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Sample records for molecular adsorbate surface

  1. Interplay of adsorbate-adsorbate and adsorbate-substrate interactions in self-assembled molecular surface nanostructures

    DEFF Research Database (Denmark)

    Schnadt, Joachim; Xu, Wei; Vang, Ronnie Thorbjørn

    2010-01-01

    a large tolerance to monatomic surface steps on the Ag(110) surface. The observed behaviour is explained in terms of strong intermolecular hydrogen bonding and a strong surface-mediated directionality, assisted by a sufficient degree of molecular backbone flexibility. In contrast, the same kind of step......-edge crossing is not observed when the molecules are adsorbed on the isotropic Ag(111) or more reactive Cu(110) surfaces. On Ag(111), similar 1-D assemblies are formed to those on Ag(110), but they are oriented along the step edges. On Cu(110), the carboxylic groups of NDCA are deprotonated and form covalent...... bonds to the surface, a situation which is also achieved on Ag(110) by annealing to 200 degrees C. These results show that the formation of particular self-assembled molecular nanostructures depends significantly on a subtle balance between the adsorbate-adsorbate and adsorbate-substrate interactions...

  2. Molecular analysis of petroleum derived compounds that adsorb onto gas hydrate surfaces

    International Nuclear Information System (INIS)

    Borgund, Anna E.; Hoiland, Sylvi; Barth, Tanja; Fotland, Per; Askvik, Kjell M.

    2009-01-01

    Field observations have shown that some streams of water, gas and crude oil do not form gas hydrate plugs during petroleum production even when operating within thermodynamic conditions for hydrate formation. Also, when studied under controlled laboratory conditions, some oils are found to form hydrate dispersed systems whereas others form plugs. Oils with low tendency to form hydrate plugs are believed to contain natural hydrate plug inhibiting components (NICs) that adsorb onto the hydrate surface, making them less water-wet and preventing the particles from agglomerating into large hydrate clusters. The molecular structure of the NICs is currently unknown. In this work, hydrate adsorbing components were extracted from crude oils using freon hydrates as an extraction phase. The fractions were found to be enriched in polar material, and more polar material is associated with hydrates generated in biodegraded crude oils than in non-biodegraded oils. Various fractionation schemes and analytical techniques have been applied in the search for molecular characterisation. The average molecular weights were found to be approximately 500 g/mole. GC-MS chromatograms show a large UCM (Unresolved Complex Mixture). Thus, GC-MS has a limited potential for identification of compounds. A commercial biosurfactant was used as a model compound in the search for similar structures in the extracts. The results from analysis of the hydrate adsorbing components suggest that the type and structure are more important for hydrate morphology than the amount of material adsorbed.

  3. Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni

    Energy Technology Data Exchange (ETDEWEB)

    López-Moreno, S., E-mail: sinlopez@uacam.mx [Centro de Investigación en Corrosión, Universidad Autónoma de Campeche, Av. Héroe de Nacozari 480, Campeche, Campeche 24029 (Mexico); Romero, A. H. [Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    2015-04-21

    Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O{sub 2} molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered.

  4. Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni

    Science.gov (United States)

    López-Moreno, S.; Romero, A. H.

    2015-04-01

    Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O2 molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered.

  5. Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni

    International Nuclear Information System (INIS)

    López-Moreno, S.; Romero, A. H.

    2015-01-01

    Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O 2 molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered

  6. A molecular surface science study of the structure of adsorbates on surfaces: Importance to lubrication

    International Nuclear Information System (INIS)

    Mate, C.M.

    1986-09-01

    The interaction and bonding of atoms and molecules on metal surfaces is explored under ultra-high vacuum conditions using a variety of surface science techniques: high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES), work function measurements, and second harmonic generation (SHG). 164 refs., 51 figs., 3 tabs

  7. Removal of cyanotoxins from surface water resources using reusable molecularly imprinted polymer adsorbents.

    Science.gov (United States)

    Krupadam, Reddithota J; Patel, Govind P; Balasubramanian, Rajasekhar

    2012-06-01

    Microcystins (MCs; cyclic heptapeptides) are produced by freshwater cyanobacteria and cause public health concern in potable water supplies. There are more than 60 types of MCs identified to date, of which MC-LR is the most common found worldwide. For MC-LR, the WHO has established a threshold value of 1 μg L(-1) for drinking water. The present MCs removal methods such as coagulation, flocculation, adsorption, and filtration showed low efficiency for removing dissolved MC fraction from surface waters to the stipulated limit prescribed by WHO based on MC health impacts. The search for cost-effective and efficient removal method is still warranted for remediation of dissolved MC-LR-contaminated water resources. Molecularly imprinted polymer (MIP) adsorbent has been prepared using non-covalent imprinting approach. Using MC-LR as a template, itaconic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linking monomer, a MIP has been synthesized. Computer simulations were used to design effective binding sites for MC-LR binding in aqueous solutions. Batch binding adsorption assay was followed to determine binding capacity of MIP under the influence of environmental parameters such as total dissolved solids and pH. The adsorptive removal of MC-LR from lake water has been investigated using MIPs. The MIP showed excellent adsorption potential toward MC-LR in aqueous solutions with a binding capacity of 3.64 μg mg(-1) which is about 60% and 70% more than the commercially used powdered activated carbon (PAC) and resin XAD, respectively. Environmental parameters such as total organic carbon (represented as chemical oxygen demand (COD)) and total dissolved solids (TDS) showed no significant interference up to 300 mg L(-1) for MC-LR removal from lake water samples. It was found that the binding sites on PAC and XAD have more affinity toward COD and TDS than the MC-LR. Further, the adsorption capacity of the MIP was evaluated rigorously by its repeated

  8. Black Sprayable Molecular Adsorber Coating

    Data.gov (United States)

    National Aeronautics and Space Administration — The main objective of this technology project is to develop, optimize, and flight qualify a black version of the molecular adsorber coating and a conductive version...

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

    DEFF Research Database (Denmark)

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

    1993-01-01

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

  10. Black molecular adsorber coatings for spaceflight applications

    Science.gov (United States)

    Abraham, Nithin S.; Hasegawa, Mark M.; Straka, Sharon A.

    2014-09-01

    The molecular adsorber coating is a new technology that was developed to mitigate the risk of on-orbit molecular contamination on spaceflight missions. The application of this coating would be ideal near highly sensitive, interior surfaces and instruments that are negatively impacted by outgassed molecules from materials, such as plastics, adhesives, lubricants, epoxies, and other similar compounds. This current, sprayable paint technology is comprised of inorganic white materials made from highly porous zeolite. In addition to good adhesion performance, thermal stability, and adsorptive capability, the molecular adsorber coating offers favorable thermal control characteristics. However, low reflectivity properties, which are typically offered by black thermal control coatings, are desired for some spaceflight applications. For example, black coatings are used on interior surfaces, in particular, on instrument baffles for optical stray light control. Similarly, they are also used within light paths between optical systems, such as telescopes, to absorb light. Recent efforts have been made to transform the white molecular adsorber coating into a black coating with similar adsorptive properties. This result is achieved by optimizing the current formulation with black pigments, while still maintaining its adsorption capability for outgassing control. Different binder to pigment ratios, coating thicknesses, and spray application techniques were explored to develop a black version of the molecular adsorber coating. During the development process, coating performance and adsorption characteristics were studied. The preliminary work performed on black molecular adsorber coatings thus far is very promising. Continued development and testing is necessary for its use on future contamination sensitive spaceflight missions.

  11. 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

  12. Novel ion-molecular surface reaction to result in CH3 adsorbates on (111) surface of chemical vapor deposition diamond from ethane and surface anionic sites

    International Nuclear Information System (INIS)

    Komatsu, Shojiro; Okada, Katsuyuki; Shimizu, Yoshiki; Moriyoshi, Yusuke

    2001-01-01

    The existence of CH 3 adsorbates on (111) surface of chemical vapor deposited diamond, which was observed by scanning tunneling microscopy, was explained by the following S N 2 (bimolecular, substitutional, and nucleophilic) type surface reaction; C(s) - +C 2 H 6 ->C(s)-CH 3 +CH 3 - , where C(s) denotes a surface carbon atom. The activation energy was estimated to be 36.78 kcal/mol and the reaction proved to be exothermic with the enthalpy change of -9.250 kcal/mol, according to ab initio molecular orbital calculations at MP2/3-21+G * //RHF/3-21G * level; this result is consistent with typical substrate temperatures, namely about 900 degree C, for chemical vapor deposition of diamond. Charge transfer from the highest occupied molecular orbital of the surface anionic site to the lowest unoccupied molecular orbital of ethane, that is antibonding at the CH 3 - CH 3 bond, has been clearly visualized. A characteristic configuration of an ethane molecule which is associated with an anionic vacant site C(s) - on hydrogenated (111) surface of diamond was also found. [copyright] 2001 American Institute of Physics

  13. Photoemission-monitored x-ray standing wave studies of molecular adsorbate surface structure

    International Nuclear Information System (INIS)

    Lee, John Jethro

    2002-01-01

    The influence of non-dipole photoemission terms on the accuracy of photoemission-monitored NIXSW structure determinations has been studied. An experimental survey has been made of values of the incoherent dipole-quadrupole parameter as a function of energy and atomic number for the Is states of elements between carbon and chlorine inclusive. These values are compared with recent theoretical calculations. The contribution of the coherent dipole-quadrupole interference terms, whose form has been theoretically derived recently, has been experimentally measured for Is photoemission from clean Al(111). The coherent dipole-quadrupole effect is found to be small and easily corrected for, while the previously-known incoherent effect is shown to result in tolerable errors in most cases. Adsorption of methyl thiol (CH 3 SH) on Pt(111), followed by annealing to ∼ 220 K is believed to result in the formation of methyl thiolate (-SCH 3 ). Two structural models are consistent with NIXSW data presented here: co-occupation of fcc and hcp sites, and a tilted atop-bonded geometry. On annealing to ∼500 K, complete dissociation occurs, and the remaining S atoms are found to lie in fcc sites, with evidence of partial occupation of a more complex phase. The adsorption of CO, NO and O on Ni(111), and the O+CO and O+NO coadsorbate systems have been investigated with NIXSW. The sites found for O, CO and NO are consistent with previous quantitative structure determinations. In the presence of a precoverage of oxygen, the conclusion of a recent photoelectron diffraction study that the preferred CO site is atop a substrate Ni atom is confirmed. In contrast, NO adsorption onto a (2 x 2)-O precovered surface is found to result in the restructuring of the oxygen layer, with NO adsorbing in the hollow sites, as in the pure-NO layer. Discrepancies in bond lengths between these NIXSW results and previous quantitative determinations are discussed. (author)

  14. Friction and diffusion dynamics of adsorbates at surfaces

    NARCIS (Netherlands)

    Fusco, C.

    2005-01-01

    A theoretical study of the motion of adsorbates (e. g. atoms, molecules or clusters) on solid surfaces is presented, with a focus on surface diffusion and atomic-scale friction. These two phenomena are inextricably linked, because when an atomic or molecular adsorbate diffuses, or is pulled, it

  15. Second-harmonic generation from sub-monolayer molecular adsorbates using a c-w diode laser: Maui surface experiment

    International Nuclear Information System (INIS)

    Boyd, G.T.; Shen, Y.R.; Hansch, T.W.

    1985-06-01

    Optical second-harmonic generation (SHG) can be an extremely sensitive tool for surface studies. The technique is capable of probing adsorbed molecules at various interfaces. It is based on the idea that SHG is forbidden in a medium with inversion symmetry, but necessarily allowed at a surface. To see such a surface nonlinear optical effect, high laser intensity is often needed. Thus, in the experiments reported so far, pulsed lasers were used exclusively. From the consideration for practical applications, however, the technique would look much more attractive if the bulky pulsed laser can be replaced by a simple inexpensive c-w diode laser. This paper describes the first demonstration of surface SHG with a c-w laser. 3 refs., 1 fig

  16. A novel superparamagnetic surface molecularly imprinted nanoparticle adopting dummy template: an efficient solid-phase extraction adsorbent for bisphenol A.

    Science.gov (United States)

    Lin, Zhenkun; Cheng, Wenjing; Li, Yanyan; Liu, Zhiren; Chen, Xiangping; Huang, Changjiang

    2012-03-30

    Leakage of the residual template molecules is one of the biggest challenges for application of molecularly imprinted polymer (MIP) in solid-phase extraction (SPE). In this study, bisphenol F (BPF) was adopted as a dummy template to prepare MIP of bisphenol A (BPA) with a superparamagnetic core-shell nanoparticle as the supporter, aiming to avoid residual template leakage and to increase the efficiency of SPE. Characterization and test of the obtained products (called mag-DMIP beads) revealed that these novel nanoparticles not only had excellent magnetic property but also displayed high selectivity to the target molecule BPA. As mag-DMIP beads were adopted as the adsorbents of solid-phase extraction for detecting BPA in real water samples, the recoveries of spiked samples ranged from 84.7% to 93.8% with the limit of detection of 2.50 pg mL(-1), revealing that mag-DMIP beads were efficient SPE adsorbents. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Alkali metal adsorbate sputtering by molecular impact

    International Nuclear Information System (INIS)

    Moran, J.P.; Wachman, H.Y.; Trilling, L.

    1974-01-01

    An exploratory study of the sputtering by a krypton molecular beam of rubidium adsorbed at low coverage on a tungsten substrate has been described in a previous paper. An extension of this work is reported now

  18. Black Sprayable Molecular Adsorber Coating Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The main objective of this technology project is to develop, optimize, and flight qualify a black version of the molecular adsorber coating and a conductive version...

  19. On the widths of Stokes lines in Raman scattering from molecules adsorbed at metal surfaces and in molecular conduction junctions

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yi, E-mail: yig057@ucsd.edu; Galperin, Michael, E-mail: migalperin@ucsd.edu [Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093 (United States); Nitzan, Abraham, E-mail: nitzan@post.tau.ac.il [Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA and School of Chemistry, Tel Aviv University, Tel Aviv 69978 (Israel)

    2016-06-28

    Within a generic model we analyze the Stokes linewidth in surface enhanced Raman scattering (SERS) from molecules embedded as bridges in molecular junctions. We identify four main contributions to the off-resonant Stokes signal and show that under zero voltage bias (a situation pertaining also to standard SERS experiments) and at low bias junctions only one of these contributions is pronounced. The linewidth of this component is determined by the molecular vibrational relaxation rate, which is dominated by interactions with the essentially bosonic thermal environment when the relevant molecular electronic energy is far from the metal(s) Fermi energy(ies). It increases when the molecular electronic level is close to the metal Fermi level so that an additional vibrational relaxation channel due to electron-hole (eh) exciton in the molecule opens. Other contributions to the Raman signal, of considerably broader linewidths, can become important at larger junction bias.

  20. Lotus Dust Mitigation Coating and Molecular Adsorber Coating

    Science.gov (United States)

    O'Connor, Kenneth M.; Abraham, Nithin S.

    2015-01-01

    NASA Goddard Space Flight Center has developed two unique coating formulations that will keep surfaces clean and sanitary and contain contaminants.The Lotus Dust Mitigation Coating, modeled after the self-cleaning, water-repellant lotus leaf, disallows buildup of dust, dirt, water, and more on surfaces. This coating, has been successfully tested on painted, aluminum, glass, silica, and some composite surfaces, could aid in keeping medical assets clean.The Molecular Adsorber Coating is a zeolite-based, sprayable molecular adsorber coating, designed to prevent outgassing in materials in vacuums. The coating works well to adsorb volatiles and contaminates in manufacturing and processing, such as in pharmaceutical production. The addition of a biocide would also aid in controlling bacteria levels.

  1. Electronic spectral properties of surfaces and adsorbates and atom-adsorbate van der Waals interactions

    International Nuclear Information System (INIS)

    Lovric, D.; Gumhalter, B.

    1988-01-01

    The relevance of van der Waals interactions in the scattering of neutral atoms from adsorbates has been recently confirmed by highly sensitive molecular-beam techniques. The theoretical descriptions of the collision dynamics which followed the experimental studies have necessitated very careful qualitative and quantitative examinations and evaluations of the properties of atom-adsorbate van der Waals interactions for specific systems. In this work we present a microscopic calculation of the strengths and reference-plane positions for van der Waals potentials relevant for scattering of He atoms from CO adsorbed on various metallic substrates. In order to take into account the specificities of the polarization properties of real metals (noble and transition metals) and of chemisorbed CO, we first calculate the spectra of the electronic excitations characteristic of the respective electronic subsystems by using various data sources available and combine them with the existing theoretical models. The reliability of the calculated spectra is then verified in each particular case by universal sum rules which may be established for the electronic excitations of surfaces and adsorbates. The substrate and adsorbate polarization properties which derive from these calculations serve as input data for the evaluation of the strengths and reference-plane positions of van der Waals potentials whose computed values are tabulated for a number of real chemisorption systems. The implications of the obtained results are discussed in regard to the atom-adsorbate scattering cross sections pertinent to molecular-beam scattering experiments

  2. Kinetics of conformational changes of fibronectin adsorbed onto model surfaces.

    Science.gov (United States)

    Baujard-Lamotte, L; Noinville, S; Goubard, F; Marque, P; Pauthe, E

    2008-05-01

    Fibronectin (FN), a large glycoprotein found in body fluids and in the extracellular matrix, plays a key role in numerous cellular behaviours. We investigate FN adsorption onto hydrophilic bare silica and hydrophobic polystyrene (PS) surfaces using Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) in aqueous medium. Adsorption kinetics using different bulk concentrations of FN were followed for 2h and the surface density of adsorbed FN and its time-dependent conformational changes were determined. When adsorption occurs onto the hydrophilic surface, FN molecules keep their native conformation independent of the adsorption conditions, but the amount of adsorbed FN increases with time and the bulk concentration. Although the protein surface density is the same on the hydrophobic PS surface, this has a strong impact on the average conformation of the adsorbed FN layer. Indeed, interfacial hydration changes induced by adsorption onto the hydrophobic surface lead to a decrease in unhydrated beta-sheet content and cause an increase in hydrated beta-strand and hydrated random domain content of adsorbed FN. This conformational change is mainly dependent on the bulk concentration. Indeed, at low bulk concentrations, the secondary structures of adsorbed FN molecules undergo strong unfolding, allowing an extended and hydrated conformation of the protein. At high bulk concentrations, the molecular packing reduces the unfolding of the stereoregular structures of the FN molecules, preventing stronger spreading of the protein.

  3. Electronic structure of benzene adsorbed on Ni and Cu surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Weinelt, M.; Nilsson, A.; Wassdahl, N. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    Benzene has for a long time served as a prototype adsorption system of large molecules. It adsorbs with the molecular plane parallel to the surface. The bonding of benzene to a transition metal is typically viewed to involve the {pi} system. Benzene adsorbs weakly on Cu and strongly on Ni. It is interesting to study how the adsorption strength is reflected in the electronic structure of the adsorbate-substrate complex. The authors have used X-ray Emission (XE) and X-ray Absorption (XA) spectroscopies to selectively study the electronic states localized on the adsorbed benzene molecule. Using XES the occupied states can be studies and with XAS the unoccupied states. The authors have used beamline 8.0 and the Swedish endstation equipped with a grazing incidence x-ray spectrometer and a partial yield absorption detector. The resolution in the XES and XAS were 0.5 eV and 0.05 eV, respectively.

  4. Photoemission spectroscopy of surfaces and adsorbates

    International Nuclear Information System (INIS)

    Chiang, T.C.; Kaindl, G.; Himpsel, F.J.; Eastman, D.E.

    1982-01-01

    Core level photoelectron spectroscopy is providing new information concerning the electronic properties of adsorbates and surfaces. Several examples will be discussed, including studies of adsorbed rare gas submonolayers and multilayers as well as clean metal surfaces. For rare gas multilayers adsorbed on metal surfaces, the photoelectrons and Auger electrons exhibit well-resolved increases in kinetic energy with decreasing distance between the excited atom and the substrate, allowing a direct labeling of the layers. These energy shifts are mainly due to the substrate screening effects, and can be described well by an image-charge model. For a Kr/Xe bilayer system prepared by first coating a Pd substrate with a monolayer of Kr and then overcoating with a layer of Xe, a thermally activated layer inversion process is observed when the temperature is raised, with Xe coming in direct contact with the substrate. For rare gas submonolayers adsorbed on the Al(111) surface, coverage-dependent core level shift and work function measurements provide information about the adatom spatial distributions, polarizabilities, and dipole moments for the ground and excited states. We have also studied the 2p core level shifts for a clean Al(001) surface relative to the bulk. The shifts have a large contribution from the initial-state effects

  5. 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

  6. Bioavailability of Carbon Nanomaterial-Adsorbed Polycyclic Aromatic Hydrocarbons to Pimphales promelas: Influence of Adsorbate Molecular Size and Configuration.

    Science.gov (United States)

    Linard, Erica N; Apul, Onur G; Karanfil, Tanju; van den Hurk, Peter; Klaine, Stephen J

    2017-08-15

    Despite carbon nanomaterials' (CNMs) potential to alter the bioavailability of adsorbed contaminants, information characterizing the relationship between adsorption behavior and bioavailability of CNM-adsorbed contaminants is still limited. To investigate the influence of CNM morphology and organic contaminant (OC) physicochemical properties on this relationship, adsorption isotherms were generated for a suite of polycyclic aromatic hydrocarbons (PAHs) on multiwalled carbon nanotubes (MWCNTs) and exfoliated graphene (GN) in conjunction with determining the bioavailability of the adsorbed PAHs to Pimphales promelas using bile analysis via fluorescence spectroscopy. Although it appeared that GN adsorbed PAHs indiscriminately compared to MWCNTs, the subsequent bioavailability of GN-adsorbed PAHs was more sensitive to PAH morphology than MWCNTs. GN was effective at reducing bioavailability of linear PAHs by ∼70%, but had little impact on angular PAHs. MWCNTs were sensitive to molecular size, where bioavailability of two-ringed naphthalene was reduced by ∼80%, while bioavailability of the larger PAHs was reduced by less than 50%. Furthermore, the reduction in bioavailability of CNM-adsorbed PAHs was negatively correlated with the amount of CNM surface area covered by the adsorbed-PAHs. This study shows that the variability in bioavailability of CNM-adsorbed PAHs is largely driven by PAH size, configuration and surface area coverage.

  7. Structures of adsorbed CO on atomically smooth and on stepped sngle crystal surfaces

    International Nuclear Information System (INIS)

    Madey, T.E.; Houston, J.E.

    1980-01-01

    The structures of molecular CO adsorbed on atomically smooth surfaces and on surfaces containing monatomic steps have been studied using the electron stimulated desorption ion angular distribution (ESDIAD) method. For CO adsorbed on the close packed Ru(001) and W(110) surfaces, the dominant bonding mode is via the carbon atom, with the CO molecular axis perpendicular to the plane of the surface. For CO on atomicaly rough Pd(210), and for CO adsorbed at step sites on four different surfaces vicinal to W(110), the axis of the molecule is tilted or inclined away from the normal to the surface. The ESDIAD method, in which ion desorption angles are related to surface bond angles, provides a direct determination of the structures of adsorbed molecules and molecular complexes on surfaces

  8. Quantum chemical investigation on the role of Li adsorbed on anatase (101) surface nano-materials on the storage of molecular hydrogen.

    Science.gov (United States)

    Srinivasadesikan, V; Raghunath, P; Lin, M C

    2015-06-01

    Lithiation of TiO2 has been shown to enhance the storage of hydrogen up to 5.6 wt% (Hu et al. J Am Chem Soc 128:11740-11741, 2006). The mechanism for the process is still unknown. In this work we have carried out a study on the adsorption and diffusion of Li atoms on the surface and migration into subsurface layers of anatase (101) by periodic density functional theory calculations implementing on-site Coulomb interactions (DFT+U). The model consists of 24 [TiO2] units with 11.097 × 7.655 Å(2) surface area. Adsorption energies have been calculated for different Li atoms (1-14) on the surface. A maximum of 13 Li atoms can be accommodated on the surface at two bridged O, Ti-O, and Ti atom adsorption sites, with 83 kcal mol(-1) adsorption energy for a single Li atom adsorbed between two bridged O atoms from where it can migrate into the subsurface layer with 27 kcal mol(-1) energy barrier. The predicted adsorption energies for H2 on the lithiated TiO2 (101) surface with 1-10 Li atoms revealed that the highest adsorption energies occurred on 1-Li, 5-Li, and 9-Li surfaces with 3.5, 4.4, and 7.6 kcal mol(-1), respectively. The values decrease rapidly with additional H2 co-adsorbed on the lithiated surfaces; the maximum H2 adsorption on the 9Li-TiO2(a) surface was estimated to be only 0.32 wt% under 100 atm H2 pressure at 77 K. The result of Bader charge analysis indicated that the reduction of Ti occurred depending on the Li atoms covered on the TiO2 surface.

  9. Surface characterization of Ag/Titania adsorbents

    International Nuclear Information System (INIS)

    Samokhvalov, Alexander; Nair, Sachin; Duin, Evert C.; Tatarchuk, Bruce J.

    2010-01-01

    The Ag/Titania adsorbent for selective removal of the desulfurization-refractive polycyclic aromatic sulfur heterocycles (PASHs) from liquid hydrocarbon fuels was prepared, its total and the Ag specific surface area were determined and the surface reaction sites in the sorbent that may be active in the adsorptive selective desulfurization were characterized by several spectroscopic and surface science techniques. The sorbent contains Ag, Ti, O and spurious C on its surface, as by the XPS measurements. Silver is present as an oxide, as judged by the XPS Auger parameter (AP). The complementary electron spin resonance (ESR) spectroscopy confirms that the majority of Ag is present in the diamagnetic Ag 1+ form, with the minor concentration (∼0.1% of total Ag) present as Ag 2+ . The findings by XPS and ESR are confirmed by the XRD, UV-vis spectroscopy and thermodynamic considerations. The supported Ag is highly dispersed on the surface of the titania support, with the particle size of ∼30-60 A depending on Ag content, with an Ag specific surface area of ∼7-14 m 2 /g, vs. the total surface area of ∼114-58 m 2 /g.

  10. Scattering of atoms by molecules adsorbed at solid surfaces

    International Nuclear Information System (INIS)

    Parra, Zaida.

    1988-01-01

    The formalism of collisional time-correlation functions, appropriate for scattering by many-body targets, is implemented to study energy transfer in the scattering of atoms and ions from molecules adsorbed on metal surfaces. Double differential cross-sections for the energy and angular distributions of atoms and ions scattered by a molecule adsorbed on a metal surface are derived in the limit of impulsive collisions and within a statistical model that accounts for single and double collisions. They are found to be given by the product of an effective cross-section that accounts for the probability of deflection into a solid angle times a probability per unit energy transfer. A cluster model is introduced for the vibrations of an adsorbed molecule which includes the molecular atoms, the surface atoms binding the molecule, and their nearest neighbors. The vibrational modes of CO adsorbed on a Ni(001) metal surface are obtained using two different cluster models to represent the on-top and bridge-bonding situations. A He/OC-Ni(001) potential is constructed from a strongly repulsive potential of He interacting with the oxygen atom in the CO molecule and a van der Waals attraction accounting for the He interaction with the free Ni(001) surface. A potential is presented for the Li + /OC-Ni(001) where a coulombic term is introduced to account for the image force. Trajectory studies are performed and analyzed in three dimensions to obtain effective classical cross-sections for the He/OC-Ni(001) and Li + /OC-Ni(001) systems. Results for the double differential cross-sections are presented as functions of scattering angles, energy transfer and collisional energy. Temperature dependence results are also analyzed. Extensions of the approach and inclusion of effects such as anharmonicity, collisions at lower energies, and applications of the approach to higher coverages are discussed

  11. Surface characterization of adsorbed asphaltene on a stainless steel surface

    International Nuclear Information System (INIS)

    Abdallah, W.A.; Taylor, S.D.

    2007-01-01

    X-ray photoelectron spectroscopy was used to characterize a single layer of adsorbed asphaltene on a metallic surface. The deposits were created by immersing a stainless steel disc into a dilute asphaltene solution with either toluene or dichloromethane as the solvent, although the toluene solution allowed for better control of the adsorbed asphaltene layer and less atmospheric oxygen contamination. The analyses for C 1s, S 2p 3/2 , N 1s and O 1s photoemission peaks indicated that different functional groups are present in the asphaltene layer including carboxylic, pyrrolic, pyridininc, thiophenic and sulfite, with slight differences in their binding energies

  12. Substrate induced ordering of molecular adsorbates on Au(111)

    International Nuclear Information System (INIS)

    Schott, J.H.; White, H.S.; Arana, C.R.

    1992-01-01

    Using scanning tunneling microscopy in dimethylformate, [Ru(bpy) 2 (bpy-(CH 2 ) x -bpy) 2+ ] (x = 4 and 5) monolayers adsorbed on the unreconstructed and √3 x 22 reconstructed surfaces of Au(111) were imaged in this paper. The substrate had a highly ordered pattern on the reconstructed surface, but random spatial distribution on the unreconstructed surface. 17 refs., 3 figs

  13. Dispersion and Solvation Effects on the Structure and Dynamics of N719 Adsorbed to Anatase Titania (101) Surfaces in Room-Temperature Ionic Liquids: An ab Initio Molecular Simulation Study

    KAUST Repository

    Byrne, Aaron

    2015-12-24

    Ab initio, density functional theory (DFT)-based molecular dynamics (MD) has been carried out to investigate the effect of explicit solvation on the dynamical and structural properties of a [bmim][NTf2] room-temperature ionic liquid (RTIL), solvating a N719 sensitizing dye adsorbed onto an anatase titania (101) surface. The effect of explicit dispersion on the properties of this dye-sensitized solar cell (DSC) interface has also been studied. Upon inclusion of dispersion interactions in simulations of the solvated system, the average separation between the cations and anions decreases by 0.6 Å; the mean distance between the cations and the surface decreases by about 0.5 Å; and the layering of the RTIL is significantly altered in the first layer surrounding the dye, with the cation being on average 1.5 Å further from the center of the dye. Inclusion of dispersion effects when a solvent is not explicitly included (to dampen longer-range interactions) can result in unphysical "kinking" of the adsorbed dye\\'s configuration. The inclusion of solvent shifts the HOMO and LUMO levels of the titania surface by +3 eV. At this interface, the interplay between the effects of dispersion and solvation combines in ways that are often subtle, such as enhancement or inhibition of specific vibrational modes. © 2015 American Chemical Society.

  14. The Dynamics and Structures of Adsorbed Surfaces

    DEFF Research Database (Denmark)

    Nielsen, M; Ellenson, W. D.; McTague, J. P.

    1978-01-01

    . Elastic neutron diffraction measurements, determining the two-dimensional structural ordering of the adsorbed films, have been performed on layers of N2, Ar, H2, D2, O2, Kr, and He. Measurements on layers of larger molecules such as CD4 and ND3 have also been reported. Inelastic neutron scattering...... measurements, studying the dynamics of the adsorbed films are only possible in a few especially favourable cases such as 36Ar and D2 films, where the coherent phonon scattering cross-sections are very large. In other cases incoherent scattering from hydrogen can give information about e.g. the mobility...

  15. In-situ quartz crystal microgravimetric studies of molecular adsorbates containing thiol and hydroquinone moieties bound to Au(111) surfaces in aqueous electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Y.; Sukenik, C.; Sandifer, M. [Case Western Univ., Cleveland, OH (United States); Barriga, R.J.; Soriaga, M.P.; Scherson, D. [Texas A& M Univ., College Station, TX (United States)

    1995-12-01

    The microgravimetric properties of monolayers of 2, 5-dihydroxythiophenol, 2,5-dihydroxybenzyl mercaptan, and 2, 5-dihydroxy-4-methylbenzyl mercaptan adsorbed on Au(111) single crystal electrodes were examined by in situ quartz crystal microbalance techniques in aqueous perchloric acid electrolytes. The results obtained are consistent with the reversible loss of an average of about three waters per adsorbed molecule as the layers are oxidized and subsequently reduced. These observations provide evidence for discrete changes in the extent of bound water within the hydroquinone/quinone layer as the oxidation state of the monolayer is changed. 9 refs., 4 figs.

  16. Generating Atomistic Slab Surfaces with Adsorbates

    Science.gov (United States)

    2017-12-01

    slabs of various thickness and with various vacuum spacing need be calculated. This can occur in serial or simultaneously . If performed in serial, the...the user. Although the optimization of the slab thickness and vacuum padding can be done simultaneously , it is more computationally conservative to...monolayer is a slab (True if slab), the type of mesh desired (adsorbates.py was written for “Gamma”), how detailed the mesh should be (in units of inverse

  17. Theoretical Insight of Physical Adsorption for a Single-Component Adsorbent + Adsorbate System: I. Thermodynamic Property Surfaces

    KAUST Repository

    Chakraborty, Anutosh; Saha, Bidyut Baran; Ng, Kim Choon; Koyama, Shigeru; Srinivasan, Kandadai

    2009-01-01

    Thermodynamic property surfaces for a single-component adsorbent + adsorbate system are derived and developed from the viewpoint of classical thermodynamics, thermodynamic requirements of chemical equilibrium, Gibbs law, and Maxwell relations

  18. Adsorbate-driven cooling of carbene-based molecular junctions

    Czech Academy of Sciences Publication Activity Database

    Foti, Giuseppe; Vázquez, Héctor

    2017-01-01

    Roč. 8, Oct (2017), s. 2060-2068 ISSN 2190-4286 R&D Projects: GA ČR GA15-19672S EU Projects: European Commission(XE) 702114 - HEATEXMOL Institutional support: RVO:68378271 Keywords : adsorbate * carbene * current-induced heating and cooling * molecular junction * vibrations Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.127, year: 2016

  19. Diffusion of particles adsorbed on reconstructive surface

    Czech Academy of Sciences Publication Activity Database

    Tarasenko A., Nataliya; Tarasenko, Alexander; Jastrabík, Lubomír

    2005-01-01

    Roč. 11, č. 1 (2005), s. 485-489 ISSN 0929-5607 R&D Projects: GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z10100522 Keywords : lattice gas * surface reconstruction * surface diffusion * phase transitions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.323, year: 2005

  20. Linear response theory of activated surface diffusion with interacting adsorbates

    Energy Technology Data Exchange (ETDEWEB)

    Marti' nez-Casado, R. [Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Sanz, A.S.; Vega, J.L. [Instituto de Fi' sica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain); Rojas-Lorenzo, G. [Instituto Superior de Tecnologi' as y Ciencias Aplicadas, Ave. Salvador Allende, esq. Luaces, 10400 La Habana (Cuba); Instituto de Fi' sica Fundamental, Consejo Superior de Investigaciones Cienti' ficas, Serrano 123, 28006 Madrid (Spain); Miret-Artes, S., E-mail: s.miret@imaff.cfmac.csic.es [Instituto de Fi' sica Fundamental, Consejo Superior de Investigaciones Cienti' ficas, Serrano 123, 28006 Madrid (Spain)

    2010-05-12

    Graphical abstract: Activated surface diffusion with interacting adsorbates is analyzed within the Linear Response Theory framework. The so-called interacting single adsorbate model is justified by means of a two-bath model, where one harmonic bath takes into account the interaction with the surface phonons, while the other one describes the surface coverage, this leading to defining a collisional friction. Here, the corresponding theory is applied to simple systems, such as diffusion on flat surfaces and the frustrated translational motion in a harmonic potential. Classical and quantum closed formulas are obtained. Furthermore, a more realistic problem, such as atomic Na diffusion on the corrugated Cu(0 0 1) surface, is presented and discussed within the classical context as well as within the framework of Kramer's theory. Quantum corrections to the classical results are also analyzed and discussed. - Abstract: Activated surface diffusion with interacting adsorbates is analyzed within the Linear Response Theory framework. The so-called interacting single adsorbate model is justified by means of a two-bath model, where one harmonic bath takes into account the interaction with the surface phonons, while the other one describes the surface coverage, this leading to defining a collisional friction. Here, the corresponding theory is applied to simple systems, such as diffusion on flat surfaces and the frustrated translational motion in a harmonic potential. Classical and quantum closed formulas are obtained. Furthermore, a more realistic problem, such as atomic Na diffusion on the corrugated Cu(0 0 1) surface, is presented and discussed within the classical context as well as within the framework of Kramer's theory. Quantum corrections to the classical results are also analyzed and discussed.

  1. Graphene symmetry-breaking with molecular adsorbates: modeling and experiment

    Science.gov (United States)

    Groce, M. A.; Hawkins, M. K.; Wang, Y. L.; Cullen, W. G.; Einstein, T. L.

    2012-02-01

    Graphene's structure and electronic properties provide a framework for understanding molecule-substrate interactions and developing techniques for band gap engineering. Controlled deposition of molecular adsorbates can create superlattices which break the degeneracy of graphene's two-atom unit cell, opening a band gap. We simulate scanning tunneling microscopy and spectroscopy measurements for a variety of organic molecule/graphene systems, including pyridine, trimesic acid, and isonicotinic acid, based on density functional theory calculations using VASP. We also compare our simulations to ultra-high vacuum STM and STS results.

  2. A surface-enhanced Raman study of N-methylquinolinium tricyanoquinodimethanide adsorbed on Ag nanospheres: Determination of molecular orientation and order

    Science.gov (United States)

    Fletcher, Melissa C.; Alexson, Dimitri M.; Prokes, Sharka M.; Glembocki, Orest J.; Vivoni, Alberto; Hosten, Charles M.

    2015-08-01

    Quinolinium tricyanoquinodimethanides are among the most promising molecules for electronic applications. Disorder can be detrimental to the desired electronic properties of a monolayer, and as such, a reliable method to characterize a monolayer without destroying or creating defects is paramount to determining potential applications. Here, the normal and surface-enhanced Raman scattering spectra of N-methylquinolinium tricyanoquinodimethanide (CH3Q-3CNQ) on silver coated nanosurfaces have been obtained and analyzed. Theoretical treatment of CH3Q-3CNQ was performed. Optimization and frequency search was conducted using the B3LYP functional with the 6-31G(d) basis set. A complete list of frequencies and assignments for the molecules are presented. The spectroscopic evidence points to the fact that a monolayer of CH3Q-3CNQ can be formed through the self-assembly process, and the SERS data indicate that the monolayer attaches to the silver surface through the nitrile groups.

  3. Infrared Analysis Of Enzymes Adsorbed Onto Model Surfaces

    Science.gov (United States)

    Story, Gloria M.; Rauch, Deborah S.; Brode, Philip F.; Marcott, Curtis A.

    1989-12-01

    The adsorption of the enzymes, subtilisin BPN' and lysozyme, onto model surfaces was examined using attenuated total reflectance (ATR) infrared (IR) spectroscopy. Using a cylindrical internal reflection (CIRcle) cell with a Germanium (Ge) internal reflection element (IRE), model hydrophilic surfaces were made by plasma cleaning the IRE and model hydrophobic surfaces were made by precoating the IRE with a thin film of polystyrene. Gas chromatography (GC)-IR data collection software was used to monitor adsorption kinetics during the first five minutes after injection of the enzyme into the CIRcle cell. It was found that for both lysozyme and BPN', most of the enzyme that was going to adsorb onto the model surface did so within ten seconds after injection. Nearly an order-of-magnitude more BPN' adsorbed on the hydrophobic Ge surface than the hydrophilic one, while lysozyme adsorbed somewhat more strongly to the hydrophilic Ge surface. Overnight, the lysozyme layer continued to increase in thickness, while BPN' maintained its initial coverage. The appearance of carboxylate bands in some of the adsorbed BPN' spectra suggests the occurrence of peptide bond hydrolysis. A Au/Pd coating on the CIRcle cell o-rings had a significant effect on the adsorption of BPN'. (This coating was applied in an attempt to eliminate interfering Teflon absorption bands.) An apparent electrochemical reaction occurred, involving BPN', Ge, Au/Pd, and the salt solution used to stabilize BPN'. The result of this reaction was enhanced adsorption of the enzyme around the coated o-rings, etching of the Ge IRE at the o-ring site, and some autolysis of the enzyme. No such reaction was observed with lysozyme.

  4. Electrochemical Properties of Alkanethiol Monolayers Adsorbed on Nanoporous Au Surfaces

    International Nuclear Information System (INIS)

    Chu, Yeon Yi; Seo, Bora; Kim, Jong Won

    2010-01-01

    We investigated the electrochemical properties of alkanethiol monolayers adsorbed on NPG surfaces by cyclic voltammetry and electrochemical impedance spectroscopy, and the results are compared to those on flat Au surfaces. The reductive desorption of alkanethiols on NPG surfaces is observed in more negative potential regions than that on flat Au surfaces due the stronger S-Au interaction on NPG surfaces. While the electron transfer through alkanethiol monolayers on flat Au surfaces occurs via a tunneling process through the monolayer films, the redox species can permeate through the monolayers on NPG surfaces to transfer the electrons to the Au surfaces. The results presented here will help to elucidate the intrinsic electrochemical properties of alkanethiol monolayers adsorbed on curved Au surfaces, particularly on the surface of AuNPs. Self-assembled monolayers (SAMs) of thiolate molecules on Au surfaces have been the subject of intensive research for the last few decades due to their unique physical and chemical properties. The well-organized surface structures of thiolate SAMs with various end-group functionalities can be further utilized for many applications in biology and nanotechnology. In addition to the practical applications, SAMs of thiolate molecules on Au surfaces also provide unique opportunities to address fundamental issues in surface chemistry such as self-organized surface structures, electron transfer behaviors, and moleculesubstrate interactions. Although there have been numerous reports on the fundamental physical and chemical properties of thiolate SAMs on Au surfaces, most of them were investigated on flat Au surfaces, typically on well-defined Au(111) surfaces

  5. Stochastic Description of Activated Surface Diffusion with Interacting Adsorbates

    Science.gov (United States)

    Martínez-Casado, Ruth; Vega, José Luis; Sanz, Ángel S.; Miret-Artés, Salvador

    Activated surface diffusion on metal surfaces is receiving much attention both experimentally and theoretically. One of the main theoretical problems in this field is to explain the line-shape broadening observed when the surface coverage is increased. Recently, we have proposed a fully stochastic model, the interacting single adsorbate (ISA) model, aimed at explaining and understanding this type of experiments, which essentially consists of considering the classical Langevin formulation with two types of noise forces: (i) a Gaussian white noise accounting for the substrate friction, and (ii) a shot noise simulating the interacting adsorbates at different coverages. No interaction potential between adsorbates is included because any trace of microscopic interaction seems to be wiped out in a Markovian regime. This model describes in a good approximation, and at a very low computational cost, the line-shape broadening observed experimentally. Furthermore, its mathematical simplicity also allows to derive some analytical expressions which are of much help in the interpretation of the physics underlying surface diffusion processes.

  6. Theoretical Insight of Physical Adsorption for a Single-Component Adsorbent + Adsorbate System: I. Thermodynamic Property Surfaces

    KAUST Repository

    Chakraborty, Anutosh

    2009-02-17

    Thermodynamic property surfaces for a single-component adsorbent + adsorbate system are derived and developed from the viewpoint of classical thermodynamics, thermodynamic requirements of chemical equilibrium, Gibbs law, and Maxwell relations. They enable us to compute the entropy and enthalpy of the adsorbed phase, the isosteric heat of adsorption, specific heat capacity, and the adsorbed phase volume thoroughly. These equations are very simple and easy to handle for calculating the energetic performances of any adsorption system. We have shown here that the derived thermodynamic formulations fill up the information gap with respect to the state of adsorbed phase to dispel the confusion as to what is the actual state of the adsorbed phase. We have also discussed and established the temperature-entropy diagrams of (i) CaCl 2-in-silica gel + water system for cooling applications, and (ii) activated carbon (Maxsorb III) + methane system for gas storage. © Copyright 2009 American Chemical Society.

  7. CHEMICAL REACTIONS ON ADSORBING SURFACE: KINETIC LEVEL OF DESCRIPTION

    Directory of Open Access Journals (Sweden)

    P.P.Kostrobii

    2003-01-01

    Full Text Available Based on the effective Hubbard model we suggest a statistical description of reaction-diffusion processes for bimolecular chemical reactions of gas particles adsorbed on the metallic surface. The system of transport equations for description of particles diffusion as well as reactions is obtained. We carry out the analysis of the contributions of all physical processes to the formation of diffusion coefficients and chemical reactions constants.

  8. EDITORIAL: Molecular switches at surfaces Molecular switches at surfaces

    Science.gov (United States)

    Weinelt, Martin; von Oppen, Felix

    2012-10-01

    In nature, molecules exploit interaction with their environment to realize complex functionalities on the nanometer length scale. Physical, chemical and/or biological specificity is frequently achieved by the switching of molecules between microscopically different states. Paradigmatic examples are the energy production in proton pumps of bacteria or the signal conversion in human vision, which rely on switching molecules between different configurations or conformations by external stimuli. The remarkable reproducibility and unparalleled fatigue resistance of these natural processes makes it highly desirable to emulate nature and develop artificial systems with molecular functionalities. A promising avenue towards this goal is to anchor the molecular switches at surfaces, offering new pathways to control their functional properties, to apply electrical contacts, or to integrate switches into larger systems. Anchoring at surfaces allows one to access the full range from individual molecular switches to self-assembled monolayers of well-defined geometry and to customize the coupling between molecules and substrate or between adsorbed molecules. Progress in this field requires both synthesis and preparation of appropriate molecular systems and control over suitable external stimuli, such as light, heat, or electrical currents. To optimize switching and generate function, it is essential to unravel the geometric structure, the electronic properties and the dynamic interactions of the molecular switches on surfaces. This special section, Molecular Switches at Surfaces, collects 17 contributions describing different aspects of this research field. They analyze elementary processes, both in single molecules and in ensembles of molecules, which involve molecular switching and concomitant changes of optical, electronic, or magnetic properties. Two topical reviews summarize the current status, including both challenges and achievements in the field of molecular switches on

  9. Controllable Catalysis with Nanoparticles: Bimetallic Alloy Systems and Surface Adsorbates

    KAUST Repository

    Chen, Tianyou

    2016-05-16

    Transition metal nanoparticles are privileged materials in catalysis due to their high specific surface areas and abundance of active catalytic sites. While many of these catalysts are quite useful, we are only beginning to understand the underlying catalytic mechanisms. Opening the “black box” of nanoparticle catalysis is essential to achieve the ultimate goal of catalysis by design. In this Perspective we highlight recent work addressing the topic of controlled catalysis with bimetallic alloy and “designer” adsorbate-stabilized metal nanoparticles.

  10. Controllable Catalysis with Nanoparticles: Bimetallic Alloy Systems and Surface Adsorbates

    KAUST Repository

    Chen, Tianyou; Rodionov, Valentin

    2016-01-01

    Transition metal nanoparticles are privileged materials in catalysis due to their high specific surface areas and abundance of active catalytic sites. While many of these catalysts are quite useful, we are only beginning to understand the underlying catalytic mechanisms. Opening the “black box” of nanoparticle catalysis is essential to achieve the ultimate goal of catalysis by design. In this Perspective we highlight recent work addressing the topic of controlled catalysis with bimetallic alloy and “designer” adsorbate-stabilized metal nanoparticles.

  11. Band mapping of surface states vs. adsorbate coverage

    International Nuclear Information System (INIS)

    Rotenberg, E.; Kevan, S.D.; Denlinger, J.D.; Chung, Jin-Wook

    1997-01-01

    The theory of electron bands, which arises from basic quantum mechanical principles, has been the cornerstone of solid state physics for over 60 years. Simply put, an energy band is an electron state in a solid whose energy varies with its momentum (similar to, but with a more complicated dependence than, how a free electron's energy is proportional to its momentum squared). Much attention over the last 15 years has been given to the study of band structure of surfaces and interfaces, especially as the applications of these two-dimensional systems have become increasingly important to industry and science. The ultraESCA endstation at beamline 7.01 at the Advanced Light Source was developed for very high-energy - (∼50 meV) and angular - ( 12 photons/sec) makes the detailed study of the evolution of bands possible. The authors are interested in learning how, when one forms a chemical bond between a metal and an overlaying atom or molecule, the resulting charge transfer to or from the adsorbate affects the surface bands. In some cases of interest, intermediate coverages lead to different band structure than at the extremes of clean and saturated surfaces. Surfaces of tungsten are particularly interesting, as their atomic geometry has been shown to be exquisitely sensitive to both the surface vibrational and electronic properties. In this study, the authors looked at the surface bands of tungsten ((110) surface), as a function both of coverage and mass of overlaying atoms. The adsorbed atoms were hydrogen and the alkali atoms lithium and cesium

  12. Photoelectron diffraction studies of small adsorbates on single crystal surfaces

    International Nuclear Information System (INIS)

    Pascal, Mathieu

    2002-01-01

    The structural determination of small molecules adsorbed on single crystal surfaces has been investigated using scanned energy mode photoelectron diffraction (PhD). The experimental PhD data were compared to theoretical models using a simulation program based on multiple scattering calculations. Three adsorption systems have been examined on Ag(110), Cu(110) and Cu(111) crystals. The structure of the (2x1)-O adsorption phase on Ag(110) revealed that the O atoms occupied the long bridge site and are almost co-planar with the top layer of Ag atoms. The best agreement between multiple scattering theory and experiment has been obtained for a missing-row (or equivalently an 'added- row') reconstruction. Alternative buckled-row and unreconstructed surface models can be excluded. The adsorption of the benzoate species on Cu(110) has been found to occur via the carboxylate group. The molecules occupy short bridge sites with the O atoms being slightly displaced from atop sites and are aligned along the close-packed azimuth. The tilt of the molecule with respect to the surface and the degree to which the surface is relaxed have also been investigated. The adsorption of methyl on Cu(111) was studied using either azomethane or methyl iodide to prepare the surface layers. At saturation coverage the preferred adsorption site is the fcc threefold hollow site, whereas at half saturation coverage ∼ 30 % of the methyl species occupy the hop threefold hollow sites. Best agreement between theory and experiment corresponded to a methyl group adsorbed with C 3v symmetry. The height of the C above the surface in a pure methyl layer was 1.66 ± 0.02 A, but was reduced to 1.62 ± 0.02 A in the presence of co-adsorbed iodine, suggesting that iodine increases the strength of adsorption. Iodine was also found to occupy the fee threefold hollow sites with a Cu-l bondlength of 2.61 ± 0.02 A. (author)

  13. LEED crystallography studies of the structure of clean and adsorbate-covered Ir, Pt and Rh crystal surfaces

    International Nuclear Information System (INIS)

    Koestner, R.J.

    1982-08-01

    There have only been a few Low Energy Electron Diffraction (LEED) intensity analyses carried out to determine the structure of molecules adsorbed on metal surfaces; most surface crystallography studies concentrated on the structure of clean unreconstructed or atomic adsorbate-covered transition metal faces. The few molecular adsorption systems already investigated by dynamical LEED are CO on Ni(100), Cu(100) and Pd(100) as well as C 2 H 2 and C 2 H 4 adsorbed on Pt(111). The emphasis of this thesis research has been to extend the applicability of LEED crystallography to the more complicated unit cells found in molecular overlayers on transition metals or in there constructed surfaces of clean transition metals

  14. LEED crystallography studies of the structure of clean and adsorbate-covered Ir, Pt and Rh crystal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Koestner, R.J.

    1982-08-01

    There have only been a few Low Energy Electron Diffraction (LEED) intensity analyses carried out to determine the structure of molecules adsorbed on metal surfaces; most surface crystallography studies concentrated on the structure of clean unreconstructed or atomic adsorbate-covered transition metal faces. The few molecular adsorption systems already investigated by dynamical LEED are CO on Ni(100), Cu(100) and Pd(100) as well as C/sub 2/H/sub 2/ and C/sub 2/H/sub 4/ adsorbed on Pt(111). The emphasis of this thesis research has been to extend the applicability of LEED crystallography to the more complicated unit cells found in molecular overlayers on transition metals or in there constructed surfaces of clean transition metals.

  15. Clarification of the mechanism of sulfur trioxide electrolysis. Evaluation of SO3 and O atom adsorbed on Pt surface

    International Nuclear Information System (INIS)

    Suzuki, Chikashi; Nakagiri, Toshio

    2008-01-01

    We developed a hybrid thermo-chemical process, which included a SO 3 electrolysis process utilizing the heat supplied by a fast breeder reactor (FBR), as a new hydrogen production process. To clarify the mechanism of SO 3 electrolysis, we evaluated the electronic states of SO 3 and O atom adsorbed on the Pt (111) surface using first-principles calculations with a slab model. Moreover, we evaluated the chemical bonding states of SO 3 and adsorbed O using molecular orbital calculation on the basis of the calculations using a slab model. We found that there were two stable adsorbed SO 3 configurations on the Pt surface. From the molecular orbital calculation, it was found that the S-O bond became weak by SO 3 absorption, and it was conjectured that SO 3 dissociation proceeded through the intermediate state of adsorbed SO 2 and adsorbed O on the Pt surface. Moreover, we derived the O coverage considering the adsorbed SO 2 and evaluated the influence of SO 3 adsorption energy on the O coverage. (author)

  16. The molecular mechanism of mediation of adsorbed serum proteins to endothelial cells adhesion and growth on biomaterials.

    Science.gov (United States)

    Yang, Dayun; Lü, Xiaoying; Hong, Ying; Xi, Tingfei; Zhang, Deyuan

    2013-07-01

    To explore molecular mechanism of mediation of adsorbed proteins to cell adhesion and growth on biomaterials, this study examined endothelial cell adhesion, morphology and viability on bare and titanium nitride (TiN) coated nickel titanium (NiTi) alloys and chitosan film firstly, and then identified the type and amount of serum proteins adsorbed on the three surfaces by proteomic technology. Subsequently, the mediation role of the identified proteins to cell adhesion and growth was investigated with bioinformatics analyses, and further confirmed by a series of cellular and molecular biological experiments. Results showed that the type and amount of adsorbed serum proteins associated with cell adhesion and growth was obviously higher on the alloys than on the chitosan film, and these proteins mediated endothelial cell adhesion and growth on the alloys via four ways. First, proteins such as adiponectin in the adsorbed protein layer bound with cell surface receptors to generate signal transduction, which activated cell surface integrins through increasing intracellular calcium level. Another way, thrombospondin 1 in the adsorbed protein layer promoted TGF-β signaling pathway activation and enhanced integrins expression. The third, RGD sequence containing proteins such as fibronectin 1, vitronectin and thrombospondin 1 in the adsorbed protein layer bound with activated integrins to activate focal adhesion pathway, increased focal adhesion formation and actin cytoskeleton organization and mediated cell adhesion and spreading. In addition, the activated focal adhesion pathway promoted the expression of cell growth related genes and resulted in cell proliferation. The fourth route, coagulation factor II (F2) and fibronectin 1 in the adsorbed protein layer bound with cell surface F2 receptor and integrin, activated regulation of actin cytoskeleton pathway and regulated actin cytoskeleton organization. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Surface-enhanced Raman Spectroscopy of Ethephone Adsorbed on Silver Surface

    International Nuclear Information System (INIS)

    Lee, Chul Jae; Kim, Hee Jin; Karim, Mohammad Rezaul; Lee, Mu Sang

    2006-01-01

    We investigated the Surface-enhanced Raman Spectroscopy (SERS) spectrum of ethephone (2- chloroethylphosphonic acid). We observed significant signals in the ordinary Raman spectrum for solid-state ethephone as well as when it was adsorbed on a colloidal silver surface, strong vibrational signals were obtained at a very low concentration. The SERS spectra were obtained by silver colloids that were prepared by the γ - irradiation method. The influence of pH and the influence of anion (Cl - , Br - , I - ) on the adsorption orientation were investigated. Two different adsorption mechanisms were deduced, depending on the experimental conditions. The chlorine atom or the chlorine and two oxygen atoms were adsorbed on the colloidal silver surface. Among halide ions, Br - and I - were more strongly adsorbed on the colloidal silver surfaces. As a result, the adsorption of ethephone was less effective due to their steric hinderance

  18. Organic adsorbates on metal surfaces. PTCDA and NTCDA on AG(110)

    Energy Technology Data Exchange (ETDEWEB)

    Abbasi, Afshin

    2010-02-22

    Polyaromatic molecules functionalized with carboxylic groups have served as model systems for the growth of organic semiconducting films on a large variety of substrates. Most non-reactive substrates allow for a growth mode compatible with the bulk phase of the molecular crystal with two molecules in the unit cell, but some more reactive substrates including Ag(111) and Ag(110) can induce substantial changes in the first monolayer (ML). In the specific case of Ag(110), the adsorbate unit cell of both NTCDA and PTCDA resembles a brickwall structure, with a single molecule in the unit cell. From this finding, it can be concluded that the adsorbate-substrate interaction is stronger than typical inter-molecular binding energies in the respective bulk phases. In the present work, the interactions between small Ag(110) clusters and a single NTCDA or PTCDA molecule are investigated with different ab initio techniques. Four major ingredients contribute to the binding between adsorbate and substrate: Directional bonds between Ag atoms in the topmost layer and the oxygen atoms of the molecule, Pauli repulsion between filled orbitals of molecule and substrate, an attractive van-der-Waals interaction, and a negative net charge on the molecule inducing positive image charges in the substrate, resulting therefore in an attractive Coulomb interaction between these opposite charges. As both Hartree-Fock theory and density functional theory with typical gradient-corrected density functional do not contain any long range correlation energy required for dispersion interactions, we compare these approaches with the fastest numerical technique where the leading term of the van-der-Waals interaction is included, i.e. second order Moeller-Plesset theory (MP2). Both Hartree-Fock and density functional theory result in bended optimized geometries where the adsorbate is interacting mainly via the oxygen atoms, with the core of the molecule repelled from the substrate. Only at the MP2 level

  19. Application of Molecular Adsorber Coatings in Chamber A for the James Webb Space Telescope

    Science.gov (United States)

    Abraham, Nithin S.

    2017-01-01

    As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test facility called Chamber A. This presentation summarizes the background, fabrication, installation, chemical analysis test results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination. As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test

  20. Modeling adsorption: Investigating adsorbate and adsorbent properties

    Science.gov (United States)

    Webster, Charles Edwin

    1999-12-01

    Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

  1. Resonance studies of H atoms adsorbed on frozen H2 surfaces

    International Nuclear Information System (INIS)

    Crampton, S.B.

    1980-01-01

    Observations are reported of the ground state hyperfine resonance of hydrogen atoms stored in a 5 cm. diameter bottle coated with frozen molecular hydrogen. Dephasing of the hyperfine resonance while the atoms are adsorbed produces frequency shifts which vary by a factor of two over the temperature range 3.7 K to 4.6 K and radiative decay rates which vary by a factor of five over this range. The magnitudes and temperature dependences of the frequency shifts and decay rates are consistent with a non-uniform distribution of surface adsorption energies with mean about 38(8) K, in agreement with theoretical estimates for a smooth surface. Extrapolation of the 30 nanosec. mean adsorption times at 4.2 K predicts very long adsorption times for H on H 2 below 1 K. Studies of level population recovery rates provide evidence for surface electron spin exchange collisions between adsorbed atoms with collision duration long compared to the hyperfine period, suggesting that the atoms are partially mobile on the surface. The lowest rates observed for level population recovery set a lower limit of about 500 atom-surface collisions at 4.2 K without recombination

  2. A COMPREHENSIVE STUDY OF HYDROGEN ADSORBING TO AMORPHOUS WATER ICE: DEFINING ADSORPTION IN CLASSICAL MOLECULAR DYNAMICS

    Energy Technology Data Exchange (ETDEWEB)

    Dupuy, John L.; Lewis, Steven P.; Stancil, P. C. [Department of Physics and Astronomy and the Center for Simulational Physics, University of Georgia, Athens, GA 30602 (United States)

    2016-11-01

    Gas–grain and gas–phase reactions dominate the formation of molecules in the interstellar medium (ISM). Gas–grain reactions require a substrate (e.g., a dust or ice grain) on which the reaction is able to occur. The formation of molecular hydrogen (H{sub 2}) in the ISM is the prototypical example of a gas–grain reaction. In these reactions, an atom of hydrogen will strike a surface, stick to it, and diffuse across it. When it encounters another adsorbed hydrogen atom, the two can react to form molecular hydrogen and then be ejected from the surface by the energy released in the reaction. We perform in-depth classical molecular dynamics simulations of hydrogen atoms interacting with an amorphous water-ice surface. This study focuses on the first step in the formation process; the sticking of the hydrogen atom to the substrate. We find that careful attention must be paid in dealing with the ambiguities in defining a sticking event. The technical definition of a sticking event will affect the computed sticking probabilities and coefficients. Here, using our new definition of a sticking event, we report sticking probabilities and sticking coefficients for nine different incident kinetic energies of hydrogen atoms [5–400 K] across seven different temperatures of dust grains [10–70 K]. We find that probabilities and coefficients vary both as a function of grain temperature and incident kinetic energy over the range of 0.99–0.22.

  3. Structure of solid surfaces and of adsorbates by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Somorjai, G.A.

    1977-01-01

    LEED theory has developed to the point where the diffraction beam intensities can be computed using the locations of the surface atoms as the only adjustable parameters. The position of atoms in many clean monatomic solid surfaces and the surface structures of ordered monolayers of adsorbed atoms have been determined this way. Surface crystallography studies are now extended to small hydrocarbon molecules that are adsorbed on metal surfaces. These studies are reviewed

  4. Electronic properties of adsorbates and clean surfaces of metals and semiconductors

    International Nuclear Information System (INIS)

    Lecante, J.

    1980-01-01

    This paper surveys recent progress in experimental studies on electronic properties of adsorbates and clean metal surfaces. Electron spectroscopy and particularly angle resolved photoelectron spectroscopy appears to be a very powerful tool to get informations on electronic levels of adsorbates or clean surfaces. Moreover this technique may also give informations about the atomic geometry of the surface. Experimental investigation about surface plasmons, surface states, core level shifts are presented for clean surfaces. As examples of adsorbate covered surfaces two typical cases are chosen: two dimensional band structure and oriented molecules. Finally the photoelectron diffraction may be used for surface structure determination either in the case of an adsorbate or a clean metal surface [fr

  5. Order-disorder transitions in adsorbed systems on magnetic surfaces

    International Nuclear Information System (INIS)

    Aguilera-Granja, F.; Moran-Lopez, J.L.; Instituto Politecnico Nacional, Mexico City. Centro de Investigacion y de Estudios Avanzados); Falicov, L.M.

    1984-01-01

    It is investigated the effect of adsorbed atoms on the magnetic properties of ferromagnets. The Ising model is employed considering nearest neigbours with antiferromagnetic coupling between atoms. (M.W.O.) [pt

  6. 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...

  7. Oil adsorbing package, also procedure to remove oil from a water surface

    Energy Technology Data Exchange (ETDEWEB)

    1971-05-01

    A method is given to remove oil from water to prevent water pollution. Use is made of an oil-adsorbing packet having a specific gravity which is lower than the specific gravity of water. The hull is manufactured from any material which is not a water-insoluble nonpolar material. The hull is partly permeable to water and encloses a solid oil-adsorbing compound having a large adsorbing surface. (10 claims)

  8. High resolution spectroscopy on adsorbed molecules on a Ni (110)-surface: vibrational states and electronic levels

    International Nuclear Information System (INIS)

    Kardinal, I.

    1998-01-01

    The complementary techniques of HR-XPS and HREELS have been applied to two distinct problems. The first studies adsorption and dissociation of C 2 N 2 on Ni (110) at room temperature (RT) and at 90 K and its co-adsorption with CO. At RT C 2 N 2 dissociates and forms a c(2x2)-CN structure. The resulting CN is found to be bound in the grooves of the (110) surface yielding the lowest C-N vibrational energy yet observed. C 2 N 2 was found to dissociate even at 90 K however the resulting CN overlayer after warming to RT showed remarkable differences to that of the RT adsorption. As well as the in-groove species a number of adsorption sites on the ridges with a bond order higher have been identified. Preadsorbed CO is completely driven of the Ni (110) surface by co-adsorption of CN at RT. HREELS indicates that first CO is desorbed from the on-top-sites and then from the bridge-sites of the (110)-ridges involving a considerable increase of the HREELS cross section for the CO on the bridge-sites. Also the signal intensity of the coadsorbed CN is suppressed by the CO present on the surface. The second study investigated the adsorption of bithiophene (BiT) on clean Ni (110) and the S-modified c(2x2)-S-Ni (110) and p(4x1)-S-Ni (110). The latter provided a strongly structured substrate which forced the assembly of the adsorbed BiT-molecules. The high degree of order of this adsorbate/substrate system was obvious in both the HR-XPS results and the BREELS results with strong azimuthal anisotropy. This system was used to asses the ability to use the HREELS impact selection rules to determine molecular orientation of a reasonably complex adsorbate overlayer. (author)

  9. The metrics of surface adsorbed small molecules on the Young's fringe dual-slab waveguide interferometer

    International Nuclear Information System (INIS)

    Cross, Graham H; Reeves, Andrew; Brand, Stuart; Swann, Marcus J; Peel, Louise L; Freeman, Neville J; Lu, Jian R

    2004-01-01

    A method for analysing thin films using a dual-waveguide interferometric technique is described. Alternate dual polarization addressing of the interferometer sensor using a ferroelectric liquid crystal polarization switch allowed the opto-geometrical properties (density and thickness) of adsorbed layers at a solid-liquid interface to be determined. Differences in the waveguide mode dispersion between the transverse electric and transverse magnetic modes allowed unique combinations of layer thickness and refractive index to be determined at all stages of the layer formation process. The technique has been verified by comparing the analysis of the surface adsorption of surfactants with data obtained using neutron scattering techniques, observing their behaviour on trimethylsilane coated silicon oxynitride surfaces. The data obtained were found to be in excellent agreement with analogous neutron scattering experiments and the precision of the measurements taken to be of the order of 40 pm with respect to adsorbed layer thicknesses. The study was extended to a series of surfactants whose layer morphology could be correlated with their hydrophilicity/lipophilicity balance. Those in the series with longer alkyl chains were observed to form thinner, denser layers at the hydrophobic solid/aqueous liquid interface and the degree of order attained at sub-critical micelle concentrations to be correlated with molecular fluidity. The technique is expected to find utility with those interested in thin film analysis. An important and growing area of application is within the life sciences, especially in the field of protein structure and function

  10. Adsorption of moisture on molecular sieve adsorbents at low humidity

    International Nuclear Information System (INIS)

    Singh, V.P.; Ruthven, D.M.

    1984-07-01

    This report summarizes the results and conclusions of a contractor's study on the performance of 4A molecular sieve under very low humidity conditions, e.g., as expected in fusion reactor plants. The results suggest that: (a) very efficient regeneration of the sieve to low residual moisture contents ( 2 O/4A sieve system

  11. Revisiting the inelastic electron tunneling spectroscopy of single hydrogen atom adsorbed on the Cu(100) surface

    International Nuclear Information System (INIS)

    Jiang, Zhuoling; Wang, Hao; Sanvito, Stefano; Hou, Shimin

    2015-01-01

    Inelastic electron tunneling spectroscopy (IETS) of a single hydrogen atom on the Cu(100) surface in a scanning tunneling microscopy (STM) configuration has been investigated by employing the non-equilibrium Green’s function formalism combined with density functional theory. The electron-vibration interaction is treated at the level of lowest order expansion. Our calculations show that the single peak observed in the previous STM-IETS experiments is dominated by the perpendicular mode of the adsorbed H atom, while the parallel one only makes a negligible contribution even when the STM tip is laterally displaced from the top position of the H atom. This propensity of the IETS is deeply rooted in the symmetry of the vibrational modes and the characteristics of the conduction channel of the Cu-H-Cu tunneling junction, which is mainly composed of the 4s and 4p z atomic orbitals of the Cu apex atom and the 1s orbital of the adsorbed H atom. These findings are helpful for deepening our understanding of the propensity rules for IETS and promoting IETS as a more popular spectroscopic tool for molecular devices

  12. Fulminant hepatic failure following marijuana drug abuse: Molecular adsorbent recirculation system therapy

    Directory of Open Access Journals (Sweden)

    G Swarnalatha

    2013-01-01

    Full Text Available Marijuana is used for psychoactive and recreational purpose. We report a case of fulminant hepatic failure following marijuana drug abuse who recovered following artificial support systems for acute liver failure. There is no published literature of management of marijuana intoxication with molecular adsorbent recirculation system (MARS. MARS is effective and safe in patients with fulminant hepatic failure following marijuana intoxication.

  13. Aminopropyl-modified mesoporous molecular sieves as efficient adsorbents for removal of auxins

    International Nuclear Information System (INIS)

    Moritz, Michał; Geszke-Moritz, Małgorzata

    2015-01-01

    Graphical abstract: Adsorption of indole-3-acetic acid (IAA) on aminopropyl-modified mesoporous sieves. - Highlights: • Four types of mesoporous molecular sieves were used as sorbents for removal of auxins. • SBA-15, MCF, PHTS and SBA-16 were grafted with (3-aminopropyl)triethoxysilane. • The adsorption capacity of modified materials was higher as compared to pure silicas. • Surface modification and pore volume play important role in adsorption process. - Abstract: In the present study, mesoporous siliceous materials grafted with 3-aminopropyltriethoxysilane (APTES) were examined as sorbents for removal of chosen plant growth factors (auxins) such as 1-naphthaleneacetic acid (NAA), indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). Four different types of mesoporous molecular sieves including SBA-15, PHTS, SBA-16 and MCF have been prepared via non-ionic surfactant-assisted soft templating method. Silica molecular sieves were thoroughly characterized by nitrogen adsorption–desorption analysis, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The maximum adsorption capacity (Q max ) for NAA, IAA and IBA was in the range from 51.0 to 140.8 mg/g and from 4.3 to 7.3 mg/g for aminopropyl-modified adsorbents and pure silicas, respectively. The best adsorption performance was observed for IAA entrapment using both APTES-functionalized SBA-15 and MCF matrices (Q max of 140.8 and 137.0 mg/g, respectively) which can be ascribed to their larger pore volumes and pore diameters. Moreover, these silicas were characterized by the highest adsorption efficiency exceeding 90% at low pollutant concentration. The experimental points for adsorption of plant growth factors onto aminopropyl-modified mesoporous molecular sieves fitted well to the Langmuir equation

  14. Aminopropyl-modified mesoporous molecular sieves as efficient adsorbents for removal of auxins

    Energy Technology Data Exchange (ETDEWEB)

    Moritz, Michał, E-mail: michal.moritz@put.poznan.pl [Poznan University of Technology, Faculty of Chemical Technology, Institute of Chemistry and Technical Electrochemistry, Berdychowo 4, 60-965 Poznań (Poland); Geszke-Moritz, Małgorzata, E-mail: Malgorzata.Geszke-Moritz@amu.edu.pl [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2015-03-15

    Graphical abstract: Adsorption of indole-3-acetic acid (IAA) on aminopropyl-modified mesoporous sieves. - Highlights: • Four types of mesoporous molecular sieves were used as sorbents for removal of auxins. • SBA-15, MCF, PHTS and SBA-16 were grafted with (3-aminopropyl)triethoxysilane. • The adsorption capacity of modified materials was higher as compared to pure silicas. • Surface modification and pore volume play important role in adsorption process. - Abstract: In the present study, mesoporous siliceous materials grafted with 3-aminopropyltriethoxysilane (APTES) were examined as sorbents for removal of chosen plant growth factors (auxins) such as 1-naphthaleneacetic acid (NAA), indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). Four different types of mesoporous molecular sieves including SBA-15, PHTS, SBA-16 and MCF have been prepared via non-ionic surfactant-assisted soft templating method. Silica molecular sieves were thoroughly characterized by nitrogen adsorption–desorption analysis, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The maximum adsorption capacity (Q{sub max}) for NAA, IAA and IBA was in the range from 51.0 to 140.8 mg/g and from 4.3 to 7.3 mg/g for aminopropyl-modified adsorbents and pure silicas, respectively. The best adsorption performance was observed for IAA entrapment using both APTES-functionalized SBA-15 and MCF matrices (Q{sub max} of 140.8 and 137.0 mg/g, respectively) which can be ascribed to their larger pore volumes and pore diameters. Moreover, these silicas were characterized by the highest adsorption efficiency exceeding 90% at low pollutant concentration. The experimental points for adsorption of plant growth factors onto aminopropyl-modified mesoporous molecular sieves fitted well to the Langmuir equation.

  15. Surface-enhanced Raman spectrum of Gly-Gly adsorbed on the silver colloidal surface

    Science.gov (United States)

    Xiaojuan, Yuan; Huaimin, Gu; Jiwei, Wu

    2010-08-01

    Raman and SERS spectra of homodipeptide Gly-Gly and Gly were recorded and compared in this paper, and band assignment for the functional groups contained in these molecules was analyzed in detail. Time-dependent and pH-dependent SERS spectra of Gly-Gly molecule adsorbed on nano-colloidal silver surface were also studied. The time-dependent SERS spectra of Gly-Gly are characterized by the increase in intensity of bands primarily representing the vibrational signatures emanating from the amino and amide moiety of Gly-Gly molecule. It is found that the adsorption style of Gly-Gly on the silver colloid changes as time goes on; at 5 min after adding the sample to the silver colloid, Gly-Gly adsorbs on silver surface firstly through the carboxylate, amino and amide groups, and then the carboxylate group is far away from the silver surface at 10 min to 3 days. The SERS variation of Gly-Gly with the change of pH suggests that the adsorption style is pH-dependent, the different adsorption behavior of the Gly-Gly occurs on silver surface at different pH values.

  16. Adsorbate-induced lifting of substrate relaxation is a general mechanism governing titania surface chemistry.

    Science.gov (United States)

    Silber, David; Kowalski, Piotr M; Traeger, Franziska; Buchholz, Maria; Bebensee, Fabian; Meyer, Bernd; Wöll, Christof

    2016-09-30

    Under ambient conditions, almost all metals are coated by an oxide. These coatings, the result of a chemical reaction, are not passive. Many of them bind, activate and modify adsorbed molecules, processes that are exploited, for example, in heterogeneous catalysis and photochemistry. Here we report an effect of general importance that governs the bonding, structure formation and dissociation of molecules on oxidic substrates. For a specific example, methanol adsorbed on the rutile TiO 2 (110) single crystal surface, we demonstrate by using a combination of experimental and theoretical techniques that strongly bonding adsorbates can lift surface relaxations beyond their adsorption site, which leads to a significant substrate-mediated interaction between adsorbates. The result is a complex superstructure consisting of pairs of methanol molecules and unoccupied adsorption sites. Infrared spectroscopy reveals that the paired methanol molecules remain intact and do not deprotonate on the defect-free terraces of the rutile TiO 2 (110) surface.

  17. Nano-nitride cathode catalysts of Ti, Ta, and Nb for polymer electrolyte fuel cells: Temperature-programmed desorption investigation of molecularly adsorbed oxygen at low temperature

    KAUST Repository

    Ohnishi, Ryohji

    2013-01-10

    TiN, NbN, TaN, and Ta3N5 nanoparticles synthesized using mesoporous graphitic (mpg)-C3N4 templates were investigated for the oxygen reduction reaction (ORR) as cathode catalysts for polymer electrolyte fuel cells. The temperature-programmed desorption (TPD) of molecularly adsorbed O2 at 120-170 K from these nanoparticles was examined, and the resulting amount and temperature of desorption were key factors determining the ORR activity. The size-dependent TiN nanoparticles (5-8 and 100 nm) were then examined. With decreasing particle size, the density of molecularly adsorbed O2 per unit of surface area increased, indicating that a decrease in particle size increases the number of active sites. It is hard to determine the electrochemical active surface area for nonmetal electrocatalysts (such as oxides or nitrides), because of the absence of proton adsorption/desorption peaks in the voltammograms. In this study, O2-TPD for molecularly adsorbed O2 at low temperature demonstrated that the amount and strength of adsorbed O2 were key factors determining the ORR activity. The properties of molecularly adsorbed O2 on cathode catalysts are discussed against the ORR activity. © 2012 American Chemical Society.

  18. An Energy Conservation Approach to Adsorbate-Induced Surface Stress and the Extraction of Binding Energy Using Nanomechanics

    Energy Technology Data Exchange (ETDEWEB)

    Pinnaduwage, Lal A [ORNL; Boiadjiev, Vassil I [ORNL; Fernando, G. W. [University of Connecticut, Storrs; Hawk, J. E. [Oak Ridge National Laboratory (ORNL); Wijewardhana, L.C. R. [University of Cincinnati; Gehl, Anthony C [ORNL

    2008-01-01

    Microcantilevers are ideally-suited for the study of surface phenomena due to their large surface-to-volume ratios, which amplify surface effects. We show that when guest molecules bind to atoms/molecules on a microcantilever surface, the released binding energy is retained in the host surface, leading to a metastable state where the excess energy on the surface is manifested as an increase in surface stress leading to the bending of the microcantilever. When the excess energy is released, the microcantilever relaxes back to the original state, and the relaxation time depends on the particular binding process involved. Such experiments were conducted for three binding processes in vapor phase experiments: physisorption, hydrogen bonding, and chemisorption. To our knowledge, such an energy conservation approach has not been taken into account in adsorbate-induced surface effect investigations. Furthermore, these experiments illustrate that detailed molecular-level information on binding energies can be extracted from this simple micromechanical sensor.

  19. Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

    Science.gov (United States)

    Chohan, Urslaan K.; Jimenez-Melero, Enrique; Koehler, Sven P. K.

    2016-11-01

    We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber-Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe-H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm-1, for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.

  20. Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Chohan, Urslaan K.; Jimenez-Melero, Enrique [School of Materials, The University of Manchester, Manchester M13 9PL (United Kingdom); Dalton Cumbrian Facility, The University of Manchester, Moor Row CA24 3HA (United Kingdom); Koehler, Sven P.K., E-mail: sven.koehler@manchester.ac.uk [Dalton Cumbrian Facility, The University of Manchester, Moor Row CA24 3HA (United Kingdom); School of Chemistry, The University of Manchester, Manchester M13 9PL (United Kingdom); Photon Science Institute, The University of Manchester, Manchester M13 9PL (United Kingdom)

    2016-11-30

    Highlights: • Potential energy surfaces for H diffusion on Fe(110) calculated. • Full vibrational analysis of surface modes performed. • Vibrational analysis establishes lb site as a transition state to the 3f site. • Pronounced buckling observed in the Fe surface layer. - Abstract: We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber–Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe–H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm{sup −1}, for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.

  1. Infrared spectroscopic and voltammetric study of adsorbed CO on stepped surfaces of copper monocrystalline electrodes

    International Nuclear Information System (INIS)

    Koga, O.; Teruya, S.; Matsuda, K.; Minami, M.; Hoshi, N.; Hori, Y.

    2005-01-01

    Voltammetric and infrared (IR) spectroscopic measurements were carried out to study adsorbed CO on two series of copper single crystal electrodes n(111)-(111) and n(111)-(100) in 0.1M KH 2 PO 4 +0.1M K 2 HPO 4 at 0 o C. Reversible voltammetric waves were observed below -0.55V versus SHE for adsorption of CO which displaces preadsorbed phosphate anions. The electric charge of the redox waves is proportional to the step atom density for both single crystal series. This fact indicates that phosphate anions are specifically adsorbed on the step sites below -0.55V versus SHE. Voltammetric measurements indicated that (111) terrace of Cu is covered with adsorbed CO below -0.5V versus SHE. Nevertheless, no IR absorption band of adsorbed CO is detected from (111) terrace. Presence of adsorbed CO on (111) terrace is presumed which is not visible by the potential difference spectroscopy used in the present work. IR spectroscopic measurements showed that CO is reversibly adsorbed with an on-top manner on copper single crystal electrodes of n(111)-(111) and n(111)-(100) with approximately same wavenumber of C?O stretching vibration of 2070cm -1 . The IR band intensity is proportional to the step atom density. Thus CO is adsorbed on (111) or (100) steps on the single crystal surfaces. An analysis of the IR band intensity suggested that one CO molecule is adsorbed on every two or more Cu step atom of the monocrystalline surface. The spectroscopic data were compared with those reported for uhv system. The C-O stretching wavenumber of adsorbed CO in the electrode-electrolyte system is 30-40cm -1 lower than those in uhv system

  2. Nano-Sized Cyclodextrin-Based Molecularly Imprinted Polymer Adsorbents for Perfluorinated Compounds—A Mini-Review

    Directory of Open Access Journals (Sweden)

    Abdalla H. Karoyo

    2015-06-01

    Full Text Available Recent efforts have been directed towards the design of efficient and contaminant selective remediation technology for the removal of perfluorinated compounds (PFCs from soils, sediments, and aquatic environments. While there is a general consensus on adsorption-based processes as the most suitable methodology for the removal of PFCs from aquatic environments, challenges exist regarding the optimal materials design of sorbents for selective uptake of PFCs. This article reviews the sorptive uptake of PFCs using cyclodextrin (CD-based polymer adsorbents with nano- to micron-sized structural attributes. The relationship between synthesis of adsorbent materials and their structure relate to the overall sorption properties. Hence, the adsorptive uptake properties of CD-based molecularly imprinted polymers (CD-MIPs are reviewed and compared with conventional MIPs. Further comparison is made with non-imprinted polymers (NIPs that are based on cross-linking of pre-polymer units such as chitosan with epichlorohydrin in the absence of a molecular template. In general, MIPs offer the advantage of selectivity, chemical tunability, high stability and mechanical strength, ease of regeneration, and overall lower cost compared to NIPs. In particular, CD-MIPs offer the added advantage of possessing multiple binding sites with unique physicochemical properties such as tunable surface properties and morphology that may vary considerably. This mini-review provides a rationale for the design of unique polymer adsorbent materials that employ an intrinsic porogen via incorporation of a macrocyclic compound in the polymer framework to afford adsorbent materials with tunable physicochemical properties and unique nanostructure properties.

  3. Nano-Sized Cyclodextrin-Based Molecularly Imprinted Polymer Adsorbents for Perfluorinated Compounds—A Mini-Review

    Science.gov (United States)

    Karoyo, Abdalla H.; Wilson, Lee D.

    2015-01-01

    Recent efforts have been directed towards the design of efficient and contaminant selective remediation technology for the removal of perfluorinated compounds (PFCs) from soils, sediments, and aquatic environments. While there is a general consensus on adsorption-based processes as the most suitable methodology for the removal of PFCs from aquatic environments, challenges exist regarding the optimal materials design of sorbents for selective uptake of PFCs. This article reviews the sorptive uptake of PFCs using cyclodextrin (CD)-based polymer adsorbents with nano- to micron-sized structural attributes. The relationship between synthesis of adsorbent materials and their structure relate to the overall sorption properties. Hence, the adsorptive uptake properties of CD-based molecularly imprinted polymers (CD-MIPs) are reviewed and compared with conventional MIPs. Further comparison is made with non-imprinted polymers (NIPs) that are based on cross-linking of pre-polymer units such as chitosan with epichlorohydrin in the absence of a molecular template. In general, MIPs offer the advantage of selectivity, chemical tunability, high stability and mechanical strength, ease of regeneration, and overall lower cost compared to NIPs. In particular, CD-MIPs offer the added advantage of possessing multiple binding sites with unique physicochemical properties such as tunable surface properties and morphology that may vary considerably. This mini-review provides a rationale for the design of unique polymer adsorbent materials that employ an intrinsic porogen via incorporation of a macrocyclic compound in the polymer framework to afford adsorbent materials with tunable physicochemical properties and unique nanostructure properties. PMID:28347047

  4. Shock compression and flash-heating of molecular adsorbates on the picosecond time scale

    Science.gov (United States)

    Berg, Christopher Michael

    An ultrafast nonlinear coherent laser spectroscopy termed broadband multiplex vibrational sum-frequency generation (SFG) with nonresonant suppression was employed to monitor vibrational transitions of molecular adsorbates on metallic substrates during laser-driven shock compression and flash-heating. Adsorbates were in the form of well-ordered self-assembled monolayers (SAMs) and included molecular explosive simulants, such as nitroaromatics, and long chain-length alkanethiols. Based on reflectance measurements of the metallic substrates, femtosecond flash-heating pulses were capable of producing large-amplitude temperature jumps with DeltaT = 500 K. Laser-driven shock compression of SAMs produced pressures up to 2 GPa, where 1 GPa ≈ 1 x 104 atm. Shock pressures were estimated via comparison with frequency shifts observed in the monolayer vibrational transitions during hydrostatic pressure measurements in a SiC anvil cell. Molecular dynamics during flash-heating and shock loading were probed with vibrational SFG spectroscopy with picosecond temporal resolution and sub-nanometer spatial resolution. Flash-heating studies of 4-nitrobenzenethiolate (NBT) on Au provided insight into effects from hot-electron excitation of the molecular adsorbates at early pump-probe delay times. At longer delay times, effects from the excitation of SAM lattice modes and lower-energy NBT vibrations were shown. In addition, flash-heating studies of alkanethiolates demonstrated chain disordering behaviors as well as interface thermal conductances across the Au-SAM junction, which was of specific interest within the context of molecular electronics. Shock compression studies of molecular explosive simulants, such as 4-nitrobenzoate (NBA), demonstrated the proficiency of this technique to observe shock-induced molecular dynamics, in this case orientational dynamics, on the picosecond time scale. Results validated the utilization of these refined shock loading techniques to probe the shock

  5. Magnetic susceptibility of oxygen adsorbed on the surface of spherical and fibrous activated carbon.

    Directory of Open Access Journals (Sweden)

    Kiyoshi Kawamura

    2009-02-01

    Full Text Available The magnetic susceptibilities of oxygen adsorbed on the surface of bead-shaped activated carbon and activated carbon fibers were evaluated as a function of temperature between 4.2 K and 300 K, and found to exhibit a sharp peak at around 50 K. This implies that the adsorbed oxygen molecules form an antiferromagnetic state. The relation between the susceptibility and the adsorbed mass suggest that the thickness of the adsorbed oxygen is thin enough to consider a two-dimensional structure for bead–shaped activated carbon and carbon fibers across the fiber axis but thick enough to regard it as three-dimensional along the fiber axis. The result is discussed with reference to the study on one-dimensional oxygen array.

  6. Adsorbates on cobalt and platinum single crystal surfaces studied by STM

    Energy Technology Data Exchange (ETDEWEB)

    Venvik, Hilde Johnsen

    1998-12-31

    This thesis on surface physics may contribute to the understanding of catalysts and so be of interest to companies working on oil and natural gas refining. The thesis deals with room temperature experimental investigations of adsorbates of CO and C{sub 2}H{sub 4} gases on Co and Pt single crystal surfaces. 252 refs., 51 figs., 1 table

  7. Phase transitions and adsorbate restructuring at metal surface

    CERN Document Server

    King, DA

    1994-01-01

    The objective in initiating this series in 1980 was to provide an in-depth review of advances made in the understanding key aspects of surface chemistry and physics through the application of new techniques to the study of well-defined surfaces. Since then the field of surface science has greatly matured, and further important techniques, particularly scanning probe microscopies, have been successfully assimilated into the applications armoury of the surface scientist. The present volume is a series of timely reviews by many of the current experts in the field of phase transitions an

  8. Reduction in Friction and Wear of Alumina Surfaces as Assisted with Surface-Adsorbing Polymers in Aqueous Solutions

    DEFF Research Database (Denmark)

    Røn, Troels; Lee, Seunghwan

    2016-01-01

    We have investigated the aqueous lubricating effects of various polymers for the sliding contacts of self-mated alumina surfaces in neutral aqueous environment. Given that isoelectric point (IEP) of alumina is ca. pH 9, polyanions can readily adsorb onto alumina surface at neutral pH via electros......We have investigated the aqueous lubricating effects of various polymers for the sliding contacts of self-mated alumina surfaces in neutral aqueous environment. Given that isoelectric point (IEP) of alumina is ca. pH 9, polyanions can readily adsorb onto alumina surface at neutral pH via...

  9. Dispersion and Solvation Effects on the Structure and Dynamics of N719 Adsorbed to Anatase Titania (101) Surfaces in Room-Temperature Ionic Liquids: An ab Initio Molecular Simulation Study

    KAUST Repository

    Byrne, Aaron; English, Niall J.; Schwingenschlö gl, Udo; Coker, David F.

    2015-01-01

    Ab initio, density functional theory (DFT)-based molecular dynamics (MD) has been carried out to investigate the effect of explicit solvation on the dynamical and structural properties of a [bmim][NTf2] room-temperature ionic liquid (RTIL

  10. Radiation-induced reactions in D, L-α-alanine adsorbed in solid surfaces

    International Nuclear Information System (INIS)

    Aguilar, E; Negrón-Mendoza, A.; Camargo, C.

    2013-01-01

    The aim of this work is to study the behavior under irradiation of D, L and D-L α-alanine adsorbed in solid surfaces, as possible phase in the chemical evolution that may have occurred on the primitive Earth or in extraterrestrial environments and to evaluate the contribution of solids (a clay mineral) as shields for the adsorbed amino acids against a external energy source. The results show that α-alanine is adsorbed in the surfaces as function of pH and its yield of decomposition in mineral suspension is lower than the system without the solid surface. These results show the importance of nuclear techniques in these types of studies. (author)

  11. Computer representation of molecular surfaces

    International Nuclear Information System (INIS)

    Max, N.L.

    1981-01-01

    This review article surveys recent work on computer representation of molecular surfaces. Several different algorithms are discussed for producing vector or raster drawings of space-filling models formed as the union of spheres. Other smoother surfaces are also considered

  12. Adherence of platelets to in situ albumin-binding surfaces under flow conditions: role of surface-adsorbed albumin

    International Nuclear Information System (INIS)

    Guha Thakurta, Sanjukta; Miller, Robert; Subramanian, Anuradha

    2012-01-01

    Surfaces that preferentially bind human serum albumin (HSA) were generated by grafting albumin-binding linear peptide (LP1) onto silicon surfaces. The research aim was to evaluate the adsorption pattern of proteins and the adhesion of platelets from platelet-poor plasma and platelet-rich plasma, respectively, by albumin-binding surfaces under physiological shear rate (96 and 319 s −1 ) conditions. Bound proteins were quantified using enzyme-linked immunosorbent assays (ELISAs) and two-dimensional gel electrophoresis. A ratio of ∼1000:100:1 of adsorbed HSA, human immunoglobulin (HIgG) and human fibrinogen (HFib) was noted, respectively, on LP1-functionalized surfaces, and a ratio of ∼5:2:1 of the same was noted on control surfaces, as confirmed by ELISAs. The surface-adsorbed von Willebrand factor was undetectable by sensitive ELISAs. The amount of adhered platelets correlated with the ratio of adsorbed HSA/HFib. Platelet morphology was more rounded on LP1-functionalized surfaces when compared to control surfaces. The platelet adhesion response on albumin-binding surfaces can be explained by the reduction in the co-adsorption of other plasma proteins in a surface environment where there is an excess of albumin molecules, coupled with restrictions in the conformational transitions of other surface-adsorbed proteins into hemostatically active forms. (paper)

  13. Vibrational spectroscopy and molecular dynamics of water monomers and dimers adsorbed on polycyclic aromatic hydrocarbons.

    Science.gov (United States)

    Simon, Aude; Rapacioli, Mathias; Mascetti, Joëlle; Spiegelman, Fernand

    2012-05-21

    This paper reports structures, energetics, dynamics and spectroscopy of H2O and (H2O)2 systems adsorbed on coronene (C24H12), a compact polycyclic aromatic hydrocarbon (PAH). On-the-fly Born-Oppenheimer molecular dynamics simulations are performed for temperatures T varying from 10 to 300 K, on a potential energy surface obtained within the self-consistent-charge density-functional based tight-binding (SCC-DFTB) approach. Anharmonic infrared (IR) spectra are extracted from these simulations. We first benchmark the SCC-DFTB semi-empirical hamiltonian vs. DFT (Density Functional Theory) calculations that include dispersion, on (C6H6)(H2O)1,2 small complexes. We find that charge corrections and inclusion of dispersion contributions in DFTB are necessary to obtain consistent structures, energetics and IR spectra. Using this Hamiltonian, the structures, energetics and IR features of the low-energy isomers of (C24H12)(H2O)1,2 are found to be similar to the DFT ones, with evidence for a stabilizing edge-coordination. The temperature dependence of the motions of H2O and (H2O)2 on the surface of C24H12 is analysed, revealing ultra-fast periodic motion. The water dimer starts diffusing at a higher temperature than the water monomer (150 K vs. 10 K respectively), which appears to be consistent with the binding energies. Qualitative and quantitative analyses of the effects of T on the IR spectra are performed. Anharmonic factors in particular are derived and it is shown that they can be used as signatures for the presence of PAH-water complexes. Finally, this paper lays the foundations for the studies of larger (PAH)m(H2O)n clusters, that can be treated with the efficient computational approach benchmarked in this paper.

  14. Surface Chirality of Gly-Pro Dipeptide Adsorbed on a Cu(110) Surface.

    Science.gov (United States)

    Cruguel, Hervé; Méthivier, Christophe; Pradier, Claire-Marie; Humblot, Vincent

    2015-07-01

    The adsorption of chiral Gly-Pro dipeptide on Cu(110) has been characterized by combining in situ polarization modulation infrared reflection absorption spectroscopy (PM-RAIRS) and X-ray photoelectron spectroscopy (XPS). The chemical state of the dipeptide, and its anchoring points and adsorption geometry, were determined at various coverage values. Gly-Pro molecules are present on Cu(110) in their anionic form (NH2 /COO(-)) and adsorb under a 3-point binding via both oxygen atoms of the carboxylate group and via the nitrogen atom of the amine group. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) have shown the presence of an extended 2D chiral array, sustained via intermolecular H-bonds interactions. Furthermore, due to the particular shape of the molecule, only one homochiral domain is formed, creating thus a truly chiral surface. © 2015 Wiley Periodicals, Inc.

  15. Surface free energy analysis of adsorbents used for radioiodine adsorption

    International Nuclear Information System (INIS)

    González-García, C.M.; Román, S.; González, J.F.; Sabio, E.; Ledesma, B.

    2013-01-01

    In this work, the surface free energy of biomass-based activated carbons, both fresh and impregnated with triethylenediamine, has been evaluated. The contribution of Lifshitz van der Waals components was determined by the model proposed by van Oss et al. The results obtained allowed predicting the most probable configurations of the impregnant onto the carbon surface and its influence on the subsequent adsorption of radioactive methyl iodide.

  16. Complexation of lysozyme with adsorbed PtBS-b-SCPI block polyelectrolyte micelles on silver surface.

    Science.gov (United States)

    Papagiannopoulos, Aristeidis; Christoulaki, Anastasia; Spiliopoulos, Nikolaos; Vradis, Alexandros; Toprakcioglu, Chris; Pispas, Stergios

    2015-01-20

    We present a study of the interaction of the positively charged model protein lysozyme with the negatively charged amphiphilic diblock polyelectrolyte micelles of poly(tert-butylstyrene-b-sodium (sulfamate/carboxylate)isoprene) (PtBS-b-SCPI) on the silver/water interface. The adsorption kinetics are monitored by surface plasmon resonance, and the surface morphology is probed by atomic force microscopy. The micellar adsorption is described by stretched-exponential kinetics, and the micellar layer morphology shows that the micelles do not lose their integrity upon adsorption. The complexation of lysozyme with the adsorbed micellar layers depends on the micelles arrangement and density in the underlying layer, and lysozyme follows the local morphology of the underlying roughness. When the micellar adsorbed amount is small, the layers show low capacity in protein complexation and low resistance in loading. When the micellar adsorbed amount is high, the situation is reversed. The adsorbed layers both with or without added protein are found to be irreversibly adsorbed on the Ag surface.

  17. Tunable Complex Stability in Surface Molecular Recognition Mediated by Self-Complementary Quadruple Hydrogen Bonds

    NARCIS (Netherlands)

    Zou, S(han); Zhang, Zhihong; Forch, Renate; Knoll, Wolfgang; Schönherr, Holger; Vancso, Gyula J.

    2003-01-01

    We show that surfaces modified with asymmetric 2-ureido-4[1H]-pyrimidinone-hydroxyalkane disulfide adsorbates exhibit efficient and controllable self-complementary molecular recognition of the pyrimidinone moieties. Two novel asymmetric 2-ureido-4[1H]-pyrimidinone-hydroxyalkane disulfide adsorbates,

  18. Potential Energy Surface of NO on Pt(997: Adsorbed States and Surface Diffusion

    Directory of Open Access Journals (Sweden)

    N. Tsukahara

    2012-01-01

    Full Text Available The potential energy surface (PES of NO on Pt(997 has been elucidated: the adsorption states and diffusion processes of NO on Pt(997 at low coverage were investigated by using infrared reflection absorption spectroscopy (IRAS and scanning tunneling microscopy (STM. When NO molecules adsorb on a surface at a low temperature (11 K, each molecule transiently migrates on the surface from the first impact point to a possible adsorption site. We found that there are four stable adsorption sites for NO on Pt(997: a bridge site of the upper step, an fcc- (or hcp- hollow site of the terrace, an on-top site of the terrace, and an fcc-hollow site of the lower step. At higher temperatures above 45 K, NO molecules start to migrate thermally to more stable adsorption sites on a terrace, and they are finally trapped at the bridge sites of the step, which are the most stable among the four sites.

  19. Phosphate adsorption on aluminum-impregnated mesoporous silicates : surface structure and behavior of adsorbents

    Science.gov (United States)

    Eun Woo Shin; James S. Han; Min Jang; Soo-Hong Min; Jae Kwang Park; Roger M. Rowell

    2004-01-01

    Phosphorus from excess fertilizers and detergents ends up washing into lakes, creeks, and rivers. This overabundance of phosphorus causes excessive aquatic plant and algae growth and depletes the dissolved oxygen supply in the water. In this study, aluminum-impregnated mesoporous adsorbents were tested for their ability to remove phosphate from water. The surface...

  20. Many-body dispersion effects in the binding of adsorbates on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Maurer, Reinhard J. [Department of Chemistry, Yale University, New Haven, Connecticut 06520 (United States); Ruiz, Victor G.; Tkatchenko, Alexandre [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

    2015-09-14

    A correct description of electronic exchange and correlation effects for molecules in contact with extended (metal) surfaces is a challenging task for first-principles modeling. In this work, we demonstrate the importance of collective van der Waals dispersion effects beyond the pairwise approximation for organic–inorganic systems on the example of atoms, molecules, and nanostructures adsorbed on metals. We use the recently developed many-body dispersion (MBD) approach in the context of density-functional theory [Tkatchenko et al., Phys. Rev. Lett. 108, 236402 (2012) and Ambrosetti et al., J. Chem. Phys. 140, 18A508 (2014)] and assess its ability to correctly describe the binding of adsorbates on metal surfaces. We briefly review the MBD method and highlight its similarities to quantum-chemical approaches to electron correlation in a quasiparticle picture. In particular, we study the binding properties of xenon, 3,4,9,10-perylene-tetracarboxylic acid, and a graphene sheet adsorbed on the Ag(111) surface. Accounting for MBD effects, we are able to describe changes in the anisotropic polarizability tensor, improve the description of adsorbate vibrations, and correctly capture the adsorbate–surface interaction screening. Comparison to other methods and experiment reveals that inclusion of MBD effects improves adsorption energies and geometries, by reducing the overbinding typically found in pairwise additive dispersion-correction approaches.

  1. 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...

  2. Potential energy surfaces of adsorbates on periodic substrates: Application of the Morse theory

    Czech Academy of Sciences Publication Activity Database

    Pick, Štěpán

    2009-01-01

    Roč. 79, č. 4 (2009), 045403-1-5 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z40400503 Keywords : adsorbed layers * Morse potential * potential energy surfaces * substrates Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.475, year: 2009

  3. Theory of Covalent Adsorbate Frontier Orbital Energies on Functionalized Light-Absorbing Semiconductor Surfaces.

    Science.gov (United States)

    Yu, Min; Doak, Peter; Tamblyn, Isaac; Neaton, Jeffrey B

    2013-05-16

    Functional hybrid interfaces between organic molecules and semiconductors are central to many emerging information and solar energy conversion technologies. Here we demonstrate a general, empirical parameter-free approach for computing and understanding frontier orbital energies - or redox levels - of a broad class of covalently bonded organic-semiconductor surfaces. We develop this framework in the context of specific density functional theory (DFT) and many-body perturbation theory calculations, within the GW approximation, of an exemplar interface, thiophene-functionalized silicon (111). Through detailed calculations taking into account structural and binding energetics of mixed-monolayers consisting of both covalently attached thiophene and hydrogen, chlorine, methyl, and other passivating groups, we quantify the impact of coverage, nonlocal polarization, and interface dipole effects on the alignment of the thiophene frontier orbital energies with the silicon band edges. For thiophene adsorbate frontier orbital energies, we observe significant corrections to standard DFT (∼1 eV), including large nonlocal electrostatic polarization effects (∼1.6 eV). Importantly, both results can be rationalized from knowledge of the electronic structure of the isolated thiophene molecule and silicon substrate systems. Silicon band edge energies are predicted to vary by more than 2.5 eV, while molecular orbital energies stay similar, with the different functional groups studied, suggesting the prospect of tuning energy alignment over a wide range for photoelectrochemistry and other applications.

  4. 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

  5. Protection of silica surfaces with an adsorbed polymer

    International Nuclear Information System (INIS)

    Ilekti, Philippe

    2000-01-01

    This research thesis addresses the issue of re-dispersion of particles in a solvent after drying, and more particularly the case of nano particles with very reactive surfaces (silica particles) for which any contact is irreversible. The approach consists in decomposing dispersion drying into several phases in function of sample water content. For each step, the causes of particle aggregation are analysed. Thus, the author reports the study of particle stability in a diluted regime during the passage in an unfavourable ionic medium (acid pH or high ionic force). Then, a method is presented to concentrate particles and to test the resistance of the protective layer. This assessment is performed by centrifugation of particles protected by a polymer or a surfactant. Finally, the author studies the efficiency of the behaviour of protective layers during the dispersion drying [fr

  6. Radiation-induced reactions of amino acids adsorbed on solid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Esquivel Kranksith, L.; Negron-Mendoza, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, UNAM. Cd. Universitaria, A.P. 70-543, 04510 Mexico D.F. (Mexico); Mosqueira, F.G. [Direcion General de Divulgacion de la Ciencia, Universidad Nacional Autonoma de Mexico, Cd. Universitaria, AP. 70-487 Mexico D.F. (Mexico); Ramos-Bernal, Sergio, E-mail: ramos@nucleares.unam.m [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, UNAM. Cd. Universitaria, A.P. 70-543, 04510 Mexico D.F. (Mexico)

    2010-07-21

    The purpose of this work is to study the adsorption of compounds such as amino acids on clays and carbon nanotubes (CNTs) as a possible phase in the chemical evolution that may have occurred on the primitive Earth or in extraterrestrial environments. We further study the behavior of amino acids adsorbed on these solid surfaces at different conditions of pH and levels of irradiation, simulating a high-radiation field at early Earth conditions. The relevance of this work is to explain the possible contribution of solids (clays and CNTs) as promoters of polymerization and as shields for the adsorbed organic compounds against external sources of energy. To this end, tryptophan, aspartic acid, and glutamic acid were adsorbed on fixed amounts of solid surfaces and were irradiated by a {sup 60}Co source for different periods of time at fixed dose rates. After irradiation, the amino acids were extracted from the solid and analyzed with UV and IR spectroscopes and high-performance liquid chromatography. The most efficient surface for adsorption of amino acids was clay, followed by CNTs. Studies of the gamma irradiation of amino acids adsorbed on clay (in the solid phase) show a low yield of recovery of the amino acid.

  7. Collective migration of adsorbed atoms on a solid surface in the laser radiation field

    International Nuclear Information System (INIS)

    Andreev, V V; Ignat'ev, D V; Telegin, Gennadii G

    2004-01-01

    The lateral (in the substrate plane) interaction between dipoles induced in particles adsorbed on a solid surface is studied in a comparatively weak laser radiation field with a Gaussian transverse distribution. It is shown that the particles migrate over the surface in the radial direction either outside an illuminated spot with the formation of a 'crater' or inside the spot with the formation of a 'mound'. (interaction of laser radiation with matter. laser plasma)

  8. INTRODUCTION: Surface Dynamics, Phonons, Adsorbate Vibrations and Diffusion

    Science.gov (United States)

    Bruch, L. W.

    2004-07-01

    understanding of the underlying factors determining the optical quality of GaInNAs, such as composition, growth and annealing conditions. We are still far from establishing an understanding of the band structure and its dependence on composition. Fundamental electronic interactions such as electron-electron and electron-phonon scattering, dependence of effective mass on composition, strain and orientation, quantum confinement effects, effects of localized nitrogen states on high field transport and on galvanometric properties, and mechanisms for light emission in these materials, are yet to be fully understood. Nature and formation mechanisms of grown-in and processing-induced defects that are important for material quality and device performance are still unknown. Such knowledge is required in order to design strategies to efficiently control and eliminate harmful defects. For many potential applications (such as solar cells, HBTs) it is essential to get more information on the transport properties of dilute nitride materials. The mobility of minority carriers is known to be low in GaInNAs and related material. The experimental values are far from reaching the theoretical ones, due to defects and impurities introduced in the material during the growth. The role of the material inhomogeneities on the lateral carrier transport also needs further investigation. From the device's point of view most attention to date has been focused on the GaInNAs/GaAs system, mainly because of its potential for optoelectronic devices covering the 1.3-1.55 µm data and telecommunications wavelength bands. As is now widely appreciated, these GaAs-compatible structures allow monolithic integration of AlGaAs-based distributed Bragg reflector mirrors (DBRs) for vertical cavity surface-emitting lasers with low temperature sensitivity and compatibility with AlOx-based confinement techniques. In terms of conventional edge-emitting lasers (EELs), the next step is to extend the wavelength range for cw room

  9. Adsorbate shape selectivity: Separation of the HF/134a azeotrope over carbogenic molecular sieve

    Energy Technology Data Exchange (ETDEWEB)

    Hong, A.; Mariwala, R.K.; Kane, M.S.; Foley, H.C. [Univ. of Delaware, Nework, DE (United States)

    1995-03-01

    Experimental evidence is provided for adsorptive shape selectivity in the separation of the azeotrope between HF and 1,1,1,2-tetrafluoroethane (134a) over pyrolyzed poly(furfuryl alcohol)-derived carbogenic molecular sieve (PPFA-CMS). The separation can be accomplished over coconut charcoal or Carbosieve G on the basis of the differences in the extent of equilibrium adsorption of HF and 134a. On these adsorbents 134a is more strongly bound than HF, thus it elutes much more slowly from the bed. The heat of adsorption for 134a in the vicinity of 200 C on Carbosieve G is {approximately}8.8 kcal/mol. In contrast, when the same azeotropic mixture is separated over PPFA-CMS prepared at 500 C, 134a is not adsorbed. As a result 134a elutes from the bed first, followed by HF. The reversal is brought about by the narrower pore size and pore size distribution of the PPFA-CMS versus that for Carbosieve G. Thus the separation over PPFA-CMS is an example of adsorbate shape selectivity and represents a limiting case of kinetic separation.

  10. Volumetric interpretation of protein adsorption: interfacial packing of protein adsorbed to hydrophobic surfaces from surface-saturating solution concentrations.

    Science.gov (United States)

    Kao, Ping; Parhi, Purnendu; Krishnan, Anandi; Noh, Hyeran; Haider, Waseem; Tadigadapa, Srinivas; Allara, David L; Vogler, Erwin A

    2011-02-01

    The maximum capacity of a hydrophobic adsorbent is interpreted in terms of square or hexagonal (cubic and face-centered-cubic, FCC) interfacial packing models of adsorbed blood proteins in a way that accommodates experimental measurements by the solution-depletion method and quartz-crystal-microbalance (QCM) for the human proteins serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa). A simple analysis shows that adsorbent capacity is capped by a fixed mass/volume (e.g. mg/mL) surface-region (interphase) concentration and not molar concentration. Nearly analytical agreement between the packing models and experiment suggests that, at surface saturation, above-mentioned proteins assemble within the interphase in a manner that approximates a well-ordered array. HSA saturates a hydrophobic adsorbent with the equivalent of a single square or hexagonally-packed layer of hydrated molecules whereas the larger proteins occupy two-or-more layers, depending on the specific protein under consideration and analytical method used to measure adsorbate mass (solution depletion or QCM). Square or hexagonal (cubic and FCC) packing models cannot be clearly distinguished by comparison to experimental data. QCM measurement of adsorbent capacity is shown to be significantly different than that measured by solution depletion for similar hydrophobic adsorbents. The underlying reason is traced to the fact that QCM measures contribution of both core protein, water of hydration, and interphase water whereas solution depletion measures only the contribution of core protein. It is further shown that thickness of the interphase directly measured by QCM systematically exceeds that inferred from solution-depletion measurements, presumably because the static model used to interpret solution depletion does not accurately capture the complexities of the viscoelastic interfacial environment probed by QCM. Copyright © 2010

  11. Metal nanostructures for the enhancement of the Raman response of molecular adsorbates

    Science.gov (United States)

    Giorgetti, Emilia; Giammanco, Francesco; Margheri, Giancarlo; Trigari, Silvana; Muniz-Miranda, Maurizio

    2011-08-01

    Spectroscopic investigation of metallic nanostructures of different size and morphology is presented, with particular focus on the capability of enhancing the Raman response of molecular adsorbates, namely on their SERS properties. In this framework, we describe recent results obtained with Au/Ag nanocages and Au nanostars, which can be used conveniently to shift the extinction spectra and the SERS activity up to the near infrared. In the case of nanostars, we present a synthesis procedure which permits fine tuning of their morphology and extinction, thus allowing preparation of structures with controlled SERS activity from 500 up to 1500 nm.

  12. Novel structures of oxygen adsorbed on a Zr(0001) surface predicted from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Bo [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Beijing computational science research center, Beijing,100084 (China); Wang, Jianyun [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Lv, Jian [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); College of Materials Science and Engineering, Jilin University, Changchun, 130012 (China); Gao, Xingyu [Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing, 100088 (China); CAEP Software Center for High Performance Numerical Simulation, Beijing, 100088 (China); Zhao, Yafan [CAEP Software Center for High Performance Numerical Simulation, Beijing, 100088 (China); Wang, Yanchao, E-mail: wyc@calypso.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Beijing computational science research center, Beijing,100084 (China); College of Materials Science and Engineering, Jilin University, Changchun, 130012 (China); Song, Haifeng, E-mail: song_haifeng@iapcm.ac.cn [Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing, 100088 (China); CAEP Software Center for High Performance Numerical Simulation, Beijing, 100088 (China); Ma, Yanming [State Key Laboratory of Superhard Materials, Jilin University, Changchun, 130012 (China); Beijing computational science research center, Beijing,100084 (China)

    2017-01-30

    Highlights: • Two stable structures of O adsorbed on a Zr(0001) surface are predicted with SLAM. • A stable structure of O adsorbed on a Zr(0001) surface is proposed with MLAM. • The calculated work function change is agreement with experimental value. - Abstract: The structures of O atoms adsorbed on a metal surface influence the metal properties significantly. Thus, studying O chemisorption on a Zr surface is of great interest. We investigated O adsorption on a Zr(0001) surface using our newly developed structure-searching method combined with first-principles calculations. A novel structural prototype with a unique combination of surface face-centered cubic (SFCC) and surface hexagonal close-packed (SHCP) O adsorption sites was predicted using a single-layer adsorption model (SLAM) for a 0.5 and 1.0 monolayer (ML) O coverage. First-principles calculations based on the SLAM revealed that the new predicted structures are energetically favorable compared with the well-known SFCC structures for a low O coverage (0.5 and 1.0 ML). Furthermore, on basis of our predicted SFCC + SHCP structures, a new structure within multi-layer adsorption model (MLAM) was proposed to be more stable at the O coverage of 1.0 ML, in which adsorbed O atoms occupy the SFCC + SHCP sites and the substitutional octahedral sites. The calculated work functions indicate that the SFCC + SHCP configuration has the lowest work function of all known structures at an O coverage of 0.5 ML within the SLAM, which agrees with the experimental trend of work function with variation in O coverage.

  13. Concentration and saturation effects of tethered polymer chains on adsorbing surfaces

    Science.gov (United States)

    Descas, Radu; Sommer, Jens-Uwe; Blumen, Alexander

    2006-12-01

    We consider end-grafted chains at an adsorbing surface under good solvent conditions using Monte Carlo simulations and scaling arguments. Grafting of chains allows us to fix the surface concentration and to study a wide range of surface concentrations from the undersaturated state of the surface up to the brushlike regime. The average extension of single chains in the direction parallel and perpendicular to the surface is analyzed using scaling arguments for the two-dimensional semidilute surface state according to Bouchaud and Daoud [J. Phys. (Paris) 48, 1991 (1987)]. We find good agreement with the scaling predictions for the scaling in the direction parallel to the surface and for surface concentrations much below the saturation concentration (dense packing of adsorption blobs). Increasing the grafting density we study the saturation effects and the oversaturation of the adsorption layer. In order to account for the effect of excluded volume on the adsorption free energy we introduce a new scaling variable related with the saturation concentration of the adsorption layer (saturation scaling). We show that the decrease of the single chain order parameter (the fraction of adsorbed monomers on the surface) with increasing concentration, being constant in the ideal semidilute surface state, is properly described by saturation scaling only. Furthermore, the simulation results for the chains' extension from higher surface concentrations up to the oversaturated state support the new scaling approach. The oversaturated state can be understood using a geometrical model which assumes a brushlike layer on top of a saturated adsorption layer. We provide evidence that adsorbed polymer layers are very sensitive to saturation effects, which start to influence the semidilute surface scaling even much below the saturation threshold.

  14. A molecular dynamics study on the transport of a charged biomolecule in a polymeric adsorbent medium and its adsorption onto a charged ligand.

    Science.gov (United States)

    Riccardi, E; Wang, J-C; Liapis, A I

    2010-08-28

    The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes shape, orientation, and lateral position in order to proceed toward the site where adsorption occurs and exhibits decreased mass transport coefficients as it approaches closer to the immobilized ligand. Furthermore, because the ligands are surrounded by counterions carrying the same type of charge as the adsorbate biomolecule, it takes the biomolecule repeated attempts to approach toward a ligand in order to displace the counterions in the proximity of the ligand and to finally become adsorbed. The formed adsorbate-ligand complex interacts with the counterions and polymeric molecules and is found to evolve slowly and continuously from one-site (monovalent) interaction to multisite (multivalent) interactions. Such a transition of the nature of adsorption reduces the overall adsorption capacity of the ligands in the adsorbent medium and results in a type of surface exclusion effect. Also, the adsorption of the biomolecule also presents certain volume exclusion effects by not only directly reducing the pore volume and the availability of the ligands in the adjacent regions, but also causing the polymeric molecules to change to more compact structures that could further shield certain ligands from being accessible to subsequent adsorbate molecules. These

  15. Antimicrobial activity of nisin adsorbed to surfaces commonly used in the food industry.

    Science.gov (United States)

    Guerra, Nelson P; Araujo, Ana Belén; Barrera, Ana M; Agrasar, Ana Torrado; Macías, Cristina López; Carballo, Julia; Pastrana, Lorenzo

    2005-05-01

    The adsorption isotherms of nisin to three food contact surfaces, stainless steel, polyethyleneterephthalate (PET), and rubber at 8, 25, 40, and 60 degrees C, were calculated. For all surfaces, the increase in temperature led to a decrease in the affinity between nisin and the surface. The rubber adsorbed a higher amount of nisin (0.697 microg/cm2) in comparison with PET (0.665 microg/cm2) and stainless steel (0.396 microg/cm2). Adsorption of nisin to the stainless steel surface described L-2 type curves for all temperatures assayed. However, for PET and rubber surfaces, the isotherms were L-2 type (at 40 and 60 degrees C) and L-4 type curves (at 8 and 25 degrees C). Nisin retained its antibacterial activity once adsorbed to the food contact surfaces and was able to inhibit the growth of Enterococcus hirae CECT 279 on Rothe agar medium. The attachment of three Listeria monocytogenes strains to the three surfaces was found to be dependent on the surface, the strain, and the initial bacterial suspension in contact with the surface. The adsorption of Nisaplin on surfaces reduced the attachment of all L. monocytogenes strains tested. The effect of PET-based bioactive packaging in food was very encouraging. When applied to a food system, nisin-adsorbed PET bottles reduced significantly (P < 0.05) the levels of the total aerobic plate counts in skim milk by approximately 1.4 log units after 24 days of refrigerated storage (4 degrees C), thus extending its shelf life.

  16. Adsorption separation of carbon dioxide from flue gas by a molecularly imprinted adsorbent.

    Science.gov (United States)

    Zhao, Yi; Shen, Yanmei; Ma, Guoyi; Hao, Rongjie

    2014-01-01

    CO2 separation by molecularly imprinted adsorbent from coal-fired flue gas after desulfurization system has been studied. The adsorbent was synthesized by molecular imprinted technique, using ethanedioic acid, acrylamide, and ethylene glycol dimethacrylate as the template, functional monomer, and cross-linker, respectively. According to the conditions of coal-fired flue gas, the influencing factors, including adsorption temperature, desorption temperature, gas flow rate, and concentrations of CO2, H2O, O2, SO2, and NO, were studied by fixed bed breakthrough experiments. The experimental conditions were optimized to gain the best adsorption performance and reduce unnecessary energy consumption in future practical use. The optimized adsorption temperature, desorption temperature, concentrations of CO2, and gas flow rate are 60 °C, 80 °C, 13%, and 170 mL/min, respectively, which correspond to conditions of practical flue gases to the most extent. The CO2 adsorption performance was nearly unaffected by H2O, O2, and NO in the flue gas, and was promoted by SO2 within the emission limit stipulated in the Chinese emission standards of air pollutants for a thermal power plant. The maximum CO2 adsorption capacity, 0.57 mmol/g, was obtained under the optimized experimental conditions, and the SO2 concentration was 150 mg/m(3). The influence mechanisms of H2O, O2, SO2, and NO on CO2 adsorption capacity were investigated by infrared spectroscopic analysis.

  17. Surface enhanced Raman scattering of new acridine based fluorophore adsorbed on silver electrode

    Science.gov (United States)

    Solovyeva, Elena V.; Myund, Liubov A.; Denisova, Anna S.

    2015-10-01

    4,5-Bis(N,N-di(2-hydroxyethyl)iminomethyl)acridine (BHIA) is a new acridine based fluoroionophore and a highly-selective sensor for cadmium ion. The direct interaction of the aromatic nitrogen atom with a surface is impossible since there are bulky substituents in the 4,5-positions of the acridine fragment. Nevertheless BHIA molecule shows a reliable SERS spectrum while adsorbed on a silver electrode. The analysis of SERS spectra pH dependence reveals that BHIA species adsorbed on a surface can exist in both non-protonated and protonated forms. The adsorption of BHIA from alkaline solution is accompanied by carbonaceous species formation at the surface. The intensity of such "carbon bands" turned out to be related with the supporting electrolyte (KCl) concentration. Upon lowering the electrode potential the SERS spectra of BHIA do not undergo changes but the intensity of bands decreases. This indicates that the adsorption mechanism on the silver surface is realized via aromatic system of acridine fragment. In case of such an adsorption mechanism the chelate fragment of the BHIA molecule is capable of interaction with the solution components. Addition of Cd2+ ions to a system containing BHIA adsorbed on a silver electrode in equilibrium with the solution leads to the formation of BHIA/Cd2+ complex which desorption causes the loss of SERS signal.

  18. SFG investigation of adsorbed CO and NO on NiO(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Bandara, Athula; Dobashi, Shinsaku; Kubota, Jun; Onda, Ken; Wada, Akihide; Domen, Kazunari; Hirose, Chiaki [Tokyo Inst. of Tech., Yokohama (Japan). Research Lab. of Resources Utilization; Kano, S.S.

    1997-07-01

    Adsorption structures of CO and NO on the NiO(111) film grown on Ni(111) crystal have been investigated by sum frequency generation (SFG) spectroscopy and infrared reflection absorption spectroscopy (IRAS). The CO stretching band of adsorbed CO on NiO(111) was observed at 2144 cm{sup -1} on the SFG spectra for both p- and s-polarized visible light. However, adsorbed NO on NiO(111) was observed at 1805 cm{sup -1} on the SFG spectra only for the p-polarized visible light. The results suggest that the adsorbed CO molecule was tilted from the surface normal but the NO molecule was perpendicular to the surface. These orientations of CO and NO reflect the surface structure of NiO(111) which has (2 x 2)-reconstructed microfacets. Adsorption of CO on Ni(111) instead of NiO(111) was also examined by SFG and IRAS. Absorption bands due to linear and bridged CO were observed at 2076 and 1918 cm{sup -1}, respectively, by IRAS. On the other hand, the linear CO molecules on Ni(111) gave an SFG peak at 2076 cm{sup -1} only for the p-polarized visible light indicating the CO molecules are perpendicular to the surface, and bridged CO molecules did not give any SFG signal. The absence of the bridged CO signal is believed to be due to the smaller Raman tensor of bridged CO. (author)

  19. SFG investigation of adsorbed CO and NO on NiO(111) surface

    International Nuclear Information System (INIS)

    Bandara, Athula; Dobashi, Shinsaku; Kubota, Jun; Onda, Ken; Wada, Akihide; Domen, Kazunari; Hirose, Chiaki; Kano, S.S.

    1997-01-01

    Adsorption structures of CO and NO on the NiO(111) film grown on Ni(111) crystal have been investigated by sum frequency generation (SFG) spectroscopy and infrared reflection absorption spectroscopy (IRAS). The CO stretching band of adsorbed CO on NiO(111) was observed at 2144 cm -1 on the SFG spectra for both p- and s-polarized visible light. However, adsorbed NO on NiO(111) was observed at 1805 cm -1 on the SFG spectra only for the p-polarized visible light. The results suggest that the adsorbed CO molecule was tilted from the surface normal but the NO molecule was perpendicular to the surface. These orientations of CO and NO reflect the surface structure of NiO(111) which has (2 x 2)-reconstructed microfacets. Adsorption of CO on Ni(111) instead of NiO(111) was also examined by SFG and IRAS. Absorption bands due to linear and bridged CO were observed at 2076 and 1918 cm -1 , respectively, by IRAS. On the other hand, the linear CO molecules on Ni(111) gave an SFG peak at 2076 cm -1 only for the p-polarized visible light indicating the CO molecules are perpendicular to the surface, and bridged CO molecules did not give any SFG signal. The absence of the bridged CO signal is believed to be due to the smaller Raman tensor of bridged CO. (author)

  20. Stability of therapeutic albumin solutions used for molecular adsorbent recirculating system-based liver dialysis.

    Science.gov (United States)

    De Bruyn, Tom; Meijers, Björn; Evenepoel, Pieter; Laub, Ruth; Willems, Ludo; Augustijns, Patrick; Annaert, Pieter

    2012-01-01

    Mounting evidence suggests beneficial effects of albumin dialysis-based liver support in patients suffering from acute-on-chronic liver failure. Molecular adsorbent recirculating system (MARS) is a nonbiological liver support device, based on the exchange of albumin-bound toxins between the patient's blood and a 20% human serum albumin solution in a secondary circuit. Bound toxins are continuously removed from the circulating albumin by exposure to activated charcoal and an ion-exchange resin. The aim of the present in vitro study was to determine the impact of exposure to charcoal and resin on the ligand binding properties of albumins, containing various levels of stabilizers and obtained from different suppliers (Baxter, CAF-DCF [Red Cross], and Sigma-Aldrich). Albumin binding properties were assessed by measuring equilibrium binding properties of warfarin, diazepam, and salicylate before and after incubation (for up to 7 h) with adsorbing materials; albumin-associated esterase-like activities were also determined. Notable changes in albumin binding upon incubation with adsorbing materials were only observed when using warfarin as a ligand. Affinity of warfarin for the Baxter and Sigma albumins showed a pronounced decrease (higher K(d) ) after the 1-7-h exposure to charcoal or resin. In the absence of adsorbing materials, similar effects were found, indicating that incubation time per se affects albumin binding properties. Following exposure to resin, Baxter albumin binding capacity (B(max)) increased about twofold. For albumin obtained from CAF-DCF, binding affinity and capacity for warfarin were constant under all conditions tested. Esterase-like activities associated with these albumins were either maintained or enhanced (up to 2.5-fold in case of Sigma albumin) following 7-h incubations with adsorbing materials. Our data suggest limited direct influence of the presence of stabilizers in therapeutic albumin solutions on baseline binding properties of human

  1. Scanning tunneling microscopy studies of organic monolayers adsorbed on the rhodium(111) crystal surface

    Energy Technology Data Exchange (ETDEWEB)

    Cernota, Paul Davis [Univ. of California, Berkeley, CA (United States)

    1999-08-01

    Scanning Tunneling Microscopy studies were carried out on ordered overlayers on the (111) surface of rhodium. These adsorbates include carbon monoxide (CO), cyclohexane, cyclohexene, 1,4-cyclohexadiene, para-xylene, and meta-xylene. Coadsorbate systems included: CO with ethylidyne, CO with para- and meta-xylene, and para-xylene with meta-xylene. In the case of CO, the structure of the low coverage (2x2) overlayer has been observed. The symmetry of the unit cell in this layer suggests that the CO is adsorbed in the 3-fold hollow sites. There were also two higher coverage surface structures with (√7x√7) unit cells. One of these is composed of trimers of CO and has three CO molecules in each unit cell. The other structure has an additional CO molecule, making a total of four. This extra CO sits on a top site.

  2. Electrochemical characterization of irreversibly adsorbed germanium on platinum stepped surfaces vicinal to Pt(1 0 0)

    International Nuclear Information System (INIS)

    Rodriguez, P.; Herrero, E.; Solla-Gullon, J.; Vidal-Iglesias, F.J.; Aldaz, A.; Feliu, J.M.

    2005-01-01

    The electrochemical behavior of germanium irreversibly adsorbed at stepped surfaces vicinal to the Pt(1 0 0) pole is reported. The process taking part on the (1 0 0) terraces is evaluated from charge density measurements and calibration lines versus the terrace dimension are plotted. On the series Pt(2n - 1,1,1) having (1 1 1) monoatomic steps, the charge involved in the redox process undergone by the irreversibly adsorbed germanium is able to account for (n - 0.5) terrace atoms, thus suggesting some steric difficulties in the growth of the adlayer on the (1 0 0) terraces. Conversely, no steric problems are apparent in the series Pt(n,1,0) in which more open (1 0 0) steps are present on the (1 0 0) terraces. In this latter case the charge density under the germanium redox peaks is proportional to the number of terrace atoms. Some comparison is made with other stepped surfaces to understand the behavior and stability of germanium irreversibly adsorbed on the different platinum surface sites

  3. Electronic excited states as a probe of surface adsorbate structure and dynamics in liquid xenon

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, E.S.

    1992-08-01

    A combination of second harmonic generation (SHG) and a simple dipole-dipole interaction model is presented as a new technique for determining adsorbate geometries on surfaces. The polarization dependence of SHG is used to define possible geometries of the adsorbate about the surface normal. Absorption band shifts using geometry constraints imposed by SHG data are derived for a dimer constructed from two arbitrarily placed monomers on the surface using the dipole-dipole interaction potential. These formulae can be used to determine the orientation of the two monomers relative to each other. A simplified version of this formalism is used to interpret absorption band shifts for rhodamine B adsorbed on fused silica. A brief history of the exciton is given with particular detail to Xe. Data are presented for transient absorption at RT in liquid xenon on the picosecond time scale. These are observations of both tunneling through the barrier that separates the free and trapped exciton states and the subsequent trapping of the exciton. In high densities both of these processes are found to occur within 2 to 6 picoseconds in agreement with theories of Kmiecik and Schreiber and of Martin. A threshold density is observed that separates relaxation via single binary collisions and relaxation that proceeds via Martin's resonant energy transfer hopping mechanism.

  4. Electronic excited states as a probe of surface adsorbate structure and dynamics in liquid xenon

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Eric Scott [Univ. of California, Berkeley, CA (United States)

    1992-08-01

    A combination of second harmonic generation (SHG) and a simple dipole-dipole interaction model is presented as a new technique for determining adsorbate geometries on surfaces. The polarization dependence of SHG is used to define possible geometries of the adsorbate about the surface normal. Absorption band shifts using geometry constraints imposed by SHG data are derived for a dimer constructed from two arbitrarily placed monomers on the surface using the dipole-dipole interaction potential. These formulae can be used to determine the orientation of the two monomers relative to each other. A simplified version of this formalism is used to interpret absorption band shifts for rhodamine B adsorbed on fused silica. A brief history of the exciton is given with particular detail to Xe. Data are presented for transient absorption at RT in liquid xenon on the picosecond time scale. These are observations of both tunneling through the barrier that separates the free and trapped exciton states and the subsequent trapping of the exciton. In high densities both of these processes are found to occur within 2 to 6 picoseconds in agreement with theories of Kmiecik and Schreiber and of Martin. A threshold density is observed that separates relaxation via single binary collisions and relaxation that proceeds via Martin`s resonant energy transfer hopping mechanism.

  5. Surface-state mediated three-adsorbate interaction: exact and numerical results and simple asymptotic expression

    International Nuclear Information System (INIS)

    Hyldgaard, Per; Einstein, T.L.

    2003-01-01

    The interaction energy of three adsorbates on a surface consists of the sum of the three-pair interactions plus a trio contribution produced primarily by interference of electrons which traverse the entire perimeter, d 123 , of the three-adsorbate cluster. Here, we investigate this three-adatom interaction when mediated by the isotropic Shockley surface-state band found on noble-metal (1 1 1) surfaces, extending work on pair interactions. Our experimentally testable result depends on the s-wave phase-shift, characterizing the standing-wave patterns seen in scanning-tunneling microscopy (STM) images. Compared with the adsorbate-pair interactions, and in contrast to bulk-mediated interactions, the trio contribution exhibits a slightly weaker amplitude and a slightly faster asymptotic envelope decay, d 123 -5/2 . It also has a different but well-defined oscillation period dependent on d 123 and little dependence on the shape of the cluster. We finally compare the asymptotic description with exact model calculations assuming short-range interactions, which are viable even in the non-asymptotic range (when not outweighed by bulk-mediated interactions)

  6. Molecular modeling of alkyl monolayers on the Si (100)-2 x 1 surface

    NARCIS (Netherlands)

    Lee, M.V.; Guo, D.; Linford, M.R.; Zuilhof, H.

    2004-01-01

    Molecular modeling was used to simulate various surfaces derived from the addition of 1-alkenes and 1-alkynes to Si=Si dimers on the Si(100)-2 × 1 surface. The primary aim was to better understand the interactions between adsorbates on the surface and distortions of the underlying silicon crystal

  7. Accelerator Analysis of Tributyltin Adsorbed onto the Surface of a Tributyltin Resistant Marine Pseudoalteromonas sp. Cell

    Directory of Open Access Journals (Sweden)

    Akira Kitamura

    2008-10-01

    Full Text Available Tributyltin (TBT released into seawater from ship hulls is a stable marine pollutant and obviously remains in marine environments. We isolated a TBT resistant marine Pseudoalteromonas sp. TBT1 from sediment of a ship’s ballast water. The isolate (109.3 ± 0.2 colony-forming units mL-1 adsorbed TBT in proportion to the concentrations of TBTCl externally added up to 3 mM, where the number of TBT adsorbed by a single cell was estimated to be 108.2. The value was reduced to about one-fifth when the lysozyme-treated cells were used. The surface of ethanol treated cells became rough, but the capacity of TBT adsorption was the same as that for native cells. These results indicate that the function of the cell surface, rather than that structure, plays an important role to the adsorption of TBT. The adsorption state of TBT seems to be multi-layer when the number of more than 106.8 TBT molecules is adsorbed by a single cell.

  8. Emission of positive oxygen ions from ion bombardment of adsorbate-covered metal surfaces

    International Nuclear Information System (INIS)

    Kaurin, M.G.

    1989-01-01

    During ion bombardment of metal surfaces, collision cascades can result in the emission of sputtered secondary ions. Recent experiments, however, have suggested that the emission of positive ions of electronegative adsorbates can result from electronic processes rather than from processes involving elastic collisions. This dissertation presents the results of experiments studying the emission of positive oxygen ions from oxygen- and carbon-monoxide-covered transition metal surfaces during bombardment by 25-250 keV ions of neon, argon, and krypton. The systems studied may be grouped into four categories. For a nickel substrate with adsorbed oxygen, the emission of positive oxygen ions proceeds through collision cascades. For titanium and niobium with adsorbed oxygen, the emission of positive oxygen ions is proportional to the primary ion velocity, consistent with emission from electronic processes; for a given primary ion velocity, the oxygen ion yield is independent of primary ion species. For substrates of molybdenum and tungsten, the oxygen yield is proportional to primary ion velocity, but the yield also depends on the primary ion species for a given primary ion velocity in a manner that is consistent with emission resulting from electronic processes. For these two groups, except for titanium, the yields during neon ion bombardment do not extrapolate (assuming linearity with primary ion velocity) to a nonzero value at zero beam velocity. The magnitude of the oxygen ion yields from these targets is not consistent with that expected if the emission were induced by secondary electrons emitted during the ion bombardment

  9. Photoemission studies of clean and adsorbate covered metal surfaces using synchrotron and uv radiation sources

    International Nuclear Information System (INIS)

    Apai, G.R. II.

    1977-09-01

    Photoemission energy distribution experiments on clean metal and adsorbate-covered surfaces were performed under ultrahigh vacuum conditions by using x-ray and ultraviolet photon sources in the laboratory as well as continuously-tunable, highly polarized synchrotron radiation obtainable at the Stanford Synchrotron Radiation Laboratory (SSRL). Studies focused on two general areas: cross-section modulation in the photoemission process was studied as a function of photon energy and orbital composition. Sharp decreases in intensity of the valence bands of several transition metals (i.e., Ag, Au, and Pt) are attributed to the radial nodes in the respective wave functions. Adsorbate photoemission studies of CO adsorbed on platinum single crystals have demonstrated a very high spectral sensitivity to the 4sigma and (1π + 5sigma) peaks of CO at photon energies of 150 eV. Angle-resolved photoemission allowed determination of the orientation of CO chemisorbed on a Pt (111) or Ni(111) surface. Prelinimary results at high photon energies (approximately 150 eV) indicated scattering from the substrate which could yield chemisorption site geometries

  10. Molecular Insights into the pH-Dependent Adsorption and Removal of Ionizable Antibiotic Oxytetracycline by Adsorbent Cyclodextrin Polymers

    Science.gov (United States)

    Zhang, Yu; Cai, Xiyun; Xiong, Weina; Jiang, Hao; Zhao, Haitong; Yang, Xianhai; Li, Chao; Fu, Zhiqiang; Chen, Jingwen

    2014-01-01

    Effects of pH on adsorption and removal efficiency of ionizable organic compounds (IOCs) by environmental adsorbents are an area of debate, because of its dual mediation towards adsorbents and adsorbate. Here, we probe the pH-dependent adsorption of ionizable antibiotic oxytetracycline (comprising OTCH2 +, OTCH±, OTC−, and OTC2−) onto cyclodextrin polymers (CDPs) with the nature of molecular recognition and pH inertness. OTCH± commonly has high adsorption affinity, OTC− exhibits moderate affinity, and the other two species have negligible affinity. These species are evidenced to selectively interact with structural units (e.g., CD cavity, pore channel, and network) of the polymers and thus immobilized onto the adsorbents to different extents. The differences in adsorption affinity and mechanisms of the species account for the pH-dependent adsorption of OTC. The mathematical equations are derived from the multiple linear regression (MLR) analysis of quantitatively relating adsorption affinity of OTC at varying pH to adsorbent properties. A combination of the MLR analysis for OTC and molecular recognition of adsorption of the species illustrates the nature of the pH-dependent adsorption of OTC. Based on this finding, γ-HP-CDP is chosen to adsorb and remove OTC at pH 5.0 and 7.0, showing high removal efficiency and strong resistance to the interference of coexisting components. PMID:24465975

  11. Quantitative surface studies of protein adsorption by infrared spectroscopy. II. Quantification of adsorbed and bulk proteins

    International Nuclear Information System (INIS)

    Fink, D.J.; Hutson, T.B.; Chittur, K.K.; Gendreau, R.M.

    1987-01-01

    Attenuated total reflectance Fourier transform infrared spectra of surface-adsorbed proteins are correlated with concentration measurements determined by 125 I-labeled proteins. This paper demonstrates that linear correlations between the intensity of the major bands of proteins and the quantity of proteins can be obtained for human albumin and immunoglobulin G up to surface concentrations of approximately 0.25 microgram/cm2. A poorer correlation was observed for human fibrinogen. A linear correlation was also observed between the concentration in the bulk solution and the major bands of albumin up to a concentration of 60 mg/ml

  12. Self-interacting polymer chains terminally anchored to adsorbing surfaces of three-dimensional fractal lattices

    Science.gov (United States)

    Živić, I.; Elezović-Hadžić, S.; Milošević, S.

    2018-01-01

    We have studied the adsorption problem of self-attracting linear polymers, modeled by self-avoiding walks (SAWs), situated on three-dimensional fractal structures, exemplified by 3d Sierpinski gasket (SG) family of fractals as containers of a poor solvent. Members of SG family are enumerated by an integer b (b ≥ 2), and it is assumed that one side of each SG fractal is an impenetrable adsorbing surface. We calculate the critical exponents γ1 ,γ11, and γs, which are related to the numbers of all possible SAWs with one, both, and no ends anchored to the adsorbing boundary, respectively. By applying the exact renormalization group (RG) method (for the first three members of the SG fractal family, b = 2 , 3, and 4), we have obtained specific values of these exponents, for θ-chain and globular polymer phase. We discuss their mutual relations and relations with corresponding values pertinent to extended polymer chain phase.

  13. Formation of Molecular Networks: Tailored Quantum Boxes and Behavior of Adsorbed CO in Them

    Science.gov (United States)

    Wyrick, Jon; Sun, Dezheng; Kim, Dae-Ho; Cheng, Zhihai; Lu, Wenhao; Zhu, Yeming; Luo, Miaomiao; Kim, Yong Su; Rotenberg, Eli; Kim, Kwangmoo; Einstein, T. L.; Bartels, Ludwig

    2011-03-01

    We show that the behavior of CO adsorbed into the pores of large regular networks on Cu(111) is significantly affected by their nano-scale lateral confinement and that formation of the networks themselves is directed by the Shockley surface state. Saturation coverages of CO are found to exhibit persistent dislocation lines; at lower coverages their mobility increases. Individual CO within the pores titrate the surface state, providing crucial information for understanding formation of the network as a result of optimization of the number N of electrons bound within each pore. Determination of N is based on quinone-coverage-dependent UPS data and an analysis of states of particles in a pore-shaped box (verified by CO's titration); a wide range of possible pore shapes and sizes has been considered. Work at UCR supported by NSF CHE 07-49949; at UMD by NSF CHE 07-50334 & UMD NSF-MRSEC DMR 05-20471.

  14. Artificial liver support with the molecular adsorbent recirculating system: activation of coagulation and bleeding complications.

    Science.gov (United States)

    Bachli, Esther B; Schuepbach, Reto A; Maggiorini, Marco; Stocker, Reto; Müllhaupt, Beat; Renner, Eberhard L

    2007-05-01

    Numerous, mostly uncontrolled, observations suggest that artificial liver support with the Molecular Adsorbent Recirculating System (MARS) improves pathophysiologic sequelae and outcome of acute and acute-on-chronic liver failure. MARS is felt to be safe, but extracorporeal circuits may activate coagulation. To assess the frequency of and risk factors for activation of coagulation during MARS treatment. Retrospective analysis of coagulopathy/bleeding complications observed during 83 consecutive MARS sessions in 21 patients (11 men; median age 46 years; median three sessions per patient; median duration of session 8 h). Nine clinically relevant episodes of coagulopathy/bleeding were observed in eight patients, forced to premature cessation of MARS in seven and ended lethal in four. Four complications occurred during the first, five during later (third to seventh) MARS sessions and two bleeders tolerated further sessions without complications. Coagulation parameters worsened significantly also during MARS sessions not associated with bleeding (PMARS therapy, potentially leading to bleeding complications and mortality.

  15. Molecular orbital study of the chemisorption of carbon monoxide on a tungsten (100) surface

    International Nuclear Information System (INIS)

    Lee, T.H.; Rabalais, J.W.

    1978-01-01

    The adsorption energies of carbon monoxide chemisorbed at various sites on a tungsten (100) surface have been calculated by extended Hueckel molecular orbital theory (EHMO). The concept of a 'surface molecule' in which CO is bonded to an array of tungsten atoms Wsub(n) has been employed. Dissociative adsorption in which C occupies a four-fold, five-coordination site and O occupies either a four- or two-fold site has been found to be the most stable form for CO on a W surface. Stable one-fold and two-fold sites of molecularly adsorbed CO have also been found in which the CO group is normal to the surface plane and the C atom is nearest the surface. Adsorption energies and molecular orbitals for the stable molecularly and dissociatively adsorbed CO sites are compared with the experimental data on various types of adsorbed CO, i.e. virgin-, α-, and β-CO. Models are suggested for each of these adsorption types. The strongest bonding interactions occur between the CO 5sigma orbital and the totally symmetric 5d and 6s orbitals of the Wsub(n) cluster. Possible mechanisms for conversion of molecularly adsorbed CO to dissociatively adsorbed CO are proposed and the corresponding activation energies are estimated. (Auth.)

  16. Molecular tailoring of solid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Evenson, Simon Alan

    1997-07-01

    The overall performance of a material can be dramatically improved by tailoring its surface at the molecular level. The aim of this project was to develop a universal technique for attaching dendrimers (well-defined, nanoscale, functional polymers) and Jeffamines (high molecular weight polymer chains) to the surface of any shaped solid substrate. This desire for controlled functionalization is ultimately driven by the need to improve material compatibility in various biomedical applications. Atomic force microscopy (AFM) was used initially to study the packing and structure of Langmuir-Blodgett films on surfaces, and subsequently resulted in the first visualization of individual, spherically shaped, nanoscopic polyamidoamine dendrimers. The next goal was to develop a methodology for attaching such macromolecules to inert surfaces. Thin copolymer films were deposited onto solid substrates to produce materials with a fixed concentration of surface anhydride groups. Vapor-phase functionalization reactions were then carried out with trifluorinated amines to confirm the viability of this technique to bond molecules to surfaces. Finally, pulsed plasma polymerization of maleic anhydride took this approach one stage further, by forming well-adhered polymer films containing a predetermined concentration of reactive anhydride groups. Subsequent functionalization reactions led to the secure attachment of dendrimers and Jeffamines at any desired packing density. An alternative route to biocompatibilization used 1,2-ethanedithiol to yield thiolated surfaces containing very high polymeric sulfur : carbon ratios. (author)

  17. Molecular tailoring of solid surfaces

    International Nuclear Information System (INIS)

    Evenson, Simon Alan

    1997-01-01

    The overall performance of a material can be dramatically improved by tailoring its surface at the molecular level. The aim of this project was to develop a universal technique for attaching dendrimers (well-defined, nanoscale, functional polymers) and Jeffamines (high molecular weight polymer chains) to the surface of any shaped solid substrate. This desire for controlled functionalization is ultimately driven by the need to improve material compatibility in various biomedical applications. Atomic force microscopy (AFM) was used initially to study the packing and structure of Langmuir-Blodgett films on surfaces, and subsequently resulted in the first visualization of individual, spherically shaped, nanoscopic polyamidoamine dendrimers. The next goal was to develop a methodology for attaching such macromolecules to inert surfaces. Thin copolymer films were deposited onto solid substrates to produce materials with a fixed concentration of surface anhydride groups. Vapor-phase functionalization reactions were then carried out with trifluorinated amines to confirm the viability of this technique to bond molecules to surfaces. Finally, pulsed plasma polymerization of maleic anhydride took this approach one stage further, by forming well-adhered polymer films containing a predetermined concentration of reactive anhydride groups. Subsequent functionalization reactions led to the secure attachment of dendrimers and Jeffamines at any desired packing density. An alternative route to biocompatibilization used 1,2-ethanedithiol to yield thiolated surfaces containing very high polymeric sulfur : carbon ratios. (author)

  18. Kinetics of the homogeneous exchange of alpha-lactalbumin adsorbed on titanium oxide surface.

    Science.gov (United States)

    Bentaleb, A; Haïkel, Y; Voegel, J C; Schaaf, P

    1998-06-05

    The homogeneous exchange process whereby alpha-lactalbumine molecules adsorbed on hydrophilic titanium oxide particles are replaced by alpha-lactalbumine molecules in solution has been investigated by means of a 125I radio-labeling technique, alpha-lactalbumine is a compact and highly negatively charged protein, making this study complementary to previous work devoted to the general understanding of the exchange mechanisms of adsorbed proteins on solid surfaces. The isotherm of alpha-lactalbumine exhibits bimodal adsorption shape, and the exchange process whereby adsorbed proteins are replaced by new incoming ones from the bulk solution has been studied at both the upper and the lower plateau of the isotherm. In the upper plateau the exchange process was found to be of first order with respect to the bulk molecules, and the release rate constant was equal to 0.914 L. mol-1.s-1. This behavior is identical to what has been observed with other proteinic systems. In the lower plateau domain, in contrast, the protein release process is independent of the concentration of proteins in the bulk, but the release rates are higher than the pure desorption rates. This constitutes, to our knowledge, a behavior that never before has been observed and that remains to be explained.

  19. Surface-enhanced raman spectroscopy of quinomethionate adsorbed on silver colloids

    International Nuclear Information System (INIS)

    Kim, Mak Soon; Kang, Jae Soo; Park, Si Bum; Lee, Mu Sang

    2003-01-01

    We have studied the surface-enhanced Raman spectroscopy (SERS) spectrum of quinomethionate (6-methyl-1,3-dithiolo(4,5-b)quinoxalin-2-one), which is an insecticide or fungicide used on vegetables and wheat. We observed no signals in the ordinary Raman spectra of solid-state quinomethionate, but when it was adsorbed on a colloidal silver surface, strong vibrational signals were obtained at a very low concentration. The SERS spectra were obtained by silver colloids prepared by the Creighton et al. method. The influence of pH and the aggregation inductors (Cl - , Br - , I - , F - ) on the adsorption mechanism was investigated. Two different adsorption mechanisms were deduced, depending on the experimental conditions: The one N atom or two N atoms are chemisorbed on an Ag surface. An important contribution of the chemical mechanism was inferred when the one N atom was perpendicularly adsorbed on a surface. It is possible that quinomethionate can be detected to about 10 -5 M

  20. Theory and Monte-Carlo simulation of adsorbates on corrugated surfaces

    DEFF Research Database (Denmark)

    Vives, E.; Lindgård, P.-A.

    1993-01-01

    -phase between the commensurate and incommensurate phase stabilized by defects. Special attention has been given to the study of the epitaxial rotation angles of the different phases. Available experimental data is in agreement with the simulations and with a general theory for the epitaxial rotation which takes......Phase transitions in systems of adsorbed molecules on corrugated surfaces are studied by means of Monte Carlo simulation. Particularly, we have studied the phase diagram of D2 on graphite as a function of coverage and temperature. We have demonstrated the existence of an intermediate gamma...

  1. Surfaces of Microparticles in Colloids: Structure and Molecular Adsorption Kinetics

    Science.gov (United States)

    Dai, Hai-Lung

    2002-03-01

    Surfaces of micron and sub-micron size particles in liquid solution are probed by second harmonic generation (SHG) facilitated with femtosecond laser pulses. The particles probed include inorganic objects such as carbon black and color pigments, polymeric species like polystyrene beads, and biological systems such as blood cells and ecoli. In the experiments, dye molecules are first adsorbed onto the particle surface to allow generation of second harmonics upon light irradiation. Competition for adsorption between these surface dye molecules and the molecules of interest in the solution is then monitored by the SHG signal to reveal the molecular adsorption kinetics and surface structure. Specifically, surfactant adsorption on polymer surfaces, the structure of carbon black surface, and protein adsorption on biological surfaces, monitored by this technique, will be discussed.

  2. Tuning Surface Energy Landscapes in Metallic Quantum Films using Alkali Adsorbates

    Science.gov (United States)

    Khajetoorians, Alexander; Qin, Shengyong; Zhu, Wenguang; Eisele, Holger; Zhang, Zhenyu; Shih, Chih-Kang

    2008-03-01

    Quantum confinement shows a strong interplay with growth and kinetics in thin metal systems where the Fermi wavelength has a special relationship to the surface normal lattice constant. In the case of Pb/Si(111) systems, this relationship reveals an interesting thickness-dependent bilayer oscillation in the density of states and surface energy up to a phase. In this paper, we report on a novel effect: tuning of the energy landscape of a flat-top quantum Pb mesa using Cs adsorbates. Using STM/STS, we show that depositing Cs adsorbates on a thin Pb mesa promotes quantum stable Pb nanoislands on preferentially unstable thicknesses. Thickness-dependent nanoisland densities show a strong bilayer oscillation correlating with quantum stability. By modifying the Cs coverage on the mesa surface, we can tune the lateral size distribution of the nanoislands and the overall amplitude of the island density oscillation. Nanoisland formation is linked to a step decoration of Cs adatoms along the step edge of the nanoisland.

  3. Controlled enzymatic cutting of DNA molecules adsorbed on surfaces using soft lithography

    Science.gov (United States)

    Auerbach, Alyssa; Budassi, Julia; Shea, Emily; Zhu, Ke; Sokolov, Jonathan

    2013-03-01

    The enzyme DNase I was applied to adsorbed and aligned DNA molecules (Lamda, 48.5 kilobase pairs (kbp), and T4, 165.6 kbp), stretched linearly on a surface, by stamping with a polydimethylsiloxane (PDMS) grating. The DNAs were cut by the enzyme into separated, micron-sized segments along the length of the molecules at positions determined by the grating dimensions (3-20 microns). Ozone-treated PDMS stamps were coated with DNase I solutions and placed in contact with surface-adsorbed DNA molecules deposited on a 750 polymethylmethacrylate (PMMA) film spun-cast onto a silicon substrate. The stamps were applied under pressure for times up to 15 minutes at 37 C. The cutting was observed by fluorescence microscopy imaging of DNA labeled with YOYO dye. Cutting was found to be efficient despite the steric hindrance due to surface attachment of the molecules. Methods for detaching and separating the cut segments for sequencing applications will be discussed. Supported by NSF-DMR program.

  4. On the formation of polymer non-grafted onto the surface during radiation-induced polymerization of monomers adsorbed on mineral substrates

    International Nuclear Information System (INIS)

    Bruk, M.A.; Mund, S.L.; Aksman, I.B.; Abkin, A.D.

    1977-01-01

    It has been established that during radiation polymerization of vinylacetate and acrylonitrile, adsorbed on aerosil from the vapour phase, considerable amounts of the polymer are formed even at the initial stage of the process which is extracted by the organic solvents. It has been shown for polyvinylacetate as an example that probability of the polymer chain located on the surface to transfer into the solution depends not only on the ''quality'' of the solvent with respect to the given polymer but on the energy of solvent interaction with the surface adsorption centers as well. It has been observed that the molecular mass of PVA extracted from the aerosil surface by acetone is several times lower than that of PVA which remains on the surface after treating with acetone. Probable participation of low-molecular radicals in the formation of polymer chains not forming a chemical bond with the surface has been considered

  5. Linear and nonlinear surface spectroscopy of supported size selected metal clusters and organic adsorbates

    Energy Technology Data Exchange (ETDEWEB)

    Thaemer, Martin Georg

    2012-03-08

    The spectroscopic investigation of supported size selected metal clusters over a wide wavelength range plays an important role for understanding their outstanding catalytic properties. The challenge which must be overcome to perform such measurements is the difficult detection of the weak spectroscopic signals from these samples. As a consequence, highly sensitive spectroscopic methods are applied, such as surface Cavity Ringdown Spectroscopy and surface Second Harmonic Generation Spectroscopy. The spectroscopic apparatus developed is shown to have a sensitivity which is high enough to detect sub-monolayer coverages of adsorbates on surfaces. In the measured spectra of small supported silver clusters of the sizes Ag{sub 4}2, Ag{sub 2}1, Ag{sub 9}, and Ag atoms a stepwise transition from particles with purely metallic character to particles with molecule-like properties can be observed within this size range.

  6. Dry powder pulmonary delivery of cationic PGA-co-PDL nanoparticles with surface adsorbed model protein.

    Science.gov (United States)

    Kunda, Nitesh K; Alfagih, Iman M; Dennison, Sarah R; Somavarapu, Satyanarayana; Merchant, Zahra; Hutcheon, Gillian A; Saleem, Imran Y

    2015-08-15

    Pulmonary delivery of macromolecules has been the focus of attention as an alternate route of delivery with benefits such as; large surface area, thin alveolar epithelium, rapid absorption and extensive vasculature. In this study, a model protein, bovine serum albumin (BSA) was adsorbed onto cationic PGA-co-PDL polymeric nanoparticles (NPs) prepared by a single emulsion solvent evaporation method using a cationic surfactant didodecyldimethylammonium bromide (DMAB) at 2% w/w (particle size: 128.64±06.01 nm and zeta-potential: +42.32±02.70 mV). The optimum cationic NPs were then surface adsorbed with BSA, NP:BSA (100:4) ratio yielded 10.01±1.19 μg of BSA per mg of NPs. The BSA adsorbed NPs (5 mg/ml) were then spray-dried in an aqueous suspension of L-leucine (7.5 mg/ml, corresponding to a ratio of 1:1.5/NP:L-leu) using a Büchi-290 mini-spray dryer to produce nanocomposite microparticles (NCMPs) containing cationic NPs. The aerosol properties showed a fine particle fraction (FPF, dae<4.46 μm) of 70.67±4.07% and mass median aerodynamic diameter (MMAD) of 2.80±0.21 μm suggesting a deposition in the respiratory bronchiolar region of the lungs.The cell viability was 75.76±03.55% (A549 cell line) at 156.25 μg/ml concentration after 24 h exposure. SDS-PAGE and circular dichroism (CD) confirmed that the primary and secondary structure of the released BSA was maintained. Moreover, the released BSA showed 78.76±1.54% relative esterolytic activity compared to standard BSA. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Effective embedded-atom potential for metallic adsorbates on crystalline surfaces

    International Nuclear Information System (INIS)

    Förster, G D; Magnin, Y; Rabilloud, F; Calvo, F

    2014-01-01

    Based on the embedded-atom method (EAM), an analytical effective potential is developed to model the interaction of a metallic adsorbate on a perfect crystalline substrate, which is also metallic. The many-body character of the original EAM potential is preserved in the adsorbate energy and in the alteration of the substrate energy due to the presence of the adsorbate. A mean-field-type version neglecting corrugation of the substrate is first derived based on rigorous integration of individual monolayers, followed by an approximate form for the perturbation of the substrate energy. Lateral corrugation is subsequently included by additional phenomenological terms respecting the symmetry of the substrate, again preserving the many-body nature of the original potential. The effective model contains four parameters to describe uncorrugated substrates and eight extra parameters to describe every order of the Fourier lateral expansion. These parameters were fitted to reproduce the adsorption energy of a sample of random configurations of realistic 2D and 3D clusters deposited on the (1 1 1) fcc surface, for metals for which popular EAM models have been parametrized. As a simple application, the local relaxation of pre-formed icosahedral or truncated octahedral clusters soft-landed and exposing (1 1 1) faces in epitaxy to the substrate has been simulated at 0 and 300 K. The deformation of small clusters to wet the substrate is correctly captured by the effective model. This agreement with the exact potential suggests that the present model should be useful for treating metallic environments in large-scale surface studies, notably in structural optimization or as a template for more general models parametrized from ab initio data. (paper)

  8. Theoretical study of PTCDA adsorbed on the coinage metal surfaces, Ag(111), Au(111) and Cu(111)

    International Nuclear Information System (INIS)

    Romaner, L; Nabok, D; Puschnig, P; Ambrosch-Draxl, C; Zojer, E

    2009-01-01

    A thorough understanding of the adsorption of molecules on metallic surfaces is a crucial prerequisite for the development and improvement of functionalized materials. A prominent representative within the class of π-conjugated molecules is 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) which, adsorbed on the Ag(111), Au(111) or Cu(111) surfaces, shows characteristic trends for work-function modification, alignment of molecular levels with the substrate Fermi energy and binding distances. We carried out density functional theory (DFT) calculations to investigate to what extent these trends can be rationalized on a theoretical basis. We used different density functionals (DF) including a fully non-local van der Waals (vdW) DF capable of describing dispersion interactions. We show that, rather independent of the DF, the calculations yield level alignments and work-function modifications consistent with ultra-violet photoelectron spectroscopy when the monolayer is placed onto the surfaces at the experimental distances (as determined from x-ray standing wave experiments). The lowest unoccupied molecular orbital is occupied on the Ag and Cu surfaces, whereas it remains unoccupied on the Au surface. Simultaneously, the work function increases for Ag but decreases for Cu and Au. Adsorption distances and energies, on the other hand, depend very sensitively on the choice of the DF. While calculations in the local density approximation bind the monolayer consistently with the experimental trends, the generalized gradient approximation in several flavors fails to reproduce realistic distances and energies. Calculations employing the vdW-DF reveal that substantial bonding contributions arise from dispersive interactions. They yield reasonable binding energies but larger binding distances than the experiments.

  9. First-principles investigations of electronic and magnetic properties of SrTiO3 (001) surfaces with adsorbed ethanol and acetone molecules

    Science.gov (United States)

    Adeagbo, Waheed A.; Fischer, Guntram; Hergert, Wolfram

    2011-05-01

    First-principles methods based on density functional theory are used to investigate the electronic and magnetic properties of molecular interaction of the TiO2 terminated SrTiO3 (100) surface with ethanol or acetone. Both the perfect surface and the surface with an oxygen or a titanium vacancy in the top layer are considered. Ethanol and acetone are preferentially adsorbed molecularly via their respective oxygen atom on top of the Ti atom on the perfect surface. In case of an oxygen vacancy the adsorption of ethanol or acetone occurs directly on top of the vacancy and does not significantly affect the magnetism caused by the vacancy. In the case of a titanium vacancy both adsorbates occupy positions above Ti atoms. During this adsorption process the ethanol molecule dissociates into a CH3CO radical and three hydrogen atoms. The latter form hydroxide bonds with three of the four dangling oxygen bonds around the Ti vacancy and any magnetic moment induced by the Ti vacancy is annihilated. Thus the ethanol and acetone have a different impact on the surface magnetism of the SrTiO3 (100) surface.

  10. Adsorbed radioactivity and radiographic imaging of surfaces of stainless steel and titanium

    Science.gov (United States)

    Jung, Haijo

    1997-11-01

    Type 304 stainless steel used for typical surface materials of spent fuel shipping casks and titanium were exposed in the spent fuel storage pool of a typical PWR power plant. Adsorption characteristics, effectiveness of decontamination by water cleaning and by electrocleaning, and swipe effectiveness on the metal surfaces were studied. A variety of environmental conditions had been manipulated to stimulate the potential 'weeping' phenomenon that often occurs with spent fuel shipping casks during transit. In a previous study, few heterogeneous effects of adsorbed contamination onto metal surfaces were observed. Radiographic images of cask surfaces were made in this study and showed clearly heterogeneous activity distributions. Acquired radiographic images were digitized and further analyzed with an image analysis computer package and compared to calibrated images by using standard sources. The measurements of activity distribution by using the radiographic image method were consistent with that using a HPGe detector. This radiographic image method was used to study the effects of electrocleaning for total and specified areas. The Modulation Transfer Function (MTF) of a film-screen system in contact with a radioactive metal surface was studied with neutron activated gold foils and showed more broad resolution properties than general diagnostic x-ray film-screen systems. Microstructure between normal areas and hot spots showed significant differences, and one hot spot appearing as a dot on the film image consisted of several small hot spots (about 10 μm in diameter). These hot spots were observed as structural defects of the metal surfaces.

  11. An eco-friendly approach for heavy metal adsorbent regeneration using CO2-responsive molecular octopus.

    Science.gov (United States)

    Bai, Yu; Liang, Yen Nan; Hu, Xiao

    2017-10-01

    Perennial problems of adsorption in wastewater treatment include adsorbent recycling, generation of waste sludge and secondary pollution because harmful concentrated acids, bases or strong chelators are often used for adsorbent regeneration and adsorbate recovery. We report, for the first time, an eco-friendly regeneration concept demonstrated with a CO 2 -responsive octopus-like polymeric adsorbent. Various heavy metals can be scavenged at very high Q e by such adsorbent through coordination. Most importantly, the rapid and complete regeneration of the adsorbent and recovery of the heavy metal ions can be readily achieved by CO 2 bubbling within a few minutes under mild conditions, i.e., room temperature and atmospheric pressure. The adsorbent can then be restored to its adsorptive state and reused upon removal of CO 2 by simply bubbling another gas. This eco-friendly, effective, ultra-fast and repeatable CO 2 -triggered regeneration process using CO 2 -responsive adsorbent with versatile structure, morphology or form can be incorporated into a sustainable closed-loop wastewater treatment process to solve the perennial problems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Excited-state potential-energy surfaces of metal-adsorbed organic molecules from linear expansion Δ-self-consistent field density-functional theory (ΔSCF-DFT).

    Science.gov (United States)

    Maurer, Reinhard J; Reuter, Karsten

    2013-07-07

    Accurate and efficient simulation of excited state properties is an important and much aspired cornerstone in the study of adsorbate dynamics on metal surfaces. To this end, the recently proposed linear expansion Δ-self-consistent field method by Gavnholt et al. [Phys. Rev. B 78, 075441 (2008)] presents an efficient alternative to time consuming quasi-particle calculations. In this method, the standard Kohn-Sham equations of density-functional theory are solved with the constraint of a non-equilibrium occupation in a region of Hilbert-space resembling gas-phase orbitals of the adsorbate. In this work, we discuss the applicability of this method for the excited-state dynamics of metal-surface mounted organic adsorbates, specifically in the context of molecular switching. We present necessary advancements to allow for a consistent quality description of excited-state potential-energy surfaces (PESs), and illustrate the concept with the application to Azobenzene adsorbed on Ag(111) and Au(111) surfaces. We find that the explicit inclusion of substrate electronic states modifies the topologies of intra-molecular excited-state PESs of the molecule due to image charge and hybridization effects. While the molecule in gas phase shows a clear energetic separation of resonances that induce isomerization and backreaction, the surface-adsorbed molecule does not. The concomitant possibly simultaneous induction of both processes would lead to a significantly reduced switching efficiency of such a mechanism.

  13. Shotgun proteomic analytical approach for studying proteins adsorbed onto liposome surface

    KAUST Repository

    Capriotti, Anna Laura

    2011-07-02

    The knowledge about the interaction between plasma proteins and nanocarriers employed for in vivo delivery is fundamental to understand their biodistribution. Protein adsorption onto nanoparticle surface (protein corona) is strongly affected by vector surface characteristics. In general, the primary interaction is thought to be electrostatic, thus surface charge of carrier is supposed to play a central role in protein adsorption. Because protein corona composition can be critical in modifying the interactive surface that is recognized by cells, characterizing its formation onto lipid particles may serve as a fundamental predictive model for the in vivo efficiency of a lipidic vector. In the present work, protein coronas adsorbed onto three differently charged cationic liposome formulations were compared by a shotgun proteomic approach based on nano-liquid chromatography-high-resolution mass spectrometry. About 130 proteins were identified in each corona, with only small differences between the different cationic liposome formulations. However, this study could be useful for the future controlled design of colloidal drug carriers and possibly in the controlled creation of biocompatible surfaces of other devices that come into contact with proteins into body fluids. © 2011 Springer-Verlag.

  14. Formation and composition of adsorbates on hydrophobic carbon surfaces from aqueous laccase-maltodextrin mixture suspension

    Energy Technology Data Exchange (ETDEWEB)

    Corrales Ureña, Yendry Regina, E-mail: yendry386@hotmail.com [UNESP São Paulo State University, Av. Eng. Luiz Edmundo Carrijo Coube, 14-01, Bauru, São Paulo (Brazil); Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen (Germany); Lisboa-Filho, Paulo Noronha [UNESP São Paulo State University, Av. Eng. Luiz Edmundo Carrijo Coube, 14-01, Bauru, São Paulo (Brazil); Szardenings, Michael [Fraunhofer Institute for Cell Therapy and Immunology IZI, Perlickstrasse 1, 04103 Leipzig (Germany); Gätjen, Linda; Noeske, Paul-Ludwig Michael; Rischka, Klaus [Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen (Germany)

    2016-11-01

    Highlights: • Less than 10 nm layer formed on carbon based materials composed by laccase and maltodextrin. • Improvement of the wettability of carbon based materials. • A protein-polysaccharide biofilm layer formation at solid liquid interface. • Stable layers formed under buffer and water rinsing. - Abstract: A robust procedure for the surface bio-functionalization of carbon surfaces was developed. It consists on the modification of carbon materials in contact with an aqueous suspension of the enzyme laccase from Trametes versicolor and the lyophilization agent maltodextrin, with the pH value adjusted close to the isoelectric point of the enzyme. We report in-situ investigations applying Quartz Crystal Microbalance with Dissipation (QCM-D) for carbon-coated sensor surfaces and, moreover, ex-situ measurements with static contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) and Scanning Force Microscopy (SFM) for smooth Highly Oriented Pyrolytic Graphite (HOPG) substrates, for contact times between the enzyme formulation and the carbon material surface ranging from 20 s to 24 h. QCM-D studies reveals the formation of rigid layer of biomaterial, a few nanometers thin, which shows a strongly improved wettability of the substrate surface upon contact angle measurements. Following spectroscopic characterization, these layers are composed of mixtures of laccase and maltodextrin. The formation of these adsorbates is attributed to attractive interactions between laccase, the maltodextrin-based lyophilization agent and the hydrophobic carbon surfaces; a short-term contact between the aqueous laccase mixture suspension and HOPG surfaces is shown to merely result in de-wetting patterns influencing the results of contact angle measurements. The new enzyme-based surface modification of carbon-based materials is suggested to be applicable for the improvement of not only the wettability of low energy substrate surfaces with fluid formulations like coatings

  15. Atomic force microscopy measurements of topography and friction on dotriacontane films adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Trogisch, S.; Simpson, M.J.; Taub, H.

    2005-01-01

    We report comprehensive atomic force microscopy (AFM) measurements at room temperature of the nanoscale topography and lateral friction on the surface of thin solid films of an intermediate-length normal alkane, dotriacontane (n-C32H66), adsorbed onto a SiO2 surface. Our topographic and frictional...

  16. Recombination of chlorine atoms on plasma-conditioned stainless steel surfaces in the presence of adsorbed Cl{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Stafford, Luc; Poirier, Jean-Sebastien; Margot, Joelle [Departement de Physique, Universite de Montreal, Montreal, Quebec, H3C 3J7 (Canada); Khare, Rohit; Guha, Joydeep; Donnelly, Vincent M, E-mail: luc.stafford@umontreal.c, E-mail: vmdonnelly@uh.ed [Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204 (United States)

    2009-03-07

    We investigated the interactions of atomic and molecular chlorine with plasma-conditioned stainless steel surfaces through both experiments and modelling. The recombination of Cl during adsorption and desorption of Cl{sub 2} was characterized using a rotating-substrate technique in which portions of the cylindrical substrate surface are periodically exposed to an inductively coupled chlorine plasma and then to an Auger electron spectrometer in separate, differentially pumped chambers. After several hours of exposure to the Cl{sub 2} plasma, the stainless steel substrate became coated with a Si-oxychloride-based layer (Fe : Si : O : Cl {approx} 1 : 13 : 13 : 3) due to chlorine adsorption and the erosion of the silica discharge tube. Desorption of Cl{sub 2} from this surface was monitored through measurements of pressure rises in the Auger chamber as a function of substrate rotation frequency. Significant adsorption and desorption of Cl{sub 2} was observed with the plasma off, similar to that observed previously on plasma-conditioned anodized aluminium surfaces, but with much faster desorption rates that are most likely attributable to the smoother and non-porous stainless steel surface morphology. When the plasma was turned on, a much larger pressure rise was observed due to Langmuir-Hinshelwood recombination of Cl atoms. Recombination coefficients, {gamma}{sub Cl}, ranged from 0.004 to 0.03 and increased with Cl-to-Cl{sub 2} number density ratio. This behaviour was observed previously for anodized aluminium surfaces, and was explained by the blocking of Cl recombination sites by adsorbed Cl{sub 2}. Application of this variable recombination coefficient to the modelling of high-density chlorine plasmas gives a much better agreement with measured Cl{sub 2} percent dissociations compared with predictions obtained with a recombination coefficient that is independent of plasma conditions.

  17. Quantum corrected Langevin dynamics for adsorbates on metal surfaces interacting with hot electrons

    DEFF Research Database (Denmark)

    Olsen, Thomas; Schiøtz, Jakob

    2010-01-01

    We investigate the importance of including quantized initial conditions in Langevin dynamics for adsorbates interacting with a thermal reservoir of electrons. For quadratic potentials the time evolution is exactly described by a classical Langevin equation and it is shown how to rigorously obtain...... quantum mechanical probabilities from the classical phase space distributions resulting from the dynamics. At short time scales, classical and quasiclassical initial conditions lead to wrong results and only correctly quantized initial conditions give a close agreement with an inherently quantum...... mechanical master equation approach. With CO on Cu(100) as an example, we demonstrate the effect for a system with ab initio frictional tensor and potential energy surfaces and show that quantizing the initial conditions can have a large impact on both the desorption probability and the distribution...

  18. Composition of Surface Adsorbed Layer of TiO2 Stored in Ambient Air

    Directory of Open Access Journals (Sweden)

    Zakharenko V.S.

    2017-11-01

    Full Text Available The processes of dark, UV, and visible light promoted desorption of surface species were investigated for three different TiO2 samples: TiO2 prepared by dispersion of the titania single crystal, TiO2 prepared by combustion of a pyrotechnic mixture in air, and commercial TiO2 P25. The composition of the adsorbed layer was identified in the dark and under UV and visible light irradiation. The composition of desorption products showed the dependence of the adsorption layer state on the TiO2 nature. Methane photodesorption was detected only for the commercial TiO2 P25. Possible reasons for methane emission include the capturing of complete molecules during the TiO2 production process and photocatalytic hydrogenation of CO2 under UV-light.

  19. XPS and NEXAFS analysis of dimethyl sulfide adsorbed on the Rh(PVP) nanoparticle surface

    International Nuclear Information System (INIS)

    Niwa, Hironori; Ogawa, Satoshi; Yagi, Shinya; Kutluk, Galif

    2010-01-01

    We have studied the adsorption reaction of dimethyl sulfide (DMS: (CH 3 ) 2 S) on the surface of Rh(PVP) nanoparticles by using AFM, XPS and NEXAFS techniques. The AFM images show the degree of dispersion of the Rh(PVP) nanoparticles depends on the amount of them. The in-situ XPS results indicate that the dissociation reaction of DMS into atomic S does not depend upon the existence of the Rh(PVP) nanoparticles. The NEXAFS results show that there is a strong chemical bonding between Rh(PVP) nanoparticle and atomic S. The ex-situ XPS results show the atomic S adsorbed on the Rh(PVP) nanoparticles partially desorb by exposing to the air. (author)

  20. Expansion Hamiltonian model for a diatomic molecule adsorbed on a surface: Vibrational states of the CO/Cu(100) system including surface vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Qingyong, E-mail: mengqingyong@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, 116023 Dalian (China); Meyer, Hans-Dieter, E-mail: hans-dieter.meyer@pci.uni-heidelberg.de [Theoretische Chemie, Physikalisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany)

    2015-10-28

    Molecular-surface studies are often done by assuming a corrugated, static (i.e., rigid) surface. To be able to investigate the effects that vibrations of surface atoms may have on spectra and cross sections, an expansion Hamiltonian model is proposed on the basis of the recently reported [R. Marquardt et al., J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES), which was built for the CO/Cu(100) system with a rigid surface. In contrast to other molecule-surface coupling models, such as the modified surface oscillator model, the coupling between the adsorbed molecule and the surface atoms is already included in the present expansion SAP-PES model, in which a Taylor expansion around the equilibrium positions of the surface atoms is performed. To test the quality of the Taylor expansion, a direct model, that is avoiding the expansion, is also studied. The latter, however, requests that there is only one movable surface atom included. On the basis of the present expansion and direct models, the effects of a moving top copper atom (the one to which CO is bound) on the energy levels of a bound CO/Cu(100) system are studied. For this purpose, the multiconfiguration time-dependent Hartree calculations are carried out to obtain the vibrational fundamentals and overtones of the CO/Cu(100) system including a movable top copper atom. In order to interpret the results, a simple model consisting of two coupled harmonic oscillators is introduced. From these calculations, the vibrational levels of the CO/Cu(100) system as function of the frequency of the top copper atom are discussed.

  1. 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.

  2. Integrin-mediated adhesion of human mesenchymal stem cells to extracellular matrix proteins adsorbed to polymer surfaces

    International Nuclear Information System (INIS)

    Dånmark, S; Mustafa, K; Finne-Wistrand, A; Albertsson, A-C; Patarroyo, M

    2012-01-01

    In vitro, degradable aliphatic polyesters are widely used as cell carriers for bone tissue engineering, despite their lack of biological cues. Their biological active surface is rather determined by an adsorbed layer of proteins from the surrounding media. Initial cell fate, including adhesion and proliferation, which are key properties for efficient cell carriers, is determined by the adsorbed layer of proteins. Herein we have investigated the ability of human bone marrow derived stem cells (hBMSC) to adhere to extracellular matrix (ECM) proteins, including fibronectin and vitronectin which are present in plasma and serum. hBMSC expressed integrins for collagens, laminins, fibronectin and vitronectin. Accordingly, hBMSC strongly adhered to these purified ECM proteins by using the corresponding integrins. Although purified fibronectin and vitronectin adsorbed to aliphatic polyesters to a lower extent than to cell culture polystyrene, these low levels were sufficient to mediate adhesion of hBMSC. It was found that plasma- and serum-coated polystyrene adsorbed significant levels of both fibronectin and vitronectin, and fibronectin was identified as the major adhesive component of plasma for hBMSC; however, aliphatic polyesters adsorbed minimal levels of fibronectin under similar conditions resulting in impaired cell adhesion. Altogether, the results suggest that the efficiency of aliphatic polyesters cell carriers could be improved by increasing their ability to adsorb fibronectin. (paper)

  3. Preparation of theoretical scanning tunneling microscope images of adsorbed molecules: a theoretical study of benzene on the Cu(110) surface

    International Nuclear Information System (INIS)

    Shapter, J.G.; Rogers, B.L.; Ford, M.J.

    2003-01-01

    Full text: Since its development in 1982, the Scanning Tunneling Microscope (STM) has developed into a powerful tool for the study of surfaces and adsorbates. However, the utility of the technique can be further enhanced through the development of techniques for generating theoretical STM images. This is particularly true when studying molecules adsorbed on a substrate, as the results are often interpreted superficially due to an inadequate understanding of the orbital overlap probed in the experiment. A method of preparing theoretical scanning tunneling microscope (STM) images using comparatively inexpensive desktop computers and the commercially available CRYSTAL98 package is presented through a study of benzene adsorbed on the Cu(110) surface. Density Functional Theory (DFT) and Hartree-Fock (HF) methods are used to model clean Cu(110) slabs of various thicknesses and to simulate the adsorption of benzene onto these slabs. Eight possible orientations of benzene on the Cu(110) surface are proposed, and the optimum orientation according to the calculations is presented. Theoretical STM images of the Cu(110) surface and benzene adsorbed on the Cu(110) surface are compared with experimental STM images of the system from a published study. Significant differences are observed and are examined in detail

  4. Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces.

    Science.gov (United States)

    Raber, McKenzie; Brady, Matthew David; Troian-Gautier, Ludovic; Dickenson, John; Marquard, Seth L; Hyde, Jacob; Lopez, Santiago; Meyer, Gerald J; Meyer, Thomas J; Harrison, Daniel P

    2018-06-08

    A series of 18 ruthenium(II) polypyridyl complexes were synthesized and evaluated under electrochemically oxidative conditions, which generates the Ru(III) oxidation state and mimics the harsh conditions experienced during the kinetically-limited regime that can occur in dye-sensitized solar cells (DSSCs) and dye-sensitized photoelectrosynthesis cells (DSPECs), to further develop fundamental insights into the factors governing molecular sensitizer surface stability in aqueous 0.1 M HClO4 (aq). Both desorption and oxidatively induced ligand substitution were observed on planar fluorine doped tin oxide, FTO, electrodes, with a dependence on the E1/2 Ru(III/II) redox potential dictating the comparative ratios of the processes. Complexes such as RuP4OMe (E1/2 = 0.91 vs Ag/AgCl) displayed virtually only desorption, while complexes such as RuPbpz (E1/2 > 1.62 V vs Ag/AgCl) displayed only chemical decomposition. Comparing isomers of 4,4'- and 5,5-disubstituted-2,2'-bipyridine ancillary polypyridyl ligands, a dramatic increase in the rate of desorption of the Ru(III) complexes was observed for the 5,5'-ligands. Nanoscopic indium doped tin oxide thin films, nanoITO, were also sensitized and analyzed with cyclic voltammetry, UV-Vis absorption spectroscopy, and XPS, allowing for further distinction of desorption versus ligand substitution processes. Desorption loss to bulk solution associated with the planar surface of FTO is essentially non-existent on nanoITO, where both desorption and ligand substitution are shut down with RuP4OMe. These results revealed that minimizing time spent in the oxidized form, incorporating electron donating groups, maximizing hydrophobicity, and minimizing molecular bulk near the adsorbed ligand are critical to optimizing the performance of ruthenium(II) polypyridyl complexes in dye-sensitized solar cell devices.

  5. Adsorption of trace gases to ice surfaces: surface, bulk and co-adsorbate effects

    Science.gov (United States)

    Kerbrat, Michael; Bartels-Rausch, Thorsten; Huthwelker, Thomas; Schneebeli, Martin; Pinzer, Bernd; Ammann, Markus

    2010-05-01

    Atmospheric ices frequently interact with trace gases and aerosol making them an important storage, transport or reaction medium in the global ecosystem. Further, this also alters the physical properties of the ice particles with potential consequences for the global irradiation balance and for the relative humidity of surrounding air masses. We present recent results from a set of laboratory experiments of atmospheric relevance to investigate the nature of the uptake processes. The focus of this talk will be placed on the partitioning of acidic acid and nitrous acid on ice surfaces.The presented results span from very simple reversible adsorption experiments of a single trace gas onto ice surfaces to more complex, but well controlled, experimental procedures that successfully allowed us to - Disentangle surface adsorption and uptake into the ice matrix using radioactive labelled trace gases. - Show that simultaneous adsorption of acetic acid and nitrous acid to an ice surface is consistent with the Langmuir co-adsorption model. The experiments were done in a packed ice bed flow tube at atmospheric pressure and at temperatures between 213 and 253 K. The HONO gas phase mixing ratio was between 0.4 and 137 ppbv, the mixing ratio of acetic acid between 5 and 160 ppbv . The use of the radioactive labelled nitrous acid molecules for these experiments enabled in situ monitoring of the migration of trace gas in the flow tube. The measurements showed that the interactions do not only occur through adsorption but also via diffusion into polycrystalline ice. A method is suggested to disentangle the bulk and the surface processes. The co-adsorption of acetic and nitrous acids was also investigated. The measurements are well reproduced by a competitive Langmuir adsorption model.

  6. Ultrafast electron dynamics at alkali/ice structures adsorbed on a metal surface

    International Nuclear Information System (INIS)

    Meyer, Michael

    2011-01-01

    The goal of this work is to study the interaction between excess electrons in water ice structures adsorbed on metal surfaces and other charged or neutral species, like alkali ions, or chemically reactive molecules, like chlorofluorocarbons (CFC), respectively. The excess electrons in the ice can interact with the ions directly or indirectly via the hydrogen bonded water molecules. In both cases the presence of the alkali influences the population, localization, and lifetime of electronic states of excess electrons in the ice adlayer. These properties are of great relevance when considering the highly reactive character of the excess electrons, which can mediate chemical reactions by dissociative electron attachment (DEA). The influence of alkali adsorption on electron solvation and transfer dynamics in ice structures is investigated for two types of adsorption configurations using femtosecond time-resolved two-photon photoelectron spectroscopy. In the first system alkali atoms are coadsorbed on top of a wetting amorphous ice film adsorbed on Cu(111). At temperatures between 60 and 100 K alkali adsorption leads to the formation of positively charged alkali ions at the ice/vacuum interface. The interaction between the alkali ions at the surface and the dipole moments of the surrounding water molecules results in a reorientation of the water molecules. As a consequence new electron trapping sites, i.e. at local potential minima, are formed. Photoinjection of excess electrons into these alkali-ion covered amorphous ice layers, results in the trapping of a solvated electron at an alkali-ion/water complex. In contrast to solvation in pure amorphous ice films, where the electrons are located in the bulk of the ice layer, solvated electrons at alkali-ion/water complexes are located at the ice/vacuum interface. They exhibit lifetimes of several picoseconds and show a fast energetic stabilization. With ongoing solvation, i.e. pump-probe time delay, the electron transfer is

  7. Nuclear magnetic resonance study of the structure of simple molecules adsorbed on metal surfaces: acetylene on platinum

    International Nuclear Information System (INIS)

    Wang, P.K.

    1984-01-01

    We have used NMR to determine the structure of acetylene (HC - CH) adsorbed at room temperature on small platinum particles by studying the 13 C- 13 C, 13 C- 1 H, and 1 H- 1 H dipolar interactions among the nuclei in the adsorbed molecules. We find a model of 77% CCH 2 and 23% HCCH to be the only one consistent with all of our data. The C-C bond length of the majority species, CCH 2 , is determined as 1.44 +- 0.02 A, midway between a single and double bond, suggesting that both carbon atoms bond to the surface. 36 references, 29 figures, 1 table

  8. Nonadiabatic effects on surfaces: Kohn anomaly, electronic damping of adsorbate vibrations, and local heating of single molecules

    International Nuclear Information System (INIS)

    Kroeger, J

    2008-01-01

    Three aspects of electron-phonon coupling at metal surfaces are reviewed. One aspect is the Kohn effect, which describes an anomalous dispersion relation of surface phonons due to quasi-one-dimensional nesting of Fermi surface contours. The combination of electron energy loss spectroscopy and angle-resolved photoelectron spectroscopy allows us to unambiguously characterize Kohn anomaly systems. A second aspect is the nonadiabatic damping of adsorbate vibrations. Characteristic spectroscopic line shapes of vibrational modes allow us to estimate the amount of energy transfer between the vibrational mode and electron-hole pairs. Case studies of a Kohn anomaly and nonadiabatic damping are provided by the hydrogen- and deuterium-covered Mo(110) surface. As a third aspect of interaction between electrons and phonons, local heating of a C 60 molecule adsorbed on Cu(100) and in contact with the tip of a scanning tunnelling microscope is covered

  9. In Situ Evaluation of Density, Viscosity and Thickness of Adsorbed Soft Layers by Combined Surface Acoustic Wave and Surface Plasmon Resonance

    OpenAIRE

    Francis, L.; Friedt, J. -M.; Zhou, C.; Bertrand, P.

    2003-01-01

    We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is...

  10. Atomic and molecular adsorption on transition-metal carbide (111) surfaces from density-functional theory: a trend study of surface electronic factors

    DEFF Research Database (Denmark)

    Vojvodic, Aleksandra; Ruberto, C.; Lundqvist, Bengt

    2010-01-01

    ) surfaces. The spatial extent and the dangling bond nature of these SRs are supported by real-space analyses of the calculated Kohn-Sham wavefunctions. Then, atomic and molecular adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOSs...

  11. Molecular adsorbates on HOPG: Toward modulation of graphene density of states

    Science.gov (United States)

    Groce, Michelle; Einstein, Theodore; Cullen, William

    2013-03-01

    Ordered molecular superlattices, particularly those made of planar aromatics with their attendant pi orbitals, have the potential to break the graphene sublattice degeneracy and create a band gap. Trimesic acid (TMA) is a promising candidate due to its self-assembly into symmetry-breaking superlattices nearly commensurate with that of graphene. We have used the graphite (0001) surface as a model system to explore the impact of TMA thin films on band structure. By examining correlations between STM topography and STS maps of corresponding regions, we are able to investigate the effects of TMA on the local density of states. Work supported by the University of Maryland NSF-MRSEC, DMR 0520471 and Shared Experimental Facilities.

  12. Adsorption of 1-naphthyl methyl carbamate in water by utilizing a surface molecularly imprinted polymer

    Science.gov (United States)

    So, Juhyok; Pang, Cholho; Dong, Hongxing; Jang, Paeksan; U, Juhyok; Ri, Kumchol; Yun, Cholyong

    2018-05-01

    Surface molecularly imprinting polymer (SMIP) was utilized in the removal of a residual pesticide (carbaryl (CBL)) in water and simulated fruit juice. Being the crosslinking agent, ethylene glycol dimethacrylate (EGDMA) was copolymerized with the monomer, methacrylic acid (MAA) and CBL as the template molecules on the surface of the silica gel particles to produce the SMIP adsorbents. The SMIP adsorbents showed good selectivity and good adsorption capacity for CBL in the competitive adsorptions with two structurally related carbamate pesticides. The effect of the pretreatment solvents on the adsorption capacity of the SMIP adsorbent was investigated with the results of the numerical simulations. The adsorption isotherms and the adsorption kinetics were well described by the Freundlich equilibrium model and the pseudo-second-order kinetic model, respectively. Scatchard plot analysis revealed that there were two classes of binding sites populated in the SMIP adsorbents. In addition, the good selective adsorption of CBL by the SMIP adsorbent in a simulated fruit juice containing vitamin C and fructose indicated the great potential of the SMIP adsorbents to remove residual pesticide in food industry and processing industry for agricultural products.

  13. Monitoring peptide-surface interaction by means of molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Nonella, Marco, E-mail: mnonella@pci.uzh.ch [Physikalisch-Chemisches Institut, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Seeger, Stefan, E-mail: sseeger@pci.uzh.ch [Physikalisch-Chemisches Institut, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)

    2010-12-09

    Graphical abstract: Protein-surface interactions play a crucial role in a wide field of research areas like biology, biotechnology, or pharmacology. Only recently, it has been shown that not only peptide adsorption represents an important process but also spreading and clustering of adsorbed proteins. By means of classical molecular dynamics, peptide adsorption as well as the dynamics of adsorbed peptides have been investigated in order to gain deeper insight into such processes. The picture shows a snapshot of an adsorbed peptide on a silica surface showing strong direct hydrogen bonding. Research highlights: {yields} Simulation of peptide surface interaction. {yields} Dynamics of hydrogen bond formation and destruction. {yields} Internal flexibility of adsorbed peptides. - Abstract: Protein adsorption and protein surface interactions have become an important research topic in recent years. Very recently, for example, it has been shown that protein clusters can undergo a surface-induced spreading after adsorption. Such phenomena emphasize the need of a more detailed insight into protein-silica interaction at an atomic level. Therefore, we have studied a model system consisting of a short peptide, a silica slab, and water molecules by means of classical molecular dynamics simulations. The study reveals that, besides of electrostatic interactions caused by the chosen charge distribution, the peptide interacts with the silica surface through formation of direct peptide-surface hydrogen bonds as well as indirect peptide-water-surface hydrogen bonds. The number of created hydrogen bonds varies considerably among the simulated structures. The strength of hydrogen bonding determines the mobility of the peptide on the surface and the internal flexibility of the adsorbed peptide.

  14. Simulations of the Static Friction Due to Adsorbed Molecules

    OpenAIRE

    He, Gang; Robbins, Mark O.

    2001-01-01

    The static friction between crystalline surfaces separated by a molecularly thin layer of adsorbed molecules is calculated using molecular dynamics simulations. These molecules naturally lead to a finite static friction that is consistent with macroscopic friction laws. Crystalline alignment, sliding direction, and the number of adsorbed molecules are not controlled in most experiments and are shown to have little effect on the friction. Temperature, molecular geometry and interaction potenti...

  15. Surface Chemistry Dependence of Mechanochemical Reaction of Adsorbed Molecules-An Experimental Study on Tribopolymerization of α-Pinene on Metal, Metal Oxide, and Carbon Surfaces.

    Science.gov (United States)

    He, Xin; Kim, Seong H

    2018-02-20

    Mechanochemical reactions between adsorbate molecules sheared at tribological interfaces can induce association of adsorbed molecules, forming oligomeric and polymeric products often called tribopolymers). This study revealed the role or effect of surface chemistry of the solid substrate in mechanochemical polymerization reactions. As a model reactant, α-pinene was chosen because it was known to readily form tribopolymers at the sliding interface of stainless steel under vapor-phase lubrication conditions. Eight different substrate materials were tested-palladium, nickel, copper, stainless steel, gold, silicon oxide, aluminum oxide, and diamond-like carbon (DLC). All metal substrates and DLC were initially covered with surface oxide species formed naturally in air or during the oxidative sample cleaning. It was found that the tribopolymerization yield of α-pinene is much higher on the substrates that can chemisorb α-pinene, compared to the ones on which only physisorption occurs. From the load dependence of the tribopolymerization yield, it was found that the surfaces capable of chemisorption give a smaller critical activation volume for the mechanochemical reaction, compared to the ones capable of physisorption only. On the basis of these observations and infrared spectroscopy analyses of the adsorbed molecules and the produced polymers, it was concluded that the mechanochemical reaction mechanisms might be different between chemically reactive and inert surfaces and that the chemical reactivity of the substrate surface greatly influences the tribochemical polymerization reactions of adsorbed molecules.

  16. Characterization of as-grown and adsorbate-covered N-polar InN surfaces using in situ photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Eisenhardt, Anja; Himmerlich, Marcel; Krischok, Stefan

    2012-01-01

    The surface electronic properties and adsorption behaviour of as-grown and oxidized N-polar InN films are characterized by photoelectron spectroscopy (XPS, UPS). The epitaxial growth of the InN layers was performed by plasma-assisted molecular beam epitaxy on GaN/6H-SiC(000-1). After growth and in situ characterization the InN surfaces were exposed to molecular oxygen to evaluate the adsorption behaviour of O 2 on N-polar InN and to study its impact on the surface electronic properties of the III-nitride material. The results are compared with studies on In-polar InN on GaN/sapphire templates. The as-grown N-polar InN surface exhibits a pronounced surface state at a binding energy of ∝1.6 eV. The valence band minimum lies about 0.8-1.0 eV below the surface Fermi level. Additionally, the XPS core level binding energies for InN(000-1) are reduced compared to InN(0001) films, indicating different surface band bending for clean N-polar and In-polar InN, respectively. The interaction of molecular oxygen with the InN(000-1) surface leads to a downward band bending by 0.1 eV compared to the initial state. Additional adsorption of species from the residual gas of the UHV chamber increases the surface downward band bending. Furthermore two pronounced oxygen related states with an energy distance of ∝5 eV could be detected in the valence band region. The adsorbed oxygen results in an additional component in the N1s core level spectra, which is interpreted as formation of NO x bonds. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Surface Photochemistry of Adsorbed Nitrate: The Role of Adsorbed Water in the Formation of Reduced Nitrogen Species on α-Fe2O3 Particle Surfaces

    NARCIS (Netherlands)

    Nanayakkara, C.E.; Jayaweera, P.M.; Rubasinghege, G; Baltrusaitis, Jonas; Grassian, V.H.

    2014-01-01

    The surface photochemistry of nitrate, formed from nitric acid adsorption, on hematite (α-Fe2O3) particle surfaces under different environmental conditions is investigated using X-ray photoelectron spectroscopy (XPS). Following exposure of α-Fe2O3 particle surfaces to gas-phase nitric acid, a peak

  18. Quasielastic neutron scattering and molecular dynamics simulation studies of the melting transition in butane and hexane monolayers adsorbed on graphite

    DEFF Research Database (Denmark)

    Hervig, K.W.; Wu, Z.; Dai, P.

    1997-01-01

    Quasielastic neutron scattering experiments and molecular dynamics (MD) simulations have been used to investigate molecular diffusive motion near the melting transition of monolayers of flexible rod-shaped molecules. The experiments were conducted on butane and hexane monolayers adsorbed...... comparison with experiment, quasielastic spectra calculated from the MD simulations were analyzed using the same models and fitting algorithms as for the neutron spectra. This combination of techniques gives a microscopic picture of the melting process in these two monolayers which is consistent with earlier...... neutron diffraction experiments. Butane melts abruptly to a liquid phase where the molecules in the trans conformation translationally diffuse while rotating about their center of mass. In the case of the hexane monolayer, the MD simulations show that the appearance of quasielastic scattering below T...

  19. Molecular Adsorbent Recirculating System Can Reduce Short-Term Mortality Among Patients With Acute-on-Chronic Liver Failure-A Retrospective Analysis.

    Science.gov (United States)

    Gerth, Hans U; Pohlen, Michele; Thölking, Gerold; Pavenstädt, Hermann; Brand, Marcus; Hüsing-Kabar, Anna; Wilms, Christian; Maschmeier, Miriam; Kabar, Iyad; Torner, Josep; Pavesi, Marco; Arroyo, Vicente; Banares, Rafael; Schmidt, Hartmut H J

    2017-10-01

    Acute-on-chronic liver failure is associated with numerous consecutive organ failures and a high short-term mortality rate. Molecular adsorbent recirculating system therapy has demonstrated beneficial effects on the distinct symptoms, but the associated mortality data remain controversial. Retrospective analysis of acute-on-chronic liver failure patients receiving either standard medical treatment or standard medical treatment and molecular adsorbent recirculating system. Secondary analysis of data from the prospective randomized Recompensation of Exacerbated Liver Insufficiency with Hyperbilirubinemia and/or Encephalopathy and/or Renal Failure trial by applying the recently introduced Chronic Liver Failure-criteria. Medical Departments of University Hospital Muenster (Germany). This analysis was conducted in two parts. First, 101 patients with acute-on-chronic liver failure grades 1-3 and Chronic Liver Failure-C-Organ Failure liver subscore equals to 3 but stable pulmonary function were identified and received either standard medical treatment (standard medical treatment, n = 54) or standard medical treatment and molecular adsorbent recirculating system (n = 47) at the University Hospital Muenster. Second, the results of this retrospective analysis were tested against the Recompensation of Exacerbated Liver Insufficiency with Hyperbilirubinemia and/or Encephalopathy and/or Renal Failure trial. Standard medical treatment and molecular adsorbent recirculating system. Additionally to improved laboratory variables (bilirubin and creatinine), the short-term mortality (up to day 14) of the molecular adsorbent recirculating system group was significantly reduced compared with standard medical treatment. A reduced 14-day mortality rate was observed in the molecular adsorbent recirculating system group (9.5% vs 50.0% with standard medical treatment; p = 0.004), especially in patients with multiple organ failure (acute-on-chronic liver failure grade 2-3). Concerning the

  20. Accelerator Analysis of Tributyltin Adsorbed onto the Surface of a Tributyltin Resistant Marine Pseudoalteromonas sp. Cell

    OpenAIRE

    Mimura, Haruo; Sato, Ryusei; Sasaki, Yu; Furuyama, Yuichi; Taniike, Akira; Yoshida, Kazutoshi; Kitamura, Akira

    2008-01-01

    Tributyltin (TBT) released into seawater from ship hulls is a stable marine pollutant and obviously remains in marine environments. We isolated a TBT resistant marine Pseudoalteromonas sp. TBT1 from sediment of a ship’s ballast water. The isolate (109.3 ± 0.2 colony-forming units mL-1) adsorbed TBT in proportion to the concentrations of TBTCl externally added up to 3 mM, where the number of TBT adsorbed by a single cell was estimated to be 108.2. The value was reduced to about one-fif...

  1. Surface modification of chromatography adsorbents by low temperature low pressure plasma

    DEFF Research Database (Denmark)

    Arpanaei, Ayyoob; Winther-Jensen, Bjørn; Theodosiou, E.

    2010-01-01

    In this study we show how low temperature glow discharge plasma can be used to prepare bi-layered chromatography adsorbents with non-adsorptive exteriors. The commercial strong anion exchange expanded bed chromatography matrix, Q HyperZ, was treated with plasmas in one of two general ways. Using ...

  2. Redox Potentials and Electronic States of Iron Porphyrin IX Adsorbed on Single Crystal Gold Electrode Surfaces

    DEFF Research Database (Denmark)

    Zhang, Ling; Kepp, Kasper P.; Ulstrup, Jens

    2018-01-01

    Metalloporphyrins are active sites in metalloproteins and synthetic catalysts. They have also been studied extensively by electrochemistry as well as being prominent targets in electrochemical scanning tunneling microscopy (STM). Previous studies of FePPIX adsorbed on graphite and alkylthiol modi...

  3. CD spectroscopy of proteins adsorbed at flat hydrophilic quartz and hydrophobic Teflon surfaces

    NARCIS (Netherlands)

    Vermeer, AWP; Norde, W

    2000-01-01

    Spectroscopic methods provide a powerful tool for studying the properties of proteins at interfaces. The protein accumulated in one adsorbed layer is frequently less than the minimum mass of protein required by a detection method. In such a case las is the case in circular dichroism spectroscopy)

  4. Density functional study of TaSin (n = 1-3, 12) clusters adsorbed to graphene surface

    International Nuclear Information System (INIS)

    Guo Ping; Zheng Lin; Zheng Jiming; Zhang Ruizhi; Yang Luna; Ren, Zhaoyu

    2011-01-01

    A plane-wave density functional theory (DFT) calculations have been performed to investigate structural and electronic properties of TaSi n (n = 1-3, 12) clusters supported by graphene surface. The resulting adsorption structures are described and discussed in terms of stability, bonding, and electron transfer between the cluster and the graphene. The TaSi n clusters on graphene surface favor their free-standing ground-state structures. Especially in the cases of the linear TaSi 2 and the planar TaSi 3 , the graphene surface may catalyze the transition of the TaSi n clusters from an isomer of lower dimensionality into the ground-state structure. The adsorption site and configuration of TaSi n on graphene surface are dominated by the interaction between Ta atom and graphene. Ta atom prefers to adsorb on the hollow site of graphene, and Si atoms tend to locate on the bridge site. Further, the electron transfer is found to proceed from the cluster to the surface for n = 1 and 2, while its direction reverses as n > 2. For the case of TaSi, chemisorption is shown to prevail over physisorption as the dominant mode of surface-adsorbate interaction by charge density analysis.

  5. Molecular sieve adsorbents and membranes for applications in the production of renewable fuels and chemicals

    Science.gov (United States)

    Ranjan, Rajiv

    Metal organic frameworks (MOF), a new class of porous materials, have emerged as promising candidate for gas storage, separation membrane and chemical sensors. We used secondary growth method to grow microporous metal organic framework (MMOF) films on porous alumina supports. Examination of the film using SEM and XRD showed that the crystals were well inter-grown and preferentially oriented. Gas permeation study showed that membranes were defect free and moderate selectivity was achieved for H2/N2 gas pairs. The next project had to do with ethanol production from lignocellulosic biomass as an alternate energy source. However, toxic inhibitors produced from the hydrolysis of biomass decrease ethanol yield during the fermentation process. We demonstrated the use of zeolites for the pretreatment of hydrolyzate in order to remove inhibitors like 5-Hydroxymethylfurfuraldehyde (HMF) and furfural from aqueous solution. Zeolites exhibit preferential adsorption of the inhibitors and in effect improve the ethanol yield during fermentation. Ideal Adsorbed Solution Theory (IAST) was also used to predict adsorption isotherms for HMF-furfural mixtures using single component adsorption data. We also studied production of HMF, a potential substitute as a building block for plastic and chemical production, from renewable biomass resources. Catalytic dehydration of fructose for HMF production faces problems like low conversion and yield. Dimethyl sulfoxide (DMSO) can be used as the solvent as well as the catalyst resulting in high HMF yield. We studied a reaction-separation system for this dehydration reaction where the product (HMF) could be recovered by selective adsorption on solid adsorbents from the reaction mixture.

  6. Modification of H2O adsorbed Si(100)-(2 x 1) surface by photon and electron beam

    International Nuclear Information System (INIS)

    Moon, S.W.; Chung, S.M.; Hwang, C.C.; Ihm, K.W.; Kang, T.-H.; Chen, C.H.; Park, C.-Y.

    2004-01-01

    Full text: Oxidation of silicon has been the subject of intense scientific and technological interest due to the several uses of thin oxide films as insulating layers in microelectronic devices. The great strides have been made in understanding about the formation and thermal evolution of the Si/SiO 2 interface. In this presentation, we provide synchrotron radiation photoemission spectroscopy (SRPES) and photoemission electron microscope (PEEM) results, showing how a H 2 O adsorbed Si(100) surface evolves into an ultra-thin silicon oxide m when exposed to monochromatized synchrotron radiation and electron beam at room temperature. All SRPES, PEEM experiments have been performed at the beam line, 4B1, of Pohang Light Source (PLS) in Korea. Water dissociates into OH(a) and H(a) species upon adsorption on the Si(100)-(2 - 1) at room temperature. The bonding (b 2 ) and antibonding (a 1 ) OH orbital and the oxygen lone pair orbital (b 1 ) from the dissociated OH and H species has been identified in ultraviolet photoemission spectra (UPS). These structures gradually changed and a new silicon oxide peak appeared with the photon/E-beam irradiation. This indicates that the H 2 O adsorbed on Si surface transforms into a thin silicon oxide film by photon/E-beam irradiation. We have shown in our PEEM images that one can make micro-patterns on silicon surface by using the photon induced surface modification. The fabricated patterns can be clearly identified through the inverse contrast images between photon exposed region and unexposed one. The near edge x-ray absorption fine structure (NEXAFS) results revealed that the OH adsorbed Si surface transforms into a thin silicon oxide film by photon irradiation

  7. [Adsorbent effect of activated carbon on small molecular uremic toxin and its influence factors].

    Science.gov (United States)

    Yang, Bo; Jiang, Yun-sheng; Li, Jun

    2003-06-01

    To analyze the adsorbent effect of activated carbon on uremic toxin and its influence factors. Uremic toxins (urea, creatinine and uric acid) were dissolved in the distilled water to obtain uremic toxic solution. Activated carbon was added to the solution, and the concentrations of uremic toxins were measured at different time spots. To determine the influence factors, some possible related materials, such as bile, amino acid, Ringer's, solution of glucose, HCl or NaOH respectively were added simultaneously. The concentrations of toxins in uremic toxic solution decreased 5 min after adding the activated carbon. The concentration of urea was the lowest at 30 min, but it increased after 50 min; while the concentrations of creatinine and uric acid reached the lowest level from 10 to 30 min after adding the activated carbon, and maintained at the same level after that. The bile, amino acid, electrolyte, glucose and pH value did not influence the adsorption of uric acid significantly, but they influenced the adsorption of urea and creatinine. Bile and amino acid influenced the concentration of urea remarkably, following glucose, NaOH and HCl. The effect of pH 2.0 solution on the creatinine concentration was the most significant, following glucose. Activated carbon has adsorptive effect on uremic toxins, but its adsorptive effect decreases as time goes on. Bile, glucose, amino acid, NaOH and HCl can affect the adsorptive effect of activated carbon on uremic toxins to some extent.

  8. A Solid-State Deuterium NMR and SFG Study of the Side Chain Dynamics of Peptides Adsorbed onto Surfaces

    Science.gov (United States)

    Breen, Nicholas F.; Weidner, Tobias; Li, Kun; Castner, David G.; Drobny, Gary P.

    2011-01-01

    The artificial amphiphilic peptide LKα14 adopts a helical structure at interfaces, with opposite orientation of its leucine (L, hydrophobic) and lysine (K, hydrophilic) side chains. When adsorbed onto surfaces, different residue side chains necessarily have different proximities to the surface, depending on both their position in the helix and the composition of the surface itself. Deuterating the individual leucine residues (isopropyl-d7) permits the use of solid-state deuterium NMR as a site-specific probe of side chain dynamics. In conjunction with SFG as a probe of the peptide binding face, we demonstrate that the mobility of specific leucine side chains at the interface is quantifiable in terms of their surface proximity. PMID:19764755

  9. High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Volkmann, U.G.; Pino, M.; Altamirano, L.A.

    2002-01-01

    -crystal substrates. Our results suggest a model of a solid dotriacontane film that has a phase closest to the SiO2 surface in which the long-axis of the molecules is oriented parallel to the interface. Above this "parallel film" phase, a solid monolayer adsorbs in which the molecules are oriented perpendicular...... at higher coverages. In addition, we have performed high-resolution ellipsometry and stray-light measurements on dotriacontane films deposited from solution onto highly oriented pyrolytic graphite substrates. After film deposition, these substrates proved to be less stable in air than SiO2....

  10. A simple method for the preparation of difficult 99mTc complexes using surface adsorbed stannous ions

    International Nuclear Information System (INIS)

    Maddalena, D.J.; Snowdon, G.M.; Pojer, P.M.

    1987-01-01

    A simple new technique where stannous tin is adsorbed on the inner surface of plastic tubing and used to reduce ( 99m Tc) pertechnetate prior to labelling radiopharmaceuticals, has been evaluated, using some lipophillic and metal containing ligands. Complexes formed using the technique had good labelling efficiency and behaved the same in rat biodistribution studies as those prepared using conventional labelling methods. The labelling efficiency of the ligands was not related to their lipophillicity suggesting that this technique may be useful for labelling lipophillic and other difficult ligands such as those containing metals, which are incompatible with free stannous ions in solution. (M.E.L.) [es

  11. Surface and adsorbate structural studies by photoemission in the hν = 50-500 eV range

    International Nuclear Information System (INIS)

    Shirley, D.A.

    1979-08-01

    The present status of photoelectron spectroscopy in the 50-500 eV range is discussed in relation to its application to surface science. Instrumentation aspects of synchrotron radiation sources are reviewed. The direct transition model is shown to be applicable in this range with some limitations. Cooper minima and adsorbate sensitivity enhancement for hν > 100 eV are reviewed. A new effect--condensed phase photoelectron asymmetry--is noted. Finally, photoelectron diffraction - another new effect - is described and evaluated

  12. Reaction of Br2 with adsorbed CO on Pt, studied by the surface interrogation mode of scanning electrochemical microscopy.

    Science.gov (United States)

    Wang, Qian; Rodríguez-López, Joaquín; Bard, Allen J

    2009-12-02

    Scanning electrochemical microscopy surface interrogation (SI-SECM) in the cyclic voltammetry mode was successfully used to detect and quantify adsorbed CO on a Pt electrode by reaction with electrogenerated Br(2). The two-electrode setup used in this new technique allowed the production of Br(2) on an interrogator tip, which reported a transient positive feedback above a Pt substrate at open circuit as an indication of the reactivity of this halogen with CO((ads)). Br(-) and CO(2) are shown to be the main products of the reaction (in the absence of O(2)), which may involve the formation of bromophosgene as a hydrolyzable intermediate. Under saturation conditions, CO((ads)) was reproducibly quantified at the polycrystalline Pt surface with theta(CO) approximately = 0.5. The reaction is shown to be blocked by the action of pre-adsorbed cyanide, which demonstrates the surface character of the process. The formation of CO(2) as an end product was further tested in a bulk experiment: addition of Pt black to a mixture of Br(2) in 0.5 M H(2)SO(4) through which CO was bubbled gave a precipitate of BaCO(3) in a saturated solution of Ba(OH)(2). The use of SI-SECM allowed access to a reaction that would otherwise be difficult to prove through conventional electrochemistry on a single electrode.

  13. Scanning tunneling microscopy I general principles and applications to clean and adsorbate-covered surfaces

    CERN Document Server

    Wiesendanger, Roland

    1992-01-01

    Scanning Tunneling Microscopy I provides a unique introduction to a novel and fascinating technique that produces beautiful images of nature on an atomic scale. It is the first of three volumes that together offer a comprehensive treatment of scanning tunneling microscopy, its diverse applications, and its theoretical treatment. In this volume the reader will find a detailed description of the technique itself and of its applications to metals, semiconductors, layered materials, adsorbed molecules and superconductors. In addition to the many representative results reviewed, extensive references to original work will help to make accessible the vast body of knowledge already accumulated in this field.

  14. The Use of the Molecular Adsorber Coating Technology to Mitigate Vacuum Chamber Contamination During Pathfinder Testing for the James Webb Space Telescope

    Science.gov (United States)

    Abraham, Nithin S.; Hasegawa, Mark M.; Wooldridge, Eve M.; Henderson-Nelson, Kelly A.

    2016-01-01

    As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground based space applications, in particular, for vacuum chamber environments. This paper describes the recent use of the MAC technology during Pathfinder testing of the Optical Ground Support Equipment (OGSE) for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap persistent outgassed contaminants, specifically silicone based diffusion pump oil, from within JSC's cryogenic optical vacuum chamber test facility called Chamber A. This paper summarizes the sample fabrication, installation, laboratory testing, post-test chemical analysis results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination.

  15. Charge transfer dynamics from adsorbates to surfaces with single active electron and configuration interaction based approaches

    Energy Technology Data Exchange (ETDEWEB)

    Ramakrishnan, Raghunathan, E-mail: r.ramakrishnan@unibas.ch [Institute of Physical Chemistry, National Center for Computational Design and Discovery of Novel Materials (MARVEL), Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland); Nest, Mathias [Theoretische Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany)

    2015-01-13

    Highlights: • We model electron dynamics across cyano alkanethiolates attached to gold cluster. • We present electron transfer time scales from TD-DFT and TD-CI based simulations. • Both DFT and CI methods qualitatively predict the trend in time scales. • TD-CI predicts the experimental relative time scale very accurately. - Abstract: We employ wavepacket simulations based on many-body time-dependent configuration interaction (TD-CI), and single active electron theories, to predict the ultrafast molecule/metal electron transfer time scales, in cyano alkanethiolates bonded to model gold clusters. The initial states represent two excited states where a valence electron is promoted to one of the two virtual π{sup ∗} molecular orbitals localized on the cyanide fragment. The ratio of the two time scales indicate the efficiency of one charge transfer channel over the other. In both our one-and many-electron simulations, this ratio agree qualitatively with each other as well as with the previously reported experimental time scales (Blobner et al., 2012), measured for a macroscopic metal surface. We study the effect of cluster size and the description of electron correlation on the charge transfer process.

  16. Nano-nitride cathode catalysts of Ti, Ta, and Nb for polymer electrolyte fuel cells: Temperature-programmed desorption investigation of molecularly adsorbed oxygen at low temperature

    KAUST Repository

    Ohnishi, Ryohji; Takanabe, Kazuhiro; Katayama, Masao; Kubota, Jun; Domen, Kazunari

    2013-01-01

    -programmed desorption (TPD) of molecularly adsorbed O2 at 120-170 K from these nanoparticles was examined, and the resulting amount and temperature of desorption were key factors determining the ORR activity. The size-dependent TiN nanoparticles (5-8 and 100 nm) were

  17. Formation of a Molecular Wire Using the Chemically Adsorbed Monomolecular Layer Having Pyrrolyl Groups

    Directory of Open Access Journals (Sweden)

    Kazufumi Ogawa

    2011-01-01

    Full Text Available A molecular wire containing polypyrrolyl conjugate bonds has been prepared by a chemical adsorption technique using 1,1,1-trichloro-12-pyrrolyl-1-siladodecane (PNN and an electrooxidative polymerization technique, and the conductivity of the molecular wire without any dopant has been measured by using AFM/STM at room temperature. When sample dimension measured was about 0.3 nm (thickness of the conductive portion in the PNN monomolecular layer ×100 μm (the average width of an electric path ×2 mm (the distance between Pt positive electrode and the AFM tip covered with Au, the conductivity of the polymerized PNN molecular wire at room temperature was larger than 1.6 × 105 S/cm both in an atmosphere and in a vacuum chamber of 10−5 Torr. The activation energy obtained by Arrhenius' plots was almost zero in the temperature range between 320 and 450 K.

  18. 分子吸着グラフェンの電子構造におけるOF MOLECULAR ADSORBED GRAPHENE

    OpenAIRE

    梅原, 太一

    2016-01-01

    The charge transfer phenomena in molecular adsorbed graphene were investigated in terms of the effect of the presence of water molecules, where electronic properties were evaluated by electric conductivity measurement and Raman spectroscopy. Charge transfer in the molecular adsorption on graphene was found to proceed in electrochemical mechanism. Furthermore, the presence of water was revealed to play an important role in the electrochemical processes in the charge transfer phenomena induced...

  19. Work function dependence and isotope effect in the production of negative hydrogen ions during sputtering of adsorbed hydrogen on Cs covered Mo(100) surfaces

    International Nuclear Information System (INIS)

    Yu, M.L.

    1977-01-01

    The enhancement of the H - yield, during sputtering of adsorbed hydrogen on a Mo(100) surface, by a Cs overlayer was investigated. An exponential dependence of the H - yield on the work function was observed for a wide range of Cs coverages. A simple electron tunneling model was proposed. A large reduction in the ion yield was also observed when D 2 replaced H 2 as the adsorbate

  20. Theory of ortho-para conversion in hydrogen adsorbed on metal and paramagnetic surfaces at low temperatures

    International Nuclear Information System (INIS)

    Yucel, S.

    1989-01-01

    In order to explain the experimental results on Cu(100), Ag(111), Ag thin films, graphite, and H 2 bubbles in Cu, the ortho-para conversion rates of H 2 and D 2 adsorbed on metal and paramagnetic surfaces at low temperatures have been considered. The conversion rates due to magnetic dipole-dipole, Fermi contact, and spin-orbit interaction between the conduction electrons, and nuclear spins of H 2 (D 2 ) are calculated to elucidate the role of the metal surface. Although the rates on clean metal surfaces are found to be too slow to account for the observed rates on Ag, they may explain the catalytic conversion on H 2 bubble surfaces at 1.3 K. Additionally, effects of impurities and defects on the surface are investigated by calculating the conversion rate in two-dimensional solid D 2 (H 2 ) by emission of one (two) phonon(s). Fast conversion rates observed on Ag and graphite surfaces as well as on the surfaces of H 2 bubbles may be accounted for by paramagnetic impurities or defects. On Grafoil, both in (√3 x √3)R30 0 commensurate and incommensurate solid phase, a temperature-independent conversion rate is predicted if the mobility of the molecules is high enough to prevent concentration gradients

  1. A periodic mixed gaussians-plane waves DFT study on simple thiols on Au(111): adsorbate species, surface reconstruction, and thiols functionalization.

    Science.gov (United States)

    Rajaraman, Gopalan; Caneschi, Andrea; Gatteschi, Dante; Totti, Federico

    2011-03-07

    Here we present DFT calculations based on a periodic mixed gaussians/plane waves approach to study the energetics, structure, bonding of SAMs of simple thiols on Au(111). Several open issues such as structure, bonding and the nature of adsorbate are taken into account. We started with methyl thiols (MeSH) on Au(111) to establish the nature of the adsorbate. We have considered several structural models embracing the reconstructed surface scenario along with the MeS˙-Au(ad)-MeS˙ type motif put forward in recent years. Our calculations suggest a clear preference for the homolytic cleavage of the S-H bond leading to a stable MeS˙ on a gold surface. In agreement with the recent literature studies, the reconstructed models of the MeS˙ species are found to be energetically preferred over unreconstructed models. Besides, our calculations reveal that the model with 1:2 Au(ad)/thiols ratio, i.e. MeS˙-Au(ad)-MeS˙, is energetically preferred compared to the clean and 1:1 ratio models, in agreement with the experimental and theoretical evidences. We have also performed Molecular Orbital/Natural Bond Orbital, MO/NBO, analysis to understand the electronic structure and bonding in different structural motifs and many useful insights have been gained. Finally, the studies have then been extended to alkyl thiols of the RSR' (R, R' = Me, Et and Ph) type and here our calculations again reveal a preference for the RS˙ type species adsorption for clean as well as for reconstructed 1:2 Au(ad)/thiols ratio models.

  2. Learning surface molecular structures via machine vision

    Science.gov (United States)

    Ziatdinov, Maxim; Maksov, Artem; Kalinin, Sergei V.

    2017-08-01

    Recent advances in high resolution scanning transmission electron and scanning probe microscopies have allowed researchers to perform measurements of materials structural parameters and functional properties in real space with a picometre precision. In many technologically relevant atomic and/or molecular systems, however, the information of interest is distributed spatially in a non-uniform manner and may have a complex multi-dimensional nature. One of the critical issues, therefore, lies in being able to accurately identify (`read out') all the individual building blocks in different atomic/molecular architectures, as well as more complex patterns that these blocks may form, on a scale of hundreds and thousands of individual atomic/molecular units. Here we employ machine vision to read and recognize complex molecular assemblies on surfaces. Specifically, we combine Markov random field model and convolutional neural networks to classify structural and rotational states of all individual building blocks in molecular assembly on the metallic surface visualized in high-resolution scanning tunneling microscopy measurements. We show how the obtained full decoding of the system allows us to directly construct a pair density function—a centerpiece in analysis of disorder-property relationship paradigm—as well as to analyze spatial correlations between multiple order parameters at the nanoscale, and elucidate reaction pathway involving molecular conformation changes. The method represents a significant shift in our way of analyzing atomic and/or molecular resolved microscopic images and can be applied to variety of other microscopic measurements of structural, electronic, and magnetic orders in different condensed matter systems.

  3. Synthesis of low-cost adsorbent from rice bran for the removal of reactive dye based on the response surface methodology

    Science.gov (United States)

    Hong, Gui-Bing; Wang, Yi-Kai

    2017-11-01

    Rice bran is a major by-product of the rice milling industry and is abundant in Taiwan. This study proposed a simple method for modifying rice bran to make it a low-cost adsorbent to remove reactive blue 4 (RB4) from aqueous solutions. The effects of independent variables such as dye concentration (100-500 ppm), adsorbent dosage (20-120 mg) and temperature (30-60 °C) on the dye adsorption capacity of the modified rice bran adsorbent were investigated by using the response surface methodology (RSM). The results showed that the dye maximum adsorption capacity of the modified rice bran adsorbent was 151.3 mg g-1 with respect to a dye concentration of 500 ppm, adsorbent dosage of 65.36 mg, and temperature of 60 °C. The adsorption kinetics data followed the pseudo-second-order kinetic model, and the isotherm data fit the Langmuir isotherm model well. The maximum monolayer adsorption capacity was 178.57-185.19 mg g-1, which was comparable to that of other agricultural waste adsorbents used to remove RB4 from aqueous solutions in the literature. The thermodynamics analysis results indicated that the adsorption of RB4 onto the modified rice bran adsorbent is an endothermic, spontaneous monolayer adsorption that occurs through a physical process.

  4. Mapping the Diffusion Potential of a Reconstructed Au(111) Surface at Nanometer Scale with 2D Molecular Gas

    International Nuclear Information System (INIS)

    Yan Shi-Chao; Xie Nan; Gong Hui-Qi; Guo Yang; Shan Xin-Yan; Lu Xing-Hua; Sun Qian

    2012-01-01

    The adsorption and diffusion behaviors of benzene molecules on an Au(111) surface are investigated by low-temperature scanning tunneling microscopy. A herringbone surface reconstruction of the Au(111) surface is imaged with atomic resolution, and significantly different behaviors are observed for benzene molecules adsorbed on step edges and terraces. The electric field induced modification in the molecular diffusion potential is revealed with a 2D molecular gas model, and a new method is developed to map the diffusion potential over the reconstructed Au(111) surface at the nanometer scale. (condensed matter: structure, mechanical and thermal properties)

  5. Transporting method for adsorbing tower and the adsorbing tower

    International Nuclear Information System (INIS)

    Shimokawa, Nobuhiro.

    1996-01-01

    A cylindrical plastic bag is disposed to the upper surface of an adsorbing tower so as to surround a suspending piece. One opening of the bag is sealed, and other opening is secured in a sealed state to a bag holding portion disposed to glove box at a gate for the adsorbing tower box. The adsorbing tower is transported into the glove box, and after the completion of the operation of the adsorbing tower, the adsorbing tower is taken out in a state that the bag is restricted and sealed at a portion below the adsorbing tower. The bag may be made of a vinyl plastic, the bag holding portion may be a short-cylindrical protrusion, and may have an O-ring groove at the outer surface. Even if the adsorbing tower is heavy, the adsorbing tower can be carried out easily in a state where it is sealed gas tightly. (N.H.)

  6. In situ evaluation of density, viscosity, and thickness of adsorbed soft layers by combined surface acoustic wave and surface plasmon resonance.

    Science.gov (United States)

    Francis, Laurent A; Friedt, Jean-Michel; Zhou, Cheng; Bertrand, Patrick

    2006-06-15

    We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the waveguide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40 degrees C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.

  7. Site-discrimination by molecular imposters at dissymmetric molecular crystal surfaces

    Science.gov (United States)

    Poloni, Laura N.

    incorporation at dissymmetric surfaces because their morphology is dominated by dissymmetric {101} growth faces. Growth processes on the dissymmetric (101) surfaces of these crystalline systems were investigated using metadynamics simulations to determine the free energy of adsorption for solute and impurity attachment to different flat, stepped, and kinked (101) surface terminations. Results suggest that growth occurs via a non-Kossel crystal growth mechanism, and highlights the need for dissymmetric surface structures (i.e. steps and kinks) for a higher fidelity in the orientation of adsorbed molecules. Overall, the results presented in this thesis suggest that growth of molecular crystals, particularly at dissymmetric surfaces, is complex and requires the combination of several experimental and computational techniques to decipher the mechanisms responsible for growth phenomena. The use of molecular imposters to inhibit growth can be useful for the development of therapeutics for pathological crystals, but can also inform processes by which crystal growth occurs at complex surfaces as a result of their site selectivity.

  8. Adsorption of human serum albumin: Dependence on molecular architecture of the oppositely charged surface

    Science.gov (United States)

    Sukhishvili, Svetlana A.; Granick, Steve

    1999-05-01

    We contrast the adsorption of human serum albumin (HSA) onto two solid substrates previously primed with the same polyelectrolyte of net opposite charge to form one of two alternative structures: randomly adsorbed polymer and the "brush" configuration. These structures were formed either by the adsorption of quaternized poly-4-vinylpyridine (QPVP) or by end-grafting QPVP chains of the same chemical makeup and the same molecular weight to surfaces onto which QPVP segments did not adsorb. The adsorption of HSA was quantified by using Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). The two substrates showed striking differences with regard to HSA adsorption. First, the brush substrate induced lesser perturbations in the secondary structure of the adsorbed HSA, reflecting easier conformational adjustment for longer free segments of polyelectrolyte upon binding with the protein. Second, the penetration of HSA into the brush substrate was kinetically retarded relative to the randomly adsorbed polymer, probably due to both pore size restriction and electrostatic sticking between charged groups of HSA and QPVP molecules. Third, release of HSA from the adsorbed layer, as the ionic strength was increased from a low level up to the high level of 1 M NaCl, was largely inhibited for the brush substrate, but occurred easily and rapidly for the substrate with statistically adsorbed QPVP chains. Finally, even after addition of a strong polymeric adsorption competitor (sodium polystyrene sulfonate), HSA remained trapped within a brush substrate though it desorbed slowly from the preadsorbed QPVP layer. This method to produce irreversible trapping of the protein within a brush substrate without major conformational change may find application in biosensor design.

  9. Adsorbate induced surface alloy formation investigated by near ambient pressure X-ray photoelectron spectroscopy

    DEFF Research Database (Denmark)

    Nierhoff, Anders Ulrik Fregerslev; Conradsen, Christian Nagstrup; McCarthy, David Norman

    2014-01-01

    for engineering of more active or selective catalyst materials. Dynamical surface changes on alloy surfaces due to the adsorption of reactants in high gas pressures are challenging to investigate using standard characterization tools. Here we apply synchrotron illuminated near ambient pressure X-ray photoelectron...

  10. Ultra violet photoemission studies of CO2 and NO adsorbed on W(100) surface

    International Nuclear Information System (INIS)

    Bhattacharya, A.K.; Broughton, J.Q.; Perry, D.L.

    1978-01-01

    In the last few years ultra violet photoelectron spectroscopy (UPS) has been successfully empolyed to determine the nature and bonding of the species formed when gases absorb on metal surfaces. This information is necessary to understand the mechanism of hetergeneous catalysis. The present report deals with UPS investigation of the chemisorption of CO 2 and NO on a W(100) surface. (Auth.)

  11. Nano-indentation at the surface contact level: applying a harmonic frequency for measuring contact stiffness of self-assembled monolayers adsorbed on Au

    International Nuclear Information System (INIS)

    Chang, C.-W.; Liao, J.-D.

    2008-01-01

    In this study, the well-ordered alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths and tail groups were employed as examples for nano-characterization on their mechanical properties. A novel nano-indentation technique with a constant harmonic frequency was applied on SAMs chemically adsorbed on Au to explore their contact mechanics, and furthermore to interpret how SAM molecules respond to an infinitesimal oscillation force without pressing them. Experimental results demonstrated that the harmonic contact stiffness along with the measured displacement of SAMs/Au was distinguishable using a dynamic contact modulus with the distinct feature of phase angles. Phase angles resulted from the relaxing continuation of an applied harmonic frequency and mostly influenced by the outermost tail group of SAM molecules. The harmonic contact stiffness of SAM molecules obviously increased with the densely packed alkyl chains and relatively intense agglomeration of the head group at the anchoring site. As a consequence, the result of this work is relevant to contact mechanics at the surface contact level for the distinction of molecular substances attached on a solid surface. Furthermore it is particularly anticipated to identify biological molecules of variable qualities under a fluid-like micro-environment

  12. Nano-indentation at the surface contact level: applying a harmonic frequency for measuring contact stiffness of self-assembled monolayers adsorbed on Au

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.-W.; Liao, J.-D. [Department of Materials Science and Engineering, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan (China)], E-mail: jdliao@mail.ncku.edu.tw

    2008-08-06

    In this study, the well-ordered alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths and tail groups were employed as examples for nano-characterization on their mechanical properties. A novel nano-indentation technique with a constant harmonic frequency was applied on SAMs chemically adsorbed on Au to explore their contact mechanics, and furthermore to interpret how SAM molecules respond to an infinitesimal oscillation force without pressing them. Experimental results demonstrated that the harmonic contact stiffness along with the measured displacement of SAMs/Au was distinguishable using a dynamic contact modulus with the distinct feature of phase angles. Phase angles resulted from the relaxing continuation of an applied harmonic frequency and mostly influenced by the outermost tail group of SAM molecules. The harmonic contact stiffness of SAM molecules obviously increased with the densely packed alkyl chains and relatively intense agglomeration of the head group at the anchoring site. As a consequence, the result of this work is relevant to contact mechanics at the surface contact level for the distinction of molecular substances attached on a solid surface. Furthermore it is particularly anticipated to identify biological molecules of variable qualities under a fluid-like micro-environment.

  13. Shotgun proteomic analytical approach for studying proteins adsorbed onto liposome surface

    KAUST Repository

    Capriotti, Anna Laura; Caracciolo, Giulio; Cavaliere, Chiara; Crescenzi, Carlo; Pozzi, Daniela; Laganà , Aldo

    2011-01-01

    The knowledge about the interaction between plasma proteins and nanocarriers employed for in vivo delivery is fundamental to understand their biodistribution. Protein adsorption onto nanoparticle surface (protein corona) is strongly affected

  14. Photoionization of rhodamine dyes adsorbed at the aqueous solution surfaces investigated by synchrotron radiation

    International Nuclear Information System (INIS)

    Seno, Koichiro; Ishioka, Toshio; Harata, Akira; Hatano, Yoshihiko

    2002-01-01

    Photoionization spectroscopy using synchrotron radiation as a photon source was applied to the aqueous solution surfaces of rhodamine B (RhB), rhodamine 6G (Rh6G), and rhodamine 101 (Rh101) with their concentration of 0-100 μmol dm -3 . Synchrotron radiation was irradiated upon the solution surface between two electrodes in the photon energy range of 4-7 eV, and photoionization current was measured by a pico-ammeter. The photocurrent for each of the rhodamine aqueous solution surface showed an increase with the photon energy above a threshold photon energy. The photoionization threshold of RhB at the aqueous solution surface was 5.6 eV, which was smaller than that in the gas phase. The intensity of photoionization current of Rh6G was smaller than that of RhB or Rh101. Photoionization processes and the state of Rhodamine dye molecules at the aqueous solution surface were discussed in connection with results of surface tension measurements. (author)

  15. The inter-adsorbate interaction mediated by Shockley-type surface state electrons and dipole moment: Cs and Ba atoms absorbed on Ag (1 1 1) films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shuyuan [College of Physical Science and Technology, Sichuan University, Chengdu 610065 (China); Zhang, Hong, E-mail: hongzhang@scu.edu.cn [College of Physical Science and Technology, Sichuan University, Chengdu 610065 (China); Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Miyamoto, Yoshiyuki [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan)

    2014-01-15

    Through first-principles investigation, we display the formation process of Shockley-type surface states which emerges on silver thin films along Ag (1 1 1) orientation with increasing thicknesses from 6 to 21 layers. We look at the surface state band for various adatoms adsorbed on 6, 12, 18 layers strained Ag (1 1 1) films with different coverage, and discuss the long range interaction mediated by surface state electrons. We discovered that film's thickness can modulate the surface state mediated interaction drastically, but the dipole–dipole repulsive interaction is not affected by slab thickness. This factor had never been discussed in detail. Therefore, adatoms adsorbed on thin films have strong attractive interaction which leads to small adsorption separation and the tendency of island formation. For different coverage or different adsorbate types, both surface states and dipole moment are modulated. The three factors, film's thickness, adsorbate coverage and adatoms types, could help us learn more about the interactions between adatoms and exploit advanced ways to control surface geometry structures of self-assembly.

  16. The inter-adsorbate interaction mediated by Shockley-type surface state electrons and dipole moment: Cs and Ba atoms absorbed on Ag (1 1 1) films

    International Nuclear Information System (INIS)

    Zhang, Shuyuan; Zhang, Hong; Miyamoto, Yoshiyuki

    2014-01-01

    Through first-principles investigation, we display the formation process of Shockley-type surface states which emerges on silver thin films along Ag (1 1 1) orientation with increasing thicknesses from 6 to 21 layers. We look at the surface state band for various adatoms adsorbed on 6, 12, 18 layers strained Ag (1 1 1) films with different coverage, and discuss the long range interaction mediated by surface state electrons. We discovered that film's thickness can modulate the surface state mediated interaction drastically, but the dipole–dipole repulsive interaction is not affected by slab thickness. This factor had never been discussed in detail. Therefore, adatoms adsorbed on thin films have strong attractive interaction which leads to small adsorption separation and the tendency of island formation. For different coverage or different adsorbate types, both surface states and dipole moment are modulated. The three factors, film's thickness, adsorbate coverage and adatoms types, could help us learn more about the interactions between adatoms and exploit advanced ways to control surface geometry structures of self-assembly.

  17. Molecular dynamics study of room temperature ionic liquids with water at mica surface

    Directory of Open Access Journals (Sweden)

    Huanhuan Zhang

    2018-04-01

    Full Text Available Water in room temperature ionic liquids (RTILs could impose significant effects on their interfacial properties at a charged surface. Although the interfaces between RTILs and mica surfaces exhibit rich microstructure, the influence of water content on such interfaces is little understood, in particular, considering the fact that RTILs are always associated with water due to their hygroscopicity. In this work, we studied how different types of RTILs and different amounts of water molecules affect the RTIL-mica interfaces, especially the water distribution at mica surfaces, using molecular dynamics (MD simulation. MD results showed that (1 there is more water and a thicker water layer adsorbed on the mica surface as the water content increases, and correspondingly the average location of K+ ions is farther from mica surface; (2 more water accumulated at the interface with the hydrophobic [Emim][TFSI] than in case of the hydrophilic [Emim][BF4] due to the respective RTIL hydrophobicity and ion size. A similar trend was also observed in the hydrogen bonds formed between water molecules. Moreover, the 2D number density map of adsorbed water revealed that the high-density areas of water seem to be related to K+ ions and silicon/aluminum atoms on mica surface. These results are of great importance to understand the effects of hydrophobicity/hydrophicility of RTIL and water on the interfacial microstructure at electrified surfaces. Keywords: Room temperature ionic liquids, Hydrophobicity/hydrophicility, Water content, Electrical double layer, Mica surface

  18. Addition of Molecular Adsorbent Recirculating System (MARS® Albumin Dialysis for the Preoperative Management of Jaundiced Patients with Hilar Cholangiocarcinoma

    Directory of Open Access Journals (Sweden)

    Jean-Marc Regimbeau

    2013-09-01

    Full Text Available The preoperative management of hilar cholangiocarcinoma (HC with jaundice focuses on decreasing the total serum bilirubin level (SBL by performing preoperative biliary drainage (PBD. However, it takes about 6-8 weeks for the SBL to fall at a sufficient extent. The objective of this preliminary study was to evaluate the impact of Molecular Adsorbent Recirculating System (MARS® dialysis (in association with PBD on SBL decrease. From January 2010 to January 2011, we prospectively selected all jaundiced patients admitted to our university hospital for resectable HC and requiring PBD prior to major hepatectomy. The PBD was followed by 3 sessions of MARS dialysis over a period of 72 h. A total of 10 patients with HC were screened and two of them were included (Bismuth-Corlette stage IIIa, gender ratio 1, median age 68 years. The initial SBL in the two patients was 328 and 242 μmol/l, respectively. After three MARS dialysis sessions, the SBL had fallen by 30 and 52%, respectively. After the end of each session, there was a SBL rebound of about 10 μmol/l. The MARS decreased the serum creatinine level, the platelet count and the prothrombin index, but did not modify the serum albumin level. Pruritus disappeared after one and two sessions, respectively. MARS-related morbidity included hypotension (n = 1, tachycardia (n = 1, thrombocytopenia (n = 2 and anaemia (n = 1. When combined with PBD, MARS dialysis appears to accelerate the decrease in SBL and thus may enable earlier surgery. This hypothesis must be validated in a larger study.

  19. Quantum chemical molecular dynamical investigation of alkyl nitrite photo-dissociated on copper surfaces

    International Nuclear Information System (INIS)

    Wang Xiaojing; Wang Wei; Han Peilin; Kubo, Momoji; Miyamoto, Akira

    2008-01-01

    An accelerated quantum chemical molecular dynamical code 'Colors-Excite' was used to investigate the photolysis of alkyl nitrites series, RONO (R=CH 3 and C(CH 3 ) 3 ) on copper surfaces. Our calculations showed that the photo-dissociated processes are associated with the alkyl substituents of RONO when adsorbed on copper surfaces. For R=CH 3 , a two-step photolysis reaction occurred, yielding diverse intermediate products including RO radical, NO, and HNO, consistent with those reported in gas phase. While for R=C(CH 3 ) 3 , only one-step photolysis reaction occurred and gave intermediate products of RO radical and NO. Consequently, pure RO species were achieved to adsorb on metal surfaces by removing the NO species in photolysis reaction. The detailed photo-dissociated behaviors of RONO on copper surfaces with different alkyl substituents which are uncovered by the present simulation can be extended to explain the diverse dissociative mechanism experimentally observed. The quantum chemical molecular dynamical code 'Colors-Excite' is proved to be highly applicable to the photo-dissociations on metal surfaces

  20. C,N-bipyrazole receptor grafted onto a porous silica surface as a novel adsorbent based polymer hybrid.

    Science.gov (United States)

    Radi, Smaail; Attayibat, Ahmed; El-Massaoudi, Mohamed; Bacquet, Maryse; Jodeh, Shehdeh; Warad, Ismail; Al-Showiman, Salim S; Mabkhot, Yahia N

    2015-10-01

    A simple heterogeneous synthesis of pure adsorbent based polymer hybrid made by condensing a functionalized C,N-bipyrazole with a 3-glycidoxypropyl-trimethoxysilane silylant agent, previously anchored on a silica surface was developed. The formed material (SG2P) was characterized through elemental analysis, FT-IR spectroscopy, (13)C NMR of solid state, scanning electron microscope (SEM), and was studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and B.J.H. pore sizes. The new material exhibits good thermal stability determined by thermogravimetry curves and good chemical stability was examined in various acidic and buffer solutions (pH 1-7). The binding and adsorption abilities of SG2P were investigated for Hg(2+), Cd(2+), Pb(2+), Zn(2+), K(+), Na(+) and Li(+) cations and compared to the results of classical liquid-liquid extraction with the unbound C,N-bipyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the SG2P exhibits a high selectivity toward Hg(2+) ion with no complexation being observed towards zinc and alkali metals. The extracted and the complexing cation percentages were determined by atomic absorption measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Temperature and magnetic field dependence of the Yosida-Kondo resonance for a single magnetic atom adsorbed on a surface

    International Nuclear Information System (INIS)

    Dino, Wilson Agerico; Kasai, Hideaki; Rodulfo, Emmanuel Tapas; Nishi, Mayuko

    2006-01-01

    Manifestations of the Kondo effect on an atomic length scale on and around a magnetic atom adsorbed on a nonmagnetic surface differ depending on the spectroscopic mode of operation of the scanning tunneling microscope. Two prominent signatures of the Kondo effect that can be observed at surfaces are the development of a sharp resonance (Yosida-Kondo resonance) at the Fermi level, which broadens with increasing temperature, and the splitting of this sharp resonance upon application of an external magnetic field. Until recently, observing the temperature and magnetic field dependence has been a challenge, because the experimental conditions strongly depend on the system's critical temperature, the so-called Kondo temperature T K . In order to clearly observe the temperature dependence, one needs to choose a system with a large T K . One can thus perform the experiments at temperatures T K . However, because the applied external magnetic field necessary to observe the magnetic field dependence scales with T K , one needs to choose a system with a very small T K . This in turn means that one should perform the experiments at very low temperatures, e.g., in the mK range. Here we discuss the temperature and magnetic field dependence of the Yosida-Kondo resonance for a single magnetic atom on a metal surface, in relation to recent experimental developments

  2. Ion-beam crystallography of clean and adsorbate covered metal surfaces

    International Nuclear Information System (INIS)

    Veen, J.F. van der.

    1978-01-01

    This thesis deals with the precise determination of atomic positions in the very first layer of a single-crystal surface. The technique of medium energy ion scattering in conjunction with channeling and blocking is used. The principle of this method is based on simple shadowing and blocking effects and relies on geometrical considerations only. (Auth.)

  3. Atomistic simulation study of the interaction of organic adsorbates with fluorapatite surfaces

    CSIR Research Space (South Africa)

    Mkhonto, D

    2006-04-01

    Full Text Available MMM 2006 UL Methodology Block I Block II surface •Region I : ions relaxed •Region II : ions kept at bulk equilibrium position } } Metadise program • Static lattice minimisation technique • Forces between species described by potential model... + - + - + - + - + - - + - + - + - + - + + - + - + - + - + - - + - + - + - + - + + - + - + - + - + - - + - + - + - + - + + - + - + - + - + - - + - + - + - + - + + - + - + - + - + - - + - + - + - + - + + - + - + - + - + - - + - + - + - + - + + - + - + - + - + - - + - + - + - + - + Region II Region I Region I Region II interface...

  4. Surface speciation and interactions between adsorbed chloride and water on cerium dioxide

    Science.gov (United States)

    Sutherland-Harper, Sophie; Taylor, Robin; Hobbs, Jeff; Pimblott, Simon; Pattrick, Richard; Sarsfield, Mark; Denecke, Melissa; Livens, Francis; Kaltsoyannis, Nikolas; Arey, Bruce; Kovarik, Libor; Engelhard, Mark; Waters, John; Pearce, Carolyn

    2018-06-01

    Ceria particles with different specific surface areas (SSA) were contaminated with chloride and water, then heat treated at 500 and 900 °C to investigate sorption behaviour of these species on metal oxides. Results from x-ray photoelectron spectroscopy and infrared spectroscopy showed chloride and water adsorption onto particles increased with surface area and that these species were mostly removed on heat treatment (from 6.3 to 0.8 at% Cl- on high SSA and from 1.4 to 0.4 at% on low SSA particles). X-ray diffraction revealed that chloride was not incorporated into the bulk ceria structure, but crystal size increased upon contamination. Ce LIII-edge x-ray absorption spectroscopy confirmed that chloride was not present in the first co-ordination sphere around Ce(IV) ions, so was not bonded to Ce as chloride in the bulk structure. Sintering of contaminated high SSA particles occurred with heat treatment at 900 °C, and they resembled low SSA particles synthesised at this temperature. Physical chloride-particle interactions were investigated using electron microscopy and energy dispersive x-ray analysis, showing that chloride was homogeneously distributed on ceria and that reduction of porosity did not trap surface-sorbed chloride inside the particles as surface area was reduced during sintering. This has implications for stabilisation of chloride-contaminated PuO2 for long term storage.

  5. Dynamics of cyanophenyl alkylbenzoate molecules in the bulk and in a surface layer adsorbed onto aerosil. Variation of the lengths of the alkyl chain

    Energy Technology Data Exchange (ETDEWEB)

    Frunza, Stefan [National Institute of Materials Physics, R-077125 Magurele (Romania); Schoenhals, Andreas [BAM Federal Institute of Materials Research and Testing, D-12205 Berlin (Germany); Frunza, Ligia, E-mail: lfrunza@infim.ro [National Institute of Materials Physics, R-077125 Magurele (Romania); Beica, Traian; Zgura, Irina; Ganea, Paul [National Institute of Materials Physics, R-077125 Magurele (Romania); Stoenescu, Daniel [Telecom-Bretagne, Departement d' Optique, Technopole Brest-Iroise 29238 Cedex (France)

    2010-06-16

    Graphical abstract: The temperature dependence of the molecular mobility in composites shows an Arrhenius-type regime at low temperature and a glassy-type one at higher temperature separated by a crossover phenomenon. - Abstract: The molecular mobility of 4-butyl- and 4-pentyl-4'-cyanophenyl benzoate (CP4B, CP5B) and their composites prepared from aerosil A380 was investigated by broadband dielectric spectroscopy in a large temperature range. Thermogravimetric and infrared investigations were additionally performed. High silica density (larger than 7 g aerosil/1 g of liquid crystal) was selected to observe a thin layer adsorbed on the surface of the silica particles. The data were compared with those of the member of the series with six carbon atoms in the alkyl tail. Bulk CP4B and CP5B show the dielectric behaviour expected for liquid crystals. For the composites one relaxation process is observed at frequencies much lower than those for the corresponding bulk, which was assigned to the dynamics of the molecules in a surface layer. The temperature dependence of the relaxation rates (and of the dielectric strength) shows a crossover behaviour with two distinguished regimes. At higher temperatures the data obey the Vogel-Fulcher-Tammann law, whereas an Arrhenius law is observed at lower temperature, in a close similarity to the behaviour of a constrained dynamic glass transition. The estimated Vogel and crossover temperature is independent on the tail length, while the activation energy for the low temperature branch increases weakly with increasing the alkyl tail.

  6. In situ determination of the depuration of three- and four-ringed polycyclic aromatic hydrocarbons co-adsorbed onto mangrove leaf surfaces

    International Nuclear Information System (INIS)

    Sun, Haifeng; Shi, Jing; Guo, Shuai; Zhang, Yong; Duan, Lusha

    2016-01-01

    A dual-wavelength fiber-optic fluorimetry for the in situ simultaneous determinations of fluorene (Flu), phenanthrene (Phe) and pyrene (Pyr) adsorbed onto the leaf surfaces of living Avicennia marina (Am) seedling were developed and used to study the depuration kinetics of the three PAHs, adsorbed individually or mixed together, onto living Am leaf surfaces. Limits of detection for the in situ measurements of adsorbed Flu, Phe and Pyr were 4.62, 2.75 and 1.38 ng spot"−"1, respectively. The depuration kinetics of the three selected polycyclic aromatic hydrocarbons (PAHs) are divided into rapid and slow phases; both phases followed the same first-order kinetics with relative clearance rates of Flu > Phe > Pyr during the rapid phase, and a clearance rate order of Pyr > Flu > Phe during the slow phase. For the three PAHs co-adsorbed on living Am leaf surfaces, a significant synergistic effect was detected during the rapid phase clearance; conversely, an antagonistic effect was observed during the slow phase. However, the synergistic effect dominated during both phases of the depuration process, and the co-adsorption of PAHs promoted the clearance of all three compounds from the mangrove leaf surfaces. These findings demonstrate a novel analytical method for in situ characterization of multiple PAHs adsorbed onto the plant surfaces. - Highlights: • A novel method for the in situ determination of multi-component PAHs was developed. • Synergistic and antagonistic effects separately occurred over rapid and slow phases. • The clearance of all three PAHs from leaf surfaces was promoted by co-adsorption. - The co-adsorption of PAHs promoted the depuration of all three compounds from the mangrove leaf surfaces.

  7. Control of Electronic Conduction at an Oxide Heterointerface using Surface Polar Adsorbates

    Energy Technology Data Exchange (ETDEWEB)

    Bell, Christopher

    2011-08-19

    We study the effect of the surface adsorption of a variety of common laboratory solvents on the conductivity at the interface between LaAlO{sub 3} and SrTiO{sub 3}. This interface possesses a range of intriguing physics, notably a proposed connection between the surface state of the LaAlO{sub 3} and the conductivity buried in the SrTiO{sub 3}. We show that the application of chemicals such as acetone, ethanol, and water can induce a large change (factor of three) in the conductivity. This phenomenon is observed only for polar solvents. These data provide experimental evidence for a general polarization-facilitated electronic transfer mechanism.

  8. Inter-row Adsorption Configuration and Stability of Threonine Adsorbed on the Ge(100) Surfaces

    International Nuclear Information System (INIS)

    Lee, Myungjin; Park, Youngchan; Jeong, Hyuk; Lee, Hangil

    2013-01-01

    The adsorption structures of threonine on the Ge(100) surface were investigated using core-level photoemission spectroscopy (CLPES) in conjunction with density functional theory (DFT) calculations. CLPES measurements were performed to identify the experimentally preferred adsorption structure. The preferred structure indicated the relative reactivities of the carboxyl and hydroxymethyl groups as electron donors to the Ge(100) surface during adsorption. The core-level C 1s, N 1s, and O 1s CLPES spectra indicated that the carboxyl oxygen competed more strongly with the hydroxymethyl oxygen during the adsorption reaction. Three among six possible adsorption structures were identified as energetically favorable using DFT calculation methods that considered the inter- and intra-bonding configurations upon adsorption onto the Ge(100) surface. These structures were O-H dissociated N dative inter bonding, O-H dissociated N dative intra bonding, O-H dissociation bonding. One of the adsorption structures: O-H dissociated N dative inter bonding was predicted to be stable in light of the transition state energies. We thus confirmed that the most favorable adsorption structure is the O-H dissociated N dative-inter bonding structure using CLPES and DFT calculation

  9. Surface functionalization of zirconium dioxide nano-adsorbents with 3-aminopropyl triethoxysilane and promoted adsorption activity for bovine serum albumin

    International Nuclear Information System (INIS)

    Liu, Gen; Wu, Chaochao; Zhang, Xia; Liu, Yufeng; Meng, Hao; Xu, Junli; Han, Yide; Xu, Xinxin; Xu, Yan

    2016-01-01

    Surface functionalization of zirconium dioxide (ZrO_2) nano-adsorbents was carried out by using 3-aminopropyl triethoxysilane (APTES) as the modifier. The addition amount of APTES was varied to determine the optimum modification extent, and the bulk ZrO_2 microparticles were also modified by APTES for comparison. Some means, such as TEM, XRD, FT-IR, XPS and TG-DSC were used to character these ZrO_2 particles. The results showed that the APTES molecules were chemically immobilized on the surface of ZrO_2 nanoparticles via Zr−O−Si bonds, and the nano-ZrO_2 samples showed larger special surface area. In the adsorption of bovine serum albumin (BSA), nano-ZrO_2 samples exhibited enhanced adsorption activity, and APTES modified nano-ZrO_2 with proper APTES content presented the best adsorption property. Under the same adsorption conditions, the equilibrium adsorption capacity of BSA on APTES-ZrO_2-2 was almost 2.3 times as that on pristine nano-ZrO_2 and 3.0 times as on bulk ZrO_2 microparticles. The increased adsorption capacity of APTES-ZrO_2 nano-adsorbents can be attributed to the chemical interaction between amino and carboxyl groups at APTES-ZrO_2/BSA interface. The pH-dependent experiments showed that the optimum pH value for the adsorption and desorption was 5.0 and 9.0, respectively, which suggested that the adsorption and release of BSA could be controlled simply by adjusting the solution pH condition. - Highlights: • APTES chemically immobilized on ZrO_2 nanoparticles via Zr−O−Si bond. • Enhanced adsorption capacity of BSA was observed on APTES-ZrO_2. • Chemical adsorption character of BSA on APTES-ZrO_2. • Adsorption/release of BSA on APTES-ZrO_2 accomplished by adjusting pH value.

  10. Surface functionalization of zirconium dioxide nano-adsorbents with 3-aminopropyl triethoxysilane and promoted adsorption activity for bovine serum albumin

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gen; Wu, Chaochao [Department of Chemistry, College of Sciences, Northeastern University, Shenyang 110819 (China); Zhang, Xia, E-mail: xzhang@mail.neu.edu.cn [Department of Chemistry, College of Sciences, Northeastern University, Shenyang 110819 (China); Liu, Yufeng, E-mail: liuyufeng@bjmu.edu.cn [College of Pharmacy, Liaoning University, Shenyang 110036 (China); Meng, Hao; Xu, Junli; Han, Yide; Xu, Xinxin; Xu, Yan [Department of Chemistry, College of Sciences, Northeastern University, Shenyang 110819 (China)

    2016-06-15

    Surface functionalization of zirconium dioxide (ZrO{sub 2}) nano-adsorbents was carried out by using 3-aminopropyl triethoxysilane (APTES) as the modifier. The addition amount of APTES was varied to determine the optimum modification extent, and the bulk ZrO{sub 2} microparticles were also modified by APTES for comparison. Some means, such as TEM, XRD, FT-IR, XPS and TG-DSC were used to character these ZrO{sub 2} particles. The results showed that the APTES molecules were chemically immobilized on the surface of ZrO{sub 2} nanoparticles via Zr−O−Si bonds, and the nano-ZrO{sub 2} samples showed larger special surface area. In the adsorption of bovine serum albumin (BSA), nano-ZrO{sub 2} samples exhibited enhanced adsorption activity, and APTES modified nano-ZrO{sub 2} with proper APTES content presented the best adsorption property. Under the same adsorption conditions, the equilibrium adsorption capacity of BSA on APTES-ZrO{sub 2}-2 was almost 2.3 times as that on pristine nano-ZrO{sub 2} and 3.0 times as on bulk ZrO{sub 2} microparticles. The increased adsorption capacity of APTES-ZrO{sub 2} nano-adsorbents can be attributed to the chemical interaction between amino and carboxyl groups at APTES-ZrO{sub 2}/BSA interface. The pH-dependent experiments showed that the optimum pH value for the adsorption and desorption was 5.0 and 9.0, respectively, which suggested that the adsorption and release of BSA could be controlled simply by adjusting the solution pH condition. - Highlights: • APTES chemically immobilized on ZrO{sub 2} nanoparticles via Zr−O−Si bond. • Enhanced adsorption capacity of BSA was observed on APTES-ZrO{sub 2}. • Chemical adsorption character of BSA on APTES-ZrO{sub 2}. • Adsorption/release of BSA on APTES-ZrO{sub 2} accomplished by adjusting pH value.

  11. Interlocking Molecular Gear Chains Built on Surfaces.

    Science.gov (United States)

    Zhao, Rundong; Qi, Fei; Zhao, Yan-Ling; Hermann, Klaus E; Zhang, Rui-Qin; Van Hove, Michel A

    2018-05-17

    Periodic chains of molecular gears in which molecules couple with each other and rotate on surfaces have been previously explored by us theoretically using ab initio simulation tools. On the basis of the knowledge and experience gained about the interactions between neighboring molecular gears, we here explore the transmission of rotational motion and energy over larger distances, namely, through a longer chain of gear-like passive "slave" molecules. Such microscopic gears exhibit quite different behaviors compared to rigid cogwheels in the macroscopic world due to their structural flexibility affecting intermolecular interaction. Here, we investigate the capabilities of such gear chains and reveal the mechanisms of the transmission process in terms of both quantum-level density functional theory (DFT) and simple classical mechanics. We find that the transmission of rotation along gear chains depends strongly on the gear-gear distance: short distances can cause tilting of gears and even irregular "creep-then-jump" (or "stick-slip") motion or expulsion of gears; long gear-gear distances cause weak coupling between gears, slipping and skipping. More importantly, for transmission of rotation at intermediate gear-gear distances, our modeling clearly exhibits the relative roles of several important factors: flexibility of gear arms, axles, and supports, as well as resulting rotational delays, slippages, and thermal and other effects. These studies therefore allow better informed design of future molecular machine components involving motors, gears, axles, etc.

  12. Absolute Molecular Orientation of Isopropanol at Ceria (100) Surfaces: Insight into Catalytic Selectivity from the Interfacial Structure

    Energy Technology Data Exchange (ETDEWEB)

    Doughty, Benjamin [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Goverapet Srinivasan, Sriram [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Indian Inst. of Technology (IIT), Rajasthan (India); Bryantsev, Vyacheslav S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lee, Dongkyu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lee, Ho Nyung [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ma, Ying-Zhong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lutterman, Daniel A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-06-12

    The initial mechanistic steps underlying heterogeneous chemical catalysis can be described in a framework where the composition, structure, and orientation of molecules adsorbed to reactive interfaces are known. However, extracting this vital information is the limiting step in most cases due in part to challenges in probing the interfacial monolayer with enough chemical specificity to characterize the surface molecular constituents. These challenges are exacerbated at complex or spatially heterogeneous interfaces where competing processes and a distribution of local environments can uniquely drive chemistry. To address these limitations, this work presents a distinctive combination of materials synthesis, surface specific optical experiments, and theory to probe and understand molecular structure at catalytic interfaces. Specifically, isopropanol was adsorbed to surfaces of the model CeO2 catalyst that were synthesized with only the (100) facet exposed. Vibrational sum-frequency generation was used to probe the molecular monolayer, and with the guidance of density functional theory calculations, was used to extract the structure and absolute molecular orientation of isopropanol at the CeO2 (100) surface. Our results show that isopropanol is readily deprotonated at the surface, and through the measured absolute molecular orientation of isopropanol, we obtain new insight into the selectivity of the (100) surface to form propylene. Our findings reveal key insight into the chemical and physical phenomena taking place at pristine interfaces thereby pointing to intuitive structural arguments to describe catalytic selectivity in more complex systems.

  13. 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...

  14. Spin inelastic electron tunneling spectroscopy on local spin adsorbed on surface.

    Science.gov (United States)

    Fransson, J

    2009-06-01

    The recent experimental conductance measurements taken on magnetic impurities on metallic surfaces, using scanning tunneling microscopy technique and suggesting occurrence of inelastic scattering processes, are theoretically addressed. We argue that the observed conductance signatures are caused by transitions between the spin states that have opened due to, for example, exchange coupling between the local spins and the tunneling electrons, and are directly interpretable in terms of inelastic transitions energies. Feasible measurements using spin-polarized scanning tunneling microscopy that would enable new information about the excitation spectrum of the local spins are discussed.

  15. Ionization and solvation of HCl adsorbed on the D2O-ice surface

    International Nuclear Information System (INIS)

    Kondo, M.; Kawanowa, H.; Gotoh, Y.; Souda, R.

    2004-01-01

    The interaction of HCl with the D 2 O-ice surface has been investigated in the temperature range 15-200 K by utilizing time-of-flight secondary ion mass spectroscopy, temperature-programmed desorption, and x-ray photoelectron spectroscopy. The intensities of sputtered H + (D 2 O) and Cl - ions (the H + ions) are increased (decreased) markedly above 40 K due to the hydrogen bond formation between the HCl and D 2 O molecules. The HCl molecules which form ionic hydrates undergo H/D exchange at 110-140 K and a considerable fraction of them dissolves into the bulk above 140 K. The neutral hydrates of HCl should coexist as evidenced by the desorption of HCl above 170 K. They are incorporated completely in the D 2 O layer up to 140 K. The HCl molecules embedded in the thick D 2 O layer dissolve into the bulk, and the ionic hydrate tends to segregate to the surface above 150 K

  16. Energy Transfer between U(VI) and Eu(III) Ions Adsorbed on a Silica Surface

    Energy Technology Data Exchange (ETDEWEB)

    Park, K. K.; Cha, W.; Cho, H. R.; Im, H. J.; Jung, E. C.; Song, K. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    Understanding of chemical behavior of actinide in a groundwater flow is important for assessing the possibility of their migration with water flows in a radioactive waste disposal site. Uranium is ubiquitous in the environment and a major actinide in a nuclear fuel cycle. Americium and curium having isotopes of long half life are minor actinides in a spent fuel. If a minor actinide coexists with uranium in a groundwater flow, some interactions between them could be expected such as minor actinide adsorption onto uranium precipitates and competition with each other for an adsorption to a mineral surface site. Eu(III) ion is frequently used as a chemical analogue of Am(III) and Cm(III) ions in a migration chemistry. The luminescent spectra of U(VI) and Eu(III) ions show a dependency on the coordination symmetry around them, and the changes in intensity or bandwidth of spectra can yield valuable information on their local environment. The luminescent lifetime also strongly depends on the coordination environment, and its measurement is valuable in probe studies on micro-heterogeneous systems. The excited U(VI) ion can be quenched through Stern.Volmer process, hydrolysis of excited species, exciplex formation, electron transfer or energy transfer. In case of U(VI)-Eu(III) system, the interaction between two ions can be studied by measuring the effect of Eu(III) ion on the quenching of U(VI) ion luminescence. There are only a few investigations on the interaction between an excited U(VI) ion and a lanthanide(III) ion. In perchlorate solution, the energy transfer to Eu(III) ion occurred only in solutions of pH>3.87. In this study, the quenching of U(VI) luminescence by Eu(III) on a silica surface was measured. The results will be discussed on the basis of a chemical interaction between them

  17. Characterization of the surface redox process of adsorbed morin at glassy carbon electrodes

    International Nuclear Information System (INIS)

    Tesio, Alvaro Yamil; Granero, Adrian Marcelo; Fernandez, Hector; Zon, Maria Alicia

    2011-01-01

    The thermodynamic and kinetics of the adsorption of morin (MOR) on glassy carbon (GC) electrodes in 0.2 mol dm -3 phosphate buffer solutions (PBS, pH 7.00) was studied by both cyclic (CV) and square wave (SWV) voltammetries. The Frumkin adsorption isotherm was the best to describe the specific interaction of MOR with GC electrodes. The SWV allowed to characterize the thermodynamic and kinetics of surface quasi-reversible redox couple of MOR, using the combination of the 'quasi-reversible maximum' and the 'splitting of SW net peaks' methods. Average values obtained for the formal potential and the anodic transfer coefficient were (0.27 ± 0.02) V and (0.59 ± 0.09), respectively. Moreover, a value of formal rate constant (k s ) of 87 s -1 for the overall two-electron redox process was calculated. The SWV was also employed to generate calibration curves, which were linear in the range MOR bulk concentration (c MOR *) from 1.27 x 10 -7 to 2.50 x 10 -5 mol dm -3 . The lowest concentration experimentally measured for a signal to noise ratio of 3:1 was 1.25 x 10 -8 mol dm -3 (3 ppb).

  18. 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

  19. In situ investigation of the mechanisms of the transport to tissues of polycyclic aromatic hydrocarbons adsorbed onto the root surface of Kandelia obovata seedlings

    International Nuclear Information System (INIS)

    Li, Ruilong; Zhu, Yaxian; Zhang, Yong

    2015-01-01

    A novel method for in situ determination of the polycyclic aromatic hydrocarbons (PAHs) adsorbed onto the root surface of Kandelia obovata seedlings was established using laser-induced time-resolved nanosecond fluorescence spectroscopy (LITRF). The linear dynamic ranges for the established method were 1.5–1240 ng/spot for phenanthrene, 1.0–1360 ng/spot for pyrene and 5.0–1220 ng/spot for benzo[a]pyrene. Then, the mechanisms of PAHs transport from the Ko root surface to tissues were investigated. The three-phase model including fast, slow and very slow fractions was superior to the single or dual-phase model to describe the PAHs transport processes. Moreover, the fast fraction of PAHs transport process was mainly due to passive movement, while the slow and very slow fractions were not. Passive movement was the main process of B[a]P adsorbed onto Ko root surface transport to tissues. In addition, the extent of the PAHs transport to Ko root tissues at different salinity were evaluated. - Highlights: • A novel method in situ determination PAHs adsorbed onto root surface was established. • The mechanisms of PAHs transport from root surface to tissues are investigated. • Passive movement is the main process of B[a]P transport from root surface to tissues. • Effects of salinity on the PAHs transport from root surface to tissues are evaluated. - Passive movement for the PAHs adsorbed onto Kandelia obovata root surface to tissues was observed by a newly established in situ LITRF method

  20. 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

  1. Characterizing interstate vibrational coherent dynamics of surface adsorbed catalysts by fourth-order 3D SFG spectroscopy

    Science.gov (United States)

    Li, Yingmin; Wang, Jiaxi; Clark, Melissa L.; Kubiak, Clifford P.; Xiong, Wei

    2016-04-01

    We report the first fourth-order 3D SFG spectroscopy of a monolayer of the catalyst Re(diCN-bpy)(CO)3Cl on a gold surface. Besides measuring the vibrational coherences of single vibrational modes, the fourth-order 3D SFG spectrum also measures the dynamics of interstate coherences and vibrational coherences states between two vibrational modes. By comparing the 3D SFG to the corresponding 2D and third-order 3D IR spectroscopy of the same molecules in solution, we found that the interstate coherences exist in both liquid and surface systems, suggesting that the interstate coherence is not disrupted by surface interactions. However, by analyzing the 3D spectral lineshape, we found that the interstate coherences also experience non-negligible homogenous dephasing dynamics that originate from surface interactions. This unique ability of determining interstate vibrational coherence dynamics of the molecular monolayer can help in understanding of how energy flows within surface catalysts and other molecular monolayers.

  2. Optimal Surface Amino-Functionalization Following Thermo-Alkaline Treatment of Nanostructured Silica Adsorbents for Enhanced CO2 Adsorption

    Directory of Open Access Journals (Sweden)

    Obdulia Medina-Juárez

    2016-11-01

    Full Text Available Special preparation of Santa Barbara Amorphous (SBA-15, mesoporous silica with highly hexagonal ordered, these materials have been carried out for creating adsorbents exhibiting an enhanced and partially selective adsorption toward CO2. This creation starts from an adequate conditioning of the silica surface, via a thermo-alkaline treatment to increase the population of silanol species on it. CO2 adsorption is only reasonably achieved when the SiO2 surface becomes aminated after put in contact with a solution of an amino alkoxide compound in the right solvent. Unfunctionalized and amine-functionalized substrates were characterized through X-ray diffraction, N2 sorption, Raman spectroscopy, electron microscopy, 29Si solid-state Nuclear Magnetic Resonance (NMR, and NH3 thermal programmed desorption. These analyses proved that the thermo-alkaline procedure desilicates the substrate and eliminates the micropores (without affecting the SBA-15 capillaries, present in the original solid. NMR analysis confirms that the hydroxylated solid anchors more amino functionalizing molecules than the unhydroxylated material. The SBA-15 sample subjected to hydroxylation and amino-functionalization displays a high enthalpy of interaction, a reason why this solid is suitable for a strong deposition of CO2 but with the possibility of observing a low-pressure hysteresis phenomenon. Contrastingly, CH4 adsorption on amino-functionalized, hydroxylated SBA-15 substrates becomes almost five times lower than the CO2 one, thus giving proof of their selectivity toward CO2. Although the amount of retained CO2 is not yet similar to or higher than those determined in other investigations, the methodology herein described is still susceptible to optimization.

  3. An energy conservation approach to adsorbate-induced surface stress and the extraction of binding energy using nanomechanics

    Science.gov (United States)

    Pinnaduwage, Lal A.; Boiadjiev, Vassil I.; Hawk, John E.; Gehl, Anthony C.; Fernando, Gayanath W.; Rohana Wijewardhana, L. C.

    2008-03-01

    Surface stress induced by molecular adsorption in three different binding processes has been studied experimentally using a microcantilever sensor. A comprehensive free-energy analysis based on an energy conservation approach is proposed to explain the experimental observations. We show that when guest molecules bind to atoms/molecules on a microcantilever surface, the released binding energy is retained in the host surface, leading to a metastable state where the excess energy on the surface is manifested as an increase in surface stress leading to the bending of the microcantilever. The released binding energy appears to be almost exclusively channeled to the surface energy, and energy distribution to other channels, including heat, appears to be inactive for this micromechanical system. When this excess surface energy is released, the microcantilever relaxes back to the original state, and the relaxation time depends on the particular binding process involved. Such vapor phase experiments were conducted for three binding processes: physisorption, hydrogen bonding, and chemisorption. Binding energies for these three processes were also estimated.

  4. An energy conservation approach to adsorbate-induced surface stress and the extraction of binding energy using nanomechanics

    Energy Technology Data Exchange (ETDEWEB)

    Pinnaduwage, Lal A; Boiadjiev, Vassil I; Hawk, John E; Gehl, Anthony C [Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6122 (United States); Fernando, Gayanath W [Physics Department, University of Connecticut, Storrs, CT 06269 (United States); Wijewardhana, L C Rohana [Physics Department, University of Cincinnati, Cincinnati, OH 45221 (United States)

    2008-03-12

    Surface stress induced by molecular adsorption in three different binding processes has been studied experimentally using a microcantilever sensor. A comprehensive free-energy analysis based on an energy conservation approach is proposed to explain the experimental observations. We show that when guest molecules bind to atoms/molecules on a microcantilever surface, the released binding energy is retained in the host surface, leading to a metastable state where the excess energy on the surface is manifested as an increase in surface stress leading to the bending of the microcantilever. The released binding energy appears to be almost exclusively channeled to the surface energy, and energy distribution to other channels, including heat, appears to be inactive for this micromechanical system. When this excess surface energy is released, the microcantilever relaxes back to the original state, and the relaxation time depends on the particular binding process involved. Such vapor phase experiments were conducted for three binding processes: physisorption, hydrogen bonding, and chemisorption. Binding energies for these three processes were also estimated.

  5. Visualisation of lectin binding sites on the surface of human platelets using lectins adsorbed to gold granules.

    Science.gov (United States)

    Nurden, A T; Horisberger, M; Savariau, E; Caen, J P

    1980-10-15

    Washed human platelets have been incubated with the lectins WGA, ConA and RCA1, adsorbed to different-sized gold particles. Plasma membrane receptors for each lectin were then located by scanning and transmission electron microscopy.

  6. Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

    Science.gov (United States)

    Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.

    1996-01-01

    The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

  7. SERS and in situ SERS spectroscopy of riboflavin adsorbed on silver, gold and copper substrates. Elucidation of variability of surface orientation based on both experimental and theoretical approach

    Science.gov (United States)

    Dendisová-Vyškovská, Marcela; Kokaislová, Alžběta; Ončák, Milan; Matějka, Pavel

    2013-04-01

    Surface-enhanced Raman scattering and in situ surface-enhanced Raman scattering spectra have been collected to study influences of (i) used metal and (ii) applied electrode potential on orientation of adsorbed riboflavin molecules. Special in situ SERS spectroelectrochemical cell was used to obtain in situ SERS spectra of riboflavin adsorbed on silver, gold and copper nanostructured surfaces. Varying electrode potential was applied in discrete steps forming a cycle from positive values to negative and backward. Observed spectral features in in situ SERS spectra, measured at alternate potentials, have been changing very significantly and the spectra have been compared with SERS spectra of riboflavin measured ex situ. Raman spectra of single riboflavin molecule in the vicinity to metal (Ag, Au and Cu) clusters have been calculated for different mutual positions. The results demonstrate significant changes of bands intensities which can be correlated with experimental spectra measured at different potentials. Thus, the orientation of riboflavin molecules adsorbed on metal surfaces can be elucidated. It is influenced definitely by the value of applied potential. Furthermore, the riboflavin adsorption orientation on the surface depends on the used metal. Adsorption geometries on the copper substrates are more diverse in comparison with the orientations on silver and gold substrates.

  8. Neutron scattering from adsorbed species

    International Nuclear Information System (INIS)

    Shuwang An

    1998-01-01

    Neutron reflection has been used to investigate the structure of layers of water-soluble diblock copolymers poly(2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate (poly(DMAEMA-b-MMA)) (70 mol% DMAEMA, M n = 10k, 80 mol% DMAEMA, M n = 10k, and 70 mol% DMAEMA, M n = 20k) adsorbed at the air-liquid and solid-liquid interfaces. The surface tension behaviour of these copolymers at the air-liquid interface has also been investigated. The study of the structure of layers of poly(DMAEMA-b-MMA) adsorbed at the air-water interface forms the main part of the thesis. The surface structure, the effects of pH and ionic strength, and the effects of composition and molecular weight of the copolymers have been studied systematically. For the 70%-10k copolymer at pH 7.5, the adsorption isotherm shows that there is a surface phase transition. The concentration of copolymer at which the phase transition occurs is close to that at which micellar aggregation in the bulk solution also occurs. At low concentrations (below the CMC), the two blocks of the copolymer are approximately uniformly distributed in the direction normal to the interface and the layer is partially immersed in water. At high concentrations (above the CMC), the adsorbed layer has a cross-sectional structure resembling that expected for a micelle with the majority of the MMA blocks forming the core. The outer layers, comprising predominantly DMAEMA blocks, are not equivalent, being more highly extended on the aqueous side of the interface. The effects of pH and added electrolyte on the structure of layers of the 70%-10k copolymer show that the layered structure is promoted by any changes in the bulk solution that enhance the surface coverage but is inhibited by an increase in the fractional charge on the polyelectrolyte part of the copolymer. The effect of lowering the pH is to increase the positive charge on the weak polyelectrolyte block. Addition of electrolyte generally enhances the amount adsorbed and

  9. Polymer composite adsorbents using particles of molecularly imprinted polymers or aluminium oxide nanoparticles for treatment of arsenic contaminated waters.

    Science.gov (United States)

    Önnby, L; Pakade, V; Mattiasson, B; Kirsebom, H

    2012-09-01

    Removal of As(V) by adsorption from water solutions was studied using three different synthetic adsorbents. The adsorbents, (a) aluminium nanoparticles (Alu-NPs, polymers (polymer backbones of pure polyacrylamide (MIP-cryo) were of better stability than the amine containing polymer backbone (Alu-cryo). Both composites worked well in the studied pH range of pH 2-8. Adsorption tested in real wastewater spiked with arsenic showed that co-ions (nitrate, sulphate and phosphate) affected arsenic removal for Alu-cryo more than for MIP-cryo. Both composites still adsorbed well in the presence of counter-ions (copper and zinc) present at low concentrations (μg/l). The unchanged and selective adsorption in realistic water observed for MIP-cryo was concluded to be due to a successful imprinting, here controlled using a non-imprinted polymer (NIP). A development of MIP-cryo is needed, considering its low adsorption capacity. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Phase properties of elastic waves in systems constituted of adsorbed diatomic molecules on the (001) surface of a simple cubic crystal

    Science.gov (United States)

    Deymier, P. A.; Runge, K.

    2018-03-01

    A Green's function-based numerical method is developed to calculate the phase of scattered elastic waves in a harmonic model of diatomic molecules adsorbed on the (001) surface of a simple cubic crystal. The phase properties of scattered waves depend on the configuration of the molecules. The configurations of adsorbed molecules on the crystal surface such as parallel chain-like arrays coupled via kinks are used to demonstrate not only linear but also non-linear dependency of the phase on the number of kinks along the chains. Non-linear behavior arises for scattered waves with frequencies in the vicinity of a diatomic molecule resonance. In the non-linear regime, the variation in phase with the number of kinks is formulated mathematically as unitary matrix operations leading to an analogy between phase-based elastic unitary operations and quantum gates. The advantage of elastic based unitary operations is that they are easily realizable physically and measurable.

  11. Scattering of atomic and molecular ions from single crystal surfaces of Cu, Ag and Fe

    International Nuclear Information System (INIS)

    Zoest, J.M. van.

    1986-01-01

    This thesis deals with analysis of crystal surfaces of Cu, Ag and Fe with Low Energy Ion scattering Spectroscopy (LEIS). Different atomic and molecular ions with fixed energies below 7 keV are scattered by a metal single crystal (with adsorbates). The energy and direction of the scattered particles are analysed for different selected charge states. In that way information can be obtained concerning the composition and atomic and electronic structure of the single crystal surface. Energy spectra contain information on the composition of the surface, while structural atomic information is obtained by direction measurements (photograms). In Ch.1 a description is given of the experimental equipment, in Ch.2 a characterization of the LEIS method. Ch.3 deals with the neutralization of keV-ions in surface scattering. Two different ways of data interpretation are presented. First a model is treated in which the observed directional dependence of neutralization action of the first atom layer of the surface is presented by a laterally varying thickness of the neutralizing layer. Secondly it is shown that the data can be reproduced by a more realistic, physical model based on atomic transition matrix elements. In Ch.4 the low energy hydrogen scattering is described. The study of the dissociation of H 2 + at an Ag surface r0230ted in a model based on electronic dissociation, initialized by electron capture into a repulsive (molecular) state. In Ch.5 finally the method is applied to the investigation of the surface structure of oxidized Fe. (Auth.)

  12. FTIR study of the relation, between extra-framework aluminum species and the adsorbed molecular water, and its effect on the acidity in ZSM-5 steamed zeolite

    Directory of Open Access Journals (Sweden)

    Luis Fioravanti Isernia

    2013-01-01

    Full Text Available The infrared spectroscopy study of zeolite samples, obtained by steam treatment at 560‑960 °C of the ZSM‑5 catalyst (framework Si/Al ratio of 13, suggests an association between adsorbed molecular water and extra‑framework aluminum hydroxyls generated after treatment. Moreover, infrared spectroscopy of adsorbed pyridine shows the reduction of the densities of Brönsted and Lewis sites, when treatment temperature rises, with contradicts the frequently accepted mechanism of the transformation of two bridged Si‑OH‑Al groups for each Lewis site generated. The gradual conversion of the octahedral extra-framework aluminum (Lewis‑associated in polymeric species with low acidity is the most probable cause of this behavior. On the other hand, the apparent decline of the acid Brönsted strength, with the increase in the temperature of the hydrothermal treatment, has two possible causes: a the decreasing accessibility, of the pyridine molecular probe to bridged Si-OH-Al groups with the strongest Brönsted acidity, inside the channels, and b the gradual transformation of these groups into extra framework species of weak acidity.

  13. FTIR study of the relation between extra-framework aluminum species and the adsorbed molecular water, and its effect on the acidity in ZSM-5 steamed zeolite

    Energy Technology Data Exchange (ETDEWEB)

    Isernia, Luis Fioravanti, E-mail: luis.isernia@gmail.com [Laboratorio de Tamices Moleculares, Universidad de Oriente - UO, Maturin, Monagas (Venezuela, Bolivarian Republic of)

    2013-11-01

    The infrared spectroscopy study of zeolite samples, obtained by steam treatment at 560-960 Degree-Sign C of the ZSM-5 catalyst (framework Si/Al ratio of 13), suggests an association between adsorbed molecular water and extra-framework aluminum hydroxyls generated after treatment. Moreover, infrared spectroscopy of adsorbed pyridine shows the reduction of the densities of Broensted and Lewis sites, when treatment temperature rises, with contradicts the frequently accepted mechanism of the transformation of two bridged Si-OH-Al groups for each Lewis site generated. The gradual conversion of the octahedral extra-framework aluminum (Lewis-associated) in polymeric species with low acidity is the most probable cause of this behavior. On the other hand, the apparent decline of the acid Broensted strength, with the increase in the temperature of the hydrothermal treatment, has two possible causes: a) the decreasing accessibility, of the pyridine molecular probe to bridged Si-OH-Al groups with the strongest Broensted acidity, inside the channels, and b) the gradual transformation of these groups into extra framework species of weak acidity. (author)

  14. COMBINATION OF MOLECULAR ADSORBENT RECIRCULATING SYSTEM AND RADIOIODINE FOR THE TREATMENT OF CONCURRENT HYPERTHYROIDISM AND SEVERE LIVER DYSFUNCTION: A RETROSPECTIVE COHORT STUDY.

    Science.gov (United States)

    Zhang, Qing; Guan, Yanxing; Xiang, Tianxin; Liu, Shaozheng; Chen, Qingjie; Zhang, Qing

    2017-02-01

    The treatment of hyperthyroidism associated with severe liver dysfunction (LD) is a clinical challenge, and there has been no unified examination of this problem. The objective of this study was to assess the efficacy and safety of radioiodine ( 131 I) in combination with a molecular adsorbent recirculating system (MARS) for the treatment of hyperthyroidism complicated by severe liver LD. A total of 116 hyperthyroidism patients with concomitant LD who received MARS treatment were studied retrospectively. The patients were grouped according to whether or not they also received 131 I treatment: Group 1 (59 patients) received 131 I following MARS treatment, while Group 2 (57 cases) received only MARS. Clinical outcomes, including thyroid hormone levels, liver function parameters, and therapeutic efficacy were calculated. The overall response rate was significantly greater in Group 1 than in Group 2 (Ptreatment compared with before treatment (Ptreatments (Ptreatment of hyperthyroidism complicated by severe LD was effective and safe. The use of this system could rapidly improve liver function and metabolism, allowing 131 I therapy to be applied as early as possible with a shortened recovery time of liver function. ALSS = artificial liver support system ALT = alanine transaminase AST = aspartate transaminase ATD = antithyroid drugs DBil = direct bilirubin FT3 = free tri-iodothyronine FT4 = free thyroxine 131 I = radioiodine INR = international normalized ratio LD = liver dysfunction MARS = molecular adsorbent recirculating system MELD = model for end-stage liver disease PT = prothrombin time TBil = total bilirubin TSH = thyroid-stimulating hormone.

  15. Surface-Enhanced Raman Scattering in Molecular Junctions.

    Science.gov (United States)

    Iwane, Madoka; Fujii, Shintaro; Kiguchi, Manabu

    2017-08-18

    Surface-enhanced Raman scattering (SERS) is a surface-sensitive vibrational spectroscopy that allows Raman spectroscopy on a single molecular scale. Here, we present a review of SERS from molecular junctions, in which a single molecule or molecules are made to have contact from the top to the bottom of metal surfaces. The molecular junctions are nice platforms for SERS as well as transport measurement. Electronic characterization based on the transport measurements of molecular junctions has been extensively studied for the development of miniaturized electronic devices. Simultaneous SERS and transport measurement of the molecular junctions allow both structural (geometrical) and electronic information on the single molecule scale. The improvement of SERS measurement on molecular junctions open the door toward new nanoscience and nanotechnology in molecular electronics.

  16. Electron induced conformational changes of an imine-based molecular switch on a Au(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Lotze, Christian; Henningsen, Nils; Franke, Katharina; Schulze, Gunnar; Pascual, Jose Ignacio [Inst. f. Experimentalphysik, Freie Universitaet Berlin (Germany); Luo, Ying; Haag, Rainer [Inst. f. Organische Chemie, Freie Universitaet Berlin (Germany)

    2009-07-01

    Azobenzene-based molecules exhibit a cis-trans configurational photoisomerisation in solution. Recently, the adsorption properties of azobenzene derivatives have been investigated on different metal surfaces in order to explore the possible changes in the film properties induced by external stimuli. In azobenzene, the diazo-bridge is a key group for the isomerization process. Its interaction with a metal surface is dominated through the N lone-pair electrons, which reduces the efficiency of the conformational change. In order to reduce the molecule-surface interaction, we explore an alternative molecular architecture by substituting the diazo-bridge (-N=N-) of azobenzene by an imine-group (-N=CH-). We have investigated the imine-based compound para-carboxyl-di-benzene-imine (PCI) adsorbed on a Au(111) surface. The carboxylic terminations mediates the formation of strongly bonded molecular dimers, which align in ordered rows preferentially following the fcc regions of the Au(111) herringbone reconstruction. Low temperature scanning tunneling microscopy was used to induce conformational changes between trans and cis state of individual molecules in a molecular monolayer.

  17. Molecular-level chemistry of model single-crystal oxide surfaces with model halogenated compounds

    Science.gov (United States)

    Adib, Kaveh

    Synchrotron-based X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD) and low energy electron diffraction (LEED) have been used to investigate, at a molecular level, the chemistry of different terminations of single crystal iron-oxide surfaces with probe molecules (CCl4 and D2O). Comparisons of the reactivity of these surfaces towards CCl4, indicate that the presence of an uncapped surface Fe cation (strong Lewis acid site) and an adjacent oxygen site capped by that cation can effect the C-Cl bond cleavage in CCl4, resulting in dissociatively adsorbed Cl-adatoms and carbon-containing fragments. If in addition to these sites, an uncapped surface oxygen (Lewis base) site is also available, the carbon-containing moiety can then move that site, coordinate itself with that uncapped oxygen, and stabilize itself. At a later step, the carbon-containing fragment may form a strong covalent bond with the uncapped oxygen and may even abstract that surface oxygen. On the other hand, if an uncapped oxygen is not available to stabilize the carbon-containing fragment, the surface coordination will not occur and upon the subsequent thermal annealing of the surface the Cl-adatoms and the carbon-containing fragments will recombine and desorb as CCl4. Finally, the presence of surface deuteroxyls blocking the strong Lewis acid and base sites of the reactive surface, passivates this surface. Such a deuteroxylated surface will be unreactive towards CCl 4. Such a molecular level understanding of the surface chemistry of metal-oxides will have applications in the areas of selective catalysis, including environmental catalysis, and chemical sensor technology.

  18. Tailored Surfaces/Assemblies for Molecular Plasmonics and Plasmonic Molecular Electronics.

    Science.gov (United States)

    Lacroix, Jean-Christophe; Martin, Pascal; Lacaze, Pierre-Camille

    2017-06-12

    Molecular plasmonics uses and explores molecule-plasmon interactions on metal nanostructures for spectroscopic, nanophotonic, and nanoelectronic devices. This review focuses on tailored surfaces/assemblies for molecular plasmonics and describes active molecular plasmonic devices in which functional molecules and polymers change their structural, electrical, and/or optical properties in response to external stimuli and that can dynamically tune the plasmonic properties. We also explore an emerging research field combining molecular plasmonics and molecular electronics.

  19. Molecularly-Limited Fractal Surface Area of Mineral Powders

    Directory of Open Access Journals (Sweden)

    Petr Jandacka

    2016-05-01

    Full Text Available The topic of the specific surface area (SSA of powders is not sufficiently described in the literature in spite of its nontrivial contribution to adsorption and dissolution processes. Fractal geometry provides a way to determine this parameter via relation SSA ~ x(D − 3s(2 − D, where x (m is the particle size and s (m is a scale. Such a relation respects nano-, micro-, or macro-topography on the surface. Within this theory, the fractal dimension 2 ≤ D < 3 and scale parameter s plays a significant role. The parameter D may be determined from BET or dissolution measurements on several samples, changing the powder particle sizes or sizes of adsorbate molecules. If the fractality of the surface is high, the SSA does not depend on the particle size distribution and vice versa. In this paper, the SSA parameter is analyzed from the point of view of adsorption and dissolution processes. In the case of adsorption, a new equation for the SSA, depending on the term (2 − D∙(s2 − sBET/sBET, is derived, where sBET and s2 are effective cross-sectional diameters for BET and new adsorbates. Determination of the SSA for the dissolution process appears to be very complicated, since the fractality of the surface may change in the process. Nevertheless, the presented equations have good application potential.

  20. Molecular dynamics simulation of the effect of pH on the adsorption of rhodamine laser dyes on TiO2 hydroxylated surfaces

    OpenAIRE

    2009-01-01

    Abstract We have carried out a study of the adsorption, on the (101) surface of anatase TiO2, of two industrially relevant rhodamines molecules (rhodamine 6G and rhodamine 800) employing Molecular Dynamics. These theoretical studies have shown that Rhodamine 6G must adsorb on surfaces under basic conditions. Moreover, the adsorption of this molecule shows a strong dependence upon the pH of the system, i.e. under neutral conditions the adsorption energy is quite smaller, and under ...

  1. Adsorbed Carbon Formation and Carbon Hydrogenation for CO_2 Methanation on the Ni(111) Surface: ASED-MO Study

    International Nuclear Information System (INIS)

    Choe, Sang Joon; Kang, Hae Jin; Kim, Su Jin; Park, Sung Bae; Park, Dong Ho; Huh, Do Sung

    2005-01-01

    Using the ASED-MO (Atom Superposition and Electron Delocalization-Molecular Orbital) theory, we investigated carbon formation and carbon hydrogenation for CO_2 methanation on the Ni (111) surface. For carbon formation mechanism, we calculated the following activation energies, 1.27 eV for CO_2 dissociation, 2.97 eV for the CO, 1.93 eV for 2CO dissociation, respectively. For carbon methanation mechanism, we also calculated the following activation energies, 0.72 eV for methylidyne, 0.52 eV for methylene and 0.50 eV for methane, respectively. We found that the calculated activation energy of CO dissociation is higher than that of 2CO dissociation on the clean surface and base on these results that the CO dissociation step are the ratedetermining of the process. The C-H bond lengths of CH_4 the intermediate complex are 1.21 A, 1.31 A for the C···H_(_1_), and 2.82 A for the height, with angles of 105 .deg. for H_(_1_)CH and 98 .deg. for H_(_1_)CH_(_1_)

  2. Molecular biology of the Chlamydia pneumoniae surface

    DEFF Research Database (Denmark)

    Christiansen, Gunna; Østergaard, Lars; Birkelund, Svend

    1997-01-01

    surface differs from that of Chlamydia trachomatis. In order to study the surface of C. pneumoniae we generated monoclonal antibodies (MAbs) against C. pneumoniae strain VR-1310 and selected 14 MAbs that reacted with the surface of C. pneumoniae. All MAbs reacted in immunoelectron microscopy...... with the surface of both whole C. pneumoniae VR-1310 elementary bodies and with purified sarcosyl extracted outer membrane complexes. However, only 2 of the MAbs reacted in immunoblotting with C. pneumoniae proteins and only with antigen that had not been heat treated in SDS-sample buffer. This indicates...

  3. Frontier molecular orbitals of a single molecule adsorbed on thin insulating films supported by a metal substrate: electron and hole attachment energies.

    Science.gov (United States)

    Scivetti, Iván; Persson, Mats

    2017-09-06

    We present calculations of vertical electron and hole attachment energies to the frontier orbitals of a pentacene molecule absorbed on multi-layer sodium chloride films supported by a copper substrate using a simplified density functional theory (DFT) method. The adsorbate and the film are treated fully within DFT, whereas the metal is treated implicitly by a perfect conductor model. We find that the computed energy gap between the highest and lowest unoccupied molecular orbitals-HOMO and LUMO -from the vertical attachment energies increases with the thickness of the insulating film, in agreement with experiments. This increase of the gap can be rationalised in a simple dielectric model with parameters determined from DFT calculations and is found to be dominated by the image interaction with the metal. We find, however, that this simplified model overestimates the downward shift of the energy gap in the limit of an infinitely thick film.

  4. H(D) → D(H) + Cu(111) collision system: molecular dynamics study of surface temperature effects.

    Science.gov (United States)

    Vurdu, Can D; Güvenç, Ziya B

    2011-04-28

    All the channels of the reaction dynamics of gas-phase H (or D) atoms with D (or H) atoms adsorbed onto a Cu(111) surface have been studied by quasiclassical constant energy molecular dynamics simulations. The surface is flexible and is prepared at different temperature values, such as 30 K, 94 K, and 160 K. The adsorbates were distributed randomly on the surface to create 0.18 ML, 0.28 ML, and 0.50 ML of coverages. The multi-layer slab is mimicked by a many-body embedded-atom potential energy function. The slab atoms can move according to the exerted external forces. Treating the slab atoms non-rigid has an important effect on the dynamics of the projectile atom and adsorbates. Significant energy transfer from the projectile atom to the surface lattice atoms takes place especially during the first impact that modifies significantly the details of the dynamics of the collisions. Effects of the different temperatures of the slab are investigated in this study. Interaction between the surface atoms and the adsorbates is modeled by a modified London-Eyring-Polanyi-Sato (LEPS) function. The LEPS parameters are determined by using the total energy values which were calculated by a density functional theory and a generalized gradient approximation for an exchange-correlation energy for many different orientations, and locations of one- and two-hydrogen atoms on the Cu(111) surface. The rms value of the fitting procedure is about 0.16 eV. Many different channels of the processes on the surface have been examined, such as inelastic reflection of the incident hydrogen, subsurface penetration of the incident projectile and adsorbates, sticking of the incident atom on the surface. In addition, hot-atom and Eley-Rideal direct processes are investigated. The hot-atom process is found to be more significant than the Eley-Rideal process. Furthermore, the rate of subsurface penetration is larger than the sticking rate on the surface. In addition, these results are compared and

  5. Adsorbate-induced facetting reconstruction and self-organized domain patterning of vicinal Ag(111) surfaces; Adsorbatinduzierte richtungsabhaengige Facettierung und selbstorganisierte Domaenen-Musterbildung auf vizinalen Ag(111)-Oberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Stefan

    2007-02-05

    This thesis investigates structural aspects of adsorbate-induced facetting of vicinal Ag(111) surfaces. It is mainly based on scanning tunneling microscope (STM) and low energy electron diffraction (LEED) experiments performed under UHV conditions. The planar dye-molecule perylene-3,4,9,10-tetracarboxilicacid-dianhydride (PTCDA) adsorbs preferentially at the step edges of the 8.5 Ag(111) vicinal surfaces used in the experiments. It causes a facetting reconstruction by the formation of (111) terraces and facets with a high step density. Moreover, two distinct preferential inclinations of facets were observed, which can only be explained by the selective influence of the adsorbate superstructure. In terms of thermodynamics, the facetting reconstruction can be described as an orientational phase separation, adapted to the constraints of planar surfaces. This concept is capable of explaining the local facetting phenomena. The formalism used predicts an important role of nucleation kinetics. This aspect is taken into account by introducing an additional phase of mobile molecules (2D molecular gas), which cannot be measured directly. Furthermore, strong arguments for the appearance of a critical island size for the PTCDA/ Ag(111) superstructure were found. This work presents structural information of all stable superstructures of PTCDA on vicinal Ag(111) surfaces. Altogether 16 such superstructures were found, 3 of which had been observed and published before. Density and commensurability were found to systematically depend on the step-structure. The two preferred inclinations of facets are related to two characteristic types of domain boundaries of the herringbone superstructure to the adjacent (111)-terrace. On the (111) terraces, small islands of metastable superstructures were found. Facets and (111) terraces form a regular grating-like domain pattern with a variable structural width of 5 to 75 nm. STM measurements show direct evidence for a long-range interaction

  6. Surface vibrational spectroscopy

    International Nuclear Information System (INIS)

    Erskine, J.L.

    1984-01-01

    A brief review of recent studies which combine measurements of surface vibrational energies with lattice dynamical calculations is presented. These results suggest that surface vibrational spectroscopy offers interesting prospects for use as a molecular-level probe of surface geometry, adsorbate bond distances and molecular orientations

  7. Implanting very low energy atomic ions into surface adsorbed cage molecules: the formation/emission of Cs/C60+

    International Nuclear Information System (INIS)

    Kolodney, Eli; Kaplan, Andrey; Manor, Yoni; Bekkerman, Anatoly; Tsipinyuk, Boris

    2004-01-01

    Full Text: We demonstrate the formation of an endo-complex via a collision of energetic ions with molecular overlayers on a surface. An incoming atomic ion is encapsulated inside a very large molecule or cluster by implanting the primary ion into the target species, which then recovers its original structure or rearrange itself around the implanted ion in some stable configuration. Here we describe an experiment resulting in the formation and ejection of an endo-complex, within a single collision. We study the formation and emission of endohedral fullerenes, Cs/C 60 + and Cs/C 70 + , following a single collision of Cs + ion with a sub-monolayer of C 60 (steady state coverage) on gold and silicon surfaces and with a sub-monolayer of C 70 on gold. A continuous low energy (E 0 =35-220 eV) Cs + ion beam hit the Cs + covered surface and the collisional formation and ejection of the endohedral Cs/Cs 60 + complex, within a single Cs + /C 60 collision was observed and characterized. Several experimental observations clearly demonstrate the single collision nature of the combined atom penetration endo-complex ejection event. The fullerene molecule is actually being picked up off the surface by the penetrating Cs + ion. The evidence for the trapping of the Cs + ion inside the fullerene cage is given both by the appearance of the Cs/Cs (602-2n) + (n=1-5) sequence and its termination at Cs/Cs 50 + . Kinetic Energy Distributions (KEDs) of the outgoing Cs/Cs 60 + were measured for two different Cs + impact energies under field-free conditions. The most striking observation is the near independence of the KEDs on the impact energy. Both KEDs peak around 1.2 eV with similar line shapes. A simple model for the formation/ejection/fragmentation dynamics of the endohedral complex is proposed and is found to be in good agreement with the experimental results

  8. Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

    Directory of Open Access Journals (Sweden)

    Krishnamoorthy Arumugam

    2014-04-01

    reduction of actinides and their subsequent immobilization. Highly under-investigated is the role of redox-active semiconducting mineral surfaces as catalysts for promoting natural redox processes. Such knowledge is crucial to derive process-oriented mechanisms, kinetics, and rate laws for inorganic and organic redox processes in nature. In addition, molecular-level details still need to be explored and understood to plan for safer disposal of hazardous materials. In light of this, we include new research on the effect of iron-sulfide mineral surfaces, such as pyrite and mackinawite, on the redox chemistry of actinyl aqua complexes in aqueous solution.

  9. A study of structure and properties of molecularly thin methanol film using the modified surface forces apparatus.

    Science.gov (United States)

    Zhao, Gutian; Cai, Di; Wu, Gensheng; Tan, Qiyan; Xiang, Li; Zhang, Yin; Xiang, Nan

    2014-11-01

    A novel approach for studying the adsorption and evaporation processes of molecularly thin methanol film by the modified surface forces apparatus (M-SFA) is reported. This method can be used precisely to measure the thickness, morphology, and mechanical properties of the film confined between two mica surfaces in a real-time manner at gas atmosphere. By observing the adsorption and evaporation processes of the methanol molecule, it is found that the first adsorbed layer of the methanol film on the mica surface behaves as a solid-like structure. The thickness of this layer is measured to be about 3.2 Å, approximately equal to the diameter of a methanol molecule. Besides, this first adsorbed layer can carry normalized loads of more than 5.6 atm due to the carrying capacity conserved by the bond of mica-OH. The outer layers of the methanol film are further adsorbed with the increase of the exposure time, which are liquid-like and can be easily eliminated out from the substrate. The present study suggests that the interacting mode between hydroxy and mica is of great potential in material science and biomedical systems. © 2014 Wiley Periodicals, Inc.

  10. Probing gas-surface interactions with a molecular beam

    International Nuclear Information System (INIS)

    Spruit, M.E.M.

    1988-01-01

    The dynamics of direct scattering, trapping and sticking in molecular beam scattering is probed. The O 2 /Ag interaction was chosen, using the close-packed (111) plane of Ag as target surface. 170 refs.; 22 figs.; 3 tabs

  11. Adsorption and switching properties of a N-benzylideneaniline based molecular switch on a Au(111) surface

    International Nuclear Information System (INIS)

    Ovari, Laszlo; Luo, Ying; Haag, Rainer; Leyssner, Felix; Tegeder, Petra; Wolf, Martin

    2010-01-01

    High resolution electron energy loss spectroscopy has been employed to analyze the adsorption geometry and the photoisomerization ability of the molecular switch carboxy-benzylideneaniline (CBA) adsorbed on Au(111). CBA on Au(111) adopts a planar (trans) configuration in the first monolayer (ML) as well as for higher coverages (up to 6 ML), in contrast to the strongly nonplanar geometry of the molecule in solution. Illumination with UV light of CBA in direct contact with the Au(111) surface (≤1 ML) caused no changes in the vibrational structure, whereas at higher coverages (>1 ML) pronounced modifications of vibrational features were observed, which we assign to a trans→cis isomerization. Thermal activation induced the back reaction to trans-CBA. We propose that the photoisomerization is driven by a direct (intramolecular) electronic excitation of the adsorbed CBA molecules in the second ML (and above) analogous to CBA in the liquid phase.

  12. Supersonic molecular beam experiments on surface chemical reactions.

    Science.gov (United States)

    Okada, Michio

    2014-10-01

    The interaction of a molecule and a surface is important in various fields, and in particular in complex systems like biomaterials and their related chemistry. However, the detailed understanding of the elementary steps in the surface chemistry, for example, stereodynamics, is still insufficient even for simple model systems. In this Personal Account, I review our recent studies of chemical reactions on single-crystalline Cu and Si surfaces induced by hyperthermal oxygen molecular beams and by oriented molecular beams, respectively. Studies of oxide formation on Cu induced by hyperthermal molecular beams demonstrate a significant role of the translational energy of the incident molecules. The use of hyperthermal molecular beams enables us to open up new chemical reaction paths specific for the hyperthermal energy region, and to develop new methods for the fabrication of thin films. On the other hand, oriented molecular beams also demonstrate the possibility of understanding surface chemical reactions in detail by varying the orientation of the incident molecules. The steric effects found on Si surfaces hint at new ways of material fabrication on Si surfaces. Controlling the initial conditions of incoming molecules is a powerful tool for finely monitoring the elementary step of the surface chemical reactions and creating new materials on surfaces. Copyright © 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. From an equilibrium based MOF adsorbent to a kinetic selective carbon molecular sieve for paraffin/iso-paraffin separation

    KAUST Repository

    Li, Baiyan

    2016-11-04

    We unveil a unique kinetic driven separation material for selectively removing linear paraffins from iso-paraffins via a molecular sieving mechanism. Subsequent carbonization and thermal treatment of CD-MOF-2, the cyclodextrin metal-organic framework, afforded a carbon molecular sieve with a uniform and reduced pore size of ca. 5.0 Å, and it exhibited highly selective kinetic separation of n-butane and n-pentane from iso-butane and iso-pentane, respectively. © The Royal Society of Chemistry.

  14. Preparation and surface properties of mesoporous silica particles modified with poly(N-vinyl-2-pyrrolidone) as a potential adsorbent for bilirubin removal

    Energy Technology Data Exchange (ETDEWEB)

    Timin, Alexander, E-mail: a_timin@mail.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); Rumyantsev, Evgeniy, E-mail: evr@isuct.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); Lanin, Sergey N., E-mail: SNLanin@phys.chem.msu.ru [Chemistry Department, Physical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow (Russian Federation); Rychkova, Sveta A. [Chemistry Department, Physical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow (Russian Federation); Guseynov, Sabir S. [Krestov Institute of Solution Chemistry of Russian Academy of Sciences, 153000 Ivanovo (Russian Federation); Solomonov, Alexey V. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); Antina, Elena V. [Krestov Institute of Solution Chemistry of Russian Academy of Sciences, 153000 Ivanovo (Russian Federation)

    2014-10-15

    The surface of silica particles was modified with polyvinyl pyrrolidone (PVP) through sol–gel process. The different experimental techniques, i.e., thermogravimetric analysis (TGA and DTG), nitrogen adsorption, scanning electron microscopy (SEM), laser diffraction analysis (LDA), fourier transform spectroscopy (FTIR) are used to characterize the pure non-functionalized and functionalized silicas containing different amount of PVP. It was shown that PVP-modified silica samples have well developed porous structure; the values of specific surface area for PVP-modified silicas are in the range of 140–264 m{sup 2} g{sup −1}. While the non-functionalized silica shows the low surface area (S{sub BET} = 40 m{sup 2} g{sup −1}). The BJH analysis showed that PVP can be used as an effective agent to increase an average pore size and total pore volume. The results indicate that PVP functionalized silicas show a potential as effective adsorbents for bilirubin removal compared to other available adsorbents. - Highlights: • PVP functionalized silicas were synthesized via sol–gel method. • Modification of silica by PVP leads to the formation of mesoporous structure. • PVP functionalized mesoporous silicas demonstrate good adsorption properties for bilirubin removal.

  15. One-of-A-Kind: A Microporous Metal-Organic Framework Capable of Adsorptive Separation of Linear, Mono- and Di-branched Alkane Isomers via Temperature- and Adsorbate-Dependent Molecular Sieving

    KAUST Repository

    Wang, Hao

    2018-03-29

    Separation of alkane isomers represents a crucial process in the petrochemical industry in order to achieve high octane rating of gasoline. Herein, we report the first example of complete separation of linear, monobranched and dibranched alkane isomers by a single adsorbent. A calcium-based robust microporous metal-organic framework, Ca(H2tcpb) (tcpb = 1,2,4,5-tetrakis(4-carboxyphenyl)-benzene) exhibits unique molecular exclusion behavior which enables full separation of binary or ternary mixtures of alkane isomers into pure form of each isomerate. The successful separation of monobranched and dibranched hexane isomers will not only lead to the production of higher quality gasoline with maximum possible octane numbers but also fill the gap in the current separation technology. Exploration of separation mechanism indicates that structural flexibility and adsorbate-dependent structure change of the porous framework plays a vital role for the observed temperature-dependent molecular sieving property of the adsorbent.

  16. Molecular surface mesh generation by filtering electron density map.

    Science.gov (United States)

    Giard, Joachim; Macq, Benoît

    2010-01-01

    Bioinformatics applied to macromolecules are now widely spread and in continuous expansion. In this context, representing external molecular surface such as the Van der Waals Surface or the Solvent Excluded Surface can be useful for several applications. We propose a fast and parameterizable algorithm giving good visual quality meshes representing molecular surfaces. It is obtained by isosurfacing a filtered electron density map. The density map is the result of the maximum of Gaussian functions placed around atom centers. This map is filtered by an ideal low-pass filter applied on the Fourier Transform of the density map. Applying the marching cubes algorithm on the inverse transform provides a mesh representation of the molecular surface.

  17. Molecular Surface Mesh Generation by Filtering Electron Density Map

    Directory of Open Access Journals (Sweden)

    Joachim Giard

    2010-01-01

    Full Text Available Bioinformatics applied to macromolecules are now widely spread and in continuous expansion. In this context, representing external molecular surface such as the Van der Waals Surface or the Solvent Excluded Surface can be useful for several applications. We propose a fast and parameterizable algorithm giving good visual quality meshes representing molecular surfaces. It is obtained by isosurfacing a filtered electron density map. The density map is the result of the maximum of Gaussian functions placed around atom centers. This map is filtered by an ideal low-pass filter applied on the Fourier Transform of the density map. Applying the marching cubes algorithm on the inverse transform provides a mesh representation of the molecular surface.

  18. Patterned gallium surfaces as molecular mirrors.

    Science.gov (United States)

    Bossi, Alessandra; Rivetti, Claudio; Mangiarotti, Laura; Whitcombe, Michael J; Turner, Anthony P F; Piletsky, Sergey A

    2007-09-30

    An entirely new means of printing molecular information on a planar film, involving casting nanoscale impressions of the template protein molecules in molten gallium, is presented here for the first time. The metallic imprints not only replicate the shape and size of the proteins used as template. They also show specific binding for the template species. Such a simple approach to the creation of antibody-like properties in metallic mirrors can lead to applications in separations, microfluidic devices, and the development of new optical and electronic sensors, and will be of interest to chemists, materials scientists, analytical specialists, and electronic engineers.

  19. Precambrian Surface Temperatures and Molecular Phylogeny

    Science.gov (United States)

    Schwartzman, David; Lineweaver, Charles H.

    2004-06-01

    The timing of emergence of major organismal groups is consistent with the climatic temperature being equal to their upper temperature limit of growth (T_{max}), implying a temperature constraint on the evolution of each group, with the climatic temperature inferred from the oxygen isotope record of marine cherts. Support for this constraint comes from the correlation of T_{max} with the rRNA molecular phylogenetic distance from the last common ancestor (LCA) for both thermophilic Archaea and Bacteria. In particular, this correlation for hyperthermophilic Archaea suggests a climatic temperature of about 120°C at the time of the LCA, likely in the Hadean.

  20. Surface Design in Solid-State Dye Sensitized Solar Cells: Effects of Zwitterionic Co-adsorbents on Photovoltaic Performance

    KAUST Repository

    Wang, Mingkui

    2009-07-10

    In solid-state dye sensitized solar cells (SSDSCs) charge recombination at the dye-hole transporting material interface plays a critical role in the cell efficiency. For the first time we report on the influence of dipolar coadsorbents on the photovoltaic performance of sensitized hetero-junction solar cells. In the present study, we investigated the effect of two zwitterionic butyric acid derivatives differing only in the polar moiety attached to their common 4 carbon-chain acid, i.e., 4-guanidinobutyric acid (GBA) and 4-aminobutyric acid (ABA). These two molecules were implemented as coadsorbents in conjunction with Z907Na dye on the SSDSC. It was found that a Z907Na/GBA dye/co-adsorbent combination increases both the open circuit voltage (V oc) and short-circuit current density ( Jsc) as compared to using Z907Na dye alone. The Z907Na/ABA dye/co-adsorbent combination increases the Jsc. Impedance and transient photovoltage investigations elucidate the cause of these remarkable observations. ©2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Evaluation of the potential cationic dye removal using adsorption by graphene and carbon nanotubes as adsorbents surfaces

    Directory of Open Access Journals (Sweden)

    Akbar Elsagh

    2017-05-01

    Full Text Available We are employed in the present study of single-walled carbon nanotubes (SWCNTs, carboxylate group functionalized single-walled carbon nanotubes (SWCNT-COOH, graphene (G and graphene oxide (GO as alternative adsorbents for the removal of cationic dye Basic Red 46 (BR 46, from aqueous solution. Various physico-chemical parameters were studied such as electrical conductivity behaviors, contact time, solution pH, and dye concentration. The experimental results show that SWCNTs, SWCNT-COOH, G and GO are promising adsorbents for removing BR 46. The adsorption equilibrium data were analyzed using various adsorption isotherms, and the results have shown that adsorption behavior of BR 46 could be described reasonably well by the Langmuir isotherm. Results showed that the removal of BR 46 increased with increasing initial dye concentration, contact time and pH. Adsorption kinetics data were modeled using the pseudo-first and pseudo-second order, and intra-particle diffusion models. Results show that the pseudo-first order kinetic model for SWCNTs, SWCNT-COOH and the pseudo-second order for G and GO were found to correlate the experimental data well.

  2. Wetting Properties of Molecularly Rough Surfaces

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Martin; Malijevský, Alexandr; Lísal, Martin

    2015-01-01

    Roč. 143, č. 10 (2015), s. 104701 ISSN 0021-9606 R&D Projects: GA ČR GA13-09914S; GA MŠk LH12020 Institutional support: RVO:67985858 Keywords : contant-angle * solid-surface * dynamics Subject RIV: BJ - Thermodynamics Impact factor: 2.894, year: 2015

  3. Surface-Enhanced Raman Spectroscopy of Dye and Thiol Molecules Adsorbed on Triangular Silver Nanostructures: A Study of Near-Field Enhancement, Localization of Hot-Spots, and Passivation of Adsorbed Carbonaceous Species

    Directory of Open Access Journals (Sweden)

    Manuel R. Gonçalves

    2012-01-01

    Full Text Available Surface-enhanced Raman spectroscopy (SERS of thiols and dye molecules adsorbed on triangular silver nanostructures was investigated. The SERS hot-spots are localized at the edges and corners of the silver triangular particles. AFM and SEM measurements permit to observe many small clusters formed at the edges of triangular particles fabricated by nanosphere lithography. Finite-element calculations show that near-field enhancements can reach values of more than 200 at visible wavelengths, in the gaps between small spherical particles and large triangular particles, although for the later no plasmon resonance was found at the wavelengths investigated. The regions near the particles showing strong near-field enhancement are well correlated with spatial localization of SERS hot-spots done by confocal microscopy. Silver nanostructures fabricated by thermal evaporation present strong and fast fluctuating SERS activity, due to amorphous carbon contamination. Thiols and dye molecules seem to be able to passivate the undesired SERS activity on fresh evaporated silver.

  4. Surface-Enhanced Raman Spectroscopy of Dye and Thiol Molecules Adsorbed on Triangular Silver Nano structures: A Study of Near-Field Enhancement, Localization of Hot-Spots, and Passivation of Adsorbed Carbonaceous Species

    International Nuclear Information System (INIS)

    Goncalves, M.R.; Marti, O.; Fabian Enderle, F.

    2012-01-01

    Surface-enhanced Raman spectroscopy (SERS) of thiols and dye molecules adsorbed on triangular silver nanostructures was investigated. The SERS hot-spots are localized at the edges and corners of the silver triangular particles. AFM and SEM measurements permit to observe many small clusters formed at the edges of triangular particles fabricated by nanosphere lithography. Finite-element calculations show that near-field enhancements can reach values of more than 200 at visible wavelengths, in the gaps between small spherical particles and large triangular particles, although for the later no plasmon resonance was found at the wavelengths investigated. The regions near the particles showing strong near-field enhancement are well correlated with spatial localization of SERS hot-spots done by confocal microscopy. Silver nanostructures fabricated by thermal evaporation present strong and fast fluctuating SERS activity, due to amorphous carbon contamination. Thiols and dye molecules seem to be able to passivate the undesired SERS activity on fresh evaporated silver. excitation: by far-field illumination of metal nanostructures or rough metal Raman scattering cross-section of gold-palladium target Temporal Fluctuation in SERS Temporal and spectral fluctuations.

  5. Tuning the deposition of molecular graphene nanoribbons by surface functionalization

    Science.gov (United States)

    Konnerth, R.; Cervetti, C.; Narita, A.; Feng, X.; Müllen, K.; Hoyer, A.; Burghard, M.; Kern, K.; Dressel, M.; Bogani, L.

    2015-07-01

    We show that individual, isolated graphene nanoribbons, created with a molecular synthetic approach, can be assembled on functionalised wafer surfaces treated with silanes. The use of surface groups with different hydrophobicities allows tuning the density of the ribbons and assessing the products of the polymerisation process.

  6. Surface force analysis of molecular interfacial interactions of proteins and lipids with polymeric biomaterials

    International Nuclear Information System (INIS)

    Hamilton-Brown, P.; Griesser, H.J.; Meagher, L.

    2001-01-01

    Full text: Adverse biological responses to biomedical devices are often caused by the irreversible accumulation of biological deposits onto the surfaces of devices. Such deposits cause blocking of artificial blood vessels, fibrous encapsulation of soft tissue regenerative devices, 'fouling' of contact lenses, secondary cataracts on intraocular lenses, and other undesirable events that interfere with the intended functions of biomedical devices. The formation of deposits is triggered by an initial stage in which various proteins and lipids rapidly adsorb onto the synthetic material surface; further biological molecules and ultimately cellular entities (e.g., host cells, bacteria) then settle onto the initial adsorbed layer. Hence, to avoid or control the accumulation of biological deposits, molecular understanding is required of the initial adsorption processes. Such adsorption is caused by attractive interfacial forces, which we are characterising by the use of a novel method. In the present study, polymeric thin film coatings, polyethylene oxide (PEO), and polysaccharide coatings have been analysed in terms of their surface forces and the ensuing propensity for protein and lipid adsorption. Interfacial forces are measured using atomic force microscopy (AFM) with a colloid-modified tip in a liquid cell using solutions of physiological pH and ionic strength. The chemical composition and uniformity of the coatings was characterised by X-ray Photon Spectroscopy (XPS). For a polymeric solid coating, repulsive forces have been measured against a silica colloid probe, and the dominant surface force is electrostatic. For the highly hydrated, 'soft' PEO and polysaccharide coatings, on the other hand, steric/entropic forces are also significant and contribute to interfacial interactions with proteins and lipids. In one system we have observed a time dependence of the electrostatic surface potential, which affects interaction with charged proteins. Force measurements were

  7. Adsorption of molecular hydrogen on nanostructered surfaces

    International Nuclear Information System (INIS)

    Uranga Piña, Llinersy; Martínez Mesa, Aliezer; Seifert, Gotthard

    2015-01-01

    Were investigated the effect of the structural characteristics of model nanoporous environments on the adsorption of molecular hydrogen. The adsorption properties of the target nanostructures (graphene and ZnO sheets, carbon foams, metal-organic frameworks) are evaluated in a broad range of thermodynamic conditions. The study is carried out within the density functional theory for quantum fluids at finite temperature (QLDFT), which allows to account for the many-body and quantum delocalization effects in a single theoretical framework. The exchange-correlation (excess) functional is derived from the empirical equation of state of the homogeneous system. We focus on the evaluation of hydrogen storage capacities of the substrates and on the emergence of quantum effects triggered by the confinement imposed by the host structure. The approach provides accurate estimates of the hydrogen storage capacities for realistic adsorptive media. The relation between the microscopic structure of the hydrogen fluid and the calculated adsorption properties is also addressed. (full text)

  8. Adsorber fires

    International Nuclear Information System (INIS)

    Holmes, W.

    1987-01-01

    The following conclusions are offered with respect to activated charcoal filter systems in nuclear power plants: (1) The use of activated charcoal in nuclear facilities presents a potential for deep-seated fires. (2) The defense-in-depth approach to nuclear fire safety requires that if an ignition should occur, fires must be detected quickly and subsequently suppressed. (3) Deep-seated fires in charcoal beds are difficult to extinguish. (4) Automatic water sprays can be used to extinguish fires rapidly and reliably when properly introduced into the burning medium. The second part of the conclusions offered are more like challenges: (1) The problem associated with inadvertent actuations of fire protection systems is not a major one, and it can be reduced further by proper design review, installation, testing, and maintenance. Eliminating automatic fire extinguishing systems for the protection of charcoal adsorbers is not justified. (2) Removal of automatic fire protection systems due to fear of inadvertent fire protection system operation is a case of treating the effect rather than the cause. On the other hand, properly maintaining automatic fire protection systems will preserve the risk of fire loss at acceptable levels while at the same time reducing the risk of damage presented by inadvertent operation of fire protection systems

  9. Effect of polar surfaces on organic molecular crystals

    Science.gov (United States)

    Sharia, Onise; Tsyshevskiy, Roman; Kuklja, Maija; University of Maryland College Park Team

    Polar oxide materials reveal intriguing opportunities in the field of electronics, superconductivity and nanotechnology. While behavior of polar surfaces has been widely studied on oxide materials and oxide-oxide interfaces, manifestations and properties of polar surfaces in molecular crystals are still poorly understood. Here we discover that the polar catastrophe phenomenon, known on oxides, also takes place in molecular materials as illustrated with an example of cyclotetramethylene tetranitramine (HMX) crystals. We show that the surface charge separation is a feasible compensation mechanism to counterbalance the macroscopic dipole moment and remove the electrostatic instability. We discuss the role of surface charge on degradation of polar surfaces, electrical conductivity, optical band-gap closure and surface metallization. Research is supported by the US ONR (Grants N00014-16-1-2069 and N00014-16-1-2346) and NSF. We used NERSC, XSEDE and MARCC computational resources.

  10. 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

  11. 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)

  12. Molecular dynamics simulation of uranium compound adsorption on solid surface

    International Nuclear Information System (INIS)

    Omori, Yuki; Takizawa, Yuji; Okamoto, Tsuyoshi

    2010-01-01

    Particles mixed in the UF6 gas have the property of accumulating on the inside of piping or units. This type of accumulation will cause material unaccounted for (MUF) in the UF6 gas processing facilities. Development of a calculation model for estimating the accumulation rate of uranium compounds has been expected. And predicting possible part of the units where uranium compounds adsorb will contribute to design an effective detection system. The purpose of this study is to take the basic knowledge of the particle's adsorption mechanism from the microscopic point of view. In simulation analysis, UF5 model particle is produced, then two types of solid surfaces are prepared; one is a solid surface at rest and the other is a moving solid surface. The result obtained by the code 'PABS' showed that when the solid surface moves at a lower velocity, the particle's adsorption process dominates over the particle's breakup one. Besides the velocity of the solid surface, other principal factors affecting an adsorption ratio were also discussed. (author)

  13. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    International Nuclear Information System (INIS)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2√3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (√3 x √3) reconstruction on the (111) face of the α-CuAl alloy has been determined

  14. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.

  15. New Trend for Acceleration Solid Phase Extraction Process Based on Using Magnetic Nano-adsorbents along with Surface Functionalization through Microwave Assisted Solvent-free Technique.

    Science.gov (United States)

    Ahmed, Salwa A; Soliman, Ezzat M

    2015-01-01

    The use of a microwave assisted solvent-free technique for silica coating of iron magnetic nanoparticles (Fe3O4-MNPs) and their functionalization with three aliphatic diamines: 1,2-ethylenediamine (1,2EDA), 1,5-pentanediamine (1,5PDA) and 1.8-octanediamine (1,8-ODA), were successfully achieved in a very short time. Only 60 min were needed for the nano-adsorbent modification as compared with more than 1000 min using conventional methods under reflux conditions. Their surface characteristics (observed by TEM, XRD and FT-IR), in addition to Cu(II) adsorption capacities (1.805, 1.928 and 2.116 mmol g(-1)) and time of equilibration (5 s) were almost the same. Thus, the time required to accomplish the solid phase extraction process is greatly reduced. On the other hand, the phenomenon of the fast equilibration kinetics was successfully extended on using the functionalized aliphatic diamines magnetic nano-adsorbents as precursors for further microwave treatment. Three selective magnetic nano-adsorbents (Fe3O4-MNPs-SiO2-1,2EDA-3FSA, Fe3O4-MNPs-SiO2-1,5PDA-3FSA and Fe3O4-MNPs-SiO2-1,8ODA-3FSA) were obtained via the reaction with 3-formayl salicylic acid (3FSA) as a selective reagent for Fe(III). At 5 s contact time, they exhibited maximum Fe(III) uptake equal to 4.512, 4.987 and 5.367 mmol g(-1), respectively. Furthermore, modeling of values of metal uptake capacity obtained at different shaking time intervals supports pseudo-second order kinetics.

  16. Orbital tomography: Molecular band maps, momentum maps and the imaging of real space orbitals of adsorbed molecules

    Energy Technology Data Exchange (ETDEWEB)

    Offenbacher, Hannes; Lüftner, Daniel; Ules, Thomas; Reinisch, Eva Maria; Koller, Georg, E-mail: georg.koller@uni-graz.at; Puschnig, Peter; Ramsey, Michael G., E-mail: michael.ramsey@uni-graz.at

    2015-10-01

    Highlights: • Orbital tomography within the plane wave final state approximation. • One electron orbital predictions versus angle resolved photoemission experiment. • Geometric and electronic structure of organic thin films elucidated by ARUPS. • Influence of molecular conformation and orientation on ARUPS. • Retrieval of sexiphenyl and pentacene orbitals in real space. - Abstract: The frontier orbitals of molecules are the prime determinants of their chemical, optical and electronic properties. Arguably, the most direct method of addressing the (filled) frontier orbitals is ultra-violet photoemission spectroscopy (UPS). Although UPS is a mature technique from the early 1970s on, the angular distribution of the photoemitted electrons was thought to be too complex to be analysed quantitatively. Recently angle resolved UPS (ARUPS) work on conjugated molecules both, in ordered thick films and chemisorbed monolayers, has shown that the angular (momentum) distribution of the photocurrent from orbital emissions can be simply understood. The approach, based on the assumption of a plane wave final state is becoming known as orbital tomography. Here we will demonstrate, with selected examples of pentacene (5A) and sexiphenyl (6P), the potential of orbital tomography. First it will be shown how the full angular distribution of the photocurrent (momentum map) from a specific orbital is related to the real space orbital by a Fourier transform. Examples of the reconstruction of 5A orbitals will be given and the procedure for recovering the lost phase information will be outlined. We then move to examples of sexiphenyl where we interrogate the original band maps of thick sexiphenyl in the light of our understanding of orbital tomography that has developed since then. With comparison to theoretical simulations of the molecular band maps, the molecular conformation and orientation will be concluded. New results for the sexiphenyl monolayer on Al(1 1 0) will then be

  17. Hollow mesoporous structured molecularly imprinted polymer as adsorbent in pipette-tip solid-phase extraction for the determination of antiretrovirals from plasma of HIV-infected patients.

    Science.gov (United States)

    Simões, Nathália Soares; de Oliveira, Hanna Leijoto; da Silva, Ricky Cássio Santos; Teixeira, Leila Suleimara; Sales, Thaís Lorenna Souza; de Castro, Whocely Victor; de Paiva, Maria José Nunes; Sanches, Cristina; Borges, Keyller Bastos

    2018-05-17

    In this work a hollow mesoporous structured molecularly imprinted polymer was synthetized and used as adsorbent in pipette-tip solid-phase extraction for the determination of lamivudine (3TC), zidovudine (AZT) and efavirenz (EFZ) from plasma of human immunodeficiency virus (HIV) infected patients by high-performance liquid chromatography (HPLC). All parameters that influence the recovery of the pipette tip based on hollow mesoporous molecularly imprinted polymer solid-phase extraction (PT-HM-MIP-SPE) method were systematically studied and discussed in detail. The adsorbent material was prepared using methacrylic acid and 4-vinylpyridine as functional monomers, ethylene glycol dimethacrylate as crosslinker, acetonitrile as solvent, 4,4'-azobis(4-cyanovaleric acid) as radical initiator, benzalkonium chloride as surfactant), 3TC, and AZT as templates. The simultaneous separation of 3TC, AZT and EFZ by HPLC-UV was performed using a Gemini C18 Phenomenexࣨ column (250 mm × 4.6 mm, 5 μm) and mobile phase consisting of acetonitrile: water pH 3.2 (68:32, v/v), flow rate of 1.0 mL min -1 and λ = 260 nm. The method was linear over the concentration range from 0.25 to 10 μg mL -1 for 3TC and EFZ, and 0.05 to 2.0 μg mL -1 for AZT, with correlation coefficients larger than 0.99 for all analytes. Recovery ± relative standard deviations (RSDs %) were 41.99±2.38 %, 82.29±1.63 %, and 83.72±7.52 % for 3TC, AZT, and EFZ, respectively. The RSDs and relative errors (REs) were lower than 15 % for intra and interday assays. The method has been successfully applied for monitoring HIV-infected patients outside the therapeutic dosage.2 This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  18. CURVATURE-DRIVEN MOLECULAR FLOW ON MEMBRANE SURFACE.

    Science.gov (United States)

    Mikucki, Michael; Zhou, Y C

    2017-01-01

    This work presents a mathematical model for the localization of multiple species of diffusion molecules on membrane surfaces. Morphological change of bilayer membrane in vivo is generally modulated by proteins. Most of these modulations are associated with the localization of related proteins in the crowded lipid environments. We start with the energetic description of the distributions of molecules on curved membrane surface, and define the spontaneous curvature of bilayer membrane as a function of the molecule concentrations on membrane surfaces. A drift-diffusion equation governs the gradient flow of the surface molecule concentrations. We recast the energetic formulation and the related governing equations by using an Eulerian phase field description to define membrane morphology. Computational simulations with the proposed mathematical model and related numerical techniques predict (i) the molecular localization on static membrane surfaces at locations with preferred mean curvatures, and (ii) the generation of preferred mean curvature which in turn drives the molecular localization.

  19. Autonomous molecular cascades for evaluation of cell surfaces

    Science.gov (United States)

    Rudchenko, Maria; Taylor, Steven; Pallavi, Payal; Dechkovskaia, Alesia; Khan, Safana; Butler, Vincent P., Jr.; Rudchenko, Sergei; Stojanovic, Milan N.

    2013-08-01

    Molecular automata are mixtures of molecules that undergo precisely defined structural changes in response to sequential interactions with inputs. Previously studied nucleic acid-based automata include game-playing molecular devices (MAYA automata) and finite-state automata for the analysis of nucleic acids, with the latter inspiring circuits for the analysis of RNA species inside cells. Here, we describe automata based on strand-displacement cascades directed by antibodies that can analyse cells by using their surface markers as inputs. The final output of a molecular automaton that successfully completes its analysis is the presence of a unique molecular tag on the cell surface of a specific subpopulation of lymphocytes within human blood cells.

  20. Determination of adsorbable organic halogens in surface water samples by combustion-microcoulometry versus combustion-ion chromatography titration.

    Science.gov (United States)

    Kinani, Aziz; Sa Lhi, Hacène; Bouchonnet, Stéphane; Kinani, Said

    2018-03-02

    Adsorbable Organic Halogen (AOX) is an analytical parameter of considerable interest since it allows to evaluate the amount of organohalogen disinfection by-products (OXBPs) present in a water sample. Halogen speciation of AOX into adsorbable organic chlorine, bromine and iodine, respectively AOCl, AOBr and AOI, is extremely important since it has been shown that iodinated and brominated organic by-products tend to be more toxic than their chlorinated analogues. Chemical speciation of AOX can be performed by combustion-ion chromatography (C-IC). In the present work, the effectiveness of the nitrate wash according to ISO 9562 standard method protocol to eliminate halide ions interferences was firstly examined. False positive AOX values were observed when chloride concentration exceeded 100 ppm. The improvements made to the washing protocol have eliminated chloride interference for concentrations up to 1000 ppm. A C-IC method for chemical speciation of AOX into AOCl, AOBr, and AOI has been developed and validated. The most important analytical parameters were investigated. The following optimal conditions were established: an aqueous solution containing 2.4 mM sodium bicarbonate/2.0 mM sodium carbonate, and 2% acetone (v/v) as mobile phase, 2 mL of aqueous sodium thiosulfate (500 ppm) as absorption solution, 0.2 mL min -1 as water inlet flow rate for hydropyrolysis, and 10 min as post-combustion time. The method was validated according to NF T90-210 standard method. Calibration curves fitted through a quadratic equation show coefficients of determination (r 2 ) greater than 0.9998, and RSD less than 5%. The LOQs were 0.9, 4.3, and 5.7 μg L -1 Cl for AOCl, AOBr, and AOI, respectively. The accuracy, in terms of relative error, was within a ± 10% interval. The applicability of the validated method was demonstrated by the analysis of twenty four water samples from three rivers in France. The measurements reveals AOX amounts above 10

  1. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Messahel, Lyria

    2012-11-12

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage {Theta}{sub Cu,Ag,Au}=2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The

  2. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Messahel, Lyria

    2012-01-01

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage Θ Cu,Ag,Au =2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The structure

  3. Selective adsorption of bovine hemoglobin on functional TiO2 nano-adsorbents: surface physic-chemical properties determined adsorption activity

    Science.gov (United States)

    Guo, Shiguang; Zhang, Jianghua; Shao, Mingxue; Zhang, Xia; Liu, Yufeng; Xu, Junli; Meng, Hao; Han, Yide

    2015-04-01

    Surface functionalized nanoparticles are efficient adsorbents which have shown good potential for protein separation. In this work, we chose two different types of organic molecules, oleic acid (OA) and 3-glycidoxypropyltrimethoxy silane (GPTMS), to functionalize the surface of TiO2 nanoparticles, and we studied the effects of this modification on their surface physicochemical properties in correlation with their selective adsorption of proteins. The results showed that the surface zeta potential and the surface water wettability of the modified TiO2 were significantly changed in comparison with the original TiO2 nanoparticles. The adsorption activities of bovine hemoglobin (BHb) and bovine serum albumin (BSA) on these functionalized TiO2 samples were investigated under different conditions, including pH values, contact time, ion strength, and initial protein concentration. In comparison with the non-specific adsorption of original TiO2, however, both the OA-TiO2 and GPTMS-TiO2 exhibited increased BHb adsorption and decreased BSA adsorption at the same time. Using a binary protein mixture as the adsorption object, a higher separation factor (SF) was obtained for OA-TiO2 under optimum conditions. The different adsorption activities of BHb and BSA on the modified TiO2 were correlated with different interactions at the protein/solid interface, and the chemical force as well as the electrostatic force played an important role in the selective adsorption process.

  4. Enhanced binding capacity of boronate affinity adsorbent via surface modification of silica by combination of atom transfer radical polymerization and chain-end functionalization for high-efficiency enrichment of cis-diol molecules

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; He, Maofang; Wang, Chaozhan; Wei, Yinmao, E-mail: ymwei@nwu.edu.cn

    2015-07-30

    Boronate affinity materials have been widely used for specific separation and preconcentration of cis-diol molecules, but most do not have sufficient capacity due to limited binding sites on the material surface. In this work, we prepared a phenylboronic acid-functionalized adsorbent with a high binding capacity via the combination of surface-initiated atom transfer radical polymerization (SI-ATRP) and chain-end functionalization. With this method, the terminal chlorides of the polymer chains were used fully, and the proposed adsorbent contains dense boronic acid polymers chain with boronic acid on the chain end. Consequently, the proposed adsorbent possesses excellent selectivity and a high binding capacity of 513.6 μmol g{sup −1} for catechol and 736.8 μmol g{sup −1} for fructose, which are much higher than those of other reported adsorbents. The dispersed solid-phase extraction (dSPE) based on the prepared adsorbent was used for extraction of three cis-diol drugs (i.e., epinephrine, isoprenaline and caffeic acid isopropyl ester) from plasma; the eluates were analyzed by HPLC-UV. The reduced amount of adsorbent (i.e., 2.0 mg) could still eliminate interferences efficiently and yielded a recovery range of 85.6–101.1% with relative standard deviations ranging from 2.5 to 9.7% (n = 5). The results indicated that the proposed strategy could serve as a promising alternative to increase the density of surface functional groups on the adsorbent; thus, the prepared adsorbent has the potential to effectively enrich cis-diol substances in real samples. - Highlights: • Boronate adsorbent is prepared via ATRP and chain-end functionalization. • The adsorbent has quite high binding capacity for cis-diols. • Binding capacity is easily manipulated by ATRP condition. • Chain-end functionalization can improve binding capacity significantly. • Reduced adsorbent is consumed in dispersed solid-phase extraction of cis-diols.

  5. Molecular dynamics simulation of annealed ZnO surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Min, Tjun Kit; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    The effect of thermally annealing a slab of wurtzite ZnO, terminated by two surfaces, (0001) (which is oxygen-terminated) and (0001{sup ¯}) (which is Zn-terminated), is investigated via molecular dynamics simulation by using reactive force field (ReaxFF). We found that upon heating beyond a threshold temperature of ∼700 K, surface oxygen atoms begin to sublimate from the (0001) surface. The ratio of oxygen leaving the surface at a given temperature increases as the heating temperature increases. A range of phenomena occurring at the atomic level on the (0001) surface has also been explored, such as formation of oxygen dimers on the surface and evolution of partial charge distribution in the slab during the annealing process. It was found that the partial charge distribution as a function of the depth from the surface undergoes a qualitative change when the annealing temperature is above the threshold temperature.

  6. Single NdPc{sub 2} molecules on surfaces. Adsorption, interaction, and molecular magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Fahrendorf, Sarah

    2013-01-24

    They have huge potential for application in molecular-spin-transistors, molecular-spinvalves, and molecular quantum computing. SMMs are characterized by high spin ground states with zero-field splitting leading to high relaxation barriers and long relaxation times. A relevant class of molecules are the lanthanide double-decker phthalocyanines (LaPc{sub 2}) with only one metal atom sandwiched between two organic phthalocyanine (Pc) ligands. For envisaged spintronic applications it is important to understand the interaction between the molecules and the substrate and its influence on the electronic and magnetic properties. The subject of this thesis is the investigation of the adsorbed neodymium double-decker phthalocyanine (NdPc{sub 2}) by means of low temperature scanning tunneling microscopy and spectroscopy (STM and STS). The molecules are deposited by sublimation onto different substrates. It is observed that a large fraction of the double-decker molecules decomposes during deposition. The decomposition probability strongly depends on the chosen substrate. Therefore it is concluded that the substrate modifies the electronic structure of the molecule leading to a stabilization or destabilization of the molecular entity. Charge transfer from the surface to the molecule is identified as a potential stabilizing mechanism. The electronic and magnetic properties are investigated in detail for adsorbed NdPc{sub 2} molecules on Cu(100). The results of the experimental study are compared to state-of-the-art density functional theory calculations performed by our colleagues from the Peter Gruenberg Institute (PGI-1) at the Forschungszentrum Juelich. Interestingly, the lower Pc ring of the molecule hybridizes intensely with the substrate leading to strong chemisorption of the molecule, while the upper Pc ring keeps its molecular type electronic states, which can be energetically shifted by an external electric field. Importantly, it is possible to get direct access to the

  7. Single NdPc2 molecules on surfaces. Adsorption, interaction, and molecular magnetism

    International Nuclear Information System (INIS)

    Fahrendorf, Sarah

    2013-01-01

    They have huge potential for application in molecular-spin-transistors, molecular-spinvalves, and molecular quantum computing. SMMs are characterized by high spin ground states with zero-field splitting leading to high relaxation barriers and long relaxation times. A relevant class of molecules are the lanthanide double-decker phthalocyanines (LaPc 2 ) with only one metal atom sandwiched between two organic phthalocyanine (Pc) ligands. For envisaged spintronic applications it is important to understand the interaction between the molecules and the substrate and its influence on the electronic and magnetic properties. The subject of this thesis is the investigation of the adsorbed neodymium double-decker phthalocyanine (NdPc 2 ) by means of low temperature scanning tunneling microscopy and spectroscopy (STM and STS). The molecules are deposited by sublimation onto different substrates. It is observed that a large fraction of the double-decker molecules decomposes during deposition. The decomposition probability strongly depends on the chosen substrate. Therefore it is concluded that the substrate modifies the electronic structure of the molecule leading to a stabilization or destabilization of the molecular entity. Charge transfer from the surface to the molecule is identified as a potential stabilizing mechanism. The electronic and magnetic properties are investigated in detail for adsorbed NdPc 2 molecules on Cu(100). The results of the experimental study are compared to state-of-the-art density functional theory calculations performed by our colleagues from the Peter Gruenberg Institute (PGI-1) at the Forschungszentrum Juelich. Interestingly, the lower Pc ring of the molecule hybridizes intensely with the substrate leading to strong chemisorption of the molecule, while the upper Pc ring keeps its molecular type electronic states, which can be energetically shifted by an external electric field. Importantly, it is possible to get direct access to the spin

  8. In-plane conductance of thin films as a probe of surface chemical environment: Adsorbate effects on film electronic properties of indium tin oxide and gold

    Science.gov (United States)

    Swint, Amy Lynn

    Changes in the in-plane conductance of conductive thin films are observed as a result of chemical adsorption at the surface. Reaction of the indium tin oxide (ITO) surface with Bronsted acids (bases) leads to increases (decreases) in its in-plane conductance as measured by a four-point probe configuration. The conductance varies monotonically with pH suggesting that the degree of surface protonation or hydroxylation controls the surface charge density, which in turn affects the width of the n-type depletion layer, and ultimately the in-plane conductance. Measurements at constant pH with a series of tetraalkylammonium hydroxide species of varying cation size indicate that surface dipoles also affect ITO conductance by modulating the magnitude of the surface polarization. Modulating the double layer with varying aqueous salt solutions also affects ITO conductance, though not to the same degree as strong Bronsted acids and bases. Solvents of varying dielectric constant and proton donating ability (ethanol, dimethylformamide) decrease ITO conductance relative to H2O. In addition, changing solvent gives rise to thermally-derived conductance transients, which result from exothermic solvent mixing. The self-assembly of alkanethiols at the surface increases the conductance of ITO films, most likely through carrier population effects. In all cases examined the combined effects of surface charge, adsorbed dipole layer magnitude and carrier injection are responsible for altering the ITO conductance. Besides being directly applicable to the control of electronic properties, these results also point to the use of four-point probe resistance measurements in condensed phase sensing applications. Ultrasensitive conductance-based gas phase sensing of organothiol adsorption to gold nanowires is accomplished with a limit of detection in the 105 molecule range. Further refinement of the inherently low noise resistance measurement may lead to observation of single adsorption events at

  9. Immobilized enzymes: understanding enzyme - surface interactions at the molecular level.

    Science.gov (United States)

    Hoarau, Marie; Badieyan, Somayesadat; Marsh, E Neil G

    2017-11-22

    Enzymes immobilized on solid supports have important and industrial and medical applications. However, their uses are limited by the significant reductions in activity and stability that often accompany the immobilization process. Here we review recent advances in our understanding of the molecular level interactions between proteins and supporting surfaces that contribute to changes in stability and activity. This understanding has been facilitated by the application of various surface-sensitive spectroscopic techniques that allow the structure and orientation of enzymes at the solid/liquid interface to be probed, often with monolayer sensitivity. An appreciation of the molecular interactions between enzyme and surface support has allowed the surface chemistry and method of enzyme attachement to be fine-tuned such that activity and stability can be greatly enhanced. These advances suggest that a much wider variety of enzymes may eventually be amenable to immobilization as green catalysts.

  10. Optimization of hexavalent chromium removal from aqueous solution using acid-modified granular activated carbon as adsorbent through response surface methodology

    International Nuclear Information System (INIS)

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad

    2015-01-01

    Response surface methodology (RSM) was applied to evaluate the effect of the main operational variables, including initial pH, initial chromium ion concentration, bulk density of GAC and time on the removal of hexavalent chromium Cr(Ⅵ) from contaminated groundwater by permeable reactive barriers (PRB) with acid-modified granular activated carbon (GAC) as an adsorbent material. The removal rates of Cr(Ⅵ) under different values of these parameters were investigated and results indicated high adsorption capacity at low pH and low initial metal ion concentration of Cr(Ⅵ), but the bulk density of GAC slightly influenced the process efficiency. According to the ANOVA (analysis of variance) results, the model presents high R 2 values of 94.35% for Cr(Ⅵ) removal efficiency, which indicates that the accuracy of the polynomial models was good. Also, quadratic regression models with estimated coefficients were developed to describe the pollutant removals

  11. Optimization of hexavalent chromium removal from aqueous solution using acid-modified granular activated carbon as adsorbent through response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad [Amirkabir University of Technology (Tehran Polytechnic), Tehran (Iran, Islamic Republic of)

    2015-06-15

    Response surface methodology (RSM) was applied to evaluate the effect of the main operational variables, including initial pH, initial chromium ion concentration, bulk density of GAC and time on the removal of hexavalent chromium Cr(Ⅵ) from contaminated groundwater by permeable reactive barriers (PRB) with acid-modified granular activated carbon (GAC) as an adsorbent material. The removal rates of Cr(Ⅵ) under different values of these parameters were investigated and results indicated high adsorption capacity at low pH and low initial metal ion concentration of Cr(Ⅵ), but the bulk density of GAC slightly influenced the process efficiency. According to the ANOVA (analysis of variance) results, the model presents high R{sup 2} values of 94.35% for Cr(Ⅵ) removal efficiency, which indicates that the accuracy of the polynomial models was good. Also, quadratic regression models with estimated coefficients were developed to describe the pollutant removals.

  12. Surface cleaning and adsorbate layer formation: Dual role of alkylamines in the formation of self-assembled monolayers on cuprate superconductors

    International Nuclear Information System (INIS)

    Ritchie, J.E.; Murray, W.R.; Kershan, K.; Diaz, V.; Tran, L.; McDevitt, J.T.

    1999-01-01

    The development of monolayer adsorption chemistry for superconductor surfaces is particularly important for a number of practical and fundamental reasons. As high-T c superconductors begin to approach the marketplace in areas of communications, power industries, medical applications, and scientific instrumentation, the development of new soft chemistry approaches for the surface modification of these technologically relevant electronic materials becomes increasingly important. Monolayer adsorption chemistry has been developed extensively for electronic materials such as metals, semiconductors, and insulators. These methodologies have been expanded recently to include a variety of high-temperature superconductors (HTSCs). The authors describe a series of new X-ray photoelectron spectroscopy (XPS), four-point conductivity, critical current, atomic absorption spectroscopy (AAS), grazing angle infrared spectroscopy, and GE--MS experiments, which lead the suggestion that an entirely different mechanism is involved in the formation of HTSC-localized monolayers. According to the new model, the amine reagents serve two chemically distinct roles. In the initial phase, the degraded superconductor exteriors is etched away with the help of the amine compounds. The etching process proceeds to the point where fresh YBa 2 Cu 3 O 7 is exposed, and only at this point do the amines adsorb and remain at the YBa 2 Cu 3 O 7 surface. As the adsorption process continues, there is an accumulation of an organized monolayer at the surface, which prevents further etching of the YBa 2 Cu 3 O 7 material

  13. Influence of polymer additive molecular weight on surface and ...

    Indian Academy of Sciences (India)

    2, April 2011, pp. 347–356. c Indian Academy of Sciences. Influence of polymer additive molecular weight on surface and microstructural characteristics of electrodeposited copper. R MANU. ∗ and SOBHA JAYAKRISHNAN. Electroplating and Metal Finishing Technology Division, Central Electrochemical Research Institute,.

  14. Solid surface vs. liquid surface: nanoarchitectonics, molecular machines, and DNA origami.

    Science.gov (United States)

    Ariga, Katsuhiko; Mori, Taizo; Nakanishi, Waka; Hill, Jonathan P

    2017-09-13

    The investigation of molecules and materials at interfaces is critical for the accumulation of new scientific insights and technological advances in the chemical and physical sciences. Immobilization on solid surfaces permits the investigation of different properties of functional molecules or materials with high sensitivity and high spatial resolution. Liquid surfaces also present important media for physicochemical innovation and insight based on their great flexibility and dynamicity, rapid diffusion of molecular components for mixing and rearrangements, as well as drastic spatial variation in the prevailing dielectric environment. Therefore, a comparative discussion of the relative merits of the properties of materials when positioned at solid or liquid surfaces would be informative regarding present-to-future developments of surface-based technologies. In this perspective article, recent research examples of nanoarchitectonics, molecular machines, DNA nanotechnology, and DNA origami are compared with respect to the type of surface used, i.e. solid surfaces vs. liquid surfaces, for future perspectives of interfacial physics and chemistry.

  15. Facile preparation of surface-exchangeable core@shell iron oxide@gold nanoparticles for magnetic solid-phase extraction: Use of gold shell as the intermediate platform for versatile adsorbents with varying self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yaping [Beijing National Laboratory of Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Graduate School, University of Chinese Academy of Sciences, Beijing 100049 (China); Qi, Li, E-mail: qili@iccas.ac.cn [Beijing National Laboratory of Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Shen, Ying [Beijing National Laboratory of Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Graduate School, University of Chinese Academy of Sciences, Beijing 100049 (China); Ma, Huimin [Beijing National Laboratory of Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-02-06

    Graphical abstract: -- Highlights: •The core@shell Fe{sub 3}O{sub 4}@Au nanoparticles functionalized with SAMs were successfully constructed. •The SAMs could be transformed from one kind to another via thiol exchange process. •The developed nanomaterials could be applied in mode switching MSPE. -- Abstract: The core@shell Fe{sub 3}O{sub 4}@Au nanoparticles (NPs) functionalized with exchangeable self-assembled monolayers have been developed for mode switching magnetic solid-phase extraction (MSPE) using high performance liquid chromatography with ultraviolet detection. The adsorbents were synthesized by chemical coprecipitation to prepare magnetic cores followed by sonolysis to produce gold shells. Functionalization of Fe{sub 3}O{sub 4}@Au NPs surface was realized through self-assembly of commercially available low molecular weight thiol-containing ligands using gold shells as intermediate platform and the dynamic nature of Au–S chemistry allowed substituent of one thiol-containing ligand with another simply by thiol exchange process. The resultant adsorbents were characterized by transmission electronic microscopy, Fourier transform infrared spectroscopy, elemental analysis, contact angle measurement, and vibrating sample magnetometry. To evaluate the versatile performance of the developed MSPE adsorbents, they were applied for normal-phase SPE followed by reversed-phase SPE. A few kinds of diphenols and polycyclic aromatic hydrocarbons (PAHs) were employed as model analytes, respectively. The predominant parameters affecting extraction efficiency were investigated and optimized. Under the optimum experimental conditions, wide dynamic linear range (6.25–1600 μg L{sup −1} for diphenols and 1.56–100 μg L{sup −1} for PAHs) with good linearity (r{sup 2} ≥ 0.989) and low detection limits (0.34–16.67 μg L{sup −1} for diphenols and 0.26–0.52 μg L{sup −1} for PAHs) were achieved. The advantage of the developed method is that the Fe{sub 3}O

  16. Ti and Zr surfaces studied by molecular dynamics

    International Nuclear Information System (INIS)

    Pascuet, Maria I.; Passianot, Roberto C.; Monti, Ana M.

    2003-01-01

    The interaction between point defects technique and the (0001), (1-210), (10-10) surfaces in Ti and Zr is studied by the molecular dynamics technique. Both of metals are in the hexagonal structure and within a temperature range of 100 to 900 K. The atomic interactions are modeled by EAM-type many-body potentials, that were used previously in static simulations. New migration mechanisms are unraveled and others are verified with respect to those already proposed in the static studies. Also included is an analysis of the vacancy stability in the sub-surface layers of the prismatic surfaces. (author)

  17. 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.

  18. Molecularly engineered graphene surfaces for sensing applications: A review

    International Nuclear Information System (INIS)

    Liu, Jingquan; Liu, Zhen; Barrow, Colin J.; Yang, Wenrong

    2015-01-01

    Highlights: • The importance of surface chemistry of graphene materials is clearly described. • We discuss molecularly engineered graphene surfaces for sensing applications. • We describe the latest developments of these materials for sensing technology. - Abstract: Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis

  19. Molecularly engineered graphene surfaces for sensing applications: A review

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jingquan, E-mail: jliu@qdu.edu.cn [College of Chemical Science and Engineering, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao (China); Liu, Zhen; Barrow, Colin J. [Centre for Chemistry and Biotechnology, Deakin University, Geelong, VIC 3217 (Australia); Yang, Wenrong, E-mail: wenrong.yang@deakin.edu.au [Centre for Chemistry and Biotechnology, Deakin University, Geelong, VIC 3217 (Australia)

    2015-02-15

    Highlights: • The importance of surface chemistry of graphene materials is clearly described. • We discuss molecularly engineered graphene surfaces for sensing applications. • We describe the latest developments of these materials for sensing technology. - Abstract: Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis.

  20. Microporous carbonaceous adsorbents for CO2 separation via selective adsorption

    KAUST Repository

    Zhao, Yunfeng

    2015-01-01

    Selective adsorption of CO2 has important implications for many energy and environment-related processes, which require the separation of CO2 from other gases (e.g. N2 and CH4) with high uptakes and selectivity. The development of high-performance adsorbents is one of the most promising solutions to the success of these processes. The present review is focused on the state-of-the-art of carbon-based (carbonaceous) adsorbents, covering microporous inorganic carbons and microporous organic polymers, with emphasis on the correlation between their textural and compositional properties and their CO2 adsorption/separation performance. Special attention is given to the most recently developed materials that were not covered in previous reviews. We summarize various effective strategies (N-doping, surface functionalization, extra-framework ions, molecular design, and pore size engineering) for enhancing the CO2 adsorption capacity and selectivity of carbonaceous adsorbents. Our discussion focuses on CO2/N2 separation and CO2/CH4 separation, while including an introduction to the methods and criteria used for evaluating the performance of the adsorbents. Critical issues and challenges regarding the development of high-performance adsorbents as well as some overlooked facts and misconceptions are also discussed, with the aim of providing important insights into the design of novel carbonaceous porous materials for various selective adsorption based applications. This journal is © The Royal Society of Chemistry.

  1. Tolerance of topological surface state towards adsorbed magnetic moments: Fe on Bi{sub 2}Te{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, Markus; Marchenko, Dmitry; Sanchez-Barriga, Jaime; Varykhalov, Andrei; Rader, Oliver [Helmholtz-Zentrum fuer Materialien und Energie, Berlin (Germany); Volykhov, Andrei; Yashina, Lada [Moscow State University, Moskau, Russland (Russian Federation)

    2011-07-01

    Topological surface states on Bi{sub 2}Se{sub 3} and Bi{sub 2}Te{sub 3} are protected by time reversal symmetry. Magnetic fields break time-reversal symmetry, and they have been used in two-dimensional spin quantum-Hall systems to destroy the topological edge states. Another possibility is to introduce magnetic moments. This has been done by substitution of Mn and Fe into the bulk. For Fe a small gap of 44meV was created, however, at very large amounts (12%). In this work, we deposit Fe directly onto the surface where the topological surface state is localized. We show for coverages of 0.25 and 1 ML Fe that the Dirac point remains intact and no gap appears. Core level spectroscopy of Bi and Te states gives insight into the interaction between substrate and adatoms. In addition, extra surface states appear at the Fermi energy which show a large Rashba-type spin-orbit splitting. The orientation of the spin of both, the topological as well as the Rashba-type split surface states is analysed.

  2. Iron phthalocyanine on Cu(111): Coverage-dependent assembly and symmetry breaking, temperature-induced homocoupling, and modification of the adsorbate-surface interaction by annealing.

    Science.gov (United States)

    Snezhkova, Olesia; Bischoff, Felix; He, Yuanqin; Wiengarten, Alissa; Chaudhary, Shilpi; Johansson, Niclas; Schulte, Karina; Knudsen, Jan; Barth, Johannes V; Seufert, Knud; Auwärter, Willi; Schnadt, Joachim

    2016-03-07

    We have examined the geometric and electronic structures of iron phthalocyanine assemblies on a Cu(111) surface at different sub- to mono-layer coverages and the changes induced by thermal annealing at temperatures between 250 and 320 °C by scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. The symmetry breaking observed in scanning tunneling microscopy images is found to be coverage dependent and to persist upon annealing. Further, we find that annealing to temperatures between 300 and 320 °C leads to both desorption of iron phthalocyanine molecules from the surface and their agglomeration. We see clear evidence of temperature-induced homocoupling reactions of the iron phthalocyanine molecules following dehydrogenation of their isoindole rings, similar to what has been observed for related tetrapyrroles on transition metal surfaces. Finally, spectroscopy indicates a modified substrate-adsorbate interaction upon annealing with a shortened bond distance. This finding could potentially explain a changed reactivity of Cu-supported iron phthalocyanine in comparison to that of the pristine compound.

  3. Molecular adsorbents recirculating system treatment in acute-on-chronic hepatitis patients on the transplant waiting list improves model for end-stage liver disease scores.

    Science.gov (United States)

    Novelli, G; Rossi, M; Pugliese, F; Poli, I; Ruberto, E; Martelli, S; Nudo, F; Morabito, V; Mennini, G; Berloco, P B

    2007-01-01

    The aim of our study was to show an improvement in Model for End-Stage Liver Disease (MELD) score after treatment with Molecular adsorbents recirculating system (MARS) in acute-on-chronic hepatitis (AoCHF) patients. MELD was adopted to determine the prognosis of patients with liver chronic desease. We evaluated the possibility to improve the MELD score of patients awaiting liver transplantation using a liver support device, namely, MARS. From September 1999 to April 2006, we treated 80 patients whose diagnoses were hepatitis C, 41.25%; hepatitis B, 27.5%; alcholic, 17.5%; intoxication, 8.75%; primary biliary cirrhosis, 5%. The overall mean age was 45 years (23 to 62), the cohort included 56 men and 24 women. Inclusion criteria were bilirubin >15 mg/dL; MELD >20; encephalopathy >II; and International Normalized Ratio, >2.1. Other parameters evaluated included ammonia, creatinine, lactate, glutamic oxalic transminase, and guanosine 5'-triphosphate. All patients were treated with a mean of 6-hour cycles of MARS (range, 5 to 8 hours) for a minimum of three treatments and a maximum of 20 treatments over 3 months. Clinical conditions were evaluated by improved hemodynamic parameters, kidney function, liver function, coagulation, neurologic status using the SOFA score, Glasgow Coma Scale (GCS), and Acute Physiology and Chronic Health Evaluation II Criteria. The MELD score for all categories of living patients showed significant improvements at the end of treatment and at 3-months follow-up, but the small number of patients was a limitation to determine prediction of mortality. Our study shows that MARS treatment improved multiple organ functions-liver, renal, neurologic, and hemodynamic. The improved MELD score gave patients on the transplant waiting list longer survival, allowing them a greater opportunity for liver transplantation.

  4. The transition from the adsorbed state to a surface alloy in the Sn/Ni(111) system

    Czech Academy of Sciences Publication Activity Database

    Karakalos, S.; Kennou, S.; Ladas, S.; Janeček, P.; Šutara, F.; Nehasil, V.; Fabík, S.; Tsud, N.; Prince, K. C.; Matolín, V.; Cháb, Vladimír

    2006-01-01

    Roč. 600, - (2006), s. 4067-4071 ISSN 0039-6028 Grant - others:Greek-Czech Bilateral Project(GR) KONTAKT 2003-2005 Institutional research plan: CEZ:AV0Z10100521 Keywords : nickel * tin * surface alloying * synchrotron radiation photoelectron spectroscopy * LEED * CO adsorption Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.880, year: 2006

  5. Combined Molecular Dynamics Simulation-Molecular-Thermodynamic Theory Framework for Predicting Surface Tensions.

    Science.gov (United States)

    Sresht, Vishnu; Lewandowski, Eric P; Blankschtein, Daniel; Jusufi, Arben

    2017-08-22

    A molecular modeling approach is presented with a focus on quantitative predictions of the surface tension of aqueous surfactant solutions. The approach combines classical Molecular Dynamics (MD) simulations with a molecular-thermodynamic theory (MTT) [ Y. J. Nikas, S. Puvvada, D. Blankschtein, Langmuir 1992 , 8 , 2680 ]. The MD component is used to calculate thermodynamic and molecular parameters that are needed in the MTT model to determine the surface tension isotherm. The MD/MTT approach provides the important link between the surfactant bulk concentration, the experimental control parameter, and the surfactant surface concentration, the MD control parameter. We demonstrate the capability of the MD/MTT modeling approach on nonionic alkyl polyethylene glycol surfactants at the air-water interface and observe reasonable agreement of the predicted surface tensions and the experimental surface tension data over a wide range of surfactant concentrations below the critical micelle concentration. Our modeling approach can be extended to ionic surfactants and their mixtures with both ionic and nonionic surfactants at liquid-liquid interfaces.

  6. Membrane adsorber for endotoxin removal

    Directory of Open Access Journals (Sweden)

    Karina Moita de Almeida

    Full Text Available ABSTRACT The surface of flat-sheet nylon membranes was modified using bisoxirane as the spacer and polyvinyl alcohol as the coating polymer. The amino acid histidine was explored as a ligand for endotoxins, aiming at its application for endotoxin removal from aqueous solutions. Characterization of the membrane adsorber, analysis of the depyrogenation procedures and the evaluation of endotoxin removal efficiency in static mode are discussed. Ligand density of the membranes was around 7 mg/g dry membrane, allowing removal of up to 65% of the endotoxins. The performance of the membrane adsorber prepared using nylon coated with polyvinyl alcohol and containing histidine as the ligand proved superior to other membrane adsorbers reported in the literature. The lack of endotoxin adsorption on nylon membranes without histidine confirmed that endotoxin removal was due to the presence of the ligand at the membrane surface. Modified membranes were highly stable, exhibiting a lifespan of approximately thirty months.

  7. Atomic and molecular layer deposition for surface modification

    Energy Technology Data Exchange (ETDEWEB)

    Vähä-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland); Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland); Johansson, Leena-Sisko, E-mail: leena-sisko.johansson@aalto.fi [Aalto University, School of Chemical Technology, Department of Forest Products Technology, PO Box 16100, FI‐00076 AALTO (Finland); Koskinen, Jorma T.; Harlin, Ali [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland)

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas–solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin – even non-uniform – atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid. - Graphical abstract: Print quality of a polylactide film surface modified with atomic layer deposition prior to inkjet printing (360 dpi) with an aqueous ink. Number of printed dots illustrated as a function of 0, 5, 15 and 25 deposition cycles of trimethylaluminum and water. - Highlights: • ALD/MLD can be used to adjust surface characteristics of films and fiber materials. • Hydrophobicity after few deposition cycles of Al{sub 2}O{sub 3} due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO{sub 2}. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt.

  8. Non-linear optical studies of adsorbates: Spectroscopy and dynamics

    International Nuclear Information System (INIS)

    Zhu, Xiangdong.

    1989-08-01

    In the first part of this thesis, we have established a systematic procedure to apply the surface optical second-harmonic generation (SHG) technique to study surface dynamics of adsorbates. In particular, we have developed a novel technique for studies of molecular surface diffusions. In this technique, the laser-induced desorption with two interfering laser beams is used to produce a monolayer grating of adsorbates. The monolayer grating is detected with diffractions of optical SHG. By monitoring the first-order second-harmonic diffraction, we can follow the time evolution of the grating modulation from which we are able to deduce the diffusion constant of the adsorbates on the surface. We have successfully applied this technique to investigate the surface diffusion of CO on Ni(111). The unique advantages of this novel technique will enable us to readily study anisotropy of a surface diffusion with variable grating orientation, and to investigate diffusion processes of a large dynamic range with variable grating spacings. In the second part of this work, we demonstrate that optical infrared-visible sum-frequency generation (SFG) from surfaces can be used as a viable surface vibrational spectroscopic technique. We have successfully recorded the first vibrational spectrum of a monolayer of adsorbates using optical infrared-visible SFG. The qualitative and quantitative correlation of optical SFG with infrared absorption and Raman scattering spectroscopies are examined and experimentally demonstrated. We have further investigated the possibility to use transient infrared-visible SFG to probe vibrational transients and ultrafast relaxations on surfaces. 146 refs

  9. Non-linear optical studies of adsorbates: Spectroscopy and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiangdong.

    1989-08-01

    In the first part of this thesis, we have established a systematic procedure to apply the surface optical second-harmonic generation (SHG) technique to study surface dynamics of adsorbates. In particular, we have developed a novel technique for studies of molecular surface diffusions. In this technique, the laser-induced desorption with two interfering laser beams is used to produce a monolayer grating of adsorbates. The monolayer grating is detected with diffractions of optical SHG. By monitoring the first-order second-harmonic diffraction, we can follow the time evolution of the grating modulation from which we are able to deduce the diffusion constant of the adsorbates on the surface. We have successfully applied this technique to investigate the surface diffusion of CO on Ni(111). The unique advantages of this novel technique will enable us to readily study anisotropy of a surface diffusion with variable grating orientation, and to investigate diffusion processes of a large dynamic range with variable grating spacings. In the second part of this work, we demonstrate that optical infrared-visible sum-frequency generation (SFG) from surfaces can be used as a viable surface vibrational spectroscopic technique. We have successfully recorded the first vibrational spectrum of a monolayer of adsorbates using optical infrared-visible SFG. The qualitative and quantitative correlation of optical SFG with infrared absorption and Raman scattering spectroscopies are examined and experimentally demonstrated. We have further investigated the possibility to use transient infrared-visible SFG to probe vibrational transients and ultrafast relaxations on surfaces. 146 refs.

  10. Waves on the surface of the Orion molecular cloud.

    Science.gov (United States)

    Berné, Olivier; Marcelino, Núria; Cernicharo, José

    2010-08-19

    Massive stars influence their parental molecular cloud, and it has long been suspected that the development of hydrodynamical instabilities can compress or fragment the cloud. Identifying such instabilities has proved difficult. It has been suggested that elongated structures (such as the 'pillars of creation') and other shapes arise because of instabilities, but alternative explanations are available. One key signature of an instability is a wave-like structure in the gas, which has hitherto not been seen. Here we report the presence of 'waves' at the surface of the Orion molecular cloud near where massive stars are forming. The waves seem to be a Kelvin-Helmholtz instability that arises during the expansion of the nebula as gas heated and ionized by massive stars is blown over pre-existing molecular gas.

  11. THE SURFACE-MEDIATED UNFOLDING KINETICS OF GLOBULAR PROTEINS IS DEPENDENT ON MOLECULAR WEIGHT AND TEMPERATURE

    Energy Technology Data Exchange (ETDEWEB)

    Patananan, A.N.; Goheen, S.C.

    2008-01-01

    The adsorption and unfolding pathways of proteins on rigid surfaces are essential in numerous complex processes associated with biomedical engineering, nanotechnology, and chromatography. It is now well accepted that the kinetics of unfolding are characterized by chemical and physical interactions dependent on protein deformability and structure, as well as environmental pH, temperature, and surface chemistry. Although this fundamental process has broad implications in medicine and industry, little is known about the mechanism because of the atomic lengths and rapid time scales involved. Therefore, the unfolding kinetics of myoglobin, β-glucosidase, and ovalbumin were investigated by adsorbing the globular proteins to non-porous cationic polymer beads. The protein fractions were adsorbed at different residence times (0, 9, 10, 20, and 30 min) at near-physiological conditions using a gradient elution system similar to that in high-performance liquid chromatography. The elution profi les and retention times were obtained by ultraviolet/visible spectrophotometry. A decrease in recovery was observed with time for almost all proteins and was attributed to irreversible protein unfolding on the non-porous surfaces. These data, and those of previous studies, fi t a positively increasing linear trend between percent unfolding after a fi xed (9 min) residence time (71.8%, 31.1%, and 32.1% of myoglobin, β-glucosidase, and ovalbumin, respectively) and molecular weight. Of all the proteins examined so far, only myoglobin deviated from this trend with higher than predicted unfolding rates. Myoglobin also exhibited an increase in retention time over a wide temperature range (0°C and 55°C, 4.39 min and 5.74 min, respectively) whereas ovalbumin and β-glucosidase did not. Further studies using a larger set of proteins are required to better understand the physiological and physiochemical implications of protein unfolding kinetics. This study confi rms that surface

  12. Reaction dynamics of molecular hydrogen on silicon surfaces

    DEFF Research Database (Denmark)

    Bratu, P.; Brenig, W.; Gross, A.

    1996-01-01

    of the preexponential factor by about one order of magnitude per lateral degree of freedom. Molecular vibrations have practically no effect on the adsorption/desorption dynamics itself, but lead to vibrational heating in desorption with a strong isotope effect. Ab initio calculations for the H-2 interaction...... between the two surfaces. These results indicate that tunneling, molecular vibrations, and the structural details of the surface play only a minor role for the adsorption dynamics. Instead, they appear to be governed by the localized H-Si bonding and Si-Si lattice vibrations. Theoretically, an effective......Experimental and theoretical results on the dynamics of dissociative adsorption and recombinative desorption of hydrogen on silicon are presented. Using optical second-harmonic generation, extremely small sticking probabilities in the range 10(-9)-10(-5) could be measured for H-2 and D-2 on Si(111...

  13. Molecular cartography of the human skin surface in 3D

    Science.gov (United States)

    Bouslimani, Amina; Porto, Carla; Rath, Christopher M.; Wang, Mingxun; Guo, Yurong; Gonzalez, Antonio; Berg-Lyon, Donna; Ackermann, Gail; Moeller Christensen, Gitte Julie; Nakatsuji, Teruaki; Zhang, Lingjuan; Borkowski, Andrew W.; Meehan, Michael J.; Dorrestein, Kathleen; Gallo, Richard L.; Bandeira, Nuno; Knight, Rob; Alexandrov, Theodore; Dorrestein, Pieter C.

    2015-01-01

    The human skin is an organ with a surface area of 1.5–2 m2 that provides our interface with the environment. The molecular composition of this organ is derived from host cells, microbiota, and external molecules. The chemical makeup of the skin surface is largely undefined. Here we advance the technologies needed to explore the topographical distribution of skin molecules, using 3D mapping of mass spectrometry data and microbial 16S rRNA amplicon sequences. Our 3D maps reveal that the molecular composition of skin has diverse distributions and that the composition is defined not only by skin cells and microbes but also by our daily routines, including the application of hygiene products. The technological development of these maps lays a foundation for studying the spatial relationships of human skin with hygiene, the microbiota, and environment, with potential for developing predictive models of skin phenotypes tailored to individual health. PMID:25825778

  14. Surface-enhanced Raman scattering of amorphous silica gel adsorbed on gold substrates for optical fiber sensors

    Science.gov (United States)

    Degioanni, S.; Jurdyc, A. M.; Cheap, A.; Champagnon, B.; Bessueille, F.; Coulm, J.; Bois, L.; Vouagner, D.

    2015-10-01

    Two kinds of gold substrates are used to produce surface-enhanced Raman scattering (SERS) of amorphous silica obtained via the sol-gel route using tetraethoxysilane Si(OC2H5)4 (TEOS) solution. The first substrate consists of a gold nanometric film elaborated on a glass slide by sputter deposition, controlling the desired gold thickness and sputtering current intensity. The second substrate consists of an array of micrometer-sized gold inverted pyramidal pits able to confine surface plasmon (SP) enhancing electric field, which results in a distribution of electromagnetic energy inside the cavities. These substrates are optically characterized to observe SPR with, respectively, extinction and reflectance spectrometries. Once coated with thin layers of amorphous silica (SiO2) gel, these samples show Raman amplification of amorphous SiO2 bands. This enhancement can occur in SERS sensors using amorphous SiO2 gel as shells, spacers, protective coatings, or waveguides, and represents particularly a potential interest in the field of Raman distributed sensors, which use the amorphous SiO2 core of optical fibers as a transducer to make temperature measurements.

  15. Protein signatures using electrostatic molecular surfaces in harmonic space

    Directory of Open Access Journals (Sweden)

    C. Sofia Carvalho

    2013-10-01

    Full Text Available We developed a novel method based on the Fourier analysis of protein molecular surfaces to speed up the analysis of the vast structural data generated in the post-genomic era. This method computes the power spectrum of surfaces of the molecular electrostatic potential, whose three-dimensional coordinates have been either experimentally or theoretically determined. Thus we achieve a reduction of the initial three-dimensional information on the molecular surface to the one-dimensional information on pairs of points at a fixed scale apart. Consequently, the similarity search in our method is computationally less demanding and significantly faster than shape comparison methods. As proof of principle, we applied our method to a training set of viral proteins that are involved in major diseases such as Hepatitis C, Dengue fever, Yellow fever, Bovine viral diarrhea and West Nile fever. The training set contains proteins of four different protein families, as well as a mammalian representative enzyme. We found that the power spectrum successfully assigns a unique signature to each protein included in our training set, thus providing a direct probe of functional similarity among proteins. The results agree with established biological data from conventional structural biochemistry analyses.

  16. Adsorption of aromatic compounds by carbonaceous adsorbents: a comparative study on granular activated carbon, activated carbon fiber, and carbon nanotubes.

    Science.gov (United States)

    Zhang, Shujuan; Shao, Ting; Kose, H Selcen; Karanfil, Tanju

    2010-08-15

    Adsorption of three aromatic organic compounds (AOCs) by four types of carbonaceous adsorbents [a granular activated carbon (HD4000), an activated carbon fiber (ACF10), two single-walled carbon nanotubes (SWNT, SWNT-HT), and a multiwalled carbon nanotube (MWNT)] with different structural characteristics but similar surface polarities was examined in aqueous solutions. Isotherm results demonstrated the importance of molecular sieving and micropore effects in the adsorption of AOCs by carbonaceous porous adsorbents. In the absence of the molecular sieving effect, a linear relationship was found between the adsorption capacities of AOCs and the surface areas of adsorbents, independent of the type of adsorbent. On the other hand, the pore volume occupancies of the adsorbents followed the order of ACF10 > HD4000 > SWNT > MWNT, indicating that the availability of adsorption site was related to the pore size distributions of the adsorbents. ACF10 and HD4000 with higher microporous volumes exhibited higher adsorption affinities to low molecular weight AOCs than SWNT and MWNT with higher mesopore and macropore volumes. Due to their larger pore sizes, SWNTs and MWNTs are expected to be more efficient in adsorption of large size molecules. Removal of surface oxygen-containing functional groups from the SWNT enhanced adsorption of AOCs.

  17. ε-Polylysine-based thermo-responsive adsorbents for immunoglobulin adsorption-desorption under mild conditions.

    Science.gov (United States)

    Maruyama, Masashi; Shibuya, Keisuke

    2017-08-22

    Thermo-responsive adsorbents for immunoglobulin G (IgG) employing ε-polylysine (EPL) as a polymer backbone were developed. The introduction of mercaptoethylpyridine (MEP) as an IgG-binding ligand and hydrophobization of side chains afforded thermo-responsive IgG adsorbents, whose thermo-responsive IgG desorption ratio was up to 88% (EPL/MEP derivative 3m). The changes in surface densities of active MEP groups, which are caused by thermal conformational changes of the adsorbents, play key roles for IgG desorption. Although a trade-off of IgG adsorption capacity and IgG desorption ratio was observed, the present study offers a novel molecular design for thermo-responsive adsorbents with high synthetic accessibility and potentially low toxicity.

  18. Chemical and Molecular Characterization of Biofilm on Metal Surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    Bhosle, N.B.

    analytical instrumental techniques to assess the kinetics and chemical composition of the conditioning film developed on stainless steel panels deployed in seawater. These studies suggest that proteins are the first compounds to adsorb onto stainless steel...., 1990; Bott 1993; 159 stainless steel by the Time of flight secondary ion mass spectrometer (ToF-SIMS) (Poleunis et al., 2002, 2003). Further the nature of the substratum influences the chemical composition and quality of adsorbed organic matter...

  19. Synchrotron x-ray-diffraction study of the structure and growth of Xe films adsorbed on the Ag(111) surface

    International Nuclear Information System (INIS)

    Dai, P.; Wu, Z.; Angot, T.; Wang, S.; Taub, H.; Ehrlich, S.N.

    1999-01-01

    Synchrotron x-ray scattering has been used to investigate the structure and growth of perhaps the simplest of all films: xenon physisorbed on the Ag(111) surface. High-resolution x-ray scans of the in-plane structure and lower-resolution scans (specular and nonspecular) of the out-of-plane order were performed. The Xe films were prepared under both quasiequilibrium and kinetic growth conditions, and have fewer structural defects than those investigated previously by others on graphite substrates. Under quasiequilibrium conditions, the bulk Xe-Xe spacing is reached at monolayer completion, and the monolayer and bilayer lattice constants at coexistence are inferred equal to within 0.005 Angstrom, consistent with theoretical calculations. The Xe/vacuum interface profile for a complete monolayer and bilayer grown at quasiequilibrium is found to be sharper than for kinetically grown films. At coverages above two layers, diffraction scans along the Xe(01l) rod for quasiequilibrated films are consistent with the presence of two domains having predominantly an ABC stacking sequence and rotated 60 degree with respect to each other about the surface normal. Annealing of these films alters neither the population of the two domains nor the fraction of ABA stacking faults. The thickest film grown under quasiequilibrium conditions exceeds 220 Angstrom (resolution limited). Under kinetic growth conditions, x-ray intensity oscillations at the Xe anti-Bragg position of the specular rod are observed as a function of time, indicating nearly layer-by-layer growth. Up to four complete oscillations corresponding to a film of eight layers have been observed before the intensity is damped out; the number of oscillations is found to depend on the substrate temperature, the growth rate, and the quality of the Ag(111) substrate. The specular reflectivity from kinetically grown films at nominal coverages of three and four layers has been analyzed using a Gaussian model which gives a film

  20. Balancing an accurate representation of the molecular surface in generalized Born formalisms with integrator stability in molecular dynamics simulations

    Czech Academy of Sciences Publication Activity Database

    Chocholoušová, Jana; Feig, M.

    2006-01-01

    Roč. 27, č. 6 (2006), s. 719-729 ISSN 0192-8651 Keywords : molecular surface * generalized Born formalisms * molecular dynamic simulations Subject RIV: CC - Organic Chemistry Impact factor: 4.893, year: 2006

  1. Multiresolution molecular mechanics: Surface effects in nanoscale materials

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Qingcheng, E-mail: qiy9@pitt.edu; To, Albert C., E-mail: albertto@pitt.edu

    2017-05-01

    Surface effects have been observed to contribute significantly to the mechanical response of nanoscale structures. The newly proposed energy-based coarse-grained atomistic method Multiresolution Molecular Mechanics (MMM) (Yang, To (2015), ) is applied to capture surface effect for nanosized structures by designing a surface summation rule SR{sup S} within the framework of MMM. Combined with previously proposed bulk summation rule SR{sup B}, the MMM summation rule SR{sup MMM} is completed. SR{sup S} and SR{sup B} are consistently formed within SR{sup MMM} for general finite element shape functions. Analogous to quadrature rules in finite element method (FEM), the key idea to the good performance of SR{sup MMM} lies in that the order or distribution of energy for coarse-grained atomistic model is mathematically derived such that the number, position and weight of quadrature-type (sampling) atoms can be determined. Mathematically, the derived energy distribution of surface area is different from that of bulk region. Physically, the difference is due to the fact that surface atoms lack neighboring bonding. As such, SR{sup S} and SR{sup B} are employed for surface and bulk domains, respectively. Two- and three-dimensional numerical examples using the respective 4-node bilinear quadrilateral, 8-node quadratic quadrilateral and 8-node hexahedral meshes are employed to verify and validate the proposed approach. It is shown that MMM with SR{sup MMM} accurately captures corner, edge and surface effects with less 0.3% degrees of freedom of the original atomistic system, compared against full atomistic simulation. The effectiveness of SR{sup MMM} with respect to high order element is also demonstrated by employing the 8-node quadratic quadrilateral to solve a beam bending problem considering surface effect. In addition, the introduced sampling error with SR{sup MMM} that is analogous to numerical integration error with quadrature rule in FEM is very small. - Highlights:

  2. Influence of helium-ion bombardment on the surface properties of pure and ammonia-adsorbed water thin films

    International Nuclear Information System (INIS)

    Kondo, M.; Shibata, T.; Kawanowa, H.; Gotoh, Y.; Souda, R.

    2005-01-01

    The influence of the ion bombardment on the surface properties of water-ice films has been investigated. The films are irradiated with 1.5 keV He + ions and analyzed sequentially on the basis of time-of-flight secondary-ion mass spectrometry (TOF-SIMS). In order to minimize any temperature-induced effects, the measurements were made at 15 K. The damage of the films, as estimated from the H/D exchange between NH 3 and the D 2 O ice and the intermixing of NH 3 with the H 2 18 O ice, is recognized at the fluence above 2 x 10 14 ions/cm 2 . The sputtering yield of the D 2 O ice is determined as 0.9 ± 0.2 molecules per incoming He + ion. The temperature-programmed TOF-SIMS analysis of the water-ice films has been completed within the fluence of 5.8 x 10 12 ions/cm 2 , so that no appreciable damage of the film should be induced during the measurement

  3. Comparison of gas-solid chromatography and MM2 force field molecular binding energies for greenhouse gases on a carbonaceous surface.

    Science.gov (United States)

    Rybolt, Thomas R; Bivona, Kevin T; Thomas, Howard E; O'Dell, Casey M

    2009-10-01

    Gas-solid chromatography was used to determine B(2s) (gas-solid virial coefficient) values for eight molecular adsorbates interacting with a carbon powder (Carbopack B, Supelco). B(2s) values were determined by multiple size variant injections within the temperature range of 313-553 K. The molecular adsorbates included: carbon dioxide (CO(2)); tetrafluoromethane (CF(4)); hexafluoroethane (C(2)F(6)); 1,1-difluoroethane (C(2)H(4)F(2)); 1-chloro-1,1-difluoroethane (C(2)H(3)ClF(2)); dichlorodifluoromethane (CCl(2)F(2)); trichlorofluoromethane (CCl(3)F); and 1,1,1-trichloroethane (C(2)H(3)Cl(3)). Two of these molecules are of special interest because they are "super greenhouse gases". The global warming potential, GWP, for CF(4) is 6500 and for C(2)F(6) is 9200 relative to the reference value of 1 for CO(2). The GWP index considers both radiative blocking and molecular lifetime. For these and other industrial greenhouse gases, adsorptive trapping on a carbonaceous solid, which depends on molecule-surface binding energy, could avoid atmospheric release. The temperature variations of the gas-solid virial coefficients in conjunction with van't Hoff plots were used to find the experimental adsorption energy or binding energy values (E(*)) for each adsorbate. A molecular mechanics based, rough-surface model was used to calculate the molecule-surface binding energy (Ecal(*)) using augmented MM2 parameters. The surface model consisted of parallel graphene layers with two separated nanostructures each containing 17 benzene rings arranged in linear strips. The separation of the parallel nanostructures had been optimized in a prior study to appropriately represent molecule-surface interactions for Carbopack B. Linear regressions of E(*) versus Ecal(*) for the current data set of eight molecules and the same surface model gave E(*)=0.926 Ecal(*) and r(2)=0.956. A combined set of the current and prior Carbopack B adsorbates studied (linear alkanes, branched alkanes, cyclic alkanes

  4. Preparation of High Purity, High Molecular-Weight Chitin from Ionic Liquids for Use as an Adsorbate for the Extraction of Uranium from Seawater

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Robin [Univ. of Alabama, Tuscaloosa, AL (United States)

    2013-12-21

    Ensuring a domestic supply of uranium is a key issue facing the wider implementation of nuclear power. Uranium is mostly mined in Kazakhstan, Australia, and Canada, and there are few high-grade uranium reserves left worldwide. Therefore, one of the most appealing potential sources of uranium is the vast quantity dissolved in the oceans (estimated to be 4.4 billion tons worldwide). There have been research efforts centered on finding a means to extract uranium from seawater for decades, but so far none have resulted in an economically viable product, due in part to the fact that the materials that have been successfully demonstrated to date are too costly (in terms of money and energy) to produce on the necessary scale. Ionic Liquids (salts which melt below 100{degrees}C) can completely dissolve raw crustacean shells, leading to recovery of a high purity, high molecular weight chitin powder and to fibers and films which can be spun directly from the extract solution suggesting that continuous processing might be feasible. The work proposed here will utilize the unprecedented control this makes possible over the chitin fiber a) to prepare electrospun nanofibers of very high surface area and in specific architectures, b) to modify the fiber surfaces chemically with selective extractant capacity, and c) to demonstrate their utility in the direct extraction and recovery of uranium from seawater. This approach will 1) provide direct extraction of chitin from shellfish waste thus saving energy over the current industrial process for obtaining chitin; 2) allow continuous processing of nanofibers for very high surface area fibers in an economical operation; 3) provide a unique high molecular weight chitin not available from the current industrial process, leading to stronger, more durable fibers; and 4) allow easy chemical modification of the large surface areas of the fibers for appending uranyl selective functionality providing selectivity and ease of stripping. The

  5. Preparation of High Purity, High Molecular-Weight Chitin from Ionic Liquids for Use as an Adsorbate for the Extraction of Uranium from Seawater

    International Nuclear Information System (INIS)

    Rogers, Robin

    2013-01-01

    Ensuring a domestic supply of uranium is a key issue facing the wider implementation of nuclear power. Uranium is mostly mined in Kazakhstan, Australia, and Canada, and there are few high-grade uranium reserves left worldwide. Therefore, one of the most appealing potential sources of uranium is the vast quantity dissolved in the oceans (estimated to be 4.4 billion tons worldwide). There have been research efforts centered on finding a means to extract uranium from seawater for decades, but so far none have resulted in an economically viable product, due in part to the fact that the materials that have been successfully demonstrated to date are too costly (in terms of money and energy) to produce on the necessary scale. Ionic Liquids (salts which melt below 100 deg C) can completely dissolve raw crustacean shells, leading to recovery of a high purity, high molecular weight chitin powder and to fibers and films which can be spun directly from the extract solution suggesting that continuous processing might be feasible. The work proposed here will utilize the unprecedented control this makes possible over the chitin fiber a) to prepare electrospun nanofibers of very high surface area and in specific architectures, b) to modify the fiber surfaces chemically with selective extractant capacity, and c) to demonstrate their utility in the direct extraction and recovery of uranium from seawater. This approach will 1) provide direct extraction of chitin from shellfish waste thus saving energy over the current industrial process for obtaining chitin; 2) allow continuous processing of nanofibers for very high surface area fibers in an economical operation; 3) provide a unique high molecular weight chitin not available from the current industrial process, leading to stronger, more durable fibers; and 4) allow easy chemical modification of the large surface areas of the fibers for appending uranyl selective functionality providing selectivity and ease of stripping. The resulting

  6. Miscibility and interaction between 1-alkanol and short-chain phosphocholine in the adsorbed film and micelles.

    Science.gov (United States)

    Takajo, Yuichi; Matsuki, Hitoshi; Kaneshina, Shoji; Aratono, Makoto; Yamanaka, Michio

    2007-09-01

    The miscibility and interaction of 1-hexanol (C6OH) and 1-heptanol (C7OH) with 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) in the adsorbed films and micelles were investigated by measuring the surface tension of aqueous C6OH-DHPC and aqueous C7OH-DHPC solutions. The surface density, the mean molecular area, the composition of the adsorbed film, and the excess Gibbs energy of adsorption g(H,E), were estimated. Further, the critical micelle concentration of the mixtures was determined from the surface tension versus molality curves; the micellar composition was calculated. The miscibility of the 1-alkanols and DHPC molecules in the adsorbed film and micelles was examined using the phase diagram of adsorption (PDA) and that of micellization (PDM). The PDA and the composition dependence of g(H,E) indicated the non-ideal mixing of the 1-alkanols and DHPC molecules due to the attractive interaction between the molecules in the adsorbed film, while the PDM indicated that the 1-alkanol molecules were not incorporated in the micelles within DHPC rich region. The dependence of the mean molecular area of the mixtures on the surface composition suggested that the packing property of the adsorbed film depends on the chain length of 1-alkanol: C6OH expands the DHPC adsorbed film more than C7OH.

  7. Molecular recognition on a cavitand-functionalized silicon surface.

    Science.gov (United States)

    Biavardi, Elisa; Favazza, Maria; Motta, Alessandro; Fragalà, Ignazio L; Massera, Chiara; Prodi, Luca; Montalti, Marco; Melegari, Monica; Condorelli, Guglielmo G; Dalcanale, Enrico

    2009-06-03

    A Si(100) surface featuring molecular recognition properties was obtained by covalent functionalization with a tetraphosphonate cavitand (Tiiii), able to complex positively charged species. Tiiii cavitand was grafted onto the Si by photochemical hydrosilylation together with 1-octene as a spatial spectator. The recognition properties of the Si-Tiiii surface were demonstrated through two independent analytical techniques, namely XPS and fluorescence spectroscopy, during the course of reversible complexation-guest exchange-decomplexation cycles with specifically designed ammonium and pyridinium salts. Control experiments employing a Si(100) surface functionalized with a structurally similar, but complexation inactive, tetrathiophosphonate cavitand (TSiiii) demonstrated no recognition events. This provides evidence for the complexation properties of the Si-Tiiii surface, ruling out the possibility of nonspecific interactions between the substrate and the guests. The residual Si-O(-) terminations on the surface replace the guests' original counterions, thus stabilizing the complex ion pairs. These results represent a further step toward the control of self-assembly of complex supramolecular architectures on surfaces.

  8. Neutralization of Rubidium Adsorbate Electric Fields by Electron Attachment

    Energy Technology Data Exchange (ETDEWEB)

    Sedlacek, J. A. [Univ. of Oklahoma, Norman, OK (United States); Kim, E. [Univ. of Nevada, Las Vegas, NV (United States); Rittenhouse, S. T. [Western Washington Univ., Bellingham, WA (United States); US Naval Academy, Annapolis, MD (United States); Weck, Philippe F [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sadeghpour, H. R. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Shaffer, J. P. [Univ. of Oklahoma, Norman, OK (United States)

    2015-10-01

    We investigate the (0001) surface of single crystal quartz with a submonolayer of Rb adsorbates. Using Rydberg atom electromagnetically induced transparency, we investigate the electric elds resulting from Rb adsorbed on the quartz surface, and measure the activation energy of the Rb adsorbates. We show that the Rb induces a negative electron affnity (NEA) on the quartz surface. The NEA surface allows for low energy electrons to bind to the surface and cancel the electric eld from the Rb adsorbates. Our results have implications for integrating Rydberg atoms into hybrid quantum systems and the fundamental study of atom-surface interactions, as well as applications for electrons bound to a 2D surface.

  9. Forces on nuclei moving on autoionizing molecular potential energy surfaces.

    Science.gov (United States)

    Moiseyev, Nimrod

    2017-01-14

    Autoionization of molecular systems occurs in diatomic molecules and in small biochemical systems. Quantum chemistry packages enable calculation of complex potential energy surfaces (CPESs). The imaginary part of the CPES is associated with the autoionization decay rate, which is a function of the molecular structure. Molecular dynamics simulations, within the framework of the Born-Oppenheimer approximation, require the definition of a force field. The ability to calculate the forces on the nuclei in bio-systems when autoionization takes place seems to rely on an understanding of radiative damages in RNA and DNA arising from the release of slow moving electrons which have long de Broglie wavelengths. This work addresses calculation of the real forces on the nuclei moving on the CPES. By using the transformation of the time-dependent Schrödinger equation, previously used by Madelung, we proved that the classical forces on nuclei moving on the CPES correlated with the gradient of the real part of the CPES. It was proved that the force on the nuclei of the metastable molecules is time independent although the probability to detect metastable molecules exponentially decays. The classical force is obtained from the transformed Schrödinger equation when ℏ=0 and the Schrödinger equation is reduced to the classical (Newtonian) equations of motion. The forces on the nuclei regardless on what potential energy surface they move (parent CPES or product real PESs) vary in time due to the autoionization process.

  10. Passivation of nanocrystalline TiO2 junctions by surface adsorbed phosphinate amphiphiles enhances the photovoltaic performance of dye sensitized solar cells

    KAUST Repository

    Wang, Mingkui

    2009-01-01

    We report a new class of molecular insulators that electronically passivate the surface of nanocrystalline titania films for high performance dye sensitized solar cells (DSC). Using electrical impedance measurements we demonstrate that co-adsorption of dineohexyl bis-(3,3-dimethyl-butyl)-phosphinic acid (DINHOP), along with the amphiphilic ruthenium sensitizer Z907Na increased substantially the power output of the cells mainly due to a retardation of interfacial recombination of photo-generated charge carriers. The use of phosphinates as anchoring groups opens up new avenues for modification of the surface by molecular insulators, sensitizers and other electro-active molecules to realize the desired optoelectronic performance of devices based on oxide junctions. © 2009 The Royal Society of Chemistry.

  11. Room temperature discrimination of adsorbed molecules and attachment sites on the Si(111)–7 × 7 surface using a qPlus sensor

    Czech Academy of Sciences Publication Activity Database

    Majzik, Zsolt; Drevniok, B.; Kamiński, W.; Ondráček, Martin; McLean, A.B.; Jelínek, Pavel

    2013-01-01

    Roč. 7, č. 3 (2013), 2686-2692 ISSN 1936-0851 R&D Projects: GA ČR(CZ) GPP204/11/P578; GA ČR GAP204/10/0952 Grant - others:AVČR(CZ) M100101207 Institutional support: RVO:68378271 Keywords : nc-AFM * STM * DFT * molecular recognition * Si surface Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 12.033, year: 2013

  12. Heterogeneous reactions between ions NH3+and NH+andhydrocarbons adsorbed on a tungsten surface.Formation of HCN+in NH+-surface hydrocarbon collisions

    Czech Academy of Sciences Publication Activity Database

    Harnisch, M.; Scheier, P.; Herman, Zdeněk

    2015-01-01

    Roč. 392, DEC 2015 (2015), s. 139-144 ISSN 1387-3806 Institutional support: RVO:61388955 Keywords : ion-surface collisions * NH3+ and NH+projectiles * surface hydrocarbons Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.183, year: 2015

  13. Molecular-level removal of proteinaceous contamination from model surfaces and biomedical device materials by air plasma treatment.

    Science.gov (United States)

    Banerjee, K K; Kumar, S; Bremmell, K E; Griesser, H J

    2010-11-01

    Established methods for cleaning and sterilising biomedical devices may achieve removal of bioburden only at the macroscopic level while leaving behind molecular levels of contamination (mainly proteinaceous). This is of particular concern if the residue might contain prions. We investigated at the molecular level the removal of model and real-life proteinaceous contamination from model and practical surfaces by air plasma (ionised air) treatment. The surface-sensitive technique of X-ray photoelectron spectroscopy (XPS) was used to assess the removal of proteinaceous contamination, with the nitrogen (N1s) photoelectron signal as its marker. Model proteinaceous contamination (bovine serum albumin) adsorbed on to a model surface (silicon wafer) and the residual proteinaceous contamination resulting from incubating surgical stainless steel (a practical biomaterial) in whole human blood exhibited strong N1s signals [16.8 and 18.5 atomic percent (at.%), respectively] after thorough washing. After 5min air plasma treatment, XPS detected no nitrogen on the sample surfaces, indicating complete removal of proteinaceous contamination, down to the estimated XPS detection limit 10ng/cm(2). Applying the same plasma treatment, the 7.7at.% nitrogen observed on a clinically cleaned dental bur was reduced to a level reflective of new, as-received burs. Contact angle measurements and atomic force microscopy also indicated complete molecular-level removal of the proteinaceous contamination upon air plasma treatment. This study demonstrates the effectiveness of air plasma treatment for removing proteinaceous contamination from both model and practical surfaces and offers a method for ensuring that no molecular residual contamination such as prions is transferred upon re-use of surgical and dental instruments. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

  14. Vibrational energy on surfaces: Ultrafast flash-thermal conductance of molecular monolayers

    Science.gov (United States)

    Dlott, Dana

    2008-03-01

    Vibrational energy flow through molecules remains a perennial problem in chemical physics. Usually vibrational energy dynamics are viewed through the lens of time-dependent level populations. This is natural because lasers naturally pump and probe vibrational transitions, but it is also useful to think of vibrational energy as being conducted from one location in a molecule to another. We have developed a new technique where energy is driven into a specific part of molecules adsorbed on a metal surface, and ultrafast nonlinear coherent vibrational spectroscopy is used to watch the energy arrive at another part. This technique is the analog of a flash thermal conductance apparatus, except it probes energy flow with angstrom spatial and femtosecond temporal resolution. Specific examples to be presented include energy flow along alkane chains, and energy flow into substituted benzenes. Ref: Z. Wang, J. A. Carter, A. Lagutchev, Y. K. Koh, N.-H. Seong, D. G. Cahill, and D. D. Dlott, Ultrafast flash thermal conductance of molecular chains, Science 317, 787-790 (2007). This material is based upon work supported by the National Science Foundation under award DMR 0504038 and the Air Force Office of Scientific Research under award FA9550-06-1-0235.

  15. Implementation of surface hopping molecular dynamics using semiempirical methods

    International Nuclear Information System (INIS)

    Fabiano, E.; Keal, T.W.; Thiel, W.

    2008-01-01

    A molecular dynamics driver and surface hopping algorithm for nonadiabatic dynamics has been implemented in a development version of the MNDO semiempirical electronic structure package. The required energies, gradients and nonadiabatic couplings are efficiently evaluated on the fly using semiempirical configuration interaction methods. The choice of algorithms for the time evolution of the nuclear motion and quantum amplitudes is discussed, and different schemes for the computation of nonadiabatic couplings are analysed. The importance of molecular orbital tracking and electronic state following is underlined in the context of configuration interaction calculations. The method is applied to three case studies (ethylene, methaniminium ion, and methanimine) using the orthogonalization corrected OM2 Hamiltonian. In all three cases decay times and dynamics paths similar to high-level ab initio results are obtained

  16. Molecular beam scattering from clean surfaces of alkali halides

    International Nuclear Information System (INIS)

    Meyers, J.A.

    1975-01-01

    Molecular beam scattering of light gases from in situ cleaved alkali halide surfaces has been studied as a means of developing molecular beam scattering as a surface characterization tool and as a means of obtaining information about the gas atom-solid surface potential interaction. For 4 He scattering from LiF carried out under improved resolution the main results are: (1) there are four bound states in the surface potential well, as energies of -5.8, -2.2, -0.6 and -0.1 MeV. (2) Most of the structure designated as ''fine structure'' is due either to transitions to these four levels via various small reciprocal lattice vectors or to the opening of diffraction channels. (3) The transitions involving the (01) and (0 anti 1) reciprocal lattice vectors (i.e., the ones nearly perpendicular to the incident wavevector) are strong; as much as 85 percent of the specular intensity may be removed. Transitions via the other small reciprocal lattice vectors are much weaker. (4) The widths of the lines are consistent with the velocity distribution, which has a half-width of about 2 percent. (5) The observed energies agree fairly well with those calculated for a zeta-function potential, but are not consistent with a Morse potential. The preliminary results for 4 He/NaF scattering are that there are three bound-states in the surface potential well and are quite similar to the LiF results. These energies are -5.0, -1.9, and -0.5 MeV. 4 He/NaF selective adsorption also shows ''fine structure'' and a more detailed analysis is called for here

  17. Surface confined assemblies and polymers for sensing and molecular logic

    Science.gov (United States)

    de Ruiter, Graham; Altman, Marc; Motiei, Leila; Lahav, Michal; van der Boom, Milko E.

    2013-05-01

    Since the development of molecule-based sensors and the introduction of molecules mimicking the behavior of the AND gate in solution by de Silva in 1993, molecular (Boolean) Logic and Computing (MBLC) has become increasingly popular. The molecular approach toward Boolean logic resulted in intriguing proofs of concepts in solution including logic gates, half-adders, multiplexers, and flip-flop logic circuits. Molecular assemblies can perform diverse logic tasks by reconfiguring their inputs. Our recent research activities focus on MBLC with electrochromic polymers and immobilized polypyridyl complexes on solid support. We have designed a series of coordination-based thin films that are formed linearly by stepwise wet-chemical deposition or by self-propagating molecular assembly. The electrochromic properties of these films can be used for (i) detecting various analytes in solution and in the air, (ii) MBLC, (iii) electron-transfer studies, and (iv) interlayers for efficient inverted bulk-heterojunction solar cells. Our concept toward MBLC with functionalized surfaces is applicable to electrochemical and chemical inputs coupled with optical readout. Using this approach, we demonstrated various logic architectures with redox-active functionalized surfaces. Electrochemically operated sequential logic systems (e.g., flip-flops), multi-valued logic, and multi-state memory have been designed, which can improve computational power without increasing spatial requirements. Applying multi-valued digits in data storage and information processing could exponentially increase memory capacity. Our approach is applicable to highly diverse electrochromic thin films that operate at practical voltages (< 1.5 V).

  18. Volatile organic compounds adsorption using different types of adsorbent

    Directory of Open Access Journals (Sweden)

    Pimanmes Chanayotha

    2014-09-01

    Full Text Available Adsorbents were synthesized from coconut shell, coal and coke by pyrolysis followed by chemical activation process. These synthesized materials were used as adsorbents in adsorption test to determine the amount of volatile organic compounds (VOCs namely, 2-Hydroxyethyl methacrylate (HEMA, Octamethylcyclotetrasiloxane and Alkanes standard solution (C8-C20. The adsorption capacities of both synthesized adsorbents and commercial grade adsorbents (Carbotrap™ B and Carbotrap™ C were also compared. It was found that adsorbent A402, which was produced from coconut shell, activated with 40% (wt. potassium hydroxide and at activating temperature of 800°C for 1 hr, could adsorb higher amount of both HEMA and Octamethylcyclotetrasiloxane than other synthesized adsorbents. The maximum adsorption capacity of adsorbent A402 in adsorbing HEMA and Octamethylcyclotetrasiloxane were 77.87% and 50.82% respectively. These adsorption capabilities were 79.73% and 70.07% of the adsorption capacity of the commercial adsorbent Carbotrap™ B respectively. All three types of the synthesized adsorbent (A402, C302, C402 showed the capability to adsorb alkanes standard solution through the range of C8-C20 . However, their adsorption capacities were high in a specific range of C10-C11. The result from the isotherm plot was indicated that surface adsorption of synthesized adsorbent was isotherm type I while the surface adsorption of commercial adsorbent was isotherm type III.

  19. Molecular characterization of charcoal to identify adsorbed SOM and assess the effectiveness of common SOM-removing pretreatments prior to radiocarbon dating

    NARCIS (Netherlands)

    Wagner, T.V.; Mouter, A.K.; Parsons, J.R.; Sevink, J.; van der Plicht, J.; Jansen, B.

    A significant part of our knowledge on Holocene landscape development and associated human history in northwestern Europe is based on radiocarbon dating of charcoal originating from podzols. However, these soils are characterized by leaching of soil organic matter (SOM) that may adsorb to older

  20. Molecular Dynamics Simulations of Water Nanodroplets on Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    and DNA microarrays technologies.4,5,6,7,8 Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water,2,9-16 at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle...... computations of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems.3,16,17,18 For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence...

  1. Molecular approach of uranyl/mineral surfaces: theoretical approach

    International Nuclear Information System (INIS)

    Roques, J.

    2009-01-01

    As migration of radio-toxic elements through the geosphere is one of the processes which may affect the safety of a radioactive waste storage site, the author shows that numerical modelling is a support to experimental result exploitation, and allows the development of new interpretation and prediction codes. He shows that molecular modelling can be used to study processes of interaction between an actinide ion (notably a uranyl ion) and a mineral surface (a TiO 2 substrate). He also reports the predictive theoretical study of the interaction between an uranyl ion and a gibbsite substrate

  2. Analyzing the Molecular Kinetics of Water Spreading on Hydrophobic Surfaces via Molecular Dynamics Simulation.

    Science.gov (United States)

    Zhao, Lei; Cheng, Jiangtao

    2017-09-07

    In this paper, we report molecular kinetic analyses of water spreading on hydrophobic surfaces via molecular dynamics simulation. The hydrophobic surfaces are composed of amorphous polytetrafluoroethylene (PTFE) with a static contact angle of ~112.4° for water. On the basis of the molecular kinetic theory (MKT), the influences of both viscous damping and solid-liquid retarding were analyzed in evaluating contact line friction, which characterizes the frictional force on the contact line. The unit displacement length on PTFE was estimated to be ~0.621 nm and is ~4 times as long as the bond length of C-C backbone. The static friction coefficient was found to be ~[Formula: see text] Pa·s, which is on the same order of magnitude as the dynamic viscosity of water, and increases with the droplet size. A nondimensional number defined by the ratio of the standard deviation of wetting velocity to the characteristic wetting velocity was put forward to signify the strength of the inherent contact line fluctuation and unveil the mechanism of enhanced energy dissipation in nanoscale, whereas such effect would become insignificant in macroscale. Moreover, regarding a liquid droplet on hydrophobic or superhydrophobic surfaces, an approximate solution to the base radius development was derived by an asymptotic expansion approach.

  3. An energy-filtering device coupled to a quadrupole mass spectrometer for soft-landing molecular ions on surfaces with controlled energy

    Energy Technology Data Exchange (ETDEWEB)

    Bodin, A.; Laloo, R.; Abeilhou, P.; Guiraud, L.; Gauthier, S.; Martrou, D. [Nanosciences Group, CEMES, CNRS UPR 8011 and University Toulouse III - Paul Sabatier, 29 rue Jeanne Marvig, BP94347, F-31055 Toulouse Cedex 4 (France)

    2013-09-15

    We have developed an energy-filtering device coupled to a quadrupole mass spectrometer to deposit ionized molecules on surfaces with controlled energy in ultra high vacuum environment. Extensive numerical simulations as well as direct measurements show that the ion beam flying out of a quadrupole exhibits a high-energy tail decreasing slowly up to several hundred eV. This energy distribution renders impossible any direct soft-landing deposition of molecular ions. To remove this high-energy tail by energy filtering, a 127° electrostatic sector and a specific triplet lenses were designed and added after the last quadrupole of a triple quadrupole mass spectrometer. The results obtained with this energy-filtering device show clearly the elimination of the high-energy tail. The ion beam that impinges on the sample surface satisfies now the soft-landing criterion for molecular ions, opening new research opportunities in the numerous scientific domains involving charges adsorbed on insulating surfaces.

  4. Ecological applications of the irradiated adsorbents

    International Nuclear Information System (INIS)

    Tusseyev, T.

    2004-01-01

    Full text: In our previous works it was shown that after irradiation some adsorbents gain new interesting properties such as increasing (or decreasing) of their adsorption capacity, selectivity in relation to some gases, change of chemical bounds of gas molecules with adsorbent surface as well as other properties. We investigated a lot of adsorbents with semiconducting and dielectric properties. A high temperature superconductor was investigated also. Adsorbents were irradiated by ultraviolet (UV) and gamma - radiation, reactor (n.γ) - radiation, α-particles (E=40-50 MeV), protons ( E=30 MeV), and also He-3 ions (E-29-60 MeV). The following techniques were used: volumetric (manometrical), mass-spectrometer and IR spectroscopic methods, and also method of electronic - paramagnetic resonance (spin paramagnetic resonance) The obtained results allow to speak about creation of new adsorbents for gas purification (clearing) from harmful impurities, gas selection into components, an increasing of adsorbing surface. Thus one more advantage of the irradiated adsorbents is that they have 'memory effect', i.e. they can be used enough long time after irradiation. In laboratory conditions we built the small-sized adsorptive pump on the basis of the irradiated zeolites which are capable to work in autonomous conditions. It was found, that some of adsorbents after irradiation gain (or lose) selectivity in relation to definite gases. So, silica gel, which one in initial state does not adsorb hydrogen, after gamma irradiation it becomes active in relation to hydrogen. Some of rare earths oxides also show selectivity in relation to hydrogen and oxygen depending on a type of irradiation. Thus, it is possible to create different absorbents, depending on a solved problem, using a way or selection of adsorbents, either of radiation type and energy, as a result obtained adsorbents can be used for various ecological purposes

  5. Water structure and aqueous uranyl(VI) adsorption equilibria onto external surfaces of beidellite, montmorillonite, and pyrophyllite: results from molecular simulations.

    Science.gov (United States)

    Greathouse, Jeffery A; Cygan, Randall T

    2006-06-15

    Molecular dynamics simulations were performed to provide a systematic study of aqueous uranyl adsorption onto the external surface of 2:1 dioctahedral clays. Our understanding of this key process is critical in predicting the fate of radioactive contaminants in natural groundwaters. These simulations provide atomistic detail to help explain experimental trends in uranyl adsorption onto natural media containing smectite clays. Aqueous uranyl concentrations ranged from 0.027 to 0.162 M. Sodium ions and carbonate ions (0.027-0.243 M) were also present in the aqueous regions to more faithfully model a stream of uranyl-containing groundwater contacting a mineral system comprised of Na-smectite. No adsorption occurred near the pyrophyllite surface, and there was little difference in uranyl adsorption onto the beidellite and montmorillonite, despite the difference in location of clay layer charge between the two. At low uranyl concentration, the pentaaquouranyl complex dominates in solution and readily adsorbs to the clay basal plane. At higher uranyl (and carbonate) concentrations, the mono(carbonato) complex forms in solution, and uranyl adsorption decreases. Sodium adsorption onto beidellite occurred both as inner- and outer-sphere surface complexes, again with little effect on uranyl adsorption. Uranyl surface complexes consisted primarily of the pentaaquo cation (85%) and to a lesser extent the mono(carbonato) species (15%). Speciation diagrams of the aqueous region indicate that the mono(carbonato)uranyl complex is abundant at high ionic strength. Oligomeric uranyl complexes are observed at high ionic strength, particularly near the pyrophyllite and montmorillonite surfaces. Atomic density profiles of water oxygen and hydrogen atoms are nearly identical near the beidellite and montmorillonite surfaces. Water structure therefore appears to be governed by the presence of adsorbed ions and not by the location of layer charge associated with the substrate. The water

  6. DFT, NBO and molecular docking studies of the adsorption of fluoxetine into and on the surface of simple and sulfur-doped carbon nanotubes

    Science.gov (United States)

    Shahabi, Dana; Tavakol, Hossein

    2017-10-01

    In this study, noncovalent interactions between Fluoxetine (FX) and different carbon nanotubes (CNTs) or sulfur doped carbon nanotubes (SCNTs) were fully considered using DFT, natural bond orbital (NBO) and molecular docking calculations. Two different CNTs (and SCNTs) with 7,7 and 8,8 chiralities were considered as the adsorbents and the adsorption of FX by these adsorbents were studied in two cases: into the nanotubes and on their surfaces. The results of DFT and NBO calculations proposed that the 8,8 nanotubes are more suitable adsorbents for FX because the energies of their adsorptions are minimum. Population: analyses were also proposed that the adsorption of FX by SCNTs lead to more changes in electronic and sensing properties than the adsorption by CNTs. Moreover, the adsorption energies, obtained from molecular docking calculations (using 94 different models), proposed that the adsorption of FX into (versus out of) the nanotubes, adsorption processes by double-walled or triple-walled (versus single-walled) nanotubes and the adsorption by nanotubes with 8,8 chiralities are the most favorable adsorption processes.

  7. Molecular identification of a malaria merozoite surface sheddase.

    Directory of Open Access Journals (Sweden)

    Philippa K Harris

    2005-11-01

    Full Text Available Proteolytic shedding of surface proteins during invasion by apicomplexan parasites is a widespread phenomenon, thought to represent a mechanism by which the parasites disengage adhesin-receptor complexes in order to gain entry into their host cell. Erythrocyte invasion by merozoites of the malaria parasite Plasmodium falciparum requires the shedding of ectodomain components of two essential surface proteins, called MSP1 and AMA1. Both are released by the same merozoite surface "sheddase," but the molecular identity and mode of action of this protease is unknown. Here we identify it as PfSUB2, an integral membrane subtilisin-like protease (subtilase. We show that PfSUB2 is stored in apical secretory organelles called micronemes. Upon merozoite release it is secreted onto the parasite surface and translocates to its posterior pole in an actin-dependent manner, a trafficking pattern predicted of the sheddase. Subtilase propeptides are usually selective inhibitors of their cognate protease, and the PfSUB2 propeptide is no exception; we show that recombinant PfSUB2 propeptide binds specifically to mature parasite-derived PfSUB2 and is a potent, selective inhibitor of MSP1 and AMA1 shedding, directly establishing PfSUB2 as the sheddase. PfSUB2 is a new potential target for drugs designed to prevent erythrocyte invasion by the malaria parasite.

  8. Molecular Dynamics Simulations of Slip on Curved Surfaces

    Directory of Open Access Journals (Sweden)

    Ross D.A.

    2016-07-01

    Full Text Available We present Molecular Dynamics (MD simulations of liquid water confined within nanoscale geometries, including slit-like and cylindrical graphitic pores. These equilibrium results are used for calculating friction coefficients, which in turn can be used to calculate slip lengths. The slip length is a material property independent of the fluid flow rate. It is therefore a better quantity for study than the fluid velocity at the wall, also known as the slip velocity. Once the slip length has been found as a function of surface curvature, it can be used to parameterise Lattice Boltzmann (LB simulations. These larger scale simulations are able to tell us about how fluid transport is affected by slip in complex geometries; not just limited to single pores. Applications include flow and transport in nano-porous engine valve deposits and gas shales. The friction coefficient is found to be a function of curvature and is higher for fluid on convex surfaces and lower for concave surfaces. Both concave and convex surfaces approach the same value of the friction coefficient, which is constant above some critical radius of curvature, here found to be 7.4 ± 2.9 nm. The constant value of the friction coefficient is 10,000 ± 600 kg m−2 s−1, which is equivalent to a slip length of approximately 67 ± 4 nm.

  9. The use of angle resolved electron and photon stimulated desorption for the determination of molecular structure at surfaces

    International Nuclear Information System (INIS)

    Madey, T.E.; Stockbauer, R.

    1983-01-01

    A brief review of recent data related to the use of angle-resolved electron stimulated desorption and photon stimulated desorption in determining the structures of molecules at surfaces is made. Examples include a variety of structural assignments based on ESIAD (electron stimulated desorption ion angular distributions), the observation of short-range local ordering effects induced in adsorbed molecules by surface impurities, and the application of photon stimulated desorption to both ionic and covalent adsorbate systems. (Author) [pt

  10. Protein purification using magnetic adsorbent particles

    DEFF Research Database (Denmark)

    Franzreb, M; Siemann-Herzberg, M.; Hobley, Timothy John

    2006-01-01

    The application of functionalised magnetic adsorbent particles in combination with magnetic separation techniques has received considerable attention in recent years. The magnetically responsive nature of such adsorbent particles permits their selective manipulation and separation in the presence...... separations are fast, gentle, scaleable, easily automated, can achieve separations that would be impossible or impractical to achieve by other techniques, and have demonstrated credibility in a wide range of disciplines, including minerals processing, wastewater treatment, molecular biology, cell sorting...

  11. Adsorption removal of hydrogen sulfide gas. IV. Characteristics of adsorbents for the adsorption removal of hydrogen sulfide gas

    Energy Technology Data Exchange (ETDEWEB)

    Boki, K

    1974-10-25

    The amount of hydrogen sulfide gas adsorbed was affected by the surface properties (surface pH, acid strength, acid amount, and basic amount), the surface structure (pore volume), and the surface form (scanning electron microscopic observation) of 32 tested adsorbents. In general, the amount adsorption increased in the following order, amount of H/sub 2/S adsorbed on the silicate adsorbents, on the active carbon adsorbents, and on the zeolite adsorbents. The amount of H/sub 2/S adsorbed on magnesium silicate and silica gel adsorbents was mainly affected by the surface structure, and the amount adsorbed on the aluminum silicate adsorbents was affected by the distinctions on the surface forms of the adsorbents. The amount of H/sub 2/S adsorbed on 10 kinds of active carbon was determined by the surface properties and the surface structures of the adsorbents. The amount adsorbed on 12 kinds of zeolites was determined by either the surface properties or by the surface structures of the adsorbents. The amount of H/sub 2/S adsorbed on the silicate, active carbon, and zeolite adsorbents interacted with the heat of adsorption, and among the same kinds of adsorbents, the amount adsorbed was linearly related to the heat of adsorption.

  12. New apparatus for measuring radon adsorption on solid adsorbents

    International Nuclear Information System (INIS)

    Hassan, N.M.; Hines, A.L.; Ghosh, T.K.; Loyalka, S.K.; Ketring, A.R.

    1991-01-01

    A new experimental system was designed to measure radon uptake by solid adsorbents from air or other carrier gases/vapors. The total amount of radon adsorbed corresponding to a specific gas-phase concentration was determined by simultaneously measuring the solid-phase and gas-phase concentrations. The system was used to measure radon adsorption isotherms on BPL activated carbon at 288, 298, and 308 K and on silica gel and molecular sieve 13X at 298 K. The isotherms were of type III according to Brunauer's classification. The heat of adsorption data indicated that the BPL activated carbon provided a heterogeneous surface for radon adsorption. The equilibrium data were correlated by the Freundlich equation. In this paper the possible adsorption mechanism and the use of the adsorption isotherms to measure indoor radon concentrations are discussed

  13. High performance of a unique mesoporous polystyrene-based adsorbent for blood purification.

    Science.gov (United States)

    Chen, Jian; Han, Wenyan; Chen, Jie; Zong, Wenhui; Wang, Weichao; Wang, Yue; Cheng, Guanghui; Li, Chunran; Ou, Lailiang; Yu, Yaoting

    2017-02-01

    A multi-functional polystyrene based adsorbent (NKU-9) with a unique mesoporous and a high surface area was prepared by suspension polymerization for removal of therapeutic toxins in blood purification. The adsorbent produced had an almost equal amount of mesopore distribution in the range from 2 to 50 nm. The adsorption of serum toxins with different molecular weights were examined by in vitro adsorption assays and compared with some clinical currently used adsorbents such as HA-330, Cytosorb and BL-300 which are produced by China, America and Japan, respectively. Test results indicated that the adsorption rate for pentobarbital by NKU-9 was 81.24% which is nearly as high as HA-330 (81.44%). The latter adsorbent is currently used for acute detoxification treatment in China. To reach adsorption equilibrium, NKU-9 was faster than HA-330, which implies short treatment time. For the removal of middle molecular toxins such as β2-microglobulin (98.88%), NKU-9 performed better adsorptive selectivity than Cytosorb (92.80%). In addition, NKU-9 showed high performance for the removal of albumin-bound toxins (e.g., bilirubin), and its adsorption rate for total bilirubin (80.79%) in plasma was 8.4% higher than that of anion exchange resin BL-300 which is currently used to eliminate bilirubin in clinic. Therefore, our results indicate that the newly developed adsorbent with a wide distribution and almost equal amount of mesopores is a multifunctional adsorbent for high efficient removal of serum toxins with different molecular weights which might be an excellent blood purification adsorbent especially to treat diseases that conventional medical methods are low or not efficient.

  14. Molecular biogeochemical provinces in the Atlantic Surface Ocean

    Science.gov (United States)

    Koch, B. P.; Flerus, R.; Schmitt-Kopplin, P.; Lechtenfeld, O. J.; Bracher, A.; Cooper, W.; Frka, S.; Gašparović, B.; Gonsior, M.; Hertkorn, N.; Jaffe, R.; Jenkins, A.; Kuss, J.; Lara, R. J.; Lucio, M.; McCallister, S. L.; Neogi, S. B.; Pohl, C.; Roettgers, R.; Rohardt, G.; Schmitt, B. B.; Stuart, A.; Theis, A.; Ying, W.; Witt, M.; Xie, Z.; Yamashita, Y.; Zhang, L.; Zhu, Z. Y.; Kattner, G.

    2010-12-01

    One of the most important aspects to understand marine organic carbon fluxes is to resolve the molecular mechanisms which convert fresh, labile biomolecules into semi-labile and refractory dissolved and particulate organic compounds in the ocean. In this interdisciplinary project, which was performed on a cruise with RV Polarstern, we carried out a detailed molecular characterisation of dissolved organic matter (DOM) on a North-South transect in the Atlantic surface ocean in order to relate the data to different biological, climatic, oceanographic, and meteorological regimes as well as to terrestrial input from riverine and atmospheric sources. Our goal was to achieve a high resolution data set for the biogeochemical characterisation of the sources and reactivity of DOM. We applied ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS), nutrient, trace element, amino acid, and lipid analyses and other biogeochemical measurements for 220 samples from the upper water column (0-200m) and eight deep profiles. Various spectroscopic techniques were applied continuously in a constant sample water flow supplied by a fish system and the moon pool. Radiocarbon dating enabled assessing DOC residence time. Bacterial abundance and production provided a metabolic context for the DOM characterization work and pCO2 concentrations. Combining molecular organic techniques and inductively coupled plasma mass spectrometry (ICP-MS) established an important link between organic and inorganic biogeochemical studies. Multivariate statistics, primarily based on FT-ICR-MS data for 220 samples, allowed identifying geographical clusters which matched ecological provinces proposed previously by Longhurst (2007). Our study demonstrated that marine DOM carries molecular information reflecting the “history” of ocean water masses. This information can be used to define molecular biogeochemical provinces and to improve our understanding of element fluxes in

  15. A surprising way to control the charge transport in molecular electronics: the subtle impact of the coverage of self-assembled monolayers of floppy molecules adsorbed on metallic electrodes.

    Science.gov (United States)

    Bâldea, Ioan

    2017-10-26

    Inspired by earlier attempts in organic electronics aiming at controlling charge injection from metals into organic materials by manipulating the Schottky energy barrier using self-assembled monolayers (SAMs), recent experimental and theoretical work in molecular electronics showed that metal-organic interfaces can be controlled via changes in the metal work function that are induced by SAMs. In this paper we indicate a different route to achieve interface-driven control over the charge transfer/transport at the molecular scale. It is based on the fact that, in floppy molecule based SAMs, the molecular conformation can be tuned by varying the coverage of the adsorbate. We demonstrate this effect with the aid of benchmark molecules that are often used to fabricate nanojunctions and consist of two rings that can easily rotate relative to each other. We show that, by varying the coverage of the SAM, the twisting angle φ of the considered molecular species can be modified by a factor of two. Given the fact that the low bias conductance G scales as cos 2  φ, this results in a change in G of over one order of magnitude for the considered molecular species. Tuning the twisting angle by controlling the SAM coverage may be significant, e.g., for current efforts to fabricate molecular switches. Conversely, the lack of control over the local SAM coverage may be problematic for the reproducibility and interpretation of the STM (scanning tunneling microscope) measurements on repeatedly forming single molecule break junctions.

  16. Distribution of metal and adsorbed guest species in zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Chmelka, B.F.

    1989-12-01

    Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes {sup 129}Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of {sup 129}Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, {sup 129}Xe NMR is insensitive to fine structural details at room temperature.

  17. Distribution of metal and adsorbed guest species in zeolites

    International Nuclear Information System (INIS)

    Chmelka, B.F.

    1989-12-01

    Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes 129 Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of 129 Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, 129 Xe NMR is insensitive to fine structural details at room temperature

  18. Surface and Electrical Characterization of Conjugated Molecular Wires

    Science.gov (United States)

    Demissie, Abel Tesfahun

    This thesis describes the surface and electrical characterization of ultrathin organic films and interfaces. These films were synthesized on the surface of gold by utilizing layer by layer synthesis via imine condensation. Film growth by imine click (condensation) chemistry is particularly useful for molecular electronics experiments because it provides a convenient means to obtain and extend ?-conjugation in the growth direction. However, in the context of film growth from a solid substrate, the reaction yield per step has not been characterized previously, though it is critically important. To address these issues, my research focused on a comprehensive characterization of oligophenyleneimine (OPI) wires via Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), reflection-absorption infrared spectroscopy (RAIRS), and cyclic voltammetry (CV). In addition, we had the unique opportunity of developing the first of its kind implementation of nuclear reaction analysis (NRA) to probe the intensity of carbon atoms after each addition step. Overall the combination of various techniques indicated that film growth proceeds in a quantitative manner. Furthermore, the NRA experiment was optimized to measure the carbon content in self-assembled monolayers of alkyl thiols. The results indicated well-resolved coverage values for ultrathin films with consecutive steps of 2 carbon atoms per molecule. Another fundamental problem in molecular electronics is the vast discrepancy in the values of measured resistance per molecule between small and large area molecular junctions. In collaboration with researchers at the National University of Singapore, we addressed these issues by comparing the electrical properties of OPI wires with the eutectic gallium indium alloy (EGaIn) junction (1000 mum2), and conducting probe atomic force microscopy (CP-AFM) junction (50 nm2). Our results showed that intensive (i.e., area

  19. Molecular Dynamics Simulations of Water Droplets On Hydrophilic Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    and DNA microarrays technologies.Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water, at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle computations...... dynamics (MD) simulations of a hydrophilic air-water-silica system using the MD package FASTTUBE. We employ quantum chemistry calculation to obtain air-silica interaction parameters for the simulations. Our simulations are based in the following force fields: i) The silica-silica interaction is based...... of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems. For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence of air. Hence...

  20. Molecular ordering of ethanol at the calcite surface.

    Science.gov (United States)

    Pasarín, I S; Yang, M; Bovet, N; Glyvradal, M; Nielsen, M M; Bohr, J; Feidenhans'l, R; Stipp, S L S

    2012-02-07

    To produce biominerals, such as shells, bones, and teeth, living beings create organic compounds that control the growth of the solid phase. Investigating the atomic scale behavior of individual functional groups at the mineral-fluid interface provides fundamental information that is useful for constructing accurate predictive models for natural systems. Previous investigations of the activity of coccolith-associated polysaccharides (CAP) on calcite, using atomic force microscopy (AFM) [Henriksen, K., Young, J. R., Bown, P. R., and Stipp, S. L. S. Palentology 2004, 43 (Part 3), 725-743] and molecular dynamics (MD) modeling [Yang, M., Stipp, S. L. S., and Harding, J. H. Cryst. Growth Des. 2008, 8 (11), 4066-4074], have suggested that OH functional groups control polysaccharide attachment. The purpose of this work was to characterize, using X-ray reflectivity (XR) combined with molecular dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH(3)-CH(2)-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol molecules stand up perpendicularly at the interface or nearly so. As a consequence, the fatty, CH(3) ends form a new surface, about 6 Å from the termination of the bulk calcite, and beyond that, there is a thin gap where ethanol density is low. Following is a more disordered layer that is two to three ethanol molecules thick, about 14 Å, where density more resembles that of bulk liquid ethanol. The good agreement between theory and experiment gives confidence that a theoretical approach can offer information about behavior in more complex systems.

  1. Molecular metal catalysts on supports: organometallic chemistry meets surface science.

    Science.gov (United States)

    Serna, Pedro; Gates, Bruce C

    2014-08-19

    Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal

  2. Molecular dimensions of dried glucose oxidase on a Au(1 1 1) surface studied by dynamic mode scanning force microscopy

    International Nuclear Information System (INIS)

    Otsuka, Ichiro; Yaoita, Masashi; Nagashima, Seiichi; Higano, Michi

    2005-01-01

    We have investigated the molecular dimensions of a dried single glucose oxidase (GO) molecule adsorbed on a Au(1 1 1) surface with the UHV non-contact atomic force microscopy (NC-AFM) and tapping mode atomic force microcopy (TMAFM). The smallest air-dried GO particles in a TMAFM-measured size distribution are found to be 10-11 nm wide and 0.3-0.4 nm high. We find each collapsed ellipsoidal feature with a groove in a NC-AFM image, which measured 12 nm x 10 nm x 0.5 nm. The lateral dimensions (12 nm x 10 nm) of the observed feature is close to those of a GO monomer measured by scanning tunneling microscopy (STM) [Quijin et al., 12.2 nm x 8.9 nm as the size of one wing of an opening butterfly (dimer) appeared in a STM image] and by contact mode AFM [Quinto et al., 14 nm x 8 nm]. Our value of the vertical dimension (0.5 nm) is consistent with AFM results and molecular dynamics simulations that suggest a surface-induced complete unfolding, showing the average diameter of amino acid residues

  3. Molecular Dynamics Studies of Overbased Detergents on a Water Surface.

    Science.gov (United States)

    Bodnarchuk, M S; Dini, D; Heyes, D M; Breakspear, A; Chahine, S

    2017-07-25

    Molecular dynamics (MD) simulations are reported of model overbased detergent nanoparticles on a model water surface which mimic their behavior on a Langmuir trough or large water droplet in engine oil. The simulations predict that the structure of the nanoparticle on a water surface is different to when it is immersed in a bulk hydrophobic solvent. The surfactant tails are partly directed out of the water, while the carbonate core maximizes its extent of contact with the water. Umbrella sampling calculations of the potential of mean force between two particles showed that they are associated with varying degrees with a maximum binding free energy of ca. 10 k B T for the salicylate stabilized particle, ca. 8 k B T for a sulfurized alkyl phenate stabilized particle, and ca. 5 k B T for a sulfonate stabilized particle. The differences in the strength of attraction depend on the proximity of nearest approach and the energy penalty associated with the disruption of the hydration shell of water molecules around the calcium carbonate core when the two particles approach. This is greatest for the sulfonate particle, which partially loses the surfactant ions to the solution, and least for the salicylate, which forms the weakest water "cage". The particles are separated by a water hydration layer, even at the point of closest approach.

  4. Melamine-based dendrimer amine-modified magnetic nanoparticles as an efficient Pb(II) adsorbent for wastewater treatment: Adsorption optimization by response surface methodology.

    Science.gov (United States)

    Jiryaei Sharahi, Fatemeh; Shahbazi, Afsaneh

    2017-12-01

    Magnetic Fe 3 O 4 nanoparticles with an average diameter of 64 nm was synthesized solvothermically and subsequently modified with melamine-based dendrimer amine (MDA-Fe 3 O 4 ) via grafting method. The synthesized materials were characterized using DLS, SEM, XRD, FTIR, VSM, TGA and elemental analysis techniques. The MDA-Fe 3 O 4 was employed for the efficient removal of Pb(II) ions from an aqueous solution. The adsorption efficiency was investigated in relation to the independent variables of Pb(II) concentration (80-250 mg L -1 ), pH of the solution (3-7), adsorbent dosage (0.1-0.5 g L -1 ) and temperature (10-40 °C) via a central composite design (CCD) using response surface methodology (RSM). The significance of independent variables and their interactions was tested using ANOVA at a 95% confidence limit (α = 0.05). A second-order quadratic model was established to predict the adsorption efficiency. Under the optimum condition (initial Pb(II) concentration = 110 mg L -1 , MDA-Fe 3 O 4 dosage = 0.49 g L -1 , pH = 5 and temperature = 30 °C) a removal percentage of 85.6% was obtained. The isotherm data fitted well to the Freundlich model within the concentration range of the experimental study. A maximum adsorption capacity of 333.3 mg g -1 was predicted by the Langmuir model. The adsorption rate of Pb(II) ions onto MDA-Fe 3 O 4 was in good agreement with the pseudo-second-order model (R 2  = 0.999; k 2  = 4.7 × 10 -4  g mg -1 min -1 ). Thermodynamically, adsorption was spontaneous and endothermic. The MDA-Fe 3 O 4 was successfully regenerated using 0.3 M HCl with little loss of adsorption capacity (≈7%) for five successive adsorption cycles. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Theoretical Insight of Physical Adsorption for a Single Component Adsorbent + Adsorbate System: II. The Henry Region

    KAUST Repository

    Chakraborty, Anutosh

    2009-07-07

    The Henry coefficients of a single component adsorbent + adsorbate system are calculated from experimentally measured adsorption isotherm data, from which the heat of adsorption at zero coverage is evaluated. The first part of the papers relates to the development of thermodynamic property surfaces for a single-component adsorbent + adsorbate system1 (Chakraborty, A.; Saha, B. B.; Ng, K. C.; Koyama, S.; Srinivasan, K. Langmuir 2009, 25, 2204). A thermodynamic framework is presented to capture the relationship between the specific surface area (Ai) and the energy factor, and the surface structural and the surface energy heterogeneity distribution factors are analyzed. Using the outlined approach, the maximum possible amount of adsorbate uptake has been evaluated and compared with experimental data. It is found that the adsorbents with higher specific surface areas tend to possess lower heat of adsorption (ΔH°) at the Henry regime. In this paper, we have established the definitive relation between Ai and ΔH° for (i) carbonaceous materials, metal organic frameworks (MOFs), carbon nanotubes, zeolites + hydrogen, and (ii) activated carbons + methane systems. The proposed theoretical framework of At and AH0 provides valuable guides for researchers in developing advanced porous adsorbents for methane and hydrogen uptake. © 2009 American Chemical Society.

  6. Carbon 1s photoemission line analysis of C-based adsorbate on (111)In{sub 2}O{sub 3} surface: The influence of reducing and oxidizing conditions

    Energy Technology Data Exchange (ETDEWEB)

    Brinzari, V., E-mail: vbrinzari@mail.ru [State University of Moldova, Chisinau, str. Mateevich 60A, MD-2009, Republic of Moldova (Moldova, Republic of); Cho, B.K. [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Korotcenkov, G., E-mail: ghkoro@yahoo.com [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of)

    2016-12-30

    Highlights: • C 1s PE line of (111)In{sub 2}O{sub 3} layer after cleaning and gas probing in HV was studied. • C 1s line fine structure is formed by various residual C-based adsorbates. • Some C 1s line features were interpreted as CO adsorption and dissociation. • Redox properties of surface determine either adsorption or dissociation of CO. • Dissociation of CO on oxidized surface is responsible for acceptor-like effect. - Abstract: Synchrotron radiation photoemission study of C 1s line of (111) In{sub 2}O{sub 3} surface was carried out under HV (high vacuum) doses of oxygen, carbon monoxide and water. Gas interaction with the surface was activated by heating of In{sub 2}O{sub 3} monocrystalline film at temperatures of 160 or 250 °C. The study of complex structure of C 1 s line and evolution of its fine components allowed to establish their nature and to propose possible surface adsorbed species and reactions, including a direct chemisorption and dissociation of CO molecules. Reduction or oxidation of the surface determines whether the first (chemisorption) or the second (dissociation) process takes place. The latter is responsible for additional formation of ionosorbed oxygen. Both processes have not been previously reported for In{sub 2}O{sub 3} and for conductive metal oxides.

  7. Chemistry of CCl 4 on Fe 3O 4(1 1 1)-(2 × 2) surfaces in the presence of adsorbed D 2O studied by temperature programmed desorption

    Science.gov (United States)

    Adib, K.; Totir, G. G.; Fitts, J. P.; Rim, K. T.; Mueller, T.; Flynn, G. W.; Joyce, S. A.; Osgood, R. M.

    2003-07-01

    Temperature programmed desorption (TPD) was used to study surface reactions of Fe 3O 4(1 1 1)-(2 × 2) sequentially exposed, at ˜100 K, to vapor-phase D 2O and CCl 4. Previous TPD and XPS results have indicated that in the absence of D 2O, CCl 4 dissociatively adsorbs on Fe 3O 4(1 1 1) producing chemisorbed Cl and CCl 2. Subsequent heating of the surface results in abstraction of lattice iron and oxygen atoms and causes them to desorb as FeCl 2 and OCCl 2, respectively. This study shows that when this Fe 3O 4 surface is exposed only to D 2O, TPD measures a rich surface chemistry with multiple desorption events extending as high as ˜800 K, indicating dissociative adsorption of D 2O on the Fe 3O 4(1 1 1) surface. After sequential exposure to D 2O and then CCl 4, the production of FeCl 2 and OCCl 2 from adsorbed CCl 4 is suppressed, indicating that D 2O fragments block the surface reactive sites.

  8. Polarization-induced renormalization of molecular levels at metallic and semiconducting surfaces

    DEFF Research Database (Denmark)

    García Lastra, Juan Maria; Rostgaard, Carsten; Rubio, A.

    2009-01-01

    On the basis of first-principles G0W0 calculations we systematically study how the electronic levels of a benzene molecule are renormalized by substrate polarization when physisorbed on different metallic and semiconducting surfaces. The polarization-induced reduction in the energy gap between oc...... find that error cancellations lead to remarkably good agreement between the G0W0 and Kohn-Sham energies for the occupied orbitals of the adsorbed molecule....

  9. Properties and selection criteria for adsorbents

    International Nuclear Information System (INIS)

    Wirth, H.

    1976-01-01

    The paper gives a survey of the most important industrial adsorbents and of their suitability for different purposes. With special consideration of activated carbon, the properties and characteristic data are discussed which are used for assessing adsorbents. These, among other things, are as follows: specific surface area, pore size distribution, adsorption isotherms, hydrophobic properties, catalytic properties, chemical resistance, heat resistance, particle size and hardness. (orig.) [de

  10. Synthesis and characterization of the core-shell magnetic molecularly imprinted polymers (Fe₃O₄@MIPs) adsorbents for effective extraction and determination of sulfonamides in the poultry feed.

    Science.gov (United States)

    Kong, Xuan; Gao, Ruixia; He, Xiwen; Chen, Langxing; Zhang, Yukui

    2012-07-06

    In this study, we present a general method to prepare the core-shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs) for sulfamethazine (SMZ). The resulting Fe₃O₄@MIPs NPs possess a highly improved imprinting effect, fast adsorption kinetics and high adsorption capacity, and can be applied to extract sulfonamide in the poultry feed. In this protocol, the magnetite NPs were synthesized by co-precipitating Fe²⁺ and Fe³⁺ in an ammonia solution first. Silica was then coated on the Fe₃O₄ NPs using a sol-gel method to obtain silica shell magnetic NPs. Subsequently, the vinyl groups were grated onto silica-modified Fe₃O₄ surface by 3-methacryloyloxypropyltrimethoxysilane. Finally, the MIPs films were formed on the surface of Fe₃O₄@SiO₂ by the copolymerization of vinyl end groups with functional monomer, methacrylic acid, cross-linking agent, ethylene glycol dimethacrylate, the initiator azo-bis-isobutyronitrile and template molecule, sulfamethazine. The morphology, magnetic, adsorption and recognition properties of Fe₃O₄@MIPs NPs were characterized using transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrometer, vibrating sample magnetometer (VSM) and re-binding experiments. The results showed that the binding sites of Fe₃O₄@MIPs were good accessibility, fast adsorption rate and the maximum adsorption capacity of Fe₃O₄@MIPs to SMZ was 344.8 μg g⁻¹. The selectivity of the obtained Fe₃O₄@MIPs NPs were elucidated by the different rebinding capability of SMZ and structural related sulfonamides in the mixed solution. The results indicated that the Fe₃O₄@MIPs had high imprinting factor 9.5 and significant selectivity. A method was developed for enrichment and determination of SMZ in the poultry feed samples with recoveries of duck and chicken feed ranging from 63.3 to 76.5% and 68.7 to 74.7%, respectively and the relative standard deviations (RSD

  11. Molecular beam photoionization and gas-surface scattering

    International Nuclear Information System (INIS)

    Ceyer, S.T.

    1979-09-01

    The energetics of the ethylene ion-molecule reactions was investigated in more detail than previously possible in two body collision experiments by photoionization of the neutral van der Waals ethylene dimer. The stability of the (C 2 H 4 ) + C 2 H 4 ion-molecule collision complex has been determined to be 18.2 +- 0.5 kcal. The highest potential barriers along the reaction coordinate for decomposition of this collision complex into C 4 H 7 + + H and C 3 H 5 + + CH 3 have been determined to be 0 +- 1.5 and 8.7 +- 1.5 kcal. In a similar manner, the energetics of the solvated ethylene dimer ion was investigated by the photoionization of the ethylene trimer. The absolute proton affinity of NH 3 (203.6 +- 1.3 kcal/mole) and the proton solvation energies by more than one NH 3 have been determined by molecular beam photoionization. In addition, the NH 3 + -NH 3 interaction energy (0.79 +- 0.05 eV) was measured by photoionization of the neutral van der Waals dimer. These experiments have shown that photoionization of van der Waals clusters is a very powerful method of determining the energetics of gas phase proton solvation. The scattering of helium atomic beams from a high Miller index platinum surface that exhibits ordered, periodic steps on the atomic scale to probe the effect of atomic steps on the scattering distribution is explored. Rainbow scattering is observed when the step edges are perpendicular to the incident helium atoms. The design, construction and operation of a beam-surface scattering apparatus are described. The first data obtained in this apparatus are presented and the interesting dynamical aspects of the oxidation of D, D 2 and CO are discussed. 75 references

  12. Surface molecular aggregation structure and surface physicochemical properties of poly(fluoroalkyl acrylate) thin films

    International Nuclear Information System (INIS)

    Honda, K; Yamaguchi, H; Takahara, A; Kobayashi, M; Morita, M

    2008-01-01

    Effect of side chain length on the molecular aggregation states and surface properties of poly(fluoroalkyl acrylate)s [PFA-C y , where y is fluoromethylene number in R f group] thin films were systematically investigated. Spin-coated PFA-C y thin films were characterized by static and dynamic contact angle measurements, X-ray photoelectron spectroscopy (XPS), and grazing- incidence X-ray diffraction (GIXD). The receding contact angles showed small values for PFA-C y with short side chain (y≤6) and increased above y≥8. GIXD revealed that fluoroalkyl side chain of PFA-C y with y≥8 was crystallized and formed ordered structures at the surface region as well as bulk one. These results suggest that water repellent mechanism of PFA-C y can be attributed to the presence of highly ordered fluoroalkyl side chains at the outermost surfaces. The results of XPS in the dry and hydrated states and contact angle measurement in water support the mechanism of lowering contact angle for water by exposure of carbonyl group to the water interface through reorientation of short fluoroalkyl chains. The surface nanotextured PFA-C 8 through imprinting of anodic aluminum oxide mold showed extremely high hydrophobicity as well as high oleophobicity

  13. Molecular dynamics simulation of potentiometric sensor response: the effect of biomolecules, surface morphology and surface charge.

    Science.gov (United States)

    Lowe, B M; Skylaris, C-K; Green, N G; Shibuta, Y; Sakata, T

    2018-05-10

    The silica-water interface is critical to many modern technologies in chemical engineering and biosensing. One technology used commonly in biosensors, the potentiometric sensor, operates by measuring the changes in electric potential due to changes in the interfacial electric field. Predictive modelling of this response caused by surface binding of biomolecules remains highly challenging. In this work, through the most extensive molecular dynamics simulation of the silica-water interfacial potential and electric field to date, we report a novel prediction and explanation of the effects of nano-morphology on sensor response. Amorphous silica demonstrated a larger potentiometric response than an equivalent crystalline silica model due to increased sodium adsorption, in agreement with experiments showing improved sensor response with nano-texturing. We provide proof-of-concept that molecular dynamics can be used as a complementary tool for potentiometric biosensor response prediction. Effects that are conventionally neglected, such as surface morphology, water polarisation, biomolecule dynamics and finite-size effects, are explicitly modelled.

  14. Atomistic interactions of clusters on surfaces using molecular dynamics and hyper molecular dynamics

    International Nuclear Information System (INIS)

    Sanz-Navarro, Carlos F.

    2002-01-01

    The work presented in this thesis describes the results of Molecular Dynamics (MD) simulations applied to the interaction of silver clusters with graphite surfaces and some numerical and theoretical methods concerning the extension of MD simulations to longer time scales (hyper-MD). The first part of this thesis studies the implantation of clusters at normal incidence onto a graphite surface in order to determine the scaling of the penetration depth (PD) against the impact energy. A comparison with experimental results is made with good agreement. The main physical observations of the impact process are described and analysed. It is shown that there is a threshold impact velocity above which the linear dependence on PD on impact energy changes to a linear dependence on velocity. Implantation of silver clusters at oblique incidence is also considered. The second part of this work analyses the validity and feasibility of the three minimisation methods for the hyper-MD simulation method whereby time scales of an MD simulation can be extended. A correct mathematical basis for the iterative method is derived. It is found that one of the iterative methods, upon which hyper-lD is based, is very likely to fail in high-dimensional situations because it requires a too expensive convergence. Two new approximations to the hyper-MD approach are proposed, which reduce the computational effort considerably. Both approaches, although not exact, can help to search for some of the most likely transitions in the system. Some examples are given to illustrate this. (author)

  15. Interaction of atomic hydrogen with ethylene adsorbed on nickel films

    International Nuclear Information System (INIS)

    Korchak, V.N.; Tret'yakov, I.I.; Kislyuk, M.U.

    1976-01-01

    The reactivity of ethylene adsorbed on the pure films of nickel at various temperatures was studied with respect to hydrogen atoms generated in the gaseous phase. The experiments were conducted in a glass vacuum apparatus enabling one to obtain the highest vacuum up to 2x20 -10 torr. The catalyst, nickel films, was produced by their deposition onto the walls of the glass reactor at a pressure of the residual gas of 10 -9 torr and a temperature of the walls of 25 deg C. Gas purity was analyzed by the mass spectrometric method. The ethylene adsorbed at the temperatures below 173 deg K reacted readily with the hydrogen atoms to yield ethane. The process ran without practically any activation energy involved and was limited by the attachment of the first hydrogen atom to the ethylene molecule. The efficiency of this interaction was 0.02 of the number of the hydrogen atoms collisions against the surface occupied by the ethylene. The adsorption of the ethylene at room and higher temperatures was accompanied by its disproportioning with the release of the hydrogen into the gaseous phase and a serious destruction of the ethylene molecules adsorbed to produce hydrogen residues interacting with neither molecular nor atomic hydrogen [ru

  16. Selective Dispersive Solid Phase Extraction of Ser-traline Using Surface Molecularly Imprinted Polymer Grafted on SiO2/Graphene Oxide

    Directory of Open Access Journals (Sweden)

    Faezeh Khalilian

    2017-01-01

    Full Text Available A surface molecularly imprinted dispersive solid phase extraction coupled with liquid chromatography–ultraviolet detection is proposed as a selective and fast clean-up technique for the determination of sertraline in biological sample. Surface sertraline-molecular imprinted polymer was grafted and synthesized on the SiO2/graphene oxide surface. Firstly SiO2 was coated on synthesized graphene oxide sheet using sol-gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO2/graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross-linker and progen, respectively. Non-imprinted polymer was also prepared for comparing purposes. The properties of the molecular imprinted polymer were characterized using field emission-scanning electron microscopy and Fourier transform infrared spectroscopy methods. The surface molecular imprinted polymer was utilized as an adsorbent of dispersive solid phase extraction for separation and preconcentration of sertraline. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the non-imprinted polymer was examined in absence and presence of competitive drugs. Sertraline calibration curve showed linearity in the ranges 1–500 µg L-1. The limits of detection and quantification under optimized conditions were obtained 0.2 and 0.5 µg L-1. The within-day and between-day relative standard deviations (n=3 were 4.3 and 7.1%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 92%.

  17. Comparison of reactivity on step and terrace sites of Pd (3 3 2) surface for the dissociative adsorption of hydrogen: A quantum chemical molecular dynamics study

    International Nuclear Information System (INIS)

    Ahmed, Farouq; Nagumo, Ryo; Miura, Ryuji; Ai, Suzuki; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Miyamoto, Akira

    2011-01-01

    The notion of 'active sites' is fundamental to heterogeneous catalysis. However, the exact nature of the active sites, and hence the mechanism by which they act, are still largely a matter of speculation. In this study, we have presented a systematic quantum chemical molecular dynamics (QCMD) calculations for the interaction of hydrogen on different step and terrace sites of the Pd (3 3 2) surface. Finally the dissociative adsorption of hydrogen on step and terrace as well as the influence of surface hydrogen vacancy for the dissociative adsorption of hydrogen has been investigated through QCMD. This is a state-of-the-art method for calculating the interaction of atoms and molecules with metal surfaces. It is found that fully hydrogen covered (saturated) step sites can dissociate hydrogen moderately and that a monovacancy surface is suitable for significant dissociative adsorption of hydrogen. However in terrace site of the surface we have found that dissociation of hydrogen takes place only on Pd sites where the metal atom is not bound to any pre-adsorbed hydrogen atoms. Furthermore, from the molecular dynamics and electronic structure calculations, we identify a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage and directional dependence of atomic hydrogen diffusion on stepped palladium surface.

  18. Structure and redox properties of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20 adsorbed on a silica surface. M05 computational study

    Directory of Open Access Journals (Sweden)

    Liudmyla K. Sviatenko

    2016-03-01

    Full Text Available The cluster approximation was applied at M05/tzvp level to model adsorption of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20 on (001 surface of α-quartz. Structures of the obtained CL-20–silica complexes confirm close to parallel orientation of the nitrocompound toward surface. The binding between CL-20 and silica surface was analyzed and bond energies were calculated applying the atoms in molecules (AIM method. Hydrogen bonds were found to significantly contribute in adsorption energy. An attaching of electron leads to significant deviation from coplanarity in complexes and to strengthening of hydrogen bonding. Redox properties of adsorbed CL-20 were compared with those of gas-phase and hydrated species by calculation of electron affinity, ionization potential, reduction Gibbs free energy, oxidation Gibbs free energy, reduction and oxidation potentials. It was shown that adsorbed CL-20 has lower ability to redox transformation as compared with hydrated one.

  19. Regenerative adsorbent heat pump

    Science.gov (United States)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative adsorbent heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system and at least a portion of the heat of adsorption. A series of at least four compressors containing an adsorbent is provided. A large amount of heat is transferred from compressor to compressor so that heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  20. Fundamental properties of molecules on surfaces. Molecular switching and interaction of magnetic molecules with superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hatter, Nino

    2016-12-14

    In this thesis, we investigate individual molecular switches and metal-organic complexes on surfaces with scanning tunneling microscopy (STM) and spectroscopy (STS) at low temperatures. One focus addresses the switching ability and mechanism of diarylethene on Ag(111). The other focus lies on resolving and tuning magnetic interactions of individual molecules with superconductors. 4,4'-(4,4'-(perfluorocyclopent-1-ene-1,2-diyl)bis (5-methylthiophene-4,2-diyl)dip yridine (PDTE) is a prototypical photochromic switch. We can induce a structural change of individual PDTE molecules on Ag(111) with the STM tip. This change is accompanied by a reduction of the energy gap between the occupied and unoccupied molecular orbitals. Density functional theory (DFT) calculations reveal that the induced switching corresponds to a ring-closing reaction from an open isomer in a flat adsorption configuration to a ring-closed isomer with its methyl groups in a cis configuration. The final product is thermodynamically stabilized by strong dispersion interactions with the surface. A linear dependence of the switching threshold with the tip-sample distance with a minimal threshold of 1.4 V is found, which we assign to a combination of an electric-field induced process and a tunneling-electron contribution. DFT calculations suggest a large activation barrier for a ring-closing reaction from the open flat configuration into the closed cis configuration. The interaction of magnetic molecules with superconductors is studied on manganese phthalocyanine (MnPc) adsorbed on Pb(111). We find triplets of Shiba states inside the superconducting gap. Different adsorption sites of MnPc provide a large variety of exchange coupling strengths, which lead to a collective energy shift of the Shiba triplets. We can assign the splitting of the Shiba states to be an effect of magnetic anisotropy in the system. A quantum phase transition from a ''Kondo screened'' to a &apos

  1. Reactivity of etoricoxib based on computational study of molecular orbitals, molecular electrostatic potential surface and Mulliken charge analysis

    Science.gov (United States)

    Sachdeva, Ritika; Soni, Abhinav; Singh, V. P.; Saini, G. S. S.

    2018-05-01

    Etoricoxib is one of the selective cyclooxygenase inhibitor drug which plays a significant role in the pharmacological management of arthritis and pain. The theoretical investigation of its reactivity is done using Density Functional Theory calculations. Molecular Electrostatic Potential Surface of etoricoxib and its Mulliken atomic charge distribution are used for the prediction of its electrophilic and nucleophilic sites. The detailed analysis of its frontier molecular orbitals is also done.

  2. Creation of the technical adsorbent from local raw materials

    International Nuclear Information System (INIS)

    Isobaev, M.D.; Davlatnazarova, M.D.; Abdullaev, T.H.

    2016-01-01

    The results showed the possibility of obtaining effective adsorbents of walnut shell and the sunflower for environmental purposes, in particular for the purification of polluted waters from heavy metals. It has been shown, that 1 g of walnut shell adsorbent can adsorb on its surface ions of lead in amount of 47% by weight. The dependence of the adsorption activity of the semi-coke received from walnut shell from particle size and concentration of the solution. (author)

  3. Electron and photon-beam induced reactions of adsorbed disilane: Low-temperature thin-film growth

    International Nuclear Information System (INIS)

    Bozso, F.; Avouris, Ph.

    1991-01-01

    Electrons and photons of sufficient energy can cause fragmentation and desorption of adsorbed molecules or fragments of them, by inducing electronic excitations to dissociative states. The surface species after such excitations are mostly of highly reactive radical character, which readily react with the substrate and with other molecular or radical species in the adsorbed layer. This paper discusses the adsorption, thermal and electron/photon-beam induced reactions of disilane, oxygen and ammonia on Si(111)-7x7, and the electron/photon-induced growth of silicon, silicon dioxide and silicon nitride films at 100K

  4. Flow boundary conditions for chain-end adsorbing polymer blends.

    Science.gov (United States)

    Zhou, Xin; Andrienko, Denis; Delle Site, Luigi; Kremer, Kurt

    2005-09-08

    Using the phenol-terminated polycarbonate blend as an example, we demonstrate that the hydrodynamic boundary conditions for a flow of an adsorbing polymer melt are extremely sensitive to the structure of the epitaxial layer. Under shear, the adsorbed parts (chain ends) of the polymer melt move along the equipotential lines of the surface potential whereas the adsorbed additives serve as the surface defects. In response to the increase of the number of the adsorbed additives the surface layer becomes thinner and solidifies. This results in a gradual transition from the slip to the no-slip boundary condition for the melt flow, with a nonmonotonic dependence of the slip length on the surface concentration of the adsorbed ends.

  5. Molecular recognition of chromophore molecules to amine terminated surfaces

    International Nuclear Information System (INIS)

    Flores-Perez, Rosangelly; Ivanisevic, Albena

    2007-01-01

    We report the design and characterization of quartz surfaces that can bind to three retinal based chromophores. The amine terminated surfaces were engineered in order to mimic the environment of the opsin protein that accommodates binding of chromophore molecules in the human eye. Each surface coupling step was characterized by water contact angle measurements, ellipsometry, atomic force microscopy, X-ray photoelectron spectroscopy, and transmission infrared spectroscopy. The spectroscopic techniques confirmed that the three chromophore molecules can bind to the surface using a Schiff base mode. Our data suggests that the availability of the amine groups on the surface is critical in the accommodation of the binding of different chromophores

  6. Quantum mechanics capacitance molecular mechanics modeling of core-electron binding energies of methanol and methyl nitrite on Ag(111) surface.

    Science.gov (United States)

    Löytynoja, T; Li, X; Jänkälä, K; Rinkevicius, Z; Ågren, H

    2016-07-14

    We study a newly devised quantum mechanics capacitance molecular mechanics (QMCMM) method for the calculation of core-electron binding energies in the case of molecules adsorbed on metal surfaces. This yet untested methodology is applied to systems with monolayer of methanol/methyl nitrite on an Ag(111) surface at 100 K temperature. It was found out that the studied C, N, and O 1s core-hole energies converge very slowly as a function of the radius of the metallic cluster, which was ascribed to build up of positive charge on the edge of the Ag slab. Further analysis revealed that an extrapolation process can be used to obtain binding energies that deviated less than 0.5 eV against experiments, except in the case of methanol O 1s where the difference was as large as 1.8 eV. Additional QM-cluster calculations suggest that the latter error can be connected to the lack of charge transfer over the QM-CMM boundary. Thus, the results indicate that the QMCMM and QM-cluster methods can complement each other in a holistic picture of molecule-adsorbate core-ionization studies, where all types of intermolecular interactions are considered.

  7. Adsorbate Diffusion on Transition Metal Nanoparticles

    Science.gov (United States)

    2015-01-01

    correlation is a Bronsted-Evans-Polanyi ( BEP )- type of correlation, similar to other BEP correlations established earlier for surface-catalyzed bond- breaking...bond-making reactions.6-9 The universal BEP -type correlation is independent of the nature of the adsorbed species and that of the metal surface. For...a certain class of surface-catalyzed reactions, the existence of a BEP -type correlation reflects a similarity between the geometry of the transition

  8. 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.

  9. Molecular Dynamics Simulation for Surface and Transport Properties of Fluorinated Silica Nanoparticles in Water or Decane: Application to Gas Recovery Enhancement

    Directory of Open Access Journals (Sweden)

    Sepehrinia Kazem

    2017-05-01

    Full Text Available Determination of surface and transport properties of nanoparticles (NPs is essential for a variety of applications in enhanced oil and gas recoveries. In this paper, the impact of the surface chemistry of silica NPs on their hydro- and oleo-phobic properties as well as their transport properties are investigated in water or decane using molecular dynamics simulation. Trifluoromethyl or pentafluoroethyl groups as water and oil repellents are placed on the NPs. It is found that the density and residence time of liquid molecules around the NPs are modulated considerably with the existence of the functional groups on the NPs’ surfaces. Also, much larger density fluctuations for liquids close to the surface of the NPs are observed when the number of the groups on the NPs increases, indicating increased hydrophobicity. In addition, the diffusion coefficient of the NPs in either water or decane increases with increasing the number or length of the fluorocarbon chains, demonstrating non-Brownian behavior for the NPs. The surface chemistry imparts a considerable contribution on the diffusion coefficient of the NPs. Finally, potential of mean force calculations are undertaken. It is observed that the free energy of adsorption of the NPs on a mineral surface is more favorable than that of the aggregation of the NPs, which suggests the NPs adsorb preferably on the mineral surface.

  10. Manipulation and control of a single molecular rotor on Au (111) surface

    International Nuclear Information System (INIS)

    Hai-Gang, Zhang; Jin-Hai, Mao; Qi, Liu; Nan, Jiang; Hai-Tao, Zhou; Hai-Ming, Guo; Dong-Xia, Shi; Hong-Jun, Gao

    2010-01-01

    Three different methods are used to manipulate and control phthalocyanine based single molecular rotors on Au (111) surface: (1) changing the molecular structure to alter the rotation potential; (2) using the tunnelling current of the scanning tunnelling microscope (STM) to change the thermal equilibrium of the molecular rotor; (3) artificial manipulation of the molecular rotor to switch the rotation on or off by an STM tip. Furthermore, a molecular 'gear wheel' is successfully achieved with two neighbouring molecules. (cross-disciplinary physics and related areas of science and technology)

  11. Designing molecular printboards: a photolithographic platform for recodable surfaces

    Czech Academy of Sciences Publication Activity Database

    Abt, D.; Schmidt, B. V. K. J.; Pop-Georgievski, Ognen; Quick, A. S.; Danilov, D.; Kostina, Nina Yu.; Bruns, M.; Wenzel, W.; Wegener, M.; Rodriguez-Emmenegger, Cesar; Barner-Kowollik, C.

    2015-01-01

    Roč. 21, č. 38 (2015), s. 13186-13190 ISSN 0947-6539 R&D Projects: GA ČR(CZ) GJ15-09368Y Institutional support: RVO:61389013 Keywords : cyclodextrin * molecular printboard * photoconjugation Subject RIV: BO - Biophysics Impact factor: 5.771, year: 2015

  12. Molecular dynamics simulations of disjoining pressure effects in ultra-thin water films on a metal surface

    Science.gov (United States)

    Hu, Han; Sun, Ying

    2013-11-01

    Disjoining pressure, the excess pressure in an ultra-thin liquid film as a result of van der Waals interactions, is important in lubrication, wetting, flow boiling, and thin film evaporation. The classic theory of disjoining pressure is developed for simple monoatomic liquids. However, real world applications often utilize water, a polar liquid, for which fundamental understanding of disjoining pressure is lacking. In the present study, molecular dynamics (MD) simulations are used to gain insights into the effect of disjoining pressure in a water thin film. Our MD models were firstly validated against Derjaguin's experiments on gold-gold interactions across a water film and then verified against disjoining pressure in an argon thin film using the Lennard-Jones potential. Next, a water thin film adsorbed on a gold surface was simulated to examine the change of vapor pressure with film thickness. The results agree well with the classic theory of disjoining pressure, which implies that the polar nature of water molecules does not play an important role. Finally, the effects of disjoining pressure on thin film evaporation in nanoporous membrane and on bubble nucleation are discussed.

  13. Role of structure and glycosylation of adsorbed protein films in biolubrication.

    Directory of Open Access Journals (Sweden)

    Deepak H Veeregowda

    Full Text Available Water forms the basis of lubrication in the human body, but is unable to provide sufficient lubrication without additives. The importance of biolubrication becomes evident upon aging and disease, particularly under conditions that affect secretion or composition of body fluids. Insufficient biolubrication, may impede proper speech, mastication and swallowing, underlie excessive friction and wear of articulating cartilage surfaces in hips and knees, cause vaginal dryness, and result in dry, irritated eyes. Currently, our understanding of biolubrication is insufficient to design effective therapeutics to restore biolubrication. Aim of this study was to establish the role of structure and glycosylation of adsorbed protein films in biolubrication, taking the oral cavity as a model and making use of its dynamics with daily perturbations due to different glandular secretions, speech, drinking and eating, and tooth brushing. Using different surface analytical techniques (a quartz crystal microbalance with dissipation monitoring, colloidal probe atomic force microscopy, contact angle measurements and X-ray photo-electron spectroscopy, we demonstrated that adsorbed salivary conditioning films in vitro are more lubricious when their hydrophilicity and degree of glycosylation increase, meanwhile decreasing their structural softness. High-molecular-weight, glycosylated proteins adsorbing in loops and trains, are described as necessary scaffolds impeding removal of water during loading of articulating surfaces. Comparing in vitro and in vivo water contact angles measured intra-orally, these findings were extrapolated to the in vivo situation. Accordingly, lubricating properties of teeth, as perceived in 20 volunteers comprising of equal numbers of male and female subjects, could be related with structural softness and glycosylation of adsorbed protein films on tooth surfaces. Summarizing, biolubrication is due to a combination of structure and glycosylation

  14. Molecular and electronic structure of osmium complexes confined to Au(111) surfaces using a self-assembled molecular bridge

    Energy Technology Data Exchange (ETDEWEB)

    Llave, Ezequiel de la; Herrera, Santiago E.; Adam, Catherine; Méndez De Leo, Lucila P.; Calvo, Ernesto J.; Williams, Federico J., E-mail: fwilliams@qi.fcen.uba.ar [INQUIMAE-CONICET, Departamento de Química Inorgánica, Analítica y Química-Física, Facultad Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, Buenos Aires C1428EHA (Argentina)

    2015-11-14

    The molecular and electronic structure of Os(II) complexes covalently bonded to self-assembled monolayers (SAMs) on Au(111) surfaces was studied by means of polarization modulation infrared reflection absorption spectroscopy, photoelectron spectroscopies, scanning tunneling microscopy, scanning tunneling spectroscopy, and density functional theory calculations. Attachment of the Os complex to the SAM proceeds via an amide covalent bond with the SAM alkyl chain 40° tilted with respect to the surface normal and a total thickness of 26 Å. The highest occupied molecular orbital of the Os complex is mainly based on the Os(II) center located 2.2 eV below the Fermi edge and the LUMO molecular orbital is mainly based on the bipyridine ligands located 1.5 eV above the Fermi edge.

  15. The state of physically adsorbed substances in microporous adsorbents

    International Nuclear Information System (INIS)

    Fomkin, A.A.

    1987-01-01

    Xe, Kr, Ar, CF 3 Cl, CH 4 adsorption in NaX microporous zeolite of 0.98 Na 2 OxAl 2 O 3 x2.36SiO 2 x0.02H 2 O is studied. Some properties of adsorbates (density, coefficients of expansion, enthalpy, heat capacity) are determined and discussed. The adsorbate in the microporous adsorbent is shown to be a particular state of a substance. Liniarity of adsorption isosteres and sharp changes during isosteric heat capacity of the adsorbate points to the fact that in microporous adsorbents phase transformations of the second type are possible

  16. En route to surface-bound electric field-driven molecular motors.

    Science.gov (United States)

    Jian, Huahua; Tour, James M

    2003-06-27

    Four caltrop-shaped molecules that might be useful as surface-bound electric field-driven molecular motors have been synthesized. The caltrops are comprised of a pair of electron donor-acceptor arms and a tripod base. The molecular arms are based on a carbazole or oligo(phenylene ethynylene) core with a strong net dipole. The tripod base uses a silicon atom as its core. The legs of the tripod bear sulfur-tipped bonding units, as acetyl-protected benzylic thiols, for bonding to a gold surface. The geometry of the tripod base allows the caltrop to project upward from a metallic surface after self-assembly. Ellipsometric studies show that self-assembled monolayers of the caltrops are formed on Au surfaces with molecular thicknesses consistent with the desired upright-shaft arrangement. As a result, the zwitterionic molecular arms might be controllable when electric fields are applied around the caltrops, thereby constituting field-driven motors.

  17. Formation and structure of inhibitive molecular film of imidazole on iron surface

    International Nuclear Information System (INIS)

    Kokalj, Anton

    2013-01-01

    Highlights: ► Atomic scale details of interaction between imidazole and Fe(1 0 0) elucidated by DFT calculations. ► Imidazole dehydrogenates upon adsorption with the C2-H bond cleaved. ► Stablest identified structure consists of high coverage C2 dehydrogenated imidazoles. ► Passivation of Fe(1 0 0) due to strong adsorbate-surface bond and high adsorbate coverage. ► Previously suggested polymerization of imidazole molecules at high coverage is found improbable. - Abstract: Adsorption of imidazole on clean Fe(1 0 0) was addressed by DFT calculations. It is shown that even though the imidazole in protonated form binds stronger to the surface than the neutral form, it is prone to deprotonation (dehydrogenation) resulting in neutral form, which further dehydrogenates due to the breaking of the C2–H bond. Thermodynamically the stablest identified structures thus consist of strongly bound and densely packed C2 dehydrogenated imidazole molecules, which may act as a thin protective film. On the other hand, the polymerization of imidazole molecules upon adsorption has been found improbable.

  18. Surface tension and contact angles: Molecular origins and associated microstructure

    Science.gov (United States)

    Davis, H. T.

    1982-01-01

    Gradient theory converts the molecular theory of inhomogeneous fluid into nonlinear boundary value problems for density and stress distributions in fluid interfaces, contact line regions, nuclei and microdroplets, and other fluid microstructures. The relationship between the basic patterns of fluid phase behavior and the occurrence and stability of fluid microstructures was clearly established by the theory. All the inputs of the theory have molecular expressions which are computable from simple models. On another level, the theory becomes a phenomenological framework in which the equation of state of homogeneous fluid and sets of influence parameters of inhomogeneous fluids are the inputs and the structures, stress tensions and contact angles of menisci are the outputs. These outputs, which find applications in the science and technology of drops and bubbles, are discussed.

  19. Orientational epitaxy in adsorbed monolayers

    International Nuclear Information System (INIS)

    Novaco, A.D.; McTague, J.P.

    1977-01-01

    The ground state for adsorbed monolayers on crystalline substrates is shown to involve a definite relative orientation of the substrate and adsorbate crystal axes, even when the relative lattice parameters are incommensurate. The rotation angle which defines the structure of the monolayer-substrate system is determined by the competition between adsorbate-substrate and adsorbate-adsorbate energy terms, and is generally not a symmetry angle. Numerical predictions are presented for the rare gas-graphite systems, whose interaction potentials are rather well known. Recent LEED data for some of these systems appear to corroborate these predictions

  20. A Molecular-Level Account of the Antigenic Hantaviral Surface

    Directory of Open Access Journals (Sweden)

    Sai Li

    2016-05-01

    Full Text Available Hantaviruses, a geographically diverse group of zoonotic pathogens, initiate cell infection through the concerted action of Gn and Gc viral surface glycoproteins. Here, we describe the high-resolution crystal structure of the antigenic ectodomain of Gn from Puumala hantavirus (PUUV, a causative agent of hemorrhagic fever with renal syndrome. Fitting of PUUV Gn into an electron cryomicroscopy reconstruction of intact Gn-Gc spike complexes from the closely related but non-pathogenic Tula hantavirus localized Gn tetramers to the membrane-distal surface of the virion. The accuracy of the fitting was corroborated by epitope mapping and genetic analysis of available PUUV sequences. Interestingly, Gn exhibits greater non-synonymous sequence diversity than the less accessible Gc, supporting a role of the host humoral immune response in exerting selective pressure on the virus surface. The fold of PUUV Gn is likely to be widely conserved across hantaviruses.

  1. Adhesion of Photon-Driven Molecular Motors to Surfaces via 1,3-Dipolar Cycloadditions : Effect of Interfacial Interactions on Molecular Motion

    NARCIS (Netherlands)

    Carroll, Gregory T.; London, Gabor; Fernández Landaluce, Tatiana; Rudolf, Petra; Feringa, Ben L.

    We report the attachment of altitudinal light-driven molecular motors to surfaces using 1,3-dipolar cycloaddition reactions. Molecular motors were designed containing azide or alkyne groups for attachment to alkyne- or azide-modified surfaces. Surface attachment was characterized by UV-vis, IR, XPS,

  2. An adaptive interpolation scheme for molecular potential energy surfaces

    Science.gov (United States)

    Kowalewski, Markus; Larsson, Elisabeth; Heryudono, Alfa

    2016-08-01

    The calculation of potential energy surfaces for quantum dynamics can be a time consuming task—especially when a high level of theory for the electronic structure calculation is required. We propose an adaptive interpolation algorithm based on polyharmonic splines combined with a partition of unity approach. The adaptive node refinement allows to greatly reduce the number of sample points by employing a local error estimate. The algorithm and its scaling behavior are evaluated for a model function in 2, 3, and 4 dimensions. The developed algorithm allows for a more rapid and reliable interpolation of a potential energy surface within a given accuracy compared to the non-adaptive version.

  3. On the stability of surface-confined nanoporous molecular networks

    Energy Technology Data Exchange (ETDEWEB)

    Ghijsens, Elke; Adisoejoso, Jinne, E-mail: Jinne.adisoejoso@chem.kuleuven.be, E-mail: tobe@chem.es.osaka-u.ac.jp, E-mail: Steven.DeFeyter@chem.kuleuven.be; Van Gorp, Hans; Destoop, Iris; Ivasenko, Oleksandr; Van der Auweraer, Mark; De Feyter, Steven, E-mail: Jinne.adisoejoso@chem.kuleuven.be, E-mail: tobe@chem.es.osaka-u.ac.jp, E-mail: Steven.DeFeyter@chem.kuleuven.be [Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven—University of Leuven, Celestijnenlaan 200 F, B-3001 Leuven (Belgium); Noguchi, Aya; Tahara, Kazukuni; Tobe, Yoshito, E-mail: Jinne.adisoejoso@chem.kuleuven.be, E-mail: tobe@chem.es.osaka-u.ac.jp, E-mail: Steven.DeFeyter@chem.kuleuven.be [Graduate School of Engineering Science, Division of Frontier Materials Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan)

    2015-03-14

    Self-assembly of molecular building blocks into two-dimensional nanoporous networks has been a topic of broad interest for many years. However, various factors govern the specific outcome of the self-assembly process, and understanding and controlling these are key to successful creation. In this work, the self-assembly of two alkylated dehydrobenzo[12]annulene building blocks was compared at the liquid-solid interface. It turned out that only a small chemical modification within the building blocks resulted in enhanced domain sizes and stability of the porous packing relative to the dense linear packing. Applying a thermodynamic model for phase transition revealed some key aspects for network formation.

  4. Inelastic surface collisions and the desorption of massive molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Macfarlane, R D [Texas A and M Univ., College Station (USA). Dept. of Chemistry

    1983-01-01

    The interaction of high energy ions in the region of electronic stopping (1 MeV u/sup -1/) stimulates the desorption of massive molecular ions of biomolecules such as insulin. The experimental details of the measurements are given with some examples of application for analytical mass spectrometry. Studies on the role of the incident ion (accelerator beam experiments) are reviewed as well as the contribution of the matrix to the desorption-ionization process. How the electronic relaxation process couples to desorption-ionization is a central question in understanding the overall mechanism of the process.

  5. Surface engineering: molecularly imprinted affinity membranes by photograft polymerization

    Science.gov (United States)

    Matuschewski, Heike; Sergeyeva, Tatiana A.; Bendig, Juergen; Piletsky, Sergey A.; Ulbricht, Matthies; Schedler, Uwe

    2001-02-01

    Commercial polymer microfiltration membranes were surface-modified with a graft copolymer of a functional monomer and a crosslinker in the presence of a template (triazine-herbicide). As result, membranes covered with a thin layer of imprinted polymer (MIP) selective to the template were obtained. The influence of the polymerization conditions on membrane recognition properties was studied by membranes

  6. Surface plasmon-enhanced molecular fluorescence induced by gold nanostructures

    International Nuclear Information System (INIS)

    Teng, Y.; Ueno, K.; Shi, X.; Aoyo, D.; Misawa, H.; Qiu, J.

    2012-01-01

    The authors report on surface plasmon-enhanced fluorescence of Eosin Y molecules induced by gold nanostructures. Al 2 O 3 films deposited by atomic layer deposition with sub-nanometer resolution were used as the spacer layer to control the distance between molecules and the gold surface. As the thickness of the Al 2 O 3 film increased, the fluorescence intensity first increased and then decreased. The highest enhancement factor is achieved with a 1 nm Al 2 O 3 film. However, the trend for the fluorescence lifetime is the opposite. It first decreased and then increased. The changes in the fluorescence quantum yield were also calculated. The yield shows a similar trend to the fluorescence intensity. The competition between the surface plasmon-induced increase in the radiative decay rate and the gold-induced fluorescence quenching is responsible for the observed phenomenon. In addition, this competition strongly depends on the thickness of the spacer layer between Eosin Y molecules and the gold surface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Suppression of material transfer at contacting surfaces: the effect of adsorbates on Al/TiN and Cu/diamond interfaces from first-principles calculations

    Science.gov (United States)

    Feldbauer, Gregor; Wolloch, Michael; Bedolla, Pedro O.; Redinger, Josef; Vernes, András; Mohn, Peter

    2018-03-01

    The effect of monolayers of oxygen (O) and hydrogen (H) on the possibility of material transfer at aluminium/titanium nitride (Al/TiN) and copper/diamond (Cu/Cdia) interfaces, respectively, were investigated within the framework of density functional theory (DFT). To this end the approach, contact, and subsequent separation of two atomically flat surfaces consisting of the aforementioned pairs of materials were simulated. These calculations were performed for the clean as well as oxygenated and hydrogenated Al and Cdia surfaces, respectively. Various contact configurations were considered by studying several lateral arrangements of the involved surfaces at the interface. Material transfer is typically possible at interfaces between the investigated clean surfaces; however, the addition of O to the Al and H to the Cdia surfaces was found to hinder material transfer. This passivation occurs because of a significant reduction of the adhesion energy at the examined interfaces, which can be explained by the distinct bonding situations.

  8. Machine learning and pattern recognition from surface molecular architectures.

    Science.gov (United States)

    Maksov, Artem; Ziatdinov, Maxim; Fujii, Shintaro; Sumpter, Bobby; Kalinin, Sergei

    The ability to utilize molecular assemblies as data storage devices requires capability to identify individual molecular states on a scale of thousands of molecules. We present a novel method of applying machine learning techniques for extraction of positional and rotational information from ultra-high vacuum scanning tunneling microscopy (STM) images and apply it to self-assembled monolayer of π-bowl sumanene molecules on gold. From density functional theory (DFT) simulations, we assume existence of distinct polar and multiple azimuthal rotational states. We use DFT-generated templates in conjunction with Markov Chain Monte Carlo (MCMC) sampler and noise modeling to create synthetic images representative of our model. We extract positional information of each molecule and use nearest neighbor criteria to construct a graph input to Markov Random Field (MRF) model to identify polar rotational states. We train a convolutional Neural Network (cNN) on a synthetic dataset and combine it with MRF model to classify molecules based on their azimuthal rotational state. We demonstrate effectiveness of such approach compared to other methods. Finally, we apply our approach to experimental images and achieve complete rotational class information extraction. This research was sponsored by the Division of Materials Sciences and Engineering, Office of Science, Basic Energy Sciences, US DOE.

  9. Ionogenic adsorbents based on local raw materials for radiation protection

    International Nuclear Information System (INIS)

    Isobaev, M.D.; Davlatnazarova, M.; Turdialiev, M.Z.; Abdullayev, T.H.; Pulatov, E.H.

    2012-01-01

    The successful management of uranium wastes and creating the conditions for effective rehabilitation activities require special adsorbents capable of holding on the surface complexes, including radioactive elements. Currently tested and have shown promising synthetic adsorbents based pitted apricot fruits and other fruit plants. This report presents data for the establishment of ionic type available adsorbents based on Tajikistan coal. As the base for the creation of this type of adsorbent were taken the coal of the 'Ziddi' deposits. As follows from our data on the chemical composition, the studied coals contain more than 20% of the ash. According to the available literature theses ashes contains various minerals compositions that can form the adsorbent's active surface. Thus, the model for this type of activated carbon can serve as a mixture of zeolite, ion exchange resins and activated carbon itself.

  10. Characterization of the molecular structure and mechanical properties of polymer surfaces and protein/polymer interfaces by sum frequency generation vibrational spectroscopy and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Koffas, Telly Stelianos [Univ. of California, Berkeley, CA (United States)

    2004-01-01

    Sum frequency generation (SFG) vibrational spectroscopy, atomic force microscopy (AFM), and other complementary surface-sensitive techniques have been used to study the surface molecular structure and surface mechanical behavior of biologically-relevant polymer systems. SFG and AFM have emerged as powerful analytical tools to deduce structure/property relationships, in situ, for polymers at air, liquid and solid interfaces. The experiments described in this dissertation have been performed to understand how polymer surface properties are linked to polymer bulk composition, substrate hydrophobicity, changes in the ambient environment (e.g., humidity and temperature), or the adsorption of macromolecules. The correlation of spectroscopic and mechanical data by SFG and AFM can become a powerful methodology to study and engineer materials with tailored surface properties. The overarching theme of this research is the interrogation of systems of increasing structural complexity, which allows us to extend conclusions made on simpler model systems. We begin by systematically describing the surface molecular composition and mechanical properties of polymers, copolymers, and blends having simple linear architectures. Subsequent chapters focus on networked hydrogel materials used as soft contact lenses and the adsorption of protein and surfactant at the polymer/liquid interface. The power of SFG is immediately demonstrated in experiments which identify the chemical parameters that influence the molecular composition and ordering of a polymer chain's side groups at the polymer/air and polymer/liquid interfaces. In general, side groups with increasingly greater hydrophobic character will be more surface active in air. Larger side groups impose steric restrictions, thus they will tend to be more randomly ordered than smaller hydrophobic groups. If exposed to a hydrophilic environment, such as water, the polymer chain will attempt to orient more of its hydrophilic groups to

  11. Electronic structure of surface-supported bis(phthalocyaninato) terbium(III) single molecular magnets.

    Science.gov (United States)

    Vitali, Lucia; Fabris, Stefano; Conte, Adriano Mosca; Brink, Susan; Ruben, Mario; Baroni, Stefano; Kern, Klaus

    2008-10-01

    The electronic structure of isolated bis(phthalocyaninato) terbium(III) molecules, a novel single-molecular-magnet (SMM), supported on the Cu(111) surface has been characterized by density functional theory and scanning tunneling spectroscopy. These studies reveal that the interaction with the metal surface preserves both the molecular structure and the large spin magnetic moment of the metal center. The 4f electron states are not perturbed by the adsorption while a strong molecular/metal interaction can induce the suppression of the minor spin contribution delocalized over the molecular ligands. The calculations show that the inherent spin magnetic moment of the molecule is only weakly affected by the interaction with the surface and suggest that the SMM character might be preserved.

  12. Structural features of resorcinol–formaldehyde resin chars and interfacial behavior of water co-adsorbed with low-molecular weight organics

    International Nuclear Information System (INIS)

    Gun’ko, Vladimir M.; Bogatyrov, Viktor M.; Turov, Vladimir V.; Leboda, Roman; Skubiszewska-Zięba, Jadwiga; Urubkov, Iliya V.

    2013-01-01

    Products of resorcinol–formaldehyde resin carbonization (chars) are characterized by different morphology (particle shape and sizes) and texture (specific surface area, pore volume and pore size distribution) depending on water content during resin polymerization. At a low amount of water (C w = 37.8 wt.%) during synthesis resulting in strongly cross-linked polymers, carbonization gives nonporous particles. An increase in the water content to 62.7 wt.% results in a nano/mesoporous char, but if C w = 73.3 wt.%, a char is purely nanoporous. Despite these textural differences, the Raman spectra of all the chars are similar because of the similarity in the structure of their carbon sheets with a significant contribution of sp 3 C atoms. However, the difference in the spatial organization of the carbon sheet stacks in the particles results in the significant differences in the textural and morphological characteristics and in the adsorption properties of chars with respect to water, methane, benzene, hydrogen, methylene chloride, and dimethylsulfoxide.

  13. Structural features of resorcinol–formaldehyde resin chars and interfacial behavior of water co-adsorbed with low-molecular weight organics

    Energy Technology Data Exchange (ETDEWEB)

    Gun’ko, Vladimir M., E-mail: vlad_gunko@ukr.net [Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kyiv (Ukraine); Bogatyrov, Viktor M.; Turov, Vladimir V. [Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kyiv (Ukraine); Leboda, Roman; Skubiszewska-Zięba, Jadwiga [Faculty of Chemistry, Maria Curie-Skłodowska University, 20031 Lublin (Poland); Urubkov, Iliya V. [Kurdyumov Institute of Metal Physics, 36 Vernadsky Boulevard, 03142 Kyiv (Ukraine)

    2013-10-15

    Products of resorcinol–formaldehyde resin carbonization (chars) are characterized by different morphology (particle shape and sizes) and texture (specific surface area, pore volume and pore size distribution) depending on water content during resin polymerization. At a low amount of water (C{sub w} = 37.8 wt.%) during synthesis resulting in strongly cross-linked polymers, carbonization gives nonporous particles. An increase in the water content to 62.7 wt.% results in a nano/mesoporous char, but if C{sub w} = 73.3 wt.%, a char is purely nanoporous. Despite these textural differences, the Raman spectra of all the chars are similar because of the similarity in the structure of their carbon sheets with a significant contribution of sp{sup 3} C atoms. However, the difference in the spatial organization of the carbon sheet stacks in the particles results in the significant differences in the textural and morphological characteristics and in the adsorption properties of chars with respect to water, methane, benzene, hydrogen, methylene chloride, and dimethylsulfoxide.

  14. Molecular dynamics simulations of water on a hydrophilic silica surface at high air pressures

    DEFF Research Database (Denmark)

    Zambrano, H.A.; Walther, Jens Honore; Jaffe, R.L.

    2014-01-01

    Wepresent a force field forMolecular Dynamics (MD) simulations ofwater and air in contactwith an amorphous silica surface. We calibrate the interactions of each species present in the systemusing dedicated criteria such as the contact angle of a water droplet on a silica surface, and the solubility...

  15. Electronic structure, molecular bonding and potential energy surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ruedenberg, K. [Ames Laboratory, IA (United States)

    1993-12-01

    By virtue of the universal validity of the generalized Born-Oppenheimer separation, potential energy surfaces (PES`) represent the central conceptual as well as quantitative entities of chemical physics and provide the basis for the understanding of most physicochemical phenomena in many diverse fields. The research in this group deals with the elucidation of general properties of PES` as well as with the quantitative determination of PES` for concrete systems, in particular pertaining to reactions involving carbon, oxygen, nitrogen and hydrogen molecules.

  16. Proceedings (1st) of the Topical Meeting on the Microphysics of Surfaces, Beams, and Adsorbates Held in Santa Fe, New Mexico on 4-6 February 1985.

    Science.gov (United States)

    1985-12-18

    ORGANIZATION 6b. OFFICE SYMBOL 7. NAME OF MONITORING ORGANIZATIONIfl apph¢cabi, Optical Society of America AFOSR/NC 6r. ADDRESS ICity State and ZIP...process, namely semiconductor surfaces. The collisional processes leading to , scrambling of chemical composition in the layer affected by surface...etaan be tkenint acountwhe inerpetig exerientllyob- SERS will provide a spectroscopic image of the interactione taken into account when interpreting

  17. Experimental and theoretical characterization of adsorbed water on self-assembled monolayers: Understanding the interaction of water with atmospherically relevant surfaces

    Czech Academy of Sciences Publication Activity Database

    Moussa, S. G.; McIntire, T. M.; Szöri, Milan; Roeselová, Martina; Tobias, D. J.; Grimm, R. L.; Hemminger, J. C.; Finlayson-Pitts, B. J.

    2009-01-01

    Roč. 113, č. 10 (2009), s. 2060-2069 ISSN 1089-5639 R&D Projects: GA ČR GA203/06/1488; GA MŠk LC512; GA MŠk 1P05ME798 Grant - others:NSF(US) 0431312 Institutional research plan: CEZ:AV0Z40550506 Keywords : molecular dynamics * hydrophobic * hydrophilic Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.899, year: 2009

  18. Molecular dynamics simulations and quantum chemical calculations ...

    African Journals Online (AJOL)

    Molecular dynamic simulation results indicate that the imidazoline derivative molecules uses the imidazoline ring to effectively adsorb on the surface of iron, with the alkyl hydrophobic tail forming an n shape (canopy like covering) at geometry optimization and at 353 K. The n shape canopy like covering to a large extent may ...

  19. Hydration of excess electrons trapped in charge pockets on molecular surfaces

    Science.gov (United States)

    Jalbout, Abraham F.; Del Castillo, R.; Adamowicz, Ludwik

    2007-01-01

    In this work we strive to design a novel electron trap located on a molecular surface. The process of electron trapping involves hydration of the trapped electron. Previous calculations on surface electron trapping revealed that clusters of OH groups can form stable hydrogen-bonded networks on one side of a hydrocarbon surface (i.e. cyclohexane sheets), while the hydrogen atoms on the opposite side of the surface form pockets of positive charge that can attract extra negative charge. The excess electron density on such surfaces can be further stabilized by interactions with water molecules. Our calculations show that these anionic systems are stable with respect to vertical electron detachment (VDE).

  20. Synthesis and Surface-Specific Analysis of Molecular Constituents Relevant to Biogenic Secondary Organic Aerosol Material

    Science.gov (United States)

    Be, A. G.; Upshur, M. A.; Chase, H. M.; Geiger, F.; Thomson, R. J.

    2017-12-01

    Secondary organic aerosol (SOA) particles formed from the oxidation of biogenic volatile organic compounds (BVOCs) remain a principal, yet elusive, class of airborne particulate matter that impacts the Earth's radiation budget. Given the characteristic molecular complexity comprising biogenic SOA particles, chemical information selective to the gas-aerosol interface may be valuable in the investigation of such systems, as surface considerations likely dictate the phenomena driving particle evolution mechanisms and climate effects. In particular, cloud activation processes may be parameterized using the surface tension depression that coincides with partitioning of surface-active organic species to the gas-droplet interface. However, the extent to which surface chemical processes, such as cloud droplet condensation, are influenced by the chemical structure and reactivity of individual surface-active molecules in SOA particles is largely unknown. We seek to study terpene-derived organic species relevant to the surfaces of biogenic SOA particles via synthesis of putative oxidation products followed by analysis using surface-selective physicochemical measurements. Using dynamic surface tension measurements, considerable differences are observed in the surface tension depression of aqueous pendant droplets that contain synthetically prepared ozonolysis products derived from abundant terpene precursors. Furthermore, sum frequency generation spectroscopy is utilized for comparison of the surface vibrational spectral responses of synthesized reference compounds with those observed for laboratory aerosol toward probing the surface composition of SOA material. Such ongoing findings highlight the underlying importance of molecular structure and reactivity when considering the surface chemistry of biogenic terpene-derived atmospheric aerosols.

  1. Thermodynamic foundations of applications of ab initio methods for determination of the adsorbate equilibria: hydrogen at the GaN(0001) surface.

    Science.gov (United States)

    Kempisty, Pawel; Strąk, Paweł; Sakowski, Konrad; Kangawa, Yoshihiro; Krukowski, Stanisław

    2017-11-08

    Thermodynamic foundations of ab initio modeling of vapor-solid and vapor-surface equilibria are introduced. The chemical potential change is divided into enthalpy and entropy terms. The enthalpy path passes through vapor-solid transition at zero temperature. The entropy path avoids the singular point at zero temperature passing a solid-vapor transition under normal conditions, where evaporation entropy is employed. In addition, the thermal changes are calculated. The chemical potential difference contribution of the following terms: vaporization enthalpy, vaporization entropy, the temperature-entropy related change, the thermal enthalpy change and mechanical pressure is obtained. The latter term is negligibly small for the pressure typical for epitaxy. The thermal enthalpy change is two orders smaller than the first three terms which have to be taken into account explicitly. The configurational vaporization entropy change is derived for adsorption processes. The same formulation is derived for vapor-surface equilibria using hydrogen at the GaN(0001) surface as an example. The critical factor is the dependence of the enthalpy of evaporation (desorption energy) on the pinning of the Fermi level bringing a drastic change of the value from 2.24 eV to -2.38 eV. In addition it is shown that entropic contributions considerable change the hydrogen equilibrium pressure over the GaN(0001) surface by several orders of magnitude. Thus a complete and exact formulation of vapor-solid and vapor-surface equilibria is presented.

  2. Development and characterization of nifedipine-amino methacrylate copolymer solid dispersion powders with various adsorbents

    Directory of Open Access Journals (Sweden)

    Yotsanan Weerapol

    2017-07-01

    Full Text Available Solid dispersions of nifedipine (NDP, a poorly water-soluble drug, and amino methacrylate copolymer (AMCP with aid of adsorbent, that is, fumed silica, talcum, calcium carbonate, titanium dioxide, and mesoporous silica from rice husks (SRH, were prepared by solvent method. The physicochemical properties of solid dispersions, compared to their physical mixtures, were determined using powder X-ray diffractometry (PXRD and differential scanning calorimetry (DSC. The surface morphology of the prepared solid dispersions was examined by scanning electron microscopy (SEM. The dissolution of NDP from solid dispersions was compared to NDP powders. The effect of adsorbent type on NDP dissolution was also examined. The dissolution of NDP increased with the ratio of NDP:AMCP:adsorbent of 1:4:1 when compared to the other formulations. As indicated from PXRD patterns, DSC thermograms and SEM images, NDP was molecularly dispersed within polymer carrier or in an amorphous form, which confirmed the better dissolution of solid dispersions. Solid dispersions containing SRH provided the highest NDP dissolution, due to a porous nature of SRH, allowing dissolved drug to fill in the pores and consequently dissolve in the medium. The results suggested that solid dispersions containing adsorbents (SRH in particular demonstrated improved dissolution of poorly water-soluble drug when compared to NDP powder.

  3. Mapping Hydrophobicity on the Protein Molecular Surface at Atom-Level Resolution

    Science.gov (United States)

    Nicolau Jr., Dan V.; Paszek, Ewa; Fulga, Florin; Nicolau, Dan V.

    2014-01-01

    A precise representation of the spatial distribution of hydrophobicity, hydrophilicity and charges on the molecular surface of proteins is critical for the understanding of the interaction with small molecules and larger systems. The representation of hydrophobicity is rarely done at atom-level, as this property is generally assigned to residues. A new methodology for the derivation of atomic hydrophobicity from any amino acid-based hydrophobicity scale was used to derive 8 sets of atomic hydrophobicities, one of which was used to generate the molecular surfaces for 35 proteins with convex structures, 5 of which, i.e., lysozyme, ribonuclease, hemoglobin, albumin and IgG, have been analyzed in more detail. Sets of the molecular surfaces of the model proteins have been constructed using spherical probes with increasingly large radii, from 1.4 to 20 Å, followed by the quantification of (i) the surface hydrophobicity; (ii) their respective molecular surface areas, i.e., total, hydrophilic and hydrophobic area; and (iii) their relative densities, i.e., divided by the total molecular area; or specific densities, i.e., divided by property-specific area. Compared with the amino acid-based formalism, the atom-level description reveals molecular surfaces which (i) present an approximately two times more hydrophilic areas; with (ii) less extended, but between 2 to 5 times more intense hydrophilic patches; and (iii) 3 to 20 times more extended hydrophobic areas. The hydrophobic areas are also approximately 2 times more hydrophobicity-intense. This, more pronounced “leopard skin”-like, design of the protein molecular surface has been confirmed by comparing the results for a restricted set of homologous proteins, i.e., hemoglobins diverging by only one residue (Trp37). These results suggest that the representation of hydrophobicity on the protein molecular surfaces at atom-level resolution, coupled with the probing of the molecular surface at different geometric resolutions

  4. Exchange of adsorbed serum proteins during adhesion of Staphylococcus aureus to an abiotic surface and Candida albicans hyphae--an AFM study.

    Science.gov (United States)

    Ovchinnikova, Ekaterina S; van der Mei, Henny C; Krom, Bastiaan P; Busscher, Henk J

    2013-10-01

    Staphylococcus aureus and Candida albicans are the second and third most commonly isolated microorganisms in hospital-related-infections, that are often multi-species in nature causing high morbidity and mortality. Here, adhesion forces between a S. aureus strain and abiotic (tissue-culture-polystyrene, TCPS) or partly biotic (TCPS with adhering hyphae of C. albicans) surfaces were investigated in presence of fetal-bovine-serum or individual serum proteins and related with staphylococcal adhesion. Atomic-force-microscopy was used to measure adhesion forces between S. aureus and the abiotic and biotic surfaces. Adsorption of individual serum proteins like albumin and apo-transferrin to abiotic TCPS surfaces during 60min, impeded development of strong adhesion forces as compared to fibronectin, while 60min adsorption of proteins from fetal-bovine-serum yielded a decrease in adhesion force from -5.7nN in phosphate-buffered-saline to -0.6nN. Adsorption of albumin and apo-transferrin also decreased staphylococcal adhesion forces to hyphae as compared with fibronectin. During 60min exposure to fetal-bovine-serum however, initial (5min protein adsorption) staphylococcal adhesion forces were low (-1.6nN), but strong adhesion forces of around -5.5nN were restored within 60min. This suggests for the first time that in whole fetal-bovine-serum exchange of non-adhesive proteins by fibronectin occurs on biotic C. albicans hyphal surfaces. No evidence was found for such protein exchange on abiotic TCPS surfaces. Staphylococcal adhesion of abiotic and biotic surfaces varied in line with the adhesion forces and was low on TCPS in presence of fetal-bovine-serum. On partly biotic TCPS, staphylococci aggregated in presence of fetal-bovine-serum around adhering C. albicans hyphae. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. A classical trajectory study of the adatom -surface bond dissociation in the collision reaction between an adsorbed H atom and an N2 molecule

    International Nuclear Information System (INIS)

    Bayhan, U.

    2005-01-01

    The collisionnal dissociation of the Adatom-Surface bond in the diatomic molecule N2(gas)/H(ads) collision taking place on a W(100) bcc-structure surface have been studied by classical trajectory method over the collision energy ranges (0.1-2.0 eV ) and the attractive well depth (0.19-4.0 eV). of the N2 molecule (gas)/H(ads) interactions. When the energy accumulate into the adatom bond, thus leading to a a large dissociation probability

  6. Memory effects in nonadiabatic molecular dynamics at metal surfaces

    DEFF Research Database (Denmark)

    Olsen, Thomas; Schiøtz, Jakob

    2010-01-01

    We study the effect of temporal correlation in a Langevin equation describing nonadiabatic dynamics at metal surfaces. For a harmonic oscillator, the Langevin equation preserves the quantum dynamics exactly and it is demonstrated that memory effects are needed in order to conserve the ground state...... energy of the oscillator. We then compare the result of Langevin dynamics in a harmonic potential with a perturbative master equation approach and show that the Langevin equation gives a better description in the nonperturbative range of high temperatures and large friction. Unlike the master equation......, this approach is readily extended to anharmonic potentials. Using density functional theory, we calculate representative Langevin trajectories for associative desorption of N-2 from Ru(0001) and find that memory effects lower the dissipation of energy. Finally, we propose an ab initio scheme to calculate...

  7. Molecular ordering of ethanol at the calcite surface

    DEFF Research Database (Denmark)

    Pasarín, I. S.; Yang, M.; Bovet, Nicolas Emile

    2012-01-01

    To produce biominerals, such as shells, bones, and teeth, living beings create organic compounds that control the growth of the solid phase. Investigating the atomic scale behavior of individual functional groups at the mineral-fluid interface provides fundamental information that is useful...... for constructing accurate predictive models for natural systems. Previous investigations of the activity of coccolith-associated polysaccharides (CAP) on calcite, using atomic force microscopy (AFM) [ Henriksen, K., Young, J. R., Bown, P. R., and Stipp, S. L. S.Palentology 2004, 43 (Part 3), 725...... dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH 3-CH2-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol...

  8. Active molecular plasmonics: tuning surface plasmon resonances by exploiting molecular dimensions

    Science.gov (United States)

    Chen, Kai; Leong, Eunice Sok Ping; Rukavina, Michael; Nagao, Tadaaki; Liu, Yan Jun; Zheng, Yuebing

    2015-06-01

    Molecular plasmonics explores and exploits the molecule-plasmon interactions on metal nanostructures to harness light at the nanoscale for nanophotonic spectroscopy and devices. With the functional molecules and polymers that change their structural, electrical, and/or optical properties in response to external stimuli such as electric fields and light, one can dynamically tune the plasmonic properties for enhanced or new applications, leading to a new research area known as active molecular plasmonics (AMP). Recent progress in molecular design, tailored synthesis, and self-assembly has enabled a variety of scenarios of plasmonic tuning for a broad range of AMP applications. Dimension (i.e., zero-, two-, and threedimensional) of the molecules on metal nanostructures has proved to be an effective indicator for defining the specific scenarios. In this review article, we focus on structuring the field of AMP based on the dimension of molecules and discussing the state of the art of AMP. Our perspective on the upcoming challenges and opportunities in the emerging field of AMP is also included.

  9. Active molecular plasmonics: tuning surface plasmon resonances by exploiting molecular dimensions

    Directory of Open Access Journals (Sweden)

    Chen Kai

    2015-06-01

    Full Text Available Molecular plasmonics explores and exploits the molecule–plasmon interactions on metal nanostructures to harness light at the nanoscale for nanophotonic spectroscopy and devices. With the functional molecules and polymers that change their structural, electrical, and/or optical properties in response to external stimuli such as electric fields and light, one can dynamically tune the plasmonic properties for enhanced or new applications, leading to a new research area known as active molecular plasmonics (AMP. Recent progress in molecular design, tailored synthesis, and self-assembly has enabled a variety of scenarios of plasmonic tuning for a broad range of AMP applications. Dimension (i.e., zero-, two-, and threedimensional of the molecules on metal nanostructures has proved to be an effective indicator for defining the specific scenarios. In this review article, we focus on structuring the field of AMP based on the dimension of molecules and discussing the state of the art of AMP. Our perspective on the upcoming challenges and opportunities in the emerging field of AMP is also included.

  10. Combining density functional and incremental post-Hartree-Fock approaches for van der Waals dominated adsorbate-surface interactions: Ag2/graphene

    International Nuclear Information System (INIS)

    Lara-Castells, María Pilar de; Mitrushchenkov, Alexander O.; Stoll, Hermann

    2015-01-01

    A combined density functional (DFT) and incremental post-Hartree-Fock (post-HF) approach, proven earlier to calculate He-surface potential energy surfaces [de Lara-Castells et al., J. Chem. Phys. 141, 151102 (2014)], is applied to describe the van der Waals dominated Ag 2 /graphene interaction. It extends the dispersionless density functional theory developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] by including periodic boundary conditions while the dispersion is parametrized via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. Starting with the elementary cluster unit of the target surface (benzene), continuing through the realistic cluster model (coronene), and ending with the periodic model of the extended system, modern ab initio methodologies for intermolecular interactions as well as state-of-the-art van der Waals-corrected density functional-based approaches are put together both to assess the accuracy of the composite scheme and to better characterize the Ag 2 /graphene interaction. The present work illustrates how the combination of DFT and post-HF perspectives may be efficient to design simple and reliable ab initio-based schemes in extended systems for surface science applications

  11. Combining density functional and incremental post-Hartree-Fock approaches for van der Waals dominated adsorbate-surface interactions: Ag{sub 2}/graphene

    Energy Technology Data Exchange (ETDEWEB)

    Lara-Castells, María Pilar de, E-mail: Pilar.deLara.Castells@csic.es [Instituto de Física Fundamental (C.S.I.C.), Serrano 123, E-28006 Madrid (Spain); Mitrushchenkov, Alexander O. [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée (France); Stoll, Hermann [Institut für Theoretische Chemie, Universität Stuttgart, D-70550 Stuttgart (Germany)

    2015-09-14

    A combined density functional (DFT) and incremental post-Hartree-Fock (post-HF) approach, proven earlier to calculate He-surface potential energy surfaces [de Lara-Castells et al., J. Chem. Phys. 141, 151102 (2014)], is applied to describe the van der Waals dominated Ag{sub 2}/graphene interaction. It extends the dispersionless density functional theory developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] by including periodic boundary conditions while the dispersion is parametrized via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. Starting with the elementary cluster unit of the target surface (benzene), continuing through the realistic cluster model (coronene), and ending with the periodic model of the extended system, modern ab initio methodologies for intermolecular interactions as well as state-of-the-art van der Waals-corrected density functional-based approaches are put together both to assess the accuracy of the composite scheme and to better characterize the Ag{sub 2}/graphene interaction. The present work illustrates how the combination of DFT and post-HF perspectives may be efficient to design simple and reliable ab initio-based schemes in extended systems for surface science applications.

  12. Revealing Surface Waters on an Antifreeze Protein by Fusion Protein Crystallography Combined with Molecular Dynamic Simulations.

    Science.gov (United States)

    Sun, Tianjun; Gauthier, Sherry Y; Campbell, Robert L; Davies, Peter L

    2015-10-08

    Antifreeze proteins (AFPs) adsorb to ice through an extensive, flat, relatively hydrophobic surface. It has been suggested that this ice-binding site (IBS) organizes surface waters into an ice-like clathrate arrangement that matches and fuses to the quasi-liquid layer on the ice surface. On cooling, these waters join the ice lattice and freeze the AFP to its ligand. Evidence for the generality of this binding mechanism is limited because AFPs tend to crystallize with their IBS as a preferred protein-protein contact surface, which displaces some bound waters. Type III AFP is a 7 kDa globular protein with an IBS made up two adjacent surfaces. In the crystal structure of the most active isoform (QAE1), the part of the IBS that docks to the primary prism plane of ice is partially exposed to solvent and has clathrate waters present that match this plane of ice. The adjacent IBS, which matches the pyramidal plane of ice, is involved in protein-protein crystal contacts with few surface waters. Here we have changed the protein-protein contacts in the ice-binding region by crystallizing a fusion of QAE1 to maltose-binding protein. In this 1.9 Å structure, the IBS that fits the pyramidal plane of ice is exposed to solvent. By combining crystallography data with MD simulations, the surface waters on both sides of the IBS were revealed and match well with the target ice planes. The waters on the pyramidal plane IBS were loosely constrained, which might explain why other isoforms of type III AFP that lack the prism plane IBS are less active than QAE1. The AFP fusion crystallization method can potentially be used to force the exposure to solvent of the IBS on other AFPs to reveal the locations of key surface waters.

  13. High performance Mo adsorbent PZC

    Energy Technology Data Exchange (ETDEWEB)

    Anon,

    1998-10-01

    We have developed Mo adsorbents for natural Mo(n, {gamma}){sup 99}Mo-{sup 99m}Tc generator. Among them, we called the highest performance adsorbent PZC that could adsorb about 250 mg-Mo/g. In this report, we will show the structure, adsorption mechanism of Mo, and the other useful properties of PZC when you carry out the examination of Mo adsorption and elution of {sup 99m}Tc. (author)

  14. The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

    DEFF Research Database (Denmark)

    Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

    2004-01-01

    Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding......-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time...

  15. The Soft-Confined Method for Creating Molecular Models of Amorphous Polymer Surfaces

    KAUST Repository

    Liu, Hongyi; Li, Yan; Krause, Wendy E.; Rojas, Orlando J.; Pasquinelli, Melissa A.

    2012-01-01

    The goal of this work was to use molecular dynamics (MD) simulations to build amorphous surface layers of polypropylene (PP) and cellulose and to inspect their physical and interfacial properties. A new method to produce molecular models for these surfaces was developed, which involved the use of a "soft" confining layer comprised of a xenon crystal. This method compacts the polymers into a density distribution and a degree of molecular surface roughness that corresponds well to experimental values. In addition, calculated properties such as density, cohesive energy density, coefficient of thermal expansion, and the surface energy agree with experimental values and thus validate the use of soft confining layers. The method can be applied to polymers with a linear backbone such as PP as well as those whose backbones contain rings, such as cellulose. The developed PP and cellulose surfaces were characterized by their interactions with water. It was found that a water nanodroplet spreads on the amorphous cellulose surfaces, but there was no significant change in the dimension of the droplet on the PP surface; the resulting MD water contact angles on PP and amorphous cellulose surfaces were determined to be 106 and 33°, respectively. © 2012 American Chemical Society.

  16. The Soft-Confined Method for Creating Molecular Models of Amorphous Polymer Surfaces

    KAUST Repository

    Liu, Hongyi

    2012-02-09

    The goal of this work was to use molecular dynamics (MD) simulations to build amorphous surface layers of polypropylene (PP) and cellulose and to inspect their physical and interfacial properties. A new method to produce molecular models for these surfaces was developed, which involved the use of a "soft" confining layer comprised of a xenon crystal. This method compacts the polymers into a density distribution and a degree of molecular surface roughness that corresponds well to experimental values. In addition, calculated properties such as density, cohesive energy density, coefficient of thermal expansion, and the surface energy agree with experimental values and thus validate the use of soft confining layers. The method can be applied to polymers with a linear backbone such as PP as well as those whose backbones contain rings, such as cellulose. The developed PP and cellulose surfaces were characterized by their interactions with water. It was found that a water nanodroplet spreads on the amorphous cellulose surfaces, but there was no significant change in the dimension of the droplet on the PP surface; the resulting MD water contact angles on PP and amorphous cellulose surfaces were determined to be 106 and 33°, respectively. © 2012 American Chemical Society.

  17. Positronium chemistry in porous adsorbents

    International Nuclear Information System (INIS)

    Foti, G.; Nagy, L.G.; Moravcsik, G.; Schay, G.

    1981-01-01

    Kinetic studies on the annihilation of orthopositronium in porous adsorbents have been performed using lifetime spectroscopy. The positron source applied was 22 Na with 0.2 MBq activity. The adsorbents investigated were silica gels of different particle size and pore structure. The appearance of the long-lived component in the lifetime spectra can be explained by the diffusion of the orthopositronium into the pores affected by the particle size and the pore size of the adsorbent, the coverage on it and the chemical nature of the adsorbate. The long-term aim of the work is to determine and to explain these effects. (author)

  18. Coupling molecular catalysts with nanostructured surfaces for efficient solar fuel production

    Science.gov (United States)

    Jin, Tong

    Solar fuel generation via carbon dioxide (CO2) reduction is a promising approach to meet the increasing global demand for energy and to minimize the impact of energy consumption on climate change. However, CO2 is thermodynamically stable; its activation often requires the use of appropriate catalysts. In particular, molecular catalysts with well-defined structures and tunability have shown excellent activity in photochemical CO2 reduction. These homogenous catalysts, however, suffer from poor stability under photochemical conditions and difficulty in recycling from the reaction media. Heterogenized molecular catalysts, particularly those prepared by coupling molecular catalysts with solid-state surfaces, have attracted more attention in recent years as potential solutions to address the issues associated with molecular catalysts. In this work, solar CO2 reduction is investigated using systems coupling molecular catalysts with robust nanostructured surfaces. In Chapter 2, heterogenization of macrocyclic cobalt(III) and nickel (II) complexes on mesoporous silica surface was achieved by different methods. Direct ligand derivatization significantly lowered the catalytic activity of Co(III) complex, while grafting the Co(III) complex onto silica surface through Si-O-Co linkage resulted in hybrid catalysts with excellent activity in CO2 reduction in the presence of p-terphenyl as a molecular photosensitizer. An interesting loading effect was observed, in which the optimal activity was achieved at a medium Co(III) surface density. Heterogenization of the Ni(II) complex on silica surface has also been implemented, the poor photocatalytic activity of the hybrid catalyst can be attributed to the intrinsic nature of the homogeneous analogue. This study highlighted the importance of appropriate linking strategies in preparing functional heterogenized molecular catalysts. Coupling molecular complexes with light-harvesting surfaces could avoid the use of expensive molecular

  19. Heat-resistant organic molecular layer as a joint interface for metal reduction on plastics surfaces

    International Nuclear Information System (INIS)

    Sang, Jing; Aisawa, Sumio; Hirahara, Hidetoshi; Kudo, Takahiro; Mori, Kunio

    2016-01-01

    Graphical abstract: - Highlights: • In situ adsorption behaviors of TES on PA6 surface were clarified by QCM. • Highest adsorption of TES on PA6 was obtained in pH 3 and 0.1 M solution. • Molecular layers of TES with uniform structures were prepared on PA6 surface. • TES layer improved PA6 local heat resistance from 150 °C to 230 °C. • TES molecular layer successfully reduced Ag ion to Ag"0. - Abstract: Heat-resistant organic molecular layers have been fabricated by triazine-based silane coupling agent for metal reduction on plastic surfaces using adsorption method. These molecular layers were used as an interfacial layer between polyamide (PA6) and metal solution to reduce Ag"+ ion to Ag"0. The interfacial behaviors of triazine molecular layer at the interfaces between PA6 and Ag solution were investigated using quartz crystal microbalance (QCM). The kinetics of molecular adsorption on PA6 was investigated by using triazine-based silane coupling agent solutions at different pH and concentration. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and local nano thermal analysis were employed to characterize the surfaces and interfaces. The nano thermal analysis results show that molecular layers of triazine-based silane coupling agent greatly improved heat resistance of PA6 resin from 170 °C up to 230 °C. This research developed an in-depth insight for molecular behaviors of triazine-based silane coupling agent at the PA6 and Ag solution interfaces and should be of significant value for interfacial research between plastics and metal solution in plating industry.

  20. Heat-resistant organic molecular layer as a joint interface for metal reduction on plastics surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Jing [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Aisawa, Sumio, E-mail: aisawa@iwate-u.ac.jp [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Hirahara, Hidetoshi [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Kudo, Takahiro [Sulfur Chemical Institute, 210, Collabo MIU, 4-3-5, Ueda, Morioka 020-0066 (Japan); Mori, Kunio [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Sulfur Chemical Institute, 210, Collabo MIU, 4-3-5, Ueda, Morioka 020-0066 (Japan)

    2016-04-15

    Graphical abstract: - Highlights: • In situ adsorption behaviors of TES on PA6 surface were clarified by QCM. • Highest adsorption of TES on PA6 was obtained in pH 3 and 0.1 M solution. • Molecular layers of TES with uniform structures were prepared on PA6 surface. • TES layer improved PA6 local heat resistance from 150 °C to 230 °C. • TES molecular layer successfully reduced Ag ion to Ag{sup 0}. - Abstract: Heat-resistant organic molecular layers have been fabricated by triazine-based silane coupling agent for metal reduction on plastic surfaces using adsorption method. These molecular layers were used as an interfacial layer between polyamide (PA6) and metal solution to reduce Ag{sup +} ion to Ag{sup 0}. The interfacial behaviors of triazine molecular layer at the interfaces between PA6 and Ag solution were investigated using quartz crystal microbalance (QCM). The kinetics of molecular adsorption on PA6 was investigated by using triazine-based silane coupling agent solutions at different pH and concentration. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and local nano thermal analysis were employed to characterize the surfaces and interfaces. The nano thermal analysis results show that molecular layers of triazine-based silane coupling agent greatly improved heat resistance of PA6 resin from 170 °C up to 230 °C. This research developed an in-depth insight for molecular behaviors of triazine-based silane coupling agent at the PA6 and Ag solution interfaces and should be of significant value for interfacial research between plastics and metal solution in plating industry.

  1. Water-resistance of macromolecules adsorbed on CH3NH3PbI3 surfaces: A first-principles study

    Science.gov (United States)

    Chen, Po-Tuan; Yung, Tung-Yuan; Liu, Ting-Yu; Sher, Chin-Wei; Hayashi, Michitoshi

    2017-10-01

    Encapsulation within resin films is a promising approach for isolating perovskite materials from water. To gain fundamental insight into these systems, we performed first-principles calculations of macromolecule (polymerized siloxane; epoxy cured by phthalic anhydride; graphene sheet) coatings for the waterproofing of methylammonium lead iodide perovskite (MAPbI3) surfaces. Our calculations reveal that alternating attractive/resistant functional groups on the siloxane- or epoxy-modified MAPbI3 surfaces hinder the water diffusion process. Moreover, we examined a no-defect graphene sheet for its ability to isolate MAPbI3 from water molecules. The hydrophobicity of the graphene resulted in water molecules forming clusters, rather than dispersing, upon the sheet.

  2. Competitive Adsorption of a Two-Component Gas on a Deformable Adsorbent

    OpenAIRE

    Usenko, A. S.

    2013-01-01

    We investigate the competitive adsorption of a two-component gas on the surface of an adsorbent whose adsorption properties vary in adsorption due to the adsorbent deformation. The essential difference of adsorption isotherms for a deformable adsorbent both from the classical Langmuir adsorption isotherms of a two-component gas and from the adsorption isotherms of a one-component gas taking into account variations in adsorption properties of the adsorbent in adsorption is obtained. We establi...

  3. Intramolecular charge separation in spirobifluorene-based donor–acceptor compounds adsorbed on Au and indium tin oxide electrodes

    International Nuclear Information System (INIS)

    Heredia, Daniel; Otero, Luis; Gervaldo, Miguel; Fungo, Fernando; Dittrich, Thomas; Lin, Chih-Yen; Chi, Liang-Chen; Fang, Fu-Chuan; Wong, Ken-Tsung

    2013-01-01

    Surface photovoltage (SPV) measurements were performed with a Kelvin-probe in spirobifluorene-based donor (diphenylamine)–acceptor (dicyano or cyanoacrylic acid moieties) compounds adsorbed from highly diluted solutions onto Au and indium tin oxide electrode surfaces. Strong intramolecular charge separation (negative SPV signals up to more than 0.1 V) due to directed molecule adsorption was observed only for spirobifluorene donor–acceptor compounds with carboxylic acid moiety. SPV signals and onset energies of electronic transitions depended on ambience conditions. - Highlights: ► Fluorene donor–acceptor derivatives were adsorbed at Au and indium tin oxide. ► Surface photovoltage measurements were performed with a Kelvin-probe. ► Strong intra-molecular charge separation was observed. ► SPV signals depended on ambience conditions

  4. Theoretical Insight of Physical Adsorption for a Single Component Adsorbent + Adsorbate System: II. The Henry Region

    KAUST Repository

    Chakraborty, Anutosh; Saha, Bidyut Baran; Ng, Kim Choon; Koyama, Shigeru; Srinivasan, Kandadai

    2009-01-01

    evaluated and compared with experimental data. It is found that the adsorbents with higher specific surface areas tend to possess lower heat of adsorption (ΔH°) at the Henry regime. In this paper, we have established the definitive relation between Ai and ΔH

  5. Molecularly oriented surface relief formation in polymethacrylates comprising N-benzylideneaniline derivative side groups

    Science.gov (United States)

    Kawatsuki, Nobuhiro; Hosoda, Risa; Kondo, Mizuho; Sasaki, Tomoyuki; Ono, Hiroshi

    2014-12-01

    Molecularly oriented surface relief (SR) formation in polymethacrylates with N-benzylideneaniline (NBA) derivative side groups is investigated by holographic exposure using a 325 nm He-Cd laser. Because the NBA moieties show a photoinduced orientation perpendicular to the polarization of light, polarization holography successfully forms a molecularly oriented SR structure in accordance with the polarization distribution that includes p-polarized components. Although intensity holography induces molecular orientation, it does not generate a satisfactory SR structure. In all the holographic modes, the SR depth depends on the direction of the C=N bonds in the NBA moieties and the photoproducts affect the SR formation ability.

  6. Molecular dynamics simulation of temperature effects on low energy near-surface cascades and surface damage in Cu

    Science.gov (United States)

    Zhu, Guo; Sun, Jiangping; Guo, Xiongxiong; Zou, Xixi; Zhang, Libin; Gan, Zhiyin

    2017-06-01

    The temperature effects on near-surface cascades and surface damage in Cu(0 0 1) surface under 500 eV argon ion bombardment were studied using molecular dynamics (MD) method. In present MD model, substrate system was fully relaxed for 1 ns and a read-restart scheme was introduced to save total computation time. The temperature dependence of damage production was calculated. The evolution of near-surface cascades and spatial distribution of adatoms at varying temperature were analyzed and compared. It was found that near-surface vacancies increased with temperature, which was mainly due to the fact that more atoms initially located in top two layers became adatoms with the decrease of surface binding energy. Moreover, with the increase of temperature, displacement cascades altered from channeling-like structure to branching structure, and the length of collision sequence decreased gradually, because a larger portion of energy of primary knock-on atom (PKA) was scattered out of focused chain. Furthermore, increasing temperature reduced the anisotropy of distribution of adatoms, which can be ascribed to that regular registry of surface lattice atoms was changed with the increase of thermal vibration amplitude of surface atoms.

  7. Molecular dynamics simulation of temperature effects on low energy near-surface cascades and surface damage in Cu

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Guo; Sun, Jiangping; Guo, Xiongxiong; Zou, Xixi; Zhang, Libin; Gan, Zhiyin, E-mail: ganzhiyin@126.com

    2017-06-15

    The temperature effects on near-surface cascades and surface damage in Cu(0 0 1) surface under 500 eV argon ion bombardment were studied using molecular dynamics (MD) method. In present MD model, substrate system was fully relaxed for 1 ns and a read-restart scheme was introduced to save total computation time. The temperature dependence of damage production was calculated. The evolution of near-surface cascades and spatial distribution of adatoms at varying temperature were analyzed and compared. It was found that near-surface vacancies increased with temperature, which was mainly due to the fact that more atoms initially located in top two layers became adatoms with the decrease of surface binding energy. Moreover, with the increase of temperature, displacement cascades altered from channeling-like structure to branching structure, and the length of collision sequence decreased gradually, because a larger portion of energy of primary knock-on atom (PKA) was scattered out of focused chain. Furthermore, increasing temperature reduced the anisotropy of distribution of adatoms, which can be ascribed to that regular registry of surface lattice atoms was changed with the increase of thermal vibration amplitude of surface atoms.

  8. Role of molecular properties of ulvans on their ability to elaborate antiadhesive surfaces.

    Science.gov (United States)

    Gadenne, Virginie; Lebrun, Laurent; Jouenne, Thierry; Thebault, Pascal

    2015-03-01

    Antiadhesive properties of polysaccharides (such ulvans) once immobilized on a surface are described in the literature but the parameters governing their antifouling properties are not yet well identified. In the present study, the relationship between molecular parameters of ulvans and the inhibition of bacterial adhesion was investigated. To this aim, various ulvans were grafted on silicon wafers under two different experimental immobilization conditions. Results showed that the experimental immobilization conditions and the polysaccharides molecular weight led to specific layer conformations which exhibited a key role in the surface antiadhesive properties. © 2014 Wiley Periodicals, Inc.

  9. Molecular weight evaluation of poly-dimethylsiloxane on solid surfaces using silver deposition/TOF-SIMS

    Science.gov (United States)

    Inoue, Masae; Murase, Atsushi

    2004-06-01

    Molecular ions include information about end groups, functional groups and molecular weight. A method for directly detecting this in the high-mass region of the spectrum (>1000 amu) from poly-dimethylsiloxane (PDMS) on a solid surface was investigated. It was found that a TOF-SIMS analysis of silver-deposited surfaces (silver deposition/TOF-SIMS) is useful for this purpose. Two methods for silver deposition, the diode sputtering method and the vacuum evaporation coating method, were tried. The former required the sample to be cooled so as to prevent the damage of the sample surface due to thermal oxidation; the latter caused no damage to sample surfaces at room temperature. Using silver deposition/TOF-SIMS analysis, silver-cationized quasi-molecular ions were clearly detected from PDMS on solid surfaces and their images were observed without the interference of deposited silver. By applying to the analysis of paint defects, etc., it was confirmed that this technique is useful to analyze practical industrial materials. Silver-cationized ions were detected not only from PDMS, but also from other organic materials, such as some kinds of lubricant additives and fluorine oils on solid surfaces. Therefore, silver deposition/TOF-SIMS was proved to be useful for the analysis of thin substances on solid surfaces.

  10. Ultrafast time-resolved electron diffraction on adsorbate systems on silicon surfaces. Vibrational excitation in monllayers and dynamics of phase transitions; Ultraschnelle zeitaufgeloeste Elektronenbeugung an Adsorbatsystemen auf Siliziumoberflaechen. Vibrationsanregung in Monolagen und Dynamik von Phasenuebergaengen

    Energy Technology Data Exchange (ETDEWEB)

    Moellenbeck, Simone

    2011-04-11

    surface phase transitions was analysed for the first time with TR-RHEED. As a first modell system, the Si(0 0 1) c(4 x 2)-(2 x 1) order disorder phase transition was analyzed. The dynamics of this phase transition can be observed with TR-RHEED, as the Laue rings on which the c(4 x 2)-spots are located vanishes almost completely in the temporal overlap. The observed intensity decrease of the (2 x 1)-reflexes is however quiet small. Due to the direct bandgap of Silicon, a direct absorption of the photons in the Silicon substrate can be excluded. Instead, the excitation of the phase transition is explained by absorption in the surface state of the tilted dimer. Furthermore, the Peierls like phase transition of In/Si(1 1 1) (4 x 1)-(8 x ''2'') was analyzed in detail. This phase transition can be observed excellently in TR-RHEED: the diffraction spots of the (8 x ''2'')-reconstruction vanish whereas the intensity of the (4 x 1)-spots increases simultaneously. The intensity increase cannot be explained with a simple Debye-Waller effect. A real structural transiton at the surface takes place. Fluence and base temperature dependent measurements are presented to confirm, that the electronic excitation instead of thermal excitation destroys the low temperature phase. Furthermore, a complete structural formation of the (8 x ''2'')-reconstruction (time constant of approx. 500 ps) and growth from seeds around adsorbates (down to 50 ps) can be distinguished. In addition, the thermal cooling before the structural change can be observed when the surface is heated above the phase transition temperature (time constant up to 2000 ps). (orig.)

  11. Calculation of surface potentials at the silica–water interface using molecular dynamics: Challenges and opportunities

    Science.gov (United States)

    Lowe, Benjamin M.; Skylaris, Chris-Kriton; Green, Nicolas G.; Shibuta, Yasushi; Sakata, Toshiya

    2018-04-01

    Continuum-based methods are important in calculating electrostatic properties of interfacial systems such as the electric field and surface potential but are incapable of providing sufficient insight into a range of fundamentally and technologically important phenomena which occur at atomistic length-scales. In this work a molecular dynamics methodology is presented for interfacial electric field and potential calculations. The silica–water interface was chosen as an example system, which is highly relevant for understanding the response of field-effect transistors sensors (FET sensors). Detailed validation work is presented, followed by the simulated surface charge/surface potential relationship. This showed good agreement with experiment at low surface charge density but at high surface charge density the results highlighted challenges presented by an atomistic definition of the surface potential. This methodology will be used to investigate the effect of surface morphology and biomolecule addition; both factors which are challenging using conventional continuum models.

  12. Inorganic chemically active adsorbents (ICAAs)

    Energy Technology Data Exchange (ETDEWEB)

    Ally, M.R. [Oak Ridge National Lab., TN (United States); Tavlarides, L.

    1997-10-01

    Oak Ridge National Laboratory (ORNL) researchers are developing a technology that combines metal chelation extraction technology and synthesis chemistry. They begin with a ceramic substrate such as alumina, titanium oxide or silica gel because they provide high surface area, high mechanical strength, and radiolytic stability. One preparation method involves silylation to hydrophobize the surface, followed by chemisorption of a suitable chelation agent using vapor deposition. Another route attaches newly designed chelating agents through covalent bonding by the use of coupling agents. These approaches provide stable and selective, inorganic chemically active adsorbents (ICAAs) tailored for removal of metals. The technology has the following advantages over ion exchange: (1) higher mechanical strength, (2) higher resistance to radiation fields, (3) higher selectivity for the desired metal ion, (4) no cation exchange, (5) reduced or no interference from accompanying anions, (6) faster kinetics, and (7) easy and selective regeneration. Target waste streams include metal-containing groundwater/process wastewater at ORNL`s Y-12 Plant (multiple metals), Savannah River Site (SRS), Rocky Flats (multiple metals), and Hanford; aqueous mixed wastes at Idaho National Engineering Laboratory (INEL); and scrubber water generated at SRS and INEL. Focus Areas that will benefit from this research include Mixed Waste, and Subsurface Contaminants.

  13. Computational investigation of CO adsorbed on Aux, Agx and (AuAg)x nanoclusters (x = 1 - 5, 147) and monometallic Au and Ag low-energy surfaces*

    Science.gov (United States)

    Gould, Anna L.; Catlow, C. Richard A.; Logsdail, Andrew J.

    2018-02-01

    Density functional theory calculations have been performed to investigate the use of CO as a probe molecule for the determination of the structure and composition of Au, Ag and AuAg nanoparticles. For very small nanoclusters (x = 1 - 5), the CO vibrational frequencies can be directly correlated to CO adsorption strength, whereas larger 147-atom nanoparticles show a strong energetic preference for CO adsorption at a vertex position but the highest wavenumbers are for the bridge positions. We also studied CO adsorption on Au and Ag (100) and (111) surfaces, for a 1 monolayer coverage, which proves to be energetically favourable on atop only and bridge positions for Au (100) and atop for Ag (100); vibrational frequencies of the CO molecules red-shift to lower wavenumbers as a result of increased metal coordination. We conclude that CO vibrational frequencies cannot be solely relied upon in order to obtain accurate compositional analysis, but we do propose that elemental rearrangement in the core@shell nanoclusters, from Ag@Au (or Au@Ag) to an alloy, would result in a shift in the CO vibrational frequencies that indicate changes in the surface composition. Contribution to the Topical Issue "Shaping Nanocatalysts", edited by Francesca Baletto, Roy L. Johnston, Jochen Blumberger and Alex Shluger.Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjb/e2017-80280-7

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

    Science.gov (United States)

    Onclin, Steffen; Mulder, Alart; Huskens, Jurriaan; Ravoo, Bart Jan; Reinhoudt, David N

    2004-06-22

    Monolayers of beta-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, 1,4-phenylene diisothiocyanate was used to react with the amine monolayer where it acts as a linking molecule, exposing isothiocyanates that can be derivatized further. Finally, per-6-amino beta-cyclodextrin was reacted with these isothiocyanate functions to yield a monolayer exposing beta-cyclodextrin. All monolayers were characterized by contact angle measurements, ellipsometric thickness measurements, Brewster angle Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry, which indicate the formation of a densely packed cyclodextrin surface. It was demonstrated that the beta-cyclodextrin monolayer could bind suitable guest molecules in a reversible manner. A fluorescent molecule (1), equipped with two adamantyl groups for complexation, was adsorbed onto the host monolayer from solution to form a monolayer of guest molecules. Subsequently, the guest molecules were desorbed from the surface by competition with increasing beta-cyclodextrin concentration in solution. The data were fitted using a model. An intrinsic binding constant of 3.3 +/- 1 x 10(5) M(-1) was obtained, which corresponds well to previously obtained results with a divalent guest molecule on beta-cyclodextrin monolayers on gold. In addition, the number of guest molecules bound to the host surface was determined, and a surface coverage of ca. 30% was found.

  15. First principles study of NH3 molecular adsorption on LiH (100) surfaces

    International Nuclear Information System (INIS)

    Lu Xiaoxia; Chen Yuhong; Dong Xiao

    2012-01-01

    The adsorption of NH 3 on LiH (100) crystal surfaces was studied by first principles method. The preferred adsorption sites, adsorption energy, dissociation energy and electronic structure of the LiH (100)/NH 3 systems were calculated separately. It is found that chemical adsorption happened mainly when NH 3 molecules are on the LiH (100) crystal surfaces. When NH 3 is adsorbed on the Li top site, NH 2 is formed on the LiH (100) crystal surfaces after loss of H atom, the calculated adsorption energy, 0.511 eV, belongs to strong chemical adsorption, then the interaction is strongest. The interaction between NH 2 and the neighboring Li, H are ionic. The covalent bonds are formed between N and H atoms in NH 2 . One H 2 molecule is formed by another H atom in NH 3 and H atom from LiH (100) crystal sur- faces. The covalent bonds are formed between H and H atoms in H 2 . (authors)

  16. 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...

  17. Control of chemical bonding of the ZnO surface grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Ogata, K.; Komuro, T.; Hama, K.; Koike, K.; Sasa, S.; Inoue, M.; Yano, M.

    2004-01-01

    Toward the fabrication of enzyme modified field effect transistors (EnFETs) as one of organic/inorganic hybridized structures, surface bonding of the ZnO grown by molecular beam epitaxy was controlled by ex situ treatments. Angle resolved X-ray photoelectron spectroscopy (XPS) measurement revealed that O-H bonds exist at the surface of ZnO. It was found that the number of O-H bond could be changed with reversibility using plasma and thermal treatments

  18. Milestone Report - Complete New Adsorbent Materials for Marine Testing to Demonstrate 4.5 g-U/kg Adsorbent

    Energy Technology Data Exchange (ETDEWEB)

    Janke, Christopher James [ORNL; Das, Sadananda [ORNL; Oyola, Yatsandra [ORNL; Mayes, Richard T. [ORNL; Saito, Tomonori [ORNL; Brown, Suree [ORNL; Gill, Gary [PNNL; Kuo, Li-Jung [PNNL; Wood, Jordana [PNNL

    2014-08-01

    This report describes work on the successful completion of Milestone M2FT-14OR03100115 (8/20/2014) entitled, “Complete new adsorbent materials for marine testing to demonstrate 4.5 g-U/kg adsorbent”. This effort is part of the Seawater Uranium Recovery Program, sponsored by the U.S. Department of Energy, Office of Nuclear Energy, and involved the development of new adsorbent materials at the Oak Ridge National Laboratory (ORNL) and marine testing at the Pacific Northwest National Laboratory (PNNL). ORNL has recently developed two new families of fiber adsorbents that have demonstrated uranium adsorption capacities greater than 4.5 g-U/kg adsorbent after marine testing at PNNL. One adsorbent was synthesized by radiation-induced graft polymerization of itaconic acid and acrylonitrile onto high surface area polyethylene fibers followed by amidoximation and base conditioning. This fiber showed a capacity of 4.6 g-U/kg adsorbent in marine testing at PNNL. The second adsorbent was prepared by atom-transfer radical polymerization of t-butyl acrylate and acrylonitrile onto halide-functionalized round fibers followed by amidoximation and base hydrolysis. This fiber demonstrated uranium adsorption capacity of 5.4 g-U/kg adsorbent in marine testing at PNNL.

  19. Mercury adsorption properties of sulfur-impregnated adsorbents

    Science.gov (United States)

    Hsi, N.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

    2002-01-01

    Carbonaceous and noncarbonaceous adsorbents were impregnated with elemental sulfur to evaluate the chemical and physical properties of the adsorbents and their equilibrium mercury adsorption capacities. Simulated coal combustion flue gas conditions were used to determine the equilibrium adsorption capacities for Hg0 and HgCl2 gases to better understand how to remove mercury from gas streams generated by coal-fired utility power plants. Sulfur was deposited onto the adsorbents by monolayer surface deposition or volume pore filling. Sulfur impregnation increased the total sulfur content and decreased the total and micropore surface areas and pore volumes for all of the adsorbents tested. Adsorbents with sufficient amounts of active adsorption sites and sufficient microporous structure had mercury adsorption capacities up to 4,509 ??g Hg/g adsorbent. Elemental sulfur, organic sulfur, and sulfate were formed on the adsorbents during sulfur impregnation. Correlations were established with R2>0.92 between the equilibrium Hg0/HgCl2 adsorption capacities and the mass concentrations of elemental and organic sulfur. This result indicates that elemental and organic sulfur are important active adsorption sites for Hg0 and HgCl2.

  20. Recoil-ion fractions in collisions of keV Ar sup + and Kr sup + ions with clean and adsorbate covered GaAs(1 1 0) surfaces

    CERN Document Server

    Gayone, J E; Grizzi, O; Vergara, L I; Passeggi, M C G; Vidal, R; Ferron, J

    2002-01-01

    Ion scattering and recoiling spectroscopy with time of flight analysis is used to study the ion fractions of Ga and As atoms recoiled in collisions of 5 keV Ar sup + and Kr sup + with clean GaAs(1 1 0) and with GaAs(1 1 0) covered with H, alkali metals (K and Cs) and fluorides (AlF sub 3). For the case of the clean surface, the Ga ion fraction is positive, large (approx 50%) and independent of the projectile type. The As ion fraction is also positive, low for Ar sup + (<10%) and relatively large (25%) for Kr sup + projectiles. The adsorption of H produces slight changes in both the As and Ga ion fractions, which is in agreement with the adsorption model where H reacts with both As and Ga atoms. The adsorption of alkalis produces strong changes in the ion fractions. At the beginning of the alkali adsorption the neutralization of Ga recoils increases fast with the coverage and follows approximately the variation of the work function. At coverages above half of the saturation value, where the work function ha...

  1. Interaction of nucleic acids with electrically charged surfaces. VII. The effect of ionic strength of neutral medium on the conformation of dna adsorbed on the mercury electrode.

    Science.gov (United States)

    Brabec, V

    1980-02-01

    Triangular-wave direct current (d.c.) voltammetry at a hanging mercury drop electrode and phase-selective alternating current (a.c.) polarography at a dropping mercury electrode were used for the investigation of adsorption of double-helical (ds) DNA at mercury electrode surfaces from neutral solutions of 0.05-0.4 M HCOONH4. It was found for the potential region T (from -0.1 V up to ca. -1.0 V) that the height of voltammetric peaks of ds DNA is markedly influenced by the initial potential only at relatively low ionic strength (mu) (from 0.05 up to ca. 0.3). Also a decrease of differential capacity (measured by means of a.c. polarography) in the region T depended markedly on the electrode potential only at relatively low ionic strength. The following conclusions were made concerning the interaction of ds DNA with a mercury electrode charged to potentials of the region T in neutral medium of relatively low ionic strength mu potentials in the Vicinity of the zero charge potential a higher number of ds DNA segments can be opened, probably as a consequence of the strain which could act on the ds DNA molecule in the course of the segmental adsorption/desorption process.

  2. Surface functionalization of SPR chip for specific molecular interaction analysis under flow condition

    Directory of Open Access Journals (Sweden)

    Tao Ma

    2017-03-01

    Full Text Available Surface functionalization of sensor chip for probe immobilization is crucial for the biosensing applications of surface plasmon resonance (SPR sensors. In this paper, we report a method circulating the dopamine aqueous solution to coat polydopamine film on sensing surface for surface functionalization of SPR chip. The polydopamine film with available thickness can be easily prepared by controlling the circulation time and the biorecognition elements can be immobilized on the polydopamine film for specific molecular interaction analysis. These operations are all performed under flow condition in the fluidic system, and have the advantages of easy implementation, less time consuming, and low cost, because the reagents and devices used in the operations are routinely applied in most laboratories. In this study, the specific absorption between the protein A probe immobilized on the sensing surface and human immunoglobulin G in the buffer is monitored based on this surface functionalization strategy to demonstrated its feasibility for SPR biosensing applications.

  3. Condition of granulating titanium-activated carbon composite adsorbent and its adsorption for uranium

    International Nuclear Information System (INIS)

    Miyai, Yoshitaka; Kitamura, Takao; Katoh, Shunsaku; Miyazaki, Hidetoshi

    1979-01-01

    The powdery titanium-activated carbon composite adsorbent was granulated, and the strength and uranium adsorptivity of the granulated adsorbent were studied in relation to its granulating condition. By use of polyvinylalcohol (PVA) with degree of polymerization above 2,000 as binder, the granular adsorbent with as much the same strength as commercial granular activated carbon was obtained. Addition of PVA did not affect the amount of adsorbed uranium in equilibrium, but decreased the adsorption rate. Effect of granule size between 2-5 mm on the uranium adsorption rate was that the uranium adsorption rate changed proportionally to surface area of assumed sphere. As a test for practical use, 5 times repetitions of adsorption and desorption were carried out on the same granular adsorbent. During this repetition the adsorbent containing formalized PVA revealed smaller weight loss than non-treated adsorbent. The amount of adsorbed uranium decreased with increasing repetition times, and reason of this was discussed. (author)

  4. Influence of molecular weight and pH on adsorption of chitosan at the surface of large and giant vesicles.

    Science.gov (United States)

    Quemeneur, Francois; Rinaudo, Marguerite; Pépin-Donat, Brigitte

    2008-01-01

    This paper describes the mechanisms of adsorption of chitosan, a positively charged polyelectrolyte, on the DOPC lipid membrane of large and giant unilamellar vesicles (respectively, LUVs and GUVs). We observe that the variation of the zeta potential of LUVs as a function of chitosan concentration is independent on the chitosan molecular weight (Mw). This result is interpreted in terms of electrostatic interactions, which induce a flat adsorption of the chitosan on the surface of the membrane. The role of electrostatic interactions is further studied by observing the variation of the zeta potential as a function of the chitosan concentration for two different charge densities tuned by the pH. Results show a stronger chitosan-membrane affinity at pH 6 (lipids are negatively charged, and 40% chitosan amino groups are protonated) than at pH 3.4 (100% of protonated amino groups but zwitterionic lipids are positively charged) which confirms that adsorption is of electrostatic origin. Then, we investigate the stability of decorated LUVs and GUVs in a large range of pH (6.0 pH variation of the zeta potential as a function of the pH (2.0 pH pH pH > 10.0, in the absence of chitosan, the vesicles present complex shapes, contrary to the chitosan-decorated vesicles which remain spherical, confirming thus that chitosan remains adsorbed on vesicles in basic conditions up to pH = 12.0. These results, in addition with our previous data, show that the chitosan-decorated vesicles are stable over a very broad range of pH (2.0 pH < 12.0), which holds promise for their in vivo applications. Finally, the quantification of the chitosan adsorption on a LUV membrane is performed by zeta potential and fluorescence measurements. The fraction of membrane surface covered by chitosan is estimated to be lower than 40 %, which corresponds to the formation of a flat layer of chitosan on the membrane surface on an electrostatic basis.

  5. High-Resolution Scanning Tunneling Microscopy Studies of Molecular Nanostructures on Surfaces

    DEFF Research Database (Denmark)

    Song, Xin

    . First, to study the role of hydrogen bonding in self-assembly, we investigate the monomolecular self-assembled system of pyrene-4,5,9,10-tetrone and phenanthrene- 9,10-dione molecules on Au(111) and HOPG surface respectively and the binary molecular self-assembled system of stearic acid and guanine...

  6. Comparison of molecular dynamics and kinetic modeling of gas-surface interactions

    NARCIS (Netherlands)

    Frezzotti, A.; Gaastra - Nedea, S.V.; Markvoort, A.J.; Spijker, P.; Gibelli, L.

    2008-01-01

    The interaction of a dilute monatomic gas with a solid surface is studied byMolecular Dynamics (MD) simulations and by numerical solutions of a recently proposed kinetic model. Following previous investigations, the heat transport between parallel walls and Couette flow have been adopted as test

  7. DYNAMIC SURFACE BOUNDARY-CONDITIONS - A SIMPLE BOUNDARY MODEL FOR MOLECULAR-DYNAMICS SIMULATIONS

    NARCIS (Netherlands)

    JUFFER, AH; BERENDSEN, HJC

    1993-01-01

    A simple model for the treatment of boundaries in molecular dynamics simulations is presented. The method involves the positioning of boundary atoms on a surface that surrounds a system of interest. The boundary atoms interact with the inner region and represent the effect of atoms outside the

  8. Surface enhanced raman scattering on tardigrada - Towards monitoring and imaging molecular structures in live cryptobiotic organisms

    DEFF Research Database (Denmark)

    Kneipp, Harald; Møbjerg, Nadja; Jørgensen, Aslak

    2013-01-01

    Tardigrades are microscopic metazoans which are able to survive extreme physical and chemical conditions by entering a stress tolerant state called cryptobiosis. At present, the molecular mechanisms behind cryptobiosis are still poorly understood. We show that surface enhanced Raman scattering su...

  9. Free-Molecular Gas Flow in Channels (Pores) with Physico-Chemical Transformation on the Surface

    Czech Academy of Sciences Publication Activity Database

    Levdansky, V.V.; Smolík, Jiří; Moravec, Pavel

    2006-01-01

    Roč. 49, 13-14 (2006), s. 2356-2365 ISSN 0017-9310 Institutional research plan: CEZ:AV0Z40720504 Keywords : free-molecular flow * surface * spatial distribution Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.482, year: 2006

  10. Squeezing Molecularly thin Lubricant Films between curved Corrugated Surfaces with long range Elasticity

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, Vladimir N.; Persson, Bo N. J.

    2010-01-01

    3H8, C4H10, C8H18, C9H20, C10H22, C14H30 and C16H34, confined between corrugated gold surfaces. Well defined molecular layers develop in the lubricant film when the width is of the order of a few atomic diameters. An external squeezing pressure induces discontinuous, thermally activated changes...

  11. Adsorption and recognition characteristics of surface molecularly imprinted polymethacrylic acid/silica toward genistein.

    Science.gov (United States)

    Zhang, Yanyan; Gao, Baojiao; An, Fuqiang; Xu, Zeqing; Zhang, Tingting

    2014-09-12

    In this paper, on the basis of surface-initiated graft polymerization, a new surface molecular imprinting technique is established by molecular design. And molecularly imprinted polymer MIP-PMAA/SiO2 is successfully prepared with genistein as template. The adsorption and recognition characteristics of MIP-PMAA/SiO2 for genistein are studied in depth by using static method, dynamic method and competitive adsorption experiment. The experimental results show that MIP-PMAA/SiO2 possesses very strong adsorption affinity and specific recognition for genistein. The saturated adsorption capacity could reach to 0.36mmolg(-1). The selectivity coefficients relative to quercetin and rutin are 5.4 and 11.8, respectively. Besides, MIP-PMAA/SiO2 is regenerated easily and exhibits excellent reusability. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Surface charge method for molecular surfaces with curved areal elements I. Spherical triangles

    Science.gov (United States)

    Yu, Yi-Kuo

    2018-03-01

    Parametrizing a curved surface with flat triangles in electrostatics problems creates a diverging electric field. One way to avoid this is to have curved areal elements. However, charge density integration over curved patches appears difficult. This paper, dealing with spherical triangles, is the first in a series aiming to solve this problem. Here, we lay the ground work for employing curved patches for applying the surface charge method to electrostatics. We show analytically how one may control the accuracy by expanding in powers of the the arc length (multiplied by the curvature). To accommodate not extremely small curved areal elements, we have provided enough details to include higher order corrections that are needed for better accuracy when slightly larger surface elements are used.

  13. 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.

  14. Surface based detection schemes for molecular interferometry experiments - implications and possible applications

    Science.gov (United States)

    Juffmann, Thomas; Milic, Adriana; Muellneritsch, Michael; Arndt, Markus

    2011-03-01

    Surface based detection schemes for molecular interferometry experiments might be crucial in the search for the quantum properties of larger and larger objects since they provide single particle sensitivity. Here we report on molecular interferograms of different biomolecules imaged using fluorescence microscopy. Being able to watch the build-up of an interferogram live and in situ reveals the matter-wave behavior of these complex molecules in an unprecedented way. We examine several problems encountered due to van-der-Waals forces between the molecules and the diffraction grating and discuss possible ways to circumvent these. Especially the advent of ultra-thin (1-100 atomic layers) diffraction masks might path the way towards molecular holography. We also discuss other possible applications such as coherent molecular microscopy.

  15. TESTING OF CARBONACEOUS ADSORBENTS FOR REMOVAL OF POLLUTANTS FROM WATER

    Directory of Open Access Journals (Sweden)

    RAISA NASTAS

    2012-03-01

    Full Text Available Testing of carbonaceous adsorbents for removal of pollutants from water. Relevant direction for improving of quality of potable water is application of active carbons at various stages of water treatments. This work includes complex research dealing with testing of a broad spectrum of carbonaceous adsorbents for removal of hydrogen sulfide and nitrite ions from water. The role of the surface functional groups of carbonaceous adsorbents, their acid-basic properties, and the influence of the type of impregnated heteroatom (N, O, or metals (Fe, Cu, Ni, on removal of hydrogen sulfide species and nitrite ions have been researched. The efficiency of the catalyst obtained from peach stones by impregnation with Cu2+ ions of oxidized active carbon was established, being recommended for practical purposes to remove the hydrogen sulfide species from the sulfurous ground waters. Comparative analysis of carbonaceous adsorbents reveals the importance of surface chemistry for oxidation of nitrite ions.

  16. Adsorption of β-galactosidase on silica and aluminosilicate adsorbents

    Science.gov (United States)

    Atyaksheva, L. F.; Dobryakova, I. V.; Pilipenko, O. S.

    2015-03-01

    It is shown that adsorption of β-galactosidase of Aspergillus oryzae fungi on mesoporous and biporous silica and aluminosilicate adsorbents and the rate of the process grow along with the diameter of the pores of the adsorbent. It is found that the shape of the adsorption isotherms changes as well, depending on the texture of the adsorbent: the Michaelis constant rises from 0.3 mM for the enzyme in solution to 0.4-0.5 mM for the enzyme on a surface in the hydrolysis of o-nitrophenyl-β-D-galactopyranoside. It is concluded that β-galactosidase displays its maximum activity on the surface of biporous adsorbents.