Science.gov

Sample records for adsorbent surface area

  1. Effects of excluded surface area and adsorbate clustering on surface adsorption of proteins. II. Kinetic models.

    PubMed Central

    Minton, A P

    2001-01-01

    Models for equilibrium surface adsorption of proteins have been recently proposed (Minton, A. P., 2000. Biophys. Chem. 86:239-247) in which negative cooperativity due to area exclusion by adsorbate molecules is compensated to a variable extent by the formation of a heterogeneous population of monolayer surface clusters of adsorbed protein molecules. In the present work this concept is extended to treat the kinetics of protein adsorption. It is postulated that clusters may grow via two distinct kinetic pathways. The first pathway is the diffusion of adsorbed monomer to the edge of a preexisting cluster and subsequent accretion. The second pathway consists of direct deposition of a monomer in solution onto the upper (solution-facing) surface of a preexisting cluster ("piggyback" deposition) and subsequent incorporation into the cluster. Results of calculations of the time course of adsorption, carried out for two different limiting models of cluster structure and energetics, show that in the absence of piggyback deposition, enhancement of the tendency of adsorbate to cluster can reduce, but not eliminate, the negative kinetic cooperativity due to surface area exclusion by adsorbate. Apparently noncooperative (Langmuir-like) and positively cooperative adsorption progress curves, qualitatively similar to those reported in several published experimental studies, require a significant fraction of total adsorption flux through the piggyback deposition pathway. According to the model developed here and in the above-mentioned reference, the formation of surface clusters should be a common concomitant of non-site-specific surface adsorption of proteins, and may provide an important mechanism for assembly of organized "protein machines" in vivo. PMID:11259279

  2. Universal singularities of multilayer adsorption isotherms and determination of surface area of adsorbents

    SciTech Connect

    Aranovich, G.L.; Donohue, M.D.

    1996-07-15

    The singularity in the adsorption isotherm for macroporous and nonporous adsorbents is considered as a universal function that can be characterized with two parameters: a coefficient of proportionality, K, and an exponent, d. It is shown that the value of K is proportional to the adsorbent surface area but does not depend on the nature of the adsorbent. This leads to a new method to determine the surface area of an adsorbent, S, that is independent of the form of the adsorption isotherm at low and moderate reduced pressures. Comparison with the BET areas for nitrogen shows that the new method gives the values of S which are very close to the BET results if K = 1.47 {times} 10{sup {minus}5} mol/m{sup 2} (for nitrogen). Analysis of adsorption data for macroporous adsorbents shows that the BET isotherm gives systematic deviations and that the experimental amount adsorbed is smaller than the value predicted by the BET equation (even in the range of the best agreement with experiment). These deviations lead to systematic error in the values of S of about 43%. Using K equal to K{sub f} = 1/{sigma}N{sub A} (=1.025 {times} 10{sup {minus}5} mol/m{sup 2} for nitrogen), the authors are able to eliminate systematic error in the surface area determination. Here {sigma} is the area occupied by one molecule and N{sub A} is the Avogadro number.

  3. Siloxanes removal from biogas by high surface area adsorbents.

    PubMed

    Gislon, P; Galli, S; Monteleone, G

    2013-12-01

    Biogas utilized for energy production needs to be free from organic silicon compounds, as their burning has damaging effects on turbines and engines; organic silicon compounds in the form of siloxanes can be found in biogas produced from urban wastes, due to their massive industrial use in synthetic product, such as cosmetics, detergents and paints. Siloxanes removal from biogas can be carried out by various methods (Mona, 2009; Ajhar et al., 2010 May; Schweigkofler and Niessner, 2001); aim of the present work is to find a single practical and economic way to drastically and simultaneously reduce both the hydrogen sulphide and the siloxanes concentration to less than 1 ppm. Some commercial activated carbons previously selected (Monteleone et al., 2011) as being effective in hydrogen sulfide up taking have been tested in an adsorption measurement apparatus, by flowing the most volatile siloxane (hexamethyldisiloxane or L2) in a nitrogen stream, typically 100-200 ppm L2 over N2, through an activated carbon powder bed; the adsorption process was analyzed by varying some experimental parameters (concentration, grain size, bed height). The best activated carbon shows an adsorption capacity of 0.1g L2 per gram of carbon. The next thermogravimetric analysis (TGA) confirms the capacity data obtained experimentally by the breakthrough curve tests. The capacity results depend on L2 concentration. A regenerative carbon process is then carried out by heating the carbon bed up to 200 °C and flushing out the adsorbed L2 samples in a nitrogen stream in a three step heating procedure up to 200 °C. The adsorption capacity is observed to degrade after cycling the samples through several adsorption-desorption cycles.

  4. Influences of Dilute Organic Adsorbates on the Hydration of Low-Surface-Area Silicates.

    PubMed

    Sangodkar, Rahul P; Smith, Benjamin J; Gajan, David; Rossini, Aaron J; Roberts, Lawrence R; Funkhouser, Gary P; Lesage, Anne; Emsley, Lyndon; Chmelka, Bradley F

    2015-07-01

    Competitive adsorption of dilute quantities of certain organic molecules and water at silicate surfaces strongly influence the rates of silicate dissolution, hydration, and crystallization. Here, we determine the molecular-level structures, compositions, and site-specific interactions of adsorbed organic molecules at low absolute bulk concentrations on heterogeneous silicate particle surfaces at early stages of hydration. Specifically, dilute quantities (∼0.1% by weight of solids) of the disaccharide sucrose or industrially important phosphonic acid species slow dramatically the hydration of low-surface-area (∼1 m(2)/g) silicate particles. Here, the physicochemically distinct adsorption interactions of these organic species are established by using dynamic nuclear polarization (DNP) surface-enhanced solid-state NMR techniques. These measurements provide significantly improved signal sensitivity for near-surface species that is crucial for the detection and analysis of dilute adsorbed organic molecules and silicate species on low-surface-area particles, which until now have been infeasible to characterize. DNP-enhanced 2D (29)Si{(1)H}, (13)C{(1)H}, and (31)P{(1)H} heteronuclear correlation and 1D (29)Si{(13)C} rotational-echo double-resonance NMR measurements establish hydrogen-bond-mediated adsorption of sucrose at distinct nonhydrated and hydrated silicate surface sites and electrostatic interactions with surface Ca(2+) cations. By comparison, phosphonic acid molecules are found to adsorb electrostatically at or near cationic calcium surface sites to form Ca(2+)-phosphonate complexes. Although dilute quantities of both types of organic molecules effectively inhibit hydration, they do so by adsorbing in distinct ways that depend on their specific architectures and physicochemical interactions. The results demonstrate the feasibility of using DNP-enhanced NMR techniques to measure and assess dilute adsorbed molecules and their molecular interactions on low-surface-area

  5. Surface area of vermiculite with nitrogen and carbon dioxide as adsorbates

    USGS Publications Warehouse

    Thomas, J.; Bohor, B.F.

    1969-01-01

    Surface-area studies were made on several homoionic vermiculites with both nitrogen and carbon dioxide as adsorbates. These studies show that only very slight penetration occurs between individual vermiculite platelets. This is in contrast to an earlier investigation of montmorillonite where it was found that the degree of penetration between layers is quite high, particularly for carbon dioxide, and is governed by the size and charge of the interlayer cation. The inability of these adsorbates to penetrate substantially between vermiculite platelets is due primarily to this mineral's high surface-charge density. The extent of penetration of nitrogen and carbon dioxide at the edges of vermiculite platelets, though slight, is influenced by the coordinated water retained within the sample at a given degassing temperature. Forces between layers are weakened with increasing water content, which permits slightly greater penetration by adsorbate gases. Thus, the surface area of vermiculite, as determined by gas adsorption, is larger than the calculated external surface area based upon particle size and shape considerations. In addition, "extra" surface is provided by the lifting and scrolling of terminal platelets. These morphological features are shown in scanning electron micrographs of a naturally occuring vermiculite. ?? 1969.

  6. Adsorbed Natural Gas Storage in Optimized High Surface Area Microporous Carbon

    NASA Astrophysics Data System (ADS)

    Romanos, Jimmy; Rash, Tyler; Nordwald, Erik; Shocklee, Joshua Shawn; Wexler, Carlos; Pfeifer, Peter

    2011-03-01

    Adsorbed natural gas (ANG) is an attractive alternative technology to compressed natural gas (CNG) or liquefied natural gas (LNG) for the efficient storage of natural gas, in particular for vehicular applications. In adsorbants engineered to have pores of a few molecular diameters, a strong van der Walls force allows reversible physisorption of methane at low pressures and room temperature. Activated carbons were optimized for storage by varying KOH:C ratio and activation temperature. We also consider the effect of mechanical compression of powders to further enhance the volumetric storage capacity. We will present standard porous material characterization (BET surface area and pore-size distribution from subcritical N2 adsorption) and methane isotherms up to 250 bar at 293K. At sufficiently high pressure, specific surface area, methane binding energy and film density can be extracted from supercritical methane adsorption isotherms. Research supported by the California Energy Commission (500-08-022).

  7. Preparation and characterization of polar polymeric adsorbents with high surface area for the removal of phenol from water.

    PubMed

    Zeng, Xiaowei; Yu, Tingjun; Wang, Peng; Yuan, Ronghua; Wen, Qing; Fan, Yunge; Wang, Chunhong; Shi, Rongfu

    2010-05-15

    Preparation of methyl methacrylate (MMA)/divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA)/DVB copolymers via suspension polymerization yielded precursors which possess residual vinyl groups. Post-crosslinking of appropriate dichloroethane swollen precursors without external crosslinking agent in the presence of anhydrous ferric chloride (FeCl(3)) yielded post-crosslinked resins with high surface area and suitable polarity. FT-IR spectrum indicated that increasing the proportion of MMA or EGDMA in monomer mixtures notably reduces the amount of the pendant vinyl groups onto the matrix of the precursors. Furthermore, the pendant vinyl groups of precursors were almost absent when the content of MMA and EGDMA increased to 40 mol% and 20 mol% in the monomers, respectively. The specific surface areas and pore volumes of copolymers showed a remarkable increase after post-crosslinking. Experimental results showed that isotherms of phenol adsorption onto these polymeric adsorbents could be represented by Freundlich model and Langmuir model reasonably. PDE-5 pc exhibited higher adsorption capacity of phenol than other adsorbents, which resulted from synergistic effect of larger specific surface area and polar groups onto the network. Column adsorption/desorption dynamic curves suggested that PDE-5 pc is a potential candidate for treatment of chemical effluent containing phenol and phenolic pollutants.

  8. "False" cytotoxicity of ions-adsorbing hydroxyapatite - Corrected method of cytotoxicity evaluation for ceramics of high specific surface area.

    PubMed

    Klimek, Katarzyna; Belcarz, Anna; Pazik, Robert; Sobierajska, Paulina; Han, Tomasz; Wiglusz, Rafal J; Ginalska, Grazyna

    2016-08-01

    An assessment of biomaterial cytotoxicity is a prerequisite for evaluation of its clinical potential. A material is considered toxic while the cell viability decreases under 70% of the control. However, extracts of certain materials are likely to reduce the cell viability due to the intense ions adsorption from culture medium (e.g. highly bioactive ceramics of high surface area). Thus, the standard ISO 10993-5 procedure is inappropriate for cytotoxicity evaluation of ceramics of high specific surface area because biomaterial extract obtained in this method (ions-depleted medium) is not optimal for cell cultures per se. Therefore, a simple test was designed as an alternative to ISO 10993-5 standard for cytotoxicity evaluation of the biomaterials of high surface area and high ions absorption capacity. The method, presented in this paper, included the evaluation of ceramics extract prepared according to corrected procedure. The corrected extract was found not cytotoxic (cell viability above 70%), suggesting that modified method for cytotoxicity evaluation of ions-adsorbing ceramics is more appropriate than ISO 10993-5 standard. For such biomaterials, the term "false" cytotoxicity is more suitable. Moreover, it was noted that NRU assay and microscopic observations should be recommended for cytotoxicity evaluation of ceramics of high surface area.

  9. Synthesis, Development, and Testing of High-Surface-Area Polymer-Based Adsorbents for the Selective Recovery of Uranium from Seawater

    SciTech Connect

    Oyola, Yatsandra; Janke, Christopher J.; Dai, Sheng

    2016-02-29

    The ocean contains uranium with an approximate concentration of 3.34 ppb, which can serve as an incredible supply source to sustain nuclear energy in the United States. Unfortunately, technology currently available to recover uranium from seawater is not efficient enough and mining uranium on land is still more economical. For this study, we have developed polymer-based adsorbents with high uranium adsorption capacities by grafting amidoxime onto high-surface-area polyethylene (PE) fibers. Various process conditions have been screened, in combination with developing a rapid testing protocol (<24 h), to optimize the process. These adsorbents are synthesized through radiation-induced grafting of acrylonitrile (AN) and methacrylic acid (MAA) onto PE fibers, followed by the conversion of nitriles to amidoximes and basic conditioning. In addition, the uranium adsorption capacity, measured in units of gU/kgads, is greatly increased by reducing the diameter of the PE fiber or changing its morphology. An increase in the surface area of the PE polymer fiber allows for more grafting sites that are positioned in more-accessible locations, thereby increasing access to grafted molecules that would normally be located in the interior of a fiber with a larger diameter. Polymer fibers with hollow morphologies are able to adsorb beyond 1 order of magnitude more uranium from simulated seawater than current commercially available adsorbents. Finally, several high-surface-area fibers were tested in natural seawater and were able to extract 5–7 times more uranium than any adsorbent reported to date.

  10. Synthesis, Development, and Testing of High-Surface-Area Polymer-Based Adsorbents for the Selective Recovery of Uranium from Seawater

    DOE PAGES

    Oyola, Yatsandra; Janke, Christopher J.; Dai, Sheng

    2016-02-29

    The ocean contains uranium with an approximate concentration of 3.34 ppb, which can serve as an incredible supply source to sustain nuclear energy in the United States. Unfortunately, technology currently available to recover uranium from seawater is not efficient enough and mining uranium on land is still more economical. For this study, we have developed polymer-based adsorbents with high uranium adsorption capacities by grafting amidoxime onto high-surface-area polyethylene (PE) fibers. Various process conditions have been screened, in combination with developing a rapid testing protocol (<24 h), to optimize the process. These adsorbents are synthesized through radiation-induced grafting of acrylonitrile (AN)more » and methacrylic acid (MAA) onto PE fibers, followed by the conversion of nitriles to amidoximes and basic conditioning. In addition, the uranium adsorption capacity, measured in units of gU/kgads, is greatly increased by reducing the diameter of the PE fiber or changing its morphology. An increase in the surface area of the PE polymer fiber allows for more grafting sites that are positioned in more-accessible locations, thereby increasing access to grafted molecules that would normally be located in the interior of a fiber with a larger diameter. Polymer fibers with hollow morphologies are able to adsorb beyond 1 order of magnitude more uranium from simulated seawater than current commercially available adsorbents. Finally, several high-surface-area fibers were tested in natural seawater and were able to extract 5–7 times more uranium than any adsorbent reported to date.« less

  11. Ultrathin calcium silicate hydrate nanosheets with large specific surface areas: synthesis, crystallization, layered self-assembly and applications as excellent adsorbents for drug, protein, and metal ions.

    PubMed

    Wu, Jin; Zhu, Ying-Jie; Chen, Feng

    2013-09-09

    A simple and low-cost solution synthesis is reported for low-crystalline 1.4 nm tobermorite-like calcium silicate hydrate (CSH) ultrathin nanosheets with a thickness of ~2.8 nm and with a large specific surface area (SSA), via a reaction-rate-controlled precipitation process. The BET SSA of the CSH ultrathin nanosheets can reach as high as 505 m(2) g(-1) . The CSH ultrathin nanosheets have little cytotoxicity and can be converted to anhydrous calcium silicate (ACS) ultrathin nanosheets with a well preserved morphology via a heat treatment process. The crystallinity of CSH ultrathin nanosheets can be improved by solvothermal treatment in water/ethanol binary solvents or a single solvent of water, producing well-crystalline 1.1 nm tobermorite-like CSH nanobelts or nanosheets. CSH ultrathin nanosheets acting as building blocks can self-assemble into layered nanostructures via three different routes. The CSH ultrathin nanosheets are investigated as promising adsorbents for protein (hemoglobin, Hb), drug (ibuprofen, IBU), and metal ions (Cr(3+) , Ni(2+) , Cu(2+) , Zn(2+) , Cd(2+) , Pb(2+) ). The highest adsorbed percentages of Hb and IBU are found to be 83% and 94%, respectively. The highest adsorption capacities of Hb and IBU are found to be as high as 878 milligram Hb per gram CSH and 2.2 gram IBU per gram CSH, respectively. The ppm level metal ions can be totally adsorbed from aqueous solution in just a few minutes. Thus, the CSH ultrathin nanosheets are a promising candidate as excellent adsorbents in the biomedical field and for waste water treatment. Several empirical laws are summarized based on the adsorption profiles of Hb and IBU using CSH ultrathin nanosheets as the adsorbent. Furthermore, the ACS ultrathin nanosheets as adsorbents for Hb protein and IBU drug are investigated.

  12. Simple template-free synthesis of high surface area mesoporous ceria and its new use as a potential adsorbent for carbon dioxide capture.

    PubMed

    Kamimura, Yoshihiro; Shimomura, Marie; Endo, Akira

    2014-12-15

    The development of an efficient technique for carbon dioxide (CO2) capture from a variety of large stationary sources is in important global issue. If we are to achieve an energy-efficient and effectively higher CO2 capture process based on an adsorption approach, we need new adsorbent materials realistic enough to provide higher CO2 loading on a volumetric basis. For this reason we have focused on the practical use of high surface area mesoporous ceria as a new application in the field of CO2 capture. In this regard, we demonstrate the simple and inexpensive template-free synthesis of mesoporous ceria with a high surface area up to 200 m(2) g(-1), and characterize it as an effective CO2 adsorbent for the first time. The mesoporous ceria is prepared based on sol-gel chemistry, where the product is simply precipitated by the self-assembly of ceria nanoparticles within a short reaction period at room temperature under highly alkaline conditions with optimized chemical compositions. The results of CO2 adsorption-desorption measurement at 298 K show that the obtained ceria with an enhanced surface area exhibits a noticeably higher CO2 adsorption capacity per volume than commercially available non-porous ceria, activated carbon and zeolite 13X over a wide pressure range with robust stability as well as regenerability. This work enables us to prepare promising new materials for the CO2 capture process based on an easy-to-handle synthesis system, and this effective material will have a broad applicability to the efficient CO2 separation from variety of industrial emission sources. The features of the obtained mesoporous ceria are reported and discussed.

  13. IR investigations of surfaces and adsorbates

    SciTech Connect

    Gwyn Williams

    2001-12-10

    Synchrotron infrared reflection-absorption measurements on single crystal metal surfaces with adsorbates have led to the determination of many key parameters related to the bonding vibrational modes and the dynamics of adsorbates. In particular, energy couplings between electrons and adsorbate motion have been shown to be a dominant mechanism on metal surfaces. Excellent agreement has been obtained with calculations for many of the observations, and the synergy between theory and experiment has led to a deeper understanding of the roles of electrons and phonons in determining the properties of interfaces and their roles in phenomena as diverse as friction, lubrication, catalysis and adhesion. Nonetheless, as the experiments are pushed harder, to describe such effects as co-adsorbed systems, disagreements continue to challenge the theory and our comprehension also is still evolving.

  14. Synthesis of high surface area carbon adsorbents prepared from pine sawdust-Onopordum acanthium L. for nonsteroidal anti-inflammatory drugs adsorption.

    PubMed

    Álvarez-Torrellas, S; Muñoz, M; Zazo, J A; Casas, J A; García, J

    2016-12-01

    Chemically activated carbon materials prepared from pine sawdust-Onopordum acanthium L. were studied for the removal of diclofenac and naproxen from aqueous solution. Several carbons, using different proportions of precursors were obtained (carbon C1 to carbon C5) and the chemical modification by liquid acid and basic treatments of C1 were carried out. The textural properties of the carbons, evaluated by N2 adsorption-desorption isotherms, revealed that the treatments with nitric acid and potassium hydroxide dramatically reduced the specific surface area and the pore volume of the carbon samples. The surface chemistry characterization, made by thermal programmed decomposition studies, determination of isoelectric point and Boehm's titration, showed the major presence of lactone and phenol groups on the activated carbons surface, being higher the content when the acidic strength of the carbon increased. Diclofenac and naproxen kinetic data onto C1 carbon followed pseudo-second order model. The adsorption equilibrium isotherms of C1 and the modified carbons were well described by both Sips and GAB isotherm equations. The highest adsorption capacity was found for naproxen onto C1 activated carbon, 325 mg g(-1), since the liquid acid and basic functionalization of the carbon led to a severe decreasing in the adsorption removal of the target compounds.

  15. Negatively charged ions on Mg(0001) surfaces: appearance and origin of attractive adsorbate-adsorbate interactions.

    PubMed

    Cheng, Su-Ting; Todorova, Mira; Freysoldt, Christoph; Neugebauer, Jörg

    2014-09-26

    Adsorption of electronegative elements on a metal surface usually leads to an increase in the work function and decrease in the binding energy as the adsorbate coverage rises. Using density-functional theory calculations, we show that Cl adsorbed on a Mg(0001) surface complies with these expectations, but adsorption of {N,O,F} causes a decrease in the work function and an increase in the binding energy. Analyzing the electronic structure, we show that the presence of a highly polarizable electron spill-out in front of Mg(0001) causes this unusual adsorption behavior and is responsible for the appearance of a hitherto unknown net-attractive lateral electrostatic interaction between same charged adsorbates.

  16. Direct measurement of core-level relaxation dynamics on a surface- adsorbate system

    NASA Astrophysics Data System (ADS)

    Yin, Jing; Miaja-Avila, Luis; Saathoff, Guido; La-O-Vorakiat, Chan; Murnane, Margaret; Kapteyn, Henry; Mathias, Stefan; Aeschlimann, Martin; Bauer, Michael

    2008-03-01

    Electronic coupling between an adsorbate and the surface on which it resides is fundamental to the understanding of many surface interactions. However, the interaction of highly-excited adsorbate states is an area that has been explored only indirectly to-date. In this work, we present the first direct time-resolved observations of the lifetime of core-excited states of an atom adsorbed onto a surface. By implementing laser-assisted Auger decay on an adsorbate/surface system, we directly measure the lifetime of the 4d-1 core level of Xenon on Pt(111) to be 7.1 ± 1.1 fs. This result opens up time domain measurements of highly-excited state dynamics in materials systems where, because of complex interactions, energy-resolved measurements provide incomplete information.

  17. Direct measurement of core-level relaxation dynamics on a surface- adsorbate system

    NASA Astrophysics Data System (ADS)

    Yin, Jing; Miaja-Avila, Luis; Saathoff, Guido; La-O-Vorakiat, Chan; Murnane, Margaret; Kapteyn, Henry; Mathias, Stefan; Aeschlimann, Martin; Bauer, Michael

    2008-05-01

    Electronic coupling between an adsorbate and the surface on which it resides is fundamental to the understanding of many surface interactions. However, the interaction of highly-excited adsorbate states is an area that has been explored only indirectly to-date. In this work, we present the first direct time-resolved observations of the lifetime of core-excited states of an atom adsorbed onto a surface. By implementing laser-assisted Auger decay on an adsorbate/surface system, we directly measure the lifetime of the 4d-1 core level of Xenon on Pt(111) to be 7.1 ± 1.1 fs. This result opens up time domain measurements of highly-excited state dynamics in materials systems where, because of complex interactions, energy-resolved measurements provide incomplete information.

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

    SciTech Connect

    Weinelt, M.; Nilsson, A.; Wassdahl, N.

    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.

  19. Dynamics of adsorbed polymers on attractive homogeneous surfaces

    PubMed Central

    Yang, Qing-Hui; Luo, Meng-Bo

    2016-01-01

    Dynamic behaviors of polymer chains adsorbed on an attractive, homogeneous surface are studied by using dynamic Monte Carlo simulations. The translational diffusion coefficient Dxy parallel to the surface decreases as the intra-polymer attraction strength EPP or the polymer-surface attraction strength EPS increases. The rotational relaxation time τR increases with EPS, but the dependence of τR on EPP is dependent on the adsorption state of the polymer. We find that τR decreases with increasing EPP for a partially adsorbed polymer but it increases with EPP for a fully adsorbed polymer. Scaling relations Dxy ~ N−α and τR ~ Nβ are found for long polymers. The scaling exponent α is independent of EPS for long polymers but increases with EPP from α = 1.06 at EPP = 0. While β ≈ 2.7 is also roughly independent of EPS for the adsorbed polymer at EPP = 0, but β increases with EPS at EPP > 0. Moreover, we find that β always decreases with increasing EPP. Our results reveal different effects of the attractive surface on the diffusion and rotation of adsorbed polymers. PMID:27849002

  20. Vibrational Studies of Adsorbate-Induced Reconstruction on Molybdenum Surfaces.

    NASA Astrophysics Data System (ADS)

    Lopinski, Gregory Peter

    Adsorbate-induced rearrangement of the substrate structure strongly modifies the adsorbate-substrate and adsorbate-adsorbate interactions, leading to the complex behavior observed in many chemisorption systems. In this thesis the H/Mo(211), O/Mo(211) and Na/Mo(100) systems have been studied using high resolution electron energy loss spectroscopy (HREELS) to observe vibrations of the adsorbed atoms. The vibrational data is correlated with observations of the long-range order probed by LEED as well as the work function changes induced by adsorption. Adsorbate -induced substrate reconstruction plays an important role in all three of these systems. Studies of the coadsorption systems O+H/Mo(211) and Na+O/Mo(100) indicate how these effects can influence interactions between adsorbates. For H/Mo(211), above 1ML a (1 x 1) to (1 x 2) transition is observed and attributed to modification of the substrate periodicity. Below 1ML, H atoms are bridge bonded and induce local distortions of the substrate. The transition to the (1 x 2) phase involves the ordering of these displacements and occupation of three-fold sites partially populated by conversion of the bridge bonded species. This conversion accounts for the sawtooth-like coverage dependence of the work function. The structural model proposed for this system is also supported by the desorption parameters and partial molar entropy extracted from adsorption isobars. Oxygen adsorption on Mo(211) involves the occupation of multiple binding sites, with both the long-range order and the local geometry of the adsorbate phases strongly temperature dependent. Coadsorption of low coverages of oxygen and hydrogen leads to segregation of the two adsorbates which can be understood in terms of a substrate-mediated repulsive interaction between O and H. For Na/Mo(100), the frequency of the Na-Mo symmetric stretch mode does not shift with coverage although the mode intensity is strongly coverage dependent. The absence of a frequency shift

  1. Silver diffusion over silicon surfaces with adsorbed tin atoms

    SciTech Connect

    Dolbak, A. E. Olshanetskii, B. Z.

    2015-02-15

    Silver diffusion over the (111), (100), and (110) surfaces of silicon with preliminarily adsorbed tin atoms is studied by Auger electron spectroscopy and low-energy electron diffraction. Diffusion is observed only on the surface of Si(111)-2√3 × 2√3-Sn. The diffusion mechanism is established. It is found that the diffusion coefficient depends on the concentration of diffusing atoms. The diffusion coefficient decreases with increasing silver concentration, while the activation energy and the preexponential factor increase.

  2. Do methanethiol adsorbates on the Au(111) surface dissociate?

    PubMed

    Zhou, Jian-Ge; Hagelberg, Frank

    2006-07-28

    The interaction of methanethiol molecules CH3SH with the Au(111) surface is investigated, and it is found for the first time that the S-H bond remains intact when the methanethiol molecules are adsorbed on the regular Au(111) surface. However, it breaks if defects are present in the Au(111) surface. At low coverage, the fcc region is favored for S atom adsorption, but at saturated coverage the adsorption energies at various sites are almost isoenergetic. The presented calculations show that a methanethiol layer on the regular Au(111) surface does not dimerize.

  3. Do Methanethiol Adsorbates on the Au(111) Surface Dissociate?

    NASA Astrophysics Data System (ADS)

    Zhou, Jian-Ge; Hagelberg, Frank

    2006-07-01

    The interaction of methanethiol molecules CH3SH with the Au(111) surface is investigated, and it is found for the first time that the S-H bond remains intact when the methanethiol molecules are adsorbed on the regular Au(111) surface. However, it breaks if defects are present in the Au(111) surface. At low coverage, the fcc region is favored for S atom adsorption, but at saturated coverage the adsorption energies at various sites are almost isoenergetic. The presented calculations show that a methanethiol layer on the regular Au(111) surface does not dimerize.

  4. Infrared Analysis Of Enzymes Adsorbed Onto Model Surfaces

    NASA Astrophysics Data System (ADS)

    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.

  5. Chemical speciation of adsorbed glycine on metal surfaces

    NASA Astrophysics Data System (ADS)

    Han, Jeong Woo; James, Joanna N.; Sholl, David S.

    2011-07-01

    Experimental studies have reported that glycine is adsorbed on the Cu(110) and Cu(100) surfaces in its deprotonated form at room temperature, but in its zwitterionic form on Pd(111) and Pt(111). In contrast, recent density functional theory (DFT) calculations indicated that the deprotonated molecules are thermodynamically favored on Cu(110), Cu(100), and Pd(111). To explore the source of this disagreement, we have tested three possible hypotheses. Using DFT calculations, we first show that the kinetic barrier for the deprotonation reaction of glycine on Pd(111) is larger than on Cu(110) or Cu(100). We then report that the presence of excess hydrogen would have little influence on the experimentally observed results, especially for Pd(111). Lastly, we perform Monte Carlo simulations to demonstrate that the aggregates of zwitterionic species on Pt(111) are energetically preferred to those of neutral species. Our results strongly suggest that the formation of aggregates with relatively large numbers of adsorbed molecules is favored under experimentally relevant conditions and that the adsorbate-adsorbate interactions in these aggregates stabilize the zwitterionic species.

  6. Induced rupture of vesicles adsorbed on glass by pore formation at the surface-bilayer interface.

    PubMed

    Kataoka-Hamai, Chiho; Yamazaki, Tomohiko

    2015-02-03

    Supported lipid bilayers (SLBs) are often formed by spontaneous vesicle rupture and fusion on a solid surface. A well-characterized rupture mechanism for isolated vesicles is pore nucleation and expansion in the solution-exposed nonadsorbed area. In contrast, pore formation in the adsorbed bilayer region has not been investigated to date. In this work, we studied the detailed mechanisms of asymmetric rupture of giant unilamellar vesicles (GUVs) adsorbed on glass using fluorescence microscopy. Asymmetric rupture is the pathway where a rupture pore forms in a GUV near the edge of the glass-bilayer interface with high curvature and then expansion of the pore yields a planar bilayer patch. We show that asymmetric rupture occasionally resulted in SLB patches bearing a defect pore. The defect formation probability depended on lipid composition, salt concentration, and pH. Approximately 40% of negatively charged GUVs under physiological conditions formed pore-containing SLB patches, while negatively charged GUVs at low salt concentration or pH 4.0 and positively charged GUVs exhibited a low probability of defect inclusion. The edge of the defect pore was either in contact with (on-edge) or away from (off-edge) the edge of the planar bilayer. On-edge pores were predominantly formed over off-edge defects. Pores initially formed in the glass-adsorbed region before rupture, most frequently in close contact with the edge of the adsorbed region. When a pore formed near the edge of the adsorbed area or when the edge of a pore reached that of the adsorbed area by pore expansion, asymmetric rupture was induced from the defect site. These induced rupture mechanisms yielded SLB patches with an on-edge pore. In contrast, off-edge pores were produced when defect pore generation and subsequent vesicle rupture were uncoupled. The current results demonstrate that pore formation in the surface-adsorbed region of GUVs is not a negligible event.

  7. Molecular switches from benzene derivatives adsorbed on metal surfaces

    PubMed Central

    Liu, Wei; Filimonov, Sergey N.; Carrasco, Javier; Tkatchenko, Alexandre

    2013-01-01

    Transient precursor states are often experimentally observed for molecules adsorbing on surfaces. However, such precursor states are typically rather short-lived, quickly yielding to more stable adsorption configurations. Here we employ first-principles calculations to systematically explore the interaction mechanism for benzene derivatives on metal surfaces, enabling us to selectively tune the stability and the barrier between two metastable adsorption states. In particular, in the case of the tetrachloropyrazine molecule, two equally stable adsorption states are identified with a moderate and conceivably reversible barrier between them. We address the feasibility of experimentally detecting the predicted bistable behaviour and discuss its potential usefulness in a molecular switch. PMID:24157660

  8. Structures of multidomain proteins adsorbed on hydrophobic interaction chromatography surfaces.

    PubMed

    Gospodarek, Adrian M; Sun, Weitong; O'Connell, John P; Fernandez, Erik J

    2014-12-05

    In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized.

  9. Graphene protected surface state on Ir(111) with adsorbed lithium

    NASA Astrophysics Data System (ADS)

    Lazic, Predrag; Pervan, Petar; Petrovic, Marin; Srut-Rakic, Iva; Pletikosic, Ivo; Kralj, Marko; Milun, Milorad; Valla, Tonica

    It is well known that electronic surface states (SS) get strongly perturbed upon the chemical adsorption of very small amount of adsorbates. Adsorption of lithium atoms on Ir(111) is no exception to that rule. Iridium SS gets strongly perturbed and is practically eradicated - it can not be seen as a sharp peak in the ARPES measurement. However, if the system is prepared with graphene on top of Ir/Li system, the iridium SS reappears. We present a combined experimental and theoretical study of the described system. Using the density functional theory calculations for large unit cells with disordered lithium atoms geometries on the (111) surface of iridium we were able to reproduce the results of the ARPES measurements - showing clearly that the SS signal is strongly suppressed when lithium is adsorbed, while it is almost unchanged when lithium is intercalated (i.e. with graphene on top of it). Looking at the projected density of states we constructed a rather simple model explaining this behavior which seems to be general.

  10. Vibrational spectroscopic studies of adsorbates on bimetallic surfaces. Doctoral thesis

    SciTech Connect

    Kuhn, W.K.

    1992-12-01

    In this work, well-defined bimetallic surfaces have been studied using carbon monoxide adsorption in conjunction with infrared reflection absorption spectroscopy (IRAS). These studies have indicated that for CO adsorbed on Cu overlayers, the bond between the CO and the Cu adatoms is comprised of both pi-back-donation and polarization interaction components. The sum of the contributions from these effects determines the observed bond strength with the observed CO stretching frequency being determined by the relative contributions of the components. In addition, it was determined that IR spectra of adsorbed CO show a remarkable sensitivity to surface structure. Three-dimensional Cu clusters, well-ordered two dimensional Cu islands and isolated Cu atoms are distinctively characterized by their CO IR peaks. In addition, both disorder-order and order-order transitions are observed for the metal overlayers on the single crystal metal substrates. It was also observed that localized segregation and ordering of mixed Co and S overlayers on a Mo(110) substrate occurs upon annealing.

  11. Structure of CO2 adsorbed on the KCl(100) surface.

    PubMed

    Traeger, Franziska; Hadnadjev, Milica; Vogt, Jochen; Weiss, Helmut

    2011-06-30

    The structure and dynamics of the adsorbate CO(2)/KCl(100) from a diluted phase to a saturated monolayer have been investigated with He atom scattering (HAS), low-energy electron diffraction (LEED), and polarization dependent infrared spectroscopy (PIRS). Two adsorbate phases with different CO(2) coverage have been found. The low-coverage phase is disordered at temperatures near 80 K and becomes at least partially ordered at lower temperatures, characterized by a (2√2×√2)R45° diffraction pattern. The saturated 2D phase has a high long-range order and exhibits (6√2×√2)R45° symmetry. Its isosteric heat of adsorption is 26 ± 4 kJ mol(-1). According to PIRS, the molecules are oriented nearly parallel to the surface, the average tilt angle in the saturated monolayer phase is 10° with respect to the surface plane. For both phases, structure models are proposed by means of potential calculations. For the saturated monolayer phase, a striped herringbone structure with 12 inequivalent molecules is deduced. The simulation of infrared spectra based on the proposed structures and the vibrational exciton approach gives reasonable agreement between experimental and simulated infrared spectra.

  12. Effects of dilution of poly(ethylvinylbenzene-divinylbenzene) adsorbent on the adsorption of aliphatic, alicyclic, and aromatic hydrocarbon adsorbates from effective zero to finite surface coverage

    SciTech Connect

    Djordjevic, N.M.; Laub, R.J.

    1988-01-15

    The chromatographic measurement and systematic interpretation of the solidgas partition coefficients K/sub s/ and related thermodynamic properties of a number of hydrocarbon adsorbates (n-pentane through n-octane, cyclohexane, methylcyclohexane, benzene, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, thiophene, and acetone) at effective zero surface coverage with a 1:10 admixture of the title adsorbent-inert diluent from 393 to 443 K are reported. Despite a difference of an order of magnitude in the surface areas of bulk and admixed packings, the adsorbate relative retentions were in good agreement with those found in previous work with neat Porapak Q. The heats of adsorption also coincided to within an experimental error of ca. +- 5%. The GSC technique of elution by characteristic point was then used to derive the finite-concentration adsorption isotherms and isosteric heats of adsorption on n-hexane, cyclohexane, benzene, carbon tetrachloride, and acetone adsorbates with diluted Porapak Q over the temperature range 393-433 K. All exhibited BET Type IV isotherms, as well as changes in the respective isotherm temperature coefficients. The latter is said to be a consequence of the microporous substructure of this adsorbent.

  13. Long-term storage of surface-adsorbed protein machines.

    PubMed

    Albet-Torres, Nuria; Månsson, Alf

    2011-06-07

    The effective and simple long-term storage of complex functional proteins is critical in achieving commercially viable biosensors. This issue is particularly challenging in recently proposed types of nanobiosensors, where molecular-motor-driven transportation substitutes microfluidics and forms the basis for novel detection schemes. Importantly, therefore, we here describe that delicate heavy meromyosin (HMM)-based nanodevices (HMM motor fragments adsorbed to silanized surfaces and actin bound to HMM) fully maintain their function when stored at -20 °C for more than a month. The mechanisms for the excellent preservation of acto-HMM motor function upon repeated freeze-thaw cycles are discussed. The results are important to the future commercial implementation of motor-based nanodevices and are of more general value to the long-term storage of any protein-based bionanodevice.

  14. Surface properties of mesoporous carbon-silica gel adsorbents

    SciTech Connect

    Leboda, R.; Turov, V.V.; Charmas, B.; Skubiszewska-Zieba, J.; Gun'ko, V.M.

    2000-03-01

    Carbon/silica (carbosil) samples prepared utilizing mesoporous silica gel (Si-60) modified by methylene chloride pyrolysis were studied by nitrogen adsorption, quasi-isothermal thermogravimetry, p-nitrophenol adsorption from aqueous solution, and {sup 1}H NMR methods. The structural characteristics and other properties of carbosils depend markedly on the synthetic conditions and the amount of carbon deposited. The changes in the pore size distribution with increasing carbon concentration suggest grafting of carbon mainly in pores, leading to diminution of the mesopore radii. However, heating pure silica gel at the pyrolysis temperature of 550 C leads to an increase in the pore radii. The quasi-isothermal thermogravimetry and {sup 1}H NMR spectroscopy methods used to investigate the water layers on carbosils showed a significant capability of carbosils to adsorb water despite a relatively large content of the hydrophobic carbon deposit, which represents a nonuniform layer incompletely covering the oxide surface.

  15. Topical Meeting on Microphysics of Surfaces, Beams and Adsorbates held at Santa Fe, New Mexico on 4 - 6 February 1985

    NASA Astrophysics Data System (ADS)

    Quinn, J. W.

    1985-12-01

    The Topical Meeting on Microphysics of Surfaces, Beams, and Adsorbates was organized within the interdisciplinary area of molecule/surface interactions induced, or studied, by laser and ion beam techniques. Especially emphasized was the molecular physics and electromagnetism of beam activated chemical reactions for applications in fabrication of semiconductor devices, in photocatalysis, and in optical recording. Emphasis was on the laser spectroscopy of molecular collision and reaction processes on surfaces, new sensitive or high resolution spectroscopies for studies of adsorbates, and optical methods applied to surface characterization.

  16. Collision-induced migration of adsorbates on solid surfaces: an experimental approach.

    PubMed

    Danziger, I M; Asscher, M

    2006-07-13

    Collision-induced migration (CIM) is a process in which energetic gas-phase atoms or molecules at the tail of the Boltzmann distribution enhance surface migration of adsorbates upon collision. It is believed to exist and play an important role in any realistic high pressure-high-temperature heterogeneous catalytic system. Combining supersonic beam-surface collision setup with in-situ optical second harmonic generation diffraction technique from a coverage grating, we have shown, for the first time, that indeed energetic collisions (Kr seeded in He) promote surface mobility of CO-K surface complex on Ru(001) with a threshold total kinetic energy of 3 eV. An average migration distance/collision of more than 30 adsorption sites was estimated from the experimental data at Kr total energy of 3.8 eV. This long-range migration distance per collision is understood in terms of a cascade migration mechanism, where adsorbed CO molecules collide and push their neighbors from high to low coverage areas, in a direction dictated by the collision momentum vector. A similar mechanism has recently been suggested to explain adsorbate mobility at high coverage induced by an STM tip.

  17. Regulating the interactions of adsorbates on surfaces by scanning tunneling microscopy manipulation.

    PubMed

    Sun, Qiang; Xu, Wei

    2014-09-15

    Scanning tunneling microscopy (STM) manipulation has received wide attention in the surface science community since the pioneering work of Eigler to construct surface nanostructures in an atom by atom fashion. Lots of scientists have been inspired and devoted to study the surface issues with the help of STM manipulations and great achievements have been obtained. In this Minireview, we mainly describe the recent progress in applying STM manipulations to regulate the inter-adsorbate and adsorbate-substrate interactions on solid surfaces. It was shown that this technique could not only differentiate intermolecular interactions but also construct molecular nanostructures by regulating different kinds of inter-adsorbate interactions or adsorbate-substrate interactions.

  18. Removing adsorbed heavy metal ions from sand surfaces via applying interfacial properties of rhamnolipid.

    PubMed

    Haryanto, Bode; Chang, Chien-Hsiang

    2015-01-01

    In this study, the interfacial properties of biosurfactant rhamnolipid were investigated and were applied to remove adsorbed heavy metal ions from sand surfaces with flushing operations. The surface tension-lowering activity, micelle charge characteristic, and foaming ability of rhamnolipid were identified first. For rhamnolipid in water, the negatively charged characteristic of micelles or aggregates was confirmed and the foaming ability at concentrations higher than 40 mg/L was evaluated. By using the rhamnolipid solutions in a batch washing approach, the potential of applying the interfacial properties of rhamnolipid to remove adsorbed copper ions from sand surfaces was then demonstrated. In rhamnolipid solution flushing operations for sand-packed medium, higher efficiency was found for the removal of adsorbed copper ions with residual type than with inner-sphere interaction type, implying the important role of interaction type between the copper ion and the sand surface in the removal efficiency. In addition, the channeling effect of rhamnolipid solution flow in the sand-packed medium was clearly observed in the solution flushing operations and was responsible for the low removal efficiency with low contact areas between solution and sand. By using rhamnolipid solution with foam to flush the sand-packed medium, one could find that the channeling effect of the solution flow was reduced and became less pronounced with the increase in the rhamnolipid concentration, or with the enhanced foaming ability. With the reduced channeling effect in the flushing operations, the removal efficiency for adsorbed copper ions was significantly improved. The results suggested that the foam-enhanced rhamnolipid solution flushing operation was efficient in terms of surfactant usage and operation time.

  19. Properties of competitively adsorbed BSA and fibrinogen from their mixture on mixed and hybrid surfaces

    NASA Astrophysics Data System (ADS)

    Pandey, Lalit M.; Pattanayek, Sudip K.

    2013-01-01

    We have studied the adsorption of BSA and fibrinogen from their mixture onto surfaces with mixed self-assembled monolayer (SAM) of amine and octyl (ratio 1:1) and hybrid SAM. The properties of adsorbed proteins obtained from individual protein solution differ considerably from the properties of the adsorbed proteins obtained from mixture of proteins at same total concentration. The adsorbed amount of proteins is lesser and the adsorbed protein is more elastic if it is adsorbing from mixture of proteins. It is found that with increasing total protein concentration, adsorbed amount increases and elasticity of the adsorbed proteins decreases. The apparent displacements of BSA with Fb are observed on the graphs of change in frequency with time, which are obtained from quartz crystal microbalance.

  20. Role of specific amine surface configurations for grafted surfaces: implications for nanostructured CO2 adsorbents.

    PubMed

    Shimizu, Steven; Song, Changsik; Strano, Michael

    2011-03-15

    Amine-grafted porous materials that capture CO2 from emission streams have been considered to be potential alternatives to the more energy-intensive liquid amine systems currently employed. An underappreciated fact in the uptake mechanism of these materials is that under dry, anhydrous conditions each CO2 molecule must react with two adjacent amine groups to adsorb onto the surface, which makes the configuration of amine groups on the surface critically important. Using this chemical mechanism, we developed a semiempirical adsorption isotherm equation that allows straightforward computation of the adsorption isotherm from an arbitrary surface configuration of grafted amines for honeycomb, square, and triangular lattices. The model makes use of the fact that the distribution of amines with respect to the number of nearest neighbors, referred to as the z-histogram, along with the amine loading and equilibrium constant, uniquely determine the adsorption characteristics to a very good approximation. This model was used to predict the range of uptakes possible just through surface configuration, and it was used to fit experimental data in the literature to give a meaningful equilibrium constant and show how efficiently amines were utilized. We also demonstrate how the model can be utilized to design more efficient nanostructured adsorbents and polymer-based adsorbents. Recommendations for exploiting the role of surface configuration include the use of linear instead of branched polyamines, higher amine grafting densities, the use of flexible, less bulky, long, and rotationally free amine groups, and increased silanol densities.

  1. A computer modelling study of the interaction of organic adsorbates with fluorapatite surfaces

    NASA Astrophysics Data System (ADS)

    Mkhonto, Donald; Ngoepe, Phuti E.; Cooper, Timothy G.; de Leeuw, Nora H.

    2006-08-01

    Computer modelling techniques were employed to investigate the adsorption of a selection of organic surfactant molecules to a range of fluorapatite surfaces, and new interatomic potential models for the apatite/adsorbate interactions are presented. The adsorbates coordinate mainly to the surfaces through interaction between their oxygen (or nitrogen) atoms to surface calcium ions, followed by hydrogen-bonded interactions to surface oxygen ions and, to a much lesser extent, surface fluorides. Bridging between two surface calcium ions is the preferred mode of adsorption, when the geometry of the adsorbates allows it, and multiple interactions between surfaces and adsorbate molecules lead to the largest adsorption energies. All adsorbates containing carbonyl and hydroxy groups interact strongly with the surfaces, releasing energies between approximately 100 and 215 kJ mol-1, but methylamine containing only the NH2 functional group adsorbs to the surfaces to a much lesser extent (25 95 kJ mol-1). Both hydroxy methanamide and hydroxy ethanal prefer to adsorb to some surfaces in an eclipsed conformation, which is a requisite for these functional groups. Sorption of the organic material by replacement of pre-adsorbed water at different surface features is calculated to be mainly exothermic for methanoic acid, hydroxy methanamide and hydroxy ethanal molecules, whereas methyl amine would not replace pre-adsorbed water at the fluorapatite surfaces. The efficacy of the surfactant molecules is calculated to be hydroxy aldehydes > alkyl hydroxamates > carboxylic acids ≫ alkyl amines. The results from this study suggest that computer simulations may provide a route to the identification or even design of particular organic surfactants for use in mineral separation by flotation.

  2. Efficient conformational sampling of peptides adsorbed onto inorganic surfaces: insights from a quartz binding peptide.

    PubMed

    Wright, Louise B; Walsh, Tiffany R

    2013-04-07

    Harnessing the properties of biomolecules, such as peptides, adsorbed on inorganic surfaces is of interest to many cross-disciplinary areas of science, ranging from biomineralisation to nanomedicine. Key to advancing research in this area is determination of the peptide conformation(s) in its adsorbed state, at the aqueous interface. Molecular simulation is one such approach for accomplishing this goal. In this respect, use of temperature-based replica-exchange molecular dynamics (T-REMD) can yield enhanced sampling of the interfacial conformations, but does so at great computational expense, chiefly because of the need to include an explicit representation of water at the interface. Here, we investigate a number of more economical variations on REMD, chiefly those based on Replica Exchange with Solvent Tempering (REST), using the aqueous quartz-binding peptide S1-(100) α-quartz interfacial system as a benchmark. We also incorporate additional implementation details specifically targeted at improving sampling of biomolecules at interfaces. We find the REST-based variants yield configurational sampling of the peptide-surface system comparable with T-REMD, at a fraction of the computational time and resource. Our findings also deliver novel insights into the binding behaviour of the S1 peptide at the quartz (100) surface that are consistent with available experimental data.

  3. Direct Measurement of Core-Level Relaxation Dynamics on a Surface-Adsorbate System

    NASA Astrophysics Data System (ADS)

    Miaja-Avila, L.; Saathoff, G.; Mathias, S.; Yin, J.; La-O-Vorakiat, C.; Bauer, M.; Aeschlimann, M.; Murnane, M. M.; Kapteyn, H. C.

    2008-07-01

    The coupling between electronic states in a surface-adsorbate system is fundamental to the understanding of many surface interactions. In this Letter, we present the first direct time-resolved observations of the lifetime of core-excited states of an atom adsorbed onto a surface. By comparing laser-assisted photoemission from a substrate with a delayed Auger decay process from an adsorbate, we measure the lifetime of the 4d-1 core level of xenon on Pt(111) to be 7.1±1.1fs. This result opens up time-domain measurements of surface dynamics where energy-resolved measurements may provide incomplete information.

  4. Comparisons between Surface-Enhanced Raman and Surface Infrared Spectroscopies for Strongly Perturbed Adsorbates: Thiocyanate at Gold Electrodes.

    DTIC Science & Technology

    1986-07-30

    tu. 3. iptt FCSa, s CATALOG NUtof SBetween Surface -Enhanced Raman anj$ YEO EOTI EIDCvfr Surface Infared Spectroscopies for StrongiV Technical Report...REPORT 8 49 0Comparisons Between Surface-Enhanced Raman and Surface Infrared Spectroscopies for Strongly Perturbed Adsorbates: Thiocyanate at Gold...for thiocyanate adsorbed at the gold-aqueous interface is examined by both surface-enhanced Raman spectroscopy (SERS) and subtractively normalized

  5. Gas-Solid Dynamics at Disordered and Adsorbate Covered Surfaces.

    DTIC Science & Technology

    1987-05-15

    Schrodinger equation . Specific numerical results are presented for pulses of area equal to v, 21r, 31r, 4r and 51r for both symmetric and asymmetric... Semiclassical Perturbation Theory for Atom Scattering from Surfaces with Defects 1 Presented here is an extension of semiclassical perturbation theory (SCP...Involved in solving the AWM equations in equivalent to that Involved for elastic scattering in the same formulation. As an initial Illustration, expUclt

  6. High surface area calcite

    NASA Astrophysics Data System (ADS)

    Schultz, L. N.; Andersson, M. P.; Dalby, K. N.; Müter, D.; Okhrimenko, D. V.; Fordsmand, H.; Stipp, S. L. S.

    2013-05-01

    Calcite (CaCO3) is important in many fields—in nature, because it is a component of aquifers, oil reservoirs and prospective CO2 storage sites, and in industry, where it is used in products as diverse as paper, toothpaste, paint, plastic and aspirin. It is difficult to obtain high purity calcite with a high surface area but such material is necessary for industrial applications and for fundamental calcite research. Commercial powder is nearly always contaminated with growth inhibitors such as sugars, citrate or pectin and most laboratory synthesis methods deliver large precipitates, often containing vaterite or aragonite. To address this problem, we (i) adapted the method of carbonating a Ca(OH)2 slurry with CO2 gas to develop the first simple, cheap, safe and reproducible procedure using common laboratory equipment, to obtain calcite that reproducibly had a surface area of 14-17 m2/g and (ii) conducted a thorough characterization of the product. Scanning electron microscopy (SEM) revealed nanometer scale, rhombohedral crystals. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) confirmed highly crystalline, pure calcite that more closely resembles the dimensions of the biogenic calcite produced by algae in coccoliths than other methods for synthesizing calcite. We suggest that this calcite is useful when purity and high surface area are important.

  7. Adsorbate-metal bond effect on empirical determination of surface plasmon penetration depth.

    PubMed

    Kegel, Laurel L; Menegazzo, Nicola; Booksh, Karl S

    2013-05-21

    The penetration depth of surface plasmons is commonly determined empirically from the observed response for adsorbate loading on gold surface plasmon resonance (SPR) substrates. However, changes in the SPR spectrum may originate from both changes in the effective refractive index near the metal surface and changes in the metal permittivity following covalent binding of the adsorbate layer. Herein, the significance of incorporating an additional adsorbate-metal bonding effect in the calculation is demonstrated in theory and in practice. The bonding effect is determined from the nonzero intercept of a SPR shift versus adsorbate thickness calibration and incorporated into the calculation of penetration depth at various excitation wavelengths. Determinations of plasmon penetration depth with and without the bonding response for alkanethiolate-gold are compared and are shown to be significantly different for a thiol monolayer adsorbate system. Additionally, plasmon penetration depth evaluated with bonding effect compensation shows greater consistency over different adsorbate thicknesses and better agreement with theory derived from Maxwell's equation, particularly for adsorbate thicknesses that are much smaller (<5%) than the plasmon penetration depth. The method is also extended to a more practically applicable polyelectrolyte multilayer adsorbate system.

  8. Heterogeneous Ozonolysis of Surface Adsorbed Lignin Pyrolysis Products

    NASA Astrophysics Data System (ADS)

    Hinrichs, R. Z.

    2012-12-01

    Biomass combustion releases semi-volatile organic compounds into the troposphere, including many phenols and methoxyphenols as the result of lignin pyrolysis. Given their relatively low vapor pressures, these compounds readily adsorb on inorganic and organic aerosol substrates where they may alter aerosol properties and undergo heterogeneous chemistry. We use infrared spectroscopy (DRIFTS and ATR-FTIR) to monitor the adsorption and subsequent heterogeneous ozonolysis of model lignin pyrolysis products, including catechol, eugenol, and 4-propylguaiacol. Ozonolysis reaction kinetics were compared on various inorganic substrates - such as Al2O3 and NaCl, which serve as mineral and sea salt aerosol substrates, respectively - and as a function of ozone concentration and relative humidity. Following in situ FTIR analysis, the adsorbed organics were extracted and analyzed using gas chromatography-mass spectroscopy to identify reaction products and quantify product branching ratios. Ozonolysis of catechol and 4-propylguaiacol readily resulted in ring cleavage forming dicarboxylic acids (e.g., muconic acid). Eugenol ozonolysis proceeded rapidly at the alkene side chain producing homovanillic acid and homovanillin in an approximate 2:1 branching ratio at 0% RH; ring cleavage was also observed. For all lignin pyrolysis products, heterogeneous ozonolysis was faster on NaCl versus Al2O3. Implications for the atmospheric chemistry of semi-volatile methoxylphenols adsorbed on aerosol substrates will be discussed.

  9. Particle reflection and its energy spectrum from solid surfaces with adsorbate atoms

    NASA Astrophysics Data System (ADS)

    Yamamura, Y.

    1988-06-01

    Using the ACAT and ACOCT codes, the particle reflection coefficients and energy spectra reflected from solid surfaces covered with adsorbated atoms have been calculated in the low-energy region. It is found that the particle reflection coefficients of low energy ions are much reduced due to the collision between an incoming ion and an adsorbate atom, especially for M1 > M3 ( M1 and M3 being the atomic masses of an ion and an adsorbate atom, respectively), and the surface peak from a substrate atom becomes strongly suppressed as the coverage increases.

  10. Photoexcitation of adsorbates on metal surfaces: One-step or three-step

    SciTech Connect

    Petek, Hrvoje

    2012-09-07

    In this essay we discuss the light-matter interactions at molecule-covered metal surfaces that initiate surface photochemistry. The hot-electron mechanism for surface photochemistry, whereby the absorption of light by a metal surface creates an electron-hole pair, and the hot electron scatters through an unoccupied resonance of adsorbate to initiate nuclear dynamics leading to photochemistry, has become widely accepted. Yet, ultrafast spectroscopic measurements of molecule-surface electronic structure and photoexcitation dynamics provide scant support for the hot electron mechanism. Instead, in most cases the adsorbate resonances are excited through photoinduced substrate-to-adsorbate charge transfer. Based on recent studies of the role of coherence in adsorbate photoexcitation, as measured by the optical phase and momentum resolved two-photon photoemission measurements, we examine critically the hot electron mechanism, and propose an alternative description based on direct charge transfer of electrons from the substrate to adsorbate. The advantage of this more quantum mechanically rigorous description is that it informs how material properties of the substrate and adsorbate, as well as their interaction, influence the frequency dependent probability of photoexcitation and ultimately how light can be used to probe and control surface femtochemistry.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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 TiO2(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 TiO2(110) surface.

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

    PubMed

    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 TiO2(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 TiO2(110) surface.

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

    PubMed Central

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

    2016-01-01

    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 TiO2(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 TiO2(110) surface. PMID:27686286

  14. Surface properties and adsorption characteristics to methylene blue and iodine of adsorbents from sludge.

    PubMed

    Deng, L Y; Xu, G R; Li, G B

    2010-01-01

    Adsorbent materials created from wastewater sludge have unique surface characteristics and could be effective in adsorption applications. In this research, the sludge-adsorbents were generated by pyrolyzing mixtures of sewage sludge and H(2)SO(4). Scanning electron microscope (SEM), thermal analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscope (XPS) were used to analyze the properties of sludge-adsorbent. XPS results show that the adsorbent surface functional groups with high contents of oxygen-containing groups serve as active sites for the adsorption and affect the surface characteristics; the adsorption mechanism of methylene blue (MB) is mainly Brönsted acid-base reaction between the adsorbent surface and MB; and iodine atoms are bonded to the surface of the adsorbent mainly by dispersive interactions rather than by electrostatic interactions. The results also show that H(2)SO(4) level, pyrolysis temperature and sulfuric acid/sludge weight ratio actually affected the adsorption characteristics. Using the conditions (H(2)SO(4) level of 1-18 M, pyrolysis temperature of 650°C, and weight ratio of 0.8), the adsorption capacities for MB and iodine were 74.7-62.3 mg g(-1) and 169.5-209.3 mg g(-1), respectively.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Heterogeneous Reactions of Surface-Adsorbed Catechol: A Comparison of Tropospheric Aerosol Surrogates

    NASA Astrophysics Data System (ADS)

    Hinrichs, R. Z.; Woodill, L. A.

    2009-12-01

    Surface-adsorbed organics can alter the chemistry of tropospheric solid-air interfaces, such as aerosol and ground level surfaces, thereby impacting photochemical cycles and altering aerosol properties. The nature of the surface can also influence the chemistry of the surface-adsorbed organic. We employed diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to monitor the adsorption of gaseous catechol on several tropospheric aerosol surrogates and to investigate the subsequent reactivity of adsorbed-catechol with nitrogen dioxide and, in separate preliminary experiments, ozone. Graphite, kaolinite, and sodium halide (NaF, NaCl, NaBr) powders served as carbonaceous, mineral and sea salt aerosol surrogates, respectively. Broad OH stretching bands for adsorbed catechol shifted to lower wavenumber with peak frequencies following the trend NaBr > NaCl > NaF ≈ kaolinite, consistent with the increasing basicity of the halide anions and basic Brønsted sites on kaolinite. The dark heterogeneous reaction of NO2 with NaCl-adsorbed catechol at relative humidity (RH) <2% promoted nitration forming 4-nitrocatechol and oxidation forming 1,2-benzoquinone and the ring cleavage product muconic acid, with product yields of 88%, 8%, and 4%, respectively. 4-Nitrocatechol was the dominant product for catechol adsorbed on NaF and kaolinite, while NaBr-adsorbed catechol produced less 4-nitrocatechol and more 1,2-benzoquinone and muconic acid. For all three sodium halides, the reactions of NO2 with adsorbed catechol were orders of magnitude faster than between NO2 and each NaX substrate. 4-Nitrocatechol rates and product yields were consistent with the relative ability of each substrate to enhance the deprotonated nature of adsorbed-catechol. Increasing the relative humidity caused the rate of each product channel to decrease and also altered the product branching ratios. Most notably, 1,2-benzoquinone formation decreased significantly even at 13% RH. The dramatic

  17. Substrate-mediated interactions and intermolecular forces between molecules adsorbed on surfaces.

    PubMed

    Sykes, E Charles H; Han, Patrick; Kandel, S Alex; Kelly, Kevin F; McCarty, Gregory S; Weiss, Paul S

    2003-12-01

    Adsorbate interactions and reactions on metal surfaces have been investigated using scanning tunneling microscopy. The manners in which adsorbates perturb the surface electronic structure in their vicinity are discussed. The effects these perturbations have on other molecules are shown to be important in overlayer growth. Interactions of molecules with surface steps are addressed, and each molecule's electron affinity is shown to dictate its adsorption sites at step edges. Standing waves emanating from steps are demonstrated to effect transient molecular adsorption up to 40 A away from the step edge. Halobenzene derivatives are used to demonstrate how the surface is important in aligning reactive intermediates.

  18. Parallel pore and surface diffusion of levulinic acid in basic polymeric adsorbents.

    PubMed

    Liu, Baojian; Yang, Yiwen; Ren, Qilong

    2006-11-03

    The equilibrium and kinetics of levulinic acid (LA) adsorption on two basic polymeric adsorbents, 335 (highly porous gel) and D315 (macroreticular), were investigated. Experimental adsorption rates in batch stirred vessels under a variety of operating conditions were described successfully by the parallel pore and surface diffusion model taking into account external mass transfer and nonlinear Toth isotherm. The film-pore diffusion model was matched with the rate data and the resulting apparent pore diffusivities were strongly concentration-dependent and approached to a constant value for 335 adsorbent. Thus, the constant value was taken as the accurate pore diffusivity, while the pore diffusivity in D315 was estimated from the particle porosity. The surface diffusivities decreased with increasing initial bulk concentration for both adsorbents. The inverse concentration dependence was correlated reasonably well to the change of isosteric heat of adsorption as amount adsorbed.

  19. Application of 1H NMR spectroscopy method for determination of characteristics of thin layers of water adsorbed on the surface of dispersed and porous adsorbents.

    PubMed

    Turov, V V; Leboda, R

    1999-02-01

    The paper presents 1H NMR spectroscopy as a perspective method of the studies of the characteristics of water boundary layers in the hydrated powders and aqueous dispergated suspensions of the adsorbents. The method involves measurements of temperature dependence proton signals intensity in the adsorbed water at temperatures lower than 273 K. Free energy of water molecules at the adsorbent/water interface is diminished due to the adsorption interactions causing the water dosed to the adsorbent surface freezes at T < 273 K. Thickness of a non-freezing layer of water can be determined from the intensity of the water signal of 1H NMR during the freezing-thawing process. Due to a disturbing action of the adsorbent surface, water occurs in the quasi-liquid state. As a result, it is observed in the 1H NMR spectra as a relatively narrow signal. The signal of ice is not registered due to great differences in the transverse relaxation times of the adsorbed water and ice. The method of measuring the free surface energy of the adsorbents from the temperature dependence of the signal intensity of non-freezing water is based on the fact that the temperature of water freezing decreases by the quantity which depends on the surface energy and the distance of the adsorbed molecules from the solid surface. The water at the interface freezes when the free energies of the adsorbed water and ice are equal. To illustrate the applicability of the method under consideration the series of adsorption systems in which the absorbents used differed in the surface chemistry and porous structure. In particular, the behaviour of water on the surface of the following adsorbents is discussed: non-porous and porous silica (aerosils, silica gels); chemically and physically modified non-porous and porous silica (silanization, carbonization, biopolymer deposition); and pyrogeneous Al2O3 and aluminasilicas. The effect of preliminary treatment of the adsorbent (thermal, high pressure, wetting with polar

  20. On the HSAB based estimate of charge transfer between adsorbates and metal surfaces

    NASA Astrophysics Data System (ADS)

    Kokalj, Anton

    2012-01-01

    The applicability of the HSAB based electron charge transfer parameter, Δ N, is analyzed for molecular and atomic adsorbates on metal surfaces by means of explicit DFT calculations. For molecular adsorbates Δ N gives reasonable trends of charge transfer if work function is used for electronegativity of metal surface. For this reason, calculated work functions of low Miller index surfaces for 11 different metals are reported. As for reactive atomic adsorbates, e.g., N, O, and Cl, the charge transfer is proportional to the adatom valence times the electronegativity difference between the metal surface and the adatom, where the electronegativity of metal is represented by a linear combination of atomic Mulliken electronegativity and the work function of metal surface. It is further shown that the adatom-metal bond strength is linearly proportional to the metal-to-adatom charge transfer thus making the Δ N parameter a useful indicator to anticipate the corresponding adsorption energy trends.

  1. Role(s) of adsorbed water in the surface chemistry of environmental interfaces.

    PubMed

    Rubasinghege, Gayan; Grassian, Vicki H

    2013-04-18

    The chemistry of environmental interfaces such as oxide and carbonate surfaces under ambient conditions of temperature and relative humidity is of great interest from many perspectives including heterogeneous atmospheric chemistry, heterogeneous catalysis, photocatalysis, sensor technology, corrosion science, and cultural heritage science. As discussed here, adsorbed water plays important roles in the reaction chemistry of oxide and carbonate surfaces with indoor and outdoor pollutant molecules including nitrogen oxides, sulfur dioxide, carbon dioxide, ozone and organic acids. Mechanisms of these reactions are just beginning to be unraveled and found to depend on the details of the reaction mechanism as well as the coverage of water on the surface. As discussed here, adsorbed water can: (i) alter reaction pathways and surface speciation relative to the dry surface; (ii) hydrolyze reactants, intermediates and products; (iii) enhance surface reactivity by providing a medium for ionic dissociation; (iv) inhibit surface reactivity by blocking sites; (v) solvate ions; (vi) enhance ion mobility on surfaces and (vii) alter the stability of surface adsorbed species. In this feature article, drawing on research that has been going on for over a decade on the reaction chemistry of oxide and carbonate surfaces under ambient conditions of temperature and relative humidity, a number of specific examples showing the multi-faceted roles of adsorbed water are presented.

  2. Modeling adsorption: Investigating adsorbate and adsorbent properties

    NASA Astrophysics Data System (ADS)

    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

  3. Adsorption of globular proteins on locally planar surfaces. II. Models for the effect of multiple adsorbate conformations on adsorption equilibria and kinetics.

    PubMed Central

    Minton, A P

    1999-01-01

    Equilibrium and kinetic models for nonspecific adsorption of proteins to planar surfaces are presented. These models allow for the possibility of multiple interconvertible surface conformations of adsorbed protein. Steric repulsion resulting in area exclusion by adsorbed molecules is taken into account by treating the adsorbate as a thermodynamically nonideal two-dimensional fluid. In the equilibrium model, the possibility of attractive interactions between adsorbed molecules is taken into account in a limited fashion by permitting one of the adsorbed species to self-associate. Calculated equilibrium adsorption isotherms exhibit apparent high-affinity and low-affinity binding regions, corresponding respectively to adsorption of ligand at low fractional area occupancy in an energetically favorable side-on conformation and conversion at higher fractional area occupancy of the side-on conformation to an entropically favored end-on conformation. Adsorbate self-association may lead to considerable steepening of the adsorption isotherm, compensating to a variable extent for the broadening effect of steric repulsion. Kinetic calculations suggest that in the absence of attractive interactions between adsorbate molecules, the process of adsorption may be highly "stretched" along the time axis, rendering the attainment of adsorption equilibrium in the context of conventional experiments problematic. PMID:9876132

  4. In Situ Investigation the Photolysis of the PAHs Adsorbed on Mangrove Leaf Surfaces by Synchronous Solid Surface Fluorimetry

    PubMed Central

    Wang, Ping; Wu, Tun-Hua; Zhang, Yong

    2014-01-01

    An established synchronous solid surface fluorimetry (S-SSF) was utilized for in situ study the photolysis processes of anthracene (An) and pyrene (Py) adsorbed on the leaf surfaces of Kandelia obovata seedlings (Ko) and Aegiceras corniculata (L.) Blanco seedlings (Ac). Experimental results demonstrated that the photolysis of An and Py adsorbed on the leaf surfaces of two mangrove species under the laboratory conditions, followed first-order kinetics with their photolysis rates in the order of Ac>Ko. In addition, with the same amount of substances, the photolysis rate of An adsorbed on the same mangrove leaf surfaces was much faster than the adsorbed Py. In order to investigate further, the photolysis processes of An and Py in water were also studied for comparison. And the photolysis of An and Py in water also followed first-order kinetics. Moreover, for the same initial amount, the photolysis rate of the PAH in water was faster than that adsorbed on the leaf surfaces of two mangrove species. Therefore, photochemical behaviors of PAHs were dependent not only on their molecular structures but also the physical-chemical properties of the substrates on which they are adsorbed. PMID:24404158

  5. Effects due to adsorbed atoms upon angular and energy distributions of surface produced negative hydrogen ions

    NASA Astrophysics Data System (ADS)

    Wada, M.; Bacal, M.; Kasuya, T.; Kato, S.; Kenmotsu, T.; Sasao, M.

    2013-02-01

    Exposure to Cs added hydrogen discharge makes surface of plasma grid of a negative hydrogen ion source covered with Cs and hydrogen. A Monte-Carlo particle simulation code ACAT was run to evaluate the effects due to adsorbed Cs and H atoms upon the angular and energy distributions of H atoms leaving the surface. Accumulation of H atoms on the surface reduces particle reflection coefficients and the mean energy of backscattered H atoms. Angular distributions of H atoms reflected from the hydrogen covered surface tend to be under-cosine at lower energies. Desorption of adsorbed H atoms is more efficient for hydrogen positive ions than for Cs positive ions at lower incident energy. At higher energy more than 100 eV, Cs ions desorb adsorbed H atoms more efficiently than hydrogen ions.

  6. Chemisorption on surfaces — an historical look at a representative adsorbate: carbon monoxide

    NASA Astrophysics Data System (ADS)

    Yates, John T.

    1994-01-01

    The study of the interaction of molecules with clean surfaces extends back to the work of Irving Langmuir. In this historical account, the development of selected experimental methods for the study of molecular adsorption will be discussed. This will be done by historically reviewing research on one of the most well-studied adsorbate molecules, carbon monoxide. Many of the modern surface science techniques have first been used to study chemisorbed carbon monoxide, and the CO molecule is employed even today as a test molecule for currently developing surface measurement instruments such as the low temperature STM. In addition to being a good test molecule for new surface measurement techniques, adsorbed carbon monoxide is one of the centrally important molecules in the field of heterogeneous catalysis where the production of synthetic fuels and useful organic molecules often depends on the catalytic behavior of the adsorbed CO molecule. Interestingly, the carbon monoxide molecule also serves as a bridge between surface chemistry on the transition metals and the field of organometallic chemistry. Concepts about the chemical bonding and the reactive behavior of CO chemisorbed on transition metal surfaces and CO bound in transition metal carbonyls link these two fields together in a significant manner. The carbon monoxide molecule has been the historical focal point of many endeavors in surface chemistry and surface physics, and research on adsorbed carbon monoxide well represents many of the key advances which characterize the first thirty years of the development of surface science.

  7. Resonant electron scattering by molecules adsorbed on a surface: N2-Ag system

    NASA Astrophysics Data System (ADS)

    Teillet-Billy, D.; Djamo, V.; Gauyacq, J. P.

    1992-05-01

    A model study of resonant electron scattering by static molecules adsorbed on a metal surface is presented, using the recently developed coupled angular mode (CAM) method. It is applied to the case of N2 molecules adsorbed on an Ag surface. The N2-2πg resonance characteristics (energy position and width) are determined and shown to be modified by the presence of the surface in qualitative agreement with the experimental results of Demuth et al. [Phys. Rev. Lett. 47 (1981) 1166].

  8. Novel adsorbent based on multi-walled carbon nanotubes bonding on the external surface of porous silica gel particulates for trapping volatile organic compounds.

    PubMed

    Wang, Li; Liu, Jiemin; Zhao, Peng; Ning, Zhanwu; Fan, Huili

    2010-09-10

    A novel adsorbent, 3-amino-propylsilica gel-multi-walled carbon nanotubes (APSG-MW), was prepared by chemical bonding multi-walled carbon nanotubes on silica gel. The surface area of APSG-MW was 98 m(2)/g, and the particle size was between 60 and 80 mesh with the average size of 215.0 microm. The adsorption capability of the new adsorbent to volatile organic compounds (VOCs) was measured. The effect of water to the adsorbent and its stability during storage were also investigated. Duplicate precision (DP) and distributed volume pair (DVP) on the basis of the EPA TO-17 criteria were estimated. The results showed that the sampling precision of the adsorbent was more superior compared to the MWCNTs because of the better air permeability. The new adsorbent was successfully applied in the determination of VOCs in ambient indoor air.

  9. Activity of catalase adsorbed to carbon nanotubes: effects of carbon nanotube surface properties.

    PubMed

    Zhang, Chengdong; Luo, Shuiming; Chen, Wei

    2013-09-15

    Nanomaterials have been studied widely as the supporting materials for enzyme immobilization. However, the interactions between enzymes and carbon nanotubes (CNT) with different morphologies and surface functionalities may vary, hence influencing activities of the immobilized enzyme. To date how the adsorption mechanisms affect the activities of immobilized enzyme is not well understood. In this study the adsorption of catalase (CAT) on pristine single-walled carbon nanotubes (SWNT), oxidized single-walled carbon nanotubes (O-SWNT), and multi-walled carbon nanotubes (MWNT) was investigated. The adsorbed enzyme activities decreased in the order of O-SWNT>SWNT>MWNT. Fourier transforms infrared spectroscopy (FTIR) and circular dichrois (CD) analyses reveal more significant loss of α-helix and β-sheet of MWNT-adsorbed than SWNT-adsorbed CAT. The difference in enzyme activities between MWNT-adsorbed and SWNT-adsorbed CAT indicates that the curvature of surface plays an important role in the activity of immobilized enzyme. Interestingly, an increase of β-sheet content was observed for CAT adsorbed to O-SWNT. This is likely because as opposed to SWNT and MWNT, O-SWNT binds CAT largely via hydrogen bonding and such interaction allows the CAT molecule to maintain the rigidity of enzyme structure and thus the biological function.

  10. Ultrafast photo-induced electron-transfer from coumarin dyes adsorbed on semiconductor nanoclusters surfaces

    SciTech Connect

    Castner, E.W. Jr.; Murakoshi, Kei; Yanagida, Shozo

    1997-12-31

    Photosensitizers adsorbed directly on semiconductor surfaces provide the basis for solar photoelectrochemical devices. Semiconductor nanoclusters in solution allow for simple preparation of the photosensitized surface, with very large surface area. To optimize the efficiency of the photoelectrochemical cycle, one must know the rates of forward and reverse electron-transfer from the excited state dye to the semiconductor conduction band. We present measurements of the ultrafast forward electron-transfer rates for three coumarin dyes (Coumarins 343, D-1421, and D-126) bound by the carboxylic acid group to the metal cationic sites of TiO{sub 2} and ZnO semiconductor nanocluster surfaces. These rates are obtained directly from the ultrafast fluorescence dynamics, measured using the femotosecond upconversion technique. Coumarins 343 and D-1421 on TiO{sub 2} nanoclusters in aqueous solution display very rapid forward electron-transfer with rate constants exceeding 10{sup 13} s{sup -1}. Substantially slower rates are observed for the same coumarin TiO{sub 2} systems in methanol solution.

  11. New surfaces stabilized by adsorbate-induced faceting

    NASA Astrophysics Data System (ADS)

    Kaghazchi, Payam; Jacob, Timo; Ermanoski, Ivan; Chen, Wenhua; Madey, Theodore E.

    2012-07-01

    Faceting is a form of self-assembly of single-crystal surfaces at the nanometer-scale in which an initially planar surface converts to a ‘hill-and-valley’ structure, exposing new faces of low-index surfaces. Our recent studies revealed that, upon annealing in O2, three-sided nanoscale pyramids form on Ir(210) exposing smooth {311} and partially restructured (110) faces. Through a combination of scanning tunneling microscopy and density functional theory, we identify this structure to be a stepped double-missing-row reconstruction, which is only stable on nanopyramidal facets, not on a planar Ir(110) surface. This faceting-enabled stabilization of a hitherto unstable surface points to a new approach to prepare nanoscale model catalysts for structure-sensitivity studies in heterogeneous (electro-)catalysis with high selectivity and reactivity.

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

    PubMed

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

    2012-08-01

    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.

  13. Influence of Polymers on the Crystal Growth Rate of Felodipine: Correlating Adsorbed Polymer Surface Coverage to Solution Crystal Growth Inhibition.

    PubMed

    Schram, Caitlin J; Taylor, Lynne S; Beaudoin, Stephen P

    2015-10-20

    The bioavailability of orally administered drugs that exhibit poor aqueous solubility can be enhanced with the use of supersaturating dosage forms. Stabilization of these forms by preventing or inhibiting crystallization in solution is an important area of study. Polymers can be used to stabilize supersaturated systems; however, the properties that impact their effectiveness as crystal growth rate inhibitors are not yet fully understood. In this study, the impact of various polymers on the crystal growth rate of felodipine and the conformation of these polymers adsorbed to crystalline felodipine was investigated in order to gain a mechanistic understanding of crystal growth inhibition. It was determined that polymer hydrophobicity impacted polymer adsorption as well as adsorbed polymer conformation. Polymer conformation impacts its surface coverage, which was shown to directly correlate to the polymer's effectiveness as a growth rate inhibitor. By modeling this correlation, it is possible to predict polymer effectiveness given the surface coverage of the polymer.

  14. Vibrational Spectroscopic Studies of Adsorbates on Bimetallic Surfaces.

    DTIC Science & Technology

    1992-12-01

    sublimed. Prior to use, the metal evaporator was outgassed extensively. No measurable contaminants accumulated on the surface during metal deposition...substrate was an annealed c(2X2) S/Mo(110) surface which can be thought of as roughly approximating the surface of a MoS2 crystallite. Increasing Co...catalytic activity of Co promoted MoS2 would be that the active site is a Co promoted Mo-S site. As a final point, it is notewoi chy that in all the co

  15. Structure of water adsorbed on a mica surface

    SciTech Connect

    Park, Sung-Ho; Sposito, Garrison

    2002-01-29

    Monte Carlo simulations of hydration water on the mica (001) surface under ambient conditions revealed water molecules bound closely to the ditrigonal cavities in the surface, with a lateral distribution of approximately one per cavity, and water molecules interposed between K{sup +} counter ions in a layer situated about 2.5 {angstrom} from a surface O along a direction normal to the (001) plane. The calculated water O density profile was in quantitative agreement with recent X-ray reflectivity measurements indicating strong lateral ordering of the hydration water but liquid-like disorder otherwise.

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

    NASA Astrophysics Data System (ADS)

    Bruch, L. W.

    2004-07-01

    Dilute nitrides have emerged from conventional III-V semiconductors such as GaAs or InP by the insertion of nitrogen into the group V sub-lattice, which has a profound influence on the electronic properties of these materials and allows widely extended band structure engineering. This is expected to lead to novel devices, e.g. for optical data transmission, solar cells, biophotonics or gas sensing, some of which are already making their way into the market. Unlike in all other cases, where a reduction in bandgap energy is achieved by inserting an element that increases the lattice constant, N accomplishes this and at the same time reduces the lattice constant. Thus smaller bandgaps can be achieved and the unusual role of N in the lattice also allows a tailoring of band alignments. Both of these effects have opened up a new dimension of bandgap engineering and the rapid progress in the field led to the demonstration of high quality 1300 nm lasers on GaAs and eventually to the realization of the first VCSELs that can be mass produced at low cost and emit at 1300 nm. This in turn will allow extending inexpensive data transmission through optical fibers from the present range of about 300 m to a distance of 10 to 20 km and at the same time increasing the data rate by about a factor of four. Thus it will enable metro-area data links, which are presently considered to be the bottleneck for large-scale optical communications. Furthermore, the fact that GaNP and related alloys can be grown lattice-matched on Si substrates has offered intriguing new possibilities of OEIC and integration of efficient III-V optoelectronic devices with the mainstream microelectronics based on Si. Despite their promising applications and the first encouraging experimental results, very little is known about the physical properties of such alloys. For instance the difficulty of incorporating nitrogen into GaInAs while maintaining good optical quality has provoked much work to establish an

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

    PubMed

    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.

  18. Enhanced removal of nitrate from water using surface modification of adsorbents--a review.

    PubMed

    Loganathan, Paripurnanda; Vigneswaran, Saravanamuthu; Kandasamy, Jaya

    2013-12-15

    Elevated concentration of nitrate results in eutrophication of natural water bodies affecting the aquatic environment and reduces the quality of drinking water. This in turn causes harm to people's health, especially that of infants and livestock. Adsorbents with the high capacity to selectively adsorb nitrate are required to effectively remove nitrate from water. Surface modifications of adsorbents have been reported to enhance their adsorption of nitrate. The major techniques of surface modification are: protonation, impregnation of metals and metal oxides, grafting of amine groups, organic compounds including surfactant coating of aluminosilicate minerals, and heat treatment. This paper reviews current information on these techniques, compares the enhanced nitrate adsorption capacities achieved by the modifications, and the mechanisms of adsorption, and presents advantages and drawbacks of the techniques. Most studies on this subject have been conducted in batch experiments. These studies need to include continuous mode column trials which have more relevance to real operating systems and pilot-plant trials. Reusability of adsorbents is important for economic reasons and practical treatment applications. However, only limited information is available on the regeneration of surface modified adsorbents.

  19. Relaxation dynamics of surface-adsorbed water molecules in nanoporous silica probed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Ru; Liu, Kao-Hsiang; Mou, Chung-Yuan; Sun, Chi-Kuang

    2015-08-01

    Relaxation dynamics of an exclusively adsorbed water molecule in mesoporous silica MCM-41-S was studied by using terahertz spectroscopy. With the temperature controlled from 0 to 50 °C, we observed strongly frequency- and temperature-dependent dielectric relaxation responses, implying that, unlike ice, surface-adsorbed water molecules retained flourishing picosecond dynamics. Based on the Debye relaxation model, a relaxation time constant was found to increase from 1.77 to 4.83 ps when the water molecule was cooled from 50 to 0 °C. An activation energy of ˜15 kJ/mol, which was in close agreement with a hydrogen-bonding energy, was further extracted from the Arrhenius analysis. Combined with previous molecular dynamics simulations, our results indicate that the reorientation relaxation originated from the "flip-flop" rotation of a three hydrogen-bonded surface-adsorbed water molecule.

  20. Plasma-induced conversion of surface-adsorbed hydrocarbons

    SciTech Connect

    Sackinger, W.M.

    1992-01-01

    Experimental results are reported for an electrical device for direct conversion of methane into higher hydrocarbons. A microchannel plate is excited with electrons from a photoemissive source, and electron impact ionization of methane on the inner surfaces of the microchannels creates an ion feedback process. The resulting low-density plasma creates higher hydrocarbons when charged particles impact the surfaces at grazing incidence. The production Of C{sub 2} to C{sub 8}-containing gases was noted, with a selectivity for C{sub 2} of 39% in one case. The proportions of converted products and the conversion rates depend upon the electrical voltage, the microchannel geometry, and the operating pressure. Conversion rates increase with operating pressure.

  1. Plasma-induced conversion of surface-adsorbed hydrocarbons

    SciTech Connect

    Sackinger, W.M.

    1992-07-01

    Experimental results are reported for an electrical device for direct conversion of methane into higher hydrocarbons. A microchannel plate is excited with electrons from a photoemissive source, and electron impact ionization of methane on the inner surfaces of the microchannels creates an ion feedback process. The resulting low-density plasma creates higher hydrocarbons when charged particles impact the surfaces at grazing incidence. The production Of C{sub 2} to C{sub 8}-containing gases was noted, with a selectivity for C{sub 2} of 39% in one case. The proportions of converted products and the conversion rates depend upon the electrical voltage, the microchannel geometry, and the operating pressure. Conversion rates increase with operating pressure.

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

    SciTech Connect

    Maurer, Reinhard J.; Ruiz, Victor G.; Tkatchenko, Alexandre

    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.

  3. The influence of surface chemistry on adsorbed fibrinogen conformation, orientation, fiber formation and platelet adhesion.

    PubMed

    Zhang, Liudi; Casey, Brendan; Galanakis, Dennis K; Marmorat, Clement; Skoog, Shelby; Vorvolakos, Katherine; Simon, Marcia; Rafailovich, Miriam H

    2017-03-02

    Thrombosis is a clear risk when any foreign material is in contact with the bloodstream. Here we propose an immunohistological stain-based model for non-enzymatic clot formation that enables a facile screen for the thrombogenicity of blood-contacting materials. We exposed polymers with different surface chemistries to protease-free human fibrinogen. We observed that on hydrophilic surfaces, fibrinogen is adsorbed via αC regions, while the γ400-411 platelet-binding dodecapeptide on the D region becomes exposed, and fibrinogen fibers do not form. In contrast, fibrinogen is adsorbed on hydrophobic surfaces via the relatively hydrophobic D and E regions, exposing the αC regions while rendering the γ400-411 inaccessible. Fibrinogen adsorbed on hydrophobic surfaces is thus able to recruit other fibrinogen molecules through αC regions and polymerize into large fibrinogen fibers, similar to those formed in vivo in the presence of thrombin. Moreover, the γ400-411 is available only on the large fibers not elsewhere throughout the hydrophobic surface after fibrinogen fiber formation. When these surfaces were exposed to gel-sieved platelets or platelet rich plasma, a uniform monolayer of platelets, which appeared to be activated, was observed on the hydrophilic surfaces. In contrast, large agglomerates of platelets were clustered on fibers on the hydrophobic surfaces, resembling small nucleating thrombi. Endothelial cells were also able to adhere to the monomeric coating of fibrinogen on hydrophobic surfaces. These observations reveal that the extent and type of fibrinogen adsorption, as well as the propensity of adsorbed fibrinogen to bind platelets, may be modulated by careful selection of surface chemistry.

  4. Semiconducting electronic property of graphene adsorbed on (0001) surfaces of SiO2.

    PubMed

    Nguyen, Thanh Cuong; Otani, Minoru; Okada, Susumu

    2011-03-11

    First-principles total energy calculations are performed to investigate the energetics and electronic structures of graphene adsorbed on both an oxygen-terminated SiO2 (0001) surface and a fully hydroxylated SiO2 (0001) surface. We find that there are several stable adsorption sites for graphene on both O-terminated and hydroxylated SiO2 surfaces. The binding energy in the most stable geometry is found to be 15 meV per C atom, indicating a weak interaction between graphene and SiO2 (0001) surfaces. We also find that the graphene adsorbed on SiO2 is a semiconductor irrespective of the adsorption arrangement due to the variation of on-site energy induced by the SiO2 substrate.

  5. Effects of surface curvature and surface chemistry on the structure and activity of proteins adsorbed in nanopores.

    PubMed

    Sang, Lung-Ching; Coppens, Marc-Olivier

    2011-04-14

    The interactions of proteins with the surface of cylindrical nanopores are systematically investigated to elucidate how surface curvature and surface chemistry affect the conformation and activity of confined proteins in an aqueous, buffered environment. Two globular proteins, lysozyme and myoglobin, with different catalytic functions, were used as model proteins to analyze structural changes in proteins after adsorption on ordered mesoporous silica SBA-15 and propyl-functionalized SBA-15 (C(3)SBA-15) with carefully controlled pore size. Liquid phase ATR-FTIR spectroscopy was used to study the amide I and II bands of the adsorbed proteins. The amide I bands showed that the secondary structures of free and adsorbed protein molecules differ, and that the secondary structure of the adsorbed protein is influenced by the local geometry as well as by the surface chemistry of the nanopores. The conformation of the adsorbed proteins inside the nanopores of SBA-15 and C(3)SBA-15 is strongly correlated with the local geometry and the surface properties of the nanoporous materials, which results in different catalytic activities. Adsorption by electrostatic interaction of proteins in nanopores of an optimal size provides a favorably confining and protecting environment, which may lead to considerably enhanced structural stability and catalytic activity.

  6. Spin-polarized metastable-atom deexcitation spectroscopy study of Xenon-adsorbed iron surfaces

    NASA Astrophysics Data System (ADS)

    Yamauchi, Yasushi; Kurahashi, Mitsunori; Suzuki, Taku; Sun, Xia; Wang, Zhongping

    2007-03-01

    The electron spin polarization at the interface between nonmagnetic and ferromagnetic medias is one of the essential factors that may alter the spin transport phenomena. To investigate fundamental aspects of induced spin polarization we have examined the adsorbate-covered magnetic surfaces by means of spin polarized metastable-atom deexcitation spectroscopy (SPMDS). Use of spin-polarized metastable helium atoms in triplet states moving at thermal energies gives rise to the ultimate surface sensitivity. Although Xenon can adsorb on surfaces at low temperatures by the van der Waals force, no electron exchange with surfaces, especially no spin interaction, is expected because of its closed shell structure. SPMDS spectra measured for Xenon-adsorbed iron surfaces show three prominent peaks that are the same as those previously reported for other surfaces by D. M. Oro, et al. [Phys. Rev. A 49 (1994) 4703]. Two peaks (^2P1/2, ^2P3/2) at higher kinetic energies exhibit clear spin asymmetries while the other low energy peak has no appreciable spin asymmetry. The spin asymmetries will be discussed on the basis of spin polarization and deexcitation processes of metastable atoms.

  7. Study for Reduction of Outgassing Property of Adsorbed Water Gas for Improved Surface Finished Titanium Material

    NASA Astrophysics Data System (ADS)

    Takeda, Masatoshi; Kurisu, Hiroki; Uchida, Takashi; Yamamoto, Setsuo; Ishizawa, Katsunobu; Nomura, Takeru; Eda, Takahiro; Murashige, Nobuyuki

    This paper addresses the development of the surface finishing for a titanium material and the study for the reduction of outgassing property of adsorbed water (H2O) molecules. Developed surface finishing is composed of the buffing for the reduction of the surface roughness and improved chemical polishing for the thick surface oxide layer compared with the chemical polishing so far. The surface roughness of the surface finished titanium material is reduced 35% and the thickness of the surface oxide layer increases by 30%. The total amount of thermal desorbed H2O gas for the new surface finished titanium is reduced 30%. It is considered that the origin for the decrease of the amount of desorption H2O gas is the reduction of the adsorption sites due to the decrease of the surface roughness and the reduction of adsorption energy of H2O gas due to the strong surface oxidation for a titanium material.

  8. The Impact of Adsorbed Triethylene Glycol on Water Wettability of the {1014} Calcium Carbonate Surface

    NASA Astrophysics Data System (ADS)

    Olsen, R.

    2015-12-01

    Water flooding is increasingly being used as a method of enhanced oil recovery and frequently involves calcium carbonate reservoirs. Very often, thermodynamic conditions in the upper few hundred meters allow for hydrate formation. One possible method of preventing hydrates is to inject hydrate inhibitors such as triethylene glycol (TEG) into the reservoir. Thus, it is of importance to know how such glycols affect water wettability, which is an important factor defining the oil behavior in such reservoirs. Wettability of a surface is defined by the contact angle of a liquid drop on the surface. The stronger the liquid is attracted to the surface, the smaller the wetting angle becomes, implying an increased degree of wetting. Therefore, it is possible to gain qualitative knowledge of the change in wetting properties with respect to external influences by studying corresponding changes in free energy of adsorption of the liquid. In our work [1], we used molecular dynamics (MD) and Born-Oppenheimer molecular dynamics (BOMD) to study how adsorbed TEG on the {1014} calcium carbonate surface affected adsorbed water. We used the changes in density profiles of water to estimate changes in adsorption free energy of water. The adaptive biasing force (ABF) method was applied to TEG to calculate the adsorption free energy of TEG on the calcium carbonate surface. We found that water wetting of the calcium carbonate surface decreased in the presence of adsorbed TEG. [1] - Olsen, R.; Leirvik, K.; Kvamme, B.; Kuznetsova, T. Adsorption Properties of Triethylene Glycol on a Hydrated {1014} Calcite Surface and Its Effect on Adsorbed Water, Langmuir 2015, DOI: 10.1021/acs.langmuir.5b02228

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Speciation of adsorbed yttrium and rare earth elements on oxide surfaces

    NASA Astrophysics Data System (ADS)

    Piasecki, Wojciech; Sverjensky, Dimitri A.

    2008-08-01

    The distribution of yttrium and the rare earth elements (YREE) between natural waters and oxide mineral surfaces depends on adsorption reactions, which in turn depend on the specific way in which YREE are coordinated to mineral surfaces. Recent X-ray studies have established that Y 3+ is adsorbed to the rutile (1 1 0) surface as a distinctive tetranuclear species. However, the hydrolysis state of the adsorbed cation is not known from experiment. Previous surface complexation models of YREE adsorption have suggested two to four cation hydrolysis states coexisting on oxide surfaces. In the present study, we investigate the applicability of the X-ray results to rare earth elements and to several oxides in addition to rutile using the extended triple-layer surface complexation model. The reaction producing a hydrolyzed tetranuclear surface species 4>SOH+M+2HO=(>SOH)2_M(OH)2++4H was found to account for a significant fraction of the adsorbed Y 3+, La 3+, Nd 3+, Gd 3+, and Yb 3+ on rutile, hematite, alumina and silica over wide ranges of pH and ionic strength. Where adsorption data were available as a function of surface coverage for hematite and silica, an additional reaction involving a mononuclear species could be used to account for the higher surface coverages. However, it is also possible that some of the higher surface coverage data refer to surface precipitation rather than adsorption. The results of the present study provide an internally consistent basis for describing YREE adsorption which could be used to investigate more complex systems in which YREE compete both in aqueous solution and on mineral surfaces with alkaline earths and ligands such as carbonate, sulfate, chloride and organic species, in order to build a predictive adsorption model applicable to natural waters.

  11. General trend for adsorbate-induced segregation of subsurface metal atoms in bimetallic surfaces

    NASA Astrophysics Data System (ADS)

    Menning, Carl A.; Chen, Jingguang G.

    2009-05-01

    It is well known that the unique chemical properties of transition metal alloys depend on the configuration of metal atoms of the bimetallic surfaces. Using density functional theory calculations, the thermodynamic potential for segregation of an admetal from the subsurface to surface configuration is shown to correlate linearly with the difference in occupied d-band center, Δɛd, between these two configurations for a wide range of bimetallic systems. The thermodynamic potential for segregation is also shown to increase with the Pauling electronegativity for several adsorbates, including atomic H, O, C, N, S, and Se. A generalized equation is provided to predict the stable surface configuration for the bimetallic systems with different adsorbates.

  12. Surface chemistry of ferrihydrite: Part 1. EXAFS studies of the geometry of coprecipitated and adsorbed arsenate

    USGS Publications Warehouse

    Waychunas, G.A.; Rea, B.A.; Fuller, C.C.; Davis, J.A.

    1993-01-01

    EXAFS spectra were collected on both the As and Fe K-edges from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages. Spectra also were collected for arsenate adsorbed on the surfaces of three FeOOH crystalline polymorphs, ?? (goethite), ?? (akaganeite), and ?? (lepidocrocite), and as a free ion in aqueous: solution. Analyses of the As EXAFS show clear evidence for inner sphere bidentate (bridging) arsenate complexes on the ferrihydrite surface and on the surfaces of the crystalline FeOOH polymorphs. The bridging arsenate is attached to adjacent apices of edge-sharing Fe oxyhydroxyl octahedra. The arsenic-iron distance at the interface (3.28 ??0.01 A ??) is close to that expected for this geometry on the FeOOH polymorph surfaces, but is slightly shorter on the ferrihydrite surfaces (3.25 ?? 0.02 A ??). Mono-dentate arsenate linkages (3.60 ?? 0.03 A ??) also occur on the ferrihydrite, but are not generally observed on the crystalline FeOOH polymorphs. The proportion of monodentate bonds appears largest for adsorption samples with the smallest As Fe molar ratio. In all cases the arsenate tetrahedral complex is relatively undistorted with As-O bonds of 1.66 ?? 0.01 A ??. Precipitation of arsenate or scorodite-like phases was not observed for any samples, all of which were prepared at a pH value of 8. The Fe EXAFS results confirm that the Fe-Fe correlations in the ferrihydrite are progressively disrupted in the CPT samples as the As Fe ratio is increased. Coherent crystallite size is probably no more than 10 A?? in diameter and no Fe oxyhydroxyl octahedra corner-sharing linkages (as would be present in FeOOH polymorphs) are observed at the largest As Fe ratios. Comparison of the number and type of Fe-Fe neighbors with the topological constraints imposed by the arsenate saturation limit in the CPT samples (about 0.7 As Fe) indicates ferrihydrite units consisting mainly

  13. Evaluation of Adsorbed Arsenic and Potential Contribution to Shallow Groundwater in Tulare Lake Bed Area, Tulare Basin, California

    USGS Publications Warehouse

    Gao, S.; Fujii, R.; Chalmers, A.T.; Tanji, K.K.

    2004-01-01

    Elevated As concentrations in shallow groundwater in parts of the Tulare Basin, California, are a concern because of potential migration into deeper aquifers that could serve as a source of future drinking water. The objectives of this study were to evaluate adsorbed As and the potential contribution to groundwater using (i) isotopic dilution, (ii) successive extraction with an electrolyte solution resembling the pore-water chemical composition, and (iii) PO4 exchange for As. Sediment samples collected from 2 to 4 m below land surface in the Tulare Lake bed area contained a total As concentration of 24 mg As kg-1. Pore water extracted under hydraulic pressure contained a total As concentration of 590 ??g As L-1, which predominantly contained As as arsenate [As(V), 97%], a minor amount of arsenite [As(III), 3%], and non-detectable organic As. The isotopic dilution method [73As(V)] estimated that the concentration of adsorbed As(V) on the sediment was 5.7 mg As kg-1 at pH 8.5 and 6.7 mg As kg-1 at pH 7.5, respectively. Fourteen successive 24-h extractions with the artificial pore water released up to 57 to 61% of the adsorbed As(V) that was determined by isotopic dilution, indicating that only a portion of the adsorbed As could be released to groundwater. The phosphate-exchangeable As (0.1 M PO4, pH 8.5 or 7.5) was 63% of the isotopically exchangeable As(V). Thus, extraction of As by 0.1 M PO4 at ambient pHs is recommended as a method to determine the potential amount of As(V) on sediments that could be released to the solution phase. The overall results indicated that adsorbed As could be a significant source of As to groundwater. However, other factors that affect As transport such as the leaching rate need to be considered.

  14. Electrohydrodynamic manipulation of particles adsorbed on the surface of a drop.

    PubMed

    Amah, Edison; Shah, Kinnari; Fischer, Ian; Singh, Pushpendra

    2016-02-14

    In our previous studies we have shown that particles adsorbed on the surface of a drop can be concentrated at its poles or equator by applying a uniform electric field. This happens because even when the applied electric field is uniform the electric field on the surface of the drop is nonuniform, and so particles adsorbed on the surface are subjected to dielectrophoretic (DEP) forces. In this paper, we study the behavior of adsorbed particles at low electric field frequencies when the drop and ambient liquids are weakly conducting dielectric liquids, and model it using a leaky dielectric model. The electrohydrodynamic (EHD) flow which arises because of the accumulation of charge on the surface of the drop can be from pole-to-equator or equator-to-pole depending on the properties of the drop and ambient liquids. The flow however diminishes with increasing frequency and there is a critical frequency at which the drag force on a particle due to the EHD flow becomes equal to the DEP force, and above this critical frequency the DEP force dominates. When the fluid and particles properties are such that the EHD and DEP forces are in the opposite directions, particles can be collected at the poles or the equator, and also can be moved from the poles to the equator, or vice versa, by varying the frequency. Also, it is possible to separate the particles of a binary mixture when the critical frequencies of the two types of particles are different.

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

    SciTech Connect

    Cernota, Paul Davis

    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.

  16. TOF-SIMS measurements for toxic air pollutants adsorbed on the surface of airborne particles

    NASA Astrophysics Data System (ADS)

    Tomiyasu, Bunbunoshin; Hoshi, Takahiro; Owari, Masanori; Nihei, Yoshimasa

    2003-01-01

    Three kinds of particulate matter were collected: diesel and gasoline exhaust particles emitted directly from exhaust nozzle, and suspended particulate matter (SPM) near the traffic route. Soxhlet extraction was performed on each sample. By gas-chromatograph-mass spectrometer (GC-MS) analysis of these extracts, di-ethyl phthalate and di- n-butyl phthalate were detected from the extract of SPM and diesel exhaust particles (DEPs). Because these phthalates were sometimes suspected as contamination, time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements were also performed on the samples collected at the same environment. By comparing obtained spectra, it is clear that these environmental endocrine disrupters (EEDs) were adsorbed on DEP surface. Thus, we concluded that the combination of conventional method and TOF-SIMS measurement is one of the most powerful techniques for analyzing the toxic air pollutants adsorbed on SPM surface.

  17. MOF-Graphite Oxide Nanocomposites: Surface Characterization and Evaluation as Adsorbents of Ammonia

    DTIC Science & Technology

    2009-01-01

    July 2009 DOI: 10.1039/b908862h Metal-organic framework (MOF-5)–graphite oxide (GO) composite was synthesized using a solvothermal synthesis route. The...restacked and their degree of orientation depends on the method of drying. Our recent studies demonstrate that graphite oxide can be an efficient adsorbent...parent materials and the nanocomposite is fol- lowed by their surface characterization using a range of experi- mental methods . Then, their

  18. Controlling the Electronic Structure of Graphene Using Surface-adsorbate Interactions

    DTIC Science & Technology

    2015-07-21

    before and after adsorption [in Fig. 4(a)] and structural changes to Gr/Ni(111) [in Fig. 4(b)]. Before adsorption, the atomic orbitals of graphene (pz...RAPID COMMUNICATIONS PHYSICAL REVIEW B 92, 041407(R) (2015) Controlling the electronic structure of graphene using surface-adsorbate interactions...manuscript received 3 May 2015; published 21 July 2015) Hybridization of atomic orbitals in graphene on Ni(111) opens up a large energy gap of ≈2.8 eV

  19. Unsaturated hydrocarbons adsorbed on low coordinated Pd surface: A periodic DFT study

    NASA Astrophysics Data System (ADS)

    Belelli, Patricia G.; Ferullo, Ricardo M.; Castellani, Norberto J.

    2010-02-01

    In this work, the adsorption of several unsaturated hydrocarbon molecules on a stepped Pd(4 2 2) surface was studied. Using a periodic method based on the Density Functional Theory (DFT) formalism, different adsorption geometries for ethylene, three butene isomers ( cis/ trans-2-butene and 1-butene), acetylene and 2-butyne were investigated. The results were compared with those obtained for a free defect surface as Pd(1 1 1). The 1-butene is more stable on the free defect surface than on Pd(4 2 2). On the stepped surface, the olefins adsorb tilted towards the step and increases, in almost all the cases, the magnitude of the adsorption energy. Conversely, the 3-fold site is the most stable for the alkynes adsorption on the stepped surface, as it was found on Pd(1 1 1). The analysis of the dipole moment change indicate a charge transfer from the double bond of the olefin to the metallic surface, being higher for the Pd(1 1 1) surface. In case of the alkynes, an important back-donation is produced. Except the alkynes and the 1-butene molecule, the results show the preference of ethylene and cis/ trans-2-butene to be adsorbed on the stepped surface. These observations are related with experimental catalytic results.

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

    SciTech Connect

    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.

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

    SciTech Connect

    Peterson, Eric Scott

    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.

  2. Rod-like cyanophenyl probe molecules nanoconfined to oxide particles: Density of adsorbed surface species

    NASA Astrophysics Data System (ADS)

    Frunza, Stefan; Frunza, Ligia; Ganea, Constantin Paul; Zgura, Irina; Brás, Ana Rita; Schönhals, Andreas

    2016-02-01

    Surface layers have already been observed by broadband dielectric spectroscopy for composite systems formed by adsorption of rod-like cyanophenyl derivates as probe molecules on the surface of oxide particles. In this work, features of the surface layer are reported; samples with different amounts of the probe molecules adsorbed onto oxide (nano) particles were prepared in order to study their interactions with the surface. Thermogravimetric analysis (TGA) was applied to analyze the amount of loaded probe molecules. The density of the surface species ns was introduced and its values were estimated from quantitative Fourier transform infrared spectroscopy (FTIR) coupled with TGA. This parameter allows discriminating the composites into several groups assuming a similar interaction of the probe molecules with the hosts of a given group. An influence factor H is further proposed as the ratio of the number of molecules in the surface layer showing a glassy dynamics and the number of molecules adsorbed tightly on the surface of the support: It was found for aerosil composites and used for calculating the maximum filling degree of partially filled silica MCM-41 composites showing only one dielectric process characteristic for glass-forming liquids and a bulk behavior for higher filling degrees.

  3. Direct imaging of Pt single atoms adsorbed on TiO2 (110) surfaces.

    PubMed

    Chang, Teng-Yuan; Tanaka, Yusuke; Ishikawa, Ryo; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Ikuhara, Yuichi; Shibata, Naoya

    2014-01-08

    Noble metal nanoparticles (e.g., gold and platinum) supported on TiO2 surfaces are utilized in many technological applications such as heterogeneous catalysts. To fully understand their enhanced catalytic activity, it is essential to unravel the interfacial interaction between the metal atoms and TiO2 surfaces at the level of atomic dimensions. However, it has been extremely difficult to directly characterize the atomic-scale structures that result when individual metal atoms are adsorbed on the TiO2 surfaces. Here, we show direct atomic-resolution images of individual Pt atoms adsorbed on TiO2 (110) surfaces using aberration-corrected scanning transmission electron microscopy. Subangstrom spatial resolution enables us to identify five different Pt atom adsorption sites on the TiO2 (110) surface. Combining this with systematic density functional theory calculations reveals that the most favorable Pt adsorption sites are on vacancy sites of basal oxygen atoms that are located in subsurface positions relative to the top surface bridging oxygen atoms.

  4. Changes in the quaternary structure of amelogenin when adsorbed onto surfaces

    SciTech Connect

    Tarasevich, Barbara J.; Lea, Alan S.; Bernt, William; Engelhard, Mark H.; Shaw, Wendy J.

    2009-02-02

    The amelogenin protein is involved in the formation of highly controlled and anisotropic hydroxyapatite crystals in tooth enamel. Amelogenin is unique in that it self assembles to form supramolecular quaternary structures called “nanospheres,” spherical aggregates of amelogenin monomers typically 20-60 nm in diameter. Although nanospheres have been observed in solution, the quaternary structure of amelogenin adsorbed onto surfaces is not well known. A better understanding of the surface structure is of great importance, however, because the function of amelogenin depends on it. We report studies of the adsorption of amelogenin onto self-assembled monolayers (SAMs) containing COOH and CH3 end group functionality as well as single crystal fluoroapatite (FAP), a biologically relevant surface. The supramolecular structures of the protein in solution as determined by dynamic light scattering (DLS) were compared with the supramolecular structures of the protein physisorbed onto surfaces as studied by atomic force microscopy (AFM). We found that although our solutions contained only nanospheres of narrow size distribution, smaller structures such as monomers and dimers were observed onto both hydrophilic and hydrophobic surfaces. This suggests that amelogenin can adsorb onto surfaces as small structures that peel away or “shed” from the nanospheres that are present in solution.

  5. The reaction of propylene with ordered and disordered oxygen atoms adsorbed on the Ag(110) surface

    NASA Astrophysics Data System (ADS)

    Ranney, Jeffrey T.; Bare, Simon R.

    1997-06-01

    The adsorption and reaction of propylene on oxygen covered Ag(110) was investigated using temperature programmed desorption spectroscopy. Propylene oxidation was compared on the oxygen reconstructed (ordered) Ag(110) surface and on the unreconstructed (disordered) oxygen dosed surface. Oxygen atoms adsorbed < 185 K do not incorporate into long silver-oxygen chains on the (110) surface and are referred to as disordered. Propylene desorbs from clean Ag(110) with an activation energy of 9.8 kcal mol -1. The desorption activation energy increases by 30% as the coverage of oxygen is increased up to 0.33 monolayers. While the desorption activation energy increase was the same on the reconstructed and unreconstructed surface, the reactivity of the adsorbed oxygen for propylene oxidation was quite different. Disordered oxygen adatoms were determined to be at least ten times more active for propylene oxidation than ordered oxygen atoms on the reconstructed surface. The decrease in activity of the oxygen atoms is attributed to the embedding of the oxygen adatoms into long silver-oxygen chains at higher temperatures. With increasing propylene coverage on the oxygen pre-covered surface the water yield increases and the yield of carbon dioxide decreases, indicating that water formation through hydrogen abstraction consumes the bulk of the oxygen at higher propylene coverages.

  6. Accelerator analysis of tributyltin adsorbed onto the surface of a tributyltin resistant marine Pseudoalteromonas sp. cell.

    PubMed

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

    2008-10-01

    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 (10(9.3 +/- 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 10(8.2). 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 10(6.8) TBT molecules is adsorbed by a single cell.

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

    PubMed Central

    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-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. PMID:19325731

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

    PubMed

    Arpanaei, A; Winther-Jensen, B; Theodosiou, E; Kingshott, P; Hobley, T J; Thomas, O R T

    2010-10-29

    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 a purpose-designed rotating reactor, plasmas were employed to either: (i) remove anion exchange ligands at or close to the exterior surface of Q HyperZ, and replace them with polar oxygen containing functions ('plasma etching and oxidation'); or (ii) bury the same surface exposed ligands beneath thin polymer coatings ('plasma polymerization coating') using appropriate monomers (vinyl acetate, vinyl pyrrolidone, safrole) and argon as the carrier gas. X-ray photoelectron spectroscopy analysis (first ∼10 nm depth) of Q HyperZ before and after the various plasma treatments confirmed that substantial changes to the elemental composition of Q HyperZ's exterior had been inflicted in all cases. The atomic percent changes in carbon, nitrogen, oxygen, yttrium and zirconium observed after being exposed to air plasma etching were entirely consistent with: the removal of pendant Q (trimethylammonium) functions; increased exposure of the underlying yttrium-stabilised zirconia shell; and introduction of hydroxyl and carbonyl functions. Following plasma polymerization treatments (with all three monomers tested), the increased atomic percent levels of carbon and parallel drops in nitrogen, yttrium and zirconium provided clear evidence that thin polymer coats had been created at the exteriors of Q HyperZ adsorbent particles. No changes in adsorbent size and surface morphology, nor any evidence of plasma-induced damage could be discerned from scanning electron micrographs, light micrographs and measurements of particle size distributions following 3 h exposure to air (220 V; 35.8 W L(-1)) or 'vinyl acetate/argon' (170 V; 16.5 W L(-1)) plasmas. Losses in bulk chloride exchange capacity

  9. Isocyanide ligands adsorbed on metal surfaces: applications in catalysis, nanochemistry, and molecular electronics.

    PubMed

    Angelici, Robert J; Lazar, Mihaela

    2008-10-20

    Knowledge of the coordination chemistry and reactivity of isocyanide ligands in transition-metal complexes forms the basis for understanding the adsorption and reactions of isocyanides on metal surfaces. In this overview, we explore reactions (often catalytic) of isocyanides adsorbed on metal surfaces that reflect their patterns of reactivity in metal complexes. We also examine applications of isocyanide adsorption to the stabilization of metal nanoparticles, the functionalization of metal electrodes, and the creation of conducting organic-metal junctions in molecule-scale electronic devices.

  10. Intervalence transfer of ferrocene moieties adsorbed on electrode surfaces by a conjugated linkage

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Brown, Lauren E.; Konopelski, Joseph P.; Chen, Shaowei

    2009-03-01

    Effective intervalence transfer occurred between the metal centers of ferrocene moieties that were adsorbed onto a ruthenium thin film surface by ruthenium-carbene π bonds, a direct verification of Hush's four-decade-old prediction. Electrochemical measurements showed two pairs of voltammetric peaks where the separation of the formal potentials suggested a Class II behavior. Additionally, the potential spacing increased with increasing ferrocene surface coverage, most probably as a consequence of the enhanced contribution from through-space electronic interactions between the metal centers. In contrast, the incorporation of a sp 3 carbon spacer into the ferrocene-ruthenium linkage led to the diminishment of interfacial electronic communication.

  11. Controlling the Electronic Structure of Graphene Using Surface-Adsorbate Interactions

    DTIC Science & Technology

    2015-07-21

    is cut-off from the substrate, and the band structure in Fig. 3(d). The hybridization is blocked by an atomic spacer of Na and thus there is only a...the underlying layer. 44. Gamo, Y., et al., Atomic structure of monolayer graphite formed on Ni(111). Surface Science, 1997. 374(1-3): p. 61-64. 45...1 Controlling the electronic structure of graphene using surface-adsorbate interactions Piotr Matyba, Adra V. Carr, Cong Chen, David L. Miller

  12. In situ ion gun cleaning of surface adsorbates and its effect on electrostatic forces

    NASA Astrophysics Data System (ADS)

    Schafer, Robert; Xu, Jun; Mohideen, Umar

    2016-01-01

    To obtain precise measurements of the Casimir force, it is crucial to take into account the electrostatic interactions that exist between the two boundaries. Two otherwise grounded conductors will continue to have residual electrostatic effects from patch potentials existing on the surfaces. In this paper, we look at the effect of in situ cleaning of adsorbate patches, and the resultant effect on the net electrostatic potential difference between two surfaces. We find a significant reduction in the residual potential due to in situ Ar+ cleaning for the samples used.

  13. Detrimental adsorbate fields in experiments with cold Rydberg gases near surfaces

    NASA Astrophysics Data System (ADS)

    Hattermann, H.; Mack, M.; Karlewski, F.; Jessen, F.; Cano, D.; Fortágh, J.

    2012-08-01

    We observe the shift of Rydberg levels of rubidium close to a copper surface when atomic clouds are repeatedly deposited on it. We measure transition frequencies of rubidium to S and D Rydberg states with principal quantum numbers n between 31 and 48 using the technique of electromagnetically induced transparency. The spectroscopic measurement shows a strong increase of electric fields towards the surface that evolves with the deposition of atoms. Starting with a clean surface, we measure the evolution of electrostatic fields in the range between 30 and 300 μm from the surface. We find that after the deposition of a few hundred atomic clouds, each containing ˜106 atoms, the field of adsorbates reaches 1 V/cm for a distance of 30 μm from the surface. This evolution of the electrostatic field sets serious limitations on cavity QED experiments proposed for Rydberg atoms on atom chips.

  14. The leucine rich amelogenin protein (LRAP) adsorbs as monomers or dimers onto surfaces

    SciTech Connect

    Tarasevich, Barbara J.; Lea, Alan S.; Shaw, Wendy J.

    2010-03-15

    Amelogenin and amelogenin splice variants are believed to be involved in controlling the formation of the highly anisotropic and ordered hydroxyapatite crystallites that form enamel. The adsorption behavior of amelogenin proteins onto substrates is very important because protein-surface interactions are critical to it’s function. We have studied the adsorption of LRAP, a splice variant of amelogenin which may also contribute to enamel function, onto model self-assembled monolayers on gold containing of COOH, CH3, and NH2 end groups. Dynamic light scattering (DLS) experiments indicated that LRAP in phosphate buffered saline (PBS) and solutions at saturation with calcium phosphate contained aggregates of nanospheres. Null ellipsometry and atomic force microscopy (AFM) were used to study protein adsorption amounts and structures. Relatively high amounts of adsorption occurred onto the CH3 and NH2 surfaces from both calcium phosphate and PBS solutions. Adsorption was also promoted onto COOH surfaces when calcium was present in the solutions suggesting an interaction that involves calcium bridging with the negatively charged C-terminus. The ellipsometry and AFM studies suggested that the protein adsorbed onto all surfaces as LRAP monomers. We propose that the monomers adsorb onto the surfaces by disassembling or “shedding” from the nanospheres that are present in solution. This work reveals the importance of small subnanosphere-sized structures of LRAP at interfaces, structures that may be important in the biomineralization of tooth enamel.

  15. Self-Assembly of Thiol Adsorbates on the Au(111)surface

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank; Williams, Quinton; Zhou, Jian-Ge

    2007-03-01

    A long-standing controversy related to the dimer pattern formed by methanethiol (CH3SH) and methylthiolate (CH3S) on the Au(111) surface has been resolved using density functional theory within periodic boundary conditions. It is found that the S atoms of methanethiol adsorbates on the Au(111) surface form Van der Waals dimers. For methylthiolate, it is shown that no dimerization occurs at high coverage. At intermediate coverage, however, a Van der Waals dimer pattern emerges. The presence of defects in the Au(111) surface does not change this conclusion. Molecular dynamics simulation at high coverage demonstrates that the observed dialkyl disulfide species emerge during the desorption process, and thus are not attached to the surface. A meta-stable monomer pattern has been shown to be only marginally higher in adsorption energy than the dimer configuration which explains the observed fragility of the dimers. For the understanding of these results, it is of crucial importance that methanethiol molecules, contrary to a widely held assumption, remain stable when deposited on clean Au(111) surfaces /1, 2/. In the presence of defects, however, methanethiol adsorbates dissociate and form methylthiolate. /1/ I. Rzeznicka, J. Lee, P. Maksymovych, J. Yates, Jr., J. Phys. Chem. B109, 15992 (2005). /2/ J. Zhou, F. Hagelberg, Phys. Rev. Lett. 97, 45505 (2006).

  16. Surface diffusion of gold nanoclusters on Ru(0001): effects of cluster size, surface defects and adsorbed oxygen atoms.

    PubMed

    Stein, Ori; Ankri, Jonathan; Asscher, Micha

    2013-08-28

    Understanding thermal behavior of metallic clusters on their solid supports is important for avoiding sintering and aggregation of the active supported metallic particles in heterogeneous catalysis. As a model system we have studied the diffusion of gold nano-clusters on modified Ru(0001) single crystal surfaces, employing surface density grating formation via a laser induced ablation technique. Surface modifications included damage induced by varying periods of Ne(+) ion sputtering at a collision energy of 2.8 keV and the effect of pre-adsorbed oxygen on the clean, defect free ruthenium surface. High density of surface damage, obtained at long sputter times, has led to enhanced diffusivity with lower onset temperature for diffusion. It is attributed to reduced cluster-surface commensurability which gives rise to smaller effective activation energy for diffusion. The diffusion of gold nano-clusters, 2 nm in size, was found to be insensitive to the oxygen surface concentration. The adsorbed oxygen acted as an "atomic layer lubricant", reducing friction between the cluster and the underlying surface. This has led to lower diffusivity onset temperatures (150 K) of the nano-clusters, with a stronger effect on smaller clusters.

  17. Thrombocyte adhesion and release of extracellular microvesicles correlate with surface morphology of adsorbent polymers for lipid apheresis.

    PubMed

    Weiss, René; Spittler, Andreas; Schmitz, Gerd; Fischer, Michael B; Weber, Viktoria

    2014-07-14

    Whole blood lipid apheresis is clinically applied to reduce low density lipoprotein cholesterol in patients with homozygous familial hypercholesterolemia. Here, we studied the correlation between physicochemical parameters, in particular, surface roughness and blood compatibility, of two polyacrylate-based and a dextran sulfate-based polymer for lipid apheresis. The adsorbent surface roughness was assessed by atomic force microscopy. Freshly isolated human thrombocytes were circulated over adsorbent columns downscaled equivalent to clinical use to study thrombocyte adhesion and microvesicle generation. Quantification of thrombocytes and microvesicles in the flow-through of the columns revealed that both thrombocyte adhesion and microvesicle generation increased with increasing adsorbent surface roughness. Activation of thrombocytes with thrombin receptor-activating peptide-6 favored their adhesion to the adsorbents, as demonstrated by preferential depletion of CD62(+) and PAC-1(+) thrombocytes. Taken together, enhanced polymer surface roughness fostered cell adhesion and microvesicle release, underscoring the role of extracellular microvesicles as markers of cellular activation and of blood compatibility.

  18. Formation of Adsorbed Oxygen Radicals on Minerals at the Martian Surface and the Decomposition of Organic Molecules

    NASA Technical Reports Server (NTRS)

    Yen, A. S.; Kim, S. S.; Freeman, B. A.; Hecht, M. H.

    2000-01-01

    We present experimental evidence that superoxide ions form on mineral grains at the martian surface and show that these adsorbates can explain the unusual reactivity of the soil as well as the apparent absence of organic molecules.

  19. Utilization of microfluidic V-junction device to prepare surface itraconazole adsorbed nanospheres.

    PubMed

    Kucuk, Israfil; Ahmad, Zeeshan; Edirisinghe, Mohan; Orlu-Gul, Mine

    2014-09-10

    Itraconazole is widely used as an anti-fungal drug to treat infections. However, its poor aqueous solubility results in low bioavailability. The aim of the present study was to improve the drug release profile by preparing surface itraconazole adsorbed polymethylsilsesquioxane (PMSQ) nanospheres using a V-junction microfluidic (VJM) device. In order to generate nanospheres with rough surface, the process flow rate of perfluorohexane (PFH) was set between 50 and 300 μl min(-1) while the flow rate of PMSQ and itraconazole solution were constant at 300 μl min(-1). Variations in the PFH flow rate enable the controlled size generation of nanospheres. PMSQ nanospheres adsorbing itraconazole were characterized by SEM, FTIR and Zetasizer. The release of itraconazole from PMSQ nanosphere surface was measured using UV spectroscopy. Nanosphere formulations with a range of sphere size (120, 320 and 800 nm diameter) were generated and drug release was studied. 120 nm itraconazole coated PMSQ nanospheres were found to present highest drug encapsulation efficiency and 13% drug loading in a more reproducible manner compared to 320 nm and 800 nm sized nanosphere formulations. Moreover, 120 nm itraconazole coated PMSQ nanospheres (encapsulation efficiency: 88%) showed higher encapsulation efficiency compared to 320 nm (encapsulation efficiency: 74%) and 800 nm (encapsulation efficiency: 62%) sized nanosphere formulations. The itraconazole coated PMSQ nanospheres were prepared continuously at the rate of 2.6 × 10(6) per minute via VJM device. Overall the VJM device enabled the preparation of monodisperse surface itraconazole adsorbed nanospheres with controlled in vitro drug release profile.

  20. Characterization of silver ions adsorbed on gold nanorods: surface analysis by using surface-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Niidome, Yasuro; Nakamura, Yuki; Honda, Kanako; Akiyama, Yasuyuki; Nishioka, Koji; Kawasaki, Hideya; Nakashima, Naotoshi

    2009-04-07

    Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-MS) indicated AgBr2-, which adsorbed on gold nanorod surfaces, was a key material to control the anisotropic growth of gold nanorods.

  1. Development of drug adsorbates onto soluble inorganic silicate glass surface: example with acetaminophen.

    PubMed

    Hristova, Yoanna; Djambaski, Peter; Samuneva, Biserka; Rangelova, Nadya; Bogdanova, Svetla

    2008-02-01

    A ternary melt-derived inorganic glass system (Igl) of composition corresponding to 62SiO(2), 35Na(2)O, 3Al(2)O(3 )(wt.%) has been formulated and studied as a drug carrier. The [Al(2)O(3)/Na(2)O] ratio is less than one and the aluminium ion is a network former that retards the glass dissolution. The processing conditions lead to a brittle, easily grinding, amorphous product. The Igl structure was proven by IR-spectroscopy, energy-dispersive spectrometry, X-ray diffraction, scanning electron microscopy. A very important fact established is that the Igl corrosion (dissolution) is pH-dependent. Inorganic glass system was transformed into model acetaminophen (APH) adsorbate (APH/Igla 1:1(w/w)) with mild experimental conditions and evaluated as a drug carrier. No interactions between Igl and APH during the processing were proven. Besides, APH settles onto the glass surface as crystalline phase. A lower extent of corrosion, apparent solubility and delayed in vitro APH release from the adsorbate in water and artificial gastric juice in comparison to the samples untreated drug and APH/Iglm physical mixture were established. It is hypothesized that the glass decomposition products, formed into contact with a solvent, initiate interactions with APH at the glass/solution interface. Similar behaviour of the Igl and its drug adsorbates could be expected in gastro-intestinal tract.

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

    SciTech Connect

    López-Moreno, S.; Romero, A. H.

    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.

  3. Self-assembly of acetate adsorbates drives atomic rearrangement on the Au(110) surface

    PubMed Central

    Hiebel, Fanny; Shong, Bonggeun; Chen, Wei; Madix, Robert J.; Kaxiras, Efthimios; Friend, Cynthia M.

    2016-01-01

    Weak inter-adsorbate interactions are shown to play a crucial role in determining surface structure, with major implications for its catalytic reactivity. This is exemplified here in the case of acetate bound to Au(110), where the small extra energy of the van der Waals interactions among the surface-bound groups drives massive restructuring of the underlying Au. Acetate is a key intermediate in electro-oxidation of CO2 and a poison in partial oxidation reactions. Metal atom migration originates at surface defects and is likely facilitated by weakened Au–Au interactions due to bonding with the acetate. Even though the acetate is a relatively small molecule, weak intermolecular interaction provides the energy required for molecular self-assembly and reorganization of the metal surface. PMID:27731407

  4. Self-assembly of acetate adsorbates drives atomic rearrangement on the Au(110) surface

    NASA Astrophysics Data System (ADS)

    Hiebel, Fanny; Shong, Bonggeun; Chen, Wei; Madix, Robert J.; Kaxiras, Efthimios; Friend, Cynthia M.

    2016-10-01

    Weak inter-adsorbate interactions are shown to play a crucial role in determining surface structure, with major implications for its catalytic reactivity. This is exemplified here in the case of acetate bound to Au(110), where the small extra energy of the van der Waals interactions among the surface-bound groups drives massive restructuring of the underlying Au. Acetate is a key intermediate in electro-oxidation of CO2 and a poison in partial oxidation reactions. Metal atom migration originates at surface defects and is likely facilitated by weakened Au-Au interactions due to bonding with the acetate. Even though the acetate is a relatively small molecule, weak intermolecular interaction provides the energy required for molecular self-assembly and reorganization of the metal surface.

  5. Solid particles adsorbed on capillary-bridge-shaped fluid polystyrene surfaces.

    PubMed

    McEnnis, Kathleen; Dinsmore, Anthony D; Russell, Thomas P

    2015-05-19

    Particles adsorbed on microscopic polystyrene (PS) capillary bridge surfaces were observed to investigate their motion under capillary forces arising from a nonuniform shape. Capillary bridges were created by placing thin PS films, heated above the glass transition temperature (Tg), between two electrodes with an air gap between the surface of the PS and the upper electrode. Silica particles, 100 nm in diameter, were placed on the surface of the PS capillary bridges, and the sample was heated above the Tg of PS to enable particle motion. Samples were cooled to below Tg, and the locations of the particles were observed using scanning electron microscopy. The particles did not preferentially locate around the center of the capillary bridge, as predicted by others, but instead segregated to the edges. These results indicate that the forces driving particles to the three-phase contact line (air/PS/electrode surface) are greater than those locating particles around the center.

  6. Chemical effects on vibrational properties of adsorbed molecules on metal surfaces: Coverage dependence

    NASA Astrophysics Data System (ADS)

    Ueba, H.

    1987-10-01

    Vibrational properties of chemisorbed molecules on metal surfaces are studied with a focus on the coverage dependent chemical shift of the frequencies. Available experimental data of a CO adsorption on transition metal and noble metal surfaces are analyzed in the light of the coverage dependent back-donation into the 2 π* orbitals of chemisorbed CO molecules. The vibrational frequency ωCO of the intramolecular stretching mode exhibits a downward shift of varying magnitude, depending on the amount of back-donation into the 2 π* orbitals of the chemisorbed CO. On increasing the coverage θ, ωCO usually increases due to the dipole-dipole interaction. On Cu surfaces, however, the shifts are relatively small, or in some cases, negative. So far, this anomalous frequency shift with θ is understood as a result of competitive effect between the upward dipole Ωdip and the downward chemical shift Ωchem associated with back-donation. The purpose of this paper is to establish the possible origin of the downward frequency shift through the electronic properties of an incomplete monolayer of adsorbates. The adsorbate density of states ρa is calculated by means of the coherent potential approximation, in which the electron hopping between the adsorbates (band formation effect) and the depolarization effect due to the proximity of ionized adsorbed molecules are taken into account. The change of the occupied portion of ρa and ρa ( ɛF) at the Fermi level ɛF with increasing θ then manifests itself in the coverage dependent Ωchem not only due to the static back-donation, but also due to the dynamical charge fluctuation during vibrational excitation. It is found that in a weakly chemisorbed system, such as CO/Cu, the negative Ωchem amounts to Ωdip at low θ. Consequently the apparent total frequency shift remains almost constant. As the coverage increases, Ωchem becomes larger than Ωdip due to the band effect. It is also shown that the variation of the back

  7. Progress in our understanding of structure bonding and reactivity of metal surfaces and adsorbed monolayers at the molecular level: A 25 year perspective

    NASA Astrophysics Data System (ADS)

    Somorjai, G. A.

    1995-12-01

    Over fifty techniques have been developed during the past 25 years that permit molecular level investigation of structure and bonding of the surface monolayer. Among them, low-energy electron diffraction surface crystallography and vibrational spectroscopies using photons and electrons have contributed the lion's share of quantitative experimental data. (Most of these investigations have utilized small area (~1 cm 2) external surfaces, although microporous large internal surface area samples were also scrutinized.) From these studies, the physical picture of the surface which emerges is one of a separate phase with distinct structure, composition, and bonding that is distinguishable from the solid bulk. The new surface phenomena which were discovered include clean surface reconstruction, adsorbate-induced restructuring, ordering and reactivity of surface defects (steps and kinks), cluster-like bonding, the large mobility of adsorbates, and the coadsorption bond. Techniques were also developed that permit in situ molecular level study of surfaces during reactions at high pressures and temperatures with good time resolution (10 -12-10 -3 sec). Molecular surface science has had a great impact in major applications involving surface phenomena-selective adsorption, heterogeneous catalysis, coatings, microelectronics, electrochemistry, and tribology-and spawned new surface technologies. The demands of these applications focus attention on the behavior of the buried interface, both solid-liquid and solid-solid.

  8. Homeotropic orientation of a nematic liquid crystal by bent-core molecules adsorbed on its surface

    NASA Astrophysics Data System (ADS)

    Hwang, Jiyong; Yang, Seungbin; Lee, Hyojin; Kim, Jongyoon; Lee, Ji-Hoon; Kang, Shin-Woong; Choi, E.-Joon

    2015-06-01

    We reported the promotion of a homeotropic alignment of a nematic liquid crystal (NLC) by bent-core liquid-crystal (BLC) Molecules adsorbed its surface. The BLC was mixed at various concentrations with the NLC, and the mixtures were injected into an empty cell with a cell gap of 13 μm. Although the pure NLC showed a heterogeneous orientation, the BLC-NLC mixture was gradually transformed to a homeotropic alignment with increasing concentration of the BLC. We investigated the surface topography of the samples by using an atomic force microscopy (AFM) and found that the BLC molecules were segregated into a polyimide (PI) surface and formed protrusion domains with diameters of 50-100 nm. The BLC protrusions might promote the homeotropic orientation of the NLC molecules.

  9. Large spin splitting of metallic surface-state bands at adsorbate-modified gold/silicon surfaces

    PubMed Central

    Bondarenko, L. V.; Gruznev, D. V.; Yakovlev, A. A.; Tupchaya, A. Y.; Usachov, D.; Vilkov, O.; Fedorov, A.; Vyalikh, D. V.; Eremeev, S. V.; Chulkov, E. V.; Zotov, A. V.; Saranin, A. A.

    2013-01-01

    Finding appropriate systems with a large spin splitting of metallic surface-state band which can be fabricated on silicon using routine technique is an essential step in combining Rashba-effect based spintronics with silicon technology. We have found that originally poor structural and electronic properties of the surface can be substantially improved by adsorbing small amounts of suitable species (e.g., Tl, In, Na, Cs). The resultant surfaces exhibit a highly-ordered atomic structure and spin-split metallic surface-state band with a momentum splitting of up to 0.052 Å−1 and an energy splitting of up to 190 meV at the Fermi level. The family of adsorbate-modified surfaces, on the one hand, is thought to be a fascinating playground for exploring spin-splitting effects in the metal monolayers on a semiconductor and, on the other hand, expands greatly the list of material systems prospective for spintronics applications. PMID:23661151

  10. Large spin splitting of metallic surface-state bands at adsorbate-modified gold/silicon surfaces.

    PubMed

    Bondarenko, L V; Gruznev, D V; Yakovlev, A A; Tupchaya, A Y; Usachov, D; Vilkov, O; Fedorov, A; Vyalikh, D V; Eremeev, S V; Chulkov, E V; Zotov, A V; Saranin, A A

    2013-01-01

    Finding appropriate systems with a large spin splitting of metallic surface-state band which can be fabricated on silicon using routine technique is an essential step in combining Rashba-effect based spintronics with silicon technology. We have found that originally poor structural and electronic properties of the Au/Si(111) √3 x √3 surface can be substantially improved by adsorbing small amounts of suitable species (e.g., Tl, In, Na, Cs). The resultant surfaces exhibit a highly-ordered atomic structure and spin-split metallic surface-state band with a momentum splitting of up to 0.052 Å(-1) and an energy splitting of up to 190 meV at the Fermi level. The family of adsorbate-modified Au/Si(111) √3 x √3 surfaces, on the one hand, is thought to be a fascinating playground for exploring spin-splitting effects in the metal monolayers on a semiconductor and, on the other hand, expands greatly the list of material systems prospective for spintronics applications.

  11. Infrared spectral investigations of UV irradiated nucleobases adsorbed on mineral surfaces

    NASA Astrophysics Data System (ADS)

    Fornaro, Teresa; Brucato, John Robert; Pace, Emanuele; Guidi, Mariangela Cestelli; Branciamore, Sergio; Pucci, Amaranta

    2013-09-01

    The interaction between electromagnetic radiation and bio-molecules in heterogeneous environments is a prebiotically relevant process. Minerals may have a pivotal role in the prebiotic evolution of complex chemical systems, mediating the effects of electromagnetic radiation, influencing the photostability of bio-molecules, catalyzing important chemical reactions and/or protecting molecules against degradation. In particular, nucleobases are relevant bio-molecules to investigate both in the prebiotic context, because they are coding components of nucleic acids, and from the standpoint of the survival of biological systems in space conditions. Several studies on the photodynamics of nucleobases suggest that their structure could have been naturally selected for the ability to dissipate electronic energy through ultrafast photophysical decay. Considering the putative involvement of minerals in the prebiotic chemistry, it is necessary to study the photostability of nucleobases under space conditions in the presence of mineral matrices, to investigate both the prebiotic processes that might have had a role in the development of the first living entities on Earth and the physical and chemical processes occurring in extraterrestrial environments. We focused our study on the characterization of the nature of the interaction between nucleobases and the surface of the minerals magnesium oxide and forsterite by infrared vibrational spectroscopy. We observed that most of the characteristic bands of pure nucleobases vanished when adsorbed on magnesium oxide. On the contrary, in the case of adenine and uracil adsorbed on forsterite, very intense nucleobase absorption peaks appeared. This phenomenon pertains to the surface selection rules changes related to molecular orientation. Moreover, based on the vibrational shifts, we deduced the molecular interaction sites with the mineral surfaces. Furthermore, we investigated the photostability of nucleobases adsorbed on such minerals

  12. Infrared spectral investigations of UV irradiated nucleobases adsorbed on mineral surfaces

    NASA Astrophysics Data System (ADS)

    Brucato, J. R.; Fornaro, T.

    2014-04-01

    Spectroscopic studies of the effects of UV radiation on biomolecules such as nucleobases in heterogeneous environments are particularly relevant in prebiotic chemistry to unravel the role of minerals in the transformation/preservation of biomolecules in abiotic environments. Minerals may have a pivotal role in the prebiotic evolution of complex chemical systems, mediating the effects of electromagnetic radiation, influencing the photostability of biomolecules, catalyzing important chemical reactions and/or protecting molecules against degradation. Studies on the photodegradation of biomolecules adsorbed on minerals have applications also in the life detection context to identify potential biomarkers for future space mission and hence to develop suitable sample-extraction protocols for bioanalytical instruments [1]. Moreover, the characterization of the spectroscopic features of biomolecules-mineral complexes provides a support in remote sensing spectroscopy for detecting organic compounds on planetary surfaces or cometary grains and asteroid surfaces. In this context we will present laboratory results on UV photostability of nucleobases adsorbed on magnesium oxide and forsterite minerals and analysed with infrared spectroscopic [2,3].

  13. ``QM/Me'' - a novel embedding approach for adsorbate dynamics on metal surfaces

    NASA Astrophysics Data System (ADS)

    Meyer, Jörg; Reuter, Karsten

    2010-03-01

    The dissociative adsorption of oxygen molecules on metal surfaces is a commonly known, highly exothermic reaction and in its slow or fast form of great importance for corrosion or oxidation catalysis, respectively. However, knowledge about atomistic details of the heat dissipation, a central conceptual concern, is very limited at best. Even on the level of Born-Oppenheimer potential energy surfaces, accurate dynamical ab-initio descriptions of such reactions are quite challenging from a computational point of view: Modeling the excitations of substrate phonons within periodic boundary conditions requires huge supercells, whereas traditional ``QM/MM'' embedding schemes would need unfeasibly large metal clusters. In the novel ``QM/Me'' approach presented here, the adsorbate- interaction is obtained from periodic first-principles calculations in convenient supercells and combined with the description of a 'bath-like' substrate based on classical potentials, which are parametrized to seamlessly fit the first-principles data. We apply our approach to the dissociative adsorption of O2 and H2 on Pd(100) using density-functional theory and a modified embedded atom potential. In both cases, a dominant fraction of the released chemisorption energy is dissipated into the bulk already on a femtosecond time scale. Implications for the adsorbate dynamics will be discussed.

  14. Spin-polarized hydrogen adsorbed on the surface of superfluid {sup 4}He

    SciTech Connect

    Marín, J. M.; Boronat, J.; Markić, L. Vranješ

    2013-12-14

    The experimental realization of a thin layer of spin-polarized hydrogen H↓ adsorbed on top of the surface of superfluid {sup 4}He provides one of the best examples of a stable, nearly two-dimensional (2D) quantum Bose gas. We report a theoretical study of this system using quantum Monte Carlo methods in the limit of zero temperature. Using the full Hamiltonian of the system, composed of a superfluid {sup 4}He slab and the adsorbed H↓ layer, we calculate the main properties of its ground state using accurate models for the pair interatomic potentials. Comparing the results for the layer with the ones obtained for a strictly 2D setup, we analyze the departure from the 2D character when the density increases. Only when the coverage is rather small the use of a purely 2D model is justified. The condensate fraction of the layer is significantly larger than in 2D at the same surface density, being as large as 60% at the largest coverage studied.

  15. Classical dynamics of adsorbate-surface systems: Application to nonthermal desorption

    NASA Astrophysics Data System (ADS)

    Dzegilenko, Fedor; Herbst, Eric

    1994-06-01

    The classical trajectory approach has been used to study the nonthermal desorption of CO from a variety of model surfaces to which it is weakly adsorbed. In addition to three degrees of freedom for the CO adsorbate (bond stretching, physisorption, libration), a significant number of lattice degrees of freedom have been included using the generalized Langevin approximation. Nonthermal amounts of energy have been put into both the CO stretching and librational modes at t=0. We find that for initial values of the stretching quantum number vstr=0-10, desorption does not take place at all within 12.5 ps unless there is also significant librational excitation. The detailed mechanism by which librational energy causes desorption is discussed. The role of the surface is also explored; we find that the probability of desorption is a nonmonotonic function of the Debye frequency of the solid in the range 28-915 cm-1, and is larger for lattices with either ``high'' or ``low'' Debye frequencies than for lattices with ``intermediate'' Debye frequencies. This result is partially explained in terms of resonances between low frequency libration and physisorption modes and high frequency phonon modes.

  16. Validation of thermodesorption method for analysis of semi-volatile organic compounds adsorbed on wafer surface.

    PubMed

    Hayeck, Nathalie; Gligorovski, Sasho; Poulet, Irène; Wortham, Henri

    2014-05-01

    To prevent the degradation of the device characteristics it is important to detect the organic contaminants adsorbed on the wafers. In this respect, a reliable qualitative and quantitative analytical method for analysis of semi-volatile organic compounds which can adsorb on wafer surfaces is of paramount importance. Here, we present a new analytical method based on Wafer Outgassing System (WOS) coupled to Automated Thermal Desorber-Gas chromatography-Mass spectrometry (ATD-GC-MS) to identify and quantify volatile and semi-volatile organic compounds from 6", 8" and 12" wafers. WOS technique allows the desorption of organic compounds from one side of the wafers. This method was tested on three important airborne contaminants in cleanroom i.e. tris-(2-chloroethyl) phosphate (TCEP), tris-(2-chloroisopropyl) phosphate (TCPP) and diethyl phthalate (DEP). In addition, we validated this method for the analysis and quantification of DEP, TCEP and TCPP and we estimated the backside organic contamination which may contribute to the front side of the contaminated wafers. We are demonstrating that WOS/ATD-GC-MS is a suitable and highly efficient technique for desorption and quantitative analysis of organophosphorous compounds and phthalate ester which could be found on the wafer surface.

  17. Assembly and function of the tRNA-modifying GTPase MnmE adsorbed to surface functionalized bioactive glass.

    PubMed

    Gruian, C; Boehme, S; Simon, S; Steinhoff, H-J; Klare, J P

    2014-05-28

    Protein adsorption onto solid surfaces is a common phenomenon in tissue engineering related applications, and considerable progress was achieved in this field. However, there are still unanswered questions or contradictory opinions concerning details of the protein's structure, conformational changes, or aggregation once adsorbed onto solid surfaces. Electron paramagnetic resonance (EPR) spectroscopy and site-directed spin labeling (SDSL) were employed in this work to investigate the conformational changes and dynamics of the tRNA-modifying dimeric protein MnmE from E. coli, an ortholog of the human GTPBP3, upon adsorption on bioactive glass mimicking the composition of the classical 45S5 Bioglass. In addition, prior to protein attachment, the bioactive glass surface was modified with the protein coupling agent glutaraldehyde. Continuous wave EPR spectra of different spin labeled MnmE mutants were recorded to assess the dynamics of the attached spin labels before and after protein adsorption. The area of the continuous wave (cw)-EPR absorption spectrum was further used to determine the amount of the attached protein. Double electron-electron resonance (DEER) experiments were conducted to measure distances between the spin labels before and after adsorption. The results revealed that the contact regions between MnmE and the bioactive glass surface are located at the G domains and at the N-terminal domains. The low modulation depths of all DEER time traces recorded for the adsorbed single MnmE mutants, corroborated with the DEER measurements performed on MnmE double mutants, show that the adsorption process leads to dissociation of the dimer and alters the tertiary structure of MnmE, thereby abolishing its functionality. However, glutaraldehyde reduces the aggressiveness of the adsorption process and improves the stability of the protein attachment.

  18. Molecular resonant dissociation of surface-adsorbed molecules by plasmonic nanoscissors

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenglong; Sheng, Shaoxiang; Zheng, Hairong; Xu, Hongxing; Sun, Mengtao

    2014-04-01

    The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis, photosynthesis and the degradation of plastic, it is hard to break individual molecular bonds for those molecules adsorbed on the surface because of the weak light-absorption in molecules and the redistribution of the resulting vibrational energy both inside the molecule and to its surrounding environment. Here we show how to overcome these obstacles with a plasmonic hot-electron mediated process and demonstrate a new method that allows the sensitive control of resonant dissociation of surface-adsorbed molecules by `plasmonic' scissors. To that end, we used a high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) setup to dissociate resonantly excited NC2H6 fragments from Malachite green. The surface plasmons (SPs) excited at the sharp metal tip not only enhance the local electric field to harvest the light incident from the laser, but crucially supply `hot electrons' whose energy can be transferred to individual bonds. These processes are resonant Raman, which result in some active chemical bonds and then weaken these bonds, followed by dumping in lots of indiscriminant energy and breaking the weakest bond. The method allows for sensitive control of both the rate and probability of dissociation through their dependence on the density of hot electrons, which can be manipulated by tuning the laser intensity or tunneling current/bias voltage in the HV-TERS setup, respectively. The concepts of plasmonic scissors open up new versatile avenues for the deep understanding of in situ surface-catalyzed chemistry.The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis

  19. Using Microcontact Printing as a Novel Method for Patterned Dyeing of Surface-adsorbed DNA

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    We use microcontact printing (MCP)^1 to stain individual DNA molecules adsorbed and combed onto a polymer-coated silicon surface. Polydimethylsiloxane (PDMS) stamps with micron-sized features have been used to selectively stain lambda DNA molecules with SyBr Gold dye. DNA was deposited out of dilute solution onto polymethylmethacrylate (PMMA) layers, 70nm thick, spun-coated on Si wafers, producing linearly stretched and aligned molecules. The stamps were soaked in dye solutions for one minute, followed by wiping of excess solution with a swap. The stamp was pressed onto the surface, varying the pressure and time of application (typically 5-10 minutes) to control the staining. The DNA molecules were imaged with a fluorescence microscope equipped with a cooled CCD camera. Single molecules of DNA were successfully dyed and imaged with stamps having a grating pattern either parallel to or perpendicular to the DNA orientation. Supported by NSF-DMR MRSEC program.

  20. Ozonolysis of surface adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2013-07-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (±0.8) × 10-7 and 2 (±1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ>300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(±1) but had no effect on ozonolysis of the alkene side-chain.

  1. Adsorption of aliphatic, alicyclic, and aromatic hydrocarbons on poly(ethylvinylbenzene-divinylbenzene) adsorbent at from effective zero to finite adsorbate surface coverage

    SciTech Connect

    Djordjevic, N.M.; Laub, R.J.; Kopecni, M.M.; Milonjic, S.K.

    1986-06-01

    The solid/gas partition coefficients, K/sub s/, and related thermodynamic properties of a number of hydrocarbon adsorbates at effective zero surface coverage on commercial samples of the title adsorbent, Porapak Q, were measured over the temperature range 293-443 K. The enthalpies of adsorption derived from the averaged absolute K/sub s/ gave incremental ..delta..H/sub s//sup 0/ of -7.5 kJ mol/sup -1/ for aliphatic and alicyclic -CH/sub 2/-, as well as aromatic -CH=, and -12 kJ mol/sup -1/ for -CH/sub 3/, while the differential entropies calculated in terms of translational motions were found to predict correctly the trends observed in the experimental ..delta..S/sub s//sup 0/. The technique of elution by characteristic point (ECP) was then used to derive the finite concentration adsorption isotherms and isosteric heats of adsorption of n-hexane, n-heptane, cyclohexane, benzene, carbon tetrachloride, and acetone at fractional adsorbate pressures, p/p/sup 0/, of no greater than 10/sup -2/ on a particular sample of the title absorbent at 20/sup 0/ intervals over the temperature range 413-493 K.

  2. Benzene derivatives adsorbed to the Ag(111) surface: Binding sites and electronic structure

    SciTech Connect

    Miller, Daniel P.; Tymińska, Nina; Zurek, Eva; Simpson, Scott

    2015-03-14

    Dispersion corrected Density Functional Theory calculations were employed to study the adsorption of benzenes derivatized with functional groups encompassing a large region of the activated/deactivated spectrum to the Ag(111) surface. Benzenes substituted with weak activating or deactivating groups, such as methyl and fluoro, do not have a strong preference for adsorbing to a particular site on the substrate, with the corrugations in the potential energy surface being similar to those of benzene. Strong activating (N(CH{sub 3}){sub 2}) and deactivating (NO{sub 2}) groups, on the other hand, possess a distinct site preference. The nitrogen in the former prefers to lie above a silver atom (top site), but in the latter a hollow hexagonal-closed-packed (H{sub hcp}) site of the Ag(111) surface is favored instead. Benzenes derivatized with classic activating groups donate electron density from their highest occupied molecular orbital to the surface, and those functionalized with deactivating groups withdraw electron density from the surface into orbitals that are unoccupied in the gas phase. For benzenes functionalized with two substituents, the groups that are strongly activating or deactivating control the site preference and the other groups assume sites that are, to a large degree, dictated by their positions on the benzene ring. The relative stabilities of the ortho, meta, and para positional isomers of disubstituted benzenes can, in some cases, be modified by adsorption to the surface.

  3. β-Cristobalite (001) surface as 4-formaminoantipyrine adsorbent: First principle study of the effect on adsorption of surface modification.

    PubMed

    Simonetti, S; Compañy, A Díaz; Brizuela, G; Juan, A

    2016-12-01

    Silica based materials find applications as excipients and particularly as drug delivery agents for pharmaceutical drugs. Their performance can be crucially affected by surface treatments, as it can modify the adsorption (and release) of these formulations. The role of surface modification on the features of 4-formaminoantipyrine (FAA) adsorbed on β-cristobalite (001) surface is studied by means of simulations based on the Density Functional Theory (DFT). Starting from the results of FAA in interaction with a dehydroxylated surface; a fully hydroxylated surface and a functionalized surface with benzalkonium chloride (BC) surfactant have been added to study the configurational landscape. Calculations suggest that the trend for FAA preferential adsorption on silica surfaces is: dehydroxylated>hydroxylated>BC-functionalized. The potential for hydrogen bonding causes the main contribution to the bonding while dispersion forces present an additional contribution independently of whether the drug is hydrogen-bonded or BC-bonded to the surface. Adsorption takes mainly place through nitrogen atoms in the heterocyclic ring, the carbonyl and amine functional groups. Associated mode's shifts and concurrent changes in bond length are also observed showing accordance between electronic and geometrical structure results. BC surfactant reduces the number of formed H-bonds and lowers the attractive molecule-surface interaction being it useful to prevent particle agglomeration and could favor drug release in therapies that requires faster but controlled delivery.

  4. Surface enhanced Raman scattering of pyridine adsorbed on Au@Pd core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Yang, Zhilin; Li, Yan; Li, Zhipeng; Wu, Deyin; Kang, Junyong; Xu, Hongxing; Sun, Mengtao

    2009-06-01

    Surface enhanced Raman scattering (SERS) of pyridine adsorbed on Au@Pd core/shell nanoparticles has been investigated theoretically with quantum chemical method, generalized Mie theory and three-dimensional finite-difference time domain (3D-FDTD) method. We first studied the influence of the coated Pd on the electronic structure of Au nanoparticle, and compared the electronic structure of Au20 cluster with that of Au10Pd10 (core/shell) cluster. Second, we studied SERS spectroscopy of pyridine on Au@Pd core/shell nanoparticles, which revealed the rate of static chemical enhancement and electromagnetic enhancement in the experimental reports. Third, the influence of the Pd shell thickness to the optical absorption of Au@Pd core/shell nanoparticles was investigated with generalized Mie theory. Fourth, we studied the influence of the shell thickness to the local electric field enhancement with 3D-FDTD method. The theoretical results reveal that the static chemical enhancement and electromagnetic enhancement are in the order of 10 and 103, respectively. These theoretical studies promote the deeper understanding of the electronic structure and optical absorption properties of Au@Pd, and the mechanisms for SERS of molecule adsorbed on Au@Pd.

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

    SciTech Connect

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

    2015-12-21

    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{sub 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.

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

    PubMed

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

    2015-12-21

    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 4pz 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.

  7. Impacts of surface adsorbed catechol on tropospheric aerosol surrogates: heterogeneous ozonolysis and its effects on water uptake.

    PubMed

    Woodill, Laurie A; O'Neill, Erinn M; Hinrichs, Ryan Z

    2013-07-11

    Surface adsorbed organics are ubiquitous components of inorganic tropospheric aerosols and have the potential to alter aerosol chemical and physical properties. To assess the impact of adsorbed organics on water uptake by inorganic substrates, we used diffuse reflectance infrared spectroscopy to compared water adsorption isotherms for uncoated NaCl and α-Al2O3 samples, samples containing a monolayer of adsorbed catechol, and adsorbed catechol samples following ozonolysis. Adsorption of gaseous catechol on to the inorganic substrates produced vibrational features indicating physisorption on NaCl and displacement of surface hydroxyl groups forming binuclear bidentate catecholate on α-Al2O3, with surface concentrations of 2-3 × 10(18) molecules m(-2). Subsequent heterogeneous ozonolysis produced muconic acid at a rate 4-5 times faster on NaCl compared to α-Al2O3, with predicted atmospheric lifetimes of 4.3 and 18 h, respectively, assuming a tropospheric ozone concentration of 40 ppb. Water adsorption isotherms for all NaCl samples were indistinguishable within experimental uncertainty, indicating that these organic monolayers had negligible impact on coadsorbed water surface concentrations for these systems. α-Al2O3-catechol samples exhibited dramatically less water uptake compared to uncoated α-Al2O3, while oxidation of surface adsorbed catechol had no effect on the extent of water uptake. For both substrates, adsorbed organics increased the relative abundance of "ice-like" versus "liquid-like" water, with the effect larger for catechol than oxidized ozonolysis products. These results highlight the importance of aerosol substrate in understanding the heterogeneous ozonolysis of adsorbed polyphenols and suggest such coatings may impair ice nucleation by aluminosilicate mineral aerosol.

  8. Investigation of interparticle forces in natural waters: effects of adsorbed humic acids on iron oxide and alumina surface properties.

    PubMed

    Sander, Sylvia; Mosley, Luke M; Hunter, Keith A

    2004-09-15

    The nature of interparticle forces acting on colloid particle surfaces with adsorbed surface films of the internationally used humic acid standard material, Suwannee River Humic Acid (SHA), has been investigated using an atomic force microscope (AFM). Two particle surfaces were used, alumina and a hydrous iron oxide film coated onto silica particles. Adsorbed SHA dominated the interactive forces for both surface types when present. At low ionic strength and pH > 4, the force curves were dominated by electrostatic repulsion of the electrical double layers, with the extent of repulsion decreasing as electrolyte (NaCl) concentration increased, scaling with the Debye length (kappa(-1)) of the electrolyte according to classical theory. At pH approximately 4, electrostatic forces were largely absent, indicating almost complete protonation of carboxylic acid (-COOH) functional groups on the adsorbed SHA. Under these conditions and also at high electrolyte concentration ([NaCl] > 0.1 M), the absence of electrostatic forces allowed observation of repulsion forces arising from steric interaction of adsorbed SHA as the oxide surfaces approached closely to each other (separation < 10 nm). This steric barrier shrank as electrolyte concentration increased, implying tighter coiling of the adsorbed SHA molecules. In addition, adhesive bridging between surfaces was observed only in the presence of SHA films, implying a strong energy barrier to spontaneous detachment of the surfaces from each other once joined. This adhesion was especially strong in the presence of Ca2+ which appears to bridge SHA layers on each surface. Overall, our results show that SHA is a good model for the NOM adsorbed on colloids.

  9. Surface packing determines the redox potential shift of cytochrome c adsorbed on gold.

    PubMed

    Zanetti-Polzi, Laura; Daidone, Isabella; Bortolotti, Carlo Augusto; Corni, Stefano

    2014-09-17

    Thermodynamic and dynamic properties of iso-1-cytochrome c covalently bound to a bare gold surface are here investigated by large scale atomistic simulations. The reduction potential of the protein for low and high surface concentrations is calculated showing a good agreement with experimental estimates. The origin of the dependence of the reduction potential on the surface concentration is investigated and is demonstrated to stem from the changing polarizability of the environment surrounding the protein, a mechanism reminiscent of crowding effects. Moreover, structural analyses are performed revealing relevant changes induced by the presence of the electrode on the dynamic properties of cytochrome c. In particular, one of the two cavities previously identified on the protein surface [Bortolotti et al. J. Am. Chem. Soc., 2012, 134, 13670], and that reversibly open in cytochrome c freely diffusing in solution, is found to be deformed when the protein is adsorbed on gold. This modification exemplifies a mechanism that potentially leads to changes in the protein properties by surface-induced modification of its dynamical behavior.

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

    PubMed

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

    2011-09-01

    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 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.

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

    NASA Astrophysics Data System (ADS)

    Corrales Ureña, Yendry Regina; Lisboa-Filho, Paulo Noronha; Szardenings, Michael; Gätjen, Linda; Noeske, Paul-Ludwig Michael; Rischka, Klaus

    2016-11-01

    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 or adhesives, but also their adhesion in contact with hardened polymers.

  12. Characterization of molecular and atomic species adsorbed on ferroelectric and semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Bharath, Satyaveda Chavi

    In order to clarify the mechanisms behind the adsorption of atomic and molecular species adsorbed on ferroelectric surfaces, single crystalline lithium niobate (LiNbO3, LN), 'Z-cut' along the (0001) plane, has been prepared, characterized and subsequently exposed to molecular and atomic species. 4-n-octyl-4'-cyanobiphenyl (8CB) liquid crystal was chosen as a polar molecule for our model system for this study. Low-energy electron diffraction (LEED), atomic force microscopy (AFM), surface contact angles (CA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface of LN as well as the nature of the liquid crystal films grown on the surface. Atomically flat LN surfaces were prepared as a support for monolayer thick, 8CB molecular domains. Also, for the purpose of gaining a fundamental understanding of low coverage interactions of metal atoms on ferroelectric surfaces, we choose to deposit gold onto the LN surface. These gold atomic layers were grown under UHV conditions and characterized. Understanding anchoring mechanisms and thin film organization for LC molecules and metal atoms on uniformly poled surfaces allows for a fuller appreciation of how molecular deposition of other polarizable molecules on patterned poled LN surfaces would occur as well as yielding greater insight on the atomic characteristics of metal on ferroelectric interfaces. Also, to reveal the mechanisms involved in the adsorption of organic aromatic molecules on high-index Si surfaces, thiophene (C4H 4S) and pyrrole (C4H5N) molecules were dosed on prepared Si(5 5 12)-2x1 surfaces as our experimental system. The Si(5 5 12) surface was prepared to produce a 2x1 reconstruction after which molecules were dosed at low exposure to observe the preferred adsorption sites on the surface. All surface preparation and experiments were performed in UHV and measurements of the surface before and after deposition were performed using scanning tunneling microscopy (STM). Fundamental

  13. Determination of surface properties of iron hydroxide-coated alumina adsorbent prepared for removal of arsenic from drinking water.

    PubMed

    Hlavay, József; Polyák, Klára

    2005-04-01

    A novel type adsorbent was prepared by in situ precipitation of Fe(OH)3 on the surface of activated Al2O3 as a support material. The iron content of the adsorbent was 0.31+/-0.003% m/m (56.1 mmol/g); its mechanical and chemical stability proved to be appropriate in solutions. The total capacity of the adsorbent was 0.12 mmol/g, and the pH of zero point of charge, pH(zpc) = 6.9+/-0.3. Depending on the pH of solutions, the adsorbent can be used for binding of both anions and cations, if pH(eq) < pH(zpc) anions are sorbed on the surface of adsorbent (S) through [SOH2+] and [SOH] groups. A graphical method was used for the determination of pH(iep) (isoelectric points) of the adsorbent and values of pH(iep) = 6.1+/-0.3 for As(III) and pH(iep) = 8.0+/-0.3 for As(V) ions were found. The amount of surface charged groups (Q) was about zero within the a pH range of 6.5-8.6, due to the practically neutral surface formed on the adsorption of As(V) ions. At acidic pH (pH 4.7), Q = 0.19 mol/kg was obtained. The adsorption of arsenate and arsenite ions from solutions of 0.1-0.4 mmol/L was represented by Langmuir-type isotherms. A great advantage of the adsorbent is that it can be used in adsorption columns, and low waste technology for removal of arsenic from drinking water can be developed.

  14. Pseudo Order Kinetics Model to Predict the Adsorption Interaction of Corn-Stalk Adsorbent Surface with Metal Ion Adsorbate Cu (II) and Fe (II)

    NASA Astrophysics Data System (ADS)

    Haryanto, B.; Singh, W. B.; Barus, E. S.; Ridho, A.; Rawa, M. R.

    2017-01-01

    The adsorption process using cornstalk as adsorbent was used to remove the single metal ion such as copper ion and cadmium ion. The adsorption kinetics of each contaminant then used to predict the interaction type of metal ion on surface of corn stalk by calculating pseudo order 1st and 2nd. The identification type as chemically or physically interaction was predicted from the quality of r2 by plotting the adsorption capacity (q) and time (t). The r2 were 0.01 and 0.99 for pseudo order 1st and 2nd respectively for Fe (II). The r2 were 0.26 and 0.999 for pseudo order 1st and 2nd respectively for Cu (II). The result of adsorption interaction of metal ion and surface function of corn stalk is chemical type. SEM/EDX confirmed the Cu2+ presence on cornstalk surface.

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

    SciTech Connect

    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.

  16. Self-avoiding walks adsorbed at a surface and pulled at their mid-point

    NASA Astrophysics Data System (ADS)

    Janse van Rensburg, E. J.; Whittington, S. G.

    2017-02-01

    We consider a self-avoiding walk on the d-dimensional hypercubic lattice, terminally attached to an impenetrable hyperplane at which it can adsorb. When a force is applied the walk can be pulled off the surface and we consider the situation where the force is applied at the middle vertex of the walk. We show that the temperature dependence of the critical force required for desorption differs from the corresponding value when the force is applied at the end-point of the walk. This is of interest in single molecule pulling experiments since it shows that the required force can depend on where the force is applied. We also briefly consider the situation when the force is applied at other interior vertices of the walk.

  17. Redox kinetics of adriamycin adsorbed on the surface of graphite and mercury electrodes.

    PubMed

    Komorsky-Lovrić, Sebojka

    2006-09-01

    Kinetics of the surface redox reactions of adriamycin (doxorubicin hydrochloride) adsorbed on paraffin-impregnated graphite electrode (PIGE) and on mercury electrode is measured by square-wave voltammetry. In 0.9 mol/L KNO3 buffered to pH 4.65, the standard electrode reaction rate constants of the first quinone/hydroquinone redox couple (see Scheme 2) on PIGE and mercury are k(s1)=49+/-12 s(-1) and k(s1)=147+/-36 s(-1), respectively. Under the same conditions, the standard rate constant of the second redox couple on the PIGE is smaller than 4 s(-1) and the electron transfer coefficient of the reduction is alpha2=0.35.

  18. Structural Studies of Clean and Adsorbate-Covered Fcc Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Statiris, Panayiotis Athanasiou

    We have used medium energy ion scattering (MEIS) to study the structural and vibrational properties of the clean metal surfaces of Ni(110) and Ag(111), the structural changes induced by the presence of small amounts ( {~}1 atomic layer) of heteroatoms on the Ni(001) and Ni(110) surfaces (Cs, K, K and CO on Ni(110) and Au on Ni(001)) as well as the arrangement of the heteroatoms on the surface. The thesis consists of five chapters two of which serve as an introduction and provide general information about metal surfaces and medium energy ion scattering (chapters 1 and 2) and three chapters (3, 4, 5) in which the experimental results are being presented, and structural models are proposed for the surfaces studied. The purpose of the material contained in chapter one is to familiarize the reader with the general concepts, and provide an overview of the progress (experimental and theoretical) in the field of clean and adsorbate covered metal surfaces. The second chapter contains an extensive discussion about the principles and applications of medium energy ion scattering. A study of the structure of the clean Ni(001) surface and the K/Ni(110) and K/CO/Ni(110) surfaces is presented in chapter 3. Both the K/Ni(110) and K/CO/Ni(110) exhibit the missing row reconstruction. The change in the surface unit cell observed upon adsorption of CO atoms on the K/Ni(110) surface observed with low energy electron diffraction is due to the ordering of the CO molecules. The growth and structure of thin Au films (0.35 -3 layers) deposited on the Ni(001) surface is the subject of chapter 4. Au forms an almost incommensurate overlayer with a c(2 times 8) unit cell whose structure resembles that of fcc Au(111). The Au atoms exhibit unusually high vibrational amplitudes, indicating the presence of a soft phonon mode as predicted by theoretical work. The growth mode resembles the Stranski-Krastanov mode without exactly following it. The temperature dependence of the vibrational amplitudes

  19. Helium diffraction from adsorbate-covered surfaces: A study of the O-Ni(001) system

    NASA Astrophysics Data System (ADS)

    Batra, Inder P.; Barker, J. A.

    1984-05-01

    Elastic helium-atom-surface scattering is currently being used to obtain important structural information from adsorbate-covered surfaces. Since our earlier work on helium diffraction from p(2×2) and c(2×2) phases of oxygen on Ni(001) there have been three new developments. These are (i) the suggestion by Rieder of a prolate charge distribution on oxygen, (ii) the pseudobridge site proposal of Demuth et al., and (iii) the self-consistent calculation of the helium-surface interaction potential due to Lang and Nørskov. In this paper we present results for a wide range of calculational parameters for the c(2×2) phase of oxygen on Ni(001) and comment on the above developments. Specifically, based on the results in (iii), we are able to explore the implications of the use of the Esbjerg-Nørskov-Lang relation with and without helium averaged surface-charge density. We conclude that the prolate charge distribution produces a shape function in better agreement with experiment. Changes in corrugation coefficients introduced by shifting to the pseudobridge site from the centered site are noted to be small.

  20. Positron States at Li- and O-adsorbed Fe(001) Ferromagnetic Surfaces Studied by Two-Component Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Hagiwara, Satoshi; Watanabe, Kazuyuki

    2016-11-01

    The positron states for Li- and O-adsorbed Fe(001) ferromagnetic surfaces are studied by using two-component density functional theory. Positron surface lifetimes and positron binding energies are found to be sensitive to changes in the surface structure and the dipole barrier induced by adatoms, which can be understood by the positron density distribution and surface potential. Spin-dependent positron lifetime fractions are in excellent agreement with spin-polarization fractions at the topmost surface, because the localized positrons at the surface are sensitive to the surface magnetic state. Therefore, the present results show that spin-polarized positron annihilation spectroscopy can extract the outermost surface magnetic state.

  1. Effect of Polarity of Activated Carbon Surface, Solvent and Adsorbate on Adsorption of Aromatic Compounds from Liquid Phase.

    PubMed

    Goto, Tatsuru; Amano, Yoshimasa; Machida, Motoi; Imazeki, Fumio

    2015-01-01

    In this study, introduction of acidic functional groups onto a carbon surface and their removal were carried out through two oxidation methods and outgassing to investigate the adsorption mechanism of aromatic compounds which have different polarity (benzene and nitrobenzene). Adsorption experiments for these aromatics in aqueous solution and n-hexane solution were conducted in order to obtain the adsorption isotherms for commercial activated carbon (BAC) as a starting material, its two types of oxidized BAC samples (OXs), and their outgassed samples at 900 °C (OGs). Adsorption and desorption kinetics of nitrobenzene for the BAC, OXs and OGs in aqueous solution were also examined. The results showed that the adsorption of benzene molecules was significantly hindered by abundant acidic functional groups in aqueous solution, whereas the adsorbed amount of nitrobenzene on OXs gradually increased as the solution concentration increased, indicating that nitrobenzene can adsorb favourably on a hydrophilic surface due to its high dipole moment, in contrast to benzene. In n-hexane solution, it was difficult for benzene to adsorb on any sample owing to the high affinity between benzene and n-hexane solvent. On the other hand, adsorbed amounts of nitrobenzene on OXs were larger than those of OGs in n-hexane solution, implying that nitrobenzene can adsorb two adsorption sites, graphene layers and surface acidic functional groups. The observed adsorption and desorption rate constants of nitrobenzene on the OXs were lower than those on the BAC due to disturbance of diffusion by the acidic functional groups.

  2. Attenuated total reflectance Fourier-transform infrared spectroscopy of carboxylic acids adsorbed onto mineral surfaces

    NASA Astrophysics Data System (ADS)

    Kubicki, J. D.; Schroeter, L. M.; Itoh, M. J.; Nguyen, B. N.; Apitz, S. E.

    1999-09-01

    A suite of naturally-occurring carboxylic acids (acetic, oxalic, citric, benzoic, salicylic and phthalic) and their corresponding sodium salts were adsorbed onto a set of common mineral substrates (quartz, albite, illite, kaolinite and montmorillonite) in batch slurry experiments. Solution pH's of approximately 3 and 6 were used to examine the effects of pH on sorption mechanisms. Attenuated total reflectance Fourier-transform infrared (ATR FTIR) spectroscopy was employed to obtain vibrational frequencies of the organic ligands on the mineral surfaces and in solution. UV/visible spectroscopy on supernatant solutions was also employed to confirm that adsorption from solution had taken place for benzoic, salicylic and phthalic acids. Molecular orbital calculations were used to model possible surface complexes and interpret the experimental spectra. In general, the tectosilicates, quartz and albite feldspar, did not chemisorb (i.e., strong, inner-sphere adsorption) the carboxylate anions in sufficient amounts to produce infrared spectra of the organics after rinsing in distilled water. The clays (illite, kaolinite and montmorillonite) each exhibited similar ATR FTIR spectra. However, the illite sample used in this study reacted to form strong surface and aqueous complexes with salicylic acid before being treated to remove free Fe-hydroxides. Chemisorption of carboxylic acids onto clays is shown to be limited without the presence of Fe-hydroxides within the clay matrix.

  3. Infrared-Laser Excitation of the Internal Vibrational Mode of a Diatomic Molecule Adsorbed on a Metal Surface.

    DTIC Science & Technology

    1986-11-01

    Excitation of the Internal Vibrational Mode of a Diatomic Molecule Adsorbed on a Metal Surface m by ’ Andre Peremans, Jacques Darville , Jean-Marie...Andre Peremans, Jacques Darville , Jean-Marie Gilles and Thomas F. George 13. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Yr. Mo.. Dayl As...ON A METAL SURFACE h Andr& Peremans , Jacques Darville and Jean-Marie Gilles _ _ _ _ Laboratoire de Spectroscopie Mol6culaire de Surface Accesnion

  4. Theory of surface light scattering from a fluid-fluid interface with adsorbed polymeric surfactants

    NASA Astrophysics Data System (ADS)

    Buzza, D. M. A.; Jones, J. L.; McLeish, T. C. B.; Richards, R. W.

    1998-09-01

    We present a microscopic theory for the interfacial rheology of a fluid-fluid interface with adsorbed surfactant and calculate the effect of this on surface light scattering from the interface. We model the head and tail groups of the surfactant as polymer chains, a description that becomes increasingly accurate for large molecular weight surfactants, i.e., polymeric surfactants. Assuming high surface concentrations so that we have a double-sided polymer brush monolayer, we derive microscopic scaling expressions for the surface viscoelastic constants using the Alexander-deGennes model. Our results for the surface elastic constants agree with those in the literature, while the results for the viscous constants are new. We find that four elastic constants, i.e., γ (surface tension), ɛ (dilational elasticity), κ (bending modulus), λ (coupling constant), and three viscous constants, i.e., ɛ',κ',λ' (the viscous counterparts of ɛ, κ, and λ, respectively) are required for a general description of interfacial viscoelasticity (neglecting in-plane shear). In contrast to current phenomenological models, we find (1) there is no viscous counterpart to γ, i.e., γ'≡0; (2) there are two additional complex surface constants (i.e., λ+iωλ' and κ+iωκ') due to the finite thickness of the monolayer. Excellent agreement is found comparing our microscopic theory with measurements on diblock copolymer monolayers. We further derive the dispersion relation governing surface hydrodynamic modes and the power spectrum for surface quasielastic light scattering (SQELS) for a general interface parameterized by all the surface viscoelastic constants. Limiting results are presented for (1) liquid-air interfaces; (2) liquid-liquid interfaces with ultralow γ. The significant contribution of κ in the latter case opens up the possibility for a direct measurement of κ using SQELS for polymeric surfactant monolayers. Finally, we show that the coupling constant λ can lead to

  5. Mechanisms for aqueous photolysis of adsorbed benzoate, oxalate, and succinate on iron oxyhydroxide (goethite) surfaces

    USGS Publications Warehouse

    Cunningham, K.M.

    1988-01-01

    Photolysis of carboxylate anions adsorbed onto highly crystalline goethite (??-FeOOH) with 300-400-nm light produces Fe2+(aq) and ??OH from surface and solution redox reactions. The production of Fe2+(aq) and ??OH was studied in N2-purged and aerated aqueous suspensions, respectively, of goethite containing equimolar (10-3 M) concentrations of oxalate and benzoate (ob + g), succinate and benzoate (sb + g), benzoate alone (b + g), and goethite alone (g). The hydroxyl radical was measured by fluorescence analysis of salicylate formed in a reaction between benzoate and ??OH. Fe2+(aq) was determined colorimetrically. A proposed reaction mechanism includes the photoexcitation of Fe(III) surface complexes with OH-, HCO3-, and RCOO- ligands to form Fe2+(aq) and corresponding ligand radicals. Additional ??OH is made by the O2 oxidation of Fe2+(aq) (Haber-Weiss mechanism). Comparison of Fe2+(aq) and ??OH yields permitted an estimate of the relative importance of pathways leading to ??OH.

  6. Surface-enhanced Raman scattering of Ethyl carbamate adsorbed on Ag20 cluster: Enhancement mechanism

    NASA Astrophysics Data System (ADS)

    Du, Junmei; Wang, Hongyan; Wang, Hui; Chen, Yuanzheng; Guo, Chunsheng; Gan, Liyong; Du, Muying

    2017-03-01

    The normal and surface-enhanced Raman scattering of EC are studied by using the M06-2X functional. Different contributions to Raman enhancements of EC adsorbed on Ag20 cluster are analyzed in detail to explore the enhancement mechanism. The adsorption of EC on Ag20 cluster involves the static chemical enhancement with enhancements factor (EF) of 10 by forming a new EC-Ag20 complex. The charge-transfer enhancement with EF of 104 is found when a 352 nm wavelength, corresponding to the absorption maximum of EC-Ag20 complex, is taken as an incident light. The electromagnetic enhancement EF of 3.6 × 106 due to the localized surface plasmon resonance (LSPR) of Ag nanosphere at the same excitation wavelength are acquired by the discrete dipole approximation (DDA) method. The combined effect of the chemical and electromagnetic enhancement results in the total relative enhancements factor up to 3.6 × 1010. The enhancement mechanisms are successfully explained by the combination of ab initio calculation and discrete dipole appropriation method.

  7. Surface-enhanced raman spectra and molecular orientation of phthalazine adsorbed on a silver electrode

    NASA Astrophysics Data System (ADS)

    Takahashi, Machiko; Fujita, Masato; Ito, Masatoki

    1984-08-01

    SERS from phthalazine adsorbed on an Ag electrode was investigated under several conditions of applied voltage and solution concentration. Spectral assignments of the Raman bands were successfully performed and two differently oriented adsorbates, i.e. flat and end-on species, were identified. The contribution of the image field to the SERS intensity was considerable.

  8. In situ UV-visible reflection absorption wavelength modulation spectroscopy of species irreversibly adsorbed on electrode surfaces

    SciTech Connect

    Kim, Sunghyun; Scherson, D.A. )

    1992-12-15

    A method is herein described for the in situ detection of species adsorbed on electrode surfaces which employs a vibrating grating to modulate the wavelength of the incident light. This technique denoted as reflection absorption wavelength modulation spectroscopy (RAWMS) has made it possible to obtain at a fixed electrode potential normalized, differential UV-visible spectra of a single, irreversibly adsorbed monolayer of cobalt tetrasulfonated phthalocyanine (Co[sup II]TsPc) on the basal plane of highly oriented pyrolytic graphite (HOPG(bp)) and of methylene blue (MB) on graphite. The (wavelength) integrated difference RAWMS spectra for these adsorbed species were remarkably similar to those observed for the same compounds in aqueous solutions when present in the monomeric form. Complementary wavelength modulation experiments involving a conventional transmission geometry have shown that the instrument involved in the in situ RAWMS measurements is capable of resolving absorbance changes on the order of 0.002 units. 20 refs.

  9. Outer-sphere Pb(II) adsorbed at specific surface sites on single crystal α-alumina

    USGS Publications Warehouse

    Bargar, John R.; Towle, Steven N.; Brown, Gordon E.; Parks, George A.

    1996-01-01

    Solvated Pb(II) ions were found to adsorb as structurally well-defined outer-sphere complexes at specific sites on the α-Al2O3 (0001) single crystal surface, as determined by grazing-incidence X-ray absorption fine structure (GI-XAFS) measurements. The XAFS results suggest that the distance between Pb(II) adions and the alumina surface is approximately 4.2 Å. In contrast, Pb(II) adsorbs as more strongly bound inner-sphere complexes on α-Al2O3 (102). The difference in reactivities of the two alumina surfaces has implications for modeling surface complexation reactions of contaminants in natural environments, catalysis, and compositional sector zoning of oxide crystals.

  10. Polarity of an MCM-41 adsorbent surface modified with methyl and phenyl groups based on data from gas chromatography

    NASA Astrophysics Data System (ADS)

    Sukhareva, D. A.; Gus'kov, V. Yu.; Karpov, S. I.; Kudasheva, F. Kh.; Roessner, F.; Borodina, E. V.

    2016-02-01

    The polarity of an MCM-41 adsorbent surface and organosilylated composites based on it with grafted trimethylsilane and dimethylphenylsilane groups is studied via inverse gas chromatography at infinite dilution. The dispersion and specific components of the value proportional to the Helmholtz adsorption energy are calculated, and a comparative analysis of the surface polarity of MCM-41 and its modified analogs relative to the commercially available C-120 silica gel is performed. The electrostatic and donor-acceptor components of the specific Helmholtz adsorption energy are calculated through linear decomposition of the adsorption energy. It is established that MCM-41 is less polar than C-120. The modification of the initial adsorbent surface leads to a reduction in polarity, due mainly to the weakening of induction and orientation interactions. It is concluded that the surfaces of the modified samples retain the ability to form hydrogen bonds.

  11. Effect of Amine Surface Coverage on the Co-Adsorption of CO2 and Water: Spectral Deconvolution of Adsorbed Species.

    PubMed

    Didas, Stephanie A; Sakwa-Novak, Miles A; Foo, Guo Shiou; Sievers, Carsten; Jones, Christopher W

    2014-12-04

    Three primary amine materials functionalized onto mesoporous silica with low, medium, and high surface amine coverages are prepared and evaluated for binary CO2/H2O adsorption under dilute conditions. Enhancement of amine efficiency due to humid adsorption is most pronounced for low surface amine coverage materials. In situ FT-IR spectra of adsorbed CO2 on these materials suggest this enhancement may be associated with the formation of bicarbonate species during adsorption on materials with low surface amine coverage, though such species are not observed on high surface coverage materials. On the materials with the lowest amine loading, bicarbonate is observed on longer time scales of adsorption, but only after spectral contributions from rapidly forming alkylammonium carbamate species are removed. This is the first time that direct evidence for bicarbonate formation, which is known to occur in liquid aqueous amine solutions, has been presented for CO2 adsorption on solid amine adsorbents.

  12. Zeta potential, contact angles, and AFM imaging of protein conformation adsorbed on hybrid nanocomposite surfaces.

    PubMed

    Pinho, Ana C; Piedade, Ana P

    2013-08-28

    The sputtering deposition of gold (Au) and poly(tetrafluoroethylene) (PTFE) was used to prepare a nanocomposite hybrid thin film suitable for protein adsorption while maintaining the native conformation of the biological material. The monolithic PTFE and the nanocomposite PTFE/Au thin films, with Au content up to 1 at %, were co-deposited by r.f. magnetron sputtering using argon as a discharge gas and deposited onto 316L stainless steel substrates, the most commonly used steel in biomaterials. The deposited thin films, before and after bovine serum albumin (BSA) adsorption, were thoroughly characterized with special emphasis on the surface properties/characteristics by atomic force microscopy (AFM), zeta potential, and static and dynamic contact angle measurements, in order to assess the relationship between structure and conformational changes. The influence of a pre-adsorbed peptide (RGD) was also evaluated. The nanotopographic and chemical changes induced by the presence of gold in the nanocomposite thin films enable RGD bonding, which is critical for the maintenance of the BSA native conformation after adsorption.

  13. Evolution of the surface area of a snow layer

    SciTech Connect

    Hanot, L.; Domine, F.

    1999-12-01

    Atmospheric trace gases can partition between the atmosphere and the snow surface. Because snow has a large surface-to-volume ratio, an important interaction potential between ice and atmospheric trace gases exists. Quantifying this partitioning requires the knowledge of the surface area (SA) of snow. Eleven samples were taken from a 50 cm thick snow fall at Col de Porte, near Grenoble (French Alps) between January 20 and February 4, 1998. Fresh snow and 3, 8, and 15-day-old snow were sampled at three different depths. Surface hoar, formed after the fall, was also sampled. Air and surface snow temperature, snow density, and snow fall rate were measured. Snow temperature always remained below freezing. Snow SA was measured using methane adsorption at 77.15 K. Values ranged from 2.25 m{sup 2}/g for fresh snow to 0.25 m{sup 2}/g for surface hoar and surface snow after 15 days. These values are much too high to be explained by the macroscopic aspect of snow crystals, and microstructures such as small rime droplets must have been present. Large decrease in SA with time were observed. The first meter of snowpack had a total surface area of about 50,000 m{sup 2} per m{sup 2} of ground. Reduction in SA will lead to the emission of adsorbed species by the snowpack, with possible considerable increase in atmospheric concentrations.

  14. Electrochemical hydrogenation of a homogeneous nickel complex to form a surface adsorbed hydrogen-evolving species.

    PubMed

    Martin, Daniel J; McCarthy, Brian D; Donley, Carrie L; Dempsey, Jillian L

    2015-03-28

    A Ni(II) complex degrades electrochemically in the presence of acid in acetonitrile to form an electrode adsorbed film that catalytically evolves hydrogen. Comparison with a similar compound permitted investigation of the degradation mechanism.

  15. Friction and transfer of copper, silver, and gold to iron in the presence of various adsorbed surface films

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with the noble metals copper, silver, and gold and two binary alloys of these metals contacting iron in the presence of various adsorbates including, oxygen, methyl mercaptan, and methyl chloride. A pin on disk specimen configuration was used with a load of 100 grams, sliding velocity of 60 mm/min; at 25 C with the surfaces saturated with the adsorbates. Auger emission spectroscopy was used to monitor surface films. Results of the experiments indicate that friction and transfer characteristics are highly specific with respect to both the noble metal and surface film present. With all three metals and films transfer of the noble metal to iron occurred very rapidly. With all metals and films transfer of the noble metal to iron continuously increased with repeated passes except for silver and copper sliding on iron sulfide.

  16. Energy loss in gas-surface dynamics: Electron-hole pair and phonon excitation upon adsorbate relaxation

    NASA Astrophysics Data System (ADS)

    Novko, D.; Blanco-Rey, M.; Juaristi, J. I.; Alducin, M.

    2016-09-01

    We study the effect of electron and phonon degrees of freedom on the relaxation dynamics of adsorption processes in gas-surface systems by using ab initio molecular dynamics that incorporates an electronic friction force (AIMDEF). As representative cases we have chosen three systems with different adsorption energies and adsorbate-to-surface atom mass ratios: H on Pd(1 0 0), N on Ag(1 1 1), and N2 on Fe(1 1 0). We show, through inspection of the total energies and trajectories of the hot adsorbates on the surface, that electron-hole (e-h) pair excitations dominate relaxation of the light gas species, while the phonon channel is dominant for the heavy species. In the latter case e-h pairs become more important at the final thermalization stages.

  17. Light harvesting, energy transfer and electron cycling of a native photosynthetic membrane adsorbed onto a gold surface.

    PubMed

    Magis, Gerhard J; den Hollander, Mart-Jan; Onderwaater, Willem G; Olsen, John D; Hunter, C Neil; Aartsma, Thijs J; Frese, Raoul N

    2010-03-01

    Photosynthetic membranes comprise a network of light harvesting and reaction center pigment-protein complexes responsible for the primary photoconversion reactions: light absorption, energy transfer and electron cycling. The structural organization of membranes of the purple bacterial species Rb. sphaeroides has been elucidated in most detail by means of polarized light spectroscopy and atomic force microscopy. Here we report a functional characterization of native and untreated membranes of the same species adsorbed onto a gold surface. Employing fluorescence confocal spectroscopy and light-induced electrochemistry we show that adsorbed membranes maintain their energy and electron transferring functionality. Gold-adsorbed membranes are shown to generate a steady high photocurrent of 10 microA/cm(2) for several minutes and to maintain activity for up to three days while continuously illuminated. The surface-adsorbed membranes exhibit a remarkable functionality under aerobic conditions, even when exposed to light intensities well above that of direct solar irradiation. The component at the interface of light harvesting and electron cycling, the LH1 complex, displays exceptional stability, likely contributing to the robustness of the membranes. Peripheral light harvesting LH2 complexes show a light intensity dependent decoupling from photoconversion. LH2 can act as a reversible switch at low-light, an increased emitter at medium light and photobleaches at high light.

  18. Defatted algal biomass as a non-conventional low-cost adsorbent: surface characterization and methylene blue adsorption characteristics.

    PubMed

    Sarat Chandra, T; Mudliar, S N; Vidyashankar, S; Mukherji, S; Sarada, R; Krishnamurthi, K; Chauhan, V S

    2015-05-01

    The present study investigates the use of defatted algal biomass (DAB) as a non-conventional low cost adsorbent. The maximum adsorption capacity of biomass (raw, defatted and sulfuric acid pretreated DAB) was determined by liquid phase adsorption studies in batch mode for the removal of methylene blue present at various concentrations (1, 2, 3, 4, and 5 mg L(-1)) from aqueous solutions. The data was well fitted with Langmuir and Freundlich isotherms. The maximum adsorption capacity for raw, defatted and sulfuric acid pretreated DAB was found to be 6.0, 7.73 and 7.80 mg g(-1), respectively. The specific surface area of raw, defatted and sulfuric acid pretreated DAB was estimated to be 14.70, 18.94, and 19.10 m(2) g(-1), respectively. To evaluate the kinetic mechanism that controls the adsorption process, pseudo-first order, pseudo-second order, intraparticle diffusion and particle diffusion has been tested. The data fitted quite well with pseudo-second order kinetic model.

  19. Sorption of organic molecules on surfaces of a microporous polymer adsorbent modified with different quantities of uracil

    NASA Astrophysics Data System (ADS)

    Gus'kov, V. Yu.; Ganieva, A. G.; Kudasheva, F. Kh.

    2016-11-01

    The sorption of organic molecules on the surfaces of a number of adsorbents based on a microporous copolymer of styrene and divinylbenzene modified with different quantities of uracil is studied by means of inverse gas chromatography at infinite dilution. Samples containing 10-6, 10-5, 10-4, 10-3, 10-2, and 0.5 × 10‒1 weight parts of uracil (the pC of uracil ranges from 1.3 to 6) are studied. The contributions from different intermolecular interactions to the Helmholtz energy of sorption are calculated via the linear free energy relationship. It is found that as the concentration of uracil on the surface of the polymer adsorbent grows, the contributions from different intermolecular interactions and the conventional polarity of the surface have a bend at pC = 3, due probably to the formation of a supramolecular structure of uracil. Based on the obtained results, it is concluded that the formation of the supramolecular structure of uracil on the surface of the polymer adsorbent starts when pC < 3.

  20. STM observation of the chemical reaction of atomic hydrogen on the N-adsorbed Cu(001) surface

    NASA Astrophysics Data System (ADS)

    Hattori, Takuma; Yamada, Masamichi; Komori, Fumio

    2017-01-01

    Chemical reaction of atomic hydrogen with the N-adsorbed Cu(001) surfaces was investigated at room temperature by scanning tunnel microscopy. At the low exposure of atomic hydrogen, it reacted with the N atoms and turned to be the NH species on the surface. The reaction rate is proportional to the amount of the unreacted N atoms. By increasing the exposure of atomic hydrogen from this condition, the amount of nitrogen species on the surface decreased. This is attributed to the formation of ammonia and its desorption from the surface. The NH species on the surface turn to NH3 through the surface NH2 species by atomic hydrogen. Coexistence of the clean Cu surface enhances the rate of ammonia formation owing to atomic hydrogen migrating on the clean surface.

  1. Electronic structure and binding geometry of tetraphenylporphyrin-derived molecules adsorbed on metal and metal oxide surfaces

    NASA Astrophysics Data System (ADS)

    Coh, Senia

    Tetraphenylporphyrin (TPP)-derived molecules have been studied extensively as efficient photosensitizers when chemisorbed on the metal oxide substrates in dye-sensitized solar cells. Still, many fundamental electronic properties of the dye/oxide interface are not understood and need careful consideration. In this thesis we present a comprehensive study of the electronic structure, energy level alignment and the adsorption geometry of the TPP-derived dye molecules adsorbed on TiO2(110), ZnO(1120) and Ag(100) single crystal surfaces using ultra-high vacuum (UHV) based surface sensitive techniques. The alignment of the molecular energy levels with respect to the TiO 2 and ZnO band edges for all TPP-derived molecules we studied was found to be insensitive to either the nature of the functional groups located on the phenyl rings, presence of zinc as a central metal ion and different binding geometry of the molecules. Binding geometry, molecule-molecule interaction and the aggregation effects in the adsorbed layer, that were observed in the UV-visible spectra of the molecules adsorbed on ZnO substrate were not observed in the ultraviolet photoemission (UPS) and inverse photoemission (IPS) spectra of the occupied and unoccupied molecular states. Using near edge X-ray absorption fine structure (NEXAFS) and scanning tunneling microscopy (STM), binding geometry of the two representative TPP-derivatives was directly determined to be upright, with the porphyrin ring under large angle with respect to the surface for the p-ZnTCPP molecules and with the porphyrin ring parallel to the surface for the m-ZnTCPP molecules. We observe that the energies and the energy level alignment of the ZnTPP molecular levels measured in UPS and IPS depend on the substrate on which the molecules are adsorbed (Ag(100) or TiO2(110) single crystal surfaces). The differences are attributed to different charge screening properties of these two materials. Image charges created in the substrates during

  2. Recombination of 5-eV O(3P) atoms with surface-adsorbed NO - Spectra and their dependence on surface material and temperature

    NASA Technical Reports Server (NTRS)

    Orient, O. J.; Martus, K. E.; Chutjian, A.; Murad, E.

    1992-01-01

    Measurements have been conducted of the 300-850 nm recombination spectra associated with 5-eV collisions of O(3P) atoms with NO adsorbed on surfaces of MgF2, Ni, and Ti. Attention is given to the dependence of chemiluminescence intensity on surface temperature over the 240-340 K range. While all three materials tend to emit at the lower temperatures, MgF2 exhibits the greatest tendency to chemiluminescence. Both results are reflective of the greater packing density of surface-adsorbed NO at the lower temperatures for each surface. The activation energy for each surface is independent of emission wavelength, so that the same species is emitting throughout the wavelength range.

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

    PubMed

    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.

  4. The surface area of soil organic matter

    USGS Publications Warehouse

    Chiou, C.T.; Lee, J.-F.; Boyd, S.A.

    1990-01-01

    The previously reported surface area for soil organic matter (SOM) of 560-800 m2/g as determined by the ethylene glycol (EG) retention method was reexamined by the standard BET method based on nitrogen adsorption at liquid nitrogen temperature. Test samples consisted of two high organic content soils, a freeze-dried soil humic acid, and an oven-dried soil humic acid. The measured BET areas for these samples were less than 1 m2/g, except for the freeze-dried humic acid. The results suggest that surface adsorption of nonionic organic compounds by SOM is practically insignificant in comparison to uptake by partition. The discrepancy between the surface areas of SOM obtained by BET and EG methods was explained in terms of the 'free surface area' and the 'apparent surface area' associated with these measurements.The previously reported surface area for soil organic matter (SOM) of 560-800 m2/g as determined by the ethylene glycol (EG) retention method was reexamined by the standard BET method based on nitrogen adsorption at liquid nitrogen temperature. Test samples consisted of two high organic content soils, a freeze-dried soil humic acid, and an oven-dried soil humic acid. The measured BET areas for these samples were less than 1 m2/g, except for the freeze-dried humic acid. The results suggest that surface adsorption of nonionic organic compounds by SOM is practically insignificant in comparison to uptake by partition. The discrepancy between the surface areas of SOM obtained by BET and EG methods was explained in terms of the 'free surface area' and the 'apparent surface area' associated with these measurements.

  5. Hydrogen Bonding Controls the Dynamics of Catechol Adsorbed on a TiO2(110) Surface

    NASA Astrophysics Data System (ADS)

    Diebold, Ulrike; Li, Shao-Chun; Chu, Li-Na; Gong, Xue-Qing

    2011-03-01

    Direct studies of how organic molecules diffuse on metal oxide surfaces can provide insights into catalysis and molecular assembly processes. We studied individual catechol molecules, C6 H4 (OH)2 , on a rutile Ti O2 (110) surface with scanning tunnelingmicroscopy. Surface hydroxyls enhanced the diffusivity of adsorbed catecholates. The capture and release of a proton caused individual molecules to switch between mobile and immobile states within a measurement period of minutes. Density functional theory calculations showed that the transfer of hydrogen from surface hydroxyls to the molecule and its interaction with surface hydroxyls substantially lowered the activation barrier for rotational motion across the surface. Hydrogen bonding can play an essential role in the initial stages of the dynamics of molecular assembly.

  6. Reduction of electron accumulation at InN(0001) surfaces via saturation of surface states by potassium and oxygen as donor- or acceptor-type adsorbates

    SciTech Connect

    Eisenhardt, A.; Reiß, S.; Krischok, S. Himmerlich, M.

    2014-01-28

    The influence of selected donor- and acceptor-type adsorbates on the electronic properties of InN(0001) surfaces is investigated implementing in-situ photoelectron spectroscopy. The changes in work function, surface band alignment, and chemical bond configurations are characterized during deposition of potassium and exposure to oxygen. Although an expected opponent charge transfer characteristic is observed with potassium donating its free electron to InN, while dissociated oxygen species extract partial charge from the substrate, a reduction of the surface electron accumulation occurs in both cases. This observation can be explained by adsorbate-induced saturation of free dangling bonds at the InN resulting in the disappearance of surface states, which initially pin the Fermi level and induce downward band bending.

  7. Adsorption of neon and tetrafluoromethane on carbon nanohorn aggregates: differences in specific surface area values

    NASA Astrophysics Data System (ADS)

    Krungleviciute, Vaiva; Yudasaka, Masako; Iijima, Sumio; Migone, Aldo

    2008-03-01

    We have measured adsorption isotherms for two different adsorbates, neon and tetrafluoromethane, on dahlia-like carbon nanohorn aggregates. The experiments were performed at similar relative temperatures for both gases. The measurements were conducted to explore the effect of adsorbate diameter on the behavior of the resulting adsorbed systems. We measured the effective specific surface area value of the nanohorn sample using both gases, and we found that this quantity was about 22% smaller when we determined this quantity using tetrafluoromethane, the larger molecule. Isosteric heat and binding energy values were also determined from our measurements. We will compare our experimental results with those from a computer simulation study performed by Prof. M. Calbi. The simulations help us understand the source of the observed differences in the measured specific surface values, as well as the coverage dependence of the isosteric heat of adsorption for both gases.

  8. Abstraction of sulfur from Pt( 1 1 1 ) surfaces with thermal H atoms toward adsorbed and gaseous H 2S

    NASA Astrophysics Data System (ADS)

    Güttler, A.; Kolovos-Vellianitis, D.; Zecho, T.; Küppers, J.

    2002-09-01

    Sulphur layers on Pt(1 1 1) surfaces with coverages of 0.25 and 0.33 were prepared by H 2S adsorption at 85 K and subsequent annealing. H 2S adsorption on Pt, S/Pt and H/Pt surfaces and S adsorbate layers were characterized by Auger electron and thermal desorption spectroscopies. Admission of thermal H atoms to S covered Pt(1 1 1) at 85 K leads to formation of gaseous (80%) as well as adsorbed H 2S (20%). The yield of adsorbed H 2S decreases due to its isothermal desorption above 90 K. The interaction of H(g) with S(a) involves three reaction steps: 1. H(g)+S(a)→SH(a), 2. H(g)+SH(a)→H 2S(g,a), and 3. H(g)+SH(a)→H 2(g)+S(a) with apparent cross-sections σ1=0.3 Å 2, σ2=0.6 Å 2 and σ3=0.03 Å 2. Above 140 K the hydrogenation of SH toward H 2S(a,g) is blocked by thermal decomposition of H 2S. Impact of D on coadsorbed S, SH, and H 2S leads to desorption of H 2S.

  9. The Dependence of the Oxidation Enhancement of InP(100) Surface on the Coverage of the Adsorbed Cs

    SciTech Connect

    Sun, Yun

    2010-06-07

    We report the oxidation of the InP(100) surface promoted by adsorbed Cs by synchrotron radiation photoemission. Oxygen exposure causes reduction of the charge transferred to the InP substrate from Cs and the growth of indium oxide and phosphorous oxide. The oxide growth displays a clear dependence on the Cs coverage. The oxidation of phosphorous is negligible up to 1000 L of O{sub 2} exposure when the Cs coverage is less than half a monolayer (ML), but the formation of the second half monolayer of Cs greatly accelerates the oxidation. This different enhancement of the InP oxidation by the first and the second half monolayer of Cs is due to the double layer structure of the adsorbed Cs atoms, and consequently the higher 6s electron density in the Cs atoms when Cs coverage is larger than 0.5 ML.

  10. Derivatization and fluorescence detection of amino acids and peptides with 9-fluorenylmethyl chloroformate on the surface of a solid adsorbent.

    PubMed

    Shangguan, D; Zhao, Y; Han, H; Zhao, R; Liu, G

    2001-05-01

    An approach that exploits the surface of a solid adsorbent is proposed for precolumn FMOC derivatization of amino acids and peptides. Amino acids (Ser, Glu, GABA, Val, Phe, Lys) and two neuropeptides (substance P and Leuenkephalin) were adsorbed on alkaline silica gel cartridges. After drying, they were reacted with 9-fluorenyl-methyl chloroformate (FMOC-Cl) in toluene. After washing off the excess FMOC-Cl with ethyl acetate, the derivatives were eluted with aqueous eluant. The eluates were separated and detected by means of HPLC with fluorescence detection. Compared with the traditional derivatization in the liquid phase, the extent of formation of byproducts of FMOC-Cl with water was greatly decreased, and the excess FMOC-Cl was eliminated completely.

  11. Optimization of operating parameters of novel composite adsorbent for organic pollutants removal from POME using response surface methodology.

    PubMed

    Adeleke, A O; Latiff, Ab Aziz Ab; Al-Gheethi, A A; Daud, Zawawi

    2017-05-01

    The present work aimed to develop a novel composite material made up of activated cow bone powder (CBP) as a starting material for reducing chemical oxygen demand (COD) and ammonia-nitrogen (NH3N) from palm oil mill effluent (POME). The optimization of the reduction efficiency was investigated using response surface methodology (RSM). Six independent variables used in the optimization experiments include pH (4-10), speed (0.27-9.66 rcf), contact time (2-24 h), particle size (1-4.35 mm), dilution factor (100-500) and adsorbent dosage (65-125 g/L). The chemical functional groups were determined using Fourier transform irradiation (FTIR). The elemental composition were detected using SEM-EDX, while thermal decomposition was investigated using thermo gravimetric analysis (TGA) in order to determine the effects of carbonization temperature on the adsorbent. The results revealed that the optimal reduction of COD and NH3N from raw POME was observed at pH 10, 50 rpm, within 2 h and 3 mm of particle size as well as at dilution factor of 500 and 125 g L(-1) of adsorbent dosage, the observed and predicted reduction were 89.60 vs. 85.01 and 75.61 vs. 74.04%, respectively for COD and NH3N. The main functional groups in the adsorbent were OH, NH, CO, CC, COC, COH, and CH. The SEM-EDX analysis revealed that the CBP-composite has a smooth surface with high contents of carbon. The activated CBP has very stable temperature profile with no significant weight loss (9.85%). In conclusion, the CBP-composite investigated here has characteristics high potential for the remediation of COD and NH3N from raw POME.

  12. Hybridization of poly(rI) with poly(rC) adsorbed to the carbon nanotube surface

    PubMed Central

    2014-01-01

    Hybridization of homopolynucleotide poly(rC) adsorbed to the carbon nanotube surface with poly(rI) free in solution has been studied by absorption spectroscopy and molecular dynamics method. It was found that hybridization on the nanotube surface has a slow kinetics, the behavior of which differs essentially from fast hybridization of free polymers. The duplex obtained is characterized with the reduced thermostability and a lower hyperchromic coefficient than it was observed when the duplex was formed in the absence of the nanotube. These features point to the imperfectness in the structure of the duplex hybridized on the nanotube surface. Computer simulation showed that the strong interaction of nitrogen bases with the nanotube surface weakens significantly hybridization of two complementary oligomers, as the surface prevents the necessary conformational mobility of the polymer to be hybridized. PMID:24690381

  13. Hybridization of poly(rI) with poly(rC) adsorbed to the carbon nanotube surface.

    PubMed

    Karachevtsev, Maksym V; Gladchenko, Galyna O; Leontiev, Victor S; Karachevtsev, Victor A

    2014-04-01

    Hybridization of homopolynucleotide poly(rC) adsorbed to the carbon nanotube surface with poly(rI) free in solution has been studied by absorption spectroscopy and molecular dynamics method. It was found that hybridization on the nanotube surface has a slow kinetics, the behavior of which differs essentially from fast hybridization of free polymers. The duplex obtained is characterized with the reduced thermostability and a lower hyperchromic coefficient than it was observed when the duplex was formed in the absence of the nanotube. These features point to the imperfectness in the structure of the duplex hybridized on the nanotube surface. Computer simulation showed that the strong interaction of nitrogen bases with the nanotube surface weakens significantly hybridization of two complementary oligomers, as the surface prevents the necessary conformational mobility of the polymer to be hybridized.

  14. Hybridization of poly(rI) with poly(rC) adsorbed to the carbon nanotube surface

    NASA Astrophysics Data System (ADS)

    Karachevtsev, Maksym V.; Gladchenko, Galyna O.; Leontiev, Victor S.; Karachevtsev, Victor A.

    2014-04-01

    Hybridization of homopolynucleotide poly(rC) adsorbed to the carbon nanotube surface with poly(rI) free in solution has been studied by absorption spectroscopy and molecular dynamics method. It was found that hybridization on the nanotube surface has a slow kinetics, the behavior of which differs essentially from fast hybridization of free polymers. The duplex obtained is characterized with the reduced thermostability and a lower hyperchromic coefficient than it was observed when the duplex was formed in the absence of the nanotube. These features point to the imperfectness in the structure of the duplex hybridized on the nanotube surface. Computer simulation showed that the strong interaction of nitrogen bases with the nanotube surface weakens significantly hybridization of two complementary oligomers, as the surface prevents the necessary conformational mobility of the polymer to be hybridized.

  15. Angular dependence of the electron energy loss spectra from a clean and adsorbate covered W(001) surface

    NASA Astrophysics Data System (ADS)

    Avery, N. R.

    1981-11-01

    A dispersion analysis of the EELS from a W(001) surface in the range 1 < ΔE < 35 eV has been performed and compared with recent and complete optical data for tungsten. The non-dispersive ( k ˜ 0) EELS correlated well with a combination of the surface and bulk loss functions calculated from the optical data. Losses at 1-5 eV and a pair at 32 and 34.5 eV were assigned to interband and N 6,7 core ionization excitations respectively. The principal bulk and surface plasmon losses were identified at 24.0 and 20.3 eV respectively. Two further losses at 14.0 and 9.6 eV were also observed and assigned to subsidiary plasmon losses. All four plasmon losses showed only minimal energy dispersion, never exceeding 1.5 eV. A momentum selectivity for separating bulk and surface interband losses was demonstrated with the non-dispersive losses arising from excitations within the bulk even with incident energies as low as 88 eV, whereas their dispersive counterparts were extremely sensitive to the chemical state of the surface. New adsorbate derived losses which develop during adsorption were associated with excitations from the new deep lying adsorbate levels to final state levels at or near the Fermi level. It was concluded that this final state was also responsible for the N 6,7 ionization losses.

  16. In Situ Surface X-Ray Scattering of Metal Monolayers Adsorbed at Solid-Liquid Interfaces

    DTIC Science & Technology

    1991-11-09

    2D spreading pressure, a is the atomic area (.JTa,.,,2/2 for a hexagonal monolayer such as TI), p is the monolayer chemical potential, Z is the number...supported by the U.S. l)epartment of lEnergy. D)ivision of Material Sciences and )ivision of Chemical Sciences. REFERENCES 1. P . Eiscnberger and W.C. Marra...Wicslcr, P ). Yecc, and 1,.B. Sorensen, I Angmuir 7, 796 (199 1). 10. M. F. Toncy, in The Application of Surface A nalysis Methods to Dw’ttiromtzital

  17. Surface area coefficients for airship envelopes

    NASA Technical Reports Server (NTRS)

    Diehl, W S

    1922-01-01

    In naval architecture, it is customary to determine the wetted surface of a ship by means of some formula which involves the principal dimensions of the design and suitable constants. These formulas of naval architecture may be extended and applied to the calculation of the surface area of airship envelopes by the use of new values of the constants determined for this purpose. Surface area coefficients were calculated from the actual dimensions, surfaces, and volumes of 52 streamline bodies, which form a series covering the entire range of shapes used in the present aeronautical practice.

  18. Morphological changes in adsorbed protein films at the air-water interface subjected to large area variations, as observed by brewster angle microscopy.

    PubMed

    Xu, Rong; Dickinson, Eric; Murray, Brent S

    2007-04-24

    Adsorbed films of proteins at the air-water interface have been imaged using Brewster angle microscopy (BAM). The proteins beta-lactoglobulin (beta-L) and ovalbumin (OA) were studied at a range of protein concentrations and surface ages at 25.0 degrees C and two pH values (7 and 5) in a Langmuir trough. The adsorbed films were periodically subjected to compression and expansion cycles such that the film area was typically varied between 125% and 50% of the original film area. With beta-L on its own, no structural changes were observable at pH 7. When a low-area fraction (less than 0.01%) of 20 mum polystyrene latex particles was spread at the interface before adsorption of beta-L, the particles became randomly distributed throughout the interface, but after protein adsorption and compression/expansion, the particles highlighted notable structural features not visible in their absence. Such features included the appearance of long (several hundred micrometers or more) folds and cracks in the films, generally oriented at right angles to the direction of compression, and also aggregates of protein and/or particles. Such structuring was more visible the longer the film was aged or at higher initial protein concentrations for shorter adsorption times. At pH 5, close to the isoelectric pH of beta-L, such features were just noticeable in the absence of particles but were much more pronounced than at pH 7 in the presence of particles. Similar experiments with OA revealed even more pronounced structural features, both in the absence and presence of particles, particularly at pH 5 (close to the isoelectric pH of OA also), producing striking stripelike and meshlike domains. Changes in the dilatational elasticity of the films could be correlated with the variations in the structural integrity of the films as observed via BAM. The results indicate that interfacial area changes of this type, typical of those that occur in food colloid processing, will lead to highly

  19. Surface alloy formation of noble adatoms adsorbed on Si(111)-\\sqrt {3}\\times \\sqrt {3} -Pb surface: a first-principles study

    NASA Astrophysics Data System (ADS)

    Li, Chong; Wang, Fei; Sun, Q.; Jia, Yu

    2011-07-01

    The geometric structures, stability and electronic properties of initial stages of surface alloy formation for noble atoms adsorbed on Si(111)-\\sqrt {3}\\times \\sqrt {3} -Pb surfaces have been comparatively and extensively studied by using first-principles calculations within density functional theory. Our results revealed that an Au trimer rather than a tetramer adsorption induces a surface alloy by combining with Pb atoms in covalent bonds, exhibiting semiconducting characteristics due to the localization of surface states. The stability of the two-dimensional (2D) surface alloy obeys the Hume-Rothery rule. The electronic structures of the 2D surface alloy are sensitive to the number of Au adatoms and can be modulated by the quantity of Au adatoms. Unlike the Au atoms, our further calculations indicated that adsorption of Ag or Cu atoms on the surface cannot form a surface alloy with Pb atoms in the surface layer due to a weaker interaction or smaller radius.

  20. Surface Photochemistry: 3,3′-Dialkylthia and Selenocarbocyanine Dyes Adsorbed onto Microcrystalline Cellulose

    PubMed Central

    Vieira Ferreira, Luís F.; Ferreira, Diana P.; Duarte, Paulo; Oliveira, A. S.; Torres, E.; Machado, I. Ferreira; Almeida, P.; Reis, Lucinda V.; Santos, Paulo F.

    2012-01-01

    In this work, thia and selenocarbocyanines with n-alkyl chains of different length, namely with methyl, ethyl, propyl, hexyl and decyl substituents, were studied in homogeneous and heterogeneous media for comparison purposes. For both carbocyanine dyes adsorbed onto microcrystalline cellulose, a remarkable increase in the fluorescence quantum yields and lifetimes were detected, when compared with solution. Contrary to the solution behaviour, where the increase in the n-alkyl chains length increases to a certain extent the fluorescence emission ΦF and τF, on powdered solid samples a decrease of ΦF and τF was observed. The use of an integrating sphere enabled us to obtain absolute ΦF’s for all the powdered samples. The main difference for liquid homogeneous samples is that the increase of the alkyl chain strongly decreases the ΦF values, both for thiacarbocyanines and selenocarbocyanines. A lifetime distribution analysis for the fluorescence of these dyes adsorbed onto microcrystalline cellulose, evidenced location on the ordered and crystalline part of the substrate, as well as on the more disordered region where the lifetime is smaller. The increase of the n-alkyl chains length decreases the photoisomer emission for the dyes adsorbed onto microcrystalline cellulose, as detected for high fluences of the laser excitation, for most samples. PMID:22312274

  1. Surface photochemistry: 3,3'-dialkylthia and selenocarbocyanine dyes adsorbed onto microcrystalline cellulose.

    PubMed

    Vieira Ferreira, Luís F; Ferreira, Diana P; Duarte, Paulo; Oliveira, A S; Torres, E; Machado, I Ferreira; Almeida, P; Reis, Lucinda V; Santos, Paulo F

    2012-01-01

    In this work, thia and selenocarbocyanines with n-alkyl chains of different length, namely with methyl, ethyl, propyl, hexyl and decyl substituents, were studied in homogeneous and heterogeneous media for comparison purposes. For both carbocyanine dyes adsorbed onto microcrystalline cellulose, a remarkable increase in the fluorescence quantum yields and lifetimes were detected, when compared with solution. Contrary to the solution behaviour, where the increase in the n-alkyl chains length increases to a certain extent the fluorescence emission Φ(F) and τ(F), on powdered solid samples a decrease of Φ(F) and τ(F) was observed. The use of an integrating sphere enabled us to obtain absolute Φ(F)'s for all the powdered samples. The main difference for liquid homogeneous samples is that the increase of the alkyl chain strongly decreases the Φ(F) values, both for thiacarbocyanines and selenocarbocyanines. A lifetime distribution analysis for the fluorescence of these dyes adsorbed onto microcrystalline cellulose, evidenced location on the ordered and crystalline part of the substrate, as well as on the more disordered region where the lifetime is smaller. The increase of the n-alkyl chains length decreases the photoisomer emission for the dyes adsorbed onto microcrystalline cellulose, as detected for high fluences of the laser excitation, for most samples.

  2. Multiple-overtone resonance Raman scattering and fluorescence from I{sub 2} species adsorbed on silver surfaces

    SciTech Connect

    Sibbald, M.S.; Chumanov, G.; Small, G.; Cotton, T.M.

    1998-07-01

    A detailed excitation profile of a Raman progression consisting of up to six overtones and a fundamental band at 123 cm{sup {minus}1} observed from iodide adsorbed on an electrochemically roughened silver surface at 20 K is analyzed. The excitation profile was constructed from 77 spectra obtained by tuning the laser wavelength in {approximately}0.25 nm steps through the spectral range 409 nm{endash}433 nm. The shift between resonances in the excitation profile, corresponding to the spacing between vibronic levels in the excited state, is also equal to 123 cm{sup {minus}1} indicating that the ground state and excited state potential energy surfaces have the same shape. Only two distinct resonances spaced three vibrational quanta apart were evident in the profile for each band in the progression. Curve fitting of the Raman band shapes indicates that each overtone is composed of one sharp and one broad band, whereas the fundamental contains only one sharp component. The measured width of the fundamental was less than 2.5 cm{sup {minus}1} FWHM, limited by the instrument function. It is proposed that the sharp Raman bands represent a normal vibrational mode of a surface-adsorbed I{sub 2}-like species with the width determined by the intrinsic vibrational dephasing in the ground state. On the other hand, the broad Raman bands reflect vibronic coupling between different I{sub 2}-like species adsorbed on the same Ag cluster. The broad bandwidths result from both dephasing associated with the vibronic coupling and the intrinsic vibrational dephasing. Other weak emission bands are attributed to resonance fluorescence corresponding to direct transitions from higher vibronic levels of the excited state to the ground state. An emission at 429.9 nm is assigned to exciton recombination in small silver iodide clusters which are formed after spontaneous oxidation of the iodide-modified silver surface. {copyright} {ital 1998 American Institute of Physics.}

  3. NO2 interaction with Au atom adsorbed on perfect and defective MgO(100) surfaces: density functional theory calculations.

    PubMed

    Ammar, H Y; Eid, Kh M

    2013-10-01

    The interactions of nitrogen dioxide molecule (NO2) on Au atom adsorbed on the surfaces of metal oxide MgO (100) on both anionic (O2-) and defect (F(s) and F(s)(+)-centers) sites have been studied using the Density Functional Theory (DFT) in combination with embedded cluster model. The adsorption energies of NO2 molecule (N-down as well as O-down) on O(-2), F(s) and F(s)(+)-sites were considered. Full optimization for the additive materials and partial optimization for MgO substrate surfaces have been done. The formation energies were evaluated for F(s) and F(s)(+) of MgO substrate surfaces. Some parameters, the Ionization Potential (IP) and electron Affinity (eA), for defect free and defect containing surfaces have been calculated. The interaction properties of NO2 have been analyzed in terms of the adsorption energy, the electron donation (basicity), the elongation of N-O bond length and the charge distribution by using Natural Bond Orbital (NBO) analysis. The adsorption properties were examined by calculation of the Density of State (DOS). The presence of the Au atom increases the surface chemistry of the anionic O(2-)-site of MgO substrate surfaces. On the other hand, the presence of the Au atom decreases the surface chemistry of the F(s) and F(s)(+)-sites of MgO substrate surfaces. Generally, the NO2 molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing F(s) and F(s)(+)-centers.

  4. Ratio of the surface-enhanced anti-Stokes scattering to the surface-enhanced Stokes-Raman scattering for molecules adsorbed on a silver electrode

    NASA Astrophysics Data System (ADS)

    Brolo, A. G.; Sanderson, A. C.; Smith, A. P.

    2004-01-01

    Surface-enhanced Raman scattering (SERS) from oxazine 720 (oxa), rhodamine 6G (R6G), and pyridine (py) adsorbed on a rough silver surface was observed. The silver electrode was immersed in aqueous solutions permitting control of the potential bias applied to the surface. SERS spectra in the Stokes and anti-Stokes regions were obtained for several applied potentials and two laser excitation energies. Normalized ratios between the anti-Stokes and the Stokes intensities K were calculated from the SERS spectra. The K ratios differed from unity for all the systems investigated. A preferential enhancement of the (surface-enhanced) Stokes scattering was observed for oxa and py. In contrast, the K ratios were higher than unity for R6G, indicating an increase in the anti-Stokes signal. The K ratios measured in this work decreased with the excitation energy and showed a dependence on the energy of the vibrational modes. These results were satisfactorily explained using resonance models, based on the charge-transfer and electromagnetic theories for SERS. No evidence for a SERS-induced nonthermal population distribution among the vibrational states of the adsorbed molecules (vibrational optical pumping) was found. Therefore, we conclude that the main features of the preferential enhancement of the anti-Stokes scattering for an adsorbed molecule on rough silver can be fully understood in the context of current SERS theories.

  5. Tunable surface charge of ZnS:Cu nano-adsorbent induced the selective preconcentration of cationic dyes from wastewater.

    PubMed

    Wang, Yongjing; Chen, Dagui; Wang, Yandi; Huang, Feng; Hu, Qichang; Lin, Zhang

    2012-06-21

    A novel environmentally friendly nano-adsorbent is developed by doping Cu(+) cations into the lattice of ZnS microspheres. The adsorbent shows selective adsorbability for cationic dyes in low concentrations in wastewater. The adsorbed dye could be successfully eluted with alcohol, resulting in a 1000 fold enrichment of the dye solution.

  6. Phase transition of 2×2 adsorbates on FCC(1 1 1) and HCP(0 0 0 1) surfaces

    NASA Astrophysics Data System (ADS)

    Sakamoto, Yoshifumi

    2003-04-01

    Order-disorder transition of adsorbates at metal surfaces is discussed based on Monte Carlo calculations for a lattice gas model on a triangular net. Repulsive interactions up to second neighbour sites and fixed concentration 1/4 of particles of lattice gas, are assumed for the 2×2 ordered structure. Calculated phase diagram and the critical exponent for susceptibility are presented. Stress is put on cases other than the second-order transition belonging to the four-state Potts universality class.

  7. A grazing incidence surface X-ray absorption fine structure (GIXAFS) study of alkanethiols adsorbed on Au, Ag, and Cu

    NASA Astrophysics Data System (ADS)

    Floriano, Pierre N.; Schlieben, Olaf; Doomes, Edward E.; Klein, Ingo; Janssen, J.; Hormes, Josef; Poliakoff, E. D.; McCarley, Robin L.

    2000-04-01

    Self-assembled monolayers of n-alkanethiols, CH 3-(CH 2) x-SH, on Au, Ag, and Cu have been studied with GIXAFS at the sulfur K-edge. For both pentanethiol and decanethiol monolayers on Ag and Cu, the three-fold hollow site is found to be the most probable sulfur binding site. However, observations for octadecanethiol indicate that the three-fold hollow site is not the exclusive binding site. In addition, the possible existence of disulfide bonds on the metal surface (adsorbed dialkyldisulfides) is not supported by the data. Preliminary results from monolayers on Au are also reported.

  8. Surface moisture estimation in urban areas

    NASA Astrophysics Data System (ADS)

    Jiang, Yitong

    Surface moisture is an important parameter because it modifies urban microclimate and surface layer meteorology. The primary objectives of this paper are: 1) to analyze the impact of surface roughness from buildings on surface moisture in urban areas; and 2) to quantify the impact of surface roughness resulting from urban trees on surface moisture. To achieve the objectives, two hypotheses were tested: 1) the distribution of surface moisture is associated with the structural complexity of buildings in urban areas; and 2) The distribution and change of surface moisture is associated with the distribution and vigor of urban trees. The study area is Indianapolis, Indiana, USA. In the part of the morphology of urban trees, Warren Township was selected due to the limitation of tree inventory data. To test the hypotheses, the research design was made to extract the aerodynamic parameters, such as frontal areas, roughness length and displacement height of buildings and trees from Terrestrial and Airborne LiDAR data, then to input the aerodynamic parameters into the urban surface energy balance model. The methodology was developed for comparing the impact of aerodynamic parameters from LiDAR data with the parameters that were derived empirically from land use and land cover data. The analytical procedures are discussed below: 1) to capture the spatial and temporal variation of surface moisture, daily and hourly Land Surface Temperature (LST) were downscaled from 4 km to 1 km, and 960 m to 30 m, respectively, by regression between LST and various components that impact LST; 2) to estimate surface moisture, namely soil moisture and evapotranspiration (ET), land surfaces were classified into soil, vegetation, and impervious surfaces, using Linear Spectral Mixture Analysis (LSMA); 3) aerodynamic parameters of buildings and trees were extracted from Airborne and Terrestrial LiDAR data; 4) the Temperature-Vegetation-Index (TVX) method, and the Two-Source-Energy-Balance (TSEB

  9. Infrared spectral investigations of UV irradiated nucleobases adsorbed on mineral surfaces

    NASA Astrophysics Data System (ADS)

    Brucato, John Robert; Pace, Emanuele; Pucci, Amaranta; Branciamore, Sergio; Cestelli Guidi, Mariangela; Fornaro, Teresa

    The interaction between electromagnetic radiation and bio-molecules in heterogeneous environments is a prebiotically relevant process. Minerals may have a pivotal role in the prebiotic evolution of complex chemical systems, mediating the effects of electromagnetic radiation, influencing the photostability of bio-molecules, catalyzing important chemical reactions and/or protecting molecules against degradation. In particular, nucleobases are relevant bio-molecules to investigate both in the prebiotic context, because they are coding components of nucleic acids, and from the standpoint of the survival of biological systems in space conditions. In this talk, laboratory results on photostability of nucleobases adsorbed on minerals will be presented.

  10. Nano-materials for adhesive-free adsorbers for bakable extreme high vacuum cryopump surfaces

    SciTech Connect

    Stutzman, Marcy; Jordan, Kevin; Whitney, Roy R.

    2016-10-11

    A cryosorber panel having nanomaterials used for the cryosorption material, with nanomaterial either grown directly on the cryopanel or freestanding nanomaterials attached to the cryopanel mechanically without the use of adhesives. Such nanomaterial cryosorber materials can be used in place of conventional charcoals that are attached to cryosorber panels with special low outgassing, low temperature capable adhesives. Carbon nanotubes and other nanomaterials could serve the same purpose as conventional charcoal cryosorbers, providing a large surface area for cryosorption without the need for adhesive since the nanomaterials can be grown directly on a metallic substrate or mechanically attached. The nanomaterials would be capable of being fully baked by heating above 100.degree. C., thereby eliminating water vapor from the system, eliminating adhesives from the system, and allowing a full bake of the system to reduce hydrogen outgassing, with the goal of obtaining extreme high vacuum where the pump can produce pressures below 1.times.10.sup.-12 Torr.

  11. High-productivity membrane adsorbers: Polymer surface-modification studies for ion-exchange and affinity bioseparations

    NASA Astrophysics Data System (ADS)

    Chenette, Heather C. S.

    This dissertation centers on the surface-modification of macroporous membranes to make them selective adsorbers for different proteins, and the analysis of the performance of these membranes relative to existing technology. The common approach used in these studies, which is using membrane technology for chromatographic applications and using atom transfer radical polymerization (ATRP) as a surface modification technique, will be introduced and supported by a brief review in Chapter 1. The specific approaches to address the unique challenges and motivations of each study system are given in the introduction sections of the respective dissertation chapters. Chapter 2 describes my work to develop cation-exchange membranes. I discuss the polymer growth kinetics and characterization of the membrane surface. I also present an analysis of productivity, which measures the mass of protein that can bind to the stationary phase per volume of stationary phase adsorbing material per time. Surprisingly and despite its importance, this performance measure was not described in previous literature. Because of the significantly shorter residence time necessary for binding to occur, the productivity of these cation-exchange membrane adsorbers (300 mg/mL/min) is nearly two orders of magnitude higher than the productivity of a commercial resin product (4 mg/mL/min). My work studying membrane adsorbers for affinity separations was built on the productivity potential of this approach, as articulated in the conclusion of Chapter 2. Chapter 3 focuses on the chemical formulation work to incorporate glycoligands into the backbone of polymer tentacles grown from the surface of the same membrane stationary phase. Emphasis is given to characterizing and testing the working formulation for ligand incorporation, and details about how I arrived at this formulation are given in Appendix B. The plant protein, or lectin, Concanavalin A (conA) was used as the target protein. The carbohydrate affinity

  12. Density matrix treatment of combined instantaneous and delayed dissipation for an electronically excited adsorbate on a solid surface

    NASA Astrophysics Data System (ADS)

    Leathers, Andrew S.; Micha, David A.; Kilin, Dmitri S.

    2009-10-01

    The interaction of an excited adsorbate with a medium undergoing electronic and vibrational transitions leads to fast dissipation due to electronic energy relaxation and slow (or delayed) dissipation from vibrational energy relaxation. A theoretical and computational treatment of these phenomena has been done in terms of a reduced density matrix satisfying a generalized Liouville-von Neumann equation, with instantaneous dissipation constructed from state-to-state transition rates, and delayed dissipation given by a memory term derived from the time-correlation function (TCF) of atomic displacements in the medium. Two representative applications are presented here, where electronic excitation may enhance vibrational relaxation of an adsorbate. They involve femtosecond excitation of (a) a CO molecule adsorbed on the Cu(001) metal surface and (b) a metal cluster on a semiconductor surface, Ag3Si(111):H, both electronically excited by visible light and undergoing electron transfer and dissipative dynamics by electronic and vibrational relaxations. Models have been parametrized in both cases from electronic structure calculations and known TCFs for the medium, which are slowly decaying in case (a) and fast decaying in case (b). This requires different numerical procedures in the solution of the integrodifferential equations for the reduced density matrix, which have been solved with an extension of the Runge-Kutta algorithm. Results for the populations of vibronic states versus time show that they oscillate due to vibrational coupling through dissipative interaction with the substrate and show quantum coherence. The total population of electronic states is, however, little affected by vibrational motions. Vibrational relaxation is important only at very long times to establish thermal equilibrium.

  13. Assessment of fibronectin conformation adsorbed to polytetrafluoroethylene surfaces from serum protein mixtures and correlation to support of cell attachment in culture.

    PubMed

    Grainger, David W; Pavon-Djavid, Graciella; Migonney, Veronique; Josefowicz, Marcel

    2003-01-01

    Surfaces of polytetrafluoroethylene (PTFE) were exposed to buffered aqueous solutions containing radio-labeled human fibronectin ([125I]Fn), Fn/bovine serum albumin (BSA) binary mixtures of various ratios or whole human plasma dilutions for 1 h. Total adsorbed Fn and albumin adsorption following rinsing was quantified on this surface. 125I-labeled monoclonal antibodies against either the tenth type-III Fn repeat unit (containing the cell-binding RGDS integrin recognition motif) or the Fn amino-terminal domain were used to probe the accessibility of each of these respective Fn regions post-adsorption. Human umbilical vein endothelial cells (HUVECs) were cultured on PTFE surfaces pre-exposed to each of these protein adsorption conditions and compared to identical conditions on tissue culture polystyrene (TCPS). Fn adsorption to PTFE is dependent upon the concentration of albumin co-adsorbing from solution: albumin out-competes Fn for PTFE surface sites even at non-physiological Fn/HSA ratios 10-100-fold biased in Fn. Antibodies against Fn do not readily recognize Fn adsorbed on PTFE as the HSA co-adsorption concentration in either binary mixtures or in plasma increases, indicating albumin masking of adsorbed Fn. At Fn/HSA ratios rich in Fn (1:1, 1:100), albumin co-adsorption actually improves anti-Fn antibody recognition of adsorbed Fn. HUVEC attachment efficiency to PTFE after protein adsorption correlates with amounts of Fn adsorbed and levels of anti-Fn antibody recognition of Fn on PTFE, linking cell attachment to integrin recognition of both adsorbed Fn density and Fn adsorbed conformation on PTFE surfaces.

  14. FTIR investigation of adsorption and chemical decomposition of CCl4 by high surface-area aluminum oxide.

    PubMed

    Khaleel, Abbas; Dellinger, Barry

    2002-04-01

    Chlorinated hydrocarbons are among the most recalcitrant pollutants for control by sorption or catalytic destruction. High surface-area alumina holds promise as a catalytic media as well as a component of other binary catalyst systems. We have prepared an alumina catalyst using the aerogel technique that has a very high surface area of 550 m2/g. This catalyst destroys carbon tetrachloride with an efficiency >99% at 400 degrees C. Its reactivity toward carbon tetrachloride is remarkably higher than that of commercial alumina, which has a surface area of 155 m2/g. Carbon dioxide is the major product. Minor products include hydrogen chloride and tetrachloroethylene along with traces of phosgene. Some of the carbon tetrachloride reacts with the alumina to form aluminum chloride, which vaporizes to reveal a fresh catalytic surface. A mechanism for adsorption and destruction has been developed that involves chemisorption followed by surface to adsorbate oxygen transfer and adsorbate to surface chlorine transfer.

  15. Surface induced vibrational modes in the fluorescence spectra of PTCDA adsorbed on the KCl(100) and NaCl(100) surfaces.

    PubMed

    Paulheim, A; Marquardt, C; Sokolowski, M; Hochheim, M; Bredow, T; Aldahhak, H; Rauls, E; Schmidt, W G

    2016-12-07

    We report a combined experiment-theory study on low energy vibrational modes in fluorescence spectra of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) molecules. Using very low coverages, isolated molecules were adsorbed on terrace sites or at sites located at residual steps on (100) oriented alkali halide films (KCl and NaCl). The low energy modes couple to the optical transition only because the PTCDA molecule is geometrically distorted (C2v) upon adsorption on the surface; they would be absent for the parent planar (D2h) PTCDA molecule. The modes differ in number and energy for molecules adsorbed on regular terrace sites and molecules adsorbed at step edge sites. Modes appearing for step edge sites have the character of frustrated rotations. Their coupling to the optical transition is a consequence of the further reduced symmetry of the step edge sites. We find a larger number of vibrational modes on NaCl than on KCl. We explain this by the stronger electrostatic bonding of the PTCDA on NaCl compared to KCl. It causes the optical transition to induce stronger changes in the molecular coordinates, thus leading to larger Franck-Condon factors and thus stronger coupling. Our results demonstrate how optical spectroscopy can be used to gain information on adsorption sites of molecules at low surface concentrations.

  16. Crystalline structures of alkylamide monolayers adsorbed on the surface of graphite.

    PubMed

    Bhinde, Tej; Clarke, Stuart M; Phillips, Tamsin K; Arnold, Thomas; Parker, Julia E

    2010-06-01

    Synchrotron X-ray and neutron diffraction have been used to determine the two-dimensional crystalline structures of alkylamides adsorbed on graphite at submonolayer coverage. The calculated structures show that the plane of the carbon backbone of the amide molecules is parallel to the graphite substrate. The molecules form hydrogen-bonded dimers, and adjacent dimers form additional hydrogen bonds yielding extended chains. By presenting data from a number of members of the homologous series, we have identified that these chains pack in different arrangements depending on the number of carbons in the amide molecule. The amide monolayers are found to be very stable relative to other closely related alkyl species, a feature which is attributed to the extensive hydrogen bonding present in these systems. The characteristics of the hydrogen bonds have been determined and are found to be in close agreement with those present in the bulk materials.

  17. Surface-Enhanced Raman Scattering for Redox-Active Adsorbates: Pentaammineosmium(III)/(II) and Pentaammineruthenium(II) Containing Nitrogen Heterocycle Ligands.

    DTIC Science & Technology

    1984-04-01

    electrode reactions involving simple one- electron transfer for which both redox states are detectably adsorbed and structurally similar. Although... Taube at Stanford University. We also thank Henry Taube for his advice and encouragement. The research program of M.J.W. is supported in part by the...k AD-Ai42 418 SURFACE-ENHANCED RAMAN SCATTERING FOR REDOX -ACTIVE ii ADSORBATES: PENTRNIN..(U) PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY S

  18. Effect of side by side interactions on the thermodynamic properties of adsorbed CO molecules on the Ni(111) surface: a cluster model study

    NASA Astrophysics Data System (ADS)

    Shamkhali, Amir N.; Parsafar, Gholamabbas

    2010-05-01

    The effect of electrostatic interactions on vibrational frequencies and thermodynamic properties of CO adsorbate on the Ni(111) surface is calculated by taking the first and second nearest-neighbour interactions into account. In order to obtain reasonable results, the cluster model of various surface adsorption sites with CO adsorbate is partially optimized, using Density Functional Theory and also the MP2 method for the hcp site. Comparison between DFT and MP2 results shows that DFT results are more reliable for this system. The stretching and bending frequencies of CO adsorbate are calculated using both Partial Hessian Analysis and Cluster-Adsorbate Coupling methods. Stretching and bending frequencies are both shifted by the side by side interactions. The coupling of surface phonons and adsorbate vibrations reduces the side effects. The largest side effects on the vibrational internal energy, isochoric heat capacity, entropy and total Helmholtz free energy of adsorbed CO molecule calculated using the CAC method are found for 0.5 ML coverage. The results of the CAC method are better, but the PHA method can be used as a simple upper bound estimation. The adsorptive phase acts as an intelligent material in such a way that it changes its configuration in order to reduce the side effects.

  19. Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2014-01-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion, and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near-monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (± 0.8) × 10-7 and 2 (± 1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ > 300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(± 1) but had no effect on ozonolysis of the alkene side chain.

  20. Characterization of polar molecular species adsorbed on LiNbO3 surfaces

    NASA Astrophysics Data System (ADS)

    Bharath, Satyaveda; Pearl, Thomas

    2008-10-01

    In order to explore the mechanisms of adsorption on ferroelectric surfaces, single crystalline lithium niobate (LiNbO3: LN), `Z-cut'; along the (0001) plane, has been prepared and characterized and subsequently exposed to a polar molecule. 4-n-octyl-4'-cyanobiphenyl (8CB) liquid crystal was chosen as our model system. Low-energy electron diffraction, atomic force microscopy, surface contact angle measurement, and X-ray photoelectron spectroscopy were used to characterize the surface of LN as well as the nature of the films grown on the surface. Atomically flat LN surfaces were prepared as a support for monolayer thick, 8CB molecular domains. Preferential attachment for positive domains was observed indicating an interaction between the polar end group of the molecule and the surface charge of the surface. Understanding anchoring mechanisms for polarizable molecules on uniformly poled surfaces allows for a fuller appreciation of how ferroelectric surfaces can be used for controlling molecular organization.

  1. Classical and Mixed Quantum-Classical Dynamics of Adsorbate-Surface Systems: Application to Non-Thermal Desorption

    NASA Astrophysics Data System (ADS)

    Dzegilenko, Fedor N.

    1995-01-01

    Both classical and mixed quantum-classical approaches have been used to study the non-thermal desorption of CO from a variety of model surfaces to which it is weakly adsorbed. In addition to three degrees of freedom for the CO adsorbate (bond stretching, physisorption, libration) which are treated quantum mechanically in the mixed method, a significant number of lattice degrees of freedom have been included using the generalized Langevin approximation. In the mixed method, two sets of equations for the quantum and classical subsystems (coupled via the Ehrenfest theorem) are solved self-consistently using the discrete variable representation method for the propagation of the quantum wave function. Non-thermal amounts of energy have been put into both the CO stretching and librational modes at t = 0. We find that for initial values of the stretching quantum number vstr = 0 -4 desorption does not take place at all within the simulation time unless there is also significant librational excitation. The detailed mechanism by which librational energy causes desorption is discussed. The role of the surface is also explored; we find that the probability of desorption is a non-monotonic function of the Debye frequency of the solid in the range 28-5000 cm^{-1}, and is larger for "non-rigid" lattices with low Debye frequencies in both of the methods. The classical results are explained in terms of resonances between low frequency libration and physisorption modes and high frequency phonon modes. For the combined method, two different mechanisms for desorption (due to lattice effects and due to symmetry properties of wave function) have been found and analyzed in detail. A comparative analysis of the two methods is presented and the limitations of the mixed scheme are discussed. An indirect mechanism for populating rapidly desorbing, highly excited levels of surface CO, based on intermolecular V to V,R energy exchange between the CO and vibrationally excited surface hydroxyl

  2. Effect of surface modifiers on the electrode reactions and conformation of cytochrome c3 adsorbed on a silver electrode.

    PubMed

    Hobara, D; Niki, K; Cotton, T M

    1998-01-01

    Surface-enhanced resonance Raman scattering and electroreflectance voltammetry were used to investigate the effect of electrode surface modification on the structure and redox properties of cytochrome c3 immobilized on Ag surfaces. It is shown that the redox reactions of cytochrome c3 are more reversible at an 11-mercaptoundecanoic acid modified Ag electrode as compared to a bare metal surface. The heme of cytochrome c3 is in a mixed low and high spin state when adsorbed at the bare electrode, whereas only the low spin form is present on the 11-mercaptoundecanoic acid modified electrode, suggesting that the native conformation is maintained in the latter case. The reduction potential is close to that of the most positive macroscopic potential as determined by electroreflectance spectroscopy. In contrast, the reduction potential as determined by SERRS undergoes a large positive shift in the presence of 4,4'-bipyridine, the magnitude of which is dependent upon the concentration of 4,4'-bipyridine. These results indicate that the effect of the cytochrome c3 interaction with the 4,4'-bipyridine-modified surface is significantly different as compared to its interaction with the 11-mercaptoundecaodoic acid modified surface. Moreover, the results emphasize that electrode modifiers can have dramatically different effects on the redox properties of different proteins. It is well known that 4,4'-bipyridine acts as a redox promoter in the case of cytochrome c, whereas no electrochemical or electroreflectance response was observed in the case of cytochrome c3.

  3. Surface-enhanced nonlinear optical effects and detection of adsorbed molecular monolayers

    SciTech Connect

    Shen, Y.R.; Chen, C.K.; Heinz, T.F.; Ricard, D.

    1981-01-01

    The observation of a number of surface-enhanced nonlinear optical effects is discussed. The feasibility of using second-harmonic generation to detect the adsorption of molecular monolayers on a metal surface in an electrolytic solution is shown.

  4. Volumes and surface areas of pendular rings

    USGS Publications Warehouse

    Rose, W.

    1958-01-01

    A packing of spheres is taken as a suitable model of porous media. The packing may be regular and the sphere size may be uniform, but in general, both should be random. Approximations are developed to give the volumes and surface areas of pendular rings that exist at points of sphere contact. From these, the total free volume and interfacial specific surface area are derived as expressive of the textural character of the packing. It was found that the log-log plot of volumes and surface areas of pendular rings vary linearly with the angle made by the line joining the sphere centers and the line from the center of the largest sphere to the closest edge of the pendular ring. The relationship, moreover, was found not to be very sensitive to variation in the size ratio of the spheres in contact. It also was found that the addition of pendular ring material to various sphere packings results in an unexpected decrease in the surface area of the boundaries that confine the resulting pore space. ?? 1958 The American Institute of Physics.

  5. Osmosis and Surface Area to Volume Ratio.

    ERIC Educational Resources Information Center

    Barrett, D. R. B.

    1984-01-01

    Describes an experiment designed to help students understand the concepts of osmosis and surface area to volume ratio (SA:VOL). The task for students is to compare water uptake in different sizes of potato cubes and relate differences to their SA:VOL ratios. (JN)

  6. THE EFFECT OF ADSORBED SULFUR ON THE SURFACE SELF-DIFFUSION OF COPPER.

    DTIC Science & Technology

    SULFUR), * DIFFUSION ), (*ADSORPTION, (*COPPER, SURFACES, HYDROGEN, SINGLE CRYSTALS, ANNEALING, HYDROGEN COMPOUNDS, SULFIDES, GRAIN BOUNDARIES, HIGH TEMPERATURE, IMPURITIES, ENTHALPY, CHEMISORPTION, MOBILITY.

  7. Preparation and Characterization of Chitosan/Feldspar Biohybrid as an Adsorbent: Optimization of Adsorption Process via Response Surface Modeling

    PubMed Central

    Yazdani, Maryam; Bahrami, Hajir; Arami, Mokhtar

    2014-01-01

    Chitosan/feldspar biobased beads were synthesized, characterized, and tested for the removal of Acid Black 1 dye from aquatic phases. A four-factor central composite design (CCD) accompanied by response surface modeling (RSM) and optimization was used to optimize the dye adsorption by the adsorbent (chitosan/feldspar composite) in 31 different batch experiments. Independent variables of temperature, pH, initial dye concentration, and adsorbent dose were used to change to coded values. To anticipate the responses, a quadratic model was applied. Analysis of variance (ANOVA) tested the significance of the process factors and their interactions. The adequacy of the model was investigated by the correlation between experimental and predicted data of the adsorption and the calculation of prediction errors. The results showed that the predicted maximum adsorption amount of 21.63 mg/g under the optimum conditions (pH 3, temperature 15°C, initial dye concentration 125 mg/L, and dose 0.2 g/50 mL) was close to the experimental value of 19.85 mg/g. In addition, the results of adsorption behaviors of the dye illustrated that the adsorption process followed the Langmuir isotherm model and the pseudo-second-order kinetic model. Langmuir sorption capacity was found to be 17.86 mg/g. Besides, thermodynamic parameters were evaluated and revealed that the adsorption process was exothermic and favourable. PMID:24587722

  8. Residence time determination for adsorbent beds of different configurations

    SciTech Connect

    Otermat, J.E.; Wikoff, W.O.; Kovach, J.L.

    1995-02-01

    The residence time calculations of ASME AG-1 Code, Section FC, currently specify a screen surface area method, that is technically incorrect. Test data has been obtained on Type II adsorber trays of different configurations to establish residence time in the adsorber trays. These data indicate that the air volume/carbon volume ratio or the average screen area are more appropriate for the calculation of the residence time calculation than the currently used, smallest screen area basis.

  9. Structure of collagen adsorbed on a model implant surface resolved by polarization modulation infrared reflection-absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Brand, Izabella; Habecker, Florian; Ahlers, Michael; Klüner, Thorsten

    2015-03-01

    The polarization modulation infrared reflection-absorption spectra of collagen adsorbed on a titania surface and quantum chemical calculations are used to describe components of the amide I mode to the protein structure at a sub-molecular level. In this study, imino acid rich and poor fragments, representing the entire collagen molecule, are taken into account. The amide I mode of the collagen triple helix is composed of three absorption bands which involve: (i) (∼1690 cm-1) the Cdbnd O stretching modes at unhydrated groups, (ii) (1655-1673 cm-1) the Cdbnd O stretching at carbonyl groups at imino acids and glycine forming intramolecular hydrogen bonds with H atoms at both NH2 and, unusual for proteins, CH2 groups at glycine at a neighbouring chain and (iii) (∼1640 cm-1) the Cdbnd O stretching at carbonyl groups forming hydrogen bonds between two, often charged, amino acids as well as hydrogen bonds to water along the entire helix. The IR spectrum of films prepared from diluted solutions (c < 50 μg ml-1) corresponds to solution spectra indicating that native collagen molecules interact with water adsorbed on the titania surface. In films prepared from solutions (c ⩾ 50 μg ml-1) collagen multilayers are formed. The amide I mode is blue-shifted by 18 cm-1, indicating that intramolecular hydrogen bonds at imino acid rich fragments are weakened. Simultaneous red-shift of the amide A mode implies that the strength of hydrogen bonds at the imino acid poor fragments increases. Theoretically predicted distortion of the collagen structure upon adsorption on the titania surface is experimentally confirmed.

  10. Structure of collagen adsorbed on a model implant surface resolved by polarization modulation infrared reflection-absorption spectroscopy.

    PubMed

    Brand, Izabella; Habecker, Florian; Ahlers, Michael; Klüner, Thorsten

    2015-03-05

    The polarization modulation infrared reflection-absorption spectra of collagen adsorbed on a titania surface and quantum chemical calculations are used to describe components of the amide I mode to the protein structure at a sub-molecular level. In this study, imino acid rich and poor fragments, representing the entire collagen molecule, are taken into account. The amide I mode of the collagen triple helix is composed of three absorption bands which involve: (i) (∼1690cm(-1)) the CO stretching modes at unhydrated groups, (ii) (1655-1673cm(-1)) the CO stretching at carbonyl groups at imino acids and glycine forming intramolecular hydrogen bonds with H atoms at both NH2 and, unusual for proteins, CH2 groups at glycine at a neighbouring chain and (iii) (∼1640cm(-1)) the CO stretching at carbonyl groups forming hydrogen bonds between two, often charged, amino acids as well as hydrogen bonds to water along the entire helix. The IR spectrum of films prepared from diluted solutions (c<50μgml(-1)) corresponds to solution spectra indicating that native collagen molecules interact with water adsorbed on the titania surface. In films prepared from solutions (c⩾50μgml(-1)) collagen multilayers are formed. The amide I mode is blue-shifted by 18cm(-1), indicating that intramolecular hydrogen bonds at imino acid rich fragments are weakened. Simultaneous red-shift of the amide A mode implies that the strength of hydrogen bonds at the imino acid poor fragments increases. Theoretically predicted distortion of the collagen structure upon adsorption on the titania surface is experimentally confirmed.

  11. Synthesis and characterization of large specific surface area nanostructured amorphous silica materials.

    PubMed

    Marquez-Linares, Francisco; Roque-Malherbe, Rolando M A

    2006-04-01

    Large specific surface area materials attract wide attention because of their applications in adsorption, catalysis, and nanotechnology. In the present study, we describe the synthesis and characterization of nanostructured amorphous silica materials. These materials were obtained by means of a modification of the Stobe-Fink-Bohn (SFB) method. The morphology and essential features of the synthesized materials have been studied using an automated surface area and pore size analyzer and scanning electron microscopy. The existence of a micro/mesoporous structure in the obtained materials has been established. It was also found that the obtained particle packing materials show large specific surface area up to 1,600 m2/g. (To our best knowledge, there is no any reported amorphous silica material with such a higher specific surface area.) The obtained materials could be useful in the manufacture of adsorbents, catalyst supports, and other nanotechnological applications.

  12. Porous silicon structures with high surface area/specific pore size

    DOEpatents

    Northrup, M. Allen; Yu, Conrad M.; Raley, Norman F.

    1999-01-01

    Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gasses in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters.

  13. Porous silicon structures with high surface area/specific pore size

    DOEpatents

    Northrup, M.A.; Yu, C.M.; Raley, N.F.

    1999-03-16

    Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gases in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters. 9 figs.

  14. Human body surface area: a theoretical approach.

    PubMed

    Wang, Jianfeng; Hihara, Eiji

    2004-04-01

    Knowledge of the human body surface area has important applications in medical practice, garment design, and other engineering sizing. Therefore, it is not surprising that several expressions correlating body surface area with direct measurements of body mass and length have been reported in the literature. In the present study, based on the assumption that the exterior shape of the human body is the result of convex and concave deformations from a basic cylinder, we derive a theoretical equation minimizing body surface area (BSA) at a fixed volume (V): BSA=(9pi VL)(0.5), where L is the reference length of the body. Assuming a body density value of 1,000 kg.m(-3), the equation becomes BSA=(BM.BH/35.37)(0.5), where BSA is in square meters, BM is the body mass in kilograms, and BH is the body height in meters. BSA values calculated by means of this equation fall within +/-7% of the values obtained by means of the equations available in the literature, in the range of BSA from children to adults. It is also suggested that the above equation, which is obtained by minimizing the outer body surface at a fixed volume, implies a fundamental relation set by the geometrical constraints governing the growth and the development of the human body.

  15. The structures and dynamics of atomic and molecular adsorbates on metal surfaces by scanning tunneling microscopy and low energy electron diffraction

    SciTech Connect

    Yoon, Hyungsuk Alexander

    1996-12-01

    Studies of surface structure and dynamics of atoms and molecules on metal surfaces are presented. My research has focused on understanding the nature of adsorbate-adsorbate and adsorbate-substrate interactions through surface studies of coverage dependency and coadsorption using both scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The effect of adsorbate coverage on the surface structures of sulfur on Pt(111) and Rh(111) was examined. On Pt(111), sulfur forms p(2x2) at 0.25 ML of sulfur, which transforms into a more compressed (√3x√3)R30° at 0.33 ML. On both structures, it was found that sulfur adsorbs only in fcc sites. When the coverage of sulfur exceeds 0.33 ML, it formed more complex c(√3x7)rect structure with 3 sulfur atoms per unit cell. In this structure, two different adsorption sites for sulfur atoms were observed - two on fcc sites and one on hcp site within the unit cell.

  16. High-resolution electron-energy-loss spectroscopy and photoelectron-diffraction studies of the geometric structure of adsorbates on single-crystal metal surfaces

    SciTech Connect

    Rosenblatt, D.H.

    1982-11-01

    Two techniques which have made important contributions to the understanding of surface phenomena are high resolution electron energy loss spectroscopy (EELS) and photoelectron diffraction (PD). EELS is capable of directly measuring the vibrational modes of clean and adsorbate covered metal surfaces. In this work, the design, construction, and performance of a new EELS spectrometer are described. These results are discussed in terms of possible structures of the O-Cu(001) system. Recommendations for improvements in this EELS spectrometer and guidelines for future spectrometers are given. PD experiments provide accurate quantitative information about the geometry of atoms and molecules adsorbed on metal surfaces. The technique has advantages when used to study disordered overlayers, molecular overlayers, multiple site systems, and adsorbates which are weak electron scatterers. Four experiments were carried out which exploit these advantages.

  17. Observation of UV-induced Auger features in catechol adsorbed on anatase TiO2 (101) single crystal surface

    NASA Astrophysics Data System (ADS)

    Thomas, Andrew G.; Syres, Karen L.

    2012-04-01

    We have investigated the electronic structure of catechol adsorbed on the anatase TiO2 (101) surface under illumination with ultraviolet (UV) light (4.75 eV) using resonant photoemission spectroscopy. UV illumination results in the appearance of a strong Ti MVV (M refers to photoionization of 3p level and VV the Auger decay process via the valence levels) feature at a kinetic energy of 26.2 eV. This is attributed to the creation of localised states following catechol to Ti-3d excitation by the UV source. A sharp resonance attributed to excitation from Ti 3p states into these localised states is observed in constant final state spectra.

  18. On the possible mechanism of the W(001) surface reconstruction with adsorbed hydrogen

    NASA Astrophysics Data System (ADS)

    Egorushkin, V. E.; Savushkin, E. V.

    1990-12-01

    The reconstruction of the (001) face of tungsten is treated as a Jahn-Teller transition connected with two narrow surface electronic bands along the Γ M lines. The surface periodic lattice distortion is found to be accompanied by the occurence of the hydrogen ordering in an adlayer with the result that the reconstruction temperature raises.

  19. Modeling of transmittance degradation caused by optical surface contamination by atomic oxygen reaction with adsorbed silicones

    NASA Astrophysics Data System (ADS)

    Snyder, Aaron; Banks, Bruce A.; Miller, Sharon K.; Stueber, Thomas; Sechkar, Edward

    2000-09-01

    A numerical procedure is presented to calculate transmittance degradation caused by contaminant films on spacecraft surfaces produced through the interaction of orbital atomic oxygen (AO) with volatile silicones and hydrocarbons from spacecraft components. In the model, contaminant accretion is dependent on the adsorption of species, depletion reactions due to gas-surface collisions, desorption, and surface reactions between AO and silicon producing SiOx (where x is near 2). A detailed description of the procedure used to calculate the constituents of the contaminant layer is presented, including the equations that govern the evolution of fractional coverage by specie type. As an illustrative example of film growth, calculation results using a prototype code that calculates the evolution of surface coverage by specie type is presented and discussed. An example of the transmittance degradation caused by surface interaction of AO with deposited contaminant is presented for the case of exponentially decaying contaminant flux. These examples are performed using hypothetical values for the process parameters.

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

    PubMed

    Zhi, Yue; Liu, Jinxia

    2015-07-01

    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.

  1. Ambient DESI and LESA-MS Analysis of Proteins Adsorbed to a Biomaterial Surface Using In-Situ Surface Tryptic Digestion

    NASA Astrophysics Data System (ADS)

    Rao, Wei; Celiz, Adam D.; Scurr, David J.; Alexander, Morgan R.; Barrett, David A.

    2013-12-01

    The detection and identification of proteins adsorbed onto biomaterial surfaces under ambient conditions has significant experimental advantages but has proven to be difficult to achieve with conventional measuring technologies. In this study, we present an adaptation of desorption electrospray ionization (DESI) and liquid extraction surface analysis (LESA) mass spectrometry (MS) coupled with in-situ surface tryptic digestion to identify protein species from a biomaterial surface. Cytochrome c, myoglobin, and BSA in a combination of single and mixture spots were printed in an array format onto Permanox slides, followed by in-situ surface digestion and detection via MS. Automated tandem MS performed on surface peptides was able to identify the proteins via MASCOT. Limits of detection were determined for DESI-MS and a comparison of DESI and LESA-MS peptide spectra characteristics and sensitivity was made. DESI-MS images of the arrays were produced and analyzed with imaging multivariate analysis to automatically separate peptide peaks for each of the proteins within a mixture into distinct components. This is the first time that DESI and LESA-MS have been used for the in-situ detection of surface digested proteins on biomaterial surfaces and presents a promising proof of concept for the use of ambient MS in the rapid and automated analysis of surface proteins.

  2. Electrostatic fluctuation interactions between neutral surfaces with adsorbed, mobile ions or dipoles

    NASA Astrophysics Data System (ADS)

    Attard, Phil; Kjellander, Roland; Mitchell, D. John; Jönsson, Bo

    1988-08-01

    The electrostatic fluctuation interactions between two surfaces which carry charged or dipolar, laterally mobile particles, are investigated using both a formally exact theory and approximate methods. Each surface constitutes the boundary between two dielectric continua and has no net charge. The exact analysis demonstrates the interdependence of the van der Waals interaction between the dielectric media and the electrostatic image interactions of the particles. General asymptotic laws for the pressure between the surfaces, valid at large separations, are extracted from the exact equations. Even at relatively small separations, the asymptotic expressions give surprisingly good estimates of the actual interactions, as calculated using the hypernetted chain equation and Monte Carlo techniques. A simple mean field perturbation approximation is also investigated and is shown to give good results, provided accurate pair distributions are known for the corresponding isolated, single surface.

  3. Kosterlitz-Thouless transition for 4He films adsorbed to rough surfaces.

    PubMed

    Luhman, D R; Hallock, R B

    2004-08-20

    We report the study of adsorption isotherms of 4He on several well characterized rough CaF2 surfaces using a quartz crystal microbalance technique at 1.672 K. The signature of decoupled mass observed on crossing the Kosterlitz-Thouless transition as a function of 4He film thickness decreases and becomes increasingly difficult to identify as the surface roughness is increased. A peak in the dissipation, indicative of the onset of superfluidity, changes little with roughness.

  4. Soft X-Ray Spectroscopy of Glycyl-Glycine Adsorbed on Cu(110) Surface

    NASA Astrophysics Data System (ADS)

    Feyer, V.; Plekan, O.; Lyamayev, V.; Skala, T.; Prince, K. C.; Chab, V.; Tsud, N.; Matolin, V.; Carravetta, V.

    2010-06-01

    Studies of the interaction between organic compounds and surfaces are motivated by their application as bio sensors, and their relevance to biocompatibility of implants and the origin of life. In the present work interaction of the simplest peptide, glycyl-glycine, with the Cu surface has been studied. Multilayer, monolayer and sub-monolayer films of this dipeptide on the clean and oxygen modified Cu(110) surface were prepared by thermal evaporation in high vacuum. The techniques used were soft X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy and density functional theory calculations. By comparing the experimental and theoretical spectra, detailed models of the electronic structure and adsorption geometry for each coverage have been proposed, which are in good agreement with the theoretical calculations. The carboxylic acid group of glycyl-glycine loses hydrogen and the molecule is coordinated via the carboxylate oxygen atoms to the surface. At low coverage the amino group bonds to the surface via a hydrogen atom, while at higher coverage the bonding is via the nitrogen lone pair. The peptide group is not involved in the bonding to the surface.

  5. Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption.

    PubMed

    Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Littunen, Kuisma; Pastinen, Ossi; Laakso, Simo

    2014-10-01

    A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m(2)/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available.

  6. Modeling of Transmittance Degradation Caused by Optical Surface Contamination by Atomic Oxygen Reaction with Adsorbed Silicones

    NASA Technical Reports Server (NTRS)

    Snyder, Aaron; Banks, Bruce; Miller, Sharon; Stueber, Thomas; Sechkar, Edward

    2001-01-01

    A numerical procedure is presented to calculate transmittance degradation caused by contaminant films on spacecraft surfaces produced through the interaction of orbital atomic oxygen (AO) with volatile silicones and hydrocarbons from spacecraft components. In the model, contaminant accretion is dependent on the adsorption of species, depletion reactions due to gas-surface collisions, desorption, and surface reactions between AO and silicone producing SiO(x), (where x is near 2). A detailed description of the procedure used to calculate the constituents of the contaminant layer is presented, including the equations that govern the evolution of fractional coverage by specie type. As an illustrative example of film growth, calculation results using a prototype code that calculates the evolution of surface coverage by specie type is presented and discussed. An example of the transmittance degradation caused by surface interaction of AO with deposited contaminant is presented for the case of exponentially decaying contaminant flux. These examples are performed using hypothetical values for the process parameters.

  7. Surface hopping dynamics of direct trans --> cis photoswitching of an azobenzene derivative in constrained adsorbate geometries

    NASA Astrophysics Data System (ADS)

    Floß, Gereon; Granucci, Giovanni; Saalfrank, Peter

    2012-12-01

    With ongoing miniaturization of electronic devices, the need for individually addressable, switchable molecules arises. An example are azobenzenes on surfaces which have been shown to be switchable between trans and cis forms. Here, we examine the "direct" (rather than substrate-mediated) channel of the trans → cis photoisomerization after ππ* excitation of tetra-tert-butyl-azobenzene physisorbed on surfaces mimicking Au(111) and Bi(111), respectively. In spirit of the direct channel, the electronic structure of the surface is neglected, the latter merely acting as a rigid platform which weakly interacts with the molecule via Van-der-Waals forces. Starting from thermal ensembles which represent the trans-form, sudden excitations promote the molecules to ππ*-excited states which are non-adiabatically coupled among themselves and to a nπ*-excited and the ground state, respectively. After excitation, relaxation to the ground state by internal conversion takes place, possibly accompanied by isomerization. The process is described here by "on the fly" semiclassical surface hopping dynamics in conjunction with a semiempirical Hamiltonian (AM1) and configuration-interaction type methods. It is found that steric constraints imposed by the substrate lead to reduced but non-vanishing, trans → cis reaction yields and longer internal conversion times than for the isolated molecule. Implications for recent experiments for azobenzenes on surfaces are discussed.

  8. The Role of Non-Bonded Interactions in the Conformational Dynamics of Organophosphorous Hydrolase Adsorbed onto Functionalized Mesoporous Silica Surfaces

    PubMed Central

    Gomes, Diego E.B.; Lins, Roberto D.; Pascutti, Pedro G.; Lei, Chenghong; Soares, Thereza A.

    2009-01-01

    The enzyme organophosphorous hydrolase (OPH) catalyzes the hydrolysis of a wide variety of organophosphorous compounds with high catalytic efficiency and broad substrate specificity. The immobilization of OPH in functionalized mesoporous silica (FMS) surfaces increases significantly its catalytic specific activity compared to the enzyme in solution with important applications for the detection and decontamination of insecticides and chemical warfare agents. Experimental measurements of immobilization efficiency as function of the charge and coverage percentage of different functional groups have been interpreted as electrostatic forces being the predominant interactions underlying the adsorption of OPH onto FMS surfaces. Explicit solvent molecular dynamics simulations have been performed for OPH in bulk solution and adsorbed onto two distinct interaction potential models of the FMS functional groups in order to investigate the relative contributions of non-bonded interactions to the conformational dynamics and adsorption of the protein. Our results support the conclusion that electrostatic interactions are responsible for the binding of OPH to the FMS surface. However, these results also show that van der Waals forces are detrimental for interfacial adhesion. In addition, it is found that OPH adsorption onto the FMS models favors a protein conformation whose active site is fully accessible to the substrate in contrast to the unconfined protein. PMID:19938866

  9. Surface activity of Janus particles adsorbed at fluid-fluid interfaces: Theoretical and experimental aspects.

    PubMed

    Fernandez-Rodriguez, Miguel Angel; Rodriguez-Valverde, Miguel Angel; Cabrerizo-Vilchez, Miguel Angel; Hidalgo-Alvarez, Roque

    2016-07-01

    Since de Gennes coined in 1992 the term Janus particle (JP), there has been a continued effort to develop this field. The purpose of this review is to present the most relevant theoretical and experimental results obtained so far on the surface activity of amphiphilic JPs at fluid interfaces. The surface activity of JPs at fluid-fluid interfaces can be experimentally determined using two different methods: the classical Langmuir balance or the pendant drop tensiometry. The second method requires much less amount of sample than the first one, but it has also some experimental limitations. In all cases collected here the JPs exhibited a higher surface or interfacial activity than the corresponding homogeneous particles. This reveals the significant advantage of JPs for the stabilization of emulsions and foams.

  10. Segregation at the surfaces of CuxPd1-x alloys in the presence of adsorbed S

    SciTech Connect

    Miller, James B.; Priyadarshini, Deepika; Gellman, Andrew J.

    2012-10-01

    The influence of adsorbed S on surface segregation in Cu{sub x}Pd{sub 1 - x} alloys (S/Cu{sub x}Pd{sub 1 - x)} was characterized over a wide range of bulk alloy compositions (x = 0.05 to 0.95) using high-throughput Composition Spread Alloy Film (CSAF) sample libraries. Top-surface and near-surface compositions of the CSAFs were measured as functions of bulk Cu composition, x, and temperature using spatially resolved low energy ion scattering spectroscopy (LEISS) and X-ray photoemission spectroscopy (XPS). Preferential segregation of Cu to the top-surface of the S/Cu{sub x}Pd{sub 1 - x} CSAF was observed at all bulk compositions, x, but the extent of Cu segregation to the S/Cu{sub x}Pd{sub 1 - x} surface was lower than the Cu segregation to the surface of a clean Cu{sub x}Pd{sub 1 - x} CSAF, clear evidence of an S-induced “segregation reversal.” The Langmuir–McLean formulation of the Gibbs isotherm was used to estimate the enthalpy and entropy of Cu segregation to the top-surface, ΔH{sub seg}(x) and ΔS{sub seg}(x), at saturation sulfur coverages. While Cu segregation to the top-surface of the clean Cu{sub x}Pd{sub 1 - x} is exothermic (ΔH{sub seg} < 0) for all bulk Cu compositions, it is endothermic (ΔH{sub seg} > 0) for S/Cu{sub x}Pd{sub 1 - x}. Segregation to the S/Cu{sub x}Pd{sub 1 - x} surface is driven by entropy. Changes in segregation patterns that occur upon adsorption of S onto Cu{sub x}Pd{sub 1 - x} appear to be related to formation of energetically favored Pd{single bond}S bonds at the surface, which counterbalance the enthalpic driving forces for Cu segregation to the clean surface.

  11. Surface area of montmorillonite from the dynamic sorption of nitrogen and carbon dioxide

    USGS Publications Warehouse

    Thomas, J.; Bohor, B.F.

    1968-01-01

    Surface area determinations were made on a montmorillonite with various cations emplaced on the exchangeable sites, utilizing nitrogen and carbon dioxide as adsorbates at 77 ??K and 195 ??K, respectively, in a dynamic system. From the fraction of a Mississippi montmorillonite less than about 1 ?? in size, samples were prepared by replacing the original exchangeable cations with Li+, Na+, K+, Rb+, Cs+, Mg++, Ca++, Ba++, and NH4+, forming a series of homoionic montmorillonite species. Surface areas from 3-point B.E.T. plots (half-hour adsorption points), with nitrogen as the adsorbate, ranged from 61 m2/g for Li-montmorillonite to 138 m2/g for Cs-montmorillonite, thus reflecting a certain degree of nitrogen penetration between layers. Complete penetration should theoretically result in a surface area of over 300 m2/g for this clay with a nitrogen monolayer between each pair of platelets. The experimental data indicate that the extent of penetration is time-dependent and is also a function of the interlayer forces as governed by the size and charge of the replaceable cation. This finding negates the generally accepted concept that nitrogen at 77 ??K does not penetrate the layers and provides a measure only of the external surface of expandable clay minerals. A further measure of the variation of interlayer forces is provided by the adsorption of carbon dioxide at 195 ??K. Surface area values ranged from 99 m2/g for Li-montmorillonite to 315 m2/g for Csmontmorillonite. Although the carbon dioxide molecule is larger than the nitrogen molecule, its greater penetration apparently is a result of its being kinetically more energetic (with a larger diffusion coefficient) at its higher adsorption temperature. Similar differences have been found with both adsorbates in the study of microporous substances, such as coal, where activated diffusion is of considerable significance. ?? 1968.

  12. Tunable surface charge of ZnS : Cu nano-adsorbent induced the selective preconcentration of cationic dyes from wastewater

    NASA Astrophysics Data System (ADS)

    Wang, Yongjing; Chen, Dagui; Wang, Yandi; Huang, Feng; Hu, Qichang; Lin, Zhang

    2012-05-01

    A novel environmentally friendly nano-adsorbent is developed by doping Cu+ cations into the lattice of ZnS microspheres. The adsorbent shows selective adsorbability for cationic dyes in low concentrations in wastewater. The adsorbed dye could be successfully eluted with alcohol, resulting in a 1000 fold enrichment of the dye solution.A novel environmentally friendly nano-adsorbent is developed by doping Cu+ cations into the lattice of ZnS microspheres. The adsorbent shows selective adsorbability for cationic dyes in low concentrations in wastewater. The adsorbed dye could be successfully eluted with alcohol, resulting in a 1000 fold enrichment of the dye solution. Electronic supplementary information (ESI) available: Synthesis, structural details of ZnS : Cu, adsorption isotherm of RhB on ZnS : Cu, control experiments for the adsorption measurements, pH effect on the adsorbability, and preliminary assessment of the adsorption efficiency for real industrial wastewater. See DOI: 10.1039/c2nr30689a

  13. Comprehensive study of pore evolution, mesostructural stability, and simultaneous surface functionalization of ordered mesoporous carbon (FDU-15) by wet oxidation as a promising adsorbent.

    PubMed

    Wu, Zhangxiong; Webley, Paul A; Zhao, Dongyuan

    2010-06-15

    Fuctionalization of porous carbon materials through chemical methods orientates the development of new hybrid materials with specific functions. In this paper, a comprehensive study of pore evolution, mesostructural oxidation resistance, and simultaneous surface functionalization of ordered mesoporous carbon FDU-15 under various oxidation conditions is presented for the first time. The mesostructure and pore evolution with increasing oxidative strength are retrieved from XRD, TEM, and N(2) sorption techniques. The textural properties can be conveniently manipulated by changing the oxidation parameters, including different oxidative solution, temperature, and duration. It is revealed that the mesoporous carbon FDU-15 shows excellent structural stability under severe oxidation treatments by acidic (NH(4))(2)S(2)O(8), HNO(3), and H(2)O(2) solutions, much more stable than the mesostructural analogue CMK-3 carbon prepared by the nanocasting method. The surface area and porosity deteriorate to a large extent compared to the pristine carbon, with the micropores/small mesopores as the major contribution to the deterioration. The micropore/small mesopore can be blocked by the attached surface oxides under mild oxidation, while reopened with more carbon layer dissolution under more severe conditions. Simultaneously, high densities of surface oxygen complexes, especially carboxylic groups, can be generated. The contents and properties of the surface oxygen-containing groups are extensively studied by FTIR, TG, elemental analyses, and water and ammonia adsorption techniques. Such surface-functionalized mesoporous carbons can be used as a highly efficient adsorbent for immobilization of heavy metal ions as well as functional organic and biomolecules, with high capacities and excellent binding capabilities. Thus, we believe that the functionalized mesoporous carbon materials can be utilized as a promising solid and stable support for water treatment and organic

  14. Effects of the surface mobility on the oxidation of adsorbed CO on platinum electrodes in alkaline media. The role of the adlayer and surface defects.

    PubMed

    Herrero, Enrique; Chen, Qing-Song; Hernández, Javier; Sun, Shi-Gang; Feliu, Juan M

    2011-10-06

    The oxidation of adsorbed CO on Pt single crystal electrodes has been studied in alkaline media. The surfaces used in this study were the Pt(111) electrode and vicinal stepped and kinked surfaces with (111) terraces. The kinked surfaces have either (110) steps broken by (100) kinks or (100) steps broken by (110) kinks and different kink densities. The voltammetric profiles for the CO stripping on those electrodes show peaks corresponding to the oxidation of CO on the (111) terraces, on the (100) steps/kinks and on the (110) steps/kinks at very distinctive potentials. Additionally, the stripping voltammograms always present a prewave. The analysis of the results with the different stepped and kinked surfaces indicates that the presence of the prewave is not associated with defects or kinks in the electrode surface. Also, the clear separation of the CO stripping process in different peak contributions indicates that the mobility of CO on the surface is very low. Using partial CO stripping experiments and studies at different pH, it has been proposed that the low mobility is a consequence of the negative absolute potential at which the adlayers are formed in alkaline media. Also, the surface diffusion coefficient for CO in these media has been estimated from the dependence of the stripping charge of the peaks with the scan rate of the voltammetry.

  15. Spectromicroscopy of C60 and azafullerene C59N: Identifying surface adsorbed water

    PubMed Central

    Erbahar, Dogan; Susi, Toma; Rocquefelte, Xavier; Bittencourt, Carla; Scardamaglia, Mattia; Blaha, Peter; Guttmann, Peter; Rotas, Georgios; Tagmatarchis, Nikos; Zhu, Xiaohui; Hitchcock, Adam P.; Ewels, Chris P.

    2016-01-01

    C60 fullerene crystals may serve as important catalysts for interstellar organic chemistry. To explore this possibility, the electronic structures of free-standing powders of C60 and (C59N)2 azafullerenes are characterized using X-ray microscopy with near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy, closely coupled with density functional theory (DFT) calculations. This is supported with X-ray photoelectron spectroscopy (XPS) measurements and associated core-level shift DFT calculations. We compare the oxygen 1s spectra from oxygen impurities in C60 and C59N, and calculate a range of possible oxidized and hydroxylated structures and associated formation barriers. These results allow us to propose a model for the oxygen present in these samples, notably the importance of water surface adsorption and possible ice formation. Water adsorption on C60 crystal surfaces may prove important for astrobiological studies of interstellar amino acid formation. PMID:27748425

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

    SciTech Connect

    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.

  17. Spectromicroscopy of C60 and azafullerene C59N: Identifying surface adsorbed water

    NASA Astrophysics Data System (ADS)

    Erbahar, Dogan; Susi, Toma; Rocquefelte, Xavier; Bittencourt, Carla; Scardamaglia, Mattia; Blaha, Peter; Guttmann, Peter; Rotas, Georgios; Tagmatarchis, Nikos; Zhu, Xiaohui; Hitchcock, Adam P.; Ewels, Chris P.

    2016-10-01

    C60 fullerene crystals may serve as important catalysts for interstellar organic chemistry. To explore this possibility, the electronic structures of free-standing powders of C60 and (C59N)2 azafullerenes are characterized using X-ray microscopy with near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy, closely coupled with density functional theory (DFT) calculations. This is supported with X-ray photoelectron spectroscopy (XPS) measurements and associated core-level shift DFT calculations. We compare the oxygen 1s spectra from oxygen impurities in C60 and C59N, and calculate a range of possible oxidized and hydroxylated structures and associated formation barriers. These results allow us to propose a model for the oxygen present in these samples, notably the importance of water surface adsorption and possible ice formation. Water adsorption on C60 crystal surfaces may prove important for astrobiological studies of interstellar amino acid formation.

  18. Time-resolved spectroscopy at surfaces and adsorbate dynamics: Insights from a model-system approach

    NASA Astrophysics Data System (ADS)

    Boström, Emil; Mikkelsen, Anders; Verdozzi, Claudio

    2016-05-01

    We introduce a model description of femtosecond laser induced desorption at surfaces. The substrate part of the system is taken into account as a (possibly semi-infinite) linear chain. Here, being especially interested in the early stages of dissociation, we consider a finite-size implementation of the model (i.e., a finite substrate), for which an exact numerical solution is possible. By time-evolving the many-body wave function, and also using results from a time-dependent density functional theory description for electron-nuclear systems, we analyze the competition between several surface-response mechanisms and electronic correlations in the transient and longer time dynamics under the influence of dipole-coupled fields. Our model allows us to explore how coherent multiple-pulse protocols can impact desorption in a variety of prototypical experiments.

  19. Annual Report 2013-2014: Theoretical Studies of Nerve Agents Adsorbed on Surfaces

    DTIC Science & Technology

    2014-07-08

    L Whitten Professor of Chemistry North Carolina State University Raleigh, NC 27695 Telephone Number: 919-515-7960 Email: whitten@ncsu.edu...electronic states accurately and to identify factors that affect desorption energies and kinetics, solvation of nerve agents by water and the spectral...to describe surface interactions and low energy electronic states at high aaccuracy using theory in order to understand the details of bonding to

  20. Raman spectra of adsorbed layers on space shuttle and AOTV thermal protection system surface

    NASA Technical Reports Server (NTRS)

    Willey, Ronald J.

    1987-01-01

    Surfaces of interest to space vehicle heat shield design were struck by a 2 W argon ion laser line while subjected to supersonic arc jet flow conditions. Emission spectra were taken at 90 deg to the angle of laser incidence on the test object. Results showed possible weak Raman shifts which could not be directly tied to any particular parameter such as surface temperature or gas composition. The investigation must be considered exploratory in terms of findings. Many undesirable effects were found and corrected as the project progressed. For instance, initial spectra settings led to ghosts which were eliminated by closing the intermediate of filter slit of the Spex from 8 to 3 mm. Further, under certain conditions, plasma lines from the laser were observed. Several materials were also investigated at room temperature for Raman shifts. Results showed Raman shifts for RCC and TEOS coated materials. The HRSI materials showed only weak Raman shifts, however, substantial efforts were made in studying these materials. Baseline materials showed the technique to be sound. The original goal was to find a Raman shift for the High-temperature Reusable Surface Insulation (HRSI) Reaction Cured borosilicate Glass (RCG) coated material and tie the amplitude of this peak to Arc jet conditions. Weak Raman shifts may be present, however, time limitations prevented confirmation.

  1. Removal of acutely hazardous pharmaceuticals from water using multi-template imprinted polymer adsorbent.

    PubMed

    Venkatesh, Avinash; Chopra, Nikita; Krupadam, Reddithota J

    2014-05-01

    Molecularly imprinted polymer adsorbent has been prepared to remove a group of recalcitrant and acutely hazardous (p-type) chemicals from water and wastewaters. The polymer adsorbent exhibited twofold higher adsorption capacity than the commercially used polystyrene divinylbenzene resin (XAD) and powdered activated carbon adsorbents. Higher adsorption capacity of the polymer adsorbent was explained on the basis of high specific surface area formed during molecular imprinting process. Freundlich isotherms drawn showed that the adsorption of p-type chemicals onto polymer adsorbent was kinetically faster than the other reference adsorbents. Matrix effect on adsorption of p-type chemicals was minimal, and also polymer adsorbent was amenable to regeneration by washing with water/methanol (3:1, v/v) solution. The polymer adsorbent was unaltered in its adsorption capacity up to 10 cycles of adsorption and desorption, which will be more desirable in cost reduction of treatment compared with single-time-use activated carbon.

  2. Phthalocyaninato complexes with peripheral alkylthio chains: disk-like adsorbate species for the vertical anchoring of ligands on gold surfaces

    PubMed Central

    Siemeling, Ulrich; Schirrmacher, Christian; Glebe, Ulrich; Bruhn, Clemens; Baio, Joe E.; Árnadóttir, Líney; Castner, David G.; Weidner, Tobias

    2011-01-01

    Thin metalorganic films were prepared on gold by self-assembly of thioether-functionalised phthalocyaninato complexes from solution. The phthalocyaninato ligands used contain eight peripheral, β-positioned, alkylthio substituents SR (1a: R = n-C8H17, 1b: R = n-C12H25), which serve as headgroups for surface binding and promote lateral assembly, while the disk-like phthalocyaninato core offers the scope for the attachment of axial ligands to the adsorbed molecules. This process was mimicked by coordination of pyridine (Py) to [Zn(1a)] and [Zn(1b)], respectively. The crystal structures of the products [Zn(1a)(Py)] and [Zn(1b)(Py)] were determined. The crystal structures of 4,5-bis(octylthio)phthalodinitrile and 4,5-bis(dodecylthio)phthalodinitrile were also determined. The films fabricated from [Mn(1a)Cl] and [Mn(1b)Cl] on gold were characterised by XPS, ToF-SIMS and NEXAFS spectroscopy, which revealed the presence of well-defined and homogeneous self-assembled monolayers (SAMs), whose constituents are bound to the substrate by thioether–gold linkages. The orientation of the macrocycles is predominantly parallel to the surface. Strong electronic interaction of the manganese(III) centre with the substrate leads to Cl loss upon adsorption and its reduction to MnII. PMID:21857743

  3. Oscillating electric-field effects on adsorbed-water at rutile- and anatase-TiO2 surfaces

    NASA Astrophysics Data System (ADS)

    Futera, Zdenek; English, Niall J.

    2016-11-01

    We have performed non-equilibrium molecular dynamics simulations of various TiO2/water interfaces at ambient temperature in presence of oscillating electric fields in frequency range 20-100 GHz and RMS intensities 0.05-0.25 V/Å. Although the externally applied fields are by one order of magnitude lower than the intrinsic electric field present on the interfaces (˜1.5-4.5 V/Å), significant non-thermal coupling of rotational and translational motion of water molecules was clearly observed. Enhancement of the motion, manifested by increase of diffusivity, was detected in the first hydration layer, which is known to be heavily confined by adsorption to the TiO2 surface. Interestingly, the diffusivity increases more rapidly on anatase than on rutile facets where the adsorbed water was found to be more organized and restrained. We observed that the applied oscillating field reduces number of hydrogen bonds on the interface. The remaining H-bonds are weaker than those detected under zero-field conditions; however, their lifetime increases on most of the surfaces when the low-frequency fields are applied. Reduction of adsorption interaction was observed also in IR spectra of interfacial water where the directional patterns are smeared as the intensities of applied fields increase.

  4. Order disorder phase transition on the Pb-adsorbed Si(1 1 0) surface

    NASA Astrophysics Data System (ADS)

    Kim, Y. K.; Ahn, J. R.; Cho, E. S.; An, K.-S.; Yeom, H. W.; Koh, H.; Rotenberg, E.; Park, C. Y.

    2005-12-01

    A new reversible temperature-dependent phase transition on Pb/Si(1 1 0) was found by photoemission spectroscopy and low energy electron diffraction. The room temperature 1 × 1 surface was found to transit into low temperature 4 × 2 with a transition temperature of roughly 200 K. The phase transition does not induce a temperature-dependent variation in both the energy bands and the Si 2p and Pb 5d spectra. This indicates that the phase transition is close to an order-disorder one.

  5. Theoretical Study on Surface-Enhanced Raman Spectra of Water Adsorbed on Noble Metal Cathodes of Nanostructures

    NASA Astrophysics Data System (ADS)

    Wu, De-Yin; Pang, Ran; Tian, Zhong-Qun

    2016-06-01

    The observed surface-enhanced Raman scattering (SERS) spectra of water adsorbed on metal film electrodes of silver, gold, and platinum nanoparticles were used to infer interfacial water structures. The basis is the change of the electrochemical vibrational Stark tuning rates and the relative Raman intensity of the stretching and bending modes. How it is not completely understood the reason why the relative Raman intensity ratio of the bending and stretching vibrations of interfacial water increases at the very negative potential region. Density functional theory calculations provide the conceptual model. The specific enhancement effect for the bending mode was closely associated with the water adsorption structure in a hydrogen bonded configuration through its H-end binding to surface sites with large polarizability due to strong cathodic polarization. The present theoretical results allow us to propose that interfacial water molecules exist on these metal cathodes with different hydrogen bonding interactions, the HO-H…Ag(Au) for silver and gold. In acidic solution, a surface electron-hydronium ion-pair was proposed as an adsorption configuration of interfacial water structures on silver and gold cathodes based on density functional theory (DFT) calculations. The EHIP is in the configuration of H3O+(H2O)ne-, where the hydronium H3O+ and the surface electron is separated by water layers. The electron bound in the EHIP can first be excited under light irradiation, subsequently inducing a structural relaxation into a hydrated hydrogen atom. Thus, Raman intensities of the interfacial water in the EHIP species are signifcantly enhanced due to the cathodic polarization on silver and gold electrodes.

  6. Targeted Mutagenesis and Combinatorial Library Screening Enables Control of Protein Orientation on Surfaces and Increased Activity of Adsorbed Proteins.

    PubMed

    Cruz-Teran, Carlos A; Carlin, Kevin B; Efimenko, Kirill; Genzer, Jan; Rao, Balaji M

    2016-08-30

    While nonspecific adsorption is widely used for immobilizing proteins on solid surfaces, the random nature of protein adsorption may reduce the activity of immobilized proteins due to occlusion of the active site. We hypothesized that the orientation a protein assumes on a given surface can be controlled by systematically introducing mutations into a region distant from its active site, thereby retaining activity of the immobilized protein. To test this hypothesis, we generated a combinatorial protein library by randomizing six targeted residues in a binding protein derived from highly stable, nonimmunoglobulin Sso7d scaffold; mutations were targeted in a region that is distant from the binding site. This library was screened to isolate binders that retain binding to its cognate target (chicken immunoglobulin Y, cIgY) as well as exhibit adsorption on unmodified silica at pH 7.4 and high ionic strength conditions. A single mutant, Sso7d-2B5, was selected for further characterization. Sso7d-2B5 retained binding to cIgY with an apparent dissociation constant similar to that of the parent protein; both mutant and parent proteins saturated the surface of silica with similar densities. Strikingly, however, silica beads coated with Sso7d-2B5 could achieve up to 7-fold higher capture of cIgY than beads coated with the parent protein. These results strongly suggest that mutations introduced in Sso7d-2B5 alter its orientation relative to the parent protein, when adsorbed on silica surfaces. Our approach also provides a generalizable strategy for introducing mutations in proteins so as to improve their activity upon immobilization, and has direct relevance to development of protein-based biosensors and biocatalysts.

  7. Study of IR laser photoacoustic spectra of organic molecules adsorbed on metal surface

    NASA Astrophysics Data System (ADS)

    Lu, Huizong; Chen, Kaitai; Wang, Zhaoyong

    1987-06-01

    Using a branch-tuning CW CO2 laser in the range of 0.2 to 10.8 microns, the IR photoacoustic spectra of organic molecules absorbed on a silver surface were studied. The absorbed molecular spectra of four layers of arachidic acid and cellulose diacetate with different surface densities was studied. No peak shift was found in a comparison between IR photoacoustic spectra of solid arachidic acid near 944/cm and the corresponding IR Fourier spectra of solid archidic acid. The IR photoacoustic spectra of cellulose diacetate with sigma sub 1 = 14,000/sq cm and sigma sub 1 = 5.5 x 10 to the 15th/sq cm respectively was compared with the corresponding transmission spectra of solid cellulose diacetate. It was found that the peak of the former near 1054/cm had a red shift of about 5/cm while the peak of the latter had no obvious shift within the range of accuracy of the experiment.

  8. Powder-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-05-03

    A powder-based adsorbent and a related method of manufacture are provided. The powder-based adsorbent includes polymer powder with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the powder-based adsorbent includes irradiating polymer powder, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Powder-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  9. Foam-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2015-06-02

    Foam-based adsorbents and a related method of manufacture are provided. The foam-based adsorbents include polymer foam with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the foam-based adsorbents includes irradiating polymer foam, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Foam-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  10. Adsorbent phosphates

    NASA Technical Reports Server (NTRS)

    Watanabe, S.

    1983-01-01

    An adsorbent which uses as its primary ingredient phosphoric acid salts of zirconium or titanium is presented. Production methods are discussed and several examples are detailed. Measurements of separating characteristics of some gases using the salts are given.

  11. Enhanced Raman scattering by molecules adsorbed at the surface of colloidal spheroids

    NASA Astrophysics Data System (ADS)

    Wang, D.-S.; Kerker, M.

    1981-08-01

    Equations are derived and calculations are presented for the electrodynamic mechanism of enhanced Raman scattering by molecules at the surface of prolate and oblate spheroids in the small-particle limit. The molecules may be arbitrarily distributed; the particles may be arbitrarily oriented. Calculations are presented for a monolayer distributed over randomly oriented spheroids. The effects of particle shape are considered for Ag, Au, and Cu hydrosols. The peak enhancement moves to longer wavelengths, and in the case of Au and Cu the magnitude of the enhancement increases strikingly as the eccentricity increases. The relation between the dependence of the Raman enhancement upon excitation wavelength and the extinction spectra is discussed, including the precariousness of extrapolating such relations beyond the small-particle limit.

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

    NASA Astrophysics Data System (ADS)

    Meng, Qingyong; Meyer, Hans-Dieter

    2015-10-01

    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.

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

    SciTech Connect

    Meng, Qingyong; Meyer, Hans-Dieter

    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.

  14. Characterization of surface runoff in urban areas.

    PubMed

    Choe, J S; Bang, K W; Lee, J H

    2002-01-01

    Water quality measurements of surface runoff have been carried out in selected residential and industrial zones in urban areas, in which yearly mean precipitation is 1,225 mm. The concentrations of constituents in the surface runoff were measured at sampling sites categorized by land use type in the residential zone, and by industry type in the industrial zone. The water quality constituents of BOD5, COD, SS, NO3-N, TKN, PO4-P, TP, n-Hexane extracts, Cr, Cu, Pb and Fe were analyzed. The event mean concentrations (EMCs) of COD, SS, TKN and TP in the residential zone were 313 mg/L, 279 mg/L, 8.45 mg/L, 1.98 mg/L, and those in the industrial zone were 80 mg/L, 106 mg/L, 5.07 mg/L, and 1.93 mg/L, respectively. Cumulative load curves were created to analyze the first-flushing effect of each pollutant related to the pollutant, the rainfall event, and the land use type. No general relationship between the cumulative load and runoff has been established. The degree of first-flushing effect by constituents was in the following order; TKN>COD>SS>HEM>TP>PO4-P. The correlations between SS and other constituents were analyzed to evaluate the efficiency of the physical treatment process to control the surface runoff in urban areas. Based on the correlation of constituents with SS, high treatment efficiency of SS, heavy metals, organic matter, and TP was expected. The unit pollutant loading rates of COD, SS, TKN, TP, Cr and Pb in the residential zone were 2,392, 2,130, 64.6, 15.1, 0.31, and 1.83 kg/ha/yr, and those in the industrial zone were 612, 812, 38.7, 14.8, 0.51 and 0.82 kg/ha/yr, respectively.

  15. Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides.

    PubMed

    Wiederkehr, Rodrigo S; Hoops, Geoffrey C; Aslan, Mustafa M; Byard, Courtney L; Mendes, Sergio B

    2009-05-14

    In this work, we report experimental results on the molar absorptivity of cytochrome c adsorbed at different submonolayer levels onto an aluminum oxide waveguide surface; our data show a clear dependence of the protein optical properties on its surface density. The measurements were performed using the broadband, single-mode, integrated optical waveguide spectroscopic technique, which is an extremely sensitive tool able to reach submonolayer levels of detection required for this type of studies. This investigation focuses on the molar absorptivity at the Q-band (centered at 525 nm) and, for the first time to our knowledge, the weak charge transfer (CT) band (centered at 695 nm) of surface-adsorbed cyt c. Polarized light in the spectral region from 450 to 775 nm was all-coupled into an alumina thin film, which functioned as a single-mode planar optical waveguide. The alumina thin-film waveguide used for this work had a thickness of 180 nm and was deposited on a glass substrate by the atomic layer deposition process. The protein submonolayer was formed on the alumina waveguide surface through electrostatic adsorption from an aqueous buffer solution at neutral pH. The optical properties of the surface-adsorbed cyt c were investigated for bulk protein concentrations ranging from 5 nM to 8200 nM in the aqueous buffer solution. For a protein surface density of 2.3 pmol/cm(2), the molar absorptivity measured at the charge transfer band was 335 M(-1) cm(-1), and for a surface density of 15 pmol/cm(2) was 720 M(-1) cm(-1), which is much closer to the value of cyt c dissolved in an aqueous neutral buffer (830 M(-1) cm(-1)). The modification of the protein molar absorptivity and its dependence on the surface density can most likely be attributed to conformational changes of the surface-adsorbed species.

  16. Photon-exposure-dependent photon-stimulated desorption for obtaining photolysis cross section of molecules adsorbed on surface by monochromatic soft x-ray photons.

    PubMed

    Chou, L-C; Jang, C-Y; Wu, Y-H; Tsai, W-C; Wang, S-K; Chen, J; Chang, S-C; Liu, C-C; Shai, Y; Wen, C-R

    2008-12-07

    Photon-exposure-dependent positive- and negative-ion photon-stimulated desorption (PSD) was proposed to study the photoreactions and obtain the photolysis cross sections of molecules adsorbed on a single-crystal surface by monochromatic soft x-ray photons with energy near the core level of adsorbate. The changes in the F(+) and F(-) PSD ion yields were measured from CF(3)Cl molecules adsorbed on Si(111)-7x7 at 30 K (CF(3)Cl dose=0.3x10(15) molecules/cm(2), approximately 0.75 monolayer) during irradiation of monochromatic soft x-ray photons near the F(1s) edge. The PSD ion yield data show the following characteristics: (a) The dissociation of adsorbed CF(3)Cl molecules is due to a combination of direct photodissociation via excitation of F(1s) core level and substrate-mediated dissociation [dissociative attachment and dipolar dissociation induced by the photoelectrons emitting from the silicon substrate]. (b) the F(+) ion desorption is associated with the bond breaking of the surface CF(3)Cl, CF(2)Cl, CFCl, and SiF species. (c) the F(-) yield is mainly due to DA and DD of the adsorbed CF(3)Cl molecules. (d) The surface SiF is formed by reaction of the surface Si atom with the neutral fluorine atom, F(+), or F(-) ion produced by scission of C-F bond of CF(3)Cl, CF(2)Cl, or CFCl species. A kinetic model was proposed for the explanation of the photolysis of this submonolayer CF(3)Cl-covered surface. Based on this model and the variation rates of the F(+)F(-) signals during fixed-energy monochromatic photon bombardment at 690.2 and 692.6 eV [near the F(1s) edge], the photolysis cross section was deduced as a function of energy.

  17. Abstraction of Si and SiH x ( x=1, 2, 3) adsorbed on Cu(1 0 0) surfaces with gaseous H(D) towards silane

    NASA Astrophysics Data System (ADS)

    Kolovos-Vellianitis, D.; Kammler, Th.; Zecho, Th.; Küppers, J.

    2001-09-01

    The interaction of silane and disilane with Cu(1 0 0) surfaces was studied in the temperature range 77-650 K with thermal desorption and Auger electron spectroscopies. Silane admission to Cu(1 0 0) at low temperatures initially leads to a complete decomposition of the silanes into adsorbed Si and H. Close to saturation of the surface with H, SiH x species remain intact on the surface. They were identified as SiH 3 and to a smaller extent SiH 2 by monitoring the silane abstraction products and their kinetics during admitting gaseous D to the surface between 77 and 200 K. Silane desorption through recombination of SiH 3 and SiH 2 with adsorbed H occurs around 157 and 224 K, respectively. After hydrogen desorption around 300 K a Si covered surface remains, which can be converted to a clean Cu(1 0 0) surface by activating Si bulk diffusion around 700 K. Adsorbed Si is abstracted from the surface below 200 K by gaseous H via formation of silane through a sequence of four hydrogenation steps. The first hydrogenation reaction is rate determining and is significantly accelerated by increasing the temperature between 77 and 200 K. Above 200 K a thermally unstable SiH x species blocks the abstraction reaction. The reaction kinetics phenomenology is in accordance with an Eley-Rideal scenario.

  18. Switching orientation of adsorbed molecules: Reverse domino on a metal surface

    NASA Astrophysics Data System (ADS)

    Braatz, C. R.; Esat, T.; Wagner, C.; Temirov, R.; Tautz, F. S.; Jakob, P.

    2016-01-01

    A thus far unknown phase of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) on Ag(111), characterized by an all perpendicular orientation of the planar molecules and bound to the Ag substrate through the carboxyl oxygen atoms has been identified using infrared absorption spectroscopy and scanning tunneling microscopy. Its formation process requires second layer NTCDA to squeeze into empty spaces between relaxed monolayer NTCDA molecules. Remarkably, this process causes initially parallel oriented NTCDA to likewise adopt the new, highly inclined adsorption geometry. According to our SPA-LEED and STM findings, the new phase displays a distinct long range order and shows a pronounced tendency to form 1D rows or narrow islands. We suggest that extra NTCDA preferentially transforms into the upright configuration close to existing islands and attaches to them, i.e. the transformation process proceeds in a directed and recurrent manner (reverse domino scenario). Identical processing starting with a compressed NTCDA/Ag(111) monolayer leads to a purely parallel oriented bilayer, that is, the NTCDA monolayer phase is retained and merely acts as a passive template for bilayer NTCDA. The new vertical NTCDA phase represents an unusual molecular system with π-orbitals oriented parallel to a metal surface. A substantially reduced coupling of these orbitals to Ag(111) electronic levels is conjectured, which will have a major impact on intermolecular couplings and electronically excited state lifetimes.

  19. Chemical Potential of Triethylene Glycol Adsorbed on Surfaces Relevant to Gas Transport and Processing - Studies Using Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Kvamme, B.; Olsen, R.; Sjöblom, S.; Leirvik, K. N.; Kuznetsova, T.

    2014-12-01

    Natural gas will inevitably contain trace amounts of water and other impurities during different stages of processing and transport. Glycols, such as triethylene glycol (TEG), will in many cases follow the water. The glycol contents of the gas can originate from preceding glycol-drying units or it can be a residue from the direct injection of glycols used to prevent hydrate formation. Thus, it is important to know how glycol contents will affect the different paths leading to hydrate formation. Glycols may in some cases dominate the condensed water phase. If this occurs, it will lead to the well-documented shift in the hydrate stability curve, due to the altered activity of the water. A great deal of information on the molecular path of a glycol through the system can be obtained from calculating the chemical potential. Due to difficulties in measuring interfacial chemical potentials, these often need to be estimated using theoretical tools. We used molecular dynamics (MD) to study how TEG behaves in the vicinity of mineral surfaces such as calcite and hematite. Many methods exist for estimating chemical potentials based on MD trajectories. These include techniques such as free energy perturbation theory (FEP) and thermodynamic integration (TI). Such methods require sufficient sampling of configurations where free energy is to be estimated. Thus, it can be difficult to estimate chemical potentials on surfaces. There are several methods to circumvent this problem, such as blue moon sampling and umbrella sampling. These have been considered and the most important have been used to estimate chemical potentials of TEG adsorbed on the mineral surfaces. The resulting chemical potentials were compared to the chemical potential of TEG in bulk water, which was estimated using temperature thermodynamic integration.

  20. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Collective migration of adsorbed atoms on a solid surface in the laser radiation field

    NASA Astrophysics Data System (ADS)

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

    2004-02-01

    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'.

  1. Surface-enhanced Raman spectroscopy for detection of toxic amyloid β oligomers adsorbed on self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Voiciuk, Vladislava; Valincius, Gintaras; Budvytytė, Rima; Matijoška, Algirdas; Matulaitienė, Ieva; Niaura, Gediminas

    Surface-enhanced Raman spectroscopy (SERS) was used to detect different spectral features of small (1-2 nm) and large (5-10 nm) synthetic amyloid Aβ-42 oligomers, exhibiting high and no detectable neurotoxicities, respectively. Adsorption of peptides at self-assembled monolayers (SAM) terminated by methyl and pyridinium groups was employed to differentiate toxic and non-toxic oligomers. Three SAMs were analyzed: hydrophobic heptanethiol (HT) and octadecanethiol (ODT) as well as positively charged N-(6-mercapto)hexylpyridinium (MHP) chloride. SERS study revealed twofold adsorption effect, changes in the monolayer structure and appearance of new bands associated with the adsorbed peptides. A band at 1387 cm-1, observed as a result of the SAM and Aβ-42 interaction, is tentatively assigned to the peptide symmetric stretching vibration of carboxylate groups, and appears to be the most prominent spectral feature distinguishing toxic oligomers from the non-toxic Aβ-42 forms. This band was identified in the spectra of Aβ-42 adsorption on heptanethiol and MHP monolayers, while no clear perturbations were observed in the case of ODT monolayer.

  2. Development of an enzymatic reactor applying spontaneously adsorbed trypsin on the surface of a PDMS microfluidic device.

    PubMed

    Kecskemeti, Adam; Bako, Jozsef; Csarnovics, Istvan; Csosz, Eva; Gaspar, Attila

    2017-03-15

    Herein, a microfluidic device (MD) containing immobilized trypsin for rapid and efficient proteolysis was described. Trypsin was immobilized via non-specific protein adsorption onto the hydrophobic poly(dimethylsiloxane) (PDMS) channel wall of the MD. Peptide mapping of bovine serum albumin (BSA) samples was carried out to estimate the stability of trypsin adsorbed on PDMS surface. Peptide maps of BSA samples were obtained by capillary zone electrophoresis (CZE), the RSD% for migration times were under 1%. Several proteins (hemoglobin, myoglobin, lysozyme, and BSA) in a wide molecular size range (15-70 kDa) were digested efficiently with ∼50 s contact time. The number of separated peaks correlated well with the expected number of peptides formed in the complete tryptic digestion of the proteins. Peptide mass fingerprinting of BSA and human serum was carried out. Trypsin retained its activity for 2 h; within this period, the MD can be used for multiple digestions. The main properties of this device are simple channel pattern, simple immobilization procedure, regenerability, and disposability; all these features make this MD one of the simplest yet applicable enzymatic microreactors. Graphical abstract Development of microfluidic device including a serpentine channel as an enzyme reactor for protein digestion.

  3. Effects of electronic relaxation processes on vibrational linewidths of adsorbates on surfaces: The case of CO/Cu(100)

    NASA Astrophysics Data System (ADS)

    Novko, D.; Alducin, M.; Blanco-Rey, M.; Juaristi, J. I.

    2016-12-01

    We investigate nonadiabatic effects for the vibrational stretch mode of the CO molecule adsorbed on the top site of the Cu(100) surface. By studying the long-wavelength (q ≈0 ) imaginary and real parts of the density functional theory based phonon self-energy due to the electron-phonon coupling Πλ we obtain the phonon linewidth and the frequency renormalization of the CO stretch mode, respectively. To simulate electronic scattering processes that lead to further damping of the phonon modes we include a phenomenological damping in the phonon self-energy, as well as in the single-electron spectral function that enters Πλ, through the momentum distribution function. For the specific case of electron-impurity scattering we explicitly show how this process opens the indirect intraband channel and broadens the linewidth of the CO stretch mode. To emphasize the importance of accounting for electronic scattering processes we compare the phonon linewidths in the clean noninteracting limit (infinite electron lifetime) and when electronic scattering processes are phenomenologically included (finite electron lifetime) with available experimental data. We find that the agreement with experiments is improved in the latter case.

  4. Dehydrochlorination of adsorbed 1,1,2,2-tetrachloroethane on graphene oxide-based materials' surface: Comparison with dissolved form in aqueous environment.

    PubMed

    Chen, Weifeng; Ni, Jinzhi

    2017-02-15

    Dehydrochlorination of 1,1,2,2-tetrachloroethane (TeCA) in graphene oxide (GO)-based materials-water two-phase system can be enhanced strongly. However, the dehydrochlorination kinetic of adsorbed TeCA on GO-based materials' surface is still unclear. Thus, in this study the dehydrochlorination kinetics of adsorbed TeCA on GO based-materials' surface was compared to the kinetics of dissolved TeCA in aqueous solution. The results showed that the dehydrochlorination kinetic constants of adsorbed TeCA on GO-based materials' surface (ks_F) were much greater than those of dissolved TeCA in aqueous solution (ka) due to the deprotonated surface oxygen-containing functional groups (e.g. COO(-), and O(-)) served as conjugated bases to catalyze the reaction. In particular, at pH 8.0 and 9.0, the ks_F values for GO (20mg/L) were approximately 3 orders magnitude greater than ka values. Furthermore, the ks_F values of adsorbed TeCA for the low concentration of GO (20mg/L) were always greater than that for the high concentration of GO (100mg/L). The primary mechanism was that GO was apt to aggregate at high concentration, which enhanced the steric hindrance between O-containing functional groups and TeCA molecular. Consequently, the interfacial effects of GO-based materials at their low concentration could strongly enhance the transformation of adsorbed TeCA in aqueous environment.

  5. First-Principles Study of the Electric Field Effect on the Water-Adsorbed Rutile Titanium Dioxide Surface

    NASA Astrophysics Data System (ADS)

    Hmiel, Abraham L.

    TiO2 is a semiconducting material that has been used extensively in many industrial applications, and recently has become a candidate for photocatalytic water splitting, fuel cell anode support materials, sensors, and other novel nanodevices. The interface of TiO2 with water, historically well-studied but still poorly understood, presents a ubiquitous environmental challenge towards the ultimate practical usefulness of these technologies. Ground-state density functional theory (DFT) calculations studying the characteristics of molecular adsorption on model surfaces have been studied for decades, showing constant improvement in the description of the energetics and electronic structure at interfaces. These simulations are invaluable in the materials science innovation pipeline because they can interpret the results of experiments and investigate properties at the nanoscale that traditional methods cannot reach. In this work, spin-polarized DFT calculations within the generalized gradient approximation and with the recent self-consistent opt-B88 van der Waals functional have been applied to investigate the problem of molecularly adsorbed water on the rutile (110) TiO2 surface under the influence of an applied electric field. The effective screening medium theory is used to break the symmetry of the simulation in the slab normal direction and implement a metal-like boundary condition at the edges of the simulation cell to model the charged capacitor in a real electrochemical device. This study begins with an investigation of bulk and surface properties of TiO2 to obtain a sound theoretical baseline. Following that, an attempt to obtain simple and meaningful structure-property relationships of rectangular TiO 2 nanowires with (110) facets resulting from quantum confinement. Finally, a systematic study of energetics, geometrical configuration, charge partitioning, and electronic structure of water in monomer coverage up to monolayer coverage provides insight into the

  6. Damage areas on selected LDEF aluminum surfaces

    NASA Technical Reports Server (NTRS)

    Coombs, Cassandra R.; Atkinson, Dale R.; Allbrooks, Martha K.; Watts, Alan J.; Hennessy, Corey J.; Wagner, John D.

    1993-01-01

    With the U.S. about to embark on a new space age, the effects of the space environment on a spacecraft during its mission lifetime become more relevant. Included among these potential effects are degradation and erosion due to micrometeoroid and debris impacts, atomic oxygen and ultraviolet light exposure as well as material alteration from thermal cycling, and electron and proton exposure. This paper focuses on the effects caused by micrometeoroid and debris impacts on several LDEF aluminum plates from four different bay locations: C-12, C-10, C-01, and E-09. Each plate was coated with either a white, black, or gray thermal paint. Since the plates were located at different orientations on the satellite, their responses to the hypervelocity impacts varied. Crater morphologies range from a series of craters, spall zones, domes, spaces, and rings to simple craters with little or no spall zones. In addition, each of these crater morphologies is associated with varying damage areas, which appear to be related to their respective bay locations and thus exposure angles. More than 5% of the exposed surface area examined was damaged by impact cratering and its coincident effects (i.e., spallation, delamination and blow-off). Thus, results from this analysis may be significant for mission and spacecraft planners and designers.

  7. Structure and Redox Properties of 5-Amino-3-nitro-1H-1,2,4-triazole (ANTA) Adsorbed on a Silica Surface: A DFT M05 Computational Study.

    PubMed

    Sviatenko, Liudmyla K; Gorb, Leonid; Hill, Frances C; Leszczynska, Danuta; Leszczynski, Jerzy

    2015-07-23

    A cluster approximation was applied at the M05/tzvp level to model an adsorption of 5-amino-3-nitro-1H-1,2,4-triazole (ANTA) on the (001) surface of α-quartz. Structures of the obtained ANTA-silica complexes confirm a nearly parallel orientation of the nitro compound toward the surface. The atoms in molecules (AIM) method was applied to analyze binding between ANTA and the silica surface. Attachment or loss of an electron was found to lead to a significant deviation from coplanarity in the complexes and to a strengthening of a hydrogen bonding. Redox properties of the adsorbed ANTA were compared with those of gas-phase and hydrated species by calculation of the ionization potential, electron affinity, oxidation and reduction Gibbs free energies, and oxidation and reduction potentials. It was shown that the adsorbed ANTA has a lower ability to undergo redox transformations as compared to that of the hydrated one.

  8. 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

    USGS Publications Warehouse

    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.

  9. Entropy-Driven Conformational Control of α,ω-Difunctional Bidentate-Dithiol Azo-Based Adsorbates Enables the Fabrication of Thermally Stable Surface-Grafted Polymer Films.

    PubMed

    Lee, Han Ju; Jamison, Andrew C; Lee, T Randall

    2016-06-22

    Thermally stable radical initiator monolayers were prepared from uniquely designed α,ω-difunctional adsorbates with bidentate headgroups for the growth of nanoscale polymer films on metal surfaces. The length of the spacer separating the bidentate headgroups was varied to afford 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercaptomethyl)phenoxy)hexadecyl)-4-cyanopentanamide) (B16), 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercapto-methyl)phenoxy)decyl)-4-cyanopentanamide) (B10), and 4,4'-(diazene-1,2-diyl)bis(N-(4-(3,5-bis(mercaptomethyl)phenoxy)butyl)-4-cyanopentanamide) (B4). The structural features of the self-assembled monolayers (SAMs) derived from B16, B10, and B4 were characterized by X-ray photoelectron spectroscopy (XPS), ellipsometry, and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and compared to those derived from an analogous α,ω-difunctional adsorbate with monodentate headgroups, 4,4'-(diazene-1,2-diyl)bis(4-cyano-N-(16-mercaptohexadecyl)pentanamide (M). These studies demonstrate that the conformation (i.e., hairpin vs standing up) of the bidentate initiator adsorbates on gold surfaces was easily controlled by adjusting the concentration of the adsorbates in solution. The results of solution-phase thermal desorption tests revealed that the radical initiator monolayers generated from B16, B10, and B4 exhibit an enhanced thermal stability when compared to those generated from M. Furthermore, a study of the growth of polymer films was performed to evaluate the utility of these new bidentate adsorbate SAMs as film-development platforms for new functional materials and devices. Specifically, surface-grafted polystyrene films were successfully generated from SAMs derived from B16. In contrast, attempts to grow polystyrene films from SAMs derived from M under a variety of analogous conditions were unsuccessful.

  10. Surface area control of organic carbon accumulation in continental shelf sediments

    SciTech Connect

    Mayer, L.M. )

    1994-02-01

    The relationship between organic carbon (OC) and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments. Cores from many North American shelf environments show downcore decreases in OC to similar refractory background concentrations if expressed relative to the surface area of the sediments. This consistent concentration is 0.86 mg-OC m[sup [minus]2], which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces. A more global collection of sediment-water interface samples show that this relationship is even more extensive, with exceptions occurring in areas of very high riverine sediment input, organic pollution, or low-oxygen water columns. Density separations indicate that organic matter is largely adsorbed to mineral grains. The microtopography of surfaces was examined with N[sub 2] sorption and most surface area was found to be inside pores of <10 nm width. These data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay. Such protection would likely work in concert with other protection mechanisms such as humification. This consistent surface area correlation with OC concentration may explain control of spatial and temporal variations in OC burial rates by sedimentation rates; the pore protection hypothesis provides a causal mechanism for this observed control.

  11. Body surface area formulae: an alarming ambiguity

    PubMed Central

    Redlarski, Grzegorz; Palkowski, Aleksander; Krawczuk, Marek

    2016-01-01

    Body surface area (BSA) plays a key role in several medical fields, including cancer chemotherapy, transplantology, burn treatment and toxicology. BSA is often a major factor in the determination of the course of treatment and drug dosage. A series of formulae to simplify the process have been developed. Because easy-to-identify, yet general, body coefficient results of those formulae vary considerably, the question arises as to whether the choice of a particular formula is valid and safe for patients. Here we show that discrepancies between most of the known BSA formulae can reach 0.5 m2 for the standard adult physique. Although many previous studies have demonstrated that certain BSA formulae provide an almost exact fit with the patients examined, all of these studies have been performed on a limited and isolated group of people. Our analysis presents a broader perspective, considering 25 BSA formulae. The analysis revealed that the choice of a particular formula is a difficult task. Differences among calculations made by the formulae are so great that, in certain cases, they may considerably affect patients’ mortality, especially for people with an abnormal physique or for children. PMID:27323883

  12. Body surface area formulae: an alarming ambiguity.

    PubMed

    Redlarski, Grzegorz; Palkowski, Aleksander; Krawczuk, Marek

    2016-06-21

    Body surface area (BSA) plays a key role in several medical fields, including cancer chemotherapy, transplantology, burn treatment and toxicology. BSA is often a major factor in the determination of the course of treatment and drug dosage. A series of formulae to simplify the process have been developed. Because easy-to-identify, yet general, body coefficient results of those formulae vary considerably, the question arises as to whether the choice of a particular formula is valid and safe for patients. Here we show that discrepancies between most of the known BSA formulae can reach 0.5 m(2) for the standard adult physique. Although many previous studies have demonstrated that certain BSA formulae provide an almost exact fit with the patients examined, all of these studies have been performed on a limited and isolated group of people. Our analysis presents a broader perspective, considering 25 BSA formulae. The analysis revealed that the choice of a particular formula is a difficult task. Differences among calculations made by the formulae are so great that, in certain cases, they may considerably affect patients' mortality, especially for people with an abnormal physique or for children.

  13. Lotus-leaf-like topography predominates over adsorbed ECM proteins in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) surface/cell interactions.

    PubMed

    Zheng, Jun; Li, Dan; Yuan, Lin; Liu, Xiaoli; Chen, Hong

    2013-06-26

    It is well-known that extracellular matrix (ECM) proteins mediate cell/surface interactions. However, introduction of a specific surface topography may disturb the correlation between ECM proteins adsorption and cells adhesion on a given surface. In present study, lotus-leaf-like topography was introduced on the surface of a biodegradable material, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx). Protein adsorption and cell interactions with this lotus-leaf-like surface (designated PHBHHx-L) were investigated. Water contact angle data indicated that the hydrophobicity of PHBHHx was enhanced by the introduction of lotus-leaf-like topography. The adsorption of extracellular matrix proteins (fibronectin and vitronectin) on PHBHHx-L was measured by enzyme linked immunosorbent assay (ELISA). Compared with flat PHBHHx, adsorption on the PHBHHx-L surface increased by ~260% for fibronectin and ~40% for vitronectin. In contrast, fibroblast and endothelial cell adhesion and proliferation were reduced on the PHBHHx-L compared to the flat polymer surface. These results suggest that the inhibition of cell adhesion and proliferation caused by the lotus-leaf-like topography dominates over the effect of the adsorbed adhesive proteins in promoting adhesion and proliferation. It can be concluded that the lotus-leaf-like topography plays a dominant role in cell/PHBHHx-L interactions. The present findings indicate the complexity of the interplay among surface topography, adsorbed proteins, and cell-surface interactions.

  14. Determination of the surface area and sizes of supported copper nanoparticles through organothiol adsorption-Chemisorption

    NASA Astrophysics Data System (ADS)

    Ndolomingo, Matumuene Joe; Meijboom, Reinout

    2016-12-01

    The mechanisms involving the nanoparticle surfaces in catalytic reactions are more difficult to elucidate due to the nanoparticle surface unevenness, size distributions, and morphological irregularity. True surface area and particle sizes determination are key aspects of the activity of metal nanoparticle catalysts. Here we report on the organothiol adsorption-based technique for the determination of specific surface area of Cu nanoparticles, and their resultant sizes on γ-Al2O3 supports. Quantification of ligand packing density on copper nanoparticles is also reported. The concentration of the probe ligand, 2-mercaptobenzimidazole (2-MBI) before and after immersion of supported copper catalysts was determined by ultraviolet-visible spectrometry (UV-vis). The amount of ligand adsorbed was found to be proportional to the copper nanoparticles surface area. Atomic absorption spectrometry (AAS), N2-physisorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used for the characterization of the catalysts. A fair agreement was found between particle sizes obtained from ligand adsorption and TEM methods. The catalytic activity of the copper nanoparticles related to their inherent surface area was evaluated using the model reaction of the oxidation of morin by hydrogen peroxide.

  15. Inelastic neutron scattering (INS) observations of rotational tunneling within partially deuterated methane monolayers adsorbed on MgO(1 0 0) surfaces

    NASA Astrophysics Data System (ADS)

    Hicks, Andy S.; Larese, J. Z.

    2013-12-01

    High resolution inelastic neutron scattering (INS) measurements of the low temperature (T ∼ 2.0 K) rotational dynamics of isotopically substituted methane monolayers adsorbed on MgO(1 0 0) are presented. These spectra, obtained using BASIS at SNS, represent the most detailed measurements available for surface-adsorbed monolayer films of methane. Distinct excitations are readily observed at 15, 31, 45 and 127 μeV for the CH2D2 on MgO monolayer and at 40, 51, 95 and 138 μeV for CH3D/MgO. These features are attributed to tunneling transitions between sublevels within the ground librational state and are interpreted using the pocket state (PS) formalism first proposed by Hüller. This theoretical analysis employs the findings of earlier studies of CH4 on MgO(1 0 0) which suggest that molecules adsorb with their C2v axes normal to the surface plane. The comparison between theory and experiment provides direct insight into the impact of molecular versus surface symmetry on the observed tunneling spectra.

  16. Effect of nanographene platelets (NGP) surface area on organic dye adsorption using Fe3O4-NGP composites

    NASA Astrophysics Data System (ADS)

    Taufik, A.; Saleh, R.

    2016-11-01

    Fe3O4-NanoGraphene Platelets (NGP) composites with different surface area were successfully synthesized using sol gel method. The inverse cubic spinel structures as well as graphitic like structure from NGP were detected using X-Ray Diffraction (XRD) Measurement, while the ferromagnetic behavior for all samples were detected using Vibrating Sample Magnetometry (VSM) measurement. The vibrational mode for all samples were characterized using Fourier Transform Infrared Spectroscopy (FT-IR), and thermal stability for all samples were characterized using Thermogravimetric Analysis (TGA). The adsorption process were tested using methylene blue (MB) as a model of organic pollutant. The result showed that the higher NGP surface area could enhance the adsorption capacity of the samples. The kinetic model of adsorption shows that the adsorption process of Fe3O4-NGP materials followed the second order kinetic reaction. The reusability of adsorbent were also performed to analyze the stability of the adsorbent.

  17. Adsorption characteristics of water vapor on gear-pellet and honeycomb-pellet types of adsorbents containing A-type zeolite

    SciTech Connect

    Nakamura, A.; Munakata, K.; Hara, K.; Narita, S.; Sugiyama, T.; Kotoh, K.; Tanaka, M.; Uda, T.

    2015-03-15

    It is necessary to recover or process tritiated species that are extensively coexistent in nuclear fusion installations. A conventional way to recover tritium release to atmosphere is catalytic oxidation of tritiated species and adsorption of tritiated water vapor on adsorbents with high surface areas. Therefore, new adsorbents with low pressure loss and high surface areas need to be developed and utilized for such large-scale adsorption systems. In this study, attention was focused on new adsorbents, which are gear-type pellet MS5A adsorbent, gear-type pellet MS4A adsorbent and honeycomb-type pellet MS5A adsorbent. The adsorption characteristics of the new adsorbent were comparatively studied with conventional type of adsorbents (pellet-type MS5A adsorbent and pebble-type MS5A adsorbent), in terms of adsorption capacity, pressure loss and adsorption rate. It was found that the adsorption capacity of water vapor on the gear-type adsorbents is higher than that on a honeycomb-type adsorbent. The experimental breakthrough curves indicate that the adsorption rates of water vapor on gear-type and honeycomb-type adsorbents are smaller than that on conventional type adsorbents. Various adsorption models were also tested to correlate the experimental isotherms. It was found that the Langmuir-Freundlich model could properly correlate the experimental adsorption isotherms.

  18. The structure, energetics, and nature of the chemical bonding of phenylthiol adsorbed on the Au(111) surface: implications for density-functional calculations of molecular-electronic conduction.

    PubMed

    Bilić, Ante; Reimers, Jeffrey R; Hush, Noel S

    2005-03-01

    The adsorption of phenylthiol on the Au(111) surface is modeled using Perdew and Wang density-functional calculations. Both direct molecular physisorption and dissociative chemisorption via S-H bond cleavage are considered as well as dimerization to form disulfides. For the major observed product, the chemisorbed thiol, an extensive potential-energy surface is produced as a function of both the azimuthal orientation of the adsorbate and the linear translation of the adsorbate through the key fcc, hcp, bridge, and top binding sites. Key structures are characterized, the lowest-energy one being a broad minimum of tilted orientation ranging from the bridge structure halfway towards the fcc one. The vertically oriented threefold binding sites, often assumed to dominate molecular electronics measurements, are identified as transition states at low coverage but become favored in dense monolayers. A similar surface is also produced for chemisorption of phenylthiol on Ag(111); this displays significant qualitative differences, consistent with the qualitatively different observed structures for thiol chemisorption on Ag and Au. Full contours of the minimum potential energy as a function of sulfur translation over the crystal face are described, from which the barrier to diffusion is deduced to be 5.8 kcal mol(-1), indicating that the potential-energy surface has low corrugation. The calculated bond lengths, adsorbate charge and spin density, and the density of electronic states all indicate that, at all sulfur locations, the adsorbate can be regarded as a thiyl species that forms a net single covalent bond to the surface of strength 31 kcal mol(-1). No detectable thiolate character is predicted, however, contrary to experimental results for alkyl thiols that indicate up to 20%-30% thiolate involvement. This effect is attributed to the asymptotic-potential error of all modern density functionals that becomes manifest through a 3-4 eV error in the lineup of the adsorbate and

  19. Surface atmospheric extremes (Launch and transportation areas)

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The effects of extreme values of surface and low altitude atmospheric parameters on space vehicle design, tests, and operations are discussed. Atmospheric extremes from the surface to 150 meters for geographic locations of interest to NASA are given. Thermal parameters (temperature and solar radiation), humidity, pressure, and atmospheric electricity (lighting and static) are presented. Weather charts and tables are included.

  20. Milestone Report - Complete New Adsorbent Materials for Marine Testing to Demonstrate 4.5 g-U/kg Adsorbent

    SciTech Connect

    Janke, Christopher James; Das, Sadananda; Oyola, Yatsandra; Mayes, Richard T.; Saito, Tomonori; Brown, Suree; Gill, Gary; Kuo, Li-Jung; Wood, Jordana

    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.

  1. Effect of surface corrugation on low temperature phases of adsorbed (p-H2)7: A quantum path integral Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Cruz, Anthony; López, Gustavo E.

    2014-04-01

    By using path integral Monte Carlo simulations coupled to Replica Exchange algorithms, various phases of (p-H2)7 physically adsorbed on a model graphite surface were identified at low temperatures. At T=0.5 K, the expected superfluid phase was observed for flat and slightly corrugated surfaces. At intermediate and high corrugations, a "supersolid" phase in C7/16 registry and a solid phase in C1/3 registry were observed, respectively. At higher temperatures, the superfluid is converted to a fluid and the "supersolid" to a solid.

  2. The origin of 1560 cm-1 band in experimental IR spectra of water adsorbed on TiO2 surface: Ab initio assessment

    NASA Astrophysics Data System (ADS)

    Kevorkyants, Ruslan; Rudakova, Aida V.; Chizhov, Yuri V.; Bulanin, Kirill M.

    2016-10-01

    We present DFT study on vibrational spectrum of water layer on a surface of TiO2 which is modeled via Ti8O16 nanocluster. In contrast to ν2 mode's frequency of liquid water (1645 cm-1) for the water layer theory predicts considerably lower ν2 frequency (1570 cm-1) which matches experimentally observed shoulder in IR spectrum (1560 cm-1). We demonstrate that the calculated ν2 frequencies depend linearly on a distance between adsorbed water molecules and a surface of Ti8O16 nanocluster! We also show that hydrogen bonding strongly affects ν1 vibrational frequencies but leaves ν2 and ν3 ones almost intact.

  3. Chemical reactivity of polycyclic organic compounds adsorbed on coal fly ash and related solid surfaces. Progress report, May 1985-April 1986

    SciTech Connect

    Mamantov, G.; Wehry, E.L.

    1986-04-01

    The fundamental objectives of this research are to characterize and understand the photochemical and nonphotochemical reactivity of polycyclic aromatic hydrocarbons (PAHs) and their derivatives as adsorbates on the surface of coal fly ash and related particulate solids. Specific efforts undertaken and results obtained during this period are summarized with detailed discussions presented in the form of Appendices. Results are tabulated from a thorough examination of the photochemistry of pyrene, benzo(a)pyrene (BaP), anthracene, phenanthrene, and benz(a)anthracene (BaA) as adsorbates on eight coal stack ashes. A procedure was developed to separate coal ashes into carbon and iron contents. Attempts to measure heats of absorption of PAHs on various coal ashes were made. Pyrene nitration occurred only when NO/sub 2/ was contaminated with nitric acid.

  4. 30 CFR 56.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Illumination of surface working areas. 56.17001... § 56.17001 Illumination of surface working areas. Illumination sufficient to provide safe working conditions shall be provided in and on all surface structures, paths, walkways, stairways, switch...

  5. 30 CFR 57.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Illumination of surface working areas. 57.17001... Illumination § 57.17001 Illumination of surface working areas. Illumination sufficient to provide safe working conditions shall be provided in and on all surface structures, paths, walkways, stairways, switch...

  6. 30 CFR 57.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Illumination of surface working areas. 57.17001... Illumination § 57.17001 Illumination of surface working areas. Illumination sufficient to provide safe working conditions shall be provided in and on all surface structures, paths, walkways, stairways, switch...

  7. 30 CFR 56.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Illumination of surface working areas. 56.17001... NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Illumination § 56.17001 Illumination of surface working areas. Illumination sufficient to provide safe...

  8. Mercury adsorption properties of sulfur-impregnated adsorbents

    USGS Publications Warehouse

    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.

  9. A study of the alumina-silica gel adsorbent for the removal of silicic acid from geothermal water: increase in adsorption capacity of the adsorbent due to formation of amorphous aluminosilicate by adsorption of silicic acid.

    PubMed

    Yokoyama, Takushi; Ueda, Akira; Kato, Koichi; Mogi, Katsumi; Matsuo, Shorin

    2002-08-01

    Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids.

  10. Adsorbed poly(ethyleneoxide)-poly(propyleneoxide) copolymers on synthetic surfaces: spectroscopy and microscopy of polymer structures and effects on adhesion of skin-borne bacteria.

    PubMed

    Marsh, Lorraine H; Coke, Mark; Dettmar, Peter W; Ewen, Richard J; Havler, Michael; Nevell, Thomas G; Smart, John D; Smith, James R; Timmins, Barry; Tsibouklis, John; Alexander, Cameron

    2002-09-15

    Poly(ethyleneoxide)-copoly(propyleneoxide) (PEO-PPO) polymer coatings were evaluated for their resistance to the attachment of the marker organism Serratia marcescens and the skin-borne bacteria Staphylococcus epidermidis. The copolymers were adsorbed onto poly(styrene) films-chosen as simplified physicochemical models of skin surfaces-and their surface characteristics probed by contact angle goniometry, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). These functional surfaces were then presented to microbial cultures, bacterial attachment was assessed by fluorescence microscopy and AFM, and the structures of the polymer films examined again spectroscopically. Surface characterization data suggest that the adsorbed copolymer was partially retained at the surface and resisted bacterial attachment for 24 h. Quantitative evaluation of cell attachment was carried out by scintillation counting of (14)C-labeled microorganisms in conjunction with plate counts. The results show that a densely packed layer of PEO-PPO copolymer can reduce attachment of skin commensals by an order of magnitude, even when the coating is applied by a simple adsorptive process. The work supports the hypothesis that adhesion of microorganisms to biological substrates can be reduced if a pretreatment with an appropriate copolymer can be effected in vivo.

  11. Photodegradation of Stearic Acid Adsorbed on Superhydrophilic TiO2 Surface: In Situ FT-IR and LDI Study

    NASA Astrophysics Data System (ADS)

    Smirnova, Natalia; Fesenko, Tatiana; Zhukovsky, Maxim; Goworek, Jacek; Eremenko, Anna

    2015-12-01

    TiO2 films prepared by template-assisted sol-gel method were characterized by X-ray diffraction spectroscopy, scanning and atomic force electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy. Based on the hexane adsorption-desorption analysis, the films have a surface area of 390-540 m2/g with pore size distribution narrowly centered around 10 nm. Optimal component ratio and condition of heat treatment of mesoporous titania films have been found. Photocatalytic activity of the coatings was determined by the destruction of stearic acid layers, monitored using FT-IR spectroscopy and laser desorption-ionization (LDI) mass spectrometry. Under UV illumination, all the used films reach hydrophilicity with water contact angle of 0°. As the result, hydrophobic fat acid molecules undergo self-association and active desorption from the hydrophilic surface during mass-spectrometric experiment.

  12. Surface area and travel time relationships in aquifer treatment systems.

    PubMed

    Fox, Peter; Makam, Roshan

    2009-11-01

    Soil aquifer treatment (SAT) and bank filtration use natural attenuation processes to purify water for subsequent use. Soil aquifer treatment may constitute both unsaturated and saturated flow conditions, while bank filtration systems are primarily saturated flow. This analysis focuses on the saturated zone, where the majority of residence time occurs, in both SAT and bank filtration systems. Sustainable removal mechanisms during subsurface flow are primarily surface-mediated and therefore depend on surface area. By analyzing saturated subsurface flow hydraulics in granular media, a relationship between surface area and travel time was developed. For saturated subsurface flow, the ratio of surface area-to-travel time varied by approximately a factor of 3, for common aquifer materials subject to identical hydraulic gradients. Because travel time criteria often are used to regulate SAT and bank filtration systems, these criteria also may determine the surface area and associated surface-mediated reactions for water purification. The ratio of surface area-to-travel time increases with increasing hydraulic gradient, implying that surface area is relatively constant for specific travel times, even if the hydraulic gradient changes; however, the increasing hydraulic gradient will increase the distance from the recharge zone to the recovery well. Therefore, travel time assessments based on maximum possible hydraulic gradients increase surface area and could provide a conservative limit for surface-mediated reactions. This analysis demonstrates that travel time criteria for SAT and bank filtration systems indirectly provide a minimum surface area that may support sustainable removal mechanisms.

  13. Changes in the surfaces on DDOAB organoclays adsorbed with paranitrophenol-An XRD, TEM and TG study

    SciTech Connect

    Zhou Qin; He Hongping; Frost, Ray L. Xi Yunfei

    2008-12-01

    The adsorption of paranitrophenol on organoclays synthesised by the ion exchange of the surfactant molecule dimethyldioctadecylammonium bromide (DDOAB) of formula (CH{sub 3}(CH{sub 2}){sub 17}){sub 2}NBr(CH{sub 3}){sub 2} has been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis. The expansion of the montmorillonite depends on the loading of the montmorillonite with dimethyldioctadecylammonium bromide and is related to the arrangement of the surfactant molecules within the clay interlayer. This expansion is altered by the adsorbed paranitrophenol and is observed in the transmission electron microscopic images of the organoclay with adsorbed paranitrophenol. Changes in the surfactant molecular arrangements were analysed by thermogravimetry. The paranitrophenol is sublimed simultaneously with the loss of surfactant. The dehydroxylation temperature of the montmorillonite is decreased upon adsorption of the paranitrophenol indicating a bonding between the paranitrophenol and the hydroxyl units of the montmorillonite.

  14. Surface atmospheric extremes (launch and transportation areas)

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Criteria are provided on atmospheric extremes from the surface to 150 meters for geographical locations of interest to NASA. Thermal parameters (temperature and solar radiation), humidity, precipitation, pressure, and atmospheric electricity (lightning and static) are presented. Available data are also provided for the entire continental United States for use in future space programs.

  15. Simultaneous determination of cation exchange capacity and surface area of acid activated bentonite powders by methylene blue sorption

    NASA Astrophysics Data System (ADS)

    Yener, Nilgün; Biçer, Cengiz; Önal, Müşerref; Sarıkaya, Yüksel

    2012-01-01

    To distinguish the ion exchanged and physically adsorbed methylene blue cations (MB+) on ionic surfaces, acid activated bentonite samples were used as porous adsorbents. A natural calcium bentonite (CaB) sample from Enez/Edirne, Turkey, was acid activated at 90 °C for 16 h with various HCl/CaB ratios. The irreversible exchange and physical adsorption of MB+ cations on the ionic solids have simultaneously occurred. The ion exchanged (mex) and physically adsorbed (mad) MB+ contents were obtained as the values of sorption capacity at c = 0 and the increase to a plateaus of adsorption isotherms, respectively. The mad value was taken to be monolayer adsorption capacity. Cation exchange capacity (CEC) and specific surface area (SMB) for each sample were calculated from the mex and mad values, respectively. Also, the BET specific surface areas (SBET) and pore size distribution were determined from low temperature nitrogen adsorption/desorption data. A linear correlation between the SMB and SBET values was found.

  16. Carbon 1s photoemission line analysis of C-based adsorbate on (111)In2O3 surface: The influence of reducing and oxidizing conditions

    NASA Astrophysics Data System (ADS)

    Brinzari, V.; Cho, B. K.; Korotcenkov, G.

    2016-12-01

    Synchrotron radiation photoemission study of C 1s line of (111) In2O3 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 In2O3 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 In2O3 and for conductive metal oxides.

  17. In situ Fourier transform-infrared internal reflection spectroscopic analysis of hydrocarbon chain ordering of surfactants adsorbed at mineral oxide surfaces

    NASA Astrophysics Data System (ADS)

    Cross, William Murray

    The adsorption of surfactants at mineral oxide surfaces was investigated by in situ Fourier transform infrared internal reflection spectroscopy (FT-IR/IRS), and contact angle goniometry. FT-IR/IRS was used to determine both adsorption isotherms and the enthalpy of adsorption. Furthermore, the conformation and orientation of the hydrocarbon chain of SDS adsorbed at a sapphire internal reflection element (IRE) were determined. Contact angle goniometry was used to measure the effect of the surface phase of the surfactant on the hydrophobic character of sapphire surfaces in aqueous solutions. For SDS adsorbed by sapphire, in situ FT-IR/IRS experiments indicate that a surface phase transition occurs at an adsorption density of 2 to 3 x 10-10 mol/cm2 for both pD 2.9 and 6.9. This transition is characterized by a two to four wavenumber shift in the position of the asymmetric -CH2 stretching band. Based on solution spectroscopy studies, the surface phase was found to be similar to solution phase micelles and liquid crystals for adsorption densities less than the adsorption density of the surface phase transition. Whereas for adsorption densities in excess of the adsorption density of the surface phase transition, the surface phase resembled a solution phase coagel species. It was also found that the contact angle of an air bubble at the sapphire surface exhibited a sharp decrease at the adsorption density corresponding to the surface phase transition The effect of temperature on adsorption and phase behavior of SDS at the sapphire IRE surface was also determined. It was shown that a surface phase transition similar to that discussed occurred at approximately 298 K. The adsorption reaction was found to be exothermic, with a heat of adsorption of --1.3 kcal/mole for adsorption densities less than the adsorption density of the surface phase transition at 298 K and --4.1 kcal/mole for adsorption densities greater than the adsorption density of the surface phase transition

  18. Why Do We Need the Derivative for the Surface Area?

    ERIC Educational Resources Information Center

    Hristova, Yulia; Zeytuncu, Yunus E.

    2016-01-01

    Surface area and volume computations are the most common applications of integration in calculus books. When computing the surface area of a solid of revolution, students are usually told to use the frustum method instead of the disc method; however, a rigorous explanation is rarely provided. In this note, we provide one by using geometric…

  19. Density functional theory study of SO2-adsorbed Ni(1 1 1) and hydroxylated NiO(1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Wei, Xin; Dong, Chaofang; Chen, Zhanghua; Xiao, Kui; Li, Xiaogang

    2015-11-01

    Spin polarized, DFT + U periodic calculation is used as an effective way to model the adsorption process of SO2 on hydroxylated NiO(1 1 1) surface. The adsorption of atomic O and O2 on the clean Ni(1 1 1) surface is calculated to investigate the forming process of passive film. The molecular and dissociated adsorptions of H2O on NiO(1 1 1) surface are evaluated to construct defect-free hydroxylated NiO(1 1 1) surface. The adsorption of SO2 and atomic O on clean Ni(1 1 1) surface is also investigated to compare with the adsorption capacity between passive film and substrate. With respect to the single adsorption process of SO2 on defect-free hydroxylated NiO(1 1 1) surface, the effects of O vacancy of surface and atomic O closed to the surface are investigated. The calculation results show that there is no chemical adsorption of SO2 on the defect-free hydroxylated NiO(1 1 1) surface with or without atomic O. Either single SO2 or SO2 with atomic O prefer adsorbing on the hydroxylated NiO(1 1 1) surface with O vacancies. The adsorption behavior is strengthened with the increase of percentage of surface O vacancy. The existence of atomic O leads to the production of SO3 on the hydroxylated NiO(1 1 1) surface and strengthens the adsorption capacity of SO2. Furthermore, the results also reveal the relationship between the charge transfer and the adsorption energy of SO2 and atomic O on the hydroxylated NiO(1 1 1) surface and clean Ni(1 1 1) surface. We inferred that broken passive film susceptibility to corrosion compare with substrate when surface O vacancies aggregate and its concentration large enough.

  20. Modeling of thorium (IV) ions adsorption onto a novel adsorbent material silicon dioxide nano-balls using response surface methodology.

    PubMed

    Kaynar, Ümit H; Şabikoğlu, Israfil; Kaynar, Sermin Çam; Eral, Meral

    2016-09-01

    The silicon dioxide nano-balls (nano-SiO2) were prepared for the adsorption of thorium (IV) ions from aqueous solution. The synthesized silicon dioxide nano-balls were characterized by Scanning Electron Microscopy/Energy Dispersive X-ray, X-ray Diffraction, Fourier Transform Infrared and BET surface area measurement spectroscopy. The effects of pH, concentration, temperature and the solid-liquid ratio on the adsorption of thorium by nano-balls were optimized using central composite design of response surface methodology. The interaction between four variables was studied and modelled. Furthermore, the statistical analysis of the results was done. Analysis of variance revealed that all of the single effects found statistically significant on the sorption of Th(IV). Probability F-values (F=4.64-14) and correlation coefficients (R(2)=0.99 for Th(IV)) indicate that model fit the experimental data well. The ability of this material to remove Th(IV) from aqueous solution was characterized by Langmuir, Freunlinch and Temkin adsorption isotherms. The adsorption capacity of thorium (IV) achieved 188.2mgg(-1). Thermodynamic parameters were determined and discussed. The batch adsorption condition with respect to interfering ions was tested. The results indicated that silicon dioxide nano-balls were suitable as sorbent material for adsorption and recovery of Th(IV) ions from aqueous solutions.

  1. Metal-free phthalocyanine (H2Pc) molecule adsorbed on the Au(111) surface: formation of a wide domain along a single lattice direction

    PubMed Central

    Komeda, Tadahiro; Isshiki, Hironari; Liu, Jie

    2010-01-01

    Using low-temperature scanning tunneling microscopy (STM), we observed the bonding configuration of the metal-free phthalocyanine (H2Pc) molecule adsorbed on the Au(111) surface. A local lattice formation started from a quasi-square lattice aligned to the close-packed directions of the Au(111) surface. Although we expected the lattice alignment to be equally distributed along the three crystallographically equivalent directions, the domain aligned normal to the ridge of the herringbone structure was missing in the STM images. We attribute this effect to the uniaxial contraction of the reconstructed Au(111) surface that can account for the formation of a large lattice domain along a single crystallographical direction. PMID:27877365

  2. Application of response surface methodology to optimize the adsorption performance of a magnetic graphene oxide nanocomposite adsorbent for removal of methadone from the environment.

    PubMed

    Kumar Gupta, Vinod; Agarwal, Shilpi; Asif, Mohammad; Fakhri, Ali; Sadeghi, Nima

    2017-03-03

    Magnetic graphene oxide (MGO) nanocomposites have been synthesized by the co-precipitation route. The surface structure of MGO nanocomposites were analyzed by XRD, TEM, SEM, VSM and nitrogen adsorption-desorption instrumental technique. Response surface methodology was used to optimize the removal of methadone by MGO nanocomposites in aqueous solution. Experiments were conducted based on Box-Behnken design (BBD). The influence of three parameters on the removal of methadone was examined using the response surface methodological approach. The significance of independent variables and their interactions were tested by analysis of variance (ANOVA). The optimum pH, adsorbent dose and temperature were found to be 6.2, 0.0098g and 295.7K, respectively. Under these conditions, removal efficiency of methadone was found to be 87.20mg/g.

  3. Control of the dipole layer of polar organic molecules adsorbed on metal surfaces via different charge-transfer channels

    NASA Astrophysics Data System (ADS)

    Lin, Meng-Kai; Nakayama, Yasuo; Zhuang, Ying-Jie; Su, Kai-Jun; Wang, Chin-Yung; Pi, Tun-Wen; Metz, Sebastian; Papadopoulos, Theodoros A.; Chiang, T.-C.; Ishii, Hisao; Tang, S.-J.

    2017-02-01

    Organic molecules with a permanent electric dipole moment have been widely used as a template for further growth of molecular layers in device structures. Key properties of the resulting organic films such as energy level alignment (ELA), work function, and injection/collection barrier are linked to the magnitude and direction of the dipole moment at the interface. Using angle-resolved photoemission spectroscopy (ARPES), we have systematically investigated the coverage-dependent work function and spectral line shapes of occupied molecular energy states (MESs) of chloroaluminium-phthalocyanine (ClAlPc) grown on Ag(111). We demonstrate that the dipole orientation of the first ClAlPc layer can be controlled by adjusting the deposition rate and postannealing conditions, and we find that the ELA at the interface differs by ˜0.4 eV between the Cl up and down configurations of the adsorbed ClAlPc molecules. These observations are rationalized by density functional theory (DFT) calculations based on a realistic model of the ClAlPc/Ag(111) interface, which reveal that the different orientations of the ClAlPc dipole layer lead to different charge-transfer channels between the adsorbed ClAlPc and Ag(111) substrate. Our findings provide a useful framework toward method development for ELA tuning.

  4. Adsorption of proteins at physiological concentrations on pegylated surfaces and the compatibilizing role of adsorbed albumin with respect to other proteins according to optical waveguide lightmode spectroscopy (OWLS).

    PubMed

    Leclercq, Laurent; Modena, Enrico; Vert, Michel

    2013-01-01

    In literature, contacts between pegylated compounds and blood proteins are generally discussed in terms of excluded volume-related repulsions although adsorption and compatibility have been reported for some of these proteins occasionally. The major problem to investigate the behavior of blood in contact with pegylated surfaces is the complexity of the medium and especially the presence of albumin in large excess. In a model approach, optical waveguide lightmode spectroscopy (OWLS) was used to monitor the fate of albumin, fibrinogen, and γ-globulins at physiological concentrations in pH = 7.4 isotonic HEPES buffer after contact with SiTiO2 chips coated with diblock poly(DL-lactic acid)-block-poly(ethylene oxide)s and triblock poly(DL-lactic acid)-block-poly(ethylene oxide)-block-poly(DL-lactic acid) copolymers. Corresponding homopolymers were used as controls. The three protein systems were investigated separately, as a mixture and when added successively according to different orders of addition. OWLS gave access to the mass and the thickness of adhering protein layers that resist washing with HEPES buffer. Protein depositions were detected regardless of the presence of poly(ethylene glycol) segments on surfaces. Adsorption depended on the protein, on the surface and also on the presence of the other proteins. Unexpectedly any surface coated with a layer of adsorbed albumin prevented deposition of other proteins, including albumin itself. This outstanding finding suggests that it was the presence of albumin adsorbed on a surface, pegylated or not, that made that surface compatible with other proteins. As a consequence, dipping a device to be in contact with the blood of a patient in a solution of albumin could be a very simple means to avoid further protein deposition and maybe platelets adhesion after in vivo implantation.

  5. Measuring the specific surface area of natural and manmade glasses: effects of formation process, morphology, and particle size

    SciTech Connect

    Papelis, Charalambos; Um, Wooyong; Russel, Charles E.; Chapman, Jenny B.

    2003-03-28

    The specific surface area of natural and manmade solid materials is a key parameter controlling important interfacial processes in natural environments and engineered systems, including dissolution reactions and sorption processes at solid-fluid interfaces. To improve our ability to quantify the release of trace elements trapped in natural glasses, the release of hazardous compounds trapped in manmade glasses, or the release of radionuclides from nuclear melt glass, we measured the specific surface area of natural and manmade glasses as a function of particle size, morphology, and composition. Volcanic ash, volcanic tuff, tektites, obsidian glass, and in situ vitrified rock were analyzed. Specific surface area estimates were obtained using krypton as gas adsorbent and the BET model. The range of surface areas measured exceeded three orders of magnitude. A tektite sample had the highest surface area (1.65 m2/g), while one of the samples of in situ vitrified rock had the lowest surf ace area (0.0016 m2/g). The specific surface area of the samples was a function of particle size, decreasing with increasing particle size. Different types of materials, however, showed variable dependence on particle size, and could be assigned to one of three distinct groups: (1) samples with low surface area dependence on particle size and surface areas approximately two orders of magnitude higher than the surface area of smooth spheres of equivalent size. The specific surface area of these materials was attributed mostly to internal porosity and surface roughness. (2) samples that showed a trend of decreasing surface area dependence on particle size as the particle size increased. The minimum specific surface area of these materials was between 0.1 and 0.01 m2/g and was also attributed to internal porosity and surface roughness. (3) samples whose surface area showed a monotonic decrease with increasing particle size, never reaching an ultimate surface area limit within the particle

  6. The role of surface oxygenated-species and adsorbed hydrogen in the oxygen reduction reaction (ORR) mechanism and product selectivity on Pd-based catalysts in acid media.

    PubMed

    Rahul, R; Singh, R K; Bera, B; Devivaraprasad, R; Neergat, M

    2015-06-21

    Oxygen reduction reaction (ORR) is investigated on bulk PdO-based catalysts (oxides of Pd and Pd3Co) in oxygen-saturated 0.1 M HClO4 to establish the role of surface oxides and adsorbed hydrogen in the activity and product selectivity (H2O/H2O2). The initial voltammetric features suggest that the oxides are inactive toward ORR. The evolution of the ORR voltammograms and potential-dependent H2O2 generation features on the PdO catalyst suggest gradual and parallel in situ reduction of the bulk PdO phase below ∼0.4 V in the hydrogen underpotential deposition (Hupd) region; the reduction of the bulk PdO catalyst is confirmed from the X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD) patterns. The potential-dependent H2O2 generation features originate due to the presence of surface oxides and adsorbed hydrogen; this is further confirmed using halide ions (Cl(-) and Br(-)) and peroxide as the external impurities.

  7. Conformational changes of adsorbed proteins

    NASA Astrophysics Data System (ADS)

    Allen, Scott

    2005-03-01

    The adsorption of bovine serum albumin (BSA) and pepsin to gold surfaces has been studied using surface plasmon resonance (SPR). Proteins are adsorbed from solution onto a gold surface and changes in the conformation of the adsorbed proteins are induced by changing the buffer solution. We selected pH and ionic strength values for the buffer solutions that are known from our circular dichroism measurements to cause conformational changes of the proteins in bulk solution. We find that for both BSA and pepsin the changes in conformation are impeded by the interaction of the protein with the gold surface.

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

    PubMed

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

    2015-04-07

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

  9. Mesoporous carbon adsorbents from melamine-formaldehyde resin using nanocasting technique for CO2 adsorption.

    PubMed

    Goel, Chitrakshi; Bhunia, Haripada; Bajpai, Pramod K

    2015-06-01

    Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine-formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), elemental (CHN) analysis, Fourier transform infrared (FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO2 capture. The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO2 adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO2 adsorption capacity among the synthesized adsorbents. Breakthrough time and CO2 equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent-CO2 system was found to be reversible with stable adsorption capacity over four consecutive adsorption-desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface.

  10. 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

    SciTech Connect

    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.

  11. Analysis of structural changes in active site of luciferase adsorbed on nanofabricated hydrophilic Si surface by molecular-dynamics simulations

    SciTech Connect

    Nishiyama, Katsuhiko; Hoshino, Tadatsugu

    2007-05-21

    Interactions between luciferase and a nanofabricated hydrophilic Si surface were explored by molecular-dynamics simulations. The structural changes in the active-site residues, the residues affecting the luciferin binding, and the residues affecting the bioluminescence color were smaller on the nanofabricated hydrophilic Si surface than on both a hydrophobic Si surface and a hydrophilic Si surface. The nanofabrication and wet-treatment techniques are expected to prevent the decrease in activity of luciferase on the Si surface.

  12. Accessing the structural and thermodynamic properties of ultra-thin layers of C32 adsorbed on a SiO2 surface

    NASA Astrophysics Data System (ADS)

    Gutierrez-Maldonado, Sebastian E.; Garate, Jose Antonio; Retamal, Maria Jose; Cisternas, Marcelo A.; Volkmann, Ulrich G.; Perez-Acle, Tomas

    2017-04-01

    Medium-chain alkanes are important molecules with applications in biology and industry. Notably, their structural properties are scarcely understood. To assess structural and thermodynamic properties of dotriacontane (C32) molecules adsorbed on a SiO2 surface, we conducted all-atom molecular dynamics (MD) simulations. By analyzing potentials of mean force, order parameters and self-diffusion, we compared the stability and preferential orientation between ordered and disordered systems. Our data confirm the presence of one parallel layer of C32 followed by a mixture of disordered C32 segments exhibiting no thermodynamic preference. This semi-ordered structural model shed light to the interactions between C32 and a SiO2 surface.

  13. Attention to surfaces modulates motion processing in extrastriate area MT.

    PubMed

    Wannig, Aurel; Rodríguez, Valia; Freiwald, Winrich A

    2007-05-24

    In the visual system, early atomized representations are grouped into higher-level entities through processes of perceptual organization. Here we present neurophysiological evidence that a representation of a simple object, a surface defined by color and motion, can be the unit of attentional selection at an early stage of visual processing. Monkeys were cued by the color of a fixation spot to attend to one of two transparent random-dot surfaces, one red and one green, which occupied the same region of space. Motion of the attended surface drove neurons in the middle temporal (MT) visual area more strongly than physically identical motion of the non-attended surface, even though both occurred within the spotlight of attention. Surface-based effects of attention persisted even without differential surface coloring, but attentional modulation was stronger with color. These results show that attention can select surface representations to modulate visual processing as early as cortical area MT.

  14. Effective bacterial inactivation and removal of copper by porous ceramics with high surface area.

    PubMed

    Klein, Tanja Yvonne; Wehling, Julia; Treccani, Laura; Rezwan, Kurosch

    2013-01-15

    In this study, we present porous ceramics combining the antibacterial effect of copper with an integrated copper removal adsorbent. After preparing and characterizing the antibacterial copper-doped microbeads and monoliths (CuBs and CuMs), their antibacterial efficiency is probed against different nonpathogenic and pathogenic bacteria (Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa). An antibacterial efficiency of 100% is reached within 15 min to 3 h for all tested strains under static conditions. Dynamic tests with B. subtilis and E. coli showed high antibacterial efficiency up to 99.93% even at continuous flux. To avoid any adverse effects on the environment, continuous removal of released copper-ions is accomplished with porous, high surface area monolithic adsorbents (MAds). MAds are prepared similarly to the CuMs but without adding copper during the manufacturing process. MAds reduce the amount of copper released from the CuMs ≥ 99% during the first 15 min, ≥90% up to 2 h, and after 22 h of continuous filtration up to 56% of the released copper is removed.

  15. MOISTURE AND SURFACE AREA MEASUREMENTS OF PLUTONIUM-BEARING OXIDES

    SciTech Connect

    Crowder, M.; Duffey, J.; Livingston, R.; Scogin, J.; Kessinger, G.; Almond, P.

    2009-09-28

    To ensure safe storage, plutonium-bearing oxides are stabilized at 950 C for at least two hours in an oxidizing atmosphere. Stabilization conditions are expected to decompose organic impurities, convert metals to oxides, and result in moisture content below 0.5 wt%. During stabilization, the specific surface area is reduced, which minimizes readsorption of water onto the oxide surface. Plutonium oxides stabilized according to these criteria were sampled and analyzed to determine moisture content and surface area. In addition, samples were leached in water to identify water-soluble chloride impurity content. Results of these analyses for seven samples showed that the stabilization process produced low moisture materials (< 0.2 wt %) with low surface area ({le} 1 m{sup 2}/g). For relatively pure materials, the amount of water per unit surface area corresponded to 1.5 to 3.5 molecular layers of water. For materials with chloride content > 360 ppm, the calculated amount of water per unit surface area increased with chloride content, indicating hydration of hygroscopic salts present in the impure PuO{sub 2}-containing materials. The low moisture, low surface area materials in this study did not generate detectable hydrogen during storage of four or more years.

  16. Binding modes of phosphonic acid derivatives adsorbed on TiO2 surfaces: Assignments of experimental IR and NMR spectra based on DFT/PBC calculations

    NASA Astrophysics Data System (ADS)

    Geldof, D.; Tassi, M.; Carleer, R.; Adriaensens, P.; Roevens, A.; Meynen, V.; Blockhuys, F.

    2017-01-01

    A DFT study on the adsorption of a series of phosphonic acids (PAs) on the TiO2 anatase (101) and (001) surfaces was performed. The adsorption energies and geometries of the most stable binding modes were compared to literature data and the effect of the inclusion of dispersion forces in the energy calculations was gauged. As the (101) surface is the most exposed surface of TiO2 anatase, the calculated chemical shifts and vibrational frequencies of PAs adsorbed on this surface were compared to experimental 31P and 17O NMR and IR data in order to assign the two possible binding modes (mono- and bidentate) to peaks and bands in these spectra; due to the corrugated nature of anatase (101) tridentate binding is not possible on this surface. Analysis of the calculated and experimental 31P chemical shifts indicates that both monodentate and bidentate binding modes are present. For the reactive (001) surface, the results of the calculations indicate that both bi- and tridentate binding modes result in stable systems. Due to the particular sensitivity of 17O chemical shifts to hydrogen bonding and solvent effects, the model used is insufficient to assign these spectra at present. Comparison of calculated and experimental IR spectra leads to the conclusion that IR spectroscopy is not suitable for the characterization of the different binding modes of the adsorption complexes.

  17. Preparation and Characteristics of SiOx Coated Carbon Nanotubes with High Surface Area

    PubMed Central

    Kim, Aeran; Lim, Seongyop; Peck, Dong-Hyun; Kim, Sang-Kyung; Lee, Byungrok; Jung, Doohwan

    2012-01-01

    An easy method to synthesize SiOx coated carbon nanotubes (SiOx-CNT) through thermal decomposition of polycarbomethylsilane adsorbed on the surface of CNTs is reported. Physical properties of SiOx-CNT samples depending on various Si contents and synthesis conditions are examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen isotherm, scanning electron microscope (SEM), and transmission electron microscope (TEM). Morphology of the SiOx-CNT appears to be perfectly identical to that of the pristine CNT. It is confirmed that SiOx is formed in a thin layer of approximately 1 nm thickness over the surface of CNTs. The specific surface area is significantly increased by the coating, because thin layer of SiOx is highly porous. The surface properties such as porosity and thickness of SiOx layers are found to be controlled by SiOx contents and heat treatment conditions. The preparation method in this study is to provide useful nano-hybrid composite materials with multi-functional surface properties.

  18. Towards understanding KOH conditioning of amidoxime-based oolymer adsorbents for sequestering uranium from seawater

    DOE PAGES

    Pan, Horng-Bin; Kuo, Li-Jung; Wood, Jordana; ...

    2015-11-17

    Conditioning of polymer fiber adsorbents grafted with amidoxime and carboxylic acid groups is necessary to make the materials hydrophilic for sequestering uranium from seawater. In this paper, spectroscopic techniques were employed to study the effectiveness of the traditional KOH conditioning method (2.5% KOH at 80⁰C) on recently developed high-surface-area amidoxime-based polymer fiber adsorbents developed at Oak Ridge National Laboratory. FTIR spectra reveal that the KOH conditioning process removes the proton from the carboxylic acids and also converts the amidoxime groups to carboxylate groups in the adsorbent. With prolonged KOH treatment (>1 hr) at 80⁰C, physical damage to the adsorbent materialmore » occurs which can lead to a significant reduction in the adsorbent's uranium adsorption capability in real seawater during extended exposure times (>21 days). The physical damage to the adsorbent can be minimized by lowering KOH conditioning temperature. For the high-surface-area amidoxime-based adsorbents, 20 min of conditioning in 2.5% KOH at 80⁰C or 1 hr of conditioning in 2.5% KOH at 60⁰C appears sufficient to achieve de-protonation of the carboxylic acid with minimal harmful effects to the adsorbent material. Lastly, the use of NaOH instead of KOH can also reduce the cost of the base treatment process required for conditioning the amidoxime-based sorbents with minimal loss of adsorption capacity (≤7%).« less

  19. Towards understanding KOH conditioning of amidoxime-based oolymer adsorbents for sequestering uranium from seawater

    SciTech Connect

    Pan, Horng-Bin; Kuo, Li-Jung; Wood, Jordana; Strivens, Jonathan E.; Gill, Gary A.; Janke, Christopher James; Wai, Chien M.

    2015-11-17

    Conditioning of polymer fiber adsorbents grafted with amidoxime and carboxylic acid groups is necessary to make the materials hydrophilic for sequestering uranium from seawater. In this paper, spectroscopic techniques were employed to study the effectiveness of the traditional KOH conditioning method (2.5% KOH at 80⁰C) on recently developed high-surface-area amidoxime-based polymer fiber adsorbents developed at Oak Ridge National Laboratory. FTIR spectra reveal that the KOH conditioning process removes the proton from the carboxylic acids and also converts the amidoxime groups to carboxylate groups in the adsorbent. With prolonged KOH treatment (>1 hr) at 80⁰C, physical damage to the adsorbent material occurs which can lead to a significant reduction in the adsorbent's uranium adsorption capability in real seawater during extended exposure times (>21 days). The physical damage to the adsorbent can be minimized by lowering KOH conditioning temperature. For the high-surface-area amidoxime-based adsorbents, 20 min of conditioning in 2.5% KOH at 80⁰C or 1 hr of conditioning in 2.5% KOH at 60⁰C appears sufficient to achieve de-protonation of the carboxylic acid with minimal harmful effects to the adsorbent material. Lastly, the use of NaOH instead of KOH can also reduce the cost of the base treatment process required for conditioning the amidoxime-based sorbents with minimal loss of adsorption capacity (≤7%).

  20. MTBE adsorption on alternative adsorbents and packed bed adsorber performance.

    PubMed

    Rossner, Alfred; Knappe, Detlef R U

    2008-04-01

    Widespread use of the fuel additive methyl tertiary-butyl ether (MTBE) has led to frequent MTBE detections in North American and European drinking water sources. The overall objective of this research was to evaluate the effectiveness of a silicalite zeolite, a carbonaceous resin, and a coconut-shell-based granular activated carbon (GAC) for the removal of MTBE from water. Isotherm and short bed adsorber tests were conducted in ultrapure water and river water to obtain parameters describing MTBE adsorption equilibria and kinetics and to quantify the effect of natural organic matter (NOM) on MTBE adsorption. Both the silicalite zeolite and the carbonaceous resin exhibited larger MTBE adsorption uptakes than the tested GAC. Surface diffusion coefficients describing intraparticle MTBE mass transfer rates were largest for the GAC and smallest for the carbonaceous resin. Pilot tests were conducted to verify MTBE breakthrough curve predictions obtained with the homogeneous surface diffusion model and to evaluate the effect of NOM preloading on packed bed adsorber performance. Results showed that GAC was the most cost-competitive adsorbent when considering adsorbent usage rate only; however, the useful life of an adsorber containing silicalite zeolite was predicted to be approximately 5-6 times longer than that of an equally sized adsorber containing GAC. Pilot column results also showed that NOM preloading did not impair the MTBE removal efficiency of the silicalite zeolite. Thus, it may be possible to regenerate spent silicalite with less energy-intensive methods than those required to regenerate GAC.

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

    NASA Astrophysics Data System (ADS)

    Maurer, Reinhard J.; Reuter, Karsten

    2013-07-01

    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)], 10.1103/PhysRevB.78.075441 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.

  2. Cyclic voltammetry, spectroelectrochemical and photochemical studies of 7,7{prime}-diphenyl-7,7{prime}-diapocarotene cation radicals and dications adsorbed on the surface of electrodes

    SciTech Connect

    Gao, G.; Kispert, L.D.

    1996-10-01

    7,7{prime}-diphenyl-7,7{prime}-diapocarotene in dichloromethane can adsorb on glassy carbon, platinum and gold electrode surfaces upon electrochemical oxidation, resulting in an intense cyclic voltammogram(CV) cathodic peak. Spectroelectrochemical studies of the adsorbed material on ITO electrode surfaces showed that cation radicals, dications and possibly dimers were formed. Irradiation of the surface with visible light resulting in changes in the optical absorption bands. Similar adsorption behavior was also observed by using various supporting electrolytes and solvents. However CV and simultaneous bulk electrolysis-optical spectra obtained in anhydrous acetonitrile show no adsorption. A mechanism involving electrode reactions and adsorption equilibria will be presented.

  3. The structure and reactivity of adsorbates on stepped Rh and Pt surfaces investigated by LEED, HREELS, TPD, XPS and STM

    SciTech Connect

    Batteas, J.D. |

    1995-06-01

    Defects on surfaces such as steps play an important role in surface chemistry. In order to obtain an understanding of the influence of steps in surface chemical reactions, the structure and reactivity of small molecules (O{sub 2}, CO, H{sub 2}S, and C{sub 2}H{sub 4}) on atomically stepped surfaces of RH and Pt have been investigated. The detailed structures of CO and oxygen bonded to the Rh(110) surface were determined. The CO molecules bond near the short bridge sites with the CO molecular axis tilted approximately 24{degree} from the surface normal. Oxygen atoms are bound asymmetrically in the 3-fold fcc hollow-sites to the (111) facets of the steps. The interactions of CO and oxygen on the Rh(311) surface were examined. The reaction of CO with the ordered phases of O shows two distinct reaction channels, a low temperature reaction limited channel (200 K) and a high temperature diffusion limited channel (350 K). Models of the reaction geometry and dynamics are proposed. The thermal decomposition of ethylene was examined on the Rh(311) surface. The stable decomposition species (C{sub 2}H, CH and C{sub 2}) are formed near 300 K, approximately 100 K lower on the stepped Rh(311) than on the flatter Rh(111) surface. The formation of these species at lower temperatures is attributed to the stepped nature of the surface. Finally, in situ STM was used to examine surface structural changes of a stepped Pt(111) crystal under coadsorption of sulfur and CO. This is the first direct evidence for a new mechanism by which a surface covered with an unreactive, strongly chemisorbed overlayer can form new sites, for bonding and reactions to occur, by massive surface restructuring at the step edges. This new surface phenomenon answers some of the puzzles of metal surface catalysis and its implications are described. 278 refs.

  4. Determination of Reactive Surface Area of Melt Glass

    SciTech Connect

    Bourcier,W.L.; Roberts, S.; Smith, D.K.; Hulsey, S.; Newton,L.; Sawvel, A.; Bruton, C.; Papelis, C.; Um, W.; Russell, C. E.; Chapman,J.

    2000-10-01

    A comprehensive investigation of natural and manmade silicate glasses, and nuclear melt glass was undertaken in order to derive an estimate of glass reactive surface area. Reactive surface area is needed to model release rates of radionuclides from nuclear melt glass in the subsurface. Because of the limited availability of nuclear melt glasses, natural volcanic glass samples were collected which had similar textures and compositions as those of melt glass. A flow-through reactor was used to measure the reactive surface area of the analog glasses in the presence of simplified NTS site ground waters. A measure of the physical surface area of these glasses was obtained using the BET gas-adsorption method. The studies on analog glasses were supplemented by measurement of the surface areas of pieces of actual melt glass using the BET method. The variability of the results reflect the sample preparation and measurement techniques used, as well as textural heterogeneity inherent to these samples. Based on measurements of analog and actual samples, it is recommended that the hydraulic source term calculations employ a range of 0.001 to 0.01 m{sup 2}/g for the reactive surface area of nuclear melt glass.

  5. Unique developmental trajectories of cortical thickness and surface area.

    PubMed

    Wierenga, Lara M; Langen, Marieke; Oranje, Bob; Durston, Sarah

    2014-02-15

    There is evidence that the timing of developmental changes in cortical volume and thickness varies across the brain, although the processes behind these differences are not well understood. In contrast to volume and thickness, the regional developmental trajectories of cortical surface area have not yet been described. The present study used a combined cross-sectional and longitudinal design with 201 MRI-scans (acquired at 1.5-T) from 135 typically developing children and adolescents. Scans were processed using FreeSurfer software and the Desikan-Killiany atlas. Developmental trajectories were estimated using mixed model regression analysis. Within most regions, cortical thickness showed linear decreases with age, whereas both cortical volume and surface area showed curvilinear trajectories. On average, maximum surface area occurred later in development than maximum volume. Global gender differences were more pronounced in cortical volume and surface area than in average thickness. Our findings suggest that developmental trajectories of surface area and thickness differ across the brain, both in their pattern and their timing, and that they also differ from the developmental trajectory of global cortical volume. Taken together, these findings indicate that the development of surface area and thickness is driven by different processes, at least in part.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Determination of anisotropic optical constants and surface coverage of molecular films using polarized visible ATR spectroscopy. Application to adsorbed cytochrome c films.

    PubMed

    Runge, Anne F; Rasmussen, Nicole C; Saavedra, S Scott; Mendes, Sergio B

    2005-01-13

    This article describes a method to determine the anisotropic optical constants and surface coverage of molecular films using polarized attenuated total reflectance (ATR) absorbance measurements. We have extended the transfer-matrix formalism to describe birefringent and dichroic films in ATR geometries and have combined it with an iterative numerical procedure to determine the anisotropic values of both the real (n) and imaginary (k) parts of the complex refractive index of the film under investigation. Anisotropic values of the imaginary part of the refractive index (k) allow for the determination of the surface coverage and one order parameter of the film. To illustrate this approach, we have used cytochrome c (cyt c) protein films adsorbed to glass and indium tin oxide (ITO) surfaces. Experimental results show that cyt c films on these surfaces, which were formed under identical conditions, have significant differences in their surface coverages (11.2 +/- 0.4 pmol/cm(2) on glass and 21.7 +/- 0.9 pmol/cm(2) on ITO); however, their order parameters are similar (0.30 +/- 0.02 on glass and 0.36 +/- 0.04 on ITO).

  8. Quantifying object and material surface areas in residences

    SciTech Connect

    Hodgson, Alfred T.; Ming, Katherine Y.; Singer, Brett C.

    2005-01-05

    The dynamic behavior of volatile organic compounds (VOCs) in indoor environments depends, in part, on sorptive interactions between VOCs in the gas phase and material surfaces. Since information on the types and quantities of interior material surfaces is not generally available, this pilot-scale study was conducted in occupied residences to develop and demonstrate a method for quantifying surface areas of objects and materials in rooms. Access to 33 rooms in nine residences consisting of bathrooms, bedroom/offices and common areas was solicited from among research group members living in the East San Francisco Bay Area. A systematic approach was implemented for measuring rooms and objects from 300 cm{sup 2} and larger. The ventilated air volumes of the rooms were estimated and surface area-to-volume ratios were calculated for objects and materials, each segregated into 20 or more categories. Total surface area-to-volume ratios also were determined for each room. The bathrooms had the highest total surface area-to-volume ratios. Bedrooms generally had higher ratios than common areas consisting of kitchens, living/dining rooms and transitional rooms. Total surface area-to-volume ratios for the 12 bedrooms ranged between 2.3 and 4.7 m{sup 2} m{sup -3}. The importance of individual objects and materials with respect to sorption will depend upon the sorption coefficients for the various VOC/materials combinations. When combined, the highly permeable material categories, which may contribute to significant interactions, had a median ratio of about 0.5 m{sup 2} m{sup -3} for all three types of rooms.

  9. Inverse gas chromatography for natural fibre characterisation: Identification of the critical parameters to determine the Brunauer-Emmett-Teller specific surface area.

    PubMed

    Legras, A; Kondor, A; Heitzmann, M T; Truss, R W

    2015-12-18

    Inverse gas chromatography (IGC) is an alternative technique to determine the specific surface area of natural fibres. Natural fibres have a complex surface chemistry and unique microstructure that challenge the current capabilities to perform surface characterisation. This study investigated the influence of multiple parameters on the measured Brunauer-Emmett-Teller (BET) specific surface area for samples of flax, kenaf and BioMid(®) cellulose fibres using IGC. The BET surface area of kenaf and flax differed with 0.51m(2)g(-1) and 1.35m(2)g(-1) respectively, the former being similar to the cellulose fibres (0.54m(2)g(-1)). The data was calculated under conditions where the BET equation showed good linearity (R(2)⩾0.995). Repeatability was excellent so that two runs sufficed to obtain representative BET surface area values. The findings showed the choice of solvent was important for all specimens to avoid any misleading data comparison due to molecular orientation effects that impact the adsorbent-adsorbate interactions. The higher surface area of the flax sample, and its higher variability, was correlated with a higher surface roughness observed under optical microscopy. Packing the chromatography column with long or chopped fibres produced results that were statistically insignificant.

  10. Extracting Uranium from Seawater: Promising AF Series Adsorbents

    SciTech Connect

    Das, S.; Oyola, Y.; Mayes, Richard T.; Janke, Chris J.; Kuo, L. -J.; Gill, G.; Wood, J. R.; Dai, S.

    2016-04-20

    A new family of high-surface-area polyethylene fiber adsorbents named the AF series was recently developed at the Oak Ridge National Laboratory (ORNL). The AF series adsorbents were synthesized by radiation-induced graft polymerization of acrylonitrile and itaconic acid (at different monomer/comonomer mol ratios) onto high surface area polyethylene fibers. The degree of grafting (%DOG) of AF series adsorbents was found to be 154-354%. The grafted nitrile groups were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with 0.44 M KOH at 80 °C followed by screening at ORNL with sodium-based synthetic aqueous solution, spiked with 8 ppm uranium. The uranium adsorption capacity in simulated seawater screening ranged from 170 to 200 g-U/kg-ads irrespective of %DOG. A monomer/comonomer molar ratio in the range of 7.57-10.14 seemed to be optimum for highest uranium loading capacity. Subsequently, the adsorbents were also tested with natural seawater at Pacific Northwest National Laboratory (PNNL) using flow-through column experiments to determine uranium loading capacity with varying KOH conditioning times at 80 °C. The highest adsorption capacity of AF1 measured after 56 days of marine testing was demonstrated as 3.9 g-U/kg-adsorbent and 3.2 g-U/kg-adsorbent for 1 and 3 h of KOH conditioning at 80 °C, respectively. Based on capacity values of several AF1 samples, it was observed that changing KOH conditioning from 1 to 3 h at 80 °C resulted in a 22-27% decrease in uranium adsorption capacity in seawater.

  11. Surface enhanced Raman spectroscopy of L-alanyl-L-tryptophan dipeptide adsorbed on Si substrate decorated with triangular silver nanoplates

    NASA Astrophysics Data System (ADS)

    Ramanauskaite, Lina; Snitka, Valentinas

    2015-03-01

    Raman and surface enhanced Raman spectroscopies have been used to investigate interaction of L-alanyl-L-tryptophan (Ala-Trp) dipeptide with nanostructured silver surface. A highly sensitive surface enhanced Raman scattering (SERS)-based biosensor has been employed for label-free dipeptide detection and its orientation on the nanostructured surface. The synthesis of SERS substrate was based on direct silver ions reduction on hydrofluoric acid etched silicon wafer. Raman and SERS spectra of Ala-Trp were recorded in liquid to keep native environment for dipeptide. To the best of our knowledge, this work is a first attempt to analyze the structure of Ala-Trp dipeptide by Raman spectroscopy.

  12. Minimal adhesion surface area in tangentially loaded digital contacts.

    PubMed

    Terekhov, Alexander V; Hayward, Vincent

    2011-09-02

    The stick-to-slip transition of a fingertip in contact with a planar surface does not occur instantaneously. As the tangential load increases, portions of the skin adhere while others slip, giving rise to an evolution of the contact state, termed partial slip. We develop a quasi-static model that predicts that if the coefficient of kinetic friction is larger than the coefficient of static friction, then the stuck surface area diminishes as the tangential load increases until reaching a 'minimal adhesion surface area' where it vanishes abruptly. This phenomenon was observed in recently measured finger-slip image data (André et al., 2011) that were processed by an optic flow detection algorithm. We examined the results of 10 trials. Four of them exhibited the minimal adhesion surface area phenomenon, four of them did not, and two were inconclusive.

  13. Cryogenic adsorber design in a helium refrigeration system

    NASA Astrophysics Data System (ADS)

    Hu, Zhongjun; Zhang, Ning; Li, Zhengyu; Li, Q.

    2012-06-01

    The cryogenic adsorber is specially designed to eliminate impurities in gaseous helium such as O2, and N2 which is normally difficult to remove, based on the reversible cryotrapping of impurities on an activated carbon bed. The coconut shell activated carbon is adopted because of its developed micropore structure and specific surface area. This activated carbon adsorption is mostly determined by the micropore structure, and the adsorption rate of impurities is inversely proportional to the square of the particle sizes. The active carbon absorber's maximum permissible flow velocity is 0.25 m/s. When the gas flow velocity increases, the adsorption diffusion rate of the adsorbent is reduced, because an increase in the magnitude of the velocity resulted in a reduced amount of heat transfer to a unit volume of impure gas. According to the numerical simulation of N2 adsorption dynamics, the appropriate void tower link speed and the saturated adsorption capacity are determined. Then the diameter and height of the adsorber are designed. The mass transfer length should be taken into account in the adsorber height design. The pressure decrease is also calculated. The important factors that influence the adsorber pressure decrease are the void tower speed, the adsorbed layer height, and the active carbon particle shape and size.

  14. To-date spacecraft applications and demonstration testing results, and future product development for new molecular adsorber technologies

    NASA Technical Reports Server (NTRS)

    Thomson, Shaun; Hansen, Patricia; Straka, Sharon; Chen, Philip; Triolo, Jack; Bettini, Ron; Carosso, Paolo; Carosso, Nancy

    1997-01-01

    The use of molecular adsorbers, in order to aid in the reduction of the spacecraft contamination levels, is discussed. Molecular adsorbers are characterized by an extremely large surface area, molecularly-porous substructure, and processing charged sites capable of retaining molecular contaminant species. Molecular adsorbers were applied on two Hubble Space Telescope servicing missions, as well as on the tropical rainfall measuring mission. The use of molecular adsorbers carries the potential for low cost, easy fabrication and integration of reliable means for reducing the contamination level around spacecraft.

  15. Structure and stability of weakly chemisorbed ethene adsorbed on low-index Cu surfaces: performance of density functionals with van der Waals interactions.

    PubMed

    Hanke, Felix; Dyer, Matthew S; Björk, Jonas; Persson, Mats

    2012-10-24

    We have investigated the performance of popular density functionals that include van der Waals interactions for the experimentally well-characterized problem of ethene (C(2)H(4)) adsorbed on the low-index surfaces of copper. This set of functionals does not only include three van der Waals density functionals-vdwDF-PBE, vdwDF-revPBE and optB86b-vdwDF-and two dispersion-corrected functionals-Grimme and TS-but also local and semi-local functionals such as LDA and PBE. The adsorption system of ethene on copper was chosen because it is a weakly chemisorbed system for which the vdW interactions are expected to give a significant contribution to the adsorption energy. Overall the density functionals that include vdW interactions increased substantially the adsorption energies compared to the PBE density functional but predicted the same adsorption sites and very similar C-C bonding distances except for two of the van der Waals functionals. The top adsorption site was predicted almost exclusively for all functionals on the (110), (100) and (111) surfaces, which is in agreement with experiment for the (110) surface but not for the (100) surface. On the (100) surface, all functionals except two van der Waals density functionals singled out the observed cross-hollow site from the calculated C-C bonding distances and adsorption heights. On the top sites on the (110) surface and the cross-hollow site on the Cu(100) surface, the ethene molecule was found to form a weak chemisorption bond. On the (111) surface, all functionals gave a C-C bonding distance and an adsorption height more typical for physisorption, in agreement with experiments.

  16. Observation of UV-induced Auger features in catechol adsorbed on anatase TiO{sub 2} (101) single crystal surface

    SciTech Connect

    Thomas, Andrew G.; Syres, Karen L.

    2012-04-23

    We have investigated the electronic structure of catechol adsorbed on the anatase TiO{sub 2} (101) surface under illumination with ultraviolet (UV) light (4.75 eV) using resonant photoemission spectroscopy. UV illumination results in the appearance of a strong Ti MVV (M refers to photoionization of 3p level and VV the Auger decay process via the valence levels) feature at a kinetic energy of 26.2 eV. This is attributed to the creation of localised states following catechol to Ti-3d excitation by the UV source. A sharp resonance attributed to excitation from Ti 3p states into these localised states is observed in constant final state spectra.

  17. A framework for predicting surface areas in microporous coordination polymers.

    PubMed

    Schnobrich, Jennifer K; Koh, Kyoungmoo; Sura, Kush N; Matzger, Adam J

    2010-04-20

    A predictive tool termed the linker to metal cluster (LiMe) ratio is introduced as a method for understanding surface area in microporous coordination polymers (MCPs). Calibrated with geometric accessible surface area computations, the LiMe ratio uses molecular weight of building block components to indicate the maximum attainable surface area for a given linker and metal cluster combination. MOF-5 and HKUST-1 are used as prototypical structures to analyze MCPs with octahedral M(4)O(CO(2)R)(6) and paddlewheel M(2)(CO(2)R)(4) metal clusters. Insight into the effects of linker size, geometry, number of coordinating groups, and framework interpenetration is revealed through the LiMe ratio analysis of various MCPs. Experimental surface area deviation provides indication that a material may suffer from incomplete guest removal, structural collapse, or interpenetration. Because minimal data input are required, the LiMe ratio surface area analysis is suggested as a quick method for experimental verification as well as a guide for the design of new materials.

  18. Fabricating electrospun cellulose nanofibre adsorbents for ion-exchange chromatography.

    PubMed

    Dods, Stewart R; Hardick, Oliver; Stevens, Bob; Bracewell, Daniel G

    2015-01-09

    Protein separation is an integral step in biopharmaceutical manufacture with diffusion-limited packed bed chromatography remaining the default choice for industry. Rapid bind-elute separation using convective mass transfer media offers advantages in productivity by operating at high flowrates. Electrospun nanofibre adsorbents are a non-woven fibre matrix of high surface area and porosity previously investigated as a bioseparation medium. The effects of compression and bed layers, and subsequent heat treatment after electrospinning cellulose acetate nanofibres were investigated using diethylaminoethyl (DEAE) or carboxylate (COO) functionalisations. Transbed pressures were measured and compared by compression load, COO adsorbents were 30%, 70% and 90% higher than DEAE for compressions 1, 5 and 10MPa, respectively, which was attributed to the swelling effect of hydrophilic COO groups. Dynamic binding capacities (DBCs) at 10% breakthrough were measured between 2000 and 12,000CV/h (2s and 0.3s residence times) under normal binding conditions, and DBCs increased with reactant concentration from 4 to 12mgBSA/mL for DEAE and from 10 to 21mglysozyme/mL for COO adsorbents. Comparing capacities of compression loads applied after electrospinning showed that the lowest load tested, 1MPa, yielded the highest DBCs for DEAE and COO adsorbents at 20mgBSA/mL and 27mglysozyme/mL, respectively. At 1MPa, DBCs were the highest for the lowest flowrate tested but stabilised for flowrates above 2000CV/h. For compression loads of 5MPa and 10MPa, adsorbents recorded lower DBCs than 1MPa as a result of nanofibre packing and reduced surface area. Increasing the number of bed layers from 4 to 12 showed decreasing DBCs for both adsorbents. Tensile strengths were recorded to indicate the mechanical robustness of the adsorbent and be related to packing the nanofibre adsorbents in large scale configurations such as pleated cartridges. Compared with an uncompressed adsorbent, compressions of 1, 5

  19. Fabricating electrospun cellulose nanofibre adsorbents for ion-exchange chromatography

    PubMed Central

    Dods, Stewart R.; Hardick, Oliver; Stevens, Bob; Bracewell, Daniel G.

    2015-01-01

    Protein separation is an integral step in biopharmaceutical manufacture with diffusion-limited packed bed chromatography remaining the default choice for industry. Rapid bind-elute separation using convective mass transfer media offers advantages in productivity by operating at high flowrates. Electrospun nanofibre adsorbents are a non-woven fibre matrix of high surface area and porosity previously investigated as a bioseparation medium. The effects of compression and bed layers, and subsequent heat treatment after electrospinning cellulose acetate nanofibres were investigated using diethylaminoethyl (DEAE) or carboxylate (COO) functionalisations. Transbed pressures were measured and compared by compression load, COO adsorbents were 30%, 70% and 90% higher than DEAE for compressions 1, 5 and 10 MPa, respectively, which was attributed to the swelling effect of hydrophilic COO groups. Dynamic binding capacities (DBCs) at 10% breakthrough were measured between 2000 and 12,000 CV/h (2 s and 0.3 s residence times) under normal binding conditions, and DBCs increased with reactant concentration from 4 to 12 mg BSA/mL for DEAE and from 10 to 21 mg lysozyme/mL for COO adsorbents. Comparing capacities of compression loads applied after electrospinning showed that the lowest load tested, 1 MPa, yielded the highest DBCs for DEAE and COO adsorbents at 20 mg BSA/mL and 27 mg lysozyme/mL, respectively. At 1 MPa, DBCs were the highest for the lowest flowrate tested but stabilised for flowrates above 2000 CV/h. For compression loads of 5 MPa and 10 MPa, adsorbents recorded lower DBCs than 1 MPa as a result of nanofibre packing and reduced surface area. Increasing the number of bed layers from 4 to 12 showed decreasing DBCs for both adsorbents. Tensile strengths were recorded to indicate the mechanical robustness of the adsorbent and be related to packing the nanofibre adsorbents in large scale configurations such as pleated cartridges. Compared with an

  20. Roles of surface water areas for water and solute cycle in Hanoi city, Viet Nam

    NASA Astrophysics Data System (ADS)

    Hayashi, Takeshi; Kuroda, Keisuke; Do Thuan, An; Tran Thi Viet, Nga; Takizawa, Satoshi

    2013-04-01

    water of the pond sediments were much higher than the pond water and closed to that of groundwater. Also, other metal elements showed the same trend. This result suggested that Arsenic and other metal elements recharged to these ponds is probably adsorbed and removed by sediments (including organic matters). That is, pond sediment plays an important role for solute transport as a filter of Arsenic and metal elements. The results of this study strongly suggest that the natural and artificial surface water areas have important roles for water cycle and solute transport in Hanoi city. Although the number of the natural water areas is decreasing, dredging of artificial water areas increases the infiltration from the surface to aquifers. Therefore, qualitative and quantitative preservation of the surface water areas is important for conservation of groundwater environment and contribute to sustainable groundwater management in Hanoi city.

  1. Specific Interactions of Neutral Side Chains of an Adsorbed Protein with the Surface of α-Quartz and Silica Gel.

    PubMed

    Odinokov, Alexey V; Bagaturyants, Alexander A

    2015-07-16

    Many key features of the protein adsorption on the silica surfaces still remain unraveled. One of the open questions is the interaction of nonpolar side chains with siloxane cavities. Here, we use nonequilibrium molecular dynamics simulations for the detailed investigation of the binding of several hydrophobic and amphiphilic protein side chains with silica surface. These interactions were found to be a possible driving force for protein adsorption. The free energy gain was larger for the disordered surface of amorphous silica gel as compared to α-quartz, but the impact depended on the type of amino acid. The dependence was analyzed from the structural point of view. For every amino acid an enthalpy-entropy compensation behavior was observed. These results confirm a hypothesis of an essential role of hydrophobic interactions in protein unfolding and irreversible adsorption on the silica surface.

  2. Removal of copper from aqueous solution using iron-containing adsorbents derived from methane fermentation sludge.

    PubMed

    Qian, Qingrong; Mochidzuki, Kazuhiro; Fujii, Takao; Sakoda, Akiyoshi

    2009-12-30

    Iron-containing adsorbents prepared from methane fermentation sludge (MFS) were characterized by N(2) adsorption, XRD, SEM, EDX, pH determination and elemental analysis. The experiments for copper removal from aqueous solution using the MFS-derived adsorbents were performed, and the effects of iron content, forms of the iron (hydr)oxides, surface basicity and pH of the aqueous solution on copper removal were elucidated respectively. The desorption studies were also performed and the mechanism of Cu(II) adsorption was proposed. The results indicated that the adsorbent obtained at 700 degrees C for 1h in a steam atmosphere possessed the highest capability for Cu(II) adsorption. The high copper removal ability of the MFS-derived materials is attributed to their intermediate surface area, strong surface basicity and the presence of iron (hydr)oxides on their surface. The Cu(II) adsorption onto the composite adsorbents is via ion-exchange with H, Ca and K ions, surface precipitation and binding with active sites on the surface of iron (hydr)oxides at various pH values. The desorption of copper in deionized water is quite low. The irreversibility of copper adsorption on the iron-containing adsorbents is attributed to the formation of strong bonds between Cu(II) and the iron (hydr)oxides. The adsorbent can be applied to remove copper from water or soil by fixation onto the surface.

  3. Inorganic chemically active adsorbents (ICAAs)

    SciTech Connect

    Ally, M.R.; 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.

  4. Observed Asteroid Surface Area in the Thermal Infrared

    NASA Astrophysics Data System (ADS)

    Nugent, C. R.; Mainzer, A.; Masiero, J.; Wright, E. L.; Bauer, J.; Grav, T.; Kramer, E.; Sonnett, S.

    2017-02-01

    The rapid accumulation of thermal infrared observations and shape models of asteroids has led to increased interest in thermophysical modeling. Most of these infrared observations are unresolved. We consider what fraction of an asteroid’s surface area contributes the bulk of the emitted thermal flux for two model asteroids of different shapes over a range of thermal parameters. The resulting observed surface in the infrared is generally more fragmented than the area observed in visible wavelengths, indicating high sensitivity to shape. For objects with low values of the thermal parameter, small fractions of the surface contribute the majority of thermally emitted flux. Calculating observed areas could enable the production of spatially resolved thermal inertia maps from non-resolved observations of asteroids.

  5. High surface area electrode for high efficient microbial electrosynthesis

    NASA Astrophysics Data System (ADS)

    Nie, Huarong; Cui, Mengmeng; Lu, Haiyun; Zhang, Tian; Russell, Thomas; Lovley, Derek

    2012-02-01

    Microbial electrosynthesis, a process in which microorganisms directly accept electrons from an electrode to convert carbon dioxide and water into multi carbon organic compounds, affords a novel route for the generation of valuable products from electricity or even wastewater. The surface area of the electrode is critical for high production. A biocompatible, highly conductive, three-dimensional cathode was fabricated from a carbon nanotube textile composite to support the microorganism to produce acetate from carbon dioxide. The high surface area and macroscale porous structure of the intertwined CNT coated textile ?bers provides easy microbe access. The production of acetate using this cathode is 5 fold larger than that using a planar graphite electrode with the same volume. Nickel-nanowire-modified carbon electrodes, fabricated by microwave welding, increased the surface area greatly, were able to absorb more bacteria and showed a 1.5 fold increase in performance

  6. Magnetism in non-stoichiometric goethite of varying total water content and surface area

    NASA Astrophysics Data System (ADS)

    Barrero, C. A.; Betancur, J. D.; Greneche, J. M.; Goya, G. F.; Berquó, T. S.

    2006-02-01

    In this work, the magnetic properties of four non-stoichiometric goethites with varying total water content and surface area have been investigated. The samples were prepared using two different hydrothermal methods, deriving either from Fe(II) precursors or from Fe(III) precursors. The effects of both agitation during mixing solutions and drying time during synthesis upon the physical properties of the final products were also studied. The samples were characterized by XRD, TGA, BET, 57Fe Mössbauer spectrometry at 300 K, 77 K and 4.2 K, ZFC and FC curves, and magnetization curves. The goethites synthesized from the Fe(II) precursors result less crystalline, contain higher water content than those prepared from the Fe(III) precursor. In addition, ferrous precursor goethites exhibit superparamagnetic relaxation effects, while the ferric precursor goethites exhibit magnetic ordering of clusters. It is found that the stirring process during synthesis can affect the total water content and the magnetic behaviour of the goethites. Our results suggest that structural water content decreases the magnetic hyperfine field at 4.2 K. The adsorbed water content also affects this parameter as suggested by in situ annealing cycles of the goethites in a Mössbauer cryofurnace. Finally, we propose an unique 2-D phase diagram to describe all the magnetic properties of present goethites observed as a function of temperature, surface area (or particle size) and total water content.

  7. A reexamination of the effects of adsorbates on the Raman spectrum of gibbsite.

    USGS Publications Warehouse

    Cunningham, K.W.; Goldberg, M.C.

    1983-01-01

    Previous workers have attributed substantial changes in the Raman intensities of the OH stretching bands in solid, powdered gibbsite of surface area 10 m2/g to surface interactions with the adsorbates 093Ca2+,HxPO43x- and SiO2.xH2O. These changes apparently resulted from an unsatisfactory Raman measurement procedure as a re-examination using an internal intensity standard (Na2C2O4 crystals) with gibbsite of surface area 39 m2/g showed no significant changes in the low-frequency band-height ratios of gibbsite and adsorbates.-D.J.M.

  8. Protein-resistant polymer coatings based on surface-adsorbed poly(aminoethyl methacrylate)/poly(ethylene glycol) copolymers.

    PubMed

    Ionov, Leonid; Synytska, Alla; Kaul, Elisabeth; Diez, Stefan

    2010-01-11

    We report on the protein-resistant properties of glass substrates coated with novel copolymers of 2-aminoethyl methacrylate hydrochloride and poly(ethylene glycol) methyl ether methacrylate (AEM-PEG). In comparison to currently available protein-blocking polymer systems, such as poly-l-lysine-poly(ethylene glycol), silane-based poly(ethylene glycol), and poly(ethylene glycol) brushes prepared by surface-initiated polymerization, the proposed AEM-PEG offers the combined advantages of low cost, simplicity of use, and applicability in aqueous solutions. We demonstrate the capability of AEM-PEG to block the surface binding of globular proteins (tubulin), their assemblies (microtubules), and functional motor proteins (kinesin-1). Moreover, we demonstrate the applicability of AEM-PEG for surface patterning of proteins in microfluidic devices.

  9. Preparation and characterization of high-specific-surface-area activated carbons from K2CO3-treated waste polyurethane.

    PubMed

    Hayashi, J; Yamamoto, N; Horikawa, T; Muroyama, K; Gomes, V G

    2005-01-15

    An activated carbon with high specific surface area was prepared from polyurethane foam by chemical activation with K2CO3 and the influences of carbonization temperature and impregnation ratio on the pore structure of the prepared activated carbon were investigated. It was found that the specific surface area of the activated carbon was at a maximum value (about 2800 m(2)/g) at a carbonization temperature of 1073 K and at an impregnation ratio of 1.0. It was concluded that the polyurethane foam structure was modified during impregnation by K2CO3, K2CO3 promoted charring during carbonization, and then the weight loss behavior was changed below 700 and above 1000 K, carbon in the char was consumed by K2CO3 reduction, and this led to the high specific surface area. The prepared activated carbon had a very sharp micropore size distribution, compared with the commercial activated carbon having high specific surface area. The amounts of three organic vapors (benzene, acetone, and octane) adsorbed on the prepared activated carbons was much larger than those on the traditional coconut shell AC and the same as those on the commercial activated carbon except for octane. We surmised that the high specific surface area was due to the modification of the carbonization behavior of polyurethane foam by K2CO3.

  10. Preparation and characterization of pure and mixed monolayers of poly(ethylene glycol) brushes chemically adsorbed to silica surfaces.

    PubMed

    McNamee, Cathy E; Yamamoto, Shinpei; Higashitani, Ko

    2007-04-10

    We prepared pure and mixed monolayers of methoxy-terminated poly(ethylene glycol)s (m-PEG's) chemically attached to silica surfaces by using m-PEG silane coupling agents of three different molecular weights. These films were subsequently characterized in water by atomic force microscopy (AFM). Images of pure m-PEG monolayers showed the formation of polymer brushes on silica. Force curves between two modified surfaces suggested that an increase in the number of oxyethylene (OE) groups from 6 (PEG6 surface) to 43 (PEG43 surface) to 113 (PEG113 surface) decreased the flexibility of the m-PEG chains in the m-PEG brushes. Frictional force measurements also showed that the friction increased in the order PEG6 < PEG43 surfaces suggested that the flexibility of the mixed monolayers decreased as the fraction of PEG113 increased. Frictional force measurements also showed that the friction decreased as the fraction of PEG6 in the PEG6-PEG113 mixed film increased. Entanglements were therefore thought to decrease as the fraction of PEG113 in the mixed monolayer decreased.

  11. Electrochemical capacitors utilizing low surface area carbon fiber

    SciTech Connect

    Lipka, S.M.

    1997-12-01

    The performance of electrochemical capacitors containing different commercial carbon fibers is reviewed. High specific capacitances (ca. 300 F/g) are obtained with low surface area carbon fiber (<1 m2/g) using a proprietary activation process. Capacitance is primarily achieved through pseudocapacitance resulting from surface functional groups. The performance of these devices is dependent on the type of carbon fiber, its carbon content, aspect ratio and microstructure. These devices can achieve high cycle life (ca. 100k) without significant loss in capacitance.

  12. Effective surface areas of coals measured by dye adsorption

    SciTech Connect

    Spitzer, D.P.

    1988-01-01

    The primary interest has been to examine adsorption behavior especially at short contact times, ten minutes to an hour, to determine whether such measurements might give useful data on effective surface areas - i.e., the surface that would be accessible to reagents within times comparable to those typical of most coal processing. Accordingly, most of the emphasis is on the effect of time on adsorption, rather than on traditional adsorption isotherms. Although most literature on cationic dye adsorption (mostly on carbons) uses methylene blue, it happened that the authors originally used safranin O instead because this dye was reported to be useful in distinguishing oxidized coals from fresh coals. Many of their experiments were repeated using methylene blue (in water), with very similar results. It was noted early that swelling of coals in water was common, especially for more oxidized or lower rank coals, and adsorption experiments were also done in another solvent, namely methanol. This produced quite striking differences for some coals. Coal surfaces that are readily accessible to adsorption by safranin are found to correlate well with N/sub 2/ surface areas, with adsorption of 1.0 mg safranin per gram of coal corresponding to essentially a surface area of 1.0 m/sup 2//g. Highly oxidized coals were found to swell considerably in water, with correspondingly increased adsorption. Areas of such coals can be estimated by adsorption of safranin from methanol solutions.

  13. Time-resolved spectroscopy at surfaces and adsorbate dynamics:insights from a model-system approach

    NASA Astrophysics Data System (ADS)

    Boström, Emil; Mikkelsen, Anders; Verdozzi, Claudio

    We introduce a finite-system, model description of the initial stages of femtosecond laser induced desorption at surfaces. Using the exact many-body time evolution and also results from a novel time-dependent DFT description for electron-nuclear systems, we analyse the competition between several surface-response mechanisms and electronic correlations in the transient and longer time dynamics under the influence of dipole-coupled fields. Our model allows us to explore how coherent multiple-pulse protocols impact desorption in a variety of prototypical experiments.

  14. High surface area carbon and process for its production

    DOEpatents

    Romanos, Jimmy; Burress, Jacob; Pfeifer, Peter; Rash, Tyler; Shah, Parag; Suppes, Galen

    2016-12-13

    Activated carbon materials and methods of producing and using activated carbon materials are provided. In particular, biomass-derived activated carbon materials and processes of producing the activated carbon materials with prespecified surface areas and pore size distributions are provided. Activated carbon materials with preselected high specific surface areas, porosities, sub-nm (<1 nm) pore volumes, and supra-nm (1-5 nm) pore volumes may be achieved by controlling the degree of carbon consumption and metallic potassium intercalation into the carbon lattice during the activation process.

  15. Large area, surface discharge pumped, vacuum ultraviolet light source

    DOEpatents

    Sze, Robert C.; Quigley, Gerard P.

    1996-01-01

    Large area, surface discharge pumped, vacuum ultraviolet (VUV) light source. A contamination-free VUV light source having a 225 cm.sup.2 emission area in the 240-340 nm region of the electromagnetic spectrum with an average output power in this band of about 2 J/cm.sup.2 at a wall-plug efficiency of approximately 5% is described. Only ceramics and metal parts are employed in this surface discharge source. Because of the contamination-free, high photon energy and flux, and short pulse characteristics of the source, it is suitable for semiconductor and flat panel display material processing.

  16. Large area, surface discharge pumped, vacuum ultraviolet light source

    DOEpatents

    Sze, R.C.; Quigley, G.P.

    1996-12-17

    Large area, surface discharge pumped, vacuum ultraviolet (VUV) light source is disclosed. A contamination-free VUV light source having a 225 cm{sup 2} emission area in the 240-340 nm region of the electromagnetic spectrum with an average output power in this band of about 2 J/cm{sup 2} at a wall-plug efficiency of approximately 5% is described. Only ceramics and metal parts are employed in this surface discharge source. Because of the contamination-free, high photon energy and flux, and short pulse characteristics of the source, it is suitable for semiconductor and flat panel display material processing. 3 figs.

  17. Removal of cationic dyes from aqueous solution using magnetic multi-wall carbon nanotube nanocomposite as adsorbent.

    PubMed

    Gong, Ji-Lai; Wang, Bin; Zeng, Guang-Ming; Yang, Chun-Ping; Niu, Cheng-Gang; Niu, Qiu-Ya; Zhou, Wen-Jin; Liang, Yi

    2009-05-30

    A magnetic multi-wall carbon nanotube (MMWCNT) nanocomposite was synthesized and was used as an adsorbent for removal of cationic dyes from aqueous solutions. The MMWCNT nanocomposite was composed of commercial multi-wall carbon nanotubes and iron oxide nanoparticles. The properties of this magnetic adsorbent were characterized by scanning electron microscopy, X-ray diffraction and BET surface area measurements. Adsorption characteristics of the MMWCNT nanocomposite adsorbent were examined using methylene blue, neutral red and brilliant cresyl blue as adsorbates. Experiments were carried out to investigate adsorption kinetics, adsorption capacity of the adsorbent and the effect of adsorption dosage and solution pH values on the removal of cationic dyes. Kinetic data were well fitted by a pseudo second-order model. Freundlich model was used to study the adsorption isotherms. The prepared MMWCNT adsorbent displayed the main advantage of separation convenience compared to the present adsorption treatment.

  18. Determining Surface Roughness in Urban Areas Using Lidar Data

    NASA Technical Reports Server (NTRS)

    Holland, Donald

    2009-01-01

    An automated procedure has been developed to derive relevant factors, which can increase the ability to produce objective, repeatable methods for determining aerodynamic surface roughness. Aerodynamic surface roughness is used for many applications, like atmospheric dispersive models and wind-damage models. For this technique, existing lidar data was used that was originally collected for terrain analysis, and demonstrated that surface roughness values can be automatically derived, and then subsequently utilized in disaster-management and homeland security models. The developed lidar-processing algorithm effectively distinguishes buildings from trees and characterizes their size, density, orientation, and spacing (see figure); all of these variables are parameters that are required to calculate the estimated surface roughness for a specified area. By using this algorithm, aerodynamic surface roughness values in urban areas can then be extracted automatically. The user can also adjust the algorithm for local conditions and lidar characteristics, like summer/winter vegetation and dense/sparse lidar point spacing. Additionally, the user can also survey variations in surface roughness that occurs due to wind direction; for example, during a hurricane, when wind direction can change dramatically, this variable can be extremely significant. In its current state, the algorithm calculates an estimated surface roughness for a square kilometer area; techniques using the lidar data to calculate the surface roughness for a point, whereby only roughness elements that are upstream from the point of interest are used and the wind direction is a vital concern, are being investigated. This technological advancement will improve the reliability and accuracy of models that use and incorporate surface roughness.

  19. Quartz Crystal Microbalance Investigation of the Structure of Adsorbed Soybean Oil and Methyl Oleate onto Steel Surface

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The adsorption of soybean oil (SBO) and methyl oleate (MO) onto steel was investigated using quartz crystal microbalance with dissipation monitoring (QCM-D). Adsorption of both SBO and MO increased with increasing concentrations. At full surface coverage, SBO and MO formed rigid thin films and ach...

  20. Surface X-Ray Scattering Measurements of the Substrate Induced Spatial Modulation of an Incommensurate Adsorbed Monolayer

    DTIC Science & Technology

    1991-01-29

    oa=0) mode. 24 IV. Results Before describing our x-ray measurements, we first discuss the underpotential electrochemical deposition of TI on Ag(l I...thus termed underpotential deposition (UPD). On single crystals, these initial deposits are believed to be well defined, ordered layers. 27 The UPI...necessary and irantify by block number) We report in-situ surface X-ray scattering measurements of electrochemically deposited TI monolayers on Ag(III). We

  1. Laser-Induced Thermal Desorption and Fourier Transform Mass Spectrometry for the Analysis of Molecular Adsorbates on Surfaces.

    NASA Astrophysics Data System (ADS)

    Land, Donald Paul

    The field of surface science is growing rapidly, fueled by the needs to refine petroleum more efficiently, to clean up automobile exhaust, to protect against corrosion and wear, and to shrink the size of electronic components and information storage systems. These are important aspects of daily life, all of which could benefit from a better understanding of the fundamental processes that occur at the interfaces between different phases of matter. For the technologies mentioned, the most important interface is that between the gas and the solid phases. The technique described in this dissertation merges several recently established methods into a powerful instrument for the analysis of the solid-gas interface, yielding information on the chemical nature of species at this interface, relative concentrations, and even reactivities and intermediates. Details of the design and construction of the instrument are followed by a performance evaluation and a presentation of characterization studies for postionization methods, including electron impact ionization, resonance -enhanced multiphoton ionization, and chemical ionization. The use of the technique for the analysis of unknowns on surfaces is then detailed, highlighting the ability to obtain accurate mass measurement using the high resolution capabilities of FTMS. The use of ion storage techniques results in further unique analysis methods via gas-phase charge exchange reactions. This technique opens the door to the study of more complex molecules on surfaces, as well as mixtures of surface species, because FT mass spectrometry is well suited for such analyses. In this dissertation, data is presented for desorption of tens of molecular species encompassing nearly every organic functional group and including species as widely varying as cyanogen, ethylene, cyclohexane, methanol, and even a tetra-peptide. In-depth analyses of the kinetics of ethylene dehydrogenation and the identification of cyclohexene and 1,6-hexa

  2. Estimating 3-dimensional colony surface area of field corals

    EPA Science Inventory

    Colony surface area is a critical descriptor for biological and physical attributes of reef-building (scleractinian, stony) corals. The three-dimensional (3D) size and structure of corals are directly related to many ecosystem values and functions. Most methods to estimate colony...

  3. Increasing biochar surface area: effects of various milling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar produced from corn stover is a renewable, plentiful source of carbon that is a potential substitute for carbon black as rubber composite filler and also as binder/filter media for water or beverage purification applications. However, to be successful in these applications, the surface area o...

  4. Increasing biochar surface area: Optimization of ball milling parameters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar produced from corn stover is a renewable, plentiful source of carbon that is a potential substitute for carbon black as rubber composite filler and also as binder/filter media for water or beverage purification applications. However, to be successful in these applications, the surface area o...

  5. Interface Surface Area Tracking for the Conservative Level Set Method

    NASA Astrophysics Data System (ADS)

    Firehammer, Stephanie; Desjardins, Olivier

    2015-11-01

    One key question in liquid-gas flows is how to model the interface between phases in a way that is mass, momentum, and energy conserving. The accurate conservative level set (ACLS) method of Desjardins et al. provides a tool for tracking a liquid-gas interface with minimal mass conservation issues; however, it does not explicitly compute the interface surface area and thus nothing can be said a priori about the balance between kinetic energy and surface energy. This work examines an equation for the transport of interface surface area density, which can be written in terms of the gradient of the volume fraction. Furthermore this presentation will outline a numerical method for jointly transporting a conservative level set and surface area density. Finally, we will explore oppportunities for energy conservation via the accurate exchange of energy between the flow field and the interface through surface tension, with test cases to show the results of our extended ACLS method. Funding from the National Science Foundation is gratefully acknowledged.

  6. Effect of milling temperatures on surface area, surface energy and cohesion of pharmaceutical powders.

    PubMed

    Shah, Umang V; Wang, Zihua; Olusanmi, Dolapo; Narang, Ajit S; Hussain, Munir A; Tobyn, Michael J; Heng, Jerry Y Y

    2015-11-10

    Particle bulk and surface properties are influenced by the powder processing routes. This study demonstrates the effect of milling temperatures on the particle surface properties, particularly surface energy and surface area, and ultimately on powder cohesion. An active pharmaceutical ingredient (API) of industrial relevance (brivanib alaninate, BA) was used to demonstrate the effect of two different, but most commonly used milling temperatures (cryogenic vs. ambient). The surface energy of powders milled at both cryogenic and room temperatures increased with increasing milling cycles. The increase in surface energy could be related to the generation of surface amorphous regions. Cohesion for both cryogenic and room temperature milled powders was measured and found to increase with increasing milling cycles. For cryogenic milling, BA had a surface area ∼ 5× higher than the one obtained at room temperature. This was due to the brittle nature of this compound at cryogenic temperature. By decoupling average contributions of surface area and surface energy on cohesion by salinization post-milling, the average contribution of surface energy on cohesion for powders milled at room temperature was 83% and 55% at cryogenic temperature.

  7. Sorption of N[sub 2] and EGME vapors on some soils, clays, and mineral oxides and determination of sample surface areas by use of sorption data

    SciTech Connect

    Chlou, C.T.; Rutherford, D.W. ); Manes, M. )

    1993-08-01

    Vapor sorption isotherms of ethylene glycol monoethyl ether (EGME) at room temperature and isotherms of N[sub 2] gas at liquid nitrogen temperature were determined for various soils and minerals. The N[sub 2] monolayer capacities [Q[sub m](N[sub 2])] were calculated from the BET equation and used to determine the surface areas. To examine whether EGME is an appropriate adsorbate for determination of surface areas, the apparent EGME monolayer capacities [Q[sub m](EGME)[sub ap

  8. Surface-enhanced Raman scattering of 4-aminothiophenol adsorbed on silver nanosheets deposited onto cubic boron nitride films.

    PubMed

    Zhou, Yanli; Zhi, Jinfang; Zhao, Jianwen; Xu, Maotian

    2010-01-01

    A simple method was found for the fabrication of silver nanosheets (AgNS) by the catalysis of gold nanoparticles (AuNP) on an amine-terminated cubic boron nitride (cBN) surface deposited on a Si(001) substrate in the presence of reductant. The morphology of the AgNS/AuNP/NH(2)-cBN/Si(001) sample was characterized by scanning electron microscopy and X-ray diffraction. The performance of the AgNS/AuNP/NH(2)-cBN/Si(001) sample as surface-enhanced Raman scattering (SERS) active substrate was evaluated by using 4-aminothiophenol (PATP) as the probe molecule. The SERS measurements showed that the maximum intensity was obtained on the AgNS/AuNP/NH(2)-cBN/Si(001) sample for 5 min silver deposition. Compared with the AuNP/NH(2)-cBN/Si(001) sample and a silver film/cBN/Si(001) prepared by the mirror reaction, the SERS signal of PATP was obviously improved on the above AgNS/AuNP/NH(2)-cBN/Si(001) film. The sensitivity and the stability of the AgNS/AuNP/NH(2)-cBN/Si(001) sample were also investigated.

  9. Does L to D-amino acid substitution trigger helix→sheet conformations in collagen like peptides adsorbed to surfaces?

    PubMed

    Velmurugan, Punitha; Jonnalagadda, Raghava Rao; Sankaranarayanan, Kamatchi; Dhathathreyan, Aruna

    2015-12-01

    The present work reports on the structural order, self assembling behaviour and the role in adsorption to hydrophilic or hydrophobic solid surfaces of modified sequence from the triple helical peptide model of the collagenase cleavage site in type I collagen (Uniprot accession number P02452 residues from 935 to 970) using (D)Ala and (D)Ile substitutions as given in the models below: Model-1: GSOGADGPAGAOGTOGPQGIAGQRGVV GLOGQRGER. Model-2: GSOGADGP(D)AGAOGTOGPQGIAGQRGVVGLOGQRGER. Model-3: GSOGADGPAGAOGTOGPQG(D)IAGQRGVVGLOGQRGER. Collagenase is an important enzyme that plays an important role in degrading collagen in wound healing, cancer metastasis and even in embryonic development. However, the mechanism by which this degradation occurs is not completely understood. Our results show that adsorption of the peptides to the solid surfaces, specifically hydrophobic triggers a helix to beta transition with order increasing in peptide models 2 and 3. This restricts the collagenolytic behaviour of collagenase and may find application in design of peptides and peptidomimetics for enzyme-substrate interaction, specifically with reference to collagen and other extra cellular matrix proteins.

  10. Force measurements on myelin basic protein adsorbed to mica and lipid bilayer surfaces done with the atomic force microscope.

    PubMed Central

    Mueller, H; Butt, H J; Bamberg, E

    1999-01-01

    The mechanical and adhesion properties of myelin basic protein (MBP) are important for its function, namely the compaction of the myelin sheath. To get more information about these properties we used atomic force microscopy to study tip-sample interaction of mica and mixed dioleoylphosphatidylserine (DOPS) (20%)/egg phosphatidylcholine (EPC) (80%) lipid bilayer surfaces in the absence and presence of bovine MBP. On mica or DOPS/EPC bilayers a short-range repulsive force (decay length 1.0-1.3 nm) was observed during the approach. The presence of MBP always led to an attractive force between tip and sample. When retracting the tip again, force curves on mica and on lipid layers were different. While attached to the mica surface, the MBP molecules exhibited elastic stretching behavior that agreed with the worm-like chain model, yielding a persistence length of 0.5 +/- 0.25 nm and an average contour length of 53 +/- 19 nm. MBP attached to a lipid bilayer did not show elastic stretching behavior. This shows that the protein adopts a different conformation when in contact with lipids. The lipid bilayer is strongly modified by MBP attachment, indicating formation of MBP-lipid complexes and possibly disruption of the original bilayer structure. PMID:9916039

  11. Extracting uranium from seawater: Promising AF series adsorbents

    SciTech Connect

    Das, Sadananda; Oyola, Y.; Mayes, Richard T.; Janke, Christopher James; Kuo, Li-Jung; Gill, Gary; Wood, Jordana; Dai, Sheng

    2015-11-02

    Here, a new family of high surface area polyethylene fiber adsorbents (AF series) was recently developed at the Oak Ridge National Laboratory (ORNL). The AF series of were synthesized by radiation-induced graft polymerization of acrylonitrile and itaconic acid (at different monomer/co-monomer mol ratios) onto high surface area polyethylene fibers. The degree of grafting (%DOG) of AF series adsorbents was found to be 154 354%. The grafted nitrile groups were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with 0.44M KOH at 80 C followed by screening at ORNL with simulated seawater spiked with 8 ppm uranium. Uranium adsorption capacity in simulated seawater screening ranged from 170-200 g-U/kg-ads irrespective of %DOG. A monomer/co-monomer mol ratio in the range of 7.57-10.14 seemed to be optimum for highest uranium loading capacity. Subsequently, the adsorbents were also tested with natural seawater at Pacific Northwest National Laboratory (PNNL) using flow-through exposure uptake experiments to determine uranium loading capacity with varying KOH conditioning time at 80 C. The highest adsorption capacity of AF1 measured after 56 days of marine testing was demonstrated as 3.9 g-U/kg-adsorbent and 3.2 g-U/kg-adsorbent for 1hr and 3hrs of KOH conditioning at 80 C, respectively. Based on capacity values of several AF1 samples, it was observed that changing KOH conditioning from 3hrs to 1hr at 80 C resulted in 22-27% increase in uranium loading capacity in seawater.

  12. Extracting uranium from seawater: Promising AF series adsorbents

    DOE PAGES

    Das, Sadananda; Oyola, Y.; Mayes, Richard T.; ...

    2015-11-02

    Here, a new family of high surface area polyethylene fiber adsorbents (AF series) was recently developed at the Oak Ridge National Laboratory (ORNL). The AF series of were synthesized by radiation-induced graft polymerization of acrylonitrile and itaconic acid (at different monomer/co-monomer mol ratios) onto high surface area polyethylene fibers. The degree of grafting (%DOG) of AF series adsorbents was found to be 154 354%. The grafted nitrile groups were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with 0.44M KOH at 80 C followed by screening at ORNL with simulated seawater spiked with 8more » ppm uranium. Uranium adsorption capacity in simulated seawater screening ranged from 170-200 g-U/kg-ads irrespective of %DOG. A monomer/co-monomer mol ratio in the range of 7.57-10.14 seemed to be optimum for highest uranium loading capacity. Subsequently, the adsorbents were also tested with natural seawater at Pacific Northwest National Laboratory (PNNL) using flow-through exposure uptake experiments to determine uranium loading capacity with varying KOH conditioning time at 80 C. The highest adsorption capacity of AF1 measured after 56 days of marine testing was demonstrated as 3.9 g-U/kg-adsorbent and 3.2 g-U/kg-adsorbent for 1hr and 3hrs of KOH conditioning at 80 C, respectively. Based on capacity values of several AF1 samples, it was observed that changing KOH conditioning from 3hrs to 1hr at 80 C resulted in 22-27% increase in uranium loading capacity in seawater.« less

  13. Picosecond adsorbate dynamics at condensed phase interfaces

    SciTech Connect

    Scott, T.W.; Chang, Y.J.; Martorell, J.

    1993-12-31

    Picosecond surface second harmonic generation has been used to probe a variety of elementary adsorbate reactions at liquid-solid interfaces. Electron transfer reactions at semiconductor-liquid junctions, geminate recombination of photogenerated free radical pairs and the orientational dynamics of dipolar adsorbates have all been explored in varying degrees of detail. These kinetic studies have led to a detailed analysis of adsorbate detection on the surface of non-centrosymmetric substrates as well as the use of total internal reflection geometries for signal enhancement from optically absorbing liquids. Particular emphasis has been placed on the static and dynamic characterization of adsorbate orientational distribution functions and how these are determined from the torque exerted on adsorbates by the angular part of the molecule-surface interaction potential.

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

    NASA Astrophysics Data System (ADS)

    Gao, Yi; Galperin, Michael; Nitzan, Abraham

    2016-06-01

    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.

  15. Neutron and Raman scattering studies of surface adsorbed molecular vibrations and bulk phonons in ZrO{sub 2} nanoparticles

    SciTech Connect

    Ozawa, Masakuni; Suzuki, Suguru; Loong, C.K.; Nipko, J.C.

    1996-12-31

    Inelastic neutron scattering was used to study the phonon densities of states of zirconia nanoparticles, the O-H stretch vibrations of physisorbed water molecules, and chemisorbed hydroxyl groups on the surface. Raman scattering was also used to measure the zone-center phonon modes. The observed distinct phonon frequencies and band widths at 10-120 meV reflect the different crystalline symmetries and compositional fluctuations in the small grain and interfacial regions of monoclinic ZrO{sub 2}, tetragonal or mixed cubic and tetragonal rare-earth-modified zirconia. The dynamics of water and hydroxyl groups on varying local structures of these zirconias result in the different frequencies of the O-H stretch vibrations at 400-600 meV.

  16. Analysis of TQCM surface contamination adsorbed during the Spacelab I Mission. [Temperature-controlled Quartz Crystal Microbalance

    NASA Technical Reports Server (NTRS)

    Mckeown, D.; Fountain, J. A.; Cox, V. H.; Peterson, R. V.

    1985-01-01

    The Temperature-Controlled Quartz Crystal Microbalance (TQCM) system was flown on the Spacelab I Mission as part of the Induced Environment Contamination Monitor to monitor surface contamination (SC) in the payload bay. SC on the five sensors of the TQCM was analyzed by means of IR spectroscopy, scanning electron spectroscopy, and energy dispersive X-ray fluorescence. The amount of SC ranged from 1.4 micrograms/sq cm for the -Z sensor to 39.9 micrograms/sq cm for the +X sensor. The IR analysis showed strong CH2, CH3, and carbonyl absorption bands, indicative of ester and polyester compounds found in adhesives, plasticizers, and tape. The particulates (mostly ranging from 1 micron to 20 microns in size) were mainly composed of Mg, Al, Al2O3, and Si, and probably originated in the solid rocket firings.

  17. Excess surface area in bioelectrochemical systems causes ion transport limitations

    PubMed Central

    Harrington, Timothy D.; Babauta, Jerome T.; Davenport, Emily K.; Renslow, Ryan S.; Beyenal, Haluk

    2014-01-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: 1) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions, 2) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and 3) showing that un-colonized surface area remained even after steady-state current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential at the electrode surface. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant. PMID:25421463

  18. Surface area and conductivity of polyaniline synthesized under UV irradiation

    NASA Astrophysics Data System (ADS)

    Budi, S.; Fitri, E.; Paristiowati, M.; Cahyana, U.; Pusparini, E.; Nasbey, H.; Imaddudin, A.

    2017-02-01

    This paper reports our study on the synthesis of high electrical conductivity and surface area polyaniline using oxidative polymerization under UV light irradiation. The formation of emeraldine structures of polyaniline was revealed by major absorption bands of FTIR (Fourier transform infrared spectroscopy) spectra attributed to C-N stretching, C=C stretching in the benzenoid ring, C=C stretching in the quinoid ring and QNH+B stretching. XRD (X-ray diffractometer) measurements confirmed typical diffraction patterns with a crystallinity of 13% and 16% for polyaniline prepared under non-stirred and stirred reaction, respectively. SEM (Scanning electron microscope) studies showed more uniform morphology of polyaniline was obtained with stirring reaction process compare to those prepared without stirring. Surface analysis using SAA (surface area analyzer) showed that pure polyaniline with the relatively high surface area of ca.28 m2/g was successfully prepared in this work. Based on four point probe measurement, the prepared polyaniline possesses high conductivity which is important in electrode application.

  19. A fast pairwise evaluation of molecular surface area.

    PubMed

    Vasilyev, Vladislav; Purisima, Enrico O

    2002-05-01

    A fast and general analytical approach was developed for the calculation of the approximate van der Waals and solvent-accessible surface areas. The method is based on three basic ideas: the use of the Lorentz transformation formula, a rigid-geometry approximation, and a single fitting parameter that can be refitted on the fly during a simulation. The Lorentz transformation equation is used for the summation of the areas of an atom buried by its neighboring contacting atoms, and implies that a sum of the buried pairwise areas cannot be larger than the surface area of the isolated spherical atom itself. In a rigid-geometry approximation we numerically calculate and keep constant the surface of each atom buried by the atoms involved in 1-2 and 1-3 interactions. Only the contributions from the nonbonded atoms (1-4 and higher interactions) are considered in terms of the pairwise approximation. The accuracy and speed of the method is competitive with other pairwise algorithms. A major strength of the method is the ease of parametrization.

  20. Tropical cyclone rainfall area controlled by relative sea surface temperature

    PubMed Central

    Lin, Yanluan; Zhao, Ming; Zhang, Minghua

    2015-01-01

    Tropical cyclone rainfall rates have been projected to increase in a warmer climate. The area coverage of tropical cyclones influences their impact on human lives, yet little is known about how tropical cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that tropical cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the tropical mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between tropical cyclone size and mid-tropospheric relative humidity. Global statistics of tropical cyclone rainfall area are not expected to change markedly under a warmer climate provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates. PMID:25761457

  1. Surface enhanced fluorescence of anti-tumoral drug emodin adsorbed on silver nanoparticles and loaded on porous silicon

    NASA Astrophysics Data System (ADS)

    Hernandez, Margarita; Recio, Gonzalo; Martin-Palma, Raul J.; Garcia-Ramos, Jose V.; Domingo, Concepcion; Sevilla, Paz

    2012-07-01

    Fluorescence spectra of anti-tumoral drug emodin loaded on nanostructured porous silicon have been recorded. The use of colloidal nanoparticles allowed embedding of the drug without previous porous silicon functionalization and leads to the observation of an enhancement of fluorescence of the drug. Mean pore size of porous silicon matrices was 60 nm, while silver nanoparticles mean diameter was 50 nm. Atmospheric and vacuum conditions at room temperature were used to infiltrate emodin-silver nanoparticles complexes into porous silicon matrices. The drug was loaded after adsorption on metal surface, alone, and bound to bovine serum albumin. Methanol and water were used as solvents. Spectra with 1 μm spatial resolution of cross-section of porous silicon layers were recorded to observe the penetration of the drug. A maximum fluorescence enhancement factor of 24 was obtained when protein was loaded bound to albumin, and atmospheric conditions of inclusion were used. A better penetration was obtained using methanol as solvent when comparing with water. Complexes of emodin remain loaded for 30 days after preparation without an apparent degradation of the drug, although a decrease in the enhancement factor is observed. The study reported here constitutes the basis for designing a new drug delivery system with future applications in medicine and pharmacy.

  2. [Adsorption behavior and influence factors of p-nitroaniline on high surface area activated carbons prepared from plant stems].

    PubMed

    Li, Kun-quan; Zheng, Zheng; Luo, Xing-zhang

    2010-08-01

    Low-cost and high surface area microporous activated carbons were prepared from Spartina alternilora and cotton stalk with KOH activation under the conditions of impregnation ratio of 3.0, activation temperature at 800 degrees C and activation time of 1.5 h. The adsorption behavior of p-nitroaniline on the activated carbons was investigated by batch sorption experiments. The influences of solution pH value, adsorbent dose and temperature were investigated. The adsorption isotherm and thermodynamic characteristics were also discussed. The Spartina alterniflora activated carbon (SA-AC) has a high surface area of 2825 m2 x g(-1) and a micropore volume of 1.192 cm3 x g(-1). The BET surface area and micropore volume of the cotton stalk activated carbon (CS-AC) are 2135 m2 x g(-1) and 1.011 cm3 x g(-1), respectively. The sorption experiments show that both the activated carbons have high sorption capacity for p-nitroaniline. The Langmuir maximum sorption amount was found to be 719 mg x g(-1) for SA-AC and 716 mg x g(-1) for CS-AC, respectively. The sorption was found to depend on solution pH, adsorbent dose, and temperature. The optimum pH for the removal of p-nitroaniline was found to be 7.0. The Freundlich model and Redlich-Peterson model can describe the experimental data effectively. The negative changes in free energy (delta G0) and enthalpy (delta H0) indicate that the sorption is a spontaneous and exothermic procedure. The negative values of the adsorption entropy delta S0 indicate that the mobility of p-nitroaniline on the carbon surface becomes more restricted as compared with that of those in solution.

  3. Photocatalytic degradation of 1,10-dichlorodecane in aqueous suspensions of TiO{sub 2}: A reaction of adsorbed chlorinated alkane with surface hydroxyl radicals

    SciTech Connect

    El-Morsi, T.M.; Bubakowski, W.R.; Abd-El-Aziz, A.S.; Friesen, K.J.

    2000-03-15

    1,10-Dichlorodecane (D{sub 2}C{sub 10}) is shown to be effectively photodegraded in aqueous suspensions of TiO{sub 2} using a photoreactor equipped with 300 nm lamps. Solutions exposed to UV light intensities of 3.6 x 10{sup {minus}5} Ein L{sup {minus}1} min{sup {minus}1}, established by ferrioxalate actinometry, showed negligible direct photolysis in the absence of TiO{sub 2} and a D{sub 2}C{sub 10} concentration approaching its solubility limit. Kinetics of photodegradation followed a Langmuir-Hinshelwood model suggesting that the reaction occurred on the surface of the photocatalyst. The presence of h{sup +}{sub vb} and OH{sm_bullet} radical scavengers, including methanol and iodide, inhibited the degradation supporting a photooxidation reaction. Electron scavengers (Ag{sup +}, Cu{sup 2+}, and Fe{sup 3+}) had small effects on the degradation rate. The lack of transformation of D{sub 2}C{sub 10} in acetonitrile as solvent indicated that the major oxidants were OH{sm_bullet} radicals. The presence of tetranitromethane, effectively eliminating the formation of free OH{sm_bullet} radicals, did not affect the degradation rates significantly. This result, combined with observed increases in photolysis rates with the degree of adsorption of D{sub 2}C{sub 10} onto the surface of the photocatalyst, confirmed that the reaction involved adsorbed 1,10-dichlorodecane and surface bound OH{sm_bullet} radicals.

  4. A theoretical study of the XP and NEXAFS spectra of alanine: gas phase molecule, crystal, and adsorbate at the ZnO(10 ̅10) surface.

    PubMed

    Gao, You Kun; Traeger, Franziska; Kotsis, Konstantinos; Staemmler, Volker

    2011-06-14

    The adsorption of alanine on the mixed-terminated ZnO(10 ̅10) surface is studied by means of quantum-chemical ab initio calculations. Using a finite cluster model and the adsorption geometry as obtained both by periodic CPMD and embedded cluster calculations, the C1s, N1s and O1s X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra are calculated for single alanine molecules on ZnO(10 ̅10). These spectra are compared with the spectra calculated for alanine in the gas phase and in its crystalline form and with experimental XPS and NEXAFS data for the isolated alanine molecule and for alanine adsorbed on ZnO(10 ̅10) at multilayer and monolayer coverage. The excellent agreement between the experimental and calculated XP and NEXAFS spectra confirms the calculated adsorption geometry: A single alanine molecule is bound to ZnO(10 ̅10) in a dissociated bidentate form with the two O atoms of the acid group bound to two Zn atoms of the surface and the proton transferred to one O atom of the surface. Other possible structures, such as adsorption of alanine in one of its neutral or zwitterionic forms in which the proton of the -COOH group remains at this group or is transferred to the amino group, can be excluded since they would give rise to quite different XP spectra. In the multilayer coverage regime, on the other hand, alanine is in its crystalline form as is also shown by the analysis of the XP spectra.

  5. Adsorption and Desorption of Carbon Dioxide and Water Mixtures on Synthetic Hydrophobic Carbonaceous Adsorbents

    NASA Technical Reports Server (NTRS)

    Finn, John E.; Harper, Lynn D. (Technical Monitor)

    1994-01-01

    Several synthetic carbonaceous adsorbents produced through pyrolysis of polymeric materials are available commercially. Some appear to have advantages over activated carbon for certain adsorption applications. In particular, they can have tailored hydrophobicities that are significantly greater than that of activated carbon, while moderately high surfaces areas are retained. These sorbents are being investigated for possible use in removing trace contaminants and excess carbon dioxide from air in closed habitats, plant growth chambers, and other applications involving purification of humid gas streams. We have analyzed the characteristics of a few of these adsorbents through adsorption and desorption experiments and standard characterization techniques. This paper presents pure and multicomponent adsorption data collected for carbon dioxide and water on two synthetic carbonaceous adsorbents having different hydrophobicities and capillary condensation characteristics. The observations are interpreted through consideration of the pore structure and surface chemistry of the solids and interactions between adsorbed carbon dioxide, water, and the solvent gas.

  6. Extra adsorption and adsorbate superlattice formation in metal-organic frameworks.

    PubMed

    Sung Cho, Hae; Deng, Hexiang; Miyasaka, Keiichi; Dong, Zhiyue; Cho, Minhyung; Neimark, Alexander V; Ku Kang, Jeung; Yaghi, Omar M; Terasaki, Osamu

    2015-11-26

    Metal-organic frameworks (MOFs) have a high internal surface area and widely tunable composition, which make them useful for applications involving adsorption, such as hydrogen, methane or carbon dioxide storage. The selectivity and uptake capacity of the adsorption process are determined by interactions involving the adsorbates and their porous host materials. But, although the interactions of adsorbate molecules with the internal MOF surface and also amongst themselves within individual pores have been extensively studied, adsorbate-adsorbate interactions across pore walls have not been explored. Here we show that local strain in the MOF, induced by pore filling, can give rise to collective and long-range adsorbate-adsorbate interactions and the formation of adsorbate superlattices that extend beyond an original MOF unit cell. Specifically, we use in situ small-angle X-ray scattering to track and map the distribution and ordering of adsorbate molecules in five members of the mesoporous MOF-74 series along entire adsorption-desorption isotherms. We find in all cases that the capillary condensation that fills the pores gives rise to the formation of 'extra adsorption domains'-that is, domains spanning several neighbouring pores, which have a higher adsorbate density than non-domain pores. In the case of one MOF, IRMOF-74-V-hex, these domains form a superlattice structure that is difficult to reconcile with the prevailing view of pore-filling as a stochastic process. The visualization of the adsorption process provided by our data, with clear evidence for initial adsorbate aggregation in distinct domains and ordering before an even distribution is finally reached, should help to improve our understanding of this process and may thereby improve our ability to exploit it practically.

  7. Extra adsorption and adsorbate superlattice formation in metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Sung Cho, Hae; Deng, Hexiang; Miyasaka, Keiichi; Dong, Zhiyue; Cho, Minhyung; Neimark, Alexander V.; Ku Kang, Jeung; Yaghi, Omar M.; Terasaki, Osamu

    2015-11-01

    Metal-organic frameworks (MOFs) have a high internal surface area and widely tunable composition, which make them useful for applications involving adsorption, such as hydrogen, methane or carbon dioxide storage. The selectivity and uptake capacity of the adsorption process are determined by interactions involving the adsorbates and their porous host materials. But, although the interactions of adsorbate molecules with the internal MOF surface and also amongst themselves within individual pores have been extensively studied, adsorbate-adsorbate interactions across pore walls have not been explored. Here we show that local strain in the MOF, induced by pore filling, can give rise to collective and long-range adsorbate-adsorbate interactions and the formation of adsorbate superlattices that extend beyond an original MOF unit cell. Specifically, we use in situ small-angle X-ray scattering to track and map the distribution and ordering of adsorbate molecules in five members of the mesoporous MOF-74 series along entire adsorption-desorption isotherms. We find in all cases that the capillary condensation that fills the pores gives rise to the formation of ‘extra adsorption domains’—that is, domains spanning several neighbouring pores, which have a higher adsorbate density than non-domain pores. In the case of one MOF, IRMOF-74-V-hex, these domains form a superlattice structure that is difficult to reconcile with the prevailing view of pore-filling as a stochastic process. The visualization of the adsorption process provided by our data, with clear evidence for initial adsorbate aggregation in distinct domains and ordering before an even distribution is finally reached, should help to improve our understanding of this process and may thereby improve our ability to exploit it practically.

  8. Factors affecting cellulose hydrolysis based on inactivation of adsorbed enzymes.

    PubMed

    Ye, Zhuoliang; Berson, R Eric

    2014-09-01

    The rate of enzymatic hydrolysis of cellulose reaction is known to decrease significantly as the reaction proceeds. Factors such as reaction temperature, time, and surface area of substrate that affect cellulose conversion were analyzed relative to their role in a mechanistic model based on first order inactivation of adsorbed cellulases. The activation energies for the hydrolytic step and inactivation step were very close in magnitude: 16.3 kcal mol(-1) for hydrolysis and 18.0 kcal mol(-1) for inactivation, respectively. Therefore, increasing reaction temperature would cause a significant increase in the inactivation rate in addition to the catalytic reaction rate. Vmax,app was only 20% or less of the value at 72 h compared to at 2h as a result of inactivation of adsorbed cellulases, suggesting prolonged hydrolysis is not an efficient way to improve cellulose hydrolysis. Hydrolysis rate increased with corresponding increases in available substrate surface binding area.

  9. High Surface Area Nanoporous Polymers for Reversible HydrogenStorage

    SciTech Connect

    Germain, Jonathan; Hradil, Jiri; Frechet, Jean M.J.; Svec,Frantisek

    2006-06-29

    Hydrogen adsorption using a series of nanoporous synthetic polymers has been studied. Promising results were obtained during the screening of commercially available porous polymer beads; of the polymers considered, hypercrosslinked Hypersol-Macronet MN200 resin exhibited the highest adsorption capacity for hydrogen. This initial success triggered the development of our own high surface area hypercrosslinked materials. Subjecting gel-type and macroporous vinylbenzyl chloride-based precursors swollen in dichloroethane to a Friedel-Crafts reaction catalyzed by iron trichloride afforded beads with surface areas of 1 930 and 1 300 m{sup 2}/g, respectively, as calculated using the BET equation. The former polymer reversibly stores up to 1.5 wt % H{sub 2} at a pressure of 0.12 MPa and a temperature of 77.3 K. The initial heat of adsorption of hydrogen molecules onto this polymer is 6.6 kJ/mol.

  10. The hydrophobic character of nonsulfide mineral surfaces as influenced by double-bond reactions of adsorbed unsaturated collector species. Progress report

    SciTech Connect

    Miller, J.D.

    1992-06-01

    The primary goal of this research is to improve the flotation efficiency of nonsulfide mineral systems by establishing the fundamental features of collector adsorption reactions and developing appropriate chemical control strategies. In situ real-time FR-IR/IRS measurements, nonequilibrium electrophoresis, vacuum flotation, contact-angle goniometry, and laser Raman spectroscopy have been used to accomplish this goal. These experimental techniques have led to the determination of important information concerning collector adsorption phenomena in each nonsulfide mineral system. For example, the demonstration of polymerization of adsorbed unsaturated surfactant species has added a new dimension to semi-soluble salt flotation chemistry and may have more general utility. Furthermore, refinement of the in situ FT-IR/IRS analysis has been accomplished particularly for the examination of surfactant aggregation phenomena at nonsulfide mineral surfaces. Finally, the significance of the lattice ion hydration theory has been demonstrated by nonequilibrium electrophoretic mobility measurements, and the new results will provide a better basis for the understanding of soluble-salt flotation phenomena.

  11. Optimization of air-borne butyl acetate adsorption on dual-function Ag-Y adsorbent-catalyst using response surface methodology.

    PubMed

    Bhatia, Subhash; Wong, Cheng Teng; Abdullah, Ahmad Zuhairi

    2009-05-30

    The low concentration and high flow rate of air-borne butyl acetate (BA) could be effectively removed using combined adsorption-catalytic oxidation system. Ag-Y (Si/Al=80) dual-function adsorbent was investigated for the adsorption step of 1000 ppm of butyl acetate at gas hourly space velocity of 13,000 h(-1) at ambient temperature under dry and humid feeds. A central composite design (CCD) coupled with response surface methodology (RSM) was employed to obtain the optimum process conditions and the interactions between process variables were demonstrated and elucidated. Humidity and increasing organic concentration shortened the adsorption service time. The effect of moisture was more pronounced at low BA concentration. The interactions between the BA concentration and humidity were statistically significant at 95% confidence level. The optimum conditions were found to be at 4500 ppm of BA with 37 min saturation time to give 58 mg BA/g as adsorption capacity. The simulated data fitted the experimental data satisfactorily. The simulated data also correctly demonstrated the overall behaviors of the adsorption process.

  12. How mobile are dye adsorbates and acetonitrile molecules on the surface of TiO2 nanoparticles? A quasi-elastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Vaissier, Valerie; Sakai, Victoria Garcia; Li, Xiaoe; Cabral, João T.; Nelson, Jenny; Barnes, Piers R. F.

    2016-12-01

    Motions of molecules adsorbed to surfaces may control the rate of charge transport within monolayers in systems such as dye sensitized solar cells. We used quasi-elastic neutron scattering (QENS) to evaluate the possible dynamics of two small dye moieties, isonicotinic acid (INA) and bis-isonicotinic acid (BINA), attached to TiO2 nanoparticles via carboxylate groups. The scattering data indicate that moieties are immobile and do not rotate around the anchoring groups on timescales between around 10 ps and a few ns (corresponding to the instrumental range). This gives an upper limit for the rate at which conformational fluctuations can assist charge transport between anchored molecules. Our observations suggest that if the conformation of larger dye molecules varies with time, it does so on longer timescales and/or in parts of the molecule which are not directly connected to the anchoring group. The QENS measurements also indicate that several layers of acetonitrile solvent molecules are immobilized at the interface with the TiO2 on the measurement time scale, in reasonable agreement with recent classical molecular dynamics results.

  13. How mobile are dye adsorbates and acetonitrile molecules on the surface of TiO2 nanoparticles? A quasi-elastic neutron scattering study

    PubMed Central

    Vaissier, Valerie; Sakai, Victoria Garcia; Li, Xiaoe; Cabral, João T.; Nelson, Jenny; Barnes, Piers R. F.

    2016-01-01

    Motions of molecules adsorbed to surfaces may control the rate of charge transport within monolayers in systems such as dye sensitized solar cells. We used quasi-elastic neutron scattering (QENS) to evaluate the possible dynamics of two small dye moieties, isonicotinic acid (INA) and bis-isonicotinic acid (BINA), attached to TiO2 nanoparticles via carboxylate groups. The scattering data indicate that moieties are immobile and do not rotate around the anchoring groups on timescales between around 10 ps and a few ns (corresponding to the instrumental range). This gives an upper limit for the rate at which conformational fluctuations can assist charge transport between anchored molecules. Our observations suggest that if the conformation of larger dye molecules varies with time, it does so on longer timescales and/or in parts of the molecule which are not directly connected to the anchoring group. The QENS measurements also indicate that several layers of acetonitrile solvent molecules are immobilized at the interface with the TiO2 on the measurement time scale, in reasonable agreement with recent classical molecular dynamics results. PMID:27991538

  14. High Surface Area Inorganic Membrane for Water Removal

    SciTech Connect

    2008-12-01

    This factsheet describes a research project whose objective is to demonstrate the fabrication and performance advantages of minichannel planar membrane modules made of porous metallic supports of surface area packing density one order of magnitude higher than the conventional membrane tube. The new, transformational, ceramic/metallic, hybrid membrane technology will be used for water/ethanol separations and reduce energy consumption by >20% over distillation and adsorption.

  15. Excess Surface Area in Bioelectrochemical Systems Causes ion Transport Limitations

    SciTech Connect

    Harrington, Timothy D.; Babauta, Jerome T.; Davenport, Emily K.; Renslow, Ryan S.; Beyenal, Haluk

    2015-05-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200mM increased current linearly up to a total of þ273% vs. 0mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and (iii) showing that un-colonized surface area remained even after steadystate current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant.

  16. Solvothermal synthesis of ceria nanoparticles with large surface areas

    SciTech Connect

    Hosokawa, S.; Shimamura, K.; Inoue, M.

    2011-11-15

    Highlights: {yields} Thermal decomposition of Ce(C{sub 7}H{sub 15}COO){sub 3}.xH{sub 2}O synthesized by solvothermal method. {yields} CeO{sub 2} having an extremely large surface area of 180 m{sup 2}/g. {yields} High catalytic activity of Ru catalyst supported on the CeO{sub 2} having high surface area. -- Abstract: Ceria nanoparticles were obtained by the calcination of precursors synthesised via the solvothermal reaction of cerium acetate. The CeO{sub 2} samples obtained by the thermal decomposition of Ce(C{sub 7}H{sub 15}COO){sub 3}.xH{sub 2}O synthesised by solvothermal reaction in 1,4-butanediol in the presence of octanoic acid had an extremely large surface area of 180 m{sup 2}/g. The Ru catalyst supported on this CeO{sub 2} sample showed a high catalytic activity for benzyl alcohol oxidation.

  17. Excess surface area in bioelectrochemical systems causes ion transport limitations.

    PubMed

    Harrington, Timothy D; Babauta, Jerome T; Davenport, Emily K; Renslow, Ryan S; Beyenal, Haluk

    2015-05-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and (iii) showing that un-colonized surface area remained even after steady-state current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant.

  18. Facile synthesis of high surface area molybdenum nitride and carbide

    SciTech Connect

    Roy, Aaron; Serov, Alexey; Artyushkova, Kateryna; Brosha, Eric L.; Atanassov, Plamen; Ward, Tim L.

    2015-08-15

    The synthesis of high surface area γ-Mo{sub 2}N and α-Mo{sub 2}C is reported (116 and 120 m{sup 2}/g) without the temperature programmed reduction of MoO{sub 3}. γ-Mo{sub 2}N was prepared in an NH{sub 3}-free synthesis using forming gas (7 at% H{sub 2}, N{sub 2}-balance) as the reactive atmosphere. Three precursors were studied ((NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}·4H{sub 2}O, (NH{sub 4}){sub 2} Mg(MoO{sub 4}){sub 2}, and MgMoO{sub 4}) along with the sacrificial support method (SSM) as a means of reducing the particle size of Mo{sub 2}N and Mo{sub 2}C. In situ X-ray diffraction (XRD) studies were carried out to identify reaction intermediates, the temperature at which various intermediates form, and the average domain size of the Mo{sub 2}N products. Materials were synthesized in bulk and further characterized by XRD, HRTEM, XPS, and BET. - Highlights: • Facile synthesis of γ-Mo2N and α-Mo2C with surface area exceeding 100 m{sup 2}/g. • Sacrificial support method was used to achieve these high surface areas. • Materials can serve as catalysts or supports in (electro)chemical processes.

  19. Determination of Glacier Surface Area Using Spaceborne SAR Imagery

    NASA Astrophysics Data System (ADS)

    Fang, L.; Maksymiuk, O.; Schmitt, M.; Stilla, U.

    2013-04-01

    Glaciers are very important climate indicators. Although visible remote sensing techniques can be used to extract glacier variations effectively and accurately, the necessary data are depending on good weather conditions. In this paper, a method for determination of glacier surface area using multi-temporal and multi-angle high resolution TerraSAR-X data sets is presented. We reduce the "data holes" in the SAR scenes affected by radar shadowing and specular backscattering of smooth ice surfaces by combining the two complementary different imaging geometries (from ascending and descending satellite tracks). Then, a set of suitable features is derived from the intensity image, the texture information generated based on the gray level co-occurrence matrix (GLCM), glacier velocity estimated by speckle tracking, and the interferometric coherence map. Furthermore, the features are selected by 10-foldcross- validation based on the feature relevance importance on classification accuracy using a Random Forests (RF) classifier. With these most relevant features, the glacier surface is discriminated from the background by RF classification in order to calculate the corresponding surface area.

  20. Estimation of surface runoff and water-covered area during filling of surface microrelief depressions

    NASA Astrophysics Data System (ADS)

    Hansen, B.

    2000-05-01

    During the filling of surface microrelief depressions the precipitation excess (precipitation minus infiltration and interception) is divided between surface storage and runoff, i.e. runoff starts before the surface depressions are filled. Information on the division of precipitation excess is needed for modelling surface runoff during the filling of surface depressions. Furthermore, information on the surface of the area covered with water is needed for calculating infiltration of water stored in soil surface depressions. Thirty-two soil surface microreliefs were determined in Danish erosion study plots. The slope was c. 10% for all plots. Data were treated initially by removing the slope, after which 20 artificial slopes (1-20%) were introduced producing 640 new data sets. Runoff during filling of the microrelief storage was calculated for each of the 640 data sets using a model developed for calculating surface storage and runoff from grid elevation measurements. Runoff started immediately after the first addition of water for all data sets. On a field scale, however, runoff has to travel some distance as overland flow and storage in smaller and larger depressions below the runoff initiation point must be taken into consideration. The runoff increases by intermittent steps. Whenever a depression starts to overflow to the border of the plot, the runoff jumps accordingly. In spite of the jumps, the distribution between surface storage and runoff was closely related to the quotient between precipitation excess and depression storage capacity. Surface area covered with water was exponentially related to the amount of water stored in surface depressions. Models for calculating surface storage and runoff from grid elevation measurements are cumbersome and require time-consuming measurements of the soil surface microrelief. Therefore, estimation from roughness indices requiring fewer measurements is desirable. New improved equations for such estimations are suggested.

  1. C70 self-assembly on In- and Tl-adsorbed Si(111)√{ 3 } ×√{ 3 } -Au surfaces

    NASA Astrophysics Data System (ADS)

    Olyanich, D. A.; Mararov, V. V.; Utas, T. V.; Zotov, A. V.; Saranin, A. A.

    2017-02-01

    Behavior of C70 fullerenes adsorbed onto the In- and Tl-modified Si(111)√{ 3 } ×√{ 3 } -Au surfaces at room temperature (RT) and 112 K has been studied using scanning tunneling microscopy observations and compared with the known results for the C60s on the same surfaces. During island growth at 112 K, both C70 and C60 are characterized by the same critical island size i=1. The difference is in an island shape as C70s tend to form chain-like islands built of double or triple molecular rows along the [ 1 bar 10 ] Si(111) substrate directions. At RT, C70s have a lower mobility as compared to C60s. In contrast to the C60 magic islands, the C70 islands do not demonstrate any strong preference for specific shapes or sizes. Extended C70 arrays exhibit a stripe-like 3×1 reconstruction where a single row of bright fullerenes mediated by a double row of dim fullerenes. The reconstruction is due to the different orientations of C70s within the layer which does not relate to the structure of the underlying Au/Si(111) substrate. This is in contrast to the hexagonal reconstructions of C60s where the bright fullerenes occupy the specific adsorption site atop Au trimers. The difference in the behavior of C70 and C60 is plausibly affected by the non-spherical shape of C70 molecule and a greater intermolecular C70-C70 interaction.

  2. Surface Structure and Chemical Switching of Thioctic Acid Adsorbed on Au(111) as Observed Using Near-Edge X-ray Absorption Fine Structure

    SciTech Connect

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

    2004-01-06

    Thioctic acid (alpha-lipoic acid) is a molecule with a large disulfide-containing base, a short alkyl-chain with four CH{sub 2} units, and a carboxyl termination. Self-assembled monolayer (SAM) films of thioctic acid adsorbed on Au(111) have been investigated with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and x-ray photoelectron spectroscopy (XPS) to determine film quality, bonding and morphology. Using standard preparation protocols for SAMs, that is, dissolving thioctic acid in ethanol and exposing gold to the solution, results in poor films. These films are highly disordered, contain a mixture of carboxyl and carboxylate terminations, have more than monolayer coverage, and exhibit unbound disulfide. Conversely, forming films by dissolving 1 mmol thioctic acid into 5% acetic acid in ethanol (as previously reported with carboxyl-terminated alkyl-thiols) forms ordered monolayers with small amounts of unbound sulfur. NEXAFS indicates tilted over endgroups with the carboxyl group normal on average 38{sup o} from the surface normal. Slight dichroism in other features indicates alkyl chains statistically more upright than prostrate on the surface. Reflection-absorption Fourier transform infrared (RA-FTIR) spectra indicate hydrogen bonding between neighboring molecules. In such well-formed monolayers, a stark reorientation occurs upon deprotonation of the endgroup by rinsing in a KOH solution. The carboxylate plane normal is now about 66{sup o} from sample normal, a much more upright orientation. Data indicate this reorientation may also cause a more upright orientation to the alkyl portion of the molecules.

  3. Characteristics of adsorbents made from biological, chemical and hybrid sludges and their effect on organics removal in wastewater treatment.

    PubMed

    Pan, Zhi-hui; Tian, Jia-yu; Xu, Guo-ren; Li, Jun-jing; Li, Gui-bai

    2011-01-01

    Meso-macropore adsorbents were prepared from biological sludge, chemical sludge and hybrid sludge of biological and chemical sludges, by chemically activating with 18.0 M H(2)SO(4) in the mass ratio of 1:3, and then pyrolyzing at 550 °C for 1 h in anoxic atmosphere. The physical and chemical characteristics of the sludge-based adsorbents were examined in terms of surface physical morphology, specific surface area and pore size distribution, aluminum and iron contents, surface functional groups and crystal structure. Furthermore, the adsorption effect of these adsorbents on the organic substances in wastewater was also investigated. The results indicated that the adsorption capacities of the sludge-based adsorbents for UV(254) were lower than that of commercial activated carbon (AC), whereas the adsorption capacities of the adsorbents prepared from hybrid sludge (HA) and chemical sludge (CA) for soluble COD(Cr) (SCOD(Cr)) were comparable or even higher than that of the commercial AC. The reasons might be that the HA and CA possessed well-developed mesopore and macropore structure, as well as abundant acidic surface functional groups. However, the lowest adsorption efficiency was observed for the biological sludge-based adsorbent, which might be due to the lowest metal content and overabundance of surface acidic functional groups in this adsorbent.

  4. High surface area aerogels for energy storage and efficiency

    NASA Astrophysics Data System (ADS)

    Maloney, Ryan Patrick

    ADAI are demonstrated in a third-generation prototypical thermoelectric generator for automotive waste heat recovery. The second chapter then details two different aerogel-based materials for electrochemical energy storage. It begins with lithium titanate aerogel, which takes advantage of the high surface area of the aerogel morphology to display a batt-cap behavior. This should allow the lithium titanate aerogel to perform at higher rates than would normally be expected for the bulk oxide material. Additionally, the flexibility of the sol-gel process is demonstrated through the incorporation of electrically conductive high-surface area exfoliated graphite nanoplatelets in the oxide. The last section describes the characterization of a LiMn2O 4 spinel coated carbon nanofoam in a non-aqueous electrolyte. The short diffusion path, high surface area and intimately wired architecture of the nanofoam allows the oxide to retain its capacity at significantly higher rates when compared with literature values for the bulk oxide. Additionally, the nanometric length scale improves cycle life, and the high surface area dramatically increases the insertion capacity by providing a higher concentration of surface defects. Taken together, it is clear that aerogels are an extremely attractive class of material for applications pertaining to energy and efficiency, and further research in this area will provide valuable solutions for pressing societal needs. (Abstract shortened by UMI.).

  5. Conceptual Design of Large Surface Area Porous Polymeric Hybrid Media Based on Polyhedral Oligomeric Silsesquioxane Precursors: Preparation, Tailoring of Porous Properties, and Internal Surface Functionalization

    PubMed Central

    2013-01-01

    We report on the preparation of hybrid, organic–inorganic porous materials derived from polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) via a single-step molding process. The monolithic, large surface area materials are studied with a particular focus on morphology and porous properties. Radical vinyl polymerization of the nanometer-sized POSS building blocks is therefore utilized via a thermally initiated route and in porogenic diluents such as tetrahydrofuran and polyethylene glycols of varying composition. Careful choice of these porogenic solvents and proper choice of initiator concentration lead to highly porous monolithic building entities which show a rigid, 3D-adhered, porous structure, macroscopically adapting the shape of a given mold. The described materials reflect Brunauer–Emmett–Teller (BET) surface areas of 700 m2/g or more and maximum tunable mesopore volumes of up to 2 cm3/g. Experimental investigations demonstrate the option to tailor nanoporosity and macroporosity in the single-step free-radical polymerization process. While studies on the influence of the used porogenic solvents reveal tuneability of pore sizes due to the unique pore formation process, tailored existence of residual vinyl groups allows facile postpolymerization modification of the highly porous, large surface area hybrid materials exploited via thiol–ene “click” chemistry. Our developed, simply realizable preparation process explores a new route to derive porous organic–inorganic hybrid adsorbents for a wide variety of applications such as extraction, separation science, and catalysis. PMID:23489022

  6. Interaction between surface water areas and groundwater in Hanoi city, Viet Nam

    NASA Astrophysics Data System (ADS)

    Hayashi, T.; Kuroda, K.; Do Thuan, A.; Tran Thi Viet, N.; Takizawa, S.

    2012-12-01

    the Red river. Groundwater samples were also distributed along the LEL and there was no seasonal change. Thus, groundwater in these communities was mainly recharged by mixing of precipitation/the Red River and evaporated water bodies. Considering the land use in these communities, evaporated water bodies were considered to be not only ponds but also paddy fields. As for solute transport, concentration of dissolved Arsenic (filtered by 0.45μm) of the pond water (3 - 10 μg/L) was slightly higher than the Red River (~ 3 μg/L) and was much lower than that of groundwater (~ 60 μg/L). On the other hand, concentration of dissolved Arsenic in the pore water of sediments (10 - 85 μg/L) was close to groundwater. Also, other metal elements showed the same trend. Therefore, Arsenic and other metal elements recharged to these ponds were considered to be adsorbed by sediments (including organic matters). That is, pond sediments played an important role as a filter of metal elements. The results of this study strongly suggested that the surface water areas such as ponds and paddy fields are one of main groundwater sources. Also, ponds play important role for solute transport of metal elements. Therefore, management of these surface water areas is important to conserve groundwater environment.

  7. Adsorbed Water Illustration

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Thermal and Electrical Conductivity Probe on NASA's Phoenix Mars Lander detected small and variable amounts of water in the Martian soil.

    In this schematic illustration, water molecules are represented in red and white; soil minerals are represented in green and blue. The water, neither liquid, vapor, nor solid, adheres in very thin films of molecules to the surfaces of soil minerals. The left half illustrates an interpretation of less water being adsorbed onto the soil-particle surface during a period when the tilt, or obliquity, of Mars' rotation axis is small, as it is in the present. The right half illustrates a thicker film of water during a time when the obliquity is greater, as it is during cycles on time scales of hundreds of thousands of years. As the humidity of the atmosphere increases, more water accumulates on mineral surfaces. Thicker films behave increasingly like liquid water.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  8. Dye-adsorption capacity of high surface-area hydrogen titanate nanosheets processed via modified hydrothermal method.

    PubMed

    Padinhattayil, Hareesh; Augustine, Rimesh; Shukla, Satyajit

    2013-04-01

    High surface-area (380 m2 x g(-1)) hydrogen titanate nanosheets (HTNS) processed via the modified hydrothermal method have been utilized for the removal of methylene blue (MB) dye from an aqueous solution via the surface-adsorption process involving the electrostatic attraction mechanism. The HTNS have been characterized using the transmission electron microscope (TEM), selected-area electron diffraction (SAED), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) specific surface-area measurement techniques. The amount of MB dye adsorbed on the surface of HTNS at equilibrium (q(e)) has been examined as a function of contact time, initial dye-concentration, and initial solution-pH. Within the investigated range of initial solution-pH (2.5-11), the MB dye adsorption on the surface of HTNS has been observed to follow the pseudo-second-order kinetics with the dye-adsorption capacity of 119 mg x g(-1) at the initial solution-pH of - 10. The adsorption equilibrium follows the Langmuir isotherm within the initial solution-pH range of 2.5-10. However, in a highly basic solution (initial solution-pH -11), the adsorption equilibrium has been observed to follow the Langmuir, Freundlich, and Dubinin-Kaganer-Radushkevich (DKR) models in the different ranges of initial MB dye concentration. The mere dependence on the DKR model has not been observed within the investigated range of initial solution-pH. The differences in the dye-adsorption characteristics and capacity of HTNS, compared with those of hydrogen titanate nanotubes, have been attributed to the difference in their specific surface-area. Irrespective of the morphology, the maximum coverage of MB dye on the surface of hydrogen titanate has been noted to be the same (52%).

  9. Surface area-dependent second harmonic generation from silver nanorods.

    PubMed

    Ngo, Hoang Minh; Luong, Thanh Tuyen; Ledoux-Rak, Isabelle

    2016-08-17

    The nonlinear optical (NLO) properties of metallic nanoparticles strongly depend on their size and shape. Metallic gold nanorods have already been widely investigated, but other noble metals could also be used for nanorod fabrication towards applications in photonics. Here we report on the synthesis and NLO characterization of silver nanorods (AgNRs) with controllable localized surface plasmon resonance. We have implemented an original, one-step and seedless synthesis method, based on a spontaneous particle growth technique in the presence of polyvinylpyrrolidone (PVP) as a capping agent. Colloidal solutions of AgNRs with various aspect ratios (5.0; 6.3; 7.5; 8.2 and 9.7) have been obtained and characterized using Harmonic light scattering (HLS) at 1064 nm, in order to investigate their quadratic NLO properties. From HLS experiments, we demonstrate that hyperpolarizability (β) values of AgNRs display a strong dependence on their surface area.

  10. Fabrication of large area nanostructures with surface modified silica spheres

    NASA Astrophysics Data System (ADS)

    Kang, Kwang-Sun

    2014-03-01

    Surface modification of silica spheres with 3-(trimethoxysilyl)propylmethacrylate (TMSPM) has been performed at ambient condition. However, the FTIR spectra and field emission scanning electron microscope (FESEM) images show no evidence of the surface modification. The reaction temperatures were varied from 60 to 80 °C with various reaction periods. Small absorption shoulder of the CO stretching vibration was at 1700 cm-1, and slightly increased with the increase of the reaction time at 60 °C. The clear absorption peak appeared at 1698 cm-1 for the spheres reacted for 80 min at 70 °C and shifted toward 1720 cm-1 with the increase the reaction time. Strong absorption peak showed at 1698 cm-1 and shifted toward 1725 cm-1 with the increase of the reaction time at 80 °C. The spheres were dispersed to methanol and added photoinitiator (Irgacure-184). The solution was poured to a patterned glass substrate and exposed to the 254 nm UV-light during a self-assembly process. A large area and crack-free silica sphere film was formed. To increase the mechanical stability, a cellulose acetate solution was spin-coated to the film. The film was lift-off from the glass substrate to analyze the surface nanostructures. The surface nanostructures were maintained, and the film is stable enough to use as a mold to duplicate the nanopattern and flexible.

  11. High-surface-area carbon molecular sieves for selective CO(2) adsorption.

    PubMed

    Wahby, Anass; Ramos-Fernández, José M; Martínez-Escandell, Manuel; Sepúlveda-Escribano, Antonio; Silvestre-Albero, Joaquín; Rodríguez-Reinoso, Francisco

    2010-08-23

    A series of carbon molecular sieves (CMSs) has been prepared, either as powders or monoliths, from petroleum pitch using potassium hydroxide as the activating agent. The CMS monoliths are prepared without the use of a binder based on the self-sintering ability of the mesophase pitch. Characterization results show that these CMSs combine a large apparent surface area (up to ca. 3100 m(2) g(-1)) together with a well-developed narrow microporosity (V(n) up to ca. 1.4 cm(3) g(-1)). The materials exhibit high adsorption capacities for CO(2) at 1 bar and 273 K (up to ca. 380 mg CO(2) g sorbent(-1)). To our knowledge, this is the best result obtained for CO(2) adsorption using carbon-based materials. Furthermore, although the CO(2) adsorption capacity for activated carbons has usually been considered lower than that of zeolites, the reported values exceed the total amount adsorbed on traditional 13X and 5A zeolites (ca. 230 mg and 180 mg CO(2) g sorbent(-1), respectively), under identical experimental conditions. Additionally, the narrow pore openings found in the CMS samples (ca. 0.4 nm) allows for the selective adsorption of CO(2) from molecules of similar dimensions (e.g., CH(4) and N(2)).

  12. Real-time specific surface area measurements via laser-induced breakdown spectroscopy

    USGS Publications Warehouse

    Washburn, Kathryn E.; Birdwell, Justin E.; Howard, James E.

    2017-01-01

    From healthcare to cosmetics to environmental science, the specific surface area (SSA) of micro- and mesoporous materials or products can greatly affect their chemical and physical properties. SSA results are also widely used to examine source rocks in conventional and unconventional petroleum resource plays. Despite its importance, current methods to measure SSA are often cumbersome, time-consuming, or require cryogenic consumables (e.g., liquid nitrogen). These methods are not amenable to high-throughput environments, have stringent sample preparation requirements, and are not practical for use in the field. We present a new application of laser-induced breakdown spectroscopy for rapid measurement of SSA. This study evaluates geological samples, specifically organic-rich oil shales, but the approach is expected to be applicable to many other types of materials. The method uses optical emission spectroscopy to examine laser-generated plasma and quantify the amount of argon adsorbed to a sample during an inert gas purge. The technique can accommodate a wide range of sample sizes and geometries and has the potential for field use. These advantages for SSA measurement combined with the simultaneous acquisition of composition information make this a promising new approach for characterizing geologic samples and other materials.

  13. Thermodynamic surface system of static black holes and area law

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Huang, Yong-Chang

    2016-11-01

    We propose a new picture of black holes through a special holographic screen. This holographic screen contains all the degrees of freedom of a black hole. We find that this holographic screen is similar to the ordinary thermodynamic surface system. Meanwhile, through the “white-wall box” and the formula of sound velocity, we find some similarities between gravitons and photons. We further assume that such a holographic screen is a kind of Bose-Einstein condensate of gravitons. Through this assumption and those similarities, we finally get the area law of static black holes. Supported by National Natural Science Foundation of China (11275017, 11173028)

  14. Hydroetching of high surface area ceramics using moist supercritical fluids

    DOEpatents

    Fryxell, Glen; Zemanian, Thomas S.

    2004-11-02

    Aerogels having a high density of hydroxyl groups and a more uniform pore size with fewer bottlenecks are described. The aerogel is exposed to a mixture of a supercritical fluid and water, whereupon the aerogel forms a high density of hydroxyl groups. The process also relaxes the aerogel into a more open uniform internal structure, in a process referred to as hydroetching. The hydroetching process removes bottlenecks from the aerogels, and forms the hydrogels into more standard pore sizes while preserving their high surface area.

  15. High surface area graphene-supported metal chalcogenide assembly

    DOEpatents

    Worsley, Marcus A.; Kuntz, Joshua; Orme, Christine A.

    2016-04-19

    A composition comprising at least one graphene-supported assembly, which comprises a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds, and at least one metal chalcogenide compound disposed on said graphene sheets, wherein the chalcogen of said metal chalcogenide compound is selected from S, Se and Te. Also disclosed are methods for making and using the graphene-supported assembly, including graphene-supported MoS.sub.2. Monoliths with high surface area and conductivity can be achieved. Lower operating temperatures in some applications can be achieved. Pore size and volume can be tuned.

  16. Metal-organic framework materials with ultrahigh surface areas

    DOEpatents

    Farha, Omar K.; Hupp, Joseph T.; Wilmer, Christopher E.; Eryazici, Ibrahim; Snurr, Randall Q.; Gomez-Gualdron, Diego A.; Borah, Bhaskarjyoti

    2015-12-22

    A metal organic framework (MOF) material including a Brunauer-Emmett-Teller (BET) surface area greater than 7,010 m.sup.2/g. Also a metal organic framework (MOF) material including hexa-carboxylated linkers including alkyne bond. Also a metal organic framework (MOF) material including three types of cuboctahedron cages fused to provide continuous channels. Also a method of making a metal organic framework (MOF) material including saponifying hexaester precursors having alkyne bonds to form a plurality of hexa-carboxylated linkers including alkyne bonds and performing a solvothermal reaction with the plurality of hexa-carboxylated linkers and one or more metal containing compounds to form the MOF material.

  17. Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-09-06

    A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  18. Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J; Dai, Sheng; Oyola, Yatsandra

    2014-05-13

    A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  19. High specific surface area aerogel cryoadsorber for vacuum pumping applications

    DOEpatents

    Hill, Randal M.; Fought, Eric R.; Biltoft, Peter J.

    2000-01-01

    A cryogenic pumping system is provided, comprising a vacuum environment, an aerogel sorbent formed from a carbon aerogel disposed within the vacuum environment, and cooling means for cooling the aerogel sorbent sufficiently to adsorb molecules from the vacuum environment onto the aerogel sorbent. Embodiments of the invention include a liquid refrigerant cryosorption pump, a compressed helium cryogenic pump, a cryopanel and a Meissner coil, each of which uses carbon aerogel as a sorbent material.

  20. Urban areas impact on surface water quality during rainfall events

    NASA Astrophysics Data System (ADS)

    Ferreira, C. S. S.; Soares, D.; Ferreira, A. J. D.; Costa, M. L.; Steenhuis, T. S.; Coelho, C. O. A.; Walsh, R. P. D.

    2012-04-01

    Increasing population and welfare puts water management under stress, especially in what concerns water quality. Surface water properties are strongly linked with hydrological processes and are affected by stream flow variability. Changes in some chemical substances concentrations can be ascribed to different water sources. Runoff generated in urban areas is considered the main responsible for water quality degradation inside catchments. This poster presents the methodology and first results of a study that is being developed to assess the impact of urbanization on surface water quality, during rainfall events. It focuses on the Ribeira dos Covões catchment (620 ha) located in central Portugal. Due to its proximity to the Coimbra city in central region, the urban areas sprawled during the last decades. In 2008, urban areas represented 32% of the area. Recently a highway was constructed crossing the catchment and a technological industrial park is being build-up in the headwaters. Several water samples were collected at four different locations: the catchment outlet and in three sub-catchments with distinct urbanization patterns - Espírito Santo that represents a highly urbanized area (45%) located over sandstone, Porto do Bordalo with 30% of urbanized area located over limestone, and IParque, mainly forest and just downstream the disturbed technological industrial park construction area. The samples were collected at different times during rainfall events to monitor the variability along the hydrograph. Six monitoring campaigns were performed: two in April 2011, at the end of the winter period, and the others between October and November 2011, after the dry summer. The number of samples collected per monitoring campaign is variable according with rainfall pattern. Parameters such as pH, conductivity, turbidity and total suspended sediments were immediately analyzed. The samples were then preserved, after filtered (0.45µm), and later analyzed for dissolved

  1. Nitridation under ammonia of high surface area vanadium aerogels

    SciTech Connect

    Merdrignac-Conanec, Odile . E-mail: odile.merdrignac@univ-rennes1.fr; El Badraoui, Khadija; L'Haridon, Paul

    2005-01-15

    Vanadium pentoxide gels have been obtained from decavanadic acid prepared by ion exchange on a resin from ammonium metavanadate solution. The progressive removal of water by solvent exchange in supercritical conditions led to the formation of high surface area V{sub 2}O{sub 5}, 1.6H{sub 2}O aerogels. Heat treatment under ammonia has been performed on these aerogels in the 450-900 deg. C temperature range. The oxide precursors and oxynitrides have been characterized by XRD, SEM, TGA, BET. Nitridation leads to divided oxynitride powders in which the fibrous structure of the aerogel is maintained. The use of both very low heating rates and high surface area aerogel precursors allows a higher rate and a lower threshold of nitridation than those reported in previous works. By adjusting the nitridation temperature, it has been possible to prepare oxynitrides with various nitrogen enrichment and vanadium valency states. Whatever the V(O,N) composition, the oxidation of the oxynitrides in air starts between 250 and 300 deg. C. This determines their potential use as chemical gas sensors at a maximum working temperature of 250 deg. C.

  2. High surface area, low weight composite nickel fiber electrodes

    NASA Technical Reports Server (NTRS)

    Johnson, Bradley A.; Ferro, Richard E.; Swain, Greg M.; Tatarchuk, Bruce J.

    1993-01-01

    The energy density and power density of light weight aerospace batteries utilizing the nickel oxide electrode are often limited by the microstructures of both the collector and the resulting active deposit in/on the collector. Heretofore, these two microstructures were intimately linked to one another by the materials used to prepare the collector grid as well as the methods and conditions used to deposit the active material. Significant weight and performance advantages were demonstrated by Britton and Reid at NASA-LeRC using FIBREX nickel mats of ca. 28-32 microns diameter. Work in our laboratory investigated the potential performance advantages offered by nickel fiber composite electrodes containing a mixture of fibers as small as 2 microns diameter (Available from Memtec America Corporation). These electrode collectors possess in excess of an order of magnitude more surface area per gram of collector than FIBREX nickel. The increase in surface area of the collector roughly translates into an order of magnitude thinner layer of active material. Performance data and advantages of these thin layer structures are presented. Attributes and limitations of their electrode microstructure to independently control void volume, pore structure of the Ni(OH)2 deposition, and resulting electrical properties are discussed.

  3. Nanosilver on nanostructured silica: Antibacterial activity and Ag surface area

    PubMed Central

    Sotiriou, Georgios A.; Teleki, Alexandra; Camenzind, Adrian; Krumeich, Frank; Meyer, Andreas; Panke, Sven; Pratsinis, Sotiris E.

    2013-01-01

    Nanosilver is one of the first nanomaterials to be closely monitored by regulatory agencies worldwide motivating research to better understand the relationship between Ag characteristics and antibacterial activity. Nanosilver immobilized on nanostructured silica facilitates such investigations as the SiO2 support hinders the growth of nanosilver during its synthesis and, most importantly, its flocculation in bacterial suspensions. Here, such composite Ag/silica nanoparticles were made by flame spray pyrolysis of appropriate solutions of Ag-acetate or Ag-nitrate and hexamethyldisiloxane or tetraethylorthosilicate in ethanol, propanol, diethylene glucolmonobutyl ether, acetonitrile or ethylhexanoic acid. The effect of solution composition on nanosilver characteristics and antibacterial activity against the Gram negative Escherichia coli was investigated by monitoring their recombinantly synthesized green fluorescent protein. Suspensions with identical Ag mass concentration exhibited drastically different antibacterial activity pointing out that the nanosilver surface area concentration rather than its mass or molar or number concentration determine best its antibacterial activity. Nanosilver made from Ag-acetate showed a unimodal size distribution, while that made from inexpensive Ag-nitrate exhibited a bimodal one. Regardless of precursor composition or nanosilver size distribution, the antibacterial activity of nanosilver was correlated best with its surface area concentration in solution. PMID:23730198

  4. High surface area graphene foams by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Drieschner, Simon; Weber, Michael; Wohlketzetter, Jörg; Vieten, Josua; Makrygiannis, Evangelos; Blaschke, Benno M.; Morandi, Vittorio; Colombo, Luigi; Bonaccorso, Francesco; Garrido, Jose A.

    2016-12-01

    Three-dimensional (3D) graphene-based structures combine the unique physical properties of graphene with the opportunity to get high electrochemically available surface area per unit of geometric surface area. Several preparation techniques have been reported to fabricate 3D graphene-based macroscopic structures for energy storage applications such as supercapacitors. Although reaserch has been focused so far on achieving either high specific capacitance or high volumetric capacitance, much less attention has been dedicated to obtain high specific and high volumetric capacitance simultaneously. Here, we present a facile technique to fabricate graphene foams (GF) of high crystal quality with tunable pore size grown by chemical vapor deposition. We exploited porous sacrificial templates prepared by sintering nickel and copper metal powders. Tuning the particle size of the metal powders and the growth temperature allow fine control of the resulting pore size of the 3D graphene-based structures smaller than 1 μm. The as-produced 3D graphene structures provide a high volumetric electric double layer capacitance (165 mF cm-3). High specific capacitance (100 Fg-1) is obtained by lowering the number of layers down to single layer graphene. Furthermore, the small pore size increases the stability of these GFs in contrast to the ones that have been grown so far on commercial metal foams. Electrodes based on the as-prepared GFs can be a boost for the development of supercapacitors, where both low volume and mass are required.

  5. Nanosilver on nanostructured silica: Antibacterial activity and Ag surface area.

    PubMed

    Sotiriou, Georgios A; Teleki, Alexandra; Camenzind, Adrian; Krumeich, Frank; Meyer, Andreas; Panke, Sven; Pratsinis, Sotiris E

    2011-06-01

    Nanosilver is one of the first nanomaterials to be closely monitored by regulatory agencies worldwide motivating research to better understand the relationship between Ag characteristics and antibacterial activity. Nanosilver immobilized on nanostructured silica facilitates such investigations as the SiO2 support hinders the growth of nanosilver during its synthesis and, most importantly, its flocculation in bacterial suspensions. Here, such composite Ag/silica nanoparticles were made by flame spray pyrolysis of appropriate solutions of Ag-acetate or Ag-nitrate and hexamethyldisiloxane or tetraethylorthosilicate in ethanol, propanol, diethylene glucolmonobutyl ether, acetonitrile or ethylhexanoic acid. The effect of solution composition on nanosilver characteristics and antibacterial activity against the Gram negative Escherichia coli was investigated by monitoring their recombinantly synthesized green fluorescent protein. Suspensions with identical Ag mass concentration exhibited drastically different antibacterial activity pointing out that the nanosilver surface area concentration rather than its mass or molar or number concentration determine best its antibacterial activity. Nanosilver made from Ag-acetate showed a unimodal size distribution, while that made from inexpensive Ag-nitrate exhibited a bimodal one. Regardless of precursor composition or nanosilver size distribution, the antibacterial activity of nanosilver was correlated best with its surface area concentration in solution.

  6. Selective cesium removal from radioactive liquid waste by crown ether immobilized new class conjugate adsorbent.

    PubMed

    Awual, Md Rabiul; Yaita, Tsuyoshi; Taguchi, Tomitsugu; Shiwaku, Hideaki; Suzuki, Shinichi; Okamoto, Yoshihiro

    2014-08-15

    Conjugate materials can provide chemical functionality, enabling an assembly of the ligand complexation ability to metal ions that are important for applications, such as separation and removal devices. In this study, we developed ligand immobilized conjugate adsorbent for selective cesium (Cs) removal from wastewater. The adsorbent was synthesized by direct immobilization of dibenzo-24-crown-8 ether onto inorganic mesoporous silica. The effective parameters such as solution pH, contact time, initial Cs concentration and ionic strength of Na and K ion concentrations were evaluated and optimized systematically. This adsorbent was exhibited the high surface area-to-volume ratios and uniformly shaped pores in case cavities, and its active sites kept open functionality to taking up Cs. The obtained results revealed that adsorbent had higher selectivity toward Cs even in the presence of a high concentration of Na and K and this is probably due to the Cs-π interaction of the benzene ring. The proposed adsorbent was successfully applied for radioactive Cs removal to be used as the potential candidate in Fukushima nuclear wastewater treatment. The adsorbed Cs was eluted with suitable eluent and simultaneously regenerated into the initial form for the next removal operation after rinsing with water. The adsorbent retained functionality despite several cycles during sorption-elution-regeneration operations.

  7. Investigation of Sea Surface Temperature (SST) anomalies over Cyprus area

    NASA Astrophysics Data System (ADS)

    Georgiou, Andreas; Akçit, Nuhcan

    2016-08-01

    The temperature of the sea surface has been identified as an important parameter of the natural environment, governing processes that occur in the upper ocean. This paper focuses on the analysis of the Sea Surface Temperature (SST) anomalies at the greater area of Cyprus. For that, SST data derived from MODerate-resolution Imaging Spectroradiometer (MODIS) instrument on board both Aqua and Terra sun synchronous satellites were used. A four year period was chosen as a first approach to address and describe this phenomenon. Geographical Information Systems (GIS) has been used as an integrated platform of analysis and presentation in addition of the support of MATLAB®. The methodology consists of five steps: (i) Collection of MODIS SST imagery, (ii) Development of the digital geo-database; (iii) Model and run the methodology in GIS as a script; (iv) Calculation of SST anomalies; and (v) Visualization of the results. The SST anomaly values have presented a symmetric distribution over the study area with an increase trend through the years of analysis. The calculated monthly and annual average SST anomalies (ASST) make more obvious this trend, with negative and positive SST changes to be distributed over the study area. In terms of seasons, the same increase trend presented during spring, summer, autumn and winter with 2013 to be the year with maximum ASST observed values. Innovative aspects comprise of straightforward integration and modeling of available tools, providing a versatile platform of analysis and semi-automation of the operation. In addition, the fine resolution maps that extracted from the analysis with a wide spatial coverage, allows the detail representation of SST and ASST respectively in the region.

  8. Surface States and Effective Surface Area on Photoluminescent P-Type Porous Silicon

    NASA Technical Reports Server (NTRS)

    Weisz, S. Z.; Porras, A. Ramirez; Resto, O.; Goldstein, Y.; Many, A.; Savir, E.

    1997-01-01

    The present study is motivated by the possibility of utilizing porous silicon for spectral sensors. Pulse measurements on the porous-Si/electrolyte system are employed to determine the surface effective area and the surface-state density at various stages of the anodization process used to produce the porous material. Such measurements were combined with studies of the photoluminescence spectra. These spectra were found to shift progressively to the blue as a function of anodization time. The luminescence intensity increases initially with anodization time, reaches a maximum and then decreases with further anodization. The surface state density, on the other hand, increases with anodization time from an initial value of about 2 x 10(exp 12)/sq cm surface to about 1013 sq cm for the anodized surface. This value is attained already after -2 min anodization and upon further anodization remains fairly constant. In parallel, the effective surface area increases by a factor of 10-30. This behavior is markedly different from the one observed previously for n-type porous Si.

  9. Idealized Shale Sorption Isotherm Measurements to Determine Pore Volume, Pore Size Distribution, and Surface Area

    NASA Astrophysics Data System (ADS)

    Holmes, R.; Wang, B.; Aljama, H.; Rupp, E.; Wilcox, J.

    2014-12-01

    One method for mitigating the impacts of anthropogenic CO2-related climate change is the sequestration of CO2 in depleted gas and oil reservoirs, including shale. The accurate characterization of the heterogeneous material properties of shale, including pore volume, surface area, pore size distributions (PSDs) and composition is needed to understand the interaction of CO2 with shale. Idealized powdered shale sorption isotherms were created by varying incremental amounts of four essential components by weight. The first two components, organic carbon and clay, have been shown to be the most important components for CO2 uptake in shales. Organic carbon was represented by kerogen isolated from a Silurian shale, and clay groups were represented by illite from the Green River shale formation. The rest of the idealized shale was composed of equal parts by weight of SiO2 to represent quartz and CaCO3 to represent carbonate components. Baltic, Eagle Ford, and Barnett shale sorption measurements were used to validate the idealized samples. The idealized and validation shale sorption isotherms were measured volumetrically using low pressure N2 (77K) and CO2 (273K) adsorbates on a Quantachrome Autosorb IQ2. Gravimetric isotherms were also produced for a subset of these samples using CO2 and CH4adsorbates under subsurface temperature and pressure conditions using a Rubotherm magnetic suspension balance. Preliminary analyses were inconclusive in validating the idealized samples. This could be a result of conflicting reports of total organic carbon (TOC) content in each sample, a problem stemming from the heterogeneity of the samples and different techniques used for measuring TOC content. The TOC content of the validation samples (Eagle Ford and Barnett) was measured by Rock-Eval pyrolysis at Weatherford Laboratories, while the TOC content in the Baltic validation samples was determined by LECO TOC. Development of a uniform process for measuring TOC in the validation samples is

  10. Development of nitrogen enriched nanostructured carbon adsorbents for CO2 capture.

    PubMed

    Goel, Chitrakshi; Bhunia, Haripada; Bajpai, Pramod K

    2015-10-01

    Nanostructured carbon adsorbents containing high nitrogen content were developed by templating melamine-formaldehyde resin in the pores of mesoporous silica by nanocasting technique. A series of adsorbents were prepared by altering the carbonization temperature from 400 to 700 °C and characterized in terms of their textural and morphological properties. CO2 adsorption performance was investigated at various temperatures from 30 to 100 °C by using a thermogravimetric analyzer under varying CO2 concentrations. Multiple adsorption-desorption experiments were also carried out to investigate the adsorbent regenerability. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the development of nanostructured materials. Fourier transform infrared spectroscopy (FTIR) and elemental analysis indicated the development of carbon adsorbents having high nitrogen content. The surface area and pore volume of the adsorbent carbonized at 700 °C were found to be 266 m(2) g(-1) and 0.25 cm(3) g(-1) respectively. CO2 uptake profile for the developed adsorbents showed that the maximum CO2 adsorption occurred within ca. 100 s. CO2 uptake of 0.792 mmol g(-1) at 30 °C was exhibited by carbon obtained at 700 °C with complete regenerability in three adsorption-desorption cycles. Furthermore, kinetics of CO2 adsorption on the developed adsorbents was studied by fitting the experimental data of CO2 uptake to three kinetic models with best fit being obtained by fractional order kinetic model with error% within range of 5%. Adsorbent surface was found to be energetically heterogeneous as suggested by Temkin isotherm model. Also the isosteric heat of adsorption for CO2 was observed to increase from ca. 30-44 kJ mol(-1) with increase in surface coverage.

  11. Development and characterization of activated hydrochars from orange peels as potential adsorbents for emerging organic contaminants.

    PubMed

    Fernandez, M E; Ledesma, B; Román, S; Bonelli, P R; Cukierman, A L

    2015-05-01

    Activated hydrochars obtained from the hydrothermal carbonization of orange peels (Citrus sinensis) followed by various thermochemical processing were assessed as adsorbents for emerging contaminants in water. Thermal activation under flows of CO2 or air as well as chemical activation with phosphoric acid were applied to the hydrochars. Their characteristics were analyzed and related to their ability to uptake three pharmaceuticals (diclofenac sodium, salicylic acid and flurbiprofen) considered as emerging contaminants. The hydrothermal carbonization and subsequent activations promoted substantial chemical transformations which affected the surface properties of the activated hydrochars; they exhibited specific surface areas ranging from 300 to ∼620 m(2)/g. Morphological characterization showed the development of coral-like microspheres dominating the surface of most hydrochars. Their ability to adsorb the three pharmaceuticals selected was found largely dependent on whether the molecules were ionized or in their neutral form and on the porosity developed by the new adsorbents.

  12. Miscibility and interaction between 1-alkanol and short-chain phosphocholine in the adsorbed film and micelles.

    PubMed

    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.

  13. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    PubMed Central

    Bhakta, Snehasis; Dixit, Chandra K; Bist, Itti; Jalil, Karim Abdel; Suib, Steven L; Rusling, James F

    2016-01-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ~60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ~3-fold higher silane can be used as efficient probes for biosensor applications. PMID:27606068

  14. High surface area ThO/sub 2/ catalyst

    DOEpatents

    Colmenares, C.A.; Somorjai, G.A.; Maj, J.J.

    1983-06-21

    A ThO/sub 2/ catalyst having a high surface area of about 80 to 125m/sup 2//g is synthesized. The compound is synthesized by simultaneously mixing an aqueous solution of ThNO/sub 3/(NO/sub 3/)/sub 4/.4H/sub 2/O with an aqueous solution of Na/sub 2/CO/sub 3/.H/sub 2/O, to produce a solution and solid ThOCO/sub 3/. The solid ThOCO/sub 3/ is separated from the solution, and then calcined at a temperature of about 225 to 300/sup 0/C for about 40 to 55 hours to produce ThO/sub 2/. The ThO/sub 2/ catalyst produced includes Na present as a substitutional cation in an amount equal to about 5 to 10 at. %.

  15. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Bhakta, Snehasis; Dixit, Chandra K.; Bist, Itti; Abdel Jalil, Karim; Suib, Steven L.; Rusling, James F.

    2016-07-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ∼60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ∼3-fold higher silane can be used as efficient probes for biosensor applications.

  16. Method for producing high surface area chromia materials for catalysis

    DOEpatents

    Gash, Alexander E.; Satcher, Joe; Tillotson, Thomas; Hrubesh, Lawrence; Simpson, Randall

    2007-05-01

    Nanostructured chromium(III)-oxide-based materials using sol-gel processing and a synthetic route for producing such materials are disclosed herein. Monolithic aerogels and xerogels having surface areas between 150 m.sup.2/g and 520 m.sup.2/g have been produced. The synthetic method employs the use of stable and inexpensive hydrated-chromium(III) inorganic salts and common solvents such as water, ethanol, methanol, 1-propanol, t-butanol, 2-ethoxy ethanol, and ethylene glycol, DMSO, and dimethyl formamide. The synthesis involves the dissolution of the metal salt in a solvent followed by an addition of a proton scavenger, such as an epoxide, which induces gel formation in a timely manner. Both critical point (supercritical extraction) and atmospheric (low temperature evaporation) drying may be employed to produce monolithic aerogels and xerogels, respectively.

  17. Enhancing pilot situational awareness of the airport surface movement area

    NASA Technical Reports Server (NTRS)

    Jones, D. R.; Young, S. D.

    1994-01-01

    Two studies are being conducted to address airport surface movement area safety and capacity issues by providing enhanced situational awareness information to pilots. One study focuses on obtaining pilot opinion of the Runway Status Light System (RSLS). This system has been designed to reduce the likelihood of runway incursions by informing pilots when a runway is occupied. The second study is a flight demonstration of an rate integrated system consisting of an electronic moving map in the cockpit and display of the aircraft identification to the controller. Taxi route and hold warning information will be sent to the aircraft data link for display on the electronic moving map. This paper describes the plans for the two studies.

  18. VERUCLAY – a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant

    EPA Science Inventory

    Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, a...

  19. Graphene nanosheets and graphite oxide as promising adsorbents for removal of organic contaminants from aqueous solution.

    PubMed

    Ji, Liangliang; Chen, Wei; Xu, Zhaoyi; Zheng, Shourong; Zhu, Dongqiang

    2013-01-01

    Graphenes are an emerging class of carbon nanomaterials whose adsorption properties toward organic compounds have not been well understood. In the present study, graphene nanosheets were prepared by reoxidation and abrupt heating of graphite oxide, which was prepared by sequential chemical oxidation of commercial nonporous graphite powder. Adsorption properties of three aromatic compounds (naphthalene, 2-naphthol, and 1-naphthylamine) and one pharmaceutical compound (tylosin) on graphene nanosheets and graphite oxide were examined to explore the potential of these two adsorbents for the removal of organic contaminants from aqueous solutions. Compared with the literature data of adsorption on carbon nanotubes, adsorption of bulky, flexible tylosin on graphene nanosheets exhibited markedly faster adsorption kinetics, which can be attributed to their opened-up layer structure. Graphene nanosheets and graphite oxide showed similar sequences of adsorption affinity: 1-naphthylamine > 2-naphthol > tylosin > naphthalene (with much larger differences observed on graphite oxide). It was proposed that the strong adsorption of the three aromatic compounds was mainly due to π-π electron donor-acceptor interactions with the graphitic surfaces of adsorbents. Additionally, Lewis acid-base interaction was likely an important factor contributing to the strong adsorption of 1-naphthylamine and tylosin, especially for the O-functionality-abundant graphite oxide. After being normalized on the basis of adsorbent surface area, adsorption affinities of all four tested adsorbates on graphene nanosheets were very close to those on nonporous graphite powder, reflecting complete accessibility of the adsorbent surface area in adsorption.

  20. Adsorbent Alkali Conditioning for Uranium Adsorption from Seawater. Adsorbent Performance and Technology Cost Evaluation

    SciTech Connect

    Tsouris, Costas; Mayes, Richard T.; Janke, Christopher James; Dai, Sheng; Das, S.; Liao, W. -P.; Kuo, Li-Jung; Wood, Jordana; Gill, Gary; Byers, Maggie Flicker; Schneider, Eric

    2015-09-30

    The Fuel Resources program of the Fuel Cycle Research and Development program of the Office of Nuclear Energy (NE) is focused on identifying and implementing actions to assure that nuclear fuel resources are available in the United States. An immense source of uranium is seawater, which contains an estimated amount of 4.5 billion tonnes of dissolved uranium. This unconventional resource can provide a price cap and ensure centuries of uranium supply for future nuclear energy production. NE initiated a multidisciplinary program with participants from national laboratories, universities, and research institutes to enable technical breakthroughs related to uranium recovery from seawater. The goal is to develop advanced adsorbents to reduce the seawater uranium recovery technology cost and uncertainties. Under this program, Oak Ridge National Laboratory (ORNL) has developed a new amidoxime-based adsorbent of high surface area, which tripled the uranium capacity of leading Japanese adsorbents. Parallel efforts have been focused on the optimization of the physicochemical and operating parameters used during the preparation of the adsorbent for deployment. A set of parameters that need to be optimized are related to the conditioning of the adsorbent with alkali solution, which is necessary prior to adsorbent deployment. Previous work indicated that alkali-conditioning parameters significantly affect the adsorbent performance. Initiated in 2014, this study had as a goal to determine optimal parameters such as base type and concentration, temperature, and duration of conditioning that maximize the uranium adsorption performance of amidoxime functionalized adsorbent, while keeping the cost of uranium production low. After base-treatment at various conditions, samples of adsorbent developed at ORNL were tested in this study with batch simulated seawater solution of 8-ppm uranium concentration, batch seawater spiked with uranium nitrate at 75-100 ppb uranium, and continuous

  1. Extracting uranium from seawater: Promising AI series adsorbents

    DOE PAGES

    Das, Sadananda; Oyola, Y.; Mayes, Richard T.; ...

    2015-11-10

    A series of adsorbent (AI10 through AI17) were successfully developed at ORNL by radiation induced graft polymerization (RIGP) of acrylonitrile (AN) and vinylphosphonic acid (VPA) (at different mole/mole ratios) onto high surface area polyethylene fiber, with higher degree of grafting which ranges from 110 300%. The grafted nitrile groups were converted to amidoxime groups by reaction with 10 wt% hydroxylamine at 80 C for 72 hours. The amidoximated adsorbents were then conditioned with 0.44M KOH at 80 C followed by screening at ORNL with simulated seawater spiked with 8 ppm uranium. Uranium adsorption capacity in simulated seawater screening ranged frommore » 171-187 g-U/kg-ads irrespective of %DOG. The performance of the adsorbents for uranium adsorption in natural seawater was also carried out using flow-through-column at Pacific Northwest National Laboratory (PNNL). The three hours KOH conditioning was better for higher uranium uptake than one hour. The adsorbent AI11 containing AN and VPA at the mole ration of 3.52, emerged as the potential candidate for higher uranium adsorption (3.35 g-U/Kg-ads.) after 56 days of exposure in the seawater in the flow-through-column. The rate vanadium adsorption over uranium was linearly increased throughout the 56 days exposure. The total vanadium uptake was ~5 times over uranium after 56 days.« less

  2. Extracting Uranium from Seawater: Promising AI Series Adsorbents

    SciTech Connect

    Das, S.; Oyola, Y.; Mayes, R. T.; Janke, C. J.; Kuo, L. -J.; Gill, G.; Wood, J. R.; Dai, S.

    2016-04-20

    A new series of adsorbents (AI10 through AI17) were successfully developed at ORNL by radiation induced graft polymerization (RIGP) of acrylonitrile (AN) and vinylphosphonic acid (VPA) (at different mole to mole ratios) onto high surface area polyethylene fiber, with high degrees of grafting (DOG) varying from 110 to 300%. The grafted nitrile groups were converted to amidoxime groups by reaction with 5 wt % hydroxylamine at 80 °C for 72 h. The amidoximated adsorbents were then conditioned with 0.44 M KOH at 80 °C followed by screening at ORNL with prescreening brine spiked with 8 ppm uranium. Uranium adsorption capacities in prescreening ranged from 171 to 187 g-U/kg-ads irrespective of percent DOG. The performance of the adsorbents with respect to uranium adsorption in natural seawater was also investigated using flow-throughcolumn testing at the Pacific Northwest National Laboratory (PNNL). Three hours of KOH conditioning led to higher uranium uptake than 1 h of conditioning. The adsorbent AI11, containing AN and VPA at the mole ratio of 3.52, emerged as the potential candidate for the highest uranium adsorption (3.35 g-U/kg-ads.) after 56 days of exposure in seawater flow-through-columns. The rate of vanadium adsorption over uranium linearly increased throughout the 56 days of exposure. The total mass of vanadium uptake was ~5 times greater than uranium after 56 days.

  3. Enhanced encapsulation of metoprolol tartrate with carbon nanotubes as adsorbent

    NASA Astrophysics Data System (ADS)

    Garala, Kevin; Patel, Jaydeep; Patel, Anjali; Dharamsi, Abhay

    2011-12-01

    A highly water-soluble antihypertensive drug, metoprolol tartrate (MT), was selected as a model drug for preparation of multi-walled carbon nanotubes (MWCNTs)-impregnated ethyl cellulose (EC) microspheres. The present investigation was aimed to increase encapsulation efficiency of MT with excellent adsorbent properties of MWCNTs. The unique surface area, stiffness, strength and resilience of MWCNTs have drawn much anticipation as carrier for highly water-soluble drugs. Carbon nanotubes drug adsorbate (MWCNTs:MT)-loaded EC microspheres were further optimized by the central composite design of the experiment. The effects of independent variables (MWCNTs:MT and EC:adsorbate) were evaluated on responses like entrapment efficiency (EE) and t 50 (time required for 50% drug release). The optimized batch was compared with drug alone EC microspheres. The results revealed high degree of improvement in encapsulation efficiency for MWCNTs:MT-loaded EC microspheres. In vitro drug release study exhibited complete release form drug alone microspheres within 15 h, while by the same time only 50-60% drug was released for MWCNTs-impregnated EC microspheres. The optimized batch was further characterized by various instrumental analyses such as scanning electron microscopy, powder X-ray diffraction and differential scanning calorimetry. The results endorse encapsulation of MWCNTs:MT adsorbate inside the matrix of EC microspheres, which might have resulted in enhanced encapsulation and sustained effect of MT. Hence, MWCNTs can be utilized as novel carriers for extended drug release and enhanced encapsulation of highly water-soluble drug, MT.

  4. Extracting uranium from seawater: Promising AI series adsorbents

    SciTech Connect

    Das, Sadananda; Oyola, Y.; Mayes, Richard T.; Janke, Christopher James; Kuo, Li-Jung; Gill, Gary; Wood, Jordana; Dai, Sheng

    2015-11-10

    A series of adsorbent (AI10 through AI17) were successfully developed at ORNL by radiation induced graft polymerization (RIGP) of acrylonitrile (AN) and vinylphosphonic acid (VPA) (at different mole/mole ratios) onto high surface area polyethylene fiber, with higher degree of grafting which ranges from 110 300%. The grafted nitrile groups were converted to amidoxime groups by reaction with 10 wt% hydroxylamine at 80 C for 72 hours. The amidoximated adsorbents were then conditioned with 0.44M KOH at 80 C followed by screening at ORNL with simulated seawater spiked with 8 ppm uranium. Uranium adsorption capacity in simulated seawater screening ranged from 171-187 g-U/kg-ads irrespective of %DOG. The performance of the adsorbents for uranium adsorption in natural seawater was also carried out using flow-through-column at Pacific Northwest National Laboratory (PNNL). The three hours KOH conditioning was better for higher uranium uptake than one hour. The adsorbent AI11 containing AN and VPA at the mole ration of 3.52, emerged as the potential candidate for higher uranium adsorption (3.35 g-U/Kg-ads.) after 56 days of exposure in the seawater in the flow-through-column. The rate vanadium adsorption over uranium was linearly increased throughout the 56 days exposure. The total vanadium uptake was ~5 times over uranium after 56 days.

  5. Hydraulic properties of adsorbed water films in unsaturated porous media

    SciTech Connect

    Tokunaga, Tetsu K.

    2009-03-01

    Adsorbed water films strongly influence residual water saturations and hydraulic conductivities in porous media at low saturations. Hydraulic properties of adsorbed water films in unsaturated porous media were investigated through combining Langmuir's film model with scaling analysis, without use of any adjustable parameters. Diffuse double layer influences are predicted to be important through the strong dependence of adsorbed water film thickness (f) on matric potential ({Psi}) and ion charge (z). Film thickness, film velocity, and unsaturated hydraulic conductivity are predicted to vary with z{sup -1}, z{sup -2}, and z{sup -3}, respectively. In monodisperse granular media, the characteristic grain size ({lambda}) controls film hydraulics through {lambda}{sup -1} scaling of (1) the perimeter length per unit cross sectional area over which films occur, (2) the critical matric potential ({Psi}{sub c}) below which films control flow, and (3) the magnitude of the unsaturated hydraulic conductivity when {Psi} < {Psi}{sub c}. While it is recognized that finer textured sediments have higher unsaturated hydraulic conductivities than coarser sands at intermediate {Psi}, the {lambda}{sup -1} scaling of hydraulic conductivity predicted here extends this understanding to very low saturations where all pores are drained. Extremely low unsaturated hydraulic conductivities are predicted under adsorbed film-controlled conditions (generally < 0.1 mm y{sup -1}). On flat surfaces, the film hydraulic diffusivity is shown to be constant (invariant with respect to {Psi}).

  6. Are the reduction and oxidation properties of nitrocompounds dissolved in water different from those produced when adsorbed on a silica surface? A DFT M05-2X computational study.

    PubMed

    Sviatenko, Liudmyla K; Isayev, Olexandr; Gorb, Leonid; Hill, Frances C; Leszczynska, Danuta; Leszczynski, Jerzy

    2015-05-30

    The reduction and oxidation properties of four nitrocompounds (trinitrotoluene [TNT], 2,4-dinitrotoluene, 2,4-dinitroanisole, and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one [NTO]) dissolved in water as compared with the same properties for compounds adsorbed on a silica surface were studied. To consider the influence of adsorption, cluster models were developed at the M05/tzvp level. A hydroxylated silica (001) surface was chosen to represent a key component of soil. The PCM(Pauling) and SMD solvation models were used to model water bulk influence. The following properties were analyzed: electron affinity, ionization potential, reduction Gibbs free energy, oxidation Gibbs free energy, and reduction and oxidation potentials. It was found that adsorption and solvation decrease gas phase electron affinity, ionization potential, and Gibbs free energy of reduction and oxidation, and thus, promote redox transformation of nitrocompounds. However, in case of solvation, the changes are more significant than for adsorption. This means that nitrocompounds dissolved in water are easier to transform by reduction or oxidation than adsorbed ones. Among the considered compounds, TNT was found to be the most reactive in an electron attachment process and the least reactive for an electron detachment transformation. During ionization, a deprotonation of adsorbed NTO was found to occur.

  7. The configuration of water on rough natural surfaces: Implications for understanding air-water interfacial area, film thickness, and imaging resolution

    NASA Astrophysics Data System (ADS)

    Kibbey, Tohren C. G.

    2013-08-01

    Previous studies of air-water interfacial areas in unsaturated porous media have often distinguished between interfacial area corresponding to water held by capillary forces between grains and area corresponding to water associated with solid surfaces. The focus of this work was on developing a better understanding of the nature of interfacial area associated with solid surfaces following drainage of porous media. Stereoscopic scanning electron microscopy was used to determine surface elevation maps for eight different surfaces of varying roughness. An algorithm was developed to calculate the true configuration of an air-water interface in contact with the solid surface as a function of capillary pressure. The algorithm was used to calculate surface-associated water configurations for capillary pressures ranging from 10 to 100 cm water. The results of the work show that, following drainage, the configuration of surface-associated water is dominated by bridging of macroscopic surface roughness features over the range of capillary pressures studied, and nearly all of the surface-associated water is capillary held. As such, the thicknesses of surface-associated water were found to be orders-of-magnitude greater than might be expected at the same capillary pressures based on calculations of adsorbed film thickness. The fact that capillary forces in air-water interfaces dominate surface-associated water configuration means that interface shapes are largely unaffected by microscopic surface roughness, and interfaces are considerably smoother than the underlying solid. As such, calculations suggest that microscopic surface roughness likely has minimal impact on the accuracy of surface-associated air-water interfacial areas determined by limited-resolution imaging methods such as computed microtomography.

  8. Observations of Nuclear Explosive Melt Glass Textures and Surface Areas

    SciTech Connect

    Kersting, A B; Smith, D K

    2006-01-17

    This memo report summarizes our current knowledge of the appearance of melt glass formed and subsequently deposited in the subsurface after an underground nuclear test. We have collected archived pictures and melt glass samples from a variety of underground nuclear tests that were conducted at the Nevada Test Site (NTS) during the U.S. nuclear testing program. The purpose of our work is to better determine the actual variation in texture and surface area of the melt glass material. This study is motivated by our need to better determine the rate at which the radionuclides incorporated in the melt glass are released into the subsurface under saturated and partially saturated conditions. The rate at which radionuclides are released from the glass is controlled by the dissolution rate of the glass. Glass dissolution, in turn, is a strong function of surface area, glass composition, water temperature and water chemistry (Bourcier, 1994). This work feeds into an ongoing experimental effort to measure the change in surface area of analog glasses as a function of dissolution rate. The conclusions drawn from this study help bound the variation in the textures of analog glass samples needed for the experimental studies. The experimental work is a collaboration between Desert Research Institute (DRI) and Earth and Environmental Sciences-Lawrence Livermore National Laboratory (EES-LLNL). On March 4, 1999 we hosted a meeting at LLNL to present and discuss our findings. The names of the attendees appear at the end of this memo. This memo report further serves to outline and summarize the conclusions drawn from our meeting. The United States detonated over 800 underground nuclear tests at the NTS between 1951 and 1992. In an effort to evaluate the performance of the nuclear tests, drill-back operations were carried out to retrieve samples of rock in the vicinity of the nuclear test. Drill-back samples were sent to Los Alamos National Laboratory (LANL) and Lawrence Livermore

  9. Accessible reactive surface area and abiotic redox reactivity of iron oxyhydroxides in acidic brines

    NASA Astrophysics Data System (ADS)

    Strehlau, Jennifer H.; Toner, Brandy M.; Arnold, William A.; Penn, R. Lee

    2017-01-01

    The reactivity of iron oxyhydroxide nanoparticles in low pH and high ionic strength solutions was quantified to assess abiotic contributions to oxidation-reduction chemistry in acidic brine environments, such as mine groundwater seepage, lakes in Western Australia, and acid mine drainage settings, which are of global interest for their environmental impacts and unique geomicrobiology. Factors expected to influence accessible and reactive surface area, including Fe(II) adsorption and aggregate size, were measured as a function of pH and CaCl2 concentration and related to the kinetics of redox reactions in aqueous suspensions of synthetic goethite (α-FeOOH), akaganeite (β-FeOOH), and ferrihydrite (Fe10O14(OH)2) nanoparticles. Aqueous conditions and iron oxyhydroxides were chosen based on characterization of natural iron-rich mine microbial mats located in Soudan Underground Mine State Park, Minnesota, USA. Quinone species were used as redox sensors because they are well-defined probes and are present in natural organic matter. Fe(II) adsorption to the iron oxyhydroxide mineral surfaces from aqueous solution was measurable only at pH values above 4 and either decreased or was not affected by CaCl2 concentration. Concentrations at or above 0.020 M CaCl2 in acetate buffer (pH 4.5) induced particle aggregation. Assessment of Fe(II) adsorption and particle aggregation in acidic brine suggested that accessible reactive surface area may be limited in acidic brines. This was supported by observations of decreasing benzoquinone reduction rate by adsorbed Fe(II) at high CaCl2 concentration. In contrast, the hydroquinone oxidation rate increased at high CaCl2 concentrations, which may be due to suppressed adsorption of Fe(II) generated by the reaction. Results suggest that iron geochemical cycling in acidic brine environments will be substantially different than for iron oxyhydroxides in low-saline waters with circumneutral pH. These findings have implications for acidic

  10. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  11. The impact of built-up surfaces on land surface temperatures in Italian urban areas.

    PubMed

    Morabito, Marco; Crisci, Alfonso; Messeri, Alessandro; Orlandini, Simone; Raschi, Antonio; Maracchi, Giampiero; Munafò, Michele

    2016-05-01

    Urban areas are characterized by the very high degree of soil sealing and continuous built-up areas: Italy is one of the European countries with the highest artificial land cover rate, which causes a substantial spatial variation in the land surface temperature (LST), modifying the urban microclimate and contributing to the urban heat island effect. Nevertheless, quantitative data regarding the contribution of different densities of built-up surfaces in determining urban spatial LST changes is currently lacking in Italy. This study, which aimed to provide clear and quantitative city-specific information on annual and seasonal spatial LST modifications resulting from increased urban built-up coverage, was conducted generally throughout the whole year, and specifically in two different periods (cool/cold and warm/hot periods). Four cities (Milan, Rome, Bologna and Florence) were included in the study. The LST layer and the built-up-surface indicator were obtained via use of MODIS remote sensing data products (1km) and a very high-resolution map (5m) of built-up surfaces recently developed by the Italian National Institute for Environmental Protection and Research. The relationships between the dependent (mean daily, daytime and nighttime LST values) and independent (built-up surfaces) variables were investigated through linear regression analyses, and comprehensive built-up-surface-related LST maps were also developed. Statistically significant linear relationships (p<0.001) between built-up surfaces and spatial LST variations were observed in all the cities studied, with a higher impact during the warm/hot period than in the cool/cold ones. Daytime and nighttime LST slope patterns depend on the city size and relative urban morphology. If implemented in the existing city plan, the urban maps of built-up-surface-related LST developed in this study might be able to support more sustainable urban land management practices by identifying the critical areas (Hot

  12. Lung deposited surface area size distributions of particulate matter in different urban areas

    NASA Astrophysics Data System (ADS)

    Kuuluvainen, Heino; Rönkkö, Topi; Järvinen, Anssi; Saari, Sampo; Karjalainen, Panu; Lähde, Tero; Pirjola, Liisa; Niemi, Jarkko V.; Hillamo, Risto; Keskinen, Jorma

    2016-07-01

    Lung deposited surface area (LDSA) concentration is considered as a relevant metric for the negative health effects of aerosol particles. We report for the first time the size distributions of the LDSA measured in urban air. The measurements were carried out in the metropolitan area of Helsinki, including mobile laboratory and stationary measurements in different outdoor environments, such as traffic sites, a park area, the city center and residential areas. The main instrument in this study was an electrical low pressure impactor (ELPI), which was calibrated in the field to measure the LDSA concentration. The calibration factor was determined to be 60 μm2/(cm3 pA). In the experiments, the LDSA size distributions were found to form two modes at the traffic sites and in the city center. Both of these traffic related particle modes, the nucleation mode and the soot mode, had a clear contribution to the total LDSA concentration. The average total concentrations varied from 12 to 94 μm2/cm3, measured in the park area and at the traffic site next to a major road, respectively. The LDSA concentration was found to correlate with the mass of fine particles (PM2.5), but the relation of these two metrics varied between different environments, emphasizing the influence of traffic on the LDSA. The results of this study provide valuable information on the total concentrations and size distributions of the LDSA for epidemiological studies. The size distributions are especially important in estimating the contribution of outdoor concentrations on the concentrations inside buildings and vehicles through size-dependent penetration factors.

  13. Optimum BET surface areas for activated carbon produced from textile sewage sludges and its application as dye removal.

    PubMed

    Kacan, Erdal

    2016-01-15

    The purpose of this experimental study is to determine optimum preparation conditions for activated carbons obtained from textile sewage sludge (TSS) for removal of dyes from aqueous solutions. The textile sewage sludge activated carbon (TSSAC) was prepared by chemical activation with potassium hydroxide using Response Surface Methodology (RSM). The most influential factor on each experimental design responses was identified via ANNOVA analysis. Based on the central composite design (CCD), quadratic model was developed to correlate the preparation variables for one response which is the Brunauer-Emmelt-Teller (BET) surface area. RSM based on a three-variable CCD was used to determine the effect of pyrolyzed temperature (400-700 °C), carbonization time (45-180 min) and KOH: weight of TSS (wt%) impregnation ratio (0.5:1-1.5:1) on BET surface area. According to the results, pyrolyzed temperature and impregnation ratio were found as the significant factors for maximizing the BET surface area. The major effect which influences the BET surface area was found as pyrolyzed temperature. Both carbonization time and impregnation ratio of KOH had no significant effect. The optimum conditions for preparing TSSAC, based on response surface and contour plots, were found as follows: pyrolyzed temperature 700 °C, carbonization time of 45 min and chemical impregnation ratio of 0.5. The maximum and optimum BET surface area of TSSAC were found as 336 m(2)/g and 310.62 m(2)/g, respectively. Synozol Blue reactive (RSB) and Setapers Yellow-Brown (P2RFL) industrial textile dyes adsorption capacities were investigated. As expected the TSSAC which has the biggest BET surface area (336 m(2)/g) adsorbed dye best. The maximum (RSB) and (P2RFL) uptake capacities were found as 8.5383 mg/g and 5.4 mg/g, respectively. The results of this study indicated the applicability of TSSAC for removing industrial dyes from aqueous solution.

  14. Does mineral surface area affect chemical weathering rates?

    NASA Astrophysics Data System (ADS)

    Salome Eiriksdottir, Eydis; Reynir Gislason, Sigurdur; Oelkers, Eric H.

    2010-05-01

    Iceland is a basaltic volcanic island representative of the high relief, volcanic and tectonic active islands that contribute over 45% of river suspended material to the oceans worldwide (Milliman and Syvitski, 1992). These islands have enormous mechanical and chemical weathering rates due to the combined effects of high relief, high runoff, the presence of glaciers and easily weathered volcanic rocks, and a lack of sedimentary traps. In total, Iceland delivers 0.7% of the worldwide river suspended matter flux to the ocean, which is approximately one fourth that of Africa (Tómasson, 1990). River suspended matter from volcanic islands is highly reactive in seawater and might play an important role in the global carbon cycle (Gislason et al., 2006). Thus it is important to define and understand the mechanical and chemical weathering rates of these islands. Experimental dissolution experiments performed in the laboratory suggest that chemical weathering rates should be proportional to rock-water interfacial surface area. This hypothesis is tested in the present study through a study of the chemical composition of suspended material collected from rivers located in Northeast Iceland. These rivers were selected for this study because their catchments essentially monolithic, consisting of uniform compositioned and aged basalts. Gaillardet (1999) described weathering intensities of the worlds river systems to be from 1 (low weathering intensity) to 25 (high weathering intensity). These indexes were calculated to be from 1.8 to 3.2 in rivers in NE-Iceland (Eiriksdottir et al., 2008). The surface area of sediments is inversely proportional to particle size; smaller particles have larger specific surface areas. As a result, smaller particles should weather faster. This trend is confirmed by the measured compositions of analyzed suspended material. The concentration of insoluble elements (Zr, Fe, Cu, Ni, Y) is found to increase in the suspended material, whereas the

  15. Sorption of N2 and EGME vapors on some soils, clays, and mineral oxides and determination of sample surface areas by use of sorption data

    USGS Publications Warehouse

    Chiou, C.T.; Rutherford, D.W.; Manes, M.

    1993-01-01

    Vapor sorption isotherms of ethylene glycol monoethyl ether (EGME) at room temperature and isotherms of N2 gas at liquid nitrogen temperature were determined for various soils and minerals. The N2 monolayer capacities [Qm (N2)] were calculated from the BET equation and used to determine the surface areas. To examine whether EGME is an appropriate adsorbate for determination of surface areas, the apparent EGME monolayer capacities [Qm (EGME)ap] were also obtained by use of the BET equation. For sand, aluminum oxide, kaolinite, hematite, and synthetic hydrous iron oxide, which are relatively free of organic impurity and expanding/solvating minerals, the Qm (EGME)ap values are in good conformity with the corresponding Qm (N2) values and would give surface areas consistent with BET (N2) values. For other samples (Woodburn soil, a natural hydrous iron oxide, illite, and montmorillonite), the Qm (EGME)ap values overestimate the Qm (N2) values from a moderate to a large extent, depending on the sample. A high-organic-content peat shows a very small BET (N2) surface area; the EGME/ peat isotherm is linear and does not yield a calculation of the surface area. Large discrepancies between results of the two methods for some samples are attributed to the high solubility of polar EGME in soil organic matter and/ or to the cation solvation of EGME with solvating clays. The agreement for other samples is illustrative of the consistency of the BET method when different adsorbates are used, so long as they do not exhibit bulk penetration and/or cation solvation. ?? 1993 American Chemical Society.

  16. The possible role of solid surface area in condensation reactions during chemical evolution - Reevaluation

    NASA Technical Reports Server (NTRS)

    Lahav, N.; Chang, S.

    1976-01-01

    Using surface concentration and reaction rate as the main criteria for the feasibility of condensation reactions, four types of prebiotic environments were analyzed: (1) an ocean-sediment system, (2) a dehydrated lagoon bed produced by evaporation, (3) the surface of a frozen sediment, and (4) a fluctuating system where hydration (rainstorms, tidal variations, flooding) and dehydration (evaporation) take place in a cyclic manner. With the possible exception of nucleotides, low adsorption of organomonomers on sediment surfaces of a prebiotic ocean (pH 8) is expected, and significant condensation is considered unlikely. In dehydrated and frozen systems, high surface concentrations are probable and condensation is more likely. In fluctuating environments, condensation rates will be enhanced and the size distribution of the oligomers formed during dehydration may be influenced by a 'redistribution mechanism' in which adsorbed oligomers and monomers are desorbed and redistributed on the solid surface during the next hydration-dehydration cycle.

  17. Molecular Adsorber Coating

    NASA Technical Reports Server (NTRS)

    Straka, Sharon; Peters, Wanda; Hasegawa, Mark; Hedgeland, Randy; Petro, John; Novo-Gradac, Kevin; Wong, Alfred; Triolo, Jack; Miller, Cory

    2011-01-01

    A document discusses a zeolite-based sprayable molecular adsorber coating that has been developed to alleviate the size and weight issues of current ceramic puck-based technology, while providing a configuration that more projects can use to protect against degradation from outgassed materials within a spacecraft, particularly contamination-sensitive instruments. This coating system demonstrates five times the adsorption capacity of previously developed adsorber coating slurries. The molecular adsorber formulation was developed and refined, and a procedure for spray application was developed. Samples were spray-coated and tested for capacity, thermal optical/radiative properties, coating adhesion, and thermal cycling. Work performed during this study indicates that the molecular adsorber formulation can be applied to aluminum, stainless steel, or other metal substrates that can accept silicate-based coatings. The coating can also function as a thermal- control coating. This adsorber will dramatically reduce the mass and volume restrictions, and is less expensive than the currently used molecular adsorber puck design.

  18. Bicontinuous ceramics with high surface area from block copolymer templates.

    PubMed

    Hsueh, Han-Yu; Ho, Rong-Ming

    2012-06-05

    Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol-gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol-gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO(2) with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO(2) by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established.

  19. 30 CFR 905.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE CALIFORNIA § 905.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  20. 30 CFR 937.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE OREGON § 937.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  1. 30 CFR 941.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE SOUTH DAKOTA § 941.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  2. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  3. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  4. 30 CFR 912.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE IDAHO § 912.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  5. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  6. 30 CFR 903.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE ARIZONA § 903.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, applies to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  7. 30 CFR 947.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE WASHINGTON § 947.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  8. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  9. 30 CFR 947.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE WASHINGTON § 947.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  10. 30 CFR 942.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  11. 30 CFR 941.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE SOUTH DAKOTA § 941.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  12. 30 CFR 910.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE GEORGIA § 910.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  13. 30 CFR 942.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  14. 30 CFR 903.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE ARIZONA § 903.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, applies to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  15. 30 CFR 922.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE MICHIGAN § 922.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  16. 30 CFR 910.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE GEORGIA § 910.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  17. 30 CFR 905.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE CALIFORNIA § 905.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  18. 30 CFR 937.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE OREGON § 937.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  19. 30 CFR 912.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE IDAHO § 912.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designa