WorldWideScience

Sample records for bioassay surface chemistry

  1. Acarine attractants: Chemoreception, bioassay, chemistry and control.

    Science.gov (United States)

    Carr, Ann L; Roe, Michael

    2016-07-01

    The Acari are of significant economic importance in crop production and human and animal health. Acaricides are essential for the control of these pests, but at the same time, the number of available pesticides is limited, especially for applications in animal production. The Acari consist of two major groups, the mites that demonstrate a wide variety of life strategies, i.e., herbivory, predation and ectoparasitism, and ticks which have evolved obligatory hematophagy. The major sites of chemoreception in the acarines are the chelicerae, palps and tarsi on the forelegs. A unifying name, the "foretarsal sensory organ" (FSO), is proposed for the first time in this review for the sensory site on the forelegs of all acarines. The FSO has multiple sensory functions including olfaction, gustation, and heat detection. Preliminary transcriptomic data in ticks suggest that chemoreception in the FSO is achieved by a different mechanism from insects. There are a variety of laboratory and field bioassay methods that have been developed for the identification and characterization of attractants but minimal techniques for electrophysiology studies. Over the past three to four decades, significant progress has been made in the chemistry and analysis of function for acarine attractants in mites and ticks. In mites, attractants include aggregation, immature female, female sex and alarm pheromones; in ticks, the attraction-aggregation-attachment, assembly and sex pheromones; in mites and ticks host kairomones and plant allomones; and in mites, fungal allomones. There are still large gaps in our knowledge of chemical communication in the acarines compared to insects, especially relative to acarine pheromones, and more so for mites than ticks. However, the use of lure-and-kill and lure-enhanced biocontrol strategies has been investigated for tick and mite control, respectively, with significant environmental advantages which warrant further study. PMID:27265828

  2. Surface chemistry

    CERN Document Server

    Desai, KR

    2008-01-01

    The surface Chemistry of a material as a whole is crucially dependent upon the Nature and type of surfaces exposed on crystallites. It is therefore vitally important to independently Study different, well - defined surfaces through surface analytical techniques. In addition to composition and structure of surface, the subject also provides information on dynamic light scattering, micro emulsions, colloid Stability control and nanostructures. The present book endeavour to bring before the reader that the understanding and exploitation of Solid state phenomena depended largely on the ability to

  3. Surface chemistry essentials

    CERN Document Server

    Birdi, K S

    2013-01-01

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

  4. Impact of surface chemistry

    OpenAIRE

    Somorjai, Gabor A.; Li, Yimin

    2010-01-01

    The applications of molecular surface chemistry in heterogeneous catalyst technology, semiconductor-based technology, medical technology, anticorrosion and lubricant technology, and nanotechnology are highlighted in this perspective. The evolution of surface chemistry at the molecular level is reviewed, and the key roles of surface instrumentation developments for in situ studies of the gas–solid, liquid–solid, and solid–solid interfaces under reaction conditions are emphasized.

  5. Nanoscale surface chemistry

    OpenAIRE

    Madey, Theodore E.; Pelhos, Kalman; WU, QIFEI; Barnes, Robin; Ermanoski, Ivan; Chen, Wenhua; Kolodziej, Jacek J.; Rowe, John E.

    2002-01-01

    We report evidence in several experiments for nanometer-size effects in surface chemistry. The evidence concerns bimetallic systems, monolayer films of Pt or Pd on W(111) surfaces. Pyramidal facets with {211} faces are formed on annealing on physical monolayer of Pt, Pd on a W(111) substrate, and facet sizes increase with annealing temperature. We used synchrotron radiation-based soft x-ray photoemission to show that monolayer films of Pt, Pd, on W “float” on the outer surface, whereas multil...

  6. Organometallic chemistry of metal surfaces

    International Nuclear Information System (INIS)

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

  7. Surface chemistry theory and applications

    CERN Document Server

    Bikerman, J J

    2013-01-01

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

  8. Surface Chemistry in Nanoscale Materials

    Directory of Open Access Journals (Sweden)

    Alex V. Hamza

    2009-12-01

    Full Text Available Although surfaces or, more precisely, the surface atomic and electronic structure, determine the way materials interact with their environment, the influence of surface chemistry on the bulk of the material is generally considered to be small. However, in the case of high surface area materials such as nanoporous solids, surface properties can start to dominate the overall material behavior. This allows one to create new materials with physical and chemical properties that are no longer determined by the bulk material, but by their nanoscale architectures. Here, we discuss several examples, ranging from nanoporous gold to surface engineered carbon aerogels that demonstrate the tuneability of nanoporous solids for sustainable energy applications.

  9. Surface chemistry in photodissociation regions

    Science.gov (United States)

    Esplugues, G. B.; Cazaux, S.; Meijerink, R.; Spaans, M.; Caselli, P.

    2016-06-01

    Context. The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Aims: Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. Methods: We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. Results: We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in different environments. In addition, we study how chemistry is affected by the presence/absence of ice mantles (bare dust or icy dust) and the impact of considering different desorption probabilities. Conclusions: The type of substrate (bare dust or icy dust) and the probability of desorption can significantly alter the chemistry occurring on grain surfaces, leading to differences of several orders of magnitude in the abundances of gas-phase species, such as CO, H2CO, and CH3OH. The type of substrate, together with the density and intensity of the radiation field, also determine the threshold extinction to form ices of CO2 and H2O. We also conclude that H2CO and CH3OH are mainly released into the gas phase of low, far-ultraviolet illuminated PDRs through chemical desorption upon two-body surface reactions, rather than through photodesorption.

  10. Surface chemistry in photodissociation regions

    CERN Document Server

    Esplugues, G B; Meijerink, R; Spaans, M; Caselli, P

    2016-01-01

    The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in d...

  11. Surface Chemistry Enhanced Microbial Bioelectrocatalysis

    Science.gov (United States)

    Santoro, Carlo; Babanova, Sofia; Artyushkova, Kateryna; Cornejo, Jose’ A.; Ista, Linnea; Bretschger, Orianna; Marsili, Enrico; Atanassov, Plamen; Schuler, Andrew J.

    2016-01-01

    Self-assembled monolayers (SAMs) modified gold anodes are used in single chamber microbial fuel cells (SCMFC) for organics removal and electricity generation. Hydrophilic (−N(CH3)3+, −OH, −COOH) and hydrophobic (−CH3) SAMs are examined for their effect on bacterial attachment, current and power output. The different substratum chemistry affects both the current and power output and the community composition of the electrochemically active biofilm formed. Of the four SAM-modified anode tested, −N(CH3)3+ results in shortest start up time, highest single electrode polarization and power density, followed by −OH and –COOH SAMs. Hydrophobic SAM decreases bacteria attachment and anodes performance in comparison to hydrophilic SAMs. Electron transfer rate is faster on the N(CH3)3+-surface than on other surfaces, and correlates with a high abundance of δ-Proteobacteria, including electrochemically active species. A consortium of Clostridia and δ-Proteobacteria is found on all the anode surfaces, suggesting a synergistic cooperation under anodic conditions. PMID:26025340

  12. Surface chemistry of solid and liquid interfaces

    CERN Document Server

    Erbil, Husnu Yildirim

    2009-01-01

    A detailed understanding of the chemistry of surfaces and interfaces is required by many research personnel in the chemical and life science industries, as surfaces and interfaces play a critical role in many of the processes they seek to influence.Surface Chemistry of Solid and Liquid Interfaces provides a concise and easily accessible introduction to this fascinating subject. With a smooth evolution of ideas from familiar physical chemistry principles, the student can develop a sophisticated understanding of the chemistry of surfaces and interfaces. The book is also highly relevant to new re

  13. Evaluation of bioassays to monitor surface microlayer toxicity in tropical marine waters.

    Science.gov (United States)

    Rumbold, D G; Snedaker, S C

    1997-02-01

    Bioassays were developed, using embryos of: coral,Montastraea faveolata; graysby, Epinephelus cruentatus;grouper, Epinephelus adscensionis x gruttatus (hybrid); queenconch, Strombus gigas; rock-boring urchin, Echinodermatalucunter; spotted seatrout, Cynoscion nebulosus; variegatedurchin, Lytechinus variegatus; winged pearl oyster, Pteriacolymbus; and yellowtail snapper, Ocyurus chrysurus. Relativesensitivities and precison of various species-endpoint combinations wereevaluated using three reference toxicants: copper, sodium dodecyl sulfate,and Dibrom(R). The 24-h P. colymbus embryo test had the best overallsensitivity and exhibited a high degree of precision. However, oyster embryoswere difficult to obtain and did not aggregate at the air-water interface.Therefore, the P. colymbus embryo test was deemed unsuitable for useas a bioassay for monitoring sea-surface microlayer (SSML) toxicity. Testsbased on normal development of L. variegatus to the early pluteus 3stage and percent normal-live C. nebulosus larvae at 48 h wererelatively sensitive and exhibited good replicability and repeatability. TheL. variegatus urchin embryo test was also found to be highlyreproducible. The results of this comparative study indicated that L.variegatus and C. nebulosus were suitable surrogates forcoral-reef species in toxicity assessments of the SSML. PMID:9069187

  14. Desulfurization chemistry on tungsten surfaces

    International Nuclear Information System (INIS)

    Desulfurization on tungsten surfaces was studied by Auger spectroscopy, temperature programmed desorption, and infrared spectroscopy. Aliphatic compounds reacted by electrophilic interaction of sulfur with the surface. On sulfided surfaces adsorption occurred by disulfide linkages, but C-S bond scission required vacant metal sites. Thiophene underwent electrophilic attack on the ring at the α-carbon by metal sites

  15. Surface chemistry in three dimensions

    DEFF Research Database (Denmark)

    Bollinger, Mikkel; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    2000-01-01

    Based on self-consistent density functional calculations it is shown that a new dissociation process for CO adsorbed on a Ru(0001) surface is made possible when the distance to a second Ru(0001) surface placed just above it is below some critical value. This '3D' process is more facile than the u...

  16. Surface chemistry of "unprotected" nanoparticles

    DEFF Research Database (Denmark)

    Schrader, Imke; Warneke, Jonas; Neumann, Sarah;

    2015-01-01

    The preparation of colloidal nanoparticles in alkaline ethylene glycol is a powerful approach for the preparation of model catalysts and ligand-functionalized nanoparticles. For these systems the term "unprotected" nanoparticles has been established because no strongly binding stabilizers...... study. "Unprotected" Pt and Ru nanoparticles were characterized by NMR spectroscopy, which does not evidence the presence of any C-H containing species bound to the particle surface. Instead, the colloids were found to be covered by CO, as demonstrated by IR spectroscopy. However, analysis...

  17. The Plasma Chemistry of Polymer Surfaces

    CERN Document Server

    Friedrich, Jö

    2012-01-01

    This book illustrates plasma properties, polymer characteristics, surface specifics, and how to purposefully combine plasma and polymer chemistry. In so doing, it covers plasma polymerization, surface functionalization, etching, crosslinking, and deposition of monotype functional-group-bearing plasma polymers. It explains different techniques and plasma types, such as pressure-pulsed, remote, low-wattage plasmas and plasma polymerization in liquids. Finally, among the numerous applications discussed are plasmas for chemical synthesis, industrial processes or the modification of membranes and p

  18. Chip-Scale Bioassays Based on Surface-Enhanced Raman Scattering: Fundamentals and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Hye-Young Park

    2005-12-17

    This work explores the development and application of chip-scale bioassays based on surface-enhanced Raman scattering (SERS) for high throughput and high sensitivity analysis of biomolecules. The size effect of gold nanoparticles on the intensity of SERS is first presented. A sandwich immunoassay was performed using Raman-labeled immunogold nanoparticles with various sizes. The SERS responses were correlated to particle densities, which were obtained by atomic force microscopy (AFM). The response of individual particles was also investigated using Raman-microscope and an array of gold islands on a silicon substrate. The location and the size of individual particles were mapped using AFM. The next study describes a low-level detection of Escherichia coli 0157:H7 and simulants of biological warfare agents in a sandwich immunoassay format using SERS labels, which have been termed Extrinsic Raman labels (ERLs). A new ERL scheme based on a mixed monolayer is also introduced. The mixed monolayer ERLs were created by covering the gold nanoparticles with a mixture of two thiolates, one thiolate for covalently binding antibody to the particle and the other thiolate for producing a strong Raman signal. An assay platform based on mixed self-assembled monolayers (SAMs) on gold is then presented. The mixed SAMs were prepared from dithiobis(succinimidyl undecanoate) (DSU) to covalently bind antibodies on gold substrate and oligo(ethylene glycol)-terminated thiol to prevent nonspecific adsorption of antibodies. After the mixed SAMs surfaces, formed from various mole fraction of DSU were incubated with antibodies, AFM was used to image individual antibodies on the surface. The final study presents a collaborative work on the single molecule adsorption of YOYO-I labeled {lambda}-DNA at compositionally patterned SAMs using total internal reflection fluorescence microscopy. The role of solution pH, {lambda}-DNA concentration, and domain size was investigated. This work also revealed

  19. The Surface Chemistry of Metal Chalcogenide Nanocrystals

    Science.gov (United States)

    Anderson, Nicholas Charles

    The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu

  20. Surface chemistry and mineralogy. [of planet Mars

    Science.gov (United States)

    Banin, A.; Clark, B. C.; Waenke, H.

    1992-01-01

    The accumulated knowledge on the chemistry and mineralogy of Martian surface materials is reviewed. Pertinent information obtained by direct analyses of the soil on Mars by the Viking Landers, by remote sensing of Mars from flyby and orbiting spacecraft, by telescopic observations from earth, and through detailed analyses of the SNC meteorites presumed to be Martian rocks are summarized and analyzed. A compositional model for Mars soil, giving selected average elemental concentrations of major and trace elements, is suggested. It is proposed that the fine surface materials on Mars are a multicomponent mixture of weathered and nonweathered minerals. Smectite clays, silicate mineraloids similar to palagonite, and scapolite are suggested as possible major candidate components among the weathered minerals.

  1. Bioassay-guided extraction of crude fucose-containing sulphated polysaccharides from Sargassum fusiforme with response surface methodology

    Science.gov (United States)

    Fu, Zhifei; Li, Haihua; Liu, Hongbing; Hu, Shuman; Li, Yueying; Wang, Mengxue; Guan, Huashi

    2016-06-01

    The response surface methodology (RSM) combined with bioassays was employed to optimize the extraction process of crude fucose-containing sulphated polysaccharides (cFCSP) from Sargassum fusiforme. The central composite design (CCD) was used with four variables, five levels, and four responses. The four variables were pH value of hydrochloric acid solution, extraction temperature (°C), ratio of liquid to raw material (mL g-1), and extraction time (h), respectively. Chemical and bioassay indices were used in combination as the response parameters, which included the yield of cFCSP, fucose content, proliferation rate of spleen cells, and lipopolysaccharide-induced proliferation of splenocytes. The experimental data were fitted to a second-order polynomial equation using multiple regression analysis, and examined using the appropriate statistical methods. The best extraction conditions were as follows: the pH value of hydrochloric acid solution was 3.50; the extraction temperature was 100°C; the ratio of liquid to raw material was 15.00 mL g-1 and the extraction time was 2.50 h. The experimental yield was close to the predicted from the model. The extract could promote spleen lymphocyte proliferation, especially the lipopolysaccharide-induced lymphocyte proliferation in vitro, which suggested that its immunomodulatory effect on B lymphocytes. Therefore, cFCSP extracted from S. fusiforme could be utilized as an immunostimulant in functional foods and pharmaceutical industry in future.

  2. Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides

    OpenAIRE

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

    1996-01-01

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

  3. Surface chemistry: Key to control and advance myriad technologies

    OpenAIRE

    Yates, John T.; Campbell, Charles T.

    2011-01-01

    This special issue on surface chemistry is introduced with a brief history of the field, a summary of the importance of surface chemistry in technological applications, a brief overview of some of the most important recent developments in this field, and a look forward to some of its most exciting future directions. This collection of invited articles is intended to provide a snapshot of current developments in the field, exemplify the state of the art in fundamental research in surface chemi...

  4. Bioinspired catecholic chemistry for surface modification.

    Science.gov (United States)

    Ye, Qian; Zhou, Feng; Liu, Weimin

    2011-07-01

    The attachment strategy based on catecholic chemistry has been arousing renewed interest since the work on polymerized catecholic amine (polydopamine) (Messersmith et al., Science, 2007, 318, 426) was published. Catechols and their derived compounds can self-assemble on various inorganic and organic materials, including noble metals, metals, metal oxides, mica, silica, ceramics and even polymers. It opens a new route to the modification of various substrates and the preparation of functional composite materials by simple chemistry. However, there is still not a full review so far about the attachment chemistry despite the dramatically increasing number of publications. This critical review describes the state-of-the-art research in the area: the design and synthesis of catecholic molecules, their adsorption mechanisms and the stability of assemblies in solution, and their applications etc. Some perspectives on future development are raised (195 references). PMID:21603689

  5. Surface Chemistry in Heterogeneous Catalysis: An Emerging Discipline.

    Science.gov (United States)

    White, J. M.; Campbell, Charles T.

    1980-01-01

    Provides background data on surface chemistry as an emerging discipline. Highlights the important role which surfaces play in catalysis by focusing on the catalyzed oxidation of carbon monoxide. Provides a demonstration of how surfaces exert their influences in heterogeneous phenomena and illustrates how experimental problems in this field are…

  6. Integrin binding specificity regulates biomaterial surface chemistry effects on cell differentiation

    OpenAIRE

    Keselowsky, Benjamin G.; Collard, David M.; Andrés J. García

    2005-01-01

    Biomaterial surface chemistry has profound consequences on cellular and host responses, but the underlying molecular mechanisms remain poorly understood. Using self-assembled monolayers as model biomaterial surfaces presenting well defined chemistries, we demonstrate that surface chemistry modulates osteoblastic differentiation and matrix mineralization independently from alterations in cell proliferation. Surfaces were precoated with equal densities of fibronectin (FN), and surface chemistry...

  7. Gas Plasma Surface Chemistry for Biological Assays.

    Science.gov (United States)

    Sahagian, Khoren; Larner, Mikki

    2015-01-01

    Biological systems respond to and interact with surfaces. Gas plasma provides a scalable surface treatment method for designing interactive surfaces. There are many commercial examples of plasma-modified products. These include well plates, filtration membranes, dispensing tools, and medical devices. This chapter presents an overview of gas plasma technology and provides a guide to using gas plasma for modifying surfaces for research or product development. PMID:26160577

  8. Chemistry - Toward efficient hydrogen production at surfaces

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Christensen, Claus H.

    2006-01-01

    Calculations are providing a molecular picture of hydrogen production on catalytic surfaces and within enzymes, knowledge that may guide the design of new, more efficient catalysts for the hydrogen economy.......Calculations are providing a molecular picture of hydrogen production on catalytic surfaces and within enzymes, knowledge that may guide the design of new, more efficient catalysts for the hydrogen economy....

  9. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    OpenAIRE

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

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, ...

  10. Surface chemistry of mineral powders: 1

    International Nuclear Information System (INIS)

    Low surface areas of non-porous mineral and oxide powders have been determined by adsorption calorimetry to a precision of +-15 percent. Five standards with surface areas in the range 0.64 to 24.3 m2/g were examined to check the internal consistency of our method. Our surface area values agree within +-10 percent with supplied values, obtained by the Brunauer, Emmett and Teller (BET) nitrogen adsorption technique at -196 deg C. The present technique is less time consuming than commercial systems and requires small sample size (< 1 g per run). Also, the technique works at 25 degrees C, rather than at -196 degrees C, and can be adapted for routine operation. Finally, the technique appears preferable to a relatively tedious gas-solid chromatographic method, which uses large samples (200 to 300 g), and yields values in poor agreement with BET results

  11. 2D chemistry on Au(111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rauls, Eva; Blankenburg, Stephan; Schmidt, Wolf Gero [Theoretische Physik, Universitaet Paderborn (Germany)

    2009-07-01

    The design of functional two-dimensional molecular networks has become an area of intense research. The constraint to 2 in contrast to the availability of 3 dimensions has a large impact on many chemical reactions. Chemical reactions between surface adsorbed molecules may lead to products very different from those obtained in solutions or the gas phase. The imide formation between a diaminoterphenyl (DATP) and a PTCDA molecule is one very interesting example in this respect. In scanning tunneling microscopy (STM) experiments, it has been observed that the Au surface changes both the reaction path and the reaction product compared to 3D. In order to understand these experimental observations, we have studied the chemical reactions both in solution and on the Au(111) surface by density-functional theory calculations in the generalized-gradient approximation.

  12. Organic chemistry on Titan: Surface interactions

    Science.gov (United States)

    Thompson, W. Reid; Sagan, Carl

    1992-01-01

    The interaction of Titan's organic sediments with the surface (solubility in nonpolar fluids) is discussed. How Titan's sediments can be exposed to an aqueous medium for short, but perhaps significant, periods of time is also discussed. Interactions with hydrocarbons and with volcanic magmas are considered. The alteration of Titan's organic sediments over geologic time by the impacts of meteorites and comets is discussed.

  13. SOIL CHEMISTRY AND MINERALOGY: SURFACE COMPLEXATION MODELING

    Science.gov (United States)

    Ion adsorption in soils has been described using both empirical and chemical models. Empirical adsorption isotherm equations will be presented and their limitations discussed. Chemical surface complexation models and their applications to soils will be introduced. Advantages and limitations of su...

  14. Gas-grain chemistry in cold interstellar cloud cores with a microscopic Monte Carlo approach to surface chemistry

    OpenAIRE

    Chang, Q; Cuppen, H. M.; Herbst, E.

    2007-01-01

    AIM: We have recently developed a microscopic Monte Carlo approach to study surface chemistry on interstellar grains and the morphology of ice mantles. The method is designed to eliminate the problems inherent in the rate-equation formalism to surface chemistry. Here we report the first use of this method in a chemical model of cold interstellar cloud cores that includes both gas-phase and surface chemistry. The surface chemical network consists of a small number of diffusive reactions that c...

  15. Quantification of air plasma chemistry for surface disinfection

    Science.gov (United States)

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

    2014-12-01

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

  16. Quantification of air plasma chemistry for surface disinfection

    International Nuclear Information System (INIS)

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

  17. Density functional theory in surface chemistry and catalysis

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  18. Density Functional Theory in Surface Chemistry and Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Norskov, Jens

    2011-05-19

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

  19. Smart Surface Chemistries of Conducting Polymers

    DEFF Research Database (Denmark)

    Lind, Johan Ulrik

    In this thesis we investigate post-polymerization covalent modifications of poly(3,4-dioxythiophene (PEDOT)-type conducting polymers. The aim of the modifications is to gain specific control of the interaction between the material and living mammalian cells. The use of “click-chemistry” to modify......-N3 thin film substrates. Complementing these findings, we introduce a novel technique for fabricating surface chemical gradients on PEDOT-N3 substrates. The technique is based on applying “electro-click chemistry” to locally induce covalent modifications. Further supplementing these results, we...... fabrication of dense poly-ethylene-glycol-coatings of the conducting polymer substrates. These coatings render the substrates resistant to protein adsorption. Hence, the choice of solvent is found to be a key parameter for achieving functional post-polymerization modifications of PEDOT-N3. The methods...

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

    CERN Document Server

    Busca, Guido

    2014-01-01

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

  1. Surface chemistry and durability of borosilicate glass

    International Nuclear Information System (INIS)

    Important glass-water interactions are poorly understood for borosilicate glass radioactive waste forms. Preliminary results show that glass durability is dependent on reactions occurring at the glass-solution interface. CSG glass (18.2 wt. % Na2O, 5.97 wt. % CaO, 11.68 wt. % Al2O3, 8.43 wt. % B2O3, and 55.73 wt. % SiO2) dissolution and net surface H+ and OH- adsorption are minimal at near neutral pH. In the acid and alkaline pH regions, CSG glass dissolution rates are proportional to [H+]adsorbed2 and [OH-]adsorbed0.8, respectively. In contrast, silica gel dissolution and net H+ and OH- adsorption are minimal and independent of pH in acid to neutral solutions. In the alkaline pH region, silica gel dissolution is proportional to [OH-]adsorbed0.9adsorbed. Although Na adsorption is significant for CSG glass and silica gel in the alkaline pH regions, it is not clear if it enhances dissolution, or is an artifact of depolymerization of the framework bonds

  2. Gas-grain chemistry in cold interstellar cloud cores with a microscopic Monte Carlo approach to surface chemistry

    CERN Document Server

    Chang, Q; Herbst, E

    2007-01-01

    AIM: We have recently developed a microscopic Monte Carlo approach to study surface chemistry on interstellar grains and the morphology of ice mantles. The method is designed to eliminate the problems inherent in the rate-equation formalism to surface chemistry. Here we report the first use of this method in a chemical model of cold interstellar cloud cores that includes both gas-phase and surface chemistry. The surface chemical network consists of a small number of diffusive reactions that can produce molecular oxygen, water, carbon dioxide, formaldehyde, methanol and assorted radicals. METHOD: The simulation is started by running a gas-phase model including accretion onto grains but no surface chemistry or evaporation. The starting surface consists of either flat or rough olivine. We introduce the surface chemistry of the three species H, O and CO in an iterative manner using our stochastic technique. Under the conditions of the simulation, only atomic hydrogen can evaporate to a significant extent. Althoug...

  3. Engineered microtopographies and surface chemistries direct cell attachment and function

    Science.gov (United States)

    Magin, Chelsea Marie

    Harrison, in 1914, first recognized that cells respond to physicochemical cues such as substratum topography when he observed that fibroblasts elongated while cultured on spider silk. Recently, techniques developed in the micro-electronics industry have been used to create molds for producing microscaled topographies with various shapes and spatial arrangements. Although these patterning techniques are well-established, very little is known about the mechanisms underlying cell sensing and response to microtopographies. In this work cellular micro-environments with varying surface topographies and chemistries were evaluated with marine organisms and mammalian cells to investigate cellular sensing and response. Biofouling---the accumulation of micro-organisms, plants, and animals on submerged surfaces---is an environmental and economic concern. Engineered topographies, replicated in polydimethylsiloxane elastomer (PDMSe) and functionalized poly(ethylene glycol)-dimethacrylate (PEGDMA) hydrogels, were evaluated for inhibition of marine fouling organism attachment. Microtopographies replicated in PDMSe inhibited attachment of the marine bacterium, Cobetia marina up to 99% versus smooth. The average normalized attachment densities of cells of C. marina and zoospores of the green algae Ulva on PDMSe topographies scaled inversely with the Engineered Roughness Index (ERIII), a representation of surface energy. Attachment densities of Ulva from four assays and C. marina from two growth phases to PDMSe surfaces scaled inversely with one equation: ERI II multiplied by the Reynolds number of the organism (Re) (R 2 = 0.77). The same microtopographies created in PDMSe reduced the initial attachment density and attachment strength of cells of the diatoms Navicula incerta and Seminavis robusta compared to smooth PDMSe. The average normalized attachment density of Navicula after exposure to shear stress (48 Pa) was correlated with the contact area between the diatom and a

  4. Influence of surface chemistry on inkjet printed carbon nanotube films

    International Nuclear Information System (INIS)

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

  5. Ferroelectrics: A pathway to switchable surface chemistry and catalysis

    Science.gov (United States)

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

    2016-08-01

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

  6. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    Science.gov (United States)

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

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

  7. Quantitative Evaluation of Bioorthogonal Chemistries for Surface Functionalization of Nanoparticles

    DEFF Research Database (Denmark)

    Feldborg, Lise Nørkjær; Jølck, Rasmus Irming; Andresen, Thomas Lars

    2012-01-01

    -of-the-art conjugation reactions in the field. Targeted liposomes that recognize overexpressed receptors or antigens on diseased cells have great potential in therapeutic and diagnostic applications. However, chemical modifications of nanoparticle surfaces by postfunctionalization approaches are less effective than in...... variety of functionalities that have been used for surface conjugation of nanoparticles. The reaction kinetics and overall yield were quantified by HPLC. Reactions were conducted in solution as well as by postfunctionalization of liposomes in order to study the effects of steric hindrance and possible...... affinity between the peptide and the liposome surface. These studies demonstrate the importance of hoosing the correct chemistry in order to obtain a quantitative surface functionalization of liposomes....

  8. Gridded global surface ozone metrics for atmospheric chemistry model evaluation

    Directory of Open Access Journals (Sweden)

    E. D. Sofen

    2015-07-01

    Full Text Available The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent dataset for the evaluation of chemical transport and chemistry-climate (Earth System models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total dataset of approximately 6600 sites and 500 million hourly observations from 1971–2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regional background locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This dataset is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily eight-hour average (MDA8, SOMO35, AOT40, and metrics related to air quality regulatory thresholds. Gridded datasets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi:10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452. We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

  9. Gridded global surface ozone metrics for atmospheric chemistry model evaluation

    Science.gov (United States)

    Sofen, E. D.; Bowdalo, D.; Evans, M. J.; Apadula, F.; Bonasoni, P.; Cupeiro, M.; Ellul, R.; Galbally, I. E.; Girgzdiene, R.; Luppo, S.; Mimouni, M.; Nahas, A. C.; Saliba, M.; Tørseth, K.

    2016-02-01

    The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent data set for the evaluation of chemical transport and chemistry-climate (Earth System) models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total data set of approximately 6600 sites and 500 million hourly observations from 1971-2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regionally representative locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This data set is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily 8-hour average (MDA8), sum of means over 35 ppb (daily maximum 8-h; SOMO35), accumulated ozone exposure above a threshold of 40 ppbv (AOT40), and metrics related to air quality regulatory thresholds. Gridded data sets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi: 10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452). We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

  10. Quantifying the surface chemistry of 3D matrices in situ

    Science.gov (United States)

    Tzeranis, Dimitrios S.; So, Peter T. C.; Yannas, Ioannis V.

    2014-03-01

    Despite the major role of the matrix (the insoluble environment around cells) in physiology and pathology, there are very few and limited methods that can quantify the surface chemistry of a 3D matrix such as a biomaterial or tissue ECM. This study describes a novel optical-based methodology that can quantify the surface chemistry (density of adhesion ligands for particular cell adhesion receptors) of a matrix in situ. The methodology utilizes fluorescent analogs (markers) of the receptor of interest and a series of binding assays, where the amount of bound markers on the matrix is quantified via spectral multi-photon imaging. The study provides preliminary results for the quantification of the ligands for the two major collagen-binding integrins (α1β1, α2β1) in porous collagen scaffolds that have been shown to be able to induce maximum regeneration in transected peripheral nerves. The developed methodology opens the way for quantitative descriptions of the insoluble microenvironment of cells in physiology and pathology, and for integrating the matrix in quantitative models of cell signaling. α

  11. Modulation of human osteoblasts by metal surface chemistry.

    Science.gov (United States)

    Hofstetter, Wilhelm; Sehr, Harald; de Wild, Michael; Portenier, Jeannette; Gobrecht, Jens; Hunziker, Ernst B

    2013-08-01

    The use of metal implants in dental and orthopedic surgery is continuously expanding and highly successful. While today longevity and load-bearing capacity of the implants fulfill the expectations of the patients, acceleration of osseointegration would be of particular benefit to shorten the period of convalescence. To further clarify the options to accelerate the kinetics of osseointegration, within this study, the osteogenic properties of structurally identical surfaces with different metal coatings were investigated. To assess the development and function of primary human osteoblasts on metal surfaces, cell viability, differentiation, and gene expression were determined. Titanium surfaces were used as positive, and surfaces coated with gold were used as negative controls. Little differences in the cellular parameters tested for were found when the cells were grown on titanium discs sputter coated with titanium, zirconium, niobium, tantalum, gold, and chromium. Cell number, activity of cell layer-associated alkaline phosphatase (ALP), and levels of transcripts encoding COL1A1 and BGLAP did not vary significantly in dependence of the surface chemistry. Treatment of the cell cultures with 1,25(OH)2 D3 /Dex, however, significantly increased ALP activity and BGLAP messenger RNA levels. The data demonstrate that the metal layer coated onto the titanium discs exerted little modulatory effects on cell behavior. It is suggested that the microenvironment regulated by the peri-implant tissues is more effective in regulating the tissue response than is the material of the implant itself. PMID:23359530

  12. The chemistry and physics of zinc oxide surfaces

    Science.gov (United States)

    Wöll, Christof

    Metal oxides are virtually everywhere - only gold has the property not to form an oxide on its surface when exposed to the ambient. As a result, understanding the physics and chemistry of oxide surfaces is a topic of pronounced general interest and, of course, also a necessary prerequisite for many technical applications. The most important of these is certainly heterogeneous catalysis, but one has to realize that - under ambient conditions - virtually all phenomena occurring at liquid/metal and gas/metal interfaces are determined by the corresponding oxide. This applies in particular to friction phenomena, adhesion and corrosion. A necessary - but not necessarily sufficient - condition for unravelling the fundamentals governing this complex field is to analyze in some detail elementary chemical and physical processes at oxide surfaces. Although the Surface Science of metal surfaces has seen a major progress in the past decades, for oxides detailed experimental investigations for well-defined single crystal surfaces still represent a formidable challenge - mostly because of technical difficulties (charging), but to some extent also due to fundamental problems related to the stabilization of polar surfaces. As a result, the amount of information available for this class of materials is - compared to that at hand for metals - clearly not satisfactory. A particular disturbing lack of information is that about the presence of hydrogen at oxide surfaces - either as hydroxy-species or in form of metal hydrides. In the present review we will summarize recent experimental and theoretical information which has become available from single crystal studies on ZnO surfaces. While the number of papers dealing with another oxide, rutile TiO 2, is significantly larger (although titania does not exhibit a polar surface), also for zinc oxide a basis of experimental and theoretical knowledge as been accumulated, which - at least for the non-polar surfaces - allows to understand

  13. Surface chemistry interventions to control boiler tube fouling - Part II

    International Nuclear Information System (INIS)

    This is the third in a series of reports from an investigation co-funded by the Electric Power Research Institute (EPRI) and by Atomic Energy of Canada Limited (AECL) into the effectiveness of alternative amines for controlling the rate of tube-bundle fouling under steam generator (SG) operating conditions. The objectives of this investigation are to determine whether the fouling rate depends on the amine used for pH control, to identify those factors that influence the effectiveness, and use this information to optimize the selection of an amine for chemistry control and deposit control in the steam cycle and steam generator, respectively. Work to date has demonstrated that the rate of particle deposition under steam generator operating conditions is strongly influenced by surface chemistry (Turner et al., 1997; Turner et al., 1999). This dependence upon surface chemistry is illustrated by the difference between the deposition rates measured for hematite and magnetite, and by the dependence of the particle deposition rate on the amine used for pH control. Deposition rates of hematite were found to be more than 10 times greater than those for magnetite under similar test conditions (Turner et al., 1997). At 270oC and pHT 6.2, the surfaces of hematite and magnetite are predicted to be positively charged and negatively charged, respectively (Shoonen, 1994). Measurements of the point of zero charge (PZC) of magnetite at temperatures from 25oC to 290oC by Wesolowski et al. (1999) have confirmed that magnetite is negatively charged at the stated conditions. A PZC of 4.2 was measured for Alloy 600 at 25oC (Balakrishnan and Turner, un-published results), and its surface is expected to remain negatively charged for alkaline chemistry over the temperature range of interest. Therefore, there will be a repulsive force between the surfaces of magnetite particles and Alloy 600 at 270oC and pHT 6.2 that is absent for hematite particles depositing under the same conditions. This

  14. Surface chemistry of CO2 - Adsorption of carbon dioxide on clean surfaces at ultrahigh vacuum

    Science.gov (United States)

    Burghaus, Uwe

    2014-05-01

    Carbon dioxide chemistry has attracted significant interest in recent years. Although the field is diverse, a current and more comprehensive review of the surface science literature may be of interest for a variety of communities since environmental chemistry, energy technology, materials science, catalysis, and nanocatalysis are certainly affected by gas-surface properties. The review describes surface phenomena and characterization strategies highlighting similarities and differences, instead of providing only a list of system-specific information. The various systems are roughly distinguished as those that clearly form carbonates and those that merely physisorb CO2 at ultra-high vacuum conditions. Nevertheless, extended sections about specific systems including rarely studied surfaces and unusual materials are included, making this review also useful as a reference.

  15. Tailoring on-surface chemistry of (hetero)aromatics on transition metal surfaces

    OpenAIRE

    Pinardi, Anna Lisa

    2013-01-01

    This thesis deals about on-surface chemistry, one of the most powerful bottom-up approaches employed in nanotechnology to assemble molecular networks, and driving to a modification of the structure and the electronic properties of the deposited organic molecules. A subject of fundamental relevance and technological importance. In the experimental work of the thesis, different organic molecule-metal systems have been grown and analysed in depth with Ultra High Vacuum surface science techni...

  16. What's on the Surface? Physics and Chemistry of Delta-Doped Surfaces

    Science.gov (United States)

    Hoenk, Michael

    2011-01-01

    Outline of presentation: 1. Detector surfaces and the problem of stability 2. Delta-doped detectors 3. Physics of Delta-doped Silicon 4. Chemistry of the Si-SiO2 Interface 5. Physics and Chemistry of Delta-doped Surfaces a. Compensation b. Inversion c. Quantum exclusion. Conclusions: 1. Quantum confinement of electrons and holes dominates the behavior of delta-doped surfaces. 2. Stability of delta-doped detectors: Delta-layer creates an approx 1 eV tunnel barrier between bulk and surface. 3. At high surface charge densities, Tamm-Shockley states form at the surface. 4. Surface passivation by quantum exclusion: Near-surface delta-layer suppresses T-S trapping of minority carriers. 5. The Si-SiO2 interface compensates the surface 6. For delta-layers at intermediate depth, surface inversion layer forms 7. Density of Si-SiO2 interface charge can be extremely high (>10(exp 14)/sq cm)

  17. Plant surface reactions: an ozone defence mechanism impacting atmospheric chemistry

    Directory of Open Access Journals (Sweden)

    W. Jud

    2015-07-01

    Full Text Available Elevated tropospheric ozone concentrations are considered a toxic threat to plants, responsible for global crop losses with associated economic costs of several billion dollars per year. Plant injuries have been linked to the uptake of ozone through stomatal pores and oxidative damage of the internal leaf tissue. But a striking question remains: how much ozone effectively enters the plant through open stomata and how much is lost by chemical reactions at the plant surface? In this laboratory study we could show that semi-volatile organic compounds exuded by the glandular trichomes of different Nicotiana tabacum varieties are an efficient ozone sink at the plant surface. In our experiments, different diterpenoid compounds were responsible for a strongly variety dependent ozone uptake of plants under dark conditions, when stomatal pores are almost closed. Surface reactions of ozone were accompanied by prompt release of oxygenated volatile organic compounds, which could be linked to the corresponding precursor compounds: ozonolysis of cis-abienol (C20H34O – a diterpenoid with two exocyclic double bonds – caused emissions of formaldehyde (HCHO and methyl vinyl ketone (C4H6O. The ring-structured cembratrien-diols (C20H34O2 with three endocyclic double bonds need at least two ozonolysis steps to form volatile carbonyls such as 4-oxopentanal (C5H8O2, which we could observe in the gas phase, too. Fluid dynamic calculations were used to model ozone distribution in the diffusion limited leaf boundary layer under daylight conditions. In the case of an ozone-reactive leaf surface, ozone gradients in the vicinity of stomatal pores are changed in such a way, that ozone flux through the open stomata is strongly reduced. Our results show that unsaturated semi-volatile compounds at the plant surface should be considered as a source of oxygenated volatile organic compounds, impacting gas phase chemistry, as well as efficient ozone sink improving the ozone

  18. Role of Surface Chemistry in Nanoscale Electrokinetic Transport

    Science.gov (United States)

    Atalay, Selcuk

    This dissertation work presents the efforts to study the electrofluidics phenomena, with a focus on surface charge properties in nanoscale systems with the potential applications in imaging, energy conversion, ultrafiltration, DNA analysis/sequencing, DNA and protein transport, drug delivery, biological/chemical agent detection and micro/nano chip sensors. Since the ion or molecular or particle transport and also liquid confinement in nano-structures are strongly dominated by the surface charge properties, in regards of the fundamental understanding of electrofluidics at nanoscale, we have used surface charge chemistry properties based on 2-pK charging mechanism. Using this mechanism, we theoretically and analytically showed the surface charge properties of silica nanoparticles as a function of their size, pH level and salt ionic strength of aqueous solution. For a fixed particle size, the magnitude of the surface charge typically increases with an increase in pH or background salt concentration. Furthermore, we investigated the surface charge properties of a charged dielectric nanoparticle and flat wall in electrostatic interactions. According to the theoretical results strong interactions cause a non-uniform surface charge density on the nanoparticle and the plate as a result of the enhancement of proton concentration in the gap between the particle and the plate. This effect increases with decreased separation distance (Kh). We moreover investigated the ion confinement inside the nanospaces and using a continuum model, we showed the proton enhancement in extended nanochannels. The proton enrichment at the center of the nanochannel is significant when the bulk pH is medium high and the salt concentration is relatively low. The results gathered are informative for the development of biomimetic nanofluidic apparatuses and the interpretation of relevant experimental data. Later, we have developed an analytical model for electroosmotic ion transport inside p

  19. Surface Chemistry at Size-Selected Nano-Aerosol Particles

    Science.gov (United States)

    Roberts, Jeffrey

    2005-03-01

    A method has been developed to conduct surface chemistry and extract surface kinetic rates from size-selected aerosol nanoparticles. The measurements encompass broad ranges of particle size, phase, and composition. Results will be presented on the uptake of water by aerosolized soot nanoparticles of radius between 10 and 40 nm. Water uptake was monitored by tandem differential mobility analysis (T-DMA), which is capable of measuring changes in particle diameter as little as 0.2 nm. Soot particles were produced in an ethene diffusion flame and extracted into an atmospheric pressure aerosol flow tube reactor. The particles were subjected to various thermal and oxidative treatments, and the effects of these treatments on the ability of soot to adsorb monolayer quantities of water was determined. The results are important because soot nucleates atmospheric cloud particles. More generally, the results represent one of the first kinetic and mechanistic studies of gas-phase nanoparticle reactivity. Co-author: Henry Ajo, University of Minnesota

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

    Science.gov (United States)

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

    2016-01-01

    Temporal evolution of surface chemistry during oxidation of silicon quantum dot (Si-QD) surfaces were probed using surface-enhanced Raman scattering (SERS). A monolayer of hydrogen and chlorine terminated plasma-synthesized Si-QDs were spin-coated on silver oxide thin films. A clearly enhanced signal of surface modes, including Si-Clx and Si-Hx modes were observed from as-synthesized Si-QDs as a result of the plasmonic enhancement of the Raman signal at Si-QD/silver oxide interface. Upon oxidation, a gradual decrease of Si-Clx and Si-Hx modes, and an emergence of Si-Ox and Si-O-Hx modes have been observed. In addition, first, second and third transverse optical modes of Si-QDs were also observed in the SERS spectra, revealing information on the crystalline morphology of Si-QDs. An absence of any of the abovementioned spectral features, but only the first transverse optical mode of Si-QDs from thick Si-QD films validated that the spectral features observed from Si-QDs on silver oxide thin films are originated from the SERS effect. These results indicate that real-time SERS is a powerful diagnostic tool and a novel approach to probe the dynamic surface/interface chemistry of quantum dots, especially when they involve in oxidative, catalytic, and electrochemical surface/interface reactions. PMID:27389331

  1. Reproductive toxicity assessment of surface water of the Tai section of the Yangtze River, China by in vitro bioassays coupled with chemical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xiaoyi [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China); Jiangsu Academy of Environmental Science, Nanjing 210036 (China); Wu Jiang [Laboratory of Immunology and Reproductive Biology, School of Medicine, Nanjing University, Nanjing 210093 (China); Hao Yingqun [Environmental Monitoring Center of Jiangsu Province, Nanjing 210036 (China); Zhu Bingqing [State Key Laboratory in Marine Pollution, Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong (Hong Kong); Shi Wei [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China); Hu Guanjiu [Environmental Monitoring Center of Jiangsu Province, Nanjing 210036 (China); Han Xiaodong [Laboratory of Immunology and Reproductive Biology, School of Medicine, Nanjing University, Nanjing 210093 (China); Giesy, John P. [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China); State Key Laboratory in Marine Pollution, Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong (Hong Kong); Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan (Canada); Zoology Department, College of Science, King Saud University, Riyadh (Saudi Arabia); Yu Hongxia, E-mail: yuhx@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China)

    2011-10-15

    Reproductive toxicity of organic extracts of the surface water from the Tai section of the Yangtze River was assessed by in vitro cytotoxity assays and selected persistent organic pollutants including PCBs, OCPs and PAHs were quantified by instrumental analysis. Eleven of the US EPA priority PAHs were detected. Individual PAHs were found to range from 0.7 to 20 ng/L. Concentrations of BaP did not exceed the national drinking water source quality standard of China. However, a 286-fold concentrated organic extract induced significant reproductive toxicity in adult male rats. The morphology of cells, MTT assay and LDH release assay were all affected by exposure to the organic extracts of water. The results of the reproductive toxicity indicated that PAHs posed the greatest risk of the chemicals studied. The compounds present in the water could be bioconcentrated and result in adverse effects. - Highlights: > Only 11 PAHs of US EPA priority PAHs were detected in surface water the Yangtze River. > Level of BaP didn't exceed national drinking water source quality standard of China. > 286-fold concentrated organic extracts induced great reproductive toxicity in rats. > PAHs posed the greatest risk of the chemicals studied. > The compounds in the water could be bioconcentrated and result in adverse effects. - In vitro bioassay responses observed in Yangtze River source water extracts showed great reproductive toxicity, and PAHs were responsible.

  2. Reproductive toxicity assessment of surface water of the Tai section of the Yangtze River, China by in vitro bioassays coupled with chemical analysis

    International Nuclear Information System (INIS)

    Reproductive toxicity of organic extracts of the surface water from the Tai section of the Yangtze River was assessed by in vitro cytotoxity assays and selected persistent organic pollutants including PCBs, OCPs and PAHs were quantified by instrumental analysis. Eleven of the US EPA priority PAHs were detected. Individual PAHs were found to range from 0.7 to 20 ng/L. Concentrations of BaP did not exceed the national drinking water source quality standard of China. However, a 286-fold concentrated organic extract induced significant reproductive toxicity in adult male rats. The morphology of cells, MTT assay and LDH release assay were all affected by exposure to the organic extracts of water. The results of the reproductive toxicity indicated that PAHs posed the greatest risk of the chemicals studied. The compounds present in the water could be bioconcentrated and result in adverse effects. - Highlights: → Only 11 PAHs of US EPA priority PAHs were detected in surface water the Yangtze River. → Level of BaP didn't exceed national drinking water source quality standard of China. → 286-fold concentrated organic extracts induced great reproductive toxicity in rats. → PAHs posed the greatest risk of the chemicals studied. → The compounds in the water could be bioconcentrated and result in adverse effects. - In vitro bioassay responses observed in Yangtze River source water extracts showed great reproductive toxicity, and PAHs were responsible.

  3. The relationship of surface chemistry and albedo of lunar soil samples

    Science.gov (United States)

    Gold, T.; Bilson, E.; Baron, R. L.

    1977-01-01

    A relation between the albedo and the surface iron concentration (determined by Auger electron spectroscopy) of lunar soil samples is described. The effect of solar wind sputtering on the surface chemistry and albedo of the soil is discussed.

  4. Ettringite surface chemistry: Interplay of electrostatic and ion specificity.

    Science.gov (United States)

    Medala, Marta; Labbez, Christophe; Pochard, Isabelle; Nonat, André

    2011-02-15

    This paper presents a detailed experimental study combined with Monte Carlo (MC) simulations within the primitive model of the physical chemistry at the ettringite-water interface over a wide range of pH and bulk conditions for which ettringite exists thanks to its solubility in aqueous solutions. Ettringite, which is an important phase in hydrated cement-based systems, bears a permanent and positive structural charge. In contrast with previous studies, electrokinetic measurements together with the careful chemical analysis of the equilibrium solutions of the dispersions have brought strong support to designate sulfate as being the ion determining the potential. Simulations showed that electrostatics, through ion-ion correlations, are not strong enough to explain the charge reversal of ettringite immersed in sulfate salt solutions. However, an excellent agreement between simulated and experimental data was obtained including a short-range nonelectrostatic adsorption potential for the sulfate ion. This result strongly suggests the existence of a chemical specificity of sulfate ions for an ettringite surface. PMID:21146176

  5. ATR-FTIR Spectroscopy in the Undergraduate Chemistry Laboratory: Part II--A Physical Chemistry Laboratory Experiment on Surface Adsorption

    Science.gov (United States)

    Schuttlefield, Jennifer D.; Larsen, Sarah C.; Grassian, Vicki H.

    2008-01-01

    Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is a useful technique for measuring the infrared spectra of solids and liquids as well as probing adsorption on particle surfaces. The use of FTIR-ATR spectroscopy in organic and inorganic chemistry laboratory courses as well as in undergraduate research was presented…

  6. Tuning of nanoparticle biological functionality through controlled surface chemistry and characterisation at the bioconjugated nanoparticle surface

    Science.gov (United States)

    Hristov, Delyan R.; Rocks, Louise; Kelly, Philip M.; Thomas, Steffi S.; Pitek, Andrzej S.; Verderio, Paolo; Mahon, Eugene; Dawson, Kenneth A.

    2015-12-01

    We have used a silica - PEG based bionanoconjugate synthetic scheme to study the subtle connection between cell receptor specific recognition and architecture of surface functionalization chemistry. Extensive physicochemical characterization of the grafted architecture is capable of capturing significant levels of detail of both the linker and grafted organization, allowing for improved reproducibility and ultimately insight into biological functionality. Our data suggest that scaffold details, propagating PEG layer architecture effects, determine not only the rate of uptake of conjugated nanoparticles into cells but also, more significantly, the specificity of pathways via which uptake occurs.

  7. Plug-Based Microfluidics with Defined Surface Chemistry to Miniaturize and Control Aggregation of Amyloidogenic Peptides**

    OpenAIRE

    Meier, Matthias; Kennedy-Darling, Julia; Choi, Se Hoon; Norstrom, Eric M.; Sisodia, Sangram S; Ismagilov, Rustem F.

    2009-01-01

    Small with control: For miniaturization of protein aggregation experiments the interfacial chemistry must be controlled to avoid protein aggregation caused by interfacial adsorption. Plug-based microfluidics with defined surface chemistry (see schematic picture) can then be used to perform hundreds of aggregation experiments with volume-limited samples, such as cerebrospinal fluid from mice.

  8. Surface chemistry and surface reactivity of fibrous amphiboles that are not regulated as asbestos

    Energy Technology Data Exchange (ETDEWEB)

    Fantauzzi, M.; Rossi, A. [Universita di Cagliari, ' ' Dipartimento di Scienze Chimiche e Geologiche' ' Centro Grandi Strumenti, Cagliari (Italy); INSTM unit, Monserrato, Cagliari (Italy); Pacella, A.; Gianfagna, A.; Andreozzi, G.B. [Sapienza Universita di Roma, Dipartimento di Scienze della Terra, Roma (Italy); Fournier, J. [Laboratoire de Reactivite de Surface, ' ' Le St Raphael' ' , UPMC Paris VI, UMR 7197, Ivry-sur-Seine, Paris (France)

    2012-08-15

    Three fibrous amphiboles that are not regulated as asbestos - two from Biancavilla (Sicily, Italy) and one from Libby (MT, USA) - were studied in order to establish relationships between surface chemistry and surface reactivity. The three fibrous samples, plus one prismatic fluoro-edenite from Biancavilla that was used for comparison, were investigated by X-ray photoelectron spectroscopy (XPS) in order to obtain their quantitative surface compositions and to determine the chemical environment of the Fe in each case. In particular, the Fe 2p{sub 3/2} peak was fitted and, for the first for these materials, the binding energies of Fe(II) oxide, Fe(III) oxide and Fe(III) oxyhydroxide were identified. Bulk chemistries and Fe oxidation states were obtained from previous studies for the samples from Biancavilla, and were investigated in the present work by electron microprobe (EMP) and {sup 57}Fe Moessbauer spectroscopy (MS) for the sample from Libby. Comparison between surface and bulk data revealed that the sample with the lowest bulk Fe oxidation state was the one most affected by surface oxidation, while the samples with bulk highly-oxidised Fe were showing very high signal of Fe (III) oxy-hydroxide probably due to weathering. The surface reactivities of the fibrous amphiboles were investigated by measuring the production of the [DMPO, HO] circle radical adduct using electron paramagnetic resonance (EPR) spectroscopy. Notably, significant chemical reactivity was observed; it was found to be comparable with - or, for the Libby sample, even higher than - that of fibrous tremolite (one of the six asbestos minerals). A positive linear correlation was observed when the production of HO circle radical was plotted versus the Fe(II) content on the fibre surface. Data on fibrous tremolite obtained from previous studies were added to substantiate the correlation. These results provide evidence that Fe(II) at the fibre surface controls the production of radicals at the fibre

  9. Detection of Tetrodotoxins in Puffer Fish by a Self-Assembled Monolayer-Based Immunoassay and Comparison with Surface Plasmon Resonance, LC-MS/MS, and Mouse Bioassay.

    Science.gov (United States)

    Reverté, Laia; de la Iglesia, Pablo; del Río, Vanessa; Campbell, Katrina; Elliott, Christopher T; Kawatsu, Kentaro; Katikou, Panagiota; Diogène, Jorge; Campàs, Mònica

    2015-11-01

    The increasing occurrence of puffer fish containing tetrodotoxin (TTX) in the Mediterranean could represent a major food safety risk for European consumers and threaten the fishing industry. The work presented herein describes the development of a new enzyme linked immunosorbent assay (mELISA) based on the immobilization of TTX through dithiol monolayers self-assembled on maleimide plates, which provides an ordered and oriented antigen immobilization and favors the antigen-antibody affinity interaction. The mELISA was found to have a limit of detection (LOD) of TTX of 0.23 mg/kg of puffer fish matrix. The mELISA and a surface plasmon resonance (SPR) immunosensor previously developed were employed to establish the cross-reactivity factors (CRFs) of 5,6,11-trideoxy-TTX, 5,11-deoxy-TTX, 11-nor-TTX-6-ol, and 5,6,11-trideoxy-4-anhydro-TTX, as well as to determine TTX equivalent contents in puffer fish samples. Results obtained by both immunochemical tools were correlated (R(2) = 0.977). The puffer fish samples were also analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the corresponding CRFs were applied to the individual TTX contents. Results provided by the immunochemical tools, when compared with those obtained by LC-MS/MS, showed a good degree of correlation (R(2) = 0.991 and 0.979 for mELISA and SPR, respectively). The mouse bioassay (MBA) slightly overestimated the CRF adjusted TTX content of samples when compared with the data obtained from the other techniques. The mELISA has been demonstrated to be fit for the purpose for screening samples in monitoring programs and in research activities. PMID:26424329

  10. Complex Surface Concentration Gradients by Stenciled "Electro Click Chemistry"

    DEFF Research Database (Denmark)

    Hansen, Thomas Steen; Lind, Johan Ulrik; Daugaard, Anders Egede;

    2010-01-01

    Complex one- or two-dimensional concentration gradients of alkynated molecules are produced on azidized conducting polymer substrates by stenciled "electro click chemistry". The latter describes the local electrochemical generation of catalytically active Cu(I) required to complete a "click...

  11. Characterisation of the inorganic chemistry of surface waters in South Africa

    OpenAIRE

    Huizenga, Jan Marten

    2011-01-01

    The main purpose of this study was to determine a simple inorganic chemistry index that can be used for all surface waters in South Africa, in order to characterise the inorganic chemistry of surface waters. Water quality data collected up until 1999 from all sample monitoring stations (2 068 monitoring stations, 364 659 samples) in South Africa were transformed into an Excel dataset and subsequently quality screened using the stoichiometric charge balance, after which 196 570 (41%) of the wa...

  12. Influence of the carbon fiber surface microstructure on the surface chemistry generated by a thermo-chemical surface treatment

    Science.gov (United States)

    Vautard, F.; Ozcan, S.; Paulauskas, F.; Spruiell, J. E.; Meyer, H.; Lance, M. J.

    2012-11-01

    Carbon fibers made of textile and aerospace grade polyacrylonitrile precursor fibers were surface treated by a continuous gas phase thermochemical treatment. The surface chemistry generated by the surface treatment was characterized by X-ray photoelectron spectroscopy. The surface and the average entire microstructure of the fibers were characterized by Raman spectroscopy and X-ray diffraction, respectively. Depending on the grade of the precursor, the final surface concentration of oxygen was comprised between 14% and 24%, whereas the typical commercial electrochemical surface treatments led to concentrations of around 8% with the same fibers. The final concentration of oxygen was directly correlated to the size of the crystallites which was a function of the grade of the polyacrylonitrile precursor and to the corresponding surface microstructure. The thermochemical surface treatment enabled a better control of the nature of the oxygen-containing functionalities as well. Whatever the grade of the precursor, desired hydroxyl groups and carboxylic acid functionalities were preferably generated, which is observed to be difficult with electrochemical surface treatments.

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

    DEFF Research Database (Denmark)

    Vadapoo, Sundar Raja

    2014-01-01

    molecular electronics and surface functionalization. In this thesis, a well-defined click chemistry approach is followed, with the study of azide-alkyne cycloaddition on Cu(111) surface in UHV environment. A successful achievement of the click reaction product via on-surface synthesis has been shown, which...

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    1990-03-01

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

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

    Directory of Open Access Journals (Sweden)

    Sheikh Uddin

    2013-05-01

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

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

    International Nuclear Information System (INIS)

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

  18. Chemistry

    International Nuclear Information System (INIS)

    The chemical research and development efforts related to the design and ultimate operation of molten-salt breeder reactor systems are concentrated on fuel- and coolant-salt chemistry, including the development of analytical methods for use in these systems. The chemistry of tellurium in fuel salt is being studied to help elucidate the role of this element in the intergranular cracking of Hastelloy N. Studies were continued of the effect of oxygen-containing species on the equilibrium between dissolved UF3 and dissolved UF4, and, in some cases, between the dissolved uranium fluorides and graphite, and the UC2. Several aspects of coolant-salt chemistry are under investigation. Hydroxy and oxy compounds that could be formed in molten NaBF4 are being synthesized and characterized. Studies of the chemistry of chromium (III) compounds in fluoroborate melts were continued as part of a systematic investigation of the corrosion of structural alloys by coolant salt. An in-line voltammetric method for determining U4+/U3+ ratios in fuel salt was tested in a forced-convection loop over a six-month period. (LK)

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

    DEFF Research Database (Denmark)

    Zhang, Wenjing; Jiang, Pengfei; Chen, Wei;

    2016-01-01

    The surface chemistry of nanoparticles (NPs) is one of the critical factors determining their cellular responses. In this study, the cytotoxicity and genotoxicity of copper oxide (CuO) NPs with a similar size but different surface chemistry to rat bone marrow mesenchymal stem cells (MSCs) were...... chemistry had influence on the toxicity to some extent too. The intracellular reactive oxygen species (ROS) level of MSCs was then quantified. Finally, the genotoxicity of the CuO NPs was studied by comet assay. The results suggest that the genotoxicity of CuO NPs was mainly dependent on NPs concentration......, and was only slightly influenced by their surface chemistry. The osteogenic and adipogenic differentiation abilities of the MSCs exposed to different CuO NPs were studied by Alizarin Res S and Oil Red O staining. The preliminary results showed that the exposure to 10 μg/mL CuO NPs will not lead to...

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

    Science.gov (United States)

    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. PMID:23417201

  1. The Role of Surface Chemistry in Adhesion and Wetting of Gecko Toe Pads

    Science.gov (United States)

    Badge, Ila; Stark, Alyssa Y.; Paoloni, Eva L.; Niewiarowski, Peter H.; Dhinojwala, Ali

    2014-10-01

    An array of micron-sized setal hairs offers geckos a unique ability to walk on vertical surfaces using van der Waals interactions. Although many studies have focused on the role of surface morphology of the hairs, very little is known about the role of surface chemistry on wetting and adhesion. We expect that both surface chemistry and morphology are important, not only to achieve optimum dry adhesion but also for increased efficiency in self-cleaning of water and adhesion under wet conditions. Here, we used a plasma-based vapor deposition process to coat the hairy patterns on gecko toe pad sheds with polar and non-polar coatings without significantly perturbing the setal morphology. By a comparison of wetting across treatments, we show that the intrinsic surface of gecko setae has a water contact angle between 70-90°. As expected, under wet conditions, adhesion on a hydrophilic surface (glass) was lower than that on a hydrophobic surface (alkyl-silane monolayer on glass). Surprisingly under wet and dry conditions the adhesion was comparable on the hydrophobic surface, independent of the surface chemistry of the setal hairs. This work highlights the need to utilize morphology and surface chemistry in developing successful synthetic adhesives with desirable adhesion and self-cleaning properties.

  2. THE INTEGRATED USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY, AND VIRTUAL REALITY TO PREDICT THE CHEMICAL REACTIVITY OF ENVIRONMENTAL SURFACES

    Science.gov (United States)

    In the last decade three new techniques scanning probe microscopy (SPM), virtual reality (YR) and computational chemistry ave emerged with the combined capability of a priori predicting the chemically reactivity of environmental surfaces. Computational chemistry provides the cap...

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

    International Nuclear Information System (INIS)

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

  4. The surface chemistry of metal-oxygen interactions

    DEFF Research Database (Denmark)

    Stokbro, Kurt; Baroni, Stefano

    1997-01-01

    We report on a computational study of the clean and oxygen-covered Rh(110) surface, based on density-functional theory within the local-density approximation. We have used plane-wave basis sets and Vanderbilt ultra-soft pseudopotentials. For the clean surface, we present results for the equilibrium...... structure, surface energy and surface stress of the unreconstructed and (1 x 2) reconstructed structures. For the oxygen-covered surface we have performed a geometry optimization at 0.5, 1, and 2 monolayer oxygen coverages, and we present results for the equilibrium configurations, workfunctions and oxygen...... chemisorption energies. At half monolayer coverage, we find that oxygen induces a (1 x 2) reconstruction of the surface, while at one monolayer coverage the chemisorption energy is highest for the unreconstructed surface. Our results are rationalized by a simple tight-binding description of the interaction...

  5. Chemistry and material science at the cell surface

    OpenAIRE

    Weian Zhao; Grace Sock Leng Teo; Namit Kumar; Karp, Jeffrey M.

    2010-01-01

    Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment cell functions and phenotypes. This not only helps to answer basic biology questions but also has diagnostic and therapeutic applications. In this review, we summarize the most recent advances in the engineering of the cell surface. In particular, we focus on the potential applications of surface engineered cells for 1) targeting cells to desirable sites in cell therapy, 2) programming assembly of c...

  6. On the use of SPM to probe the interplay between polymer surface chemistry and polymer surface mechanics

    Science.gov (United States)

    Brogly, Maurice; Noel, Olivier; Awada, Houssein; Castelein, Gilles

    2007-03-01

    Adhesive properties of a polymer surface results from the complex contribution of surface chemistry and activation of sliding and dissipating mechanisms within the polymer surface layer. The purpose of this study is to dissociate the different contributions (chemical and mechanical) included in an AFM force-distance curve in order to establish relationships between the surface viscoelastic properties of the polymer, the surface chemistry of functionalized polymer surfaces and the adhesive forces, as determined by C-AFM experiments. Indeed we are interested in the measurements of local attractive or adhesive forces in AFM contact mode, of controlled chemical and mechanical model substrates. In order to investigate the interplay between mechanical or viscoelastic mechanisms and surface chemistry during the tip - polymer contact, we achieved force measurements on model PDMS polymer networks, whose surfaces are chemically controlled with the same functional groups as before (silicon substrates). On the basis of AFM nano-indentation experiments, surface Young moduli have been determined. The results show that the viscoelastic contribution is dominating in the adhesion force measurement. We propose an original model, which express the local adhesion force to the energy dissipated within the contact and the surface properties of the material (thermodynamic work of adhesion). Moreover we show that the dissipation function is related to Mc, the mass between crosslinks of the network.

  7. On the use of SPM to probe the interplay between polymer surface chemistry and polymer surface mechanics

    International Nuclear Information System (INIS)

    Adhesive properties of a polymer surface results from the complex contribution of surface chemistry and activation of sliding and dissipating mechanisms within the polymer surface layer. The purpose of this study is to dissociate the different contributions (chemical and mechanical) included in an AFM force-distance curve in order to establish relationships between the surface viscoelastic properties of the polymer, the surface chemistry of functionalized polymer surfaces and the adhesive forces, as determined by C-AFM experiments. Indeed we are interested in the measurements of local attractive or adhesive forces in AFM contact mode, of controlled chemical and mechanical model substrates. In order to investigate the interplay between mechanical or viscoelastic mechanisms and surface chemistry during the tip - polymer contact, we achieved force measurements on model PDMS polymer networks, whose surfaces are chemically controlled with the same functional groups as before (silicon substrates). On the basis of AFM nano-indentation experiments, surface Young moduli have been determined. The results show that the viscoelastic contribution is dominating in the adhesion force measurement. We propose an original model, which express the local adhesion force to the energy dissipated within the contact and the surface properties of the material (thermodynamic work of adhesion). Moreover we show that the dissipation function is related to Mc, the mass between crosslinks of the network

  8. Surface chemistry and preferential crystal orientation on the H and Cl terminated silicon surface

    International Nuclear Information System (INIS)

    Surface chemistry and determining factors of the preferential crystal orientation are discussed through the deposition studies on hydrogenated chlorinated crystalline silicon films by rf plasma-enhanced chemical vapor deposition of a dichlorosilane, SiH2Cl2, and H2 mixture. The growth of randomly oriented crystal Si films occurred from the initial growth stage. On the other hand, the incubation layer of amorphous Si was formed in the initial stage, and subsequently, the growth of (220) preferred crystal orientation proceeded. They are determined by the thermal abstraction of H from the growing surface at substrate temperature above 350 degree sign C. Higher degree of Cl termination was effective in suppressing the oxygen incorporation into the Si network, although it did not contribute directly to the preferred crystal orientation. The insertion of atomic hydrogen to the Si-Si back bond in the subsurface region promoted the SiHClx complex formation, which was the most possible nucleation site for promoting the (220) preferential crystal orientation

  9. Electron induced surface chemistry at the Cs/sapphire interface

    International Nuclear Information System (INIS)

    Electron induced etching of sapphire in the presence of Cs has been studied using a variety of surface analytical techniques. We find that this process occurs on both the (0001) and (1 bar 102) orientations of sapphire. Monolayer amounts of Al and sub-oxides of Al are thermally desorbed from the surface at temperatures as low as 1000 K when the surface is irradiated with electrons in the presence of Cs. Etching is highly dependent on Cs coverage with the (0001) and (1 bar 102) surfaces requiring 2.0x1014 and 3.4x1014 atoms/cm2 to support etching, respectively. Adsorption profiles demonstrate that these coverages correspond to initial saturation of the surface with Cs. Electron damage of the surface in the absence of Cs also produces desorption of Al and sub-oxides of Al, indicating a possible mechanism for etching. The impact of etching on the surface is to increase the adsorption capacity on the (0001) surface while decreasing both initial adsorption probability and capacity on the (1 bar 102) surface. copyright 1996 American Institute of Physics

  10. 3D Printed Potential and Free Energy Surfaces for Teaching Fundamental Concepts in Physical Chemistry

    Science.gov (United States)

    Kaliakin, Danil S.; Zaari, Ryan R.; Varganov, Sergey A.

    2015-01-01

    Teaching fundamental physical chemistry concepts such as the potential energy surface, transition state, and reaction path is a challenging task. The traditionally used oversimplified 2D representation of potential and free energy surfaces makes this task even more difficult and often confuses students. We show how this 2D representation can be…

  11. Tuning surface chemistry and nanostructure in porous silicon for molecular separation, detection and delivery /

    OpenAIRE

    Wu, Chia-Chen

    2013-01-01

    Mesoporous materials with engineered surface properties are of interest for molecular separations, catalysis, drug delivery, and chemical sensing. One of the longstanding chemical challenges in the engineering of nanomaterials is to control the placement of different chemistries in spatially distinct regions on a nanoscale object. This thesis focuses on discovering and understanding processes to prepare such spatially differentiated chemistries on porous silicon. For the porous silicon system...

  12. Chemistry

    International Nuclear Information System (INIS)

    Research progress is reported in programs on fuel-salt chemistry, properties of compounds in the Li--Te system, Te spectroscopy UF4--H equilibria, porous electrode studies of molten salts, fuel salt-coolant salt reactions, thermodynamic properties of transition-metal fluorides, and properties of sodium fluoroborate. Developmental work on analytical methods is summarized including in-line analysis of molten MSBR fuel, analysis of coolant-salts for tritium, analysis of molten LiF--BeF2--ThF4 for Fe and analysis of LiF--BeF--ThF4 for Te

  13. Geochemistry and Organic Chemistry on the Surface of Titan

    Science.gov (United States)

    Lunine, J. I.; Beauchamp, P.; Beauchamp, J.; Dougherty, D.; Welch, C.; Raulin, F.; Shapiro, R.; Smith, M.

    2001-01-01

    Titan's atmosphere produces a wealth of organic products from methane and nitrogen. These products, deposited on the surface in liquid and solid form, may interact with surface ices and energy sources to produce compounds of exobiological interest. Additional information is contained in the original extended abstract.

  14. Surface chemistry interventions to control boiler tube fouling

    International Nuclear Information System (INIS)

    The adsorption of ammonia, morpholine, ethanolamine, and dimethylamine onto the surfaces of colloidal magnetite and hematite was measured at 25oC. The effect of the adsorption on the surface potential was quantified by measuring the resulting shift in the isoelectric point of the corrosion products and by the direct measurement of the surface interaction force between the corrosion products and Inconel 600. These measurements have served to support the hypothesis that adsorption of amine affects the magnetite deposition rate by lowering the force of repulsion between magnetite and the surface of Inconel 600. The deposition rate of hematite increased as the oxygen concentration increased. A mechanism to account for enhanced deposition rates at high mixture qualities (> 0.35) has been identified and shown to predict behaviour that is consistent with both experimental and plant data. As a result of this investigation, several criteria are proposed to reduce the extent of corrosion product deposition on the tube bundle. Low hematite deposition is favoured by a low concentration of dissolved oxygen, and low magnetite deposition is favoured by choosing an amine for pH control that has little tendency to adsorb onto the surface of magnetite. To minimize adsorption the amine should have a high base strength and a large 'footprint' on the surface of magnetite. To prevent enhanced deposition at high mixture qualities, it is proposed that a modified amine be used that will reduce the surface tension or the elasticity of the steam-water interface or both

  15. Chemistry and material science at the cell surface

    Directory of Open Access Journals (Sweden)

    Weian Zhao

    2010-04-01

    Full Text Available Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment cell functions and phenotypes. This not only helps to answer basic biology questions but also has diagnostic and therapeutic applications. In this review, we summarize the most recent advances in the engineering of the cell surface. In particular, we focus on the potential applications of surface engineered cells for 1 targeting cells to desirable sites in cell therapy, 2 programming assembly of cells for tissue engineering, 3 bioimaging and sensing, and ultimately 4 manipulating cell biology.

  16. Mechanical work makes important contributions to surface chemistry at steps

    OpenAIRE

    Francis, M. F.; Curtin, W. A.

    2015-01-01

    The effect of mechanical strain on the binding energy of adsorbates to late transition metals is believed to be entirely controlled by electronic factors, with tensile stress inducing stronger binding. Here we show, via computation, that mechanical strain of late transition metals can modify binding at stepped surfaces opposite to well-established trends on flat surfaces. The mechanism driving the trend is mechanical, arising from the relaxation of stored mechanical energy. The mechanical ene...

  17. The surface chemistry of metal–organic frameworks

    OpenAIRE

    McGuire, Christina V.; Forgan, Ross S.

    2015-01-01

    Metal–organic frameworks (MOFs) have received particular attention over the last 20 years as a result of their attractive properties offering potential applications in a number of areas. Typically, these characteristics are tuned by functionalisation of the bulk of the MOF material itself. This Feature Article focuses instead on modification of MOF particles at their surfaces only, which can also offer control over the bulk properties of the material. The differing surface modification techni...

  18. The effect of surface chemistry on the glass transition of amorphous polycarbonate inside cylindrical nanopores

    Science.gov (United States)

    Reid, Dariya; Alves Freire, Marcela; Lutkenhaus, Jodie

    2015-03-01

    Nanoporous anodic aluminum oxide (AAO) templates are used to study the effect of confinement on the glass transition of amorphous polycarbonate (PC). In order to further study the effect of surface chemistry on physical behavior, the bare AAO surface is modified using alkyl- and fluoro-silanes of varying length. PC nanowires (200 nm in diameter) are prepared by melt-wetting the polymer into AAO templates under applied pressure. Using modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA), it is found that the hydrophilic surface of bare AAO contributes to the degradation of the polymer. Modifying the AAO surface using silane chemistry prevents polymer degradation and introduces additional features in MDSC thermograms, which could be due to the interaction of the polymer with the nanopore surface. Using scanning electron microscopy (SEM), changes are observed in the tips of the PC nanowires as the AAO surface transitions from hydrophilic to hydrophobic.

  19. Recovering ferromagnetic metal surfaces to fully exploit chemistry in molecular spintronics

    Directory of Open Access Journals (Sweden)

    Marta Galbiati

    2015-05-01

    Full Text Available Organic spintronics is a new emerging field that promises to offer the full potential of chemistry to spintronics, as for example high versatility through chemical engineering and simple low cost processing. However, one key challenge that remains to be unlocked for further applications is the high incompatibility between spintronics key materials such as high Curie temperature Co, Ni, Fe (and their alloys and wet chemistry. Indeed, the transition metal proneness to oxidation has so far hampered the integration of wet chemistry processes into the development of room temperature organic spintronics devices. As a result, they had mainly to rely on high vacuum physical processes, restraining the choice of available organic materials to a small set of sublimable molecules. In this letter, focusing on cobalt as an example, we show a wet chemistry method to easily and selectively recover a metallic surface from an air exposed oxidized surface for further integration into spintronics devices. The oxide etching process, using a glycolic acid based solution, proceeds without increasing the surface roughness and allows the retrieval of an oxygen-free chemically active cobalt layer. This unlocks the full potential of wet chemistry processes towards room temperature molecular spintronics with transition metals electrodes. We demonstrate this by the grafting of alkylthiols self-assembled monolayers on recovered oxidized cobalt surfaces.

  20. Adsorption of atrazine on hemp stem-based activated carbons with different surface chemistry

    OpenAIRE

    Lupul, Iwona; Yperman, Jan; Carleer, Robert; Gryglewicz, Grazyna

    2015-01-01

    Surface-modified hemp stem-based activated carbons (HACs) were prepared and used for the adsorption of atrazine from aqueous solution, and their adsorption performance was examined. A series of HACs were prepared by potassium hydroxide activation of hemp stems, followed by subsequent modification by thermal annealing, oxidation with nitric acid and amination. The resultant HACs differed in surface chemistry, while possessing similar porous structure. The surface group characteristics were exa...

  1. PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes

    OpenAIRE

    Norhan Nady

    2016-01-01

    A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled “green surface modification”. This modification can be ...

  2. Surface chemistry of atmospheric plasma modified polycarbonate substrates

    International Nuclear Information System (INIS)

    Surface of polycarbonate substrates were activated by atmospheric plasma torch using different gas pressure, distance from the substrates, velocity of the torch and number of treatments. The modifications were analyzed by contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV-vis spectrophotometry. Plasma treatment caused the surface characteristics to become more hydrophilic as measured by the water contact angle, which decreased from 88 deg. to 18 deg. The decrease in contact angle was mainly due to oxidation of the surface groups, leading to formation of polar groups with hydrophilic property. XPS results showed an increase in the intensity of -(C-O)- groups and also introduction of new functional groups i.e. -(O-C=O)- after the treatment process. AFM topographic images demonstrated an increase in the rms roughness of the surface from 2.0 nm to 4.0 nm caused by the treatment. Increase in rms roughness of the surface caused relevant decrease in transmission up to ∼2-5%.

  3. Mussel-inspired surface chemistry for multifunctional coatings.

    Science.gov (United States)

    Lee, Haeshin; Dellatore, Shara M; Miller, William M; Messersmith, Phillip B

    2007-10-19

    We report a method to form multifunctional polymer coatings through simple dip-coating of objects in an aqueous solution of dopamine. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form thin, surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides, polymers, semiconductors, and ceramics. Secondary reactions can be used to create a variety of ad-layers, including self-assembled monolayers through deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioinert and bioactive surfaces via grafting of macromolecules. PMID:17947576

  4. Surface acid chemistry associated with dielectric barrier discharge (DBD) treatment of polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Dockery, K P; Sieber, K D; Knapp, F A; Wilson, T E [Eastman Kodak Company, 1999 Lake Avenue, Rochester, NY 14650-02132 (United States)

    2007-02-01

    The chemistry associated with atmospheric dielectric barrier discharges (DBDs) in air has been studied. Laboratory and industrial DBD systems have been investigated. In this work, we have emphasized the use of aqueous extractions of treated surfaces, followed by analyses by ion chromatography to study the DBD chemistry. A range of DBD factors including dose, humidity, airflow and electrode configuration (one versus two dielectric barriers) is found to influence the levels of acids, notably nitrous, nitric and oxalic acids, on the treated surfaces. A mechanistic rationale involving the primary formation of the nitrous and nitric acids in the gas phase is proposed.

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

    Science.gov (United States)

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

    2009-01-01

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

  6. Mussel-Inspired Surface Chemistry for Multifunctional Coatings

    OpenAIRE

    Lee, Haeshin; Dellatore, Shara M.; Miller, William M.; Messersmith, Phillip B.

    2007-01-01

    We report a method to form multifunctional polymer coatings through simple dip-coating of objects in an aqueous solution of dopamine. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form thin, surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides, polymers, semiconductors, and ceramics. Secondary reactions can be used to create a variety of ad-layers, including self-assemble...

  7. Engineering novel cell surface chemistry for selective tumor cell targeting

    Energy Technology Data Exchange (ETDEWEB)

    Bertozzi, C.R. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley National Lab., CA (United States)

    1997-12-31

    A common feature of many different cancers is the high expression level of the two monosaccharides sialic acid and fucose within the context of cell-surface associated glycoconjugates. A correlation has been made between hypersialylation and/or hyperfucosylation and the highly metastatic phenotype. Thus, a targeting strategy based on sialic acid or fucose expression would be a powerful tool for the development of new cancer cell-selective therapies and diagnostic agents. We have discovered that ketone groups can be incorporated metabolically into cell-surface associated sialic acids. The ketone is can be covalently ligated with hydrazide functionalized proteins or small molecules under physiological conditions. Thus, we have discovered a mechanism to selectively target hydrazide conjugates to highly sialylated cells such as cancer cells. Applications of this technology to the generation of novel cancer cell-selective toxins and MRI contrast reagents will be discussed, in addition to progress towards the use of cell surface fucose residues as vehicles for ketone expression.

  8. Surface and coordination chemistry related to GaAs

    Science.gov (United States)

    Keys, Andrea

    The vapor phase structures of Al(tBU)3 and Ga(tBU)3 have been investigated by gas phase electron diffraction and consist of planar three-coordinate monomers. Salient structural parameters (ra) include: Al-C = 2.005(3) A, Ga-C = 2.034(2) A. The geometries are controlled by inter-ligand interactions. The electron diffraction structures are compared to those determined by ab initio calculations for M(tBU)3 (M = Al, Ga, In). To understand the most suitable linkages for the surface of GaAs, model compounds were synthesized by reacting Ga(tBU)3 and [tBu2Ga(mu-Cl]2 with one molar equivalent of varying ligands. The synthesized compounds include chlorides, benzenethiolate, dithiocarbamates, carboxylates, amides, benzohydroxamate, and phenylphosphonate. The Ga ⋯ Ga and Ga-ligand interatomic distances for these compounds, as well as Group 15 and 16 donor bridging ligands, are compared to the values for the surface of GaAs and cubic-GaS in order to determine their suitability as linkage groups for self-assembled monolayers. The most suitable linkages were determined to be benzenethiol and phenylphophonic acid, and these were used to grow self-assembled monolayers on {100} GaAs. Carboxylic acid was also used, to determine the success of the organometallic model compounds in predicting the suitability of ligands for surface reaction. Self-assembled monolayers were also grown on Al2O3, using carboxylic acids and phenylphosphonic acids as the surface linkages. Metallo-organic chemical vapor deposition was performed using single-source precursors ( tBU)2Ga(S2CNR2). The tert -butyl gallium bis-dialkyl-dithiocarbamate compounds, (tBu)Ga(S2CNR2)2, are formed as minor products via ligand disproportionation reactions. Gallium sulfide (GaS) thin films have been grown at 375-425°C by atmospheric pressure metal-organic chemical vapor deposition using compounds (tBu) 2Ga(S2CNMe2) and (tBu)2Ga(S 2CNEt2) as single source precursors. Polycrystalline samples of the chalcogenides InSe, In2Se3

  9. Surface chemistry of sulfur containing heterocylcic molecules on Mo (110)

    International Nuclear Information System (INIS)

    In this work, the authors report the reactivity of the three sulfur containing heterocycles, namely thiophene, 1, thiophane, 2 and trimethylene sulfide, 3, on clean Mo(110) under ultrahigh vacuum conditions. These studies were undertaken to compare the reactivity of Mo(110) to previously reported work on Mo(100) and to investigate the role of varying the degree of unsaturation and ring size of the reactant molecule in the desulfurization process. Thermal desorption used in conjunction with isotopic exchange is the primary tool used in these investigations. Low energy electron diffraction and Auger electron spectroscopy were also used to monitor surface order and composition, respectively

  10. Chemistry

    International Nuclear Information System (INIS)

    Research and development activities dealing with the chemical problems related to design and ultimate operation of molten-salt reactor systems are described. An experimental test stand was constructed to expose metallurgical test specimens to Te2 vapor at defined temperatures and deposition rates. To better define the chemistry of fluoroborate coolant, several aspects are being investigated. The behavior of hydroxy and oxy compounds in molten NaBF4 is being investigated to define reactions and compounds that may be involved in corrosion and/or could be involved in methods for trapping tritium. Two corrosion products of Hastelloy N, Na3CrF6 and Na5Cr3F14, were identified from fluoroborate systems. The evaluation of fluoroborate and alternate coolants continued. Research on the behavior of hydrogen and its isotopes is summarized. The solubilities of hydrogen, deuterium, and helium in Li2BeF4 are very low. The sorption of tritium on graphite was found to be significant (a few milligrams of tritium per kilogram of graphite), possibly providing a means of sequestering a portion of the tritium produced. Development of analytical methods continued with emphasis on voltammetric and spectrophotometric techniques for the in-line analysis of corrosion products such as Fe2+ and Cr3+ and the determination of the U3+/U4+ ratio in MSBR fuel salt. Similar studies were conducted with the NaBF4--NaF coolant salt. Information developed during the previous operation of the CSTF has been assessed and used to formulate plans for evaluation of in-line analytical methods in future CSTF operations. Electroanalytical and spectrophotometric research suggests that an electroactive protonic species is present in molten NaBF4--NaF, and that this species rapidly equilibrates with a volatile proton-containing species. Data obtained from the CSTF indicated that tritium was concentrated in the volatile species. (JGB)

  11. Measuring the role of surface chemistry in silicon microphotonics

    CERN Document Server

    Borselli, M; Painter, O; Borselli, Matthew; Johnson, Thomas J.; Painter, Oskar

    2005-01-01

    The silicon/silicon dioxide (Si/SiO2) interface plays a crucial role in the performance, cost, and reliability of most modern microelectronic devices, from the basic transistor to flash memory, digital cameras, and solar cells. Today the gate oxide thickness of modern transistors is roughly 5 atomic layers, with 8 metal wire layers required to transport all the signals within a microprocessor. In addition to the increasing latency of such reduced-dimension metal wires, further "Moore's Law" scaling of transistor cost and density is predicted to saturate in the next decade. As a result, silicon-based microphotonics is being explored for the routing and generation of high-bandwidth signals. In comparison to the extensive knowledge of the electronic properties of the Si/SiO2 interface, little is known about the optical properties of Si surfaces used in microphotonics. In this Letter, we explore the optical properties of the Si surface in the telecommunication-relevant wavelength band of 1400-1600 nm. Utilizing a...

  12. Random Phase Approximation in Surface Chemistry: Water Splitting on Iron.

    Science.gov (United States)

    Karlický, František; Lazar, Petr; Dubecký, Matúš; Otyepka, Michal

    2013-08-13

    The reaction of water with zero-valent iron (anaerobic corrosion) is a complex chemical process involving physisorption and chemisorption events. We employ random phase approximation (RPA) along with gradient-corrected and hybrid density functional theory (DFT) functionals to study the reaction of water with the Fe atom and Fe(100) surface. We show that the involvement of the exact electron exchange and nonlocal correlation effects in RPA improves the description of all steps of the reaction on the Fe surface with respect to standard [meaning local density approximation (LDA) or generalized gradient approximation (GGA)] DFT methods. The reaction profile calculated by range-separated hybrid functional HSE06 agrees reasonably well with the RPA profile, which makes HSE06 a computationally less demanding alternative to RPA. We also investigate the reaction of the Fe atom with water using DFT, RPA, and coupled-cluster through the perturbative triples complete basis set [CCSD(T)-3s3p-DKH/CBS] method. Local DFT methods significantly underestimate reaction barriers, while the reaction kinetics and thermodynamics from RPA agree with the reference CCSD(T) data. Both systems, i.e., the Fe atom and Fe(100), provide the same reaction mechanism, indicating that anaerobic corrosion is a stepwise process involving one-electron steps, with the first reaction step (formation of the HFeOH intermediate) representing the rate-limiting step. PMID:26584120

  13. Defining an optimal surface chemistry for pluripotent stem cell culture in 2D and 3D

    Science.gov (United States)

    Zonca, Michael R., Jr.

    Surface chemistry is critical for growing pluripotent stem cells in an undifferentiated state. There is great potential to engineer the surface chemistry at the nanoscale level to regulate stem cell adhesion. However, the challenge is to identify the optimal surface chemistry of the substrata for ES cell attachment and maintenance. Using a high-throughput polymerization and screening platform, a chemically defined, synthetic polymer grafted coating that supports strong attachment and high expansion capacity of pluripotent stem cells has been discovered using mouse embryonic stem (ES) cells as a model system. This optimal substrate, N-[3-(Dimethylamino)propyl] methacrylamide (DMAPMA) that is grafted on 2D synthetic poly(ether sulfone) (PES) membrane, sustains the self-renewal of ES cells (up to 7 passages). DMAPMA supports cell attachment of ES cells through integrin beta1 in a RGD-independent manner and is similar to another recently reported polymer surface. Next, DMAPMA has been able to be transferred to 3D by grafting to synthetic, polymeric, PES fibrous matrices through both photo-induced and plasma-induced polymerization. These 3D modified fibers exhibited higher cell proliferation and greater expression of pluripotency markers of mouse ES cells than 2D PES membranes. Our results indicated that desirable surfaces in 2D can be scaled to 3D and that both surface chemistry and structural dimension strongly influence the growth and differentiation of pluripotent stem cells. Lastly, the feasibility of incorporating DMAPMA into a widely used natural polymer, alginate, has been tested. Novel adhesive alginate hydrogels have been successfully synthesized by either direct polymerization of DMAPMA and methacrylic acid blended with alginate, or photo-induced DMAPMA polymerization on alginate nanofibrous hydrogels. In particular, DMAPMA-coated alginate hydrogels support strong ES cell attachment, exhibiting a concentration dependency of DMAPMA. This research provides a

  14. Challenges in Teaching "Colloid and Surface Chemistry"--A Danish Experience

    Science.gov (United States)

    Kontogeorgis, Georgios M.; Vigild, Martin E.

    2009-01-01

    Seven years ago we were asked, as one of our first teaching duties at the Technical University of Denmark (DTU), to teach a 5 ECTS point course on "Colloid and Surface Chemistry". The topic is itself at the same time exciting and demanding, largely due to its multidisciplinary nature. Several "local" requirements posed additional challenges. The…

  15. Surface Modification of Nanoporous 1,2-Polybutadiene by Atom Transfer Radical Polymerization or Click Chemistry

    DEFF Research Database (Denmark)

    Guo, Fengxiao; Jankova Atanasova, Katja; Schulte, Lars;

    2010-01-01

    Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based oil nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls...

  16. Micropatterning of Functional Conductive Polymers with Multiple Surface Chemistries in Register

    DEFF Research Database (Denmark)

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

    2012-01-01

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

  17. Combined effects of surface conditions, boundary layer dynamics and chemistry on diurnal SOA evolution

    NARCIS (Netherlands)

    Janssen, R.H.H.; Vilà-Guerau de Arellano, J.; Ganzeveld, L.N.; Kabat, P.; Jimenez, J.L.; Farmer, D.K.; Heerwaarden, van C.C.; Mammarella, I.

    2012-01-01

    We study the combined effects of land surface conditions, atmospheric boundary layer dynamics and chemistry on the diurnal evolution of biogenic secondary organic aerosol in the atmospheric boundary layer, using a model that contains the essentials of all these components. First, we evaluate the mod

  18. Influence of surface chemistry on the electronic properties of graphene related carbon materials

    OpenAIRE

    Chutia, Arunabhirm; Cimpoesu, Fanica; Tsuboi, Hideyuki; Miyamotob, Akira

    2010-01-01

    A theoretical study on the influence of organic functional groups on the electronic properties of graphene related carbon materials was carried out. Here we report, using density functional theory and tight-binding approach, that the best candidates for conducting supramolecular devices can be obtained by engineering the surface chemistry and stacking conformation of these materials.

  19. On Surface-Initiated Atom Transfer Radical Polymerization Using Diazonium Chemistry To Introduce the Initiator Layer

    DEFF Research Database (Denmark)

    Chernyy, Sergey; Lillethorup, Mie; Ceccato, Marcel;

    2011-01-01

    This work features the controllability of surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate, initiated by a multilayered 2-bromoisobutyryl moiety formed via diazonium chemistry. The thickness as a function of polymerization time has been studied by varying di...

  20. Ammonia removal using activated carbons: effect of the surface chemistry in dry and moist conditions

    OpenAIRE

    Gonçalves, Maraisa; Sánchez García, Laura; Jardim, Erika de Oliveira; Silvestre Albero, Joaquín; Rodríguez Reinoso, Francisco

    2011-01-01

    The effect of surface chemistry (nature and amount of oxygen groups) in the removal of ammonia was studied using a modified resin-based activated carbon. NH3 breakthrough column experiments show that the modification of the original activated carbon with nitric acid, that is, the incorporation of oxygen surface groups, highly improves the adsorption behavior at room temperature. Apparently, there is a linear relationship between the total adsorption capacity and the amount of the more acidic ...

  1. Surface Chemistry of Aluminium Alloy Slid against Steel Lubricated by Organic Friction Modifier in Hydrocarbon Oil

    OpenAIRE

    Ichiro Minami; Ayumi Sugibuchi

    2012-01-01

    The lubrication mechanism of aluminium alloy slid against steel was investigated from the standpoint of surface chemistry. Low friction and low wear were observed using glycerol mono-olate in a hydrocarbon as lubricant. Increase in the silicon content in the aluminium alloy during rubbing was observed by surface analyses using (1) Auger electron spectroscopy, (2) scanning electron microscopy along with energy dispersive X-ray spectroscopy, and (3) X-ray photoelectron spectroscopy. Mild remova...

  2. Informatics guided discovery of surface structure-chemistry relationships in catalytic nanoparticles

    International Nuclear Information System (INIS)

    A data driven discovery strategy based on statistical learning principles is used to discover new correlations between electronic structure and catalytic activity of metal surfaces. From the quantitative formulations derived from this informatics based model, a high throughput computational framework for predicting binding energy as a function of surface chemistry and adsorption configuration that bypasses the need for repeated electronic structure calculations has been developed

  3. Venting temperature determines surface chemistry of magnetron sputtered TiN films

    Science.gov (United States)

    Greczynski, G.; Mráz, S.; Hultman, L.; Schneider, J. M.

    2016-01-01

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

  4. Venting temperature determines surface chemistry of magnetron sputtered TiN films

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-01-25

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

  5. Venting temperature determines surface chemistry of magnetron sputtered TiN films

    International Nuclear Information System (INIS)

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

  6. Catalyst design for enhanced sustainability through fundamental surface chemistry.

    Science.gov (United States)

    Personick, Michelle L; Montemore, Matthew M; Kaxiras, Efthimios; Madix, Robert J; Biener, Juergen; Friend, Cynthia M

    2016-02-28

    Decreasing energy consumption in the production of platform chemicals is necessary to improve the sustainability of the chemical industry, which is the largest consumer of delivered energy. The majority of industrial chemical transformations rely on catalysts, and therefore designing new materials that catalyse the production of important chemicals via more selective and energy-efficient processes is a promising pathway to reducing energy use by the chemical industry. Efficiently designing new catalysts benefits from an integrated approach involving fundamental experimental studies and theoretical modelling in addition to evaluation of materials under working catalytic conditions. In this review, we outline this approach in the context of a particular catalyst-nanoporous gold (npAu)-which is an unsupported, dilute AgAu alloy catalyst that is highly active for the selective oxidative transformation of alcohols. Fundamental surface science studies on Au single crystals and AgAu thin-film alloys in combination with theoretical modelling were used to identify the principles which define the reactivity of npAu and subsequently enabled prediction of new reactive pathways on this material. Specifically, weak van der Waals interactions are key to the selectivity of Au materials, including npAu. We also briefly describe other systems in which this integrated approach was applied. PMID:26755756

  7. Ammonia removal using activated carbons: effect of the surface chemistry in dry and moist conditions.

    Science.gov (United States)

    Gonçalves, Maraisa; Sánchez-García, Laura; Oliveira Jardim, Erika de; Silvestre-Albero, Joaquín; Rodríguez-Reinoso, Francisco

    2011-12-15

    The effect of surface chemistry (nature and amount of oxygen groups) in the removal of ammonia was studied using a modified resin-based activated carbon. NH(3) breakthrough column experiments show that the modification of the original activated carbon with nitric acid, that is, the incorporation of oxygen surface groups, highly improves the adsorption behavior at room temperature. Apparently, there is a linear relationship between the total adsorption capacity and the amount of the more acidic and less stable oxygen surface groups. Similar experiments using moist air clearly show that the effect of humidity highly depends on the surface chemistry of the carbon used. Moisture highly improves the adsorption behavior for samples with a low concentration of oxygen functionalities, probably due to the preferential adsorption of ammonia via dissolution into water. On the contrary, moisture exhibits a small effect on samples with a rich surface chemistry due to the preferential adsorption pathway via Brønsted and Lewis acid centers from the carbon surface. FTIR analyses of the exhausted oxidized samples confirm both the formation of NH(4)(+) species interacting with the Brønsted acid sites, together with the presence of NH(3) species coordinated, through the lone pair electron, to Lewis acid sites on the graphene layers. PMID:22049916

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

    Science.gov (United States)

    Syverud, Kristin

    2014-01-01

    Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups are abundant in nanocellulose materials, making the material strongly hydrophilic. Second, the surface chemistry can be modified, introducing aldehyde and carboxyl groups, which have major potential for surface functionalization. In this study, we demonstrate the production of nanocellulose with tailor-made surface chemistry, by pre-treating the raw cellulose fibres with carboxymethylation and periodate oxidation. The pre-treatments yielded a highly nanofibrillated material, with significant amounts of aldehyde and carboxyl groups. Importantly, the poly-anionic surface of the oxidized nanocellulose opens up for novel applications, i.e. micro-porous materials with pH-responsive characteristics. This is due to the swelling capacity of the 3D micro-porous structures, which have ionisable functional groups. In this study, we demonstrated that nanocellulose gels have a significantly higher swelling degree in neutral and alkaline conditions, compared to an acid environment (pH 3). Such a capability can potentially be applied in chronic wounds for controlled and intelligent release of antibacterial components into biofilms. PMID:24713295

  9. Nanoporous Gold as a Neural Interface Coating: Effects of Topography, Surface Chemistry, and Feature Size

    Science.gov (United States)

    Chapman, Christopher A. R.; Chen, Hao; Stamou, Marianna; Biener, Juergen; Biener, Monika M.; Lein, Pamela J.; Seker, Erkin

    2015-01-01

    Designing neural-electrode interfaces that maintain close physical coupling of neurons to the electrode surface remains a major challenge for both implantable and in vitro neural recording electrode arrays. Typically, low-impedance nanostructured electrode coatings rely on chemical cues from pharmaceuticals or surface-immobilized peptides to suppress glial scar tissue formation over the electrode surface (astrogliosis), which is an obstacle to reliable neuron-electrode coupling. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a promising candidate to reduce astrogliosis solely through topography by taking advantage of its tunable length scale. In the present in vitro study on np-Au’s interaction with cortical neuron-glia co-cultures, we demonstrate that the nanostructure of np-Au is achieving close physical coupling of neurons through maintaining a high neuron-to-astrocyte surface coverage ratio. Atomic layer deposition-based surface modification was employed to decouple the effect of morphology from surface chemistry. Additionally, length scale effects were systematically studied by controlling the characteristic feature size of np-Au through variations of the dealloying conditions. Our results show that np-Au nanotopography, not surface chemistry, reduces astrocyte surface coverage while maintaining high neuronal coverage, and may enhance the neuron-electrode coupling through nanostructure-mediated suppression of scar tissue formation. PMID:25706691

  10. Role of the surface chemistry of activated carbons in dye removal from aqueous solution

    Science.gov (United States)

    Zhou, Hua-lei; Zhen, Wen-juan; Zhu, Qian; Wu, Xiao-bin; Chang, Zhi-dong; Li, Wen-jun

    2015-07-01

    Commercial activated carbons were modified by a series of chemical or physical treatments using H2O2, NH3, and heating under N2 flow without notably changing their pore structures. The resultant carbons were characterized by N2 adsorption and Bohem titration and then used to remove Ponceau 4R, methyl orange and brilliant blue from aqueous solutions. Surface chemistry was found to play a significantly different role in removing these three compounds. The removal of anionic Ponceau 4R increases with increasing carbon surface basicity due to the predominant dispersive interaction mechanism. In contrast, surface chemistry has little effect on the removal of anionic methyl orange, which can be explained by two parallel mechanisms involving electrostatic and dispersive interactions due to the basic amine group in a dye molecule. The influence of surface chemistry on the removal of amphoteric brilliant blue dye can also be ignored due to a weak interaction between the carbons and dye molecules, which is resulted from strong cohesive energy from electrostatic forces inside amphoteric dye molecules.

  11. Major Successes of Theory-and-Experiment-Combined Studies in Surface Chemistry and Heterogeneous Catalysis.

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, Gabor A.; Li, Yimin

    2009-11-21

    Experimental discoveries followed by theoretical interpretations that pave the way of further advances by experimentalists is a developing pattern in modern surface chemistry and catalysis. The revolution of modern surface science started with the development of surface-sensitive techniques such as LEED, XPS, AES, ISS and SIMS, in which the close collaboration between experimentalists and theorists led to the quantitative determination of surface structure and composition. The experimental discovery of the chemical activity of surface defects and the trends in the reactivity of transitional metals followed by the explanations from the theoretical studies led to the molecular level understanding of active sites in catalysis. The molecular level knowledge, in turn, provided a guide for experiments to search for new generation of catalysts. These and many other examples of successes in experiment-and-theory-combined studies demonstrate the importance of the collaboration between experimentalists and theorists in the development of modern surface science.

  12. Modeling the surface chemistry of biomass model compounds on oxygen-covered Rh(100).

    Science.gov (United States)

    Caglar, B; Niemantsverdriet, J W Hans; Weststrate, C J Kees-Jan

    2016-08-24

    Rhodium-based catalysts are potential candidates to process biomass and serve as a representation of the class of noble metal catalysts for biomass-related processes. Biomass can be processed in aqueous media (hydrolysis and aqueous phase reforming), and in this case the surface chemistry involves hydroxyl (OH) species. In our study this was modelled by the presence of pre-adsorbed oxygen. Ethylene glycol, with a hydroxyl group on every carbon atom, serves as a model compound to understand the conversion of biomass derived molecules into desirable chemicals on catalytically active metal surfaces. Ethanol (containing one OH group) serves as a reference molecule for ethylene glycol (containing two OH groups) to understand the interaction of C-OH functionalities with a Rh(100) surface. The surface chemistry of ethylene glycol and ethanol in the presence of pre-adsorbed oxygen on a Rh(100) surface has been studied via temperature programmed reaction spectroscopy (TPRS) and reflection absorption infrared spectroscopy (RAIRS) using various coverages of O(ad) and ethylene glycol and ethanol. Pre-adsorbed oxygen alters the decomposition chemistry of both compounds, thereby affecting the product distribution. Under an oxygen-lean condition, the selectivity to produce methane from ethanol is enhanced significantly (4.5-fold with respect to that obtained on the oxygen-free surface). For ethylene glycol, oxygen-lean conditions promote the formation of formaldehyde, with 10-15% selectivity. In addition, with Oad present the fraction of molecules that decompose on the surface increases 2-fold for ethanol and 1.5-fold for ethylene glycol, due to fast O-H bond activation by pre-adsorbed oxygen. Under oxygen-rich conditions, the decomposition products are mainly oxidized to carbon dioxide and water for both molecules. In this condition, the promotion effect provided by adsorbed oxygen for the dissociative adsorption of ethanol and ethylene glycol is reduced due to the site blocking

  13. Bulk and surface energetics of crystalline lithium hydride: Benchmarks from quantum Monte Carlo and quantum chemistry

    OpenAIRE

    Binnie, S. J.; Nolan, S. J.; Drummond, Neil; Alfe`, D.; Allan, N. L; Manby, F. R.; Gillan, M. J.

    2010-01-01

    We show how accurate benchmark values of the surface formation energy of crystalline lithium hydride can be computed by the complementary techniques of quantum Monte Carlo (QMC) and wavefunction-based molecular quantum chemistry. To demonstrate the high accuracy of the QMC techniques, we present a detailed study of the energetics of the bulk LiH crystal, using both pseudopotential and all-electron approaches. We show that the equilibrium lattice parameter agrees with experiment to within 0.03...

  14. Nanoporous Anodic Alumina Platforms: Engineered Surface Chemistry and Structure for Optical Sensing Applications

    OpenAIRE

    Tushar Kumeria; Abel Santos; Dusan Losic

    2014-01-01

    Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA) structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structur...

  15. Surface chemistry and reactivity of skin-passed hot dip galvanized coating

    OpenAIRE

    Mataigne, Jean-Michel; Vaché, Véronique; Repoux, Monique

    2009-01-01

    GI coatings are covered by a very thin aluminum layer that precipitates after wiping. Anisotropic growing of zinc crystals during solidification induces a strong basal texture in GI coatings. Skin-pass induced changes in GI coating surface chemistry, crystallography and reactivity have been assessed. Local coating analyses have been performed (XPS, TOF-SIMS) in order to describe local effects of roughness indentation during skin-pass on coating characteristics. A laboratory bi-crushing device...

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

    OpenAIRE

    Chinga-Carrasco, Gary; Syverud, Kristin

    2014-01-01

    Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups ar...

  17. Enhancing single nanoparticle surface chemistry by plasmonic overheating in an optical trap

    OpenAIRE

    Weihai Ni; Haojin Ba; Lutich, A.A.; F. J\\xe4ckel; Feldmann, J.

    2012-01-01

    Surface-chemistry of individual, optically trapped plasmonic nanoparticles is modified and accelerated by plasmonic overheating. Depending on the optical trapping power, gold nanorods can exhibit red-shifts of their plasmon resonance (i.e. increasing aspect ratio) under oxidative conditions. In contrast, in bulk exclusively blue shifts (decreasing aspect ratios) are observed. Supported by calculations, we explain this finding by local temperatures in the trap exceeding the boiling point of th...

  18. Enhancing single-nanoparticle surface-chemistry by plasmonic overheating in an optical trap.

    Science.gov (United States)

    Ni, Weihai; Ba, Haojin; Lutich, Andrey A; Jäckel, Frank; Feldmann, Jochen

    2012-09-12

    Surface-chemistry of individual, optically trapped plasmonic nanoparticles is modified and accelerated by plasmonic overheating. Depending on the optical trapping power, gold nanorods can exhibit red shifts of their plasmon resonance (i.e., increasing aspect ratio) under oxidative conditions. In contrast, in bulk exclusively blue shifts (decreasing aspect ratios) are observed. Supported by calculations, we explain this finding by local temperatures in the trap exceeding the boiling point of the solvent that cannot be achieved in bulk. PMID:22924589

  19. The contribution of inflammasome components on macrophage response to surface nanotopography and chemistry

    Science.gov (United States)

    Christo, Susan; Bachhuka, Akash; Diener, Kerrilyn R.; Vasilev, Krasimir; Hayball, John D.

    2016-01-01

    Implantable devices have become an established part of medical practice. However, often a negative inflammatory host response can impede the integration and functionality of the device. In this paper, we interrogate the role of surface nanotopography and chemistry on the potential molecular role of the inflammasome in controlling macrophage responses. To achieve this goal we engineered model substrata having precisely controlled nanotopography of predetermined height and tailored outermost surface chemistry. Bone marrow derived macrophages (BMDM) were harvested from genetically engineered mice deficient in the inflammasome components ASC, NLRP3 and AIM2. These cells were then cultured on these nanoengineered substrata and assessed for their capacity to attach and express pro-inflammatory cytokines. Our data provide evidence that the inflammasome components ASC, NLRP3 and AIM2 play a role in regulating macrophage adhesion and activation in response to surface nanotopography and chemistry. The findings of this paper are important for understanding the inflammatory consequences caused by biomaterials and pave the way to the rational design of future implantable devices having controlled and predictable inflammatory outcomes. PMID:27188492

  20. The contribution of inflammasome components on macrophage response to surface nanotopography and chemistry

    Science.gov (United States)

    Christo, Susan; Bachhuka, Akash; Diener, Kerrilyn R.; Vasilev, Krasimir; Hayball, John D.

    2016-05-01

    Implantable devices have become an established part of medical practice. However, often a negative inflammatory host response can impede the integration and functionality of the device. In this paper, we interrogate the role of surface nanotopography and chemistry on the potential molecular role of the inflammasome in controlling macrophage responses. To achieve this goal we engineered model substrata having precisely controlled nanotopography of predetermined height and tailored outermost surface chemistry. Bone marrow derived macrophages (BMDM) were harvested from genetically engineered mice deficient in the inflammasome components ASC, NLRP3 and AIM2. These cells were then cultured on these nanoengineered substrata and assessed for their capacity to attach and express pro-inflammatory cytokines. Our data provide evidence that the inflammasome components ASC, NLRP3 and AIM2 play a role in regulating macrophage adhesion and activation in response to surface nanotopography and chemistry. The findings of this paper are important for understanding the inflammatory consequences caused by biomaterials and pave the way to the rational design of future implantable devices having controlled and predictable inflammatory outcomes.

  1. Regulating Biocompatibility of Carbon Spheres via Defined Nanoscale Chemistry and a Careful Selection of Surface Functionalities

    Science.gov (United States)

    Misra, Santosh K.; Chang, Huei-Huei; Mukherjee, Prabuddha; Tiwari, Saumya; Ohoka, Ayako; Pan, Dipanjan

    2015-10-01

    A plethora of nanoarchitectures have been evaluated preclincially for applications in early detection and treatment of diseases at molecular and cellular levels resulted in limited success of their clinical translation. It is important to identify the factors that directly or indirectly affect their use in human. We bring a fundamental understanding of how to adjust the biocompatibility of carbon based spherical nanoparticles (CNPs) through defined chemistry and a vigilant choice of surface functionalities. CNPs of various size are designed by tweaking size (2-250 nm), surface chemistries (positive, or negatively charged), molecular chemistries (linear, dendritic, hyperbranched) and the molecular weight of the coating agents (MW 400-20 kDa). A combination of in vitro assays as tools were performed to determine the critical parameters that may trigger toxicity. Results indicated that hydrodynamic sizes are potentially not a risk factor for triggering cellular and systemic toxicity, whereas the presence of a highly positive surface charge and increasing molecular weight enhance the chance of inducing complement activation. Bare and carboxyl-terminated CNPs did present some toxicity at the cellular level which, however, is not comparable to those caused by positively charged CNPs. Similarly, negatively charged CNPs with hydroxyl and carboxylic functionalities did not cause any hemolysis.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-15

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

  4. Chromate removal by surface-modified nanoscale zero-valent iron: Effect of different surface coatings and water chemistry.

    Science.gov (United States)

    Dong, Haoran; He, Qi; Zeng, Guangming; Tang, Lin; Zhang, Chang; Xie, Yankai; Zeng, Yalan; Zhao, Feng; Wu, Yanan

    2016-06-01

    This study investigated the correlation between the colloidal stability and reactivity of surface-modified nano zero-valent iron (SM-nZVI) as affected by the surface coating (i.e., polyacrylic acid [PAA] and starch) under various geochemical conditions. Generally, the colloidal stability of nZVI was enhanced with increasing loading of surface coating, while there is an optimum loading for the most efficient Cr(VI) removal by SM-nZVI. At lower loadings than the optimum loading, the surface coating could enhance the particle stabilization, facilitating the Cr(VI) reduction by providing more available surface sites. However, the over-loaded surface coating on the surface of nZVI particles decreased the Cr(VI) reduction due to the occupation of the reactive sites and the inhibition of the mass transfer of Cr(VI) ions from water to the particle surface by providing the electrostatic or steric repulsion. The effects of Ca(2+) ions or humic acid (HA) on the colloidal stability and reactivity of PAA-modified nZVI (P-nZVI) and starch-modified nZVI (S-nZVI) were examined. Differing stability behavior and reactivity were observed for different SM-nZVI. It was found that the presence of Ca(2+) or HA altered surface chemistry of SM-nZVI, the particle-particle interaction and the particle-contaminant interaction, and hence influencing the stability behavior and reactivity of the particles. PMID:26970032

  5. From solution to oxide. Cations condensation in aqueous solution. Surface chemistry of oxides

    International Nuclear Information System (INIS)

    How is formed a solid from a solution? What are the properties of a dispersion of particles? The aim of this book is to answer to these questions. From an overview of the condensation processes of the cations in aqueous solution and the revealing of the structural relationships between species in solution and the formed solids, this book gives a logic in the phenomenon of oxides precipitation. The relationship that is established between the solutions chemistry and the solid chemistry allows to rationalize the behaviour of cations and to discuss the various factors whose structure, morphology and particles size are depending. It is from basic concepts relative to the oxide - aqueous solution interface that is presented the surface chemistry of oxides nano-particles. This one establishes the properties and the behaviour of the dispersions. Different phenomena bound to adsorption (arranged aggregation, control of particles size, interfacial electronic transfer, magnetic interactions between particles...) are studied. This book develops some aspects of the chemistry of metallic cations which is very important in a fundamental and technological point of view (synthesis of nano-materials, ceramics powders, catalysts, geochemical processes, biological phenomena, sol-gel techniques...). It is intended for university or engineers students and industrial searchers. (O.M.)

  6. Affinity Induced Surface Functionalization of Liposomes Using Cu-Free Click Chemistry

    DEFF Research Database (Denmark)

    Bak, Martin; Jølck, Rasmus Irming; Eliasen, Rasmus;

    2016-01-01

    be used for functionalization of other nanoparticles or solid surfaces. The method exploits a synergistic effect of having both affinity and covalent anchoring tags on the surface of the liposome. This was achieved by synthesizing a peptide linker system that uses Cu-free strain-promoted click...... chemistry in combination with histidine affinity tags. The investigation of post-functionalization of PEGylated liposomes was performed with a cyclic RGDfE peptide. By exploring both affinity and covalent tags a 98 ± 2.0% coupling efficiency was achieved, even a diluted system showed a coupling efficiency...

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

    DEFF Research Database (Denmark)

    Malmström, Jenny; Shipovskov, Stepan; Christensen, Brian;

    2009-01-01

    Osteopontin is a highly charged glycoprotein present in the extra cellular matrix of a wide range of tissues. It is, in particular, relevant for biomaterials through its role in mineralized tissue remodeling. The adsorption and enzymatic cleavage of osteopontin at four different surface chemistries...... (methyl-, carboxylic-, and amine-terminated alkanethiol self-assembled monolayers and bare gold) have been studied utilizing a combination of the quartz crystal microbalance with dissipation and surface plasmon resonance. Full length bovine milk osteopontin was used which is well characterized with...

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

    Science.gov (United States)

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

    2014-06-01

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

  9. Protein Adsorption to Surface Chemistry and Crystal Structure Modification of Titanium Surfaces

    Directory of Open Access Journals (Sweden)

    Ryo Jimbo

    2010-07-01

    Full Text Available Objectives: To observe the early adsorption of extracellular matrix and blood plasma proteins to magnesium-incorporated titanium oxide surfaces, which has shown superior bone response in animal models.Material and Methods: Commercially pure titanium discs were blasted with titanium dioxide (TiO2 particles (control, and for the test group, TiO2 blasted discs were further processed with a micro-arc oxidation method (test. Surface morphology was investigated by scanning electron microscopy, surface topography by optic interferometry, characterization by X-ray photoelectron spectroscopy (XPS, and by X-ray diffraction (XRD analysis. The adsorption of 3 different proteins (fibronectin, albumin, and collagen type I was investigated by an immunoblotting technique.Results: The test surface showed a porous structure, whereas the control surface showed a typical TiO2 blasted structure. XPS data revealed magnesium-incorporation to the anodic oxide film of the surface. There was no difference in surface roughness between the control and test surfaces. For the protein adsorption test, the amount of albumin was significantly higher on the control surface whereas the amount of fibronectin was significantly higher on the test surface. Although there was no significant difference, the test surface had a tendency to adsorb more collagen type I.Conclusions: The magnesium-incorporated anodized surface showed significantly higher fibronectin adsorption and lower albumin adsorption than the blasted surface. These results may be one of the reasons for the excellent bone response previously observed in animal studies.

  10. Surface defects and chemistry on the SnO2(110) surface

    Science.gov (United States)

    Cox, David F.

    1990-01-01

    A variety of ultrahigh vacuum (UHV) surface science techniques have been used to characterize the structural, electronic and chemical properties of SnO2(110), a model catalytic surface. Two types of surface oxygen vacancies have been identified, each associated with different band gap (defect) electronic states. Adsorption experiments show that the interaction of simple gases with this surface occurs primarily through these oxygen vacancies and can show site-specificity to only one of the two types of vacancies.

  11. Use of SURFACE CHEMKIN to model multiphase atmospheric chemistry: Application to nitrogen tetroxide spills

    Science.gov (United States)

    Brady, Brian B.; Robbin Martin, L.

    SURFACE CHEMKIN is a widely available computer program developed for kinetic modeling of chemical vapor deposition. We show that it may be adapted for kinetic modeling of multiphase chemistry in the atmosphere, with broad capability to deal with complex chemistry and physics. It can deal with multiple phases having different reaction manifolds in each phase, it deals with gas, surface, and bulk reactions and mass transfer rates, it keeps track of the phase equilibria with realistic activities, and it can operate in an adiabatic mode to include the effect of heat release on the system. The adapted model is applied here to the problem of a nitrogen tetroxide spill in the troposphere. The model is able to predict the formation of a nitric acid/water aerosol and to follow the chemistry taking place in both the gas and liquid phases as the spill dilutes in the surrounding atmosphere. The model predicts that in such a spill, most (70-90%) of the nitrogen oxides released are converted to nitric acid over a wide range of relative humidity.

  12. Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces

    Science.gov (United States)

    McBriarty, Martin E.

    Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

  13. Control and Characterization of Titanium Dioxide Morphology: Applications in Surface Organometallic Chemistry

    KAUST Repository

    Jeantelot, Gabriel

    2014-05-01

    Surface Organometallic Chemistry leads to the combination of the high activity and specificity of homogeneous catalysts with the recoverability and practicality of heterogeneous catalysts. Most metal complexes used in this chemistry are grafted on metal oxide supports such as amorphous silica (SiO2) and γ-alumina (Al2O3). In this thesis, we sought to enable the use of titania (TiO2) as a new support for single-site well-defined grafting of metal complexes. This was achieved by synthesizing a special type of anatase-TiO2, bearing a high density of identical hydroxyl groups, through hydrothermal synthesis then post-treatment under high vacuum followed by oxygen flow, and characterized by several analytical techniques including X-ray diffraction, transmission electron microscopy, infrared spectroscopy and nuclear magnetic resonance. Finally, as a proof of concept, the grafting of vanadium oxychloride (VOCl3) was successfully attempted.

  14. INLAND DISSOLVED SALT CHEMISTRY: STATISTICAL EVALUATION OF BIVARIATE AND TERNARY DIAGRAM MODELS FOR SURFACE AND SUBSURFACE WATERS

    Science.gov (United States)

    We compared the use of ternary and bivariate diagrams to distinguish the effects of atmospheric precipitation, rock weathering, and evaporation on inland surface and subsurface water chemistry. The three processes could not be statistically differentiated using bivariate models e...

  15. Evolution of surface chemistry and morphology of hyperbranched polysiloxane polyimides in simulated atomic oxygen environment

    International Nuclear Information System (INIS)

    Graphical abstract: Upon AO exposure, pristine polyimide is severely eroded and exhibits linear degradation behavior, while HBPSi polyimides demonstrate high AO survivability. - Highlights: • Hyperbranched polysiloxane polyimides (HBPSi PIs) were fabricated by co-polymerizing HBPSi with imide monomers. • The degradation behavior of HBPSi PIs is assessed based on its evolution of surface chemistry and morphology. • There is a percolation threshold of HBPSi addition to achieve the most desirable atomic oxygen (AO) resistance. • Desirable AO resistance is associated with the rapid formation of a much denser and more connected silica passivating layer. • The silica passivating layer formed in situ is time-dependent and grows with AO fluence. - Abstract: Hyperbranched polysiloxane (HBPSi) polyimide membranes were fabricated by copolymerizing amine-functionalized HBPSi and imide monomers. The atomic oxygen (AO) resistance of the resulting polyimides were investigated in simulated AO environment, based on their evolution of surface chemistry and morphology. Results indicated that a silica passivating layer finally formed on the membrane surfaces and, there was a percolation threshold of HBPSi addition to achieve the most desirable AO resistance. This is explained by the formation of a much denser and more connected silica passivating layer in shorter time on the membrane surface at high HBPSi loading upon AO exposure

  16. Effect of Surface Chemistry on the Mechanisms and Governing Laws of Friction and Wear.

    Science.gov (United States)

    Dai, Ling; Sorkin, Viacheslav; Zhang, Yong-Wei

    2016-04-01

    Recent studies have shown that interface chemistry, that is, the formation and breaking of chemical bonds across contacting interfaces, is closely related to the wear and friction behavior at the nanoscale. In reality, the dangling bond density (DBD) at contacting surfaces can vary greatly. Currently, it remains unclear how friction and wear mechanisms depend on DBDs and whether the Archard's law for wear and Amonton's law for friction are still applicable for contacting surfaces with different DBDs. In this work, we address these issues by studying the wear and friction behavior between two sliding diamond-like carbon surfaces by controlling DBDs via hydrogenation using molecular dynamics simulations. It is found that the chemical bond breaking and remaking across the contacting interface play the key role in determining the friction and wear behavior. During the sliding, a higher DBD leads to more chemical bond formations across the interface, causing stronger wear via either atom or cluster detachments. With the same DBD, a mechanism transition from an atom-by-atom to cluster detachments is observed by increasing the normal load. Remarkably, a fully saturated surface can exhibit a wearless friction. We further show that after necessary modifications, the Archard's law for wear and the Amonton's law for friction may be applicable at the nanoscale. The present work reveals insights into the effect of interface chemistry on the friction and wear, and it provides guidelines for effective antiwear design. PMID:27004415

  17. The influence of carbon surface chemistry on supported palladium nanoparticles in heterogeneous reactions.

    Science.gov (United States)

    Ding, Yuxiao; Zhang, Liyun; Wu, Kuang-Hsu; Feng, Zhenbao; Shi, Wen; Gao, Qiang; Zhang, Bingsen; Su, Dang Sheng

    2016-10-15

    The surface chemistry of nanocarbon support can tailor chemical properties of precious metal nanoparticle/nanocarbon hybrid catalyst in heterogeneous reactions. We report on modified reduced graphene oxide (rGO) support with ionic liquid-derived carbonaceous surface for palladium nanoparticle (Pd NPs) decoration and their actions in different heterogeneous reactions. The surface chemistry of support materials was characterized in detail, and the influence of which on the formation and distribution of metal particles was further investigated. Three different types of reactions including Suzuki-Miyaura coupling reaction, CO oxidation and phenol reduction were examined in terms of reactivity and selectivity. The roles of substituted nitrogen in graphitic lattice and grafted groups on the carbon surface were exploited. Nitrogen-doping can give rise to changes in electronic properties of supported metals, and the Lewis basicity of the doped nitrogen atoms can favor the adsorption of acidic reactants in phenol reduction. The grafted groups derived a negative impact to the Suzuki-Miyaura coupling reaction, due to the involvement of larger reactant molecules, despite that they could prevent significant sintering of Pd NPs in the CO oxidation. PMID:27442144

  18. Thermal chemistry of the Cu-KI5 atomic layer deposition precursor on a copper surface

    International Nuclear Information System (INIS)

    The thermal chemistry of a Cu(I) ketoiminate complex, Cu-KI5, resulting from the modification of the known Air Products CupraSelect® copper CVD precursor Cu(hfac)(tmvs) designed to tether the two ligands via an isopropoxide linker, was studied under ultrahigh vacuum on a Cu(110) single-crystal surface by using a combination of temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy. Adsorption at low temperatures was determined to take place via the displacement of the vinyl ligand by the surface. Molecular desorption was seen at 210 K, and the evolution of Cu(II)-KI52 was established to take place at 280 K, presumably from a disproportionation reaction that also leads to the deposition of Cu(0). Other sets of desorption products were seen at 150, 250, and 430 K, all containing copper atoms and small organic moieties with molecular masses below 100 amu. The latter TPD peak in particular indicates significant fragmentation of the ligands, likely at the C–N bond that holds the vinylsilane-isopropoxide moiety tethered to the ketoimine fragment, and possibly also at the union between the vinylsilane and the alkoxide linker. The 430 K temperature measured for this chemistry may set an upper limit for clean Cu film deposition, but since reactivity on the surface was also found to be inhibited at higher surface coverages, it may be delayed to higher temperatures under atomic layer deposition conditions

  19. Surface chemistry dependent "switch" regulates the trafficking and therapeutic performance of drug-loaded carbon nanotubes.

    Science.gov (United States)

    Das, Manasmita; Singh, Raman Preet; Datir, Satyajit R; Jain, Sanyog

    2013-04-17

    The present study explores the possibility of exploiting surface functionality as one of the key regulators for modulating the intracellular trafficking and therapeutic performance of drug loaded carbon nanotubes (CNTs). In line with that approach, a series of biofunctionalized multiwalled carbon nanotubes (f-CNTs 1-6) decorated with various functional molecules including antifouling polymer (PEG), tumor recognition modules (folic acid/hyaluronic acid/estradiol), and fluorophores (rhodamine B isothiocyanate/Alexa Fluor) were synthesized. By loading different anticancer agents (methotrexate (MTX), doxorubicin (DOX), and paclitaxel (PTX)) onto each functionalized CNT preparation, we tried to elucidate how the surface functional molecules associated with each f-CNT influence their therapeutic potential. We observed that antiproliferative or apoptotic activity of drug-loaded CNTs critically depends on their mechanistic pathway of cellular internalization and intracellular trafficking, which in turn had an intimate rapport with their surface chemistry. To our knowledge, for the first time, we have embarked on the possibility of using a surface chemistry dependent "switch" to remote-control the second and third order targeting of chemotherapeutic agents supramolecularly complexed/adsorbed on CNTs, which in turn is expected to benefit the development of futuristic nanobots for cancer theranostics. PMID:23517108

  20. Early osseointegration driven by the surface chemistry and wettability of dental implants

    Directory of Open Access Journals (Sweden)

    Suelen Cristina SARTORETTO

    2015-06-01

    Full Text Available Objective The objective of this study was to investigate the impact of two different commercially available dental implants on osseointegration. The surfaces were sandblasting and acid etching (Group 1 and sandblasting and acid etching, then maintained in an isotonic solution of 0.9% sodium chloride (Group 2. Material and Methods X-ray photoelectron spectroscopy (XPS was employed for surface chemistry analysis. Surface morphology and topography was investigated by scanning electron microscopy (SEM and confocal microscopy (CM, respectively. Contact angle analysis (CAA was employed for wetting evaluation. Bone-implant-contact (BIC and bone area fraction occupied (BAFO analysis were performed on thin sections (30 μm 14 and 28 days after the installation of 10 implants from each group (n=20 in rabbits' tibias. Statistical analysis was performed by ANOVA at the 95% level of significance considering implantation time and implant surface as independent variables. Results Group 2 showed 3-fold less carbon on the surface and a markedly enhanced hydrophilicity compared to Group 1 but a similar surface roughness (p>0.05. BIC and BAFO levels in Group 2 at 14 days were similar to those in Group 1 at 28 days. After 28 days of installation, BIC and BAFO measurements of Group 2 were approximately 1.5-fold greater than in Group 1 (p<0.05. Conclusion The surface chemistry and wettability implants of Group 2 accelerate osseointegration and increase the area of the bone-to-implant interface when compared to those of Group 1.

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

    Science.gov (United States)

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

    2016-10-01

    Selective laser melting (SLM) has previously been shown to be a viable method for fabricating biomedical implants; however, the surface chemistry of SLM fabricated parts is poorly understood. In this study, X-ray photoelectron spectroscopy (XPS) was used to determine the surface chemistries of (a) SLM as-fabricated (SLM-AF) Ti6Al4V and (b) SLM fabricated and mechanically polished (SLM-MP) Ti6Al4V samples and compared with (c) traditionally manufactured (forged) and mechanically polished Ti6Al4V samples. The SLM-AF surface was observed to be porous with an average surface roughness (Ra) of 17.6±3.7μm. The surface chemistry of the SLM-AF was significantly different to the FGD-MP surface with respect to elemental distribution and their existence on the outermost surface. Sintered particles on the SLM-AF surface were observed to affect depth profiling of the sample due to a shadowing effect during argon ion sputtering. Surface heterogeneity was observed for all three surfaces; however, vanadium was witnessed only on the mechanically polished (SLM-MP and FGD-MP) surfaces. The direct and indirect 3T3 cell cytotoxicity studies revealed that the cells were viable on the SLM fabricated Ti6Al4V parts. The varied surface chemistry of the SLM-AF and SLM-MP did not influence the cell behaviour. PMID:27287125

  2. Elementary surface chemistry during CuO/Al nanolaminate-thermite synthesis: copper and oxygen deposition on aluminum (111) surfaces.

    Science.gov (United States)

    Lanthony, Cloé; Guiltat, Mathilde; Ducéré, Jean Marie; Verdier, Agnes; Hémeryck, Anne; Djafari-Rouhani, Mehdi; Rossi, Carole; Chabal, Yves J; Estève, Alain

    2014-09-10

    The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (γ-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species. PMID:25089744

  3. Surface chemistry and friction behavior of the silicon carbide (0001) surface at temperatures to 1500 deg C

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.

    1981-01-01

    X-ray photoelectron and Auger electron spectroscopy analyses and friction studies were conducted with a silicon carbide (0001) surface in contact with iron at various temperatures to 1200 or 1500 C in a vacuum of 10 to the minus 8th power Pa. The results indicate that there is a significant temperature influence on both the surface chemistry and friction properties of silicon carbide. The principal contaminant of adsorbed amorphous carbon on the silicon carbide surface in the as received state is removed by simply heating to 400 C. Above 400 C, graphite and carbide type carbine are the primary species on the silicon carbide surface, in addition to silicon. The coefficients of friction of polycrystalline iron sliding against a single crystal silicon carbide (0001) surface were high at temperatures to 800 C. Similar coefficients of friction were obtained at room temperature after the silicon carbide was preheated at various temperatures up 800 C. When the friction experiments were conducted above 800 C or when the specimens were preheated to above 800 C, the coefficients of friction were dramatically lower. At 800 C the silicon and carbide type carbon are at a maximum intensity in the XPS spectra. With increasing temperature above 800 C, the concentration of the graphite increases rapidly on the surface, whereas those of the carbide type carbon and silicon decrease rapidly.

  4. Nanoporous Anodic Alumina Platforms: Engineered Surface Chemistry and Structure for Optical Sensing Applications

    Directory of Open Access Journals (Sweden)

    Tushar Kumeria

    2014-07-01

    Full Text Available Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structures that can be explored for developing low-cost, portable, rapid-response and highly sensitive sensing devices in combination with surface plasmon resonance (SPR and reflective interference spectroscopy (RIfS techniques. This review article highlights the recent advances on fabrication, surface modification and structural engineering of NAA and its application and performance as a platform for SPR- and RIfS-based sensing and biosensing devices.

  5. Investigation of silicate surface chemistry and reaction mechanisms associated with mass transport in geologic media

    International Nuclear Information System (INIS)

    The concentration and rate of transport of radionuclides through geologic media can be strongly influenced by the extent of sorption on aquifer surfaces. Over time intervals relevant to such transport processes, rock and mineral surfaces cannot be considered as inert, unreactive substrates but rather as groundwater/solidphase interfaces which are commonly in a state of natural or artificially induced disequilibrium. The goal of the present research is to define experimentally the type of water/rock interactions that will influence surface chemistry and hence sorption characteristics and capacities of natural aquifers. As wide a range of silicate minerals as possible was selected for study to represent rock-forming minerals in basalt, tuff, and granite. The minerals include K-feldspar, plagioclase feldspar, olivine, hornblende, biotite, and volcanic glass

  6. In vitro biocompatibility of amorphous carbon based coatings by varying of surface chemistry and nitrogen concentrations

    International Nuclear Information System (INIS)

    The study of a-C:N coatings at different concentration of nitrogen, their surface chemistry and wettability effect on cell/material response in vitro test was performed. The surface structure of deposited coatings was investigated by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. The coatings were characterized with respect to their bonding structure by photoelectron spectroscopy (XPS) analysis. The wettability was analysed by means of advanced water contact angle method and the surface free energy (SFE) was calculated according to Robertson equation. The biocompatibility was estimated by standard protocols. The best results were obtained in the case of coatings with the greater parameters of SFE and the minimal values of ratio N2 : C7H8

  7. Relationships between precipitation and surface water chemistry in three Carolina bays

    International Nuclear Information System (INIS)

    Carolina Bays are shallow freshwater wetlands, the only naturally occurring lentic systems on the southeastern coastal plain. Bays are breeding sites for many amphibian species, but data on precipitation/surface water relationships and long-term chemical trends are lacking. Such data are essential to interpret major fluctuations in amphibian populations. Surface water and bulk precipitation were sampled bi-weekly for over two years at three bays along a 25 km transect on the Savannah River Site in South Carolina. Precipitation chemistry was similar at all sites; average pH was 4.56, and the major ions were H+ (30.8 % of total), and SO4 (50.3% of total). H+ was positively correlated with SO4, suggesting the importance of anthropogenic acids to precipitation chemistry. All three bays, Rainbow Bay (RB), Thunder Bay (TB), and Ellenton Bay (EB), contained soft (specific conductivity 5--90 microS/cm), acidic water (pH 4.0--5.9) with DOM from 4--40 mg/L. The major cation for RB, TB, and EB, respectively, was: Mg (30.8 % of total); Na (27% of total); and Ca (34.2% of total). DOM was the major anion for all bays, and SO4 represented 13 to 28 % of total anions. H+ was not correlated to DOM or SO, in RB; H+ was positively correlated to DOM and SO4 in TB, and negatively correlated to DOM and SO4 in EB. Different biogeochemical processes probably control pH and other chemical variables in each bay. While surface water H+ was not directly correlated with precipitation H+, NO3, or SO4, precipitation and shallow groundwater are dominant water sources for these bays. Atmospheric inputs of anthropogenic acids and other chemicals are important factors influencing bay chemistry

  8. Protein Adsorption to Surface Chemistry and Crystal Structure Modification of Titanium Surfaces

    OpenAIRE

    Ryo Jimbo; Mikael Ivarsson; Anita Koskela; Young-Taeg Sul; Johansson, Carina B.

    2010-01-01

    ABSTRACT Objectives To observe the early adsorption of extracellular matrix and blood plasma proteins to magnesium-incorporated titanium oxide surfaces, which has shown superior bone response in animal models. Material and Methods Commercially pure titanium discs were blasted with titanium dioxide (TiO2) particles (control), and for the test group, TiO2 blasted discs were further processed with a micro-arc oxidation method (test). Surface morphology was investigated by scanning electron micro...

  9. Diffusive grain-surface chemistry involving the atoms and diatomic molecules of two elements

    CERN Document Server

    Rae, J G L; Hartquist, T W; Pilling, M J; Toniazzo, T

    2003-01-01

    A model of the grain surface chemistry involving the accretion of atoms of two different elements, X and Y, and their reactions to form species X_2, XY, and Y_2 was examined for a wide range of choices for the values of its three free parameters - the accretion rate of X and Y, the desorption rate of X and the grain surface sweeping time of Y, all considered relative to the grain surface sweeping rate of X. Relative production rates of the diatomics were calculated with five methods involving, respectively, a high-order truncation of the master equation, a low-order truncation of the master equation, the standard deterministic rate equation approach, a modified rate equation approach and a set of approximations which are in some cases appropriate for accretion dominated chemistry. The accuracies of the relative production rates calculated with the different methods were assessed for the wide range of model parameters. The more accurate of the low-truncation master equation calculations and the standard determ...

  10. The influence of the surface chemistry of silver nanoparticles on cell death

    International Nuclear Information System (INIS)

    The influence of the surface chemistry of silver nanoparticles (AgNPs) on p53 mediated cell death was evaluated using human dermal fibroblast (HDF) and lung cancer (A549) cells. The citrate reduced AgNPs (C-AgNPs) were modified with either lactose (L-AgNPs) or a 12-base long oligonucleotide (O-AgNPs). Both unmodified and modified AgNPs showed increased concentration and time dependent cytotoxicity and genotoxicity causing an increased p53 up-regulation within 6 h and led to apoptotic or necrotic cell deaths. The C-AgNPs induced more cytotoxicity and cellular DNA damage than the surface modified AgNPs. Modifying the C-AgNPs with lactose or the oligonucleotide reduced both necrotic and apoptotic cell deaths in the HDF cells. The C-AgNPs caused an insignificant necrosis in A549 cells whereas the modified AgNPs caused necrosis and apoptosis in both cell types. Compared to the O-AgNPs, the L-AgNPs triggered more cellular DNA damage, which led to up-regulation of p53 gene inducing apoptosis in A549 cells compared to HDF cells. This suggests that the different surface chemistries of the AgNPs cause different cellular responses that may be important not only for their use in medicine but also for reducing their toxicity. (paper)

  11. Surface chemistry manipulation of gold nanorods preserves optical properties for bio-imaging applications

    Energy Technology Data Exchange (ETDEWEB)

    Polito, Anthony B.; Maurer-Gardner, Elizabeth I.; Hussain, Saber M., E-mail: saber.hussain@us.af.mil [Air Force Research Laboratory, Molecular Bioeffects Branch, Bioeffects Division, Human Effectiveness Directorate (United States)

    2015-12-15

    Due to their anisotropic shape, gold nanorods (GNRs) possess a number of advantages for biosystem use including, enhanced surface area and tunable optical properties within the near-infrared (NIR) region. However, cetyl trimethylammonium bromide-related cytotoxicity, overall poor cellular uptake following surface chemistry modifications, and loss of NIR optical properties due to material intracellular aggregation in combination remain as obstacles for nanobased biomedical GNR applications. In this article, we report that tannic acid-coated 11-mercaptoundecyl trimethylammonium bromide (MTAB) GNRs (MTAB-TA) show no significant decrease in either in vitro cell viability or stress activation after exposures to A549 human alveolar epithelial cells. In addition, MTAB-TA GNRs demonstrate a substantial level of cellular uptake while displaying a unique intracellular clustering pattern. This clustering pattern significantly reduces intracellular aggregation, preserving the GNRs NIR optical properties, vital for biomedical imaging applications. These results demonstrate how surface chemistry modifications enhance biocompatibility, allow for higher rate of internalization with low intracellular aggregation of MTAB-TA GNRs, and identify them as prime candidates for use in nanobased bio-imaging applications.Graphical Abstract.

  12. Surface chemistry manipulation of gold nanorods preserves optical properties for bio-imaging applications

    International Nuclear Information System (INIS)

    Due to their anisotropic shape, gold nanorods (GNRs) possess a number of advantages for biosystem use including, enhanced surface area and tunable optical properties within the near-infrared (NIR) region. However, cetyl trimethylammonium bromide-related cytotoxicity, overall poor cellular uptake following surface chemistry modifications, and loss of NIR optical properties due to material intracellular aggregation in combination remain as obstacles for nanobased biomedical GNR applications. In this article, we report that tannic acid-coated 11-mercaptoundecyl trimethylammonium bromide (MTAB) GNRs (MTAB-TA) show no significant decrease in either in vitro cell viability or stress activation after exposures to A549 human alveolar epithelial cells. In addition, MTAB-TA GNRs demonstrate a substantial level of cellular uptake while displaying a unique intracellular clustering pattern. This clustering pattern significantly reduces intracellular aggregation, preserving the GNRs NIR optical properties, vital for biomedical imaging applications. These results demonstrate how surface chemistry modifications enhance biocompatibility, allow for higher rate of internalization with low intracellular aggregation of MTAB-TA GNRs, and identify them as prime candidates for use in nanobased bio-imaging applications.Graphical Abstract

  13. Carbon key-properties for microcystin adsorption in drinking water treatment: structure or surface chemistry?

    OpenAIRE

    Júlio, Maria de Fátima de Jesus Leal

    2011-01-01

    The carbon key-properties (structure and surface chemistry) for microcystin-LR (MC-LR) adsorption onto activated carbon were investigated. Waters with an inorganic background matrix approaching that of the soft natural water (2.5 mM ionic strength) were used. Also, model waters with controlled ionic make-up and NOM surrogate with similar size of MC-LR (tannic acid - TA) with MC-LR extracts were tested with activated carbon NORIT 0.8 SUPRA. For this AC, two particle sizes, 125-180 μm and 63-90...

  14. Rapid changes in surface water carbonate chemistry during Antarctic sea ice melt

    OpenAIRE

    Jones, Elizabeth M.; Bakker, Dorothee C. E.; Venables, Hugh J.; Whitehouse, Michael J.; Korb, Rebecca E.; Watson, Andrew J.

    2011-01-01

    The effect of sea ice melt on the carbonate chemistry of surface waters in the Weddell–Scotia Confluence, Southern Ocean, was investigated during January 2008. Contrasting concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA) and the fugacity of carbon dioxide (fCO2) were observed in and around the receding sea ice edge. The precipitation of carbonate minerals such as ikaite (CaCO3·6H2O) in sea ice brine has the net effect of decreasing DIC and TA and increasing the fCO2 i...

  15. Succinimidyl Ester Surface Chemistry: Implications of the Competition between Aminolysis and Hydrolysis on Covalent Protein Immobilization

    OpenAIRE

    Lim, China Y.; Owens, Nicholas A.; Wampler, Ronald D.; Ying, YiXin; Granger, Jennifer H.; Porter, Marc D.; Takahashi, Makoto; Shimazu, Katsuaki

    2014-01-01

    N-Hydroxysuccinimide (NHS) ester terminal groups are commonly used to covalently couple amine-containing biomolecules (e.g., proteins and peptides) to surfaces via amide linkages. This one-step aminolysis is often performed in buffered aqueous solutions near physiological pH (pH 6 to pH 9). Under these conditions, the hydrolysis of the ester group competes with the amidization process, potentially degrading the efficiency of the coupling chemistry. The work herein examines the efficiency of c...

  16. Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Shibi [College of Physical Science and Technology, Central China Normal University, Wuhan 430079 (China); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Nguyen, Luan; Cheng, Fang [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Liu, Lacheng [Department of Physics, Nanchang University, Nanchang 350000 (China); Yu, Ying [College of Physical Science and Technology, Central China Normal University, Wuhan 430079 (China); Tao, Franklin, E-mail: franklin.tao.2011@gmail.com [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2014-11-30

    Graphical abstract: - Abstract: Near surface alloy (NSA) model catalyst Pt/Cu/Pt(1 1 1) was prepared on Pt(1 1 1) through a controlled vapor deposition of Cu atoms. Different coordination environments of Pt atoms of the topmost Pt layer with the underneath Cu atoms in the subsurface result in different local electronic structures of surface Pt atoms. Surface structure and chemistry of the NAS model catalyst in Torr pressure of CO were studied with high pressure scanning tunneling microscopy (HP-STM) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). In Torr pressure of CO, the topmost Pt layer of Pt/Cu/Pt(1 1 1) is restructured to thin nanoclusters with size of about 1 nm. Photoemission feature of O 1s of CO on Pt/Cu/Pt(1 1 1) suggests CO adsorbed on both edge and surface of these formed nanoclusters. This surface is active for CO oxidation. Atomic layers of carbon are formed on Pt/Cu/Pt(1 1 1) at 573 K in 2 Torr of CO.

  17. Quantifying the impact of PWR primary side chemistry regime utilizing surface activity data

    International Nuclear Information System (INIS)

    The collection of gamma spectroscopic data, known as gamma scanning in the US, allows for identification and quantification of radionuclides contributing to shutdown dose rates. Based on such data, plants can quantitatively assess the impact of operational and chemistry changes and optimize their source term reduction programs.. To quantify the effect of PWR primary side chemistry on activity incorporation including zinc addition, a simplistic activity balance assessment of Co-58 activity incorporation and release rate constants was developed. Under steady state conditions, the sum of the net release rates of corrosion product radionuclides to the primary coolant from fuel cladding/crud and steam generator tubing and stainless steel surfaces must be equal to the net removal rates from the coolant. Release and re-incorporation of activated corrosion products can occur from each of the referenced primary surfaces, and isotopic (and mass) balances are developed based on the net value of these processes. Net deposition is expected locally in high duty boiling regions, but the reverse is expected in regions where the boiling rate has decreased as fuel burnup occurs during the cycle, i.e., there could be a net release of nickel and iron from such regions. Although transport rates of non-radioactive species such as iron and nickel can be modelled, it is difficult to validate the models since significant transport occurs during shutdowns, surface analysis results are currently only performed after shutdown. However, release of radionuclides from out-of-core surfaces has been shown to be minimal during the shutdown evolution; and non-destructive surface analyses performed following shutdown can be used to reasonably approximate surface activity during power operation prior to the shutdown. From these measurements, net deposition or release rates from out-of-core surfaces and the core during power operation can be estimated. The observed reductions in RCS piping surface

  18. Flame treatment of low-density polyethylene: Surface chemistry across the length scales

    International Nuclear Information System (INIS)

    The relationship between surface chemistry and morphology of flame treated low-density polyethylene (LDPE) was studied by various characterization techniques across different length scales. The chemical composition of the surface was determined on the micrometer scale by X-ray photoelectron spectroscopy (XPS) as well as with time of flight secondary ion mass spectrometry (ToF-SIMS), while surface wettability was obtained through contact angle (CA) measurements on the millimeter scale. The surface concentration of hydroxyl, carbonyl and carboxyl groups, as a function of the 'number' of the flame treatment passes (which is proportional to the treatment time) was obtained. Moreover, a correlation was found with chemical composition and polarity, emphasizing the role of oxygen-containing functional groups introduced during the treatment. Carboxyl functional groups were specifically identified by fluorescent labeling and the results were compared with the ToF-SIMS data. In addition, atomic force microscopy (AFM) was used to evaluate changes in surface topography and roughness on the nanometer to micrometer length scales. After flame treatment, water-soluble low molecular weight oxidized materials (LMWOM), which were generated as products of oxidation and chain scission of the LDPE surface, agglomerated into small topographical mounds that were visible in the AFM micrographs. After rinsing the flame treated samples with water and ethanol, bead-like nodular surface structures were observed. The ionization state of flame treated LDPE surfaces was monitored by chemical force microscopy (CFM). The effective surface pKa values of carboxylic acid (-COOH) obtained by AFM were revealed by chemical force titration curves and the effective surface pKa values were found to be around 6

  19. Electrolyte effects on the surface chemistry and cellular response of anodized titanium

    International Nuclear Information System (INIS)

    Highlights: • Ti samples were anodized using various electrolytes. • Anodization decreased carbon adsorption, improving hydrophilicity. • Improved hydrophilicity led to improved cellular attachment. • Only one electrolyte showed any heteroatom incorporation into the TiO2 layer. • Choice of electrolyte played no role on the effects of anodization. - Abstract: Anodic oxidation of titanium (Ti) material is used to enhance biocompatibility, yet the effects of various electrolytes on surface characteristics and cellular behavior have not been completely elucidated. To investigate this topic, oxide layers were produced on Ti substrates by anodizing them in aqueous electrolytes of (NH4)2O·5B2O3, (NH4)2SO4, or (NH4)3PO4, after which their surface characteristics and cellular responses were examined. Overall, no surface differences between the electrolytes were visually observed. X-ray photoelectron spectroscopy (XPS) revealed that the anodized surfaces are composed of titanium dioxide (TiO2), while incorporation from electrolyte was only observed for (NH4)3PO4. Surface adsorption of carbon contaminants during sterilization was suppressed by anodization, leading to lower water contact angles. The attachment of MC3T3-E1 osteoblast-like cells was also improved by anodization, as evidenced by visibly enlarged pseudopods. This improved attachment performance is likely due to TiO2 formation. Overall, electrolyte selection showed no effect on either surface chemistry or cellular response of Ti materials

  20. Monitoring oligonucleotide hybridization at subnanomolar level by surface plasmon resonance biosensor: Optimization of surface chemistry

    Czech Academy of Sciences Publication Activity Database

    Vaisocherová, Hana; Zítová, Alice; Lachmanová, Markéta; Tobiška, Petr; Homola, Jiří

    Oxford: Elsevier, 2006. P400---. [Biosensors 2006 /9./. 10.05.2006-12.05.2006, Toronto] R&D Projects: GA ČR(CZ) GA202/05/0628 Institutional research plan: CEZ:AV0Z20670512 Keywords : surface plasmon resonance * biosensors * DNA Subject RIV: JB - Sensor s, Measurment, Regulation

  1. Immobilization of Cysteine-Tagged Proteins on Electrode Surfaces by Thiol-Ene Click Chemistry.

    Science.gov (United States)

    Zhang, Lin; Vilà, Neus; Klein, Tobias; Kohring, Gert-Wieland; Mazurenko, Ievgen; Walcarius, Alain; Etienne, Mathieu

    2016-07-13

    Thiol-ene click chemistry can be exploited for the immobilization of cysteine-tagged dehydrogenases in an active form onto carbon electrodes (glassy carbon and carbon felt). The electrode surfaces have been first modified with vinylphenyl groups by electrochemical reduction of the corresponding diazonium salts generated in situ from 4-vinylaniline. The grafting process has been optimized in order to not hinder the electrochemical regeneration of NAD(+)/NADH cofactor and soluble mediators such as ferrocenedimethanol and [Cp*Rh(bpy)Cl](+). Having demonstrated the feasibility of thiol-ene click chemistry for attaching ferrocene moieties onto those carbon surfaces, the same approach was then applied to the immobilization of d-sorbitol dehydrogenases with cysteine tag. These proteins can be effectively immobilized (as pointed out by XPS), and the cysteine tag (either 1 or 2 cysteine moieties at the N terminus of the polypeptide chain) was proven to maintain the enzymatic activity of the dehydrogenase upon grafting. The bioelectrode was applied to electroenzymatic enantioselective reduction of d-fructose to d-sorbitol, as a case study. PMID:27299176

  2. Application of Multi-Species Microbial Bioassay to Assess the Effects of Engineered Nanoparticles in the Aquatic Environment: Potential of a Luminous Microbial Array for Toxicity Risk Assessment (LumiMARA on Testing for Surface-Coated Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    YounJung Jung

    2015-07-01

    Full Text Available Four different manufactured surface-coated silver nanoparticles (AgNPs with coating of citrate, tannic acid, polyethylene glycol, and branched polyethylenimine were used in this study. The toxicity of surface-coated AgNPs was evaluated by a luminous microbial array for toxicity risk assessment (LumiMARA using multi-species of luminescent bacteria. The salt stability of four different AgNPs was measured by UV absorbance at 400 nm wavelength, and different surface-charged AgNPs in combination with bacteria were observed using scanning electron microscopy (SEM. Both branched polyethylenimine (BPEI-AgNPs and polyethylene glycol (PEG-AgNPs were shown to be stable with 2% NaCl (non-aggregation, whereas both citrate (Cit-AgNPs and tannic acid (Tan-AgNPs rapidly aggregated in 2% NaCl solution. The values of the 50% effective concentration (EC50 for BPEI-AgNPs in marine bacteria strains (1.57 to 5.19 mg/L were lower than those for the other surface-coated AgNPs (i.e., Cit-AgNPs, Tan-AgNPs, and PEG-AgNPs. It appears that the toxicity of AgNPs could be activated by the interaction of positively charged AgNPs with the negatively charged bacterial cell wall from the results of LumiMARA. LumiMARA for toxicity screening has advantageous compared to a single-species bioassay and is applicable for environmental samples as displaying ranges of assessment results.

  3. Toward Cell Selective Surfaces: Cell Adhesion and Proliferation on Breath Figures with Antifouling Surface Chemistry.

    Science.gov (United States)

    Martínez-Campos, Enrique; Elzein, Tamara; Bejjani, Alice; García-Granda, Maria Jesús; Santos-Coquillat, Ana; Ramos, Viviana; Muñoz-Bonilla, Alexandra; Rodríguez-Hernández, Juan

    2016-03-16

    We report the preparation of microporous functional polymer surfaces that have been proven to be selective surfaces toward eukaryotic cells while maintaining antifouling properties against bacteria. The fabrication of functional porous films has been carried out by the breath figures approach that allowed us to create porous interfaces with either poly(ethylene glycol) methyl ether methacrylate (PEGMA) or 2,3,4,5,6-pentafluorostyrene (5FS). For this purpose, blends of block copolymers in a polystyrene homopolymer matrix have been employed. In contrast to the case of single functional polymer, using blends enables us to vary the chemical distribution of the functional groups inside and outside the formed pores. In particular, fluorinated groups were positioned at the edges while the hydrophilic PEGMA groups were selectively located inside the pores, as demonstrated by TOF-SIMS. More interestingly, studies of cell adhesion, growth, and proliferation on these surfaces confirmed that PEGMA functionalized interfaces are excellent candidates to selectively allow cell growth and proliferation while maintaining antifouling properties. PMID:26909529

  4. Thermal chemistry of copper acetamidinate atomic layer deposition precursors on silicon oxide surfaces studied by XPS

    International Nuclear Information System (INIS)

    The thermal surface chemistry of copper(I)-N,N′-di-sec-butylacetamidinate, [Cu(sBu-amd)]2, a metalorganic complex recently proposed for the chemical-based deposition of copper films, has been characterized on SiO2 films under ultrahigh vacuum conditions by x-ray photoelectron spectroscopy (XPS). Initial adsorption at cryogenic temperatures results in the oxidation of the copper centers with Cu 2p3/2 XPS binding energies close to those seen for a +2 oxidation state, an observation that the authors interpret as the result of the additional coordination of oxygen atoms from the surface to the Cu atoms of the molecular acetamidinate dimer. Either heating to 300 K or dosing the precursor directly at that temperature leads to the loss of one of its two ligands, presumably via hydrogenation/protonation with a hydrogen/proton from a silanol group, or following a similar reaction on a defect site. By approximately 500 K the Cu 2p3/2, C 1s, and N 1s XPS data suggest that the remaining acetamidinate ligand is displaced from the copper center and bonds to the silicon oxide directly, after which temperatures above 900 K need to be reached to promote further (and only partial) decomposition of those organic moieties. It was also shown that the uptake of the Cu precursor is self-limiting at either 300 or 500 K, although the initial chemistry is somewhat different at the two temperatures, and that the nature of the substrate also defines reactivity, with the thin native silicon oxide layer always present on Si(100) surfaces being less reactive than thicker films grown by evaporation, presumably because of the lower density of surface nucleation sites

  5. Thermal chemistry of copper acetamidinate atomic layer deposition precursors on silicon oxide surfaces studied by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Yunxi; Zaera, Francisco, E-mail: zaera@ucr.edu [Department of Chemistry, University of California, Riverside, California 92521 (United States)

    2016-01-15

    The thermal surface chemistry of copper(I)-N,N′-di-sec-butylacetamidinate, [Cu({sup s}Bu-amd)]{sub 2}, a metalorganic complex recently proposed for the chemical-based deposition of copper films, has been characterized on SiO{sub 2} films under ultrahigh vacuum conditions by x-ray photoelectron spectroscopy (XPS). Initial adsorption at cryogenic temperatures results in the oxidation of the copper centers with Cu 2p{sub 3/2} XPS binding energies close to those seen for a +2 oxidation state, an observation that the authors interpret as the result of the additional coordination of oxygen atoms from the surface to the Cu atoms of the molecular acetamidinate dimer. Either heating to 300 K or dosing the precursor directly at that temperature leads to the loss of one of its two ligands, presumably via hydrogenation/protonation with a hydrogen/proton from a silanol group, or following a similar reaction on a defect site. By approximately 500 K the Cu 2p{sub 3/2}, C 1s, and N 1s XPS data suggest that the remaining acetamidinate ligand is displaced from the copper center and bonds to the silicon oxide directly, after which temperatures above 900 K need to be reached to promote further (and only partial) decomposition of those organic moieties. It was also shown that the uptake of the Cu precursor is self-limiting at either 300 or 500 K, although the initial chemistry is somewhat different at the two temperatures, and that the nature of the substrate also defines reactivity, with the thin native silicon oxide layer always present on Si(100) surfaces being less reactive than thicker films grown by evaporation, presumably because of the lower density of surface nucleation sites.

  6. Thermal chemistry of the Cu-KI5 atomic layer deposition precursor on a copper surface

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Qiang; Zaera, Francisco, E-mail: zaera@ucr.edu [Department of Chemistry, University of California, Riverside, California 92521 (United States)

    2015-01-01

    The thermal chemistry of a Cu(I) ketoiminate complex, Cu-KI5, resulting from the modification of the known Air Products CupraSelect{sup ®} copper CVD precursor Cu(hfac)(tmvs) designed to tether the two ligands via an isopropoxide linker, was studied under ultrahigh vacuum on a Cu(110) single-crystal surface by using a combination of temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy. Adsorption at low temperatures was determined to take place via the displacement of the vinyl ligand by the surface. Molecular desorption was seen at 210 K, and the evolution of Cu(II)-KI5{sub 2} was established to take place at 280 K, presumably from a disproportionation reaction that also leads to the deposition of Cu(0). Other sets of desorption products were seen at 150, 250, and 430 K, all containing copper atoms and small organic moieties with molecular masses below 100 amu. The latter TPD peak in particular indicates significant fragmentation of the ligands, likely at the C–N bond that holds the vinylsilane-isopropoxide moiety tethered to the ketoimine fragment, and possibly also at the union between the vinylsilane and the alkoxide linker. The 430 K temperature measured for this chemistry may set an upper limit for clean Cu film deposition, but since reactivity on the surface was also found to be inhibited at higher surface coverages, it may be delayed to higher temperatures under atomic layer deposition conditions.

  7. UNIFYING SCALER FOR BIOASSAY TESTS

    Science.gov (United States)

    An extensive set of interlaboratory root bioassay data was unified using centroids of individual tests as scalers. It is shown that the dose response obeys a first order differential equation with the constant of the equation related to the sensitivity of the dose response relati...

  8. In-Depth Electrochemical Investigation of Surface Attachment Chemistry via Carbodiimide Coupling.

    Science.gov (United States)

    Booth, Marsilea Adela; Kannappan, Karthik; Hosseini, Ali; Partridge, Ashton

    2015-07-28

    Aminoferrocene is used as an electroactive indicator to investigate carbodiimide coupling reactions on a carboxylic acid-functionalized self-assembled monolayer. The commonly used attachment chemistry with 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) is used for surface activation. A number of conditions are investigated, including EDC and NHS concentration, buffer solutions, incubation timing, and aminoferrocene concentration. Ferrocene is a well-documented electroactive species, and the number of surface-bound ferrocene species can be calculated using electrochemical methods. This capability allows determination of optimal conditions, as well as providing a method for comparing and investigating novel carboxylated surfaces. An EDC-mediated procedure with ∼5 mM EDC and NHS (1:1) made in water, with a full acid monolayer, with 250 μM aminoferrocene for 40 min was found to give the highest ferrocene attachment. An application of this is demonstrated for preparing a probe-DNA-coated surface for DNA sensing. By backfilling with aminoferrocene, a differential quantification of the amount of probe DNA available for sensing can be obtained. This provides an elegant method to monitor an important aspect, namely, probe surface characterization, which will be highly useful for biosensing purposes. PMID:26107592

  9. Osteoinductive activity of insulin-functionalized cell culture surfaces obtained using diazonium chemistry

    Science.gov (United States)

    Mikulska, Anna; Filipowska, Joanna; Osyczka, Anna; Nowakowska, Maria; Szczubiałka, Krzysztof

    2014-12-01

    Polymeric surfaces suitable for cell culture (DR/Pec) were constructed from diazoresin (DR) and pectin (Pec) in a form of ultrathin films using the layer-by-layer (LbL) technique. The surfaces were functionalized with insulin using diazonium chemistry. Such functionalized surfaces were used to culture human mesenchymal stem cells (hMSCs) to assess their suitability for bone tissue engineering and regeneration. The activity of insulin immobilized on the surfaces (DR/Pec/Ins) was compared to that of insulin dissolved in the culture medium. Human MSC grown on insulin-immobilized DR/Pec surfaces displayed increased proliferation and higher osteogenic activity. The latter was determined by means of alkaline phosphatase (ALP) activity, which increases at early stages of osteoblasts differentiation. Insulin dissolved in the culture medium did not stimulate cell proliferation and its osteogenic activity was significantly lower. Addition of recombinant human bone morphogenetic protein 2 (rhBMP-2) to the culture medium further increased ALP activity in hMSCs indicating additive osteogenic action of immobilized insulin and rhBMP-2

  10. PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes

    Directory of Open Access Journals (Sweden)

    Norhan Nady

    2016-04-01

    Full Text Available A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme and nontoxic modifier, which can be safely labelled “green surface modification”. This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone (PES membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers—ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid—is presented.

  11. PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes.

    Science.gov (United States)

    Nady, Norhan

    2016-01-01

    A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled "green surface modification". This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers-ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)-is presented. PMID:27096873

  12. 77 FR 14837 - Bioassay at Uranium Mills

    Science.gov (United States)

    2012-03-13

    ... COMMISSION Bioassay at Uranium Mills AGENCY: Nuclear Regulatory Commission. ACTION: Draft regulatory guide... for public comment draft regulatory guide (DG), DG-8051, ``Bioassay at Uranium Mills.'' This guide describes a bioassay program acceptable to the NRC staff for uranium mills and applicable portions...

  13. Chemistry of SOFC Cathode Surfaces: Fundamental Investigation and Tailoring of Electronic Behavior

    Energy Technology Data Exchange (ETDEWEB)

    Yildiz, Bilge; Heski, Clemens

    2013-08-31

    1) Electron tunneling characteristics on La0.7Sr0.3MnO3 (LSM) thin-film surfaces were studied up to 580oC in 10-3mbar oxygen pressure, using scanning tunneling microscopy/ spectroscopy (STM/STS). A threshold-like drop in the tunneling current was observed at positive bias in STS, which is interpreted as a unique indicator for the activation polarization in cation oxygen bonding on LSM cathodes. Sr-enrichment was found on the surface at high temperature using Auger electron spectroscopy, and was accompanied by a decrease in tunneling conductance in STS. This suggests that Sr-terminated surfaces are less active for electron transfer in oxygen reduction compared to Mn-terminated surfaces on LSM. 2) Effects of strain on the surface cation chemistry and the electronic structure are important to understand and control for attaining fast oxygen reduction kinetics on transition metal oxides. Here, we demonstrate and mechanistically interpret the strain coupling to Sr segregation, oxygen vacancy formation, and electronic structure on the surface of La0.7Sr0.3MnO3 (LSM) thin films as a model system. Our experimental results from x-ray photoelectron spectroscopy and scanning tunneling spectroscopy are discussed in light of our first principles-based calculations. A stronger Sr enrichment tendency and a more facile oxygen vacancy formation prevail for the tensile strained LSM surface. The electronic structure of the tensile strained LSM surface exhibits a larger band gap at room temperature, however, a higher tunneling conductance near the Fermi level than the compressively strained LSM at elevated temperatures in oxygen. Our findings suggest lattice strain as a key parameter to tune the reactivity of perovskite transition metal oxides with oxygen in solid oxide fuel cell cathodes. 3) Cation segregation on perovskite oxide surfaces affects vastly the oxygen reduction activity and stability of solid oxide fuel cell (SOFC) cathodes. A unified theory that explains the physical

  14. The synergy of ultrasonic treatment and organic modifiers for tuning the surface chemistry and conductivity of multiwalled carbon nanotubes

    Czech Academy of Sciences Publication Activity Database

    Omastová, M.; Mičušík, M.; Fedorko, P.; Pionteck, J.; Kovářová, Jana; Chehimi, M. M.

    2014-01-01

    Roč. 46, 10-11 (2014), s. 940-944. ISSN 0142-2421. [European Conference on Applications of Surface and Interface Analysis /15./ - ECASIA 2013. Cagliari, 13.10.2013-18.10.2013] Institutional support: RVO:61389013 Keywords : carbon nanotubes * surface modification * surfactant Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.245, year: 2014

  15. Patterned porous silicon photonic crystals with modular surface chemistry for spatial control of neural stem cell differentiation.

    Science.gov (United States)

    Huang, Tiffany H; Pei, Yi; Zhang, Douglas; Li, Yanfen; Kilian, Kristopher A

    2016-06-01

    We present a strategy to spatially define regions of gold and nanostructured silicon photonics, each with materials-specific surface chemistry, for azide-alkyne cycloaddition of different bioactive peptides. Neural stem cells are spatially directed to undergo neurogenesis and astrogenesis as a function of both surface properties and peptide identity. PMID:27173986

  16. Hot-electron-mediated surface chemistry: toward electronic control of catalytic activity.

    Science.gov (United States)

    Park, Jeong Young; Kim, Sun Mi; Lee, Hyosun; Nedrygailov, Ievgen I

    2015-08-18

    Energy dissipation at surfaces and interfaces is mediated by excitation of elementary processes, including phonons and electronic excitation, once external energy is deposited to the surface during exothermic chemical processes. Nonadiabatic electronic excitation in exothermic catalytic reactions results in the flow of energetic electrons with an energy of 1-3 eV when chemical energy is converted to electron flow on a short (femtosecond) time scale before atomic vibration adiabatically dissipates the energy (in picoseconds). These energetic electrons that are not in thermal equilibrium with the metal atoms are called "hot electrons". The detection of hot electron flow under atomic or molecular processes and understanding its role in chemical reactions have been major topics in surface chemistry. Recent studies have demonstrated electronic excitation produced during atomic or molecular processes on surfaces, and the influence of hot electrons on atomic and molecular processes. We outline research efforts aimed at identification of the intrinsic relation between the flow of hot electrons and catalytic reactions. We show various strategies for detection and use of hot electrons generated by the energy dissipation processes in surface chemical reactions and photon absorption. A Schottky barrier localized at the metal-oxide interface of either catalytic nanodiodes or hybrid nanocatalysts allows hot electrons to irreversibly transport through the interface. We show that the chemicurrent, composed of hot electrons excited by the surface reaction of CO oxidation or hydrogen oxidation, correlates well with the turnover rate measured separately by gas chromatography. Furthermore, we show that hot electron flows generated on a gold thin film by photon absorption (or internal photoemission) can be amplified by localized surface plasmon resonance. The influence of hot charge carriers on the chemistry at the metal-oxide interface are discussed for the cases of Au, Ag, and Pt

  17. An examination of the analysis of radiostrontiums in bioassay applications

    International Nuclear Information System (INIS)

    Radiostrontiums are among the most radiologically significant radionuclides in the nuclear reactor environment due to their relatively high fission yield, long physical half-life, volatility and mobility in the workplace, and long retention times in tissues such as bone. Effective bioassay programs include analytical processes that consider prospective monitoring requirements provided by screening measurements, as well as the retrospective monitoring requirements provided by screening measurements following an intake. Chromatography using crown ethers as well as the use of spectrometry techniques with advanced liquid-scintillation counters or solid-state surface-barrier detectors appear to have significant benefits for Sr bioassay programs. (author). 90 refs., 2 tabs., 3 figs

  18. Models of Gas-phase and Surface Chemistry for Plasma Enhanced Chemical Vapor Deposition

    Science.gov (United States)

    Meeks, Ellen

    1996-10-01

    Plasma enhanced chemical vapor deposition for inter-metal-layer gap-fill processes are increasingly important in semiconductor device manufacture, as the devices include increasing numbers of metal layers with decreasing linewidth and spacing. Optimization of these processes requires knowledge of the microscopic consequences of variations in reactor operating conditions. Topographical simulation can address the gap-fill performance of a depositing film, but the predictive capabiliities are limited by the ability of the model user to accurately supply ion and radical fluxes at a gas/surface interface. Critical to determining this information are the chemical kinetics between gas-phase species and the deposition surfaces. Recent improvements and extensions to the CHEMKIN and Surface CHEMKIN software allow general inclusion of detailed chemical mechanisms in plasma simulations and in models of plasma-surface interactions. In the results presented here (This work represents a collaboration with R. Larson and P. Ho at Sandia, J. Rey and J. Li at TMA, S. M. Han and E. Aydil of UCSB, and S. Huang at Lam Research Corporation), we have used a CHEMKIN-based well mixed reactor model of a high-density SiH_4/O_2/Ar plasma to predict and characterize species fluxes, oxide-deposition rates, and ion-milling rates on a flat surface. These calculated rates can be used as direct input to a topographical simulator. The gas-phase chemistry in the plasma reactor model is comprised of electron impact reactions with silane, oxygen, hydrogen, and argon, as well as neutral radical recombination, abstraction, and oxidation reactions. The surface reaction mechanism contains four classes of reactions: silicon-containing radical deposition, radical abstraction, ion-induced desorption, and physical ion sputtering. We include relative thermochemistry of the surface and gas species to allow reversible reaction dynamics. The plasma model results show good agreement with measured ion densities, as

  19. TEOS surface chemistry on SiO{sub 2} at CVD temperatures and pressures

    Energy Technology Data Exchange (ETDEWEB)

    Bartrarm, M.E.; Moffat, H.K.

    1995-12-31

    We have developed a significantly improved understanding of thermal TEOS (tetraethylorthosilicate, Si(OCH{sub 2}CH{sub 3}){sub 4}) surface chemistry at CVD (chemical vapor deposition) temperatures and pressures. This was accomplished using GCMS (gas chromatography-mass spectroscopy) and FTIR (Fourier transform infrared spectroscopy) to examine how TEOS reaction rates are influenced by factors critical to the heterogeneous reaction. This included determining the TEOS pressure dependence, testing if reaction by-products inhibit TEOS decomposition, evaluating functional groups on the SiO{sub 2} surface as potential reaction sites, and establishing the functional group coverage dependencies. Our results show that TEOS decomposition rates are first-order in TEOS pressure and independent of the surface reaction by-products and the relative coverages of siloxane bridges (Si-O-Si) and hydroxyls on SiO{sub 2}. These conclusions suggest that a precise knowledge of functional group coverages on SiO{sub 2} is not essential for modeling thermal TEOS decomposition rates at 1000K. In the absence of gas-phase reactions, growth rates should be directly proportional to TEOS pressure. Therefore, it is likely that non-uniform SiO{sub 2} depositions observed in thermal TEOS CVD are due to depletion of TEOS in the gas-phase and/or thermal gradients on the surface.

  20. The surface chemistry of 3-mercaptopropyltrimethoxysilane films deposited on magnesium alloy AZ91

    International Nuclear Information System (INIS)

    Magnesium and its alloys have desirable physical and mechanical properties for a number of applications. Unfortunately, these materials are highly susceptible to corrosion, particularly in the presence of aqueous solutions. The purpose of this study is to develop a uniform, non-toxic surface treatment to enhance the corrosion resistance of magnesium alloys. This paper reports the influence of the coating bath parameters and alloy microstructure on the deposition of 3-mercaptopropyltrimethoxysilane (MPTS) coatings on magnesium alloy AZ91. The surface chemistry at the magnesium/MPTS interface has also been explored. The results indicate that the deposition of MPTS onto AZ91 was influenced by both the pH and MPTS concentration in the coating bath. Furthermore, scanning electron microscopy results showed that the MPTS film deposited uniformly on all phases of the magnesium alloy surface. X-ray photoelectron spectroscopy studies revealed that at the magnesium/MPTS interface, the molecules bond to the surface through the thiol group in an acid-base interaction with the Mg(OH)2 layer, whereas in the bulk of the film, the molecules are randomly oriented.

  1. Corrosion product layers on magnesium alloys AZ31 and AZ61: Surface chemistry and protective ability

    Energy Technology Data Exchange (ETDEWEB)

    Feliu, S., E-mail: sfeliu@cenim.csic.es; Llorente, I.

    2015-08-30

    Highlights: • Surface chemistry of the corrosion product layers on magnesium alloys. • Influence of the type of alloy on the carbonate surface enrichment. • Relation between surface composition and protection properties. - Abstract: This paper studies the chemical composition of the corrosion product layers formed on magnesium alloys AZ31 and AZ61 following immersion in 0.6 M NaCl, with a view to better understanding their protective action. Relative differences in the chemical nature of the layers were quantified by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDX) and low-angle X-ray diffraction (XRD). Corrosion behavior was investigated by Electrochemical Impedance Spectroscopy (EIS) and hydrogen evolution measurement. An inhibitive effect from the corrosion product layers was observed from EIS, principally in the case of AZ31, as confirmed by hydrogen evolution tests. A link was found between carbonate enrichment observed by XPS in the surface of the corrosion product layer, concomitant with the increase in the protective properties observed by EIS.

  2. Corrosion product layers on magnesium alloys AZ31 and AZ61: Surface chemistry and protective ability

    International Nuclear Information System (INIS)

    Highlights: • Surface chemistry of the corrosion product layers on magnesium alloys. • Influence of the type of alloy on the carbonate surface enrichment. • Relation between surface composition and protection properties. - Abstract: This paper studies the chemical composition of the corrosion product layers formed on magnesium alloys AZ31 and AZ61 following immersion in 0.6 M NaCl, with a view to better understanding their protective action. Relative differences in the chemical nature of the layers were quantified by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDX) and low-angle X-ray diffraction (XRD). Corrosion behavior was investigated by Electrochemical Impedance Spectroscopy (EIS) and hydrogen evolution measurement. An inhibitive effect from the corrosion product layers was observed from EIS, principally in the case of AZ31, as confirmed by hydrogen evolution tests. A link was found between carbonate enrichment observed by XPS in the surface of the corrosion product layer, concomitant with the increase in the protective properties observed by EIS

  3. The effect of pesticide residue on caged mosquito bioassays.

    Science.gov (United States)

    Barber, J A S; Greer, Mike; Coughlin, Jamie

    2006-09-01

    Wind tunnel experiments showed that secondary pickup of insecticide residue by mosquitoes in cage bioassays had a significant effect on mortality. Cage bioassays using adult Ochlerotatus taeniorhynchus (Wiedemann) investigated the effect of exposure time to a contaminated surface. Cages were dosed in a wind tunnel using the LC50 for naled (0.124 mg a.i./ml) and an LC25 (0.0772 mg a.i./ml) for naled. Half of the bioassay mosquitoes were moved directly into clean cages with the other half remaining in the sprayed, hence contaminated, cage. Treatment mortality was assessed at 8, 15, 30, 60, 120, 240, and 1,440 min postapplication. Cage contamination had a significant effect on mosquito mortality for both the LC25 and LC50 between 15 and 30 min postapplication. PMID:17067048

  4. An Ab Initio Approach Towards Engineering Fischer-Tropsch Surface Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Matthew Neurock

    2006-09-11

    One of the greatest societal challenges over the next decade is the production of cheap, renewable energy for the 10 billion people that inhabit the earth. This will require the development of various energy sources which will likely include fuels derived from methane, coal, and biomass and alternatives sources such as solar, wind and nuclear energy. One approach will be to synthesize gasoline and other fuels from simpler hydrocarbons such as CO derived from methane or other U.S. based sources such as coal. Syngas (CO and H{sub 2}) can be readily converted into higher molecular weight hydrocarbons through Fischer-Tropsch synthesis. Fischer-Tropsch (FT) synthesis involves the adsorption and the activation of CO and H{sub 2}, the subsequent propagation steps including hydrogenation and carbon-carbon coupling, followed by chain termination reactions. The current commercial catalysts are supported Co and Co-alloys particles. This project set out with the following objectives in mind: (1) understand the reaction mechanisms that control FT kinetics, (2) predict how the intrinsic metal-adsorbate bond affects the sequence of elementary steps in FT, (3) establish the effects of the reaction environment on catalytic activity and selectivity, (4) construct a first-principles based algorithm that can incorporate the detailed atomic surface structure and simulate the kinetics for the myriad of elementary pathways that make up FT chemistry, and (5) suggest a set of optimal features such as alloy composition and spatial configuration, oxide support, distribution of defect sites. As part of this effort we devoted a significant portion of time to develop an ab initio based kinetic Monte Carlo simulation which can be used to follow FT surface chemistry over different transition metal and alloy surfaces defined by the user. Over the life of this program, we have used theory and have developed and applied stochastic Monte Carlo simulations in order to establish the fundamental

  5. Surface chemistry of InP ridge structures etched in Cl{sub 2}-based plasma analyzed with angular XPS

    Energy Technology Data Exchange (ETDEWEB)

    Bouchoule, Sophie, E-mail: sophie.bouchoule@lpn.cnrs.fr; Cambril, Edmond; Guilet, Stephane [Laboratoire de Photonique et Nanostructure (LPN)—UPR20, CNRS, Route de Nozay, 91460 Marcoussis (France); Chanson, Romain; Pageau, Arnaud; Rhallabi, Ahmed; Cardinaud, Christophe, E-mail: christophe.cardinaud@cnrs-imn.fr [Institut des matériaux Jean Rouxel (IMN), UMR6502, Université de Nantes, CNRS, 44322 Nantes (France)

    2015-09-15

    Two x-ray photoelectron spectroscopy configurations are proposed to analyze the surface chemistry of micron-scale InP ridge structures etched in chlorine-based inductively coupled plasma (ICP). Either a classical or a grazing configuration allows to retrieve information about the surface chemistry of the bottom surface and sidewalls of the etched features. The procedure is used to study the stoichiometry of the etched surface as a function of ridge aspect ratio for Cl{sub 2}/Ar and Cl{sub 2}/H{sub 2} plasma chemistries. The results show that the bottom surface and the etched sidewalls are P-rich, and indicate that the P-enrichment mechanism is rather chemically driven. Results also evidence that adding H{sub 2} to Cl{sub 2} does not necessarily leads to a more balanced surface stoichiometry. This is in contrast with recent experimental results obtained with the HBr ICP chemistry for which fairly stoichiometric surfaces have been obtained.

  6. Aqueous reactive species induced by a surface air discharge: Heterogeneous mass transfer and liquid chemistry pathways

    Science.gov (United States)

    Liu, D. X.; Liu, Z. C.; Chen, C.; Yang, A. J.; Li, D.; Rong, M. Z.; Chen, H. L.; Kong, M. G.

    2016-04-01

    Plasma-liquid interaction is a critical area of plasma science and a knowledge bottleneck for many promising applications. In this paper, the interaction between a surface air discharge and its downstream sample of deionized water is studied with a system-level computational model, which has previously reached good agreement with experimental results. Our computational results reveal that the plasma-induced aqueous species are mainly H+, nitrate, nitrite, H2O2 and O3. In addition, various short-lived aqueous species are also induced, regardless whether they are generated in the gas phase first. The production/loss pathways for aqueous species are quantified for an air gap width ranging from 0.1 to 2 cm, of which heterogeneous mass transfer and liquid chemistry are found to play a dominant role. The short-lived reactive oxygen species (ROS) and reactive nitrogen species (RNS) are strongly coupled in liquid-phase reactions: NO3 is an important precursor for short-lived ROS, and in turn OH, O2‑ and HO2 play a crucial role for the production of short-lived RNS. Also, heterogeneous mass transfer depends strongly on the air gap width, resulting in two distinct scenarios separated by a critical air gap of 0.5 cm. The liquid chemistry is significantly different in these two scenarios.

  7. Aqueous reactive species induced by a surface air discharge: Heterogeneous mass transfer and liquid chemistry pathways

    Science.gov (United States)

    Liu, D. X.; Liu, Z. C.; Chen, C.; Yang, A. J.; Li, D.; Rong, M. Z.; Chen, H. L.; Kong, M. G.

    2016-01-01

    Plasma-liquid interaction is a critical area of plasma science and a knowledge bottleneck for many promising applications. In this paper, the interaction between a surface air discharge and its downstream sample of deionized water is studied with a system-level computational model, which has previously reached good agreement with experimental results. Our computational results reveal that the plasma-induced aqueous species are mainly H+, nitrate, nitrite, H2O2 and O3. In addition, various short-lived aqueous species are also induced, regardless whether they are generated in the gas phase first. The production/loss pathways for aqueous species are quantified for an air gap width ranging from 0.1 to 2 cm, of which heterogeneous mass transfer and liquid chemistry are found to play a dominant role. The short-lived reactive oxygen species (ROS) and reactive nitrogen species (RNS) are strongly coupled in liquid-phase reactions: NO3 is an important precursor for short-lived ROS, and in turn OH, O2− and HO2 play a crucial role for the production of short-lived RNS. Also, heterogeneous mass transfer depends strongly on the air gap width, resulting in two distinct scenarios separated by a critical air gap of 0.5 cm. The liquid chemistry is significantly different in these two scenarios. PMID:27033381

  8. Surface chemistry and cytotoxicity of reactively sputtered tantalum oxide films on NiTi plates

    International Nuclear Information System (INIS)

    NiTi, an equiatomic alloy containing nickel and titanium, exhibits unique properties such as shape memory effect and superelasticity. NiTi also forms a spontaneous protective titanium dioxide (TiO2) layer that allows its use in biomedical applications. Despite the widely perceived biocompatibility there remain some concerns about the sustainability of the alloy's biocompatibility due to the defects in the TiO2 protective layer and the presence of high amount of sub-surface Ni, which can give allergic reactions. Many surface treatments have been investigated to try to improve both the corrosion resistance and biocompatibility of this layer. For such purposes, we have sputter deposited tantalum (Ta) oxide thin films onto the surface of the NiTi alloy. Despite being one of the promising metals for biomedical applications, Ta, and its various oxides and their interactions with cells have received relatively less attention. The oxidation chemistry, crystal structure, morphology and biocompatibility of these films have been investigated. In general, reactive sputtering especially in the presence of a low oxygen mixture yields a thicker film with better control of the film quality. The sputtering power influenced the surface oxidation states of Ta. Both microscopic and quantitative cytotoxicity measurements show that Ta films on NiTi are biocompatible with little to no variation in cytotoxic response when the surface oxidation state of Ta changes. - Highlights: • Reactive sputtering in low oxygen mixture yields thicker better quality films. • Sputtering power influenced surface oxidation states of Ta. • Cytotoxicity measurements show Ta films on NiTi are biocompatible. • Little to no variation in cytotoxic response when oxidation state changes

  9. Gold nanoparticles: role of size and surface chemistry on blood protein adsorption

    International Nuclear Information System (INIS)

    Material interaction with blood proteins is a critical issue, since it could influence the biological processes taking place in the body following implantation/injection. This is particularly important in the case of nanoparticles, where innovative properties, such as size and high surface to volume ratio can lead to a behavioral change with respect to bulk macroscopic materials and could be responsible for a potential risk for human health. The aim of this work was to compare gold nanoparticles (AuNP) and planar surfaces to study the role of surface curvature moving from the macro- to the nano-size in the process of blood protein adsorption. In the course of the study, different protocols were tested to optimize the analysis of protein adsorption on gold nanoparticles. AuNP with different size (10, 60 and 200 nm diameter) and surface coatings (citrate and polyethylene glycol) were carefully characterized. The stabilizing action of blood proteins adsorbed on AuNP was studied measuring the variation of size and solubility of the nanoparticles following incubation with single protein solutions (human serum albumin and fibrinogen) and whole blood plasma. In addition, we developed a method to elute proteins from AuNP to study the propensity of gold materials to adsorb plasma proteins in function of dimensional characteristics and surface chemistry. We showed a different efficacy of the various eluting media tested, proving that even the most aggressive agent cannot provide a complete detachment of the protein corona. Enhanced protein adsorption was evidenced on AuNP if compared to gold laminae (bare and PEGylated) used as macroscopic control, probably due to the superior AuNP surface reactivity.

  10. Surface chemistry and cytotoxicity of reactively sputtered tantalum oxide films on NiTi plates

    Energy Technology Data Exchange (ETDEWEB)

    McNamara, K. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland); Kolaj-Robin, O.; Belochapkine, S.; Laffir, F. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Gandhi, A.A. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland); Tofail, S.A.M., E-mail: tofail.syed@ul.ie [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland)

    2015-08-31

    NiTi, an equiatomic alloy containing nickel and titanium, exhibits unique properties such as shape memory effect and superelasticity. NiTi also forms a spontaneous protective titanium dioxide (TiO{sub 2}) layer that allows its use in biomedical applications. Despite the widely perceived biocompatibility there remain some concerns about the sustainability of the alloy's biocompatibility due to the defects in the TiO{sub 2} protective layer and the presence of high amount of sub-surface Ni, which can give allergic reactions. Many surface treatments have been investigated to try to improve both the corrosion resistance and biocompatibility of this layer. For such purposes, we have sputter deposited tantalum (Ta) oxide thin films onto the surface of the NiTi alloy. Despite being one of the promising metals for biomedical applications, Ta, and its various oxides and their interactions with cells have received relatively less attention. The oxidation chemistry, crystal structure, morphology and biocompatibility of these films have been investigated. In general, reactive sputtering especially in the presence of a low oxygen mixture yields a thicker film with better control of the film quality. The sputtering power influenced the surface oxidation states of Ta. Both microscopic and quantitative cytotoxicity measurements show that Ta films on NiTi are biocompatible with little to no variation in cytotoxic response when the surface oxidation state of Ta changes. - Highlights: • Reactive sputtering in low oxygen mixture yields thicker better quality films. • Sputtering power influenced surface oxidation states of Ta. • Cytotoxicity measurements show Ta films on NiTi are biocompatible. • Little to no variation in cytotoxic response when oxidation state changes.

  11. Electrolyte effects on the surface chemistry and cellular response of anodized titanium

    Energy Technology Data Exchange (ETDEWEB)

    Ohtsu, Naofumi, E-mail: nohtsu@mail.kitami-it.ac.jp [Instrumental Analysis Center, Kitami Institute of Technology, 165 Koen-cho, Kitami, Hokkaido 090-8507 (Japan); Kozuka, Taro; Hirano, Mitsuhiro [Instrumental Analysis Center, Kitami Institute of Technology, 165 Koen-cho, Kitami, Hokkaido 090-8507 (Japan); Arai, Hirofumi [Department of Biotechnology and Environmental Chemistry, Kitami Institute of Technology, Kitami, Hokkaido 090-8507 (Japan)

    2015-09-15

    Highlights: • Ti samples were anodized using various electrolytes. • Anodization decreased carbon adsorption, improving hydrophilicity. • Improved hydrophilicity led to improved cellular attachment. • Only one electrolyte showed any heteroatom incorporation into the TiO{sub 2} layer. • Choice of electrolyte played no role on the effects of anodization. - Abstract: Anodic oxidation of titanium (Ti) material is used to enhance biocompatibility, yet the effects of various electrolytes on surface characteristics and cellular behavior have not been completely elucidated. To investigate this topic, oxide layers were produced on Ti substrates by anodizing them in aqueous electrolytes of (NH{sub 4}){sub 2}O·5B{sub 2}O{sub 3}, (NH{sub 4}){sub 2}SO{sub 4}, or (NH{sub 4}){sub 3}PO{sub 4}, after which their surface characteristics and cellular responses were examined. Overall, no surface differences between the electrolytes were visually observed. X-ray photoelectron spectroscopy (XPS) revealed that the anodized surfaces are composed of titanium dioxide (TiO{sub 2}), while incorporation from electrolyte was only observed for (NH{sub 4}){sub 3}PO{sub 4}. Surface adsorption of carbon contaminants during sterilization was suppressed by anodization, leading to lower water contact angles. The attachment of MC3T3-E1 osteoblast-like cells was also improved by anodization, as evidenced by visibly enlarged pseudopods. This improved attachment performance is likely due to TiO{sub 2} formation. Overall, electrolyte selection showed no effect on either surface chemistry or cellular response of Ti materials.

  12. The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids

    Energy Technology Data Exchange (ETDEWEB)

    Koontz, S.L.; Leger, L.J.; Wu, C.; Cross, J.B.; Jurgensen, C.W. [Los Alamos National Lab., NM (United States)]|[Bell Telephone Labs., Inc., Murray Hill, NJ (United States)

    1994-05-01

    Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen `spin-off` or `dual use` technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

  13. The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids

    Science.gov (United States)

    Koontz, Steve L.; Leger, Lubert J.; Wu, Corina; Cross, Jon B.; Jurgensen, Charles W.

    1994-01-01

    Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

  14. Chemically active colloids near osmotic-responsive walls with surface-chemistry gradients

    CERN Document Server

    Popescu, M N; Dietrich, S

    2016-01-01

    Chemically active colloids move by creating gradients in the composition of the surrounding solution and by exploiting the differences in their interactions with the various molecular species in solution. If such particles move near boundaries, e.g., the walls of the container confining the suspension, gradients in the composition of the solution are also created along the wall. This give rise to chemi-osmosis (via the interactions of the wall with the molecular species forming the solution), which drives flows coupling back to the colloid and thus influences its motility. Employing an approximate "point-particle" analysis, we show analytically that -- owing to this kind of induced active response (chemi-osmosis) of the wall -- such chemically active colloids can align with, and follow, gradients in the surface chemistry of the wall. In this sense, these artificial "swimmers" exhibit a primitive form of thigmotaxis with the meaning of sensing the proximity of a (not necessarily discontinuous) physical change ...

  15. Surface modification of nanoporous 1,2-polybutadiene by atom transfer radical polymerization or click chemistry.

    Science.gov (United States)

    Guo, Fengxiao; Jankova, Katja; Schulte, Lars; Vigild, Martin E; Ndoni, Sokol

    2010-02-01

    Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based on nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide functional groups were attached onto the pore walls before click reaction with alkynated MPEG. Following ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while the morphology was investigated by small-angle X-ray scattering and transmission electron microscopy. PMID:20099923

  16. SnSe Nanocrystals: Synthesis, Structure, Optical Properties, and Surface Chemistry

    KAUST Repository

    Baumgardner, William J.

    2010-07-21

    The colloidal synthesis of SnSe nanoparticles is accomplished through the injection of bis[bis(trimethylsilyl)amino]tin(II) into hot trioctylphosphine: selenium in the presence of oleylamine. Through the manipulation of reaction temperature particles are grown with the average diameter reliably tuned to 4-10 nm. Quantum confinement is examined by establishing a relationship between particle size and band gap while the in depth growth dynamics are illuminated through UV-vis-NIR spectroscopy. Surface chemistry effects are explored, including the demonstration of useful ligand exchanges and the development of routes toward anisotropic particle growth. Finally, transient current-voltage properties of SnSe nanocrystal films in the dark and light are examined. © 2010 American Chemical Society.

  17. Modification of ilmenite surface chemistry for enhancing surfactants adsorption and bubble attachment.

    Science.gov (United States)

    Fan, Xianfeng; Waters, Kristian E; Rowson, Neil A; Parker, David J

    2009-01-01

    In this study, microwave irradiation is used to modify ilmenite surface chemistry to enhance the adsorption of surfactants and the air bubble attachment. The results indicate that microwave irradiation can increase ilmenite flotation recovery by 20%. A positron emission particle tracking technique is used to study the dynamic behaviour of ilmenite particles in a Denver cell. The data shows that the poor flotation recovery of ilmenite is not only due to the reduce probability of ilmenite being captured by air bubbles, but also the short residence time of the particles remaining in the froth phase. The ilmenite particles can be frequently captured by air bubbles, but dropped to the bulk liquid from the froth phase, normally over 15 s. Microwave irradiation changes the ilmenite flow pattern in the Denver cell. The average time of ilmenite remaining in froth phase is increased from 11.5 to 29.1 s. PMID:18950784

  18. Surface chemistry and optical property of TiO2 thin films treated by low-pressure plasma

    International Nuclear Information System (INIS)

    The low temperature RF plasma treatment was used to control the surface chemistry and optical property of TiO2 thin films deposited by RF magnetron sputtering with a very good uniformity at 300 deg. C substrate heating temperature. The XRD pattern indicates the crystalline structure of the film could be associated to amorphous structure of TiO2 in thin film. The plasma treatment of TiO2 film can increase the proportion of Ti3+ in Ti2p and decrease in carbon atoms as alcohol/ether group in C1s at the surface. The optical transmittance of the film was enhanced by 50% after the plasma treatment. The surface structure and morphology remain the same for untreated and low-pressure plasma-treated films. Therefore, increase in the optical transmission could be due to change in surface chemistry and surface cleaning by plasma treatment. - Graphical abstract: The surface chemistry and surface states of TiO2 films was modified using low-pressure RF plasma treatment. The surface roughness and crystalline structure remain unchanged for low-pressure plasma-treated films. There was an increase in the Ti3+ surface states of Ti2p at the surface and this can be useful to increase the photocatalytic activities of TiO2 films. The proportion of carbon atoms as carboxyl group in C1s was also increased after plasma treatment. All the plasma-treated films show a higher optical transmittance when untreated and it was increased when the power was increased. The increase in the optical transmission could be due to surface cleaning of films by plasma treatment and possibly due to change in the surface chemistry

  19. THE EFFECTS OF SURFACE CHEMISTRY ON THE PROPERTIES OF PROTEINS CONFINED IN NANO-POROUS MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Garrett, L. M.; O' Neill, H.

    2007-01-01

    The entrapment of proteins using the sol-gel route provides a means to retain its native properties and artifi cially reproduce the molecular crowding and confi nement experienced by proteins in the cell allowing investigation of the physico-chemical and structural properties of biomolecules at the biotic/abiotic interface. The biomolecules are spatially separated and ‘caged’ in the gel structure but solutes can freely permeate the matrix. Thus, properties such as the folding of ensembles of individual molecules can be examined in the absence of aggregation effects that can occur in solution studies. Green fl uorescent protein from Aequorea coerulescens was used as a model protein to examine the unfolding/re-folding properties of protein in silica gels. The recombinant protein was isolated and purifi ed from Escherichia coli extracts by cell lysis, three-phase partitioning, dialysis, and anion exchange chromatography. The purity of the protein was greater than 90% as judged by SDS PAGE gel analysis. Sol-gels were synthesized using tetramethylorthosilicate (TMOS) in combination with, methyltrimethoxyorthosilane (MTMOS), ethyltrimethoxyorthosilane (ETMOS), 3-aminopropyltriethoxysilane (APTES), and 3-glycidoxypropyltrimethoxysilane (GPTMS). The acid induced denaturation and renaturation of GFP was analyzed by UV-visible, fl uorescence, and circular dichroism (CD) spectroscopies. No renaturation was observed in gels that were made with TMOS only, and in the presence of APTES, MTMOS, and ETMOS. However, in gels that were made with GPTMS, the CD and UV-visible spectra indicated that the protein had refolded. The fl uorescence emission spectrum indicated that approximately 20% of fl uorescence had returned. This study highlights the importance of the surface chemistry of the silica gels for the refolding properties of the entrapped GFP. Future studies will investigate the effect of surface chemistry on the thermal and solvent stability of the entrapped protein.

  20. Combined experiment and theory approach in surface chemistry: Stairway to heaven?

    Science.gov (United States)

    Exner, Kai S.; Heß, Franziska; Over, Herbert; Seitsonen, Ari Paavo

    2015-10-01

    In this perspective we discuss how an intimate interaction of experiments with theory is able to deepen our insight into the catalytic reaction system on the molecular level. This strategy is illustrated by discussing various examples from our own research of surface chemistry and model catalysis. The particular examples were carefully chosen to balance the specific strength of both approaches - theory and experiment - and emphasize the benefit of this combined approach. We start with the determination of complex surface structures, where diffraction techniques in combination with theory are clear-cut. The promoter action of alkali metals in heterogeneous catalysis is rationalized with theory and experiment for the case of CO coadsorption. Predictive power of theory is limited as demonstrated with the apparent activity of chlorinated TiO2(110) in the oxidation of HCl: Even if we know all elementary reaction steps of a catalytic reaction mechanism, the overall kinetics may remain elusive and require the application kinetic Monte Carlo simulations. Catalysts are not always stable under reaction conditions and may chemically transform as discussed for the CO oxidation reaction over ruthenium. Under oxidizing reaction conditions ruthenium transforms into RuO2, a process which is hardly understood on the molecular level. Lastly we focus on electrochemical reactions. Here theory is clearly ahead since spectroscopic methods are not available to resolve the processes at the electrode surface.

  1. Affinity Induced Surface Functionalization of Liposomes Using Cu-Free Click Chemistry.

    Science.gov (United States)

    Bak, Martin; Jølck, Rasmus I; Eliasen, Rasmus; Andresen, Thomas L

    2016-07-20

    Functionalization of nanoparticles is a key element for improving specificity of drug delivery systems toward diseased tissue or cells. In the current study we report a highly efficient and chemoselective method for post-functionalization of liposomes with biomacromolecules, which equally well can be used for functionalization of other nanoparticles or solid surfaces. The method exploits a synergistic effect of having both affinity and covalent anchoring tags on the surface of the liposome. This was achieved by synthesizing a peptide linker system that uses Cu-free strain-promoted click chemistry in combination with histidine affinity tags. The investigation of post-functionalization of PEGylated liposomes was performed with a cyclic RGDfE peptide. By exploring both affinity and covalent tags a 98 ± 2.0% coupling efficiency was achieved, even a diluted system showed a coupling efficiency of 87 ± 0.2%. The reaction kinetics and overall yield were quantified by HPLC. The results presented here open new possibilities for constructing complex nanostructures and functionalized surfaces. PMID:27269516

  2. DNA damage response to different surface chemistry of silver nanoparticles in mammalian cells

    International Nuclear Information System (INIS)

    Silver nanoparticles (Ag NPs) have recently received much attention for their possible applications in biotechnology and life sciences. Ag NPs are of interest to defense and engineering programs for new material applications as well as for commercial purposes as an antimicrobial. However, little is known about the genotoxicity of Ag NPs following exposure to mammalian cells. This study was undertaken to examine the DNA damage response to polysaccharide surface functionalized (coated) and non-functionalized (uncoated) Ag NPs in two types of mammalian cells; mouse embryonic stem (mES) cells and mouse embryonic fibroblasts (MEF). Both types of Ag NPs up-regulated the cell cycle checkpoint protein p53 and DNA damage repair proteins Rad51 and phosphorylated-H2AX expression. Furthermore both of them induced cell death as measured by the annexin V protein expression and MTT assay. Our observations also suggested that the different surface chemistry of Ag NPs induce different DNA damage response: coated Ag NPs exhibited more severe damage than uncoated Ag NPs. The results suggest that polysaccharide coated particles are more individually distributed while agglomeration of the uncoated particles limits the surface area availability and access to membrane bound organelles

  3. Bubble formation in NiCr splat on aluminum substrate during plasma spray: Surface chemistry effect

    International Nuclear Information System (INIS)

    NiCr single splats were plasma-sprayed on aluminum substrates which were modified by thermal treatments over a range of specific temperatures. It was observed that the splat morphologies changed from highly fingered splats to disk splats with increasing thermal treatment temperature. In addition, the density of the bubble pores which formed at the underside of NiCr splats significantly reduced with an increase of substrate temperature. X-ray photoelectron spectroscopy was used to examine the variation of surface chemistry with thermal treatment. The release of water from the dehydration of an oxyhydroxide layer, which was found to form on the substrate surface, was strongly correlated with the splat morphology and bubble formation at the splat underside. It is proposed that the water desorption from the substrate surface causes turbulence in the spreading process of the splat and the bubble formation at the splat underside, which leads to the splashing of the splat. Preheating or heating the substrate during spraying can partly remove the water prior to spraying, thereby greatly improving the contact between the splats and the substrate which enhanced the formation of a disk splat and significantly reduced the bubble formation at the splat underside.

  4. Macroform and microform-induced change in redox-sensitive chemistries of river channel surface sediments

    Science.gov (United States)

    Byrne, P.; Zhang, H.; Heathwaite, A. L.; Binley, A.; Ullah, S.; Kaeser, D.; Heppell, C. M.; Lansdown, K.; Trimmer, M.

    2012-04-01

    In-stream geomorphological features such as riffle-pool sequences (macroforms) can produce steep hydraulic gradients which induce flow in and out of the riverbed - hyporheic exchange flow (HEF). The acceleration of flow over channel obstacles such as large cobbles and boulders (microforms) can create variation in surface-subsurface pressure gradients and generation of HEF. HEF in shallow surface sediments affect the transformation of redox-sensitive chemical forms and, therefore, the attenuation or release of nutrients in river systems. Here, we examine the relationship between stream geomorphological environment (microform and macroform) and concentration profiles of redox-sensitive species (nitrate, sulphate, iron, manganese) in shallow (15cm) subsurface sediments. In-situ passive samplers (diffusive equilibrium in thin films - DET) are used to obtain biogeochemical data from armoured environments at fine scale (cm) depth resolution where there is strong upwelling. The probes were deployed in a 50m reach of the River Eden, Cumbria, UK, during baseflow conditions. The experimental setup allowed for the assessment of differences in redox-sensitive chemistries between a riffle and pool environment and between smooth and rough bed surfaces in the pool. The passive sensing basis of the DET methodology provided a means for investigating how HEF systems generated at two different geomorphological scales influence the concentration and spatial patterns of redox-sensitive species. DET's capability of measuring at high spatial resolution allowed the extent of hyporheic mixing to be targeted, even though it is often limited to the top few centimetres of sediment.

  5. Preparation and application of a novel electrochemical sensing material based on surface chemistry of polyhydroquinone

    International Nuclear Information System (INIS)

    A new analogue of polydopamine (PDA), i.e., polyhydroquinone (PH2Q), was polymerized and its surface chemistry was studied by different ways of characterization. PH2Q was produced by the self-polymerization of H2Q mediated by dissolved oxygen, and the self-polymerization process was strongly dependent on the type and the pH value of the buffer solutions. PH2Q can not only achieve surface hydrophilization of different substrates like polyethylene terephthalate (PET) film, graphite strip, C12SH/Au and wax slice, but also possess several unique properties like reversible adsorption, good solubility and low cost. These properties made PH2Q an ideal polymeric modifier for the noncovalent functionalization of some nanomaterials. By simply grinding with PH2Q, pristine multi-walled carbon nanotubes (MWNTs) can be readily dispersed in water with high solubility and good stability. The resulting MWNT–PH2Q composite exhibited excellent electrochemical performance, which was employed for the simultaneous determination of dopamine (DA) and uric acid (UA). - Highlights: • Polyhydroquinone (PH2Q) was produced by the self-polymerization of hydroquinone (H2Q) mediated by dissolved oxygen. • PH2Q can achieve surface hydrophilization of a variety of substrates. • PH2Q is an ideal polymeric modifier for the functionalization of multi-walled carbon nanotubes (MWNTs). • The MWNT–PH2Q composite can be employed for the simultaneous determination of dopamine (DA) and uric acid (UA)

  6. On the photoactivity of S-doped nanoporous carbons:Importance of surface chemistry and porosity

    Institute of Scientific and Technical Information of China (English)

    Teresa J. Bandosz; Mykola Seredych

    2014-01-01

    This minireview summarizes our recent findings on the photoactivity of S-doped nanoporous car-bons. The materials were either synthesized from the sulfur-containing polymers or obtained by heat treatment of commercial carbon with hydrogen sulfide. Their surface was extensively charac-terized from the points of view of its surface chemistry, porosity, morphology, and electronic prop-erties. The carbons showed enhanced activity towards oxidation of arsine and removal of diben-zothiophenes from model diesel fuel. The latter were oxidized to various oxygen containing inter-mediates and the cleavage of C-C bonds in aromatic ring was detected when carbon with adsorbed species was exposed to UV or visible light. Irradiation resulted in generation of photocurrent in a broad range of wavelength. The presence of sulfur led to the reduction of oxygen and contributed to an increased capacitive performance. We link these effects to the presence of reduced sulfur in the small pores which enhances the dispersive interactions via inducing a positive charge to carbon atoms, to sulfur in oxygenated forms which contribute to Faradaic reactions and increase the polar interactions, and to the hydrophobicity of a surface in small pores where oxygen can be reduced by excited electrons from chromophoric-like sulfur containing groups.

  7. Assembly of linear nano-chains from iron oxide nanospheres with asymmetric surface chemistry.

    Directory of Open Access Journals (Sweden)

    Pubudu M Peiris

    Full Text Available Besides the multifunctionality, another equally important aspect of nanoparticles is their engineerability to control the geometrical and chemical properties during fabrication. In this work, we exploited this aspect to define asymmetric surface chemistry of an iron oxide nanosphere by controlling the topology of ligand expression on its surface resulting in a particle with two faces, one displaying only amines and the other only thiols. Specifically, amine-functionalized iron oxide nanospheres were attached on a solid support via a crosslinker containing a disulfide bridge. Liberation of the nanosphere using thiolytic cleavage created thiols on the portion of the particle's surface that interacted with the solid support. Employing a solid-phase strategy and a step-by-step addition of particles, the two unique faces on the same nanosphere served as fittings to assemble them into linear nano-chains. Assembly of chains with various lengths and aspect ratios was controlled by the size and number of the added nanospheres. The characteristics of those chains showed a high degree of uniformity indicating the exceptional control of the synthetic process. Notably, one of the unique properties of the iron oxide nano-chains was an increased magnetic relaxivity, indicating their potential use as contrast agents for magnetic resonance imaging.

  8. Evaluation of the Effectiveness of Surfactants and Denaturants to Elute and Denature Adsorbed Protein on Different Surface Chemistries.

    Science.gov (United States)

    Thyparambil, Aby A; Wei, Yang; Latour, Robert A

    2015-11-01

    The elution and/or denaturation of proteins from material surfaces by chemical excipients such as surfactants and denaturants is important for numerous applications including medical implant reprocessing, bioanalyses, and biodefense. The objective of this study was to develop and apply methods to quantitatively assess how surface chemistry and adsorption conditions influence the effectiveness of three commonly used surfactants (sodium dodecyl sulfate, n-octyl-β-d-glucoside, and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) and two denaturants (guanidium hydrochloride and urea) to elute protein (hen egg white lysozyme and bovine pancreatic ribonuclease A) from three different surface chemistries (silica glass, poly(methyl methacrylate), and high-density polyethylene). The structure and bioactivity of residual protein on the surface following elution were characterized using circular dichroism spectropolarimetry and enzyme assays to assess the extent of protein denaturation. Our results indicate that the denaturants were generally more effective than the surfactants in removing the adsorbed proteins from each type of surface. Also, the denaturing capacity of these excipients on the residual proteins on the surfaces was distinctly different from their influence on the proteins in solution and was unique for each of the adsorption conditions. Taken altogether, these results reveal that the effectiveness of surfactants and denaturants to elute and denature adsorbed protein is significantly influenced by surface chemistry and the conditions from which the protein was adsorbed. These results provide a basis for the selection, design, and further development of chemical agents for protein elution and surface decontamination. PMID:26449787

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

    International Nuclear Information System (INIS)

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

  10. Surface chemistry and electronic structure of nonpolar and polar GaN films

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Monu; Krishna, T.C. Shibin; Aggarwal, Neha; Gupta, Govind, E-mail: govind@nplindia.org

    2015-08-01

    Highlights: • Surface chemistry and electronic structure of polar and nonpolar GaN is reported. • Influence of polarization on electron affinity of p & np GaN films is investigated. • Correlation between surface morphology and polarity has been deduced. - Abstract: Photoemission and microscopic analysis of nonpolar (a-GaN/r-Sapphire) and polar (c-GaN/c-Sapphire) epitaxial gallium nitride (GaN) films grown via RF-Molecular Beam Epitaxy is reported. The effect of polarization on surface properties like surface states, electronic structure, chemical bonding and morphology has been investigated and correlated. It was observed that polarization lead to shifts in core level (CL) as well as valence band (VB) spectra. Angle dependent X-ray Photoelectron Spectroscopic analysis revealed higher surface oxide in polar GaN film compared to nonpolar GaN film. On varying the take off angle (TOA) from 0° to 60°, the Ga−O/Ga−N ratio varied from 0.11–0.23 for nonpolar and 0.17–0.36 for polar GaN film. The nonpolar film exhibited N-face polarity while Ga-face polarity was perceived in polar GaN film due to the inherent polarization effect. Polarization charge compensated surface states were observed on the polar GaN film and resulted in downward band bending. Ultraviolet photoelectron spectroscopic measurements revealed electron affinity and ionization energy of 3.4 ± 0.1 eV and 6.8 ± 0.1 eV for nonpolar GaN film and 3.8 ± 0.1 eV and 7.2 ± 0.1 eV for polar GaN film respectively. Field Emission Scanning Electron Microscopy measurements divulged smooth morphology with pits on polar GaN film. The nonpolar film on the other hand showed pyramidal structures having facets all over the surface.

  11. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid–base chemistry

    Science.gov (United States)

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S.; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid–base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti4+ to form planar p-type [Ti4+n(InSe)] coordination complexes. Using this strategy, we fabricate planar p–n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B3+, Al3+ and Sn4+) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid–base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.

  12. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid-base chemistry.

    Science.gov (United States)

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti(4+) to form planar p-type [Ti(4+)n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B(3+), Al(3+) and Sn(4+)) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device. PMID:26828848

  13. The evolution of the surface of the mineral schreibersite in prebiotic chemistry.

    Science.gov (United States)

    La Cruz, Nikita L; Qasim, Danna; Abbott-Lyon, Heather; Pirim, Claire; McKee, Aaron D; Orlando, Thomas; Gull, Maheen; Lindsay, Danny; Pasek, Matthew A

    2016-07-27

    We present a study of the reactions of the meteoritic mineral schreibersite (Fe,Ni)3P, focusing primarily on surface chemistry and prebiotic phosphorylation. In this work, a synthetic analogue of the mineral was synthesized by mixing stoichiometric proportions of elemental iron, nickel and phosphorus and heating in a tube furnace at 820 °C for approximately 235 hours under argon or under vacuum, a modification of the method of Skála and Drábek (2002). Once synthesized, the schreibersite was characterized to confirm the identity of the product as well as to elucidate the oxidation processes affecting the surface. In addition to characterization of the solid product, this schreibersite was reacted with water or with organic solutes in a choline chloride-urea deep eutectic mixture, to constrain potential prebiotic products. Major inorganic solutes produced by reaction of water include orthophosphate, phosphite, pyrophosphate and hypophosphate consistent with prior work on Fe3P corrosion. Additionally, schreibersite corrodes in water and dries down to form a deep eutectic solution, generating phosphorylated products, in this case phosphocholine, using this synthesized schreibersite. PMID:27157087

  14. Adsorption of dyes by ACs prepared from waste tyre reinforcing fibre. Effect of texture, surface chemistry and pH.

    Science.gov (United States)

    Acevedo, Beatriz; Rocha, Raquel P; Pereira, Manuel F R; Figueiredo, José L; Barriocanal, Carmen

    2015-12-01

    This paper compares the importance of the texture and surface chemistry of waste tyre activated carbons in the adsorption of commercial dyes. The adsorption of two commercial dyes, Basic Astrazon Yellow 7GLL and Reactive Rifafix Red 3BN on activated carbons made up of reinforcing fibres from tyre waste and low-rank bituminous coal was studied. The surface chemistry of activated carbons was modified by means of HCl-HNO3 treatment in order to increase the number of functional groups. Moreover, the influence of the pH on the process was also studied, this factor being of great importance due to the amphoteric characteristics of activated carbons. The activated carbons made with reinforcing fibre and coal had the highest SBET, but the reinforcing fibre activated carbon samples had the highest mesopore volume. The texture of the activated carbons was not modified upon acid oxidation treatment, unlike their surface chemistry which underwent considerable modification. The activated carbons made with a mixture of reinforcing fibre and coal experienced the largest degree of oxidation, and so had more acid surface groups. The adsorption of reactive dye was governed by the mesoporous volume, whilst surface chemistry played only a secondary role. However, the surface chemistry of the activated carbons and dispersive interactions played a key role in the adsorption of the basic dye. The adsorption of the reactive dye was more favored in a solution of pH 2, whereas the basic dye was adsorbed more easily in a solution of pH 12. PMID:26295195

  15. Surface-Enhanced Resonance Raman Scattering and Visible Extinction Spectroscopy of Copper Chlorophyllin: An Upper Level Chemistry Experiment

    Science.gov (United States)

    Schnitzer, Cheryl S.; Reim, Candace Lawson; Sirois, John J.; House, Paul G.

    2010-01-01

    Advanced chemistry students are introduced to surface-enhanced resonance Raman scattering (SERRS) by studying how sodium copper chlorophyllin (CuChl) adsorbs onto silver colloids (CuChl/Ag) as a function of pH. Using both SERRS and visible extinction spectroscopy, the extent of CuChl adsorption and colloidal aggregation are monitored. Initially at…

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

    International Nuclear Information System (INIS)

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

  17. Patterned porous silicon photonic crystals with modular surface chemistry for spatial control of neural stem cell differentiation

    Science.gov (United States)

    Huang, Tiffany H.; Pei, Yi; Zhang, Douglas; Li, Yanfen; Kilian, Kristopher A.

    2016-05-01

    We present a strategy to spatially define regions of gold and nanostructured silicon photonics, each with materials-specific surface chemistry, for azide-alkyne cycloaddition of different bioactive peptides. Neural stem cells are spatially directed to undergo neurogenesis and astrogenesis as a function of both surface properties and peptide identity.We present a strategy to spatially define regions of gold and nanostructured silicon photonics, each with materials-specific surface chemistry, for azide-alkyne cycloaddition of different bioactive peptides. Neural stem cells are spatially directed to undergo neurogenesis and astrogenesis as a function of both surface properties and peptide identity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08327c

  18. Studies of the surface reactivity of metal oxyhydroxides and sulfides with relevance to environmental chemistry

    Science.gov (United States)

    Pierre-Louis, Andro-Marc

    With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental problems. Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite (α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2, CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2. Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant

  19. Dual-switchable surfaces between hydrophobic and superhydrophobic fabricated by the combination of click chemistry and RAFT

    OpenAIRE

    Han, M S; Zhang, X. Y.; Li, L.; Peng, C; Bao, L.; E. C. Ou; Xiong, Y Q; Xu, W. J.

    2014-01-01

    A dual-switchable surface between hydrophobic and superhydrophobic has been fabricated successfully by combining reversible addition-fragmentation chain transfer polymerization (RAFT) polymeric technology and thiol-NCO click chemistry. Well-defined block copolymer, poly(7-(6-(acryloyloxy) hexyloxy) coumarin)-b-poly(N-Isopropylacryl amide), was synthesized by RAFT, and then the block copolymer was grafted onto the surface of SiO2 modified by toluene disocynate (TDI) via thiol-NCO click chemist...

  20. Preparation and application of a novel electrochemical sensing material based on surface chemistry of polyhydroquinone

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Xueping [Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules and College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 10080 (China); Wang, Yingkai [Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); Hu, Chengguo, E-mail: cghu@whu.edu.cn [Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 10080 (China); Huang, Jianlin; Chen, Huaixia; Wang, Shengfu [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules and College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062 (China); Hu, Shengshui, E-mail: sshu@whu.edu.cn [Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 10080 (China)

    2014-07-01

    A new analogue of polydopamine (PDA), i.e., polyhydroquinone (PH{sub 2}Q), was polymerized and its surface chemistry was studied by different ways of characterization. PH{sub 2}Q was produced by the self-polymerization of H{sub 2}Q mediated by dissolved oxygen, and the self-polymerization process was strongly dependent on the type and the pH value of the buffer solutions. PH{sub 2}Q can not only achieve surface hydrophilization of different substrates like polyethylene terephthalate (PET) film, graphite strip, C{sub 12}SH/Au and wax slice, but also possess several unique properties like reversible adsorption, good solubility and low cost. These properties made PH{sub 2}Q an ideal polymeric modifier for the noncovalent functionalization of some nanomaterials. By simply grinding with PH{sub 2}Q, pristine multi-walled carbon nanotubes (MWNTs) can be readily dispersed in water with high solubility and good stability. The resulting MWNT–PH{sub 2}Q composite exhibited excellent electrochemical performance, which was employed for the simultaneous determination of dopamine (DA) and uric acid (UA). - Highlights: • Polyhydroquinone (PH{sub 2}Q) was produced by the self-polymerization of hydroquinone (H{sub 2}Q) mediated by dissolved oxygen. • PH{sub 2}Q can achieve surface hydrophilization of a variety of substrates. • PH{sub 2}Q is an ideal polymeric modifier for the functionalization of multi-walled carbon nanotubes (MWNTs). • The MWNT–PH{sub 2}Q composite can be employed for the simultaneous determination of dopamine (DA) and uric acid (UA)

  1. Variations in snow and firn chemistry along US ITASE traverses and the effect of surface glazing

    Directory of Open Access Journals (Sweden)

    D. A. Dixon

    2013-03-01

    Full Text Available This study provides a baseline from which changes in the chemistry of the atmosphere over Antarctica can be monitored under expected warming scenarios and continued intensification of industrial activities in the Southern Hemisphere. It is the first study to measure more than 25 chemical constituents in the surface snow and firn across extensive regions of Antarctica. We present major ion, trace element, heavy metal, rare earth element and oxygen isotope data from a series of surface snow samples and shallow firn sections collected along four US ITASE traverses across East and West Antarctica. In each sample we measure dissolved concentrations of Na+, K+, Mg2+, Ca2+, Cl−, NO3+, SO42−, and MS− using ion chromatography and total concentrations of Sr, Cd, Cs, Ba, La, Ce, Pr, Pb, Bi, U, As, Al, S, Ca, Ti, V, Cr, Mn, Fe, Co, Na, Mg, Li, and K using inductively coupled plasma sector field mass spectrometry (ICP-SFMS. We also measure δ18O by isotope ratio mass spectrometry. Satellite remote sensing measurements of microwave backscatter and grain size are used to assist in the identification of glaze/dune areas across Antarctica and determine if these areas can possibly contain useful chemical climate records. The majority of the non-glaze/dune samples in this study exhibit similar, or lower, concentrations to those from previous studies. Consequently, the results presented here comprise a conservative baseline for Antarctic surface snow chemical concentrations. The elements Cd, Pb, As and Bi are enriched across Antarctica relative to both ocean and upper crust elemental ratios. Local and global volcanic outgassing may account for the majority of the Bi measured in East and West Antarctica and for a significant fraction of the Cd and As. However, significant concentrations of Cd, Pb, and As remain across much of Antarctica.

  2. Virtual screening of bioassay data

    Directory of Open Access Journals (Sweden)

    Schierz Amanda C

    2009-12-01

    Full Text Available Abstract Background There are three main problems associated with the virtual screening of bioassay data. The first is access to freely-available curated data, the second is the number of false positives that occur in the physical primary screening process, and finally the data is highly-imbalanced with a low ratio of Active compounds to Inactive compounds. This paper first discusses these three problems and then a selection of Weka cost-sensitive classifiers (Naive Bayes, SVM, C4.5 and Random Forest are applied to a variety of bioassay datasets. Results Pharmaceutical bioassay data is not readily available to the academic community. The data held at PubChem is not curated and there is a lack of detailed cross-referencing between Primary and Confirmatory screening assays. With regard to the number of false positives that occur in the primary screening process, the analysis carried out has been shallow due to the lack of cross-referencing mentioned above. In six cases found, the average percentage of false positives from the High-Throughput Primary screen is quite high at 64%. For the cost-sensitive classification, Weka's implementations of the Support Vector Machine and C4.5 decision tree learner have performed relatively well. It was also found, that the setting of the Weka cost matrix is dependent on the base classifier used and not solely on the ratio of class imbalance. Conclusions Understandably, pharmaceutical data is hard to obtain. However, it would be beneficial to both the pharmaceutical industry and to academics for curated primary screening and corresponding confirmatory data to be provided. Two benefits could be gained by employing virtual screening techniques to bioassay data. First, by reducing the search space of compounds to be screened and secondly, by analysing the false positives that occur in the primary screening process, the technology may be improved. The number of false positives arising from primary screening leads to

  3. Chemistry of the sea-surface microlayer. 3. Studies on the nutrient chemistry of the northern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Singbal, S.Y.S.; Narvekar, P.V.; Nagarajan, R.

    with Chlorophyll values at 1 m depth. Relatively high enrichment factors, sea-surface microlayer (SML), in coastal waters could be attributed to the influence of freshwater carrying considerable quantities of nutrients into the sea either from land runoff or from...

  4. The coupling effect of gas-phase chemistry and surface reactions on oxygen permeation and fuel conversion in ITM reactors

    KAUST Repository

    Hong, Jongsup

    2015-08-01

    © 2015 Elsevier B.V. The effect of the coupling between heterogeneous catalytic reactions supported by an ion transport membrane (ITM) and gas-phase chemistry on fuel conversion and oxygen permeation in ITM reactors is examined. In ITM reactors, thermochemical reactions take place in the gas-phase and on the membrane surface, both of which interact with oxygen permeation. However, this coupling between gas-phase and surface chemistry has not been examined in detail. In this study, a parametric analysis using numerical simulations is conducted to investigate this coupling and its impact on fuel conversion and oxygen permeation rates. A thermochemical model that incorporates heterogeneous chemistry on the membrane surface and detailed chemical kinetics in the gas-phase is used. Results show that fuel conversion and oxygen permeation are strongly influenced by the simultaneous action of both chemistries. It is shown that the coupling somewhat suppresses the gas-phase kinetics and reduces fuel conversion, both attributed to extensive thermal energy transfer towards the membrane which conducts it to the air side and radiates to the reactor walls. The reaction pathway and products, in the form of syngas and C2 hydrocarbons, are also affected. In addition, the operating regimes of ITM reactors in which heterogeneous- or/and homogeneous-phase reactions predominantly contribute to fuel conversion and oxygen permeation are elucidated.

  5. Surface trimming of silicon photonics devices using controlled reactive ion etching chemistry

    Science.gov (United States)

    Chandran, S.; Das, B. K.

    2015-06-01

    Surface trimming of rib waveguides fabricated in 5-μm SOI substrate has been carried out successfully without any significant increase of propagation losses. A reactive ion etching chemistry has been optimized for trimming and an empirical model has been developed to obtain the resulting waveguide geometries. This technique has been used to demonstrate smaller footprint devices like multimode interference based power splitters and ring resonators after defining them photolithographically with relatively large cross-section rib waveguides. We have been also successful to fabricate 2D tapered spot-size converter useful for monolithic integration of waveguides with varying heights and widths. The taper length is again precisely controlled by photolithographic definition. Minimum insertion loss of such a spot-size converter integrated between waveguides with 3-μm height difference has been recorded to be ∼2 dB. It has been also shown that the overall fiber-to-chip coupling loss can be reduced by >3 dB by using such spot-size converters at the input/output side of the waveguides.

  6. Surface chemistry and structures of 1,4-phenylene diisocyanide on gold films from solution

    Science.gov (United States)

    Abuflaha, Rasha; Olson, Dustin; Bennett, Dennis W.; Tysoe, Wilfred T.

    2016-07-01

    The adsorption of 1,4-phenylene diisocyanide (PDI) is studied on gold films as a function of PDI exposure from benzene solution by a combination of attenuated total internal reflection infrared (ATR-IR) spectroscopy and conductivity measurements. The infrared spectrum found for low PDI doses exhibits a single isocyanide vibrational peak consistent with the formation of -(Au-PDI)- oligomer chains that have been identified previously on a Au(111) surface dosed in ultrahigh vacuum. Larger solution doses cause the isocyanide peaks to split into two, with the lower-frequency vibrations corresponding to a free isocyanide mode, indicating the formation of a perpendicular, vertically bonded PDI molecule. This observation also rationalizes the apparent disparity between studies of the chemistry of PDI on gold in ultrahigh vacuum and with solution dosing. Since it has been shown previously that the -(Au-PDI)- oligomer chains are capable of providing conductive linkages between gold nanoparticles on an insulating mica substrate, it was proposed that higher PDI doses from solution should cause a decrease in conductivity due to chain disruption. This effect was found experimentally, thereby providing corroborative evidence for the above conclusions.

  7. Water chemistry of surface waters affected by the Fourmile Canyon wildfire, Colorado, 2010-2011

    Science.gov (United States)

    McCleskey, R. Blaine; Writer, Jeffrey H.; Murphy, Sheila F.

    2012-01-01

    In September 2010, the Fourmile Canyon fire burned about 23 percent of the Fourmile Creek watershed in Boulder County, Colo. Water-quality sampling of Fourmile Creek began within a month after the wildfire to assess its effects on surface-water chemistry. Water samples were collected from five sites along Fourmile Creek (above, within, and below the burned area) monthly during base flow, twice weekly during snowmelt runoff, and at higher frequencies during storm events. Stream discharge was also monitored. Water-quality samples were collected less frequently from an additional 6 sites on Fourmile Creek, from 11 tributaries or other inputs, and from 3 sites along Boulder Creek. The pH, electrical conductivity, temperature, specific ultraviolet absorbance, total suspended solids, and concentrations (dissolved and total) of major cations (calcium, magnesium, sodium, and potassium), anions (chloride, sulfate, alkalinity, fluoride, and bromide), nutrients (nitrate, ammonium, and phosphorus), trace metals (aluminum, arsenic, boron, barium, beryllium, cadmium, cobalt, chromium, copper, iron, mercury, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium, strontium, vanadium, and zinc), and dissolved organic carbon are here reported for 436 samples collected during 2010 and 2011.

  8. Controlling Short-Range Interactions by Tuning Surface Chemistry in HDPE/Graphene Nanoribbon Nanocomposites.

    Science.gov (United States)

    Sadeghi, Soheil; Zehtab Yazdi, Alireza; Sundararaj, Uttandaraman

    2015-09-01

    Unique dispersion states of nanoparticles in polymeric matrices have the potential to create composites with enhanced mechanical, thermal, and electrical properties. The present work aims to determine the state of dispersion from the melt-state rheological behavior of nanocomposites based on carbon nanotube and graphene nanoribbon (GNR) nanomaterials. GNRs were synthesized from nitrogen-doped carbon nanotubes via a chemical route using potassium permanganate and some second acids. High-density polyethylene (HDPE)/GNR nanocomposite samples were then prepared through a solution mixing procedure. Different nanocomposite dispersion states were achieved using different GNR synthesis methods providing different surface chemistry, interparticle interactions, and internal compartments. Prolonged relaxation of flow induced molecular orientation was observed due to the presence of both carbon nanotubes and GNRs. Based on the results of this work, due to relatively weak interactions between the polymer and the nanofillers, it is expected that short-range interactions between nanofillers play the key role in the final dispersion state. PMID:26266528

  9. Surface chemistry analysis of lithium conditioned NSTX graphite tiles correlated to plasma performance

    International Nuclear Information System (INIS)

    Lithium wall conditioning in NSTX has resulted in reduced divertor recycling, improved energy confinement, and reduced frequency of edge-localized modes (ELMs), up to the point of complete ELM suppression. NSTX tiles were removed from the vessel following the 2008 campaign and subsequently analyzed using X-ray photoelectron spectroscopy as well as nuclear reaction ion beam analysis. In this paper we relate surface chemistry to deuterium retention/recycling, develop methods for cleaning of passivated NSTX tiles, and explore a method to effectively extract bound deuterium from lithiated graphite. Li–O–D and Li–C–D complexes characteristic of deuterium retention that form during NSTX operations are revealed by sputter cleaning and heating. Heating to ∼850 °C desorbed all deuterium complexes observed in the O 1s and C 1s photoelectron energy ranges. Tile locations within approximately ±2.5 cm of the lower vertical/horizontal divertor corner appear to have unused Li-O bonds that are not saturated with deuterium, whereas locations immediately outboard of this region indicate high deuterium recycling. X-ray photo electron spectra of a specific NSTX tile with wide ranging lithium coverage indicate that a minimum lithium dose, 100–500 nm equivalent thickness, is required for effective deuterium retention. This threshold is suspected to be highly sensitive to surface morphology. The present analysis may explain why plasma discharges in NSTX continue to benefit from lithium coating thickness beyond the divertor deuterium ion implantation depth, which is nominally <10 nm

  10. The effect of surface chemistry on particulate fouling under flow-boiling conditions

    Energy Technology Data Exchange (ETDEWEB)

    Turner, C.W.; Klimas, S.J

    2001-07-01

    A model of particulate fouling has been developed that takes account of the influence of deposit consolidation on the kinetics of the fouling process. Fouling kinetics predicted by the model are linear, falling-rate or asymptotic, depending on the relative magnitudes of the rate constants for deposition, re-entrainment, and consolidation. One of the key predictions of the model is that the steady-state fouling rate is proportional to the ratio K{lambda}{sub c}/{lambda}, where K, {lambda}{sub c} and {lambda} are the rate constants for deposition, consolidation, and removal, respectively. Tests conducted in a high-temperature recirculating-water loop have demonstrated that chemistry exerts a strong influence on the fouling kinetics of particulate corrosion product under flow-boiling conditions in alkaline water at 270{sup o}C. For example, the fouling rates of lepidocrocite and hematite are 12 and 50 times greater, respectively, than the rate for magnetite. It is argued that the difference can be attributed to the sign of the surface charge that develops on the metal oxide surfaces in the high-temperature coolant, which, in turn, is a function of pH relative to the isoelectric point of the metal oxide. Chemical effects also influence fouling behaviour through the rate of consolidation. For example, when morpholine is used for the alkalizing agent the fouling rate is 3-5 times higher than the case when the pH is controlled using dimethylamine. The difference is attributed to the rate of deposit consolidation, which is 6-20 times greater than the rate of deposit removal for morpholine compared to 0.2-0.3 times the rate of removal for dimethylamine. The results of this investigation, together with the insights provided by the fouling model, are being used to guide the selection of the alkalizing amine to optimize its properties for both corrosion (pH) control and deposit control in the steam generator. (author)

  11. New insights into the fouling mechanism of dissolved organic matter applying nanofiltration membranes with a variety of surface chemistries.

    Science.gov (United States)

    Mustafa, Ghulam; Wyns, Kenny; Buekenhoudt, Anita; Meynen, Vera

    2016-04-15

    Nanofiltration (NF) membrane fouling by DOM remains a major and poorly understood issue. To acquire a better insight we studied the fouling of the DOM fractions humic acids (HAs) and fulvic acids (FAs), with and without Ca(2+), on native and grafted ceramic NF membranes. Grafting with two methods and three different grafting groups allowed to create a range of membranes with a variety of surface chemistries, and a wide range of surface polarity, much broader than ever used in previous studies. A typical polymer (polyamide) NF membrane was included for comparison. All obtained results reveal that membrane fouling is not determined by membrane hydrophilicity/hydrophobicity as a general and sole criterion, but rather on the whole of the surface chemistry determining the amount and strength of the possible foulant-membrane interactions. As a consequence the effect of inorganic ions on the fouling is also dependent on the surface chemistry. Important new insight in the DOM fouling mechanism was acquired, shedding new light on the state-of-the-art knowledge. PMID:26905798

  12. Effects of surface chemistry and microstructure of electrolyte on oxygen reduction kinetics of solid oxide fuel cells

    Science.gov (United States)

    Park, Joong Sun; An, Jihwan; Lee, Min Hwan; Prinz, Fritz B.; Lee, Wonyoung

    2015-11-01

    We report systematic investigation of the surface properties of yttria-stabilized zirconia (YSZ) electrolytes with the control of the grain boundary (GB) density at the surface, and its effects on electrochemical activities. The GB density of thin surface layers deposited on single crystal YSZ substrates is controlled by changing the annealing temperature (750-1450 °C). Higher oxygen reduction reactions (ORR) kinetics is observed in samples annealed at lower temperatures. The higher ORR activity is ascribed to the higher GB density at the YSZ surface where 'mobile' oxide ion vacancies are more populated. Meanwhile, oxide ion vacancies concurrently created with yttrium segregation at the surface at the higher annealing temperature are considered inactive to oxygen incorporation reactions. Our results provide additional insight into the interplay between the surface chemistry, microstructures, and electrochemical activity. They potentially provide important guidelines for engineering the electrolyte-electrode interfaces of solid oxide fuel cells for higher electrochemical performance.

  13. Na + and HTO diffusion in compacted bentonite: Effect of surface chemistry and related texture

    Science.gov (United States)

    Melkior, T.; Gaucher, E. C.; Brouard, C.; Yahiaoui, S.; Thoby, D.; Clinard, Ch.; Ferrage, E.; Guyonnet, D.; Tournassat, C.; Coelho, D.

    2009-05-01

    SummaryIn underground repository concepts for radioactive waste, bentonite is studied as a reference swelling material to be used as an engineered barrier. Under the changing geochemical conditions prevailing within the barrier (saturation with the fluid coming from the host formation, diffusion of various chemical plumes caused by the degradation of some constituents of the barrier-system, etc.), the surface chemistry of the clay particles could evolve. This work aims to characterize the effects of these changes on (i) the microstructure of compacted bentonite samples and (ii) the diffusion properties of HTO and Na in these samples. For this purpose, bentonite sets were equilibrated with different solutions: NaCl, CaCl 2, CsCl solutions as well as an artificial clayey porewater solution. The microstructure of the different samples was characterized by HRTEM and XRD, in a water saturated state. In parallel, effective diffusion coefficients of both HTO and 22Na were measured for the different samples. The density of the bentonite in the diffusion tests and in the HRTEM observations was set at 1.6 Mg m -3. From the microstructural observations and the results of diffusion tests, it is deduced that one key parameter is the occurrence of a gel phase in the material, which is found to depend strongly on the bentonite set: the gel phase dominates in Na-bentonite, while it is lacking in Cs-bentonite. The HTO diffusion coefficients are found to be lower in the samples with high gel phase content. Sodium diffusion does not follow the same trend: when compared with HTO, Na diffuses faster when the gel phase content is high. The latter result could indicate that the "accelerated diffusion mechanism" of cations, already mentioned in the literature, is enhanced in clayey materials that contain a gel phase.

  14. Recovering ferromagnetic metal surfaces to fully exploit chemistry in molecular spintronics

    OpenAIRE

    Marta Galbiati; Sophie Delprat; Michele Mattera; Samuel Mañas-Valero; Alicia Forment-Aliaga; Sergio Tatay; Cyrile Deranlot; Pierre Seneor; Richard Mattana; Frédéric Petroff

    2015-01-01

    Organic spintronics is a new emerging field that promises to offer the full potential of chemistry to spintronics, as for example high versatility through chemical engineering and simple low cost processing. However, one key challenge that remains to be unlocked for further applications is the high incompatibility between spintronics key materials such as high Curie temperature Co, Ni, Fe (and their alloys) and wet chemistry. Indeed, the transition metal proneness to oxidation has so far hamp...

  15. Magnetical and optical properties of nanodiamonds can be tuned by particles surface chemistry: theoretical and experimental study

    Czech Academy of Sciences Publication Activity Database

    Kratochvílová, Irena; Šebera, Jakub; Ashcheulov, Petr; Golan, Martin; Ledvina, Miroslav; Mičová, Júlia; Mravec, F.; Kovalenko, A.; Zverev, D.; Yavkin, B.; Orlinskii, S.; Záliš, Stanislav; Fišerová, Anna; Richter, Jan; Šefc, L.; Turánek, J.

    2014-01-01

    Roč. 118, č. 43 (2014), s. 25245-25252. ISSN 1932-7447 R&D Projects: GA TA ČR TA01011165; GA ČR(CZ) GA14-10279S Institutional support: RVO:68378271 ; RVO:61388971 ; RVO:61388963 ; RVO:61388955 Keywords : nano diamond particles * NV luminescent centers * surface functionalization * DFT Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.772, year: 2014

  16. Bioconjugation of trypsin onto gold nanoparticles: Effect of surface chemistry on bioactivity

    Energy Technology Data Exchange (ETDEWEB)

    Hinterwirth, Helmut; Lindner, Wolfgang [Department of Analytical Chemistry, University of Vienna, Waehringerstrasse 38, 1090 Vienna (Austria); Laemmerhofer, Michael, E-mail: michael.laemmerhofer@uni-tuebingen.de [Department of Analytical Chemistry, University of Vienna, Waehringerstrasse 38, 1090 Vienna (Austria)

    2012-07-06

    Highlights: Black-Right-Pointing-Pointer Size and spacer affect bioactivity of nanoparticulate trypsin reactor. Black-Right-Pointing-Pointer Increase of GNP's size increases activity of bound trypsin. Black-Right-Pointing-Pointer Increase of spacer length increases amount and activity of immobilized enzyme by factor 6. Black-Right-Pointing-Pointer Decrease of digestion time up to less than 1 h when trypsin immobilized onto GNPs. Black-Right-Pointing-Pointer Reduced auto-digestion compared to trypsin in-solution. - Abstract: The systematic study of activity, long-time stability and auto-digestion of trypsin immobilized onto gold nanoparticles (GNPs) is described in this paper and compared to trypsin in-solution. Thereby, the influence of GNP's size and immobilization chemistry by various linkers differing in lipophilicity/hydrophilicity and spacer lengths was investigated with regard to the bioactivity of the conjugated enzyme. GNPs with different sizes were prepared by reduction and simultaneous stabilization with trisodium citrate and characterized by UV/vis spectra, dynamic light scattering (DLS), {zeta}-potential measurements and transmission electron microscopy (TEM). GNPs were derivatized by self-assembling of bifunctional thiol reagents on the nanoparticle (NP) surface via dative thiol-gold bond yielding a carboxylic acid functionalized surface. Trypsin was either attached directly via hydrophobic and ionic interactions onto the citrate stabilized GNPs or immobilized via EDC/NHS bioconjugation onto the carboxylic functionalized GNPs, respectively. The amount of bound trypsin was quantified by measuring the absorbance at 280 nm. The activity of bound enzyme and its Michaelis Menten kinetic parameter K{sub m} and v{sub max} were measured by the standard chromogenic substrate N{sub {alpha}}-Benzoyl-DL-arginine 4-nitroanilide hydrochloride (BApNA). Finally, digestion of a standard protein mixture with the trypsin-conjugated NPs followed by analysis with

  17. Bioconjugation of trypsin onto gold nanoparticles: Effect of surface chemistry on bioactivity

    International Nuclear Information System (INIS)

    Highlights: ► Size and spacer affect bioactivity of nanoparticulate trypsin reactor. ► Increase of GNP's size increases activity of bound trypsin. ► Increase of spacer length increases amount and activity of immobilized enzyme by factor 6. ► Decrease of digestion time up to less than 1 h when trypsin immobilized onto GNPs. ► Reduced auto-digestion compared to trypsin in-solution. - Abstract: The systematic study of activity, long-time stability and auto-digestion of trypsin immobilized onto gold nanoparticles (GNPs) is described in this paper and compared to trypsin in-solution. Thereby, the influence of GNP's size and immobilization chemistry by various linkers differing in lipophilicity/hydrophilicity and spacer lengths was investigated with regard to the bioactivity of the conjugated enzyme. GNPs with different sizes were prepared by reduction and simultaneous stabilization with trisodium citrate and characterized by UV/vis spectra, dynamic light scattering (DLS), ζ-potential measurements and transmission electron microscopy (TEM). GNPs were derivatized by self-assembling of bifunctional thiol reagents on the nanoparticle (NP) surface via dative thiol-gold bond yielding a carboxylic acid functionalized surface. Trypsin was either attached directly via hydrophobic and ionic interactions onto the citrate stabilized GNPs or immobilized via EDC/NHS bioconjugation onto the carboxylic functionalized GNPs, respectively. The amount of bound trypsin was quantified by measuring the absorbance at 280 nm. The activity of bound enzyme and its Michaelis Menten kinetic parameter Km and vmax were measured by the standard chromogenic substrate Nα-Benzoyl-DL-arginine 4-nitroanilide hydrochloride (BApNA). Finally, digestion of a standard protein mixture with the trypsin-conjugated NPs followed by analysis with LC–ESI-MS and successful MASCOT search demonstrated the applicability of the new heterogenous nano-structured biocatalyst. It could be shown that the amount of

  18. Thermal chemistry of copper(I)-N,N '-di-sec-butylacetamidinate on Cu(110) single-crystal surfaces

    International Nuclear Information System (INIS)

    The surface chemistry of copper(I)-N,N'-di-sec-butylacetamidinate on Cu(110) single-crystal surfaces has been characterized under ultrahigh vacuum by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy. A series of thermal stepwise conversions were identified, starting with the partial dissociative adsorption of the copper acetamidinate dimers into a mixture of monomers and dimers on the surface. An early dissociation of a C-N bond leads to the production of N-sec-butylacetamidine, which is detected in TPD experiments in three temperature regimes, the last one centered around 480 K. Butene, and a small amount of butane, is also detected above approximately 500 K, and hydrogen production, an indication of dehydrogenation of surface fragments, is observed at 460, 550 and 670 K. In total, only about 10% of the initial copper(I)-N,N'-di-sec-butylacetamidinate adsorbed monolayer decomposes, and only about ∼3% of carbon is left behind on the surface after heating to high temperatures. The implications of this surface chemistry to the design of chemical film growth processes using copper acetamidinates as precursors are discussed.

  19. Dual-switchable surfaces between hydrophobic and superhydrophobic fabricated by the combination of click chemistry and RAFT

    Directory of Open Access Journals (Sweden)

    M. S. Han

    2014-07-01

    Full Text Available A dual-switchable surface between hydrophobic and superhydrophobic has been fabricated successfully by combining reversible addition-fragmentation chain transfer polymerization (RAFT polymeric technology and thiol-NCO click chemistry. Well-defined block copolymer, poly(7-(6-(acryloyloxy hexyloxy coumarin-b-poly(N-Isopropylacryl amide, was synthesized by RAFT, and then the block copolymer was grafted onto the surface of SiO2 modified by toluene disocynate (TDI via thiol-NCO click chemistry. The results of nuclear magnetic resonance (NMR and Fourier Transform Infrared (FTIR spectroscopies confirmed that the block copolymer (Number average molecular weight (Mn = 9400, polydispersity index (PDI = 1.22 has been synthesized successfully. The static contact angle (CA of the surface prepared by SiO2/P (7-6-AC-b-PNIPAAm switches from 98±2 to 137±2° by adjusting the temperature. Furthermore, the contact angle can also oscillate between 137±2 and 157±2° on the irradiation of UV light at 365 and 254 nm, respectively. The dual-switchable surfaces exhibit high stability between hydrophilicity and superhydrophobicity. Therefore, the method provides a new method to fabricate the dual-stimuli-responsive surface with tunable wettability, reversible switching, and also be easily extended to other dual-responsive surfaces. This ability to control the wettability by the adjustment of the temperature and UV light has applications in a broad range of fields.

  20. Characterization of surface chemistry and crystallization behavior of polypropylene composites reinforced with wood flour, cellulose, and lignin during accelerated weathering

    International Nuclear Information System (INIS)

    Highlights: • AFM was firstly used to characterize the surface morphology and roughness of weathered wood–plastic composites. • Composites containing lignin showed less loss of flexural strength and modulus and less roughness on weathered surface compared with lignin-free composites. • ATR-FTIR and XPS analyses demonstrated in detail that significant chemistry changes occurred in wood flour, lignin, and cellulose. • The crystallinity of PP increased in all weathered samples due to chain scissions and recrystallization. • The stabilization and antioxidation effects of lignin were proved. - Abstract: In this study, six groups of polypropylene composites reinforced with wood flour (WF), cellulose, and lignin at different loading levels were exposed in a QUV accelerated weathering tester for a total duration of 960 h. The changes in surface morphology, chemistry, and thermal properties of weathered samples were characterized by atomic force microscope (AFM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetric (DSC), respectively. The flexural properties of all samples were tested after different durations of weathering. The results showed that: (1) the surface roughness of all samples increased after weathering; (2) composites containing lignin showed less loss of flexural strength and modulus and less roughness on weathered surface compared with lignin-free composites, indicating the functions of stabilization and antioxidation of lignin; (3) the crystallinity of PP increased in all weathered samples due to chain scissions and recrystallization; (4) ATR-FTIR and XPS analyses demonstrated in detail that significant changes occurred in surface chemistry, accompanied by the photodegradation and photo-oxidation of lignin and cellulose with prolonged weathering time

  1. Characterization of surface chemistry and crystallization behavior of polypropylene composites reinforced with wood flour, cellulose, and lignin during accelerated weathering

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Yao; Liu, Ru; Cao, Jinzhen, E-mail: caoj@bjfu.edu.cn

    2015-03-30

    Highlights: • AFM was firstly used to characterize the surface morphology and roughness of weathered wood–plastic composites. • Composites containing lignin showed less loss of flexural strength and modulus and less roughness on weathered surface compared with lignin-free composites. • ATR-FTIR and XPS analyses demonstrated in detail that significant chemistry changes occurred in wood flour, lignin, and cellulose. • The crystallinity of PP increased in all weathered samples due to chain scissions and recrystallization. • The stabilization and antioxidation effects of lignin were proved. - Abstract: In this study, six groups of polypropylene composites reinforced with wood flour (WF), cellulose, and lignin at different loading levels were exposed in a QUV accelerated weathering tester for a total duration of 960 h. The changes in surface morphology, chemistry, and thermal properties of weathered samples were characterized by atomic force microscope (AFM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetric (DSC), respectively. The flexural properties of all samples were tested after different durations of weathering. The results showed that: (1) the surface roughness of all samples increased after weathering; (2) composites containing lignin showed less loss of flexural strength and modulus and less roughness on weathered surface compared with lignin-free composites, indicating the functions of stabilization and antioxidation of lignin; (3) the crystallinity of PP increased in all weathered samples due to chain scissions and recrystallization; (4) ATR-FTIR and XPS analyses demonstrated in detail that significant changes occurred in surface chemistry, accompanied by the photodegradation and photo-oxidation of lignin and cellulose with prolonged weathering time.

  2. Correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys

    OpenAIRE

    Feliu Jr., S.; Pardo, Angel; Merino, M. C.; Coy, A. E.; Viejo, F.; Arrabal, R.

    2009-01-01

    X-ray photoelectron spectroscopy (XPS) was used in order to investigate the correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys exposed to 98% relative humidity at 50 °C. Commercially pure magnesium, used as the reference material, revealed MgO, Mg(OH)2 and tracers of magnesium carbonate in the air-formed film. For the AZ80 and AZ91D alloys, the amount of magnesium carbonate formed on the surface reached similar values to those of M...

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

    DEFF Research Database (Denmark)

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

    1993-01-01

    The molecular organization of streptavidin (SA) bound to aqueous surface monolayers of biotin-functionalized lipids and binary lipid mixtures has been investigated with neutron reflectivity and electron and fluorescence microscopy. The substitution of deuterons (2H) for protons (1H), both in...... dependence of the structural properties of such self-assembled SA monolayers on the surface chemistry was observed: the lateral protein density depends on the length of the spacer connecting the biotin moiety and its hydrophobic anchor. The hydration of the lipid head groups in the protein-bound state...

  4. Increasing the Detection Limit of the Parkinson Disorder through a Specific Surface Chemistry Applied onto Inner Surface of the Titration Well

    Directory of Open Access Journals (Sweden)

    Fabienne Poncin-Epaillard

    2012-04-01

    Full Text Available The main objective of this paper was to illustrate the enhancement of the sensitivity of ELISA titration for neurodegenerative proteins by reducing nonspecific adsorptions that could lead to false positives. This goal was obtained thanks to the association of plasma and wet chemistries applied to the inner surface of the titration well. The polypropylene surface was plasma-activated and then, dip-coated with different amphiphilic molecules. These molecules have more or less long hydrocarbon chains and may be charged. The modified surfaces were characterized in terms of hydrophilic—phobic character, surface chemical groups and topography. Finally, the coated wells were tested during the ELISA titration of the specific antibody capture of the α-synuclein protein. The highest sensitivity is obtained with polar (Θ = 35°, negatively charged and smooth inner surface.

  5. Surface chemistry of plasma-assisted atomic layer deposition of Al2O3 studied by infrared spectroscopy

    International Nuclear Information System (INIS)

    The surface groups created during plasma-assisted atomic layer deposition (ALD) of Al2O3 were studied by infrared spectroscopy. For temperatures in the range of 25-150 deg. C, -CH3 and -OH were unveiled as dominant surface groups after the Al(CH3)3 precursor and O2 plasma half-cycles, respectively. At lower temperatures more -OH and C-related impurities were found to be incorporated in the Al2O3 film, but the impurity level could be reduced by prolonging the plasma exposure. The results demonstrate that -OH surface groups rule the surface chemistry of the Al2O3 process and likely that of plasma-assisted ALD of metal oxides from organometallic precursors in general

  6. A solid phase extraction based non-disruptive sampling technique to investigate the surface chemistry of macroalgae.

    Science.gov (United States)

    Cirri, Emilio; Grosser, Katharina; Pohnert, Georg

    2016-01-01

    The surface chemistry of aquatic organisms determines their biotic interactions. Metabolites in the spatially limited laminar boundary layer mediate processes, such as antifouling, allelopathy and chemical defense against herbivores. However, very few methods are available for the investigation of such surface metabolites. An approach is described in which surfaces are extracted by means of C18 solid phase material. By powdering wet algal surfaces with this material, organic compounds are adsorbed and can be easily recovered for subsequent liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS) investigations. The method is robust, picks up metabolites of a broad polarity range and is easy to handle. It is more universal compared to established solvent dipping protocols and it does not cause damage to the test organisms. A protocol is introduced for the macroalgae Fucus vesiculosus, Caulerpa taxifolia and Gracilaria vermiculophylla, but it can be easily transferred to other aquatic organisms. PMID:26795737

  7. XPS study of the surface chemistry on AZ31 and AZ91 magnesium alloys in dilute NaCl solution

    Science.gov (United States)

    Wang, Lei; Shinohara, Tadashi; Zhang, Bo-Ping

    2010-08-01

    The surface chemistry on AZ31 and AZ91 magnesium alloys was characterized by X-ray photoelectron spectroscopy (XPS) in the corrosion and the passivation zones. In the corrosion zone, the presence of Mg(OH) 2 and MgCO 3 species was found in the outer surface, whereas, in the inner layer, the co-existence of Mg(OH) 2, MgO and MgCO 3 species was observed for both alloys. The presence of Al 3+ in the surface electrolyte to form Al 2O 3/Al(OH) 3 and the formation of carbonate product provide a better passivation on the surfaces and retard the chloride-induced corrosion on the materials in the passivation zone.

  8. XPS study of the surface chemistry on AZ31 and AZ91 magnesium alloys in dilute NaCl solution

    Energy Technology Data Exchange (ETDEWEB)

    Wang Lei [Materials Reliability Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Shinohara, Tadashi, E-mail: SHINOHARA.Tadashi@nims.go.jp [Materials Reliability Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Zhang Boping [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2010-08-01

    The surface chemistry on AZ31 and AZ91 magnesium alloys was characterized by X-ray photoelectron spectroscopy (XPS) in the corrosion and the passivation zones. In the corrosion zone, the presence of Mg(OH){sub 2} and MgCO{sub 3} species was found in the outer surface, whereas, in the inner layer, the co-existence of Mg(OH){sub 2}, MgO and MgCO{sub 3} species was observed for both alloys. The presence of Al{sup 3+} in the surface electrolyte to form Al{sub 2}O{sub 3}/Al(OH){sub 3} and the formation of carbonate product provide a better passivation on the surfaces and retard the chloride-induced corrosion on the materials in the passivation zone.

  9. XPS study of the surface chemistry on AZ31 and AZ91 magnesium alloys in dilute NaCl solution

    International Nuclear Information System (INIS)

    The surface chemistry on AZ31 and AZ91 magnesium alloys was characterized by X-ray photoelectron spectroscopy (XPS) in the corrosion and the passivation zones. In the corrosion zone, the presence of Mg(OH)2 and MgCO3 species was found in the outer surface, whereas, in the inner layer, the co-existence of Mg(OH)2, MgO and MgCO3 species was observed for both alloys. The presence of Al3+ in the surface electrolyte to form Al2O3/Al(OH)3 and the formation of carbonate product provide a better passivation on the surfaces and retard the chloride-induced corrosion on the materials in the passivation zone.

  10. Surface chemistry and moisture sorption properties of wood coated with multifunctional alkoxysilanes by sol-gel process

    DEFF Research Database (Denmark)

    Tshabalala, M.A.; Kingshott, P.; VanLandingham, M.R.;

    2003-01-01

    ). Investigation of the surface chemistry and morphology of the wood specimens by means of ATR-FTIR, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, SEM, and atomic force microscopy indicated that the sol-gel process results in deposition of polysiloxane networks that are bonded to the wood by......Sol-gel surface deposition of a hydrophobic polysiloxane coating on wood was accomplished by using a mixture of a low molecular weight multifunctional alkoxysilane, methyltrimethoxysilane (MTMOS), and a high molecular weight multifunctional alkoxysilane, hexadecyltrimethoxysilane (HDTMOS...... polycondensation with surface hydroxyl groups. The surface hydroxyl groups involved in the bonds appear to be located predominantly on the cellulose component of the wood. The sol-gel deposit on the wood substrates lowered the rates of water and water vapor sorption. The low molecular weight MTMOS apparently...

  11. The effect of injection molding conditions on the near-surface rubber morphology, surface chemistry, and adhesion performance of semi-crystalline and amorphous polymers

    Science.gov (United States)

    Weakley-Bollin, Shannon Christine

    This thesis investigated the effect of injection molding processing variables, resin formulation and mold material on the resulting morphology and properties of semi-crystalline and amorphous polymers in parts molded on large presses with fully developed flow. Five different polymer resins and two different coating types were investigated, and the near-surface morphology was found to be dependent on material formulation, processing parameters, and geometry. For painted TPO, changes in the near-surface rubber morphology and surface chemistry based on material and processing conditions had no significant effect on the adhesion performance. For metal plated ABS, the adhesion performance was found to be heavily dependent on the rubber surface morphology, which varied with material formulation and processing conditions. One of the most significant findings was that forged aluminum injection molding tooling had little effect on the surface morphology or adhesion performance of either polypropylene or the two TPO formulations examined, despite the five-fold increase in thermal conductivity over traditional tool steel. Surface chemistry, however, was found to be affected by cooling rate, depending on material formulation. A UV stabilizer additive was found concentrated at 2.5 atomic percent on the surface of the aluminum molded part, but not the steel molded part, demonstrating a possible opportunity for using additives and aluminum tooling to create "designer surfaces". Processing conditions were found to have a competing role in metal plated ABS, where conditions that lowered surface stress and improved adhesion by a factor of 15 also increased the amount of bulk molded-in stress by nearly 7%. Both factors were found to play an important role in adhesion performance due to the effect of surface stress on the quality of the resulting etch structure. The bulk stress must be minimized to due to the large mechanical and thermal mismatch between the polymer and metal layers

  12. Experimental indications of effects of surface deprotonation on Na-bentonite pore water chemistry in a geological repository

    International Nuclear Information System (INIS)

    Bentonite-water interaction was studied using a simple equilibrium model based on experimental measurements in order to describe bentonite porewater chemistry. Direct pH measurements for highly compacted bentonite and batch-type bentonite-water interaction experiments were performed under anaerobic conditions. In the direct pH measurements, resin particles doped with a pH indicator were sandwiched between a pair of bentonite columns immersed in a test solution. The experimental results showed that the solution compositions in equilibrium with bentonite depended on the bentonite to liquid ratio (B/L) and the initial solution composition. An equilibrium model assuming only fast equilibration processes between the bentonite minerals and the solution could be used to calculate the trends of pH and other ion concentrations with B/L. This study indicates that the surface deprotonation of smectite is a very important factor influencing the porewater chemistry in highly compacted bentonite. Copyright (2001) Material Research Society

  13. A Shrinkage Estimator for Combination of Bioassays

    Institute of Scientific and Technical Information of China (English)

    Jian Xiong; D.G. Chen; Zhen-hai Yang

    2007-01-01

    A shrinkage estimator and a maximum likelihood estimator are proposed in this paper for combination of bioassays. The shrinkage estimator is obtained in closed form which incorporates prior information just on the common log relative potency after the homogeneity test for combination of bioassays is accepted. It is a practical improvement over other estimators which require iterative procedure to obtain the estimator for the relative potency. A real data is also used to show the superiorities for the newly-proposed procedures.

  14. Simulation study of the effects of surface chemistry and temperature on the conformations of ssDNA oligomers near hydrophilic and hydrophobic surfaces

    International Nuclear Information System (INIS)

    We study the effects of the presence of a hydrophilic and a hydrophobic surface on the conformations and interactions of a single-stranded DNA (ssDNA) oligomer using atomistic molecular dynamics, umbrella sampling, and temperature-replica exchange. Our simulations capture the expected interactions between the ssDNA and the two surfaces (e.g., hydrogen bonds, hydrophobic interactions), but we find that the surface chemistry does not strongly affect the exposure of the relatively hydrophobic nucleobases or the hydrophilic phosphate backbone in a 16-base ssDNA. Likewise, the surfaces do not strongly affect the preferred size of the ssDNA compared to bulk solution, although the hydrophilic surface does favor slightly more compact ssDNA conformations than the hydrophobic surface. In more compact conformations, the negative charge of the ssDNA is more concentrated, and the energetic interactions of the DNA and DNA-bound counterions with the hydrophilic surface are more favorable, which consequently favors smaller ssDNA sizes. Increasing temperature, regardless of the presence or chemistry of a surface, makes it less unfavorable for the ssDNA to assume both compact and extended conformations. With increasing temperature the free energy cost of assuming a compact conformation is reduced to a greater extent than the cost of assuming an extended conformation. The reason for this difference is the entropically favorable release of DNA-bound water molecules upon assuming a compact conformation. Increasing temperature decreases water-DNA interactions while surprisingly increasing counterion-DNA interactions, changes which are attributed to the relative balance of entropic and energetic contributions for water molecules and counterions bound to the ssDNA

  15. Bioassay criteria for environmental restoration workers

    International Nuclear Information System (INIS)

    Environmental restoration (ER) work at the U. S. Department of Energy Hanford Site posed questions concerning when to perform bioassay monitoring of workers for potential intakes of radioactivity. Application of criteria originally developed for use inside radionuclide processing facilities to ER work resulted in overly restrictive bioassay requirements. ER work typically involves site characterization or, excavating large quantities of potentially contaminated soil, rather than working with concentrated quantities of radioactivity as in a processing facility. An improved approach, tailored to ER work, provided soil contamination concentrations above which worker bioassay would be required. Soil concentrations were derived assuming acute or chronic intakes of 2% of an Annual Limit on Intake (ALI), or a potential committed effective dose equivalent of 100 mrem, and conservative dust loading of air from the work. When planning ER work, the anticipated soil concentration and corresponding need for bioassay could be estimated from work-site historical records. Once site work commenced, soil sampling and work-place surveys could be used to determine bioassay needs. This approach substantially reduced the required number of bioassay samples with corresponding reductions in analytical costs, schedules, and more flexible work-force management. (Work supported by the US Department of Energy under contract DOE-AC06-76RLO 1830.)

  16. Effect of porosity and surface chemistry on the adsorption-desorption of uranium(VI) from aqueous solution and groundwater

    International Nuclear Information System (INIS)

    Rice straw-based biochars modified with different chemical regents were used as an adsorbent for uranium(VI). Effect of pyrolysis temperature and nature of modifying agent's as well as surface chemistry, surface charge, and pore structure on U(VI) removal was investigated. Amount and nature of the surface groups has, in general, more influence than its porosity on U(VI) adsorption. The adsorption was maximum for the initial pH of 5.5. Rice straw derived biochars had comparable U(VI) adsorption as compared to other adsorbents. The U(VI) removal was 90 % from groundwater. NaHCO3 was found to be the most efficient desorbent eluent for U(VI). (author)

  17. Surface chemistry and interfacial charge-transfer mechanisms in photoinduced oxygen exchange at O2-TiO2 interfaces.

    Science.gov (United States)

    Montoya, Juan Felipe; Peral, José; Salvador, Pedro

    2011-04-01

    Experimental results obtained over the last three decades on photoinduced oxygen isotopic exchange (POIE) of TiO₂ oxygen atoms with those of adsorbed water molecules and gaseous O₂ are analyzed in the light of recent information from the literature on the interaction of water and O₂ species with the TiO₂ surface (obtained by application of surface spectroscopy techniques in combination with high-resolution scanning tunnelling microscopy). The analysis emphasizes the singular role that bridging oxygen ions and bridging oxygen vacancies play in TiO₂ surface chemistry and interfacial electron transfer at the gas phase-TiO₂ interface in the absence and presence of water. The observed competition between POIE and the photo-oxidation (PO) of organic compounds is analyzed in terms of the recently developed direct-indirect (D-I) kinetic model for heterogeneous photocatalysis (D. Monllor-Satoca et al., Catal. Today, 2007, 129, 247, and references therein). PMID:21442702

  18. Cluster Chemistry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  19. A Colorimetric Bioassay for Perchlorate

    Science.gov (United States)

    Heinnickel, M. L.; Smith, S.; Coates, J. D.

    2007-12-01

    Recognition of perchlorate (ClO4-) as a widespread contaminant across the United States and its potential adverse affects towards human health has motivated the EPA to place ClO4- on its contaminant candidate list for drinking water supplies. While a federal MCL has not yet been set, a recommended public health goal of 1 ppb (μg.L-1) was established by the US EPA in 2002. To date, methods of detection require use of sensitive ion chromatographic equipment that are expensive, time consuming, and require highly trained personnel for use. Our studies are focused on the development of a highly sensitive, simple, and robust colorimetric bioassay based on the primary enzyme involved in microbial ClO4- reduction, the perchlorate reductase (Pcr). A previously published assay used reduced methyl viologen (MV, the dye is reduced with sodium hydrosulfite) as an electron donor to demonstrate Pcr activity. The assay directly correlates the amount of MV oxidized with the amount of ClO4- reduced by assuming a transfer of four electrons. To test this assumption, we compared actual concentrations of MV oxidized to ClO4- reduced in this assay. ClO4- concentrations were determined using a Dionex ICS-500 ion chromatography system, while MV concentrations were determined using a standard curve generated at 578 nm. Comparisons between the two revealed that twelve molecules of MV were oxidized for each molecule of ClO4- reduced. The oxidation of these additional eight MV molecules is explained by the interaction of the dye with chlorite (the product of the Pcr reaction) and other contaminants that could be present in the enzyme prep. This unsettling result indicated this assay would be problematic for the detection of ClO4- in soil, which has many chemicals that could react with MV. To improve upon this assay, we have tried to reduce ClO4- using less reactive dyes and reductants. The reductants ascorbic acid, NADH, and dithiothreitol drive Pcr catalyzed ClO4- reduction, however, they

  20. Surface modification of carbon nanotubes via combination of mussel inspired chemistry and chain transfer free radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Qing; Tian, Jianwen; Liu, Meiying; Zeng, Guangjian; Huang, Qiang [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang, 330031 (China); Wang, Ke; Zhang, Qingsong [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China); Deng, Fengjie, E-mail: fengjiedeng@aliyun.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang, 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang, 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China)

    2015-08-15

    Graphical abstract: A novel strategy combination of mussel inspired chemistry and chain transfer free radical polymerization has been developed for surface modification of carbon nanotubes with polymers for the first time. - Highlights: • Surface modification of CNTs via mussel inspired chemistry. • Preparation of aminated polymers through free radical polymerization. • Functionalized CNTs with aminated polymers via Michael addition reaction. • Highly dispersed CNTs in organic and aqueous solution. - Abstract: In this work, a novel strategy for surface modification of carbon nanotubes (CNTs) was developed via combination of mussel inspired chemistry and chain transfer free radical polymerization. First, pristine CNTs were functionalized with polydopamine (PDA), which is formed via self-polymerization of dopamine in alkaline conditions. These PDA functionalized CNTs can be further reacted with amino-terminated polymers (named as PDMC), which was synthesized through chain transfer free radical polymerization using cysteamine hydrochloride as chain transfer agent and methacryloxyethyltrimethyl ammonium chloride as the monomer. PDMC perfectly conjugated with CNT-PDA was ascertained by a series of characterization techniques including transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The dispersibility of obtained CNT nanocomposites (named as CNT-PDA-PDMC) was further examined. Results showed that the dispersibility of CNT-PDA-PDMC in aqueous and organic solutions was obviously enhanced. Apart from PDMC, many other amino-terminated polymers can also be used to functionalization of CNTs via similar strategy. Therefore, the method described in this work should be a general strategy for fabrication various polymer nanocomposites.

  1. Surface modification of carbon nanotubes via combination of mussel inspired chemistry and chain transfer free radical polymerization

    International Nuclear Information System (INIS)

    Graphical abstract: A novel strategy combination of mussel inspired chemistry and chain transfer free radical polymerization has been developed for surface modification of carbon nanotubes with polymers for the first time. - Highlights: • Surface modification of CNTs via mussel inspired chemistry. • Preparation of aminated polymers through free radical polymerization. • Functionalized CNTs with aminated polymers via Michael addition reaction. • Highly dispersed CNTs in organic and aqueous solution. - Abstract: In this work, a novel strategy for surface modification of carbon nanotubes (CNTs) was developed via combination of mussel inspired chemistry and chain transfer free radical polymerization. First, pristine CNTs were functionalized with polydopamine (PDA), which is formed via self-polymerization of dopamine in alkaline conditions. These PDA functionalized CNTs can be further reacted with amino-terminated polymers (named as PDMC), which was synthesized through chain transfer free radical polymerization using cysteamine hydrochloride as chain transfer agent and methacryloxyethyltrimethyl ammonium chloride as the monomer. PDMC perfectly conjugated with CNT-PDA was ascertained by a series of characterization techniques including transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The dispersibility of obtained CNT nanocomposites (named as CNT-PDA-PDMC) was further examined. Results showed that the dispersibility of CNT-PDA-PDMC in aqueous and organic solutions was obviously enhanced. Apart from PDMC, many other amino-terminated polymers can also be used to functionalization of CNTs via similar strategy. Therefore, the method described in this work should be a general strategy for fabrication various polymer nanocomposites

  2. Surface chemistry and corrosion behaviour of 304 stainless steel in simulated seawater containing inorganic sulphide and sulphate-reducing bacteria

    International Nuclear Information System (INIS)

    Highlights: •The sulphidization of passive film by inorganic and biogenic sulphide was studied. •Rapid sulphidization of passive films by the biogenic sulphide was observed. •Different corrosion behaviours by inorganic and biogenic sulphides were determined. •Biogenic sulphide was more aggressive toward steels than its inorganic counterpart. -- Abstract: Although many studies have been carried out regarding the role of sulphide anions in promoting microbial corrosion of various metal substrates, very little is known about the differences between inorganic sulphide and biogenically-derived sulphide by sulphate-reducing bacteria (SRB) and what the reasons for differing corrosion behaviour between the two types of sulphide may be towards common metals. In this study, various electrochemical and surface analytical techniques were employed to study the effect of the inorganic and biogenic sulphide (active SRB present) on the surface chemistry and corrosion behaviour of 304 stainless steels in a simulated seawater-based modified Baar’s (SSMB) medium. Clear differences in the surface chemistry of the sulphurised passive film by inorganic and biogenic sulphide (active SRB present) were quantified by X-ray photoelectron spectroscopy (XPS). The transformation of metal sulphides in abiotic and biotic sulphide solutions with the exposure time was correlated with different corrosion behaviour of 304 stainless steels

  3. Effect of Surface Chemistry on Gene Transfer Efficiency Mediated by Surface-induced DNA-doped Nanocomposites

    OpenAIRE

    Sun, Bingbing; Yi, Minchang; Yacoob, Christina C.; Nguyen, Hai T; Shen, Hong

    2011-01-01

    Surface-induced biomineralization represents an effective way to immobilize DNA molecules onto biomaterial surfaces for introducing DNA into cells in contact with or in an approximate distance to biomaterial surfaces. Our previous studies have investigated how the composition of mineralizing solutions affects the composition and pH responsiveness of nanocomposites and thus gene transfer efficiency in different cell types. In this study, we investigated how the functional groups of a biomateri...

  4. Surface layer ozone and nitric oxides in the Arctic: The inuence of boundary layer dynamics, snowpack chemistry, surface exchanges, and seasonality

    Science.gov (United States)

    Van Dam, Brie A.

    The snowpack is a region of active chemistry. Aqueous chemistry in a quasi-liquid layer on snow grains and gas-phase chemical reactions in snow interstitial air can lead to the production or destruction of important trace gases. Physical transport parameters such as wind pumping and diffusion affect the vertical distribution of gases within the snowpack. The resulting emission or uptake of trace gases at the atmosphere-snowpack interface can have significant in uence on the chemistry of the lower atmosphere. In this work the dynamic interactions between the snowpack and atmosphere are examined from multiple perspectives. The primary focus is on ozone (O3) and nitrogen oxides (NOx) in the Arctic, a region undergoing widespread environmental change. To investigate an ice-sheet location with year round snow cover, data from a two-year campaign at Summit, Greenland are implemented. At Summit this study examines (1) the processes contributing to vigorous chemistry in snow interstitial air, and (2) the role of the boundary layer over snow in determining surface layer NOx. Physical and chemical processes are shown to contribute to distinct seasonal and diurnal cycles of O3, NO, and NO2 in the snowpack. Boundary layer depths estimated from sonic anemometer turbulence quantities are used alongside sodar-derived values to show that the depth of the stable to weakly stable boundary layer at Summit was not a primary factor in determining NO x in early summer. Motivated by observations of an increase in the length of the snow-free season in the Arctic in recent decades, data from a one-year experiment at the seasonally-snow covered location of Toolik Lake, AK are also incorporated. This study shows the first observations of springtime ozone depletion events at a location over 200 km from the coast in the Arctic. FLEXPART analysis is used to illustrate that these inland events are linked to transport conditions. Lastly at this location, eddy-covariance O3 uxes were calculated to

  5. Modulation of Protein Fouling and Interfacial Properties at Carbon Surfaces via Immobilization of Glycans Using Aryldiazonium Chemistry

    Science.gov (United States)

    Zen, Federico; Angione, M. Daniela; Behan, James A.; Cullen, Ronan J.; Duff, Thomas; Vasconcelos, Joana M.; Scanlan, Eoin M.; Colavita, Paula E.

    2016-04-01

    Carbon materials and nanomaterials are of great interest for biological applications such as implantable devices and nanoparticle vectors, however, to realize their potential it is critical to control formation and composition of the protein corona in biological media. In this work, protein adsorption studies were carried out at carbon surfaces functionalized with aryldiazonium layers bearing mono- and di-saccharide glycosides. Surface IR reflectance absorption spectroscopy and quartz crystal microbalance were used to study adsorption of albumin, lysozyme and fibrinogen. Protein adsorption was found to decrease by 30–90% with respect to bare carbon surfaces; notably, enhanced rejection was observed in the case of the tested di-saccharide vs. simple mono-saccharides for near-physiological protein concentration values. ζ-potential measurements revealed that aryldiazonium chemistry results in the immobilization of phenylglycosides without a change in surface charge density, which is known to be important for protein adsorption. Multisolvent contact angle measurements were used to calculate surface free energy and acid-base polar components of bare and modified surfaces based on the van Oss-Chaudhury-Good model: results indicate that protein resistance in these phenylglycoside layers correlates positively with wetting behavior and Lewis basicity.

  6. Modulation of Protein Fouling and Interfacial Properties at Carbon Surfaces via Immobilization of Glycans Using Aryldiazonium Chemistry

    Science.gov (United States)

    Zen, Federico; Angione, M. Daniela; Behan, James A.; Cullen, Ronan J.; Duff, Thomas; Vasconcelos, Joana M.; Scanlan, Eoin M.; Colavita, Paula E.

    2016-01-01

    Carbon materials and nanomaterials are of great interest for biological applications such as implantable devices and nanoparticle vectors, however, to realize their potential it is critical to control formation and composition of the protein corona in biological media. In this work, protein adsorption studies were carried out at carbon surfaces functionalized with aryldiazonium layers bearing mono- and di-saccharide glycosides. Surface IR reflectance absorption spectroscopy and quartz crystal microbalance were used to study adsorption of albumin, lysozyme and fibrinogen. Protein adsorption was found to decrease by 30–90% with respect to bare carbon surfaces; notably, enhanced rejection was observed in the case of the tested di-saccharide vs. simple mono-saccharides for near-physiological protein concentration values. ζ-potential measurements revealed that aryldiazonium chemistry results in the immobilization of phenylglycosides without a change in surface charge density, which is known to be important for protein adsorption. Multisolvent contact angle measurements were used to calculate surface free energy and acid-base polar components of bare and modified surfaces based on the van Oss-Chaudhury-Good model: results indicate that protein resistance in these phenylglycoside layers correlates positively with wetting behavior and Lewis basicity. PMID:27108562

  7. Numerical study of the effects of surface topography and chemistry on the wetting transition using the string method

    International Nuclear Information System (INIS)

    Droplets on a solid surface patterned with microstructures can exhibit the composite Cassie-Baxter (CB) state or the wetted Wenzel state. The stability of the CB state is determined by the energy barrier separating it from the wetted state. In this work, we study the CB to Wenzel transition using the string method [E et al., J. Chem. Phys. 126, 164103 (2007); W. Ren and E. Vanden-Eijnden, J. Chem. Phys. 138, 134105 (2013)]. We compute the transition states and energy barriers for a three-dimensional droplet on patterned surfaces. The liquid-vapor coexistence is modeled using the mean field theory. Numerical results are obtained for surfaces patterned with straight pillars and nails, respectively. It is found that on both type of surfaces, wetting occurs via infiltration of the liquid in a single groove. The reentrant geometry of nails creates large energy barrier for the wetting of the solid surface compared to straight pillars. We also study the effect of surface chemistry, pillar height, and inter-pillar spacing on the energy barrier and compare it with nails

  8. Modulation of Protein Fouling and Interfacial Properties at Carbon Surfaces via Immobilization of Glycans Using Aryldiazonium Chemistry.

    Science.gov (United States)

    Zen, Federico; Angione, M Daniela; Behan, James A; Cullen, Ronan J; Duff, Thomas; Vasconcelos, Joana M; Scanlan, Eoin M; Colavita, Paula E

    2016-01-01

    Carbon materials and nanomaterials are of great interest for biological applications such as implantable devices and nanoparticle vectors, however, to realize their potential it is critical to control formation and composition of the protein corona in biological media. In this work, protein adsorption studies were carried out at carbon surfaces functionalized with aryldiazonium layers bearing mono- and di-saccharide glycosides. Surface IR reflectance absorption spectroscopy and quartz crystal microbalance were used to study adsorption of albumin, lysozyme and fibrinogen. Protein adsorption was found to decrease by 30-90% with respect to bare carbon surfaces; notably, enhanced rejection was observed in the case of the tested di-saccharide vs. simple mono-saccharides for near-physiological protein concentration values. ζ-potential measurements revealed that aryldiazonium chemistry results in the immobilization of phenylglycosides without a change in surface charge density, which is known to be important for protein adsorption. Multisolvent contact angle measurements were used to calculate surface free energy and acid-base polar components of bare and modified surfaces based on the van Oss-Chaudhury-Good model: results indicate that protein resistance in these phenylglycoside layers correlates positively with wetting behavior and Lewis basicity. PMID:27108562

  9. Surface chemistry of carbon removal from indium tin oxide by base and plasma treatment, with implications on hydroxyl termination

    International Nuclear Information System (INIS)

    The surface chemistry of carbon removal from indium tin oxide (ITO) has been investigated with Auger electron spectroscopy (AES), high-resolution electron energy loss spectroscopy (HREELS), and high-resolution energy loss spectroscopy (HR-ELS). A vibrating Kelvin probe (KP) was used to monitor the work function (PHI) of ITO after cleaning, either by base-cleaning with alcoholic-KOH or by O2 plasma-cleaning. Base-cleaning lowered PHIITO as seen in the KP analysis, whereas plasma-cleaning slightly increased PHIITO by an oxidative process. The degree of PHIITO depression by base-cleaning was seen to depend on the initial surface, but the PHI depression itself was nonreductive to the ITO, as seen in the In-MNN AES lineshape. The nonreductive depression of PHIITO by base-cleaning was further supported by a constant charge carrier density, as estimated from the HR-ELS. Base-cleaning was slightly more effective than the oxygen plasma in removing carbon from the ITO surface. However, base-cleaning preferentially removed graphitic carbon while leaving significant hydrocarbon contaminants, as determined by vibrational analysis with HREELS. All other ITO surfaces retained a significant carbon and hydrocarbon contamination as evidenced by AES and HREELS. There was little evidence of the formation of surface hydroxyl species, as expected for such an inherently contaminated surface as ITO

  10. X-ray free electron laser as a real-time probe of chemistry on surfaces

    International Nuclear Information System (INIS)

    X-ray free electron laser has opened up new possibilities for the study of surface chemical reactions on ultrafast time scale. This article reviews the recent work on the desorption of a molecule from a surface, which is one of the most fundamental surface chemical process. (author)

  11. Soil bioassays and the 129I problem

    International Nuclear Information System (INIS)

    Iodine-129 is a very long-lived radionuclide associated with spent nuclear fuel. Because 129I has a 107-year half-life, is very mobile in the environment and is a biologically essential element, it is the most limiting radionuclide affecting disposal of spent fuel. Traditionally, the potential impacts of 129I have been estimated for human receptors, with the implicit assumption that all other organisms are less at risk. Risk is the operative word, the objective for protection of humans is to protect individuals, whereas the objective for other biota is usually to protect populations. Here, 129I poses an interesting problem: the half-life is so long it is barely radioactive. Thus, the chemical toxicity may be more limiting than the radiological impact. A series of soil bioassays were employed, including a life-cycle plant (Brassica rapa) bioassay, a modified earthworm survival bioassay, a microarthropod colonization/survival bioassay, and a series of more common soil and aquatic bioassays. Chemical toxicity was indicated at soil concentrations as low as 5 mg kg-1. At these levels, radiological impact on non-human biota would not be expected, and therefore the chemical toxicity effects are more critical. However, human food-chain model estimates show these levels, as pure 129I, would be unacceptable for human radiological exposure, so that for 129I, protection of the human environment should also be protective of non-human biota

  12. Thermal chemistry of hydrazine on clean and oxygen- and water-predosed Cu(110) single-crystal surfaces

    Science.gov (United States)

    Yao, Yunxi; Zaera, Francisco

    2016-08-01

    The chemistry of hydrazine on Cu(110) single-crystal surfaces was probed under ultrahigh vacuum (UHV) conditions by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Survey TPD experiments identified molecular nitrogen and ammonia as the main desorbing products from thermal activation of the adsorbate, but small amounts of diazene and NH2· radicals were also detected. At saturation coverage, N2 production leads NH3 desorption by approximately 10 K (with TPD peaks at 350 K versus 360 K, respectively), indicating a preference for dehydrogenation over N-N bond scission steps, and additional nitrogen was seen at even lower temperatures (320 K) in experiments starting with even higher doses of hydrazine. On the other hand, the formation of NH3 and NH2·, which desorb in a wide range of temperatures between approximately 300 K and 700 K, dominates in experiments with low N2H4 doses, presumably because a stronger interaction of the N-N bond with the metal in the flat adsorption geometry expected at such low coverages. Dosing at room temperature seems to also facilitate the dissociative adsorption, albeit via dehydrogenation steps that lead to the subsequent production of more significant amounts of diazene and of molecular hydrogen (in addition to N2, NH3, and NH2·). Preadsorption of oxygen on the Cu(110) surface helps stabilize the hydrazine, increasing its desorption temperature and helping with the low-temperature (320 K) production of N2. Coadsorption of hydrazine with water leads to facile proton exchange, as indicated by the production of NH2D in TPD experiments with N2H4 + D2O. This isotope scrambling must occur at cryogenic temperatures because all water desorbs from the surface below 200 K and no other changes in surface chemistry are observed after that. The implications of all this chemistry to practical applications that may use hydrazine in surface reactions with copper, including its use as a reducing agent in atomic layer

  13. Characterization and stability of gold nanoparticles depending on their surface chemistry: Contribution of capillary zone electrophoresis to a quality control.

    Science.gov (United States)

    Pallotta, Arnaud; Boudier, Ariane; Leroy, Pierre; Clarot, Igor

    2016-08-26

    Four kinds of gold nanoparticles (AuNP) quite similar in terms of gold core size (ca. 5nm) and shape (spherical) but differing by their surface chemistry (either negatively, or positively charged, or neutral) were synthesized. They were analyzed using both the classical physicochemical approach (spectrophotometry, dynamic light scattering coupled or not to electrophoresis and transmission electron microscopy) and capillary zone electrophoresis equipped with photodiode array detection. The results obtained by both methodologies (related to Surface Plasmon Band-maximal absorbance wavelength-, and zeta potential and electrophoretic mobilities) were well correlated. Moreover, taking advantage of the separation method, the sample heterogeneity was evaluated and an impurity profile was extracted. This allowed setting some specifications which were then applied on the one hand to a batch-to-batch survey to declare NP as conform or not after production and on the other hand to a stability study. PMID:27435685

  14. Dielectric properties of nanosilica/low-density polyethylene composites: The surface chemistry of nanoparticles and deep traps induced by nanoparticles

    Directory of Open Access Journals (Sweden)

    S. Ju

    2014-09-01

    Full Text Available Four kinds of nanosilica particles with different surface modification were employed to fabricate low-density polyethylene (LDPE composites using melt mixing and hot molding methods. The surface chemistry of modified nanosilica was analyzed by X-ray photoelectron spectroscopy. All silica nanoparticles were found to suppress the space charge injection and accumulation, increase the volume resistivity, decrease the permittivity and dielectric loss factor at low frequencies, and decrease the dielectric breakdown strength of the LDPE polymers. The modified nanoparticles, in general, showed better dielectric properties than the unmodified ones. It was found that the carrier mobility, calculated from J–V curves using the Mott-Gurney equation, was much lower for the nanocomposites than for the neat LDPE.

  15. Surface Wettability and Chemistry of Ozone Perfusion Processed Porous Collagen Scaffold

    Institute of Scientific and Technical Information of China (English)

    Chaozong Liu; Shirley Z. Shen; Zhiwu Han

    2011-01-01

    Crosslinking treatment of collagen has often been used to improve the biological stability and mechanical properties of 3D porous collagen scaffolds. However, accompanying these improvements, the collagen fibril surface becomes hydrophobic nature resulting in a reduced surface wettability. The wetting of the collagen fibril by culture medium is reduced and it is difficult for the medium to diffuse into the 3D structure of a porous collagen scaffold. This paper reports a "perfusion processing"strategy using ozone to improve the surface wettability of chemical crosslinked collagen scaffolds. Surface wettability, surface composition and biological stability were analyzed to evaluate the effectiveness of this surface processing strategy. It was observed that ozone perfusion processing improved surface wettability for both exterior and interior surfaces of the porous 3D collagen scaffold. The improvement in wettability is attributed to the incorporation of oxygen-containing functional groups onto the surface of the collagen fibrils, as confirmed by X-ray Photoelectron Spectroscopy (XPS) analysis. This leads to a significant improvement in water taking capability without compromising the bulk biological stability and mechanical properties, and confirms that ozone perfusion processing is an effective tool to modify the wettability both for interior and exterior surfaces throughout the scaffold.

  16. Effects of pretreatment on the surface chemistry and pore size properties of nitrogen functionalized and alkylated granular activated carbon

    Science.gov (United States)

    Chen, Jiajun; Zhai, Yunbo; Chen, Hongmei; Li, Caiting; Zeng, Guangming; Pang, Daoxiong; Lu, Pei

    2012-12-01

    In this paper, granular activated carbon (GAC) from coconut shell was pretreated by HNO3, H2O2 and urea-formaldehyde resin, respectively. Then the obtained materials were functionalized in the same way for nitrogen group, and then alkylated. Effects of pretreatment on the surface chemistry and pore size of modified GACs were studied. Surface area and micropore volume of modified GAC which pretreated by HNO3 were 723.88 m2/g and 0.229 cm3/g, respectively, while virgin GAC were 742.34 m2/g and 0.276 cm3/g. Surface area and micropore volume decrease of the modified GACs which pretreated by the others two methods were more drastically. The types of groups presented were analyzed by electrophoresis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Nsbnd CH3 group and Cdbnd N group were detected on the surfaces of these three kinds of modified GACs. Results of XPS showed that the nitrogen functions of modified GAC which pretreated by H2O2 was 4.07%, it was more than that of the others two pretreatment methods. However, the modified GAC which pretreated by urea-formaldehyde resin was fixed more pyridine structure, which structure percentage was 45.88%, in addition, there were more basic groups or charge on the surface than the others.

  17. An infrared study of the surface chemistry of lithium titanate spinel (Li4Ti5O12)

    International Nuclear Information System (INIS)

    While there are numerous studies examining the performance of lithium titanate spinel (LTS) as a lithium-ion battery, little is known about the surface chemistry of this material. In this paper, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy spectroscopy was used to study the type of surface groups present on LTS as a function of temperature. The surface was found to contain isolated and hydrogen-bonded TiOH groups and the dehydroxylation behavior with thermal treatment was similar to that of TiO2. In addition, hexamethyldisilazane (HMDZ) and pyridine were used to probe the reactivity of surface hydroxyl groups and the presence of Lewis acid sites, respectively. The reaction of HMDZ occurred with both LiOH and TiOH groups to form Li-O-Si and Ti-O-Si. In addition, the reaction of gaseous CO2 with the Li+ ions resulted in the formation of surface carbonate ions. The carbonate ions are removed by heating at 400 deg. C in air

  18. Trends in adsorption characteristics of benzene on transition metal surfaces: Role of surface chemistry and van der Waals interactions

    OpenAIRE

    Yildirim, Handan; Greber, Thomas; Kara, Abdelkader

    2013-01-01

    The accurate description of interface characteristics between organic molecules and metal surfaces has long been debated in theoretical studies. A well-founded description of interface geometry and adsorption energy is highly desirable for these hybrid inorganic/organic interfaces. Using first principles calculations with the inclusion of five van der Waals functionals (vdW-DF family), benzene (C6H6) adsorption on seven transition metal surfaces is studied to explore the performance of these ...

  19. In vitro bioassays to evaluate complex chemical mixtures in recycled water.

    Science.gov (United States)

    Jia, Ai; Escher, Beate I; Leusch, Frederic D L; Tang, Janet Y M; Prochazka, Erik; Dong, Bingfeng; Snyder, Erin M; Snyder, Shane A

    2015-09-01

    With burgeoning population and diminishing availability of freshwater resources, the world continues to expand the use of alternative water resources for drinking, and the quality of these sources has been a great concern for the public as well as public health professionals. In vitro bioassays are increasingly being used to enable rapid, relatively inexpensive toxicity screening that can be used in conjunction with analytical chemistry data to evaluate water quality and the effectiveness of water treatment. In this study, a comprehensive bioassay battery consisting of 36 bioassays covering 18 biological endpoints was applied to screen the bioactivity of waters of varying qualities with parallel treatments. Samples include wastewater effluent, ultraviolet light (UV) and/or ozone advanced oxidation processed (AOP) recycled water, and infiltrated recycled groundwater. Based on assay sensitivity and detection frequency in the samples, several endpoints were highlighted in the battery, including assays for genotoxicity, mutagenicity, estrogenic activity, glucocorticoid activity, arylhydrocarbon receptor activity, oxidative stress response, and cytotoxicity. Attenuation of bioactivity was found to be dependent on the treatment process and bioassay endpoint. For instance, ozone technology significantly removed oxidative stress activity, while UV based technologies were most efficient for the attenuation of glucocorticoid activity. Chlorination partially attenuated genotoxicity and greatly decreased herbicidal activity, while groundwater infiltration efficiently attenuated most of the evaluated bioactivity with the exception of genotoxicity. In some cases, bioactivity (e.g., mutagenicity, genotoxicity, and arylhydrocarbon receptor) increased following water treatment, indicating that transformation products of water treatment may be a concern. Furthermore, several types of bioassays with the same endpoint were compared in this study, which could help guide the selection

  20. A preliminary analysis of the surface chemistry of atmospheric aerosol particles in a typical urban area of Beijing.

    Science.gov (United States)

    Zhang, Zhengzheng; Li, Hong; Liu, Hongyan; Ni, Runxiang; Li, Jinjuan; Deng, Liqun; Lu, Defeng; Cheng, Xueli; Duan, Pengli; Li, Wenjun

    2016-09-01

    Atmospheric aerosol particle samples were collected using an Ambient Eight Stage (Non-Viable) Cascade Impactor Sampler in a typical urban area of Beijing from 27th Sep. to 5th Oct., 2009. The surface chemistry of these aerosol particles was analyzed using Static Time of Flight-Secondary Ion Mass Spectrometry (Static TOF-SIMS). The factors influencing surface compositions were evaluated in conjunction with the air pollution levels, meteorological factors, and air mass transport for the sampling period. The results show that a variety of organic ion groups and inorganic ions/ion groups were accumulated on the surfaces of aerosol particles in urban areas of Beijing; and hydrophobic organic compounds with short- or middle-chain alkyl as well as hydrophilic secondary inorganic compounds were observed. All these compounds have the potential to affect the atmospheric behavior of urban aerosol particles. PM1.1-2.1 and PM3.3-4.7 had similar elements on their surfaces, but some molecules and ionic groups demonstrated differences in Time of Flight-Secondary Ion Mass Spectrometry spectra. This suggests that the quantities of elements varied between PM1.1-2.1 and PM3.3-4.7. In particular, more intense research efforts into fluoride pollution are required, because the fluorides on aerosol surfaces have the potential to harm human health. The levels of air pollution had the most significant influence on the surface compositions of aerosol particles in our study. Hence, heavier air pollution was associated with more complex surface compositions on aerosol particles. In addition, wind, rainfall, and air masses from the south also greatly influenced the surface compositions of these urban aerosol particles. PMID:27593274

  1. The effects of vacuum annealing on the structure and surface chemistry of iron:nickel alloy nanoparticles

    International Nuclear Information System (INIS)

    In order to increase the longevity of contaminant retention on the particle surface, a method is sought to improve the corrosion resistance of bimetallic iron nickel nanoparticles (INNP) used for the remediation of contaminated water, and thereby extend their industrial lifetime. A multi-disciplinary approach was used to investigate changes induced by vacuum annealing (-8 mbar) at 500 oC on the bulk and surface chemistry of INNP. The particle size was determined to increase significantly as a result of annealing and the thickness of the surface oxide increased by 50%. BET analysis recorded a decrease in INP surface area from 44.88 to 8.08 m2 g-1, consistent with observations from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which indicated the diffusion bonding of previously discrete particles at points of contact. X-ray diffraction (XRD) confirmed that recrystallisation of the metallic cores had occurred, converting a significant fraction of initially amorphous iron nickel alloy into crystalline FeNi alloy. X-ray photoelectron spectroscopy (XPS) indicated a reduction in the proportion of surface iron oxide and a change in its stoichiometry related to annealing-induced disproportionation. This was also evidenced by an increased proportion of Fe(0) and Ni(0) to Fe- and Ni-oxides, respectively. The data also indicated the concurrent development of boron oxide at the metal surfaces, which accounts for the overall increase measured in surface oxide thickness. The improved core crystallinity and the presence of passivating impurity phases at the INNP surfaces may act to improve the corrosion resistance and reactive lifespan of the vacuum annealed INNP for environmental applications.

  2. Effect of water chemistry on crud deposition behavior on heated zircaloy-4 surface in simulated PWR primary water

    International Nuclear Information System (INIS)

    Japanese PWR utilities desire to employ long-term fuel cycle and high burn-up operations, in order to increase the plant utilization. Accordance with plant aging, employing the long-term fuel cycle and high burn-up operations, amounts of crud deposition on fuel cladding surface will be increased. The large amounts of crud deposition on the fuel cladding has led to an increase of the field radiation build-up in the primary coolant system and become a root cause of axial offset anomalies (AOA). Japanese PWRs has not been experienced in AOA, on the other hand, crud deposition on the PWR fuel cladding surface would become significant issue in Japanese PWRs. In order to clarify the contribution factors of the crud deposition related to the water chemistry, the effects of boron, nickel concentrations and nickel/iron ratio in the test solution on the crud deposition were investigated in a simulated Japanese PWR fuel cycle chemistry (1800ppm as B + 3.4ppm as Li + 25ml-STP/kg-H2O, 1200ppm as B + 2.2ppm as Li + 25ml-STP/kg-H2O, 350ppm as B + 2.2ppm as Li + 25ml-STP/kg-H2O solution) at 325oC under sub-cooled boiling and non-irradiated condition. The corrosion resistance of zircaloy-4 was also investigated in the simulated Japanese PWR primary chemistry. From the test results, it was revealed that the crud layer composed of NiFe2O4 and NiO was formed on the surface of zircaloy-4 fuel cladding. The oxide was easy to be formed on the heated surface of the fuel cladding. The amounts of deposited crud layer increased with increase of boron, nickel concentrations, pHT and nickel/iron ratio in the test solution. The formation of nickel borate (Ni2FeBO5) was not identified, however, boron was detected in the crud layer. Nickel and boron contents in the crud layer were increased with increase of nickel concentration in the test solution. The corrosion resistance of Zr-4 was maintained in the test condition. (author)

  3. Novel antifouling surface with improved hemocompatibility by immobilization of polyzwitterions onto silicon via click chemistry

    Science.gov (United States)

    Zheng, Sunxiang; Yang, Qian; Mi, Baoxia

    2016-02-01

    A novel procedure is presented to develop an antifouling silicon surface with improved hemocompatibility by using a zwitterionic polymer, poly(sulfobetaine methacrylate) (polySBMA). Functionalization of the silicon surface with polySBMA involved the following three steps: (1) an alkyne terminated polySBMA was synthesized by RAFT polymerization; (2) a self-assembled monolayer with bromine end groups was constructed on the silicon surface, and then the bromine end groups were replaced by azide groups; and (3) the polySBMA was attached to the silicon surface by azide-alkyne cycloaddition click reaction. Membrane characterization confirmed a successful silicon surface modification with almost 100% coverage by polySBMA and an extremely hydrophilic surface after such modification. The polySBMA-modified silicon surface was found to have excellent anti-nonspecific adsorption properties for both bovine serum albumin (BSA) protein and model bacterial cells. Whole blood adsorption experiments showed that the polySBMA-modified silicon surface exhibited excellent hemocompatibility and effective anti-adhesion to blood cells. Silicon membranes with such antifouling and hemocompatible surfaces can be advantageously used to drastically extend the service life of implantable medical devices such as artificial kidney devices.

  4. Effects of pretreatment on the surface chemistry and pore size properties of nitrogen functionalized and alkylated granular activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Chen Jiajun [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Zhai Yunbo, E-mail: ybzhai@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Chen Hongmei; Li Caiting; Zeng Guangming; Pang Daoxiong; Lu Pei [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer The effects of pretreatment on the surface chemistry and pore sizes were studied. Black-Right-Pointing-Pointer Treated GAC was nitrogen functionalized and alkylated GAC also called modified GAC. Black-Right-Pointing-Pointer HNO{sub 3} pretreatment caused a slight decrease in surface area and microporosity. Black-Right-Pointing-Pointer The nitrogen percentage of modified GAC which pretreated by H{sub 2}O{sub 2} was 4.07%. Black-Right-Pointing-Pointer The pyridine of modified GAC which pretreated by urea-formaldehyde resin was 45.88%. - Abstract: In this paper, granular activated carbon (GAC) from coconut shell was pretreated by HNO{sub 3}, H{sub 2}O{sub 2} and urea-formaldehyde resin, respectively. Then the obtained materials were functionalized in the same way for nitrogen group, and then alkylated. Effects of pretreatment on the surface chemistry and pore size of modified GACs were studied. Surface area and micropore volume of modified GAC which pretreated by HNO{sub 3} were 723.88 m{sup 2}/g and 0.229 cm{sup 3}/g, respectively, while virgin GAC were 742.34 m{sup 2}/g and 0.276 cm{sup 3}/g. Surface area and micropore volume decrease of the modified GACs which pretreated by the others two methods were more drastically. The types of groups presented were analyzed by electrophoresis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). N-CH{sub 3} group and C=N group were detected on the surfaces of these three kinds of modified GACs. Results of XPS showed that the nitrogen functions of modified GAC which pretreated by H{sub 2}O{sub 2} was 4.07%, it was more than that of the others two pretreatment methods. However, the modified GAC which pretreated by urea-formaldehyde resin was fixed more pyridine structure, which structure percentage was 45.88%, in addition, there were more basic groups or charge on the surface than the others.

  5. Plasmonic Hot Electron Transport Driven Site-Specific Surface-Chemistry with Nanoscale Spatial Resolution

    CERN Document Server

    Cortés, Emiliano; Cambiasso, Javier; Jermyn, Adam S; Sundararaman, Ravishankar; Narang, Prineha; Schlücker, Sebastian; Maier, Stefan A

    2016-01-01

    Nanoscale localization of electromagnetic fields near metallic nanostructures underpins the fundamentals and applications of plasmonics. The unavoidable energy loss from plasmon decay, initially seen as a detriment, has now expanded the scope of plasmonic applications to exploit the generated hot carriers. However, quantitative understanding of the spatial localization of these hot carriers, akin to electromagnetic near-field maps, has been elusive. Here we spatially map hot-electron-driven reduction chemistry with 15 nanometre resolution as a function of time and electromagnetic field polarization for different plasmonic nanostructures. We combine experiments employing a six-electron photo-recycling process that modify the terminal group of a self-assembled monolayer on plasmonic silver nanoantennas, with theoretical predictions from first-principles calculations of non-equilibrium hot-carrier transport in these systems. The resulting localization of reactive regions, determined by hot carrier transport from...

  6. Trends in the chemistry of atmospheric deposition and surface waters in the Lake Maggiore catchment

    Directory of Open Access Journals (Sweden)

    M. Rogora

    2001-01-01

    Full Text Available The Lake Maggiore catchment is the area of Italy most affected by acid deposition. Trend analysis was performed on long-term (15-30 years series of chemical analyses of atmospheric deposition, four small rivers draining forested catchments and four high mountain lakes. An improvement in the quality of atmospheric deposition was detected, due to decreasing sulphate concentration and increasing pH. Similar trends were also found in high mountain lakes and in small rivers. Atmospheric deposition, however, is still providing a large and steady flux of nitrogen compounds (nitrate and ammonium which is causing increasing nitrogen saturation in forest ecosystems and increasing nitrate levels in rivers. Besides atmospheric deposition, an important factor controlling water acidification and recovery is the weathering of rocks and soils which may be influenced by climate warming. A further factor is the episodic deposition of Saharan calcareous dust which contributes significantly to base cation deposition. Keywords: trend, atmospheric deposition, nitrogen, stream water chemistry.

  7. A Novel General Chemistry Laboratory: Creation of Biomimetic Superhydrophobic Surfaces through Replica Molding

    Science.gov (United States)

    Verbanic, Samuel; Brady, Owen; Sanda, Ahmed; Gustafson, Carolina; Donhauser, Zachary J.

    2014-01-01

    Biomimetic replicas of superhydrophobic lotus and taro leaf surfaces can be made using polydimethylsiloxane. These replicas faithfully reproduce the microstructures of the leaves' surface and can be analyzed using contact angle goniometry, self-cleaning experiments, and optical microscopy. These simple and adaptable experiments were used to…

  8. Organosulfur chemistry on W(211) surfaces. 2. A comparison of benzene, thiophene, and tetrahydrothiophene

    International Nuclear Information System (INIS)

    The interactions of benzene, thiophene, and tetrahydrothiophene with clean, oxidized, and sulfided W(211) surfaces were studied with LEED, AES, and temperature programmed reaction. Benzene and thiophene appear to absorb as bases making π-bonds to the surface. Benzene decomposed to yield adsorbed carbon and hydrogen. Thiophene appeared to undergo electrophilic attack at the 2-position forming a carbon bound surface intermediate. This surface intermediate was desulfurized and the resulting hydrocarbon surface intermediate underwent C-C bond scission forming C3 hydrocarbons as the dominate desorption product. The electrophilic attack at the 2-position was shown by methyl group elimination from 2,5-dimethylthiophene. Adsorbed oxygen and sulfur enhanced the adsorption of benzene and thiophene by making the surface more acidic. Tetrahydrothiophene (THT) appear to adsorb as a base, forming a bond between the S(3p) electrons and the surface. Desulfurization of adsorbed THT led to C4 hydrocarbons as the dominate desorption product. Adsorbed oxygen and sulfur inhibited reaction of THT. These results suggest that the surface reactivity and subsequent desulfurization of thiophene is controlled by electrophilic attack on the aromatic ring, and the ensuing reduction of resonance stabilization facilitates sulfur removal. 41 references, 8 figures, 4 tables

  9. Surface chemistry of Au/TiO2: Thermally and photolytically activated reactions

    Science.gov (United States)

    Panayotov, Dimitar A.; Morris, John R.

    2016-03-01

    The fascinating particle size dependence to the physical, photophysical, and chemical properties of gold has motivated thousands of studies focused on exploring the ability of supported gold nanoparticles to catalyze chemical transformations. In particular, titanium dioxide-supported gold (Au/TiO2) nanoparticles may provide the right combination of electronic structure, structural dynamics, and stability to affect catalysis in important practical applications from environmental remediation to selective hydrogenation to carbon monoxide oxidation. Harnessing the full potential of Au/TiO2 will require a detailed atomic-scale understanding of the thermal and photolytic processes that accompany chemical conversion. This review describes some of the unique properties exhibited by particulate gold before delving into how those properties affect chemistry on titania supports. Particular attention is given first to thermally driven reactions on single crystal system. This review then addresses nanoparticulate samples in an effort begin to bridge the so-called materials gap. Building on the foundation provided by the large body of work in the field of thermal catalysis, the review describes new research into light-driven catalysis on Au/TiO2. Importantly, the reader should bear in mind throughout this review that thermal chemistry and thermal effects typically accompany photochemistry. Distinguishing between thermally-driven stages of a reaction and photo-induced steps remains a significant challenge, but one that experimentalists and theorists are beginning to decipher with new approaches. Finally, a summary of several state-of-the-art studies describes how they are illuminating new frontiers in the quest to exploit Au/TiO2 as an efficient catalyst and low-energy photocatalyst.

  10. Spectators Control Selectivity in Surface Chemistry: Acrolein Partial Hydrogenation Over Pd.

    Science.gov (United States)

    Dostert, Karl-Heinz; O'Brien, Casey P; Ivars-Barceló, Francisco; Schauermann, Swetlana; Freund, Hans-Joachim

    2015-10-28

    We present a mechanistic study on selective hydrogenation of acrolein over model Pd surfaces--both single crystal Pd(111) and Pd nanoparticles supported on a model oxide support. We show for the first time that selective hydrogenation of the C═O bond in acrolein to form an unsaturated alcohol is possible over Pd(111) with nearly 100% selectivity. However, this process requires a very distinct modification of the Pd(111) surface with an overlayer of oxopropyl spectator species that are formed from acrolein during the initial stages of reaction and turn the metal surface selective toward propenol formation. By applying pulsed multimolecular beam experiments and in situ infrared reflection-absorption spectroscopy, we identified the chemical nature of the spectator and the reactive surface intermediate (propenoxy species) and experimentally followed the simultaneous evolution of the reactive intermediate on the surface and formation of the product in the gas phase. PMID:26481220

  11. Untangling the Chemical Evolution of Titan's Atmosphere and Surface -- From Homogeneous to Heterogeneous Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Ralf I.; Maksyutenko, Pavlo; Ennis, Courtney; Zhang, Fangtong; Gu, Xibin; Krishtal, Sergey P.; Mebel, Alexander M.; Kostko, Oleg; Ahmed, Musahid

    2010-03-16

    The arrival of the Cassini-Huygens probe at Saturn's moon Titan - the only Solar System body besides Earth and Venus with a solid surface and a thick atmosphere with a pressure of 1.4 atm at surface level - in 2004 opened up a new chapter in the history of Solar System exploration. The mission revealed Titan as a world with striking Earth-like landscapes involving hydrocarbon lakes and seas as well as sand dunes and lava-like features interspersed with craters and icy mountains of hitherto unknown chemical composition. The discovery of a dynamic atmosphere and active weather system illustrates further the similarities between Titan and Earth. The aerosol-based haze layers, which give Titan its orange-brownish color, are not only Titan's most prominent optically visible features, but also play a crucial role in determining Titan's thermal structure and chemistry. These smog-like haze layers are thought to be very similar to those that were present in Earth's atmosphere before life developed more than 3.8 billion years ago, absorbing the destructive ultraviolet radiation from the Sun, thus acting as 'prebiotic ozone' to preserve astrobiologically important molecules on Titan. Compared to Earth, Titan's low surface temperature of 94 K and the absence of liquid water preclude the evolution of biological chemistry as we know it. Exactly because of these low temperatures, Titan provides us with a unique prebiotic 'atmospheric laboratory' yielding vital clues - at the frozen stage - on the likely chemical composition of the atmosphere of the primitive Earth. However, the underlying chemical processes, which initiate the haze formation from simple molecules, have been not understood well to date.

  12. The effect of ozone on nicotine desorption from model surfaces:evidence for heterogeneous chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Destaillats, Hugo; Singer, Brett C.; Lee, Sharon K.; Gundel, LaraA.

    2005-05-01

    Assessment of secondhand tobacco smoke exposure using nicotine as a tracer or biomarker is affected by sorption of the alkaloid to indoor surfaces and by its long-term re-emission into the gas phase. However, surface chemical interactions of nicotine have not been sufficiently characterized. Here, the reaction of ozone with nicotine sorbed to Teflon and cotton surfaces was investigated in an environmental chamber by monitoring nicotine desorption over a week following equilibration in dry or humid air (65-70 % RH). The Teflon and cotton surfaces had N{sub 2}-BET surface areas of 0.19 and 1.17 m{sup 2} g{sup -1}, and water mass uptakes (at 70 % RH) of 0 and 7.1 % respectively. Compared with dry air baseline levels in the absence of O{sub 3}, gas phase nicotine concentrations decrease, by 2 orders of magnitude for Teflon after 50 h at 20-45 ppb O{sub 3}, and by a factor of 10 for cotton after 100 h with 13-15 ppb O{sub 3}. The ratios of pseudo first-order rate constants for surface reaction (r) to long-term desorption (k) were r/k = 3.5 and 2.0 for Teflon and cotton surfaces, respectively. These results show that surface oxidation was competitive with desorption. Hence, oxidative losses could significantly reduce long-term re-emissions of nicotine from indoor surfaces. Formaldehyde, N-methylformamide, nicotinaldehyde and cotinine were identified as oxidation products, indicating that the pyrrolidinic N was the site of electrophilic attack by O{sub 3}. The presence of water vapor had no effect on the nicotine-O{sub 3} reaction on Teflon surfaces. By contrast, nicotine desorption from cotton in humid air was unaffected by the presence of ozone. These observations are consistent with complete inhibition of ozone-nicotine surface reactions in an aqueous surface film present in cotton but not in Teflon surfaces.

  13. Surface chemistry effects in finite element modeling of heat transfer in (micron)-fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Havstad, M

    2000-12-07

    Equations for modeling surface chemical kinetics by the interaction of gaseous and surface species are presented. The formulation is embedded in a finite element heat transfer code and an ordinary differential equation package is used to solve the surface system of chemical kinetic equations for each iteration within the heat transfer solver. The method is applied to a flow which includes methane and methanol in a microreactor on a chip. A simpler more conventional method, a plug flow reactor model, is then applied to a similar problem. Initial results for steam reforming of methanol are given.

  14. Surface Chemistry of Polymers Physical Adsorption of Nitrogen, Argon, Sulfur Dioxide and Neopentane on Polyvinylidene Fluoride

    OpenAIRE

    Houriet, Jean-Philippe; Ghiste, Patrick; Stoeckli, Fritz

    2007-01-01

    The adsorption of nitrogen, argon, sulfur dioxide and neopentane on polyvinylidene fluoride has been measured by static methods and by gas-solid chromatography. The polymer has a homogeneous surface of low energy, which is not significantly affected by heating.

  15. Recent developments of surface complexation models applied to environmental aquatic chemistry

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Based on numerous latest references, the current developments in surface complexation, surface precipitation and the corresponding models (SCMs and SPMs), were reviewed. The contents involved comparison on surface charge composition and layer-structure of solid-solution interface for the classical 1-pK and 2- pK models, In addition, the fundamental concept and relations of the new models, i.e., multi-site complexation (MUSIC) and charge -distribution (CD) MUSIC models were described as well. To avoid misuse or abuse, it must be emphasized that the applicability nd limitation for each model should be considered carefully when selecting the concerned model(s). In addition, some new powerful techniques for surface characterization and analysis applied to model establishment and modification were also briefly introduced.

  16. Synthesis and processing of ELISA polymer substitute: The influence of surface chemistry and morphology on detection sensitivity

    International Nuclear Information System (INIS)

    Highlights: • Polyacrylate coatings with controlled surface functionalities. • Impact of surface chemistry and morphology on dengue antibody immobilization. • Enhancement of detection signal as a result of bio-activation of polymer surface. - Abstract: Despite the known drawbacks of enzyme-linked immunosorbent assay (ELISA), one of the deficiencies that have relatively been ignored is the performance of ELISA substrate itself. Polystyrene (PS), as the cost effective material of choice for mass production of ELISA well-plates, has shown obvious lacks of suitable physical and chemical properties for protein attachment. The general concept of this work was to develop a potential substrate that can be suggested as a material of choice for production of a new generation of ELISA analytical kits. Spin-coated thin films of polymethyl methacrylate-co-methacrylic acid (PMMA-co-MAA) on silicon surfaces were designed and processed for detection of dengue virus. Coated surfaces of different molar ratios have been investigated as carboxyl-functionalized layers for obtaining platform for biomolecule immobilization with high level of protein activity. To improve the sensitivity of detection, we have used amine functional “spacers”, hexamethylenediamine (HMDA) and polyethyleneimine (PEI), which were covalently bonded to the surfaces of PMMA-co-MAA coatings. Results demonstrate that the variation of surface concentration of carboxyl groups of PMMA-co-MAA can be used to control the amine surface concentration after carbodiimide coupling with HMDA and PEI spacers. The presence of amine spacers increases hydrophilicity of the coatings and significantly impacts the polymer surface morphology. In particular, protein immobilization via amine-bearing spacers has been achieved in two effective steps: (1) carbodiimide bonding between amine spacer molecules and PMMA-co-MAA polymer coatings; and (2) covalent immobilization of antibody via glutaraldehyde reaction with amine groups

  17. Synthesis and processing of ELISA polymer substitute: The influence of surface chemistry and morphology on detection sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Samira; Ibrahim, Fatimah [Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Center for Innovation in Medical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Djordjevic, Ivan, E-mail: ivan.djordjevic@um.edu.my [Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Center for Innovation in Medical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Rothan, Hussin A.; Yusof, Rohana [Department of Molecular Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur (Malaysia); Marel, Cees van der [Philips Materials Analysis, High Tech Campus 11, 5656 AE Eindhoven (Netherlands); Koole, Leo H. [Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Center for Innovation in Medical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Faculty of Health, Medicine and Life Sciences, Maastricht University (Netherlands)

    2014-10-30

    Highlights: • Polyacrylate coatings with controlled surface functionalities. • Impact of surface chemistry and morphology on dengue antibody immobilization. • Enhancement of detection signal as a result of bio-activation of polymer surface. - Abstract: Despite the known drawbacks of enzyme-linked immunosorbent assay (ELISA), one of the deficiencies that have relatively been ignored is the performance of ELISA substrate itself. Polystyrene (PS), as the cost effective material of choice for mass production of ELISA well-plates, has shown obvious lacks of suitable physical and chemical properties for protein attachment. The general concept of this work was to develop a potential substrate that can be suggested as a material of choice for production of a new generation of ELISA analytical kits. Spin-coated thin films of polymethyl methacrylate-co-methacrylic acid (PMMA-co-MAA) on silicon surfaces were designed and processed for detection of dengue virus. Coated surfaces of different molar ratios have been investigated as carboxyl-functionalized layers for obtaining platform for biomolecule immobilization with high level of protein activity. To improve the sensitivity of detection, we have used amine functional “spacers”, hexamethylenediamine (HMDA) and polyethyleneimine (PEI), which were covalently bonded to the surfaces of PMMA-co-MAA coatings. Results demonstrate that the variation of surface concentration of carboxyl groups of PMMA-co-MAA can be used to control the amine surface concentration after carbodiimide coupling with HMDA and PEI spacers. The presence of amine spacers increases hydrophilicity of the coatings and significantly impacts the polymer surface morphology. In particular, protein immobilization via amine-bearing spacers has been achieved in two effective steps: (1) carbodiimide bonding between amine spacer molecules and PMMA-co-MAA polymer coatings; and (2) covalent immobilization of antibody via glutaraldehyde reaction with amine groups

  18. Solid Oxide Fuel Cell Cathodes. Unraveling the Relationship Between Structure, Surface Chemistry and Oxygen Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Gopalan, Srikanth [Boston Univ., MA (United States)

    2013-03-31

    In this work we have considered oxygen reduction reaction on LSM and LSCF cathode materials. In particular we have used various spectroscopic techniques to explore the surface composition, transition metal oxidation state, and the bonding environment of oxygen to understand the changes that occur to the surface during the oxygen reduction process. In a parallel study we have employed patterned cathodes of both LSM and LSCF cathodes to extract transport and kinetic parameters associated with the oxygen reduction process.

  19. Ferroelectric polarization effect on surface chemistry and photo-catalytic activity: A review

    Science.gov (United States)

    Khan, M. A.; Nadeem, M. A.; Idriss, H.

    2016-03-01

    The current efficiency of various photocatalytic processes is limited by the recombination of photogenerated electron-hole pairs in the photocatalyst as well as the back-reaction of intermediate species. This review concentrates on the use of ferroelectric polarization to mitigate electron-hole recombination and back-reactions and therefore improve photochemical reactivity. Ferroelectric materials are considered as wide band gap polarizable semiconductors. Depending on the surface polarization, different regions of the surface experience different extents of band bending and promote different carriers to move to spatially different locations. This can lead to some interesting interactions at the surface such as spatially selective adsorption and surface redox reactions. This introductory review covers the fundamental properties of ferroelectric materials, effect of an internal electric field/polarization on charge carrier separation, effect of the polarization on the surface photochemistry and reviews the work done on the use of these ferroelectric materials for photocatalytic applications such as dye degradation and water splitting. The manipulation of photogenerated charge carriers through an internal electric field/surface polarization is a promising strategy for the design of improved photocatalysts.

  20. Grafting of poly(ethylene glycol) on click chemistry modified Si(100) surfaces.

    Science.gov (United States)

    Flavel, Benjamin S; Jasieniak, Marek; Velleman, Leonora; Ciampi, Simone; Luais, Erwann; Peterson, Joshua R; Griesser, Hans J; Shapter, Joe G; Gooding, J Justin

    2013-07-01

    Poly(ethylene glycol) (PEG) is one of the most extensively studied antifouling coatings due to its ability to reduce protein adsorption and improve biocompatibility. Although the use of PEG for antifouling coatings is well established, the stability and density of PEG layers are often inadequate to provide optimum antifouling properties. To improve on these shortcomings, we employed the stepwise construction of PEG layers onto a silicon surface. Acetylene-terminated alkyl monolayers were attached to nonoxidized crystalline silicon surfaces via a one-step hydrosilylation procedure with 1,8-nonadiyne. The acetylene-terminated surfaces were functionalized via a copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction of the surface-bound alkynes with an azide to produce an amine terminated layer. The amine terminated layer was then further conjugated with PEG to produce an antifouling surface. The antifouling surface properties were investigated by testing adsorption of human serum albumin (HSA) and lysozyme (Lys) onto PEG layers from phosphate buffer solutions. Detailed characterization of protein fouling was carried out with X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with principal component analysis (PCA). The results revealed no fouling of albumin onto PEG coatings whereas the smaller protein lysozyme adsorbed to a very low extent. PMID:23790067

  1. Urban and Suburban Influences on Water Chemistry in Washington DC: Impervious Surfaces and Urban Stream Syndrome

    Science.gov (United States)

    MacAvoy, S. E.; Petersen, E.

    2015-12-01

    Among the challenges facing urban rivers are water stormwater runoff problems and changing water chemistry, not only from air and water pollution sources, but also from altered geology with the development of "urban karst". Seventy five percent of the Anacostia River in Washington, D.C. is urban or impervious. The Anacostia River experiences environmental challenges similar to those of other urban industrial rivers (heavy metal, PCB and PAH contamination). It also has Ca/Sr ratios above 200, and Na concentrations higher than Ca, and elevated ionic strength, all associated with extended chemical interaction with concrete. While these chemical characteristics have been documented in the urban areas within DC, they have not been examined in the largely suburban/mixed development tributaries of the Anacostia. Here we examine the base-flow geochemistry of the Anacostia River and its suburban tributaries (6 locations) over a year (November 2014- August 2015), concentrating on the following water chemistry variables: pH, hardness, SAR, alkalinity, Ca, Mg, Na, K, Fe, Mn, Zn, Al, Ba, Ni, total P, S, Sr, NO3-, NH4+, PO43-. NO3- and NH4+ were generally lowest in at all sites in January, but rose to between 0.5 and 2.4 mg/L in June, with highest NO3- concentrations in suburban areas. Na and Cl concentrations were 5x higher in suburban areas than urban areas during the winter months. Ca/Sr concentration ratios, were between 120 and 200 for suburban sites but increased as the sites became more urban (to a high of 240 for the most urban site). These trends have been observed in other urban streams, and correlate with percent impervious area. The data follow patterns expected for "urban stream syndrome" and dissolution of concrete. Suburban areas, with their relatively small streams, show greater winter salting effects than more urban areas down stream. Suburban areas also show higher NO3- (and occasionally higher NH4+) than urban areas except in winter. The data presented here

  2. Acidic deposition: State of science and technology. Report 11. Historical changes in surface-water acid-base chemistry in response to acidic deposition. Final report

    International Nuclear Information System (INIS)

    The objectives of the analyses reported in the State of Science report are to: identify the lake and stream populations in the United States that have experienced chronic changes in biologically significant constituents of surface water chemistry (e.g. pH, Al) in response to acidic deposition; quantify biologically meaningful historical changes in chronic surface water chemistry associated with acidic deposition, with emphasis on ANC, pH, and Al; estimate the proportion of lakes nor acidic that were not acidic in pre-industrial times; estimate the proportional response of each of the major chemical constituents that have changed in response to acidic deposition using a subset of statistically selected Adirondack lakes for which paleolimnological reconstructions of pre-industrial surface water chemistry have been performed; evaluate and improve, where appropriate and feasible, empirical models of predicting changes in ANC; and evaluate the response of seepage lakes to acidic deposition

  3. Influence of Structure and Surface Chemistry of Porous Carbon Electrodes on Supercapacitor Performance

    Science.gov (United States)

    Dyatkin, Boris

    Electrochemical double layer capacitors, which rely on electrosorption of ions in nanostructured carbon electrodes, can supplement or even replace traditional batteries in energy harvesting and storage applications. While supercapacitors offer > 10 kW/kg power densities, their ~5 Wh/kg energy densities are insufficient for many automotive and grid storage applications. Most prior efforts have focused on novel high-performing ionic liquid electrolytes and porous carbons with tunable pore diameters and high specific surface areas. However, existing research lacks fundamental understanding of the influence of surface heterogeneity and disorder, such as graphitic defects and functional groups, on key electrosorption properties at electrode-electrolyte interfaces. These interactions significantly impact charge accumulation densities, ion transport mechanisms, and electrolyte breakdown processes. Subsequently, they must be investigated to optimize ion screening, charge mobilities, and operating voltage windows of the devices. The research in this dissertation examined the influence of surface functional groups and structural ordering on capacitance, electrosorption dynamics, and electrochemical stability of external and internal surface of carbon electrodes. High-temperature vacuum annealing, air oxidation, hydrogenation, and amination were used to tune pore surface compositions and decouple key structural and chemical properties of carbide-derived carbons. The approach combined materials characterization by a variety of techniques, neutron scattering studies of ion dynamics, electrochemical testing, and MD simulations to investigate the fundamental intermolecular interactions and dynamics of ions electrosorption in different pore architectures and on planar graphene surfaces. Contrary to expected results and existing theories, defect removal via defunctionalization and graphitization decreased capacitance. Hydrogenated surfaces benefitted electrosorption, while oxygen

  4. The Effect of Sterilization Processes on the Bioadhesive Properties and Surface Chemistry of a Plasma-Polymerized Polyethylene Glycol Film: XPS Characterization and L929 Cell Proliferation Tests

    OpenAIRE

    BRETAGNOL Frederic; Rauscher, Hubert; Hasiwa, Marina; Kylian, Ondrej; Ceccone, Giacomo; HAZELL Len; PAUL Alan J.; LEFRANC O.; ROSSI Francois

    2008-01-01

    The influence of several sterilization processes (autoclaving, c-ray irradiation, ethylene oxide exposure and Ar/H2 low pressure plasma treatment) on the surface chemistry and the bioadhesive properties of thin films (thickness ~20 nm) of plasma-polymerized diethylene glycol dimethyl ether has been studied. X-ray photoelectron spectroscopy (XPS) analysis and cell proliferation tests were used to characterize the surfaces. The XPS results revealed in all cases a change in the surface che...

  5. Tuning the surface chemistry of Pd by atomic C and H: a microscopic picture.

    Science.gov (United States)

    Aleksandrov, Hristiyan A; Viñes, Francesc; Ludwig, Wiebke; Schauermann, Swetlana; Neyman, Konstantin M

    2013-01-21

    Palladium is crucial for industry-related applications such as heterogeneous catalysis, energy production, and hydrogen technologies. In many processes, atomic H and C species are proposed to be present in the surface/near-surface area of Pd, thus noticeably affecting its chemical activity. This study provides a detail and unified view on the interactions of the H and C species with Pd nanoparticles (NPs), which is indispensable for insight into their catalytic properties. Density functional calculations of the interplay of C and H atoms at various concentrations and sites on suitable Pd NPs have been performed, accompanied by catalysis-relevant experiments on oxide-supported bare and C-modified Pd NPs. It is shown that on a Pd(79) NP a subsurface C atom destabilizes nearby atoms H at low coverage. Our experiments confirm that H atoms bind more weakly on C-containing Pd NPs than on C-free NPs. Various factors related to the presence of both H and C atoms on a Pd(79) surface, which may influence the penetration of H atoms from the surface into the subsurface area, have been investigated. Carbon atoms facilitate the subsurface penetration of atomic H both thermodynamically and kinetically when the surface is densely covered by H atoms. Moreover, subsurface H atoms are also energetically favored, even in the absence of C atoms, when several facets of the NP are covered by H atoms. PMID:23180515

  6. A two-dimensional atmospheric chemistry modeling investigation of Earth's Phanerozoic O3 and near-surface ultraviolet radiation history

    Science.gov (United States)

    Harfoot, Michael B. J.; Beerling, David J.; Lomax, Barry H.; Pyle, John A.

    2007-04-01

    We use the Cambridge two-dimensional (2-D) chemistry-radiation transport model to investigate the implications for column O3 and near-surface ultraviolet radiation (UV), of variations in atmospheric O2 content over the Phanerozoic (last 540 Myr). Model results confirm some earlier 1-D model investigations showing that global annual mean O3 column increases monotonically with atmospheric O2. Sensitivity studies indicate that changes in temperature and N2O exert a minor influence on O3 relative to O2. We reconstructed Earth's O3 history by interpolating the modeled relationship between O3 and O2 onto two Phanerozoic O2 histories. Our results indicate that the largest variation in Phanerozoic column O3 occurred between 400 and 200 Myr ago, corresponding to a rise in atmospheric O2 to ˜1.5 times the present atmospheric level (PAL) and subsequent fall to ˜0.5 PAL. The O3 response to this O2 decline shows latitudinal differences, thinning most at high latitudes (30-40 Dobson units (1 DU = 0.001 atm cm) at 66°N) and least at low latitudes (5-10 DU at 9°N) where a "self-healing" effect is evident. This O3 depletion coincides with significant increases in the near-surface biologically active UV radiation at high latitudes, +28% as weighted by the Thimijan spectral weighting function. O3 and UV changes were exacerbated when we incorporated a direct feedback of the terrestrial biosphere on atmospheric chemistry, through enhanced N2O production as the climate switched from an icehouse to a greenhouse mode. On the basis of a summary of field and laboratory experimental evidence, we suggest that these UV radiation increases may have exerted subtle rather than catastrophic effects on ecosystem processes.

  7. Analysis of Surface Chemistry and Detector Performance of Chemically Process CdZnTe crystals

    Energy Technology Data Exchange (ETDEWEB)

    HOSSAIN, A.; Yang, G.; Sutton, J.; Zergaw, T.; Babalola, O. S.; Bolotnikov, A. E.; Camarda. ZG. S.; Gul, R.; Roy, U. N., and James, R. B.

    2015-10-05

    The goal is to produce non-conductive smooth surfaces for fabricating low-noise and high-efficiency CdZnTe devices for gamma spectroscopy. Sample preparation and results are discussed. The researachers demonstrated various bulk defects (e.g., dislocations and sub-grain boundaries) and surface defects, and examined their effects on the performance of detectors. A comparison study was made between two chemical etchants to produce non-conductive smooth surfaces. A mixture of bromine and hydrogen peroxide proved more effective than conventional bromine etchant. Both energy resolution and detection efficiency of CZT planar detectors were noticeably increased after processing the detector crystals using improved chemical etchant and processing methods.

  8. Brine Shrimp Bioassays: A Useful Technique in Biological Investigations

    Science.gov (United States)

    Rice, Stanley A.; Maness, Ian B.

    2004-01-01

    A technique to measure the potency of leaf compounds against herbivores with the use of a bioassay is described. Bioassays are useful in classes where students have career plans like medicine in which bioassays can be used as tools for screening plants for possible medicinal potency.

  9. Chemistry and surface morphology of soil particles from Luna 20 LRL sample 22003.

    Science.gov (United States)

    Carter, J. L.

    1973-01-01

    Optical and scanning electron microscopy, scanning electron microprobes and energy dispersion techniques were applied in an analysis of six siliceous glass spheres, five siliceous glass-bonded agglutinates and one breccia fragment from Luna 20 sample 22003. It is theorized that local meteor impact processes might have been responsible for the formation of most of the glass spheres and that the impacts of relatively high velocity particles might have been responsible for the craters observed on the surfaces of the spheres. The concentrations of iron spherules on the surfaces of the glass spheres were generally lower than in similar Apollo 11 and 12 glass spheres.

  10. Colloid and surface chemistry a laboratory guide for exploration of the nano world

    CERN Document Server

    Bucak, Seyda

    2013-01-01

    Scientific Research The research processEthics in Science Design of Experiments Fundamentals of Scientific Computing, Nihat Baysal Recording Data: Keeping a Good Notebook Presenting Data: Writing a Laboratory ReportReferencesCharacterization Techniques Surface Tension Measurements, Seyda BucakViscosity/Rheological Measurements, Patrick UnderhillElectrokinetic Techniques, Marek KosmulskiDiffraction (XRD), Deniz RendeScattering, Ulf OlssonMicroscopy, Cem Levent Altan and Nico A.J.M. SommerdijkColloids and Surfaces Experiment 1: SedimentationExperiment 2: Determination of Critical Micelle Concent

  11. Nano-clustered Pd catalysts formed on GaN surface for green chemistry

    Science.gov (United States)

    Hirayama, Motoi; Ueta, Yukiko; Konishi, Tomoya; Tsukamoto, Shiro

    2011-05-01

    We have succeeded in observing Pd nano-clusters, catalytic prime elements, on a GaN(0 0 0 1) surface by a scanning tunneling microscope for the first time. After the sample was reused, we found that nano-clusters (width: 11 nm, height: 2.2 nm) existed on the surface which still kept the catalytic activity, resulting that the neutral Pd atoms formed the nano-cluster. Moreover, the S-termination contributed to the formation of the dense and flat structure consisting of the Pd nano-clusters.

  12. Physical-chemistry of radionuclide/mineral surface interaction: I - Thermodynamical aspect

    International Nuclear Information System (INIS)

    The Eu(III), U(VI) and Cm(III) sorption onto phosphate surfaces have been performed. The solids, synthesized and characterized (crystallinity, morphology, specific area and surface acidity) in our laboratory, are the following: Th4(PO4)4P2O7, ZrP2O7, Zr2O(PO4)2 and Ca10(PO4)6F2. Batch experiments were carried out at room temperature by reacting the solid with ions in solution. Sorption isotherms are presented and compared to the specification diagrams of the ions in solution. (authors)

  13. Atomic Scale Imaging of the Electronic Structure and Chemistry of Graphene and Its Precursors on Metal Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, George W [Columbia University

    2015-02-16

    Executive Summary of Final Report for Award DE-FG02-88ER13937 Project Title: Atomic Scale Imaging of the Electronic Structure and Chemistry of Graphene and its Precursors on Metal Surfaces Applicant/Institution: Columbia University Principal Investigator: George W. Flynn Objectives: The objectives of this project were to reveal the mechanisms and reaction processes that solid carbon materials undergo when combining with gases such as oxygen, water vapor and hydrocarbons. This research was focused on fundamental chemical events taking place on single carbon sheets of graphene, a two-dimensional, polycyclic carbon material that possesses remarkable chemical and electronic properties. Ultimately, this work is related to the role of these materials in mediating the formation of polycyclic aromatic hydrocarbons (PAH’s), their reactions at interfaces, and the growth of soot particles. Our intent has been to contribute to a fundamental understanding of carbon chemistry and the mechanisms that control the formation of PAH’s, which eventually lead to the growth of undesirable particulates. We expect increased understanding of these basic chemical mechanisms to spur development of techniques for more efficient combustion of fossil fuels and to lead to a concomitant reduction in the production of undesirable solid carbon material. Project Description: Our work treated specifically the surface chemistry aspects of carbon reactions by using proximal probe (atomic scale imaging) techniques to study model systems of graphene that have many features in common with soot forming reactions of importance in combustion flames. Scanning tunneling microscopy (STM) is the main probe technique that we used to study the interfacial structure and chemistry of graphene, mainly because of its ability to elucidate surface structure and dynamics with molecular or even atomic resolution. Scanning tunneling spectroscopy (STS), which measures the local density of quantum states over a single

  14. Synergistic effect of topography, surface chemistry and conductivity of the electrospun nanofibrous scaffold on cellular response of PC12 cells.

    Science.gov (United States)

    Tian, Lingling; Prabhakaran, Molamma P; Hu, Jue; Chen, Menglin; Besenbacher, Flemming; Ramakrishna, Seeram

    2016-09-01

    Electrospun nanofibrous nerve implants is a promising therapy for peripheral nerve injury, and its performance can be tailored by chemical cues, topographical features as well as electrical properties. In this paper, a surface modified, electrically conductive, aligned nanofibrous scaffold composed of poly (lactic acid) (PLA) and polypyrrole (Ppy), referred to as o-PLAPpy_A, was fabricated for nerve regeneration. The morphology, surface chemistry and hydrophilicity of nanofibers were characterized by Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle, respectively. The effects of these nanofibers on neuronal differentiation using PC12 cells were evaluated. A hydrophilic surface was created by Poly-ornithine coating, which was able to provide a better environment for cell attachment, and furthermore aligned fibers were proved to be able to guide PC12 cells grow along the fiber direction and be beneficial for neurite outgrowth. The cellular response of PC12 cells to pulsed electrical stimulation was evaluated by NF 200 and alpha tubulin expression, indicating that electrical stimulation with a voltage of 40mV could enhance the neurite outgrowth. The PC12 cells stimulated with electrical shock showed greater level of neurite outgrowth and smaller cell body size. Moreover, the PC12 cells under electrical stimulation showed better viability. In summary, the o-PLAPpy_A nanofibrous scaffold supported the attachment, proliferation and differentiation of PC12 cells in the absence of electrical stimulation, which could be potential candidate for nerve regeneration applications. PMID:27232305

  15. Correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys

    International Nuclear Information System (INIS)

    X-ray photoelectron spectroscopy (XPS) was used in order to investigate the correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys exposed to 98% relative humidity at 50 deg. C. Commercially pure magnesium, used as the reference material, revealed MgO, Mg(OH)2 and tracers of magnesium carbonate in the air-formed film. For the AZ80 and AZ91D alloys, the amount of magnesium carbonate formed on the surface reached similar values to those of MgO and Mg(OH)2. A linear relation between the amount of magnesium carbonate formed on the surface and the subsequent corrosion behaviour in the humid environment was found. The AZ80 alloy revealed the highest amount of magnesium carbonate in the air-formed film and the highest atmospheric corrosion resistance, even higher than the AZ91D alloy, indicating that aluminium distribution in the alloy microstructure influenced the amount of magnesium carbonate formed.

  16. Correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Feliu, S. [Centro Nacional de Investigaciones Metalurgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Pardo, A. [Departamento de Ciencia de Materiales, Facultad de Quimica, Universidad Complutense, 28040 Madrid (Spain)], E-mail: anpardo@quim.ucm.es; Merino, M.C. [Departamento de Ciencia de Materiales, Facultad de Quimica, Universidad Complutense, 28040 Madrid (Spain); Coy, A.E.; Viejo, F.; Arrabal, R. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Sackville Street, Manchester M60 1QD (United Kingdom)

    2009-01-15

    X-ray photoelectron spectroscopy (XPS) was used in order to investigate the correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys exposed to 98% relative humidity at 50 deg. C. Commercially pure magnesium, used as the reference material, revealed MgO, Mg(OH){sub 2} and tracers of magnesium carbonate in the air-formed film. For the AZ80 and AZ91D alloys, the amount of magnesium carbonate formed on the surface reached similar values to those of MgO and Mg(OH){sub 2}. A linear relation between the amount of magnesium carbonate formed on the surface and the subsequent corrosion behaviour in the humid environment was found. The AZ80 alloy revealed the highest amount of magnesium carbonate in the air-formed film and the highest atmospheric corrosion resistance, even higher than the AZ91D alloy, indicating that aluminium distribution in the alloy microstructure influenced the amount of magnesium carbonate formed.

  17. Correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys

    Science.gov (United States)

    Feliu, S., Jr.; Pardo, A.; Merino, M. C.; Coy, A. E.; Viejo, F.; Arrabal, R.

    2009-01-01

    X-ray photoelectron spectroscopy (XPS) was used in order to investigate the correlation between the surface chemistry and the atmospheric corrosion of AZ31, AZ80 and AZ91D magnesium alloys exposed to 98% relative humidity at 50 °C. Commercially pure magnesium, used as the reference material, revealed MgO, Mg(OH) 2 and tracers of magnesium carbonate in the air-formed film. For the AZ80 and AZ91D alloys, the amount of magnesium carbonate formed on the surface reached similar values to those of MgO and Mg(OH) 2. A linear relation between the amount of magnesium carbonate formed on the surface and the subsequent corrosion behaviour in the humid environment was found. The AZ80 alloy revealed the highest amount of magnesium carbonate in the air-formed film and the highest atmospheric corrosion resistance, even higher than the AZ91D alloy, indicating that aluminium distribution in the alloy microstructure influenced the amount of magnesium carbonate formed.

  18. Surface chemistry and morphology of the solid electrolyte interphase on silicon nanowire lithium-ion battery anodes

    KAUST Repository

    Chan, Candace K.

    2009-04-01

    Silicon nanowires (SiNWs) have the potential to perform as anodes for lithium-ion batteries with a much higher energy density than graphite. However, there has been little work in understanding the surface chemistry of the solid electrolyte interphase (SEI) formed on silicon due to the reduction of the electrolyte. Given that a good, passivating SEI layer plays such a crucial role in graphite anodes, we have characterized the surface composition and morphology of the SEI formed on the SiNWs using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). We have found that the SEI is composed of reduction products similar to that found on graphite electrodes, with Li2CO3 as an important component. Combined with electrochemical impedance spectroscopy, the results were used to determine the optimal cycling parameters for good cycling. The role of the native SiO2 as well as the effect of the surface area of the SiNWs on reactivity with the electrolyte were also addressed. © 2009 Elsevier B.V. All rights reserved.

  19. Use of North American and European air quality networks to evaluate global chemistry-climate modeling of surface ozone

    Directory of Open Access Journals (Sweden)

    J. L. Schnell

    2015-04-01

    Full Text Available We test the current generation of global chemistry-climate models in their ability to simulate observed, present-day surface ozone. Models are evaluated against hourly surface ozone from 4217 stations in North America and Europe that are averaged over 1° × 1° grid cells, allowing commensurate model-measurement comparison. Models are generally biased high during all hours of the day and in all regions. Most models simulate the shape of regional summertime diurnal and annual cycles well, correctly matching the timing of hourly (~ 15:00 and monthly (mid-June peak surface ozone abundance. The amplitude of these cycles is less successfully matched. The observed summertime diurnal range (~ 25 ppb is underestimated in all regions by about 7 ppb, and the observed seasonal range (~ 21 ppb is underestimated by about 5 ppb except in the most polluted regions where it is overestimated by about 5 ppb. The models generally match the pattern of the observed summertime ozone enhancement, but they overestimate its magnitude in most regions. Most models capture the observed distribution of extreme episode sizes, correctly showing that about 80% of individual extreme events occur in large-scale, multi-day episodes of more than 100 grid cells. The observed linear relationship showing increases in ozone by up to 6 ppb for larger-sized episodes is also matched.

  20. Luminescent Lanthanide Reporters for High-Sensitivity Novel Bioassays.

    Energy Technology Data Exchange (ETDEWEB)

    Anstey, Mitchell; Fruetel, Julia A.; Foster, Michael E.; Hayden, Carl C.; Buckley, Heather L.; Arnold, John

    2013-09-01

    Biological imaging and assay technologies rely on fluorescent organic dyes as reporters for a number of interesting targets and processes. However, limitations of organic dyes such as small Stokes shifts, spectral overlap of emission signals with native biological fluorescence background, and photobleaching have all inhibited the development of highly sensitive assays. To overcome the limitations of organic dyes for bioassays, we propose to develop lanthanide-based luminescent dyes and demonstrate them for molecular reporting applications. This relatively new family of dyes was selected for their attractive spectral and chemical properties. Luminescence is imparted by the lanthanide atom and allows for relatively simple chemical structures that can be tailored to the application. The photophysical properties offer unique features such as narrow and non-overlapping emission bands, long luminescent lifetimes, and long wavelength emission, which enable significant sensitivity improvements over organic dyes through spectral and temporal gating of the luminescent signal.Growth in this field has been hindered due to the necessary advanced synthetic chemistry techniques and access to experts in biological assay development. Our strategy for the development of a new lanthanide-based fluorescent reporter system is based on chelation of the lanthanide metal center using absorbing chromophores. Our first strategy involves %22Click%22 chemistry to develop 3-fold symmetric chelators and the other involves use of a new class of tetrapyrrole ligands called corroles. This two-pronged approach is geared towards the optimization of chromophores to enhance light output.

  1. Rewiring Gram-Negative Bacteria Cell Surfaces with Bio-Orthogonal Chemistry via Liposome Fusion.

    Science.gov (United States)

    Elahipanah, Sina; Radmanesh, Parham; Luo, Wei; O'Brien, Paul J; Rogozhnikov, Dmitry; Yousaf, Muhammad N

    2016-04-20

    The ability to tailor bacteria cell surfaces with non-native molecules is critical to advance the study of bacteria communication, cell behavior, and for next-generation therapeutics to improve livestock and human health. Such modifications would allow for novel control over cell behavior, cell-cell interactions, biofilm formation, adjuvant conjugation, and imaging. Current methods to engineer bacteria surfaces have made major advances but rely on complicated, slow, and often expensive molecular biology and metabolic manipulation methods with limited scope on the type of molecules installed onto the surface. In this report, we introduce a new straightforward method based on liposome fusion to engineer Gram-negative bacteria cells with bio-orthogonal groups that can subsequently be conjugated to a range of molecules (biomolecules, small molecules, probes, proteins, nucleic acids, ligands, and radiolabels) for further studies and programmed behavior of bacteria. This method is fast, efficient, inexpensive, and useful for installing a broad scope of ligands and biomolecules to Gram-negative bacteria surfaces. PMID:27019118

  2. Aqueous stabilization of carbon nanotubes: effects of surface oxidization and solution chemistry.

    Science.gov (United States)

    Bai, Yingchen; Wu, Fengchang; Lin, Daohui; Xing, Baoshan

    2014-03-01

    Surface oxygen functional groups can affect the morphological characteristics, aggregation kinetics, and adsorption capacity of multi-walled carbon nanotubes (MWCNTs). However, little is known about the quantitative relationship between oxygen content and the dispersion stability of MWCNTs. To investigate the effects of surface oxidization, MWCNTs were oxidized using concentrated H2SO4/HNO3 acids for 0, 1, 2, 4, and 8 h, respectively. Experimental results showed that the oxygen content of MWCNTs increased with surface oxidization time. Linear correlations were found to exist between the oxygen content, critical coagulation concentration (CCC) for NaCl, and critical coagulation pH values of MWCNTs detected by optical density at 800 nm. The CCC values for CaCl2 increased with oxygen contents for unmodified MWCNTs and lowly oxidized MWCNTs, while which decreased after further increasing the surface oxidization. CCC ratios in the presence of Ca(2+) to Na(+) were consistent with the empirical Schulze-Hardy rule for unmodified MWCNTs and lowly oxidized MWCNTs; however, which were much lower than the expected values for highly oxidized MWCNTs. Fulvic acid can clearly increase the stability of MWCNT suspension with unmodified MWCNTs and lowly oxidized MWCNTs, while it cannot affect the dispersion of highly oxidized MWCNTs. This study implied that the oxidation and presence of fulvic acid will possibly increase the mobility, exposure, bioavailability, and toxicity of MWCNTs. PMID:24323322

  3. Quorum sensing inhibitory activities of surface immobilized antibacterial dihydropyrrolones via click chemistry.

    Science.gov (United States)

    Ho, Kitty K K; Chen, Renxun; Willcox, Mark D P; Rice, Scott A; Cole, Nerida; Iskander, George; Kumar, Naresh

    2014-02-01

    Device-related infection remains a major barrier to the use of biomaterial implants as life-saving devices. This study aims to examine the effectiveness and mechanism of action of surface attached dihydropyrrolones (DHPs), a quorum sensing (QS) inhibitor, against bacterial colonization. DHPs were covalently attached on glass surfaces via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) click reaction. The covalent attachment of DHP surfaces was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements, and the antimicrobial efficacy of the DHP coatings was assessed by confocal laser scanning microscopy (CLSM) and image analysis. The results demonstrated that covalently bound DHP compounds are effective in reducing the adhesion by up to 97% (p technology, it is demonstrated that surface attached DHPs were able to repress the expression of a lasB-gfp reporter fusion of P. aeruginosa by 72% (p viability. This demonstrates the ability of the covalently bound QS inhibitor to inhibit QS and suggests the existence of a membrane-based pathway(s) for QS inhibition. Hence, strategies based on incorporation of QS inhibitors such as DHPs represent a potential approach for prevention of device-related infections. PMID:24345737

  4. Chemistry of the sea surface microlayer. 1. Fabrication and testing of the sampler

    Digital Repository Service at National Institute of Oceanography (India)

    Singbal, S.Y.S.; Narvekar, P.V.

    A screen sampler fabricated to study the sea surface microlayer (SML) has been described. The screen sampler was tested in the Mandovi estuary and adjacent waters. Physico-chemical parameters of the subsurface waters from a depth of 25 cm was also...

  5. Phosphate availability in the soil-root system: integration of oxide surface chemistry, transport and uptake.

    NARCIS (Netherlands)

    Geelhoed, J.S.

    1998-01-01

    A study is presented on the adsorption of phosphate on goethite, the interaction of phosphate with other adsorbing ions at the goethite surface, and the resulting availability of phosphate to plants. The plant-availability of sorbed phosphate was determined from phosphorus uptake of plants growing o

  6. Effect of nanoporous carbon surface chemistry on the removal of endocrine disruptors from water phase.

    Science.gov (United States)

    Vidal, Carla B; Seredych, Mykola; Rodríguez-Castellón, Enrique; Nascimento, Ronaldo F; Bandosz, Teresa J

    2015-07-01

    Wood-based activated carbon and its sulfur-doped counterpart were used as adsorbents of endocrine disruptor chemicals (EDC) from aqueous solution. Adsorption process was carried out in dynamic conditions and Thomas model was used to predict the performance of the column. The results showed a good fitting of the theoretical curve to the experimental data. S-doped carbon exhibited a higher adsorption capacity of trimethoprim (TMP) and smaller of sulfamethoxazole (SMX) and diclofenac (DCF) in comparison with the carbon with no sulfur incorporated into the matrix. The surface features of the initial carbons and those exposed to EDC were evaluated in order to derive the adsorption mechanism and elucidate the role of surface features. An increase in the amount of TMP from a low concentration solution (10 mg/L) on sulfur-doped carbon was linked to acid-base interactions and the reactive adsorption/oxidation of TMP. A decrease in SMX and DCF after sulfur doping was explained by a considerable increase in surface hydrophobicity, which does not favor the retention of polar DCF and SMX molecules. When the adsorption was measured from a high concentration solution at equilibrium conditions at the dark or under solar light irradiation different trends in the adsorption capacities were found. This was linked to the photoactivity of carbons and the degradation of EDC in the pore system promoted by visible light followed by the adsorption of the products of surface reactions. PMID:25527089

  7. Characterization of chemical-waste-site contamination and determination of its extent using bioassays

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, J.M.; Skalski, J.R.; Cline, J.F.; McShane, M.C.; Miller, W.E.

    1986-01-01

    The purpose of using bioassays to evaluate soils, soil elutriates, and surface and subsurface water from hazardous chemical waste sites is to provide a more-direct, integrated estimate of environmental toxicity. Based on bioassay data, chemical waste sites can be ranked according to their toxic potential or mapped for cleanup operations. The objectives of the study were to (a) assess the comparative sensitivity of test organisms to known chemicals, (b) determine if the chemical components in field soil and water samples of unknown composition could be inferred from laboratory studies using pure chemicals and (c) investigate kriging (a relatively new statistical mapping technique) of bioassay results as a method to define the areal extent of contamination. In support of these objectives, data are presented on the response of the organisms listed in the Hazardous Materials Assessment Team (HMAT) test protocol (3) to pure chemicals from three chemical subgroups (heavy metals, insecticides, and herbicides).

  8. Surface chemistry of nanoscale Fe3O4 dispersed in magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    XIA; JianHan

    2007-01-01

    The interaction between stabilizers and nanoparticles is one of the important factors to prepare stable magnetic fluids. The magnetic nano-size Fe3O4 core with single domain and the average grain size around 8-12 nm were prepared by chemical precipitation method. The O/Fe molar ratio of the particle surface was measured by X-ray photoelectron spectroscopy (XPS). The heat effects of stabilizers adsorption on nanoparticles were measured by solution calorimetry. The excess amount of oxygen was possibly the result of the hydroxygen formed on the surface of the nanoparticles. The heat effects showed that compounds containing carboxyl groups can be adsorbed chemically on magnetite by forming chemical bonds. The other stabilizers involving NH-groups, such as polyethylene-imine, can be adsorbed physically. The exothermic value is about half of the former case.

  9. Defect-free Perpendicular Diblock Copolymer Films: The Synergistic Effect of Surface Topography and Chemistry

    CERN Document Server

    Man, Xingkun; Tang, Jiuzhou; Yan, Dadong; Andelman, David

    2016-01-01

    We propose a direct self-assembly mechanism towards obtaining defect-free perpendicular lamellar phases of diblock copolymer (BCP) thin films. In our numerical study, a thin BCP film having a flat top surface is casted on a uni-directional corrugated solid substrate. The substrate is treated chemically and has a weak preference toward one of the two BCP components. Employing self-consistent field theory (SCFT), we find that there is an enhanced synergy between two substrate characteristics: its topography (geometrical roughness) combined with a weak surface preference. This synergy produces the desired perpendicular lamellar phase with perfect inplane ordering. Defect-free BCP lamellar phases are reproducible for several random initial states, and are obtained for a range of substrate roughness and chemical characteristics, even for a uni-directional multi-mode substrate roughness. Our theoretical study suggests possible experiments that will explore the interplay between uni-directional substrate corrugation...

  10. Chemistry of the interaction between azole type corrosion inhibitor molecules and metal surfaces

    International Nuclear Information System (INIS)

    By means of density functional theory calculations, it has been shown how typical organic corrosion inhibitors—molecules that have the ability to remarkably slow down the corrosion of metals and alloys—interact with bare surfaces of various types of metals. As representative model systems, benzimidazole and benzotriazole inhibitors on iron, copper, and aluminum surfaces are considered. It is found that bonding depends sensitively on the type of metal. On transition metals with open d-band the inhibitor molecules can chemisorb strongly either parallel to the surface with a pronounced π–d hybridization or perpendicularly with unsaturated N atom(s) through σ-molecular orbitals, whereas on transition metals with fully occupied d-band and on sp-metals the molecules weakly chemisorb only with the latter mode. In addition to neutral inhibitor molecules also inhibitors in deprotonated (anionic) and protonated (cationic) forms are considered, because many corrosion inhibitors possess acidic hydrogens as well as basic heteroatoms. It is shown that the chemisorptive bonding is far the strongest for deprotonated inhibitors and, moreover, that even protonated inhibitors may chemisorb, although such bonding is characteristic of more reactive metals. However adsorbed protonated inhibitors are likely to deprotonate on all considered metals, whereas further deprotonation from neutral to deprotonated form is more likely on more reactive metals. Highlights: ► Bonding of azole corrosion inhibitors onto metal surfaces characterized by DFT calculations. ► Adsorption bonding depends sensitively on the type of metal. ► Azoles bond with either π-system or σ-orbitals to transition metals with open d-band. ► Azoles bond with σ-orbitals to transition metals with fully occupied d-band and to sp-metals. ► Among various molecular forms, deprotonated molecules form the strongest chemisorption bond.

  11. Covalent Coupling of Nanoparticles with Low-Density Functional Ligands to Surfaces via Click Chemistry

    OpenAIRE

    Ina Rianasari; de Jong, Michel P.; Jurriaan Huskens; van der Wiel, Wilfred G.

    2013-01-01

    We demonstrate the application of the 1,3-dipolar cycloaddition (“click” reaction) to couple gold nanoparticles (Au NPs) functionalized with low densities of functional ligands. The ligand coverage on the citrate-stabilized Au NPs was adjusted by the ligand:Au surface atom ratio, while maintaining the colloidal stability of the Au NPs in aqueous solution. A procedure was developed to determine the driving forces governing the selectivity and reactivity of citrate-stabilized and ligand-functio...

  12. Chemistry of the interaction between azole type corrosion inhibitor molecules and metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kovacevic, Natasa [Department of Physical and Organic Chemistry, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Kokalj, Anton, E-mail: tone.kokalj@ijs.si [Department of Physical and Organic Chemistry, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia)

    2012-11-15

    By means of density functional theory calculations, it has been shown how typical organic corrosion inhibitors-molecules that have the ability to remarkably slow down the corrosion of metals and alloys-interact with bare surfaces of various types of metals. As representative model systems, benzimidazole and benzotriazole inhibitors on iron, copper, and aluminum surfaces are considered. It is found that bonding depends sensitively on the type of metal. On transition metals with open d-band the inhibitor molecules can chemisorb strongly either parallel to the surface with a pronounced {pi}-d hybridization or perpendicularly with unsaturated N atom(s) through {sigma}-molecular orbitals, whereas on transition metals with fully occupied d-band and on sp-metals the molecules weakly chemisorb only with the latter mode. In addition to neutral inhibitor molecules also inhibitors in deprotonated (anionic) and protonated (cationic) forms are considered, because many corrosion inhibitors possess acidic hydrogens as well as basic heteroatoms. It is shown that the chemisorptive bonding is far the strongest for deprotonated inhibitors and, moreover, that even protonated inhibitors may chemisorb, although such bonding is characteristic of more reactive metals. However adsorbed protonated inhibitors are likely to deprotonate on all considered metals, whereas further deprotonation from neutral to deprotonated form is more likely on more reactive metals. Highlights: Black-Right-Pointing-Pointer Bonding of azole corrosion inhibitors onto metal surfaces characterized by DFT calculations. Black-Right-Pointing-Pointer Adsorption bonding depends sensitively on the type of metal. Black-Right-Pointing-Pointer Azoles bond with either {pi}-system or {sigma}-orbitals to transition metals with open d-band. Black-Right-Pointing-Pointer Azoles bond with {sigma}-orbitals to transition metals with fully occupied d-band and to sp-metals. Black-Right-Pointing-Pointer Among various molecular forms

  13. An Assessment of Cell Culture Plate Surface Chemistry for in Vitro Studies of Tissue Engineering Scaffolds

    OpenAIRE

    Alexander Röder; Elena García-Gareta; Christina Theodoropoulos; Nikola Ristovski; Keith A. Blackwood; Woodruff, Maria A.

    2015-01-01

    The use of biopolymers as a three dimensional (3D) support structure for cell growth is a leading tissue engineering approach in regenerative medicine. Achieving consistent cell seeding and uniform cell distribution throughout 3D scaffold culture in vitro is an ongoing challenge. Traditionally, 3D scaffolds are cultured within tissue culture plates to enable reproducible cell seeding and ease of culture media change. In this study, we compared two different well-plates with different surface ...

  14. Click chemistry modification of surface-bound peptides towards applications in printable electronics

    OpenAIRE

    Schlageter, Martin

    2015-01-01

    This thesis shows the development of a method for the modification of surface-bound peptides. Initial attempts to functionalize amino acids with ferrocene derivatives led to a post-synthetic click grafting strategy, which could be shown to be feasible. This approach was extended to a two-step consecutive click sequence. Additionally, the grafting of Coordination clusters with the described method was investigated.

  15. Polyglycerol dendrimers immobilized on radiation grafted poly-HEMA hydrogels: Surface chemistry characterization and cell adhesion

    International Nuclear Information System (INIS)

    Radiation induced grafting of poly(2-hydroxyethylmethacrylate) (PHEMA) on low density polyethylene (LDPE) films and subsequent immobilization of poly(glycerol) dendrimer (PGLD) has been performed with the aim to improve cell adhesion and proliferation on the surface of the polymer, in order to enhance their properties for bone tissue engineering scaffolding applications. Radiation grafting of PHEMA onto LDPE was promoted by γ-ray radiation. The covalent immobilization of PGLD on LDPE-g-PHEMA surface was performed by using a dicyclohexyl carbodiimide (DCC)/N,N-dimethylaminopyridine (DMAP) method. The occurrence of grafting polymerization of PHEMA and further immobilization of PGLD was quantitatively confirmed by photoelectron spectroscopy (XPS) and fluorescence, respectively. The LDPE-g-PHEMA surface topography after PGLD coupling was studied by atomic force microscopy (AFM). The hydrophilicity of the LDPE-g-PHEMA film was remarkably improved compared to that of the ungrafted LDPE. The core level XPS ESCA spectrum of PHEMA-grafted LDPE showed two strong peaks at 286.6 eV (from hydroxyl groups and ester groups) and 289.1 eV (from ester groups) due to PHEMA brushes grafted onto LDPE surfaces. The results from the cell adhesion studies show that MCT3-E1 cells tended to spread more slowly on the LDPE-g-PHEMA than on the LDPE-g-PHEMA-i-PGLD. - Highlights: • Radiation-grafted PHEMA hydrogels have been obtained by simultaneous gamma-irradiation of LDPE and HEMA monomer. • PGLD dendrimer was immobilized onto PHEMA for application in tissue engineering. • The microstructural characterization of LDPE-g-PHEMA-i-PGLD by RMN, XPS, AFM and MALDI-TOF are made. • Measurements of water uptake and contact angle of LDPE-g-PHEMA are compared to those of LDPE-g-PHEMA-i-PGLD. • The MC3T-E1 osteoblast cell adhesion and growth on LDPE-g-PHEMA-i-PGLD were studied

  16. Physical-chemistry of radionuclide/mineral surface interaction: II - Structural aspect

    International Nuclear Information System (INIS)

    Most of the studies on sorption processes takes into account only the thermodynamical approach and does not have paid attention to the structural aspect (i.e. structure of the surface complex, sorption mechanism). We have here considered this structural point of view using various spectroscopic methods such as photoelectron spectroscopy (XPS), laser induced fluorescence and extended X-ray absorption fine structure (EXAFS). (authors)

  17. The influence of projectile ion induced chemistry on surface pattern formation

    Science.gov (United States)

    Karmakar, Prasanta; Satpati, Biswarup

    2016-07-01

    We report the critical role of projectile induced chemical inhomogeneity on surface nanostructure formation. Experimental inconsistency is common for low energy ion beam induced nanostructure formation in the presence of uncontrolled and complex contamination. To explore the precise role of contamination on such structure formation during low energy ion bombardment, a simple and clean experimental study is performed by selecting mono-element semiconductors as the target and chemically inert or reactive ion beams as the projectile as well as the source of controlled contamination. It is shown by Atomic Force Microscopy, Cross-sectional Transmission Electron Microscopy, and Electron Energy Loss Spectroscopy measurements that bombardment of nitrogen-like reactive ions on Silicon and Germanium surfaces forms a chemical compound at impact zones. Continuous bombardment of the same ions generates surface instability due to unequal sputtering and non-uniform re-arrangement of the elemental atom and compound. This instability leads to ripple formation during ion bombardment. For Argon-like chemically inert ion bombardment, the chemical inhomogeneity induced boost is absent; as a result, no ripples are observed in the same ion energy and fluence.

  18. Assessment of the surface chemistry of carbon blacks by TGA-MS, XPS and inverse gas chromatography using statistical chemometric analysis

    International Nuclear Information System (INIS)

    Highlights: • Carbon blacks with lower specific surface area had basic character (electron donor) due to C=O and C-O groups. • Carbon blacks with higher specific surface area had acidic character (acceptor electron) due to OH groups. • Total surface energy and its dispersive component of carbon blacks increased by increasing their specific surface area. (table) - Abstract: Four carbon blacks with different specific surface areas and surface chemistries (C32, C71, C159 and C178) were analyzed by transmission electron microscopy (TEM) and nitrogen adsorption isotherms at 77 K. Their surface chemistries were analyzed by X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis coupled with mass spectrometry (TGA-MS) and inverse gas chromatography (IGC). The carbon blacks contained 2.7–5.8 wt% volatiles corresponding to -OH, C-O, C=O and COO groups. The surface chemistry parameters obtained with the different experimental techniques were inter-related by using chemometric statistical analysis tools. The application of this methodology showed that the carbon blacks with lower specific surface area (C32 and C71) had basic character (electron donor) mainly due to C=O and C-O groups, whereas the carbon black with the highest specific surface area (C178) showed acidic character (acceptor electron) due to its high content of OH groups. Moreover, the total surface energy and the dispersive component of the surface energy of the carbon blacks increased with the increase of their specific surface area. In general the specific interactions of the carbon blacks also increased with the increase of their specific surface area although C71 is exceptional due to higher oxygen content corresponding to C-O groups

  19. Influences of Mn(II) and V(IV) on Bacterial Surface Chemistry and Metal Reactivity

    Science.gov (United States)

    French, S.; Fakra, S.; Glasauer, S.

    2009-05-01

    Microorganisms in terrestrial and marine environments are typically bathed in solutions that contain a range of metal ions, toxic and beneficial. Bacteria such as Shewanella putrefaciens CN32 are metabolically versatile in their respiration, and the reductive dissolution of widely dispersed metals such as Fe(III), Mn(IV), or V(V) can present unique challenges if nearby bodies of water are used for irrigation or drinking. In redox transition zones, dissimilatory metal reduction (DMR) by bacteria can lead to generation of high concentrations of soluble metals. It has been shown that metals will associate with negatively charged bacterial membranes, and the mechanisms of metal reduction are well defined for many species of bacteria. The interaction of metals with the cell wall during DMR is, however, not well documented; very little is known about the interaction of respired transition metals with membrane lipids. Furthermore, bacterial surfaces tend to change in response to their immediate environments. Variations in conditions such as oxygen or metal presence may affect surface component composition, including availability of metal reactive sites. Our research seeks to characterize the biochemical nature of metal-membrane interactions, as well as identify the unique changes at the cell surface that arise as a result of metal presence in their environments. We have utilized scanning transmission X-ray microscopy (STXM) to examine the dynamics of soluble Mn(II) and V(IV) interactions with purified bacterial membranes rather than whole cells. This prevents intracellular interferences, and allows for near edge X-ray absorption fine structure (NEXAFS) spectroscopic analyses of cell surface and surface-associated components. NEXAFS spectra for carbon, nitrogen, and oxygen edges indicate that Mn(II) and V(IV) induce biological modifications of the cell membrane in both aerobic and anaerobic conditions. These changes depend not only on the metal, but also on the presence of

  20. Use of North American and European air quality networks to evaluate global chemistry-climate modeling of surface ozone

    Science.gov (United States)

    Schnell, J. L.; Prather, M. J.; Josse, B.; Naik, V.; Horowitz, L. W.; Cameron-Smith, P.; Bergmann, D.; Zeng, G.; Plummer, D. A.; Sudo, K.; Nagashima, T.; Shindell, D. T.; Faluvegi, G.; Strode, S. A.

    2015-09-01

    We test the current generation of global chemistry-climate models in their ability to simulate observed, present-day surface ozone. Models are evaluated against hourly surface ozone from 4217 stations in North America and Europe that are averaged over 1° × 1° grid cells, allowing commensurate model-measurement comparison. Models are generally biased high during all hours of the day and in all regions. Most models simulate the shape of regional summertime diurnal and annual cycles well, correctly matching the timing of hourly (~ 15:00 local time (LT)) and monthly (mid-June) peak surface ozone abundance. The amplitude of these cycles is less successfully matched. The observed summertime diurnal range (~ 25 ppb) is underestimated in all regions by about 7 ppb, and the observed seasonal range (~ 21 ppb) is underestimated by about 5 ppb except in the most polluted regions, where it is overestimated by about 5 ppb. The models generally match the pattern of the observed summertime ozone enhancement, but they overestimate its magnitude in most regions. Most models capture the observed distribution of extreme episode sizes, correctly showing that about 80 % of individual extreme events occur in large-scale, multi-day episodes of more than 100 grid cells. The models also match the observed linear relationship between episode size and a measure of episode intensity, which shows increases in ozone abundance by up to 6 ppb for larger-sized episodes. We conclude that the skill of the models evaluated here provides confidence in their projections of future surface ozone.

  1. Surface chemistry and catalytic properties of VOX/Ti-MCM-41 catalysts for dibenzothiophene oxidation in a biphasic system

    Science.gov (United States)

    González, J.; Chen, L. F.; Wang, J. A.; Manríquez, Ma.; Limas, R.; Schachat, P.; Navarrete, J.; Contreras, J. L.

    2016-08-01

    A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H2O2 as oxidant. ODS activity was found to be proportional to the V5+/(V4+ + V5+) values of the catalysts, indicating that the surface vanadium pentoxide (V2O5) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e., 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Brønsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V2O5) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V2O5/Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

  2. Characterizing interactions between surface water and groundwater in the Jialu River basin using major ion chemistry and stable isotopes

    Directory of Open Access Journals (Sweden)

    L. Yang

    2012-11-01

    Full Text Available The Jialu River, a secondary tributary of the Huaihe River, has been severely contaminated from major contaminant sources, such as a number of untreated or lightly treated sewage waste in some cities. Groundwater along the river is not an isolated component of the hydrologic system, but is instead connected with the surface water. This study aims to investigate temporal and spatial variations in water chemistry affected by humans and to characterize the relationships between surface water (e.g. reservoirs, lakes and rivers and groundwater near the river in the shallow Quaternary aquifer. Concentration of Cl in north Zhengzhou City increased prominently due to the discharge of a large amount of domestic water. Nitrate and potassium show maximum concentrations in groundwater in Fugou County. These high levels can be attributed to the use of a large quantity of fertilizer over this region. Most surface water appeared to be continuously recharged from the surrounding groundwater (regional wells based on comparison surface water with groundwater levels, stable-isotopes and major ion signatures. However, the groundwater of a transitional well (location SY3 seemed to be recharged by river water via bank infiltration in September 2010. Fractional contributions of river water to the groundwater were calculated based on isotopic and chemical data using a mass-balance approach. Results show that the groundwater was approximately composed of 60–70% river water. These findings should be useful for a better understanding of hydrogeological processes at the river-aquifer interface and ultimately benefit water management in the future.

  3. Antireflection and SiO2 Surface Passivation by Liquid-Phase Chemistry for Efficient Black Silicon Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, H. C.; Oh, J.; Zhang, Y.; Kuznetsov, O. A.; Flood, D. J.; Branz, H. M.

    2012-06-01

    We report solar cells with both black Si antireflection and SiO2 surface passivation provided by inexpensive liquid-phase chemistry, rather than by conventional vacuum-based techniques. Preliminary cell efficiency has reached 16.4%. Nanoporous black Si antireflection on crystalline Si by aqueous etching promises low surface reflection for high photon utilization, together with lower manufacturing cost compared to vacuum-based antireflection coating. Ag-nanoparticle-assisted black Si etching and post-etching chemical treatment recently developed at NREL enables excellent control over the pore diameter and pore separation. Performance of black Si solar cells, including open-circuit voltage, short-circuit current density, and blue response, has benefited from these improvements. Prior to this study, our black Si solar cells were all passivated by thermal SiO2 produced in tube furnaces. Although this passivation is effective, it is not yet ideal for ultra-low-cost manufacturing. In this study, we report, for the first time, the integration of black Si with a proprietary liquid-phase deposition (LPD) passivation from Natcore Technology. The Natcore LPD forms a layer of <10-nm SiO2 on top of the black Si surface in a relatively mild chemical bath at room temperature. We demonstrate black Si solar cells with LPD SiO2 with a spectrum-weighted average reflection lower than 5%, similar to the more costly thermally grown SiO2 approach. However, LPD SiO2 provides somewhat better surface-passivation quality according to the lifetime analysis by the photo-conductivity decay measurement. Moreover, black Si solar cells with LPD SiO2 passivation exhibit higher spectral response at short wavelength compared to those passivated by thermally grown SiO2. With further optimization, the combination of aqueous black Si etching and LPD could provide a pathway for low-cost, high-efficiency crystalline Si solar cells.

  4. Influence of operating and water-chemistry parameters on fuel cladding corrosion and deposition of corrosion products on cladding surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kritsky, V.G.; Berezina, I.G.; Rodionov, Y.A., E-mail: kritsky@givnipiet.spb.ru, E-mail: alemaskina@givnipiet.ru [Leading Inst. ' VNIPIET' , Saint Petersburg (Russian Federation)

    2010-07-01

    A description of mass transfer mechanism of corrosion products in the primary coolant circuit is a complicated problem. The deposits of crud is to be proportional to the amount of corrosion products circulating in the primary coolant circuit, therefore all models of mass transfer in the circuit include the change of corrosion products concentration and the corrosion rate in time, removing these products by filters and deposition. Decontamination of the circuit equipment and replacement work needs lead to a local change of corrosion rate which results in the increase of corrosion products concentration in the circuit and the increase of deposits on surfaces. If due to incorrect water chemistry conditions for corrosion products deposition in the core are created not only the activity of the coolant increases but the hydraulic resistance of the reactor also grows which results in the increase of the pressure drop at the reactor. The phenomenon of 'pressure drop' which takes place in NPP with VVER reactors was considered. The reasons of this phenomenon are the following: the great removal of corrosion products (CP) from steam generator surfaces after decontamination, change of CP behavior and then consequent deposit of CP on the fuel element surfaces; and, sub-cooled boiling takes place on the some of fuel element and results in the acceleration of corrosion products deposit, the increase of nuclide activation period and coolant radioactivity. A model was developed to explain pressure drop rise in-core and deposits redistribution in the core and in the primary circuit of NPP with VVER-440. The physical-chemical basis of the model is the transport corrosion products dependence on temperature, pH{sub T} value of coolant, and correlation between rates of corrosion products (Fe) formation (after steam generators decontamination) and their removing from the circuit. The aim of our modeling is to predict the growth of pressure difference on the basis of regular

  5. A Surface Chemistry Approach to Enhancing Colloidal Quantum Dot Solids for Photovoltaics

    Science.gov (United States)

    Carey, Graham Hamilton

    Colloidal quantum dot (CQD) photovoltaic devices have improved rapidly over the past decade of research. By taking advantage of the quantum confinement effect, solar cells constructed using films of infrared-bandgap nanoparticles are able to capture previously untapped ranges of the solar energy spectrum. Additionally, films are fabricated using simple, cheap, reproducible solution processing techniques, enabling the creation of low-cost, flexible photovoltaic devices. A key factor limiting the creation of high efficiency CQD solar cells is the short charge carrier diffusion length in films. Driven by a combination of limited carrier mobility, poor nanoparticle surface passivation, and the presence of unexamined electrically active impurities throughout the film, the poor diffusion length limits the active layer thickness in CQD solar cells, leading to lower-than-desired light absorption, and curtailing the photocurrent generated by such devices. This thesis seeks to address poor diffusion length by addressing each of the limiting factors in turn. Electrical transport in quantum dot solids is examined in the context of improved quantum dot packing; methods are developed to improve packing by using actively densifying components, or by dramatically lowering the volume change required between quantum dots in solution and in solid state. Quantum dot surface passivation is improved by introducing a crucial secondary, small halide ligand source, and by surveying the impact of the processing environment on the final quality of the quantum dot surface. A heretofore unidentified impurity present in quantum dot solids is identified, characterized, and chemically eliminated. Finally, lessons learned through these experiments are combined into a single, novel materials system, leading to quantum dot devices with a significantly improved diffusion length (enhanced from 70 to 230 nm). This enabled thick, high current density (30 mA cm -2, compared to typical values in the 20

  6. Surface chemistry of ferrihydrite: Part 2. Kinetics of arsenate adsorption and coprecipitation

    Science.gov (United States)

    Fuller, C.C.; Dadis, J.A.; Waychunas, G.A.

    1993-01-01

    The kinetics of As(V) adsorption by ferrihydrite was investigated in coprecipitation and postsynthesis adsorption experiments conducted in the pH range 7.5-9.0. In coprecipitation experiments, As(V) was present in solution during the hydrolysis and precipitation of iron. In adsorption experiments, a period of rapid (adsorption sites on ferrihydrite surfaces within aggregates of colloidal particles. The time dependence of As(V) adsorption is well described by a general model for diffusion into a sphere if a subset of surface sites located near the exterior of aggregates is assumed to attain adsorptive equilibrium rapidly. The kinetics of As(V) desorption after an increase in pH were also consistent with diffusion as a rate-limiting process. Aging of pure ferrihydrite prior to As(V) adsorption caused a decrease in adsorption sites on the precipitate owing to crystallite growth. In coprecipitation experiments, the initial As(V) uptake was significantly greater than in post-synthesis adsorption experiments, and the rate of uptake was not diffusion limited because As(V) was coordinated by surface sites before crystallite growth and coagulation processes could proceed. After the initial adsorption, As(V) was slowly released from coprecipitates for at least one month, as crystallite growth caused desorption of As(V). Adsorption densities as high as 0.7 mole As(V) per mole of Fe were measured in coprecipitates, in comparison to 0.25 mole As(V) per mole of Fe in post-synthesis adsorption experiments. Despite the high Concentration of As(V) in the precipitates, EXAFS spectroscopy (Waychunas et al., 1993) showed that neither ferric arsenate nor any other As-bearing surface precipitate or solid solution was formed. The high adsorption densities are possible because the ferrihydrite particles are extremely small, approaching the size of small dioctahedral chains at the highest As(V) adsorption density. The results suggest that the solid solution model proposed by Fox (1989

  7. Theoretical investigations of metallic surfaces for water chemistry; Theoretische Untersuchungen metallischer Oberflaechen fuer die Wasserstoffchemie

    Energy Technology Data Exchange (ETDEWEB)

    Schnur, Sebastian

    2010-11-19

    Properties of the metal-water interface have been addressed by periodic density functional theory calculations, in particular with respect to the electronic and geometric structures of water bilayers on several transition metal surfaces. The structure and the vibrational spectra of water bilayers at room temperatures have been studied performing ab initio molecular dynamics simulations. In order to model varying electrode potentials, an explicite counter electrode has been implemented in a periodic density functional theory code, and first preliminary results using this implementation will be presented. (orig.)

  8. Orbital chemistry - Lunar surface analysis from the X-ray and gamma ray remote sensing experiments

    Science.gov (United States)

    Adler, I.; Trombka, J. I.

    1977-01-01

    The X-ray and gamma-ray lunar surface remote sensing experiments conducted by the Apollo 15 and 16 are discussed. The data indicate mare basins that are extensively basaltic and highlands of aluminum-rich anorthositic-type feldspar. An east-west asymmetry involving higher Al/Si ratios toward the east is noted; high concentrations of a KREEP-type component along the Imbrium-Procellarum edges and throughout the basin are also observed. Lunar K/Th ratios, lowest in areas of the Imbrium and higher in the surrounding mare and highlands, may lend support to the picture of the moon as a high-temperature condensate.

  9. Thermal chemistry of Mn2(CO)10 during deposition of thin manganese films on silicon oxide and on copper surfaces

    International Nuclear Information System (INIS)

    The surface chemistry of dimanganese decacarbonyl on the native oxide of Si(100) wafers was characterized with the aid of x-ray photoelectron spectroscopy. Initial experiments in a small stainless-steel reactor identified a narrow range of temperatures, between approximately 445 and 465 K, in which the deposition of manganese could be achieved in a self-limiting fashion, as is desirable for atomic layer deposition. Deposition at higher temperatures leads to multilayer growth, but the extent of this Mn deposition reverses at even higher temperatures (about 625 K), and also ifhydrogen is added to the reaction mixture. Extensive decarbonylation takes place below room temperature, but limited C-O bond dissociation and carbon deposition are still seen after high exposures at 625 K. The films deposited at low (∼450 K) temperatures are mostly in the form of MnO, but at 625 K that converts to a manganese silicate, and upon higher doses a manganese silicide forms at the SiO2/Si(100) interface as well. No metallic manganese could be deposited with this precursor on either silicon dioxide or copper surfaces.

  10. Contrasting the surface ocean distribution of bromoform and methyl iodide; implications for boundary layer physics, chemistry and climate

    International Nuclear Information System (INIS)

    Bromoform and methyl iodide are both methane-like hydrocarbons with a halogen atom replacing one or more of the hydrogen atoms. Both of these compounds occur naturally in the environment as a result of their production from seaweed and kelp. They are of interest to climate science as a result of their catalytic destruction of boundary layer ozone (a potent greenhouse gas) and, specifically for methyl iodide, the proposed role in the formation of new cloud condensation nuclei with implications for climate. In this paper, the currently available data on the distribution of bromoform and methyl iodide are analysed and contrasted to show that the concentrations of bromoform and methyl iodide do not correlate, that, in contrast to bromoform, the parameterization of sea surface methyl iodide concentrations demands only the sea surface temperature, and that the pelagic distribution of methyl iodide appears to follow the solar zenith angle. These three observations together suggest that, while the pelagic source of bromoform is mostly biogenic, the source of methyl iodide is photochemical. This has implications for the understanding of planetary boundary layer chemistry and potential organohalogen mediated feedbacks to climate.

  11. Contrasting the surface ocean distribution of bromoform and methyl iodide; implications for boundary layer physics, chemistry and climate

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, C J, E-mail: carl.j.palmer@gmail.co [Department of Oceanography, University of Cape Town, 7701 (South Africa)

    2010-08-15

    Bromoform and methyl iodide are both methane-like hydrocarbons with a halogen atom replacing one or more of the hydrogen atoms. Both of these compounds occur naturally in the environment as a result of their production from seaweed and kelp. They are of interest to climate science as a result of their catalytic destruction of boundary layer ozone (a potent greenhouse gas) and, specifically for methyl iodide, the proposed role in the formation of new cloud condensation nuclei with implications for climate. In this paper, the currently available data on the distribution of bromoform and methyl iodide are analysed and contrasted to show that the concentrations of bromoform and methyl iodide do not correlate, that, in contrast to bromoform, the parameterization of sea surface methyl iodide concentrations demands only the sea surface temperature, and that the pelagic distribution of methyl iodide appears to follow the solar zenith angle. These three observations together suggest that, while the pelagic source of bromoform is mostly biogenic, the source of methyl iodide is photochemical. This has implications for the understanding of planetary boundary layer chemistry and potential organohalogen mediated feedbacks to climate.

  12. Multilayer modeling of porous grain surface chemistry I. The GRAINOBLE model

    CERN Document Server

    Taquet, Vianney; Kahane, Claudine

    2011-01-01

    Mantles of iced water, mixed with CO, H2CO, and CH3OH are formed during the so called prestellar core phase. In addition, radicals are also thought to be formed on the grain surfaces, and to react to form complex organic molecules later on, during the warm-up phase of the protostellar evolution. The aim of this work is to study the formation of the grain mantles during the prestellar core phase and the abundance of H2CO, CH3OH, and radicals trapped in them. We have developed a macrosopic statistic multilayer model that follows the formation of grain mantles with time and that includes two effects that may increase the number of radicals trapped in the mantles: i) at each time of the mantle formation, only the surface layer is chemically active rather than the entire bulk, and ii) the porous structure of grains allows to trap reactive particles. The model considers a network of H, O and CO forming neutral species such as water, CO, formaldehyde, and methanol, plus several radicals. We run a large grid of model...

  13. Immobilized probe and glass surface chemistry as variables in microarray fabrication

    Directory of Open Access Journals (Sweden)

    Muheisen Sanaa

    2004-08-01

    Full Text Available Abstract Background Global gene expression studies with microarrays can offer biological insights never before possible. However, the technology possesses many sources of technical variability that are an obstacle to obtaining high quality data sets. Since spotted microarrays offer design/content flexibility and potential cost savings over commercial systems, we have developed prehybridization quality control strategies for spotted cDNA and oligonucleotide arrays. These approaches utilize a third fluorescent dye (fluorescein to monitor key fabrication variables, such as print/spot morphology, DNA retention, and background arising from probe redistributed during blocking. Here, our labeled cDNA array platform is used to study, 1 compression of array data using known input ratios of Arabidopsis in vitro transcripts and arrayed serial dilutions of homologous probes; 2 how curing time of in-house poly-L-lysine coated slides impacts probe retention capacity; and 3 the retention characteristics of 13 commercially available surfaces. Results When array element fluorescein intensity drops below 5,000 RFU/pixel, gene expression measurements become increasingly compressed, thereby validating this value as a prehybridization quality control threshold. We observe that the DNA retention capacity of in-house poly-L-lysine slides decreases rapidly over time (~50% reduction between 3 and 12 weeks post-coating; p Conclusions High DNA retention rates are necessary for accurate gene expression measurements. Therefore, an understanding of the characteristics and optimization of protocols to an array surface are prerequisites to fabrication of high quality arrays.

  14. Combining inkjet printing and sol-gel chemistry for making pH-sensitive surfaces.

    Science.gov (United States)

    Orsi, Gianni; De Maria, Carmelo; Montemurro, Francesca; Chauhan, Veeren M; Aylott, Jonathan W; Vozzi, Giovanni

    2015-01-01

    Today biomedical sciences are experiencing the importance of imaging biological parameters with luminescence methods. Studying 2D pH distribution with those methods allows building knowledge about complex cellular processes. Immobilizing pH sensitive nanoparticles inside hydrogel matrixes, in order to guarantee a proper SNR, could easily make stable and biocompatible 2D sensors. Inkjet printing is also well known as tool for printing images onto porous surfaces. Recently it has been used as a free-form fabrication method for building three-dimensional parts, and now is being explored as a way of printing electrical and optical devices. Inkjet printing was used either as a rapid prototyping method for custom biosensors. Sol-gel method is naturally bound with inkjet, because the picoliter-sized ink droplets evaporate quickly, thus allowing quick sol-gel transitions on the printed surface. In this work will be shown how to merge those technologies, in order to make a nanoparticles doped printable hydrogel, which could be used for making 2D/3D smart scaffolds able to monitor cell activities. An automated image analysis system was developed in order to quickly have the pH measurements from pH nanosensors fluorescence images. PMID:25547966

  15. The surface chemistry of Cu in the presence of CO2 and H2O

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Xingyi; Verdaguer, Albert; Herranz, Tirma; Weis, Christoph; Bluhm, Hendrik; Salmeron, Miquel

    2008-07-16

    The chemical nature of copper and copper oxide (Cu{sub 2}O) surfaces in the presence of CO{sub 2} and H{sub 2}O at room temperature was investigated using ambient pressure x-ray photoelectron spectroscopy. The studies reveal that in the presence of 0.1 torr CO{sub 2} several species form on the initially clean Cu, including carbonate CO{sub 3}{sup 2}, CO{sub 2}{sup {delta}-} and C{sup 0}, while no modifications occur on an oxidized surface. The addition of 0.1 ML Zn to the Cu results in the complete conversion of CO{sub 2}{sup {delta}-} to carbonate. In a mixture of 0.1 torr H{sub 2}O and 0.1 torr CO{sub 2}, new species are formed, including hydroxyl, formate and methoxy, with H{sub 2}O providing the hydrogen needed for the formation of hydrogenated species.

  16. Role of Surface Water-Groundwater Interaction in Regulating Stream Water Chemistry in Urban Streams

    Science.gov (United States)

    Ledford, S. H.; Lautz, L. K.; Holdsworth, M.

    2012-12-01

    Urbanization is a major cause of stream degradation in the United States. Surface water -groundwater interaction may naturally mitigate impaired water quality associated with urbanization. Meadowbrook Creek, in Syracuse, New York, flows along a declining urbanization gradient, from headwaters that are highly channelized with armored banks to an outlet that is unconstrained and meanders through a broad, riparian floodplain. Biweekly, longitudinal stream samples were collected every 100 - 600 m in the summer and every 500 - 1000 m in the winter and analyzed for conductivity and major ions. A five well transect in the downstream floodplain was also sampled. A constant rate tracer test was used to quantify groundwater inflow longitudinally during summer baseflow. Specific conductivity decreased along the urban, channelized reach and then increased along the meandering, unconstrained section during the summer, while the opposite occurred during the winter. Nitrate concentrations along the channelized reach were low to below detection (flood plain during spring snowmelt, resulting in a year-round winter road salt contamination issue. Overall, the geochemistry of the channelized portion of the stream is primarily controlled by surface runoff, while the unconstrained section of Meadowbrook is strongly influenced by discharging groundwater, providing a buffering capacity during winter. Nitrate, however, increases with the presence of riparian vegetation, which has potential implications for stream restoration techniques that aim to increase organic carbon inputs to streams, as organic matter also adds nitrogen to the system.

  17. Analysis of the effects of surface chemistry on the XAS spectra of CdSe nanomaterials

    Science.gov (United States)

    Whitley, Heather; Prendergast, David; Ogitsu, Tadashi; Schwegler, Eric

    2010-03-01

    X-ray absorption spectroscopy (XAS) is an element-specific probe of local electronic structure, and is an ideal method to analyze chemical bonding. We investigate the consistency of theoretically predicted structures of CdSe nanomaterials with recently measured XAS via ab initio calculations. Using plane-wave DFT, the x-ray absorption cross-section for the Cd L3-edge of small CdSe clusters with a variety of surface ligands is calculated. We also highlight the importance of including excitonic effects in our simulations of core excitation spectra. We compare our simulations to existing experimental data on the ligand dependence of XAS for ligated quantum dots up to ˜3nm in diameter. Based on the favorable comparison of our theoretical spectra with experimental measurements, we infer the validity of our DFT-derived structure and surface passivation for these quantum dots and its relevance to understanding optoelectronic properties of solution-synthesized CdSe nanocrystals. Prepared by LLNL under Contract DE-AC52-07NA27344.

  18. Understanding the Effect of Surface Chemistry on Charge Generation and Transport in Poly (3-hexylthiophene)/CdSe Hybrid Solar Cells

    DEFF Research Database (Denmark)

    Lek, Jun Yan; Xi, Lifei; Kardynal, Beata;

    2011-01-01

    For hybrid solar cells, interfacial chemistry is one of the most critical factors for good device performance. We have demonstrated that the size of the surface ligands and the dispersion of nanoparticles in the solvent and in the polymer are important criteria in obtaining optimized device...

  19. Adsorption of a Textile Dye on Commercial Activated Carbon: A Simple Experiment to Explore the Role of Surface Chemistry and Ionic Strength

    Science.gov (United States)

    Martins, Angela; Nunes, Nelson

    2015-01-01

    In this study, an adsorption experiment is proposed using commercial activated carbon as adsorbent and a textile azo dye, Mordant Blue-9, as adsorbate. The surface chemistry of the activated carbon is changed through a simple oxidation treatment and the ionic strength of the dye solution is also modified, simulating distinct conditions of water…

  20. Using Raman Spectroscopy and Surface-Enhanced Raman Scattering to Identify Colorants in Art: An Experiment for an Upper-Division Chemistry Laboratory

    Science.gov (United States)

    Mayhew, Hannah E.; Frano, Kristen A.; Svoboda, Shelley A.; Wustholz, Kristin L.

    2015-01-01

    Surface-enhanced Raman scattering (SERS) studies of art represent an attractive way to introduce undergraduate students to concepts in nanoscience, vibrational spectroscopy, and instrumental analysis. Here, we present an undergraduate analytical or physical chemistry laboratory wherein a combination of normal Raman and SERS spectroscopy is used to…

  1. The design of a bipodal bis(pentafluorophenoxy)aluminate supported on silica as an activator for ethylene polymerization using surface organometallic chemistry.

    Science.gov (United States)

    Sauter, Dominique W; Popoff, Nicolas; Bashir, Muhammad Ahsan; Szeto, Kai C; Gauvin, Régis M; Delevoye, Laurent; Taoufik, Mostafa; Boisson, Christophe

    2016-04-01

    A new class of well-defined activating supports for olefin polymerization was obtained via the surface organometallic chemistry approach. High activities in slurry polymerization of ethylene along with industrial-grade physical properties of the resulting polyethylene were obtained when these activators were combined with metallocene complexes in the presence of triisobutylaluminium. PMID:26899986

  2. Covalent Coupling of Nanoparticles with Low-Density Functional Ligands to Surfaces via Click Chemistry

    Directory of Open Access Journals (Sweden)

    Ina Rianasari

    2013-02-01

    Full Text Available We demonstrate the application of the 1,3-dipolar cycloaddition (“click” reaction to couple gold nanoparticles (Au NPs functionalized with low densities of functional ligands. The ligand coverage on the citrate-stabilized Au NPs was adjusted by the ligand:Au surface atom ratio, while maintaining the colloidal stability of the Au NPs in aqueous solution. A procedure was developed to determine the driving forces governing the selectivity and reactivity of citrate-stabilized and ligand-functionalized Au NPs on patterned self-assembled monolayers. We observed selective and remarkably stable chemical bonding of the Au NPs to the complimentarily functionalized substrate areas, even when estimating that only 1–2 chemical bonds are formed between the particles and the substrate.

  3. Revisiting 30 years of Biofunctionalization and Surface Chemistry of Inorganic Nanoparticles for Nanomedicine

    Directory of Open Access Journals (Sweden)

    João eConde

    2014-07-01

    Full Text Available In the last 30 years we have assisted to a massive advance of nanomaterials in material science. Nanomaterials and structures, in addition to their small size, have properties that differ from those of larger bulk materials, making them ideal for a host of novel applications. The spread of nanotechnology in the last years has been due to the improvement of synthesis and characterization methods on the nanoscale, a field rich in new physical phenomena and synthetic opportunities. In fact, the development of functional nanoparticles has progressed exponentially over the past two decades. This work aims to extensively review 30 years of different strategies of surface modification and functionalization of noble metal (gold nanoparticles, magnetic nanocrystals and semiconductor nanoparticles, such as quantum dots. The aim of this review is not only to provide in-depth insights into the different biofunctionalization and characterization methods, but also to give an overview of possibilities and limitations of the available nanoparticles.

  4. Revisiting 30 years of biofunctionalization and surface chemistry of inorganic nanoparticles for nanomedicine

    Science.gov (United States)

    Conde, João; Dias, Jorge T.; Grazú, Valeria; Moros, Maria; Baptista, Pedro V.; de la Fuente, Jesus M.

    2014-01-01

    In the last 30 years we have assisted to a massive advance of nanomaterials in material science. Nanomaterials and structures, in addition to their small size, have properties that differ from those of larger bulk materials, making them ideal for a host of novel applications. The spread of nanotechnology in the last years has been due to the improvement of synthesis and characterization methods on the nanoscale, a field rich in new physical phenomena and synthetic opportunities. In fact, the development of functional nanoparticles has progressed exponentially over the past two decades. This work aims to extensively review 30 years of different strategies of surface modification and functionalization of noble metal (gold) nanoparticles, magnetic nanocrystals and semiconductor nanoparticles, such as quantum dots. The aim of this review is not only to provide in-depth insights into the different biofunctionalization and characterization methods, but also to give an overview of possibilities and limitations of the available nanoparticles. PMID:25077142

  5. Tailoring the Surface Chemistry of Zeolite Templated Carbon by Electrochemical Methods

    Directory of Open Access Journals (Sweden)

    R. Berenguer

    2013-01-01

    Full Text Available One option to optimize carbon materials forsupercapacitor applications is the generation ofsurface functional groups that contribute to thepseudocapacitance without losing the designedphysical properties. This requires suitablefunctionalization techniques able to selectivelyintroduce a given amount of electroactive oxygengroups. In this work, the influence of the chemical andelectrochemical oxidation methods, on the chemicaland physical properties of a zeolite templated carbon(ZTC, as a model carbon material, have beenstudied and compared. Although both oxidationmethods generally produce a loss of the originalZTC physical properties with increasing amount ofoxidation, the electrochemical method shows muchbetter controllability and, unlike chemical treatments,enables the generation of a large number of oxygengroups (O = 11000- 3300 μmol/g, with a higherproportion of active functionalities, while retaining ahigh surface area (ranging between 1900-3500 m2/g,a high microporosity and an ordered 3-D structure.

  6. Effect of adhesion proteins and surface chemistry on the procoagulant state of adherent platelets

    Science.gov (United States)

    Grunkemeier, John Mark

    Poor hemocompatibility of a blood contacting device can lead to blood clotting, reduced blood flow, and depletion of platelets from the blood. Improved understanding of the processes by which blood-material contact leads to these responses could result in more hemocompatible materials. Platelets accelerate blood clotting by adhesion, aggregation, secretion of proteins and agonists and acceleration of thrombin generation. Platelets are said to be "procoagulant" after phosphatidylserine residues flip from the cytosolic to the extracellular face of the lipid bilayer. This then allows for the assembly of the prothrombinase complex (Xa, Va and calcium) on the platelet membrane, which can rapidly convert prothrombin to thrombin. In this study, three different methods confirmed that adhesion causes platelets to become procoagulant: shortening of clotting times of recalcified plasma, binding of FITC-annexin V, and generation of thrombin in the presence of Va, Xa and prothrombin by adherent platelets. Adherent platelets were 10--23 times more activated than bulk phase unactivated platelets and 10--24 times less activated than bulk phase platelets activated by calcium ionophore. The role of adsorbed fibrinogen, vWF, mixtures of fibrinogen and vWF, fibronectin, whole and dilute plasma, and plasma deficient in adhesion proteins in stimulating platelet procoagulant activity was investigated. The results of these experiments suggested that adhesion proteins affect procoagulant activation to varying degrees and that surfaces preadsorbed with mixtures of adhesion proteins are more activating that surfaces preadsorbed with single adhesion proteins. The hypothesis that materials that affect tightness of binding of adsorbed adhesion proteins affect platelet procoagulant activity was investigated. These studies showed that increasing fluorine content of RFGD polymerized films caused reduced platelet adhesion, but increased procoagulant activity, possibly due to their ability to adsorb

  7. An Assessment of Cell Culture Plate Surface Chemistry for in Vitro Studies of Tissue Engineering Scaffolds

    Directory of Open Access Journals (Sweden)

    Alexander Röder

    2015-11-01

    Full Text Available The use of biopolymers as a three dimensional (3D support structure for cell growth is a leading tissue engineering approach in regenerative medicine. Achieving consistent cell seeding and uniform cell distribution throughout 3D scaffold culture in vitro is an ongoing challenge. Traditionally, 3D scaffolds are cultured within tissue culture plates to enable reproducible cell seeding and ease of culture media change. In this study, we compared two different well-plates with different surface properties to assess whether seeding efficiencies and cell growth on 3D scaffolds were affected. Cell attachment and growth of murine calvarial osteoblast (MC3T3-E1 cells within a melt-electrospun poly-ε-caprolactone scaffold were assessed when cultured in either “low-adhesive” non-treated or corona discharged-treated well-plates. Increased cell adhesion was observed on the scaffold placed in the surface treated culture plates compared to the scaffold in the non-treated plates 24 h after seeding, although it was not significant. However, higher cell metabolic activity was observed on the bases of all well-plates than on the scaffold, except for day 21, well metabolic activity was higher in the scaffold contained in non-treated plate than the base. These results indicate that there is no advantage in using non-treated plates to improve initial cell seeding in 3D polymeric tissue engineering scaffolds, however non-treated plates may provide an improved metabolic environment for long-term studies.

  8. A Nisin Bioassay Based on Bioluminescence

    OpenAIRE

    Wahlström, G.; Saris, P. E. J.

    1999-01-01

    A Lactococcus lactis subsp. lactis strain that can sense the bacteriocin nisin and transduce the signal into bioluminescence was constructed. By using this strain, a bioassay based on bioluminescence was developed for quantification of nisin, for detection of nisin in milk, and for identification of nisin-producing strains. As little as 0.0125 ng of nisin per ml was detected within 3 h by this bioluminescence assay. This detection limit was lower than in previously described methods.

  9. Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy

    Science.gov (United States)

    Sarkar, Gautam

    Bioactive materials such as BioglassRTM 45S5 (45% SiO 2, 24.5% CaO, 24.5% Na2O, and 6% P2O5 by weight) are sodium-phosphosilicate glasses containing independent three-dimensional silicate and phosphate networks and Na+ and Ca2+ ions as modifying cations. Due to their bioactivity, these materials are currently used as implants and for other surgical and clinical applications. The bioactivity of BioglassesRTM is due to their unique capability to form chemical bonds to tissues through an octacalciumphosphate (OCP)- and/or hydroxyapatite-like (HA) "interfacial" matrix. The formation of OCP and/or HA is preceded by the formation of a silica-rich surface layer and the subsequent growth of an amorphous calcium phosphate (a-CP) layer. Structural characterization of a series of commercial and synthesized Bioglass materials 45S5 52S, 55S, 60S, and synthesized 17O-labelled "Bioglass materials 45S, 52S, 55S and 60S" have been obtained using solid-state single-pulse magic-angle spinning (SP/MAS) 17O, 23Na, 29Si and 31P NMR. The 17O NMR isotropic chemical shifts and estimates of the quadrupole coupling constants (Cq) [at fixed asymmetry parameter ( hQ ) values of zero] have been obtained from solid-state spin-echo 17O SP/MAS NMR spectra of 17O-labelled "Bioglasses". The simulation results of these spectra reveal the presence of both bridging-oxygens (BO, i.e. ≡ Si-17OSi ≡ ) and non-bridging oxygens (NBO, i.e. ≡ Si-17O-Na+/Ca2+ ) in the silicate networks in these materials. 17O NMR spectra of these Bioglass materials do not show any direct evidence for the presence of BO and NBO atoms in the phosphate units; however, they are expected to be present in small amounts. In vitro reactions of BioglassRTM 45S5, 60S and 77S powders have been used to study the "interfacial" surface chemistry of these materials in simulated body-fluid (SBF, Kyoto or K9 solution) and/or 17O-enriched tris-buffer solution. 29Si and 31P SP/MAS NMR have been used to identify and quantify the extent of

  10. Sensing properties of light-emitting single walled carbon nanotubes prepared via click chemistry of ylides bound to the nanotube surface.

    OpenAIRE

    Bayazit, M. K.; Palsson, L. O.; Coleman, K. S.

    2015-01-01

    Pyridinium ylide functionalized single-walled carbon nanotubes (SWCNTs) generated from simple quaternary pyridinium salts covalently bound to the SWCNT surface undergo a 1, 3 dipolar cycloaddition with dimethyl acetylenedicarboxylate in a ‘click’ chemistry type fashion to yield indolizine modified light-emitting SWCNTs. Conversion of quaternary pyridinium salts into indolizines on the SWCNT surface was confirmed by XPS, fluorescence spectroscopy and optical microscopy. The resulting modified ...

  11. Chemistry and isotopic composition of precipitation and surface waters in Khumbu valley (Nepal Himalaya): N dynamics of high elevation basins

    International Nuclear Information System (INIS)

    We monitored the chemical and isotopic compositions of wet depositions, at the Pyramid International Laboratory (5050 m a.s.l.), and surrounding surface waters, in the Khumbu basin, to understand precipitation chemistry and to obtain insights regarding ecosystem responses to atmospheric inputs. The major cations in the precipitation were NH4+ and Ca2+, whereas the main anion was HCO3−, which constituted approximately 69% of the anions, followed by NO3−, SO42− and Cl−. Data analysis suggested that Na+, Cl− and K+ were derived from the long-range transport of marine aerosols. Ca2+, Mg2+ and HCO3− were related to rock and soil dust contributions and the NO3− and SO42− concentrations were derived from anthropogenic sources. Furthermore, NH4+ was derived from gaseous NH3 scavenging. The isotopic composition of weekly precipitation ranged from − 1.9 to − 23.2‰ in δ18O, and from − 0.8 to − 174‰ in δ2H, with depleted values characterizing the central part of the monsoon period. The chemical composition of the stream water was dominated by calcite and/or gypsum dissolution. However, the isotopic composition of the stream water did not fully reflect the composition of the monsoon precipitation, which suggested that other water sources contributed to the stream flow. Precipitation contents for all ions were the lowest ones among those measured in high elevation sites around the world. During the monsoon periods the depositions were not substantially influenced by anthropogenic inputs, while in pre- and post-monsoon seasons the Himalayas could not represent an effective barrier for airborne pollution. In the late monsoon phase, the increase of ionic contents in precipitation could also be due to a change in the moisture source. The calculated atmospheric N load (0.30 kg ha−1 y−1) was considerably lower than the levels that were measured in other high-altitude environments. Nevertheless, the NO3− concentrations in the surface waters (from 2

  12. A versatile electrowetting-based digital microfluidic platform for quantitative homogeneous and heterogeneous bio-assays

    International Nuclear Information System (INIS)

    Electrowetting-on-dielectric (EWOD) lab-on-a-chip systems have already proven their potential within a broad range of bio-assays. Nevertheless, research on the analytical performance of those systems is limited, yet crucial for a further breakthrough in the diagnostic field. Therefore, this paper presents the intrinsic possibilities of an EWOD lab-on-a-chip as a versatile platform for homogeneous and heterogeneous bio-assays with high analytical performance. Both droplet dispensing and splitting cause variations in droplet size, thereby directly influencing the assay's performance. The extent to which they influence the performance is assessed by a theoretical sensitivity analysis, which allows the definition of a basic framework for the reduction of droplet size variability. Taking advantage of the optimized droplet manipulations, both homogeneous and heterogeneous bio-assays are implemented in the EWOD lab-on-a-chip to demonstrate the analytical capabilities and versatility of the device. A fully on-chip enzymatic assay is realized with high analytical performance. It demonstrates the promising capabilities of an EWOD lab-on-a-chip in food-related and medical applications, such as nutritional and blood analyses. Further, a magnetic bio-assay for IgE detection using superparamagnetic nanoparticles is presented whereby the nanoparticles are used as solid carriers during the bio-assay. Crucial elements are the precise manipulation of the superparamagnetic nanoparticles with respect to dispensing and separation. Although the principle of using nano-carriers is demonstrated for protein detection, it can be easily extended to a broader range of bio-related applications like DNA sensing. In heterogeneous bio-assays the chip surface is actively involved during the execution of the bio-assay. Through immobilization of specific biological compounds like DNA, proteins and cells a reactive chip surface is realized, which enhances the bio-assay performance. To

  13. Role of lattice mismatch and surface chemistry in the formation of epitaxial semiconductor-insulator interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Olmstead, M.A. (Department of Physics, University of California, Berkeley, Berkeley, California 94720 (USA)); Bringans, R.D. (Xerox Corporation, Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, California 94304 (USA))

    1990-04-15

    The formation of SrF{sub 2}/Si(111) and Ge/CaF{sub 2}/Si(111) interfaces is studied with photoemission and compared to previous results for the CaF{sub 2}/Si(111) interface. The interface between SrF{sub 2} and Si(111) is found to be nonstoichiometric, similar to the interface between CaF{sub 2} and Si(111): the bonding is between Si and the cation, with a layer of fluorine missing at the interface. In the case of Ge growth on CaF{sub 2}/Si(111), a variety of effects are noted: The CaF{sub 2}/Si(111) valence-band offset is reduced by about 1 eV upon deposition of Ge at room temperature. The sticking coefficient of the Ge is significantly increased by preparing the CaF{sub 2} surface with electron bombardment to remove the top layer of fluorine. For both the irradiated and nonirradiated cases, annealing of thin room-temperature-deposited films resulted in Ge island formation.

  14. Analysis Of Post-Wet-Chemistry Heat Treatment Effects On Nb SRF Surface Resistance

    International Nuclear Information System (INIS)

    Most of the current research in superconducting radio frequency (SRF) cavities is focused on ways to reduce the construction and operating cost of SRF-based accelerators as well as on the development of new or improved cavity processing techniques. The increase in quality factors is the result of the reduction of the surface resistance of the materials. A recent test on a 1.5 GHz single cell cavity made from ingot niobium of medium purity and heat treated at 1400 °C in a ultra-high vacuum induction furnace resulted in a residual resistance of ∼ 1nΩ and a quality factor at 2.0 K increasing with field up to ∼ 5A-1010 at a peak magnetic field of 90 mT. In this contribution, we present some results on the investigation of the origin of the extended Q0-increase, obtained by multiple HF rinses, oxypolishing and heat treatment of A ''all NbA'' cavities

  15. Carbon nanotubes' surface chemistry determines their potency as vaccine nanocarriers in vitro and in vivo

    Science.gov (United States)

    Hassan, Hatem A.F.M.; Smyth, Lesley; Rubio, Noelia; Ratnasothy, Kulachelvy; Wang, Julie T.-W.; Bansal, Sukhvinder S.; Summers, Huw D.; Diebold, Sandra S.; Lombardi, Giovanna; Al-Jamal, Khuloud T.

    2016-01-01

    Carbon nanotubes (CNTs) have shown marked capabilities in enhancing antigen delivery to antigen presenting cells. However, proper understanding of how altering the physical properties of CNTs may influence antigen uptake by antigen presenting cells, such as dendritic cells (DCs), has not been established yet. We hypothesized that altering the physical properties of multi-walled CNTs (MWNTs)-antigen conjugates, e.g. length and surface charge, can affect the internalization of MWNT-antigen by DCs, hence the induced immune response potency. For this purpose, pristine MWNTs (p-MWNTs) were exposed to various chemical reactions to modify their physical properties then conjugated to ovalbumin (OVA), a model antigen. The yielded MWNTs-OVA conjugates were long MWNT-OVA (~ 386 nm), bearing net positive charge (5.8 mV), or short MWNTs-OVA (~ 122 nm) of increasing negative charges (− 23.4, − 35.8 or − 39 mV). Compared to the short MWNTs-OVA bearing high negative charges, short MWNT-OVA with the lowest negative charge demonstrated better cellular uptake and OVA-specific immune response both in vitro and in vivo. However, long positively-charged MWNT-OVA showed limited cellular uptake and OVA specific immune response in contrast to short MWNT-OVA displaying the least negative charge. We suggest that reduction in charge negativity of MWNT-antigen conjugate enhances cellular uptake and thus the elicited immune response intensity. Nevertheless, length of MWNT-antigen conjugate might also affect the cellular uptake and immune response potency; highlighting the importance of physical properties as a consideration in designing a MWNT-based vaccine delivery system. PMID:26802552

  16. Surface kinetics modeling of silicon and silicon oxide plasma etching. III. Modeling of silicon oxide etching in fluorocarbon chemistry using translating mixed-layer representation

    International Nuclear Information System (INIS)

    Silicon oxide etching was modeled using a translating mixed-layer model, a novel surface kinetic modeling technique, and the model showed good agreement with measured data. Carbon and fluorine were identified as the primary contributors to deposition and etching, respectively. Atomic fluorine flux is a major factor that determines the etching behavior. With a chemistry having a small amount of atomic fluorine (such as the C4F8 chemistry), etching yield shows stronger dependence on the composition change in the gas flux

  17. Testing grain surface chemistry a survey of deuterated formaldehyde and methanol in low-mass Class 0 protostars

    CERN Document Server

    Parise, B; Caux, E; Ceccarelli, C; Le Floc'h, B; Maret, S; Tielens, A G G M

    2006-01-01

    Context : Despite the low cosmic abundance of deuterium (D/H ~ 1e-5), large degrees of deuterium fractionation in molecules are observed in star forming regions with enhancements that can reach 13 orders of magnitude, which current models have difficulties to account for. Aims : Multi-isotopologue observations are a very powerful constraint for chemical models. The aim of our observations is to understand the processes forming the observed large abundances of methanol and formaldehyde in low-mass protostellar envelopes (gas-phase processes ? chemistry on the grain surfaces ?) and better constrain the chemical models. Methods : Using the IRAM 30m single-dish telescope, we observed deuterated formaldehyde (HDCO and D2CO) and methanol (CH2DOH, CH3OD, and CHD2OH) towards a sample of seven low-mass class 0 protostars. Using population diagrams, we then derive the fractionation ratios of these species (abundance ratio between the deuterated molecule and its main isotopologue) and compare them to the predictions of ...

  18. Identification of parameters through which surface chemistry determines the lifetimes of hot electrons in small Au nanoparticles.

    Science.gov (United States)

    Aruda, Kenneth O; Tagliazucchi, Mario; Sweeney, Christina M; Hannah, Daniel C; Schatz, George C; Weiss, Emily A

    2013-03-12

    This paper describes measurements of the dynamics of hot electron cooling in photoexcited gold nanoparticles (Au NPs) with diameters of ∼3.5 nm, and passivated with either a hexadecylamine or hexadecanethiolate adlayer, using ultrafast transient absorption spectroscopy. Fits of these dynamics with temperature-dependent Mie theory reveal that both the electronic heat capacity and the electron-phonon coupling constant are larger for the thiolated NPs than for the aminated NPs, by 40% and 30%, respectively. Density functional theory calculations on ligand-functionalized Au slabs show that the increase in these quantities is due to an increased electronic density of states near the Fermi level upon ligand exchange from amines to thiolates. The lifetime of hot electrons, which have thermalized from the initial plasmon excitation, increases with increasing electronic heat capacity, but decreases with increasing electron-phonon coupling, so the effects of changing surface chemistry on these two quantities partially cancel to yield a hot electron lifetime of thiolated NPs that is only 20% longer than that of aminated NPs. This analysis also reveals that incorporation of a temperature-dependent electron-phonon coupling constant is necessary to adequately fit the dynamics of electron cooling. PMID:23440215

  19. Green chemistry focus on optimization of silver nanoparticles using response surface methodology (RSM) and mosquitocidal activity: Anopheles stephensi (Diptera: Culicidae).

    Science.gov (United States)

    Ondari Nyakundi, Erick; Padmanabhan, M Nalini

    2015-10-01

    There is an exigent necessity for development of environmental friendly bio-control agent(s) for elimination of mosquito due to increased resistance resurgence against synthetic control agents. Mosquito control strategy will lay a strong foundation to malaria exclusion or it can be curbed to certain level especially in the developing nations. In this study, silver nanoparticles were synthesized by green chemistry approach using Tridax procumbens leaf extract as a reducing agent. The reaction medium involved in the synthesis process was optimized by statistical experimental design using response surface methodology to obtain better yield, uniform size, shape and stability. Further, these synthesized nanoparticles were confirmed through UV-Visible, FT-IR spectroscopy, PSA and SEM Subsequently, the bioefficacy of these particles were investigated on Anopheles stephensi for larvicidal and pupicidal activity. Interestingly, time period of 90 min, temperature of 76±2 °C, pH 7.2±2, 2 mM silver nitrate (AgNO3), 3mM PEG and 2mM PVP showed excellent parameters for bioprocess design for large scale production of stabilized nanoparticles. A concentration of 5 ppm of PVP stabilized nanoparticles exhibited 100% mortality. Thus, the obtained results clearly suggest that silver nanoparticles stabilized by PEG and PVP may have important function as stabilizers, dispersants as well as larvicides for mosquito control. PMID:26010566

  20. Anticorrelation between Surface and Subsurface Point Defects and the Impact on the Redox Chemistry of TiO2(110)

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Yeohoon; Du, Yingge; Garcia, Juan C.; Zhu, Zihua; Wang, Zhitao; Petrik, Nikolay G.; Kimmel, Gregory A.; Dohnalek, Zdenek; Henderson, Michael A.; Rousseau, Roger J.; Deskins, N. Aaron; Lyubinetsky, Igor

    2015-02-02

    Using combination of STM, DFT and SIMS, we explored the interplay and relative impact of surface vs. subsurface defects on the surface chemistry of rutile TiO2. STM results show that surface O vacancies (VO’s) are virtually absent in the vicinity of positively-charged subsurface point-defects. This observation is consistent with DFT calculations of impact of subsurface defect proximity on VO formation energy. To monitor the influence of such lateral anticorrelation on surface redox chemistry, a test reaction of the dissociative adsorption of O2 is employed, which is observed to be suppressed around them. DFT results attribute this to a perceived absence of the intrinsic (Ti) (and likely extrinsic) interstitials in the nearest subsurface layer beneath “inhibited” areas. We also postulate that the entire nearest subsurface region could be voided of any charged point-defects, whereas prevalent VO’s are largely responsible for mediation of the redox chemistry at reduced TiO2(110) surface.

  1. Adsorption and thermal chemistry of formic acid on clean and oxygen-predosed Cu(110) single-crystal surfaces revisited

    Science.gov (United States)

    Yao, Yunxi; Zaera, Francisco

    2016-04-01

    The thermal chemistry of formic acid on clean and oxygen-predosed Cu(110) single-crystal surfaces was studied under ultrahigh-vacuum (UHV) conditions by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Key results reported in the past were confirmed, including the partial switchover from H2 to H2O desorption upon oxygen addition on the surface and the development of a second decomposition regime at 420 K, in addition to the one observed at 460 K on the clean substrate. In addition, new observations were added, including the previously missed desorption of H2 at 420 K and the existence of a normal kinetic isotope effect in both TPD peaks. Peak fitting of the XPS data afforded the identification of an asymmetric geometry for the formate intermediate, which was established to form by 200 K, and the presence of coadsorbed molecular formic acid up to the temperatures of decomposition, probably in a second layer and held by hydrogen bonding. Quantitative analysis of the TPD data indicated a one-to-one correspondence between the increase in oxygen coverage beyond θO = 0.5 ML and a decrease in formic acid uptake that mainly manifests itself in a decrease in the decomposition seen in the 460 K TPD peak. All these observations were interpreted in terms of a simple decomposition mechanism involving hydrogen abstraction from adsorbed formate species, possibly aided by coadsorbed oxygen, and a change in reaction activation energy as a function of the structure of the oxygen overlayer, which reverts from a O-c(6 × 2) structure at high oxygen coverages to the O-(2 × 1) order seen at θO = 0.5 ML.

  2. Changes in silver nanoparticles exposed to human synthetic stomach fluid: Effects of particle size and surface chemistry

    International Nuclear Information System (INIS)

    The significant rise in consumer products and applications utilizing the antibacterial properties of silver nanoparticles (AgNPs) has increased the possibility of human exposure. The mobility and bioavailability of AgNPs through the ingestion pathway will depend, in part, on properties such as particle size and the surface chemistries that will influence their physical and chemical reactivities during transit through the gastrointestinal tract. This study investigates the interactions between synthetic stomach fluid and AgNPs of different sizes and with different capping agents. Changes in morphology, size and chemical composition were determined during a 30 min exposure to synthetic human stomach fluid (SSF) using Absorbance Spectroscopy, High Resolution Transmission Electron and Scanning Electron Microscopy (TEM/SEM), Dynamic Light Scattering (DLS), and Nanoparticle Tracking Analysis (NTA). AgNPs exposed to SSF were found to aggregate significantly and also released ionic silver which physically associated with the particle aggregates as silver chloride. Generally, the smaller sized AgNPs (< 10 nm) showed higher rates of aggregation and physical transformation than larger particles (75 nm). Polyvinylpyrrolidone (pvp)-stabilized AgNPs prepared in house behaved differently in SSF than particles obtained from a commercial source despite having similar surface coating and size distribution characteristics. - Highlights: ► Interactions between synthetic stomach fluid (SSF) and silver nanoparticles (AgNPs) are described. ► AgNPs exposed to SSF aggregate and silver chloride are associated with the particle aggregates. ► Smaller AgNPs (< 10 nm) showed higher rates of aggregation and transformation than larger particles (75 nm). ► Polyvinylpyrrolidone-stabilized AgNPs obtained from different sources aggregated at different rates when exposed to SSF

  3. Surface chemistry and flotation behavior of monazite, apatite, ilmenite, quartz, rutile, and zircon using octanohydroxamic acid collector

    Science.gov (United States)

    Nduwa Mushidi, Josue

    Global increase in rare earth demand and consumption has led to further understanding their beneficiation and recovery. Monazite is the second most important rare earth mineral that can be further exploited. In this study, the surface chemistry of monazite in terms of zeta potential, adsorption density, and flotation response by microflotation using octanohydroxamic acid is determined. Apatite, ilmenite, quartz, rutile, and zircon are minerals that frequently occur with monazite among other minerals. Hence they were chosen as gangue minerals in this study. The Iso Electric Point (IEP) of monazite, apatite, ilmenite, quartz, rutile, and zircon are 5.3, 8.7, 3.8, 3.4, 6.3, and 5.1 respectively. The thermodynamic parameters of adsorption were also evaluated. Ilmenite, rutile and zircon have high driving forces for adsorption with DeltaGads. = 20.48, 22.10, and 22.4 kJ/mol respectively. The free energy of adsorption is 14.87 kJ/mol for monazite. Adsorption density testing shows that octanohydroxamic acid adsorbs on negatively charged surfaces of monazite and its gangue minerals which indicates chemisorption. This observation was further confirmed by microflotation experiments. Increasing the temperature to 80°C raises the adsorption and flotability of monazite and gangue minerals. This does not allow for effective separation. Sodium silicate appeared to be most effective to depress associated gangue minerals. Finally, the fundamentals learned were applied to the flotation of monazite ore from Mt. Weld. However, these results showed no selectivity due to the presence of goethite as fine particles and due to a low degree of liberation of monazite in the ore sample.

  4. Ground-water, surface-water, and water-chemistry data, Black Mesa area, northeastern Arizona--2003-04

    Science.gov (United States)

    Truini, Margot; Macy, Jamie P.; Porter, Thomas J.

    2005-01-01

    The N aquifer is the major source of water in the 5,400-square-mile area of Black Mesa in northeastern Arizona. Availability of water is an important issue in this area because of continued industrial and municipal use, a growing population, and precipitation of about 6 to 14 inches per year. The monitoring program in the Black Mesa area has been operating since 1971 and is designed to determine the long-term effects of ground-water withdrawals from the N aquifer for industrial and municipal uses. The monitoring program includes measurements of (1) ground-water pumping, (2) ground-water levels, (3) spring discharge, (4) surface-water discharge, (5) ground-water chemistry, and (6) periodic testing of ground-water withdrawal meters. In 2003, total ground-water withdrawals were 7,240 acre-feet, industrial withdrawals were 4,450 acre-feet, and municipal withdrawals were 2,790 acre-feet. From 2002 to 2003, total withdrawals decreased by 10 percent, industrial withdrawals decreased by 4 percent, and municipal withdrawals decreased by 20 percent. Flowmeter testing was completed for 24 municipal wells in 2004. The median difference between pumping rates for the permanent meter and a test meter for all the sites tested was -2.9 percent. Values ranged from -10.9 percent at Forest Lake NTUA 1 to +7.8 percent at Rough Rock NTUA 2. From 2003 to 2004, water levels declined in 6 of 12 wells in the unconfined part of the aquifer, and the median change was -0.1 foot. Water levels declined in 7 of 11 wells in the confined part of the aquifer, and the median change was -2.7 feet. From the prestress period (prior to 1965) to 2003, the median water-level change for 26 wells was -23.2 feet. Median water-level change were -6.1 feet for 14 wells in the unconfined parts of the aquifer and and -72.1 feet for 12 wells in the confined part. Discharges were measured once in 2003 and once in 2004 at four springs. Discharge stayed the same at Pasture Canyon Spring, increased 9 percent at

  5. A Unified Monte Carlo Treatment of Gas-Grain Chemistry for Large Reaction Networks. II. A Multiphase Gas-Surface-Layered Bulk Model

    CERN Document Server

    Vasyunin, A I

    2012-01-01

    The observed gas-phase molecular inventory of hot cores is believed to be significantly impacted by the products of chemistry in interstellar ices. In this study, we report the construction of a full macroscopic Monte Carlo model of both the gas-phase chemistry and the chemistry occurring in the icy mantles of interstellar grains. Our model treats icy grain mantles in a layer-by-layer manner, which incorporates laboratory data on ice desorption correctly. The ice treatment includes a distinction between a reactive ice surface and an inert bulk. The treatment also distinguishes between zeroth and first order desorption, and includes the entrapment of volatile species in more refractory ice mantles. We apply the model to the investigation of the chemistry in hot cores, in which a thick ice mantle built up during the previous cold phase of protostellar evolution undergoes surface reactions and is eventually evaporated. For the first time, the impact of a detailed multilayer approach to grain mantle formation on ...

  6. A Multichannel Bioluminescence Determination Platform for Bioassays.

    Science.gov (United States)

    Kim, Sung-Bae; Naganawa, Ryuichi

    2016-01-01

    The present protocol introduces a multichannel bioluminescence determination platform allowing a high sample throughput determination of weak bioluminescence with reduced standard deviations. The platform is designed to carry a multichannel conveyer, an optical filter, and a mirror cap. The platform enables us to near-simultaneously determine ligands in multiple samples without the replacement of the sample tubes. Furthermore, the optical filters beneath the multichannel conveyer are designed to easily discriminate colors during assays. This optical system provides excellent time- and labor-efficiency to users during bioassays. PMID:27424912

  7. Surface modification of Fe2O3 nanoparticles with 3-aminopropyltrimethoxysilane (APTMS): An attempt to investigate surface treatment on surface chemistry and mechanical properties of polyurethane/Fe2O3 nanocomposites

    International Nuclear Information System (INIS)

    Highlights: • Surface treatment of Fe2O3 with amino propyl tri methoxy silane. • The surface chemistry pigments were affected by the chemical treatment. • Surface treatment of the nanoparticles by silane resulted in the significant improvement of the mechanical properties of the polyurethane coating. • The improvement was most pronounced when the nanoparticles were modified with 3 gr silane/5 g nanoparticles. - Abstract: Fe2O3 nanoparticles were modified with various amounts of 3-amino propyl trimethoxy silane (APTMS). Modified and unmodified nanoparticles were introduced into the polyurethane matrix at different concentrations. Fourier transform infrared radiation (FT-IR) and X-ray photoelectron spectrophotometer (XPS) were employed in order to investigate the APTMS grafting on the nanoparticles field emission-scanning electron microscope (FE-SEM) was utilized in order to investigate nanoparticles dispersion in the polyurethane coating matrix as well as the fracture behavior of the nanocomposites. The mechanical properties of the nanocomposites were investigated by dynamic mechanical thermal analysis (DMTA) and tensile test. The FTIR spectra and XPS analysis clearly showed that APTMS was grafted on the surface of nanoparticles successfully and formed chemical bonds with the surface. Also, surface treatment of the nanoparticles by silane resulted in the significant improvement of the mechanical properties of the polyurethane coating. The improvement was most pronounced when the nanoparticles were modified with 3 gr silane/5 g nanoparticles

  8. Surface modification of Fe{sub 2}O{sub 3} nanoparticles with 3-aminopropyltrimethoxysilane (APTMS): An attempt to investigate surface treatment on surface chemistry and mechanical properties of polyurethane/Fe{sub 2}O{sub 3} nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Palimi, M.J. [Institute for Color Science and Technology (ICST), PO 16765-654, Tehran (Iran, Islamic Republic of); Rostami, M., E-mail: rostami-m@icrc.ac.ir [Department of Nanomaterials and Nanocoatings, Institute for Color Science and Technology (ICST), PO 16765-654, Tehran (Iran, Islamic Republic of); Mahdavian, M.; Ramezanzadeh, B. [Department of Surface Coatings and Corrosion, Institute for Color Science and Technology (ICST), PO 16765-654, Tehran (Iran, Islamic Republic of)

    2014-11-30

    Highlights: • Surface treatment of Fe{sub 2}O{sub 3} with amino propyl tri methoxy silane. • The surface chemistry pigments were affected by the chemical treatment. • Surface treatment of the nanoparticles by silane resulted in the significant improvement of the mechanical properties of the polyurethane coating. • The improvement was most pronounced when the nanoparticles were modified with 3 gr silane/5 g nanoparticles. - Abstract: Fe{sub 2}O{sub 3} nanoparticles were modified with various amounts of 3-amino propyl trimethoxy silane (APTMS). Modified and unmodified nanoparticles were introduced into the polyurethane matrix at different concentrations. Fourier transform infrared radiation (FT-IR) and X-ray photoelectron spectrophotometer (XPS) were employed in order to investigate the APTMS grafting on the nanoparticles field emission-scanning electron microscope (FE-SEM) was utilized in order to investigate nanoparticles dispersion in the polyurethane coating matrix as well as the fracture behavior of the nanocomposites. The mechanical properties of the nanocomposites were investigated by dynamic mechanical thermal analysis (DMTA) and tensile test. The FTIR spectra and XPS analysis clearly showed that APTMS was grafted on the surface of nanoparticles successfully and formed chemical bonds with the surface. Also, surface treatment of the nanoparticles by silane resulted in the significant improvement of the mechanical properties of the polyurethane coating. The improvement was most pronounced when the nanoparticles were modified with 3 gr silane/5 g nanoparticles.

  9. Chemistry and isotopic composition of precipitation and surface waters in Khumbu valley (Nepal Himalaya): N dynamics of high elevation basins

    Energy Technology Data Exchange (ETDEWEB)

    Balestrini, Raffaella, E-mail: balestrini@irsa.cnr.it [Water Research Institute, National Research Council (IRSA-CNR), Via del Mulino 19, Brugherio, MB (Italy); Polesello, Stefano [Water Research Institute, National Research Council (IRSA-CNR), Via del Mulino 19, Brugherio, MB (Italy); Sacchi, Elisa [Department of Earth and Environmental Sciences, University of Pavia and IGG-CNR, Via Ferrata 1, 27100 Pavia (Italy)

    2014-07-01

    We monitored the chemical and isotopic compositions of wet depositions, at the Pyramid International Laboratory (5050 m a.s.l.), and surrounding surface waters, in the Khumbu basin, to understand precipitation chemistry and to obtain insights regarding ecosystem responses to atmospheric inputs. The major cations in the precipitation were NH{sub 4}{sup +} and Ca{sup 2+}, whereas the main anion was HCO{sub 3}{sup −}, which constituted approximately 69% of the anions, followed by NO{sub 3}{sup −}, SO{sub 4}{sup 2−} and Cl{sup −}. Data analysis suggested that Na{sup +}, Cl{sup −} and K{sup +} were derived from the long-range transport of marine aerosols. Ca{sup 2+}, Mg{sup 2+} and HCO{sub 3}{sup −} were related to rock and soil dust contributions and the NO{sub 3}{sup −} and SO{sub 4}{sup 2−} concentrations were derived from anthropogenic sources. Furthermore, NH{sub 4}{sup +} was derived from gaseous NH{sub 3} scavenging. The isotopic composition of weekly precipitation ranged from − 1.9 to − 23.2‰ in δ{sup 18}O, and from − 0.8 to − 174‰ in δ{sup 2}H, with depleted values characterizing the central part of the monsoon period. The chemical composition of the stream water was dominated by calcite and/or gypsum dissolution. However, the isotopic composition of the stream water did not fully reflect the composition of the monsoon precipitation, which suggested that other water sources contributed to the stream flow. Precipitation contents for all ions were the lowest ones among those measured in high elevation sites around the world. During the monsoon periods the depositions were not substantially influenced by anthropogenic inputs, while in pre- and post-monsoon seasons the Himalayas could not represent an effective barrier for airborne pollution. In the late monsoon phase, the increase of ionic contents in precipitation could also be due to a change in the moisture source. The calculated atmospheric N load (0.30 kg ha{sup −1} y{sup −1

  10. Critical stages of a biodetection platform development from sensor chip fabrication to surface chemistry and assay development

    Science.gov (United States)

    Uludag, Yildiz

    2014-06-01

    Once viewed solely as a tool to analyse biomolecular interactions, biosensors are gaining widespread interest for diagnostics, biological defense, environmental and quality assurance in agriculture/food industries. Advanced micro fabrication techniques have facilitated integration of microfluidics with sensing functionalities on the same chip making system automation more convenient1. Biosensor devices relying on lab-on-a-chip technologies and nanotechnology has attracted much of attention in recent years for biological defense research and development. However, compared with the numerous publications and patents available, the commercialization of biosensors technology has significantly lagged behind the research output. This paper reviews the reasons behind the slow commercialisation of biosensors with an insight to the critical stages of a biosensor development from the sensor chip fabrication to surface chemistry applications and nanotechnology applications in sensing with case studies. In addition, the paper includes the description of a new biodetection platform based on Real-time Electrochemical ProfilingTM (REPTM) that comprises novel electrode arrays and nanoparticle based sensing. The performance of the REPTM platform has been tested for the detection of Planktothrix agardhii, one of the toxic bloom-forming cyanobacteria, usually found in shallow fresh water sources that can be used for human consumption. The optimised REPTM assay allowed the detection of P. agardhii DNA down to 6 pM. This study, showed the potential of REPTM as a new biodetection platform for toxic bacteria and hence further studies will involve the development of a portable multi-analyte biosensor based on REPTM technology for on-site testing.

  11. Thermal modification of activated carbon surface chemistry improves its capacity as redox mediator for azo dye reduction.

    Science.gov (United States)

    Pereira, L; Pereira, R; Pereira, M F R; van der Zee, F P; Cervantes, F J; Alves, M M

    2010-11-15

    The surface chemistry of a commercial AC (AC(0)) was selectively modified, without changing significantly its textural properties, by chemical oxidation with HNO(3) (AC(HNO3)) and O(2) (AC(O2)), and thermal treatments under H(2) (AC(H2)) or N(2) (AC(N2)) flow. The effect of modified AC on anaerobic chemical dye reduction was assayed with sulphide at different pH values 5, 7 and 9. Four dyes were tested: Acid Orange 7, Reactive Red 2, Mordant Yellow 10 and Direct Blue 71. Batch experiments with low amounts of AC (0.1 g L(-1)) demonstrated an increase of the first-order reduction rate constants, up to 9-fold, as compared with assays without AC. Optimum rates were obtained at pH 5 except for MY10, higher at pH 7. In general, rates increased with increasing the pH of point zero charge (pH(pzc)), following the trend AC(HNO3) < AC(O2) < AC(0) < AC(N2) < AC(H2). The highest reduction rate was obtained for MY10 with AC(H2) at pH 7, which corresponded to the double, as compared with non-modified AC. In a biological system using granular biomass, AC(H2) also duplicated and increase 4.5-fold the decolourisation rates of MY10 and RR2, respectively. In this last experiment, reaction rate was independent of AC concentration in the tested range 0.1-0.6 g L(-1). PMID:20800966

  12. A New Approach for Detection Improvement of the Creutzfeldt-Jakob Disorder through a Specific Surface Chemistry Applied onto Titration Well

    Directory of Open Access Journals (Sweden)

    Dominique Debarnot

    2012-10-01

    Full Text Available This work illustrates the enhancement of the sensitivity of the ELISA titration for recombinant human and native prion proteins, while reducing other non-specific adsorptions that could increase the background signal and lead to a low sensitivity and false positives. It is achieved thanks to the association of plasma chemistry and coating with different amphiphilic molecules bearing either ionic charges and/or long hydrocarbon chains. The treated support by 3-butenylamine hydrochloride improves the signal detection of recombinant protein, while surface modification with the 3,7-dimethylocta-2,6-dien-1-diamine (geranylamine enhances the sensitivity of the native protein. Beside the surface chemistry effect, these different results are associated with protein conformation.

  13. Study of surface chemistry and microstructure of TiO2 nanostructures on Pt(111)/Si wafer and FTO glass substrates: a comparative approach

    Science.gov (United States)

    Roy Moulik, Samik; Ghatak, Ankita; Ghosh, Barnali

    2016-09-01

    We report, the kinetically controlled growth of the (002)-oriented TiO2 nanorods on fluorine-doped tin oxide (FTO) coated glass substrate via a cost effective hydrothermal synthesis route of binary oxides. In addition to this, the nanoflowered like growth of TiO2 nanorods using cubic structure Pt(111)/SiO2/Si substrate has also been demonstrated. Tuning of shape, crystallographic structure issues has been discussed by controlling the surface chemistry of the substrate on which the nanostructures were grown. The crystallographic structural aspects of the grown nanorods was confirmed both on ensemble and single nanowire level using spatially resolved tools and techniques. Growth mechanism for different shape, size and crystallographic structure depending on the surface chemistry of the substrate has been proposed. Understanding of growth of oriented TiO2 nanorods and interaction mechanism is quite promising and encouraging for designing optoelectronic and photocatalytic devices to enhanced electron transport and lower exciton recombination rates.

  14. Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry

    OpenAIRE

    Abdelhaq Benkaddour; Khalil Jradi; Sylvain Robert; Claude Daneault

    2013-01-01

    Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as clic...

  15. The role of surface chemistry at ceramic/electrolyte intefaces in the generation of pulsed corona discharges in water using porous ceramic-coated rod electrodes

    Czech Academy of Sciences Publication Activity Database

    Lukeš, Petr; Člupek, Martin; Babický, Václav; Šunka, Pavel

    2009-01-01

    Roč. 6, č. 11 (2009), s. 719-728. ISSN 1612-8850 R&D Projects: GA AV ČR IAAX00430802 Institutional research plan: CEZ:AV0Z20430508 Keywords : non-thermal plasma * electrical discharge * water * surface chemistry Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.037, year: 2009 http://www3.interscience.wiley.com/cgi-bin/fulltext/122593644/PDFSTART

  16. A statistical treatment of bioassay pour fractions

    Science.gov (United States)

    Barengoltz, Jack; Hughes, David

    A bioassay is a method for estimating the number of bacterial spores on a spacecraft surface for the purpose of demonstrating compliance with planetary protection (PP) requirements (Ref. 1). The details of the process may be seen in the appropriate PP document (e.g., for NASA, Ref. 2). In general, the surface is mechanically sampled with a damp sterile swab or wipe. The completion of the process is colony formation in a growth medium in a plate (Petri dish); the colonies are counted. Consider a set of samples from randomly selected, known areas of one spacecraft surface, for simplicity. One may calculate the mean and standard deviation of the bioburden density, which is the ratio of counts to area sampled. The standard deviation represents an estimate of the variation from place to place of the true bioburden density commingled with the precision of the individual sample counts. The accuracy of individual sample results depends on the equipment used, the collection method, and the culturing method. One aspect that greatly influences the result is the pour fraction, which is the quantity of fluid added to the plates divided by the total fluid used in extracting spores from the sampling equipment. In an analysis of a single sample’s counts due to the pour fraction, one seeks to answer the question: What is the probability that if a certain number of spores are counted with a known pour fraction, that there are an additional number of spores in the part of the rinse not poured. This is given for specific values by the binomial distribution density, where detection (of culturable spores) is success and the probability of success is the pour fraction. A special summation over the binomial distribution, equivalent to adding for all possible values of the true total number of spores, is performed. This distribution when normalized will almost yield the desired quantity. It is the probability that the additional number of spores does not exceed a certain value. Of course

  17. A UNIFIED MONTE CARLO TREATMENT OF GAS-GRAIN CHEMISTRY FOR LARGE REACTION NETWORKS. II. A MULTIPHASE GAS-SURFACE-LAYERED BULK MODEL

    International Nuclear Information System (INIS)

    The observed gas-phase molecular inventory of hot cores is believed to be significantly impacted by the products of chemistry in interstellar ices. In this study, we report the construction of a full macroscopic Monte Carlo model of both the gas-phase chemistry and the chemistry occurring in the icy mantles of interstellar grains. Our model treats icy grain mantles in a layer-by-layer manner, which incorporates laboratory data on ice desorption correctly. The ice treatment includes a distinction between a reactive ice surface and an inert bulk. The treatment also distinguishes between zeroth- and first-order desorption, and includes the entrapment of volatile species in more refractory ice mantles. We apply the model to the investigation of the chemistry in hot cores, in which a thick ice mantle built up during the previous cold phase of protostellar evolution undergoes surface reactions and is eventually evaporated. For the first time, the impact of a detailed multilayer approach to grain mantle formation on the warm-up chemistry is explored. The use of a multilayer ice structure has a mixed impact on the abundances of organic species formed during the warm-up phase. For example, the abundance of gaseous HCOOCH3 is lower in the multilayer model than in previous grain models that do not distinguish between layers (so-called two phase models). Other gaseous organic species formed in the warm-up phase are affected slightly. Finally, we find that the entrapment of volatile species in water ice can explain the two-jump behavior of H2CO previously found in observations of protostars.

  18. Comprehensive integration of homogeneous bioassays via centrifugo-pneumatic cascading.

    Science.gov (United States)

    Godino, Neus; Gorkin, Robert; Linares, Ana V; Burger, Robert; Ducrée, Jens

    2013-02-21

    This work for the first time presents the full integration and automation concept for a range of bioassays leveraged by cascading a centrifugo-pneumatic valving scheme to sequentially move several liquids through shared channel segments for multi-step sample preparation into the detection zone. This novel centrifugo-pneumatic liquid handling significantly simplifies system manufacture by obviating the need for complex surface functionalization procedures or hybrid material integration, as it is common in conventional valving methods such as capillary burst valves or sacrificial valves. Based on the centrifugo-pneumatic valving scheme, this work presents a toolkit of operational elements implementing liquid loading/transfer, metering, mixing and sedimentation in a microstructured polymer disc. As a proof of concept for the broad class of homogeneous bioassays, the full integration and automation of a colorimetric nitrate/nitrite test for the detection of clinically relevant nitric oxide (NO) in whole blood is implemented. First, 40 μL of plasma is extracted from a 100 μL sample of human blood, incubated for one hour with the enzymatic mixture (60 μL), and finally reacted with 100 μL of colorimetric (Greiss) reagents. Following just a single loading phase at the beginning of the process, all of these steps are automated through the centrifugo-pneumatic cascade with a high level of flow control and synchronization. Our system shows good correlation with controls up to 50 μM of nitrate, which adequately covers the healthy human range (4 to 45.3 μM). PMID:23250328

  19. Influence of Si substrate preparation on surface chemistry and morphology of L-CVD SnO2 thin films studied by XPS and AFM

    International Nuclear Information System (INIS)

    Results of experimental studies of the influence of substrate preparation on the surface chemistry and surface morphology of the laser-assisted chemical vapour deposition (L-CVD) SnO2 thin films are presented in this paper. The native Si(1 0 0) substrate cleaned by UHV thermal annealing (TA) as well as thermally oxidized Si(1 0 0) substrate cleaned by ion bombardment (IBA) have been used as the substrates. X-ray photoemission spectroscopy (XPS) has been used for the control of surface chemistry of the substrates as well as of deposited films. Atomic force microscopy (AFM) has been used to control the surface morphology of the L-CVD SnO2 thin films deposited on differently prepared substrates. Our XPS shows that the L-CVD SnO2 thin films deposited on thermally oxidized Si(1 0 0) substrate after cleaning with ion bombardment exhibit the same stoichiometry, i.e. ratio [O]/[Sn] = 1.30 as that of the layers deposited on Si(1 0 0) substrate previously cleaned by UHV prolonged heating. AFM shows that L-CVD SnO2 thin films deposited on thermally oxidized Si(1 0 0) substrate after cleaning with ion bombardment exhibit evidently increasing rough surface topography with respect to roughness, grain size range and maximum grain height as the L-CVD SnO2 thin films deposited on atomically clean Si substrate at the same surface chemistry (nonstoichiometry) reflect the higher substrate roughness after cleaning with ion bombardment.

  20. SINGLE LABORATORY EVALUATION OF THE HYDROGEN OXIDATION SOIL BIOASSAY

    Science.gov (United States)

    The Hydrogen Oxidation Soil Bioassay was single laboratory tested as a potential method for monitoring hazardous wastes and hazardous waste sites. The bioassay is based on the rate of hydrogen consumption by soil microorganisms. Oxidation of hydrogen to water is inhibited when va...

  1. Bad chemistry

    OpenAIRE

    Petsko, Gregory A

    2004-01-01

    General chemistry courses haven't changed significantly in forty years. Because most basic chemistry students are premedical students, medical schools have enormous influence and could help us start all over again to create undergraduate chemistry education that works.

  2. Bioassays for the detection of chemicals that can form bioactivation-dependent reactive free radicals

    Energy Technology Data Exchange (ETDEWEB)

    Sanderson, J.T.; Commandeur, J.N.M.; Wezel, A. van; Vermeulen, N.P.E. (Free Univ. of Amsterdam (Netherlands). Div. of Molecular Toxicology National Inst. for Coastal and Marine Management, Den Haag (Netherlands))

    1999-06-01

    In vitro bioassays were developed for the detection of chemicals that can be bioactivated to reactive free radical species in microsomal fractions. Two methods were deployed, a down-scaled spectrophotometric method for the detection of chemicals that can cause lipid peroxidation using the measurement of thiobarbituric acid-reactive substances (TBARS) and a fluorometric method for the detection of chemicals that can undergo redox cycling to generate superoxide radicals based on the detection of hydrogen peroxide. The response of these systems to prototypical and environmentally relevant chemicals, including tetrachloromethane and paraquat, was examined. The detection limit of the lipid peroxidation bioassay, based on the formation of TBARS, was about 1 [micro]M for tetrachloromethane; that of the bioassay for redox cyclers, based on the production of hydrogen peroxide, was about 2 [micro]M for paraquat and about 100-fold lower for the potent redox cycler 2,3,5,6-tetramethylbenzoquinone (TMBQ). Several binary mixtures of chemicals were tested for potential nonadditive effects in both in vitro systems. Some antagonistic effects among halogenated methanes were observed in the lipid peroxidation assay. In the hydrogen peroxide production assay, greater than additive effects were seen between small concentrations of paraquat and TMBQ. A number of surface water concentrates from several locations in The Netherlands, with various levels of chemical contamination, exhibited a weak response in the hydrogen peroxide production assay. Acetone was found to interfere with the response of the bioassay to redox cyclers and, therefore, the water concentrates (originally in acetone) were transferred to ethanol prior to testing. A good correlation was observed between the response of the water concentrates in the hydrogen peroxide production assay and their acute toxicity in Daphnia magna. No correlation was observed between this bioassay response and toxicity in the Microtox

  3. Coupling aerosol surface and bulk chemistry with a kinetic double layer model (K2-SUB: oxidation of oleic acid by ozone

    Directory of Open Access Journals (Sweden)

    C. Pfrang

    2010-05-01

    Full Text Available We present a kinetic double layer model coupling aerosol surface and bulk chemistry (K2-SUB based on the PRA framework of gas-particle interactions (Pöschl-Rudich-Ammann, 2007. K2-SUB is applied to a popular model system of atmospheric heterogeneous chemistry: the interaction of ozone with oleic acid. We show that our modelling approach allows de-convoluting surface and bulk processes, which has been a controversial topic and remains an important challenge for the understanding and description of atmospheric aerosol transformation. In particular, we demonstrate how a detailed treatment of adsorption and reaction at the surface can be coupled to a description of bulk reaction and transport that is consistent with traditional resistor model formulations.

    From literature data we have derived a consistent set of kinetic parameters that characterise mass transport and chemical reaction of ozone at the surface and in the bulk of oleic acid droplets. Due to the wide range of rate coefficients reported from different experimental studies, the exact proportions between surface and bulk reaction rates remain uncertain. Nevertheless, the model results suggest an important role of chemical reaction in the bulk and an approximate upper limit of ~10−11 cm2 s−1 for the surface reaction rate coefficient. Sensitivity studies show that the surface accommodation coefficient of the gas-phase reactant has a strong non-linear influence on both surface and bulk chemical reactions. We suggest that K2-SUB may be used to design, interpret and analyse future experiments for better discrimination between surface and bulk processes in the oleic acid-ozone system as well as in other heterogeneous reaction systems of atmospheric relevance.

  4. Cell-based bioassays in microfluidic systems

    Science.gov (United States)

    Itle, Laura J.; Zguris, Jeanna C.; Pishko, Michael V.

    2004-12-01

    The development of cell-based bioassays for high throughput drug screening or the sensing of biotoxins is contingent on the development of whole cell sensors for specific changes in intracellular conditions and the integration of those systems into sample delivery devices. Here we show the feasibility of using a 5-(and-6)-carboxy SNARF-1, acetoxymethyl ester, acetate, a fluorescent dye capable of responding to changes in intracellular pH, as a detection method for the bacterial endotoxin, lipopolysaccharide. We used photolithography to entrap cells with this dye within poly(ethylene) glyocol diacrylate hydrogels in microfluidic channels. After 18 hours of exposure to lipopolysaccharide, we were able to see visible changes in the fluorescent pattern. This work shows the feasibility of using whole cell based biosensors within microfluidic networks to detect cellular changes in response to exogenous agents.

  5. Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions: Part 1 – general equations, parameters, and terminology

    Directory of Open Access Journals (Sweden)

    Y. Rudich

    2005-04-01

    Full Text Available Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It allows to describe mass transport and chemical reactions at the gas-particle interface and to link aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer; straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients; clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion correction, surface and bulk accommodation; clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms; mechanistic description of concentration and time dependencies; flexible inclusion/omission of chemical species and physicochemical processes; flexible convolution/deconvolution of species and processes; and full compatibility with traditional

  6. Synchrotron-based XPS studies of AlGaN and GaN surface chemistry and its relationship to ion sensor behaviour

    International Nuclear Information System (INIS)

    Highlights: • Soft X-ray was used to study the surface chemistry of GaN and AlGaN. • The surface chemistry and sensor behaviour were investigated. • The oxide of aluminum is significantly more reactive than gallium. • The Cl− ions are greater in GaN samples compared to AlGaN samples. - Abstract: Soft X-ray photoelectron spectroscopy was used to investigate the fundamental surface chemistry of both AlGaN and GaN surfaces in the context of understanding the behaviour of AlGaN/GaN heterostructures as chemical field-effect transistor (CHEMFET) ion sensors. AlGaN and GaN samples were subjected to different methods of oxide growth (native oxide and thermally grown oxide) and chemical treatment conditions. Our investigations indicate that the etching of the oxide layer is more pronounced with AlGaN compared to GaN. Also, we observed that chloride ions have a greater tendency to attach to the GaN surface relative to the AlGaN surface. Furthermore, chloride ions are comparatively more prevalent on surfaces treated with 5% HCl acid solution. The concentration of chloride ions is even higher on the HCl treated native oxide surface resulting in a very clear deconvolution of the Cl 2p1/2 and Cl 2p3/2 peaks. For GaN and AlGaN surfaces, a linear response (e.g. source-drain current) is typically seen with variation in pH of buffered solutions with constant reference electrode voltage at the surface gate; however, an inverted bath-tub type response (e.g. a maximum at neutral pH and lower values at pH values away from neutral) and a general tendency to negative charge selectivity has been also widely reported. We have shown that our XPS investigations are consistent with the different sensor response reported in the literature for these CHEMFET devices and may help to explain the differing response of these materials

  7. Synchrotron-based XPS studies of AlGaN and GaN surface chemistry and its relationship to ion sensor behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Khir, Farah Liyana Muhammad, E-mail: 21001899@student.uwa.edu.au [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Hwy., Crawley, Western Australia 6009 (Australia); Myers, Matthew, E-mail: Matt.Myers@csiro.au [School of Chemistry and Biochemistry, The University of Western Australia, 35 Stirling Hwy., Crawley, Western Australia 6009 (Australia); CSIRO Earth Science and Resource Engineering, Kensington, Western Australia 6151 (Australia); Podolska, Anna [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Hwy., Crawley, Western Australia 6009 (Australia); Department of Exploration Geophysics, Curtin University of Technology, 26 Dick Perry Avenue, ARRC, Kensington, Western Australia 6151 (Australia); Sanders, Tarun Maruthi [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Hwy., Crawley, Western Australia 6009 (Australia); Baker, Murray V., E-mail: murray.baker@uwa.edu.au [School of Chemistry and Biochemistry, The University of Western Australia, 35 Stirling Hwy., Crawley, Western Australia 6009 (Australia); Nener, Brett D., E-mail: brett.nener@uwa.edu.au [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Hwy., Crawley, Western Australia 6009 (Australia); Parish, Giacinta, E-mail: giacinta.parish@uwa.edu.au [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Hwy., Crawley, Western Australia 6009 (Australia)

    2014-09-30

    Highlights: • Soft X-ray was used to study the surface chemistry of GaN and AlGaN. • The surface chemistry and sensor behaviour were investigated. • The oxide of aluminum is significantly more reactive than gallium. • The Cl{sup −} ions are greater in GaN samples compared to AlGaN samples. - Abstract: Soft X-ray photoelectron spectroscopy was used to investigate the fundamental surface chemistry of both AlGaN and GaN surfaces in the context of understanding the behaviour of AlGaN/GaN heterostructures as chemical field-effect transistor (CHEMFET) ion sensors. AlGaN and GaN samples were subjected to different methods of oxide growth (native oxide and thermally grown oxide) and chemical treatment conditions. Our investigations indicate that the etching of the oxide layer is more pronounced with AlGaN compared to GaN. Also, we observed that chloride ions have a greater tendency to attach to the GaN surface relative to the AlGaN surface. Furthermore, chloride ions are comparatively more prevalent on surfaces treated with 5% HCl acid solution. The concentration of chloride ions is even higher on the HCl treated native oxide surface resulting in a very clear deconvolution of the Cl 2p{sub 1/2} and Cl 2p{sub 3/2} peaks. For GaN and AlGaN surfaces, a linear response (e.g. source-drain current) is typically seen with variation in pH of buffered solutions with constant reference electrode voltage at the surface gate; however, an inverted bath-tub type response (e.g. a maximum at neutral pH and lower values at pH values away from neutral) and a general tendency to negative charge selectivity has been also widely reported. We have shown that our XPS investigations are consistent with the different sensor response reported in the literature for these CHEMFET devices and may help to explain the differing response of these materials.

  8. Secondary soil phases controlling surface water chemistry during experimental acidification at the Bear Brook Watershed in Maine, USA

    Czech Academy of Sciences Publication Activity Database

    Navrátil, Tomáš; Norton, S. A.; Fernandez, I. J.; Diehl, M.

    Santa Cruz : University of Santa Cruz, 2006 - (Crow, S.). s. 158-158 [BIOGEOMON. 25.6.2006-30.6.2006, Santa Cruz, California] Institutional research plan: CEZ:AV0Z30130516 Keywords : experimental acidification * streamwater * chemistry * aluminum * sulfate Subject RIV: DD - Geochemistry

  9. Combustion chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01

    This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

  10. Defect- and electron-enhanced chemistry at silicon surfaces: Reactivity and thermal desorption of propylene on Si(100)-(2 × 1)

    Science.gov (United States)

    Bozack, M. J.; Choyke, W. J.; Muehlhoff, L.; Yates, J. T.

    1986-11-01

    The reaction of Si(100) with c 3h 6 from a molecular beam source has been studied by Auger spectroscopy and thermal desorption methods. For a thermally annealed and ordered Si(100) surface, 35% of the propylene bonds to the surface as an undissociated molecule which desorbs intact at 550 K. The remainder of the propylene dissociates. Reactivity is enhanced by prebombarding the surface with Ar + ions. Adsorption of C 3H 6 to a disordered, ion-bombarded surface results in nearly complete dissociation of C 3H 6 for Ar + fluences greater than 9 × 10 14{ions}/{cm 2}. By performing the ion irradiation before, rather than during, adsorption, it is possible to conclude that the enhancement in reactivity is due to an increase in dissociative chemisorption, which occurs at defect sites produced by ion bombardment. The increase in reactivity is also independent of gas phase radical processes and other proposed mechanisms which depend on simultaneous action of the ion beam with the chemisorbed layer. Studies of electron-stimulated chemistry of the chemisorbed overlayer showed that decomposition of adsorbed propylene occurs for electron fluences greater than 1 × 10 17{electrons}/{cm 2}. The cross section for the process was calculated to be 4 × 10 -18 cm 2. The effect of preadsorbed hydrogen on silicon surface chemistry was also investigated. Hydrogen passivates the Si(100) surface by occupation of silicon dangling bond sites, which prevents adsorption of C 3H 6. These results have fundamental implications for studies of chemical and plasma vapor deposition and reactive ion etching of semiconductor surfaces.

  11. Immobilization of poly(acrylamide) brushes onto poly(caprolactone) surface by combining ATRP and “click” chemistry: Synthesis, characterization and evaluation of protein adhesion

    International Nuclear Information System (INIS)

    Highlights: • Poly(caprolacone) (PCL) film surface was chemically modified by a novel method through combining ATRP and “click” chemistry. • Poly(acrylamide) (PAAm) of tailored chain length were synthesized and “clicked” onto PCL surface. • The modified PCL surface showed reduced BSA and Fg adsorption, and the protein resist ability in terms of chain length through its impact on grafting reaction and modified surface was investigated. - Abstract: Developments of poly(caprolactone) in blood-contacting applications are often restricted due to its intrinsic hydrophobicity. One common way to improve its hemocompatibility is to attach hydrophilic polymers. Here we developed a non-destructive method to graft hydrophilic poly(acrylamide) (PAAm) onto poly(caprolactone) (PCL) surface. In this strategy, azido-ended PCL with low molecular weights was synthesized and blended with PCL to create a surface with “clickable” property. Alkyne-ended poly(acrylamide)s with controlled chain lengths were then synthesized by atom transfer radical polymerization (ATRP), and finally were immobilized onto PCL surface by “click” reaction. The occurrence of immobilization was verified qualitatively by water contact angle measurement and quantitatively by X-ray photoelectron spectroscopy (XPS). The PAAm grafted surface exhibited fouling resistant properties, as demonstrated by reduced bovine serum albumin (BSA) and fibrinogen (Fg) adhesion

  12. Immobilization of poly(acrylamide) brushes onto poly(caprolactone) surface by combining ATRP and “click” chemistry: Synthesis, characterization and evaluation of protein adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yuhao; Bian, Xinxiu; He, Liu; Cai, Mengtan; Xie, Xiaoxiong [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China); Luo, Xianglin, E-mail: luoxl@scu.edu.cn [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China); State Key Laboratory of Polymer Material and Engineering, Sichuan University, Chengdu 610065 (China)

    2015-02-28

    Highlights: • Poly(caprolacone) (PCL) film surface was chemically modified by a novel method through combining ATRP and “click” chemistry. • Poly(acrylamide) (PAAm) of tailored chain length were synthesized and “clicked” onto PCL surface. • The modified PCL surface showed reduced BSA and Fg adsorption, and the protein resist ability in terms of chain length through its impact on grafting reaction and modified surface was investigated. - Abstract: Developments of poly(caprolactone) in blood-contacting applications are often restricted due to its intrinsic hydrophobicity. One common way to improve its hemocompatibility is to attach hydrophilic polymers. Here we developed a non-destructive method to graft hydrophilic poly(acrylamide) (PAAm) onto poly(caprolactone) (PCL) surface. In this strategy, azido-ended PCL with low molecular weights was synthesized and blended with PCL to create a surface with “clickable” property. Alkyne-ended poly(acrylamide)s with controlled chain lengths were then synthesized by atom transfer radical polymerization (ATRP), and finally were immobilized onto PCL surface by “click” reaction. The occurrence of immobilization was verified qualitatively by water contact angle measurement and quantitatively by X-ray photoelectron spectroscopy (XPS). The PAAm grafted surface exhibited fouling resistant properties, as demonstrated by reduced bovine serum albumin (BSA) and fibrinogen (Fg) adhesion.

  13. Final Technical Report. Reactivity of Iron-Bearing Minerals and CO2 Sequestration and Surface Chemistry of Pyrite. An Interdisciplinary Approach

    Energy Technology Data Exchange (ETDEWEB)

    Strongin, Daniel [Temple Univ., Philadelphia, PA (United States)

    2014-12-31

    Over the course of the scientific program, two areas of research were pursued: reactions of iron oxides with supercritical CO2 and sulfide and surface reactivity of pyrite. The latter area of interest was to understand the chemistry that results when supercritical CO2 (scCO2 ) with H2 S and/or SO2 in deep saline formations (DFS) contacts iron bearing minerals. Understanding the complexities the sulfur co-injectants introduce is a critical step in developing CO2 sequestration as a climate-mitigating strategy. The research strategy was to understand macroscopic observations of this chemistry with an atomic/molecular level view using surface analytical techniques. Research showed that the exposure of iron (oxyhdr)oxides (which included ferrihydrite, goethite, and hematite) to scCO2 in the presence of sulfide led to reactions that formed siderite (FeCO3). The results have important implications for the sequestration of CO2 via carbonation reactions in the Earth’s subsurface. An earlier area of focus in the project was to understand pyrite oxidation in microscopic detail. This understanding was used to understand macroscopic observations of pyrite reactivity. Results obtained from this research led to a better understanding how pyrite reacts in a range of chemical environments. Geochemical and modern surface science techniques were used to understand the chemistry of pyrite in important environmental conditions. The program relied on a strong integration the results of these techniques to provide a fundamental understanding to the macroscopic chemistry exhibited by pyrite in the environment. Major achievements during these studies included developing an understanding of the surface sites on pyrite that controlled its reactivity under oxidizing conditions. In particular sulfur anion vacancies and/or ferric sites were sites of reactivity. Studies also showed that the

  14. Plasmonically amplified bioassay - Total internal reflection fluorescence vs. epifluorescence geometry.

    Science.gov (United States)

    Hageneder, Simone; Bauch, Martin; Dostalek, Jakub

    2016-08-15

    This paper investigates plasmonic amplification in two commonly used optical configurations for fluorescence readout of bioassays - epifluorescence (EPF) and total internal reflection fluorescence (TIRF). The plasmonic amplification in the EPF configuration was implemented by using crossed gold diffraction grating and Kretschmann geometry of attenuated total reflection method (ATR) was employed in the TIRF configuration. Identical assay, surface architecture for analyte capture, and optics for the excitation, collection and detection of emitted fluorescence light intensity were used in both TIRF and EPF configurations. Simulations predict that the crossed gold diffraction grating (EPF) can amplify the fluorescence signal by a factor of 10(2) by the combination of surface plasmon-enhanced excitation and directional surface plasmon-coupled emission in the red part of spectrum. This factor is about order of magnitude higher than that predicted for the Kretschmann geometry (TIRF) which only took advantage of the surface plasmon-enhanced excitation. When applied for the readout of sandwich interleukin 6 (IL-6) immunoassay, the plasmonically amplified EPF geometry designed for Alexa Fluor 647 labels offered 4-times higher fluorescence signal intensity compared to TIRF. Interestingly, both geometries allowed reaching the same detection limit of 0.4pM despite of the difference in the fluorescence signal enhancement. This is attributed to inherently lower background of fluorescence signal for TIRF geometry compared to that for EPF which compensates for the weaker fluorescence signal enhancement. The analysis of the inflammation biomarker IL-6 in serum at medically relevant concentrations and the utilization of plasmonic amplification for the fluorescence measurement of kinetics of surface affinity reactions are demonstrated for both EPF and TIRF readout. PMID:27260457

  15. Complex chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bong Gon; Kim, Jae Sang; Kim, Jin Eun; Lee, Boo Yeon

    2006-06-15

    This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

  16. Complex chemistry

    International Nuclear Information System (INIS)

    This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

  17. Information for establishing bioassay measurements and evaluations of tritium exposure

    International Nuclear Information System (INIS)

    This report summarizes information and references used in developing regulatory guidance on programs for the bioassay of tritium as well as information useful in planning and conducting tritium bioassay programs and evaluating bioassay data. A review of literature on tritium radiobiology is included to provide a ready source of information useful for estimating internal doses of tritium and risks for the various tritium compounds and forms, including elemental (gaseous) tritium. Simplified and conservative dose conversion factors are derived and tabulated for easy reference in program planning, safety evaluations, and compliance determinations

  18. Information for establishing bioassay measurements and evaluations of tritium exposure

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, A.

    1983-06-01

    This report summarizes information and references used in developing regulatory guidance on programs for the bioassay of tritium as well as information useful in planning and conducting tritium bioassay programs and evaluating bioassay data. A review of literature on tritium radiobiology is included to provide a ready source of information useful for estimating internal doses of tritium and risks for the various tritium compounds and forms, including elemental (gaseous) tritium. Simplified and conservative dose conversion factors are derived and tabulated for easy reference in program planning, safety evaluations, and compliance determinations.

  19. Collection and control of tritium bioassay samples at Pantex

    International Nuclear Information System (INIS)

    Pantex is the final assembly/disassembly point for US nuclear weapons. The Pantex internal dosimetry section monitors radiation workers once a month for tritium exposure. In order to manage collection and control of the bioassay specimens efficiently, a bar code system for collection of samples was developed and implemented to speed up the process and decrease the number of errors probable when transferring data. In the past, all the bioassay data from samples were entered manually into a computer database. Transferring the bioassay data from the liquid scintillation counter to each individual's dosimetry record required as much as two weeks of concentrated effort

  20. Mathematical Chemistry

    OpenAIRE

    Trinajstić, Nenad; Gutman, Ivan

    2002-01-01

    A brief description is given of the historical development of mathematics and chemistry. A path leading to the meeting of these two sciences is described. An attempt is made to define mathematical chemistry, and journals containing the term mathematical chemistry in their titles are noted. In conclusion, the statement is made that although chemistry is an experimental science aimed at preparing new compounds and materials, mathematics is very useful in chemistry, among other things, to produc...

  1. Annual report 1985 Chemistry Department

    International Nuclear Information System (INIS)

    This annual report describes the activities carried out in 1985 by the Chemistry Department in the following fields: Chemistry, Inorganic Chemistry, Physicochemistry (Interphases, Surfaces), General Chemical Analysis, Active Materials Analysis, X Ray Fluorescence Analysis, Mass Spectroscopy (Isotopic Analysis, Instrumentation) and Optical Spectroscopy. A list of publications is enclosed. (M.E.L.)

  2. Bioassays for the determination of nitrification inhibition

    Energy Technology Data Exchange (ETDEWEB)

    Grunditz, Camilla

    1999-07-01

    Requirements for nitrogen reduction in wastewater treatment plants were introduced in Sweden in the early 1990's. This was a governmental move to reduce the nitrogen discharges to the Baltic and Kattegat in order to prevent eutrophication. The nitrification process in wastewater treatment plants is performed by nitrifying bacteria. These are susceptible to inhibition and it is of great importance that the influent water does not contain toxic compounds. Therefore, there is a need for assays for the determination of nitrification inhibition. This thesis describes the development and applications of such bioassays. Pure cultures of Nitrosomonas sp. and Nitrobacter sp. were isolated from activated sludge of a wastewater treatment plant. These cultures were used as test organisms in the development of bioassays for nitrification inhibition measurements. The assays are based on two different principles; cell suspensions of the bacteria, performed in test tubes, and mediated amperometric biosensors with the bacteria immobilised. Ammonia oxidation and nitrite oxidation are studied separately without interference from other organisms, which makes it easier to interpret the results. The cell suspension assays were applied to samples of industrial and municipal wastewater. The Nitrosomonas and Nitrobacter assays showed to have different inhibition patterns. A large percentage of the Swedish municipal wastewater treatment plants were found to receive inhibitory influent water, but the inhibition level was generally low. Compared to an assay based on activated sludge, the screening method, the pure culture assays found more samples of influent water strongly inhibitory or stimulating. The highest correlation was found between the screening method and the Nitrosomonas assay. The Nitrobacter assay was found to be the most sensitive method. Assessment of toxicity of a number of chemical substances was studied using the biosensors, together with the cell suspension assays

  3. 界面超分子化学与响应性功能表面%lnterfacial Supramolecular Chemistry for Stimuli-Responsive Functional Surfaces

    Institute of Scientific and Technical Information of China (English)

    万鹏博; Hill Eric H.; 张希

    2012-01-01

    The combination of supramolecular chemistry with interfaces enhances the development of supramolecular chemistry as well as colloid and interface science. Supramolecular chemistry at interfaces allows for the construction of various smart and soft surfaces that can adapt to environmental changes, such as biomimetic surfaces and self-cleaning surfaces. In this article, we discuss strategies for the transfer of supramolecular complexes of azobenzene and cyclodextrin from solution to surfaces for the fabrication of stimuli-responsive surfaces with novel interfacial functions including tunable surface wettability, reversible protein adsorption and resistance, and photo-switchable bioelectrocatalysis. It is anticipated that these concepts can be extended to other supramolecular systems in order to engineer functional surfaces with designed structures and functions.%超分子化学和界面的结合有效地促进了超分子化学和胶体与界面科学的发展。刺激响应性超分子界面,因在外界刺激作用下能够引起界面物理化学性质的改变并带来新的界面功能,而受到广泛的关注。近年来,溶液中基于偶氮苯.环糊精主客体相互作用的超分子组装体已经得到了广泛的研究。我们将溶液中基于偶氮苯一环糊精主客体作用的可控可逆超分子组装体转移到界面上,构筑了具有刺激响应性的功能化超分子界面,并实现了表面浸润性的可逆调控、生物大分子的可控吸附与脱附、光可控的生物电化学催化等功能。我们期待类似的概念可以拓展到其他超分子体系,构筑具有特定结构的功能界面。

  4. Final Technical Report for DOE Grant, number DE-FG02-05ER15701; Probing Surface Chemistry Under Catalytic Conditions: Olefin Hydrogenation,Cyclization and Functionalization.

    Energy Technology Data Exchange (ETDEWEB)

    Neurock, Matthew

    2011-05-26

    The specific goal of this work was to understanding the catalytic reactions pathways for the synthesis of vinyl acetate over Pd, Au and PdAu alloys. A combination of both experimental methods (X-ray and Auger spectroscopies, low-energy ion scattering (LEIS), low-energy electron diffraction (LEED) and theory (Density Functional Theory (DFT) calculations and Monte Carlo methods under various different reactions) were used to track the surface chemistry and the influence of alloying. The surface intermediates involved in the various reactions were characterized using reflection-absorption infrared spectroscopy and LEED to identify the nature of the surface species and temperature-programmed desorption (TPD) to follow the decomposition pathways and measure heats of adsorption. These results along with those from density functional theoretical calculations were used determine the kinetics for elementary steps. The results from this work showed that the reaction proceeds via the Samanos mechanism over Pd surfaces whereby the ethylene directly couples with acetate to form an acetoxyethyl intermediate that subsequently undergoes a beta-hydride elimination to form the vinyl acetate monomer. The presence of Au was found to modify the adsorption energies and surface coverages of important surface intermediates including acetate, ethylidyne and ethylene which ultimately influences the critical C-H activation and coupling steps. By controlling the surface alloy composition or structure one can begin to control the steps that control the rate and even the mechanism.

  5. Uranium (VI) chemistry at the interface solution/minerals (quartz and aluminium hydroxide): experiments and spectroscopic investigations of the uranyl surface species

    International Nuclear Information System (INIS)

    This study deals with the understanding of the uranyl chemistry at the 0.1 M NaNO3 solution/mineral (quartz and aluminium hydroxide) interface. The aims are:(i) to identify and to characterize the different uranyl surface species (mononuclear, polynuclear complexes and/or precipitates...), i.e. the coordination environments of sorbed/precipitated uranyl ions, by using X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) and time-resolved laser-induced fluorescence spectroscopy (TRLFS), and;(ii) to investigate the influence of pH, initial uranyl aqueous concentration and hydroxyl ligand concentration on the uranyl surface speciation. Our study on the speciation of uranyl ions at the quartz surface (i) confirms the formation of uranyl polynuclear/oligomers on quartz from moderate (1 μmol/m2) to high (26 μmol/m2) uranyl surface concentrations and (ii) show that theses polynuclear species coexist with uranyl mononuclear surface species over a pH range ≅ 5-8.5 and a wide range of initial uranyl concentration o f the solutions (10-100 μM). The uranyl concentration of these surface species depends on pH and on the initial uranyl aqueous concentration. Hydrate (surface-) precipitates and/or adsorbed polynuclear species and monomeric uranyl surface complexes are formed on aluminium hydroxide. Uranyl mononuclear complexes are predominant at acidic pH, as well as uranyl in solution or on the surface. Besides mononuclear species, precipitates and/or adsorbed polynuclear species are predominantly formed at neutral pH values on aluminium hydroxide. A main contribution of our investigations is that precipitation and/or adsorption of polynuclear species seem to occur at low uranyl surface concentrations (0.01-0.4 μmol/m2). The uranyl surface speciation is mainly dependent on the pH and the aluminol ligand concentration. (author)

  6. Química organometálica de superfície aplicada à preparação de catalisadores heterogêneos bem definidos Surface organometallic chemistry applied to the preparation of well defined heterogeneous catalysts

    Directory of Open Access Journals (Sweden)

    Silvana I. Wolke

    2002-11-01

    Full Text Available The study of the reactions of organometallic complexes with the surfaces of inorganic oxides, zeolites and metals constitutes the basis of Surface Organometallic Chemistry (SOMC. The basic rules of organometallic chemistry are often valid when applied to surfaces and well-defined surface organometallic complexes can be obtained. These complexes can be used as heterogeneous catalysts or, by controlled reactions, can be transformed in other species useful for a given catalytic reaction. In some cases, these catalysts exhibit higher activity and/or selectivity than their analogous molecular complexes.

  7. Bioassay Phantoms Using Medical Images and Computer Aided Manufacturing

    International Nuclear Information System (INIS)

    A radiation bioassay program relies on a set of standard human phantoms to calibrate and assess radioactivity levels inside a human body for radiation protection and nuclear medicine imaging purposes. However, the methodologies in the development and application of anthropomorphic phantoms, both physical and computational, had mostly remained the same for the past 40 years. We herein propose a 3-year research project to develop medical image-based physical and computational phantoms specifically for radiation bioassay applications involving internally deposited radionuclides. The broad, long-term objective of this research was to set the foundation for a systematic paradigm shift away from the anatomically crude phantoms in existence today to realistic and ultimately individual-specific bioassay methodologies. This long-term objective is expected to impact all areas of radiation bioassay involving nuclear power plants, U.S. DOE laboratories, and nuclear medicine clinics.

  8. Bioassay Phantoms Using Medical Images and Computer Aided Manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Dr. X. Geroge Xu

    2011-01-28

    A radiation bioassay program relies on a set of standard human phantoms to calibrate and assess radioactivity levels inside a human body for radiation protection and nuclear medicine imaging purposes. However, the methodologies in the development and application of anthropomorphic phantoms, both physical and computational, had mostly remained the same for the past 40 years. We herein propose a 3-year research project to develop medical image-based physical and computational phantoms specifically for radiation bioassay applications involving internally deposited radionuclides. The broad, long-term objective of this research was to set the foundation for a systematic paradigm shift away from the anatomically crude phantoms in existence today to realistic and ultimately individual-specific bioassay methodologies. This long-term objective is expected to impact all areas of radiation bioassay involving nuclear power plants, U.S. DOE laboratories, and nuclear medicine clinics.

  9. Bioassay-Directed Fractionation of Diesel and Biodiesel Emissions

    Science.gov (United States)

    Biofuels are being developed as alternatives to petroleum-derived products, but published research is contradictory regarding the mutagenic activity of such emissions relative to those from petroleum diesel. We performed bioassay-directed fractionation and analyzed the polycyclic...

  10. Bioassay for SF 86-327, a new antifungal agent.

    OpenAIRE

    Kan, V L; Henderson, D. K.; Bennett, J.E.

    1986-01-01

    A bioassay with Trichophyton mentagrophytes is described for SF 86-327, an allylamine antifungal agent. SF 86-327 serum concentrations were measured by bioassay in 117 serum sampler from five patients receiving 500 mg/day. The peak, trough, and area under the concentration-time curve were determined after the first dose and at steady state. Drug accumulation occurred with prolonged therapy.

  11. Plant bioassays to assess toxicity of textile sludge compost

    OpenAIRE

    Araújo Ademir Sérgio Ferreira de; Monteiro Regina Teresa Rosim

    2005-01-01

    Composting of industrial wastes is increasing because of recycling requirements set on organic wastes. The evaluation of toxicity of these wastes by biological testing is therefore extremely important for screening the suitability of waste for land application. The toxicity of a textile sludge compost was investigated using seed germination and plant growth bioassays using soybean and wheat. Compost samples were mixed with water (seed germination bioassay) or nutrient solution (plant growth b...

  12. Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions - Part 1: General equations, parameters, and terminology

    Science.gov (United States)

    Pöschl, U.; Rudich, Y.; Ammann, M.

    2007-12-01

    Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It enables a detailed description of mass transport and chemical reactions at the gas-particle interface, and it allows linking aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined and consistent rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependences (transient and steady-state conditions); flexible addition of unlimited numbers of chemical species and physicochemical processes; optional aggregation or resolution

  13. Study of deposited crud composition on fuel surfaces in the environment of hydrogen water chemistry (HWC) of a Boiling Water Reactor at Chinshan Nuclear Power Plant

    International Nuclear Information System (INIS)

    This paper aimed at the characterization of metallic composition and surface analysis on the crud of fuel rods for unit-1 of BWR-4 at Nuclear Power Plant. The inductively coupled plasma- atomic emission spectroscopy (ICPAES) and the gamma spectrometry were carried out to analyze the corrosion product distributions and to determine the elemental compositions along the fuel rod under conditions of hydrogen water chemistry (HWC) switched from normal water chemistry (NWC) of reactor coolant in this study. Most of the crud consisted of the flakes and irregular shapes via SEM morphology. The loosely adherent oxide layer was mostly composed of hematite (α- Fe2O3) with amorphous iron oxides by XRD results. The average deposited amounts of crud was the order of 0.5 mg/cm2, indicating that the fuel surface of this plant under HWC environment appeared to be one with the lower crud deposition in terms of low iron level of feedwater. It also showed no significant difference in comparison with NWC condition. (authors)

  14. Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry

    Directory of Open Access Journals (Sweden)

    Abdelhaq Benkaddour

    2013-12-01

    Full Text Available Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC using Polycaprolactone-diol (PCL as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM, Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS, and Thermogravimetry analysis (TGA. Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification.

  15. Oxygen-Induced Restructuring of Rutile TiO(2)(110): Formation Mechanism, Atomic Models, and Influence on Surface Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Li, Min; Hebenstreit, Wilhelm; Diebold, Ulrike; Henderson, Michael A.; Jennison, Dwight R.

    1999-07-07

    The rutile TiO{sub 2} (110) (1x1) surface is considered the prototypical ''well-defined'' system in the surface science of metal oxides. Its popularity results partly from two experimental advantages: bulk-reduced single crystals do not exhibit charging, and stoichiometric surfaces--as judged by electron spectroscopes--can be prepared reproducibly by sputtering and annealing in oxygen. We present results that show that this commonly-applied preparation procedure may result in a surface structure that is by far more complex than generally anticipated. Flat, (1x1) terminated surfaces are obtained by sputtering and annealing in ultrahigh vacuum. When re-annealed in oxygen at moderate temperatures (470 K to 660 K), irregular networks of partially-connected, pseudohexagonal rosettes (6.5 x 6 {angstrom} wide), one-unit cell wide strands, and small ({approximately} tens of {angstrom}) (1x1) islands appear. This new surface phase is formed through reaction of oxygen gas with interstitial Ti from the reduced bulk. Because it consists of an incomplete, kinetically-limited (1x1) layer, this phenomenon has been termed restructuring. We report a combined experimental and theoretical study that systematically explores this restructuring process. The influence of several parameters (annealing time, temperature, pressure, sample history, gas) on the surface morphology is investigated using STM. The surface coverage of the added phase as well as the kinetics of the restructuring process are quantified by LEIS and SSIMS measurements in combination with annealing in {sup 18}O-enriched gas. Atomic models of the essential structural elements are presented and are shown to be stable with first-principles density functional calculations. The effect of oxygen-induced restructuring on surface chemistry and its importance for TiO{sub 2} and other bulk-reduced oxide materials is briefly discussed.

  16. A rapid bioassay to monitor murine leukemia virus infection in mice using cellular gp71 binding

    International Nuclear Information System (INIS)

    A rapid and sensitive bioassay based on the availability of cell surface receptors for the binding of purified envelope glycoprotein, gp71, of Rauscher murine leukemia virus (R-MuLV) was developed to serially monitor viral-induced leukemogenesis in individual BALB/cAnN mice. The specificity of the bioassay was demonstrated by the competition of [125I]gp71 cellular binding with murine ecotropic viruses, purified unlabelled R-MuLV envelope glycoprotein and by antiserum to R-MuLV gp71. In contrast, there was no effect on the [125I]gp71 binding level with the addition of murine xenotropic viruses, R-MuLV p30, or several other proteins. The [125I]gp71 binding level of circulating leukocytes was significantly (P < 0.05) reduced in mice after R-MuLV infection. The reduction of cellular gp71 binding developed in two stages and the latter stage was highly dependent (P < 0.05) on circulating infections virus titer. Using this technique, the gp71 cellular binding levels of 48-60 individual mice can be assayed in a 4 h period. The advantages of this bioassay compared to standard immunological and tissue culture techniques used in studying retrovirus expression and viral-cell interactions are discussed. (Auth.)

  17. Combinatorial chemistry

    DEFF Research Database (Denmark)

    Nielsen, John

    1994-01-01

    An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds.......An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds....

  18. Positronium chemistry

    CERN Document Server

    Green, James

    1964-01-01

    Positronium Chemistry focuses on the methodologies, reactions, processes, and transformations involved in positronium chemistry. The publication first offers information on positrons and positronium and experimental methods, including mesonic atoms, angular correlation measurements, annihilation spectra, and statistical errors in delayed coincidence measurements. The text then ponders on positrons in gases and solids. The manuscript takes a look at the theoretical chemistry of positronium and positronium chemistry in gases. Topics include quenching, annihilation spectrum, delayed coincidence

  19. Role of disulfide linkages in desulfurization chemistry. The reactions of benzenethiol on a sulfur-covered Mo(110) surface

    Energy Technology Data Exchange (ETDEWEB)

    Weldon, M.K.; Napier, M.E.; Wiegand, B.C.; Friend, C.M. [Harvard Univ., Cambridge, MA (United States); Uvdal, P. [Lund Univ. (Sweden)

    1994-09-07

    The reactions of benzenethiol on a sulfur-covered Mo(110) surface were studied using temperature programmed reaction, X-ray photoelectron, and high resolution electron energy loss spectroscopies. The sulfur overlayer profoundly alters the kinetics and selectivity for desulfurization and dehydrogenation. By using isotopic labeling, we have established that phenyl disulfide (C{sub 6}H{sub 5}S-S-) is formed via S-H bond scission and S-S bond formation on Mo(110) at 100 K. The S-S- linkage is oriented perpendicular and the phenyl ring parallel to the surface. The disulfide subsequently forms an upright phenylthiolate species, bound directly to the Mo(110) surface, prior to the onset of benzene formation at 300 K. In contrast to the clean surface, where only the low-temperature state is observed, a second benzene peak is observed at 500 K on the sulfur-covered surface. This feature is attributed to disproportionation of surface phenyl groups to produce gaseous benzene and surface benzyne. In addition, gaseous phenyl also desorbs from the surface in the same temperature range, due to a lack of available surface hydrogen. The selectivity for gaseous hydrocarbon production is approximately 80%, nearly twice that on the clean surface, while the total amount of reaction remains the same. 40 refs., 5 figs., 2 tabs.

  20. Effect of the size of silica nanoparticles on wettability and surface chemistry of sol-gel superhydrophobic and oleophobic nanocomposite coatings

    Science.gov (United States)

    Lakshmi, R. V.; Bera, Parthasarathi; Anandan, C.; Basu, Bharathibai J.

    2014-11-01

    Superhydrophobic sol-gel nanocomposite coatings have been fabricated by incorporating silica nanoparticles with different particle sizes separately in an acid-catalyzed sol of methyltriethoxysilane (MTEOS). Water contact angle (WCA) of the coatings increased with increase in the concentration of silica nanoparticles in both the cases. The coatings became superhydrophobic at an optimum silica concentration. The water repellency was further improved by the addition of fluoroalkylsilane (FAS). The optimum silica concentration was found to depend on the size of silica nanoparticles and FAS content and the coatings exhibited WCA of about 160° and water sliding angle (WSA) of <2°. FAS addition also improved the oleophobicity of the coatings. The coatings exhibited oil-repellency with a lubricant oil contact angle of 126° and ethylene glycol contact angle of 153.3°. Surface morphology of the coatings analyzed using field emission scanning electron microscopy (FESEM) showed a rough surface with microscale bumps and nanoscale pores. XPS was used to study the surface composition of the coatings. The superhydrophobic property of the coatings was due to the synergistic effect of surface chemistry and surface microstructure and can be explained using Cassie-Baxter model.

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

    OpenAIRE

    Malgorzata Adamkiewicz; David O’Hagan; Georg Hähner

    2014-01-01

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

  2. The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

    Directory of Open Access Journals (Sweden)

    P. Jöckel

    2006-01-01

    Full Text Available The new Modular Earth Submodel System (MESSy describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model setup up to 0.01 hPa was used at spectral T42 resolution to simulate the lower and middle atmosphere. With the high vertical resolution the model simulates the Quasi-Biennial Oscillation. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. In the simulations presented here a Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998–2005. This allows an efficient and direct evaluation with satellite and in-situ data. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated well, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of inter-annual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy

  3. A study on the relationships between corrosion properties and chemistry of thermally oxidised surface films formed on polished commercial magnesium alloys AZ31 and AZ61

    Energy Technology Data Exchange (ETDEWEB)

    Feliu, Sebastián, E-mail: sfeliu@cenim.csic.es [Centro Nacional de Investigaciones Metalúrgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Samaniego, Alejandro [Centro Nacional de Investigaciones Metalúrgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Barranco, Violeta [Instituto de Ciencias de Materiales de Madrid, ICMM, Consejo Superior de Investigaciones Científicas, CSIC, Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049, Madrid (Spain); El-Hadad, A.A. [Physics Department, Faculty of Science, Al-Azhar University, Nasr City 11884, Cairo (Egypt); Llorente, Irene [Centro Nacional de Investigaciones Metalúrgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Serra, Carmen [Servicio de Nanotecnologia y Análisis de Superficies, CACTI, Universidade de Vigo, 36310 Vigo (Spain); Galván, J.C. [Centro Nacional de Investigaciones Metalúrgicas CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain)

    2014-03-01

    Highlights: • Surface chemistry of heat treated magnesium alloys. • Relation between heat treatment and aluminium subsurface enrichment. • Relation between surface composition and corrosion behaviour. - Abstract: This paper studies the changes in chemical composition of the thin oxide surface films induced by heating in air at 200 °C for time intervals from 5 min to 60 min on the freshly polished commercial AZ31 and AZ61 alloys with a view to better understanding their protective properties. This thermal treatment resulted in the formation of layers enriched in metallic aluminium at the interface between the outer MgO surface films and the bulk material. A strong link was found between the degree of metallic Al enrichment in the subsurface layer (from 10 to 15 at.%) observed by XPS (X-ray photoelectron spectroscopy) in the AZ61 treated samples and the increase in protective properties observed by EIS (electrochemical impedance spectroscopy) in the immersion test in 0.6 M NaCl. Heating for 5–60 min in air at 200 °C seems to be an effective, easy to perform and inexpensive method for increasing the corrosion resistance of the AZ61 alloy by approximately two or three times.

  4. Correlation between bulk- and surface chemistry of Cr-tanned leather and the release of Cr(III) and Cr(VI).

    Science.gov (United States)

    Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

    2014-09-15

    About 1-3% of the adult general population in Europe is allergic to chromium (Cr). The assessment of the potential release of Cr(III) and Cr(VI) from leather is hence important from a human health and environmental risk perspective. The Cr(VI) content in leather was recently restricted in the European Union. The aim of this study was to assess possible correlations between the bulk and surface chemistry of leather, released Cr(III) and Cr(VI), and capacities of co-released leather specific species to reduce and complex released Cr. Four differently tanned leathers were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and the diphenylcarbazide colorimetric method. Their characteristics were compared with results on Cr(III) and Cr(VI) release into artificial sweat (ASW, pHleather-specific species were shown to reduce Cr(VI), both in ASW and in PB. Their reduction capacities correlated with findings of the surface content of Cr and of released Cr. Leather samples without this capacity, and with less aromatic surface groups visible by ATR-FTIR, revealed Cr(VI) both at the surface and in solution (PB). PMID:25222930

  5. Acidic deposition: State of science and technology. Report 10. Watershed and lake processes affecting surface-water acid-base chemistry. Final report

    International Nuclear Information System (INIS)

    The acid-base chemistry of surface waters is governed by the amount and chemistry of deposition and by the biogeochemical reactions that generate acidity or acid neutralizing capacity (ANC) along the hydrologic pathways that water follows through watersheds to streams and lakes. The amount of precipitation and it chemical loading depend on the area's climate and physiography, on it proximity to natural or industrial gaseous or particulate sources, and on local or regional air movements. Vegetation interacts with the atmosphere to enhance both wet and dry deposition of chemicals to a greater or lesser extent, depending on vegetation type. Vegetation naturally acidifies the environment in humid regions through processes of excess base cation uptake and generation of organic acids associated with many biological processes. Natural acid production and atmospheric deposition of acidic materials drive the acidification process. The lake or stream NAC represents a balance between the acidity-and ANC-generating processes that occur along different flow paths in the watershed and the relative importance of each flow path

  6. Influence of Operating and Water-Chemistry Parameters on Fuel Cladding Corrosion and Steel Corrosion Products Deposition on Cladding Surfaces (2nd RCM Abstract)

    International Nuclear Information System (INIS)

    The deposits of crud is to be proportional to the amount of corrosion products circulating in the circuit, therefore all models of mass transfer in the circuit include the change of corrosion products concentration and the corrosion rate in time, removing these products by filters and deposition. During decontamination of the circuit segments and equipment replacement local change of corrosion rate occurs which results in the increase of corrosion products concentration in the circuit and the increase of deposits on surfaces. If due to incorrect water chemistry conditions for corrosion products deposition in the core are created not only the activity of the coolant increases but the hydraulic resistance of the reactor also grows which results in the increase of the pressure drop at the reactor. The problem was studied on the example of WWER-440 units. The influence was established not only of water-chemistry parameters, but also of units characteristics such as pressure drop at the beginning of cycle, number of decontaminations, the age of fuel assemblies (FA) and their alignment. The mathematical model of rate rise of pressure drop through reactor (PDR) during cycle was made. (author)

  7. Soil bioassays and the {sup 129}I problem

    Energy Technology Data Exchange (ETDEWEB)

    Sheppard, S.C. [Atomic Energy of Canada Ltd., Pinawa, Manitoba (Canada)

    1995-12-31

    Iodine-129 is a very long-lived radionuclide associated with spent nuclear fuel. Because {sup 129}I has a 10{sup 7}-year half-life, is very mobile in the environment and is a biologically essential element, it is the most limiting radionuclide affecting disposal of spent fuel. Traditionally, the potential impacts of {sup 129}I have been estimated for human receptors, with the implicit assumption that all other organisms are less at risk. Risk is the operative word, the objective for protection of humans is to protect individuals, whereas the objective for other biota is usually to protect populations. Here, {sup 129}I poses an interesting problem: the half-life is so long it is barely radioactive. Thus, the chemical toxicity may be more limiting than the radiological impact. A series of soil bioassays were employed, including a life-cycle plant (Brassica rapa) bioassay, a modified earthworm survival bioassay, a microarthropod colonization/survival bioassay, and a series of more common soil and aquatic bioassays. Chemical toxicity was indicated at soil concentrations as low as 5 mg kg{sup {minus}1}. At these levels, radiological impact on non-human biota would not be expected, and therefore the chemical toxicity effects are more critical. However, human food-chain model estimates show these levels, as pure {sup 129}I, would be unacceptable for human radiological exposure, so that for {sup 129}I, protection of the human environment should also be protective of non-human biota.

  8. [Investigation on pattern and methods of quality control for Chinese materia medica based on dao-di herbs and bioassay - bioassay for Coptis chinensis].

    Science.gov (United States)

    Yan, Dan; Xiao, Xiao-he

    2011-05-01

    Establishment of bioassay methods is the technical issues to be faced with in the bioassay of Chinese materia medica. Taking the bioassay of Coptis chinensis Franch. as an example, the establishment process and application of the bioassay methods (including bio-potency and bio-activity fingerprint) were explained from the aspects of methodology, principle of selection, experimental design, method confirmation and data analysis. The common technologies were extracted and formed with the above aspects, so as to provide technical support for constructing pattern and method of the quality control for Chinese materia medica based on the dao-di herbs and bioassay. PMID:21800546

  9. Effect of the size of silica nanoparticles on wettability and surface chemistry of sol–gel superhydrophobic and oleophobic nanocomposite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi, R.V., E-mail: lakshmi_rv@nal.res.in; Bera, Parthasarathi; Anandan, C.; Basu, Bharathibai J.

    2014-11-30

    Highlights: • Superhydrophobic coatings from Cab-O-Sil EH5 and M5 particles in MTEOS sol. • Particle size of Cab-O-Sil influenced its optimum concentration in coating. • FAS-13 modification improved the oleophobicity of the coating. • Coating surface exhibited porous structure with nanovoids and microscale bumps. • Coatings with Cab-O-Sil EH5 retained water repelling property for a long time. - Abstract: Superhydrophobic sol–gel nanocomposite coatings have been fabricated by incorporating silica nanoparticles with different particle sizes separately in an acid-catalyzed sol of methyltriethoxysilane (MTEOS). Water contact angle (WCA) of the coatings increased with increase in the concentration of silica nanoparticles in both the cases. The coatings became superhydrophobic at an optimum silica concentration. The water repellency was further improved by the addition of fluoroalkylsilane (FAS). The optimum silica concentration was found to depend on the size of silica nanoparticles and FAS content and the coatings exhibited WCA of about 160° and water sliding angle (WSA) of <2°. FAS addition also improved the oleophobicity of the coatings. The coatings exhibited oil-repellency with a lubricant oil contact angle of 126° and ethylene glycol contact angle of 153.3°. Surface morphology of the coatings analyzed using field emission scanning electron microscopy (FESEM) showed a rough surface with microscale bumps and nanoscale pores. XPS was used to study the surface composition of the coatings. The superhydrophobic property of the coatings was due to the synergistic effect of surface chemistry and surface microstructure and can be explained using Cassie-Baxter model.

  10. Effect of the size of silica nanoparticles on wettability and surface chemistry of sol–gel superhydrophobic and oleophobic nanocomposite coatings

    International Nuclear Information System (INIS)

    Highlights: • Superhydrophobic coatings from Cab-O-Sil EH5 and M5 particles in MTEOS sol. • Particle size of Cab-O-Sil influenced its optimum concentration in coating. • FAS-13 modification improved the oleophobicity of the coating. • Coating surface exhibited porous structure with nanovoids and microscale bumps. • Coatings with Cab-O-Sil EH5 retained water repelling property for a long time. - Abstract: Superhydrophobic sol–gel nanocomposite coatings have been fabricated by incorporating silica nanoparticles with different particle sizes separately in an acid-catalyzed sol of methyltriethoxysilane (MTEOS). Water contact angle (WCA) of the coatings increased with increase in the concentration of silica nanoparticles in both the cases. The coatings became superhydrophobic at an optimum silica concentration. The water repellency was further improved by the addition of fluoroalkylsilane (FAS). The optimum silica concentration was found to depend on the size of silica nanoparticles and FAS content and the coatings exhibited WCA of about 160° and water sliding angle (WSA) of <2°. FAS addition also improved the oleophobicity of the coatings. The coatings exhibited oil-repellency with a lubricant oil contact angle of 126° and ethylene glycol contact angle of 153.3°. Surface morphology of the coatings analyzed using field emission scanning electron microscopy (FESEM) showed a rough surface with microscale bumps and nanoscale pores. XPS was used to study the surface composition of the coatings. The superhydrophobic property of the coatings was due to the synergistic effect of surface chemistry and surface microstructure and can be explained using Cassie-Baxter model

  11. XPS study of surface chemistry of tungsten carbides nanopowders produced through DC thermal plasma/hydrogen annealing process

    Energy Technology Data Exchange (ETDEWEB)

    Krasovskii, Pavel V., E-mail: krasovskii@gmail.com [A.A Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Leninskii pr. 49, Moscow 119991 (Russian Federation); Malinovskaya, Olga S. [SSC Keldysh Research Centre, Onezhskaya, 8, Moscow 125438 (Russian Federation); Samokhin, Andrey V.; Blagoveshchenskiy, Yury V. [A.A Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Leninskii pr. 49, Moscow 119991 (Russian Federation); Kazakov, Valery A.; Ashmarin, Artem A. [SSC Keldysh Research Centre, Onezhskaya, 8, Moscow 125438 (Russian Federation)

    2015-06-01

    Highlights: • WC nanopowders were produced by a DC thermal plasma/H{sub 2} annealing process. • Air-exposed materials show ultra-thin chemically heterogeneous overlayers. • Carbidic, graphitic, carbon-to-oxygen, and WO{sub 3} surface bonding are involved. • Adsorbed oxygen at coverage above a monolayer is preferentially bonded to carbon. • Surface segregations of carbon are normal, even for sub-stoichiometric carbides. - Abstract: X-ray photoelectron spectroscopy (XPS) has been employed to characterize the surface composition and bonding of the tungsten carbides nanopowders produced through a DC thermal plasma/hydrogen annealing process. The XPS results were complemented with those from Raman spectroscopy, high-resolution transmission electron microscopy, and evolved gas analysis. The products of the DC plasma synthesis are the high-surface-area multicarbide mixtures composed mainly of crystalline WC{sub 1−x} and W{sub 2}C. The materials are contaminated with a pyrolitic carbonaceous deposit which forms ∼1 nm thick graphitic overlayers on the nanoparticles’ surface. The underlying carbides are not oxidized in ambient air, and show no interfacial compounds underneath the graphitic overlayers. When annealed in hydrogen, the multicarbide mixtures undergo transformation into the single-phase WC nanopowders with an average particle size of 50–60 nm. The surface of the passivated and air-exposed WC nanopowders is stabilized by an ultrathin, no more than 0.5 nm in thickness, chemically heterogeneous overlayer, involving graphitic, carbon-to-oxygen, and WO{sub 3} bonding. Oxygen presents at coverages above a monolayer preferentially in the bonding configurations with carbon. The surface segregations of carbon are normally observed, even when the bulk content of carbon is below the stoichiometric level.

  12. Chemistry data from surface ecosystems in Forsmark and Laxemar-Simpevarp. Site specific data used for estimation of CR and Kd values in SR-Site

    International Nuclear Information System (INIS)

    This report is a background report for the biosphere analysis of the SR-Site Safety Assessment. This work aims to compile information from the Forsmark and Laxemar-Simpevarp sites in order to select and provide relevant site data for parameter sed in the Radionuclide Dose Model. This report contains an overview of all available chemistry data from the surface ecosystems at Forsmark and Laxemar-Simpevarp areas, comprising hydrochemistry of shallow groundwater, porewater, lake water, stream water and sea water as well as the chemical composition of the regolith and biota of the terrestrial, limnic and marine ecosystems. Detailed references to data reports are tabulated and all sampling points are shown in a large number of maps in Chapter 2. An explorative analysis in Chapter 3 is the basis for the final selection of site data described in Chapter 4

  13. Environmental effects of dredging. A chronic sublethal sediment bioassay with the marine polychaete nereis (Neanthes) arenaceodentata

    Energy Technology Data Exchange (ETDEWEB)

    Dillon, T.M.; Moore, D.W.; Bridges, T.S.

    1995-01-01

    This note provides a general overview of a new 28-day chronic sublethal sediment bioassay designed for the regulatory evaluation of dredged material. The bioassay uses survival and growth rate endpoints with the polychaete Nereis (Neanthes) arenaceodentata. The primary technical reference for this new bioassay is Dillon, Moore, and Reish (in press), upon which this overview is based. Sediment bioassays are used to assess the aggregate toxicity of sediment associated anthropogenic chemicals. Historically, these bioassays have measured survival of highly sensitive species following acute exposures (10 days). A new generation of sediment bioassays is being developed in which the subtle, sublethal response of test species is measured following chronic sediment exposures (Dillon 1993).

  14. Method comparison for 241Am emergency urine bioassay.

    Science.gov (United States)

    Li, Chunsheng; Sadi, Baki; Benkhedda, Karima; St-Amant, Nadereh; Moodie, Gerry; Ko, Raymond; Dinardo, Anthony; Kramer, Gary

    2010-10-01

    241Am is one of the high-risk radionuclides that might be used in a terrorist attack. 241Am in urine bioassay can identify the contaminated individuals who need immediate medical intervention and decontamination. This paper compares three methods for the measurement of 241Am in urine, namely liquid scintillation counting (LSC), inductively coupled plasma mass spectrometry (ICP-MS) and gamma spectrometry (GS), at two levels, 20 and 2 Bq l(-1). All three methods satisfied the ANSI N13.30 radio-bioassay criteria for accuracy and repeatability. ICP-MS offered the best sensitivity and fastest sample turnaround; however, the ICP-MS system used in this work may not be available in many bioassay laboratories. LSC and GS are more commonly available instruments. GS requires minimal or no sample preparation, which makes it a good candidate method. Moreover, the sample throughput can be significantly improved if the GS and LSC methods are automated. PMID:20573683

  15. Surface analytical and electrochemical characterization of oxide films formed on Incoloy-800 and carbon steel in simulated secondary water chemistry conditions of PHWRs

    International Nuclear Information System (INIS)

    The water chemistry in the Steam Generator (SG) Circuits of Indian Pressurized Heavy Water Reactors (PHWRs) is controlled by the all volatile treatment (AVT) procedure, wherein volatile amines are used to maintain the alkaline pH required for minimizing the corrosion of the structural materials. Earlier, Monel and morpholine were used as the Steam Generator material and the alkalizing agent respectively. However, currently they are replaced by Incoloy-800 and Ethanolamine (ETA). ETA was chosen because of its beneficial effects due to low pKb and Kd values, loading behaviour on condensate polishing unit (CPU) and also on cost comparison with other amines. Since we have Incoloy-800 on the tube side and Carbon steel(CS) on the shell side in the SG circuits, efforts were taken to study the nature of the oxide films formed on these surfaces and to evaluate the corrosion resistance and electrochemical properties of the same, under simulated secondary water chemistry conditions of PHWRs containing different dissolved oxygen (DO) concentration. In this context, experiments were carried out by exposing finely polished CS and Incoloy -800 coupons to ETA based medium in the presence and absence of Hydrazine (pH: 9.2) at 240 oC under two different DO conditions (< 10 ppb and 200 ppb) for 24 hours. Oxide films formed under these conditions were characterized using SEM, Raman spectroscopy, electrochemical impedance, polarization and Mott-Schottky techniques. Further, studies at a controlled DO level ( < 10 ppb) were carried out for different time durations viz., 7- and 30- days. The composition, surface morphology, oxide thickness, resistance, type of semi-conductivity and defect density of the oxide films were evaluated and correlated with the DO levels and discussed elaborately in this paper. (author)

  16. Surface analytical and electrochemical characterization of oxide film layers formed on Incoloy 800 and carbon steel in simulated secondary water chemistry conditions of PHWRs

    Energy Technology Data Exchange (ETDEWEB)

    Rangarajan, Srinivasan; Chandran, Sinu; Balaji, Vadivelu; Narasimhan, Sevilmedu V. [BARC Facilities, Kalpakkam, Tamil Nadu (India). Water and Steam Chemistry Div.

    2011-06-15

    The water chemistry in the steam generator (SG) circuits of Indian pressurized heavy water reactors (PHWRs) is controlled by the all-volatile treatment (AVT) procedure, wherein volatile amines are used to maintain the alkaline pH required for minimizing the corrosion of the structural materials. Earlier, Monel and morpholine were used as the steam generator material and the alkalizing agent respectively. However, currently they have been replaced by Incoloy 800 and ethanolamine (ETA). ETA was chosen because of its beneficial effects due to low pKb and Kd values, loading behavior on the condensate polishing unit (CPU), and also based on cost comparison with other amines. Since we have Incoloy 800 on the tube side and carbon steel (CS) on the shell side in the SG circuits, efforts were taken to study the nature of the oxide films formed on these surfaces and to evaluate the corrosion resistance and electrochemical properties of the same under simulated secondary water chemistry conditions of PHWRs containing different dissolved oxygen (DO) concentrations. In this context, experiments were carried out by exposing finely polished CS and Incoloy 800 coupons to ETA-based medium in the presence and absence of hydrazine (pH: 9.2) at 240 C under two different DO conditions (< 10 {mu}g . L{sup -1} and 300 {mu}g . L{sup -1}) for 24 hours. Oxide films formed under these conditions were characterized using scanning electron microscopy, Raman spectroscopy, electrochemical impedance, polarization and Mott-Schottky techniques. Further, studies at a controlled DO level (< 10 {mu}g . L{sup -1}) were carried out for different time durations, viz., 7 and 30 days. The composition, surface morphology, oxide thickness, resistance, type of semiconductivity and defect density of the oxide films were evaluated and correlated with the DO levels and are discussed elaborately in this paper. (orig.)

  17. Surface analytical and electrochemical characterization of oxide film layers formed on Incoloy 800 and carbon steel in simulated secondary water chemistry conditions of PHWRs

    International Nuclear Information System (INIS)

    The water chemistry in the steam generator (SG) circuits of Indian pressurized heavy water reactors (PHWRs) is controlled by the all-volatile treatment (AVT) procedure, wherein volatile amines are used to maintain the alkaline pH required for minimizing the corrosion of the structural materials. Earlier, Monel and morpholine were used as the steam generator material and the alkalizing agent respectively. However, currently they have been replaced by Incoloy 800 and ethanolamine (ETA). ETA was chosen because of its beneficial effects due to low pKb and Kd values, loading behavior on the condensate polishing unit (CPU), and also based on cost comparison with other amines. Since we have Incoloy 800 on the tube side and carbon steel (CS) on the shell side in the SG circuits, efforts were taken to study the nature of the oxide films formed on these surfaces and to evaluate the corrosion resistance and electrochemical properties of the same under simulated secondary water chemistry conditions of PHWRs containing different dissolved oxygen (DO) concentrations. In this context, experiments were carried out by exposing finely polished CS and Incoloy 800 coupons to ETA-based medium in the presence and absence of hydrazine (pH: 9.2) at 240 C under two different DO conditions (-1 and 300 μg . L-1) for 24 hours. Oxide films formed under these conditions were characterized using scanning electron microscopy, Raman spectroscopy, electrochemical impedance, polarization and Mott-Schottky techniques. Further, studies at a controlled DO level (-1) were carried out for different time durations, viz., 7 and 30 days. The composition, surface morphology, oxide thickness, resistance, type of semiconductivity and defect density of the oxide films were evaluated and correlated with the DO levels and are discussed elaborately in this paper. (orig.)

  18. The effect of ethylene oxide sterilization on the surface chemistry and in vitro cytotoxicity of several kinds of chitosan.

    Science.gov (United States)

    França, Rodrigo; Mbeh, Doris A; Samani, Taraneh Djavanbakht; Le Tien, Canh; Mateescu, Mircea A; Yahia, L'Hocine; Sacher, Edward

    2013-11-01

    The surfaces of three chitosan samples, differing only in their degrees of deacetylation and of carboxyethyl chitosan were chemically characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy, X-ray diffraction, and Fourier transform infrared, both before and after sterilization with ethylene oxide. Unexpected elemental ratios suggest that surface chemical modification occurred during the processing of the original chitin, with further surface modification on subsequent sterilization, despite previous reports to the contrary. Cell viability was evaluated by direct contact methyl thiazole tetrazolium and lactate dehydrogenase assays between the chitosan particles and A549 human epithelial cells, which demonstrated that the modifications incurred on sterilization are reflected in biocompatibility changes. All the samples were found to be biocompatible and nontoxic before sterilization and remained so subsequently. PMID:24591223

  19. 粉石英表面化学的表征%The token for surface chemistry of tripoli

    Institute of Scientific and Technical Information of China (English)

    吴宏海; 崔天顺; 黄庆民

    2001-01-01

    The surface sites of tripoli (α-quartz) and its protonation arefirst analyzed and discussed, and then the surface electrochemical properties of tripoli are further investigated. The surface site density and the pHPPZC(pristine of zero charge) of tripoli (α-quartz) were determined in supporting electrolyte solution of NaNO3 to 4.3 sites/nm2,2.8,respectively.The lgKint1 and lgKint2, two surface protonation intrinsic constants of tripoli,are about -1.5, 7.0, respectively. The competing adsorption ability of Cl- and NO-3 ions on quartz surface in sequence was Cl->NO-3.The results show that the surface of tripoli is characteristic of weak acidity.%分析与探讨了粉石英的表面位及其质子化反应,对粉石英的表面电化学性质作了进一步研究。以NaNO3为支持电解质,测得粉石英的表面位密度约为4.3个/nm2,表面零质子电荷原点pHPPZC为2.8;表面质子化本征常数lgKint1约为-1.5和lgKint2约为7.0;Cl-和NO-3对石英的竞争吸附能力大小为Cl->NO-3。粉石英表面显弱酸性。

  20. Social Chemistry

    OpenAIRE

    Lichtfouse, Eric; Schwarzbauer, Jan; Robert, Didier

    2012-01-01

    International audience This article is both an essay to propose social chemistry as a new scientific discipline, and a preface of the book Environmental Chemistry for a Sustainable World. Environmental chemistry is a fast emerging discipline aiming at the understanding the fate of pollutants in ecosystems and at designing novel processes that are safe for ecosystems. Past pollution should be cleaned, future pollution should be predicted and avoided (Lichtfouse et al., 2005a). Such advices ...

  1. Computational chemistry

    OpenAIRE

    Truhlar, Donald G.; McKoy, Vincent

    2000-01-01

    Computational chemistry has come of age. With significant strides in computer hardware and software over the last few decades, computational chemistry has achieved full partnership with theory and experiment as a tool for understanding and predicting the behavior of a broad range of chemical, physical, and biological phenomena. The Nobel Prize award to John Pople and Walter Kohn in 1998 highlighted the importance of these advances in computational chemistry. With massively parallel computers ...

  2. Bioinorganic Chemistry

    OpenAIRE

    Bertini, Ivano; Gray, Harry B.; Lippard, Stephen J.; Valentine, Joan Selverstone

    1994-01-01

    This book covers material that could be included in a one-quarter or one-semester course in bioinorganic chemistry for graduate students and advanced undergraduate students in chemistry or biochemistry. We believe that such a course should provide students with the background required to follow the research literature in the field. The topics were chosen to represent those areas of bioinorganic chemistry that are mature enough for textbook presentation. Although each chapter presents material...

  3. The role of surface chemistry and solution pH on the removal of Pb2+ and Cd2+ ions via effective adsorbents from low-cost biomass.

    Science.gov (United States)

    El-Hendawy, Abdel-Nasser A

    2009-08-15

    A deep understanding of adsorption of Pb(2+) and Cd(2+) ions from their aqueous solutions on activated carbons and their HNO(3)-oxidized forms has been attempted. These activated carbons were obtained from date pits using different activation methods. Adsorption isotherms of Pb(2+) and Cd(2+) ions were determined from solutions at pH 3 and 5.9. The results revealed that all obtained isotherms exhibited the model fitting according to Langmuir equation. The oxidized samples prone, slightly, to the high affinity isotherm type. The results revealed also that the investigated carbons removed appreciable amounts of lead and cadmium ions which increased by increasing pH of solutions from 3 to 5.9. The adsorption capacity of the investigated carbons also increased by HNO(3) acid surface treatment. The results were discussed in light of a possible chemical modification by nitric acid resulting in the creation of a large number of surface functional oxygen species. This interpretation was confirmed by FTIR investigation. The solution-pH and the surface chemistry of the carbons were found to play a decisive role in the uptake of these heavy metal ions from aqueous solutions rather than the carbon texture characteristics. PMID:19195774

  4. Semi-Biosynthesis of Magnetite-Gold Composite Nanoparticles Using an Ethanol Extract of Eucalyptus camaldulensis and Study of the Surface Chemistry

    Directory of Open Access Journals (Sweden)

    Emad al din Haratifar

    2009-01-01

    Full Text Available Green synthesis of metal nanoparticles, such as silver or gold nanoparticles, has been attracting increasing attention in recent years. Functionalized magnetite nanoparticles have many uses in various applications, including nanoelectronic devices, molecular recognition, biomedical applications, drug delivery targeting, and optical devices. In this investigation, magnetic cores (Fe3O4 were synthesized using a fabrication method involving coprecipitation of Fe2+ and Fe3+. In the next step, magnetite-gold composite nanoparticles were synthesized with size ranging from 6–20 nm, using an ethanol extract of Eucalyptus camaldulensis as a natural reducing agent. Transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction spectroscopy, and visible absorption spectroscopy confirmed the fabrication of magnetite-gold composite nanoparticles. In the UV spectra diagram, a red-shift of the surface plasmon of the Au was evidence that contact between gold and Fe3O4 had occurred. The surface chemistry of the as-prepared magnetite-gold nanoparticles was studied using infrared spectroscopy. The presence of organic compounds with a carboxyl moiety was confirmed on the surface of the magnetite-gold nanoparticles fabricated by this combined chemical and biological reducing process, which we have designated as a semi-biosynthesis method.

  5. Toward selective, sensitive, and discriminative detection of Hg(2+) and Cd(2+)via pH-modulated surface chemistry of glutathione-capped gold nanoclusters.

    Science.gov (United States)

    Huang, Pengcheng; Li, Sha; Gao, Nan; Wu, Fangying

    2015-11-01

    Heavy metal pollution can exert severe effects on the environment and human health. Simple, selective, and sensitive detection of heavy metal ions, especially two or more, using a single probe, is thereby of great importance. In this study, we report a new and facile strategy for discriminative detection of Hg(2+) and Cd(2+) with high selectivity and sensitivity via pH-modulated surface chemistry of the glutathione-capped gold NCs (GSH-Au NCs). By simply adjusting pH values of the colloidal solution of the NCs, Hg(2+) could specifically turn off the fluorescence under acidic pH, however, Cd(2+) could exclusively turn on the fluorescence under alkaline pH. This enables the NCs to serve as a dual fluorescent sensor for Hg(2+) and Cd(2+). We demonstrate that these two opposing sensing modes are presumably due to different interaction mechanisms: Hg(2+) induces aggregation by dissociating GSH from the Au surface via robust coordination and, Cd(2+) could passivate the Au surface by forming a Cd-GSH complex with a compact structure. Finally, the present strategy is successfully exploited to separately determine Hg(2+) and Cd(2+) in environmental water samples. PMID:26347906

  6. Technetium chemistry

    International Nuclear Information System (INIS)

    Technetium chemistry is a young and developing field. Despite the limited knowledge of its chemistry, technetium is the workhorse for nuclear medicine. Technetium is also a significant environmental concern because it is formed as a byproduct of nuclear weapons production and fission-power generators. Development of new technetium radio-pharmaceuticals and effective environmental control depends strongly upon knowledge of basic technetium chemistry. The authors performed research into the basic coordination and organometallic chemistry of technetium and used this knowledge to address nuclear medicine and environmental applications. This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL)

  7. Surface chemistry, friction and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to he surfaces of the ferrites in sliding.

  8. ASSESSING THE REGIONAL EFFECTS OF SULFUR DEPOSITION ON SURFACE WATER CHEMISTRY: THE SOUTHERN BLUE RIDGE (JOURNAL VERSION)

    Science.gov (United States)

    A method was developed for quantifying the regional chronic acidification of surface waters which uses synoptic survey data and a conceptual titration model of acidification. The principal assumptions of the model are that stream waters have been titrated by an amount of sulfuric...

  9. Surface chemistry and catalytic activity of Ni/Al2O3 irradiated with high-energy electron beam

    International Nuclear Information System (INIS)

    The radiation effects induced effects by electron beam (EB) treatment on the catalytic activity of Ni/γ-Al2O3 were studied for the carbon dioxide reforming of methane with different EB energy and absorbed radiation dose. Transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to determine the change in structure and surface states of Ni/γ-Al2O3 catalyst before and after the EB treatment. Higher energy EB treatment is useful for increasing the proportion of the active sites (such as Ni0 and NiAl2O4-phase) on the surface. The increase of Ni/Al-ratio indicates that the Ni dispersion on the surface increased with the EB-treatment, resulting in an increase of the active sites, which leads to improving the catalytic activity. XPS measurement also showed a decrease of the surface carbon with EB dose. The maximum 20% increase in the conversion of CO2/CH4-mixture into CO/H2 gas was observed for the catalyst treated with 2 MeV energy and 600 kGy dose of EB relative to untreated

  10. Relationship between gas-phase chemistries and surface processes in fluorocarbon etch plasmas: A process rate model

    International Nuclear Information System (INIS)

    In a typical plasma tool, both etch and deposition occur simultaneously. Extensive experimental measurements are used to help develop a general model of etch and deposition processes. This model employs reaction probabilities, or surface averaged cross sections, to link the measurable surface processes, etch and deposition, to the flux of various species to the surfaces. Because the cross sections are quantum mechanical in nature, this surface rate model should be applicable to many low temperature plasma processing systems. Further, the parameters that might be important in reaction cross sections are known from quantum mechanics, e.g., species, energy, temperature, and impact angle. Such parameters might vary from system to system, causing the wide processing variability observed in plasma tools. Finally the model is used to compare measurements of ion flux, ion energy, and fluorocarbon radical flux to the measured process rates. It is found that the model appears to be consistent with calculations of gain/loss rates for the various radicals present in the discharge as well as measured etch and deposition rates.

  11. Colloidal stability of gold nanorod solution upon exposure to excised human skin: Effect of surface chemistry and protein adsorption.

    Science.gov (United States)

    Mahmoud, Nouf N; Al-Qaoud, Khaled M; Al-Bakri, Amal G; Alkilany, Alaaldin M; Khalil, Enam A

    2016-06-01

    In this study, we evaluated the colloidal stability of gold nanorods (with positive, negative and neutral surface charge) in solution upon contact with excised human skin. UV-vis absorption, plasmon peak broadening index (PPBI%) and transmission electron microscope analysis were used to follow nanoparticles aggregation in solution. Our results show that positively charged gold nanorods aggregate extensively upon exposure to excised human skin compared to negatively and neutrally charged gold nanorods. Skin-induced aggregation of cationic gold nanorods was linked to the adsorption of proteins released from the dermis layer to the surface of gold nanorods. Protein adsorption significantly screen nanorod's effective surface charge and induce their aggregation. Moreover, we demonstrate that the presence of polyethylene glycol polymer on the surface of cationic gold nanorods minimize this aggregation significantly by providing steric repulsion (non-electrostatic stabilization mechanism). This work highlights the importance of evaluating the colloidal stability of nanoparticles in solution upon contact with skin, which is a "usually overlooked" parameter when studying the nanoparticle-skin interaction. PMID:26923289

  12. Catalyst-Free Conjugation and In Situ Quantification of Nanoparticle Ligand Surface Density Using Fluorogenic Cu-Free Click Chemistry

    DEFF Research Database (Denmark)

    Jølck, Rasmus Irming; Sun, Honghao; Berg, Rolf Henrik;

    2011-01-01

    A highly efficient method for functionalizing nanoparticles and directly quantifying conjugation efficiency and ligand surface density has been developed. Attachment of 3-azido-modifed RGD-peptides to PEGylated liposomes was achieved by using Cu-free click conditions. Upon coupling a fluorophore is...

  13. The ion chemistry of surface and ground waters in the Taklimakan Desert of Tarim Basin, western China

    Institute of Scientific and Technical Information of China (English)

    ZHU BingQi; YANG XiaoPing

    2007-01-01

    The physio-chemical and chemical features of water in natural conditions are controlled by the weathering of bedrocks, local climate, landforms and other geo-environmental parameters. In order to understand the characteristics of water and the origins of the dissolved loads in the rivers and in the ground waters of the Taklimakan Desert, western China, we studied the ions in the water samples collected from rivers and wells. We collected water samples from four rivers (Keriya River, Cele River, Tumiya River and Yulongkashi River) in the southern desert and ground water samples from many parts of the desert. Major cations and anions were measured using ion-chromatograph and titration with HCl. The total dissolved solids (TDS), pH and conductivity were examined on site by a portable multi-parameter analyzer. The data show that the water in the rivers of southern Taklimakan is still of fresh water quality and slight alkalinity, although the TDS is comparatively higher than that of many other rivers of the world. The ground water is fresh to slightly saline, with TDS a little higher than that of river water in the study area. The concentration of ions is slightly different between the four rivers in the southern Taklimakan. However, the chemistries of ground water in all samples are to a large degree controlled by sodium and chloride. The ions in the ground water are concluded to be mainly from dissolving of evaporites, consistent with the dry climate in the region, whereas the ions in the rivers are mainly from rock weathering. Low-level human imprints are recognized in the ground water samples also.

  14. Probabilistic estimation of future emissions of isoprene and surface oxidant chemistry associated with land use change in response to growing food needs

    Directory of Open Access Journals (Sweden)

    C. J. Hardacre

    2012-12-01

    Full Text Available We quantify the impact of land use change, determined by our growing need for food and biofuel production, on isoprene emissions and subsequent atmospheric oxidant chemistry in 2015 and 2030, relative to 1990, ignoring compound climate change effects over that period. We estimate isoprene emissions from an ensemble (n = 1000 of land use change realizations from 1990–2050, broadly guided by the IPCC AR4/SRES scenarios A1 and B1. We also superimpose land use change required to address projected biofuel usage using two scenarios: (1 assuming that world governments make no changes to biofuel policy after 2009, and (2 assuming that world governments develop biofuel policy with the aim of keeping equivalent atmospheric CO2 at 450 ppm. We present the median and interquartile range (IQR statistics of the ensemble and show that land use change between −1.50 × 1012 m2 to +6.06 × 1012 m2 was found to drive changes in the global isoprene burden of −3.5 to +2.8 Tg yr−1 in 2015 and −7.7 to +6.4 Tg yr−1 in 2030. We use land use change realizations corresponding to the median and IQR of these emission estimates to drive the GEOS-Chem global 3-D chemistry transport model to investigate the perturbation to global and regional surface concentrations of isoprene, nitrogen oxides (NO+NO2, and the atmospheric concentration and deposition of ozone (O3. We show that across sub-continental regions the monthly surface O3 increases by 0.1–0.8 ppb, relative to a zero land-use change calculation, driven by increases (decreases in surface isoprene in high (low NOx environments. At the local scale (4° × 5° we find that surface O3 increases by 5–12 ppb over temperate North America, China and Boreal Eurasia, driven by large increases in isoprene emissions from short-rotation coppice crop cultivation for biofuel

  15. Probabilistic estimation of future emissions of isoprene and surface oxidant chemistry associated with land-use change in response to growing food needs

    Directory of Open Access Journals (Sweden)

    C. J. Hardacre

    2013-06-01

    Full Text Available We quantify the impact of land-use change, determined by our growing demand for food and biofuel production, on isoprene emissions and subsequent atmospheric oxidant chemistry in 2015 and 2030, relative to 1990, ignoring compound climate change effects over that period. We estimate isoprene emissions from an ensemble (n = 1000 of land-use change realizations from 1990–2050, broadly guided by the IPCC AR4/SRES scenarios A1 and B1. We also superimpose land-use change required to address projected biofuel usage using two scenarios: (1 assuming that world governments make no changes to biofuel policy after 2009, and (2 assuming that world governments develop biofuel policy with the aim of keeping equivalent atmospheric CO2 at 450 ppm. We present the median and interquartile range (IQR statistics of the ensemble and show that land-use change between −1.50 × 1012 m2 to +6.06 × 1012 m2 was found to drive changes in the global isoprene burden of −3.5 to +2.8 Tg yr−1 in 2015 and −7.7 to +6.4 Tg yr−1 in 2030. We use land-use change realizations corresponding to the median and IQR of these emission estimates to drive the GEOS-Chem global 3-D chemistry transport model to investigate the perturbation to global and regional surface concentrations of isoprene, nitrogen oxides (NO+NO2, and the atmospheric concentration and deposition of ozone (O3. We show that across subcontinental regions the monthly surface O3 increases by 0.1–0.8 ppb, relative to a zero land-use change calculation, driven by increases (decreases in surface isoprene in high (low NOx environments. At the local scale (4° × 5° we find that surface O3 increases by 5–12 ppb over temperate North America, China and boreal Eurasia, driven by large increases in isoprene emissions from short-rotation coppice crop cultivation for biofuel production.

  16. A novel method for standardized application of fungal spore coatings for mosquito exposure bioassays

    Directory of Open Access Journals (Sweden)

    Knols Bart GJ

    2010-01-01

    Full Text Available Abstract Background Interest in the use of fungal entomopathogens against malaria vectors is growing. Fungal spores infect insects via the cuticle and can be applied directly on the insect to evaluate infectivity. For flying insects such as mosquitoes, however, application of fungal suspensions on resting surfaces is more realistic and representative of field settings. For this type of exposure, it is essential to apply specific amounts of fungal spores homogeneously over a surface for testing the effects of fungal dose and exposure time. Contemporary methods such as spraying or brushing spore suspensions onto substrates do not produce the uniformity and consistency that standardized laboratory assays require. Two novel fungus application methods using equipment developed in the paint industry are presented and compared. Methods Wired, stainless steel K-bars were tested and optimized for coating fungal spore suspensions onto paper substrates. Different solvents and substrates were evaluated. Two types of coating techniques were compared, i.e. manual and automated coating. A standardized bioassay set-up was designed for testing coated spores against malaria mosquitoes. Results K-bar coating provided consistent applications of spore layers onto paper substrates. Viscous Ondina oil formulations were not suitable and significantly reduced spore infectivity. Evaporative Shellsol T solvent dried quickly and resulted in high spore infectivity to mosquitoes. Smooth proofing papers were the most effective substrate and showed higher infectivity than cardboard substrates. Manually and mechanically applied spore coatings showed similar and reproducible effects on mosquito survival. The standardized mosquito exposure bioassay was effective and consistent in measuring effects of fungal dose and exposure time. Conclusions K-bar coating is a simple and consistent method for applying fungal spore suspensions onto paper substrates and can produce coating layers

  17. Terbium to quantum rod Förster resonance energy transfer for homogeneous bioassays with picomolar detection limits

    International Nuclear Information System (INIS)

    We report on the proof-of-principle of using semiconductor nanorods (quantum rods; QRs) in homogeneous Förster resonance energy transfer (FRET) bioassays. Terbium complexes (Tb) with long photoluminescence lifetimes were used as FRET donors, and biological recognition was accomplished by biotin-QR to Tb-streptavidin binding. Time-resolved and steady-state spectroscopy were used to investigate varying relative donor/acceptor concentrations and different lengths of polyethylene glycol (PEG)-based surface coatings. Homogeneous bioassays displayed low picomolar detection limits in 150 μL samples, independent of whether 1 and 10 kDa biotin-PEG-SH surface ligands were used. The results suggest that the combination of Tb-to-QR FRET with time-gated detection may become a powerful tool for homogeneous biosensing. (author)

  18. Investigation of the structure and chemistry of surface layers on metals by x-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Most structural metals are very active chemically and without a passivating or protective layer would soon oxidize or corrode. The history of the industry is an attempt to minimize this process. The problem is becoming more acute, particularly in the aerospace industry, where the frames of many older airplanes are lasting longer than their outer skins. A more esoteric effect is the corrosion of metal surfaces in earth orbit by atomic oxygen. This paper is concerned with the structural and chemical characterization by x-ray absorption spectroscopy (XAS) of surface layers on aluminum alloys exposed to salt spray testing and with iron-based A-286 superalloy bolts exposed to atomic oxygen in a low earth orbit

  19. Anion-π Catalysis of Enolate Chemistry: Rigidified Leonard Turns as a General Motif to Run Reactions on Aromatic Surfaces.

    Science.gov (United States)

    Cotelle, Yoann; Benz, Sebastian; Avestro, Alyssa-Jennifer; Ward, Thomas R; Sakai, Naomi; Matile, Stefan

    2016-03-18

    To integrate anion-π, cation-π, and ion pair-π interactions in catalysis, the fundamental challenge is to run reactions reliably on aromatic surfaces. Addressing a specific question concerning enolate addition to nitroolefins, this study elaborates on Leonard turns to tackle this problem in a general manner. Increasingly refined turns are constructed to position malonate half thioesters as close as possible on π-acidic surfaces. The resulting preorganization of reactive intermediates is shown to support the disfavored addition to enolate acceptors to an absolutely unexpected extent. This decisive impact on anion-π catalysis increases with the rigidity of the turns. The new, rigidified Leonard turns are most effective with weak anion-π interactions, whereas stronger interactions do not require such ideal substrate positioning to operate well. The stunning simplicity of the motif and its surprisingly strong relevance for function should render the introduced approach generally useful. PMID:26916316

  20. Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the surface chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Jayachandran, Suseendran, E-mail: suseendran.jayachandran@imec.be [KU Leuven, Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Delabie, Annelies; Billen, Arne [KU Leuven, Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Dekkers, Harold; Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Caymax, Matty [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, Wilfried [KU Leuven, Department of Physics and Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Heyns, Marc [KU Leuven, Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2015-01-01

    Highlights: • Atomic layer is deposited by O{sub 3} chemisorption reaction on H-terminated Si(100). • O-content has critical impact on the epitaxial thickness of the above-deposited Si. • Oxygen atoms at dimer/back bond configurations enable epitaxial Si on O atomic layer. • Oxygen atoms at hydroxyl and more back bonds, disable epitaxial Si on O atomic layer. - Abstract: Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous.