Influence of surface chemistry on the structural organization of monomolecular protein layers adsorbed to functionalized aqueous interfaces

DEFF Research Database (Denmark)

Lösche, M.; Piepenstock, M.; Diederich, A.

1993-01-01

The molecular organization of streptavidin (SA) bound to aqueous surface monolayers of biotin-functionalized lipids and binary lipid mixtures has been investigated with neutron reflectivity and electron and fluorescence microscopy. The substitution of deuterons (2H) for protons (1H), both...... in subphase water molecules and in the alkyl chains of the lipid surface monolayer, was utilized to determine the interface structure on the molecular length scale. In all cases studied, the protein forms monomolecular layers underneath the interface with thickness values of apprx 40 ANG . A systematic...... dependence of the structural properties of such self-assembled SA monolayers on the surface chemistry was observed: the lateral protein density depends on the length of the spacer connecting the biotin moiety and its hydrophobic anchor. The hydration of the lipid head groups in the protein-bound state...

Molecular printboards: monolayers of beta-cyclodextrins on silicon oxide surfaces

NARCIS (Netherlands)

Onclin, S.; Mulder, A.; Huskens, Jurriaan; Ravoo, B.J.; Reinhoudt, David

2004-01-01

Monolayers of β-cyclodextrin host molecules have been prepared on SiO2 surfaces. An ordered and stable cyano-terminated monolayer was modified in three consecutive surface reactions. First, the cyanide groups were reduced to their corresponding free amines using Red Al as a reducing agent. Second,

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

NARCIS (Netherlands)

Kim, B.J.; Liebau, M.; Huskens, Jurriaan; Reinhoudt, David; 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

Characterization of self-assembled monolayers on a ruthenium surface

NARCIS (Netherlands)

Shaheen, Amrozia; Sturm, Jacobus Marinus; Ricciardi, R.; Huskens, Jurriaan; Lee, Christopher James; Bijkerk, Frederik

2017-01-01

We have modified and stabilized the ruthenium surface by depositing a self-assembled monolayer (SAM) of 1-hexadecanethiol on a polycrystalline ruthenium thin film. The growth mechanism, dynamics, and stability of these monolayers were studied. SAMs, deposited under ambient conditions, on

Surface chemistry essentials

CERN Document Server

Birdi, K S

2013-01-01

Surface chemistry plays an important role in everyday life, as the basis for many phenomena as well as technological applications. Common examples range from soap bubbles, foam, and raindrops to cosmetics, paint, adhesives, and pharmaceuticals. Additional areas that rely on surface chemistry include modern nanotechnology, medical diagnostics, and drug delivery. There is extensive literature on this subject, but most chemistry books only devote one or two chapters to it. Surface Chemistry Essentials fills a need for a reference that brings together the fundamental aspects of surface chemistry w

Surface Charge Transfer Doping of Monolayer Phosphorene via Molecular Adsorption.

Science.gov (United States)

He, Yuanyuan; Xia, Feifei; Shao, Zhibin; Zhao, Jianwei; Jie, Jiansheng

2015-12-03

Monolayer phosphorene has attracted much attention owing to its extraordinary electronic, optical, and structural properties. Rationally tuning the electrical transport characteristics of monolayer phosphorene is essential to its applications in electronic and optoelectronic devices. Herein, we study the electronic transport behaviors of monolayer phosphorene with surface charge transfer doping of electrophilic molecules, including 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), NO2, and MoO3, using density functional theory combined with the nonequilibrium Green's function formalism. F4TCNQ shows optimal performance in enhancing the p-type conductance of monolayer phosphorene. Static electronic properties indicate that the enhancement is originated from the charge transfer between adsorbed molecule and phosphorene layer. Dynamic transport behaviors demonstrate that additional channels for hole transport in host monolayer phosphorene were generated upon the adsorption of molecule. Our work unveils the great potential of surface charge transfer doping in tuning the electronic properties of monolayer phosphorene and is of significance to its application in high-performance devices.

Analysis of temporal evolution of quantum dot surface chemistry by surface-enhanced Raman scattering.

Science.gov (United States)

Doğan, İlker; Gresback, Ryan; Nozaki, Tomohiro; van de Sanden, Mauritius C M

2016-07-08

Temporal evolution of surface chemistry during oxidation of silicon quantum dot (Si-QD) surfaces were probed using surface-enhanced Raman scattering (SERS). A monolayer of hydrogen and chlorine terminated plasma-synthesized Si-QDs were spin-coated on silver oxide thin films. A clearly enhanced signal of surface modes, including Si-Clx and Si-Hx modes were observed from as-synthesized Si-QDs as a result of the plasmonic enhancement of the Raman signal at Si-QD/silver oxide interface. Upon oxidation, a gradual decrease of Si-Clx and Si-Hx modes, and an emergence of Si-Ox and Si-O-Hx modes have been observed. In addition, first, second and third transverse optical modes of Si-QDs were also observed in the SERS spectra, revealing information on the crystalline morphology of Si-QDs. An absence of any of the abovementioned spectral features, but only the first transverse optical mode of Si-QDs from thick Si-QD films validated that the spectral features observed from Si-QDs on silver oxide thin films are originated from the SERS effect. These results indicate that real-time SERS is a powerful diagnostic tool and a novel approach to probe the dynamic surface/interface chemistry of quantum dots, especially when they involve in oxidative, catalytic, and electrochemical surface/interface reactions.

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.

Temperature-dependent surface density of alkylthiol monolayers on gold nanocrystals

Science.gov (United States)

Liu, Xuepeng; Lu, Pin; Zhai, Hua; Wu, Yucheng

2018-03-01

Atomistic molecular dynamics (MD) simulations are performed to study the surface density of passivating monolayers of alkylthiol chains on gold nanocrystals at temperatures ranging from 1 to 800 K. The results show that the surface density of alkylthiol monolayer reaches a maximum value at near room temperature (200-300 K), while significantly decreases with increasing temperature in the higher temperature region (> 300 {{K}}), and slightly decreases with decreasing temperature at low temperature (< 200 {{K}}). We find that the temperature dependence of surface ligand density in the higher temperature region is attributed to the substantial ligand desorption induced by the thermal fluctuation, while that at low temperature results from the reduction in entropy caused by the change in the ordering of passivating monolayer. These results are expected helpful to understand the temperature-dependent surface coverage of gold nanocrystals.

DPPC Monolayers Exhibit an Additional Phase Transition at High Surface Pressure

DEFF Research Database (Denmark)

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

2015-01-01

Pulmonary surfactant forms a monolayer at the air/aqueous interface within the lung. During the breath process, the surface pressure (Π) periodically varies from ~40mN/m up to ~70mN/m. The film is mechanically stable during this rapid and reversible expansion. Pulmonary surfactant consists of ~90......% of lipid with 10% integrated proteins. Among its lipid compounds, di-palmitoyl-phosphatidylcholine (DPPC) dominates (~45wt%). DPPC is the only known lipid that can be compressed to very high surface pressure (~70mN/m) before its monolayer collapses. Most probably, this feature contributes to the mechanical...... stability of the alveoli monolayer. Still, to the best of our knowledge, some details of the compression isotherm presented here and the related structures of the DPPC monolayer were not studied so far. The liquid-expanded/liquid-condensed phase transition of the DPPC monolayer at ~10mN/m is well known...

Effect of Space Radiation Processing on Lunar Soil Surface Chemistry: X-Ray Photoelectron Spectroscopy Studies

Science.gov (United States)

Dukes, C.; Loeffler, M.J.; Baragiola, R.; Christoffersen, R.; Keller, J.

2009-01-01

Current understanding of the chemistry and microstructure of the surfaces of lunar soil grains is dominated by a reference frame derived mainly from electron microscopy observations [e.g. 1,2]. These studies have shown that the outermost 10-100 nm of grain surfaces in mature lunar soil finest fractions have been modified by the combined effects of solar wind exposure, surface deposition of vapors and accretion of impact melt products [1,2]. These processes produce surface-correlated nanophase Feo, host grain amorphization, formation of surface patinas and other complex changes [1,2]. What is less well understood is how these changes are reflected directly at the surface, defined as the outermost 1-5 atomic monolayers, a region not easily chemically characterized by TEM. We are currently employing X-ray Photoelectron Spectroscopy (XPS) to study the surface chemistry of lunar soil samples that have been previously studied by TEM. This work includes modification of the grain surfaces by in situ irradiation with ions at solar wind energies to better understand how irradiated surfaces in lunar grains change their chemistry once exposed to ambient conditions on earth.

Surface characterization of sulfur and alkanethiol self-assembled monolayers on Au(111)

International Nuclear Information System (INIS)

Vericat, C; Vela, M E; Benitez, G A; Gago, J A Martin; Torrelles, X; Salvarezza, R C

2006-01-01

In the last two decades surface science techniques have decisively contributed to our present knowledge of alkanethiol self-assembled monolayers (SAMs) on solid surfaces. These organic layers have been a challenge for surface scientists, in particular because of the soft nature of the organic material (which can be easily damaged by irradiation), the large number of atoms present in the molecules, and the complex physical chemistry involved in the self-assembly process. This challenge has been motivated by the appealing technological applications of SAMs that cover many fields of the emerging area of nanotechnology. Sulfur (S) is closely related to alkanethiols and can be used to understand basic aspects of the surface structure of SAMs. In this review we focus on the atomic/molecular structures of S-containing SAMs on Au(111). Particular emphasis is given to the substrate, adsorption sites, chemical state of the S-metal bond and also to the experimental and theoretical tools used to study these structures at the atomic or molecular levels. (topical review)

Surface characterization of sulfur and alkanethiol self-assembled monolayers on Au(111)

Energy Technology Data Exchange (ETDEWEB)

Vericat, C [Instituto de Investigaciones FisicoquImicas Teoricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata (Argentina); Vela, M E [Instituto de Investigaciones FisicoquImicas Teoricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata (Argentina); Benitez, G A [Instituto de Investigaciones FisicoquImicas Teoricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata (Argentina); Gago, J A Martin [Centro de AstrobiologIa (CSIC-INTA), 28850 Torrejon de Ardoz Madrid (Spain); Torrelles, X [Instituto de Ciencia de Materiales de Barcelona (ICMAB), Barcelona (Spain); Salvarezza, R C [Instituto de Investigaciones FisicoquImicas Teoricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata (Argentina)

2006-12-06

In the last two decades surface science techniques have decisively contributed to our present knowledge of alkanethiol self-assembled monolayers (SAMs) on solid surfaces. These organic layers have been a challenge for surface scientists, in particular because of the soft nature of the organic material (which can be easily damaged by irradiation), the large number of atoms present in the molecules, and the complex physical chemistry involved in the self-assembly process. This challenge has been motivated by the appealing technological applications of SAMs that cover many fields of the emerging area of nanotechnology. Sulfur (S) is closely related to alkanethiols and can be used to understand basic aspects of the surface structure of SAMs. In this review we focus on the atomic/molecular structures of S-containing SAMs on Au(111). Particular emphasis is given to the substrate, adsorption sites, chemical state of the S-metal bond and also to the experimental and theoretical tools used to study these structures at the atomic or molecular levels. (topical review)

Actinide Sequestration Using Self-Assembled Monolayers on Mesoporous Supports

International Nuclear Information System (INIS)

Fryxell, Glen E.; Lin, Yuehe; Fiskum, Sandra K.; Birnbaum, Jerome C.; Wu, Hong; Kemner, K. M.; Kelly, Shelley

2005-01-01

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

Calculated electronic structure of chromium surfaces and chromium monolayers on iron

International Nuclear Information System (INIS)

Victora, R.H.; Falicov, L.M.

1985-01-01

A self-consistent calculation of the magnetic and electronic properties of the chromium (100) and (110) surfaces and of a chromium monolayer on the (100) and (110) iron surfaces is presented. It is found that (i) the (100) chromium surface is ferromagnetic with a greatly enhanced spin polarization (3.00 electrons); (ii) a substantial enhancement of the spin imbalance exists several (>5) layers into the bulk; (iii) the (110) chromium surface is antiferromagnetic with a large (2.31) spin imbalance; (iv) the (100) chromium monolayer on ferromagnetic iron is ferromagnetic, with a huge spin imbalance (3.63), and aligned antiferromagnetically with respect to the bulk iron; (v) the (110) chromium monolayer on ferromagnetic iron is also ferromagnetic, with a spin imbalance of 2.25 and antiferromagnetically aligned to the iron. The spin imbalance of chromium on iron (100) is possibly the largest of any transition-metal system

Adsorption and enzymatic cleavage of osteopontin at interfaces with different surface chemistries

DEFF Research Database (Denmark)

Malmström, Jenny; Shipovskov, Stepan; Christensen, Brian

2009-01-01

(methyl-, carboxylic-, and amine-terminated alkanethiol self-assembled monolayers and bare gold) have been studied utilizing a combination of the quartz crystal microbalance with dissipation and surface plasmon resonance. Full length bovine milk osteopontin was used which is well characterized...... at the polar surfaces with the highest level of hydration being observed at the gold surface. The energy dissipation of these thin films (as measured by the DeltaD/DeltaF value) was altered at the different surface chemistries and interestingly a higher dissipation correlated with a higher density. Thrombin...... with respect to post-translational modifications. Osteopontin adsorbed at all the surfaces formed thin (approximately 2-5 nm) hydrated layers with the highest amount of protein and the highest density layers observed at the hydrophobic surface. Less protein and a higher level of hydration was observed...

Influence of surface chemistry on inkjet printed carbon nanotube films

International Nuclear Information System (INIS)

Hopkins, Alan R.; Straw, David C.; Spurrell, Kathryn C.

2011-01-01

Carbon nanotube ink chemistry and the proper formulation are crucial for direct-write printing of nanotubes. Moreover, the correct surface chemistry of the self-assembled monolayers that assist the direct deposition of carbon nanotubes onto the substrate is equally important to preserve orientation of the printed carbon nanotubes. We report that the successful formulation of two single walled carbon nanotube (SWNT) inks yields a consistent, homogenous printing pattern possessing the requisite viscosities needed for flow through the microcapillary nozzles of the inkjet printer with fairly modest drying times. The addition of an aqueous sodium silicate allows for a reliable method for forming a uniform carbon nanotube network deposited directly onto unfunctionalized surfaces such as glass or quartz via inkjet deposition. Furthermore, this sodium silicate ingredient helps preserve applied orientation to the printed SWNT solution. Sheet resistivity of this carbon nanotube ink formula printed on quartz decreases as a function of passes and is independent of the substrate. SWNTs were successfully patterned on Au. This amine-based surface chemistry dramatically helps improve the isolation stabilization of the printed SWNTs as seen in the atomic force microscopy (AFM) image. Lastly, using our optimized SWNT ink formula and waveform parameters in the Fuji materials printer, we are able to directly write/print SWNTs into 2D patterns. Dried ink pattern expose and help orient roped carbon nanotubes that are suspended in ordered arrays across the cracks.

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.

Electrical passivation of the silicon surface by organic monolayers of 1-octadecene

International Nuclear Information System (INIS)

Antonova, I. V.; Soots, R. A.; Seleznev, V. A.; Prints, V. Ya.

2007-01-01

The electrical properties of structures consisting of a monolayer of 1-octadecene deposited on the Si surface are investigated depending on the method of passivation of the surface prior to the deposition of the film (hydrogen and ion passivation) and the intensity of illumination which activates the addition reaction of molecules of 1-octadecene to the Si atoms. The monolayer of 1-octadecene on the Si surface is stable and provides the chemical passivation of the surface. Two types of traps are found, namely, traps for holes and electrons, whose density can be varied during deposition of the monolayer by the choice of intensity of illumination and by the method of passivation of the surface. In the case of a low level of illumination and/or the use of the iodine passivation of the surface, the electron traps prevail, and, in the case of high intensity of illumination and/or hydrogen passivation of the surface, the hole traps prevail. It is shown that the use of these films provides conductivity in thin near-surface layers of Si due to providing the mode of flat bands or accumulation of carriers near the surface

Molecular Monolayers for Electrical Passivation and Functionalization of Silicon-Based Solar Energy Devices.

Science.gov (United States)

Veerbeek, Janneke; Firet, Nienke J; Vijselaar, Wouter; Elbersen, Rick; Gardeniers, Han; Huskens, Jurriaan

2017-01-11

Silicon-based solar fuel devices require passivation for optimal performance yet at the same time need functionalization with (photo)catalysts for efficient solar fuel production. Here, we use molecular monolayers to enable electrical passivation and simultaneous functionalization of silicon-based solar cells. Organic monolayers were coupled to silicon surfaces by hydrosilylation in order to avoid an insulating silicon oxide layer at the surface. Monolayers of 1-tetradecyne were shown to passivate silicon micropillar-based solar cells with radial junctions, by which the efficiency increased from 8.7% to 9.9% for n + /p junctions and from 7.8% to 8.8% for p + /n junctions. This electrical passivation of the surface, most likely by removal of dangling bonds, is reflected in a higher shunt resistance in the J-V measurements. Monolayers of 1,8-nonadiyne were still reactive for click chemistry with a model catalyst, thus enabling simultaneous passivation and future catalyst coupling.

Monolayered Bi2WO6 nanosheets mimicking heterojunction interface with open surfaces for photocatalysis

Science.gov (United States)

Zhou, Yangen; Zhang, Yongfan; Lin, Mousheng; Long, Jinlin; Zhang, Zizhong; Lin, Huaxiang; Wu, Jeffrey C.-S.; Wang, Xuxu

2015-09-01

Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+-[WO4]2--[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

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.

Low-Temperature PM IRRAS of a Monolayer on Au: Spectra of C18D37SH

Czech Academy of Sciences Publication Activity Database

Mašát, Milan; Wen, Jin; Sofer, Z.; Michl, Josef

2017-01-01

Roč. 33, č. 23 (2017), s. 5613-5616 ISSN 0743-7463 R&D Projects: GA ČR GA14-02337S Institutional support: RVO:61388963 Keywords : self-assembled monolayers * gold surface * electrodes Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 3.833, year: 2016

Palmitic Acid on Salt Subphases and in Mixed Monolayers of Cerebrosides: Application to Atmospheric Aerosol Chemistry

Directory of Open Access Journals (Sweden)

Ellen M. Adams

2013-10-01

Full Text Available Palmitic acid (PA has been found to be a major constituent in marine aerosols, and is commonly used to investigate organic containing atmospheric aerosols, and is therefore used here as a proxy system. Surface pressure-area isotherms (π-A, Brewster angle microscopy (BAM, and vibrational sum frequency generation (VSFG were used to observe a PA monolayer during film compression on subphases of ultrapure water, CaCl2 and MgCl2 aqueous solutions, and artificial seawater (ASW. π-A isotherms indicate that salt subphases alter the phase behavior of PA, and BAM further reveals that a condensation of the monolayer occurs when compared to pure water. VSFG spectra and BAM images show that Mg2+ and Ca2+ induce ordering of the PA acyl chains, and it was determined that the interaction of Mg2+ with the monolayer is weaker than Ca2+. π-A isotherms and BAM were also used to monitor mixed monolayers of PA and cerebroside, a simple glycolipid. Results reveal that PA also has a condensing effect on the cerebroside monolayer. Thermodynamic analysis indicates that attractive interactions between the two components exist; this may be due to hydrogen bonding of the galactose and carbonyl headgroups. BAM images of the collapse structures show that mixed monolayers of PA and cerebroside are miscible at all surface pressures. These results suggest that the surface morphology of organic-coated aerosols is influenced by the chemical composition of the aqueous core and the organic film itself.

Fabrication and surface transformation of FePt nanoparticle monolayer

International Nuclear Information System (INIS)

Wang Ying; Ding Baojun; Li Hua; Zhang Xiaoyan; Cai Bingchu; Zhang Yafei

2007-01-01

The monolayer of FePt nanoparticles with the mean size of ∼4 nm was fabricated on a glass substrate by the Langmuir--Blodgett (LB) technology. The monolayer of FePt nanoparticles has a smooth surface and a high density structure as shown by the AFM image. The array structure of FePt nanoparticles on the surface of the film is clearly with a cubic symmetry in appropriate condition. Small-angle X-ray diffraction (SXRD) measurement of multilayer structure for the FePt nanoparticles has indicated that the superlattices consist of well-defined smooth layers. The transfer of nanoparticle layers onto a solid substrate surface was quite efficient for the first few layers, exhibiting a proportional increase of optical absorption in the UV-vis range. This results potentially opens up a new approach to the long-range ordered array of FePt nanoparticles capped by organic molecules on substrate and provide a promising thin film, which may exhibit the excellent ultra-high density magnetic recording properties

Fluorinated alkyne-derived monolayers on oxide-free silicon nanowires via one-step hydrosilylation

International Nuclear Information System (INIS)

Nguyen Minh, Quyen; Pujari, Sidharam P.; Wang, Bin; Wang, Zhanhua; Haick, Hossam; Zuilhof, Han; Rijn, Cees J.M. van

2016-01-01

Highlights: • Oxide-free H-terminated silicon nanowires undergo efficient surface modification by reaction with fluorinated 1-alkynes (HC≡C−(CH 2 ) 6 C 8 H 17−x F x ; x = 0–17). • These surface-modified Si NWs are chemically stable under range of conditions (including acid, base). • The surface coating yields efficient electrical passivation as demonstrated by a near-zero electrochemical activity of the surface. - Abstract: Passivation of oxide-free silicon nanowires (Si NWs) by the formation of high-quality fluorinated 1-hexadecyne-derived monolayers with varying fluorine content has been investigated. Alkyl chain monolayers (C 16 H 30−x F x ) with a varying number of fluorine substituents (x = 0, 1, 3, 9, 17) were attached onto hydrogen-terminated silicon (Si−H) surfaces with an effective one-step hydrosilylation. This surface chemistry gives well-defined monolayers on nanowires that have a cylindrical core–shell structure, as characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and static contact angle (SCA) analysis. The monolayers were stable under acidic and basic conditions, as well as under extreme conditions (such as UV exposure), and provide excellent surface passivation, which opens up applications in the fields of field effect transistors, optoelectronics and especially for disease diagnosis.

Emergence of complex chemistry on an organic monolayer.

Science.gov (United States)

Prins, Leonard J

2015-07-21

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

Tribology and stability of organic monolayers on CrN: a comparison among silane, phosphonate, alkene, and alkyne chemistries.

Science.gov (United States)

Pujari, Sidharam P; Li, Yan; Regeling, Remco; Zuilhof, Han

2013-08-20

The fabrication of chemically and mechanically stable monolayers on the surfaces of various inorganic hard materials is crucial to the development of biomedical/electronic devices. In this Article, monolayers based on the reactivity of silane, phosphonate, 1-alkene, and 1-alkyne moieties were obtained on the hydroxyl-terminated chromium nitride surface. Their chemical stability and tribology were systematically investigated. The chemical stability of the modified CrN surfaces was tested in aqueous media at 60 °C at pH 3, 7, and 11 and monitored by static water contact angle measurements, X-ray photoelectron spectroscopy (XPS), ellipsometry, and Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). The tribological properties of the resulting organic monolayers with different end groups (fluorinated or nonfluorinated) were studied using atomic force microscopy (AFM). It was found that the fluorinated monolayers exhibit a dramatic reduction of adhesion and friction force as well as excellent wear resistance compared to those of nonfluorinated coatings and bare CrN substrates. The combination of remarkable chemical stability and superior tribological properties makes these fluorinated monolayers promising candidates for the development of robust high-performance devices.

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.

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

International Nuclear Information System (INIS)

Honda, Mitsunori; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

2014-01-01

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

Mixed carboranethiol self-assembled monolayers on gold surfaces

Energy Technology Data Exchange (ETDEWEB)

Yavuz, Adem [Micro and Nanotechnology Department, Graduate School of Natural and Applied Science, Middle East Technical University, Ankara 06800 (Turkey); Sohrabnia, Nima [Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey); Yilmaz, Ayşen [Micro and Nanotechnology Department, Graduate School of Natural and Applied Science, Middle East Technical University, Ankara 06800 (Turkey); Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey); Danışman, M. Fatih, E-mail: danisman@metu.edu.tr [Micro and Nanotechnology Department, Graduate School of Natural and Applied Science, Middle East Technical University, Ankara 06800 (Turkey); Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey)

2017-08-15

Highlights: • M1 binds to the gold surface preferentially when co-deposited with M9 or O1. • Contact angles show similar trends regardless of the gold substrate roughness. • Contact angles were lower, with higher hysteresis, on template stripped gold. • Mixed carboranethiol SAMs have similar morphological properties regardless of mixing ratio. - Abstract: 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.

Structure of adsorbed monolayers. The surface chemical bond

International Nuclear Information System (INIS)

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

Fluorinated alkyne-derived monolayers on oxide-free silicon nanowires via one-step hydrosilylation

Energy Technology Data Exchange (ETDEWEB)

Nguyen Minh, Quyen [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Nanosens, IJsselkade 7, 7201 HB Zutphen (Netherlands); Pujari, Sidharam P. [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Wang, Bin [The Department of Chemical Engineering and Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology, Haifa 3200003 (Israel); Wang, Zhanhua [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Haick, Hossam [The Department of Chemical Engineering and Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology, Haifa 3200003 (Israel); Zuilhof, Han [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands); Rijn, Cees J.M. van, E-mail: cees.vanrijn@wur.nl [Laboratory of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen (Netherlands)

2016-11-30

Highlights: • Oxide-free H-terminated silicon nanowires undergo efficient surface modification by reaction with fluorinated 1-alkynes (HC≡C−(CH{sub 2}){sub 6}C{sub 8}H{sub 17−x}F{sub x}; x = 0–17). • These surface-modified Si NWs are chemically stable under range of conditions (including acid, base). • The surface coating yields efficient electrical passivation as demonstrated by a near-zero electrochemical activity of the surface. - Abstract: Passivation of oxide-free silicon nanowires (Si NWs) by the formation of high-quality fluorinated 1-hexadecyne-derived monolayers with varying fluorine content has been investigated. Alkyl chain monolayers (C{sub 16}H{sub 30−x}F{sub x}) with a varying number of fluorine substituents (x = 0, 1, 3, 9, 17) were attached onto hydrogen-terminated silicon (Si−H) surfaces with an effective one-step hydrosilylation. This surface chemistry gives well-defined monolayers on nanowires that have a cylindrical core–shell structure, as characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and static contact angle (SCA) analysis. The monolayers were stable under acidic and basic conditions, as well as under extreme conditions (such as UV exposure), and provide excellent surface passivation, which opens up applications in the fields of field effect transistors, optoelectronics and especially for disease diagnosis.

Monolayer assembly and striped architecture of Co nanoparticles on organic functionalized Si surfaces

Energy Technology Data Exchange (ETDEWEB)

Bae, S.-S.; Lim, D.K.; Park, J.-I.; Kim, S. [Korea Advanced Institute of Science and Technology, Department of Chemistry and School of Molecular Science (BK 21), Daejeon (Korea); Cheon, J. [Yonsei University, Department of Chemistry, College of Sciences, Seoul (Korea); Jeon, I.C. [Chonbuk National University, Department of Chemistry, College of Natural Sciences, Chonbuk (Korea)

2005-03-01

We present a new strategy to fabricate a monolayer assembly of Br-terminated Co nanoparticles on functionalized Si surfaces by using chemical covalent bonding and microcontact printing method. Self-assembled monolayers (SAMs) of the Co nanoparticles formed on the hydroxyl-terminated Si surface exhibit two-dimensional island networks with locally ordered arrays via covalent linkage between nanoparticles and surface. On the other hand, SAMs of the nanoparticles on the aminopropyl-terminated Si surface show an individual and random distribution over an entire surface. Furthermore, we have fabricated striped architectures of Co nanoparticles using a combination of microcontact printing and covalent linkage. Microcontact printing of octadecyltrichlorosilane and selective covalent linkage between nanoparticles and functionalized Si surfaces lead to a hybrid nanostructure with selectively assembled nanoparticles stripes on the patterned functionalized Si surfaces. (orig.)

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....

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

Science.gov (United States)

Kind, Martin; Wöll, Christof

2009-07-01

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

Lanthanide Selective Sorbents: Self-Assembled Monolayers on Mesoporous Supports (SAMMS)

Energy Technology Data Exchange (ETDEWEB)

Fryxell, Glen E.; Wu, Hong; Lin, Yuehe; Shaw, Wendy J.; Birnbaum, Jerome C.; Linehan, John C.; Nie, Zimin; Kemner, K. M.; Kelly, Shelley

2004-11-01

Through the marriage of mesoporous ceramics with self-assembled monolayer chemistry, the genesis of a powerful new class of environmental sorbent materials has been realized. By coating the mesoporous ceramic backbone with a monolayer terminated with a lanthanide-specific ligand, it is possible to couple high lanthanide binding affinity with the high loading capacity (resulting from the extremely high surface area of the support). This lanthanide-specific ligand field is created by pairing a ''hard'' anionic Lewis base with a suitable synergistic ligand, in a favorable chelating geometry. Details of the synthesis, characterization, lanthanide binding studies, binding kinetics, competition experiments and sorbent regeneration studies are summarized

Lanthanide Selective Sorbents: Self-Assembled Monolayers on Mesoporous Supports (SAMMS)

Energy Technology Data Exchange (ETDEWEB)

Fryxell, Glen E.; Wu, Hong; Lin, Yuehe; Shaw, Wendy J.; Birnbaum, Jerome C.; Linehan, John C.; Nie, Zimin; Kemner, Kenneth M.; Kelly, Shelley

2004-11-01

Through the marriage of mesoporous ceramics with self-assembled monolayer chemistry, the genesis of a powerful new class of environmental sorbent materials has been realized. By coating the mesoporous ceramic backbone with a monolayer terminated with a lanthanide-specific ligand, it is possible to couple high lanthanide binding affinity with the high loading capacity (resulting from the extremely high surface area of the support). This lanthanide-specific ligand field is created by pairing a “hard” anionic Lewis base with a suitable synergistic ligand, in a favorable chelating geometry. Details of the synthesis, characterization, lanthanide binding studies, binding kinetics, competition experiments and sorbent regeneration studies are summarized.

Tribology and Stability of Organic Monolayers on CrN: A Comparison among Silane, Phosphate, Alkene, and Alkyne Chemistries

NARCIS (Netherlands)

Pujari, S.P.; Li, F.; Regeling, R.; Zuilhof, H.

2013-01-01

The fabrication of chemically and mechanically stable monolayers on the surfaces of various inorganic hard materials is crucial to the development of biomedical/electronic devices. In this Article, monolayers based on the reactivity of silane, phosphonate, 1-alkene, and 1-alkyne moieties were

Synthesis of Graphene Based Membranes: Effect of Substrate Surface Properties on Monolayer Graphene Transfer.

Science.gov (United States)

Kafiah, Feras; Khan, Zafarullah; Ibrahim, Ahmed; Atieh, Muataz; Laoui, Tahar

2017-01-21

In this work, we report the transfer of graphene onto eight commercial microfiltration substrates having different pore sizes and surface characteristics. Monolayer graphene grown on copper by the chemical vapor deposition (CVD) process was transferred by the pressing method over the target substrates, followed by wet etching of copper to obtain monolayer graphene/polymer membranes. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) measurements were carried out to explore the graphene layer transferability. Three factors, namely, the substrate roughness, its pore size, and its surface wetting (degree of hydrophobicity) are found to affect the conformality and coverage of the transferred graphene monolayer on the substrate surface. A good quality graphene transfer is achieved on the substrate with the following characteristics; being hydrophobic (CA > 90°), having small pore size, and low surface roughness, with a CA to RMS (root mean square) ratio higher than 2.7°/nm.

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

Directory of Open Access Journals (Sweden)

Nicola H. Perry

2016-10-01

Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

Optical response of a flat metallic surface coated with a monolayer array of latex spheres

International Nuclear Information System (INIS)

Shi Lei; Liu Xiaohan; Yin Haiwei; Zi Jian

2010-01-01

We report on the fabrication, characterization and simulation of a structure consisting of a flat metallic surface coated with a monolayer array of latex spheres. This structure shows interesting optical response: over flat metallic surfaces a series of reflection minima appear in reflection spectra. Numerical simulations revealed that the structure can support two types of surface modes: surface plasmon-polaritons bound at the metallic surface and guided modes confined to the array of latex spheres, or their hybrids. Both experimental and theoretical results indicated that these surface modes show well-defined band structures due to the introduced periodicity by the monolayer array of latex spheres.

Biofunctionalization on alkylated silicon substrate surfaces via "click" chemistry.

Science.gov (United States)

Qin, Guoting; Santos, Catherine; Zhang, Wen; Li, Yan; Kumar, Amit; Erasquin, Uriel J; Liu, Kai; Muradov, Pavel; Trautner, Barbara Wells; Cai, Chengzhi

2010-11-24

Biofunctionalization of silicon substrates is important to the development of silicon-based biosensors and devices. Compared to conventional organosiloxane films on silicon oxide intermediate layers, organic monolayers directly bound to the nonoxidized silicon substrates via Si-C bonds enhance the sensitivity of detection and the stability against hydrolytic cleavage. Such monolayers presenting a high density of terminal alkynyl groups for bioconjugation via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC, a "click" reaction) were reported. However, yields of the CuAAC reactions on these monolayer platforms were low. Also, the nonspecific adsorption of proteins on the resultant surfaces remained a major obstacle for many potential biological applications. Herein, we report a new type of "clickable" monolayers grown by selective, photoactivated surface hydrosilylation of α,ω-alkenynes, where the alkynyl terminal is protected with a trimethylgermanyl (TMG) group, on hydrogen-terminated silicon substrates. The TMG groups on the film are readily removed in aqueous solutions in the presence of Cu(I). Significantly, the degermanylation and the subsequent CuAAC reaction with various azides could be combined into a single step in good yields. Thus, oligo(ethylene glycol) (OEG) with an azido tag was attached to the TMG-alkyne surfaces, leading to OEG-terminated surfaces that reduced the nonspecific adsorption of protein (fibrinogen) by >98%. The CuAAC reaction could be performed in microarray format to generate arrays of mannose and biotin with varied densities on the protein-resistant OEG background. We also demonstrated that the monolayer platform could be functionalized with mannose for highly specific capturing of living targets (Escherichia coli expressing fimbriae) onto the silicon substrates.

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 the alveolae monolayer and at the same time allows reduction of the interfacial tension to ~0mN/m....

Gold cleaning methods for preparation of cell culture surfaces for self-assembled monolayers of zwitterionic oligopeptides.

Science.gov (United States)

Enomoto, Junko; Kageyama, Tatsuto; Myasnikova, Dina; Onishi, Kisaki; Kobayashi, Yuka; Taruno, Yoko; Kanai, Takahiro; Fukuda, Junji

2018-05-01

Self-assembled monolayers (SAMs) have been used to elucidate interactions between cells and material surface chemistry. Gold surfaces modified with oligopeptide SAMs exhibit several unique characteristics, such as cell-repulsive surfaces, micropatterns of cell adhesion and non-adhesion regions for control over cell microenvironments, and dynamic release of cells upon external stimuli under culture conditions. However, basic procedures for the preparation of oligopeptide SAMs, including appropriate cleaning methods of the gold surface before modification, have not been fully established. Because gold surfaces are readily contaminated with organic compounds in the air, cleaning methods may be critical for SAM formation. In this study, we examined the effects of four gold cleaning methods: dilute aqua regia, an ozone water, atmospheric plasma, and UV irradiation. Among the methods, UV irradiation most significantly improved the formation of oligopeptide SAMs in terms of repulsion of cells on the surfaces. We fabricated an apparatus with a UV light source, a rotation table, and HEPA filter, to treat a number of gold substrates simultaneously. Furthermore, UV-cleaned gold substrates were capable of detaching cell sheets without serious cell injury. This may potentially provide a stable and robust approach to oligopeptide SAM-based experiments for biomedical studies. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

"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

Transfer plate radioassay using cell monolayers to detect anti-cell surface antibodies synthesized by lymphocyte hybridomas

International Nuclear Information System (INIS)

Schneider, M.D.; Eisenbarth, G.S.

1979-01-01

A solid phase [ 125 I] Protein A radioassay for anti-cell surface antibodies is described, which employs target cell monolayers cultured on fenestrated polyvinyl chloride 96-well plates ('transfer plates'). The calibrated aperture in the bottom of each well is small enough to retain fluid contents by surface tension during monolayer growth, but also permits fluid to enter the wells when transfer plate are lowered into receptacles containing washing buffer on test sera. To assay for antibodies directed against target cell surface antigens, transfer plates bearing monolayers are inserted into microculture plates with corresponding 96-well geometry, thereby simultaneously sampling 96 wells. This assay allows rapid screening of hundreds of hybrid cell colonies for production of antibodies with desired tissue specificity. (Auth.)

DNA-modified electrodes fabricated using copper-free click chemistry for enhanced protein detection.

Science.gov (United States)

Furst, Ariel L; Hill, Michael G; Barton, Jacqueline K

2013-12-31

A method of DNA monolayer formation has been developed using copper-free click chemistry that yields enhanced surface homogeneity and enables variation in the amount of DNA assembled; extremely low-density DNA monolayers, with as little as 5% of the monolayer being DNA, have been formed. These DNA-modified electrodes (DMEs) were characterized visually, with AFM, and electrochemically, and were found to facilitate DNA-mediated reduction of a distally bound redox probe. These low-density monolayers were found to be more homogeneous than traditional thiol-modified DNA monolayers, with greater helix accessibility through an increased surface area-to-volume ratio. Protein binding efficiency of the transcriptional activator TATA-binding protein (TBP) was also investigated on these surfaces and compared to that on DNA monolayers formed with standard thiol-modified DNA. Our low-density monolayers were found to be extremely sensitive to TBP binding, with a signal decrease in excess of 75% for 150 nM protein. This protein was detectable at 4 nM, on the order of its dissociation constant, with our low-density monolayers. The improved DNA helix accessibility and sensitivity of our low-density DNA monolayers to TBP binding reflects the general utility of this method of DNA monolayer formation for DNA-based electrochemical sensor development.

The interaction of trace heavy metal with lipid monolayer in the sea surface microlayer.

Science.gov (United States)

Li, Siyang; Du, Lin; Tsona, Narcisse T; Wang, Wenxing

2018-04-01

Lipid molecules and trace heavy metals are enriched in sea surface microlayer and can be transferred into the sea spray aerosol. To better understand their impact on marine aerosol generation and evolution, we investigated the interaction of trace heavy metals including Fe 3+ , Pb 2+ , Zn 2+ , Cu 2+ , Ni 2+ , Cr 3+ , Cd 2+ , and Co 2+ , with dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface. Phase behavior of the DPPC monolayer on heavy metal solutions was probed with surface pressure-area (π-A) isotherms. The conformation order and orientation of DPPC alkyl chains were characterized by infrared reflection-absorption spectroscopy (IRRAS). The π-A isotherms show that Zn 2+ and Fe 3+ strongly interact with DPPC molecules, and induce condensation of the monolayers in a concentration-dependent manner. IRRAS spectra show that the formation of cation-DPPC complex gives rise to conformational changes and immobilization of the headgroups. The current results suggest that the enrichment of Zn 2+ in sea spray aerosols is due to strong binding to the DPPC film. The interaction of Fe 3+ with DPPC monolayers can significantly influence their surface organizations through the formation of lipid-coated particles. These results suggest that the sea surface microlayer is capable of accumulating much higher amounts of these metals than the subsurface water. The organic and metal pollutants may transfer into the atmosphere by this interaction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chemical films and monolayers on the water surface and their interactions with ultraviolet radiation: a pilot investigation

International Nuclear Information System (INIS)

Schouten, Peter; Lemckert, Charles; Underhill, Ian; Turner, Geoff; Turnbull, David; Parisi, Alfio; Downs, Nathan

2011-01-01

Over the past 50 years numerous types of chemical films and monolayers have been deployed on top of a wide variety of water reserves in an endeavour to reduce evaporation. To date very little knowledge has been assimilated on how these chemical films and monolayers, once applied to a water surface, influence the underwater UV light field and, in turn, the delicate ecosystems that exist in aquatic environments. This manuscript presents underwater UV exposure profiles weighted to the DNA damage action spectrum measured under an octadecanol/hexadecanol/lime chemical film mixture, a silicone-based chemical film and an octadecanol monolayer applied to the water surface. UV transmission and absorption properties were also evaluated for each of these chemical films and monolayers. From this it was found that when chemical films/monolayers are applied to surface water they can reduce the penetration of biologically effective UV into the water column by up to 85% at a depth as small as 1 cm. This could have a positive influence on the aquatic ecosystem, as harmful UV radiation may be prevented from reaching and consequently damaging a variety of life forms or it could have a negative effect by potentially stopping aquatic organisms from adapting to solar ultraviolet radiation over extended application intervals. Additionally, there is currently no readily applicable system or technique available to readily detect or visualize chemical films and monolayers on the water surface. To overcome this problem a new method of monolayer and chemical film visualization, using a UV camera system, is detailed and tested and its applicability for usage in both laboratory-based trials and real-world operations is evaluated

Chemical films and monolayers on the water surface and their interactions with ultraviolet radiation: a pilot investigation

Science.gov (United States)

Schouten, Peter; Lemckert, Charles; Turnbull, David; Parisi, Alfio; Downs, Nathan; Underhill, Ian; Turner, Geoff

2011-06-01

Over the past 50 years numerous types of chemical films and monolayers have been deployed on top of a wide variety of water reserves in an endeavour to reduce evaporation. To date very little knowledge has been assimilated on how these chemical films and monolayers, once applied to a water surface, influence the underwater UV light field and, in turn, the delicate ecosystems that exist in aquatic environments. This manuscript presents underwater UV exposure profiles weighted to the DNA damage action spectrum measured under an octadecanol/hexadecanol/lime chemical film mixture, a silicone-based chemical film and an octadecanol monolayer applied to the water surface. UV transmission and absorption properties were also evaluated for each of these chemical films and monolayers. From this it was found that when chemical films/monolayers are applied to surface water they can reduce the penetration of biologically effective UV into the water column by up to 85% at a depth as small as 1 cm. This could have a positive influence on the aquatic ecosystem, as harmful UV radiation may be prevented from reaching and consequently damaging a variety of life forms or it could have a negative effect by potentially stopping aquatic organisms from adapting to solar ultraviolet radiation over extended application intervals. Additionally, there is currently no readily applicable system or technique available to readily detect or visualize chemical films and monolayers on the water surface. To overcome this problem a new method of monolayer and chemical film visualization, using a UV camera system, is detailed and tested and its applicability for usage in both laboratory-based trials and real-world operations is evaluated.

Technique for etching monolayer and multilayer materials

Science.gov (United States)

Bouet, Nathalie C. D.; Conley, Raymond P.; Divan, Ralu; Macrander, Albert

2015-10-06

A process is disclosed for sectioning by etching of monolayers and multilayers using an RIE technique with fluorine-based chemistry. In one embodiment, the process uses Reactive Ion Etching (RIE) alone or in combination with Inductively Coupled Plasma (ICP) using fluorine-based chemistry alone and using sufficient power to provide high ion energy to increase the etching rate and to obtain deeper anisotropic etching. In a second embodiment, a process is provided for sectioning of WSi.sub.2/Si multilayers using RIE in combination with ICP using a combination of fluorine-based and chlorine-based chemistries and using RF power and ICP power. According to the second embodiment, a high level of vertical anisotropy is achieved by a ratio of three gases; namely, CHF.sub.3, Cl.sub.2, and O.sub.2 with RF and ICP. Additionally, in conjunction with the second embodiment, a passivation layer can be formed on the surface of the multilayer which aids in anisotropic profile generation.

Extreme Ultraviolet (EUV) induced surface chemistry on Ru

NARCIS (Netherlands)

Liu, Feng; Sturm, Jacobus Marinus; Lee, Christopher James; Bijkerk, Frederik

2013-01-01

EUV photon induced surface chemistry can damage multilayer mirrors causing reflectivity loss and faster degradation. EUV photo chemistry involves complex processes including direct photon induced surface chemistry and secondary electron radiation chemistry. Current cleaning techniques include dry

Determining the thickness of aliphatic alcohol monolayers covalently attached to silicon oxide surfaces using angle-resolved X-ray photoelectron spectroscopy

Science.gov (United States)

Lee, Austin W. H.; Kim, Dongho; Gates, Byron D.

2018-04-01

The thickness of alcohol based monolayers on silicon oxide surfaces were investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS). Advantages of using alcohols as building blocks for the formation of monolayers include their widespread availability, ease of handling, and stability against side reactions. Recent progress in microwave assisted reactions demonstrated the ease of forming uniform monolayers with alcohol based reagents. The studies shown herein provide a detailed investigation of the thickness of monolayers prepared from a series of aliphatic alcohols of different chain lengths. Monolayers of 1-butanol, 1-hexanol, 1-octanol, 1-decanol, and 1-dodecanol were each successfully formed through microwave assisted reactions and characterized by ARXPS techniques. The thickness of these monolayers consistently increased by ∼1.0 Å for every additional methylene (CH2) within the hydrocarbon chain of the reagents. Tilt angles of the molecules covalently attached to silicon oxide surfaces were estimated to be ∼35° for each type of reagent. These results were consistent with the observations reported for thiol based or silane based monolayers on either gold or silicon oxide surfaces, respectively. The results of this study also suggest that the alcohol based monolayers are uniform at a molecular level.

Surface and catalysis science in the Materials and Molecular Research Division

International Nuclear Information System (INIS)

1980-01-01

Surface science studies at Lawrence Berkeley Laboratory are detailed. Subject areas include: structure of surfaces and adsorbed monolayers; reduction and oxidation of surfaces; catalytic chemistry; and structure of interfaces and thin films

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...

Sub-monolayer dot vertical-cavity surface-emitting lasers

International Nuclear Information System (INIS)

Blokhin, S.A.; Maleev, N.A.; Kuz'menkov, A.G.

2006-01-01

Vertical-cavity surface-emitting lasers (VCSELs) based on submonolayer InGaAs quantum-dot active region and doped with AlGaAs/GaAs distributed Bragg reflectors were grown by molecular beam epitaxy. 3 μm aperture single-mode VCSELs demonstrate lasing at 980 nm with threshold current of 0.6 mA, maximum output power of 4 mW and external differential efficiency as high as 68%. Ultimately low internal optical losses were measured for these multimode sub-monolayer quantum dot VCSELs [ru

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

KAUST Repository

Chen, Paiyen; Farhat, Mohamed; Askarpour, Amir Nader; Tymchenko, Mykhailo; Alù , Andrea

2014-01-01

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

The surface chemistry of metal-oxygen interactions

DEFF Research Database (Denmark)

Stokbro, Kurt; Baroni, Stefano

1997-01-01

We report on a computational study of the clean and oxygen-covered Rh(110) surface, based on density-functional theory within the local-density approximation. We have used plane-wave basis sets and Vanderbilt ultra-soft pseudopotentials. For the clean surface, we present results for the equilibrium...... structure, surface energy and surface stress of the unreconstructed and (1 x 2) reconstructed structures. For the oxygen-covered surface we have performed a geometry optimization at 0.5, 1, and 2 monolayer oxygen coverages, and we present results for the equilibrium configurations, workfunctions and oxygen...

Mixed DPPC/POPC Monolayers: All-atom Molecular Dynamics Simulations and Langmuir Monolayer Experiments

Czech Academy of Sciences Publication Activity Database

Olžyńska, Agnieszka; Zubek, M.; Roeselová, Martina; Korchowiec, J.; Cwiklik, Lukasz

2016-01-01

Roč. 1858, č. 12 (2016), s. 3120-3130 ISSN 0005-2736 R&D Projects: GA ČR GA15-14292S Institutional support: RVO:61388955 ; RVO:61388963 Keywords : phospholipid monolayers * Lung surfactant * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.498, year: 2016

The hidden radiation chemistry in plasma modification and XPS analysis of polymer surfaces

International Nuclear Information System (INIS)

George, G.A.; Le, T.T.; Elms, F.M.; Wood, B.J.

1996-01-01

Full text: The surface modification of polymers using plasma treatments is being widely researched to achieve changes in the surface energetics and consequent wetting and reactivity for a range of applications. These include i) adhesion for polymer bonding and composite material fabrication and ii) biocompatibility of polymers when used as orthopedic implants, catheters and prosthetics. A low pressure rf plasma produces a variety of species from the introduced gas which may react with the surface of a hydrocarbon polymer, such as polyethylene. In the case of 0 2 and H 2 0, these species include oxygen atoms, singlet molecular oxygen and hydroxyl radicals, all of which may oxidise and, depending on their energy, ablate the polymer surface. In order to better understand the reactive species formed both in and downstream from a plasma and the relative contributions of oxidation and ablation, self-assembled monolayers of n-alkane thiols on gold are being used as well characterised substrates for quantitative X-ray photoelectron spectroscopy (XPS). The identification and quantification of oxidised carbon species on plasma treated polymers from broad, asymmetric XPS signals is difficult, so derivatisation is often used to enhance sensitivity and specificity. For example, trifluoroacetic anhydride (TFAA) selectively labels hydroxyl functionality. The surface analysis of a modified polymer surface may be confounded by high energy radiation chemistry which may occur during XPS analysis. Examples include scission of carbon-halogen bonds (as in TFM adducts), decarboxylation and main-chain polyene formation. The extent of free-radical chemistry occurring in polyethylene while undergoing XPS analysis may be seen by both ESR and FT-IR analysis

“Living” Free Radical Photopolymerization Initiated from Surface-Grafted Iniferter Monolayers

NARCIS (Netherlands)

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

Evaluation of process influences on surface chemistry of epoxy acrylate based solder mask via XPS, ToF-SIMS and contact angle measurement

Energy Technology Data Exchange (ETDEWEB)

Hofmeister, Caroline, E-mail: caroline.hofmeister@de.bosch.com [Robert Bosch GmbH, Postfach 30 02 40, 70442 Stuttgart (Germany); Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Str. 12, 28359 Bremen (Germany); Maaß, Sebastian [Robert Bosch GmbH, Postfach 30 02 40, 70442 Stuttgart (Germany); Fladung, Thorsten; Mayer, Bernd [Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Str. 12, 28359 Bremen (Germany)

2017-01-01

Epoxy acrylate based solder mask formulations were conditioned by different printed circuit board (PCB) manufacturing and PCB assembly process stages. Depending on these different influences the chemistry of the solder mask surface was investigated regarding adhesion to possible adhesion partners. The combination of X-ray photoelectron spectrometry (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the contact angle method, for surface energy determination, provided a detailed understanding of the surface near region up to the topmost monolayer, which forms the contact zone in which adhesion takes place. The combination of ToF-SIMS and XPS provided molecular information of surface components comprising quantitative information. The influences of all process steps, like UV, chemical and thermal treatment, on the chemical surface composition and appearance were identified. Based on the results a chemical surface model could be created regarding the different adhesion mechanisms. It has been shown that an enrichment of siloxanes at the surface is generated by different mechanisms that were distinguished based on ToF-SIMS. Even though an oxidation process in the surface near region (10 nm) was indicated by XPS, no increase of the surface polar groups and thus no polarity increase could be observed within the first monolayer. A surface model derived from the analysis results shows generation and occupation of free sites at the surface through all stages of the process. An occupation of free sites by siloxanes from additives in the solder mask formulation results in a siloxane dominated topmost monolayer. - Highlights: • A surface model describing the process influences is proposed. • Detailed siloxane reaction analysis was possible with ToF-SIMS. • Photo-chemical, chemical and thermal surface modification occur during PCB manufacturing.

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

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...

A Smart Superwetting Surface with Responsivity in Both Surface Chemistry and Microstructure.

Science.gov (United States)

Zhang, Dongjie; Cheng, Zhongjun; Kang, Hongjun; Yu, Jianxin; Liu, Yuyan; Jiang, Lei

2018-03-26

Recently, smart surfaces with switchable wettability have aroused much attention. However, only single surface chemistry or the microstructure can be changed on these surfaces, which significantly limits their wetting performances, controllability, and applications. A new surface with both tunable surface microstructure and chemistry was prepared by grafting poly(N-isopropylacrylamide) onto the pillar-structured shape memory polymer on which multiple wetting states from superhydrophilicity to superhydrophobicity can be reversibly and precisely controlled by synergistically regulating the surface microstructure and chemistry. Meanwhile, based on the excellent controllability, we also showed the application of the surface as a rewritable platform, and various gradient wettings can be obtained. This work presents for the first time a surface with controllability in both surface chemistry and microstructure, which starts some new ideas for the design of novel superwetting materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The impact of surface coverage on the kinetics of electron transfer through redox monolayers on a silicon electrode surface

International Nuclear Information System (INIS)

Ciampi, Simone; Choudhury, Moinul H.; Ahmad, Shahrul Ainliah Binti Alang; Darwish, Nadim; Brun, Anton Le; Gooding, J.Justin

2015-01-01

Graphical abstract: The impact of surface coverage on the kinetics of electron transfer through redox monolayers on a silicon electrode surface. ABSTRACT: The impact of the coverage of ferrocene moieties, attached to a silicon electrode modified via hydrosilylation of a dialkyne, on the kinetics of electron transfer between the redox species and the electrode is explored. The coverage of ferrocene is controlled by varying the coupling time between azidomethylferrocene and the distal alkyne of the monolayer via the copper assisted azide-alkyne cycloaddition reaction. All other variables in the surface preparation are maintained identical. What is observed is that the higher the surface coverage of the ferrocene moieties the faster the apparent rates of electron transfer. This surface coverage-dependent kinetic effect is attributed to electrons hopping between ferrocene moieties across the redox film toward hotspots for the electron transfer event. The origin of these hotspots is tentatively suggested to result from minor amounts of oxide on the underlying silicon surface that reduce the barrier for the electron transfer.

The Chemistry of Inorganic Precursors during the Chemical Deposition of Films on Solid Surfaces.

Science.gov (United States)

Barry, Seán T; Teplyakov, Andrew V; Zaera, Francisco

2018-03-20

The deposition of thin solid films is central to many industrial applications, and chemical vapor deposition (CVD) methods are particularly useful for this task. For one, the isotropic nature of the adsorption of chemical species affords even coverages on surfaces with rough topographies, an increasingly common requirement in microelectronics. Furthermore, by splitting the overall film-depositing reactions into two or more complementary and self-limiting steps, as it is done in atomic layer depositions (ALD), film thicknesses can be controlled down to the sub-monolayer level. Thanks to the availability of a vast array of inorganic and metalorganic precursors, CVD and ALD are quite versatile and can be engineered to deposit virtually any type of solid material. On the negative side, the surface chemistry that takes place in these processes is often complex, and can include undesirable side reactions leading to the incorporation of impurities in the growing films. Appropriate precursors and deposition conditions need to be chosen to minimize these problems, and that requires a proper understanding of the underlying surface chemistry. The precursors for CVD and ALD are often designed and chosen based on their known thermal chemistry from inorganic chemistry studies, taking advantage of the vast knowledge developed in that field over the years. Although a good first approximation, however, this approach can lead to wrong choices, because the reactions of these precursors at gas-solid interfaces can be quite different from what is seen in solution. For one, solvents often aid in the displacement of ligands in metalorganic compounds, providing the right dielectric environment, temporarily coordinating to the metal, or facilitating multiple ligand-complex interactions to increase reaction probabilities; these options are not available in the gas-solid reactions associated with CVD and ALD. Moreover, solid surfaces act as unique "ligands", if these reactions are to be

Chemical modification of glass surface with a monolayer of nonchromophoric and chromophoric methacrylate terpolymer

Energy Technology Data Exchange (ETDEWEB)

Janik, Ryszard [Department of Polymer Engineering and Technology, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Kucharski, Stanislaw, E-mail: stanislaw.kucharski@pwr.wroc.pl [Department of Polymer Engineering and Technology, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Sobolewska, Anna [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Barille, Regis [Institut des Sciences et Techniques Moleculaires d' Angers ' Moltech Anjou' , CNRS UMR 6200, 49045 Angers (France)

2010-11-15

The methacrylate terpolymers, a nonchromophoric and chromophoric one, containing 2-hydroxyethyl groups were reacted with 3-isocyanatopropyltriethoxysilane to obtain reactive polymers able to form covalent bonding with -SiOH groups of the glass surface via triethoxysilane group condensation. Chemical modification of the Corning 2949 glass plates treated in this way resulted in increase of wetting angle from 11{sup o} to ca. 70-73{sup o}. Determination of ellipsometric parameters revealed low value of the substrate refractive index as compared with that of bulk Corning 2949 glass suggesting roughness of the surface. The AFM image of the bare glass surface and that modified with terpolymer monolayer confirmed this phenomenon. Modification of the glass with the terpolymer monolayer made it possible to create the substrate surface well suited for deposition of familiar chromophore film by spin-coating. The chromophore polymer film deposited onto the modified glass surface was found to be resistant to come unstuck in aqueous solution.

Tunable band gap and optical properties of surface functionalized Sc2C monolayer

International Nuclear Information System (INIS)

Wang Shun; Du Yu-Lei; Liao Wen-He

2017-01-01

Using the density functional theory, we have investigated the electronic and optical properties of two-dimensional Sc 2 C monolayer with OH, F, or O chemical groups. The electronic structures reveal that the functionalized Sc 2 C monolayers are semiconductors with a band gap of 0.44–1.55 eV. The band gap dependent optical parameters, like dielectric function, absorption coefficients, reflectivity, loss function, and refraction index were also calculated for photon energy up to 20 eV. At the low-energy region, each optical parameter shifts to red, and the peak increases obviously with the increase of the energy gap. Consequently, Sc 2 C monolayer with a tunable band gap by changing the type of surface chemical groups is a promising 2D material for optoelectronic devices. (paper)

Well-ordered structure of methylene blue monolayers on Au(111) surface: electrochemical scanning tunneling microscopy studies.

Science.gov (United States)

Song, Yonghai; Wang, Li

2009-02-01

Well-ordered structure of methylene blue (MB) monolayers on Au(111) surface has been successfully obtained by controlling the substrate potential. Electrochemical scanning tunneling microscopy (ECSTM) examined the monolayers of MB on Au(111) in 0.1 M HClO(4) and showed long-range ordered, interweaved arrays of MB with quadratic symmetry on the substrate in the potential range of double-layer charging. High-resolution ECSTM image further revealed the details of the MB monolayers structure of c(5 x 5 radical 3)rect and the flat-lying orientation of ad-molecules. The dependence of molecular organization on the substrate potential and the formation mechanism of well-ordered structure on Au(111) surface were investigated in detail. The obtained well-ordered structure at the interface between a metal and an aqueous electrolyte might possibly be used as high-density device for signal memory and templates for the advanced nanopatterning of surfaces. (c) 2008 Wiley-Liss, Inc.

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.

Organometallic chemistry of metal surfaces

International Nuclear Information System (INIS)

Muetterties, E.L.

1981-06-01

The organometallic chemistry of metal surfaces is defined as a function of surface crystallography and of surface composition for a set of cyclic hydrocarbons that include benzene, toluene, cyclohexadienes, cyclohexene, cyclohexane, cyclooctatetraene, cyclooctadienes, cyclooctadiene, cycloheptatriene and cyclobutane. 12 figures

The dependence of lipid monolayer lipolysis on surface pressure.

OpenAIRE

Hall, D G

1992-01-01

Brönsted-Bjerrum theory [Brönsted (1922) Z. Phys. Chem. 102, 169-207; (1925) Z. Phys. Chem. 115, 337-364; Bjerrum (1924) Z. Phys. Chem. 108, 82-100] as applied to reactions at interfaces is used to interpret published data on the lipolysis of dinonanoyl phosphatidylcholine monolayers by pancreatic phospholipase A2. Reasonable quantitative agreement between theoretical and experimental results occurs when the reported effects of surface pressure on the amount of adsorbed enzyme are used togeth...

Covalent-Bond Formation via On-Surface Chemistry.

Science.gov (United States)

Held, Philipp Alexander; Fuchs, Harald; Studer, Armido

2017-05-02

In this Review article pioneering work and recent achievements in the emerging research area of on-surface chemistry is discussed. On-surface chemistry, sometimes also called two-dimensional chemistry, shows great potential for bottom-up preparation of defined nanostructures. In contrast to traditional organic synthesis, where reactions are generally conducted in well-defined reaction flasks in solution, on-surface chemistry is performed in the cavity of a scanning probe microscope on a metal crystal under ultrahigh vacuum conditions. The metal first acts as a platform for self-assembly of the organic building blocks and in many cases it also acts as a catalyst for the given chemical transformation. Products and hence success of the reaction are directly analyzed by scanning probe microscopy. This Review provides a general overview of this chemistry highlighting advantages and disadvantages as compared to traditional reaction setups. The second part of the Review then focuses on reactions that have been successfully conducted as on-surface processes. On-surface Ullmann and Glaser couplings are addressed. In addition, cyclodehydrogenation reactions and cycloadditions are discussed and reactions involving the carbonyl functionality are highlighted. Finally, the first examples of sequential on-surface chemistry are considered in which two different functionalities are chemoselectively addressed. The Review gives an overview for experts working in the area but also offers a starting point to non-experts to enter into this exciting new interdisciplinary research field. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A monolayer of hierarchical silver hemi-mesoparticles with tunable surface topographies for highly sensitive surface-enhanced Raman spectroscopy

Science.gov (United States)

Zhu, Shuangmei; Fan, Chunzhen; Mao, Yanchao; Wang, Junqiao; He, Jinna; Liang, Erjun; Chao, Mingju

2016-02-01

We proposed a facile green synthesis system to synthesize large-scale Ag hemi-mesoparticles monolayer on Cu foil. Ag hemi-mesoparticles have different surface morphologies on their surfaces, including ridge-like, meatball-like, and fluffy-like shapes. In the reaction, silver nitrate was reduced by copper at room temperature in dimethyl sulfoxide via the galvanic displacement reaction. The different surface morphologies of the Ag hemi-mesoparticles were adjusted by changing the reaction time, and the hemi-mesoparticle surface formed fluffy-spherical nanoprotrusions at longer reaction time. At the same time, we explored the growth mechanism of silver hemi-mesoparticles with different surface morphologies. With 4-mercaptobenzoic acid as Raman probe molecules, the fluffy-like silver hemi-mesoparticles monolayer with the best activity of surface enhanced Raman scattering (SERS), the enhancement factor is up to 7.33 × 107 and the detection limit can reach 10-10M. SERS measurements demonstrate that these Ag hemi-mesoparticles can serve as sensitive SERS substrates. At the same time, using finite element method, the distribution of the localized electromagnetic field near the particle surface was simulated to verify the enhanced mechanism. This study helps us to understand the relationship between morphology Ag hemi-mesoparicles and the properties of SERS.

Surface-directed molecular assembly of pentacene on monolayer graphene for high-performance organic transistors.

Science.gov (United States)

Lee, Wi Hyoung; Park, Jaesung; Sim, Sung Hyun; Lim, Soojin; Kim, Kwang S; Hong, Byung Hee; Cho, Kilwon

2011-03-30

Organic electronic devices that use graphene electrodes have received considerable attention because graphene is regarded as an ideal candidate electrode material. Transfer and lithographic processes during fabrication of patterned graphene electrodes typically leave polymer residues on the graphene surfaces. However, the impact of these residues on the organic semiconductor growth mechanism on graphene surface has not been reported yet. Here, we demonstrate that polymer residues remaining on graphene surfaces induce a stand-up orientation of pentacene, thereby controlling pentacene growth such that the molecular assembly is optimal for charge transport. Thus, pentacene field-effect transistors (FETs) using source/drain monolayer graphene electrodes with polymer residues show a high field-effect mobility of 1.2 cm(2)/V s. In contrast, epitaxial growth of pentacene having molecular assembly of lying-down structure is facilitated by π-π interaction between pentacene and the clean graphene electrode without polymer residues, which adversely affects lateral charge transport at the interface between electrode and channel. Our studies provide that the obtained high field-effect mobility in pentacene FETs using monolayer graphene electrodes arises from the extrinsic effects of polymer residues as well as the intrinsic characteristics of the highly conductive, ultrathin two-dimensional monolayer graphene electrodes.

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.

Surface structures of normal paraffins and cyclohexane monolayers and thin crystals grown on the (111) crystal face of platinum. A low-energy electron diffraction study

International Nuclear Information System (INIS)

Firment, L.E.; Somorjai, G.A.

1977-01-01

The surfaces of the normal paraffins (C 3 --C 8 ) and cyclohexane have been studied using low-energy electron diffraction (LEED). The samples were prepared by vapor deposition on the (111) face of a platinum single crystal in ultrahigh vacuum, and were studied both as thick films and as adsorbed monolayers. These molecules form ordered monolayers on the clean metal surface in the temperature range 100--220 K and at a vapor flux corresponding to 10 -7 Torr. In the adsorbed monolayers of the normal paraffins (C 4 --C 8 ), the molecules lie with their chain axes parallel to the Pt surface and Pt[110]. The paraffin monolayer structures undergo order--disorder transitions as a function of temperature. Multilayers condensed upon the ordered monolayers maintained the same orientation and packing as found in the monolayers. The surface structures of the growing organic crystals do not corresond to planes in their reported bulk crystal structures and are evidence for epitaxial growth of pseudomorphic crystal forms. Multilayers of n-octane and n-heptane condensed upon disordered monolayers have also grown with the (001) plane of the triclinic bulk crystal structures parallel to the surface. n-Butane has three monolayer structures on Pt(111) and one of the three is maintained during growth of the crystal. Cyclohexane forms an ordered monolayer, upon which a multilayer of cyclohexane grows exhibiting the (001) surface orientation of the monoclinic bulk crystal structure. Surface structures of saturated hydrocarbons are found to be very susceptible to electron beam induced damage. Surface charging interferes with LEED only at sample thicknesses greater than 200 A

Conformation, orientation and interaction in molecular monolayers: A surface second harmonic and sum frequency generation study

International Nuclear Information System (INIS)

Superfine, R.; Huang, J.Y.; Shen, Y.R.

1988-12-01

We have used sum frequency generation (SFG) to study the order in a silane monolayer before and after the deposition of a coadsorbed liquid crystal monolayer. We observe an increase in the order of the chain of the silane molecule induced by the interpenetration of the liquid crystal molecules. By using second harmonic generation (SHG) and SFG, we have studied the orientation and conformation of the liquid crystal molecule on clean and silane coated glass surfaces. On both surfaces, the biphenyl group is tilted by 70 degree with the alkyl chain end pointing away from the surface. The shift in the C-H stretch frequencies in the coadsorbed system indicates a significant interaction between molecules. 9 refs., 3 figs

Low temperature surface chemistry and nanostructures

Science.gov (United States)

Sergeev, G. B.; Shabatina, T. I.

2002-03-01

The new scientific field of low temperature surface chemistry, which combines the low temperature chemistry (cryochemistry) and surface chemistry approaches, is reviewed in this paper. One of the most exciting achievements in this field of science is the development of methods to create highly ordered hybrid nanosized structures on different organic and inorganic surfaces and to encapsulate nanosized metal particles in organic and polymer matrices. We consider physical and chemical behaviour for the systems obtained by co-condensation of the components vapours on the surfaces cooled down to 4-10 and 70-100 K. In particular the size effect of both types, the number of atoms in the reactive species structure and the thickness of growing co-condensate film, on the chemical activity of the system is analysed in detail. The effect of the internal mechanical stresses on the growing interfacial co-condensate film formation and on the generation of fast (explosive) spontaneous reactions at low temperatures is discussed. The examples of unusual chemical interactions of metal atoms, clusters and nanosized particles, obtained in co-condensate films on the cooled surfaces under different conditions, are presented. The examples of highly ordered surface and volume hybrid nanostructures formation are analysed.

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.

Attachment chemistry of aromatic compounds on a Silicon(100) surface

Science.gov (United States)

Henriksson, Anders; Nishiori, Daiki; Maeda, Hiroaki; Miyachi, Mariko; Yamanoi, Yoshinori; Nishihara, Hiroshi

2018-03-01

A mild method was developed for the chemical attachment of aromatic compounds directly onto a hydrogen-terminated Si(100) (H-Si(100)) surface. In the presence of palladium catalyst and base, 4-iodophenylferrocene and a π-conjugated iron complex were attached to H-Si(100) electrodes and hydrogen-terminated silicon nanowires (H-SiNWs), both of which have predominant dihydride species on their surfaces. The reactions were conducted in 1,4-dioxane at 100 °C and the immobilization of both 4-ferrocenylphenyl group and π-conjugated molecular wires were confirmed and quantified by XPS and electrochemical measurements. We reported densely packed monolayer whose surface coverage (Γ), estimated from the electrochemical measurements are in analogue to similar monolayers prepared via thermal or light induced hydrosilylation reactions with alkenes or alkynes. The increase in electrochemical response observed on nanostructured silicon surfaces corresponds well to the increase in surface area, those strongly indicating that this method may be applied for the functionalization of electrodes with a variety of surface topographies.

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)

Structure and shear response of lipid monolayers

International Nuclear Information System (INIS)

Dutta, P.; Ketterson, J.B.

1990-02-01

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

Surface chemistry theory and applications

CERN Document Server

Bikerman, J J

2013-01-01

Surface Chemistry Theory and Applications focuses on liquid-gas, liquid-liquid, solid-gas, solid-liquid, and solid-solid surfaces. The book first offers information on liquid-gas surfaces, including surface tension, measurement of surface tension, rate of capillarity rise, capillary attraction, bubble pressure and pore size, and surface tension and temperature. The text then ponders on liquid-liquid and solid-gas surfaces. Discussions focus on surface energy of solids, surface roughness and cleanness, adsorption of gases and vapors, adsorption hysteresis, interfacial tension, and interfacial t

Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes.

Science.gov (United States)

Yuan, Wei; Li, Guanglei; Gil, Eun Seok; Lowe, Tao Lu; Fu, Bingmei M

2010-04-01

Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value.

Thiol-ene immobilisation of carbohydrates onto glass slides as a simple alternative to gold-thiol monolayers, amines or lipid binding.

Science.gov (United States)

Biggs, Caroline I; Edmondson, Steve; Gibson, Matthew I

2015-01-01

Carbohydrate arrays are a vital tool in studying infection, probing the mechanisms of bacterial, viral and toxin adhesion and the development of new treatments, by mimicking the structure of the glycocalyx. Current methods rely on the formation of monolayers of carbohydrates that have been chemically modified with a linker to enable interaction with a functionalised surface. This includes amines, biotin, lipids or thiols. Thiol-addition to gold to form self-assembled monolayers is perhaps the simplest method for immobilisation as thiolated glycans are readily accessible from reducing carbohydrates in a single step, but are limited to gold surfaces. Here we have developed a quick and versatile methodology which enables the use of thiolated carbohydrates to be immobilised as monolayers directly onto acrylate-functional glass slides via a 'thiol-ene'/Michael-type reaction. By combining the ease of thiol chemistry with glass slides, which are compatible with microarray scanners this offers a cost effective, but also useful method to assemble arrays.

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

2010-01-01

A ternary surface monolayer, consisting of co-assembled thiolated capture probe (SHCP) mercaptohexanol (MCH) and dithiothreitol (DTT), is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers (SAMs). Remarkably low detection limits down to 40 zmole (in 4 μL samples) as well as only 1 CFU E. coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3′,5,5′-tetramethylbenzidine (HRP/TMB) system. Such dramatic improvements in the detection limits (compared to common binary alkanethiol interfaces and to most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to non-specific 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 matrices. 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. PMID:20883023

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.

Surface chemistry and fundamental limitations on the plasma cleaning of metals

Energy Technology Data Exchange (ETDEWEB)

Dong, Bin, E-mail: bindong@my.unt.edu [Department of Chemistry, University of North Texas, 1155 Union Circle 305070, Denton, TX, 76203 (United States); Driver, M. Sky, E-mail: Marcus.Driver@unt.edu [Department of Chemistry, University of North Texas, 1155 Union Circle 305070, Denton, TX, 76203 (United States); Emesh, Ismail, E-mail: Ismail_Emesh@amat.com [Applied Materials Inc., 3050 Bowers Ave, Santa Clara, CA, 95054 (United States); Shaviv, Roey, E-mail: Roey_Shaviv@amat.com [Applied Materials Inc., 3050 Bowers Ave, Santa Clara, CA, 95054 (United States); Kelber, Jeffry A., E-mail: Jeffry.Kelber@unt.edu [Department of Chemistry, University of North Texas, 1155 Union Circle 305070, Denton, TX, 76203 (United States)

2016-10-30

Highlights: • O{sub 2}-free plasma treatment of air-exposed Co or Cu surfaces yields remnant C layers inert to further plasma cleaning. • The formation of the remnant C layer is graphitic (Cu) or carbidic (Co). • The formation of a remnant C layer is linked to plasma cleaning of a metal surface. - Abstract: In-situ X-ray photoelectron spectroscopy (XPS) studies reveal that plasma cleaning of air-exposed Co or Cu transition metal surfaces results in the formation of a remnant C film 1–3 monolayers thick, which is not reduced upon extensive further plasma exposure. This effect is observed for H{sub 2} or NH{sub 3} plasma cleaning of Co, and He or NH{sub 3} plasma cleaning of Cu, and is observed with both inductively coupled (ICP) and capacitively-coupled plasma (CCP). Changes in C 1 s XPS spectra indicate that this remnant film formation is accompanied by the formation of carbidic C on Co and of graphitic C on Cu. This is in contrast to published work showing no such remnant carbidic/carbon layer after similar treatments of Si oxynitride surfaces. The observation of the remnant carbidic C film on Co and graphitic film on Cu, but not on silicon oxynitride (SiO{sub x}N{sub y}), regardless of plasma chemistry or type, indicates that this effect is due to plasma induced secondary electron emission from the metal surface, resulting in transformation of sp{sup 3} adventitious C to either a metal carbide or graphite. These results suggest fundamental limitations to plasma-based surface cleaning procedures on metal surfaces.

Characterization of iron surface modified by 2-mercaptobenzothiazole self-assembled monolayers

Energy Technology Data Exchange (ETDEWEB)

Feng Yuanyuan [Department of Chemistry, Shandong University, Jinan 250100 (China); Chen Shenhao [Department of Chemistry, Shandong University, Jinan 250100 (China) and State Key Laboratory for Corrosion and Protection, Shenyang 110016 (China)]. E-mail: shchen@sdu.edu.cn; Zhang Honglin [Department of Chemistry, Qufu Normal University, Qufu 273165 (China); Li Ping [Department of Chemistry, Shandong University, Jinan 250100 (China); Wu Ling [Department of Chemistry, Shandong University, Jinan 250100 (China); Guo Wenjuan [Department of Chemistry, Shandong University, Jinan 250100 (China)

2006-12-30

A self-assembled monolayer of 2-mercaptobenzothiazole (MBT) adsorbed on the iron surface was prepared. The films were characterized by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared reflection spectroscopy (FT-IR) and scanning electron microscopy (SEM). Besides, the microcalorimetry method was utilized to study the self-assembled process on iron surface and the adsorption mechanism was discussed from the power-time curve. The results indicated that MBT was able to form a film spontaneously on iron surface and the presence of it could protect iron from corrosion effectively. However, the assembling time and the concentration influence the protection efficiency. Quantum chemical calculations, according to which adsorption mechanism was discussed, could explain the experimental results to some extent.

Resolving the chemical nature of nanodesigned silica surface obtained via a bottom-up approach.

Science.gov (United States)

Rahma, Hakim; Buffeteau, Thierry; Belin, Colette; Le Bourdon, Gwenaëlle; Degueil, Marie; Bennetau, Bernard; Vellutini, Luc; Heuzé, Karine

2013-08-14

The covalent grafting on silica surfaces of a functional dendritic organosilane coupling agent inserted, in a long alkyl chain monolayer, is described. In this paper, we show that depending on experimental parameters, particularly the solvent, it is possible to obtain a nanodesigned surface via a bottom-up approach. Thus, we succeed in the formation of both homogeneous dense monolayer and a heterogeneous dense monolayer, the latter being characterized by a nanosized volcano-type pattern (4-6 nm of height, 100 nm of width, and around 3 volcanos/μm(2)) randomly distributed over the surface. The dendritic attribute of the grafted silylated coupling agent affords enough anchoring sites to immobilize covalently functional gold nanoparticles (GNPs), coated with amino PEG polymer to resolve the chemical nature of the surfaces and especially the volcano type nanopattern structures of the heterogeneous monolayer. Thus, the versatile surface chemistry developed herein is particularly challenging as the nanodesign is straightforward achieved in a bottom-up approach without any specific lithography device.

Simulations of molecular self-assembled monolayers on surfaces: packing structures, formation processes and functions tuned by intermolecular and interfacial interactions.

Science.gov (United States)

Wen, Jin; Li, Wei; Chen, Shuang; Ma, Jing

2016-08-17

Surfaces modified with a functional molecular monolayer are essential for the fabrication of nano-scale electronics or machines with novel physical, chemical, and/or biological properties. Theoretical simulation based on advanced quantum chemical and classical models is at present a necessary tool in the development, design, and understanding of the interfacial nanostructure. The nanoscale surface morphology, growth processes, and functions are controlled by not only the electronic structures (molecular energy levels, dipole moments, polarizabilities, and optical properties) of building units but also the subtle balance between intermolecular and interfacial interactions. The switchable surfaces are also constructed by introducing stimuli-responsive units like azobenzene derivatives. To bridge the gap between experiments and theoretical models, opportunities and challenges for future development of modelling of ferroelectricity, entropy, and chemical reactions of surface-supported monolayers are also addressed. Theoretical simulations will allow us to obtain important and detailed information about the structure and dynamics of monolayer modified interfaces, which will guide the rational design and optimization of dynamic interfaces to meet challenges of controlling optical, electrical, and biological functions.

Better Organic Ternary Memory Performance through Self-Assembled Alkyltrichlorosilane Monolayers on Indium Tin Oxide (ITO) Surfaces.

Science.gov (United States)

Hou, Xiang; Cheng, Xue-Feng; Zhou, Jin; He, Jing-Hui; Xu, Qing-Feng; Li, Hua; Li, Na-Jun; Chen, Dong-Yun; Lu, Jian-Mei

2017-11-16

Recently, surface engineering of the indium tin oxide (ITO) electrode of sandwich-like organic electric memory devices was found to effectively improve their memory performances. However, there are few methods to modify the ITO substrates. In this paper, we have successfully prepared alkyltrichlorosilane self-assembled monolayers (SAMs) on ITO substrates, and resistive random access memory devices are fabricated on these surfaces. Compared to the unmodified ITO substrates, organic molecules (i.e., 2-((4-butylphenyl)amino)-4-((4-butylphenyl)iminio)-3-oxocyclobut-1-en-1-olate, SA-Bu) grown on these SAM-modified ITO substrates have rougher surface morphologies but a smaller mosaicity. The organic layer on the SAM-modified ITO further aged to eliminate the crystalline phase diversity. In consequence, the ternary memory yields are effectively improved to approximately 40-47 %. Our results suggest that the insertion of alkyltrichlorosilane self-assembled monolayers could be an efficient method to improve the performance of organic memory devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Linear and Star Poly(ionic liquid) Assemblies: Surface Monolayers and Multilayers.

Science.gov (United States)

Erwin, Andrew J; Xu, Weinan; He, Hongkun; Matyjaszewski, Krzysztof; Tsukruk, Vladimir V

2017-04-04

The surface morphology and organization of poly(ionic liquid)s (PILs), poly[1-(4-vinylbenzyl)-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] are explored in conjunction with their molecular architecture, adsorption conditions, and postassembly treatments. The formation of stable PIL Langmuir and Langmuir-Blodgett (LB) monolayers at the air-water and air-solid interfaces is demonstrated. The hydrophobic bis(trifluoromethylsulfonyl)imide (Tf 2 N - ) is shown to be a critical agent governing the assembly morphology, as observed in the reversible condensation of LB monolayers into dense nanodroplets. The PIL is then incorporated as an unconventional polyelectrolyte component in the layer-by-layer (LbL) films of hydrophobic character. We demonstrate that the interplay of capillary forces, macromolecular mobility, and structural relaxation of the polymer chains influence the dewetting mechanisms in the PIL multilayers, thereby enabling access to a diverse set of highly textured, porous, and interconnected network morphologies for PIL LbL films that would otherwise be absent in conventional LbL films. Their compartmentalized internal structure is relevant to molecular separation membranes, ultrathin hydrophobic coatings, targeted cargo delivery, and highly conductive films.

Monolayer collapse regulating process of adsorption-desorption of palladium nanoparticles at fatty acid monolayers at the air-water interface.

Science.gov (United States)

Goto, Thiago E; Lopez, Ricardo F; Iost, Rodrigo M; Crespilho, Frank N; Caseli, Luciano

2011-03-15

In this paper, we investigate the affinity of palladium nanoparticles, stabilized with glucose oxidase, for fatty acid monolayers at the air-water interface, exploiting the interaction between a planar system and spheroids coming from the aqueous subphase. A decrease of the monolayer collapse pressure in the second cycle of interface compression proved that the presence of the nanoparticles causes destabilization of the monolayer in a mechanism driven by the interpenetration of the enzyme into the bilayer/multilayer structure formed during collapse, which is not immediately reversible after monolayer expansion. Surface pressure and surface potential-area isotherms, as well as infrared spectroscopy [polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS)] and deposition onto solid plates as Langmuir-Blodgett (LB) films, were employed to construct a model in which the nanoparticle has a high affinity for the hydrophobic core of the structure formed after collapse, which provides a slow desorption rate from the interface after monolayer decompression. This may have important consequences on the interaction between the metallic particles and fatty acid monolayers, which implies the regulation of the multifunctional properties of the hybrid material.

Novel determination of cadmium ions using an enzyme self-assembled monolayer with surface plasmon resonance

International Nuclear Information System (INIS)

May May, Lee; Russell, David A.

2003-01-01

The activity of the enzyme urease is known to be inhibited by the heavy metal cadmium. The binding of cadmium to urease and the consequent changes of the enzyme structure are the basis of the surface plasmon resonance (SPR) biosensing system reported herein. To facilitate the formation of a self-assembled monolayer (SAM) of the urease on gold-coated glass SPR sensor disks, the enzyme has been modified with N-succinimidyl 3-(2-pyridyldithiol) propionate (SPDP). The urease monolayer was exposed to trace levels of cadmium ions and monitored by SPR. From circular dichroism (CD) data, it is believed that the conformation of the active nickel site of the urease changes upon binding of the cadmium ions. It is this change of the enzyme monolayer, measured by SPR, which has been related to the cadmium ion concentration in the range of 0-10 mg l -1 . These data are the first report of a SPR biosensor capable of detecting metal ions

Affinity of serum apolipoproteins for lipid monolayers

International Nuclear Information System (INIS)

Ibdah, J.A.

1987-01-01

The effects of lipid composition and packing as well as the structure of the protein on the affinities of apolipoproteins for lipid monolayers have been investigated. The adsorption of 14 C-reductively methylated human apolipoproteins A-I and A-II at saturating subphase concentrations to monolayers prepared with synthetic lipids or lipoprotein surface lipids spread at various initial surface pressures has been studied. The adsorption of apolipoproteins is monitored by following the surface radioactivity using a gas flow counter and Wilhelmy plate, respectively. The physical states of the lipid monolayers are evaluated by measurement of the surface pressure-molecular area isotherms using a Langmuir-Adam surface balance. The probable helical regions in various apolipoproteins have been predicted using a secondary structure analysis computer program. The mean residue hydrophobicity and mean residue hydrophobic moment for the predicted helical segments have been calculated. The surface properties of synthetic peptides which are amphipathic helix analogs have been investigated at the air-water and lipid-water interfaces

Building high-coverage monolayers of covalently bound magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Williams, Mackenzie G.; Teplyakov, Andrew V., E-mail: andrewt@udel.edu

2016-12-01

Graphical abstract: - Highlights: • A method for forming a layer of covalently bound nanoparticles is offered. • A nearly perfect monolayer of covalently bound magnetic nanoparticles was formed on gold. • Spectroscopic techniques confirmed covalent binding by the “click” reaction. • The influence of the functionalization scheme on surface coverage was investigated. - Abstract: This work presents an approach for producing a high-coverage single monolayer of magnetic nanoparticles using “click chemistry” between complementarily functionalized nanoparticles and a flat substrate. This method highlights essential aspects of the functionalization scheme for substrate surface and nanoparticles to produce exceptionally high surface coverage without sacrificing selectivity or control over the layer produced. The deposition of one single layer of magnetic particles without agglomeration, over a large area, with a nearly 100% coverage is confirmed by electron microscopy. Spectroscopic techniques, supplemented by computational predictions, are used to interrogate the chemistry of the attachment and to confirm covalent binding, rather than attachment through self-assembly or weak van der Waals bonding. Density functional theory calculations for the surface intermediate of this copper-catalyzed process provide mechanistic insight into the effects of the functionalization scheme on surface coverage. Based on this analysis, it appears that steric limitations of the intermediate structure affect nanoparticle coverage on a flat solid substrate; however, this can be overcome by designing a functionalization scheme in such a way that the copper-based intermediate is formed on the spherical nanoparticles instead. This observation can be carried over to other approaches for creating highly controlled single- or multilayered nanostructures of a wide range of materials to result in high coverage and possibly, conformal filling.

Surface chemistry: Key to control and advance myriad technologies

Science.gov (United States)

Yates, John T.; Campbell, Charles T.

2011-01-01

This special issue on surface chemistry is introduced with a brief history of the field, a summary of the importance of surface chemistry in technological applications, a brief overview of some of the most important recent developments in this field, and a look forward to some of its most exciting future directions. This collection of invited articles is intended to provide a snapshot of current developments in the field, exemplify the state of the art in fundamental research in surface chemistry, and highlight some possibilities in the future. Here, we show how those articles fit together in the bigger picture of this field. PMID:21245359

Protonation of octadecylamine Langmuir monolayer by adsorption of halide counterions

Science.gov (United States)

Sung, Woongmo; Avazbaeva, Zaure; Lee, Jonggwan; Kim, Doseok

Langmuir monolayer consisting of octadecylamine (C18H37NH2, ODA) was investigated by heterodyne vibrational sum-frequency generation (HD-VSFG) spectroscopy in conjunction with surface pressure-area (π- A) isotherm, and the result was compared with that from cationic-lipid (DPTAP) Langmuir monolayer. In case of ODA monolayer on pure water, both SF intensity of water OH band and the surface pressure were significantly smaller than those of the DPTAP monolayer implying that only small portion of the amine groups (-NH3+ is protonated in the monolayer. In the presence of sodium halides (NaCl and NaI) in the subphase water, it was found that the sign of Imχ (2) of water OH band remained the same as that of the ODA monolayer on pure water, but there was a substantial increase in the SF amplitude. From this, we propose that surface excess of the halide counterions (Cl- and I-) makes the solution condition near the ODA monolayer/water interface more acidic so that ODA molecules in the monolayer are more positively charged, which works to align the water dipoles at the interface.

Removal of dangling bonds and surface states on silicon (001) with a monolayer of selenium

International Nuclear Information System (INIS)

Tao Meng; Udeshi, Darshak; Basit, Nasir; Maldonado, Eduardo; Kirk, Wiley P.

2003-01-01

Dangling bonds and surface states are inherent to semiconductor surfaces. By passivating dangling bonds on the silicon (001) surface with a monolayer of selenium, surface states are removed from the band gap. Magnesium contacts on selenium-passivated silicon (001) behave ohmically, as expected from the work function of magnesium and the electron affinity of silicon. After rapid thermal annealing and hot-plate annealing, magnesium contacts on selenium-passivated silicon (001) show better thermal stability than on hydrogen-passivated silicon (001), which is attributed to the suppression of silicide formation by selenium passivation

From helical to planar chirality by on-surface chemistry

Czech Academy of Sciences Publication Activity Database

Stetsovych, Oleksandr; Švec, Martin; Vacek, Jaroslav; Vacek Chocholoušová, Jana; Jančařík, Andrej; Rybáček, Jiří; Kośmider, K.; Stará, Irena G.; Jelínek, Pavel; Starý, Ivo

2017-01-01

Roč. 9, č. 3 (2017), s. 213-218 ISSN 1755-4330 R&D Projects: GA ČR(CZ) GC14-16963J; GA ČR(CZ) GA14-29667S Institutional support: RVO:68378271 ; RVO:61388963 Keywords : chirality * AFM * STM * helicene * on surface chemistry * DFT Subject RIV: CF - Physical ; Theoretical Chemistry; CC - Organic Chemistry (UOCHB-X) OBOR OECD: Physical chemistry; Organic chemistry (UOCHB-X) Impact factor: 25.870, year: 2016

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

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......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...... 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...

Characterisation of the inorganic chemistry of surface waters in ...

African Journals Online (AJOL)

The main purpose of this study was to determine a simple inorganic chemistry index that can be used for all surface waters in South Africa, in order to characterise the inorganic chemistry of surface waters. Water quality data collected up until 1999 from all sample monitoring stations (2 068 monitoring stations, 364 659 ...

Monolayer alignment on azobenzene surfaces during UV light irradiation: Analysis of optical polarized absorption measurement results and theoretical treatment

International Nuclear Information System (INIS)

Zakharov, A.V.; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2006-01-01

The influence of the charge separation during the trans-cis conformational change on the surface of azobenzene 6Az10PVA monolayer on the polar liquid-crystal monolayer film, such as 4-n-pentyl-4 ' -cyanobiphenyl(5CB), is investigated. The effective anchoring energy (in the Rapini-Papolar form) is phenomenologically described in the framework of the molecular model, which takes into account the interaction between the surface polarization and surface electric field, for number of conformational states of the boundary surface. It is shown, using the experimental data for the voltage across the 6Az10PVA+5CB film, provided by the surface-potential technique, that the charge separation during the conformational changing, caused by the UV irradiation, may lead to changing of the surface alignment of liquid-crystalline molecules. The influence of the photoisomerization process on the orientational order parameter S 2 (t) using the optical polarized absorption measurement is also investigated

Microchannel-flowed-plasma modification of octadecyltrichlorosilane self-assembled-monolayers for liquid crystal alignment

International Nuclear Information System (INIS)

Zheng, W.; Chiang, C.-Y.; Underwood, I.

2013-01-01

We report that a chemical patterning technique based on local plasma modification of self-assembled monolayers has been utilized to fabricate surfaces for domain liquid crystal alignment. Highly hydrophobic octadecyltrichlorosilane monolayers deposited on glass substrates coated with Indium-Tin-Oxide were brought into contact with elastomeric stamps comprising trenches on a micro scale, and then exposed to an oxygen plasma. In the regions exposed to the plasma the monolayer was etched away leaving a patterned surface that exhibited surface energy differences between surface domains. The surfaces that bear the micropatterns have been shown to be capable of producing patterned alignment of nematic liquid crystal. - Highlights: • Chemical surface-patterning is used to fabricate liquid crystal alignment surface. • Highly hydrophobic octadecyltrichlorosilane monolayer is deposited on substrate. • O 2 plasma flow is used to etch the monolayer to form patterned surface. • The patterned surface exhibits surface energy differences between surface domains. • The surface borne the micropatterns is capable of domain liquid crystal alignment

Quantification of air plasma chemistry for surface disinfection

International Nuclear Information System (INIS)

Pavlovich, Matthew J; Clark, Douglas S; Graves, David B

2014-01-01

Atmospheric-pressure air plasmas, created by a variety of discharges, are promising sources of reactive species for the emerging field of plasma biotechnology because of their convenience and ability to operate at ambient conditions. One biological application of ambient-air plasma is microbial disinfection, and the ability of air plasmas to decontaminate both solid surfaces and liquid volumes has been thoroughly established in the literature. However, the mechanism of disinfection and which reactive species most strongly correlate with antimicrobial effects are still not well understood. We describe quantitative gas-phase measurements of plasma chemistry via infrared spectroscopy in confined volumes, focusing on air plasma generated via surface micro-discharge (SMD). Previously, it has been shown that gaseous chemistry is highly sensitive to operating conditions, and the measurements we describe here extend those findings. We quantify the gaseous concentrations of ozone (O 3 ) and nitrogen oxides (NO and NO 2 , or NO x ) throughout the established ‘regimes’ for SMD air plasma chemistry: the low-power, ozone-dominated mode; the high-power, nitrogen oxides-dominated mode; and the intermediate, unstable transition region. The results presented here are in good agreement with previously published experimental studies of aqueous chemistry and parameterized models of gaseous chemistry. The principal finding of the present study is the correlation of bacterial inactivation on dry surfaces with gaseous chemistry across these time and power regimes. Bacterial decontamination is most effective in ‘NO x mode’ and less effective in ‘ozone mode’, with the weakest antibacterial effects in the transition region. Our results underscore the dynamic nature of air plasma chemistry and the importance of careful chemical characterization of plasma devices intended for biological applications. (paper)

Quantification of air plasma chemistry for surface disinfection

Science.gov (United States)

Pavlovich, Matthew J.; Clark, Douglas S.; Graves, David B.

2014-12-01

Atmospheric-pressure air plasmas, created by a variety of discharges, are promising sources of reactive species for the emerging field of plasma biotechnology because of their convenience and ability to operate at ambient conditions. One biological application of ambient-air plasma is microbial disinfection, and the ability of air plasmas to decontaminate both solid surfaces and liquid volumes has been thoroughly established in the literature. However, the mechanism of disinfection and which reactive species most strongly correlate with antimicrobial effects are still not well understood. We describe quantitative gas-phase measurements of plasma chemistry via infrared spectroscopy in confined volumes, focusing on air plasma generated via surface micro-discharge (SMD). Previously, it has been shown that gaseous chemistry is highly sensitive to operating conditions, and the measurements we describe here extend those findings. We quantify the gaseous concentrations of ozone (O3) and nitrogen oxides (NO and NO2, or NOx) throughout the established ‘regimes’ for SMD air plasma chemistry: the low-power, ozone-dominated mode; the high-power, nitrogen oxides-dominated mode; and the intermediate, unstable transition region. The results presented here are in good agreement with previously published experimental studies of aqueous chemistry and parameterized models of gaseous chemistry. The principal finding of the present study is the correlation of bacterial inactivation on dry surfaces with gaseous chemistry across these time and power regimes. Bacterial decontamination is most effective in ‘NOx mode’ and less effective in ‘ozone mode’, with the weakest antibacterial effects in the transition region. Our results underscore the dynamic nature of air plasma chemistry and the importance of careful chemical characterization of plasma devices intended for biological applications.

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

International Nuclear Information System (INIS)

Willey, T; Willey, T

2004-01-01

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 mechanically attached

Liquid flow along a solid surface reversibly alters interfacial chemistry.

Science.gov (United States)

Lis, Dan; Backus, Ellen H G; Hunger, Johannes; Parekh, Sapun H; Bonn, Mischa

2014-06-06

In nature, aqueous solutions often move collectively along solid surfaces (for example, raindrops falling on the ground and rivers flowing through riverbeds). However, the influence of such motion on water-surface interfacial chemistry is unclear. In this work, we combine surface-specific sum frequency generation spectroscopy and microfluidics to show that at immersed calcium fluoride and fused silica surfaces, flow leads to a reversible modification of the surface charge and subsequent realignment of the interfacial water molecules. Obtaining equivalent effects under static conditions requires a substantial change in bulk solution pH (up to 2 pH units), demonstrating the coupling between flow and chemistry. These marked flow-induced variations in interfacial chemistry should substantially affect our understanding and modeling of chemical processes at immersed surfaces. Copyright © 2014, American Association for the Advancement of Science.

Covalent Surface Modification of Silicon Oxides with Alcohols in Polar Aprotic Solvents.

Science.gov (United States)

Lee, Austin W H; Gates, Byron D

2017-09-05

Alcohol-based monolayers were successfully formed on the surfaces of silicon oxides through reactions performed in polar aprotic solvents. Monolayers prepared from alcohol-based reagents have been previously introduced as an alternative approach to covalently modify the surfaces of silicon oxides. These reagents are readily available, widely distributed, and are minimally susceptible to side reactions with ambient moisture. A limitation of using alcohol-based compounds is that previous reactions required relatively high temperatures in neat solutions, which can degrade some alcohol compounds or could lead to other unwanted side reactions during the formation of the monolayers. To overcome these challenges, we investigate the condensation reaction of alcohols on silicon oxides carried out in polar aprotic solvents. In particular, propylene carbonate has been identified as a polar aprotic solvent that is relatively nontoxic, readily accessible, and can facilitate the formation of alcohol-based monolayers. We have successfully demonstrated this approach for tuning the surface chemistry of silicon oxide surfaces with a variety of alcohol containing compounds. The strategy introduced in this research can be utilized to create silicon oxide surfaces with hydrophobic, oleophobic, or charged functionalities.

Structural properties of oligonucleotide monolayers on gold surfaces probed by fluorescence investigations.

Science.gov (United States)

Rant, Ulrich; Arinaga, Kenji; Fujita, Shozo; Yokoyama, Naoki; Abstreiter, Gerhard; Tornow, Marc

2004-11-09

We present optical investigations on the conformation of oligonucleotide layers on Au surfaces. Our studies concentrate on the effect of varying surface coverage densities on the structural properties of layers of 12- and 24mer single-stranded DNA, tethered to the Au surface at one end while being labeled with a fluorescent marker at the opposing end. The distance-dependent energy transfer from the marker dye to the metal surface, which causes quenching of the observed fluorescence, is used to provide information on the orientation of the DNA strands relative to the surface. Variations in the oligonucleotide coverage density, as determined from electrochemical quantification, over 2 orders of magnitude are achieved by employing different preparation conditions. The observed enhancement in fluorescence intensity with increasing DNA coverage can be related to a model involving mutual steric interactions of oligonucleotides on the surface, as well as fluorescence quenching theory. Finally, the applicability of the presented concepts for investigations of heterogeneous monolayers is demonstrated by means of studying the coadsorption of mercaptohexanol onto DNA-modified Au surfaces.

Smart Surface Chemistries of Conducting Polymers

DEFF Research Database (Denmark)

Lind, Johan Ulrik

In this thesis we investigate post-polymerization covalent modifications of poly(3,4-dioxythiophene (PEDOT)-type conducting polymers. The aim of the modifications is to gain specific control of the interaction between the material and living mammalian cells. The use of “click-chemistry” to modify...... a straightforward and in-expensive method for patterning conducting polymer thin films into microelectrodes, without losing control of the surface chemistry of the samples. On the contrary, the method provides direct control of the surface chemistry of both the fabricated micro-electrodes and the gaps between them....... The method is based on locally removing PEDOTtype polymers to expose underlying non-conducting functional polymer substrates. Thereby, multifunctional substrates are obtained. By applying this method, we are able to fabricate allpolymer micro-systems with multiple types of localized functional (bio...

Heterogeneous catalytic materials solid state chemistry, surface chemistry and catalytic behaviour

CERN Document Server

Busca, Guido

2014-01-01

Heterogeneous Catalytic Materials discusses experimental methods and the latest developments in three areas of research: heterogeneous catalysis; surface chemistry; and the chemistry of catalysts. Catalytic materials are those solids that allow the chemical reaction to occur efficiently and cost-effectively. This book provides you with all necessary information to synthesize, characterize, and relate the properties of a catalyst to its behavior, enabling you to select the appropriate catalyst for the process and reactor system. Oxides (used both as catalysts and as supports for cata

Photopatterning of self assembled monolayers on oxide surfaces for the selective attachment of biomolecules.

Science.gov (United States)

Hazarika, Pompi; Behrendt, Jonathan M; Petersson, Linn; Wingren, Christer; Turner, Michael L

2014-03-15

The immobilization of functional biomolecules to surfaces is a critical process for the development of biosensors for disease diagnostics. In this work we report the patterned attachment of single chain fragment variable (scFv) antibodies to the surface of metal oxides by the photodeprotection of self-assembled monolayers, using near-UV light. The photodeprotection step alters the functionality at the surface; revealing amino groups that are utilized to bind biomolecules in the exposed regions of the substrate only. The patterned antibodies are used for the detection of specific disease biomarker proteins in buffer and in complex samples such as human serum. © 2013 Elsevier B.V. All rights reserved.

Permethylated 12-Vertex p-Carborane Self-Assembled Monolayers

Czech Academy of Sciences Publication Activity Database

Scholz, F.; Nothofer, H. G.; Wessels, J. M.; Nelles, G.; Wrochem von, F.; Roy, S.; Chen, X.; Michl, Josef

2011-01-01

Roč. 115, č. 46 (2011), s. 22998-23007 ISSN 1932-7447 Grant - others:National Science Foundation(US) CHE-0848477 Institutional research plan: CEZ:AV0Z40550506 Keywords : p-carbone * monolayer * scanning tunneling microscopy * ultraviolet photoelectron spectroscopy * X-ray photoelectron Subject RIV: CC - Organic Chemistry Impact factor: 4.805, year: 2011

Effect of lipid composition and packing on the adsorption of apolipoproteins to lipid monolayers

International Nuclear Information System (INIS)

Ibdah, J.A.; Lund-Katz, S.; Phillips, M.C.

1987-01-01

The monolayer system has been used to study the effects of lipoprotein surface lipid composition and packing on the affinities of apolipoproteins for the surfaces of lipoprotein particles. The adsorption of apolipoproteins injected beneath lipid monolayers prepared with pure lipids or lipoprotein surface lipids is evaluated by monitoring the surface pressure of the film and the surface concentration (Gamma) of 14 C-labelled apolipoprotein. At a given initial film pressure (π/sub i/) there is a higher adsorption of human apo A-I to unsaturated phosphatidylcholine (PC) monolayers compared to saturated PC monolayers (e.g., at π/sub i/ = 10 mN/m, Gamma = 0.35 and 0.06 mg/m 2 for egg PC and distearoyl PC, respectively, with 3 x 10 -4 mg/ml apo A-I in the subphase). In addition, adsorption of apo A-I is less to an egg sphingomyelin monolayer than to an egg PC monolayer. The adsorption of apo A-I to PC monolayers is decreased by addition of cholesterol. Generally, apo A-I adsorption diminishes as the lipid molecular area decreases. Apo A-I adsorbs more to monolayers prepared with HDL 3 surface lipids than with LDL surface lipids. These studies suggest that lipoprotein surface lipid composition and packing are crucial factors influencing the transfer and exchange of apolipoproteins among various lipoprotein classes during metabolism of lipoprotein particles

Models of gas-grain chemistry in interstellar cloud cores with a stochastic approach to surface chemistry

Science.gov (United States)

Stantcheva, T.; Herbst, E.

2004-08-01

We present a gas-grain model of homogeneous cold cloud cores with time-independent physical conditions. In the model, the gas-phase chemistry is treated via rate equations while the diffusive granular chemistry is treated stochastically. The two phases are coupled through accretion and evaporation. A small network of surface reactions accounts for the surface production of the stable molecules water, formaldehyde, methanol, carbon dioxide, ammonia, and methane. The calculations are run for a time of 107 years at three different temperatures: 10 K, 15 K, and 20 K. The results are compared with those produced in a totally deterministic gas-grain model that utilizes the rate equation method for both the gas-phase and surface chemistry. The results of the different models are in agreement for the abundances of the gaseous species except for later times when the surface chemistry begins to affect the gas. The agreement for the surface species, however, is somewhat mixed. The average abundances of highly reactive surface species can be orders of magnitude larger in the stochastic-deterministic model than in the purely deterministic one. For non-reactive species, the results of the models can disagree strongly at early times, but agree to well within an order of magnitude at later times for most molecules. Strong exceptions occur for CO and H2CO at 10 K, and for CO2 at 20 K. The agreement seems to be best at a temperature of 15 K. As opposed to the use of the normal rate equation method of surface chemistry, the modified rate method is in significantly better agreement with the stochastic-deterministic approach. Comparison with observations of molecular ices in dense clouds shows mixed agreement.

Nonlinear optical studies of organic monolayers

International Nuclear Information System (INIS)

Shen, Y.R.

1988-02-01

Second-order nonlinear optical effects are forbidden in a medium with inversion symmetry, but are necessarily allowed at a surface where the inversion summary is broken. They are often sufficiently strong so that a submonolayer perturbation of the surface can be readily detected. They can therefore be used as effective tools to study monolayers adsorbed at various interfaces. We discuss here a number of recent experiments in which optical second harmonic generation (SHG) and sum-frequency generation (SFG) are employed to probe and characterize organic monolayers. 15 refs., 5 figs

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

International Nuclear Information System (INIS)

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

2017-01-01

Highlights: • Thiophene curcuminoid molecules deposited on a gold surface by immersion. • Molecular dynamic studies of the molecular arrangement approaching the surface. • XPS and STM studies showing different arrangement of the molecules on the surface. • Molecular Interaction with surface depends on the sulfur position in thiophene rings. • Temporal evolution of the molecular arrangement on the surface. - Abstract: 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.

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

Energy Technology Data Exchange (ETDEWEB)

Berlanga, Isadora [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2008, Santiago (Chile); Etcheverry-Berríos, Álvaro; Mella, Andy; Jullian, Domingo [Departamento de Ciencia de los Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Beaucheff 851, Santiago (Chile); Gómez, Victoria Alejandra [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2008, Santiago (Chile); Aliaga-Alcalde, Núria [ICREA (Institució Catalana de Recerca i Estudis Avançats), Passeig Lluís Companys, 23, 08018, Barcelona (Spain); CSIC-ICMAB (Institut de Ciència dels Materials de Barcelona), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra (Spain); Fuenzalida, Victor [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2008, Santiago (Chile); Flores, Marcos, E-mail: mflorescarra@ing.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2008, Santiago (Chile); and others

2017-01-15

Highlights: • Thiophene curcuminoid molecules deposited on a gold surface by immersion. • Molecular dynamic studies of the molecular arrangement approaching the surface. • XPS and STM studies showing different arrangement of the molecules on the surface. • Molecular Interaction with surface depends on the sulfur position in thiophene rings. • Temporal evolution of the molecular arrangement on the surface. - Abstract: 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.

Introduction to Applied Colloid and Surface Chemistry

DEFF Research Database (Denmark)

Kontogeorgis, Georgios; Kiil, Søren

Colloid and Surface Chemistry is a subject of immense importance and implications both to our everyday life and numerous industrial sectors, ranging from coatings and materials to medicine and biotechnology. How do detergents really clean? (Why can’t we just use water ?) Why is milk “milky” Why do......, to the benefit of both the environment and our pocket. Cosmetics is also big business! Creams, lotions and other personal care products are really just complex emulsions. All of the above can be explained by the principles and methods of colloid and surface chemistry. A course on this topic is truly valuable...... to chemists, chemical engineers, biologists, material and food scientists and many more....

Self assembled monolayers of octadecyltrichlorosilane for dielectric materials

Energy Technology Data Exchange (ETDEWEB)

Kumar, Vijay, E-mail: cirivijaypilani@gmail.com [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Puri, Paridhi; Nain, Shivani [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Bhat, K. N. [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Sharma, N. N. [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); School of Automobile, Mechanical & Mechatronics, Manipal University-Jaipur (India)

2016-04-13

Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Selective modification of inorganic materials such as Si, SiO{sub 2} and Si{sub 3}N{sub 4} is of great interest in research and technology. We evaluated the chemical formation of OTS self-assembled monolayers on silicon substrates with different dielectric materials. Our investigations were focused on surface modification of formerly used common dielectric materials SiO{sub 2}, Si{sub 3}N{sub 4} and a-poly. The improvement of wetting behaviour and quality of monolayer films were characterized using Atomic force microscope, Scanning electron microscope, Contact angle goniometer, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) monolayer deposited oxide surface.

Evaluation of monolayers and mixed monolayers formed from mercaptobenzothiazole and decanethiol as sensing platforms

International Nuclear Information System (INIS)

Mary Vergheese, T.; Berchmans, Sheela

2004-01-01

In this investigation, the characterisation of monolayer and mixed monolayers formed from mercaptobenzothiazole (MBT) and decanethiol (DT) has been carried out with cyclic voltammetry. The SAMs have been tested for their stability and electron transfer blocking properties. The redox probes used in the present study are [Fe(China) 6 ] 4- , [Ru(NH 3 ) 6 ] 2+ and Cu underpotential deposition (upd). The electron transfer kinetics is investigated in acid and neutral pH range. Electron transfer kinetics is altered by the nature of charge on the redox probe and the charge on the monolayer. Electron transfer kinetics of negatively charged redox probes like ferrocyanide ions is blocked when the surface pK a medium and at pK a >pH medium reversible features is observed for negatively charged probes. An exactly reverse effect is observed in the case of positively charged redox species like [Ru(NH 3 ) 6 ] 2+/3+ . Cu under potential deposition studies reflects the structural integrity and compactness of the SAM layer. The utility of these monolayers and mixed monolayer for selective sensing of dopamine is discussed based on their ability to discriminate between positively and negatively charged redox species at different pH

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.

Chiral hierarchical self-assembly in Langmuir monolayers of diacetylenic lipids

KAUST Repository

Basnet, Prem B.

2013-01-01

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

Anisotropic surface chemistry properties and adsorption behavior of silicate mineral crystals.

Science.gov (United States)

Xu, Longhua; Tian, Jia; Wu, Houqin; Fang, Shuai; Lu, Zhongyuan; Ma, Caifeng; Sun, Wei; Hu, Yuehua

2018-03-07

Anisotropic surface properties of minerals play an important role in a variety of fields. With a focus on the two most intensively investigated silicate minerals (i.e., phyllosilicate minerals and pegmatite aluminosilicate minerals), this review highlights the research on their anisotropic surface properties based on their crystal structures. Four surface features comprise the anisotropic surface chemistry of minerals: broken bonds, energy, wettability, and charge. Analysis of surface broken bond and energy anisotropy helps to explain the cleavage and growth properties of mineral crystals, and understanding surface wettability and charge anisotropy is critical to the analysis of minerals' solution behavior, such as their flotation performance and rheological properties. In a specific reaction, the anisotropic surface properties of minerals are reflected in the adsorption strengths of reagents on different mineral surfaces. Combined with the knowledge of mineral crushing and grinding, a thorough understanding of the anisotropic surface chemistry properties and the anisotropic adsorption behavior of minerals will lead to the development of effective relational models comprising their crystal structure, surface chemistry properties, and targeted reagent adsorption. Overall, such a comprehensive approach is expected to firmly establish the connection between selective cleavage of mineral crystals for desired surfaces and designing novel reagents selectively adsorbed on the mineral surfaces. As tools to characterize the anisotropic surface chemistry properties of minerals, DLVO theory, atomic force microscopy (AFM), and molecular dynamics (MD) simulations are also reviewed. Copyright © 2017 Elsevier B.V. All rights reserved.

Ionic-Liquid-Infused Nanostructures as Repellent Surfaces.

Science.gov (United States)

Galvan, Yaraset; Phillips, Katherine R; Haumann, Marco; Wasserscheid, Peter; Zarraga, Ramon; Vogel, Nicolas

2018-02-02

In order to prepare lubricant-infused repellent coatings on silica nanostructures using low vapor pressure ionic liquids as lubricants, we study the wetting behavior of a set of imidazolium-based ionic liquids with different alkyl side chains as a function of the applied surface functionalities. We take advantage of the structural color of inverse opals prepared from a colloidal coassembly technique to study the infiltration of ionic liquids into these nanoporous structures. We find that the more hydrophobic ionic liquids with butyl and hexyl side chains can completely infiltrate inverse opals functionalized with mixed self-assembled monolayers composed of imidazole groups and aliphatic hydrocarbon chains, which we introduce via silane chemistry. These molecular species reflect the chemical nature of the ionic liquid, thereby increasing the affinity between the liquid and solid surface. The mixed surface chemistry provides sufficiently small contact angles with the ionic liquid to infiltrate the nanopores while maximizing the contact angle with water. As a result, the mixed monolayers enable the design of a stable ionic liquid/solid interface that is able to repel water as a test liquid. Our results underline the importance of matching chemical affinities to predict and control the wetting behavior in complex, multiphase systems.

Morphology and magnetism of Fe monolayers and small Fen clusters (n 2-19) supported on the Ni(111) surface

International Nuclear Information System (INIS)

Longo, R C; MartInez, E; Dieguez, O; Vega, A; Gallego, L J

2007-01-01

Using the modified embedded atom model in conjunction with a self-consistent tight-binding method, we investigated the lowest-energy structures of Fe monolayers and isolated Fe n clusters (n = 2-19) supported on the Ni(111) surface. In keeping with experimental findings, our calculations predict that the atoms of the monolayer occupy face-centred cubic (fcc) rather than hexagonal close-packed (hcp) sites. Likewise in agreement with experiment we found that Fe layers stack with a pseudomorphic fcc structure up to two monolayers, beyond which they stack as bcc(110). The structures of supported Fe clusters are predicted to be two-dimensional islands maximizing the number of nearest-neighbour bonds among the adsorbed Fe atoms, and their average magnetic moments per atom decrease towards that of the supported Fe monolayer almost monotonically as n increases. Finally, a pair of Fe 3 clusters on Ni(111) were found to exhibit virtually no interaction with each other even when separated by only one atomic row, i.e. so long as they do not coalesce they retain their individual magnetic properties

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.

Interactions of phospholipid monolayer with single-walled carbon nanotube wrapped by lysophospholipid

Energy Technology Data Exchange (ETDEWEB)

Lim, Siwool; Kim, Hyungsu, E-mail: hkim@dku.edu

2012-10-01

In this study, we prepared single-walled carbon nanotubes (SWNTs) wrapped by 1-stearoyl-2-hydroxy-sn-glycero-3-phospho-(1 Prime -rac-glycerol) (LPG), leading to a complex of SWNT-LPG. In an attempt to investigate the interactions of SWNT-LPG with a mimicked cell surface, SWNT-LPG solution was injected into the sub-phase of Langmuir trough to form a mixed monolayer with dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG), respectively. In addition to the measurement of typical surface pressure-area isotherms under compression mode, area changes occurring during insertion of SWNT-LPG into the monolayer were recorded at various surface pressures. Changes in surface potential were also measured for evident tracing of the degree of interactions between sub-phase and monolayer. A systematic comparison of relaxation patterns and insertion behavior along with surface potential data provided a rational basis to distinguish the degree of interactions between SWNT-LPG and the designated monolayer. The observed tendencies were found to be in accordance with the surface topography as revealed by the tapping mode atomic force microscopy. It was consistently observed that SWNT-LPG interacted with DPPC to a greater extent than with DPPG, when the sufficient coverage of nanotube surface by LPG molecules was assured. - Highlights: Black-Right-Pointing-Pointer Complex of single-walled carbon nanotubes and lysophospholipid (SWNT-LPG) is formed. Black-Right-Pointing-Pointer Composite monolayer is formed by inserting SWNT-LPG into the phospholipid monolayer. Black-Right-Pointing-Pointer We measure area-pressure responses and dipole potentials during the insertion process. Black-Right-Pointing-Pointer Properties of composite monolayer depend on the kind of phospholipid and LPG content.

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

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...

Bactericidal effects of plasma-modified surface chemistry of silicon nanograss

International Nuclear Information System (INIS)

Ostrikov, Kola; Macgregor-Ramiasa, Melanie; Cavallaro, Alex; Ostrikov, Kostya; Vasilev, Krasimir

2016-01-01

The surface chemistry and topography of biomaterials regulate the adhesion and growth of microorganisms in ways that are still poorly understood. Silicon nanograss structures prepared via inductively coupled plasma etching were coated with plasma deposited nanometer-thin polymeric films to produce substrates with controlled topography and defined surface chemistry. The influence of surface properties on Staphylococcus aureus proliferation is demonstrated and explained in terms of nanograss substrate wetting behaviour. With the combination of the nanograss topography; hydrophilic plasma polymer coatings enhanced antimicrobial activity while hydrophobic coatings reduced it. This study advances the understanding of the effects of surface wettability on the bactericidal properties of reactive nano-engineered surfaces. (paper)

Surface-Enhanced Raman Spectroscopy as a Probe of the Surface Chemistry of Nanostructured Materials.

Science.gov (United States)

Dick, Susan; Konrad, Magdalena P; Lee, Wendy W Y; McCabe, Hannah; McCracken, John N; Rahman, Taifur M D; Stewart, Alan; Xu, Yikai; Bell, Steven E J

2016-07-01

Surface-enhanced Raman spectroscopy (SERS) is now widely used as a rapid and inexpensive tool for chemical/biochemical analysis. The method can give enormous increases in the intensities of the Raman signals of low-concentration molecular targets if they are adsorbed on suitable enhancing substrates, which are typically composed of nanostructured Ag or Au. However, the features of SERS that allow it to be used as a chemical sensor also mean that it can be used as a powerful probe of the surface chemistry of any nanostructured material that can provide SERS enhancement. This is important because it is the surface chemistry that controls how these materials interact with their local environment and, in real applications, this interaction can be more important than more commonly measured properties such as morphology or plasmonic absorption. Here, the opportunity that this approach to SERS provides is illustrated with examples where the surface chemistry is both characterized and controlled in order to create functional nanomaterials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of perfluoroalkyl acids by carbonaceous adsorbents: Effect of carbon surface chemistry

International Nuclear Information System (INIS)

Zhi, Yue; Liu, Jinxia

2015-01-01

Adsorption by carbonaceous sorbents is among the most feasible processes to remove perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) from drinking and ground waters. However, carbon surface chemistry, which has long been recognized essential for dictating performance of such sorbents, has never been considered for PFOS and PFOA adsorption. Thus, the role of surface chemistry was systematically investigated using sorbents with a wide range in precursor material, pore structure, and surface chemistry. Sorbent surface chemistry overwhelmed physical properties in controlling the extent of uptake. The adsorption affinity was positively correlated carbon surface basicity, suggesting that high acid neutralizing or anion exchange capacity was critical for substantial uptake of PFOS and PFOA. Carbon polarity or hydrophobicity had insignificant impact on the extent of adsorption. Synthetic polymer-based Ambersorb and activated carbon fibers were more effective than activated carbon made of natural materials in removing PFOS and PFOA from aqueous solutions. - Highlights: • Adsorption of PFOS and PFOA by ten carbonaceous adsorbents were compared. • Surface chemistry of the adsorbents controlled adsorption affinity. • Carbon surface basicity was positively correlated with the extent of PFOS and PFOA uptake. • Carbon polarity or hydrophobicity was not correlated with adsorption affinity. • Synthetic polymer-based adsorbents were more effective in removing PFOS and PFOA. - Carbon surface basicity is the primary factor that influences adsorption affinity of the carbonaceous sorbents for perfluorooctane sulfonic and carboxylic acids

Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides

NARCIS (Netherlands)

Weckhuysen, B.M.; Wachs, I.E.; Schoonheydt, R.A.

1996-01-01

Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction

Energy Technology Data Exchange (ETDEWEB)

Terry, J.; Linford, M.R.; Wigren, C.; Cao, R.; Pianetta, P.; Chidsey, C.E. [Stanford University, Stanford, California 94309 (United States)

1997-08-01

The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H{endash}Si bond on the H{endash}Si(111) surface, and (ii) replacement of Cl on the Cl{endash}Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C 1s signal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C{endash}Si bond length of 1.85{plus_minus}0.05{Angstrom}. Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. {copyright} {ital 1997 American Institute of Physics.}

Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction

International Nuclear Information System (INIS)

Terry, J.; Linford, M.R.; Wigren, C.; Cao, R.; Pianetta, P.; Chidsey, C.E.

1997-01-01

The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H endash Si bond on the H endash Si(111) surface, and (ii) replacement of Cl on the Cl endash Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C 1s signal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C endash Si bond length of 1.85±0.05 Angstrom. Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. copyright 1997 American Institute of Physics

Evaluation of monolayers and mixed monolayers formed from mercaptobenzothiazole and decanethiol as sensing platforms

Energy Technology Data Exchange (ETDEWEB)

Mary Vergheese, T.; Berchmans, Sheela

2004-02-15

In this investigation, the characterisation of monolayer and mixed monolayers formed from mercaptobenzothiazole (MBT) and decanethiol (DT) has been carried out with cyclic voltammetry. The SAMs have been tested for their stability and electron transfer blocking properties. The redox probes used in the present study are [Fe(China){sub 6}]{sup 4-}, [Ru(NH{sub 3}){sub 6}]{sup 2+} and Cu underpotential deposition (upd). The electron transfer kinetics is investigated in acid and neutral pH range. Electron transfer kinetics is altered by the nature of charge on the redox probe and the charge on the monolayer. Electron transfer kinetics of negatively charged redox probes like ferrocyanide ions is blocked when the surface pK{sub a}pH{sub medium} reversible features is observed for negatively charged probes. An exactly reverse effect is observed in the case of positively charged redox species like [Ru(NH{sub 3}){sub 6}]{sup 2+/3+}. Cu under potential deposition studies reflects the structural integrity and compactness of the SAM layer. The utility of these monolayers and mixed monolayer for selective sensing of dopamine is discussed based on their ability to discriminate between positively and negatively charged redox species at different pH.

Nonequilibrium 2-hydroxyoctadecanoic acid monolayers: effect of electrolytes.

Science.gov (United States)

Lendrum, Conrad D; Ingham, Bridget; Lin, Binhua; Meron, Mati; Toney, Michael F; McGrath, Kathryn M

2011-04-19

2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position α to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of ∼6. The role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase. © 2011 American Chemical Society

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

International Nuclear Information System (INIS)

Scoles, Giacinto

2006-01-01

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

Magmatic and fragmentation controls on volcanic ash surface chemistry

Science.gov (United States)

Ayris, Paul M.; Diplas, Spyros; Damby, David E.; Hornby, Adrian J.; Cimarelli, Corrado; Delmelle, Pierre; Scheu, Bettina; Dingwell, Donald B.

2016-04-01

The chemical effects of silicate ash ejected by explosive volcanic eruptions on environmental systems are fundamentally mediated by ash particle surfaces. Ash surfaces are a composite product of magmatic properties and fragmentation mechanisms, as well as in-plume and atmospheric alteration processes acting upon those surfaces during and after the eruption. Recent attention has focused on the capacity of alteration processes to shape ash surfaces; most notably, several studies have utilised X-ray photoelectron spectroscopy (XPS), a technique probing the elemental composition and coordination state of atoms within the top 10 nm of ash surfaces, to identify patterns of elemental depletions and enrichments relative to bulk ash chemical composition. Under the presumption of surface and bulk equivalence, any disparities have been previously attributed to surface alteration processes, but the ubiquity of some depletions (e.g., Ca, Fe) across multiple ash studies, irrespective of eruptive origin, could suggest these to be features of the surface produced at the instant of magma fragmentation. To investigate this possibility further, we conducted rapid decompression experiments at different pressure conditions and at ambient and magmatic temperature on porous andesitic rocks. These experiments produced fragmented ash material untouched by secondary alteration, which were compared to particles produced by crushing of large clasts from the same experiments. We investigated a restricted size fraction (63-90 μm) from both fragmented and crushed materials, determining bulk chemistry and mineralogy via XRF, SEM-BSE and EPMA, and investigated the chemical composition of the ash surface by XPS. Analyses suggest that fragmentation under experimental conditions partitioned a greater fraction of plagioclase-rich particles into the selected size fraction, relative to particles produced by crushing. Trends in surface chemical composition in fragmented and crushed particles mirror that

The titration of carboxyl-terminated monolayers revisited: in situ calibrated fourier transform infrared study of well-defined monolayers on silicon.

Science.gov (United States)

Aureau, D; Ozanam, F; Allongue, P; Chazalviel, J-N

2008-09-02

The acid-base equilibrium at the surface of well-defined mixed carboxyl-terminated/methyl-terminated monolayers grafted on silicon (111) has been investigated using in situ calibrated infrared spectroscopy (attenuated total reflectance (ATR)) in the range of 900-4000 cm (-1). Spectra of surfaces in contact with electrolytes of various pH provide a direct observation of the COOH COO (-) conversion process. Quantitative analysis of the spectra shows that ionization of the carboxyl groups starts around pH 6 and extends over more than 6 pH units: approximately 85% ionization is measured at pH 11 (at higher pH, the layers become damaged). Observations are consistently accounted for by a single acid-base equilibrium and discussed in terms of change in ion solvation at the surface and electrostatic interactions between surface charges. The latter effect, which appears to be the main limitation, is qualitatively accounted for by a simple model taking into account the change in the Helmholtz potential associated with the surface charge. Furthermore, comparison of calculated curves with experimental titration curves of mixed monolayers suggests that acid and alkyl chains are segregated in the monolayer.

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

International Nuclear Information System (INIS)

Gokcen, Dincer; Bae, Sang-Eun; Brankovic, Stanko R.

2011-01-01

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.

X-Ray Reflectometry of DMPS Monolayers on a Water Substrate

Science.gov (United States)

Tikhonov, A. M.; Asadchikov, V. E.; Volkov, Yu. O.; Roshchin, B. S.; Ermakov, Yu. A.

2017-12-01

The molecular structure of dimyristoyl phosphatidylserine (DMPS) monolayers on a water substrate in different phase states has been investigated by X-ray reflectometry with a photon energy of 8 keV. According to the experimental data, the transition from a two-dimensional expanded liquid state to a solid gel state (liquid crystal) accompanied by the ordering of the hydrocarbon tails C14H27 of the DMPS molecule occurs in the monolayer as the surface pressure rises. The monolayer thickness is 20 ± 3 and 28 ± 2 Å in the liquid and solid phases, respectively, with the deflection angle of the molecular tail axis from the normal to the surface in the gel phase being 26° ± 8°. At least a twofold decrease in the degree of hydration of the polar lipid groups also occurs under two-dimensional monolayer compression. The reflectometry data have been analyzed using two approaches: under the assumption about the presence of two layers with different electron densities in the monolayer and without any assumptions about the transverse surface structure. Both approaches demonstrate satisfactory agreement between themselves in describing the experimental results.

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

International Nuclear Information System (INIS)

Dutta, P.; Ketterson, J.B.

1990-01-01

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

Electrical conductivity of conductive carbon blacks: influence of surface chemistry and topology

International Nuclear Information System (INIS)

Pantea, Dana; Darmstadt, Hans; Kaliaguine, Serge; Roy, Christian

2003-01-01

Conductive carbon blacks from different manufacturers were studied in order to obtain some insight into the relation between their electrical conductivity and their surface properties. The surface chemistry was studied by X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectroscopy (SIMS), whereas the topology of the carbon black surface was investigated using low-pressure nitrogen adsorption. All these techniques yield information on the graphitic character of the surface. In general, the electrical conductivity of the conductive blacks increases with the graphitic character of the surface. For low surface area conductive blacks, the electrical conductivity correlates well with the surface chemistry. In the case of the XPS and SIMS data, this correlation is also valid when other types of carbon blacks such as thermal and furnace blacks are included, confirming the determining influence of the carbon black surface chemistry on the electrical conductivity

New insights into the effects of biomaterial chemistry and topography on the morphology of kidney epithelial cells.

Science.gov (United States)

Hulshof, Frits; Schophuizen, Carolien; Mihajlovic, Milos; van Blitterswijk, Clemens; Masereeuw, Rosalinde; de Boer, Jan; Stamatialis, Dimitrios

2018-02-01

Increasing incidence of renal pathology in the western world calls for innovative research for the development of cell-based therapies such as a bioartificial kidney (BAK) device. To fulfil the multitude of kidney functions, the core component of the BAK is a living membrane consisting of a tight kidney cell monolayer with preserved functional organic ion transporters cultured on a polymeric membrane surface. This membrane, on one side, is in contact with blood and therefore should have excellent blood compatibility, whereas the other side should facilitate functional monolayer formation. This work investigated the effect of membrane chemistry and surface topography on kidney epithelial cells to improve the formation of a functional monolayer. To achieve this, microtopographies were fabricated with high resolution and reproducibility on polystyrene films and on polyethersulfone-polyvinyl pyrrolidone (PES-PVP) porous membranes. A conditionally immortalized proximal tubule epithelial cell line (ciPTEC) was cultured on both, and subsequently, the cell morphology and monolayer formation were assessed. Our results showed that L-dopamine coating of the PES-PVP was sufficient to support ciPTEC monolayer formation. The polystyrene topographies with large features were able to align the cells in various patterns without significantly disruption of monolayer formation; however, the PES-PVP topographies with large features disrupted the monolayer. In contrast, the PES-PVP membranes with small features and with large spacing supported well the ciPTEC monolayer formation. In addition, the topographical PES-PVP membranes were compatible as a substrate membrane to measure organic cation transporter activity in Transwell® systems. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Conformation, orientation and interaction in molecular monolayers

International Nuclear Information System (INIS)

Superfine, R.; Huang, J.Y.; Shen, Y.R.

1989-01-01

Knowledge of the conformation and ordering of molecular monolayers is essential for a detailed understanding of a wide variety of surface and interfacial phenomena. Over the past several years, surface second harmonic generation (SHG) has proven to be a valuable and versatile probe of monolayer systems. Our group has recently extended the technique to infrared-visible sum frequency generation (SFG) which has unique capabilities for surface vibrational spectroscopy. Like second harmonic generation, SFG is highly surface specific with submonolayer sensitivity at all interfaces accessible by light. The orientation of individual groups within an adsorbate molecule can be deduced by a polarization analysis of the SFG signal from the vibrational modes of the groups. The authors have used SHG and SFG to study orientations and conformations of surfactant and liquid crystal (LC) monolayers and their interaction on a substrate. The interfacial properties of LC are of great interest to many researchers for both basic science understanding and practical application to LC devices. It is well known that the bulk alignment of a liquid crystal in a cell is strongly affected by the surface treatment of the cell walls. The reason behind it is not yet clear. The theoretical background and experimental arrangement of SHG and SFG have been described elsewhere. In the setup, a 30 psec. Nd:YAG mode-locked laser system together with nonlinear accessories generates a visible beam at .532μm and an infrared beam tunable about 3.4μm. Both beams are focused to a common spot of 300μm dia. The typical signal off the surface from a compact ordered alkyl chain monolayer is ∼500 photons per pulse, easily detected with a photomultiplier tube

The surface pressure dynamics and appearance of mixed monolayers of cholesterol and different sized polystyrenes at an air-water interface.

Science.gov (United States)

Mudgil, Poonam; Dennis, Gary R; Millar, Thomas J

2005-02-15

Synthetic polymers are increasingly being used in situations where they are designed to interact with biological systems. As a result, it is important to investigate the interactions of the polymers with biochemicals. We have used cholesterol, as an example of an important biological surfactant component, to study its interactions with polystyrene. Mixed monolayers of cholesterol and one of two different molecular weight polystyrenes were formed at an air-water interface to investigate their interactions and to determine whether the size of the polystyrene affected the interaction. The pressure-area (pi-A) isocycles of mixed monolayers of cholesterol and polystyrene MW 2700 or polystyrene MW32700 showed that strongest attractive interactions occur at high surface pressures and in polystyrene rich films. The excess area and excess free energy of mixing were most negative at high surface pressures and at high mole fraction of polystyrene. The most stable mixed monolayers were formed with X(PS2700) = 0.9 and X(PS32700) = 0.09. Microscopic observation of the mixed monolayers of cholesterol and polystyrene showed the formation of stable islands in the cholesterol/polystyrene mixtures. These observations, the nature of the inflection points in the isocycles, and the anomalous changes in free energy lead us to conclude that there is a stable rearrangement of polystyrene into compact islands when it is mixed with cholesterol. Any excess cholesterol is excluded from these islands and remains as a separate film surrounding the islands.

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. Copyright © 2015 Elsevier Inc. All rights reserved.

Radical Initiated Hydrosilylation on Silicon Nanocrystal Surfaces: An Evaluation of Functional Group Tolerance and Mechanistic Study.

Science.gov (United States)

Yang, Zhenyu; Gonzalez, Christina M; Purkait, Tapas K; Iqbal, Muhammad; Meldrum, Al; Veinot, Jonathan G C

2015-09-29

Hydrosilylation is among the most common methods used for modifying silicon surface chemistry. It provides a wide range of surface functionalities and effective passivation of surface sites. Herein, we report a systematic study of radical initiated hydrosilylation of silicon nanocrystal (SiNC) surfaces using two common radical initiators (i.e., 2,2'-azobis(2-methylpropionitrile) and benzoyl peroxide). Compared to other widely applied hydrosilylation methods (e.g., thermal, photochemical, and catalytic), the radical initiator based approach is particle size independent, requires comparatively low reaction temperatures, and yields monolayer surface passivation after short reaction times. The effects of differing functional groups (i.e., alkene, alkyne, carboxylic acid, and ester) on the radical initiated hydrosilylation are also explored. The results indicate functionalization occurs and results in the formation of monolayer passivated surfaces.

Influence of indium-tin oxide surface structure on the ordering and coverage of carboxylic acid and thiol monolayers

International Nuclear Information System (INIS)

Cerruti, Marta; Rhodes, Crissy; Losego, Mark; Efremenko, Alina; Maria, Jon-Paul; Fischer, Daniel; Franzen, Stefan; Genzer, Jan

2007-01-01

This paper analyses the variability of self-assembled monolayers (SAMs) formation on ITO depending on the substrate surface features. In particular, we report on the formation of carboxylic acid- and thiol-based SAMs on two lots of commercially prepared indium-tin oxide (ITO) thin films. Contact angle measurements, electrochemical experiments, and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy showed that the quality of monolayers formed differed substantially between the two ITO batches. Only one of the two ITO substrates was capable of forming well-organized thiol- and carboxylic acid-based SAMs. In order to rationalize these observations, atomic force microscopy and x-ray diffraction analyses were carried out, and SAMs were prepared on ITO substrates fabricated by sputtering in our laboratories. An attempt was made to influence the film microstructure and surface morphology by varying substrate temperatures during ITO deposition. Good-quality thiol and carboxylic acid SAMs were obtained on one of the ITO substrates prepared in-house. While our characterization could not single out conclusively one specific parameter in ITO surface structure that could be responsible for good SAMs formation, we could point out homogeneous surface morphology as a relevant factor for the quality of the SAMs. Evidence was also found for ITO crystallographic orientation to be a parameter influencing SAMs organization

Growth and Functionality of Cells Cultured on Conducting and Semi-Conducting Surfaces Modified with Self-Assembled Monolayers (SAMs

Directory of Open Access Journals (Sweden)

Rajendra K. Aithal

2016-02-01

Full Text Available Bioengineering of dermal and epidermal cells on surface modified substrates is an active area of research. The cytotoxicity, maintenance of cell phenotype and long-term functionality of human dermal fibroblast (HDF cells on conducting indium tin oxide (ITO and semi-conducting, silicon (Si and gallium arsenide (GaAs, surfaces modified with self-assembled monolayers (SAMs containing amino (–NH2 and methyl (–CH3 end groups have been investigated. Contact angle measurements and infrared spectroscopic studies show that the monolayers are conformal and preserve their functional end groups. Morphological analyses indicate that HDFs grow well on all substrates except GaAs, exhibiting their normal spindle-shaped morphology and exhibit no visible signs of stress or cytoplasmic vacuolation. Cell viability analyses indicate little cell death after one week in culture on all substrates except GaAs, where cells died within 6 h. Cells on all surfaces proliferate except on GaAs and GaAs-ODT. Cell growth is observed to be greater on SAM modified ITO and Si-substrates. Preservation of cellular phenotype assessed through type I collagen immunostaining and positive staining of HDF cells were observed on all modified surfaces except that on GaAs. These results suggest that conducting and semi-conducting SAM-modified surfaces support HDF growth and functionality and represent a promising area of bioengineering research.

Large-area and bright pulsed electroluminescence in monolayer semiconductors

KAUST Repository

Lien, Der-Hsien; Amani, Matin; Desai, Sujay B.; Ahn, Geun Ho; Han, Kevin; He, Jr-Hau; Ager, Joel W.; Wu, Ming C.; Javey, Ali

2018-01-01

Transition-metal dichalcogenide monolayers have naturally terminated surfaces and can exhibit a near-unity photoluminescence quantum yield in the presence of suitable defect passivation. To date, steady-state monolayer light-emitting devices suffer from Schottky contacts or require complex heterostructures. We demonstrate a transient-mode electroluminescent device based on transition-metal dichalcogenide monolayers (MoS, WS, MoSe, and WSe) to overcome these problems. Electroluminescence from this dopant-free two-terminal device is obtained by applying an AC voltage between the gate and the semiconductor. Notably, the electroluminescence intensity is weakly dependent on the Schottky barrier height or polarity of the contact. We fabricate a monolayer seven-segment display and achieve the first transparent and bright millimeter-scale light-emitting monolayer semiconductor device.

Large-area and bright pulsed electroluminescence in monolayer semiconductors

KAUST Repository

Lien, Der-Hsien

2018-04-04

Transition-metal dichalcogenide monolayers have naturally terminated surfaces and can exhibit a near-unity photoluminescence quantum yield in the presence of suitable defect passivation. To date, steady-state monolayer light-emitting devices suffer from Schottky contacts or require complex heterostructures. We demonstrate a transient-mode electroluminescent device based on transition-metal dichalcogenide monolayers (MoS, WS, MoSe, and WSe) to overcome these problems. Electroluminescence from this dopant-free two-terminal device is obtained by applying an AC voltage between the gate and the semiconductor. Notably, the electroluminescence intensity is weakly dependent on the Schottky barrier height or polarity of the contact. We fabricate a monolayer seven-segment display and achieve the first transparent and bright millimeter-scale light-emitting monolayer semiconductor device.

Computational studies at the density functional theory (DFT) level about the surface functionalization of hexagonal monolayers by chitosan monomer

Science.gov (United States)

Ebrahimi, Javad; Ahangari, Morteza Ghorbanzadeh; Jahanshahi, Mohsen

2018-05-01

Theoretical investigations based on density functional theory have been carried out to understand the underlying interactions between the chitosan monomer and several types of hexagonal monolayers consisting of pristine and defected graphene and boron-nitride nanosheets. Based on the obtained results, it was found that the type of the interaction for all the systems is of non-covalent nature and the chitosan monomer physically interacts with the surface of mentioned nanostructures. The interaction strength was evaluated by calculating the adsorption energies for the considered systems and it was found that the adsorption of chitosan monomer accompanies by the release of about -0.67 and -0.66 eV energy for pristine graphene and h-BN monolayer, respectively. The role of structural defect has also been considered by embedding a Stone-Wales defect within the structure of mentioned monolayers and it was found that the introduced defect enhances the interactions between the chitosan monomer and nanostructures. The role of dispersion interactions has also been taken into account and it was found that these long-range interactions play the dominating role in the attachment of chitosan monomer onto the graphene sheet, while having strong contribution together with the electrostatic interactions for the stabilization of chitosan onto the surface of h-BN monolayer. For all the cases, the adsorption of chitosan monomer did not change the inherent electronic properties of the nanostructures based on the results of charge transfer analysis and energy gap calculations. The findings of the present work would be very useful in future investigations to explore the potential applications of these hybrid materials in materials science and bio-related fields.

Effect of non-equilibrium flow chemistry and surface catalysis on surface heating to AFE

Science.gov (United States)

Stewart, David A.; Henline, William D.; Chen, Yih-Kanq

1991-01-01

The effect of nonequilibrium flow chemistry on the surface temperature distribution over the forebody heat shield on the Aeroassisted Flight Experiment (AFE) vehicle was investigated using a reacting boundary-layer code. Computations were performed by using boundary-layer-edge properties determined from global iterations between the boundary-layer code and flow field solutions from a viscous shock layer (VSL) and a full Navier-Stokes solution. Surface temperature distribution over the AFE heat shield was calculated for two flight conditions during a nominal AFE trajectory. This study indicates that the surface temperature distribution is sensitive to the nonequilibrium chemistry in the shock layer. Heating distributions over the AFE forebody calculated using nonequilibrium edge properties were similar to values calculated using the VSL program.

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

Monolayers of homocysteine on Au(111)-surfaces have been investigated by voltammetry, in situ scanning tunnelling microscopy (STM) and subtractively normalised interfacial Fourier transform spectroscopy (SNIFTIRS). A pair of sharp voltammetric peaks build up in the potential range 0 to -0.1 V (vs...... potentials at pH 7.7. The molecules pack into highly ordered domains around the peak potential. High-resolution in situ STM reveals a (root 3 x 5) R30 degrees lattice with three homocysteine molecules in each unit cell. The adlayer changes into disordered structures on either side of the peak potential...

Unraveling the Reaction Chemistry of Icy Ocean World Surfaces

Science.gov (United States)

Hudson, R.; Loeffler, M. J.; Gerakines, P.

2017-12-01

The diverse endogenic chemistry of ocean worlds can be divided among interior, surface, and above-surface process, with contributions from exogenic agents such as solar, cosmic, and magnetospheric radiation. Bombardment from micrometeorites to comets also can influence chemistry by both delivering new materials and altering pre-existing ones, and providing energy to drive reactions. Geological processes further complicate the chemistry by transporting materials from one environment to another. In this presentation the focus will be on some of the thermally driven and radiation-induced changes expected from icy materials, primarily covalent and ionic compounds. Low-temperature conversions of a few relatively simple molecules into ions possessing distinct infrared (IR) features will be covered, with an emphasis on such features as might be identified through either orbiting spacecraft or landers. The low-temperature degradation of a few bioorganic molecules, such as DNA nucleobases and some common amino acids, will be used as examples of the more complex, and potentially misleading, chemistry expected for icy moons of the outer solar system. This work was supported by NASA's Emerging Worlds and Outer Planets Research programs, as well as the NASA Astrobiology Institute's Goddard Center for Astrobiology.

Variability in chemistry of surface and soil waters of an ...

African Journals Online (AJOL)

Water chemistry is important for the maintenance of wetland structure and function. Interpreting ecological patterns in a wetland system therefore requires an in-depth understanding of the water chemistry of that system. We investigated the spatial distribution of chemical solutes both in soil pore water and surface water, ...

Deconvoluting the effects of surface chemistry and nanoscale topography: Pseudomonas aeruginosa biofilm nucleation on Si-based substrates.

Science.gov (United States)

Zhang, Jing; Huang, Jinglin; Say, Carmen; Dorit, Robert L; Queeney, K T

2018-06-01

The nucleation of biofilms is known to be affected by both the chemistry and topography of the underlying substrate, particularly when topography includes nanoscale (topography vs. chemistry is complicated by concomitant variation in both as a result of typical surface modification techniques. Analyzing the behavior of biofilm-forming bacteria exposed to surfaces with systematic, independent variation of both topography and surface chemistry should allow differentiation of the two effects. Silicon surfaces with reproducible nanotopography were created by anisotropic etching in deoxygenated water. Surface chemistry was varied independently to create hydrophilic (OH-terminated) and hydrophobic (alkyl-terminated) surfaces. The attachment and proliferation of Psuedomonas aeruginosa to these surfaces was characterized over a period of 12 h using fluorescence and confocal microscopy. The number of attached bacteria as well as the structural characteristics of the nucleating biofilm were influenced by both surface nanotopography and surface chemistry. In general terms, the presence of both nanoscale features and hydrophobic surface chemistry enhance bacterial attachment and colonization. However, the structural details of the resulting biofilms suggest that surface chemistry and topography interact differently on each of the four surface types we studied. Copyright © 2018 Elsevier Inc. All rights reserved.

Step-height standards based on the rapid formation of monolayer steps on the surface of layered crystals

Energy Technology Data Exchange (ETDEWEB)

Komonov, A.I. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences (ISP SBRAS), pr. Lavrentieva 13, Novosibirsk 630090 (Russian Federation); Prinz, V.Ya., E-mail: prinz@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences (ISP SBRAS), pr. Lavrentieva 13, Novosibirsk 630090 (Russian Federation); Seleznev, V.A. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences (ISP SBRAS), pr. Lavrentieva 13, Novosibirsk 630090 (Russian Federation); Kokh, K.A. [Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences (IGM SB RAS), pr. Koptyuga 3, Novosibirsk 630090 (Russian Federation); Shlegel, V.N. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences (NIIC SB RAS), pr. Lavrentieva 3, Novosibirsk 630090 (Russian Federation)

2017-07-15

Highlights: • Easily reproducible step-height standard for SPM calibrations was proposed. • Step-height standard is monolayer steps on the surface of layered single crystal. • Long-term change in surface morphology of Bi{sub 2}Se{sub 3} and ZnWO{sub 4} was investigated. • Conducting surface of Bi{sub 2}Se{sub 3} crystals appropriate for calibrating STM. • Ability of robust SPM calibrations under ambient conditions were demonstrated. - Abstract: Metrology is essential for nanotechnology, especially for structures and devices with feature sizes going down to nm. Scanning probe microscopes (SPMs) permits measurement of nanometer- and subnanometer-scale objects. Accuracy of size measurements performed using SPMs is largely defined by the accuracy of used calibration measures. In the present publication, we demonstrate that height standards of monolayer step (∼1 and ∼0.6 nm) can be easily prepared by cleaving Bi{sub 2}Se{sub 3} and ZnWO{sub 4} layered single crystals. It was shown that the conducting surface of Bi{sub 2}Se{sub 3} crystals offers height standard appropriate for calibrating STMs and for testing conductive SPM probes. Our AFM study of the morphology of freshly cleaved (0001) Bi{sub 2}Se{sub 3} surfaces proved that such surfaces remained atomically smooth during a period of at least half a year. The (010) surfaces of ZnWO{sub 4} crystals remained atomically smooth during one day, but already two days later an additional nanorelief of amplitude ∼0.3 nm appeared on those surfaces. This relief, however, did not further grow in height, and it did not hamper the calibration. Simplicity and the possibility of rapid fabrication of the step-height standards, as well as their high stability, make these standards available for a great, permanently growing number of users involved in 3D printing activities.

Langmuir monolayer formation of metal complexes from polymerizable amphiphilic ligands

NARCIS (Netherlands)

Werkman, P.J; Schouten, A.J.

1996-01-01

The monolayer behaviour of 4-(10,12-pentacosadiynoicamidomethyl)-pyridine at the air-water interface was studied by measuring the surface pressure-area isotherms. The amphiphile formed stable monolayers with a clear liquid-expanded (LE) to liquid-condensed phase transition at various temperatures.

Grain surface chemistry in protoplanetary disks

International Nuclear Information System (INIS)

Reboussin, Laura

2015-01-01

Planetary formation occurs in the protoplanetary disks of gas and dust. Although dust represents only 1% of the total disk mass, it plays a fundamental role in disk chemical evolution since it acts as a catalyst for the formation of molecules. Understanding this chemistry is therefore essential to determine the initial conditions from which planets form. During my thesis, I studied grain-surface chemistry and its impact on the chemical evolution of molecular cloud, initial condition for disk formation, and protoplanetary disk. Thanks to numerical simulations, using the gas-grain code Nautilus, I showed the importance of diffusion reactions and gas-grain interactions for the abundances of gas-phase species. Model results combined with observations also showed the effects of the physical structure (in temperature, density, AV) on the molecular distribution in disks. (author)

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.

Growth of cells superinoculated onto irradiated and nonirradiated confluent monolayers

International Nuclear Information System (INIS)

Matsuoka, H.; Ueo, H.; Sugimachi, K.

1990-01-01

We prepared confluent monolayers of normal BALB/c 3T3 cells and compared differences in the growth of four types of cells superinoculated onto these nonirradiated and irradiated monolayers. The test cells were normal BALB/c 3T3 A31 cells, a squamous cell carcinoma from a human esophageal cancer (KSE-1), human fetal fibroblasts, and V-79 cells from Chinese hamster lung fibroblasts. Cell growth was checked by counting the cell number, determining [3H]thymidine incorporation and assessing colony formation. We found that on nonirradiated monolayers, colony formation of human fetal fibroblasts and normal BALB/c 3T3 cells was completely inhibited. On irradiated cells, test cells did exhibit some growth. KSE-1 cells, which had a low clonogenic efficiency on plastic surfaces, formed colonies on both irradiated and nonirradiated cells. On these monolayers, the clonogenic efficiency of V-79 cells was also higher than that on plastic surfaces. We conclude that the nonirradiated monolayer of BALB/c 3T3 cells completely inhibits the growth of superinoculated normal BALB/c 3T3 and human fetal fibroblasts, while on the other hand, they facilitate the growth of neoplastic KSE-1 and V-79 cells by providing a surface for cell adherence and growth, without affecting the presence of normal cells in co-cultures

Transport of surface engineered polyamidoamine (PAMAM) dendrimers across IPEC-J2 cell monolayers.

Science.gov (United States)

Pisal, Dipak S; Yellepeddi, Venkata K; Kumar, Ajay; Palakurthi, Srinath

2008-11-01

The aim of our study was to prepare arginine-and ornithine-conjugated Polyamidoamine (PAMAM) dendrimers and study their permeability across IPEC-J2 cell monolayers, a new intestinal cell line model for drug absorption studies. Arginine and ornithine were conjugated to the amine terminals of the PAMAM(G4) dendrimers by Fmoc synthesis. The apical-to-basolateral (AB) and basolateral-to-apical (BA) apparent permeability coefficients (P(app)) for the PAMAM dendrimers increased by conjugating the dendrimers with both of these polyamines. The enhancement in permeability was dependent on the dendrimer concentration and duration of incubation. Correlation between monolayer permeability and the decrease in transepithelial electrical resistance (TEER) with the PAMAM dendrimers and the polyamine-conjugated dendrimers suggests that paracellular transport is one of the mechanisms of transport across the epithelial cells. Cytotoxicity of these surface-modified dendrimers was evaluated in IPEC-J2 cells by MTT (methylthiazoletetrazolium) assay. Arginine-conjugated dendrimers were insignificantly more toxic than PAMAM dendrimer as well as ornithine-conjugated dendrimers. Though investigations on the possible involvement of other transport mechanisms are in progress, results of the present study suggest the potential of dendrimer-polyamine conjugates as the carriers for antigen/drug delivery through the oral mucosa.

Imidazolide monolayers for versatile reactive microcontact printing

NARCIS (Netherlands)

Hsu, S.H.; Reinhoudt, David; Huskens, Jurriaan; Velders, Aldrik

2008-01-01

Imidazolide monolayers prepared from the reaction of amino SAMs with N,N-carbonyldiimidazole (CDI) are used as a versatile platform for surface patterning with amino-, carboxyl- and alcohol-containing compounds through reactive microcontact printing (µCP). To demonstrate the surface reactivity of

Cation effects on phosphatidic acid monolayers at various pH conditions.

Science.gov (United States)

Zhang, Ting; Cathcart, Matthew G; Vidalis, Andrew S; Allen, Heather C

2016-10-01

The impact of pH and cations on phase behavior, stability, and surface morphology for dipalmitoylphosphatidic acid (DPPA) monolayers was investigated. At pHCations are found to expand and stabilize the monolayer in the following order of increasing magnitude at pH 5.6: Na + >K + ∼Mg 2+ >Ca 2+ . Additionally, cation complexation is tied to the pH and protonation state of DPPA, which are the primary factors controlling the monolayer surface behavior. The binding affinity of cations to the headgroup and thus deprotonation capability of the cation, ranked in the order of Ca 2+ >Mg 2+ >Na + >K + , is found to be well explained by the law of matching water affinities. Nucleation of surface 3D lipid structures is observed from Ca 2+ , Mg 2+ , and Na + , but not from K + , consistent with the lowest binding affinity of K + . Unraveling cation and pH effects on DPPA monolayers is useful in further understanding the surface properties of complex systems such as organic-coated marine aerosols where organic films are directly influenced by the pH and ionic composition of the underlying aqueous phase. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Comparison of nitric oxide binding to different pure and mixed protoporphyrin IX monolayers

NARCIS (Netherlands)

Knoben, W.; Crego-Calama, M.; Brongersma, S.H.

2012-01-01

The nitric oxide (NO) binding properties of monolayers of four different protoporphyrins IX adsorbed on aluminum oxide surfaces have been investigated. XPS and AFM results are consistent with the presence of a monolayer of porphyrins, bound to the surface by their carboxylic acid groups and with the

Monolayers and thin films of dextran hydrophobically modified

International Nuclear Information System (INIS)

Leiva, Angel; Munoz, Natalia; Gargallo, Ligia; Radic, Deodato; Urzua, Marcela

2010-01-01

A series of biodegradable graft copolymers were synthesized by grafting e-caprolactone over dextran of different molecular weights. The obtained copolymers were characterized by Fourier transform infrared spectroscopy FTIR, proton nuclear magnetic resonance 1H NMR, thermogravimetry and elemental analysis. Stable monolayers at the air-water interface and spin coated thin films were prepared and characterized by the Langmuir technique and by contact angle measurements respectively. The compressibility and static surface elasticity of the monolayers and the surface energy of copolymer thin films show dependence with the e-caprolactone content. >From these results it can be concluded that the surface properties of grafted copolymers can be modulated by their composition. Additionally, according to the obtained results, e-caprolactone grafted-dextrans show potential for being used in different applications where surface properties are important. (author)

Recent advances in study of uranium surface chemistry in China

International Nuclear Information System (INIS)

Luo, Lizhu; Lai, Xinchun; Wang, Xiaolin

2014-01-01

Uranium is very important in nuclear energy industry; however, uranium and its alloys corrode seriously in various atmospheres because of their chemical reactivities. In China, continuous investigations focused on surface chemistry have been carried out for a thorough understanding of uranium in order to provide technical support for its engineering applications. Oxidation kinetics of uranium and its alloys in oxidizing atmospheres are in good agreement with those in the literature. In addition to the traditional techniques, non-traditional methods have been applied for oxidation kinetics of uranium, and it has been verified that spectroscopic ellipsometry and X-ray diffraction are effective and nondestructive tools for in situ kinetic studies. The inhibition efficiency of oxidizing gas impurities on uranium hydrogenation is found to follow the order CO 2 > CO > O 2 , and the broadening of XPS shoulders with temperature in depth profile of hydrogenated uranium surface is discussed, which is not mentioned in the literature. Significant progress on surface chemistry of alloyed uranium (U-Nb and U-Ti) in hydrogen atmosphere is reported, and it is revealed that the hydrating nucleation and subsequent growth of alloyed uranium are closely connected with the surface states, underlying metal matrix, and it is microstructure-dependent. In this review, the recent advances in uranium surface chemistry in China, published so far mostly in Chinese language, are briefly summarized. Suggestions for further study are made. (orig.)

Click functionalization of phenyl-capped bithiophene on azide-terminated self-assembled monolayers

International Nuclear Information System (INIS)

Zheng, Yijun; Cui, Jiaxi; Ikeda, Taichi

2015-01-01

Graphical abstract: - Highlights: • Electrochemically-active self-assembled monolayers with phenyl-capped bithiophene were prepared. • Post-functionalization method based on click chemistry solved the solubility issue of phenyl-capped thiophene alkanethiol. • The capture and release of the counter anions during the redox reaction were detectable by E-QCM. - Abstract: We immobilized tetra(ethylene glycol)-substituted phenyl-capped bithiophene with alkyne terminals (Ph2TPh-alkyne) on azide-terminated self-assembled monolayers (N 3 -SAMs) by Cu-catalyzed azide-alkyne cycloaddition reaction. Ph2TPh-functionalized SAMs on a gold substrate showed reversible electrochemical response. The surface densities of the azide groups in N 3 -SAMs and Ph2TPh units in Ph2TPh-functionalized SAMs were estimated to be 7.3 ± 0.3 × 10 −10 mol cm −2 and 4.6 ± 0.3 × 10 −10 mol cm −2 , respectively, by quartz crystal microbalance (QCM). Most of Ph2TPh-alkynes are considered to be anchored on N 3 -SAMs via both terminal groups. Ph2TPh-functionalized SAMs exhibited reversible redox peaks in cyclic voltammetry (CV). In redox reaction, reversible capture and release of the counter anion could be monitored by electrochemical QCM (E-QCM).

Click functionalization of phenyl-capped bithiophene on azide-terminated self-assembled monolayers

Energy Technology Data Exchange (ETDEWEB)

Zheng, Yijun; Cui, Jiaxi [Max Planck Institute for Polymer Research (MPIP), Ackermannweg 10, Mainz 55128 (Germany); Ikeda, Taichi, E-mail: IKEDA.Taichi@nims.go.jp [Max Planck Institute for Polymer Research (MPIP), Ackermannweg 10, Mainz 55128 (Germany); Polymer Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan)

2015-11-15

Graphical abstract: - Highlights: • Electrochemically-active self-assembled monolayers with phenyl-capped bithiophene were prepared. • Post-functionalization method based on click chemistry solved the solubility issue of phenyl-capped thiophene alkanethiol. • The capture and release of the counter anions during the redox reaction were detectable by E-QCM. - Abstract: We immobilized tetra(ethylene glycol)-substituted phenyl-capped bithiophene with alkyne terminals (Ph2TPh-alkyne) on azide-terminated self-assembled monolayers (N{sub 3}-SAMs) by Cu-catalyzed azide-alkyne cycloaddition reaction. Ph2TPh-functionalized SAMs on a gold substrate showed reversible electrochemical response. The surface densities of the azide groups in N{sub 3}-SAMs and Ph2TPh units in Ph2TPh-functionalized SAMs were estimated to be 7.3 ± 0.3 × 10{sup −10} mol cm{sup −2} and 4.6 ± 0.3 × 10{sup −10} mol cm{sup −2}, respectively, by quartz crystal microbalance (QCM). Most of Ph2TPh-alkynes are considered to be anchored on N{sub 3}-SAMs via both terminal groups. Ph2TPh-functionalized SAMs exhibited reversible redox peaks in cyclic voltammetry (CV). In redox reaction, reversible capture and release of the counter anion could be monitored by electrochemical QCM (E-QCM).

ICE CHEMISTRY IN STARLESS MOLECULAR CORES

Energy Technology Data Exchange (ETDEWEB)

Kalvans, J., E-mail: juris.kalvans@venta.lv [Engineering Research Institute “Ventspils International Radio Astronomy Center” of Ventspils University College, Inzenieru 101, Ventspils, LV-3601 (Latvia)

2015-06-20

Starless molecular cores are natural laboratories for interstellar molecular chemistry research. The chemistry of ices in such objects was investigated with a three-phase (gas, surface, and mantle) model. We considered the center part of five starless cores, with their physical conditions derived from observations. The ice chemistry of oxygen, nitrogen, sulfur, and complex organic molecules (COMs) was analyzed. We found that an ice-depth dimension, measured, e.g., in monolayers, is essential for modeling of chemistry in interstellar ices. Particularly, the H{sub 2}O:CO:CO{sub 2}:N{sub 2}:NH{sub 3} ice abundance ratio regulates the production and destruction of minor species. It is suggested that photodesorption during the core-collapse period is responsible for the high abundance of interstellar H{sub 2}O{sub 2} and O{sub 2}H and other species synthesized on the surface. The calculated abundances of COMs in ice were compared to observed gas-phase values. Smaller activation barriers for CO and H{sub 2}CO hydrogenation may help explain the production of a number of COMs. The observed abundance of methyl formate HCOOCH{sub 3} could be reproduced with a 1 kyr, 20 K temperature spike. Possible desorption mechanisms, relevant for COMs, are gas turbulence (ice exposure to interstellar photons) or a weak shock within the cloud core (grain collisions). To reproduce the observed COM abundances with the present 0D model, 1%–10% of ice mass needs to be sublimated. We estimate that the lifetime for starless cores likely does not exceed 1 Myr. Taurus cores are likely to be younger than their counterparts in most other clouds.

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

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

Science.gov (United States)

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

2016-08-03

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

Supramolecular domains in mixed peptide self-assembled monolayers on gold nanoparticles.

Science.gov (United States)

Duchesne, Laurence; Wells, Geoff; Fernig, David G; Harris, Sarah A; Lévy, Raphaël

2008-09-01

Self-organization in mixed self-assembled monolayers of small molecules provides a route towards nanoparticles with complex molecular structures. Inspired by structural biology, a strategy based on chemical cross-linking is introduced to probe proximity between functional peptides embedded in a mixed self-assembled monolayer at the surface of a nanoparticle. The physical basis of the proximity measurement is a transition from intramolecular to intermolecular cross-linking as the functional peptides get closer. Experimental investigations of a binary peptide self-assembled monolayer show that this transition happens at an extremely low molar ratio of the functional versus matrix peptide. Molecular dynamics simulations of the peptide self-assembled monolayer are used to calculate the volume explored by the reactive groups. Comparison of the experimental results with a probabilistic model demonstrates that the peptides are not randomly distributed at the surface of the nanoparticle, but rather self-organize into supramolecular domains.

Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors.

Science.gov (United States)

Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T; Evoy, Stephane

2016-03-14

Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

Directory of Open Access Journals (Sweden)

Wei Zheng

2016-03-01

Full Text Available Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

Preparation of porous monolayer film by immersing the stearic acid Langmuir-Blodgett monolayer on mica in salt solution

Energy Technology Data Exchange (ETDEWEB)

Wang, S. [Institute of Near-Field Optics and Nano Technology, School of Physics and Optoelectronic Technology, Dalian University of Technology, Street No. 2 Linggong Road, Dalian 116024 (China); Li, Y.L.; Zhao, H.L.; Liang, H. [Institute of Photo-Biophysics, School of Physics and Electronic, Henan University, Jinming, Kaifeng 475004, Henan (China); Liu, B., E-mail: boliu@henu.edu.cn [Institute of Photo-Biophysics, School of Physics and Electronic, Henan University, Jinming, Kaifeng 475004, Henan (China); Pan, S., E-mail: span@dlut.edu.cn [Institute of Near-Field Optics and Nano Technology, School of Physics and Optoelectronic Technology, Dalian University of Technology, Street No. 2 Linggong Road, Dalian 116024 (China)

2012-11-15

Highlights: Black-Right-Pointing-Pointer Porous film has been prepared by immersing the stearic acid Langmuir-Blodgett monolayer on mica in salt solution. Black-Right-Pointing-Pointer The mechanism relies on the electrostatic screening effect of the cations in salt solution. Black-Right-Pointing-Pointer The factors influencing the size and area of the pores were investigated. - Abstract: Porous materials have drawn attention from scientists in many fields such as life sciences, catalysis and photonics since they can be used to induce some materials growth as expected. Especially, porous Langmuir-Blodgett (LB) film is an ideal material with controlled thickness and flat surface. In this paper, stearic acid (SA), which has been extensively explored in LB film technique, is chosen as the template material with known parameters to prepare the LB film, and then the porous SA monolayer film is obtained by means of etching in salt solution. The main etching mechanism is suggested that the cations in the solution block the electrostatic interaction between the polar carboxyl group of SA and the electronegative mica surface. The influencing factors (such as concentration of salt solution, valence of cation and surface pressure) of the porous SA film are systematically studied in this work. The novel method proposed in this paper makes it convenient to prepare porous monolayer film for designed material growth or cell culture.

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...

Monolayer arrangement of fatty hydroxystearic acids on graphite: Influence of hydroxyl groups

Energy Technology Data Exchange (ETDEWEB)

Medina, S. [Laboratorio de Rayos-X, Centro de Investigación Tecnología e Innovación, de la Universidad de Sevilla (CITIUS), Universidad de Sevilla, Avenida Reina Mercedes, 4B. 41012, Sevilla (Spain); Benítez, J.J.; Castro, M.A. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain); Cerrillos, C. [Servicio de Microscopía, Centro de Investigación Tecnología e Innovación, de la Universidad de Sevilla (CITIUS), Universidad de Sevilla, Avenida Reina Mercedes, 4B. 41012, Sevilla (Spain); Millán, C. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain); Alba, M.D., E-mail: alba@icmse.csic.es [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain)

2013-07-31

Previous studies have indicated that long-chain linear carboxylic acids form commensurate packed crystalline monolayers on graphite even at temperatures above their melting point. This study examines the effect on the monolayer formation and structure of adding one or more secondary hydroxyl, functional groups to the stearic acid skeleton (namely, 12-hydroxystearic and 9,10-dihydroxystearic acid). Moreover, a comparative study of the monolayer formation on recompressed and monocrystalline graphite has been performed through X-ray diffraction (XRD) and Scanning Tunneling Microscopy (STM), respectively. The Differential Scanning Calorimetry (DSC) and XRD data were used to confirm the formation of solid monolayers and XRD data have provided a detailed structural analysis of the monolayers in good correspondence with obtained STM images. DSC and XRD have demonstrated that, in stearic acid and 12-hydroxystearic acid adsorbed onto graphite, the monolayer melted at a higher temperature than the bulk form of the carboxylic acid. However, no difference was observed between the melting point of the monolayer and the bulk form for 9,10-dihydroxystearic acid adsorbed onto graphite. STM results indicated that all acids on the surface have a rectangular p2 monolayer structure, whose lattice parameters were uniaxially commensurate on the a-axis. This structure does not correlate with the initial structure of the pure compounds after dissolving, but it is conditioned to favor a) hydrogen bond formation between the carboxylic groups and b) formation of hydrogen bonds between secondary hydroxyl groups, if spatially permissible. Therefore, the presence of hydroxyl functional groups affects the secondary structure and behavior of stearic acid in the monolayer. - Highlights: • Hydroxyl functional groups affect structure and behavior of acids in the monolayer. • Acids on the surface have a rectangular p2 monolayer structure. • Lattice parameters of acids are uniaxially

Recent advances in study of uranium surface chemistry in China

Energy Technology Data Exchange (ETDEWEB)

Luo, Lizhu; Lai, Xinchun [Science and Technology on Surface Physics and Chemistry Laboratory, Sichuan (China); Wang, Xiaolin [China Academy of Engineering Physics, Sichuan (China)

2014-04-01

Uranium is very important in nuclear energy industry; however, uranium and its alloys corrode seriously in various atmospheres because of their chemical reactivities. In China, continuous investigations focused on surface chemistry have been carried out for a thorough understanding of uranium in order to provide technical support for its engineering applications. Oxidation kinetics of uranium and its alloys in oxidizing atmospheres are in good agreement with those in the literature. In addition to the traditional techniques, non-traditional methods have been applied for oxidation kinetics of uranium, and it has been verified that spectroscopic ellipsometry and X-ray diffraction are effective and nondestructive tools for in situ kinetic studies. The inhibition efficiency of oxidizing gas impurities on uranium hydrogenation is found to follow the order CO{sub 2} > CO > O{sub 2}, and the broadening of XPS shoulders with temperature in depth profile of hydrogenated uranium surface is discussed, which is not mentioned in the literature. Significant progress on surface chemistry of alloyed uranium (U-Nb and U-Ti) in hydrogen atmosphere is reported, and it is revealed that the hydrating nucleation and subsequent growth of alloyed uranium are closely connected with the surface states, underlying metal matrix, and it is microstructure-dependent. In this review, the recent advances in uranium surface chemistry in China, published so far mostly in Chinese language, are briefly summarized. Suggestions for further study are made. (orig.)

Characterization of self-assembled monolayers (SAMs) on silicon substrate comparative with polymer substrate for Escherichia coli O157:H7 detection

International Nuclear Information System (INIS)

Moldovan, Carmen; Mihailescu, Carmen; Stan, Dana; Ruta, Lavinia; Iosub, Rodica; Gavrila, Raluca; Purica, Munizer; Vasilica, Schiopu

2009-01-01

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.

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.

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.

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

Molecular surface science of heterogeneous catalysis. History and perspective

International Nuclear Information System (INIS)

Somorjai, G.A.

1983-08-01

A personal account is given of how the author became involved with modern surface science and how it was employed for studies of the chemistry of surfaces and heterogeneous catalysis. New techniques were developed for studying the properties of the surface monolayers: Auger electron spectroscopy, LEED, XPS, molecular beam surface scattering, etc. An apparatus was developed and used to study hydrocarbon conversion reactions on Pt, CO hydrogenation on Rh and Fe, and NH 3 synthesis on Fe. A model has been developed for the working Pt reforming catalyst. The three molecular ingredients that control catalytic properties are atomic surface structure, an active carbonaceous deposit, and the proper oxidation state of surface atoms. 40 references, 21 figures

Molecular surface science of heterogeneous catalysis. History and perspective

Energy Technology Data Exchange (ETDEWEB)

Somorjai, G.A.

1983-08-01

A personal account is given of how the author became involved with modern surface science and how it was employed for studies of the chemistry of surfaces and heterogeneous catalysis. New techniques were developed for studying the properties of the surface monolayers: Auger electron spectroscopy, LEED, XPS, molecular beam surface scattering, etc. An apparatus was developed and used to study hydrocarbon conversion reactions on Pt, CO hydrogenation on Rh and Fe, and NH/sub 3/ synthesis on Fe. A model has been developed for the working Pt reforming catalyst. The three molecular ingredients that control catalytic properties are atomic surface structure, an active carbonaceous deposit, and the proper oxidation state of surface atoms. 40 references, 21 figures. (DLC)

Surface-Enhanced Raman Spectroscopy of Carbon Nanomembranes from Aromatic Self-Assembled Monolayers.

Science.gov (United States)

Zhang, Xianghui; Mainka, Marcel; Paneff, Florian; Hachmeister, Henning; Beyer, André; Gölzhäuser, Armin; Huser, Thomas

2018-02-27

Surface-enhanced Raman scattering spectroscopy (SERS) was employed to investigate the formation of self-assembled monolayers (SAMs) of biphenylthiol, 4'-nitro-1,1'-biphenyl-4-thiol, and p-terphenylthiol on Au surfaces and their structural transformations into carbon nanomembranes (CNMs) induced by electron irradiation. The high sensitivity of SERS allows us to identify two types of Raman scattering in electron-irradiated SAMs: (1) Raman-active sites exhibit similar bands as those of pristine SAMs in the fingerprint spectral region, but with indications of an amorphization process and (2) Raman-inactive sites show almost no Raman-scattering signals, except a very weak and broad D band, indicating a lack of structural order but for the presence of graphitic domains. Statistical analysis showed that the ratio of the number of Raman-active sites to the total number of measurement sites decreases exponentially with increasing the electron irradiation dose. The maximum degree of cross-linking ranged from 97 to 99% for the three SAMs. Proof-of-concept experiments were conducted to demonstrate potential applications of Raman-inactive CNMs as a supporting membrane for Raman analysis.

Peierls instability as the insulating origin of the Na/Si(111)-(3 × 1) surface with a Na coverage of 2/3 monolayers

Science.gov (United States)

Kang, Myung Ho; Kwon, Se Gab; Jung, Sung Chul

2018-03-01

Density functional theory (DFT) calculations are used to investigate the insulating origin of the Na/Si(111)-(3 × 1) surface with a Na coverage of 2/3 monolayers. In the coverage definition, one monolayer refers to one Na atom per surface Si atom, so this surface contains an odd number of electrons (i.e., three Si dangling-bond electrons plus two Na electrons) per 3 × 1 unit cell. Interestingly, this odd-electron surface has been ascribed to a Mott-Hubbard insulator to account for the measured insulating band structure with a gap of about 0.8 eV. Here, we instead propose a Peierls instability as the origin of the experimental band gap. The concept of Peierls instability is fundamental in one-dimensional metal systems but has not been taken into account in previous studies of this surface. Our DFT calculations demonstrate that the linear chain structure of Si dangling bonds in this surface is energetically unstable with respect to a × 2 buckling modulation, and the buckling-induced band gap of 0.79 eV explains well the measured insulating nature.

Density functional theory in surface chemistry and catalysis

DEFF Research Database (Denmark)

Nørskov, Jens Kehlet; Abild-Pedersen, Frank; Studt, Felix

2011-01-01

Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future...

Antibiotic interaction with phospholipid monolayers

International Nuclear Information System (INIS)

Gambinossi, F.; Mecheri, B.; Caminati, G.; Nocentini, M.; Puggelli, M.; Gabrielli, G.

2002-01-01

We studied the interactions of tetracycline (TC) antibiotic molecules with phospholipid monolayers with the two-fold aim of elucidating the mechanism of action and providing a first step for the realization of bio-mimetic sensors for such drugs by means of the Langmuir-Blodgett technique. We examined spreading monolayers of three phospholipids in the presence of tetracycline in the subphase by means of surface pressure-area and surface potential-area isotherms as a function of bulk pH. We selected phospholipids with hydrophobic chains of the same length but polar head groups differing either in dimensions and protonation equilibria, i.e. dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidic acid (DPPA). The interaction of tetracycline with the three phospholipids was found to be highly dependent on the electric charge of the antibiotic and on the ionization state of the lipid. Significant interactions are established between the negatively charged form of dipalmitoylphosphatidic acid and the zwitterionic form of tetracycline. The drug was found to migrate at the interface where it is adsorbed underneath or/and among the head groups, depending on the surface pressure of the film, whereas penetration through the hydrophobic layer was excluded for all the three phospholipids

Antibiotic interaction with phospholipid monolayers

Energy Technology Data Exchange (ETDEWEB)

Gambinossi, F.; Mecheri, B.; Caminati, G.; Nocentini, M.; Puggelli, M.; Gabrielli, G

2002-12-01

We studied the interactions of tetracycline (TC) antibiotic molecules with phospholipid monolayers with the two-fold aim of elucidating the mechanism of action and providing a first step for the realization of bio-mimetic sensors for such drugs by means of the Langmuir-Blodgett technique. We examined spreading monolayers of three phospholipids in the presence of tetracycline in the subphase by means of surface pressure-area and surface potential-area isotherms as a function of bulk pH. We selected phospholipids with hydrophobic chains of the same length but polar head groups differing either in dimensions and protonation equilibria, i.e. dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidic acid (DPPA). The interaction of tetracycline with the three phospholipids was found to be highly dependent on the electric charge of the antibiotic and on the ionization state of the lipid. Significant interactions are established between the negatively charged form of dipalmitoylphosphatidic acid and the zwitterionic form of tetracycline. The drug was found to migrate at the interface where it is adsorbed underneath or/and among the head groups, depending on the surface pressure of the film, whereas penetration through the hydrophobic layer was excluded for all the three phospholipids.

Measurement of the Surface Dilatational Viscosity of an Insoluble Surfactant Monolayer at the Air/Water Interface Using a Pendant Drop Apparatus

Science.gov (United States)

Lorenzo, Jose; Couzis, Alex; Maldarelli, Charles; Singh, Bhim S. (Technical Monitor)

2000-01-01

When a fluid interface with surfactants is at rest, the interfacial stress is isotropic (as given by the equilibrium interfacial tension), and is described by the equation of state which relates the surface tension to the surfactant surface concentration. When surfactants are subjected to shear and dilatational flows, flow induced interaction of the surfactants; can create interfacial stresses apart from the equilibrium surface tension. The simplest relationship between surface strain rate and surface stress is the Boussinesq-Scriven constitutive equation completely characterized by three coefficients: equilibrium interfacial tension, surface shear viscosity, and surface dilatational viscosity Equilibrium interfacial tension and surface shear viscosity measurements are very well established. On the other hand, surface dilatational viscosity measurements are difficult because a flow which change the surface area also changes the surfactant surface concentration creating changes in the equilibrium interfacial tension that must be also taken into account. Surface dilatational viscosity measurements of existing techniques differ by five orders of magnitude and use spatially damped surface waves and rapidly expanding bubbles. In this presentation we introduce a new technique for measuring the surface dilatational viscosity by contracting an aqueous pendant drop attached to a needle tip and having and insoluble surfactant monolayer at the air-water interface. The isotropic total tension on the surface consists of the equilibrium surface tension and the tension due to the dilation. Compression rates are undertaken slow enough so that bulk hydrodynamic stresses are small compared to the surface tension force. Under these conditions we show that the total tension is uniform along the surface and that the Young-Laplace equation governs the drop shape with the equilibrium surface tension replaced by the constant surface isotropic stress. We illustrate this technique using

Evolution of interfacial intercalation chemistry on epitaxial graphene/SiC by surface enhanced Raman spectroscopy

International Nuclear Information System (INIS)

Ferralis, Nicola; Carraro, Carlo

2014-01-01

Highlights: • H-intercalated epitaxial graphene–SiC interface studied with surface enhanced Raman. • Evolution of graphene and H–Si interface with UV-ozone, annealing and O-exposure. • H–Si interface and quasi-freestanding graphene are retained after UV-ozone treatment. • Enhanced ozonolytic reactivity at the edges of H-intercalated defected graphene. • Novel SERS method for characterizing near-surface graphene–substrate interfaces. - Abstract: A rapid and facile evaluation of the effects of physical and chemical processes on the interfacial layer between epitaxial graphene monolayers on SiC(0 0 0 1) surfaces is essential for applications in electronics, photonics, and optoelectronics. Here, the evolution of the atomic scale epitaxial graphene-buffer-layer–SiC interface through hydrogen intercalation, thermal annealings, UV-ozone etching and oxygen exposure is studied by means of single microparticle mediated surface enhanced Raman spectroscopy (smSERS). The evolution of the interfacial chemistry in the buffer layer is monitored through the Raman band at 2132 cm −1 corresponding to the Si-H stretch mode. Graphene quality is monitored directly by the selectively enhanced Raman signal of graphene compared to the SiC substrate signal. Through smSERS, a simultaneous correlation between optimized hydrogen intercalation in epitaxial graphene/SiC and an increase in graphene quality is uncovered. Following UV-ozone treatment, a fully hydrogen passivated interface is retained, while a moderate degradation in the quality of the hydrogen intercalated quasi-freestanding graphene is observed. While hydrogen intercalated defect free quasi-freestanding graphene is expected to be robust upon UV-ozone, thermal annealing, and oxygen exposure, ozonolytic reactivity at the edges of H-intercalated defected graphene results in enhanced amorphization of the quasi-freestanding (compared to non-intercalated) graphene, leading ultimately to its complete etching

Evolution of interfacial intercalation chemistry on epitaxial graphene/SiC by surface enhanced Raman spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Ferralis, Nicola, E-mail: ferralis@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Carraro, Carlo [Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720 (United States)

2014-11-30

Highlights: • H-intercalated epitaxial graphene–SiC interface studied with surface enhanced Raman. • Evolution of graphene and H–Si interface with UV-ozone, annealing and O-exposure. • H–Si interface and quasi-freestanding graphene are retained after UV-ozone treatment. • Enhanced ozonolytic reactivity at the edges of H-intercalated defected graphene. • Novel SERS method for characterizing near-surface graphene–substrate interfaces. - Abstract: A rapid and facile evaluation of the effects of physical and chemical processes on the interfacial layer between epitaxial graphene monolayers on SiC(0 0 0 1) surfaces is essential for applications in electronics, photonics, and optoelectronics. Here, the evolution of the atomic scale epitaxial graphene-buffer-layer–SiC interface through hydrogen intercalation, thermal annealings, UV-ozone etching and oxygen exposure is studied by means of single microparticle mediated surface enhanced Raman spectroscopy (smSERS). The evolution of the interfacial chemistry in the buffer layer is monitored through the Raman band at 2132 cm{sup −1} corresponding to the Si-H stretch mode. Graphene quality is monitored directly by the selectively enhanced Raman signal of graphene compared to the SiC substrate signal. Through smSERS, a simultaneous correlation between optimized hydrogen intercalation in epitaxial graphene/SiC and an increase in graphene quality is uncovered. Following UV-ozone treatment, a fully hydrogen passivated interface is retained, while a moderate degradation in the quality of the hydrogen intercalated quasi-freestanding graphene is observed. While hydrogen intercalated defect free quasi-freestanding graphene is expected to be robust upon UV-ozone, thermal annealing, and oxygen exposure, ozonolytic reactivity at the edges of H-intercalated defected graphene results in enhanced amorphization of the quasi-freestanding (compared to non-intercalated) graphene, leading ultimately to its complete etching.

Formation of n-Alkyl Monolayers by Organomercury Deposition on Gold

Czech Academy of Sciences Publication Activity Database

Scholz, F.; Kaletová, Eva; Stensrud, Elizabeth; Ford, W. E.; Kohutová, Anna; Mucha, Malgorzata; Stibor, Ivan; Michl, Josef; Wrochem von, F.

2013-01-01

Roč. 4, č. 16 (2013), s. 2624-2629 ISSN 1948-7185 R&D Projects: GA ČR GA203/07/1619; GA ČR GA203/09/0705 EU Projects: European Commission(XE) 213382 - FUNMOL; European Commission(XE) 227756 - DIPOLAR ROTOR ARRAY Institutional support: RVO:61388963 Keywords : self-assembled monolayers * ray photoelectron-spectroscopy * altitudinal molecular rotors Subject RIV: CC - Organic Chemistry Impact factor: 6.687, year: 2013

Interactions between an anticancer drug - edelfosine - and cholesterol in Langmuir monolayers

International Nuclear Information System (INIS)

Wiecek, Agata; Dynarowicz-Latka, Patrycja; Minones, J.; Conde, Olga; Casas, Matilde

2008-01-01

Edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine, abbr. Et-18-OCH 3 ) is a new generation anticancer drug based on a phospholipids-like structure. Since its mechanism of action is believed to be related to the lipids of cellular membrane, we have investigated the interactions between edelfosine and main mammalian sterol: cholesterol, using the Langmuir monolayer technique. The interactions have been analyzed by comparing the experimental curves with theoretical ones, obtained basing on the additivity rule. The observed contraction together with negative deviations from ideality observed on the mean molecular area (A 12 ) vs film composition plots proves the existence of strong attractive forces between edelfosine and cholesterol, which have been quantified with the excess free energy of mixing (ΔG exc ) values, calculated from the surface pressure-area isotherms datapoints. The most negative values of ΔG exc have been found for the mixture of equimolar composition, proving its highest thermodynamic stability and the existence of the strongest interactions between film components. Thus, it has been postulated that at the surface edelfosine and cholesterol form stable complexes of 1:1 stoichiometry. The analysis of the collapse pressure values for the investigated mixed monolayers proves that films of edelfosine mole fraction ≤ 0.5 are miscible within the whole range of surface pressures, while monolayers richer in edelfosine mix in the pressure region below ca. 37.6 mN/m, which corresponds to the collapse of pure edelfosine monolayer. At this very surface pressure, edelfosine is expelled from the mixed monolayer and the remaining film is composed by surface complexes of high stability. The hypothesis of complex formation explains the results performed in vitro on cell cultures, indicating that the increase of cholesterol content significantly reduces the uptake of edelfosine

The role of "inert" surface chemistry in marine biofouling prevention.

Science.gov (United States)

Rosenhahn, Axel; Schilp, Sören; Kreuzer, Hans Jürgen; Grunze, Michael

2010-05-07

The settlement and colonization of marine organisms on submerged man-made surfaces is a major economic problem for many marine industries. The most apparent detrimental effects of biofouling are increased fuel consumption of ships, clogging of membranes and heat exchangers, disabled underwater sensors, and growth of biofoulers in aquaculture systems. The presently common-but environmentally very problematic-way to deal with marine biofouling is to incorporate biocides, which use biocidal products in the surface coatings to kill the colonizing organisms, into the surface coatings. Since the implementation of the International Maritime Organization Treaty on biocides in 2008, the use of tributyltin (TBT) is restricted and thus environmentally benign but effective surface coatings are required. In this short review, we summarize the different strategies which are pursued in academia and industry to better understand the mechanisms of biofouling and to develop strategies which can be used for industrial products. Our focus will be on chemically "inert" model surface coatings, in particular oligo- and poly(ethylene glycol) (OEG and PEG) functionalized surface films. The reasons for choosing this class of chemistry as an example are three-fold: Firstly, experiments on spore settlement on OEG and PEG coatings help to understand the mechanism of non-fouling of highly hydrated interfaces; secondly, these studies defy the common assumption that surface hydrophilicity-as measured by water contact angles-is an unambiguous and predictive tool to determine the fouling behavior on the surface; and thirdly, choosing this system is a good example for "interfacial systems chemistry": it connects the behavior of unicellular marine organisms with the antifouling properties of a hydrated surface coating with structural and electronic properties as derived from ab initio quantum mechanical calculations using the electronic wave functions of oxygen, hydrogen, and carbon. This short

Self-assembled monolayer structures of hexadecylamine on Cu surfaces: density-functional theory.

Science.gov (United States)

Liu, Shih-Hsien; Balankura, Tonnam; Fichthorn, Kristen A

2016-12-07

We used dispersion-corrected density-functional theory to probe possible structures for adsorbed layers of hexadecylamine (HDA) on Cu(100) and Cu(111). HDA forms self-assembled layers on these surfaces, analogous to alkanethiols on various metal surfaces, and it binds by donating electrons in the amine group to the Cu surface atoms, consistent with experiment. van der Waals interactions between the alkyl tails of HDA molecules are stronger than the interaction between the amine group and the Cu surfaces. Strong HDA-tail interactions lead to coverage-dependent tilting of the HDA layers, such that the tilt angle is larger for lower coverages. At full monolayer coverage, the energetically preferred binding configuration for HDA on Cu(100) is a (5 × 3) pattern - although we cannot rule out incommensurate structures - while the pattern is preferred on Cu(111). A major motivation for this study is to understand the experimentally observed capability of HDA as a capping agent for producing {100}-faceted Cu nanocrystals. Consistent with experiment, we find that HDA binds more strongly to Cu(100) than to Cu(111). This strong binding stems from the capability of HDA to form more densely packed layers on Cu(100), which leads to stronger HDA-tail interactions, as well as the stronger binding of the amine group to Cu(100). We estimate the surface energies of HDA-covered Cu(100) and Cu(111) surfaces and find that these surfaces are nearly isoenergetic. By drawing analogies to previous theoretical work, it seems likely that HDA-covered Cu nanocrystals could have kinetic shapes that primarily express {100} facets, as is seen experimentally.

Voltammetry and In Situ Scanning Tunnelling Microscopy of De Novo Designed Heme Protein Monolayers on Au(111)-Electrode Surfaces

DEFF Research Database (Denmark)

Albrecht, Tim; Li, Wu; Haehnel, Wolfgang

2006-01-01

to the tunnelling current, apparently due to slow electron transfer kinetics. As a consequence, STM images of heme-containing and heme-free MOP-C did not reveal any notable differences in apparent height or physical extension. The apparent height of heme-containing MOP-C did not show any dependence on the substrate...... potential being varied around the redox potential of the protein. The mere presence of an accessible molecular energy level is not sufficient to result in detectable tunnelling current modulation. (c) 2006 Elsevier B.V. All rights reserved.......In the present work, we report the electrochemical characterization and in situ scanning tunnelling microscopy (STM) studies of monolayers of an artificial de novo designed heme protein MOP-C, covalently immobilized on modified Au(111) surfaces. The protein forms closely packed monolayers, which...

Liquid-Phase Exfoliation into Monolayered BiOBr Nanosheets for Photocatalytic Oxidation and Reduction

Energy Technology Data Exchange (ETDEWEB)

Yu, Hongjian [Beijing; Huang, Hongwei [Beijing; Xu, Kang [Center; Hao, Weichang [Center; Guo, Yuxi [Beijing; Wang, Shuobo [Beijing; Shen, Xiulin [Beijing; Pan, Shaofeng [Beijing; Zhang, Yihe [Beijing

2017-09-26

Monolayered photocatalytic materials have attracted huge research interests in terms of their large specific surface area and ample active sites. Sillén-structured layered BiOX (X = Cl, Br, I) casts great prospects owing to their strong photo-oxidation ability and high stability. Fabrication of monolayered BiOX by a facile, low-cost, and scalable approach is highly challenging and anticipated. Herein, we describe the large-scale preparation of monolayered BiOBr nanosheets with a thickness of ~0.85 nm via a readily achievable liquid-phase exfoliation strategy with assistance of formamide at ambient conditions. The as-obtained monolayered BiOBr nanosheets are allowed diverse superiorities, such as enhanced specific surface area, promoted band structure, and strengthened charge separation. Profiting from these benefits, the advanced BiOBr monolayers not only show excellent adsorption and photodegradation performance for treating contaminants, but also demonstrate a greatly promoted photocatalytic activity for CO2 reduction into CO and CH4. Additionally, monolayered BiOI nanosheets have also been obtained by the same synthetic approach. Our work offers a mild and general approach for preparation of monolayered BiOX, and may have huge potential to be extended to the synthesis of other single-layer two-dimensional materials.

Tuning optoelectronic properties of small semiconductor nanocrystals through surface ligand chemistry

Science.gov (United States)

Lawrence, Katie N.

, can increase the stability of SNCs during solution-phase electrochemical characterization. Therefore, we utilized these properties to characterize solution-state electrochemical properties and photocatalytic activity of ternary copper indium diselenide (CuInSe2) SNCs as a function of their size and surface ligand chemistry. Electrochemical characterization of our PEG-thiolate-coated SNCs showed that the thermodynamic driving force (-?G) for oxygen reduction, which increased with decreasing bandgap, was a major contributor to the overall photocatalytic reaction. Additionally, phenol degradation efficiency was monitored in which the smallest diameter SNC and shortest chain length of PEG provided the highest efficiency. The information provided herein could be used to produce superior SNC photocatalysts for a variety of applications including oxidation of organic contaminants, conversion of water to hydrogen gas, and decomposition of crude oil or pesticides. Therefore, we believe our work will significantly advance quantitative electrochemical characterization of SNCs and allow for the design of highly efficient, sustainable photocatalysts resulting in economic and environmental benefits.

Using advanced surface complexation models for modelling soil chemistry under forests: Solling forest, Germany

Energy Technology Data Exchange (ETDEWEB)

Bonten, Luc T.C., E-mail: luc.bonten@wur.nl [Alterra-Wageningen UR, Soil Science Centre, P.O. Box 47, 6700 AA Wageningen (Netherlands); Groenenberg, Jan E. [Alterra-Wageningen UR, Soil Science Centre, P.O. Box 47, 6700 AA Wageningen (Netherlands); Meesenburg, Henning [Northwest German Forest Research Station, Abt. Umweltkontrolle, Sachgebiet Intensives Umweltmonitoring, Goettingen (Germany); Vries, Wim de [Alterra-Wageningen UR, Soil Science Centre, P.O. Box 47, 6700 AA Wageningen (Netherlands)

2011-10-15

Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well. - Highlights: > Surface complexation models can be well applied in field studies. > Soil chemistry under a forest site is adequately modelled using generic parameters. > The model is easily extended with extra elements within the existing framework. > Surface complexation models can show the linkages between major soil chemistry and trace element behaviour. - Surface complexation models with generic parameters make calibration of sorption superfluous in dynamic modelling of deposition impacts on soil chemistry under nature areas.

Using advanced surface complexation models for modelling soil chemistry under forests: Solling forest, Germany

International Nuclear Information System (INIS)

Bonten, Luc T.C.; Groenenberg, Jan E.; Meesenburg, Henning; Vries, Wim de

2011-01-01

Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well. - Highlights: → Surface complexation models can be well applied in field studies. → Soil chemistry under a forest site is adequately modelled using generic parameters. → The model is easily extended with extra elements within the existing framework. → Surface complexation models can show the linkages between major soil chemistry and trace element behaviour. - Surface complexation models with generic parameters make calibration of sorption superfluous in dynamic modelling of deposition impacts on soil chemistry under nature areas.

A trough for improved SFG spectroscopy of lipid monolayers

Science.gov (United States)

Franz, Johannes; van Zadel, Marc-Jan; Weidner, Tobias

2017-05-01

Lipid monolayers are indispensable model systems for biological membranes. The main advantage over bilayer model systems is that the surface pressure within the layer can be directly and reliably controlled. The sensitive interplay between surface pressure and temperature determines the molecular order within a model membrane and consequently determines the membrane phase behavior. The lipid phase is of crucial importance for a range of membrane functions such as protein interactions and membrane permeability. A very reliable method to probe the structure of lipid monolayers is sum frequency generation (SFG) vibrational spectroscopy. Not only is SFG extremely surface sensitive but it can also directly access critical parameters such as lipid order and orientation, and it can provide valuable information about protein interactions along with interfacial hydration. However, recent studies have shown that temperature gradients caused by high power laser beams perturb the lipid layers and potentially obscure the spectroscopic results. Here we demonstrate how the local heating problem can be effectively reduced by spatially distributing the laser pulses on the sample surface using a translating Langmuir trough for SFG experiments at lipid monolayers. The efficiency of the trough is illustrated by the detection of enhanced molecular order due to reduced heat load.

Applications of surface analysis and surface theory in tribology

Science.gov (United States)

Ferrante, John

1989-01-01

Tribology, the study of adhesion, friction and wear of materials, is a complex field which requires a knowledge of solid state physics, surface physics, chemistry, material science, and mechanical engineering. It has been dominated, however, by the more practical need to make equipment work. With the advent of surface analysis and advances in surface and solid-state theory, a new dimension has been added to the analysis of interactions at tribological interfaces. In this paper the applications of tribological studies and their limitations are presented. Examples from research at the NASA Lewis Research Center are given. Emphasis is on fundamental studies involving the effects of monolayer coverage and thick films on friction and wear. A summary of the current status of theoretical calculations of defect energetics is presented. In addition, some new theoretical techniques which enable simplified quantitative calculations of adhesion, fracture, and friction are discussed.

Electronic transport through organophosphonate monolayers on silicon/silicon dioxide substrates

Energy Technology Data Exchange (ETDEWEB)

Bora, Achyut; Pathak, Anshuma; Tornow, Marc [Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Liao, Kung-Ching; Schwartz, Jeffrey [Department of Chemistry, Princeton University, NJ (United States); Cattani-Scholz, Anna; Abstreiter, Gerhard [Walter Schottky Institut, TU Muenchen (Germany)

2011-07-01

Understanding the electronic transport through layered systems of organic functional layers on semiconductor surfaces is of major importance for future applications in nanoelectronics, photovoltaics and sensors. We have prepared self-assembled monolayers (SAMs) of 9,10-diphenyl-2,6-diphosphono-anthracene and 11-hydroxyundecyl phosphonic acid precursors on highly p-doped silicon surfaces coated with a 1 nm SiO{sub 2} layer. Contact angle, AFM and ellipsometry evidenced the homogeneity of the formed SAMs, and their thickness was determined to be 0.82{+-}0.07 nm and 1.13{+-}0.09 nm, respectively. We provided large area electrical contacts on top of the SAMs by a hanging Hg drop electrode. The measured I-V characteristics revealed an enhanced conductance of the aromatic vs. the aliphatic compounds, with current densities of the order of 10 A/m{sup 2} and 0.01 A/m{sup 2}, at 0.5 V, respectively. We analyzed the data in terms of non-resonant tunneling through the combined oxide-SAM barrier and found good qualitative agreement up to 0.2 V bias. Preliminary measurements on organized bilayers of anthracene bisphosphonates that were grown using techniques of coordination chemistry are discussed, too.

Penetration of Milk-Derived Antimicrobial Peptides into Phospholipid Monolayers as Model Biomembranes

Directory of Open Access Journals (Sweden)

Wanda Barzyk

2013-01-01

Full Text Available Three antimicrobial peptides derived from bovine milk proteins were examined with regard to penetration into insoluble monolayers formed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC or 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol sodium salt (DPPG. Effects on surface pressure (Π and electric surface potential (ΔV were measured, Π with a platinum Wilhelmy plate and ΔV with a vibrating plate. The penetration measurements were performed under stationary diffusion conditions and upon the compression of the monolayers. The two type measurements showed greatly different effects of the peptide-lipid interactions. Results of the stationary penetration show that the peptide interactions with DPPC monolayer are weak, repulsive, and nonspecific while the interactions with DPPG monolayer are significant, attractive, and specific. These results are in accord with the fact that antimicrobial peptides disrupt bacteria membranes (negative while no significant effect on the host membranes (neutral is observed. No such discrimination was revealed from the compression isotherms. The latter indicate that squeezing the penetrant out of the monolayer upon compression does not allow for establishing the penetration equilibrium, so the monolayer remains supersaturated with the penetrant and shows an under-equilibrium orientation within the entire compression range, practically.

Molecular layer deposition of APTES on silicon nanowire biosensors: Surface characterization, stability and pH response

International Nuclear Information System (INIS)

Liang, Yuchen; Huang, Jie; Zang, Pengyuan; Kim, Jiyoung; Hu, Walter

2014-01-01

Graphical abstract: - Abstract: We report the use of molecular layer deposition (MLD) for depositing 3-aminopropyltriethoxysilane (APTES) on a silicon dioxide surface. The APTES monolayer was characterized using spectroscopic ellipsometry, contact angle goniometry, and atomic force microscopy. Effects of reaction time of repeating pulses and simultaneous feeding of water vapor with APTES were tested. The results indicate that the synergistic effects of water vapor and reaction time are significant for the formation of a stable monolayer. Additionally, increasing the number of repeating pulses improved the APTES surface coverage but led to saturation after 10 pulses. In comparing MLD with solution-phase deposition, the APTES surface coverage and the surface quality were nearly equivalent. The hydrolytic stability of the resulting films was also studied. The results confirmed that the hydrolysis process was necessary for MLD to obtain stable surface chemistry. Furthermore, we compared the pH sensing results of Si nanowire field effect transistors (Si NWFETs) modified by both the MLD and solution methods. The highly repeatable pH sensing results reflected the stability of APTES monolayers. The results also showed an improved pH response of the sensor prepared by MLD compared to the one prepared by the solution treatment, which indicated higher surface coverage of APTES

Molecular layer deposition of APTES on silicon nanowire biosensors: Surface characterization, stability and pH response

Science.gov (United States)

Liang, Yuchen; Huang, Jie; Zang, Pengyuan; Kim, Jiyoung; Hu, Walter

2014-12-01

We report the use of molecular layer deposition (MLD) for depositing 3-aminopropyltriethoxysilane (APTES) on a silicon dioxide surface. The APTES monolayer was characterized using spectroscopic ellipsometry, contact angle goniometry, and atomic force microscopy. Effects of reaction time of repeating pulses and simultaneous feeding of water vapor with APTES were tested. The results indicate that the synergistic effects of water vapor and reaction time are significant for the formation of a stable monolayer. Additionally, increasing the number of repeating pulses improved the APTES surface coverage but led to saturation after 10 pulses. In comparing MLD with solution-phase deposition, the APTES surface coverage and the surface quality were nearly equivalent. The hydrolytic stability of the resulting films was also studied. The results confirmed that the hydrolysis process was necessary for MLD to obtain stable surface chemistry. Furthermore, we compared the pH sensing results of Si nanowire field effect transistors (Si NWFETs) modified by both the MLD and solution methods. The highly repeatable pH sensing results reflected the stability of APTES monolayers. The results also showed an improved pH response of the sensor prepared by MLD compared to the one prepared by the solution treatment, which indicated higher surface coverage of APTES.

Studying the influence of substrate conductivity on the optoelectronic properties of quantum dots langmuir monolayer

Science.gov (United States)

Al-Alwani, Ammar J.; Chumakov, A. S.; Begletsova, N. N.; Shinkarenko, O. A.; Markin, A. V.; Gorbachev, I. A.; Bratashov, D. N.; Gavrikov, M. V.; Venig, S. B.; Glukhovskoy, E. G.

2018-04-01

The formation of CdSe quantum dots (QDs) monolayers was studied by Langmuir Blodgett method. The fluorescence (PL) spectra of QD monolayers were investigated at different substrate type (glass, silicon and ITO glass) and the influence of graphene sheets layer (as a conductive surface) on the QDs properties has also been studied. The optoelectronic properties of QDs can be tuned by deposition of insulating nano-size layers of the liquid crystal between QDs and conductive substrate. The monolayer of QDs transferred on conductive surface (glass with ITO) has lowest intensity of PL spectra due to quenching effect. The PL intensity of QDs could be tuned by using various type of substrates or/and by transformed high conductive layer. Also the photooxidation processes of CdSe QDs monolayer on the solid surface can be controlled by selection of suitable substrate. The current-voltage (I–V) characteristics of QDs thin film on ITO surface was studied using scanning tunneling microscope (STM).

Epitaxially Grown Ultra-Flat Self-Assembling Monolayers with Dendrimers

Directory of Open Access Journals (Sweden)

Takane Imaoka

2018-02-01

Full Text Available Mono-molecular films formed by physical adsorption and dendrimer self-assembly were prepared on various substrate surfaces. It was demonstrated that a uniform dendrimer-based monolayer on the subnanometer scale can be easily constructed via simple dip coating. Furthermore, it was shown that an epitaxially grown monolayer film reflecting the crystal structure of the substrate (highly ordered pyrolytic graphite (HOPG can also be formed by aligning specific conditions.

Study of the interaction of lactoferricin B with phospholipid monolayers and bilayers.

Science.gov (United States)

Arseneault, Marjolaine; Bédard, Sarah; Boulet-Audet, Maxime; Pézolet, Michel

2010-03-02

Bovine lactoferricin (LfcinB) is an antimicrobial peptide obtained from the pepsin cleavage of lactoferrin. The activity of LfcinB has been extensively studied on diverse pathogens, but its mechanism of action still has to be elucidated. Because of its nonspecificity, its mode of action is assumed to be related to interactions with membranes. In this study, the interaction of LfcinB with a negatively charged monolayer of dipalmitoylphosphatidylglycerol has been investigated as a function of the surface pressure of the lipid film using in situ Brewster angle and polarization modulation infrared reflection absorption spectroscopy and on transferred monolayers by atomic force microscopy and polarized attenuated total reflection infrared spectroscopy. The data show clearly that LfcinB forms stable films at the air-water interface. They also reveal that the interaction of LfcinB with the lipid monolayer is modulated by the surface pressure. At low surface pressure, LfcinB inserts within the lipid film with its long molecular axis oriented mainly parallel to the acyl chains, while at high surface pressure, LfcinB is adsorbed under the lipid film, the hairpin being preferentially aligned parallel to the plane of the interface. The threshold for which the behavior changes is 20 mN/m. At this critical surface pressure, LfcinB interacts with the monolayer to form discoidal lipid-peptide assemblies. This structure may actually represent the mechanism of action of this peptide. The results obtained on monolayers are correlated by fluorescent probe release measurements of dye-containing vesicles made of lipids in different phases and support the important role of the lipid fluidity and packing on the activity of LfcinB.

Surface plasmon resonance spectroscopic study of UV-addressable phenylalanine sensing based on a self-assembled spirooxazine derivative monolayer

International Nuclear Information System (INIS)

Suk, Shinae; Suh, Hee-Jung; Gun An, Won; Kim, Jae-Ho; Jin, Sung-Ho; Kim, Sung-Hoon; Gal, Yeong-Soon; Koh, Kwangnak

2004-01-01

Light-addressable compounds are very interesting due to the possibilities of their practical use such as optical switches and memories or variable transmission materials. For example, transportation of phenylalanine across liposomal bilayers mediated by a photoresponsive carrier like spirooxazine through electrostatic interaction between phenylalanine and spirooxazine derivative. Thus, the spirooxazine is expected to form a UV-addressable phenylalanine sensing interface. In this study, we prepared phenylalanine sensing interface of a spirooxazine derivative by self-assembly technique and evaluated interaction between a spirooxazine moiety and phenylalanine with a surface plasmon resonance (SPR). The refractive index change of monolayer caused by interaction between a spirooxazine derivative and phenylalanine led to the SPR angle shifts upon UV irradiation. The SPR angle shift increased with increasing the concentration of phenylalanine solution. These results indicated that the spirooxazine derivative self-assembled monolayer (SAM) has an application potential for UV-addressable phenylalanine sensing

Uranium(VI) sorption onto magnetite. Increasing confidence in surface complexation models using chemically evident surface chemistry

Energy Technology Data Exchange (ETDEWEB)

Bok, Frank [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

2017-06-01

Surface complexation models have made great efforts in describing the sorption of various radionuclides on naturally occurring mineral phases. Unfortunately, many of the published sorption parameter sets are built upon unrealistic or even wrong surface chemistry. This work describes the benefit of combining spectroscopic and batch sorption experimental data to create a reliable and consistent surface complexation parameter set.

Nanoscale Trapping and Squeeze-Out of Confined Alkane Monolayers.

Science.gov (United States)

Gosvami, N N; O'Shea, S J

2015-12-01

We present combined force curve and conduction atomic force microscopy (AFM) data for the linear alkanes CnH2n+2 (n = 10, 12, 14, 16) confined between a gold-coated AFM tip and a graphite surface. Solvation layering is observed in the force curves for all liquids, and conduction AFM is used to study in detail the removal of the confined (mono)layer closest to the graphite surface. The squeeze-out behavior of the monolayer can be very different depending upon the temperature. Below the monolayer melting transition temperatures the molecules are in an ordered state on the graphite surface, and fast and complete removal of the confined molecules is observed. However, above the melting transition temperature the molecules are in a disordered state, and even at large applied pressure a few liquid molecules are trapped within the tip-sample contact zone. These findings are similar to a previous study for branched alkanes [ Gosvami Phys. Rev. Lett. 2008, 100, 076101 ], but the observation for the linear alkane homologue series demonstrates clearly the dependence of the squeeze-out and trapping on the state of the confined material.

Effect of dispersion on surface interactions of cobalt(II) octaethylporphyrin monolayer on Au(111) and HOPG(0001) substrates: a comparative first principles study.

Science.gov (United States)

Chilukuri, Bhaskar; Mazur, Ursula; Hipps, K W

2014-07-21

A density functional theory study of a cobalt(II) octaethylporphyrin (CoOEP) monolayer on Au(111) and HOPG(0001) surfaces was performed under periodic boundary conditions. Calculations with and without dispersion corrections are performed and the effect of van der Waals forces on the interface properties is analyzed. Calculations have determined that the CoOEP molecule tends to bind at the 3-fold and the 6-fold center sites on Au(111) and HOPG(0001), respectively. Geometric optimizations at the center binding sites have indicated that the porphyrin molecules (in the monolayer) lie flat on both substrates. Calculations also reveal that the CoOEP monolayer binds slightly more strongly to Au(111) than to HOPG(0001). Charge density difference plots disclose that charge is redistributed mostly around the porphyrin plane and the first layer of the substrates. Dispersion interactions cause a larger substrate to molecule charge pushback on Au(111) than on HOPG. CoOEP adsorption tends to lower the work functions of either substrate, qualitatively agreeing with the experimental photoelectron spectroscopic data. Comparison of the density of states (DOS) of the isolated CoOEP molecule with that on gold and HOPG substrates showed significant band shifts around the Fermi energy due to intermolecular orbital hybridization. Simulated STM images were plotted with the Tersoff-Hamann approach using the local density of states, which also agree with the experimental results. This study elucidates the role of dispersion for better describing porphyrin-substrate interactions. A DFT based overview of geometric, adsorption and electronic properties of a porphyrin monolayer on conductive surfaces is presented.

Vertical uniformity of cells and nuclei in epithelial monolayers.

Science.gov (United States)

Neelam, Srujana; Hayes, Peter Robert; Zhang, Qiao; Dickinson, Richard B; Lele, Tanmay P

2016-01-22

Morphological variability in cytoskeletal organization, organelle position and cell boundaries is a common feature of cultured cells. Remarkable uniformity and reproducibility in structure can be accomplished by providing cells with defined geometric cues. Cells in tissues can also self-organize in the absence of directing extracellular cues; however the mechanical principles for such self-organization are not understood. We report that unlike horizontal shapes, the vertical shapes of the cell and nucleus in the z-dimension are uniform in cells in cultured monolayers compared to isolated cells. Apical surfaces of cells and their nuclei in monolayers were flat and heights were uniform. In contrast, isolated cells, or cells with disrupted cell-cell adhesions had nuclei with curved apical surfaces and variable heights. Isolated cells cultured within micron-sized square wells displayed flat cell and nuclear shapes similar to cells in monolayers. Local disruption of nuclear-cytoskeletal linkages resulted in spatial variation in vertical uniformity. These results suggest that competition between cell-cell pulling forces that expand and shorten the vertical cell cross-section, thereby widening and flattening the nucleus, and the resistance of the nucleus to further flattening results in uniform cell and nuclear cross-sections. Our results reveal the mechanical principles of self-organized vertical uniformity in cell monolayers.

Surface reconstitution of glucose oxidase onto a norbornylogous bridge self-assembled monolayer

International Nuclear Information System (INIS)

Liu Jingquan; Paddon-Row, Michael N.; Gooding, J. Justin

2006-01-01

An electrode construct was fabricated in which a self-assembled monolayer containing a novel norbornylogous bridge was covalently attached to flavin adenine dinucleotide (FAD), the redox active centre of several oxidase enzymes. The electrochemistry of the construct was investigated before and after the reconstitution of glucose oxidase around the surface bound FAD. Rapid rates of electron transfer were observed both before and after the reconstitution of biocatalytically active enzyme. However, no biocatalytic activity was observed under anaerobic conditions suggesting the a lack of enzyme turnover through direct electron transfer. It is proposed that a decrease in the electronic coupling between the redox active FAD and the electrode following reconstitution of the glucose oxidase - a probable consequence of the FAD being immersed in a protein environment - was responsible for the inability of the enzyme to be turned over under anaerobic conditions

Morphology, defect evolutions and nano-mechanical anisotropy of behenic acid monolayer

International Nuclear Information System (INIS)

Yang Guanghong; Jiang Xiaohong; Dai Shuxi; Cheng Gang; Zhang Xingtang; Du Zuliang

2010-01-01

Langmuir-Blodgett monolayers of behenic acid (BA) were prepared by the vertical deposition method and their morphological evolutions and nano-mechanical anisotropy were studied by atomic force microscopy (AFM) and lateral force microscopy. Results show that there are platforms in the differential surface pressure-area (π-A) isotherm presenting linear relations between the chain tilting angles and surface pressures. The reorganization, appearance and disappearance of defects such as pinholes and holes can strongly affect the profile of π-A isotherm; AFM images reflect evolution rules from pinholes to holes, and from monolayer to bilayers along with compression and relaxation of structures in BA monolayer. Due to higher molecule density and larger real contact area, the tip-monolayer contacts at 15 and 25 mN/m correspond to the Derjaguin-Muller-Toporov (DMT) model showing long-ranged interaction forces. But owing to more easily-deformed conformations, contacts at 5 and 35 mN/m accord with the Johnson-Kendall-Robert and DMT transition cases exhibiting short-ranged interface interactions. A little higher friction is proved in the direction perpendicular to the deposition.

Reactions of BBr(n)(+) (n = 0--2) at fluorinated and hydrocarbon self-assembled monolayer surfaces: observations of chemical selectivity in ion--surface scattering.

Science.gov (United States)

Wade, N; Shen, J; Koskinen, J; Cooks, R G

2001-07-01

Ion-surface reactions involving BBr(n)(+) (n = 0--2) with a fluorinated self-assembled monolayer (F-SAM) surface were investigated using a multi-sector scattering mass spectrometer. Collisions of the B(+) ion yield BF(2)(+) at threshold energy with the simpler product ion BF(+)* appearing at higher collision energies and remaining of lower abundance than BF(2)(+) at all energies examined. In addition, the reactively sputtered ion CF(+) accompanies the formation of BF(2)(+) at low collision energies. These results stand in contrast with previous data on the ion-surface reactions of atomic ions with the F-SAM surface in that the threshold and most abundant reaction products in those cases involved the abstraction of a single fluorine atom. Gas-phase enthalpy data are consistent with BF(2)(+) being the thermodynamically favored product. The fact that the abundance of BF(2)(+) is relatively low and relatively insensitive to changes in collision energy suggests that this reaction proceeds through an entropically demanding intermediate at the vacuum--surface interface, one which involves interaction of the B(+) ion simultaneously with two fluorine atoms. By contrast with the reaction of B(+), the odd-electron species BBr(+)* reacts with the F-SAM surface to yield an abundant single-fluorine abstraction product, BBrF(+). Corresponding gas-phase ion--molecule experiments involving B(+) and BBr(+)* with C(6)F(14) also yield the products BF(+)* and BF(2)(+), but only in extremely low abundances and with no preference for double fluorine abstraction. Ion--surface reactions were also investigated for BBr(n)(+) (n = 0-2) with a hydrocarbon self-assembled monolayer (H-SAM) surface. Reaction of the B(+) ion and dissociative reactions of BBr(+)* result in the formation of BH(2)(+), while the thermodynamically less favorable product BH(+)* is not observed. Collisions of BBr(2)(+) with the H-SAM surface yield the dissociative ion-surface reaction products, BBrH(+) and BBrCH(3

11-Hydroxyundecyl octadecyl disulfide self-assembled monolayers on Au(1 1 1)

Energy Technology Data Exchange (ETDEWEB)

Albayrak, Erol [Department of Materials and Metallurgical Engineering, Ahi Evran University, Kırşehir 40000 (Turkey); Karabuga, Semistan [Department of Chemistry, Kahramanmaraş Sütçü İmam University, Kahramanmaraş 46030 (Turkey); Bracco, Gianangelo [CNR-IMEM and Department of Physics, University of Genoa, via Dodecaneso 33, Genoa 16146 (Italy); Danışman, M. Fatih, E-mail: danisman@metu.edu.tr [Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey)

2014-08-30

Highlights: • 11-Hydroxyundecyl octadecyl disulfide self-assembled monolayers on Au(1 1 1) surface were grown by supersonic molecular beam deposition. • Two different lying down monolayer phases were observed depending on the substrate temperature. • High temperature monolayer phase has a diffraction pattern similar to that of mercaptoundecanol SAMs. • Desorption from several different chemisorbed and physisorbed states were observed. - Abstract: Here, we report a helium atom diffraction study of 11-hydroxyundecyl octadecyl disulfide (CH{sub 3}-(CH{sub 2}){sub 17}-S-S-(CH{sub 2}){sub 11}-OH, HOD) self-assembled monolayers (SAMs) produced by supersonic molecular beam deposition (SMBD). Two different lying down monolayer phases were observed depending on the substrate temperature. At low temperatures a poorly ordered phase was observed, while the diffraction patterns of the film grown at high temperatures were similar to that of mercaptoundecanol (MUD) SAMs reported previously in the literature. The transition from the low temperature phase to the high temperature phase is due to S-S bond cleavage at the surface. Desorption from several different chemisorbed and physisorbed states were observed with energies in the same range as observed for MUD and octadecanelthiol (ODT) SAMs.

Mirror-finished superhydrophobic aluminum surfaces modified by anodic alumina nanofibers and self-assembled monolayers

Science.gov (United States)

Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

2018-05-01

We demonstrate mirror-finished superhydrophobic aluminum surfaces fabricated via the formation of anodic alumina nanofibers and subsequent modification with self-assembled monolayers (SAMs). High-density anodic alumina nanofibers were formed on the aluminum surface via anodizing in a pyrophosphoric acid solution. The alumina nanofibers became tangled and bundled by further anodizing at low temperature because of their own weight, and the aluminum surface was completely covered by the long falling nanofibers. The nanofiber-covered aluminum surface exhibited superhydrophilic behavior, with a contact angle measuring less than 10°. As the nanofiber-covered aluminum surface was modified with n-alkylphosphonic acid SAMs, the water contact angle drastically shifted to superhydrophobicity, measuring more than 150°. The contact angle increased with the applied voltage during pyrophosphoric acid anodizing, the anodizing time, and the number of carbon atoms contained in the SAM molecules modified on the alumina nanofibers. By optimizing the anodizing and SAM-modification conditions, superhydrophobic behavior could be achieved with only a brief pyrophosphoric acid anodizing period of 3 min and subsequent simple immersion in SAM solutions. The superhydrophobic aluminum surface exhibited a high reflectance, measuring approximately 99% across most of the visible spectrum, similar to that of an electropolished aluminum surface. Therefore, our mirror-finished superhydrophobic aluminum surface based on anodic alumina nanofibers and SAMs can be used as a reflective mirror in various optical applications such as concentrated solar power systems.

Ferroelectrics: A pathway to switchable surface chemistry and catalysis

Science.gov (United States)

Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

2016-08-01

It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

Surface chemistry and bonding configuration of ultrananocrystalline diamond surfaces and their effects on nanotribological properties

International Nuclear Information System (INIS)

Sumant, A. V.; Grierson, D. S.; Carpick, R. W.; Gerbi, J. E.; Carlisle, J. A.; Auciello, O.

2007-01-01

We present a comprehensive study of surface composition and nanotribology for ultrananocrystalline diamond (UNCD) surfaces, including the influence of film nucleation on these properties. We describe a methodology to characterize the underside of the films as revealed by sacrificial etching of the underlying substrate. This enables the study of the morphology and composition resulting from the nucleation and initial growth of the films, as well as the characterization of nanotribological properties which are relevant for applications including micro-/nanoelectromechanical systems. We study the surface chemistry, bonding configuration, and nanotribological properties of both the topside and the underside of the film with synchrotron-based x-ray absorption near-edge structure spectroscopy to identify the bonding state of the carbon atoms, x-ray photoelectron spectroscopy to determine the surface chemical composition, Auger electron spectroscopy to further verify the composition and bonding configuration, and quantitative atomic force microscopy to study the nanoscale topography and nanotribological properties. The films were grown on SiO 2 after mechanically polishing the surface with detonation synthesized nanodiamond powder, followed by ultrasonication in a methanol solution containing additional nanodiamond powder. The sp 2 fraction, morphology, and chemistry of the as-etched underside are distinct from the topside, exhibiting a higher sp 2 fraction, some oxidized carbon, and a smoother morphology. The nanoscale single-asperity work of adhesion between a diamond nanotip and the as-etched UNCD underside is far lower than for a silicon-silicon interface (59.2±2 vs 826±186 mJ/m 2 , respectively). Exposure to atomic hydrogen dramatically reduces nanoscale adhesion to 10.2±0.4 mJ/m 2 , at the level of van der Waals' interactions and consistent with recent ab initio calculations. Friction is substantially reduced as well, demonstrating a direct link between the

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.

Switchable Hydrophobic-Hydrophilic Surfaces

CERN Document Server

Bunker, B C; Huber, D L; Kent, M S; Kushmerick, J G; Lopez, G P; Manginell, R P; Méndez, S E; Yim, H

2002-01-01

Tethered films of poly n-isopropylacrylamide (PNIPAM) films have been developed as materials that can be used to switch the chemistry of a surface in response to thermal activation. In water, PNIPAM exhibits a thermally-activated phase transition that is accompanied by significant changes in polymer volume, water contact angle, and protein adsorption characteristics. New synthesis routes have been developed to prepare PNIPAM films via in-situ polymerization on self-assembled monolayers. Swelling transitions in tethered films have been characterized using a wide range of techniques including surface plasmon resonance, attenuated total reflectance infrared spectroscopy, interfacial force microscopy, neutron reflectivity, and theoretical modeling. PNIPAM films have been deployed in integrated microfluidic systems. Switchable PNIPAM films have been investigated for a range of fluidic applications including fluid pumping via surface energy switching and switchable protein traps for pre-concentrating and separating...

The langmuir monolayer: an efficient model for studying interfacial properties of biomembranes

International Nuclear Information System (INIS)

Cirak, J.; Sokolsky, M.; Dobrocka, E.; Weis, M.

2012-01-01

In this communication, we describe aspects of monolayer technology by focusing on effects of calcium ions on physical properties of phospholipid monolayers using results of measurements of surface pressure, x-ray reflectivity and AFM. These experiments are motivated by the search for lipid-DNA complexes with high transfection efficiency but without toxicity which might be a promising tool in gene therapy. In each part methodological importance is stressed and its specificity for studying molecular interactions at a lipid monolayer. (authors)

Monolayer-functionalized microfluidics devices for optical sensing of acidity

NARCIS (Netherlands)

Mela, P.; Onclin, S.; Goedbloed, M.H.; Levi, S.; Garcia Parajo, M.F.; van Hulst, N.F.; Ravoo, B.J.; Reinhoudt, David; van den Berg, Albert

This paper describes the integration of opto-chemosensors in microfluidics networks. Our technique exploits the internal surface of the network as a platform to build a sensing system by coating the surface with a self-assembled monolayer and subsequently binding a fluorescent sensing molecule to

Stress relaxation in quasi-two-dimensional self-assembled nanoparticle monolayers

Science.gov (United States)

Boucheron, Leandra S.; Stanley, Jacob T.; Dai, Yeling; You, Siheng Sean; Parzyck, Christopher T.; Narayanan, Suresh; Sandy, Alec R.; Jiang, Zhang; Meron, Mati; Lin, Binhua; Shpyrko, Oleg G.

2018-05-01

We experimentally probed the stress relaxation of a monolayer of iron oxide nanoparticles at the water-air interface. Upon drop-casting onto a water surface, the nanoparticles self-assembled into islands of two-dimensional hexagonally close packed crystalline domains surrounded by large voids. When compressed laterally, the voids gradually disappeared as the surface pressure increased. After the compression was stopped, the surface pressure (as measured by a Wilhelmy plate) evolved as a function of the film aging time with three distinct timescales. These aging dynamics were intrinsic to the stressed state built up during the non-equilibrium compression of the film. Utilizing x-ray photon correlation spectroscopy, we measured the characteristic relaxation time (τ ) of in-plane nanoparticle motion as a function of the aging time through both second-order and two-time autocorrelation analysis. Compressed and stretched exponential fitting of the intermediate scattering function yielded exponents (β ) indicating different relaxation mechanisms of the films under different compression stresses. For a monolayer compressed to a lower surface pressure (between 20 mN/m and 30 mN/m), the relaxation time (τ ) decreased continuously as a function of the aging time, as did the fitted exponent, which transitioned from being compressed (>1 ) to stretched (stress release through crystalline domain reorganization. However, for a monolayer compressed to a higher surface pressure (around 40 mN/m), the relaxation time increased continuously and the compressed exponent varied very little from a value of 1.6, suggesting that the system may have been highly stressed and jammed. Despite the interesting stress relaxation signatures seen in these samples, the structural ordering of the monolayer remained the same over the sample lifetime, as revealed by grazing incidence x-ray diffraction.

Thermal stability of thiol and silane monolayers: A comparative study

International Nuclear Information System (INIS)

Chandekar, Amol; Sengupta, Sandip K.; Whitten, James E.

2010-01-01

The stability of self-assembled monolayers (SAMs) at elevated temperatures is of considerable technological importance. The thermal stability of 1-octadecanethiol (ODT), 16-mercaptohexadecanoic acid (MHDA) and 1H,1H,2H,2H-perfluorodecanethiol (PFDT) SAMs on gold surfaces, and of 4-aminobutyltriethoxysilane (ABTES) and 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) assembled on hydroxylated silicon surfaces, was studied by X-ray photoelectron spectroscopy (XPS). The samples were heated in ultrahigh vacuum to temperatures in excess of that required for SAM degradation. ODT monolayers were stable to ca. 110 deg. C, while MHDA and PFDT SAMs were stable to ca. 145 deg. C. ABTES SAMs were found to be indefinitely stable to 250 deg. C, while PFDS SAMs were stable to 350 deg. C. These studies demonstrate the advantages of using silane monolayers for moderate to high temperature applications and illustrate differences that arise due to the nature of the tail group. To demonstrate the feasibility of silanes for template-directed patterning, a hydroxylated silicon oxide surface containing microcontact-printed PFDS patterns was spin-coated with a mainly hydrophilic block copolymer. Annealing the surface at 90 deg. C for 2 h caused the block copolymer to dewet the hydrophobic PFDS-patterned regions and adsorb exclusively on the unpatterned regions of the surface.

Seventh BES [Basic Energy Sciences] catalysis and surface chemistry research conference

International Nuclear Information System (INIS)

1990-03-01

Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases

Seventh BES (Basic Energy Sciences) catalysis and surface chemistry research conference

Energy Technology Data Exchange (ETDEWEB)

1990-03-01

Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases. (CBS)

Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

KAUST Repository

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

2016-01-01

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

Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

KAUST Repository

Zheng, Yu Jie

2016-01-21

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

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 length......, being members of the n-alkane series [CH3(CH2)n−2CH3] where n=4 for butane and n=6 for hexane. The simulations employ a skeletal model, which does not include the hydrogen atoms explicitly, to represent the intermolecular and molecule–substrate interactions. Nearest-neighbor intramolecular bonds...... are fixed in length, but the molecular flexibility is preserved by allowing the bend and dihedral torsion angles to vary. The simulations show a qualitatively different melting behavior for the butane and hexane monolayers consistent with neutron and x-ray scattering experiments. The melting of the low...

Adsorption of Dyes in Studying the Surface Chemistry of Ultradispersed Diamond

Science.gov (United States)

Khokhlova, T. D.; Yunusova, G. R.; Lanin, S. N.

2018-05-01

The effect the surface chemistry of ultradispersed diamond (UDD) has on the adsorption of watersoluble dyes is considered. A comparison is made to adsorption on graphitized thermal carbon black (GTCB), which has a homogeneous and nonporous surface. The adsorption isotherms of dyes and the dependence of the adsorption on the pH of solutions are measured. It is found that UDD adsorbs acid (anionic) dyes—acid orange (AO) and acid anthraquinone blue (AAB)—but barely adsorbs a basic (cationic) dye, methylene blue (MB), because of the predominance of positively charged basic groups on the surface of UDD. The maximum adsorption of AO is much lower on UDD than on GTCB, while the maximum adsorption of AAB is similar for both surfaces. The adsorption of AO on UDD depends strongly on the pH of the solution, while the adsorption of AAB is independent of this parameter. It is suggested that the adsorption of AAB is determined not only by ionic and hydrophobic interactions but also by coordination interactions with impurity metal ions on a UDD surface. It is concluded that the adsorption of dyes characterizes the chemistry of a UDD surface with high sensitivity.

MgO monolayer epitaxy on Ni (100)

Science.gov (United States)

Sarpi, B.; Putero, M.; Hemeryck, A.; Vizzini, S.

2017-11-01

The growth of two-dimensional oxide films with accurate control of their structural and electronic properties is considered challenging for engineering nanotechnological applications. We address here the particular case of MgO ultrathin films grown on Ni (100), a system for which neither crystallization nor extended surface ordering has been established previously in the monolayer range. Using Scanning Tunneling Microscopy and Auger Electron Spectroscopy, we report on experiments showing MgO monolayer (ML) epitaxy on a ferromagnetic nickel surface, down to the limit of atomic thickness. Alternate steps of Mg ML deposition, O2 gas exposure, and ultrahigh vacuum thermal treatment enable the production of a textured film of ordered MgO nano-domains. This study could open interesting prospects for controlled epitaxy of ultrathin oxide films with a high magneto-resistance ratio on ferromagnetic substrates, enabling improvement in high-efficiency spintronics and magnetic tunnel junction devices.

Specific ion effects on the properties of cationic Gemini surfactant monolayers

International Nuclear Information System (INIS)

Alejo, T.; Merchan, M.D.; Velazquez, M.M.

2011-01-01

The effects of some anions of the Hofmeister series and different divalent cations of alkaline earth metals on the properties of Langmuir monolayers of the cationic Gemini surfactant ethyl-bis (dimethyl octadecylammonium bromide) have been investigated. Surface pressure and potential isotherms at the air-water interface were obtained on aqueous subphases containing sodium salts with several anions of the Hofmeister series (Cl - , NO 3 - , Br - , I - , ClO 4 - , and SCN - ). The influence of the investigated anions on the monolayer properties can be ordered according to the Hofmeister series with a change in the order between bromide and nitrate anions. On the other hand, for a given anion, the cation of the salt also influences the surface properties of the Langmuir films. The monolayers can be transferred onto mica by the Langmuir-Blodgett technique and then the Langmuir-Blodgett films were characterized by atomic force microscopy (AFM). The AFM images show that the molecules become more closely packed and nearly vertical to the surface when anions screen the electric charge of the surfactant molecules.

Specific ion effects on the properties of cationic Gemini surfactant monolayers

Energy Technology Data Exchange (ETDEWEB)

Alejo, T.; Merchan, M.D.; Velazquez, M.M., E-mail: mvsal@usal.es

2011-06-01

The effects of some anions of the Hofmeister series and different divalent cations of alkaline earth metals on the properties of Langmuir monolayers of the cationic Gemini surfactant ethyl-bis (dimethyl octadecylammonium bromide) have been investigated. Surface pressure and potential isotherms at the air-water interface were obtained on aqueous subphases containing sodium salts with several anions of the Hofmeister series (Cl{sup -}, NO{sub 3}{sup -}, Br{sup -}, I{sup -}, ClO{sub 4}{sup -}, and SCN{sup -}). The influence of the investigated anions on the monolayer properties can be ordered according to the Hofmeister series with a change in the order between bromide and nitrate anions. On the other hand, for a given anion, the cation of the salt also influences the surface properties of the Langmuir films. The monolayers can be transferred onto mica by the Langmuir-Blodgett technique and then the Langmuir-Blodgett films were characterized by atomic force microscopy (AFM). The AFM images show that the molecules become more closely packed and nearly vertical to the surface when anions screen the electric charge of the surfactant molecules.

Infrared spectroscopy of self-assembled monolayer films on silicon

Science.gov (United States)

Rowell, N. L.; Tay, Lilin; Boukherroub, R.; Lockwood, D. J.

2007-07-01

Infrared vibrational spectroscopy in an attenuated total reflection (ATR) geometry has been employed to investigate the presence of organic thin layers on Si-wafer surfaces. The phenomena have been simulated to show there can be a field enhancement with the presented single-reflection ATR (SR-ATR) approach which is substantially larger than for conventional ATR or specular reflection. In SR-ATR, a discontinuity of the field normal to the film contributes a field enhancement in the lower index thin film causing a two order of magnitude increase in sensitivity. SR-ATR was employed to characterize a single monolayer of undecylenic acid self-assembled on Si(1 1 1) and to investigate a two monolayer system obtained by adding a monolayer of bovine serum albumin protein.

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.

Effect of fullerenol surface chemistry on nanoparticle binding-induced protein misfolding

Science.gov (United States)

Radic, Slaven; Nedumpully-Govindan, Praveen; Chen, Ran; Salonen, Emppu; Brown, Jared M.; Ke, Pu Chun; Ding, Feng

2014-06-01

Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding.Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and

The interaction of insulin, glucose, and insulin-glucose mixtures with a phospholipid monolayer.

Science.gov (United States)

Shigenobu, Hayato; McNamee, Cathy E

2012-12-15

We determined how glucose or insulin interacts with a phospholipid monolayer at the air/water interface and explained these mechanisms from a physico-chemical point of view. The 1,2-dipalmitoyl-2-sn-glycero-3-phosphatidylcholine (DPPC) monolayer at an air/water interface acted as a model membrane, which allowed the effect of the molecular packing density in the monolayer on the interactions to be determined. The interaction of glucose, insulin, and a mixture of glucose and insulin to the DPPC monolayer were investigated via surface pressure-area per molecule Langmuir isotherms and fluorescence microscopy. Glucose adsorbed to the underside of the DPPC monolayer, while insulin was able to penetrate through the monolayer when the phospholipid molecules were not densely packed. The presence of a mixture of insulin and glucose affected the molecular packing in the DPPC monolayer differently than the pure insulin or glucose solutions, and the glucose-insulin mixture was seen to be able to penetrate through the monolayer. These results indicated that glucose and insulin interact with one another, giving a material that may then transported through a pore in the monolayer or through the spaces between the molecules of the monolayer. Copyright © 2012 Elsevier Inc. All rights reserved.

Effects of self-assembled monolayer structural order, surface homogeneity and surface energy on pentacene morphology and thin film transistor device performance.

Science.gov (United States)

Hutchins, Daniel Orrin; Weidner, Tobias; Baio, Joe; Polishak, Brent; Acton, Orb; Cernetic, Nathan; Ma, Hong; Jen, Alex K-Y

2013-01-04

A systematic study of six phosphonic acid (PA) self-assembled monolayers (SAMs) with tailored molecular structures is performed to evaluate their effectiveness as dielectric modifying layers in organic field-effect transistors (OFETs) and determine the relationship between SAM structural order, surface homogeneity, and surface energy in dictating device performance. SAM structures and surface properties are examined by near edge X-ray absorption fine structure (NEXAFS) spectroscopy, contact angle goniometry, and atomic force microscopy (AFM). Top-contact pentacene OFET devices are fabricated on SAM modified Si with a thermally grown oxide layer as a dielectric. For less ordered methyl- and phenyl-terminated alkyl ~(CH 2 ) 12 PA SAMs of varying surface energies, pentacene OFETs show high charge carrier mobilities up to 4.1 cm 2 V -1 s -1 . It is hypothesized that for these SAMs, mitigation of molecular scale roughness and subsequent control of surface homogeneity allow for large pentacene grain growth leading to high performance pentacene OFET devices. PA SAMs that contain bulky terminal groups or are highly crystalline in nature do not allow for a homogenous surface at a molecular level and result in charge carrier mobilities of 1.3 cm 2 V -1 s -1 or less. For all molecules used in this study, no causal relationship between SAM surface energy and charge carrier mobility in pentacene FET devices is observed.

Behaviour of human endothelial cells on surface modified NiTi alloy.

Science.gov (United States)

Plant, Stuart D; Grant, David M; Leach, Lopa

2005-09-01

Intravascular stents are being designed which utilise the shape memory properties of NiTi alloy. Despite the clinical advantages afforded by these stents their application has been limited by concerns about the large nickel ion content of the alloy. In this study, the surface chemistry of NiTi alloy was modified by mechanical polishing and oxidising heat treatments and subsequently characterised using X-ray photon spectroscopy (XPS). The effect of these surfaces on monolayer formation and barrier integrity of human umbilical vein endothelial cells (HUVEC) was then assessed by confocal imaging of the adherens junctional molecule VE-cadherin, perijunctional actin and permeability to 42kDa dextrans. Dichlorofluoroscein assays were used to measure oxidative stress in the cells. XPS analysis of NiTi revealed its surface to be dominated by TiO(2). However, where oxidation had occurred after mechanical polishing or post polishing heat treatments at 300 and 400 degrees C in air, a significant amount of metallic nickel or nickel oxide species (10.5 and 18.5 at%) remained on the surface. Exposure of HUVECs to these surfaces resulted in increased oxidative stress within the cells, loss of VE-cadherin and F-actin and significantly increased paracellular permeability. These pathological phenomena were not found in cells grown on NiTi which had undergone heat treatment at 600 degrees C. At this temperature thickening of the TiO(2) layer had occurred due to diffusion of titanium ions from the bulk of the alloy, displacing nickel ions to sub-surface areas. This resulted in a significant reduction in nickel ions detectable on the sample surface (4.8 at%). This study proposes that the integrity of human endothelial monolayers on NiTi is dependent upon the surface chemistry of the alloy and that this can be manipulated, using simple oxidising heat treatments.

Potential-induced structural transitions of DL-homocysteine monolayers on Au(111) electrode surfaces

International Nuclear Information System (INIS)

Zhang Jingdong; Demetriou, Anna; Welinder, Anne Christina; Albrecht, Tim; Nichols, Richard J.; Ulstrup, Jens

2005-01-01

Monolayers of homocysteine on Au(111)-surfaces have been investigated by voltammetry, in situ scanning tunnelling microscopy (STM) and subtractively normalised interfacial Fourier transform spectroscopy (SNIFTIRS). A pair of sharp voltammetric peaks build up in the potential range 0 to -0.1V (vs. SCE) in phosphate buffer pH 7.7. The peak half-widths are about 25mV at a scan rate of 10mVs -1 . This is much smaller than for a one-electron Faradaic process (90.6mV) under similar conditions. The coverage of homocysteine is 6.1 (+/-0.2)x10 -10 molcm -2 , or 5.9x10 -5 Ccm -2 , from Au-S reductive desorption at -0.8V (SCE) in 0.1M NaOH, while the charge is only about 8x10 -6 Ccm -2 (pH 7.7) for the 0 to -0.1V 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 and lower pH. The midpoint potential shows biphasic behaviour, decreasing linearly with increasing pH until pH 10.4 towards a constant value at higher pH. The cathodic and anodic peak charges decay at pH both higher and lower than 7.7. The homocysteine monolayer was investigated by in situ STM at different potentials at pH 7.7. The molecules pack into highly ordered domains around the peak potential. High-resolution in situ STM reveals a (√3x5) R30 deg. lattice with three homocysteine molecules in each unit cell. The adlayer changes into disordered structures on either side of the peak potential. 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 -NH 3 + 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

The impact of surface chemistry on the performance of localized solar-driven evaporation system.

Science.gov (United States)

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-09-04

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation.

Surface chemistry of Ti6Al4V components fabricated using selective laser melting for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Vaithilingam, Jayasheelan, E-mail: Jayasheelan.Vaithilingam@nottingham.ac.uk [Additive Manufacturing and 3D Printing Research Group, EPSRC Centre for Innovative Manufacturing in Additive Manufacturing, School of Engineering, The University of Nottingham, Nottingham NG7 2RD (United Kingdom); Prina, Elisabetta [School of Pharmacy, Centre for Biomolecular Sciences, The University of Nottingham, Nottingham NG7 2RD (United Kingdom); Goodridge, Ruth D.; Hague, Richard J.M. [Additive Manufacturing and 3D Printing Research Group, EPSRC Centre for Innovative Manufacturing in Additive Manufacturing, School of Engineering, The University of Nottingham, Nottingham NG7 2RD (United Kingdom); Edmondson, Steve [School of Materials, The University of Manchester, Manchester M13 9PL (United Kingdom); Rose, Felicity R.A.J. [School of Pharmacy, Centre for Biomolecular Sciences, The University of Nottingham, Nottingham NG7 2RD (United Kingdom); Christie, Steven D.R. [Department of Chemistry, Loughborough University, Loughborough LE11 3TU (United Kingdom)

2016-10-01

Selective laser melting (SLM) has previously been shown to be a viable method for fabricating biomedical implants; however, the surface chemistry of SLM fabricated parts is poorly understood. In this study, X-ray photoelectron spectroscopy (XPS) was used to determine the surface chemistries of (a) SLM as-fabricated (SLM-AF) Ti6Al4V and (b) SLM fabricated and mechanically polished (SLM-MP) Ti6Al4V samples and compared with (c) traditionally manufactured (forged) and mechanically polished Ti6Al4V samples. The SLM–AF surface was observed to be porous with an average surface roughness (Ra) of 17.6 ± 3.7 μm. The surface chemistry of the SLM-AF was significantly different to the FGD-MP surface with respect to elemental distribution and their existence on the outermost surface. Sintered particles on the SLM-AF surface were observed to affect depth profiling of the sample due to a shadowing effect during argon ion sputtering. Surface heterogeneity was observed for all three surfaces; however, vanadium was witnessed only on the mechanically polished (SLM-MP and FGD-MP) surfaces. The direct and indirect 3T3 cell cytotoxicity studies revealed that the cells were viable on the SLM fabricated Ti6Al4V parts. The varied surface chemistry of the SLM-AF and SLM-MP did not influence the cell behaviour. - Highlights: • Surface chemistry of selective laser melted (SLM) Ti6Al4V parts was compared with conventionally forged Ti6Al4V parts. • The surface elemental compositions of the SLM as-fabricated surfaces were significantly different to the forged surface. • Surface oxide-layer of the SLM as-fabricated was thicker than the polished SLM surfaces and the forged Ti6Al4V surfaces.

Phosphatidylcholine-fatty Alcohols Equilibria in Monolayers at the Air/Water Interface.

Science.gov (United States)

Serafin, Agnieszka; Figaszewski, Zbigniew Artur; Petelska, Aneta Dorota

2015-08-01

Monolayers of phosphatidylcholine (PC), tetradecanol (TD), hexadecanol (HD), octadecanol (OD) and eicosanol (E) and their binary mixtures were investigated at the air/water interface. The surface tension values of pure and mixed monolayers were used to calculate π-A isotherms. The surface tension measurements were carried out at 22 °C using a Teflon trough and a Nima 9000 tensiometer. The interactions between phosphatidylcholine and fatty alcohols (tetradecanol, hexadecanol, octadecanol, eicosanol) result in significant deviations from the additivity rule. An equilibrium theory to describe the behavior of monolayer components at the air/water interface was developed in order to obtain the stability constants, Gibbs free energy values and areas occupied by one molecules of PC-TD, PC-HD, PC-OD and PC-E complexes. We considered the equilibrium between the individual components and the complex and established that phosphatidylcholine and fatty alcohols formed highly stable 1:1 complexes.

Recyclable surfaces for amine conjugation chemistry via redox reaction

Energy Technology Data Exchange (ETDEWEB)

Choi, Inseong; Yeo, Woon Seok [Dept. of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul (Korea, Republic of); Bae, Se Won [Green Materials and Process Group, Research Institute of Sustainable Manufacturing System, Korea Institute of Industrial Technology, Cheonan (Korea, Republic of)

2017-02-15

In this study, we extended this strategy to present a switchable surface that allows surface functionalization and removal of functional groups repeatedly. The substrate presenting a benzoquinone acid group is first used to immobilize with an amine-containing (bio)molecule using well-known conjugation chemistry. The benzoquinone group is then converted to the corresponding hydroquinone by treating with a reducing agent. We have described a strategy for the dynamic control of surface properties with recyclability via a simple reduction/ oxidation reaction. A stimuli-responsive quinone derivative was harnessed for the repeated immobilization and release of (bio)molecules, and thus, for the repeated dynamic change of the surface properties according to the characteristics of the immobilized (bio)molecules.

Transport properties in monolayer-bilayer-monolayer graphene planar junctions

Institute of Scientific and Technical Information of China (English)

Kai-Long Chu; Zi-Bo Wang; Jiao-Jiao Zhou; Hua Jiang

2017-01-01

The transport study of graphene based junctions has become one of the focuses in graphene research.There are two stacking configurations for monolayer-bilayer-monolayer graphene planar junctions.One is the two monolayer graphene contacting the same side of the bilayer graphene,and the other is the two-monolayer graphene contacting the different layers of the bilayer graphene.In this paper,according to the Landauer-Büttiker formula,we study the transport properties of these two configurations.The influences of the local gate potential in each part,the bias potential in bilayer graphene,the disorder and external magnetic field on conductance are obtained.We find the conductances of the two configurations can be manipulated by all of these effects.Especially,one can distinguish the two stacking configurations by introducing the bias potential into the bilayer graphene.The strong disorder and the external magnetic field will make the two stacking configurations indistinguishable in the transport experiment.

Effects of wood fiber surface chemistry on strength of wood–plastic composites

Energy Technology Data Exchange (ETDEWEB)

Migneault, Sébastien, E-mail: sebastien.migneault@uqat.ca [University of Quebec in Abitibi-Temiscamingue (UQAT), 445 boulevard de l’Université, Rouyn-Noranda, Québec J9X 5E4 (Canada); Koubaa, Ahmed, E-mail: ahmed.koubaa@uqat.ca [UQAT (Canada); Perré, Patrick, E-mail: patrick.perre@ecp.fr [École centrale de Paris, Grande Voie des Vignes, F-92 295 Chatenay-Malabry Cedex (France); Riedl, Bernard, E-mail: Bernard.Riedl@sbf.ulaval.ca [Université Laval, 2425 rue de la Terrasse, Québec City, Québec G1V 0A6 (Canada)

2015-07-15

Highlights: • Infrared spectroscopy and X-ray photoelectron spectroscopy analyses showed variations of surface chemical characteristics according to fiber origin. • Surface chemical characteristics of fibers could partly explain the differences in mechanical properties of the wood–plastic composites. • Fibers with carbohydrate rich surface led to stronger wood–plastic composites because the coupling between the matrix and fibers using coupling agent is achieved with polar sites mostly available on carbohydrates. • Conversely, lignin or extractives rich surface do not have oxidized functions for the esterification reaction with coupling agent and thus led to wood–plastic composites with lower mechanical properties. • Other factors such as mechanical interlocking and fiber morphology interfere with the effects of fiber surface chemistry. - Abstract: Because wood–plastic composites (WPC) strength relies on fiber-matrix interaction at fiber surface, it is likely that fiber surface chemistry plays an important role in WPC strength development. The objective of the present study is to investigate the relationships between fiber surface chemical characteristics and WPC mechanical properties. Different fibers were selected and characterized for surface chemical characteristics using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). WPC samples were manufactured at 40% fiber content and with six different fibers. High density polyethylene was used as matrix and maleated polyethylene (MAPE) was used as compatibility agent. WPC samples were tested for mechanical properties and fiber-matrix interface was observed with scanning electron microscope. It was found WPC strength decreases as the amount of unoxidized carbon (assigned to lignin and extractives) measured with XPS on fiber surface increases. In the opposite case, WPC strength increases with increasing level of oxidized carbon (assigned to carbohydrates) on fiber surface. The same

Effects of wood fiber surface chemistry on strength of wood–plastic composites

International Nuclear Information System (INIS)

Migneault, Sébastien; Koubaa, Ahmed; Perré, Patrick; Riedl, Bernard

2015-01-01

Highlights: • Infrared spectroscopy and X-ray photoelectron spectroscopy analyses showed variations of surface chemical characteristics according to fiber origin. • Surface chemical characteristics of fibers could partly explain the differences in mechanical properties of the wood–plastic composites. • Fibers with carbohydrate rich surface led to stronger wood–plastic composites because the coupling between the matrix and fibers using coupling agent is achieved with polar sites mostly available on carbohydrates. • Conversely, lignin or extractives rich surface do not have oxidized functions for the esterification reaction with coupling agent and thus led to wood–plastic composites with lower mechanical properties. • Other factors such as mechanical interlocking and fiber morphology interfere with the effects of fiber surface chemistry. - Abstract: Because wood–plastic composites (WPC) strength relies on fiber-matrix interaction at fiber surface, it is likely that fiber surface chemistry plays an important role in WPC strength development. The objective of the present study is to investigate the relationships between fiber surface chemical characteristics and WPC mechanical properties. Different fibers were selected and characterized for surface chemical characteristics using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). WPC samples were manufactured at 40% fiber content and with six different fibers. High density polyethylene was used as matrix and maleated polyethylene (MAPE) was used as compatibility agent. WPC samples were tested for mechanical properties and fiber-matrix interface was observed with scanning electron microscope. It was found WPC strength decreases as the amount of unoxidized carbon (assigned to lignin and extractives) measured with XPS on fiber surface increases. In the opposite case, WPC strength increases with increasing level of oxidized carbon (assigned to carbohydrates) on fiber surface. The same

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

Reaction of a phospholipid monolayer with gas-phase ozone at the air-water interface: measurement of surface excess and surface pressure in real time.

Science.gov (United States)

Thompson, Katherine C; Rennie, Adrian R; King, Martin D; Hardman, Samantha J O; Lucas, Claire O M; Pfrang, Christian; Hughes, Brian R; Hughes, Arwel V

2010-11-16

The reaction between gas-phase ozone and monolayers of the unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC, on aqueous solutions has been studied in real time using neutron reflection and surface pressure measurements. The reaction between ozone and lung surfactant, which contains POPC, leads to decreased pulmonary function, but little is known about the changes that occur to the interfacial material as a result of oxidation. The results reveal that the initial reaction of ozone with POPC leads to a rapid increase in surface pressure followed by a slow decrease to very low values. The neutron reflection measurements, performed on an isotopologue of POPC with a selectively deuterated palmitoyl strand, reveal that the reaction leads to loss of this strand from the air-water interface, suggesting either solubilization of the product lipid or degradation of the palmitoyl strand by a reactive species. Reactions of (1)H-POPC on D(2)O reveal that the headgroup region of the lipids in aqueous solution is not dramatically perturbed by the reaction of POPC monolayers with ozone supporting degradation of the palmitoyl strand rather than solubilization. The results are consistent with the reaction of ozone with the oleoyl strand of POPC at the air-water interface leading to the formation of OH radicals. The highly reactive OH radicals produced can then go on to react with the saturated palmitoyl strands leading to the formation of oxidized lipids with shorter alkyl tails.

Structure and stability of triglyceride monolayers on water and mica surfaces

NARCIS (Netherlands)

Zdravkova, A.N.; van der Eerden, J.P.J.M.

2007-01-01

The structure and the stability of tripalmitin (PPP), tristearin (SSS), and triarachidin (AAA) monolayers at the air-water interface are investigated with the Langmuir method. The Langmuir-Blodgett (LB) layers obtained by deposition on mica were investigated with atomic force microscopy (AFM). Our

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

Science.gov (United States)

Böke, Frederik; Schickle, Karolina; Fischer, Horst

2014-01-01

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. PMID:28788687

Switchable host-guest systems on surfaces.

Science.gov (United States)

Yang, Ying-Wei; Sun, Yu-Long; Song, Nan

2014-07-15

CONSPECTUS: For device miniaturization, nanotechnology follows either the "top-down" approach scaling down existing larger-scale devices or the "bottom-up' approach assembling the smallest possible building blocks to functional nanoscale entities. For synthetic nanodevices, self-assembly on surfaces is a superb method to achieve useful functions and enable their interactions with the surrounding world. Consequently, adaptability and responsiveness to external stimuli are other prerequisites for their successful operation. Mechanically interlocked molecules such as rotaxanes and catenanes, and their precursors, that is, molecular switches and supramolecular switches including pseudorotaxanes, are molecular machines or prototypes of machines capable of mechanical motion induced by chemical signals, biological inputs, light or redox processes as the external stimuli. Switching of these functional host-guest systems on surfaces becomes a fundamental requirement for artificial molecular machines to work, mimicking the molecular machines in nature, such as proteins and their assemblies operating at dynamic interfaces such as the surfaces of cell membranes. Current research endeavors in material science and technology are focused on developing either a new class of materials or materials with novel/multiple functionalities by shifting host-guest chemistry from solution phase to surfaces. In this Account, we present our most recent attempts of building monolayers of rotaxanes/pseudorotaxanes on surfaces, providing stimuli-induced macroscopic effects and further understanding on the switchable host-guest systems at interfaces. Biocompatible versions of molecular machines based on synthetic macrocycles, such as cucurbiturils, pillararenes, calixarenes, and cyclodextrins, have been employed to form self-assembled monolayers of gates on the surfaces of mesoporous silica nanoparticles to regulate the controlled release of cargo/drug molecules under a range of external stimuli

A surface-chemistry study of barium ferrite nanoplates with DBSa-modified surfaces

Energy Technology Data Exchange (ETDEWEB)

Lisjak, Darja, E-mail: darja.lisjak@ijs.si [Jožef Stefan Institute, Ljubljana (Slovenia); Ovtar, Simona; Kovač, Janez [Jožef Stefan Institute, Ljubljana (Slovenia); Gregoratti, Luca; Aleman, Belen; Amati, Matteo [Elettra – Sincrotrone Trieste S.C.p.A. di interesse nazionale, Trieste (Italy); Fanetti, Mattia [University of Nova Gorica, Nova Gorica (Slovenia); Istituto Officina dei Materiali CNR, Area Science Park, Trieste (Italy); Makovec, Darko [Jožef Stefan Institute, Ljubljana (Slovenia)

2014-06-01

Barium ferrite (BaFe{sub 12}O{sub 19}) is a ferrimagnetic oxide with a high magnetocrystalline anisotropy that can be exploited in magnetically aligned ceramics or films for self-biased magnetic applications. Magnetic alignment of the films can be achieved by the directed assembly of barium ferrite nanoplates. In this investigation the nanoplates were synthesized hydrothermally and suspended in 1-butanol using dodecylbenzene sulphonic acid (DBSa) as a surfactant. They were then deposited in an electric or magnetic field on flat substrates and exhibited a significant preferential alignment in the plane of the substrate, allowing a differentiation between the analysis of their basal and side planes using scanning photoelectron microscopy with a lateral resolution down to 100 nm. The surface chemistry of the nanoplates was additionally studied with X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. For a comparison, bare barium ferrite nanoplates were also analyzed after decomposing the DBSa at 460 °C. The deviation of the surface chemistry from the stoichiometric composition was observed and the adsorption of the DBSa molecules on the nanoplates was confirmed with all three methods. Different types of bonding (physi- or chemisorption) were possible and considered with respect to the assembly of the barium ferrite nanoplates into anisotropic magnetic films.

Topography and instability of monolayers near domain boundaries

International Nuclear Information System (INIS)

Diamant, H.; Witten, T. A.; Ege, C.; Gopal, A.; Lee, K. Y. C.

2001-01-01

We theoretically study the topography of a biphasic surfactant monolayer in the vicinity of domain boundaries. The differing elastic properties of the two phases generally lead to a nonflat topography of 'mesas,' where domains of one phase are elevated with respect to the other phase. The mesas are steep but low, having heights of up to 10 nm. As the monolayer is laterally compressed, the mesas develop overhangs and eventually become unstable at a surface tension of about K(δc 0 ) 2 (δc 0 being the difference in spontaneous curvature and K a bending modulus). In addition, the boundary is found to undergo a topography-induced rippling instability upon compression, if its line tension is smaller than about Kδc 0 . The effect of diffuse boundaries on these features and the topographic behavior near a critical point are also examined. We discuss the relevance of our findings to several experimental observations related to surfactant monolayers: (i) small topographic features recently found near domain boundaries; (ii) folding behavior observed in mixed phospholipid monolayers and model lung surfactants; (iii) roughening of domain boundaries seen under lateral compression; (iv) the absence of biphasic structures in tensionless surfactant films

Investigating Alkylsilane Monolayer Tribology at a Single-Asperity Contact with Molecular Dynamics Simulation.

Science.gov (United States)

Summers, Andrew Z; Iacovella, Christopher R; Cummings, Peter T; McCabe, Clare

2017-10-24

Chemisorbed monolayer films are known to possess favorable characteristics for nanoscale lubrication of micro- and nanoelectromechanical systems (MEMS/NEMS). Prior studies have shown that the friction observed for monolayer-coated surfaces features a strong dependence on the geometry of contact. Specifically, tip-like geometries have been shown to penetrate into monolayer films, inducing defects in the monolayer chains and leading to plowing mechanisms during shear, which result in higher coefficients of friction (COF) than those observed for planar geometries. In this work, we use molecular dynamics simulations to examine the tribology of model silica single-asperity contacts under shear with monolayer-coated substrates featuring various film densities. It is observed that lower monolayer densities lead to reduced COFs, in contrast to results for planar systems where COF is found to be nearly independent of monolayer density. This is attributed to a liquid-like response to shear, whereby fewer defects are imparted in monolayer chains from the asperity, and chains are easily displaced by the tip as a result of the higher free volume. This transition in the mechanism of molecular plowing suggests that liquid-like films should provide favorable lubrication at single-asperity contacts.

Subcellular topological effect of particle monolayers on cell shapes and functions.

Science.gov (United States)

Miura, Manabu; Fujimoto, Keiji

2006-12-01

We studied topological effects of subcellular roughness displayed by a closely packed particle monolayer on adhesion and growth of endothelial cells. Poly(styrene-co-acrylamide) (SA) particles were prepared by soap-free emulsion copolymerization. Particle monolayers were prepared by Langmuir-Blodgett deposition using particles, which were 527 (SA053) and 1270 nm (SA127) in diameter. After 24-h incubation, cells tightly adhered on a tissue culture polystyrene dish and randomly spread. On the other hand, cells attached on particle monolayers were stretched into a narrow stalk-like shape. Lamellipodia spread from the leading edge of cells attached on SA053 monolayer to the top of the particles and gradually gathered to form clusters. This shows that cell-cell adhesion became stronger than cell-substrate interaction. Cells attached to SA127 monolayer extended to the reverse side of a particle monolayer and engulfed particles. They remained immobile without migration 24h after incubation. This shows that the inhibition of extensions on SA127 monolayer could inhibit cell migration and cell proliferation. Cell growth on the particle monolayers was suppressed compared with a flat TCPS dish. The number of cells on SA053 gradually increased, whereas that on SA127 decreased with time. When the cell seeding density was increased to 200,000 cells cm(-2), some adherent cells gradually became into contact with adjacent cells. F-actin condensations were formed at the frame of adherent cells and the thin filaments grew from the edges to connect each other with time. For the cell culture on SA053 monolayer, elongated cells showed a little alignment. Cells showed not arrangement of actin stress fibers but F-actin condensation at the contact regions with neighboring cells. Interestingly, the formed cell monolayer could be readily peeled from the particle monolayer. These results indicate that endothelial cells could recognize the surface roughness displayed by particle monolayers and

Ordered Fe(II)Ti(IV)O3 Mixed Monolayer Oxide on Rutile TiO2(011).

Science.gov (United States)

Halpegamage, Sandamali; Ding, Pan; Gong, Xue-Qing; Batzill, Matthias

2015-08-25

Oxide monolayers supported or intermixed with an oxide support are potential nanocatalysts whose properties are determined by the interplay with the support. For fundamental studies of monolayer oxides on metal oxide supports, well-defined systems are needed, but so far, the synthesis of monolayer oxides with long-range order on single-crystal oxide surfaces is rare. Here, we show by a combination of scanning tunneling microscopy, photoemission spectroscopy, and density functional theory (DFT)-based computational analysis that the rutile TiO2(011) surface supports the formation of an ordered mixed FeTiO3 monolayer. Deposition of iron in a slightly oxidizing atmosphere (10(-8) Torr O2) and annealing to 300 °C results in a well-ordered surface structure with Fe in a 2+ charge state and Ti in a 4+ charge states. Low-energy ion scattering suggests that the cation surface composition is close to half Fe and half Ti. This surface is stable in ultrahigh vacuum to annealing temperatures of 300 °C before the iron is reduced. DFT simulations confirm that a surface structure with coverage of 50% FeO units is stable and forms an ordered structure. Although distinct from known bulk phases of the iron-titanium oxide systems, the FeTiO3 monolayer exhibits some resemblance to the ilmenite structure, which may suggest that a variety of different mixed oxide phases (of systems that exist in a bulk ilmenite phase) may be synthesized in this way on the rutile TiO2(011) substrate.

Fabrication of a platform to isolate the influences of surface nanotopography from chemistry on bacterial attachment and growth.

Science.gov (United States)

Pegalajar-Jurado, Adoracion; Easton, Christopher D; Crawford, Russell J; McArthur, Sally L

2015-03-26

Billions of dollars are spent annually worldwide to combat the adverse effects of bacterial attachment and biofilm formation in industries as varied as maritime, food, and health. While advances in the fabrication of antifouling surfaces have been reported recently, a number of the essential aspects responsible for the formation of biofilms remain unresolved, including the important initial stages of bacterial attachment to a substrate surface. The reduction of bacterial attachment to surfaces is a key concept in the prevention or minimization of biofilm formation. The chemical and physical characteristics of both the substrate and bacteria are important in understanding the attachment process, but substrate modification is likely the most practical route to enable the extent of bacterial attachment taking place to be effectively controlled. The microtopography and chemistry of the surface are known to influence bacterial attachment. The role of surface chemistry versus nanotopography and their interplay, however, remain unclear. Most methods used for imparting nanotopographical patterns onto a surface also induce changes in the surface chemistry and vice versa. In this study, the authors combine colloidal lithography and plasma polymerization to fabricate homogeneous, reproducible, and periodic nanotopographies with a controllable surface chemistry. The attachment of Escherichia coli bacteria onto carboxyl (plasma polymerized acrylic acid, ppAAc) and hydrocarbon (plasma polymerized octadiene, ppOct) rich plasma polymer films on either flat or colloidal array surfaces revealed that the surface chemistry plays a critical role in bacterial attachment, whereas the effect of surface nanotopography on the bacterial attachment appears to be more difficult to define. This platform represents a promising approach to allow a greater understanding of the role that surface chemistry and nanotopography play on bacterial attachment and the subsequent biofouling of the surface.

Diamondoid monolayers as electron emitters

Science.gov (United States)

Yang, Wanli [El Cerrito, CA; Fabbri, Jason D [San Francisco, CA; Melosh, Nicholas A [Menlo Park, CA; Hussain, Zahid [Orinda, CA; Shen, Zhi-Xun [Stanford, CA

2012-04-10

Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

Ion-enhanced gas-surface chemistry: The influence of the mass of the incident ion

International Nuclear Information System (INIS)

Gerlach-Meyer, U.; Coburn, J.W.; Kay, E.

1981-01-01

There are many examples of situations in which a gas-surface reaction rate is increased when the surface is simultaneously subjected to energetic particle bombardment. There are several possible mechanisms which could be involved in this radiation-enhanced gas-surface chemistry. In this study, the reaction rate of silicon, as determined from the etch yield, is measured during irradiation of the Si surface with 1 keV He + , Ne + , and Ar + ions while the surface is simultaneously subjected to fluxes of XeF 2 or Cl 2 molecules. Etch yields as high as 25 Si atoms/ion are observed for XeF 2 and Ar + on Si. A discussion is presented of the extent to which the results clarify the mechanisms responsible for ion-enhanced gas-surface chemistry. (orig.)

Miscibility of dl-α-tocopherol β-glucoside in DPPC monolayer at air/water and air/solid interfaces

Energy Technology Data Exchange (ETDEWEB)

Neunert, G. [Department of Physics and Biophysics, Poznan University of Life Sciences, 60-637 Poznan (Poland); Makowiecki, J.; Piosik, E.; Hertmanowski, R. [Faculty of Technical Physics, Poznan University of Technology, 60-965 Poznan (Poland); Polewski, K. [Department of Physics and Biophysics, Poznan University of Life Sciences, 60-637 Poznan (Poland); Martynski, T., E-mail: tomasz.martynski@put.poznan.pl [Faculty of Technical Physics, Poznan University of Technology, 60-965 Poznan (Poland)

2016-10-01

The role of newly synthesized tocopherol glycosidic derivative in modifying molecular organization and phase transitions of phospholipid monolayer at the air/water interface has been investigated. Two-component Langmuir films of dl-α-tocopheryl β-D-glucopyranoside (BG) mixed with dipalmitoyl phosphatidylcholine (DPPC) in the whole range of mole fractions were formed at the water surface. An analysis of surface pressure versus mean molecular area (π-A) isotherms and Brewster angle microscope images showed that the presence of BG molecules changes the structure and packing of the DPPC monolayer in a BG concentration dependent manner. BG molecules incorporated into DPPC monolayer inhibit its liquid expanded to liquid condensed phase transition proportionally to the BG concentration. The monolayers were also transferred onto solid substrates and visualized using an atomic force microscope. The results obtained indicate almost complete miscibility of BG and DPPC in the monolayers at surface pressures present in the biological cell membrane (30-35·10{sup -3} N·m{sup -1}) for a BG mole fraction as high as 0.3. This makes the monolayer less packed and more disordered, leading to an increased permeability. The results support our previous molecular dynamics simulation data. - Highlights: • Langmuir films of α-tocopherol derivative with DPPC was studied thermodynamically. • Mixed DPPC/BG films were transferred onto mica substrates for topography imaging by using AFM. • Miscibility of BG/DPPC films at surface pressures present in membranes was observed up to MF = 0.3.

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.

Reactive Landing of Dendrimer Ions onto Activated Self-assembled Monolayer Surfaces

Energy Technology Data Exchange (ETDEWEB)

Hu, Qichi; Laskin, Julia

2014-02-06

The reactivity of gaseous, amine-terminated polyamidoamine (PAMAM) dendrimer ions with activated self-assembled monolayer (SAM) surfaces terminated with N-hydroxysuccinimidyl ester groups (NHS-SAM) is examined using mass-selected ion deposition combined with in situ infrared reflection absorption spectroscopy (IRRAS). The reaction extent is determined from depletion of the infrared band at 1753 cm-1, corresponding to the stretching vibration of the NHS carbonyl groups following ion deposition. For reaction yields below 10%, NHS band depletion follows a linear dependence on the ion dose. By comparing the kinetics plots obtained for 1,12-dodecanediamine and different generations of dendrimer ions (G0–G3) containing 4, 8, 16, and 32 terminal amino group, we demonstrate that the relative reaction efficiency increases linearly with the number of NH2 groups in the molecule. This finding is rationalized assuming the formation of multiple amide bonds upon collision of higher-generation dendrimers with NHS-SAM. Furthermore, by comparing the NHS band depletion following deposition of [M+4H]4+ ions of the G2 dendrimer at 30, 80, and 120 eV, we demonstrate that the ion’s kinetic energy has no measurable effect on reaction efficiency. Similarly, the ion’s charge state only has a minor effect on the reactive landing efficiency of dendrimer ions. Our results indicate that reactive landing is an efficient approach for highly selective covalent immobilization of complex multifunctional molecules onto organic surfaces terminated with labile functional groups.

Thermal grafting of fluorinated molecular monolayers on doped amorphous silicon surfaces

International Nuclear Information System (INIS)

Sabbah, H.; Zebda, A.; Ababou-Girard, S.; Solal, F.; Godet, C.; Conde, J. P.; Chu, V.

2009-01-01

Thermally induced (160-300 deg. C) gas phase grafting of linear alkene molecules (perfluorodecene) was performed on hydrogenated amorphous silicon (a-Si:H) films, either nominally undoped or doped with different boron and phosphorus concentrations. Dense and smooth a-Si:H films were grown using plasma decomposition of silane. Quantitative analysis of in situ x-ray photoelectron spectroscopy indicates the grafting of a single layer of organic molecules. The hydrophobic properties of perfluorodecene-modified surfaces were studied as a function of surface coverage. Annealing experiments in ultrahigh vacuum show the covalent binding and the thermal stability of these immobilized layers up to 370 deg. C; this temperature corresponds to the Si-C bond cleavage temperature. In contrast with hydrogenated crystalline Si(111):H, no heavy wet chemistry surface preparation is required for thermal grafting of alkene molecules on a-Si:H films. A threshold grafting temperature is observed, with a strong dependence on the doping level which produces a large contrast in the molecular coverage for grafting performed at 230 deg. C

Thermodynamic and structural study of two-dimensional melting within monolayers or rare gases or methane physically adsorbed upon the surface of layer-like solids

International Nuclear Information System (INIS)

Tessier, Christine

1983-01-01

The 2D (two-dimensional) melting of monolayers of rare gases or methane physically adsorbed on the basal face of lamellar solids (graphite, boron nitride and lamellar halides) has been studied. Two different experimental measurements have been made: i) adsorption isotherms; ii) neutron diffraction spectra. The main part of this report deals with the 2D liquid-incommensurate solid transition within monolayers of rare gases or methane adsorbed on the basal face of lamellar halides. This transition is first order. It is observed only if certain conditions of dimensional incompatibility between the substrate and the absorbate are fulfilled. It is little affected by the structure of the underlying substrate. A number of thermodynamic parameters associated with it, are constants once properly scaled. These constants agree well with theoretical estimates for 6-12 Lennard Jones particles adsorbed on a smooth surface. For the monolayer of Xe adsorbed on graphite the temperature of the tricritical point above which melting becomes a continuous transition has been measured. The isotope effect associated with 2D melting has been investigated by comparing the behaviour of monolayers of CH 4 and CD 4 adsorbed on boron nitride. The vapor pressure of Xe has been determined in the temperature range 101-120 K. (author) [fr

Monolayers of a De Novo Designed 4-Alpha-Helix Bundle Carboprotein and Partial Structures on Au(111)-Surfaces

DEFF Research Database (Denmark)

Brask, Jesper; Wackerbarth, Hainer; Jensen, Knud Jørgen

2002-01-01

on a galactopyranoside derivative with a thiol anchor aglycon suitable for surface immobilization on gold. The galactopyranoside with thiol anchor and the thiol anchor alone were prepared for comparison. Voltammetry of the three molecules on Au(111) showed reductive desorption peaks caused by monolayer adsorption via...... thiolate-Au bonding. In situ STM of the thiol anchor disclosed an ordered adlayer with clear domains and molecular features. This holds promise, broadly for single-molecule voltammetry and the SPM and scanning tunnelling microscopy (STM) of natural and synthetic proteins....

Interfacial and thermal energy driven growth and evolution of Langmuir-Schaefer monolayers of Au-nanoparticles.

Science.gov (United States)

Mukhopadhyay, Mala; Hazra, S

2018-01-03

Structures of Langmuir-Schaefer (LS) monolayers of thiol-coated Au-nanoparticles (DT-AuNPs) deposited on H-terminated and OTS self-assembled Si substrates (of different hydrophobic strength and stability) and their evolution with time under ambient conditions, which plays an important role for their practical use as 2D-nanostructures over large areas, were investigated using the X-ray reflectivity technique. The strong effect of substrate surface energy (γ) on the initial structures and the competitive role of room temperature thermal energy (kT) and the change in interfacial energy (Δγ) at ambient conditions on the evolution and final structures of the DT-AuNP LS monolayers are evident. The strong-hydrophobic OTS-Si substrate, during transfer, seems to induce strong attraction towards hydrophobic DT-AuNPs on hydrophilic (repulsive) water to form vertically compact partially covered (with voids) monolayer structures (of perfect monolayer thickness) at low pressure and nearly covered buckled monolayer structures (of enhanced monolayer thickness) at high pressure. After transfer, the small kT-energy (in absence of repulsive water) probably fluctuates the DT-AuNPs to form vertically expanded monolayer structures, through systematic exponential growth with time. The effect is prominent for the film deposited at low pressure, where the initial film-coverage and film-thickness are low. On the other hand, the weak-hydrophobic H-Si substrate, during transfer, appears to induce optimum attraction towards DT-AuNPs to better mimic the Langmuir monolayer structures on it. After transfer, the change in the substrate surface nature, from weak-hydrophobic to weak-hydrophilic with time (i.e. Δγ-energy, apart from the kT-energy), enhances the size of the voids and weakens the monolayer/bilayer structure to form a similar expanded monolayer structure, the thickness of which is probably optimized by the available thermal energy.

Desorption of 1,3,5-Trichlorobenzene from Multi-Walled Carbon Nanotubes: Impact of Solution Chemistry and Surface Chemistry

Directory of Open Access Journals (Sweden)

Sheikh Uddin

2013-05-01

Full Text Available The strong affinity of carbon nanotubes (CNTs to environmental contaminants has raised serious concern that CNTs may function as a carrier of environmental pollutants and lead to contamination in places where the environmental pollutants are not expected. However, this concern will not be realized until the contaminants are desorbed from CNTs. It is well recognized that the desorption of environmental pollutants from pre-laden CNTs varies with the environmental conditions, such as the solution pH and ionic strength. However, comprehensive investigation on the influence of solution chemistry on the desorption process has not been carried out, even though numerous investigations have been conducted to investigate the impact of solution chemistry on the adsorption of environmental pollutants on CNTs. The main objective of this study was to determine the influence of solution chemistry (e.g., pH, ionic strength and surface functionalization on the desorption of preloaded 1,3,5-trichlorobenzene (1,3,5-TCB from multi-walled carbon nanotubes (MWNTs. The results suggested that higher pH, ionic strength and natural organic matter in solution generally led to higher desorption of 1,3,5-TCB from MWNTs. However, the extent of change varied at different values of the tested parameters (e.g., pH 7. In addition, the impact of these parameters varied with MWNTs possessing different surface functional groups, suggesting that surface functionalization could considerably alter the environmental behaviors and impact of MWNTs.

Morphology control of anatase TiO2 for well-defined surface chemistry

KAUST Repository

Jeantelot, Gabriel; Ould-Chikh, Samy; Sofack-Kreutzer, Julien; Abou-Hamad, Edy; Anjum, Dalaver H.; Lopatin, Sergei; Harb, Moussab; Cavallo, Luigi; Basset, Jean-Marie

2018-01-01

A specific allotrope of titanium dioxide (anatase) was synthesized both with a standard thermodynamic morphology ({101}-anatase) and with a highly anisotropic morphology ({001}-anatase) dominated by the {001} facet (81%). The surface chemistry of both samples after dehydroxylation was studied by 1H NMR and FT-IR. The influence of surface fluorides on the surface chemistry was also studied by 1H NMR, FT-IR and DFT. Full attribution of the IR spectra of anatase with dominant {001} facets could be provided based on experimental data and further confirmed by DFT. Our results showed that chemisorbed H2O molecules are still present on anatase after dehydroxylation at 350 °C, and that the type of surface hydroxyls present on the {001} facet is dependent on the presence of fluorides. They also provided general insight into the nature of the surface species on both fluorinated and fluorine-free anatase. The use of vanadium oxychloride (VOCl3) allowed the determination of the accessibility of the various OH groups spectroscopically observed.

Morphology control of anatase TiO2 for well-defined surface chemistry

KAUST Repository

Jeantelot, Gabriel

2018-05-16

A specific allotrope of titanium dioxide (anatase) was synthesized both with a standard thermodynamic morphology ({101}-anatase) and with a highly anisotropic morphology ({001}-anatase) dominated by the {001} facet (81%). The surface chemistry of both samples after dehydroxylation was studied by 1H NMR and FT-IR. The influence of surface fluorides on the surface chemistry was also studied by 1H NMR, FT-IR and DFT. Full attribution of the IR spectra of anatase with dominant {001} facets could be provided based on experimental data and further confirmed by DFT. Our results showed that chemisorbed H2O molecules are still present on anatase after dehydroxylation at 350 °C, and that the type of surface hydroxyls present on the {001} facet is dependent on the presence of fluorides. They also provided general insight into the nature of the surface species on both fluorinated and fluorine-free anatase. The use of vanadium oxychloride (VOCl3) allowed the determination of the accessibility of the various OH groups spectroscopically observed.

UV-induced reaction kinetics in dilinoleoylphosphatidylcholine monolayers with incorporated photosensitizers

Directory of Open Access Journals (Sweden)

DEJAN MARKOVIC

2006-04-01

Full Text Available Mixed insoluble monolayers (Langmuir films of 1,2-di-O-linoleoyl-3-sn-phosphatidylcholine (1,2-DLPC and incorporated benzophenone-type photosensitizers at an air-water interface were exposed to prolonged UV-irradiation. The irradiation was initiated at a particular fixed molecular packing value. Changes of the surface pressure during the UV-induced photolysis of the sensitizers were plotted against the irradiation time and the results were interpreted in terms of themolecular lipid / sensitizer ratios inside the monolayers.

Structure formation and surface chemistry of ionic liquids on model electrode surfaces—Model studies for the electrode | electrolyte interface in Li-ion batteries

Science.gov (United States)

Buchner, Florian; Uhl, Benedikt; Forster-Tonigold, Katrin; Bansmann, Joachim; Groß, Axel; Behm, R. Jürgen

2018-05-01

Ionic liquids (ILs) are considered as attractive electrolyte solvents in modern battery concepts such as Li-ion batteries. Here we present a comprehensive review of the results of previous model studies on the interaction of the battery relevant IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]+[TFSI]-) with a series of structurally and chemically well-defined model electrode surfaces, which are increasingly complex and relevant for battery applications [Ag(111), Au(111), Cu(111), pristine and lithiated highly oriented pyrolytic graphite (HOPG), and rutile TiO2(110)]. Combining surface science techniques such as high resolution scanning tunneling microscopy and X-ray photoelectron spectroscopy for characterizing surface structure and chemical composition in deposited (sub-)monolayer adlayers with dispersion corrected density functional theory based calculations, this work aims at a molecular scale understanding of the fundamental processes at the electrode | electrolyte interface, which are crucial for the development of the so-called solid electrolyte interphase (SEI) layer in batteries. Performed under idealized conditions, in an ultrahigh vacuum environment, these model studies provide detailed insights on the structure formation in the adlayer, the substrate-adsorbate and adsorbate-adsorbate interactions responsible for this, and the tendency for chemically induced decomposition of the IL. To mimic the situation in an electrolyte, we also investigated the interaction of adsorbed IL (sub-)monolayers with coadsorbed lithium. Even at 80 K, postdeposited Li is found to react with the IL, leading to decomposition products such as LiF, Li3N, Li2S, LixSOy, and Li2O. In the absence of a [BMP]+[TFSI]- adlayer, it tends to adsorb, dissolve, or intercalate into the substrate (metals, HOPG) or to react with the substrate (TiO2) above a critical temperature, forming LiOx and Ti3+ species in the latter case. Finally, the formation of stable

Study of structural order in porphyrin-fullerene dyad ZnDHD6ee monolayers by electron diffraction and atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

D' yakova, Yu. A.; Suvorova, E. I.; Orekhov, Andrei S.; Orekhov, Anton S. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Alekseev, A. S. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Gainutdinov, R. V.; Klechkovskaya, V. V., E-mail: klechvv@ns.crys.ras.ru; Tereschenko, E. Yu. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Tkachenko, N. V.; Lemmetyinen, H. [Tampere University of Technology (Finland); Feigin, L. A.; Kovalchuk, M. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2013-11-15

The structure of porphyrin-fullerene dyad ZnDHD6ee monolayers formed on the surface of aqueous subphase in a Langmuir trough and transferred onto solid substrates has been studied. The data obtained are interpreted using simulation of the structure of isolated molecules and their packing in monolayer and modeling of diffraction patterns from molecular aggregates having different sizes and degrees of order. Experiments on the formation of condensed ZnDHD6ee monolayers are described. The structure of these monolayers on a water surface is analyzed using {pi}-A isotherms. The structure of the monolayers transferred onto solid substrates is investigated by electron diffraction and atomic force microscopy. The unit-cell parameters of two-dimensional domains, which are characteristic of molecular packing in monolayers and deposited films, are determined. Domains are found to be organized into a texture (the molecular axes are oriented by the [001] direction perpendicular to the substrate). The monolayers contain a limited number of small 3D domains.

Surface topography and chemistry shape cellular behavior on wide band-gap semiconductors.

Science.gov (United States)

Bain, Lauren E; Collazo, Ramon; Hsu, Shu-Han; Latham, Nicole Pfiester; Manfra, Michael J; Ivanisevic, Albena

2014-06-01

The chemical stability and electrical properties of gallium nitride make it a promising material for the development of biocompatible electronics, a range of devices including biosensors as well as interfaces for probing and controlling cellular growth and signaling. To improve the interface formed between the probe material and the cell or biosystem, surface topography and chemistry can be applied to modify the ways in which the device interacts with its environment. PC12 cells are cultured on as-grown planar, unidirectionally polished, etched nanoporous and nanowire GaN surfaces with and without a physisorbed peptide sequence that promotes cell adhesion. While cells demonstrate preferential adhesion to roughened surfaces over as-grown flat surfaces, the topography of that roughness also influences the morphology of cellular adhesion and differentiation in neurotypic cells. Addition of the peptide sequence generally contributes further to cellular adhesion and promotes development of stereotypic long, thin neurite outgrowths over alternate morphologies. The dependence of cell behavior on both the topographic morphology and surface chemistry is thus demonstrated, providing further evidence for the importance of surface modification for modulating bio-inorganic interfaces. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Platinum Monolayer Electrocatalysts for Anodic Oxidation of Alcohols.

Science.gov (United States)

Li, Meng; Liu, Ping; Adzic, Radoslav R

2012-12-06

The slow, incomplete oxidation of methanol and ethanol on platinum-based anodes as well as the high price and limited reserves of Pt has hampered the practical application of direct alcohol fuel cells. We describe the electrocatalysts consisting of one Pt monolayer (one atom thick layer) placed on extended or nanoparticle surfaces having the activity and selectivity for the oxidation of alcohol molecules that can be controlled with platinum-support interaction. The suitably expanded Pt monolayer (i.e., Pt/Au(111)) exhibits a factor of 7 activity increase in catalyzing methanol electrooxidation relative to Pt(111). Sizable enhancement is also observed for ethanol electrooxidation. Furthermore, a correlation between substrate-induced lateral strain in a Pt monolayer and its activity/selectivity is established and rationalized by experimental and theoretical studies. The knowledge we gained with single-crystal model catalysts was successfully applied in designing real nanocatalysts. These findings for alcohols are likely to be applicable for the oxidation of other classes of organic molecules.

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.

Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels.

Science.gov (United States)

Chinga-Carrasco, Gary; Syverud, Kristin

2014-09-01

Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups are abundant in nanocellulose materials, making the material strongly hydrophilic. Second, the surface chemistry can be modified, introducing aldehyde and carboxyl groups, which have major potential for surface functionalization. In this study, we demonstrate the production of nanocellulose with tailor-made surface chemistry, by pre-treating the raw cellulose fibres with carboxymethylation and periodate oxidation. The pre-treatments yielded a highly nanofibrillated material, with significant amounts of aldehyde and carboxyl groups. Importantly, the poly-anionic surface of the oxidized nanocellulose opens up for novel applications, i.e. micro-porous materials with pH-responsive characteristics. This is due to the swelling capacity of the 3D micro-porous structures, which have ionisable functional groups. In this study, we demonstrated that nanocellulose gels have a significantly higher swelling degree in neutral and alkaline conditions, compared to an acid environment (pH 3). Such a capability can potentially be applied in chronic wounds for controlled and intelligent release of antibacterial components into biofilms. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Engineering of Surface Chemistry for Enhanced Sensitivity in Nanoporous Interferometric Sensing Platforms.

Science.gov (United States)

Law, Cheryl Suwen; Sylvia, Georgina M; Nemati, Madieh; Yu, Jingxian; Losic, Dusan; Abell, Andrew D; Santos, Abel

2017-03-15

We explore new approaches to engineering the surface chemistry of interferometric sensing platforms based on nanoporous anodic alumina (NAA) and reflectometric interference spectroscopy (RIfS). Two surface engineering strategies are presented, namely (i) selective chemical functionalization of the inner surface of NAA pores with amine-terminated thiol molecules and (ii) selective chemical functionalization of the top surface of NAA with dithiol molecules. The strong molecular interaction of Au 3+ ions with thiol-containing functional molecules of alkane chain or peptide character provides a model sensing system with which to assess the sensitivity of these NAA platforms by both molecular feature and surface engineering. Changes in the effective optical thickness of the functionalized NAA photonic films (i.e., sensing principle), in response to gold ions, are monitored in real-time by RIfS. 6-Amino-1-hexanethiol (inner surface) and 1,6-hexanedithiol (top surface), the most sensitive functional molecules from approaches i and ii, respectively, were combined into a third sensing strategy whereby the NAA platforms are functionalized on both the top and inner surfaces concurrently. Engineering of the surface according to this approach resulted in an additive enhancement in sensitivity of up to 5-fold compared to previously reported systems. This study advances the rational engineering of surface chemistry for interferometric sensing on nanoporous platforms with potential applications for real-time monitoring of multiple analytes in dynamic environments.

Surface chemistry of Ti6Al4V components fabricated using selective laser melting for biomedical applications.

Science.gov (United States)

Vaithilingam, Jayasheelan; Prina, Elisabetta; Goodridge, Ruth D; Hague, Richard J M; Edmondson, Steve; Rose, Felicity R A J; Christie, Steven D R

2016-10-01

Selective laser melting (SLM) has previously been shown to be a viable method for fabricating biomedical implants; however, the surface chemistry of SLM fabricated parts is poorly understood. In this study, X-ray photoelectron spectroscopy (XPS) was used to determine the surface chemistries of (a) SLM as-fabricated (SLM-AF) Ti6Al4V and (b) SLM fabricated and mechanically polished (SLM-MP) Ti6Al4V samples and compared with (c) traditionally manufactured (forged) and mechanically polished Ti6Al4V samples. The SLM-AF surface was observed to be porous with an average surface roughness (Ra) of 17.6±3.7μm. The surface chemistry of the SLM-AF was significantly different to the FGD-MP surface with respect to elemental distribution and their existence on the outermost surface. Sintered particles on the SLM-AF surface were observed to affect depth profiling of the sample due to a shadowing effect during argon ion sputtering. Surface heterogeneity was observed for all three surfaces; however, vanadium was witnessed only on the mechanically polished (SLM-MP and FGD-MP) surfaces. The direct and indirect 3T3 cell cytotoxicity studies revealed that the cells were viable on the SLM fabricated Ti6Al4V parts. The varied surface chemistry of the SLM-AF and SLM-MP did not influence the cell behaviour. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Self-assembled monolayers of semi-fluorinated thiols and disulfides with a potentially antibacterial terminal fragment on gold surfaces

International Nuclear Information System (INIS)

Thebault, P.; Taffin de Givenchy, E.; Guittard, F.; Guimon, C.; Geribaldi, S.

2008-01-01

Attempts to elaborate the best organized cationic self-assembled monolayers (SAMs) with sulfur derivatives containing potentially bactericidal quaternary ammonium salt moieties have been performed on gold with the final aim to obtain contact-active antibacterial surfaces. Four molecules bearing two hydrocarbon spacers with different lengths between the sulfur atom and the quaternized nitrogen atom, and two different terminal semi-fluorinated alkyl chains have been synthesised and used in view to evaluate their capacity for leading to the highest densities and the highest organization of potentially active molecules on the metal surface. The formation and quality of SAMs characterized by X-ray photoelectron spectroscopy, Internal Reflexion Infra Red Imaging, contact angle and blocking factor measurements depend on the lengths of both the hydrocarbon spacer and terminal perfluorinated chain

Lateral electron transport in monolayers of short chains at interfaces: A Monte Carlo study

International Nuclear Information System (INIS)

George, Christopher B.; Szleifer, Igal; Ratner, Mark A.

2010-01-01

Graphical abstract: Electron hopping between electroactive sites in a monolayer composed of redox-active and redox-passive molecules. - Abstract: Using Monte Carlo simulations, we study lateral electronic diffusion in dense monolayers composed of a mixture of redox-active and redox-passive chains tethered to a surface. Two charge transport mechanisms are considered: the physical diffusion of electroactive chains and electron hopping between redox-active sites. Results indicate that by varying the monolayer density, the mole fraction of electroactive chains, and the electron hopping range, the dominant charge transport mechanism can be changed. For high density monolayers in a semi-crystalline phase, electron diffusion proceeds via electron hopping almost exclusively, leading to static percolation behavior. In fluid monolayers, the diffusion of chains may contribute more to the overall electronic diffusion, reducing the observed static percolation effects.

Intramolecular and Lattice Melting in n-Alkane Monolayers: An Analog of Melting in Lipid Bilayers

DEFF Research Database (Denmark)

Hansen, Flemming Yssing; Herwig, K.W.; Matthies, B.

1999-01-01

Molecular dynamics (MD) simulations and neutron diffraction experiments have been performed on n-dotriacontane (n-C32D66) monolayers adsorbed on a graphite basal-plane surface. The diffraction experiments show little change in the crystalline monolayer structure up to a temperature of similar to ...

Dynamical simulation of electron transfer processes in self-assembled monolayers at metal surfaces using a density matrix approach.

Science.gov (United States)

Prucker, V; Bockstedte, M; Thoss, M; Coto, P B

2018-03-28

A single-particle density matrix approach is introduced to simulate the dynamics of heterogeneous electron transfer (ET) processes at interfaces. The characterization of the systems is based on a model Hamiltonian parametrized by electronic structure calculations and a partitioning method. The method is applied to investigate ET in a series of nitrile-substituted (poly)(p-phenylene)thiolate self-assembled monolayers adsorbed at the Au(111) surface. The results show a significant dependence of the ET on the orbital symmetry of the donor state and on the molecular and electronic structure of the spacer.

Dynamical simulation of electron transfer processes in self-assembled monolayers at metal surfaces using a density matrix approach

Science.gov (United States)

Prucker, V.; Bockstedte, M.; Thoss, M.; Coto, P. B.

2018-03-01

A single-particle density matrix approach is introduced to simulate the dynamics of heterogeneous electron transfer (ET) processes at interfaces. The characterization of the systems is based on a model Hamiltonian parametrized by electronic structure calculations and a partitioning method. The method is applied to investigate ET in a series of nitrile-substituted (poly)(p-phenylene)thiolate self-assembled monolayers adsorbed at the Au(111) surface. The results show a significant dependence of the ET on the orbital symmetry of the donor state and on the molecular and electronic structure of the spacer.

Functionalizable self-assembled trichlorosilyl-based monolayer for application in biosensor technology

Energy Technology Data Exchange (ETDEWEB)

De La Franier, Brian; Jankowski, Alexander; Thompson, Michael, E-mail: mikethom@chem.utoronto.ca

2017-08-31

This paper describes the design and synthesis of 3-(3-(trichlorosilyl)propoxy)propanoyl chloride (MEG-Cl), a compound capable of forming functionalizable monolayers on hydroxylated surfaces. The compound was synthesized in high purity, as suggested by nuclear magnetic resonance analysis, and in moderate overall yield. Contact angle measurement and X-ray photoelectron spectroscopy confirm the binding of MEG-Cl to an amorphous glass substrate and the further modification of the monolayer with a nickel (II)-binding ligand for the purpose of binding polyhistidine-tagged proteins. The compound will be useful in biosensing applications due to its ability to be easily modified with any number of nucleophilic functional groups subsequent to substrate monolayer formation.

Investigating effects of hypertonic saline solutions on lipid monolayers at the air-water interface

KAUST Repository

Nava Ocampo, Maria F.

2017-05-01

More than 70,000 people worldwide suffer from cystic fibrosis, a genetic disease characterized by chronic accumulation of mucus in patients’ lungs provoking bacterial infections, and leading to respiratory failure. An employed age-old treatment to prevent the symptoms of the disease is inhalation of hypertonic saline solution, NaCl at concentrations higher than in the human body (~150 mM). This procedure clears the mucus in the lungs, bringing relief to the patient. However, the biophysical mechanisms underlying this process are not entirely clear. We undertook a new experimental approach to understand the effects of sprayed saline solutions on model lung surfactants towards understanding the mechanisms of the treatment. The surface of lungs contains mainly 1,2-Dipalmitol-sn-glycero-3-phosphocoline (DPPC). As previously assumed by others, we considered that monolayer of DPPC at the air-water interface serves as model system for the lungs surface; we employed a Langmuir-Blodgett (LB) trough and PM-IRRAS to measure surface-specific infrared spectra of the surfactant monolayers and effects on the interfacial tensions. We investigated spraying hyper-saline solutions onto surfactant monolayers at the airwater interface in two parts: (i) validation of our methodology and techniques with stearic acid and (ii) experiments with DPPC monolayers at the air-water interface. Remarkably, when micro-droplets of NaCl were sprayed to the monolayer of stearic acid, we observed enhanced organization of the surfactant, interpreted from the intensities of the CH2 peaks in the surface-specific IR spectra. However, our results with DPPC monolayers didn’t show an effect with the salt added as aerosol, possibly indicating that the experimental methodology proposed is not adequate for the phenomena studied. In parallel, we mimicked respiratory mucous by preparing salt solutions containing 1% (wt%) agar and measured effects on their viscosities. Interestingly, we found that NaCl was much

Roles of surface chemistry on safety and electrochemistry in lithium ion batteries.

Science.gov (United States)

Lee, Kyu Tae; Jeong, Sookyung; Cho, Jaephil

2013-05-21

Motivated by new applications including electric vehicles and the smart grid, interest in advanced lithium ion batteries has increased significantly over the past decade. Therefore, research in this field has intensified to produce safer devices with better electrochemical performance. Most research has focused on the development of new electrode materials through the optimization of bulk properties such as crystal structure, ionic diffusivity, and electric conductivity. More recently, researchers have also considered the surface properties of electrodes as critical factors for optimizing performance. In particular, the electrolyte decomposition at the electrode surface relates to both a lithium ion battery's electrochemical performance and safety. In this Account, we give an overview of the major developments in the area of surface chemistry for lithium ion batteries. These ideas will provide the basis for the design of advanced electrode materials. Initially, we present a brief background to lithium ion batteries such as major chemical components and reactions that occur in lithium ion batteries. Then, we highlight the role of surface chemistry in the safety of lithium ion batteries. We examine the thermal stability of cathode materials: For example, we discuss the oxygen generation from cathode materials and describe how cells can swell and heat up in response to specific conditions. We also demonstrate how coating the surfaces of electrodes can improve safety. The surface chemistry can also affect the electrochemistry of lithium ion batteries. The surface coating strategy improved the energy density and cycle performance for layered LiCoO2, xLi2MnO3·(1 - x)LiMO2 (M = Mn, Ni, Co, and their combinations), and LiMn2O4 spinel materials, and we describe a working mechanism for these enhancements. Although coating the surfaces of cathodes with inorganic materials such as metal oxides and phosphates improves the electrochemical performance and safety properties of

Biofunctionalization on Alkylated Silicon Substrate Surfaces via “Click” Chemistry

OpenAIRE

Qin, Guoting; Santos, Catherine; Zhang, Wen; Li, Yan; Kumar, Amit; Erasquin, Uriel J.; Liu, Kai; Muradov, Pavel; Trautner, Barbara Wells; Cai, Chengzhi

2010-01-01

Biofunctionalization of silicon substrates is important to the development of silicon-based biosensors and devices. Compared to conventional organosiloxane films on silicon oxide intermediate layers, organic monolayers directly bound to the non-oxidized silicon substrates via Si-C bonds enhance the sensitivity of detection and the stability against hydrolytic cleavage. Such monolayers presenting a high density of terminal alkynyl groups for bioconjugation via copper-catalyzed azide-alkyne 1,3...

X-ray studies of the liquid/vapor interface: Water and polymer and fatty acid monolayers on water

International Nuclear Information System (INIS)

Schlossman, M.L.; Schwartz, D.K.; Kawamoto, E.H.; Kellogg, G.J.; Pershan, P.S.; Ocko, B.M.; Kim, M.W.; Chung, T.C.

1989-01-01

X-ray specular reflectivity is used to study the liquid-vapor interface of pure water and of fatty acid and polymer monolayers at that interface. For the pure water surface the reflectivity was measured for three different spectrometer resolutions and simultaneous fits with only one free parameter to all of the data are in excellent agreement with the prediction of capillary wave theory for the RMS surface roughness. Diffuse scattering away from the specular condition, at wavevectors corresponding to those of the capillary waves, yields intensities and line shapes in agreement with theory with no significant adjustable parameters. Reflectivity from separate monolayers of co-poly 1, 2-butadiene/butyl alcohol (50% random substitution) and lignoceric acid (CH 3 (CH 2 ) 22 COOH) at the water/vapor interface are interpreted to obtain profiles of the average electron density ρ(z) as a function of distance z along the surface normal. For the polymer monolayer we find the following: (1) a local maximum in the electron density approximately 10% larger than that of the bulk polymer and (2) the RMS roughness of the vapor/polymer interface agrees with capillary wave theory predictions for the lower surface pressures. For the highest surface pressure the RMS roughness exceeds the value predicted by the capillary wave model. Measurements of reflectivity from a lignoceric acid monolayer, as a function of surface pressure throughout an isotherm (near room temperature), reveal the following behavior: (1) the overall thickness of the monolayer increases with increasing pressure and (2) the head groups occupy a progressively larger region along the surface normal as the pressure increases, indicating that they rearrange normal to the interface. 15 refs., 5 figs., 2 tabs

Supramolecular chemistry at interfaces: host-guest interactions for fabricating multifunctional biointerfaces.

Science.gov (United States)

Yang, Hui; Yuan, Bin; Zhang, Xi; Scherman, Oren A

2014-07-15

. We begin by reviewing the current state of stimuli-responsive supramolecular assemblies formed by host-guest interactions, discussing how to transfer host-guest chemistry from solution onto surfaces required for fabricating multifunctional biosurfaces and biointerfaces. Then, we present different stimuli-responsive biosurfaces and biointerfaces, which have been prepared through a combination of cyclodextrin- or cucurbituril-based host-guest chemistry and various surface technologies such as self-assembled monolayers or layer-by-layer assembly. Moreover, we discuss the applications of these biointerfaces and biosurfaces in the fields of drug release, reversible adsorption and release of some organic molecules, peptides, proteins, and cells, and photoswitchable bioelectrocatalysis. In addition, we summarize the merits and current limitations of these methods for fabricating multifunctional stimuli-responsive biointerfaces in a dynamic noncovalent manner. Finally, we present possible strategies for future designs of stimuli-responsive multifunctional biointerfaces and biosurfaces by combining host-guest chemistry with surface science, which will lead to further critical development of supramolecular chemistry at interfaces.

Laboratory Activity Worksheet to Train High Order Thinking Skill of Student on Surface Chemistry Lecture

Science.gov (United States)

Yonata, B.; Nasrudin, H.

2018-01-01

A worksheet has to be a set with activity which is help students to arrange their own experiments. For this reason, this research is focused on how to train students’ higher order thinking skills in laboratory activity by developing laboratory activity worksheet on surface chemistry lecture. To ensure that the laboratory activity worksheet already contains aspects of the higher order thinking skill, it requires theoretical and empirical validation. From the data analysis results, it shows that the developed worksheet worth to use. The worksheet is worthy of theoretical and empirical feasibility. This conclusion is based on the findings: 1) Assessment from the validators about the theoretical feasibility aspects in the category is very feasible with an assessment range of 95.24% to 97.92%. 2) students’ higher thinking skill from N Gain values ranges from 0.50 (enough) to 1.00 (high) so it can be concluded that the laboratory activity worksheet on surface chemistry lecture is empirical in terms of worth. The empirical feasibility is supported by the responses of the students in very reasonable categories. It is expected that the laboratory activity worksheet on surface chemistry lecture can train students’ high order thinking skills for students who program surface chemistry lecture.

Chemically Transformable Configurations of Mercaptohexadecanoic Acid Self-Assembled Monolayers Adsorbed on Au(111)

International Nuclear Information System (INIS)

van Buuren, T; Bostedt, C; Nelson, A J; Terminello, L J; Vance, A L; Fadley, C S; Willey, T M

2003-01-01

Carboxyl terminated Self-Assembled Monolayers (SAMs) are commonly used in a variety of applications, with the assumption that the molecules form well ordered monolayers. In this work, NEXAFS verifies well ordered monolayers can be formed using acetic acid in the solvent. Disordered monolayers with unbound molecules present in the result using only ethanol. A stark reorientation occurs upon deprotonation of the endgroup by rinsing in a KOH solution. This reorientation of the endgroup is reversible with tilted over, hydrogen bound carboxyl groups while carboxylate-ion endgroups are upright. C1s photoemission shows that SAMs formed and rinsed with acetic acid in ethanol, the endgroups are protonated, while without, a large fraction of the molecules on the surface are carboxylate terminated

Monolayer-by-monolayer growth of platinum films on complex carbon fiber paper structure

Energy Technology Data Exchange (ETDEWEB)

Pang, Liuqing; Zhang, Yunxia [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Liu, Shengzhong, E-mail: szliu@dicp.ac.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Dalian National Laboratory for Clean Energy, iChEM, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

2017-06-15

Graphical abstract: A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer strategy. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. - Highlights: • Developed a controlled monolayer-by-monolayer Pt deposition using a dual buffer strategy. • The present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. • This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. - Abstract: A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer (Au/Ni) strategy. The X-ray diffraction, electrochemical quartz crystal microbalance, current density analyses, and X-ray photoelectron spectroscopy results conclude that the monolayer deposition process accomplishes full coverage on the substrate and that the thickness of the deposition layer can be controlled on a single atom scale. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value.

1-Dodecanethiol based highly stable self-assembled monolayers for germanium passivation

International Nuclear Information System (INIS)

Cai, Qi; Xu, Baojian; Ye, Lin; Di, Zengfeng; Huang, Shanluo; Du, Xiaowei; Zhang, Jishen; Jin, Qinghui; Zhao, Jianlong

2015-01-01

Highlights: • A simple and effective approach for higly stable germanium passivation. • 1-Dodecanethiol self-assembled monolayers for germanium oxidation resistance. • The influence factors of germanium passivation were systematically studied. • The stability of the passivated Ge was more than 10 days even in water conditions. - Abstract: As a typical semiconductor material, germanium has the potential to replace silicon for future-generation microelectronics, due to its better electrical properties. However, the lack of stable surface state has limited its extensive use for several decades. In this work, we demonstrated highly stable self-assembled monolayers (SAMs) on Ge surface to prevent oxidization for further applications. After the pretreatment in hydrochloric acid, the oxide-free and Cl-terminated Ge could be further coated with 1-dodecanethiol (NDM) SAMs. The influence factors including reaction time, solvent component and reaction temperature were optimized to obtain stable passivated monolayer for oxidation resistance. Contact angle analysis, atomic force microscopy, ellipsometer and X-ray photoelectron spectroscopy were performed to characterize the functionalized Ge surface respectively. Meanwhile, the reaction mechanism and stability of thiols SAMs on Ge (1 1 1) surface were investigated. Finally, highly stable passivated NDM SAMs on Ge surface could be formed through immersing oxide-free Ge in mixture solvent (water/ethanol, v/v = 1:1) at appropriately elevated temperature (∼80 °C) for 24 h. And the corresponding optimized passivated Ge surface was stable for more than 10 days even in water condition, which was much longer than the data reported and paved the way for the future practical applications of Ge.

1-Dodecanethiol based highly stable self-assembled monolayers for germanium passivation

Energy Technology Data Exchange (ETDEWEB)

Cai, Qi [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No. 865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No. 19A, Yuquan Road, Beijing 100049 (China); Xu, Baojian, E-mail: xbj@mail.sim.ac.cn [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No. 865, Changning Road, Shanghai 200050 (China); Shanghai Internet of Things Co., LTD, No. 1455, Pingcheng Road, Shanghai 201899 (China); Ye, Lin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No. 865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No. 19A, Yuquan Road, Beijing 100049 (China); Di, Zengfeng [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No. 865, Changning Road, Shanghai 200050 (China); Huang, Shanluo; Du, Xiaowei [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No. 865, Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No. 19A, Yuquan Road, Beijing 100049 (China); Zhang, Jishen; Jin, Qinghui [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No. 865, Changning Road, Shanghai 200050 (China); Zhao, Jianlong, E-mail: jlzhao@mail.sim.ac.cn [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, No. 865, Changning Road, Shanghai 200050 (China)

2015-10-30

Highlights: • A simple and effective approach for higly stable germanium passivation. • 1-Dodecanethiol self-assembled monolayers for germanium oxidation resistance. • The influence factors of germanium passivation were systematically studied. • The stability of the passivated Ge was more than 10 days even in water conditions. - Abstract: As a typical semiconductor material, germanium has the potential to replace silicon for future-generation microelectronics, due to its better electrical properties. However, the lack of stable surface state has limited its extensive use for several decades. In this work, we demonstrated highly stable self-assembled monolayers (SAMs) on Ge surface to prevent oxidization for further applications. After the pretreatment in hydrochloric acid, the oxide-free and Cl-terminated Ge could be further coated with 1-dodecanethiol (NDM) SAMs. The influence factors including reaction time, solvent component and reaction temperature were optimized to obtain stable passivated monolayer for oxidation resistance. Contact angle analysis, atomic force microscopy, ellipsometer and X-ray photoelectron spectroscopy were performed to characterize the functionalized Ge surface respectively. Meanwhile, the reaction mechanism and stability of thiols SAMs on Ge (1 1 1) surface were investigated. Finally, highly stable passivated NDM SAMs on Ge surface could be formed through immersing oxide-free Ge in mixture solvent (water/ethanol, v/v = 1:1) at appropriately elevated temperature (∼80 °C) for 24 h. And the corresponding optimized passivated Ge surface was stable for more than 10 days even in water condition, which was much longer than the data reported and paved the way for the future practical applications of Ge.

MURI Center for Materials Chemistry in the Space Environment

Science.gov (United States)

2006-11-30

ionic species in relevant reaction environments, surface photochemistry expertise, synchrotron-based measurement and irradiation, synthesis of structural...and Ne+ ions with dodecanethiolate and semifluorinated dodecanethiolate self-assembled monolayers (SAM), polyhedral oligomeric silsesquioxane (POSS...POSS/Kapton models as gas phase species, and with alkane thiol self assembled monolayers on gold surfaces, and with liquid squalane. We have also

Conformal and highly luminescent monolayers of Alq3 prepared by gas-phase molecular layer deposition.

Science.gov (United States)

Räupke, André; Albrecht, Fabian; Maibach, Julia; Behrendt, Andreas; Polywka, Andreas; Heiderhoff, Ralf; Helzel, Jonatan; Rabe, Torsten; Johannes, Hans-Hermann; Kowalsky, Wolfgang; Mankel, Eric; Mayer, Thomas; Görrn, Patrick; Riedl, Thomas

2014-01-22

The gas-phase molecular layer deposition (MLD) of conformal and highly luminescent monolayers of tris(8-hydroxyquinolinato)aluminum (Alq3) is reported. The controlled formation of Alq3 monolayers is achieved for the first time by functionalization of the substrate with amino groups, which serve as initial docking sites for trimethyl aluminum (TMA) molecules binding datively to the amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting formation of highly luminescent Alq3 monolayers is afforded. The growth process and monolayer formation were studied and verified by in situ quartz crystal monitoring, optical emission and absorption spectroscopy, and X-ray photoelectron spectroscopy. The nature of the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces and porous structures with high surface areas, as demonstrated in this work for silica aerogels. The concept presented here paves the way to highly sensitive luminescent sensors and dye-sensitized metal oxides for future applications (e.g., in photocatalysis and solar cells).

Studies of the surface structures of molecular crystals and of adsorbed molecular monolayers on the (111) crystal faces of platinum and silver by low-energy electron diffraction

International Nuclear Information System (INIS)

Firment, L.E.

1977-01-01

The structures of molecular crystal surfaces were investigated for the first time by the use of low-energy electron diffraction (LEED). The experimental results from a variety of molecular crystals were examined and compared as a first step towards understanding the properties of these surfaces on a microscopic level. The method of sample preparation employed, vapor deposition onto metal single-crystal substrates at low temperatures in ultrahigh vacuum, allowed concurrent study of the structures of adsorbed monolayers on metal surfaces and of the growth processes of molecular films on metal substrates. The systems investigated were ice, ammonia, naphthalene, benzene, the n-paraffins (C 3 to C 8 ), cyclohexane, trioxane, acetic acid, propionic acid, methanol, and methylamine adsorbed and condensed on both Pt(111) and Ag(111) surfaces. Electron-beam-induced damage of the molecular surfaces was observed after electron exposures of 10 -4 A sec cm -2 at 20 eV. Aromatic molecular crystal samples were more resistant to damage than samples of saturated molecules. The quality and orientation of the grown molecular crystal films were influenced by substrate preparation and growth conditions. Forty ordered monolayer structures were observed. 110 figures, 22 tables, 162 references

Headgroup effects of template monolayers on the adsorption behavior and conformation of glucose oxidase adsorbed at air/liquid interfaces.

Science.gov (United States)

Wang, Ke-Hsuan; Syu, Mei-Jywan; Chang, Chien-Hsiang; Lee, Yuh-Lang

2011-06-21

Stearic acid (SA) and octadecylamine (ODA) monolayers at the air/liquid interface were used as template layers to adsorb glucose oxidase (GOx) from aqueous solution. The effect of the template monolayers on the adsorption behavior of GOx was studied in terms of the variation of surface pressure, the evolution of surface morphology observed by BAM and AFM, and the conformation of adsorbed GOx. The results show that the presence of a template monolayer can enhance the adsorption rate of GOx; furthermore, ODA has a higher ability, compared to SA, to adsorb GOx, which is attributed to the electrostatic attractive interaction between ODA and GOx. For adsorption performed on a bare surface or on an SA monolayer, the surface pressure approaches an equilibrium value (ca. 8 mN/m) after 2 to 3 h of adsorption and remains nearly constant in the following adsorption process. For the adsorption on an ODA monolayer, the surface pressure will increase further 1 to 2 h after approaching the first equilibrium pressure, which is termed the second adsorption stage. The measurement of circular dichroism (CD) spectroscopy indicates that the Langmuir-Blodgett films of adsorbed GOx transferred at the first equilibrium state (π = 8 mN/m) have mainly a β-sheet conformation, which is independent of the type of template monolayers. However, the ODA/GOx LB film transferred at the second adsorption stage has mainly an α-helix conformation. It is concluded that the specific interaction between ODA and GOx not only leads to a higher adsorption rate and adsorbed amount of GOx but also induces a conformation change in adsorbed GOx from β-sheet to α-helix. The present results indicate that is possible to control the conformation of adsorbed protein by selecting the appropriate template monolayer. © 2011 American Chemical Society

Density functional study of CaN monolayer on Si(001)

Energy Technology Data Exchange (ETDEWEB)

Saati asr, Maryam; Zahedifar, Maedeh; Hashemifar, S. Javad; Akbarzadeh, Hadi

2016-01-01

In this work, the first-principles computations are performed to study the structural and magnetic properties of CaN/Si(001) interface. Bulk CaN in the zinc-blende (ZB) structure is argued to be an ionic magnetic compound with a total spin moment of 1 μ{sub B} per formula unit, originated from the p electrons of N ions. Various interface configurations of a ZB CaN monolayer on Si (001) surface are investigated and the lowest energy and the highest spin polarized interfaces are extracted. Then the minimum energy path between the lowest energy and the highest spin polarized interfaces are calculated by using the nudged elastic band method and it is argued that both these systems are unstable toward a nonmagnetic interface with a rock–salt arrangement of Ca and N atoms. - Highlights: • Ab-initio studies are done on various structures of CaN monolayer on Si (001). • The lowest energy system was found to be the N-top configuration interface, while the highest spin polarization was observed in the Ca-hollow termination. • Both Ca-hollow and N-top are unstable toward a nonmagnetic rock–salt CaN monolayer on silicon surface. • Realization of a magnetic CaN/Si (001) interface likely requires some buffer layer on silicon surface, prior to the thin film deposition.

Density functional study of CaN monolayer on Si(001)

International Nuclear Information System (INIS)

Saati asr, Maryam; Zahedifar, Maedeh; Hashemifar, S. Javad; Akbarzadeh, Hadi

2016-01-01

In this work, the first-principles computations are performed to study the structural and magnetic properties of CaN/Si(001) interface. Bulk CaN in the zinc-blende (ZB) structure is argued to be an ionic magnetic compound with a total spin moment of 1 μ_B per formula unit, originated from the p electrons of N ions. Various interface configurations of a ZB CaN monolayer on Si (001) surface are investigated and the lowest energy and the highest spin polarized interfaces are extracted. Then the minimum energy path between the lowest energy and the highest spin polarized interfaces are calculated by using the nudged elastic band method and it is argued that both these systems are unstable toward a nonmagnetic interface with a rock–salt arrangement of Ca and N atoms. - Highlights: • Ab-initio studies are done on various structures of CaN monolayer on Si (001). • The lowest energy system was found to be the N-top configuration interface, while the highest spin polarization was observed in the Ca-hollow termination. • Both Ca-hollow and N-top are unstable toward a nonmagnetic rock–salt CaN monolayer on silicon surface. • Realization of a magnetic CaN/Si (001) interface likely requires some buffer layer on silicon surface, prior to the thin film deposition.

Surface Plasmon Polariton-Assisted Long-Range Exciton Transport in Monolayer Semiconductor Lateral Heterostructure

Science.gov (United States)

Shi, Jinwei; Lin, Meng-Hsien; Chen, Yi-Tong; Estakhri, Nasim Mohammadi; Tseng, Guo-Wei; Wang, Yanrong; Chen, Hung-Ying; Chen, Chun-An; Shih, Chih-Kang; Alã¹, Andrea; Li, Xiaoqin; Lee, Yi-Hsien; Gwo, Shangjr

Recently, two-dimensional (2D) semiconductor heterostructures, i.e., atomically thin lateral heterostructures (LHSs) based on transition metal dichalcogenides (TMDs) have been demonstrated. In an optically excited LHS, exciton transport is typically limited to a rather short spatial range ( 1 micron). Furthermore, additional losses may occur at the lateral interfacial regions. Here, to overcome these challenges, we experimentally implement a planar metal-oxide-semiconductor (MOS) structure by placing a monolayer of WS2/MoS2 LHS on top of an Al2O3 capped Ag single-crystalline plate. We found that the exciton transport range can be extended to tens of microns. The process of long-range exciton transport in the MOS structure is confirmed to be mediated by an exciton-surface plasmon polariton-exciton conversion mechanism, which allows a cascaded energy transfer process. Thus, the planar MOS structure provides a platform seamlessly combining 2D light-emitting materials with plasmonic planar waveguides, offering great potential for developing integrated photonic/plasmonic functionalities.

Investigations of nitrogen oxide plasmas: Fundamental chemistry and surface reactivity and monitoring student perceptions in a general chemistry recitation

Science.gov (United States)

Blechle, Joshua M.

Part I of this dissertation focuses on investigations of nitrogen oxide plasma systems. With increasing concerns over the environmental presence of NxOy species, there is growing interest in utilizing plasma-assisted conversion techniques. Advances, however, have been limited because of the lack of knowledge regarding the fundamental chemistry of these plasma systems. Understanding the kinetics and thermodynamics of processes in these systems is vital to realizing their potential in a range of applications. Unraveling the complex chemical nature of these systems, however, presents numerous challenges. As such, this work serves as a foundational step in the diagnostics and assessment of these NxOy plasmas. The partitioning of energy within the plasma system is essential to unraveling these complications as it provides insight into both gas and surface reactivity. To obtain this information, techniques such as optical emission spectroscopy (OES), broadband absorption spectroscopy (BAS), and laser induced fluorescence (LIF) were utilized to determine species energetics (vibrational, rotational, translational temperatures). These temperature data provide mechanistic insight and establish the relationships between system parameters and energetic outcomes. Additionally, these data are also correlated to surface reactivity data collected with the Imaging of Radicals Interacting with Surfaces (IRIS) technique. IRIS data demonstrate the relationship between internal temperatures of radicals and their observed surface scatter coefficients (S), the latter of which is directly related to surface reactivity (R) [R = 1-S]. Furthermore, time-resolved (TR) spectroscopic techniques, specifically TR-OES, revealed kinetic trends in NO and N2 formation from a range of precursors (NO, N2O, N2/O2). By examining the rate constants associated with the generation and destruction of various plasma species we can investigate possible mechanistic implications. All told, such data provides

Investigation of Mixed Surfactant Films at Water Surface Using Molecular Dynamics Simulations

Czech Academy of Sciences Publication Activity Database

Habartová, Alena; Roeselová, Martina; Cwiklik, Lukasz

2015-01-01

Roč. 31, č. 42 (2015), s. 11508-11515 ISSN 0743-7463 R&D Projects: GA ČR GA13-06181S Institutional support: RVO:61388963 ; RVO:61388955 Keywords : Langmuir monolayers * acid monolayers * potentials Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.993, year: 2015

Efficient surface enhanced Raman scattering on confeito-like gold nanoparticle-adsorbed self-assembled monolayers.

Science.gov (United States)

Chang, Chia-Chi; Imae, Toyoko; Chen, Liang-Yih; Ujihara, Masaki

2015-12-28

Confeito-like gold nanoparticles (AuNPs; average diameter = 80 nm) exhibiting a plasmon absorption band at 590 nm were adsorbed through immersion-adsorption on two self-assembled monolayers (SAMs) of 3-aminopropyltriethoxysilane (APTES-SAM) and polystyrene spheres coated with amine-terminated poly(amido amine) dendrimers (DEN/PS-SAM). The surface enhanced Raman scattering (SERS) effect on the SAM substrates was examined using the molecules of a probe dye, rhodamine 6G (R6G). The Raman scattering was strongly intensified on both substrates, but the enhancement factor (>10,000) of the AuNP/DEN/PS-SAM hierarchy substrate was 5-10 times higher than that of the AuNP/APTES-SAM substrate. This strong enhancement is attributed to the large surface area of the substrate and the presence of hot spots. Furthermore, analyzing the R6G concentration dependence of SERS suggested that the enhancement mechanism effectively excited the R6G molecules in the first layer on the hot spots and invoked the strong SERS effect. These results indicate that the SERS activity of confeito-like AuNPs on SAM substrates has high potential in molecular electronic devices and ultrasensitive analyses.

Atomic force microscopy studies of lateral phase separation in mixed monolayers of dipalmitoylphosphatidylcholine and dilauroylphosphatidylcholine

Energy Technology Data Exchange (ETDEWEB)

Sanchez, Jacqueline; Badia, Antonella

2003-09-01

Atomic force microscopy imaging of dipalmitoylphosphatidylcholine (DPPC)/dilauroylphosphatidylcholine (DLPC) monolayers deposited onto alkanethiol modified-gold surfaces by the Langmuir-Schaefer technique was used to investigate domain formation in a binary system where phase separation arises from a difference in the alkyl chain lengths of the lipids. We have established how the condensed domain structure (shape and size) in DPPC/DLPC monolayers depends on the surface pressure and lipid composition. The mixed monolayers exhibit a positive deviation from an ideal mixing behavior at surface pressures of {<=}32 mN/m. Lateral compression to pressures greater than the liquid-expanded-to-liquid-condensed (LE-to-LC) phase transition pressure of the mixed monolayer ({approx}8-16 mN/m) induces extensive separation into condensed DPPC-rich domains and a fluid DLPC matrix. The condensed structures observed at a few milliNeutons per meter above the LE-to-LC transition pressure resemble those reported for pure DPPC monolayers in the LE/LC co-existence region. At a bilayer equivalence pressure of 32 mN/m and 20 deg. C, condensed domains exist between x{sub DPPC} {approx}0.25 and {approx}0.80, analogous to aqueous DPPC/DLPC dispersions. Compression from 32 to 40 mN/m results in either a striking distortion of the DPPC domain shape or a break-up of the microscopic DPPC domains into a network of nanoscopic islands (at higher DPPC mol fractions), possibly reflecting a critical mixing behavior. The results of this study provide a fundamental framework for understanding and controlling the formation of lateral domain structures in mixed phospholipid monolayers.

Melting mechanism in monolayers of flexible rod-shaped molecules

DEFF Research Database (Denmark)

Hansen, Flemming Yssing; Taub, H.

1992-01-01

The melting of butane and hexane monolayers adsorbed on a graphite basal-plane surface has been studied by molecular-dynamics simulations and experimentally by neutron diffraction. The simulation results are qualitatively consistent with the observed diffraction patterns and suggest a general...

Lanthanide-based NMR: a tool to investigate component distribution in mixed-monolayer-protected nanoparticles.

Science.gov (United States)

Guarino, Gaetano; Rastrelli, Federico; Scrimin, Paolo; Mancin, Fabrizio

2012-05-02

Gd(3+) ions, once bound to the monolayer of organic molecules coating the surface of gold nanoparticles, produce a paramagnetic relaxation enhancement (PRE) that broadens and eventually cancels the signals of the nuclear spins located nearby (within 1.6 nm distance). In the case of nanoparticles coated with mixed monolayers, the signals arising from the different coating molecules experience different PRE, depending on their distance from the binding site. As a consequence, observation of the signal broadening patterns provides direct information on the monolayer organization. © 2012 American Chemical Society

Monolayer structures of alkyl aldehydes: Odd-membered homologues

International Nuclear Information System (INIS)

Phillips, T.K.; Clarke, S.M.; Bhinde, T.; Castro, M.A.; Millan, C.; Medina, S.

2011-01-01

Crystalline monolayers of three aldehydes with an odd number of carbon atoms in the alkyl chain (C 7 , C 9 and C 11 ) at low coverages are observed by a combination of X-ray and neutron diffraction. Analysis of the diffraction data is discussed and possible monolayer crystal structures are proposed; although unique structures could not be ascertained for all molecules. We conclude that the structures are flat on the surface, with the molecules lying in the plane of the layer. The C 11 homologue is determined to have a plane group of either p2, pgb or pgg, and for the C 7 homologue the p2 plane group is preferred.

Surface Structures and Thermal Desorption Behaviors of Cyclopentanethiol Self-Assembled Monolayers on Au(111)

International Nuclear Information System (INIS)

Kang, Hun Gu; Kim, You Young; Park, Tae Sun; Noh, Jae Geun; Park, Joon B.; Ito, Eisuke; Hara, Masahiko

2011-01-01

The surface structures, adsorption conditions, and thermal desorption behaviors of cyclopentanethiol (CPT) self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and thermal desorption spectroscopy (TDS). STM imaging revealed that although the adsorption of CPT on Au(111) at room temperature generates disordered SAMs, CPT molecules at 50 .deg. C formed well-ordered SAMs with a (2√3 x √5)R41".deg. packing structure. XPS measurements showed that CPT SAMs at room temperature were formed via chemical reactions between the sulfur atoms and gold surfaces. TDS measurements showed two dominant TD peaks for the decomposed fragments (C_5H_9 "+, m/e = 69) generated via C-S bond cleavage and the parent molecular species (C_5H_9SH"+, m/e = 102) derived from a recombination of the chemisorbed thiolates and hydrogen atoms near 440 K. Interestingly, dimerization of sulfur atoms in n-alkanethiol SAMs usually occurs during thermal desorption and the same reaction did not happen for CPT SAMs, which may be due to the steric hindrance of cyclic rings of the CPT molecules. In this study, we demonstrated that the alicyclic ring of organic thiols strongly affected the surface structure and thermal desorption behavior of SAMs, thus providing a good method for controlling chemical and physical properties of organic thiol SAMs

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

International Nuclear Information System (INIS)

Strong, A.E.

1997-01-01

The aim of this project was to develop a generic method of preparing a 'molecular architecture' containing functional groups on a surface at predetermined relative positions several nm apart. This would be of great utility in molecular electronics, chemical sensors and other fields. It was proposed that such an architecture could be prepared on gold using linked, helical oligopeptides that contained the components of interest and sulphur functions able to form monolayers on gold by the self-assembly technique. Towards this ultimate aim Self-Assembled Monolayers (SAMs) of monomeric oligopeptides (13-17 residues) were prepared and characterised. Peptides containing three Met residues spaced in the sequence so that their side-chains lay on the same side of the helix were shown by circular dichroism (CD) to be strongly helical in organic solvents. Their self-assembled films on gold were characterised by Reflection-Absorption Infrared Spectroscopy (RAIRS) which showed the peptides adsorbed with the helix axes parallel to the surface, the orientation expected for self-assembly. However the surface coverage measured by cyclic voltammetry (CV) of the peptides' ferrocenyl derivatives on gold electrodes were less than expected for monolayers. Comparison of the films of ferrocenyl derivatives of Met and Cys showed that the thiolate bound more strongly than the thioether. Accordingly an oligopeptide containing two Cys residues at i, i+3, designed to be 3 10 -helical, was prepared. Transformation of the two (Trt)Cys residues of the resin-bound peptide to the intramolecular disulphide by iodine was achieved in acetonitrile but not in DMF. CD suggested that the conformation of this peptide was a mixture of helix and random coil. Films of the peptide-disulphide and the peptide-dithiol adsorbed from protic solvents were characterised as multilayers by ellipsometry. However CV and ellipsometry showed that a monolayer was successfully prepared from acetonitrile. Future targets for

Molecular dynamics and energy landscape of decanethiolates in self-assembled monolayers on Au(111) by STM

NARCIS (Netherlands)

Sotthewes, Kai; Wu, Hairong; Kumar, Avijit; Vancso, Gyula J.; Schön, Peter Manfred; Zandvliet, Henricus J.W.

2013-01-01

The energetics and dynamics of the various phases of decanethiolate self-assembled monolayers on Au(111) surfaces were studied with scanning tunneling microscopy. We have observed five different phases of the decanethiolate monolayer on Au(111): four ordered phases (β, δ, χ*, and ) and one

Chemical Modification of Semiconductor Surfaces for Molecular Electronics.

Science.gov (United States)

Vilan, Ayelet; Cahen, David

2017-03-08

Inserting molecular monolayers within metal/semiconductor interfaces provides one of the most powerful expressions of how minute chemical modifications can affect electronic devices. This topic also has direct importance for technology as it can help improve the efficiency of a variety of electronic devices such as solar cells, LEDs, sensors, and possible future bioelectronic ones. The review covers the main aspects of using chemistry to control the various aspects of interface electrostatics, such as passivation of interface states and alignment of energy levels by intrinsic molecular polarization, as well as charge rearrangement with the adjacent metal and semiconducting contacts. One of the greatest merits of molecular monolayers is their capability to form excellent thin dielectrics, yielding rich and unique current-voltage characteristics for transport across metal/molecular monolayer/semiconductor interfaces. We explain the interplay between the monolayer as tunneling barrier on the one hand, and the electrostatic barrier within the semiconductor, due to its space-charge region, on the other hand, as well as how different monolayer chemistries control each of these barriers. Practical tools to experimentally identify these two barriers and distinguish between them are given, followed by a short look to the future. This review is accompanied by another one, concerning the formation of large-area molecular junctions and charge transport that is dominated solely by molecules.

A KINETIC MODEL FOR MONO-LAYER GLOBULAR PROTEIN ADSORPTION ON SOLID/LIQUID INTERFACES

Directory of Open Access Journals (Sweden)

Kamal I. M. Al-Malah

2012-12-01

Full Text Available A kinetic model was derived for globular protein adsorption. The model takes into account the three possible scenarios of a protein molecule in solution, being exposed to an interface: adsorption step from the solution to the interface; the possible desorption back into the solution; and the surface-induced unfolding or spreading of the protein unto the substrate surface. A globular protein molecule is visualized as a sphere with radius D. In addition to the general case of protein adsorption, which portrays either the surface coverage (Theta or surface concentration (� as a function of the adsorption time, special cases, like equilibrium condition, lowsurface coverage, irreversible, and Langmuirian were also presented and treated in light of the derived model. The general model was simplified for each of the subset cases. The irreversibility versus reversibility of protein adsorption was discussed. The substrate surface energetics or effects are accounted for via the proposition of the percent relative change in D/V ratio for the adsorbing protein, called (D/VPRC parameter. (D/VPRC is calculated with respect to the monolayer surface concentration of protein, where the latter is given by D/Vratio. This can be used as a landmark to protein adsorption isotherms or even kinetics. This is visualized as an indicator for solid substrate effects on the adsorbing proteins. (D/VPRC can be zero (fresh monolayer, negative (aged monolayer, or positive (multi-layer. The reference surface concentration is reported for some selected proteins.

Self-assembly Ag nanoparticle monolayer film as SERS Substrate for pesticide detection

Energy Technology Data Exchange (ETDEWEB)

Zhang, Li, E-mail: zhlisuzh@163.com [School of Chemistry and Life Science, Anhui Key Laboratory of Spin Electron and Nanomaterials (Cultivating Base), Suzhou University, SuZhou 234000 (China)

2013-04-01

A self-assembled protocol is introduced to provide effective platforms for the fabrication of ordered Ag nanosized monolayer film. The assembled Ag nanosized monolayer film was characterized using scanning electronic microscopy and surface-enhanced Raman scattering (SERS). The results show that the assembled SERS substrate own excellent Raman enhancement and reproducibility. The synthesized SERS-active substrate was further used to detect methyl-parathion, and the limitation of detection can reach 10{sup −7} M.

Relating surface chemistry and oxygen surface exchange in LnBaCo2O(5+δ) air electrodes.

Science.gov (United States)

Téllez, Helena; Druce, John; Kilner, John A; Ishihara, Tatsumi

2015-01-01

The surface and near-surface chemical composition of electroceramic materials often shows significant deviations from that of the bulk. In particular, layered materials, such as cation-ordered LnBaCo2O(5+δ) perovskites (Ln = lanthanide), undergo surface and sub-surface restructuring due to the segregation of the divalent alkaline-earth cation. These processes can take place during synthesis and processing steps (e.g. deposition, sintering or annealing), as well as at temperatures relevant for the operation of these materials as air electrodes in solid oxide fuel cells and electrolysers. Furthermore, the surface segregation in these double perovskites shows fast kinetics, starting at temperatures as low as 400 °C over short periods of time and leading to a decrease in the transition metal surface coverage exposed to the gas phase. In this work, we use a combination of stable isotope tracer labeling and surface-sensitive ion beam techniques to study the oxygen transport properties and their relationship with the surface chemistry in ordered LnBaCo2O(5+δ) perovskites. Time-of-Flight Secondary-Ion Mass Spectrometry (ToF-SIMS) combined with (18)O isotope exchange was used to determine the oxygen tracer diffusion (D*) and surface exchange (k*) coefficients. Furthermore, Low Energy Ion Scattering (LEIS) was used for the analysis of the surface and near surface chemistry as it provides information from the first mono-atomic layer of the materials. In this way, we could relate the compositional modifications (e.g. cation segregation) taking place at the electrochemically-active surface during the exchange at high temperatures and the oxygen transport properties in double perovskite electrode materials to further our understanding of the mechanism of the surface exchange process.

An experimental study of the surface chemistry and evaporation kinetics of liquid sodium

International Nuclear Information System (INIS)

Becker, C.H.

1983-01-01

The evaporation rate and internal energy distribution of Na 2 evaporating from clean liquid Na and liquid Na exposed separately to O 2 and benzene were investigated by laser spectroscopy. The evaporating Na 2 was always found to be in thermal equilibrium with the surface. Oxygen increased the evaporation rate while benzene diminished it. A 3 keV Ar + beam was used to examine the surface by monitoring secondary ion emission. Ion emission from clean and oxygen exposed Na was extremely low; only limits could be established. Ion emission from sodium exposed to benzene could be observed only at lowered temperatures. The secondary ion emission, as well as visual observations of Na( 2 P-> 2 S) emission, are found to correspond to the evaporation rate behavior indicating that the Na surface remains very metal rich even while reacting with impinging oxygen at high (10 monolayers/s) rates. (orig.)

Inkjet-printed gold nanoparticle surfaces for the detection of low molecular weight biomolecules by laser desorption/ionization mass spectrometry.

Science.gov (United States)

Marsico, Alyssa L M; Creran, Brian; Duncan, Bradley; Elci, S Gokhan; Jiang, Ying; Onasch, Timothy B; Wormhoudt, Joda; Rotello, Vincent M; Vachet, Richard W

2015-11-01

Effective detection of low molecular weight compounds in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is often hindered by matrix interferences in the low m/z region of the mass spectrum. Here, we show that monolayer-protected gold nanoparticles (AuNPs) can serve as alternate matrices for the very sensitive detection of low molecular weight compounds such as amino acids. Amino acids can be detected at low fmol levels with minimal interferences by properly choosing the AuNP deposition method, density, size, and monolayer surface chemistry. By inkjet-printing AuNPs at various densities, we find that AuNP clusters are essential for obtaining the greatest sensitivity. Graphical Abstract ᅟ.

Structures of sub-monolayered silicon carbide films

International Nuclear Information System (INIS)

Baba, Y.; Sekiguchi, T.; Shimoyama, I.; Nath, Krishna G.

2004-01-01

The electronic and geometrical structures of silicon carbide thin films are presented. The films were deposited on graphite by ion-beam deposition using tetramethylsilane (TMS) as an ion source. In the Si K-edge near-edge X-ray absorption fine structure (NEXAFS) spectra for sub-monolayered film, sharp peaks due to the resonance from Si 1s to π*-like orbitals were observed, suggesting the existence of Si=C double bonds. On the basis of the polarization dependencies of the Si 1s → π* peak intensities, it is elucidated that the direction of the π*-like orbitals is just perpendicular to the surface. We conclude that the sub-monolayered SiC x film has a flat-lying hexagonal structure of which configuration is analogous to the single sheet of graphite

Molecular tilt on monolayer-protected nanoparticles

KAUST Repository

Giomi, L.

2012-02-01

The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.

Molecular tilt on monolayer-protected nanoparticles

KAUST Repository

Giomi, L.; Bowick, M. J.; Ma, X.; Majumdar, A.

2012-01-01

The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.

Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry

Science.gov (United States)

2016-01-01

Within the framework of The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS), this work explores the surface processes and chemistry relating to core/mantle interstellar and cometary grain structures and their influence on the nature of these fascinating particles. It appears that a realistic consideration of the nature and chemical reactivity of interstellar grain surfaces could self-consistently and within a coherent framework explain: the anomalous oxygen depletion, the nature of the CO dark gas, the formation of ‘polar ice’ mantles, the red wing on the 3 μm water ice band, the basis for the O-rich chemistry observed in hot cores, the origin of organic nano-globules and the 3.2 μm ‘carbonyl’ absorption band observed in comet reflectance spectra. It is proposed that the reaction of gas phase species with carbonaceous a-C(:H) grain surfaces in the interstellar medium, in particular the incorporation of atomic oxygen into grain surfaces in epoxide functional groups, is the key to explaining these observations. Thus, the chemistry of cosmic dust is much more intimately related with that of the interstellar gas than has previously been considered. The current models for interstellar gas and dust chemistry will therefore most likely need to be fundamentally modified to include these new grain surface processes. PMID:28083090

Effect of Surface Chemistry on the Fluorescence of Detonation Nanodiamonds.

Science.gov (United States)

Reineck, Philipp; Lau, Desmond W M; Wilson, Emma R; Fox, Kate; Field, Matthew R; Deeleepojananan, Cholaphan; Mochalin, Vadym N; Gibson, Brant C

2017-11-28

Detonation nanodiamonds (DNDs) have unique physical and chemical properties that make them invaluable in many applications. However, DNDs are generally assumed to show weak fluorescence, if any, unless chemically modified with organic molecules. We demonstrate that detonation nanodiamonds exhibit significant and excitation-wavelength-dependent fluorescence from the visible to the near-infrared spectral region above 800 nm, even without the engraftment of organic molecules to their surfaces. We show that this fluorescence depends on the surface functionality of the DND particles. The investigated functionalized DNDs, produced from the same purified DND as well as the as-received polyfunctional starting material, are hydrogen, hydroxyl, carboxyl, ethylenediamine, and octadecylamine-terminated. All DNDs are investigated in solution and on a silicon wafer substrate and compared to fluorescent high-pressure high-temperature nanodiamonds. The brightest fluorescence is observed from octadecylamine-functionalized particles and is more than 100 times brighter than the least fluorescent particles, carboxylated DNDs. The majority of photons emitted by all particle types likely originates from non-diamond carbon. However, we locally find bright and photostable fluorescence from nitrogen-vacancy centers in diamond in hydrogenated, hydroxylated, and carboxylated detonation nanodiamonds. Our results contribute to understanding the effects of surface chemistry on the fluorescence of DNDs and enable the exploration of the fluorescent properties of DNDs for applications in theranostics as nontoxic fluorescent labels, sensors, nanoscale tracers, and many others where chemically stable and brightly fluorescent nanoparticles with tailorable surface chemistry are needed.

Ethers on Si(001): A prime example for the common ground between surface science and molecular organic chemistry

KAUST Repository

Pecher, Lisa

2017-09-15

Using computational chemistry, we show that the adsorption of ether molecules on Si(001) under ultra-high vacuum conditions can be understood with textbook organic chemistry. The two-step reaction mechanism of (1) dative bond formation between the ether oxygen and a Lewis acidic surface atom and (2) a nucleophilic attack of a nearby Lewis basic surface atom is analysed in detail and found to mirror the acid-catalysed ether cleavage in solution. The O-Si dative bond is found to be the strongest of its kind and reactivity from this state defies the Bell-Evans-Polanyi principle. Electron rearrangement during the C-O bond cleavage is visualized using a newly developed bonding analysis method, which shows that the mechanism of nucleophilic substitutions on semiconductor surfaces is identical to molecular chemistry SN2 reactions. Our findings thus illustrate how the fields of surface science and molecular chemistry can mutually benefit and unexpected insight can be gained.

Ethers on Si(001): A prime example for the common ground between surface science and molecular organic chemistry

KAUST Repository

Pecher, Lisa; Laref, Slimane; Raupach, Marc; Tonner, Ralf Ewald

2017-01-01

Using computational chemistry, we show that the adsorption of ether molecules on Si(001) under ultra-high vacuum conditions can be understood with textbook organic chemistry. The two-step reaction mechanism of (1) dative bond formation between the ether oxygen and a Lewis acidic surface atom and (2) a nucleophilic attack of a nearby Lewis basic surface atom is analysed in detail and found to mirror the acid-catalysed ether cleavage in solution. The O-Si dative bond is found to be the strongest of its kind and reactivity from this state defies the Bell-Evans-Polanyi principle. Electron rearrangement during the C-O bond cleavage is visualized using a newly developed bonding analysis method, which shows that the mechanism of nucleophilic substitutions on semiconductor surfaces is identical to molecular chemistry SN2 reactions. Our findings thus illustrate how the fields of surface science and molecular chemistry can mutually benefit and unexpected insight can be gained.

Packing of ganglioside-phospholipid monolayers

DEFF Research Database (Denmark)

Majewski, J.; Kuhl, T.L.; Kjær, K.

2001-01-01

Using synchrotron grazing-incidence x-ray diffraction (GIXD) and reflectivity, the in-plane and out-of-plane structure of mixed ganglioside-phospholipid monolayers was investigated at the air-water interface. Mixed monolayers of 0, 5, 10, 20, and 100 mol% ganglioside GM, and the phospholipid...... monolayers did not affect hydrocarbon tail packing (fluidization or condensation of the hydrocarbon region). This is in contrast to previous investigations of lipopolymer-lipid mixtures, where the packing structure of phospholipid monolayers was greatly altered by the inclusion of lipids bearing hydrophilic...

Disorder-derived, strong tunneling attenuation in bis-phosphonate monolayers

Science.gov (United States)

Pathak, Anshuma; Bora, Achyut; Liao, Kung-Ching; Schmolke, Hannah; Jung, Antje; Klages, Claus-Peter; Schwartz, Jeffrey; Tornow, Marc

2016-03-01

Monolayers of alkyl bisphosphonic acids (bisPAs) of various carbon chain lengths (C4, C8, C10, C12) were grown on aluminum oxide (AlO x ) surfaces from solution. The structural and electrical properties of these self-assembled monolayers (SAMs) were compared with those of alkyl monophosphonic acids (monoPAs). Through contact angle (CA) and Kelvin-probe (KP) measurements, ellipsometry, and infrared (IR) and x-ray photoelectron (XPS) spectroscopies, it was found that bisPAs form monolayers that are relatively disordered compared to their monoPA analogs. Current-voltage (J-V) measurements made with a hanging Hg drop top contact show tunneling to be the prevailing transport mechanism. However, while the monoPAs have an observed decay constant within the typical range for dense monolayers, β mono  =  0.85  ±  0.03 per carbon atom, a surprisingly high value, β bis  =  1.40  ±  0.05 per carbon atom, was measured for the bisPAs. We attribute this to a strong contribution of ‘through-space’ tunneling, which derives from conformational disorder in the monolayer due to strong interactions of the distal phosphonic acid groups; they likely form a hydrogen-bonding network that largely determines the molecular layer structure. Since bisPA SAMs attenuate tunnel currents more effectively than do the corresponding monoPA SAMs, they may find future application as gate dielectric modification in organic thin film devices.

Nonlinear optical techniques for surface studies

International Nuclear Information System (INIS)

Shen, Y.R.

1981-09-01

Recent effort in developing nonlinear optical techniques for surface studies is reviewed. Emphasis is on monolayer detection of adsorbed molecules on surfaces. It is shown that surface coherent antiStokes Raman scattering (CARS) with picosecond pulses has the sensitivity of detecting submonolayer of molecules. On the other hand, second harmonic or sum-frequency generation is also sensitive enough to detect molecular monolayers. Surface-enhanced nonlinear optical effects on some rough metal surfaces have been observed. This facilitates the detection of molecular monolayers on such surfaces, and makes the study of molecular adsorption at a liquid-metal interface feasible. Advantages and disadvantages of the nonlinear optical techniques for surface studies are discussed

Thermodynamic and structural studies of mixed monolayers: Mutual mixing of DPPC and DPPG with DoTAP at the air-water interface

International Nuclear Information System (INIS)

Panda, Amiya Kumar; Vasilev, Krasimir; Orgeig, Sandra; Prestidge, Clive A.

2010-01-01

Phospholipid monomolecular films at the air-water interface are useful model membranes to understand miscibility among various components. Surface pressure (π)-area (A) isotherms of pure and mixed monolayers of dioleoyltrimethylammonium propane (DoTAP)-dipalmitoylphosphatidylcholine (DPPC) and DoTAP-dipalmitoyphosphatidylglycerol (DPPG) were constructed using a surface balance. DPPC and DPPG produced isotherms as expected and reported earlier. DoTAP, an unsaturated lipid, demonstrated a continuous π-A isotherm. Associative interactions were identified in DPPC-DoTAP mixtures compared to the pure components, while DPPG-DoTAP mixtures showed repulsive interaction up to an equimolar ratio. Compression moduli of the monolayers revealed that DPPC-DoTAP mixtures had increasing stability with increasing surface pressure, but addition of DoTAP to DPPG showed instability at low and intermediate concentrations. In both cases increased stability was returned at higher X DoTAP values and surface pressures. Lipid monolayer film thickness values, determined on a gold coated glass substrate by surface plasmon resonance spectroscopy (SPR), indicated a systematic change in height profile for DPPC-DoTAP mixtures with increasing X DoTAP . However, DPPG-DoTAP mixed monolayer systems demonstrated a biphasic response. The SPR data were in excellent agreement with our interpretation of the structure of solid supported lipid monolayers.

Thermodynamic and structural studies of mixed monolayers: Mutual mixing of DPPC and DPPG with DoTAP at the air-water interface

Energy Technology Data Exchange (ETDEWEB)

Panda, Amiya Kumar, E-mail: akpanda1@yahoo.com [Department of Chemistry, University of North Bengal, Darjeeling-734 013, West Bengal (India); Vasilev, Krasimir [Mawson Institute for Advanced Manufacturing, Mawson Lakes, University of South Australia, SA-5095 (Australia); Orgeig, Sandra [Sansom Institute for Health Research and School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA 5000 (Australia); Prestidge, Clive A. [Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia)

2010-05-10

Phospholipid monomolecular films at the air-water interface are useful model membranes to understand miscibility among various components. Surface pressure ({pi})-area (A) isotherms of pure and mixed monolayers of dioleoyltrimethylammonium propane (DoTAP)-dipalmitoylphosphatidylcholine (DPPC) and DoTAP-dipalmitoyphosphatidylglycerol (DPPG) were constructed using a surface balance. DPPC and DPPG produced isotherms as expected and reported earlier. DoTAP, an unsaturated lipid, demonstrated a continuous {pi}-A isotherm. Associative interactions were identified in DPPC-DoTAP mixtures compared to the pure components, while DPPG-DoTAP mixtures showed repulsive interaction up to an equimolar ratio. Compression moduli of the monolayers revealed that DPPC-DoTAP mixtures had increasing stability with increasing surface pressure, but addition of DoTAP to DPPG showed instability at low and intermediate concentrations. In both cases increased stability was returned at higher X{sub DoTAP} values and surface pressures. Lipid monolayer film thickness values, determined on a gold coated glass substrate by surface plasmon resonance spectroscopy (SPR), indicated a systematic change in height profile for DPPC-DoTAP mixtures with increasing X{sub DoTAP}. However, DPPG-DoTAP mixed monolayer systems demonstrated a biphasic response. The SPR data were in excellent agreement with our interpretation of the structure of solid supported lipid monolayers.

Experimental studies of lithium-based surface chemistry for fusion plasma-facing materials applications

International Nuclear Information System (INIS)

Allain, J.P.; Rokusek, D.L.; Harilal, S.S.; Nieto-Perez, M.; Skinner, C.H.; Kugel, H.W.; Heim, B.; Kaita, R.; Majeski, R.

2009-01-01

Lithium has enhanced the operational performance of fusion devices such as: TFTR, CDX-U, FTU, T-11 M, and NSTX. Lithium in the solid and liquid state has been studied extensively in laboratory experiments including its erosion and hydrogen-retaining properties. Reductions in physical sputtering up to 40-60% have been measured for deuterated solid and liquid lithium surfaces. Computational modeling indicates that up to a 1:1 deuterium volumetric retention in lithium is possible. This paper presents the results of systematic in situ laboratory experimental studies on the surface chemistry evolution of ATJ graphite under lithium deposition. Results are compared to post-mortem analysis of similar lithium surface coatings on graphite exposed to deuterium discharge plasmas in NSTX. Lithium coatings on plasma-facing components in NSTX have shown substantial reduction of hydrogenic recycling. Questions remain on the role lithium surface chemistry on a graphite substrate has on particle sputtering (physical and chemical) as well as hydrogen isotope recycling. This is particularly due to the lack of in situ measurements of plasma-surface interactions in tokamaks such as NSTX. Results suggest that the lithium bonding state on ATJ graphite is lithium peroxide and with sufficient exposure to ambient air conditions, lithium carbonate is generated. Correlation between both results is used to assess the role of lithium chemistry on the state of lithium bonding and implications on hydrogen pumping and lithium sputtering. In addition, reduction of factors between 10 and 30 reduction in physical sputtering from lithiated graphite compared to pure lithium or carbon is also measured.

Phase transitions in surfactant monolayers

International Nuclear Information System (INIS)

Casson, B.D.

1998-01-01

Two-dimensional phase transitions have been studied in surfactant monolayers at the air/water interface by sum-frequency spectroscopy and ellipsometry. In equilibrium monolayers of medium-chain alcohols C n H 2n+1 OH (n = 9-14) a transition from a two-dimensional crystalline phase to a liquid was observed at temperatures above the bulk melting point. The small population of gauche defects in the solid phase increased only slightly at the phase transition. A model of the hydrocarbon chains as freely rotating rigid rods allowed the area per molecule and chain tilt in the liquid phase to be determined. The area per molecule, chain tilt and density of the liquid phase all increased with increasing chain length, but for each chain length the density was higher than in a bulk liquid hydrocarbon. In a monolayer of decanol adsorbed at the air/water interface a transition from a two-dimensional liquid to a gas was observed. A clear discontinuity in the coefficient of ellipticity as a function of temperature showed that the transition is first-order. This result suggests that liquid-gas phase transitions in surfactant monolayers may be more widespread than once thought. A solid-liquid phase transition has also been studied in mixed monolayers of dodecanol with an anionic surfactant (sodium dodecyl sulphate) and with a homologous series of cationic surfactants (alkyltrimethylammonium bromides: C n TABs, n = 12, 14, 16). The composition and structure of the mixed monolayers was studied above and below the phase transition. At low temperatures the mixed monolayers were as densely packed as a monolayer of pure dodecanol in its solid phase. At a fixed temperature the monolayers under-went a first-order phase transition to form a phase that was less dense and more conformationally disordered. The proportion of ionic surfactant in the mixed monolayer was greatest in the high temperature phase. As the chain length of the C n TAB increased the number of conformational defects

Measurement of molecular length of self-assembled monolayer probed by localized surface plasmon resonance

Science.gov (United States)

Ito, Juri; Kajikawa, Kotaro

2016-02-01

We propose a method to measure the variation of the molecular length of self-assembled monolayers (SAMs) when it is exposed to solutions at different pH conditions. The surface immobilized gold nanospheres (SIGNs) shows strong absorption peak at the wavelengths of 600-800 nm when p-polarized light is illuminated. The peak wavelength depends on the length of the gap distance between the SIGNs and the substrate. The gap is supported by the SAM molecules. According to the analytical calculation based on multiple expansion, the relation between the peak wavelength of the SIGN structures and the gap distance is calculated, to evaluate the molecular length of the SAM through the optical absorption spectroscopy for the SIGN structures. The molecular length of the SIGN structure was measured in air, water, acidic, and basic solutions. It was found that the molecular lengths are longer in acidic solutions.

Highly active engineered-enzyme oriented monolayers: formation, characterization and sensing applications

Directory of Open Access Journals (Sweden)

Patolsky Fernando

2011-06-01

Full Text Available Abstract Background The interest in introducing ecologically-clean, and efficient enzymes into modern industry has been growing steadily. However, difficulties associated with controlling their orientation, and maintaining their selectivity and reactivity is still a significant obstacle. We have developed precise immobilization of biomolecules, while retaining their native functionality, and report a new, fast, easy, and reliable procedure of protein immobilization, with the use of Adenylate kinase as a model system. Methods Self-assembled monolayers of hexane-1,6-dithiol were formed on gold surfaces. The monolayers were characterized by contact-angle measurements, Elman-reagent reaction, QCM, and XPS. A specifically designed, mutated Adenylate kinase, where cysteine was inserted at the 75 residue, and the cysteine at residue 77 was replaced by serine, was used for attachment to the SAM surface via spontaneously formed disulfide (S-S bonds. QCM, and XPS were used for characterization of the immobilized protein layer. Curve fitting in XPS measurements used a Gaussian-Lorentzian function. Results and Discussion Water contact angle (65-70°, as well as all characterization techniques used, confirmed the formation of self-assembled monolayer with surface SH groups. X-ray photoelectron spectroscopy showed clearly the two types of sulfur atom, one attached to the gold (triolate and the other (SH/S-S at the ω-position for the hexane-1,6-dithiol SAMs. The formation of a protein monolayer was confirmed using XPS, and QCM, where the QCM-determined amount of protein on the surface was in agreement with a model that considered the surface area of a single protein molecule. Enzymatic activity tests of the immobilized protein confirmed that there is no change in enzymatic functionality, and reveal activity ~100 times that expected for the same amount of protein in solution. Conclusions To the best of our knowledge, immobilization of a protein by the method

OCEANFILMS-2: Representing coadsorption of saccharides in marine films and potential impacts on modeled marine aerosol chemistry

Energy Technology Data Exchange (ETDEWEB)

Burrows, Susannah M. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Gobrogge, Eric [Department of Chemistry and Biochemistry, Montana State University, Bozeman Montana USA; Fu, Li [Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland Washington USA; Link, Katie [Department of Chemistry and Biochemistry, Montana State University, Bozeman Montana USA; Elliott, Scott M. [Climate, Ocean, and Sea Ice Modelling Group, Los Alamos National Laboratory, Los Alamos New Mexico USA; Wang, Hongfei [Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland Washington USA; Walker, Rob [Department of Chemistry and Biochemistry, Montana State University, Bozeman Montana USA

2016-08-10

Here we show that the addition of chemical interactions of soluble polysaccharides with a surfactant monolayer improves agreement of modeled sea spray chemistry with observed marine aerosol chemistry. In particular, the fraction of hydroxyl functional groups in modeled sea spray organic matter is increased, improving agreement with FTIR observations of marine aerosol composition. The overall organic fraction of submicron sea spray also increases, allowing organic mass fractions in the range 0.5 – 0.7 for submicron sea spray particles over highly active phytoplankton blooms. We show results from Sum Frequency Generation (SFG) experiments that support the modeling approach, by demonstrating that soluble polysaccharides can strongly adsorb to a lipid monolayer via columbic interactions under appropriate conditions.

Formation and electrochemical investigation of ordered cobalt coordinated peptide monolayers on gold substrates

International Nuclear Information System (INIS)

Wang Xinxin; Nagata, Kenji; Higuchi, Masahiro

2012-01-01

The monolayers composed of cobalt coordinated peptides were prepared on gold substrates by two different approaches. One was the self-assembly method, which was used to prepare a peptide monolayer on the gold substrate via the spontaneous attachment of peptides owing to the interaction between gold and sulfur at the N-terminal of the peptide. The other one was the stepwise polymerization method that was utilized to fabricate the unidirectionally arranged peptide monolayer by the stepwise condensation of amino acids from the initiator fixed on the gold substrate. Leu 2 Ala(4-Pyri)Leu 6 Ala(4-Pyri)Leu 6 sequence was chosen as the cobalt coordinated peptide. The 4-pyridyl alanines, Ala(4-Pyri)s, were introduced as ligands for cobalt to the leucine-rich sequential peptide. The complexation between cobalt and pyridyl groups of the peptide induced the formation of a stable α-helical bundle, which oriented perpendicularly to the substrate surface. In the case of the monolayer fabricated by the stepwise polymerization method, the direction of the peptide macro-dipole moment aligned unidirectionally, and the cobalt complexes were fixed in the monolayer to form the ordered arrangement. On the other hand, the peptides prepared by the self-assembly method formed the mixture of parallel and antiparallel packing owing to the dipole-dipole interaction. The spatial location of the cobalt complexes in the monolayer prepared by the self-assembly method was distorted, compared with that in the monolayer fabricated by the stepwise polymerization method. The vectorial electron flow through the peptide monolayer was achieved by the regular alignment of the peptide macro-dipole moment and the cobalt complexes in the monolayer fabricated by the stepwise polymerization method. - Highlights: ► We fabricated ordered Co coordinated peptide monolayers on the gold substrates. ► The Co complexes in peptide monolayer formed an ordered arrangement of the peptide. ► The peptide macro

Surface chemistry and size influence the release of model therapeutic nanoparticles from poly(ethylene glycol) hydrogels

International Nuclear Information System (INIS)

Hume, Stephanie L.; Jeerage, Kavita M.

2013-01-01

Nanoparticles have emerged as promising therapeutic and diagnostic tools, due to their unique physicochemical properties. The specific core and surface chemistries, as well as nanoparticle size, play critical roles in particle transport and interaction with biological tissue. Localized delivery of therapeutics from hydrogels is well established, but these systems generally release molecules with hydrodynamic radii less than ∼5 nm. Here, model nanoparticles with biologically relevant surface chemistries and diameters between 10 and 35 nm are analyzed for their release from well-characterized hydrogels. Functionalized gold nanoparticles or quantum dots were encapsulated in three-dimensional poly(ethylene glycol) hydrogels with varying mesh size. Nanoparticle size, surface chemistry, and hydrogel mesh size all influenced the release of particles from the hydrogel matrix. Size influenced nanoparticle release as expected, with larger particles releasing at a slower rate. However, citrate-stabilized gold nanoparticles were not released from hydrogels. Negatively charged carboxyl or positively charged amine-functionalized quantum dots were released from hydrogels at slower rates than neutrally charged PEGylated nanoparticles of similar size. Transmission electron microscopy images of gold nanoparticles embedded within hydrogel sections demonstrated uniform particle distribution and negligible aggregation, independent of surface chemistry. The nanoparticle-hydrogel interactions observed in this work will aid in the development of localized nanoparticle delivery systems.

Venting temperature determines surface chemistry of magnetron sputtered TiN films

Energy Technology Data Exchange (ETDEWEB)

Greczynski, G. [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden); Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany); Mráz, S.; Schneider, J. M. [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany); Hultman, L. [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden)

2016-01-25

Surface properties of refractory ceramic transition metal nitride thin films grown by magnetron sputtering are essential for resistance towards oxidation necessary in all modern applications. Here, typically neglected factors, including exposure to residual process gases following the growth and the venting temperature T{sub v}, each affecting the surface chemistry, are addressed. It is demonstrated for the TiN model materials system that T{sub v} has a substantial effect on the composition and thickness-evolution of the reacted surface layer and should therefore be reported. The phenomena are also shown to have impact on the reliable surface characterization by x-ray photoelectron spectroscopy.

Micropatterning of Functional Conductive Polymers with Multiple Surface Chemistries in Register

DEFF Research Database (Denmark)

Lind, Johan Ulrik; Acikgöz, Canet; Daugaard, Anders Egede

2012-01-01

A versatile procedure is presented for fast and efficient micropatterning of multiple types of covalently bound surface chemistry in perfect register on and between conductive polymer microcircuits. The micropatterning principle is applied to several types of native and functionalized PEDOT (poly(3...... functionalized conjugated polymer systems....

Visualizing monolayers with a water-soluble fluorophore to quantify adsorption, desorption, and the double layer.

Science.gov (United States)

Shieh, Ian C; Zasadzinski, Joseph A

2015-02-24

Contrast in confocal microscopy of phase-separated monolayers at the air-water interface can be generated by the selective adsorption of water-soluble fluorescent dyes to disordered monolayer phases. Optical sectioning minimizes the fluorescence signal from the subphase, whereas convolution of the measured point spread function with a simple box model of the interface provides quantitative assessment of the excess dye concentration associated with the monolayer. Coexisting liquid-expanded, liquid-condensed, and gas phases could be visualized due to differential dye adsorption in the liquid-expanded and gas phases. Dye preferentially adsorbed to the liquid-disordered phase during immiscible liquid-liquid phase coexistence, and the contrast persisted through the critical point as shown by characteristic circle-to-stripe shape transitions. The measured dye concentration in the disordered phase depended on the phase composition and surface pressure, and the dye was expelled from the film at the end of coexistence. The excess concentration of a cationic dye within the double layer adjacent to an anionic phospholipid monolayer was quantified as a function of subphase ionic strength, and the changes in measured excess agreed with those predicted by the mean-field Gouy-Chapman equations. This provided a rapid and noninvasive optical method of measuring the fractional dissociation of lipid headgroups and the monolayer surface potential.

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

Analysis of the induction of the myelin basic protein binding to the plasma membrane phospholipid monolayer

International Nuclear Information System (INIS)

Zhang Lei; Hao Changchun; Feng Ying; Gao Feng; Lu Xiaolong; Li Junhua; Sun Runguang

2016-01-01

Myelin basic protein (MBP) is an essential structure involved in the generation of central nervous system (CNS) myelin. Myelin shape has been described as liquid crystal structure of biological membrane. The interactions of MBP with monolayers of different lipid compositions are responsible for the multi-lamellar structure and stability of myelin. In this paper, we have designed MBP-incorporated model lipid monolayers and studied the phase behavior of MBP adsorbed on the plasma membrane at the air/water interface by thermodynamic method and atomic force microscopy (AFM). By analyzing the pressure–area ( π – A ) and pressure–time ( π – T ) isotherms, univariate linear regression equation was obtained. In addition, the elastic modulus, surface pressure increase, maximal insertion pressure, and synergy factor of monolayers were detected. These parameters can be used to modulate the monolayers binding of protein, and the results show that MBP has the strongest affinity for 1,2-dipalmitoyl-sn-glycero-3- phosphoserine (DPPS) monolayer, followed by DPPC/DPPS mixed and 1,2-dipalmitoyl-sn-glycero-3-phospho-choline (DPPC) monolayers via electrostatic and hydrophobic interactions. AFM images of DPPS and DPPC/DPPS mixed monolayers in the presence of MBP (5 nM) show a phase separation texture at the surface pressure of 20 mN/m and the incorporation of MBP put into the DPPC monolayers has exerted a significant effect on the domain structure. MBP is not an integral membrane protein but, due to its positive charge, interacts with the lipid head groups and stabilizes the membranes. The interaction between MBP and phospholipid membrane to determine the nervous system of the disease has a good biophysical significance and medical value. (special topic)

He/Ar-atom scattering from molecular monolayers: C{sub 60}/Pt(111) and graphene/Pt(111)

Energy Technology Data Exchange (ETDEWEB)

Yamada, Y; Sugawara, C; Satake, Y; Yokoyama, Y; Okada, R; Nakayama, T; Sasaki, M [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki (Japan); Kondo, T; Oh, J; Nakamura, J [Institute of Material Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki (Japan); Hayes, W W [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 (United States)

2010-08-04

Supersonic He and Ar atomic beam scattering from C{sub 60} and graphene monolayers adsorbed on a Pt(111) surface are demonstrated in order to obtain detailed insight into a gas-molecule collision that has not been studied in detail so far. The effective masses and phonon spectral densities of the monolayers seen by different projectiles are discussed based on classical models such as the hard cube model and the recently developed smooth surface model. Large effective masses are deduced for both the monolayers, suggesting collective effects of surface atoms in the single collision event. The effective Debye temperature of graphene was found to be similar to that reported in highly oriented pyrolytic graphite (HOPG), indicating that the graphene is decoupled well from the Pt substrate. A much smaller Debye-Waller factor was found for the C{sub 60} layer, probably reflecting the strong C{sub 60}-Pt(111) interaction.

On-Surface Synthesis by Click Chemistry Investigated by STM and XPS

DEFF Research Database (Denmark)

Vadapoo, Sundar Raja

2014-01-01

Molecular synthesis is essential in the bottom-up approach of achieving highly stable nanostructures. On-surface synthesis is highly interesting from the basic science of view to improve the understanding of molecular behavior adsorbed on metal surfaces, and has potential applications such as mol......Molecular synthesis is essential in the bottom-up approach of achieving highly stable nanostructures. On-surface synthesis is highly interesting from the basic science of view to improve the understanding of molecular behavior adsorbed on metal surfaces, and has potential applications...... such as molecular electronics and surface functionalization. In this thesis, a well-defined click chemistry approach is followed, with the study of azide-alkyne cycloaddition on Cu(111) surface in UHV environment. A successful achievement of the click reaction product via on-surface synthesis has been shown, which...

Bioadhesion of mussels and geckos: Molecular mechanics, surface chemistry, and nanoadhesives

Science.gov (United States)

Lee, Haeshin

The adhesive strategies of living creatures are diverse, ranging from temporary to permanent adhesions with various functions such as locomotion, self-defense, communication, colony formation, and so on. The classic example of temporary adhesion is the gecko, which is known for its ability to walk along vertical and even inverted surfaces; this remarkable adhesion arises from the interfacial weak interactions of van der Waals and capillary forces. In contrast, a celerbrated example of permanent adhesion is found in marine mussels which secrete protein adhesives that function in aqueous environments without mechanical failure against turbulent conditions on the seashore. In addition, mussel adhesives stick to virtually all inorganic and organic surfaces. However, most commonly used man-made adhesives lack such unique adhesion properties compared to their natural counterparts. For example, many commercial adhesives quickly lose their adhesive strength when exposed to solvents, particularly water. The first part of this thesis focused on adhesion mechanics of mussels at a single-molecule level, in which the adhesive molecule showed surprisingly strong yet reversible adhesion on inorganic surfaces but exhibited irreversible covalent bond formation on organic surfaces. Strong and reversible adhesion on mucin surfaces was found, indicating potential application for drug delivery via mucus layers. Next, inspired by the mussel's versatile adhesion on a wide variety of material surfaces, a material-independent surface modification chemistry called 'polydopamine coating' is described. This concept was subsequently adapted to develop a surface-independent polymeric primer for layer-by-layer assembly of multifunctional coatings. Finally, a new bio-hybrid adhesive 'geckel' was developed by the functional combination of adhesion strategies of geckos and mussels. The new bio-inspired adhesive and material-independent surface chemistry can revolutionize the research areas such as

Experimental evidence for an original two-dimensional phase structure: An antiparallel semifluorinated monolayer at the air-water interface

International Nuclear Information System (INIS)

El Abed, A.; Faure, M-C.; Pouzet, E.; Abillon, O.

2002-01-01

We show the spontaneous formation of an antiparallel monolayer of diblock semifluorinated n-alkane molecules spread at the air-water interface. We used simultaneous measurements of surface pressure and surface potential versus molecular area and performed grazing x-ray reflectivity experiments to characterize the studied monolayer, which is obtained at almost zero surface pressure and precedes the formation of a bilayer at higher surface pressure. Its thickness, equal to 2.7 nm, was found to be independent of the molecular area. This behavior may be explained by van der Waals and electrostatic interactions

Proton and hydrogen transport through two-dimensional monolayers

International Nuclear Information System (INIS)

Seel, Max; Pandey, Ravindra

2016-01-01

Diffusion of protons and hydrogen atoms in representative two-dimensional materials is investigated. Specifically, density functional calculations were performed on graphene, hexagonal boron nitride (h-BN), phosphorene, silicene, and molybdenum disulfide (MoS 2 ) monolayers to study the surface interaction and penetration barriers for protons and hydrogen atoms employing finite cluster models. The calculated barrier heights correlate approximately with the size of the opening formed by the three-fold open sites in the monolayers considered. They range from 1.56 eV (proton) and 4.61 eV (H) for graphene to 0.12 eV (proton) and 0.20 eV (H) for silicene. The results indicate that only graphene and h-BN monolayers have the potential for membranes with high selective permeability. The MoS 2 monolayer behaves differently: protons and H atoms become trapped between the outer S layers in the Mo plane in a well with a depth of 1.56 eV (proton) and 1.5 eV (H atom), possibly explaining why no proton transport was detected, suggesting MoS 2 as a hydrogen storage material instead. For graphene and h-BN, off-center proton penetration reduces the barrier to 1.38 eV for graphene and 0.11 eV for h-BN. Furthermore, Pt acting as a substrate was found to have a negligible effect on the barrier height. In defective graphene, the smallest barrier for proton diffusion (1.05 eV) is found for an oxygen-terminated defect. Therefore, it seems more likely that thermal protons can penetrate a monolayer of h-BN but not graphene and defects are necessary to facilitate the proton transport in graphene. (paper)

Proton and hydrogen transport through two-dimensional monolayers

Science.gov (United States)

Seel, Max; Pandey, Ravindra

2016-06-01

Diffusion of protons and hydrogen atoms in representative two-dimensional materials is investigated. Specifically, density functional calculations were performed on graphene, hexagonal boron nitride (h-BN), phosphorene, silicene, and molybdenum disulfide (MoS2) monolayers to study the surface interaction and penetration barriers for protons and hydrogen atoms employing finite cluster models. The calculated barrier heights correlate approximately with the size of the opening formed by the three-fold open sites in the monolayers considered. They range from 1.56 eV (proton) and 4.61 eV (H) for graphene to 0.12 eV (proton) and 0.20 eV (H) for silicene. The results indicate that only graphene and h-BN monolayers have the potential for membranes with high selective permeability. The MoS2 monolayer behaves differently: protons and H atoms become trapped between the outer S layers in the Mo plane in a well with a depth of 1.56 eV (proton) and 1.5 eV (H atom), possibly explaining why no proton transport was detected, suggesting MoS2 as a hydrogen storage material instead. For graphene and h-BN, off-center proton penetration reduces the barrier to 1.38 eV for graphene and 0.11 eV for h-BN. Furthermore, Pt acting as a substrate was found to have a negligible effect on the barrier height. In defective graphene, the smallest barrier for proton diffusion (1.05 eV) is found for an oxygen-terminated defect. Therefore, it seems more likely that thermal protons can penetrate a monolayer of h-BN but not graphene and defects are necessary to facilitate the proton transport in graphene.

Layer-by-layer evolution of structure, strain, and activity for the oxygen evolution reaction in graphene-templated Pt monolayers.

Science.gov (United States)

Abdelhafiz, Ali; Vitale, Adam; Joiner, Corey; Vogel, Eric; Alamgir, Faisal M

2015-03-25

In this study, we explore the dimensional aspect of structure-driven surface properties of metal monolayers grown on a graphene/Au template. Here, surface limited redox replacement (SLRR) is used to provide precise layer-by-layer growth of Pt monolayers on graphene. We find that after a few iterations of SLRR, fully wetted 4-5 monolayer Pt films can be grown on graphene. Incorporating graphene at the Pt-Au interface modifies the growth mechanism, charge transfers, equilibrium interatomic distances, and associated strain of the synthesized Pt monolayers. We find that a single layer of sandwiched graphene is able to induce a 3.5% compressive strain on the Pt adlayer grown on it, and as a result, catalytic activity is increased due to a greater areal density of the Pt layers beyond face-centered-cubic close packing. At the same time, the sandwiched graphene does not obstruct vicinity effects of near-surface electron exchange between the substrate Au and adlayers Pt. X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) techniques are used to examine charge mediation across the Pt-graphene-Au junction and the local atomic arrangement as a function of the Pt adlayer dimension. Cyclic voltammetry (CV) and the oxygen reduction reaction (ORR) are used as probes to examine the electrochemically active area of Pt monolayers and catalyst activity, respectively. Results show that the inserted graphene monolayer results in increased activity for the Pt due to a graphene-induced compressive strain, as well as a higher resistance against loss of the catalytically active Pt surface.

Microstructure and surface chemistry of amorphous alloys important to their friction and wear behavior

Science.gov (United States)

Miyoshi, K.; Buckley, D. H.

1986-01-01

An investigation was conducted to examine the microstructure and surface chemistry of amorphous alloys, and their effects on tribological behavior. The results indicate that the surface oxide layers present on amorphous alloys are effective in providing low friction and a protective film against wear in air. Clustering and crystallization in amorphous alloys can be enhanced as a result of plastic flow during the sliding process at a low sliding velocity, at room temperature. Clusters or crystallines with sizes to 150 nm and a diffused honeycomb-shaped structure are produced on sizes to 150 nm and a diffused honeycomb-shaped structure are produced on the wear surface. Temperature effects lead to drastic changes in surface chemistry and friction behavior of the alloys at temperatures to 750 C. Contaminants can come from the bulk of the alloys to the surface upon heating and impart to the surface oxides at 350 C and boron nitride above 500 C. The oxides increase friction while the boron nitride reduces friction drastically in vacuum.

Improvement of gas-adsorption performances of Ag-functionalized monolayer MoS2 surfaces: A first-principles study

Science.gov (United States)

Song, Jian; Lou, Huan

2018-05-01

Investigations of the adsorptions of representative gases (NO2, NH3, H2S, SO2, CO, and HCHO) on different Ag-functionalized monolayer MoS2 surfaces were performed by first principles methods. The adsorption configurations, adsorption energies, electronic structure properties, and charge transfer were calculated, and the results show that the adsorption activities to gases of monolayer MoS2 are dramatically enhanced by the Ag-modification. The Ag-modified perfect MoS2 (Ag-P) and MoS2 with S-vacancy (Ag-Vs) substrates exhibit a more superior adsorption activity to NO2 than other gases, which is consistent with the experimental reports. The charge transfer processes of different molecules adsorbed on different surfaces exhibit various characteristics, with potential benefits to gas selectivity. For instance, the NO2 and SO2 obtain more electrons from both Ag-P and Ag-Vs substrates but the NH3 and H2S donate more electrons to materials than others. In addition, the CO and HCHO possess totally opposite charge transfer directs on both substrates, respectively. The BS and PDOS calculations show that semiconductor types of gas/Ag-MoS2 systems are more determined by the metal-functionalization of material, and the directs and numbers of charge transfer process between gases and adsorbents can cause the increase or decline of material resistance theoretically, which is helpful to gas detection and distinction. The further analysis indicates suitable co-operation between the gain-lost electron ability of gas and metallicity of featuring metal might adjust the resistivity of complex and contribute to new thought for metal-functionalization. Our works provide new valuable ideas and theoretical foundation for the potential improvement of MoS2-based gas sensor performances, such as sensitivity and selectivity.

Bovine insulin-phosphatidylcholine mixed Langmuir monolayers: behavior at the air-water interface.

Science.gov (United States)

Pérez-López, S; Blanco-Vila, N M; Vila-Romeu, N

2011-08-04

The behavior of the binary mixed Langmuir monolayers of bovine insulin (INS) and phosphatidylcholine (PC) spread at the air-water interface was investigated under various subphase conditions. Pure and mixed monolayers were spread on water, on NaOH and phosphate-buffered solutions of pH 7.4, and on Zn(2+)-containing solutions. Miscibility and interactions between the components were studied on the basis of the analysis of the surface pressure (π)-mean molecular area (A) isotherms, surface compression modulus (C(s)(-1))-π curves, and plots of A versus mole fraction of INS (X(INS)). Our results indicate that intermolecular interactions between INS and PC depend on both the monolayer state and the structural characteristics of INS at the interface, which are strongly influenced by the subphase pH and salt content. Brewster angle microscopy (BAM) was applied to investigate the peptide aggregation pattern at the air-water interface in the presence of the studied lipid under any experimental condition investigated. The influence of the lipid on the INS behavior at the interface strongly depends on the subphase conditions.

The Interface between Gd and Monolayer MoS2: A First-Principles Study

KAUST Repository

Zhang, Xuejing

2014-12-08

We analyze the electronic structure of interfaces between two-, four- and six-layer Gd(0001) and monolayer MoS2 by first-principles calculations. Strong chemical bonds shift the Fermi energy of MoS2 upwards into the conduction band. At the surface and interface the Gd f states shift to lower energy and new surface/interface Gd d states appear at the Fermi energy, which are strongly hybridized with the Mo 4d states and thus lead to a high spin-polarization (ferromagnetically ordered Mo magnetic moments of 0.15 μB). Gd therefore is an interesting candidate for spin injection into monolayer MoS2.

Resistance of poly(ethylene oxide)-silane monolayers to the growth of polyelectrolyte multilayers.

Science.gov (United States)

Buron, Cédric C; Callegari, Vincent; Nysten, Bernard; Jonas, Alain M

2007-09-11

The ability of poly(ethylene oxide)-silane (PEO-silane) monolayers grafted onto silicon surfaces to resist the growth of polyelectrolyte multilayers under various pH conditions is assessed for different pairs of polyelectrolytes of varying molar mass. For acidic conditions (pH 3), the PEO-silane monolayers exhibit good polyelectrolyte repellency provided the polyelectrolytes bear no moieties that are able to form hydrogen bonds with the ether groups of the PEO chains. At basic pH, PEO-silane monolayers undergo substantial hydrolysis leading to the formation of negatively charged defects in the monolayers, which then play the role of adsorption sites for the polycation. Once the polycation is adsorbed, multilayer growth ensues. Because this is defect-driven growth, the multilayer is not continuous and is made of blobs or an open network of adsorbed strands. For such conditions, the molar mass of the polyelectrolyte plays a key role, with polyelectrolyte chains of larger molar mass adsorbing on a larger number of defects, resulting in stronger anchoring of the polyelectrolyte complex on the surfaces and faster subsequent growth of the multilayer. For polyelectrolytes of sufficiently low molar mass at pH 9, the growth of the multilayer can nevertheless be prevented for as much as five cycles of deposition.

Immobilization of dendrimers on Si-C linked carboxylic acid-terminated monolayers on silicon(111)

International Nuclear Information System (INIS)

Boecking, Till; Wong, Elicia L.S.; James, Michael; Watson, Jolanta A.; Brown, Christopher L.; Chilcott, Terry C.; Barrow, Kevin D.; Coster, Hans G.L.

2006-01-01

Poly(amidoamine) dendrimers were attached to activated undecanoic acid monolayers, covalently linked to smooth silicon surfaces via Si-C bonds. The resulting ultra-thin dendrimer films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XR) and atomic force microscopy (AFM). XPS results suggested amide bond formation between the dendrimer and the surface carboxylic acid groups. XR yielded thicknesses of 10 A for the alkyl region of the undecanoic acid monolayer and 12 A for the dendrimer layer, considerably smaller than the diameter of these spherical macromolecules in solution. This was consistent with AFM images showing collapsed dendrimers on the surface. It was concluded that the deformation arose from a large number of amine groups on the surface of each dendrimer reacting efficiently with the activated surface, whereby the dendrimers can deform to fill voids while spreading over the activated surface to form a homogeneous macromolecular layer

Discharge physics and chemistry of a novel atmospheric pressure plasma source

Energy Technology Data Exchange (ETDEWEB)

Park, J.; Henins, I.; Hermann, J.W.; Selwyn, G.S.; Jeong, J.Y.; Hickis, R.

1999-07-01

The atmospheric pressure plasma jet (APPJ) is a unique plasma source operating at atmospheric pressure. The APPJ operates with RF power and produces a stable non-thermal discharge in capacitively-coupled configuration. The discharge is spatially and temporally homogeneous and provides a unique gas phase chemistry that is well suited for various applications including etching, film deposition, surface treatment and decontamination of chemical and biological warfare (CBW) agents. A theoretical model shows electron densities of 0.2--2 x 10{sup 11} cm{sup {minus}3} for a helium discharge at a power level of 3--30 W cm{sup {minus}3}. The APPJ also produces a large flux, equivalent of up to 10,000 monolayer s{sup {minus}1}, of chemically-active, atomic and metastable molecular species which can impinge surfaces several cm downstream of the confined source. In addition, the efforts are in progress to measure the electron density using microwave diagnostics and to benchmark the gas phase chemical model by using LIF and titration.

Genotoxicity of copper oxide nanoparticles with different surface chemistry on rat bone marrow mesenchymal stem cells

DEFF Research Database (Denmark)

Zhang, Wenjing; Jiang, Pengfei; Chen, Wei

2016-01-01

The surface chemistry of nanoparticles (NPs) is one of the critical factors determining their cellular responses. In this study, the cytotoxicity and genotoxicity of copper oxide (CuO) NPs with a similar size but different surface chemistry to rat bone marrow mesenchymal stem cells (MSCs) were......V and showed a similar tendency to form agglomerates with a size of ∼200 nm in cell culture environment. The cytotoxicity of CuO NPs to MSCs at various concentrations and incubation periods were firstly evaluated. The CuO NPs showed dose-dependent and time-dependent toxicity to MSCs, and their surface...

Effect of Perfluoroalkyl Endgroups on the Interactions of Tri-Block Copolymers with Monofluorinated F-DPPC Monolayers

Directory of Open Access Journals (Sweden)

Syed W. H. Shah

2017-10-01

Full Text Available We studied the interaction of amphiphilic and triphilic polymers with monolayers prepared from F-DPPC (1-palmitoyl-2-(16-fluoropalmitoyl-sn-glycero-3-phosphocholine, a phospholipid with a single fluorine atom at the terminus of the sn-2 chain, an analogue of dipalmitoyl-phosphatidylcholine (DPPC. The amphiphilic block copolymers contained a hydrophobic poly(propylene oxide block flanked by hydrophilic poly(glycerol monomethacrylate blocks (GP. F-GP was derived from GP by capping both termini with perfluoro-n-nonyl segments. We first studied the adsorption of GP and F-GP to lipid monolayers of F-DPPC. F-GP was inserted into the monolayer up to a surface pressure Π of 42.4 mN m−1, much higher than GP (32.5 mN m−1. We then studied isotherms of lipid-polymer mixtures co-spread at the air-water interface. With increasing polymer content in the mixture a continuous shift of the onset of the liquid-expanded (LE to liquid-condensed (LC transition towards higher molecular and higher area per lipid molecule was observed. F-GP had a larger effect than GP indicating that it needed more space. At a Π-value of 32 mN m−1, GP was excluded from the mixed monolayer, whereas F-GP stayed in F-DPPC monolayers up to 42 mN m−1. F-GP is thus more stably anchored in the monolayer up to higher surface pressures. Images of mixed monolayers were acquired using different fluorescent probes and showed the presence of perfluorinated segments of F-GP at LE-LC domain boundaries.

Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

Science.gov (United States)

Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

2016-04-21

We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

Epitaxial growth by monolayer restricted galvanic displacement

Directory of Open Access Journals (Sweden)

Vasilić Rastko

2012-01-01

Full Text Available The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV and scanning tunneling microscopy (STM are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111, Cu on Ag(111, and Cu on Au(111 by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process.

AFM investigation of effect of absorbed water layer structure on growth mechanism of octadecyltrichlorosilane self-assembled monolayer on oxidized silicon

International Nuclear Information System (INIS)

Li, Shaowei; Zheng, Yanjun; Chen, Changfeng

2016-01-01

The growth mechanism of an octadecyltrichlorosilane (OTS) self-assembled monolayer on a silicon oxide surface at various relative humidities has been investigated. Atomic force microscopy images show that excess water may actually hinder the nucleation and growth of OTS islands. A moderate amount of water is favorable for the nucleation and growth of OTS islands in the initial stage; however, the completion of the monolayer is very slow in the final stage. The growth of OTS islands on a low-water-content surface maintains a relatively constant speed and requires the least amount of time. The mobility of water molecules is thought to play an important role in the OTS monolayers, and a low-mobility water layer provides a steady condition for OTS monolayer growth.

Oxide/water interfaces: how the surface chemistry modifies interfacial water properties

International Nuclear Information System (INIS)

Gaigeot, Marie-Pierre; Sprik, Michiel; Sulpizi, Marialore

2012-01-01

The organization of water at the interface with silica and alumina oxides is analysed using density functional theory-based molecular dynamics simulation (DFT-MD). The interfacial hydrogen bonding is investigated in detail and related to the chemistry of the oxide surfaces by computing the surface charge density and acidity. We find that water molecules hydrogen-bonded to the surface have different orientations depending on the strength of the hydrogen bonds and use this observation to explain the features in the surface vibrational spectra measured by sum frequency generation spectroscopy. In particular, ‘ice-like’ and ‘liquid-like’ features in these spectra are interpreted as the result of hydrogen bonds of different strengths between surface silanols/aluminols and water. (paper)

Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces

Science.gov (United States)

McBriarty, Martin E.

Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

Surface Structures and Thermal Desorption Behaviors of Cyclopentanethiol Self-Assembled Monolayers on Au(111)

Energy Technology Data Exchange (ETDEWEB)

Kang, Hun Gu; Kim, You Young; Park, Tae Sun; Noh, Jae Geun [Hanyang University, Seoul (Korea, Republic of); Park, Joon B. [Chonbuk National University, Jeonju (Korea, Republic of); Ito, Eisuke; Hara, Masahiko [RIKEN-HYU Collaboration Center, Saitama (Japan)

2011-04-15

The surface structures, adsorption conditions, and thermal desorption behaviors of cyclopentanethiol (CPT) self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and thermal desorption spectroscopy (TDS). STM imaging revealed that although the adsorption of CPT on Au(111) at room temperature generates disordered SAMs, CPT molecules at 50 .deg. C formed well-ordered SAMs with a (2√3 x √5)R41{sup .}deg. packing structure. XPS measurements showed that CPT SAMs at room temperature were formed via chemical reactions between the sulfur atoms and gold surfaces. TDS measurements showed two dominant TD peaks for the decomposed fragments (C{sub 5}H{sub 9} {sup +}, m/e = 69) generated via C-S bond cleavage and the parent molecular species (C{sub 5}H{sub 9}SH{sup +}, m/e = 102) derived from a recombination of the chemisorbed thiolates and hydrogen atoms near 440 K. Interestingly, dimerization of sulfur atoms in n-alkanethiol SAMs usually occurs during thermal desorption and the same reaction did not happen for CPT SAMs, which may be due to the steric hindrance of cyclic rings of the CPT molecules. In this study, we demonstrated that the alicyclic ring of organic thiols strongly affected the surface structure and thermal desorption behavior of SAMs, thus providing a good method for controlling chemical and physical properties of organic thiol SAMs.

The hydrochemistry of glacial Ebba River (Petunia Bay, Central Spitsbergen): Groundwater influence on surface water chemistry

Science.gov (United States)

Dragon, Krzysztof; Marciniak, Marek; Szpikowski, Józef; Szpikowska, Grażyna; Wawrzyniak, Tomasz

2015-10-01

The article presents the investigation of surface water chemistry changes of the glacial Ebba River (Central Spitsbergen) during three melting seasons of 2008, 2009 and 2010. The twice daily water chemistry analyses allow recognition of the surface water chemistry differentiation. The surface water chemistry changes are related to the river discharge and changes in the influence of different water balance components during each melting season. One of the most important process that influence river water component concentration increase is groundwater inflow from active layer occurring on the valley area. The significance of this process is the most important at the end of the melting season when temperatures below 0 °C occur on glaciers (resulting in a slowdown of melting of ice and snow and a smaller recharge of the river by the water from the glaciers) while the flow of groundwater is still active, causing a relatively higher contribution of groundwater to the total river discharge. The findings presented in this paper show that groundwater contribution to the total polar river water balance is more important than previously thought and its recognition allow a better understanding of the hydrological processes occurring in a polar environment.

Disorder-derived, strong tunneling attenuation in bis-phosphonate monolayers

International Nuclear Information System (INIS)

Pathak, Anshuma; Bora, Achyut; Tornow, Marc; Liao, Kung-Ching; Schwartz, Jeffrey; Schmolke, Hannah; Jung, Antje; Klages, Claus-Peter

2016-01-01

Monolayers of alkyl bisphosphonic acids (bisPAs) of various carbon chain lengths (C4, C8, C10, C12) were grown on aluminum oxide (AlO x ) surfaces from solution. The structural and electrical properties of these self-assembled monolayers (SAMs) were compared with those of alkyl monophosphonic acids (monoPAs). Through contact angle (CA) and Kelvin-probe (KP) measurements, ellipsometry, and infrared (IR) and x-ray photoelectron (XPS) spectroscopies, it was found that bisPAs form monolayers that are relatively disordered compared to their monoPA analogs. Current–voltage (J–V) measurements made with a hanging Hg drop top contact show tunneling to be the prevailing transport mechanism. However, while the monoPAs have an observed decay constant within the typical range for dense monolayers, β mono   =  0.85  ±  0.03 per carbon atom, a surprisingly high value, β bis   =  1.40  ±  0.05 per carbon atom, was measured for the bisPAs. We attribute this to a strong contribution of ‘through-space’ tunneling, which derives from conformational disorder in the monolayer due to strong interactions of the distal phosphonic acid groups; they likely form a hydrogen-bonding network that largely determines the molecular layer structure. Since bisPA SAMs attenuate tunnel currents more effectively than do the corresponding monoPA SAMs, they may find future application as gate dielectric modification in organic thin film devices. (paper)

Atomic Scale Simulation on the Anti-Pressure and Friction Reduction Mechanisms of MoS2 Monolayer

Directory of Open Access Journals (Sweden)

Yang Liu

2018-04-01

Full Text Available MoS2 nanosheets can be used as solid lubricants or additives of lubricating oils to reduce friction and resist wear. However, the atomic scale mechanism still needs to be illustrated. Herein, molecular simulations on the indentation and scratching process of MoS2 monolayer supported by Pt(111 surface were conducted to study the anti-pressure and friction reduction mechanisms of the MoS2 monolayer. Three deformation stages of Pt-supported MoS2 monolayer were found during the indentation process: elastic deformation, plastic deformation and finally, complete rupture. The MoS2 monolayer showed an excellent friction reduction effect at the first two stages, as a result of enhanced load bearing capacity and reduced deformation degree of the substrate. Unlike graphene, rupture of the Pt-supported MoS2 monolayer was related primarily to out-of-plane compression of the monolayer. These results provide a new insight into the relationship between the mechanical properties and lubrication properties of 2D materials.

Correlation between surface chemistry and settlement behaviour in barnacle cyprids (Balanus improvisus).

Science.gov (United States)

Di Fino, A; Petrone, L; Aldred, N; Ederth, T; Liedberg, B; Clare, A S

2014-02-01

In laboratory-based biofouling assays, the influence of physico-chemical surface characteristics on barnacle settlement has been tested most frequently using the model organism Balanus amphitrite (= Amphibalanus amphitrite). Very few studies have addressed the settlement preferences of other barnacle species, such as Balanus improvisus (= Amphibalanus improvisus). This study aimed to unravel the effects of surface physico-chemical cues, in particular surface-free energy (SFE) and surface charge, on the settlement of cyprids of B. improvisus. The use of well-defined surfaces under controlled conditions further facilitates comparison of the results with recent similar data for B. amphitrite. Zero-day-old cyprids of B. improvisus were exposed to a series of model surfaces, namely self-assembled monolayers (SAMs) of alkanethiols with varying end-groups, homogenously applied to gold-coated polystyrene (PS) Petri dishes. As with B. amphitrite, settlement of cyprids of B. improvisus was influenced by both SFE and charge, with higher settlement on low-energy (hydrophobic) surfaces and negatively charged SAMs. Positively charged SAMs resulted in low settlement, with intermediate settlement on neutral SAMs of similar SFE. In conclusion, it is demonstrated that despite previous suggestions to the contrary, these two species of barnacle show similar preferences in response to SFE; they also respond similarly to charge. These findings have positive implications for the development of novel antifouling (AF) coatings and support the importance of consistency in substratum choice for assays designed to compare surface preferences of fouling organisms.

Characterisation of phase transition in adsorbed monolayers at the air/water interface.

Science.gov (United States)

Vollhardt, D; Fainerman, V B

2010-02-26

Recent work has provided experimental and theoretical evidence that a first order fluid/condensed (LE/LC) phase transition can occur in adsorbed monolayers of amphiphiles and surfactants which are dissolved in aqueous solution. Similar to Langmuir monolayers, also in the case of adsorbed monolayers, the existence of a G/LE phase transition, as assumed by several authors, is a matter of question. Representative studies, at first performed with a tailored amphiphile and later with numerous other amphiphiles, also with n-dodecanol, provide insight into the main characteristics of the adsorbed monolayer during the adsorption kinetics. The general conditions necessary for the formation of a two-phase coexistence in adsorbed monolayers can be optimally studied using dynamic surface pressure measurements, Brewster angle microscopy (BAM) and synchrotron X-ray diffraction at grazing incidence (GIXD). A characteristic break point in the time dependence of the adsorption kinetics curves indicates the phase transition which is largely affected by the concentration of the amphiphile in the aqueous solution and on the temperature. Formation and growth of condensed phase domains after the phase transition point are visualised by BAM. As demonstrated by a tailored amphiphile, various types of morphological textures of the condensed phase can occur in different temperature regions. Lattice structure and tilt angle of the alkyl chains in the condensed phase of the adsorbed monolayer are determined using GIXD. The main growth directions of the condensed phase textures are correlated with the two-dimensional lattice structure. The results, obtained for the characteristics of the condensed phase after a first order main transition, are supported by experimental bridging to the Langmuir monolayers. Phase transition of adsorbing trace impurities in model surfactants can strongly affect the characteristics of the main component. Dodecanol present as minor component in aqueous sodium

Biomimetic surface modification of polypropylene by surface chain transfer reaction based on mussel-inspired adhesion technology and thiol chemistry

Energy Technology Data Exchange (ETDEWEB)

Niu, Zhijun; Zhao, Yang; Sun, Wei; Shi, Suqing, E-mail: shisq@nwu.edu.cn; Gong, Yongkuan

2016-11-15

Highlights: • Biomimetic surface modification of PP was successfully conducted by integrating mussel-inspired technology, thiol chemistry and cell outer membranes-like structures. • The resultant biomimetic surface exhibits good interface and surface stability. • The obvious suppression of protein adsorption and platelet adhesion is also achieved. • The residue thoil groups on the surface could be further functionalized. - Abstract: Biomimetic surface modification of polypropylene (PP) is conducted by surface chain transfer reaction based on the mussel-inspired versatile adhesion technology and thiol chemistry, using 2-methacryloyloxyethylphosphorylcholine (MPC) as a hydrophilic monomer mimicking the cell outer membrane structure and 2,2-azobisisobutyronitrile (AIBN) as initiator in ethanol. A layer of polydopamine (PDA) is firstly deposited onto PP surface, which not only offers good interfacial adhesion with PP, but also supplies secondary reaction sites (-NH{sub 2}) to covalently anchor thiol groups onto PP surface. Then the radical chain transfer to surface-bonded thiol groups and surface re-initiated polymerization of MPC lead to the formation of a thin layer of polymer brush (PMPC) with cell outer membrane mimetic structure on PP surface. X-ray photoelectron spectrophotometer (XPS), atomic force microscopy (AFM) and water contact angle measurements are used to characterize the PP surfaces before and after modification. The protein adsorption and platelet adhesion experiments are also employed to evaluate the interactions of PP surface with biomolecules. The results show that PMPC is successfully grafted onto PP surface. In comparison with bare PP, the resultant PP-PMPC surface exhibits greatly improved protein and platelet resistance performance, which is the contribution of both increased surface hydrophilicity and zwitterionic structure. More importantly, the residue thiol groups on PP-PMPC surface create a new pathway to further functionalize such

Biomimetic surface modification of polypropylene by surface chain transfer reaction based on mussel-inspired adhesion technology and thiol chemistry

International Nuclear Information System (INIS)

Niu, Zhijun; Zhao, Yang; Sun, Wei; Shi, Suqing; Gong, Yongkuan

2016-01-01

Highlights: • Biomimetic surface modification of PP was successfully conducted by integrating mussel-inspired technology, thiol chemistry and cell outer membranes-like structures. • The resultant biomimetic surface exhibits good interface and surface stability. • The obvious suppression of protein adsorption and platelet adhesion is also achieved. • The residue thoil groups on the surface could be further functionalized. - Abstract: Biomimetic surface modification of polypropylene (PP) is conducted by surface chain transfer reaction based on the mussel-inspired versatile adhesion technology and thiol chemistry, using 2-methacryloyloxyethylphosphorylcholine (MPC) as a hydrophilic monomer mimicking the cell outer membrane structure and 2,2-azobisisobutyronitrile (AIBN) as initiator in ethanol. A layer of polydopamine (PDA) is firstly deposited onto PP surface, which not only offers good interfacial adhesion with PP, but also supplies secondary reaction sites (-NH 2 ) to covalently anchor thiol groups onto PP surface. Then the radical chain transfer to surface-bonded thiol groups and surface re-initiated polymerization of MPC lead to the formation of a thin layer of polymer brush (PMPC) with cell outer membrane mimetic structure on PP surface. X-ray photoelectron spectrophotometer (XPS), atomic force microscopy (AFM) and water contact angle measurements are used to characterize the PP surfaces before and after modification. The protein adsorption and platelet adhesion experiments are also employed to evaluate the interactions of PP surface with biomolecules. The results show that PMPC is successfully grafted onto PP surface. In comparison with bare PP, the resultant PP-PMPC surface exhibits greatly improved protein and platelet resistance performance, which is the contribution of both increased surface hydrophilicity and zwitterionic structure. More importantly, the residue thiol groups on PP-PMPC surface create a new pathway to further functionalize such

Influence of chemistry on wetting dynamics of nanotextured hydrophobic surfaces.

Science.gov (United States)

Di Mundo, Rosa; Palumbo, Fabio; d'Agostino, Riccardo

2010-04-06

In this work, the role of a chemical parameter, such as the degree of fluorination, on the wetting behavior of nanotextured hydrophobic surfaces is investigated. Texture and chemistry tuning of the surfaces has been accomplished with single batch radiofrequency low-pressure plasma processes. Polystyrene substrates have been textured by CF(4) plasma etching and subsequently covered by thin films with a tunable F-to-C ratio, obtained in discharges fed with C(4)F(8)-C(2)H(4). Measurements of wetting dynamics reveal a regime transition from adhesive-hydrophobic to slippery-superhydrophobic, i.e., from wet to non wet states, as the F-to-C rises at constant topography. Such achievements are strengthened by calculation of the solid fraction of surface water contact area applying Cassie-Baxter advancing and receding equations to water contact angle data of textured and flat reference surfaces.