, I. A.; Höfer, U.; Chulkov, E. V.

    2016-10-01

    The geometrical and electronic properties of the monolayer (ML) of tetracene (Tc) molecules on Ag(111) are systematically investigated by means of DFT calculations with the use of a localized basis set. The bridge and hollow adsorption positions of the molecule in the commensurate γ -Tc/Ag(111) are revealed to be the most stable and equally favorable irrespective to the approximation chosen for the exchange-correlation functional. The binding energy is entirely determined by the long-range dispersive interaction. The former lowest unoccupied molecular orbital remains being unoccupied in the case of γ -Tc/Ag(111) as well as in the α phase with increased coverage. The unit cell of the α phase with point-on-line registry was adapted for calculations based on the available experimental data and computed structures of the γ phase. The calculated position of the Tc/Ag(111) interface state is found to be noticeably dependent on the lattice constant of the substrate, however its energy shift with respect to the Shockley surface state of the unperturbed clean side of the slab is sensitive only to the adsorption distance and in good agreement with the experimentally measured energy shift.

  1. Scanning tunneling microscopy studies of organic monolayers adsorbed on the rhodium(111) crystal surface

    Energy Technology Data Exchange (ETDEWEB)

    Cernota, Paul D.

    1999-08-01

    Scanning Tunneling Microscopy studies were carried out on ordered overlayers on the (111) surface of rhodium. These adsorbates include carbon monoxide (CO), cyclohexane, cyclohexene, 1,4-cyclohexadiene, para-xylene, and meta-xylene. Coadsorbate systems included: CO with ethylidyne, CO with para- and meta-xylene, and para-xylene with meta-xylene. In the case of CO, the structure of the low coverage (2x2) overlayer has been observed. The symmetry of the unit cell in this layer suggests that the CO is adsorbed in the 3-fold hollow sites. There were also two higher coverage surface structures with ({radical}7x{radical}7) unit cells. One of these is composed of trimers of CO and has three CO molecules in each unit cell. The other structure has an additional CO molecule, making a total of four. This extra CO sits on a top site.

  2. Scanning tunneling microscopy studies of organic monolayers adsorbed on the rhodium(111) crystal surface

    Energy Technology Data Exchange (ETDEWEB)

    Cernota, Paul Davis [Univ. of California, Berkeley, CA (United States)

    1999-08-01

    Scanning Tunneling Microscopy studies were carried out on ordered overlayers on the (111) surface of rhodium. These adsorbates include carbon monoxide (CO), cyclohexane, cyclohexene, 1,4-cyclohexadiene, para-xylene, and meta-xylene. Coadsorbate systems included: CO with ethylidyne, CO with para- and meta-xylene, and para-xylene with meta-xylene. In the case of CO, the structure of the low coverage (2x2) overlayer has been observed. The symmetry of the unit cell in this layer suggests that the CO is adsorbed in the 3-fold hollow sites. There were also two higher coverage surface structures with (√7x√7) unit cells. One of these is composed of trimers of CO and has three CO molecules in each unit cell. The other structure has an additional CO molecule, making a total of four. This extra CO sits on a top site.

  3. Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals.

    Science.gov (United States)

    Meyer, Dominik; Schäfer, 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.

  4. Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Dominik; Schäfer, 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.

  5. Effects of solvent on the formation of the MUA monolayer on Si and its diffusion barrier properties for Cu metallization

    Science.gov (United States)

    Rahman, Mohammad Arifur; Han, Jung Suk; Jeong, Kyunghoon; Nam, Ho-seok; Lee, Jaegab

    2014-05-01

    We investigated the effects of solvents, such as ethanol and isooctane, on self-assembly of the mercaptoundecanoic acid (MUA) monolayer on Si and its diffusion barrier properties for Cu metallization. The use of isooctane as a solvent produced MUA self-assembled monolayers (SAMs) (˜1.3 nm thick) on Si. These acted as an effective diffusion barrier against Cu diffusion up to 200°C. In contrast, the MUA SAMs produced by ethanol allowed the diffusion of Cu to a MUA-Si interface at 200°C, stimulating the out-diffusion of Si into Cu and thus resulting in the degraded diffusion barrier properties. This was possibly due to the partial formation of interplane hydrogen bonding between the terminal groups of the bound acid and free thiol groups. This provided less dense thiol surface groups, thus leading to poor adhesion of Cu to MUA SAMs. The fabricated Cu/isooctane-assisted MUA source/drain electrode a-Si:H thin film transistors with a channel length of 10 µm exhibited an excellent electron mobility of 0.74 cm2/V-s, threshold voltage of -0.51 V, I on / I off ratio of 3.25 × 106, specific contact resistance of 4.24 Ω-cm2 after annealing at 200°C.

  6. Initiation of blood coagulation - Evaluating the relevance of specific surface functionalities using self assembled monolayers

    OpenAIRE

    Fischer, Marion

    2010-01-01

    The surface of biomaterials can induce contacting blood to coagulate, similar to the response initiated by injured blood vessels to control blood loss. This poses a challenge to the use of biomaterials as the resulting coagulation can impair the performance of hemocompatible devices such as catheters, vascular stents and various extracorporeal tubings [1], what can moreover cause severe host reactions like embolism and infarction. Biomaterial induced coagulation processes limit the therape...

  7. 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.

  8. Molecular Dynamics Simulations of Adsorption of Polymer Chains on the Surface of BmNn Graphyne-Like Monolayers

    Science.gov (United States)

    Rouhi, Saeed; Atfi, Amin

    2017-03-01

    Molecular dynamics simulations are used here to study the interactions between BmNn graphyne-like monolayers and four different polymer chains. BN, B1N9, and B2N8 graphyne-like monolayers are selected from the family of BmNn graphyne-like monolayers. It is observed that increasing the number of B atoms in the structure of BmNn graphyne-like monolayers results in larger interaction energies of nanosheet/polymer systems. It is also shown that the polymer chains with the linear adsorbed configurations on the nanosheets have larger interaction energies with the nanosheets. Investigating the effect of number of polymer repeat units on the polymer/nanosheet interaction energy, it is observed that increasing the number of repeat units of polymers leads to enhancing the polymer/nanosheet interaction energy.

  9. Comparative study of electroless copper film on different self-assembled monolayers modified ABS substrate.

    Science.gov (United States)

    Xu, Jiushuai; Fan, Ruibin; Wang, Jiaolong; Jia, Mengke; Xiong, Xuanrui; Wang, Fang

    2014-04-15

    Copper films were grown on (3-Mercaptopropyl)trimethoxysilane (MPTMS), (3-Aminopropyl)triethoxysilane (APTES) and 6-(3-(triethoxysilyl)propylamino)-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.

  10. 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.

  11. Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers

    Directory of Open Access Journals (Sweden)

    Johannes Stadler

    2011-08-01

    Full Text Available Full spectroscopic imaging by means of tip-enhanced Raman spectroscopy (TERS was used to measure the distribution of two isomeric thiols (2-mercaptopyridine (2-PySH and 4-mercaptopyridine (4-PySH in a self-assembled monolayer (SAM on a gold surface. From a patterned sample created by microcontact printing, an image with full spectral information in every pixel was acquired. The spectroscopic data is in good agreement with the expected molecular distribution on the sample surface due to the microcontact printing process. Using specific marker bands at 1000 cm−1 for 2-PySH and 1100 cm−1 for 4-PySH, both isomers could be localized on the surface and semi-quantitative information was deduced from the band intensities. Even though nanometer size resolution information was not required, the large signal enhancement of TERS was employed here to detect a monolayer coverage of weakly scattering analytes that were not detectable with normal Raman spectroscopy, emphasizing the usefulness of TERS.

  12. A modular approach for the construction and modification of glyco-SAMs utilizing 1,3-dipolar cycloaddition.

    Science.gov (United States)

    Kleinert, Mike; Winkler, Tobias; Terfort, Andreas; Lindhorst, Thisbe K

    2008-06-21

    We report the synthesis of a broad variety of functionalized molecules for assembly on gold, allowing the formation of biologically relevant SAMs by a modular approach: either utilizing 1,3-dipolar cycloaddition of alkynes and azides in solution or by 'click on SAM'. Extensive studies into the various parameters of SAM formation and stability have been carried out, leading us to deduce reliable conditions under which glyco-decorated self-assembled monolayers can be formed and studied such as in SPR-supported binding assays.

  13. Transparency and damage tolerance of patternable omniphobic lubricated surfaces based on inverse colloidal monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, N; Belisle, RA; Hatton, B; Wong, TS; Aizenberg, J

    2013-07-31

    A transparent coating that repels a wide variety of liquids, prevents staining, is capable of self-repair and is robust towards mechanical damage can have a broad technological impact, from solar cell coatings to self-cleaning optical devices. Here we employ colloidal templating to design transparent, nanoporous surface structures. A lubricant can be firmly locked into the structures and, owing to its fluidic nature, forms a defect-free, self-healing interface that eliminates the pinning of a second liquid applied to its surface, leading to efficient liquid repellency, prevention of adsorption of liquid-borne contaminants, and reduction of ice adhesion strength. We further show how this method can be applied to locally pattern the repellent character of the substrate, thus opening opportunities to spatially confine any simple or complex fluids. The coating is highly defect-tolerant due to its interconnected, honeycomb wall structure, and repellency prevails after the application of strong shear forces and mechanical damage. The regularity of the coating allows us to understand and predict the stability or failure of repellency as a function of lubricant layer thickness and defect distribution based on a simple geometric model.

  14. Effects of size and surface on the auxetic behaviour of monolayer graphene kirigami

    Science.gov (United States)

    Cai, Kun; Luo, Jing; Ling, Yiru; Wan, Jing; Qin, Qing-Hua

    2016-10-01

    Graphene is an active element used in the design of nano-electro-mechanical systems (NEMS) owing to its excellent in-plane physical properties on mechanical, electric and thermal aspects. Considering a component requiring negative Poisson’s ratio in NEMS, a graphene kirigami (GK) containing periodic re-entrant honeycombs is a natural option. This study demonstrates that a GK with specific auxetic property can be obtained by adjusting the sizes of its honeycombs. Using molecular dynamics experiments, the size effects on the auxetic behaviour of GK are investigated. In some cases, the auxetic difference between the hydrogenated GK and continuum kirigami (CK) is negligible, in which the results from macro CK can be used to predict auxetic behaviour of nano kirigami. Surface effect of GK is demonstrated from two aspects. One is to identify the difference of mechanical responses between the pure carbon GK and the hydrogenated GK at same geometry and loading condition. Another is from the difference of mechanical responses between the GK model and the CK model under same loading condition and geometric configuration. Generally, surface energy makes the GK possess higher variation of auxetic behaviour. It also results in higher modulus for the GK as comparing with that of the CK.

  15. Case studies on the formation of chalcogenide self-assembled monolayers on surfaces and dissociative processes

    Directory of Open Access Journals (Sweden)

    Yongfeng Tong

    2016-02-01

    Full Text Available This report examines the assembly of chalcogenide organic molecules on various surfaces, focusing on cases when chemisorption is accompanied by carbon–chalcogen atom-bond scission. In the case of alkane and benzyl chalcogenides, this induces formation of a chalcogenized interface layer. This process can occur during the initial stages of adsorption and then, after passivation of the surface, molecular adsorption can proceed. The characteristics of the chalcogenized interface layer can be significantly different from the metal layer and can affect various properties such as electron conduction. For chalcogenophenes, the carbon–chalcogen atom-bond breaking can lead to opening of the ring and adsorption of an alkene chalcogenide. Such a disruption of the π-electron system affects charge transport along the chains. Awareness about these effects is of importance from the point of view of molecular electronics. We discuss some recent studies based on X-ray photoelectron spectroscopy that shed light on these aspects for a series of such organic molecules.

  16. Potential-induced structural transitions of DL-homocysteine monolayers on Au(111) electrode surfaces

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Demetriou, Anna; Welinder, Anne Christina

    2005-01-01

    -S reductive desorption at -0.8 V (SCE) in 0.1 M NaOH, while the charge is only about 8 x 10(-6) C cm(-2) (pH 7.7) for the 0 to -0.1 V peak. This suggests a capacitive origin. The peak potential and shape depend on pH. At pH 7.7 both cathodic and anodic peak currents reach a maximum, but drop at both higher....... This process is reversible. We propose that the voltammetric peaks are capacitive. The ordered domains are formed only around the potential of zero charge (pzc) and dissipate at potentials on either side of the peak, inducing mirror charge flow in the metallic electrode as the charged -COO- and -NH3+ groups...... approach the surface. No bands for carboxylate coordinated to the surface were observed in SNIFTIRS implying more subtle orientation changes of the charged groups on transcending the voltammetric peak. This scenario is incorporated in a simple phenomenological model....

  17. Synchrotron radiation stimulated etching of SiO sub 2 thin films with a Co contact mask for the area-selective deposition of self-assembled monolayer

    CERN Document Server

    Wang, C

    2003-01-01

    The area-selective deposition of a self-assembled monolayer (SAM) was demonstrated on a pattern structure fabricated by synchrotron radiation (SR) stimulated etching of a SiO sub 2 thin film on the Si substrate. The etching was conducted by irradiating the SiO sub 2 thin film with SR through a Co contact mask and using a mixture of SF sub 6 + O sub 2 as the reaction gas. The SR etching stopped completely at the SiO sub 2 /Si interface. After the SR etching, the Si surface and the SiO sub 2 surface beneath the Co mask were evaluated by an atomic force microscope (AFM). A dodecene SAM was deposited on the Si surface, and trichlorosilane-derived SAMs (octadecyltrichlorosilane, and octenyltrichlorosilane) were deposited on the SiO sub 2 surface beneath the Co mask. The structure of the deposited SAMs showed a densely packed and well-ordered molecular architecture, which was characterized by infrared spectroscopy, ellipsometry, and water contact angle (WCA) measurements. (author)

  18. Characterization of surface modification on microelectrode arrays for in vitro cell culture.

    Science.gov (United States)

    Lin, Shu-Ping; Chen, Jia-Jin J; Liao, Jiunn-Der; Tzeng, Shun-Fen

    2008-02-01

    This study aims to investigate surface-modified microelectrodes on the microelectrode arrays (MEAs) for neuronal interfaces with in vitro cell culture. The polyimide (PI) MEA was fabricated by using micro-electro-mechanical systems (MEMS) techniques. Self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) were utilized to modify the microelectrode surface of the MEA. The SAMs' modified surface of microelectrodes offered a reliable interface to immobilize biological ligands through covalent bonding. To increase biocompatibility, the poly-D-lysine (PDL) was immobilized on the SAMs' modified microelectrodes. Several analytical techniques were used to define the physical structure and functional groups of surface-modified gold microelectrodes on the MEA. Spectra of the Fourier transform infrared reflection (FTIR) were applied to characterize the molecular structure of MUA-SAMs and PDL on the microelectrodes. The spectra, two peaks of amide I (at 1,613 cm(-1)) and amide II (at 1,548 cm(-1)), revealed that covalent amide bonding existed in PDL-MUA-SAMs modified surfaces. The thickness and formation of the MUA and PDL were also observed and quantified by using an atomic force microscope (AFM). The impedance measurement of PDL-MUA-SAMs modified MEA only increased slightly to an average of 524.6 +/- 55.8 kOmega from 352.9 +/- 34.4 kOmega of bare gold microelectrode (p stimulation/sensing schemes and for future implantation purposes.

  19. 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.

  20. Monolayer-directed assembly and magnetic properties of FePt nanoparticles on patterned aluminum oxide.

    Science.gov (United States)

    Yildirim, Oktay; Gang, Tian; Kinge, Sachin; Reinhoudt, David N; Blank, Dave H; van der Wiel, Wilfred G; Rijnders, Guus; Huskens, Jurriaan

    2010-03-19

    FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs onto the surface. The Al(2)O(3) substrates were functionalized with aminobutylphosphonic acid (ABP) or phosphonoundecanoic acid (PNDA) SAMs or with poly(ethyleneimine) (PEI) as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al(2)O(3), which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al(2)O(3) surface and controlling the immersion time of the modified Al(2)O(3) substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N(2)/4%H(2)) led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices.

  1. Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

    Directory of Open Access Journals (Sweden)

    Guus Rijnders

    2010-03-01

    Full Text Available FePt nanoparticles (NPs were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(onates were used as an adsorbate to form self-assembled monolayers (SAMs on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP or phosphonoundecanoic acid (PNDA SAMs or with poly(ethyleneimine (PEI as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al2O3, which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al2O3 surface and controlling the immersion time of the modified Al2O3 substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N2/4%H2 led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices.

  2. High-performance and high-sensitivity applications of graphene transistors with self-assembled monolayers.

    Science.gov (United States)

    Yeh, Chao-Hui; Kumar, Vinod; Moyano, David Ricardo; Wen, Shao-Hsuan; Parashar, Vyom; Hsiao, She-Hsin; Srivastava, Anchal; Saxena, Preeti S; Huang, Kun-Ping; Chang, Chien-Chung; Chiu, Po-Wen

    2016-03-15

    Charge impurities and polar molecules on the surface of dielectric substrates has long been a critical obstacle to using graphene for its niche applications that involve graphene's high mobility and high sensitivity nature. Self-assembled monolayers (SAMs) have been found to effectively reduce the impact of long-range scatterings induced by the external charges. Yet, demonstrations of scalable device applications using the SAMs technique remains missing due to the difficulties in the device fabrication arising from the strong surface tension of the modified dielectric environment. Here, we use patterned SAM arrays to build graphene electronic devices with transport channels confined on the modified areas. For high-mobility applications, both rigid and flexible radio-frequency graphene field-effect transistors (G-FETs) were demonstrated, with extrinsic cutoff frequency and maximum oscillation frequency enhanced by a factor of ~2 on SiO2/Si substrates. For high sensitivity applications, G-FETs were functionalized by monoclonal antibodies specific to cancer biomarker chondroitin sulfate proteoglycan 4, enabling its detection at a concentration of 0.01 fM, five orders of magnitude lower than that detectable by a conventional colorimetric assay. These devices can be very useful in the early diagnosis and monitoring of a malignant disease.

  3. System for Award Management (SAM) API

    Data.gov (United States)

    General Services Administration — The SAM API is a RESTful method of retrieving public information about the businesses, organizations, or individuals (referred to as entities) within the SAM entity...

  4. Inelastic neutron scattering (INS) observations of rotational tunneling within partially deuterated methane monolayers adsorbed on MgO(1 0 0) surfaces

    Science.gov (United States)

    Hicks, Andy S.; Larese, J. Z.

    2013-12-01

    High resolution inelastic neutron scattering (INS) measurements of the low temperature (T ∼ 2.0 K) rotational dynamics of isotopically substituted methane monolayers adsorbed on MgO(1 0 0) are presented. These spectra, obtained using BASIS at SNS, represent the most detailed measurements available for surface-adsorbed monolayer films of methane. Distinct excitations are readily observed at 15, 31, 45 and 127 μeV for the CH2D2 on MgO monolayer and at 40, 51, 95 and 138 μeV for CH3D/MgO. These features are attributed to tunneling transitions between sublevels within the ground librational state and are interpreted using the pocket state (PS) formalism first proposed by Hüller. This theoretical analysis employs the findings of earlier studies of CH4 on MgO(1 0 0) which suggest that molecules adsorb with their C2v axes normal to the surface plane. The comparison between theory and experiment provides direct insight into the impact of molecular versus surface symmetry on the observed tunneling spectra.

  5. Site-selective assembly of quantum dots on patterned self-assembled monolayers fabricated by laser direct-writing

    Science.gov (United States)

    Wu, Chong; Wang, Yongsheng; Han, Xuemingyue; Hu, Xinming; Cheng, Qianyi; Han, Baohang; Liu, Qian; Ren, Tianling; He, Yonghong; Sun, Shuqing; Ma, Hui

    2012-06-01

    A simple and efficient route for quantum dot (QDs) patterning using self-assembled monolayers (SAMs) as templates is described. By means of a laser direct-writing (LDW) technique, SAMs of octadecylphosphonic acid formed by adsorption on native oxide layer of titanium film were patterned through laser-induced ablation of the SAM molecules. This technique allows the creation of chemical-specific patterns accompanied by slight change in the topography. Using atomic force microscopy and friction force microscopy, the dependence of feature size and characteristics on the irradiation dose was demonstrated. Upon immersion of a substrate with patterned SAMs bearing thiol as the terminal group into a dispersion of QDs resulted in the assembly of QDs on the specific thiol-terminated areas. Patterns of QDs with different photoluminescent wavelength were generated. The LDW technique, which is convenient and flexible due to its path-directed and maskless fabrication process, provided a new powerful approach for patterning materials on surfaces for various applications.

  6. 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.

  7. Attraction induced frictionless sliding of rare gas monolayer on metallic surfaces: an efficient strategy for superlubricity.

    Science.gov (United States)

    Sun, Junhui; Zhang, Yanning; Lu, Zhibin; Xue, Qunji; Wang, Liping

    2017-05-10

    Friction on a nanoscale revealed rich load-dependent behavior, which departs strongly from the long-standing Amonton's law. Whilst electrostatic repulsion-induced friction collapse for rare gas sliding over metallic surfaces in a high-load regime was reported by Righi et al. (Phys. Rev. Lett., 2007, 99, 176101), the significant role of attraction on frictional properties has not been reported to date. In this study, the frictional motion of Xe/Cu(111), Xe/Pd(111) and Ar/Cu(111) was studied using van der Waals corrected density functional calculations. An attraction-induced zero friction, which is a signal of superlubricity, was found for the sliding systems. The superlubric state results from the disappearance of the potential corrugation along the favored sliding path as a consequence of the potential crossing in the attractive regime when the interfacial pressure approaches a critical-value. The finding of an attraction-driven friction drop, together with the repulsion-induced collapse in the high-load regime, which breaks down the classic Amonton's law, provides a distinct approach for the realization of inherent superlubricity in some adsorbate/substrate interfaces.

  8. 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...

  9. Role of water in polymer surface modification using organosilanes

    Science.gov (United States)

    Thallapalle, Pradeep Kumar; Zhang Newby, Bi-Min

    2002-03-01

    In general, polymers exhibit excellent bulk properties but may not possess specific surface properties for successful applications in biomaterials and nanotechnology. Surface modification of polymers with the self-assembled monolayers (SAMs) of organosilanes - ‘Silanization’ - is an attractive approach to alter surface properties without altering the polymer’s desired bulk properties. However, a pretreatment such as exposure to UV/O or plasma is normally required to generate active surface groups prior to silanization. These pretreatments cause undesirable surface changes such as severe surface roughening and excessive surface damage. Recent studies in silanization suggest that the presence of water or OH groups on the surface is essential to form SAMs. In this study we investigated the importance of surface water layer and OH groups in the formation of SAMs for a variety of polymers. The pre and post-modified polymers were examined using fourier transform infrared spectrometry, scanning probe microscopy and contact angle measurements. The results show that organosilanes can be grafted to a polymer surface as long as a water layer can be physisorbed to the surface or the polymer itself contains OH groups. However the monolayers formed are less organized compared to those formed on silicon wafers due to the amorphous nature of the polymers.

  10. Effect of Silanization on Titanium Surfaces by SAM on Biomimetic Mineralization Properties and Osteoblast Proliferation%钛表面自组装硅烷化对仿生矿化性能和细胞增殖的影响

    Institute of Scientific and Technical Information of China (English)

    张林; 谭帼馨; 宁成云; 刘绪建; 廖景文

    2012-01-01

    The pure titanium plates were modified by SAM using the organic solution with 3-aminopropyltriethoxysilane as the chief component and subsequently exposed to simulated body fluid for biomimetic mineralization. The surface morphologies and structures were characterized by attenuated total refraction-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electronic microscopy (SEM) and X-ray diffraction (XRD); Human sweat gland cells (HMSCs) were planted on the surfaces of samples before and after modification, and then the adhesion and proliferation of HMSCs on the surfaces of titanium and its action before and after modification were investigated by MTT colorimetry and SEM. The results show that HCA coating is synthesized by biomimetic method and the ratio of Ca/P is 1.3. Compared with the pure titanium samples, the adhered HMSCs on the surfaces of titanium after modification by SAM are more, and the proliferation effect is obvious.%通过自组装技术以3-氨丙基三乙氧基硅烷为主要成分的有机溶液对纯钛进行表面改性处理,进一步将改性处理后的样品浸泡在模拟体液中仿生矿化处理,利用全反射红外光谱、扫描电镜和X射线衍射研究矿化处理前后样品的表面形貌与结构特征 ;将人骨髓间充质干细胞(HMSCs)种植于改性处理前后样品表面,利用四甲基偶氮唑盐微量酶反应比色法(MTT法)和扫描电镜观察细胞在改性前后样品表面的黏附、生长和增殖行为.结果表明,仿生矿化处理后,样品表面有类骨磷灰石生成,其钙/磷比为1.3 ;与纯钛相比,自组装硅烷化处理样品表面HMSCs的黏附率高,增殖效果明显.

  11. Monolayers and multilayers of conjugated polymers as nanosized electronic components.

    Science.gov (United States)

    Zotti, Gianni; Vercelli, Barbara; Berlin, Anna

    2008-09-01

    Conjugated polymers (CPs) are interesting materials for preparing devices based on nanoscopic molecular architectures because they exhibit electrical, electronic, magnetic, and optical properties similar to those of metals or semiconductors while maintaining the flexibility and ease of processing of polymers. The production of well-defined mono- and multilayers of CPs on electrodes with nanometer-scale, one-dimensional resolution remains, however, an important challenge. In this Account, we describe the preparation and conductive properties of nanometer-sized CP molecular structures formed on electrode surfaces--namely, self-assembled monolayer (SAM), brush-type, and self-assembled multilayer CPs--and in combination with gold nanoparticles (AuNPs). We have electrochemically polymerized SAMs of carboxyalkyl-functionalized terthiophenes aligned either perpendicular or parallel to the electrode surface. Anodic coupling of various pyrrole- and thiophene-based monomers in solution with the oligothiophene-based SAMs produced brush-like films. Microcontact printing of these SAMs produced patterns that, after heterocoupling, exhibited large height enhancements, as measured using atomic force microscopy