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Sample records for stearic acid monolayer

  1. Stability of stearic acid monolayers on artificial sea water

    NARCIS (Netherlands)

    Brzozowska, A.M.; Duits, Michael H.G.; Mugele, Friedrich Gunther

    2012-01-01

    We studied the formation and stability of stearic acid (SA) based films on aqueous sub-phases via Langmuir trough and imaging ellipsometry experiments. The aqueous phase was based on Artificial Sea Water (ASW), a multicomponent salt solution with a total molarity of 0.53. The composition of this

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-11-15

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

  3. 21 CFR 184.1090 - Stearic acid.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Stearic acid. 184.1090 Section 184.1090 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1090 Stearic acid. (a) Stearic acid (C18H36O2, CAS Reg. No. 57-11-4) is a...

  4. Salt dependent stability of stearic acid Langmuir-Blodgett films exposed to aqueous electrolytes

    NARCIS (Netherlands)

    Kumar, Naveen; Wang, Lei; Sîretanu, Igor; Duits, Michael H.G.; Mugele, Friedrich Gunther

    2013-01-01

    We use contact angle goniometry, imaging ellipsometry, and atomic force microscopy to study the stability and wettability of Langmuir–Blodgett (LB) monolayers of stearic acid on silica substrates, upon drying and exposure to aqueous solutions of varying salinity. The influences of Ca2+ and Na+ ions

  5. Selective deoxygenation of stearic acid via an anhydride pathway

    NARCIS (Netherlands)

    Hollak, S.A.W.; Bitter, W.; Haveren, van J.; Es, van D.S.

    2012-01-01

    Stearic anhydride is proposed as reactive intermediate in the hydrogen free decarbonylation and ketonization of stearic acid over Pd/Al2O3 at 523 K. This information is crucial towards developing of a selective low temperature decarbonylation process of fatty acids towards olefins.

  6. Extraction of europium (3) ions with stearic acid

    International Nuclear Information System (INIS)

    Lobanov, F.I.; Gladyshchev, V.P.; Nurtaeva, A.K.; Andreeva, N.N.

    1981-01-01

    Extraction of europium (3) in nitric acid solutions with the melts of stearic acid and its mixtures with paraffin at (80+-1) deg C is studied. The constant of stearic acid dimerization in paraffin K 2 =9.6+-0.6 and the constant of stearic acid distribution in the paraffin-water system Ksub(D,HA)=(1.06+-0.07)x10sub(3) are determined. The diagram of europium ion extraction at initial concentrations of metal in the aqueous phase of 10 -4 -10 -3 mol/l is suggested. The compound extracted has the EuA 3 composition with extraction constant of lg Ksub(ex)=-7.58 [ru

  7. Adsorption properties of stearic acid onto untreated kaolinite | Sari ...

    African Journals Online (AJOL)

    The focus of the study is to investigate adsorption property and determine thermodynamic parameters for the adsorption of stearic acid onto untreated kaolinite at the temperatures of 25, 35 and 45 oC. The equilibrium adsorption isotherms were analyzed by linear Langmuir and Freundlich models. Adsorption experiments ...

  8. Effect of uncoated calcium carbonate and stearic acid coated ...

    Indian Academy of Sciences (India)

    PBT/CaCO3 composites were prepared in a single screw extruder with particle content varying from 0–30% by weight. The influence of surface treatment of the particles, with and without stearic acid (SA), on the mechanical, thermal and structural properties was studied. The experiments included tensile tests, impact tests, ...

  9. Comparative Study of Stearic Acid/Iron-Oxide Binary and Stearic Acid/Iron-Oxide/Titanium-Oxide Ternary for Use as Energy Storage Material

    International Nuclear Information System (INIS)

    Andiarto, Rizky; Nuryadin, Muhammad Khalish; Saleh, Rosari

    2016-01-01

    In this work, a series of stearic acid/Fe 3 O 4 , and stearic acid/Fe 3 O 4 /TiO 2 nanocomposites for thermal energy storage (TES) system were synthesized through a two-step process. Fe 3 O 4 nanoparticles and Fe 3 O 4 /TiO 2 nanocomposites were first prepared using sol-gel methods and then both samples were mixed into stearic acid by dispersion technique at three different weight % ratio to stearic acid: 5%, 10% and 15% to obtain stearic acid/Fe 3 O 4 , and stearic acid/Fe 3 O 4 /TiO 2 nanocomposites. Morphologies and structural properties of the samples were characterized by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy (EDX), while thermal properties of the sample were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The XRD patterns demonstrate, that stearic acid/Fe 3 O 4 contained characteristic peaks of Fe 3 O 4 and stearic acid structures, while peaks corresponded to anatase TiO 2 structures appear in stearic acid/ Fe 3 O 4 /TiO 2 nanocomposites. From the DSC measurements, it is found that the maximum latent heat was found at samples with weight ratio of 5%. Moreover, the enhancement up to 20% of latent heat in solidifying as well as melting processes was observed. TGA measurements show high degradation temperature in the range of 246 - 251°C. The TGA results also shows that the residual mass of the sample matches the composition of Fe 3 O 4 and Fe 3 O 4 /TiO 2 which is added to the stearic acid. (paper)

  10. PSI1 is responsible for the stearic acid enrichment that is characteristic of phosphatidylinositol in yeast

    DEFF Research Database (Denmark)

    Le Guédard, Marina; Bessoule, Jean-Jacques; Boyer, Valérie

    2009-01-01

    complete disappearance of stearic (but not of palmitic acid) at the sn-1 position of this phospholipid. Moreover, it was found that, whereas glycerol 3-phosphate, lysophosphatidic acid and 1-acyl lysophosphatidylinositol acyltransferase activities were similar in microsomal membranes isolated from wild......-acyl-1-lysolysophosphatidylinositol acyltransferase activity was recovered, and was accompanied by a strong increase in the stearic acid content of lysophosphatidylinositol. As previously suggested for phosphatidylinositol from animal cells (which contains almost exclusively stearic acid...... as the saturated fatty acid), the results obtained in the present study demonstrate that the existence of phosphatidylinositol species containing stearic acid in yeast results from a remodeling of neo-synthesized molecules of phosphatidylinositol....

  11. Dietary stearic acid leads to a reduction of visceral adipose tissue in athymic nude mice.

    Directory of Open Access Journals (Sweden)

    Ming-Che Shen

    Full Text Available Stearic acid (C18:0 is a long chain dietary saturated fatty acid that has been shown to reduce metastatic tumor burden. Based on preliminary observations and the growing evidence that visceral fat is related to metastasis and decreased survival, we hypothesized that dietary stearic acid may reduce visceral fat. Athymic nude mice, which are used in models of human breast cancer metastasis, were fed a stearic acid, linoleic acid (safflower oil, or oleic acid (corn oil enriched diet or a low fat diet ad libitum. Total body weight did not differ significantly between dietary groups over the course of the experiment. However visceral fat was reduced by ∼70% in the stearic acid fed group compared to other diets. In contrast total body fat was only slightly reduced in the stearic acid diet fed mice when measured by dual-energy x-ray absorptiometry and quantitative magnetic resonance. Lean body mass was increased in the stearic acid fed group compared to all other groups by dual-energy x-ray absorptiometry. Dietary stearic acid significantly reduced serum glucose compared to all other diets and increased monocyte chemotactic protein-1 (MCP-1 compared to the low fat control. The low fat control diet had increased serum leptin compared to all other diets. To investigate possible mechanisms whereby stearic acid reduced visceral fat we used 3T3L1 fibroblasts/preadipocytes. Stearic acid had no direct effects on the process of differentiation or on the viability of mature adipocytes. However, unlike oleic acid and linoleic acid, stearic acid caused increased apoptosis (programmed cell death and cytotoxicity in preadipocytes. The apoptosis was, at least in part, due to increased caspase-3 activity and was associated with decreased cellular inhibitor of apoptosis protein-2 (cIAP2 and increased Bax gene expression. In conclusion, dietary stearic acid leads to dramatically reduced visceral fat likely by causing the apoptosis of preadipocytes.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-31

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

  13. Physicochemical and Mechanical Properties of Bambara Groundnut Starch Films Modified with Stearic Acid.

    Science.gov (United States)

    Oyeyinka, Samson A; Singh, Suren; Amonsou, Eric O

    2017-01-01

    The physicochemical and mechanical properties of biofilm prepared from bambara starch modified with varying concentrations of stearic acid (0%, 2.5%, 3.5%, 5%, 7%, and 10%) were studied. By scanning electron microscopy, bambara starch films modified with stearic acid (≥3.5%) showed a progressively rough surface compared to those with 2.5% stearic acid and the control. Fourier transform infrared spectroscopy spectra revealed a peak shift of approximately 31 cm -1 , suggesting the promotion of hydrogen bond formation between hydroxyl groups of starch and stearic acid. The addition of 2.5% stearic acid to bambara starch film reduced water vapor permeability by approximately 17%. Bambara starch films modified with higher concentration of stearic acid were more opaque and showed significantly high melting temperatures. However, mechanical properties of starch films were generally negatively affected by stearic acid. Bambara starch film may be modified with 2.5% stearic acid for improved water vapor permeability and thermal stability with minimal effect on tensile strength. © 2016 Institute of Food Technologists®.

  14. Preparation and characterization of stearic acid/expanded graphite composites as thermal energy storage materials

    International Nuclear Information System (INIS)

    Fang, Guiyin; Li, Hui; Chen, Zhi; Liu, Xu

    2010-01-01

    Stearic acid/expanded graphite composites with different mass ratios were prepared by absorbing liquid stearic acid into the expanded graphite. In the composite materials, the stearic acid was used as the phase change material for thermal energy storage, and the expanded graphite acted as the supporting material. Fourier transformation infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermal diffusivity measurement were used to determine the chemical structure, crystalline phase, microstructure and thermal diffusivity of the composites, respectively. The thermal properties and thermal stability were investigated by differential scanning calorimetry and thermogravimetric analysis. The thermal analysis results indicated that the materials exhibited the same phase transition characteristics as the stearic acid and their latent heats were approximately the same as the values calculated based on the weight fraction of the stearic acid in the composites. The microstructural analysis results showed that the stearic acid was well absorbed in the porous network of the expanded graphite, and there was no leakage of the stearic acid from the composites even when it was in the molten state.

  15. Step Changes and Deactivation Behavior in the Continuous Decarboxylation of Stearic Acid

    DEFF Research Database (Denmark)

    Madsen, Anders Theilgaard; Rozmysłowicz, Bartosz; Simakova, Irina L.

    2011-01-01

    Deoxygenation of dilute and concentrated stearic acid over 2% Pd/C beads was performed in a continuous reactor at 300 °C and 20 bar pressure of Ar or 5% H2/Ar. Stable operation was obtained in 5% H2 atmosphere, with 95% conversion of 10 mol % dilute stearic acid in dodecane and 12% conversion...... of pure stearic acid. Deactivation took place in H2-deficient gas atmosphere, probably as a result of the formation of unsaturated products and coking in the pore system. Transient experiments with step changes were performed: 1 h was required for the step change to be visible in liquid sampling, whereas...

  16. Gene silencing of stearoyl-ACP desaturase enhances the stearic acid content in Chlamydomonas reinhardtii

    NARCIS (Netherlands)

    Jaeger, de L.; Springer, J.; Wolbert, E.J.H.; Martens, D.E.; Eggink, G.; Wijffels, R.H.

    2017-01-01

    In this study, stearoyl-ACP desaturase (SAD), the enzyme that converts stearic acid into oleic acid, is silenced by artificial microRNA in the green microalga Chlamydomonas reinhardtii. Two different constructs, which target different positions on the mRNA of stearoyl-ACP desaturase, were tested.

  17. Characterizing time-dependent contact angles for sands hydrophobized with oleic and stearic acids

    DEFF Research Database (Denmark)

    Subedi, S; Kawamoto, K; Jayarathna, L

    2012-01-01

    -frequency precipitation. A potential solution is to alter soil grain surfaces to become water repellent by mixing or coating the soil cover material with hydrophobic agents (HAs). In this study, hydrophobic CBs comprised of sands mixed with environmentally friendly HAs (oleic acid [OA] and stearic acid [SA]) were studied...

  18. Studies on morphology of Langmuir-Blodgett films of stearic acid deposited with different orientation of substrates with respect to compression

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, Keerti; Manjuladevi, V.; Gupta, R. K., E-mail: raj@pilani.bits-pilani.ac.in [Department of physics, Birla Institute of Technology & Science, Pilani-333031, Rajasthan (India)

    2016-05-06

    The Langmuir monolayer at an air-water interface shows remarkably different surface pressure – area isotherm, when measured with the surface normal of a Wilhemly plate parallel or perpendicular to the direction of compression of the monolayer. Such difference arises due to difference in stress exerted by the monolayer on the plate in different direction. In this article, we report the effect of changing the direction of substrate normal with respect to the compression of the monolayer during Langmuir-Blodgett (LB) film deposition on the morphology of the films. The morphology of the LB film of stearic acid was studied using an atomic force microscope (AFM). The morphology of the LB films was found to be different due to difference in the stress in different directions.

  19. Stearic acid: a possible substitute for trans fatty acids from industrial origin

    Directory of Open Access Journals (Sweden)

    Tavella, Marcelo

    2011-06-01

    Full Text Available Trans isomers, contained in partially hydrogenated oils, which are used in the food industry, have been questioned and nowadays trends are heading towards reducing their consumption. The food industry is facing a dilemma, since in order to remove trans fatty acids, hydrogenated fats should be eliminated and replaced by fats rich in saturated fatty acids. Scientific research has shown that saturated fatty acids have negative effects on the lipid profile and its consumption is associated with a higher cardiovascular risk. Therefore it is recommended to avoid their consumption. Nevertheless, not all fatty acids behave in the same way, with stearic acid (18:0 the exception. Stearic acid has a low level of intestinal absorption and its intake does not negatively modify the lipid profile. For this reason, it is considered a “neutral” fatty acid with regard to cardiovascular health. B-100 apolipoprotein, whose levels determine plasma VLDL and LDL concentration (triglycerides and cholesterol carriers, respectively, is not modified by diets which provide up to 7% of the energy as stearic acid. Markers of cardiovascular risk, such as activation of platelet aggregation factors or C-reactive protein levels, are not modified by diets providing stearic acid, as occurs with other saturated fatty acids. The confirmation of the “neutral” effect of stearic acid represents a perspective for the development of fats with high contents of this fatty acid to replace hydrogenated fats containing trans isomers. The present review discusses these aspects.Los isómeros trans que contienen los aceites parcialmente hidrogenados de origen industrial, han sido cuestionados y la recomendación es reducir su consumo. La industria de alimentos se enfrenta a un dilema, ya que para disminuir los isómeros trans debe reducir los aceites parcialmente hidrogenados y reemplazarlos por grasas ricas en ácidos grasos saturados. La investigación ha demostrado que los

  20. Step changes and deactivation behaviour in the continuous decarboxylation of stearic acid

    DEFF Research Database (Denmark)

    Madsen, Anders Theilgaard; Rozmyslowicz, B.; Simakova, I.

    2011-01-01

    % conversion of pure stearic acid. Deactivation took place in H-2-deficient gas atmosphere, probably as a result of the formation of unsaturated products and coking in the pore system. Transient experiments with step changes were performed: 1 h was required for the step change to be visible in liquid sampling...

  1. Stearic acid spin labels in lipid bilayers :  insight through atomistic simulations

    NARCIS (Netherlands)

    Stimson, L.M.; Dong, L.; Karttunen, M.E.J.; Wisniewska, A.; Dutka, M.; Róg, T.

    2007-01-01

    Spin-labeled stearic acid species are commonly used for electron paramagnetic resonance (EPR) studies of cell membranes to investigate phase transitions, fluidity, and other physical properties. In this paper, we use large-scale molecular dynamics simulations to investigate the position and behavior

  2. Isolation and characterisation of nanoparticles from tef and maize starch modified with stearic acid

    CSIR Research Space (South Africa)

    Cuthbert, WO

    2017-07-01

    Full Text Available Nanoparticles were isolated from tef and maize starch modified with added stearic acid after pasting at 90 °C for 130 min. This was followed by thermo-stable alpha-amylase hydrolysis of the paste. The resultant residues were then characterized using...

  3. Optimising Refined Bleached Deodorized Palm Stearin For Its Crude Stearic Acid Iodine Value To Provide The Stable Specification Of Blended Stearic Acid Distillate Iodine Value

    OpenAIRE

    Ritonga, Muhammad Yusuf

    2015-01-01

    On the commercial scale, the quality standard of Blended Stearic Acid Distilled (BSAD) couldn’t be achieved by normal distillation. BSAD iodine value is mostly higher than maximum quality standard (0.2 mg/100 g), with the same iodine value (0.80 g/100 g) of feed Hydrogenated Splitted RBDPS Fatty Acid or HSRBDPSFA, feed capacity 5.5 ton/hour with bottom flash distiller temperature reaching 213oC. The separation and reduction of chemical impurities (so sensitive to oxidation/temperature/heat ch...

  4. Enhancement of heat transfer for thermal energy storage application using stearic acid nanocomposite with multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Li, TingXian; Lee, Ju-Hyuk; Wang, RuZhu; Kang, Yong Tae

    2013-01-01

    A latent heat storage nanocomposite made of stearic acid (SA) and multi-walled carbon nanotube (MWCNT) is prepared for thermal energy storage application. The thermal properties of the SA/MWCNT nanocomposite are characterized by SEM (scanning electron microscopy) and DSC (differential scanning calorimeter) analysis techniques, and the effects of different volume fractions of MWCNT on the heat transfer enhancement and thermal performance of stearic acid are investigated during the charging and discharging phases. The SEM analysis shows that the additive of MWCNT is uniformly distributed in the phase change material of stearic acid, and the DSC analysis reveals that the melting point of SA/MWCNT nanocomposite shifts to a lower temperature during the charging phase and the freezing point shifts to a higher temperature during the discharging phase when compared with the pure stearic acid. The experimental results show that the addition of MWCNT can improve the thermal conductivity of stearic acid effectively, but it also weakens the natural convection of stearic acid in liquid state. In comparison with the pure stearic acid, the charging rate can be decreased by about 50% while the discharging rate can be improved by about 91% respectively by using the SA/5.0% MWCNT nanocomposite. It appears that the MWCNT is a promising candidate for enhancing the heat transfer performance of latent heat thermal energy storage system. - Highlights: • A nanocomposite made of stearic acid and multi-walled carbon nanotube is prepared for thermal energy storage application. • Effects of multi-walled carbon nanotube on the thermal performance of the nanocomposite are investigated. • Multi-walled carbon nanotube enhances the thermal conductivity but weakens the natural convection of stearic acid. • Discharging/charging rates of stearic acid are increased/decreased by using multi-walled carbon nanotube

  5. Relationship between the concentrations of plasma phospholipid stearic acid and plasma lipoprotein lipids in healthy men.

    Science.gov (United States)

    Li, D

    2001-01-01

    This study investigated the correlation between the plasma phospholipid (PL) saturated fatty acid (SFA) concentration (as a surrogate marker of SFA intake) and plasma lipid and lipoprotein lipid concentrations in 139 healthy Australian men aged 20-55 years old with widely varying intakes of saturated fat (vegans, n=18; ovolacto vegetarians, n=43; moderate meat eaters, n=60; high meat eaters, n=18). Both the ovolacto vegetarian and vegan groups demonstrated significant decreases in plasma total cholesterol (TC), low-density-lipoprotein cholesterol (LDL-C) and triacylglycerol concentrations compared with both the high-meat-eater and moderate-meat-eater groups. Total SFA and individual SFA [palmitic acid (16:0), stearic acid (18:0) and arachidic acid (20:0)] in the plasma PL were significantly lower in both the ovolacto vegetarian and vegan groups than in both the high- and moderate-meat-eater groups, while myristic acid (14:0) was significantly lower in the vegans than in the high-meat-eaters. Bivariate analysis of the results showed that the plasma PL stearic acid concentration was strongly positively correlated with plasma TC (P<0.0001), LDL-C (P<0.0001) and triacylglycerol (P<0.0001), with r(2) values of 0.655, 0.518 and 0.43 respectively. In multiple linear regression, after controlling for potential confounding factors (such as exercise, dietary group, age, body mass index, plasma PL myristic acid, palmitic acid and arachidic acid, and dietary total fat, saturated fat, cholesterol, carbohydrate and fibre intake), the plasma PL stearic acid concentration was still strongly positively correlated with plasma TC (P<0.0001) and LDL-C (P=0.006) concentrations. Based on the present data, it would seem appropriate for the population to reduce their dietary total SFA intake rather than to replace other SFA with stearic acid.

  6. Mesoporous (Ta, Nb3W7 Modified with Stearic Acid Used as Solid Acids for Esterification

    Directory of Open Access Journals (Sweden)

    Fei Chang

    2017-01-01

    Full Text Available Mesoporous solid acids Ta3W7 and Nb3W7 were prepared from TaCl5 and NbCl5 with WCl6 in the presence of stearic acid (SA via a sol-gel method, respectively. For comparison, mesoporous Ta3W7-P123 mixed oxides and mesoporous Nb3W7-P123 mixed oxides were synthesized in the same way. The catalysts were characterized through TGA, XRD, SEM, TEM, BET, and NH3-TPD. Experimental results showed that Ta3W7-SA and Nb3W7-SA exhibited several advantages such as higher activity, shorter preparation period, lower cost, stronger acid sites, and higher surface area, which had potential to be used as mesoporous heterogeneous catalysts in biodiesel production.

  7. Friction reducing behavior of stearic acid film on a textured aluminum substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Quan [School of Mechanical Engineering, Qingdao Technological University, Qingdao 266033 (China); Wan, Yong, E-mail: wanyong@qtech.edu.cn [School of Mechanical Engineering, Qingdao Technological University, Qingdao 266033 (China); Li, Yang; Yang, Shuyan [School of Mechanical Engineering, Qingdao Technological University, Qingdao 266033 (China); Yao, Wenqing [Analysis Center of Tsinghua University, Beijing 100084 (China)

    2013-09-01

    A simple two-step process was developed to render the aluminum hydrophobicity with lower friction. The textured aluminum substrate was firstly fabricated by immersed in a sodium hydroxide solution at 100 °C for 1 h. Stearic acid film was then deposited to acquire high hydrophobicity. Scanning electron microscopy, IR spectroscopy and water contact angle measurements were used to analyze the morphological features, chemical structure and hydrophobicity of prepared samples, respectively. Moreover, the friction reducing behavior of the organic–inorganic composite film on aluminum sliding against steel was evaluated in a ball-on-plate configuration. It was found that the stearic acid film on the textured aluminum led to decreased friction with significantly extended life.

  8. Effects of butter oil blends with increased concentrations of stearic, oleic and linolenic acid on blood lipids in young adults

    DEFF Research Database (Denmark)

    Becker, Claus; Lund, Pia; Hølmer, Gunhild Kofoed

    1999-01-01

    : Partially replacing milk fat with rapeseed oil seems to yield amore healthy spread. Stearic acid had a HDL-C lowering effect compared to milk fat, but did not affect LDL-Csignificantly. The addition of stearic acid did not improve the plasma lipoprotein profile for young men with lowcholesterol levels....... Bconcentrations. Fatty acid composition of plasma phospholipids, plasma cholesterol ester and platelets was alsodetermined. RESULTS: Significantly (P

  9. Polytypism in n-fatty acids and low-frequency Raman spectra: Stearic acid B form

    Science.gov (United States)

    Kobayashi, Masamichi; Kobayashi, Tohru; Itoh, Yuzo; Sato, Kiyotaka

    1984-03-01

    Single crystals of single-layered (mon) and double-layered (orth II) polytypes of stearic acid B form were obtained and their structures were investigated by the x-ray diffraction and vibrational spectroscopic methods. Two polytypes exhibited quite different Raman spectra in the frequency range from 65 to 2 cm-1. The Raman bands appeared as singlets in mon, while they split into doublets with different polarization in orth II through the interlamellar interactions between two successive layers contained in the unit cell. The frequencies of the phonon modes in orth II were found to be lower than the corresponding ones in mon, indicating that orth II (or mon) was the high-temperature (low-temperature) stable form.

  10. Ruminal microbe of biohydrogenation of trans-vaccenic acid to stearic acid in vitro

    Directory of Open Access Journals (Sweden)

    Li Dan

    2012-02-01

    Full Text Available Abstract Background Optimization of the unsaturated fatty acid composition of ruminant milk and meat is desirable. Alteration of the milk and fatty acid profile was previously attempted by the management of ruminal microbial biohydrogenation. The aim of this study was to identify the group of ruminal trans-vaccenic acid (trans-11 C18:1, t-VA hydrogenating bacteria by combining enrichment studies in vitro. Methods The enrichment culture growing on t-VA was obtained by successive transfers in medium containing t-VA. Fatty acids were detected by gas chromatograph and changes in the microbial composition during enrichment were analyzed by denaturing gradient gel electrophoresis (DGGE. Prominent DGGE bands of the enrichment cultures were identified by 16S rRNA gene sequencing. Results The growth of ruminal t-VA hydrogenating bacteria was monitored through the process of culture transfer according to the accumulation of stearic acid (C18:0, SA and ratio of the substrate (t-VA transformed to the product (SA. A significant part of the retrieved 16S rRNA gene sequences was most similar to those of uncultured bacteria. Bacteria corresponding to predominant DGGE bands in t-VA enrichment cultures clustered with t-VA biohydrogenated bacteria within Group B. Conclusions This study provides more insight into the pathway of biohydrogenation. It also may be important to control the production of t-VA, which has metabolic and physiological benefits, through management of ruminal biohydrogenation bacterium.

  11. Development of a Controlled Release of Salicylic Acid Loaded Stearic Acid-Oleic Acid Nanoparticles in Cream for Topical Delivery

    Directory of Open Access Journals (Sweden)

    J. O. Woo

    2014-01-01

    Full Text Available Lipid nanoparticles are colloidal carrier systems that have extensively been investigated for controlled drug delivery, cosmetic and pharmaceutical applications. In this work, a cost effective stearic acid-oleic acid nanoparticles (SONs with high loading of salicylic acid, was prepared by melt emulsification method combined with ultrasonication technique. The physicochemical properties, thermal analysis and encapsulation efficiency of SONs were studied. TEM micrographs revealed that incorporation of oleic acid induces the formation of elongated spherical particles. This observation is in agreement with particle size analysis which also showed that the mean particle size of SONs varied with the amount of OA in the mixture but with no effect on their zeta potential values. Differential scanning calorimetry analysis showed that the SONs prepared in this method have lower crystallinity as compared to pure stearic acid. Different amount of oleic acid incorporated gave different degree of perturbation to the crystalline matrix of SONs and hence resulted in lower degrees of crystallinity, thereby improving their encapsulation efficiencies. The optimized SON was further incorporated in cream and its in vitro release study showed a gradual release for 24 hours, denoting the incorporation of salicylic acid in solid matrix of SON and prolonging the in vitro release.

  12. Effect of stearic acid on the properties of metronidazole/methocel K4M floating matrices

    Directory of Open Access Journals (Sweden)

    Belem Lara-Hernández

    2009-09-01

    Full Text Available The properties of metronidazole/Methocel K4M sustained release floating tablets have been studied varying the proportion of the lubricant, stearic acid, on formulations with and without sodium bicarbonate. The variables studied include technological properties of the tablets such as tablet hardness and ejection pressure, the drug release profile, the hydration kinetics and the floating behaviour. The presence of stearic acid and sodium bicarbonate improves the floating behaviour for more than 8 hours. The hydration volume, the tablet hardness and the ejection pressure decrease as the stearic acid content increases and the polymer content decreases. Drug dissolution increases with increasing proportions of stearic acid and decreasing proportions of the polymer in the tablets. The presence of sodium bicarbonate extends the differences in dissolution produced by stearic acid. These results are attributed to decreasing matrices coherence with an increasing quantity of stearic acid and a reducing polymer proportion. The carbon dioxide bubbles produced by sodium bicarbonate expand the matrices facilitating the dissolution, although their presence obstructs also the diffusion path through the hydrated gel layer.Estudaram-se as propriedades de comprimidos flutuantes de metronidazol/Methocel K4M de liberação controlada, variando-se a proporção do lubrificante, ácido esteárico, nas formulações com e sem bicarbonato de sódio. As variáveis estudadas incluem propriedades tecnológicas dos comprimidos, tais como dureza, pressão de ejeção, perfil de liberação do fármaco, cinética de hidratação e comportamento de flutuação. A presença de ácido esteárico e do bicarbonato de sódio melhora o comportamento de flutuação para mais de 8 horas. O volume de hidratação, a dureza e a pressão de ejeção do comprimido decrescem à medida que o conteúdo de ácido esteárico e de polímero diminui. A dissolução do fármaco aumenta com o

  13. Spontaneous transfer of stearic acids between human serum albumin and PEG:2000-grafted DPPC membranes.

    Science.gov (United States)

    Pantusa, Manuela; Stirpe, Andrea; Sportelli, Luigi; Bartucci, Rosa

    2010-05-01

    Electron spin resonance (ESR) spectroscopy is used to study the transfer of stearic acids between human serum albumin (HSA) and sterically stabilized liposomes (SSL) composed of dipalmitoylphosphatidylcholine (DPPC) and of submicellar content of poly(ethylene glycol:2000)-dipalmitoylphosphatidylethanolamine (PEG:2000-DPPE). Protein/lipid dispersions are considered in which spin-labelled stearic acids at the 16th carbon atom along the acyl chain (16-SASL) are inserted either in the protein or in the SSL. Two component ESR spectra with different rotational mobility are obtained over a broad range of temperature and membrane composition. Indeed, superimposed to an anisotropic protein-signal, appears a more isotropic lipid-signal. Since in the samples only one matrix (protein or membranes) is spin-labelled, the other component accounts for the transfer of 16-SASL between albumin and membranes. The two components have been resolved and quantified by spectral subtractions, and the fraction, f (p) (16-SASL), of spin labels bound non-covalently to the protein has been used to monitor the transfer. It is found that it depends on the type of donor and acceptor matrix, on the physical state of the membranes and on the grafting density of the polymer-lipids. Indeed, it is favoured from SSL to HSA and the fraction of stearic acids transferred increases with temperature in both directions of transfer. Moreover, in the presence of polymer-lipids, the transfer from HSA to SSL is slightly attenuated, especially in the brush regime of the polymer-chains. Instead, the transfer from SSL to HSA is favoured by the polymer-lipids much more in the mushroom than in the brush regime.

  14. Stearic acid coating on circulating fluidized bed combustion fly ashes and its effect on the mechanical performance of polymer composites

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Nina [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Zhang, Ping, E-mail: pingzhang@swust.edu.cn [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); School of Material Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Song, Lixian; Kang, Ming; Lu, Zhongyuan [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); School of Material Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Zheng, Rong [Sichuan Jinhe Group Co., Ltd., Mianyang 621010 (China)

    2013-08-15

    The aim of this work was to test circulating fluidized bed combustion fly ashes (CFAs) for its potential to be utilized in polymer composites manufacturing to improve its toughness. CFAs was coated by stearic acid and used in the composite of polypropylene/ethylene vinyl acetate/high density polyethylene (PP/EVA/HDPE) by molding process method. The resulting coated and uncoated CFAs were fully characterized by particle size analyzer, contact angles, powder X-ray diffraction (XRD), thermogravimetric analysis/differential thermal analysis (TGA/DTA), Brunauer–Emmett–Teller (BET), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The stearic acid coated onto the surface of CFAs particles in the physical and chemical ways, and the total clad ratio reached 2.05% by measuring TGA/DTA curve. The percentage of CFAs particles focused to a narrow range 2–4 μm and the median mean size was 3.2 μm more than uncoated CFAs. The properties of hydrophobic and dispersive of CFAs particles improved and original activity was reserved after stearic acid coating. The stearic acid was verified as a coupling agent by how much effect it had on the mechanical properties. It showed the elongation at break of PP/EVA/HDPE reinforced with 15 wt% coated CFAs (c-CFAs) was 80.20% and higher than that of the uncoated. The stearic acid treatment of CFAs is a very promising approach to improve the mechanical strength due to the incorporation of stearic acid on the CFAs surface, and hence, further enhances the potential for recycling CFAs as a suitable filler material in polymer composites.

  15. Stearic acid coating on circulating fluidized bed combustion fly ashes and its effect on the mechanical performance of polymer composites

    International Nuclear Information System (INIS)

    Yao, Nina; Zhang, Ping; Song, Lixian; Kang, Ming; Lu, Zhongyuan; Zheng, Rong

    2013-01-01

    The aim of this work was to test circulating fluidized bed combustion fly ashes (CFAs) for its potential to be utilized in polymer composites manufacturing to improve its toughness. CFAs was coated by stearic acid and used in the composite of polypropylene/ethylene vinyl acetate/high density polyethylene (PP/EVA/HDPE) by molding process method. The resulting coated and uncoated CFAs were fully characterized by particle size analyzer, contact angles, powder X-ray diffraction (XRD), thermogravimetric analysis/differential thermal analysis (TGA/DTA), Brunauer–Emmett–Teller (BET), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The stearic acid coated onto the surface of CFAs particles in the physical and chemical ways, and the total clad ratio reached 2.05% by measuring TGA/DTA curve. The percentage of CFAs particles focused to a narrow range 2–4 μm and the median mean size was 3.2 μm more than uncoated CFAs. The properties of hydrophobic and dispersive of CFAs particles improved and original activity was reserved after stearic acid coating. The stearic acid was verified as a coupling agent by how much effect it had on the mechanical properties. It showed the elongation at break of PP/EVA/HDPE reinforced with 15 wt% coated CFAs (c-CFAs) was 80.20% and higher than that of the uncoated. The stearic acid treatment of CFAs is a very promising approach to improve the mechanical strength due to the incorporation of stearic acid on the CFAs surface, and hence, further enhances the potential for recycling CFAs as a suitable filler material in polymer composites.

  16. Chemical surface modification of calcium carbonate particles with stearic acid using different treating methods

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Zhi [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland); Daly, Michael [Mergon International, Castlepollard, Westmeath (Ireland); Clémence, Lopez [Polytech Grenoble, Grenoble (France); Geever, Luke M.; Major, Ian; Higginbotham, Clement L. [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland); Devine, Declan M., E-mail: ddevine@ait.ie [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland)

    2016-08-15

    Highlights: • The effects of stearic acid treatment for CaCO{sub 3} are highly influenced by the treatment method of application. • A new stearic acid treatment method, namely, combination treatment for CaCO{sub 3} was developed. • The combination treatment was compared with two of the existing methods dry and wet method. • The negative effects of void coalescence was minimised by the utilization of the combination method. - Abstract: Calcium carbonate (CaCO{sub 3}) is often treated with stearic acid (SA) to decrease its polarity. However, the method of application of the SA treatments has a strong influence on CaCO{sub 3} thermoplastic composite’s interfacial structure and distribution. Several of papers describe the promising effects of SA surface treatment, but few compare the treatment process and its effect on the properties of the final thermoplastic composite. In the current study, we assessed a new SA treatment method, namely, complex treatment for polymer composite fabrication with HDPE. Subsequently, a comparative study was performed between the “complex” process and the other existing methods. The composites were assessed using different experiments included scanning electron microscopy (SEM), void content, density, wettability, differential scanning calorimetry (DSC), and tensile tests. It was observed that the “complex” surface treatment yielded composites with a significantly lower voids content and higher density compared to other surface treatments. This indicates that after the “complex” treatment process, the CaCO{sub 3} particles and HDPE matrix are more tightly packed than other methods. DSC and wettability results suggest that the “wet” and “complex” treated CaCO{sub 3} composites had a significantly higher heat of fusion and moisture resistance compared to the “dry” treated CaCO{sub 3} composites. Furthermore, “wet” and “complex” treated CaCO{sub 3} composites have a significantly higher tensile

  17. Enzymatic Synthesis and Characterization of Hydrophilic Sugar Based Polyesters and Their Modification with Stearic Acid

    Directory of Open Access Journals (Sweden)

    Muhammad Humayun Bilal

    2016-03-01

    Full Text Available Biodegradable and hydrophilic functional polyesters were synthesized enzymatically using xylitol or d-sorbitol together with divinyl adipate and lipase B from Candida antartica (CAL-B. The resulting polyesters had pendant OH-groups from their sugar units which were esterified to different degrees with stearic acid chloride. The structure and the degrees of polymerization of the resulting graft copolymers based on poly(xylitol adipate and poly(d-sorbitol adipate were characterized by 1H NMR spectroscopy and SEC. DSC, WAXS and SAXS measurements indicated that a phase separation between polymer backbone and stearoyl side chains occurred in the graft copolymers, and, additionally, the side chains were able to crystallize which resulted in the formation of a lamellar morphology. Additionally, nanoparticles of the graft copolymers in an aqueous environment were studied by DLS and negative stain TEM.

  18. Effects of spray-drying on w/o/w multiple emulsions prepared from a stearic acid matrix

    CSIR Research Space (South Africa)

    Mlalila, N

    2014-12-01

    Full Text Available , 75, and 100 mg of stearic acid, 2% and 3% w/v polyvinyl alcohol, 5% w/v lactose, and 0.2% w/v chitosan. The emulsions were immediately spray-dried based on an optimized model of inlet temperature and pump rate, and characterized for optimized...

  19. Hydrogenation Alternatives - Effects of Trans-Fatty-Acids and Stearic-Acid Versus Linoleic-Acid on Serum-Lipids and Lipoproteins in Humans

    NARCIS (Netherlands)

    Zock, P.L.; Katan, M.B.

    1992-01-01

    The objective of this study was to compare the effects of linoleic acid (cis,cis-C18:2(n-6)) and its hydrogenation products elaidic (trans-C18:1(n-9)) and stearic acid (C18:0) on serum lipoprotein levels in humans.Twenty-six men and 30 women, all nor

  20. Bactericidal activity of self-assembled palmitic and stearic fatty acid crystals on highly ordered pyrolytic graphite.

    Science.gov (United States)

    Ivanova, Elena P; Nguyen, Song Ha; Guo, Yachong; Baulin, Vladimir A; Webb, Hayden K; Truong, Vi Khanh; Wandiyanto, Jason V; Garvey, Christopher J; Mahon, Peter J; Mainwaring, David E; Crawford, Russell J

    2017-09-01

    The wings of insects such as cicadas and dragonflies have been found to possess nanostructure arrays that are assembled from fatty acids. These arrays can physically interact with the bacterial cell membranes, leading to the death of the cell. Such mechanobactericidal surfaces are of significant interest, as they can kill bacteria without the need for antibacterial chemicals. Here, we report on the bactericidal effect of two of the main lipid components of the insect wing epicuticle, palmitic (C16) and stearic (C18) fatty acids. Films of these fatty acids were re-crystallised on the surface of highly ordered pyrolytic graphite. It appeared that the presence of two additional CH 2 groups in the alkyl chain resulted in the formation of different surface structures. Scanning electron microscopy and atomic force microscopy showed that the palmitic acid microcrystallites were more asymmetric than those of the stearic acid, where the palmitic acid microcrystallites were observed to be an angular abutment in the scanning electron micrographs. The principal differences between the two types of long-chain saturated fatty acid crystallites were the larger density of peaks in the upper contact plane of the palmitic acid crystallites, as well as their greater proportion of asymmetrical shapes, in comparison to that of the stearic acid film. These two parameters might contribute to higher bactericidal activity on surfaces derived from palmitic acid. Both the palmitic and stearic acid crystallite surfaces displayed activity against Gram-negative, rod-shaped Pseudomonas aeruginosa and Gram-positive, spherical Staphylococcus aureus cells. These microcrystallite interfaces might be a useful tool in the fabrication of effective bactericidal nanocoatings. Nanostructured cicada and dragonfly wing surfaces have been discovered to be able physically kill bacterial cells. Here, we report on the successful fabrication of bactericidal three-dimensional structures of two main lipid

  1. Thermal Characterization of Lauric-Stearic Acid/Expanded Graphite Eutectic Mixture as Phase Change Materials.

    Science.gov (United States)

    Zhu, Hua; Zhang, Peng; Meng, Zhaonan; Li, Ming

    2015-04-01

    The eutectic mixture of lauric acid (LA) and stearic acid (SA) is a desirable phase change material (PCM) due to the constant melting temperature and large latent heat. However, its poor thermal conductivity has hampered its broad utilization. In the present study, pure LA, SA and the mixtures with various mass fractions of LA-SA were used as the basic PCMs, and 10 wt% expanded graphite (EG) was added to enhance the thermal conductivities. The phase change behaviors, microstructural analysis, thermal conductivities and thermal stabilities of the mixtures of PCMs were investigated by differential scanning calorimetry (DSC), scanning electronic microscope (SEM), transient plane source (TPS) and thermogravimetric analysis (TGA), respectively. The results show that the LA-SA binary mixture of mixture ratio of 76.3 wt%: 23.7 wt% forms an eutectic mixture, which melts at 38.99 °C and has a latent heat of 159.94 J/g. The melted fatty acids are well absorbed by the porous network of EG and they have a good thermal stability. Furthermore, poor thermal conductivities can be well enhanced by the addition of EG.

  2. Stability, occurrence and step morphology of polymorphs and polytypes of stearic acid. I. Stability and occurrence

    Science.gov (United States)

    Sato, Kiyotaka; Kobayashi, Masamichi; Morishita, Hirofumi

    1988-02-01

    The thermodynamical stability and occurrence of three different structural modifications: monoclinic and pseudo-orthorhombic polytypes of the B polymorph, called B(mon) and B(orth II) respectively, and monoclinic C polymorph, C(mon), of stearic acid have been examined. The solubility measurements, overgrowth and isothermal crystallization proved that B(orth II) and C(mon) are most stable below and above 32°C, respectively, whereas B(mon) is always metastable, turning to be more stable than C(mon) below between 23 and 24°C. It was confirmed by micro-probe Raman spectroscopy that the polytypic structure of the newly-overgrown crystal on the (001) faces of the seed crystal of B(mon) changed from the original monoclinic to pseudo-orthorhombic, B(orth II), at very small supersaturations above 23°C. This conversion was caused by the solubility difference. The occurrence experiment indicated a slight tendency that B(mon) crystallized more than B(orth II) at lower temperatures.

  3. Melting properties of some structured lipids native to high stearic acid soybean oil

    Directory of Open Access Journals (Sweden)

    Dunn, R. O.

    2004-06-01

    Full Text Available A number of structured lipids native to high stearic acid soybean oil were synthesized and their physical properties were determined by pulsed nuclear magnetic resonance (NMR, Mettler dropping point and differential scanning calorimetry (DSC. 1,3 Distearo-2-olein (SOS, 1,3 distearo-2-linolein (SLS and1,3 distearo-2-linolenin (SlnS were synthesized from pure 1,3 diacylglycerols and the appropriate fatty acid. Pulsed NMR determinations over the temperature range 10-50 ºC showed that the symmetrical triacylglycerols (SUS: where S = stearic, U = oleic, linoleic or linolenic are high and sharply melting materials, all showing substantial amounts of solids at temperatures up to 33.3 ºC, yet are completely melted at only a few degrees higher. Mettler dropping points for SOS, SLS and SlnS were 44.1, 37.9 and 36.5 ºC respectively. The heats of fusion for the structured triacylglycerols were determined by DSC and shown to be of the order 29-32 cal/gm compared to 45 cal/gm for SSS. The heats of fusion were also calculated from Mettler dropping point determinations as admixtures with soybean oil and showed consistent agreement with the DSC data.Se sintetizaron algunos lípidos estructurados procedentes del aceite de soja con alto contenido en ácido esteárico y sus propiedades físicas se determinaron por resonancia magnética nuclear pulsada (NMR, punto de goteo Mettler y calorimetría diferencial de barrido (DSC. Se sintetizaron 1,3 diestearo-2-oleina (SOS, 1,3 diestearo-2-linoleina (SLS y 1,3 diestearo-2-linolenina (SlnS a partir de 1,3 diacilgliceroles y de los ácidos grasos adecuados puros. Las determinaciones de NMR pulsada en el rango de temperaturas 10- 50 ºC mostraron que los triacilgliceroles simétricos (SUS: donde S = esteárico, U = oleico, linoleico o linolénico funden a mayor temperatura y más bruscamente, todos presentan altos contenidos en sólidos a todas las temperaturas hasta los 33.3 ºC, estando completamente fundidos

  4. Improving the physical and moisture barrier properties of Lepidium perfoliatum seed gum biodegradable film with stearic and palmitic acids.

    Science.gov (United States)

    Seyedi, Samira; Koocheki, Arash; Mohebbi, Mohebbat; Zahedi, Younes

    2015-01-01

    Stearic and palmitic fatty acids (10%, 20% and 30%, W/W gum) were used to improve the barrier properties of Lepidium perfoliatum seed gum (LPSG) film. The impact of the incorporation of fatty acids into the film matrix was studied by investigating the physical, mechanical, and barrier properties of the films. Addition of stearic and palmitic fatty acids to LPSG films reduced their water vapor permeability (WVP), moisture content, water solubility and water adsorption. Increasing fatty acid concentration from 10% to 30%, reduced the elongation at break (EB). Lower values of tensile strength (TS) and elastic modulus (EM) were obtained in the presence of higher fatty acids concentrations. Incorporation of fatty acids led to production of opaque films and the opacity increased as function of fatty acids concentration. Results showed that moisture content, water solubility and WVP decreased as the chain length of fatty acid increased. Therefore, LPSG-fatty acids composite film could be used for packaging in which a low affinity toward water is needed. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Dielectric dispersion and thermodynamic behavior of stearic acid binary mixtures with alcohol as co-solvent using time domain reflectometry

    Directory of Open Access Journals (Sweden)

    M. Maria Sylvester

    2017-08-01

    Full Text Available Dielectric permittivity and relaxation dynamics of binary and ternary mixture of stearic acid on various concentration and their thermodynamic effects are studied. The static dielectric constant (ε0, dielectric permittivity (ε′ and dielectric loss (ε′′ are found by bilinear calibration. The relaxation time (τ, dielectric strength (Δε and the excess permittivity (εE are found. The thermodynamic parameters such as enthalpy (ΔH, entropy (ΔS and Gibb’s free energy (ΔG are evolved. The significant changes in dielectric parameters are due to the intramolecular and intermolecular interactions in response to the applied frequency. The permittivity spectra of stearic acid–alcohol in the frequency range of 10MHz to 30GHz have been measured using picoseconds Time Domain Reflectometry (TDR. The dielectric parameters (ε0, ε′, ε′′ are found by bilinear calibration method. Influence of temperature in intermolecular interaction and the relaxation process are also studied. The FT-IR spectral analysis reveals that the conformation of functional groups and formation for hydrogen bonding are present in both binary and ternary mixtures of stearic acid.

  6. Milk production and nutrient digestibility responses to increasing levels of stearic acid supplementation of dairy cows.

    Science.gov (United States)

    Boerman, J P; de Souza, J; Lock, A L

    2017-04-01

    The objective of our study was to evaluate the dose-response effects of a stearic acid (C18:0)-enriched supplement on nutrient digestibility, production responses, and the maximum amount of C18:0 that can be incorporated into the milk fat of dairy cows. Multiparous Holstein cows (n = 32; 145 ± 66 d in milk) with a wide range in milk yield (30 to 70 kg/d) were blocked by milk yield and assigned to replicated 4 × 4 Latin squares. Treatments were diets supplemented with a C18:0-enriched supplement (SA; 93% C18:0) at 0, 0.80, 1.50, or 2.30% of diet dry matter (DM). Periods were 21 d with the final 5 d used for data and sample collection. Dry matter intake increased linearly as SA supplementation increased. Supplementation of SA had no effect on the yield of milk or milk components. Due to the increase in DM intake, SA linearly reduced the ratio of energy-corrected milk to DM intake. Supplementation of SA did not affect body weight. Increasing SA reduced digestibility of 16-carbon, 18-carbon, and total fatty acids (FA), with the reduction in digestibility of 18-carbon FA being approximately 30 percentage units from the 0.0 to 2.30% SA supplemented diets. Supplementation of SA linearly increased concentrations of preformed milk fatty acids (FA) but did not affect the yield of preformed milk FA. Yields of C18:0 plus cis-9 C18:1 were increased by SA supplementation; however, the increase from 0 to 2.3% SA was only 16 g/d. The concentration and yield of de novo and 16-carbon milk FA were unaffected by SA supplementation. In conclusion, increasing doses of SA decreased FA digestibility and had little effect on production parameters. Although SA increased the yield of C18:0 and cis-9 C18:1 in milk fat, it had no overall effect on milk fat yield. The lack of production responses to a C18:0-enriched fat supplement was most likely associated with the marked decrease in FA digestibility. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights

  7. Construction of Bifunctional Co/H-ZSM-5 Catalysts for the Hydrodeoxygenation of Stearic Acid to Diesel-range Alkanes.

    Science.gov (United States)

    Wu, Guangjun; Zhang, Nan; Dai, Weili; Guan, Naijia; Li, Landong

    2018-04-27

    Bifunctional Co/H-ZSM-5 zeolites were prepared by surface organometallic chemistry grafting route, namely by the stoichiometric reaction between cobaltocene and the Brønsted acid sites in zeolites, and applied to the model reaction of stearic acid catalytic hydrodeoxygenation. Cobalt species existed in the form of isolated Co2+ ions at exchange positions after grafting, transformed to CoO species on the surface of zeolite and stabilized inside zeolite channels upon calcination in air, and finally reduced to metallic cobalt species of homogeneous clusters of ca. 1.5 nm by hydrogen. During this process, the Brønsted acid sites of H-ZSM-5 zeolites could be preserved with acid strength slightly reduced. The as-prepared bifunctional catalyst exhibited a ~16 times higher activity in stearic acid hydrodeoxygenation (2.11 gSAgcat-1h-1) than the reference catalyst (0.13 gSAgcat-1h-1) prepared by solid-state ion exchange, and a high C18/C17 ratio of ~24 was achieved as well. The remarkable hydrodeoxygenation performance of bifunctional Co/H-ZSM-5 could be explained from the effective synergy between the uniformed metallic cobalt clusters and the Brønsted acid sites in H-ZSM-5 zeolite. The simplified reaction network and kinetics of stearic acid hydrodeoxygenation catalyzed by the as-prepared bifunctional Co/H-ZSM-5 zeolites were also investigated. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Acid monolayer functionalized iron oxide nanoparticle catalysts

    Science.gov (United States)

    Ikenberry, Myles

    Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide

  9. Fabrication and characterization of stearic acid/polyaniline composite with electrical conductivity as phase change materials for thermal energy storage

    International Nuclear Information System (INIS)

    Wang, Yi; Ji, Hui; Shi, Huan; Zhang, Ting; Xia, TianDong

    2015-01-01

    Highlights: • Stearic acid/polyaniline composite PCM with electrical conductivity was fabricated. • Stearic acid acted as thermal energy storage media and doping acid. • Latent heats of SA/PANI are as high as the same type composites. • Improved electrical conductivity of capsules is 0.7042 S cm −1 . - Abstract: This paper presents the experimental investigation on the thermal properties and electrical conductivity of the new microencapsulated phase change material by entrapping of stearic acid (SA) into PANI (polyaniline) shell through self-assembly method. Experimental results reveal that PANI nuclei grew on the surface of SA, and then copied its original morphological structure and finally exhibited peony flower-like morphology. The two components have good compatibility and have no chemical reaction both in the process of fabrication and subsequent use, while hydrogen bondings between the imino groups and carboxyl groups exist. The maximum mass fraction of stearic acid loaded in SA/PANI is determined as high as 62.1 wt% without seepage of melted SA from capsules. Due to the secondary doping with carboxyl group, the composite phase change material embedded with SA exhibits improved electrical conductivity from 0.3968 S cm −1 to 0.7042 S cm −1 when compared to PANI. The phase change temperatures and latent heats of SA/PANI are measured to be 55.6 °C and 113.02 J/g for melting and, 50.8 °C and 112.58 J/g for freezing, respectively. TG analysis test revealed that the prepared SA/PANI composite PCM has high thermal durability in working temperature range. Moreover, the results of DSC, FT-IR, TG, conductivity investigation and thermal cycling test are all show that the thermal reliability and electrical conductivity of the SA/APNI have imperceptible changes. In total, the additional electrical conductivity, high heat storage potential and good thermal reliability and stability facilitated SA/PANI to be considered as a viable candidate for thermal

  10. Viability of the microencapsulation of a casein hydrolysate in lipid microparticles of cupuacu butter and stearic acid

    Directory of Open Access Journals (Sweden)

    Samantha Cristina Pinho

    2013-04-01

    Full Text Available Normal 0 21 false false false PT-BR X-NONE X-NONE Solid lipid microparticles produced with a mixture of cupuacu butter and stearic acid were used to microencapsulate a commercial casein hydrolysate (Hyprol 8052. The composition of the lipid matrix used for the production of the lipid microparticles was chosen according to data on the wide angle X-ray diffraction (WAXD and differential scanning calorimetry (DSC of bulk lipid mixtures, which indicated that the presence of 10 % cupuacu butter was sufficient to significantly change the crystalline arrangement of pure stearic acid. Preliminary tests indicated that a minimum proportion of 4 % of surfactant (polysorbate 80 was necessary to produce empty spherical lipid particles with average diameters below 10 mm. The lipid microparticles were produced using 20 % cupuacu butter and 80 % stearic acid and then stabilized with 4 % of polysorbate 80, exhibiting an encapsulation efficiency of approximately 74 % of the casein hydrolysate. The melting temperature of the casein hydrolysate-loaded lipid microparticles was detected at 65.2 °C, demonstrating that the particles were solid at room temperature as expected and indicating that the incorporation of peptides had not affected their thermal behavior. After 25 days of storage, however, there was a release of approximately 30 % of the initial amount of encapsulated casein hydrolysate. This release was not thought to have been caused by the liberation of encapsulated casein hydrolysate. Instead, it was attributed to the possible desorption of the adsorbed peptides present on the surface of the lipid microparticles.

  11. Effects of spray-drying on w/o/w multiple emulsions prepared from a stearic acid matrix

    Directory of Open Access Journals (Sweden)

    Mlalila N

    2014-12-01

    Full Text Available Nichrous Mlalila,1 Hulda Swai,2 Lonji Kalombo,2 Askwar Hilonga3 1School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania; 2Materials Science and Manufacturing, Council for Scientific and Industrial Research, Pretoria, South Africa; 3Department of Materials Science and Engineering, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania Abstract: The goal of this study was to explore the effects of spray-drying on w/o/w double emulsions of methyltestosterone (MT loaded in a stearic acid matrix. MT-loaded nanoparticles were formulated by a water-in-oil-in-water emulsion technique using 50, 75, and 100 mg of stearic acid, 2% and 3% w/v polyvinyl alcohol, 5% w/v lactose, and 0.2% w/v chitosan. The emulsions were immediately spray-dried based on an optimized model of inlet temperature and pump rate, and characterized for optimized responses with regard to particle size, polydispersity index, and zeta potential, for both emulsion and powder samples. Dynamic light scattering analysis shown that the nanoparticles increased in size with increasing concentrations of polyvinyl alcohol and stearic acid. Scanning electron microscopy indicated that the MT-loaded nanoparticles were spherical in shape, had a smooth surface, and were in an amorphous state, which was confirmed by differential scanning calorimetry. These MT-loaded nanoparticles are a promising candidate carrier for the delivery of MT; however, further studies are needed in order to establish the stability of the system and the cargo release profile under normal conditions of use. Keywords: double emulsions, nanoparticles, pump rate, spray-drying, testosterone

  12. Study on thermal property of lauric–palmitic–stearic acid/vermiculite composite as form-stable phase change material for energy storage

    Directory of Open Access Journals (Sweden)

    Nan Zhang

    2015-09-01

    Full Text Available The form-stable composite phase change material of lauric–palmitic–stearic acid ternary eutectic mixture/vermiculite was prepared by vacuum impregnation method for thermal energy storage. The maximum mass fraction of lauric–palmitic–stearic acid ternary eutectic mixture retained in vermiculite was determined as 50 wt% without melted phase change material seepage from the composite phase change material. Fourier transformation infrared spectroscope and scanning electron microscope were used to characterize the structure and morphology of the prepared lauric–palmitic–stearic acid ternary eutectic mixture/vermiculite form-stable composite phase change material, and the results indicate that lauric–palmitic–stearic acid ternary eutectic mixture was well confined into the layer porous structure of vermiculite by physical reaction. The melting and freezing temperatures and latent heats were measured by differential scanning calorimeter as 31.4°C and 30.3°C, and 75.8 and 73.2 J/g, respectively. Thermal cycling test showed that there was no significant change in the thermal properties of lauric–palmitic–stearic acid ternary eutectic mixture/vermiculite form-stable composite phase change material after 1000 thermal cycles. Moreover, 2 wt% expanded graphite was added to improve the thermal conductivity of lauric–palmitic–stearic acid ternary eutectic mixture/vermiculite form-stable composite phase change material. All results indicated that the prepared lauric–palmitic–stearic acid ternary eutectic mixture/vermiculite form-stable composite phase change material had suitable thermal properties and good thermal reliability for the application of thermal energy storage in building energy efficiency.

  13. Digestibility of Fatty Acids in the Gastrointestinal Tract of Dairy Cows Fed with Tallow or Saturated Fats Rich in Stearic Acid or Palmitic Acid

    DEFF Research Database (Denmark)

    Weisbjerg, Martin Riis; Hvelplund, Torben; Børsting, Christian Friis

    1992-01-01

    Fatty acid digestibility was studied with five lactating cows fed three different fat sources in a 5 × 5 latin square experiment. The treatments were 500 g of tallow, 500 or 1000 g of saturated fat rich in stearic acid (C18:0) (SARF) or 500 or 1000 g of saturated fat rich in palmitic acid (C16......:0) (PARF) per day. The total daily fatty acid intake was about 1100 g in rations with the highest fat inclusion. The fatty acid digestibilities were 76% for tallow, 74 and 64% for 500 and 1000 g SARF, respectively, and 87 and 81% for 500 and 1000 g of PARF, respectively. When compared to fatty acid...... digestibility for tallow predicted from a model based on literature values, PARF had a higher fatty acid digestibility at both fat intakes, and SARF had a lower fatty acid digestibility, especially at high fat intake....

  14. , , , , , and Gene Expression in Single- and Co-cultured Bovine Satellite Cells and Intramuscular Preadipocytes Treated with Palmitic, Stearic, Oleic, and Linoleic Acid

    Directory of Open Access Journals (Sweden)

    S. H. Choi

    2015-03-01

    Full Text Available We previously demonstrated that bovine subcutaneous preadipocytes promote adipogenic gene expression in muscle satellite cells in a co-culture system. Herein we hypothesize that saturated fatty acids would promote adipogenic/lipogenic gene expression, whereas mono- and polyunsaturated fatty acids would have the opposite effect. Bovine semimembranosus satellite cells (BSC and intramuscular preadipocytes (IPA were isolated from crossbred steers and cultured with 10% fetal bovine serum (FBS/Dulbecco’s Modified Eagle Medium (DMEM and 1% antibiotics during the 3-d proliferation period. After proliferation, cells were treated for 3 d with 3% horse serum/DMEM (BSC or 5% FBS/DMEM (IPA with antibiotics. Media also contained 10 μg/mL insulin and 10 μg/mL pioglitazone. Subsequently, differentiating BSC and IPA were cultured in their respective media with 40 μM palmitic, stearic, oleic, or linoleic acid for 4 d. Finally, BSC and IPA were single- or co-cultured for an additional 2 h. All fatty acid treatments increased (p = 0.001 carnitine palmitoyltransferase-1 beta (CPT1β gene expression, but the increase in CPT1β gene expression was especially pronounced in IPA incubated with palmitic and stearic acid (6- to 17- fold increases. Oleic and linoleic acid decreased (p = 0.001 stearoyl-CoA desaturase (SCD gene expression over 80% in both BSC and IPA. Conversely, palmitic and stearic acid increased SCD gene expression three fold in co-cultured in IPA, and stearic acid increased AMPKα gene expression in single- and co-cultured BSC and IPA. Consistent with our hypothesis, saturated fatty acids, especially stearic acid, promoted adipogenic and lipogenic gene expression, whereas unsaturated fatty acids decreased expression of those genes associated with fatty acid metabolism.

  15. Preparation and characterization of dutasteride-loaded nanostructured lipid carriers coated with stearic acid-chitosan oligomer for topical delivery.

    Science.gov (United States)

    Noor, Norhayati Mohamed; Sheikh, Khalid; Somavarapu, Satyanarayana; Taylor, Kevin M G

    2017-08-01

    Dutasteride, used for treating benign prostate hyperplasia (BPH), promotes hair growth. To enhance delivery to the hair follicles and reduce systemic effects, in this study dutasteride has been formulated for topical application, in a nanostructured lipid carrier (NLC) coated with chitosan oligomer-stearic acid (CSO-SA). CSO-SA has been successfully synthesized, as confirmed using 1 H NMR and FTIR. Formulation of dutasteride-loaded nanostructured lipid carriers (DST-NLCs) was optimized using a 2 3 full factorial design. This formulation was coated with different concentrations of stearic acid-chitosan solution. Coating DST-NLCs with 5% SA-CSO increased mean size from 187.6±7.0nm to 220.1±11.9nm, and modified surface charge, with zeta potentials being -18.3±0.9mV and +25.8±1.1mV for uncoated and coated DST-NLCs respectively. Transmission electron microscopy showed all formulations comprised approximately spherical particles. DST-NLCs, coated and uncoated with CSO-SA, exhibited particle size stability over 60days, when stored at 4-8°C. However, NLCs coated with CSO (without conjugation) showed aggregation when stored at 4-8°C after 30days. The measured particle size for all formulations stored at 25°C suggested aggregation, which was greatest for DST-NLCs coated with 10% CSO-SA and 5% CSO. All nanoparticle formulations exhibited rapid release in an in vitro release study, with uncoated NLCs exhibiting the fastest release rate. Using a Franz diffusion cell, no dutasteride permeated through pig ear skin after 48h, such that it was not detected in the receptor chamber for all samples. The amount of dutasteride in the skin was significantly different (pchitosan conjugate was successfully prepared, and modified the surface charge of DST-NLCs from negative to positive. These stable, less cytotoxic, positively-charged dutasteride-loaded nanostructured lipid carriers, with stearic acid-chitosan oligomer conjugate, are appropriate for topical delivery and have

  16. Polarized Raman and Infrared Spectroscopy and ab Initio Calculation of Palmitic and Stearic Acids in the Bm and C Forms.

    Science.gov (United States)

    L da Silva, L F; Andrade-Filho, T; Freire, P T C; Filho, J Mendes; da Silva Filho, J G; Saraiva, G D; Moreira, S G C; de Sousa, F F

    2017-06-29

    A complete experimental study on the vibrational properties of palmitic and stearic acids crystallized in the B m and C forms, both belonging to the monoclinic system with the P2 1 /a (C 2h 5 ) space group, through polarized Raman and infrared spectroscopy, is reported in this paper. Density functional theory calculations were also performed to assign the normal modes and to help in the interpretation of the experimental data. The different polarizations were compared and their influence on the spectral profiles, in both the lattice and the internal mode regions, was discussed. In general, the Raman and infrared spectra exhibit accentuated differences among the polymorphic forms, which are associated with the different molecular modifications, defined as gauche and all-trans conformations. Insights about interaction among different groups are also furnished.

  17. Thermal properties and reliability of eutectic mixture of stearic acid-acetamide as phase change material for latent heat storage

    International Nuclear Information System (INIS)

    Ma, Guixiang; Han, Lipeng; Sun, Jinhe; Jia, Yongzhong

    2017-01-01

    Highlights: • The system of stearic acid-acetamide binary mixtures were studied as phase change material. • The eutectic mixtures featured low melting temperatures and high latent heats of fusion for latent heat storage. • Solid-liquid phase diagrams for the system were constructed. • Negligible change in stability after 500 heating/cooling cycles. - Abstract: The thermal properties and reliability of the stearic acid (SA) with acetamide (AC) binary mixture were characterized using differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR). The phase diagrams for the SA-AC binary mixture with AC in the metastable and the stable form were constructed. The eutectic system with stable AC is 0.604 mol fraction SA, and displayed a melting temperature (T m ) of 64.55 °C and latent heat of melting (ΔH m ) of 193.87 J·g −1 . The eutectic systems with metastable AC are 0.397 and 0.604 mol fraction SA. The melting temperatures are 62.23 °C and 62.54 °C, and latent heats of fusion are 222.10 J·g −1 and 194.28 J·g −1 , respectively. Following accelerated thermal cycling tests, TG and FT-IR analysis indicate that the eutectic mixture (χ SA = 0.397) with the metastable AC has good cyclic and thermal stability. The results show that the SA-AC eutectic mixture use as phase change material (PCM) possess good prospect for low temperature thermal energy storage (TES) applications.

  18. Incorporation of nano-clay saponite layers in the organo-clay hybrid films using anionic amphiphile stearic acid by Langmuir–Blodgett technique

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Syed Arshad, E-mail: sa_h153@hotmail.com [Department of Physics, Tripura University, Suryamaninagar-799022 (India); Chakraborty, S.; Bhattacharjee, D. [Department of Physics, Tripura University, Suryamaninagar-799022 (India); Schoonheydt, R.A. [Centres for Surface Chemistry and Catalysis, K.U. Leuven, Kasteelpark Arenberg 23, 3001 Leuven (Belgium)

    2013-06-01

    In general cationic amphiphiles are used to prepare organo-clay hybrid film in Langmuir–Blodgett (LB) technique. In this present communication we demonstrated a unique technique to prepare the organo–clay hybrid films using an anionic amphiphile. The T–O–T type clay saponite was incorporated onto a floating stearic acid monolayer via a divalent cation Mg{sup 2+}. Salt MgCl{sub 2} was mixed along with the clay dispersion in the LB trough and amphiphile solution was spread onto the subphase in order to make the organo-clay hybrid films. It was observed that salt (MgCl{sub 2}) concentration on the subphase affects the organization of nano-dimensional clay platelet (saponite) in organo-clay hybrid films at air–water interface as well as in LB films. Noticeable changes in area per molecule and shape of the isotherms were observed and measured at subphases with different salt concentrations. Infrared reflection absorption spectroscopy studies reveal that only an in-plane (996 cm{sup −1}) vibration of ν (Si-O) band occurred when the salt concentration was 10 mM. However, both in-plane (996 cm{sup −1}) and out-of-plane (1063 cm{sup −1}) vibrations of the ν (Si-O) band of saponite occurred when the subphase salt concentration was 100 mM. Also the out-of-plane vibration of ν (OH) of saponite was prominent at higher salt concentration. This is because at lower salt concentration clay sheets remain flat on the surface whereas; at higher MgCl{sub 2} concentration they aggregated and form stacks of saponite layers. Also they may be slightly tilted with a very small tilt angle at higher salt concentration making a favorable condition for both in-plane and out-of-plane vibrations of ν (Si-O) in the hybrid films. Observed decrease in starting area per molecule in the pressure area isotherm measured at higher salt concentration also supports the tilting of clay layers at air–clay dispersion interface. Attentuated total reflectance Fourier transform infrared

  19. PSI1 is responsible for the stearic acid enrichment that is characteristic of phosphatidylinositol in yeast

    NARCIS (Netherlands)

    Le Guédard, Marina; Bessoule, Jean-Jacques; Boyer, Valérie; Ayciriex, Sophie; Velours, Gisèle; Kulik, Willem; Ejsing, Christer S.; Shevchenko, Andrej; Coulon, Denis; Lessire, René; Testet, Eric

    2009-01-01

    In yeast, both phosphatidylinositol and phosphatidylserine are synthesized from cytidine diphosphate-diacylglycerol. Because, as in other eukaryotes, phosphatidylinositol contains more saturated fatty acids than phosphatidylserine (and other phospholipids), it has been hypothesized that either

  20. Facile Fabrication of a PDMS@Stearic Acid-Kaolin Coating on Lignocellulose Composites with Superhydrophobicity and Flame Retardancy

    Directory of Open Access Journals (Sweden)

    Zhe Wang

    2018-05-01

    Full Text Available The disadvantages such as swelling after absorbing water and flammability restrict the widespread applications of lignocellulose composites (LC. Herein, a facile and effective method to fabricate superhydrophobic surfaces with flame retardancy on LC has been investigated by coating polydimethylsiloxane (PDMS and stearic acid (STA modified kaolin (KL particles. The as-prepared coatings on the LC exhibited a good repellency to water (a contact angle = 156°. Owing to the excellent flame retardancy of kaolin particles, the LC coated with PDMS@STA-KL displayed a good flame retardancy during limiting oxygen index and cone calorimeter tests. After the coating treatment, the limiting oxygen index value of the LC increased to 41.0. Cone calorimetry results indicated that the ignition time of the LC coated with PDMS@STA-KL increased by 40 s compared with that of uncoated LC. Moreover, the peak heat release rate (PHRR and the total heat release (THR of LC coated with PDMS@STA-KL reduced by 18.7% and 19.2% compared with those of uncoated LC, respectively. This LC coating with improved water repellency and flame retardancy can be considered as a potential alternative to protect the lignocellulose composite.

  1. Investigation of cutaneous penetration properties of stearic acid loaded to dendritic core-multi-shell (CMS) nanocarriers.

    Science.gov (United States)

    Lohan, S B; Icken, N; Teutloff, C; Saeidpour, S; Bittl, R; Lademann, J; Fleige, E; Haag, R; Haag, S F; Meinke, M C

    2016-03-30

    Dendritic core-multi shell (CMS) particles are polymer based systems consisting of a dendritic polar polyglycerol polymer core surrounded by a two-layer shell of nonpolar C18 alkyl chains and hydrophilic polyethylene glycol. Belonging to nanotransport systems (NTS) they allow the transport and storage of molecules with different chemical characters. Their amphipihilic character CMS-NTS permits good solubility in aqueous and organic solutions. We showed by multifrequency electron paramagnetic resonance (EPR) spectroscopy that spin-labeled 5-doxyl stearic acid (5DSA) can be loaded into the CMS-NTS. Furthermore, the release of 5DSA from the carrier into the stratum corneum of porcine skin was monitored ex vivo by EPR spectroscopy. Additionally, the penetration of the CMS-NTS into the skin was analyzed by fluorescence microscopy using indocarbocyanine (ICC) covalently bound to the nanocarrier. Thereby, no transport into the viable skin was observed, whereas the CMS-NTS had penetrated into the hair follicles down to a depth of 340 μm ± 82 μm. Thus, it could be shown that the combined application of fluorescence microscopy and multi-frequency EPR spectroscopy can be an efficient tool for investigating the loading of spin labeled drugs to nanocarrier systems, drug release and penetration into the skin as well as the localization of the NTS in the skin. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Solar Cooker Study under Oman Conditions for Late Evening Cooking Using Stearic Acid and Acetanilide as PCM Materials

    Directory of Open Access Journals (Sweden)

    Nagaraj Nayak

    2016-01-01

    Full Text Available Solar energy is an alternative source of nonrenewable energy in Oman. Sultanate of Oman government showed initiation into utilization of solar energy for domestic applications. Conversion of solar radiation into useful heat is the simplest application of solar energy, in which it can be used for late evening cooking. In this context, present work highlighted the design and development of solar cooker for Oman climatic conditions. The current work signifies usage of solar cooker for late evening cooking using stearic acid and acetanilide as phase change materials (PCM. Solar cooker parts are developed in-house and connected to water heating system compounded with evacuated tubes solar collector and storage tank. The circumference of cooker unit is incorporated with spiral stainless steel heat exchanger and annulus area of the pot is filled with PCM material. PCM releases heat at late evening and effective cooking up to 7:30 PM is noticed. The experimental results indicated the cooker efficiency of 30% and collector efficiency of 60–65% during the study. Overall, experiments showed satisfactory performance on the developed cooker.

  3. Cu2+ Montmorillonite K10 Clay Catalyst as a Green Catalyst for Production of Stearic Acid Methyl Ester: Optimization Using Response Surface Methodology (RSM

    Directory of Open Access Journals (Sweden)

    Enas A. Almadani

    2018-01-01

    Full Text Available Clay catalyst has received much attention to replace the homogeneous catalysts in the esterification reaction to produce fatty acid methyl ester as the source of biodiesel as it is low cost, easily available, as well as environmental friendly. However, the use of unmodified clay, in particular montmorillonite K10 (MMT K10, for the esterification of fatty acids showed that the acid conversion was less than 60% and this is not preferable to the production of biodiesel. In this study, synthesis of stearic acid methyl ester using Cu2+-MMT K10 (Cu-MMT K10 was successfully optimized via response surface methodo-logy (RSM based on 3-variable of Box-Behnken design (BB. The parameters were; reaction time (5-180 minutes, reaction temperature (80-120 oC and concentration of Cu2+ in MMT K10 (0.25-1 M. The use of RSM in optimizing the conversion of stearic acid was successfully developed as the actual experimental conversion of stearic acid was found similar to the actual values under the optimum conditions. The model equation predicted that the following conditions would generate the maximum conversion of stearic acid (87.05 %reaction time of 62 minutes, a reaction temperature of 80 oC and catalyst used is 1.0 M Cu-MMT K10. This finding can be considered as green catalytic process as it worked at moderate reaction temperature using low cost clay catalyst with a short reaction time. Copyright © 2018 BCREC Group. All rights reserved Received: 26th July 2017; Revised: 13rd January 2018; Accepted: 13rd January 2018; Available online: 22nd January 2018; Published regularly: 2nd April 2018 How to Cite: Almadani, E.A., Harun, F.W., Radzi, S.M., Muhamad, S.K. (2018. Cu2+ Montmorillonite K10 Clay Catalyst as a Green Catalyst for Production of Stearic Acid Methyl Ester: Optimization Using Response Surface Methodology (RSM. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (1: 187-195 (doi:10.9767/bcrec.13.1.1397.187-195

  4. Study on performance of colloidal mixtures consisted of stearic acid and Na2HPO4.12H2O for use as phase change materials of thermal energy storage

    International Nuclear Information System (INIS)

    Tang Zhiwei; Liu Aijie; Chen Zhifeng

    2010-01-01

    The thermal energy storage performance and phase change stability of mix phase change materials consisted of stearic acid and Na 2 PO 4 .12H 2 O are studied by means of Fourier transformation infrared spectrum analyses (FTIR) and Differential Scanning Calorimetry (DSC). The specific heat capacity of mix materials is also determined experimentally. The results show that all absorption peaks of functional groups and chemical bonds of stearic acid still exist, which suggests that these crystal materials composed of stearic acid and Na 2 PO 4 .12H 2 O have good phase change stability and chemical compatibility. Thus, disadvantages caused by the subcooling of Na 2 PO 4 .H 2 O and the low specific heat capacity of stearic acid can be solved, it is speculated that complement each other on the basis of organic/inorganic characteristics in itself is carried out for these two component materials of the mixture.

  5. SYNCHROTRON X-RAY OBSERVATIONS OF A MONOLAYER TEMPLATE FOR MINERALIZATION

    International Nuclear Information System (INIS)

    Dimasi, E.; Gower, L.B.

    2000-01-01

    Mineral nucleation at a Langmuir film interface has been studied by synchrotron x-ray scattering. Diluted calcium bicarbonate solutions were used as subphases for arachidic and stearic acid monolayers, compressed in a Langmuir trough. Self-assembly of the monolayer template is observed directly, and subsequent crystal growth monitored in-situ

  6. In vitro and in vivo evaluation of docetaxel-loaded stearic acid-modified Bletilla striata polysaccharide copolymer micelles.

    Directory of Open Access Journals (Sweden)

    Qingxiang Guan

    Full Text Available Bletilla striata polysaccharides (BSPs have been used in pharmaceutical and biomedical industry, the aim of the present study was to explore a BSPs amphiphilic derivative to overcome its application limit as poorly water-soluble drug carriers due to water-soluble polymers. Stearic acid (SA was selected as a hydrophobic block to modify B. striata polysaccharides (SA-BSPs. Docetaxel (DTX-loaded SA-BSPs (DTX-SA-BSPs copolymer micelles were prepared and characterized. The DTX release percentage in vitro and DTX concentration in vivo was carried out by using high performance liquid chromatography. HepG2 and HeLa cells were subjected to MTT (3-(4, 5-dimethylthiazol-2-yl-2, 5-diphenyl tetrazonium bromide assay to evaluate the cell viability. In vitro evaluation of copolymer micelles showed higher drug encapsulation and loading capacity. The release percentage of DTX from DTX-SA-BSPs copolymer micelles and docetaxel injection was 66.93 ± 1.79% and 97.06 ± 1.56% in 2 days, respectively. The DTX-SA-BSPs copolymer micelles exhibited a sustained release of DTX. A 50% increase in growth inhibition was observed for HepG2 cells treated with DTX-SA-BSPs copolymer micelles as compared to those treated with docetaxel injection for 72 h. DTX-SA-BSPs copolymer micelles presented a similar growth inhibition effect on Hela cells. Furthermore, absolute bioavailability of DTX-SA-BSPs copolymer micelles was shown to be 1.39-fold higher than that of docetaxel injection. Therefore, SA-BSPs copolymer micelles may be used as potential biocompatible polymers for cancer chemotherapy.

  7. Nonequilibrium 2-hydroxyoctadecanoic acid monolayers: effect of electrolytes.

    Science.gov (United States)

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

    2011-04-19

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

  8. Effect of the distribution of saturated fatty acids in the melting and crystallization profiles of high-oleic high-stearic oils

    International Nuclear Information System (INIS)

    Bootello, M.A.; Garces, R.; Martinez-Force, E.; Salas, J.J.

    2016-01-01

    The composition and distribution of fatty acids in triacylglycerol (TAG) molecules are commonly considered as factors that determine the physical properties of a given oil or fat. The distribution of any fatty acid in fats and oils can be described through the α coefficient of asymmetry, which can be calculated from the TAG composition and fatty acid composition of the Sn-2 position of the TAGs determined through lipase hydrolysis. High-oleic high-stearic oils and fats are considered stable and healthy, and they are good substitutes for hydrogenated vegetable oils and palm fractions in many food products, such as spreads and confectionery. Here, different high-oleic high-stearic acid oils were formulated which contained different distributions of saturated fatty acids in their TAGs, while maintaining a similar fatty acid composition. The aim of this work was to discuss the possibility of using the α coefficient to predict the physical properties of fats in function of their chemical composition and their melting and crystallization behavior as examined by differential scanning calorimetry.

  9. Effect of expanded organoclay by stearic acid to curing, mechanical and swelling properties of natural rubber nanocomposites

    Science.gov (United States)

    Ramadhan, A.; Fathurrohman, M. Irfan; Falaah, A. F.; Setyawan, N.; Soegijono, B.

    2017-07-01

    The interlayer basal spacing of organoclay (OC) could be increased with stearic acid (SA) added, thus OC changed into expanded organoclay by SA (OCSA). The effect of various loadings of OCSA on the curing, mechanical and swelling properties of natural rubber (NR) nanocomposites were studied. The natural rubber/expanded organoclay (NR/OCSA) nanocomposites were prepared by melt intercalation using a laboratory open mill. The curing characteristics of NR compounds were determined using a Moving Die Rheometer (MDR). The X-ray Diffraction (XRD), Attenuated Total Reflectance Infrared (ATR-IR) Spectroscopy and Field Emission Scanning Electron Microscopy (FESEM) were used to study the dispersion of OCSA in the NR matrix. The mechanical properties of NR/OCSA nanocomposites such as tensile strength, elongation at break and hardness were determined using ISO standard and swelling of NR/OCSA nanocomposites in toluene were determined using ISO 1817. The results showed that the SA intercalated into the gallery of OC and reacted with the hydroxyl groups in OC. It was indicated with the shifting of the negative peak 1,700 to 1,723 cm-1 in the ATR-IR spectrum and increase the d-spacing of OC. The adding of various loadings of OCSA into NR could increase the torque and accelerate the curing of nanocomposites and it also could increase the mechanical and swelling properties of nanocomposites. The change in modulus at 100% elongation significantly increased with increasing the OCSA load until maximum loading at 10 phr. This trend was same with the hardness and modulus at 300% elongation. Meanwhile, the improvement of tensile strength and elongation at break was higher at 4 phr OCSA compared with the other loading. The increase of mechanical and swelling properties of NR/OCSA nanocomposites was due to intercalation/exfoliation of OCSA in NR matrix. It was revealed by appearing of the out-of-plane Si-O-(Al) stretch with peak value 1080 cm-1 in the ATR-IR spectrum and the peaks of OCSA

  10. Preparation of silver-cuprous oxide/stearic acid composite coating with superhydrophobicity on copper substrate and evaluation of its friction-reducing and anticorrosion abilities

    Energy Technology Data Exchange (ETDEWEB)

    Li, Peipei [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Chen, Xinhua [College of Chemistry and Chemical Engineering, Xuchang University, Xuchang 461000 (China); Yang, Guangbin; Yu, Laigui [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Zhang, Pingyu, E-mail: pingyu@henu.edu.cn [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China)

    2014-01-15

    A simple two-step solution immersion process was combined with surface-modification by stearic acid to prepare superhydrophobic coatings on copper substrates so as to reduce friction coefficient, increase wear resistance and improve the anticorrosion ability of copper. Briefly, cuprous oxide (Cu{sub 2}O) crystal coating with uniform and compact tetrahedron structure was firstly created by immersing copper substrate in 2 mol L{sup −1} NaOH solution. As-obtained Cu{sub 2}O coating was then immersed in 0.33 mmol L{sup −1} AgNO{sub 3} solution to incorporate silver nanoparticles, followed by modification with stearic acid (denoted as SA) coating to achieve hydrophobicity. The surface morphology and chemical composition of silver-cuprous oxide/stearic acid (denoted as Ag-Cu{sub 2}O/SA) composite coating were investigated using a scanning electron microscope and an X-ray photoelectron spectroscope (XPS); and its phase structure was examined with an X-ray diffractometer (XRD). Moreover, the contact angle of water on as-prepared Ag-Cu{sub 2}O/SA composite coating was measured, and its friction-reducing and anticorrosion abilities were evaluated. It was found that as-prepared Ag-Cu{sub 2}O/SA composite coating has a water contact angle of as high as 152.4{sup o} and can provide effective friction-reducing, wear protection and anticorrosion protection for copper substrate, showing great potential for surface-modification of copper.

  11. Functionalities of chitosan conjugated with stearic acid and gallic acid and application of the modified chitosan in stabilizing labile aroma compounds in an oil-in-water emulsion.

    Science.gov (United States)

    Yang, Tsung-Shi; Liu, Tai-Ti; Lin, I-Hwa

    2017-08-01

    The aims of this research were to conjugate chitosan (CT) with stearic acid (SA) and gallic acid (GA), and apply the modified chitosan to stabilize labile aroma compounds such as allyl isothiocyanate (AITC) and limonene in oil-in-water emulsions. Generally, the antioxidant activity of CT-SA-GA increased as the GA content in the conjugate increased. In most assays, GA had a lower IC 50 value than that of CT-SA-GA; however, CT-SA-GA exhibited better performance than GA in the Fe 2+ -chelating activity. In accelerated tests (heating or illumination) for evaluating the chemical stability of AITC and limonene during storage, CT-SA and CT-SA-GA were used to prepare AITC and limonene O/W emulsions, respectively. Tween 80 and Span 80 (T-S-80), an emulsifier mixture, were used as a control in both emulsions for comparison. The results show that CT-SA or CT-SA-GA could protect AITC or limonene from degradation or oxidation more effectively than T-S-80. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Metabolism in humans of cis-12,trans-15-octadecadienoic acid relative to palmitic, stearic, oleic and linoleic acids

    International Nuclear Information System (INIS)

    Emken, E.A.; Rohwedder, W.K.; Adlof, R.O.; Rakoff, H.; Gulley, R.M.

    1987-01-01

    Mixtures of triglycerides containing deuterium-labeled hexadecanoic acid (16:0), octadecanoic acid (18:0), cis-9-octadecenoic acid (9c-18:1), cis-9,cis-12-octadecadienoic acid (9c, 12c-18:2) and cis-12,trans-15-octadecadienoic acid (12c,15t-18:2) were fed to two young-adult males. Plasma lipid classes were isolated from samples collected periodically over 48 hr. Incorporation and turnover of the deuterium-labeled fats in plasma lipids were followed by gas chromatography-mass spectrometry (GC-MS) analysis of the methyl ester derivatives. Absorption of the deuterated fats was followed by GC-MS analysis of chylomicron triglycerides isolated by ultracentrifugation. Results were the following: (i) endogenous fat contributed about 40% of the total fat incorporated into chylomicron triglycerides; (ii) elongation, desaturation and chain-shortened products from the deuterated fats were not detected; (iii) the polyunsaturated isomer 12c,15t-18:2 was metabolically more similar to saturated and 9c-18:1 fatty acids than to 9c,12c-18:2; (iv) relative incorporation of 9c,12c-18:2 into phospholipids did not increase proportionally with an increase of 9c,12c-18:2 in the mixture of deuterated fats fed; (v) absorption of 16:0, 18:0, 9c-18:1, 9c,12c-18:2 and 12c,15t-18:2 were similar; and (vi) data for the 1- and 2-acyl positions of phosphatidylcholine and for cholesteryl ester fractions reflected the known high specificity of phosphatidylcholine acyltransferase and lecithin:cholesteryl acyltransferase for 9c,12c-18:2. These results illustrate that incorporation of dietary fatty acids into human plasma lipid classes is selectively controlled and that incorporation of dietary 9c,12c-18:2 is limited

  13. Epoxy Stearic Acid, an Oxidative Product Derived from Oleic Acid, Induces Cytotoxicity, Oxidative Stress, and Apoptosis in HepG2 Cells.

    Science.gov (United States)

    Liu, Ying; Cheng, Yajun; Li, Jinwei; Wang, Yuanpeng; Liu, Yuanfa

    2018-05-23

    In the present study, effects of cis-9,10-epoxy stearic acid (ESA) generated by the thermal oxidation of oleic acid on HepG2 cells, including cytotoxicity, apoptosis, and oxidative stress, were investigated. Our results revealed that ESA decreased the cell viability and induced cell death. Cell cycle analysis with propidium iodide staining showed that ESA induced cell cycle arrest at the G0/G1 phase in HepG2 cells. Cell apoptosis analysis with annexin V and propidium iodide staining demonstrated that ESA induced HepG2 cell apoptotic events in a dose- and time-dependent manner; the apoptosis of cells after treated with 500 μM ESA for 12, 24, and 48 h was 32.16, 38.70, and 65.80%, respectively. Furthermore, ESA treatment to HepG2 cells resulted in an increase in reactive oxygen species and malondialdehyde (from 0.84 ± 0.02 to 8.90 ± 0.50 nmol/mg of protein) levels and a reduction in antioxidant enzyme activity, including superoxide dismutase (from 1.34 ± 0.27 to 0.10 ± 0.007 units/mg of protein), catalase (from 100.04 ± 5.05 to 20.09 ± 3.00 units/mg of protein), and glutathione peroxidase (from 120.44 ± 7.62 to 35.84 ± 5.99 milliunits/mg of protein). These findings provide critical information on the effects of ESA on HepG2 cells, particularly cytotoxicity and oxidative stress, which is important for the evaluation of the biosafety of the oxidative product of oleic acid.

  14. Preparation and properties of palmitic-stearic acid eutectic mixture/expanded graphite composite as phase change material for energy storage

    International Nuclear Information System (INIS)

    Zhang, Nan; Yuan, Yanping; Du, Yanxia; Cao, Xiaoling; Yuan, Yaguang

    2014-01-01

    A novel composite PCM (phase change material) with PA-SA (palmitic-stearic acid) eutectic mixture as PCM and EG (expanded graphite) as supporting material was prepared. The optimum absorption ratio of PA-SA/EG (Palmitic-stearic acid/expanded graphite) composite PCM was determined as PA-SA:EG = 13:1 (by mass). Scanning electron microscope and Fourier transformation infrared spectroscopy results show that PA-SA was uniformly distributed in the porous network structure of EG due to the physical action. Thermal property and thermal stability of the PA-SA/EG composite PCM were characterized by DSC (differential scanning calorimetry) and TGA (thermogravimetric analysis). DSC results indicated that the melting and freezing temperatures and latent heats of PA-SA/EG were measured as 53.89 °C and 54.37 °C, and 166.27 J/g and 166.13 J/g. TGA test results revealed that PA-SA/EG had a good thermal stability in working temperature range. Thermal cycling test results showed PA-SA/EG had a good thermal reliability after 720 thermal cycles. Thermal conductivity of the composite PCM was measured as 2.51 W/m K, much higher than that of PA-SA. The thermal energy storage and release rates of PA-SA/EG were also increased due to the high thermal conductivity of EG. In conclusion, the prepared PA-SA/EG composite PCM can be acted as a potential material for thermal energy storage due to the acceptable thermal properties, good thermal reliability and stability, high thermal conductivity. - Highlights: • PA-SA/EG (Palmitic-stearic acid/expanded graphite) composite PCM was prepared. • Optimum absorption ratio of PA-SA in EG was obtained as 13:1 (by mass). • Thermal conductivity and performance of PA-SA/EG have been significate improved. • PA-SA/EG has a good thermal reliability and thermal stability

  15. Phase change and heat transfer characteristics of a eutectic mixture of palmitic and stearic acids as PCM in a latent heat storage system

    International Nuclear Information System (INIS)

    Baran, Guelseren; Sari, Ahmet

    2003-01-01

    The phase change and heat transfer characteristics of a eutectic mixture of palmitic and stearic acids as phase change material (PCM) during the melting and solidification processes were determined experimentally in a vertical two concentric pipes energy storage system. This study deals with three important subjects. First is determination of the eutectic composition ratio of the palmitic acid (PA) and stearic acid (SA) binary system and measurement of its thermophysical properties by differential scanning calorimetry (DSC). Second is establishment of the phase transition characteristics of the mixture, such as the total melting and solidification temperatures and times, the heat transfer modes in the melted and solidified PCM and the effect of Reynolds and Stefan numbers as initial heat transfer fluid (HTF) conditions on the phase transition behaviors. Third is calculation of the heat transfer coefficients between the outside wall of the HTF pipe and the PCM, the heat recovery rates and heat fractions during the phase change processes of the mixture and also discussion of the effect of the inlet HTF parameters on these characteristics. The DSC results showed that the PA-SA binary system in the mixture ratio of 64.2:35.8 wt% forms a eutectic, which melts at 52.3 deg. C and has a latent heat of 181.7 J g -1 , and thus, these properties make it a suitable PCM for passive solar space heating and domestic water heating applications with respect to climate conditions. The experimental results also indicated that the eutectic mixture of PA-SA encapsulated in the annulus of concentric double pipes has good phase change and heat transfer characteristics during the melting and solidification processes, and it is an attractive candidate as a potential PCM for heat storage in latent heat thermal energy storage systems

  16. Effects of seed layers on controlling of the morphology of ZnO nanostructures and superhydrophobicity of ZnO nanostructure/stearic acid composite films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jing; Liu, Zhihua, E-mail: sdwfliu@163.com; Liu, Junqi; E, Lei; Liu, Zhifeng, E-mail: tjulzf@163.com

    2016-11-01

    Hydrophobic ZnO self-cleaning thin films with the nanobundles and nanocarpets structures fabricated on indium tin oxides (ITO) glass substrate are reported. The water contact angle of ZnO nanobundles and nanocarpets structures (79° and 67° respectively) is higher than that of unmodified ZnO nanorods. A subsequent chemical treatment with stearic acid (SA) contributed to a superhydrophobic surface with a water contact angle of 159°. Its superhydrophobic property is originated from the nanobundles or nanocarpets structures and surface energy of SA/ZnO nanobundles and SA/ZnO nanocarpets composite nanostructures. Moreover, this promising ZnO nanostructured materials show an important application in self-cleaning smart coatings. - Highlights: • PEG and CTAB are firstly introduced to modify the morphology of ZnO seed layers. • ZnO nanobundles and nanocarpets obtained from different seed layers. • Superhydrophobic surfaces obtained by chemcial treatment using SA.

  17. Synthesis, characterization and optical band gap of Pirochromite (MgCr2O4 Nanoparticles by Stearic Acid Sol-Gel Method

    Directory of Open Access Journals (Sweden)

    Ehsan Jafarnejad

    2016-09-01

    Full Text Available Pirochromite (MgCr2O4 nanoparticles were successfully prepared in this study. During synthesis of the pirochromite nanoparticles, a sol-gel was prepared by using magnesium acetate and potassium dichromate as magnesium and chromium sources and by using stearic acid as the network. Infrared spectroscopy (FT-IR, X-ray diffraction (XRD, transmission electron microscope (TEM, scanning electron microscope (SEM, and energy-dispersive X-ray spectroscopy (EDX were used for the elemental analysis, and diffuse reflectance spectroscopy (DRS and vibrating sample magnetometer (VSM were used in order to identify, provide a fuzzy diagnosis, and determine the size and morphology of the particles, as well as to analyze the optical and magnetic properties of the particles. The particle size of MgCr2O4 nanoparticles was observed to fall within a range of 39 nm–71 nm.

  18. Development of novel fast-disintegrating tablets by direct compression using sucrose stearic acid ester as a disintegration-accelerating agent.

    Science.gov (United States)

    Koseki, Takuma; Onishi, Hiraku; Takahashi, Yuri; Uchida, Minoru; Machida, Yoshiharu

    2008-10-01

    It was attempted to produce novel furosemide (FS) fast-disintegrating tablets by direct compression. The combination of FS, microcrystalline cellulose, croscarmellose sodium and xylitol was used as the basic formulation, and sucrose stearic acid ester (SSE) was chosen as an additional additive. The tablets with SSE were prepared by the simple addition of SSE, using a lyophilized mixture of FS and SSE or using a FS/SSE mixture obtained by evaporation of their ethanol solution. Only the tablets, produced using the FS/SSE mixture obtained by organic solvent (ethanol) evaporation, showed hardness of more than 30 N and a disintegration time of less than 20 s, which were the properties suitable for fast-disintegrating tablets. These properties were considered to result from well-mixed and fine-powdered SSE and FS.

  19. Wireless electrochemical preparation of gradient nanoclusters consisting of copper(II), stearic acid and montmorillonite on a copper wire for headspace in-tube microextraction of chlorobenzenes.

    Science.gov (United States)

    Enteshari Najafabadi, Marzieh; Bagheri, Habib

    2017-12-26

    This work introduces a new gradient fiber coating for microextraction of chlorobenzenes. Nanoclusters of organoclay-Cu(II) on a copper wire were fabricated by wireless electrofunctionalization. The resultant gradient coatings are more robust, and thermally and mechanically stable. Wireless electrofunctionalization was carried out in a bipolar cell under a constant deposition potential and using an ethanolic electrolyte solution containing stearic acid and montmorillonite. Stearic acid acts as an inexpensive and green coating while montmorillonite acts as a modifier to impart thermal stability. The gradient morphology of the nanoclusters was investigated by scanning electron microscopy, thermogravimetric analysis and energy dispersive X-ray spectroscopy. The coated wire was placed in a hollow needle and used for headspace in-tube microextraction (HS-ITME) of chlorobenzenes (CBs). Effects of various parameters affecting synthesis and extraction were optimized. Following extraction, the needles were directly inserted into the GC injector, and the CBs (chlorobenzene, 1,4-dichlorobenzene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, 1,2,3,4-tetrachlorobenzene) were quantified by GC-MS. The limits of detection under optimized conditions range from 0.5 to 10 ng.L -1 . The intra- and inter-day relative standard deviations (RSDs) (for n = 10, 5 respectively) using a single fiber are 6-10 and 10-15%, respectively. The fiber-to-fiber RSDs (for n = 3) is between 17 and 24%. The method was successfully applied to the extraction of CBs from real water samples, and relative recoveries are between 91 and 110%. Graphical abstract A gradient coating of organoclay-Cu nanoclusters was fabricated on a copper wire by wireless electrofunctionalization. The oxidation of copper takes place at the anodic pole (red) while dissolved oxygen in ethanol solution is reduced at the cathodic pole (blue).

  20. Effect of the distribution of saturated fatty acids in the melting and crystallization profiles of high-oleic high-stearic oils

    Directory of Open Access Journals (Sweden)

    Bootello, M. A.

    2016-09-01

    Full Text Available The composition and distribution of fatty acids in triacylglycerol (TAG molecules are commonly considered as factors that determine the physical properties of a given oil or fat. The distribution of any fatty acid in fats and oils can be described through the α coefficient of asymmetry, which can be calculated from the TAG composition and fatty acid composition of the sn-2 position of the TAGs determined through lipase hydrolysis. High-oleic high-stearic oils and fats are considered stable and healthy, and they are good substitutes for hydrogenated vegetable oils and palm fractions in many food products, such as spreads and confectionery. Here, different high-oleic high-stearic acid oils were formulated which contained different distributions of saturated fatty acids in their TAGs, while maintaining a similar fatty acid composition. The aim of this work was to discuss the possibility of using the α coefficient to predict the physical properties of fats in function of their chemical composition and their melting and crystallization behavior as examined by differential scanning calorimetry.La composición y distribución de los ácidos grasos en las moléculas de triglicéridos se consideran factores determinantes en las propiedades físicas de los aceites y grasas. La distribución de ácidos grasos en un determinado aceite o grasa puede caracterizarse mediante un coeficiente de asimetría α, calculado a partir de las composiciones de triglicéridos y de ácidos grasos en la posición sn-2 de la molécula de triglicérido mediante hidrólisis con lipasa. El aceite de girasol alto oleico-alto esteárico es una grasa estable y saludable, adecuada para reemplazar a los aceites vegetales hidrogenados y fracciones de palma en muchos productos alimentarios, como grasas plásticas y grasas de confitería. En el presente trabajo, se formularon diferentes aceites alto oleico-alto esteárico con diferente distribución de los ácidos grasos saturados en

  1. Stearic acid-rich interesterified fat and trans-rich fat raise the LDL/HDL ratio and plasma glucose relative to palm olein in humans

    Directory of Open Access Journals (Sweden)

    Karupaiah Tilakavati

    2007-01-01

    Full Text Available Abstract Background Dietary trans-rich and interesterified fats were compared to an unmodified saturated fat for their relative impact on blood lipids and plasma glucose. Each fat had melting characteristics, plasticity and solids fat content suitable for use as hardstock in margarine and other solid fat formulations. Methods Thirty human volunteers were fed complete, whole food diets during 4 wk periods, where total fat (~31% daily energy, >70% from the test fats and fatty acid composition were tightly controlled. A crossover design was used with 3 randomly-assigned diet rotations and repeated-measures analysis. One test fat rotation was based on palm olein (POL and provided 12.0 percent of energy (%en as palmitic acid (16:0; a second contained trans-rich partially hydrogenated soybean oil (PHSO and provided 3.2 %en as trans fatty acids plus 6.5 %en as 16:0, while the third used an interesterified fat (IE and provided 12.5 %en as stearic acid (18:0. After 4 wk the plasma lipoproteins, fatty acid profile, as well as fasting glucose and insulin were assessed. In addition, after 2 wk into each period an 8 h postprandial challenge was initiated in a subset of 19 subjects who consumed a meal containing 53 g of test fat. Results After 4 wk, both PHSO and IE fats significantly elevated both the LDL/HDL ratio and fasting blood glucose, the latter almost 20% in the IE group relative to POL. Fasting 4 wk insulin was 10% lower after PHSO (p > 0.05 and 22% lower after IE (p Conclusion Both PHSO and IE fats altered the metabolism of lipoproteins and glucose relative to an unmodified saturated fat when fed to humans under identical circumstances.

  2. Stability, occurence and step morphology of polymorphs and polytypes of stearic acid. II. Mono-lamella step morphology and composite polymorphic/polytypic transformation

    Science.gov (United States)

    Inaoka, Kimio; Kobayashi, Masamichi; Okada, Masakazu; Sato, Kiyotaka

    1988-02-01

    Surface step morphology of three structural modifications of stearic acid, B(mon), B(orth II) and C(mon), was observed by replica method (TEM). The characteristic simple and interlaced patterns were observed for monoclinic and pseudo-orthorhombic polytypes, respectively. The observation on the C crystals which were transformed from B(orth II) or B(mon) enabled to detect two different modes of lattice displacement involved in composite polymorphic-polytypic transformations from B to C. B(mon) → C(mon) was found to be caused by a collective inclination of the molecules within the lamellar plane followed by the deformation of the subcell of the aliphatic chain, keeping the symmetry-axis unchanged. In contrast, B(orth II) → C(mon) occurs via an alternate rotation of the long-chain molecules in the adjacent lamellae around the c-axis of B(orth II) prototype, keeping the subcell arrangements unchanged. This means that the polytypic structure of a double-layer type was not preserved during the composite B(orth II) → C(mon) transformation. This peculiarity was discussed in terms of the interlamellar instability of a postulated double-layered polytype of the C polymorph.

  3. Enhanced Thermal Properties of Novel Latent Heat Thermal Storage Material Through Confinement of Stearic Acid in Meso-Structured Onion-Like Silica

    Science.gov (United States)

    Gao, Junkai; Lv, Mengjiao; Lu, Jinshu; Chen, Yan; Zhang, Zijun; Zhang, Xiongjie; Zhu, Yingying

    2017-12-01

    Meso-structured onion-like silica (MOS), which had a highly ordered, onion-like multilayer; large surface area and pore volume; and highly curved mesopores, were synthesized as a support for stearic acid (SA) to develop a novel shape-stabilized phase change material (SA/MOS). The characterizations of SA/MOS were studied by the analysis technique of scanning electron microscope, infrared spectroscopy, x-ray diffraction, differential scanning calorimeter (DSC), and thermal gravimetry analysis (TGA). The results showed that the interaction between the SA and the MOS was physical adsorption and that the MOS had no effect on the crystal structure of the SA. The DSC results suggested that the melting and solidifying temperature of the SA/MOS were 72.7°C and 63.9°C with a melting latent heat of 108.0 J/g and a solidifying latent heat of 126.0 J/g, respectively, and the TGA results indicated that the SA/MOS had a good thermal stability. All of the results demonstrated that the SA/MOS was a promising thermal energy storage material candidate for practical applications.

  4. Synthesis and characterization of novel amphiphilic copolymer stearic acid-coupled F127 nanoparticles for nano-technology based drug delivery system.

    Science.gov (United States)

    Gao, Qihe; Liang, Qing; Yu, Fei; Xu, Jian; Zhao, Qihua; Sun, Baiwang

    2011-12-01

    Pluronic, F127, amphiphilic block copolymers, are used for several applications, including drug delivery systems. The critical micelle concentration (CMC) of F127 is about 0.26-0.8 wt% so that the utility of F127 in nano-technology based drug delivery system is limited since the nano-sized micelles could dissociate upon dilution. Herein, stearic acid (SA) was simply coupled to F127 between the carboxyl group of SA and the hydroxyl group of F127, which formed a novel copolymer named as SA-coupled F127, with significantly lower CMC. Above the CMC 6.9 × 10(-5)wt%, SA-coupled F127 self-assembled stable nanoparticles with Zeta potential -36 mV. Doxorubicin (DOX)-loaded nanoparticles were made, with drug loading (DL) 5.7 wt% and Zeta potential -36 to -39 mV, and the nanoparticles exhibited distinct shape with the size distribution from 20 to 50 nm. DOX-loaded nanoparticles were relatively stable and exhibited DOX dependant cytotoxicity toward MCF-7 cells in vitro. These results suggest that SA-coupled F127 potentially could be applied as a nano-technology based drug delivery method. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. A spectroscopic study of water-soluble pyronin B and pyronin Y in Langmuir-Blodgett films mixed with stearic acid

    International Nuclear Information System (INIS)

    Meral, Kadem; Erbil, H. Yıldırım; Onganer, Yavuz

    2011-01-01

    Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir-Blodgett (LB) films. The surface pressure-area (π-A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air-water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air-water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air-water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM).

  6. A spectroscopic study of water-soluble pyronin B and pyronin Y in Langmuir-Blodgett films mixed with stearic acid

    Energy Technology Data Exchange (ETDEWEB)

    Meral, Kadem [Department of Chemistry, Faculty of Sciences, Atatuerk University, 25240 Erzurum (Turkey); Erbil, H. Y Latin-Small-Letter-Dotless-I ld Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I m [Department of Chemical Engineering, Gebze Institute of Technology, Cay Latin-Small-Letter-Dotless-I rova, Gebze 41400, Kocaeli (Turkey); Onganer, Yavuz, E-mail: yonganer@atauni.edu.tr [Department of Chemistry, Faculty of Sciences, Atatuerk University, 25240 Erzurum (Turkey)

    2011-12-01

    Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir-Blodgett (LB) films. The surface pressure-area ({pi}-A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air-water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air-water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air-water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM).

  7. Stearic-acid/carbon-nanotube composites with tailored shape-stabilized phase transitions and light–heat conversion for thermal energy storage

    International Nuclear Information System (INIS)

    Li, Benxia; Nie, Shibin; Hao, Yonggan; Liu, Tongxuan; Zhu, Jinbo; Yan, Shilong

    2015-01-01

    Highlights: • A facile preparation of shape-stabilized composite PCMs for thermal energy storage. • The composite PCMs present tunable phase change temperatures and enthalpy. • Sunlight-driven phase change for photothermal conversion and storage. - Abstract: The development of functional materials with both light–heat conversion and thermal energy storage properties is of crucial importance for efficient utilization of sunlight to meet the growing demand for sustainable energy. In this work, the shape-stabilized phase change composites were designed and prepared by integration of stearic acid (SA) and acid-treated carbon nanotubes (a-CNTs). The a-CNTs not only acted as a flexible matrix but also endowed the composites high light–heat conversion ability. The reversible phase transitions shifted from high temperatures (T m = 74 °C, T f = 57 °C) of pure SA to near room temperature (T m = ∼30 °C, T f = ∼22 °C) of SA/a-CNTs composites, probably resulting from the strong interface confinement effect. The phase change enthalpy of the SA/a-CNTs composite could also be tailored by changing the mass ratio of SA and a-CNTs. The composites containing SA of 54.2 wt.%, 67.8 wt.% and 79.5 wt.% presented the melting enthalpy of 76.3 J/g, 98.8 J/g and 111.8 J/g, respectively. Moreover, the phase transition of SA/a-CNTs composite could be driven by sunlight for the energy storage/release. Therefore, this research provides a new platform for improving solar utilization, and understanding the phase transition behaviors of organic PCMs in dimensionally confined environments as well

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  9. Monolayer-functionalized microfluidics devices for optical sensing of acidity

    NARCIS (Netherlands)

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

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

  10. Impact of the oxygen defects and the hydrogen concentration on the surface of tetragonal and monoclinic ZrO2 on the reduction rates of stearic acid on Ni/ZrO2.

    Science.gov (United States)

    Foraita, Sebastian; Fulton, John L; Chase, Zizwe A; Vjunov, Aleksei; Xu, Pinghong; Baráth, Eszter; Camaioni, Donald M; Zhao, Chen; Lercher, Johannes A

    2015-02-02

    The role of the specific physicochemical properties of ZrO2 phases on Ni/ZrO2 has been explored with respect to the reduction of stearic acid. Conversion on pure m-ZrO2 is 1.3 times more active than on t-ZrO2 , whereas Ni/m-ZrO2 is three times more active than Ni/t-ZrO2 . Although the hydrodeoxygenation of stearic acid can be catalyzed solely by Ni, the synergistic interaction between Ni and the ZrO2 support causes the variations in the reaction rates. Adsorption of the carboxylic acid group on an oxygen vacancy of ZrO2 and the abstraction of the α-hydrogen atom with the elimination of the oxygen atom to produce a ketene is the key to enhance the overall rate. The hydrogenated intermediate 1-octadecanol is in turn decarbonylated to heptadecane with identical rates on all catalysts. Decarbonylation of 1-octadecanol is concluded to be limited by the competitive adsorption of reactants and intermediate. The substantially higher adsorption of propionic acid demonstrated by IR spectroscopy and the higher reactivity to O2 exchange reactions with the more active catalyst indicate that the higher concentration of active oxygen defects on m-ZrO2 compared to t-ZrO2 causes the higher activity of Ni/m-ZrO2 . © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Directory of Open Access Journals (Sweden)

    Ellen M. Adams

    2013-10-01

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

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

    Science.gov (United States)

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

    2011-03-15

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

  13. FY17-PDH-EVTest04 GodInput Impact of the Oxygen Defects1 FY17-PDH-EVTest04 Reduction Rates of Stearic AcidFY17-PDH-T04.

    Science.gov (United States)

    Foraita, Sebastian; Fulton, John L; Chase, Zizwe A; Vjunov, Aleksei; Xu, Pinghong; Baráth, Eszter; Camaioni, Donald M; Zhao, Chen; Lercher, Johannes A

    2016-08-10

    Test New Article1 GodEarlyview.Publish-on-load testing.The role of the specific physicochemical properties of ZrO 2 phases on Ni/ZrO 2 has been explored with respect to the reduction of stearic acid. Conversion on pure m?ZrO 2 is 1.3 times more active than on t?ZrO 2 , whereas Ni/m?ZrO 2 is three times more active than Ni/t?ZrO 2 . Although the hydrodeoxygenation of stearic acid can be catalyzed solely by Ni, the synergistic interaction between Ni and the ZrO 2 support causes the variations in the reaction rates. Adsorption of the carboxylic acid group on an oxygen vacancy of ZrO 2 and the abstraction of the ??hydrogen atom with the elimination of the oxygen atom to produce a ketene is the key to enhance the overall rate. The hydrogenated intermediate 1?octadecanol is in turn decarbonylated to heptadecane with identical rates on all catalysts. Decarbonylation of 1?octadecanol is concluded to be limited by the competitive adsorption of reactants and intermediate. The substantially higher adsorption of propionic acid demonstrated by IR spectroscopy and the higher reactivity to O 2 exchange reactions with the more active catalyst indicate that the higher concentration of active oxygen defects on m?ZrO 2 compared to t?ZrO 2 causes the higher activity of Ni/m?ZrO 2 . © 2015 WILEY?VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-23

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

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  16. Photoluminescence Enhancement and Structure Repairing of Monolayer MoSe 2 by Hydrohalic Acid Treatment

    KAUST Repository

    Han, Hau-Vei

    2015-12-30

    Atomically thin two-dimensional transition-metal dichalcogenides (TMDCs) have attracted much attention recently due to their unique electronic and optical properties for future optoelectronic devices. The chemical vapor deposition (CVD) method is able to generate TMDCs layers with a scalable size and a controllable thickness. However, the TMDC monolayers grown by CVD may incorporate structural defects, and it is fundamentally important to understand the relation between photoluminescence and structural defects. In this report, point defects (Se vacancies) and oxidized Se defects in CVD-grown MoSe2 monolayers are identified by transmission electron microscopy and X-ray photoelectron spectroscopy. These defects can significantly trap free charge carriers and localize excitons, leading to the smearing of free band-to-band exciton emission. Here, we report that the simple hydrohalic acid treatment (such as HBr) is able to efficiently suppress the trap-state emission and promote the neutral exciton and trion emission in defective MoSe2 monolayers through the p-doping process, where the overall photoluminescence intensity at room temperature can be enhanced by a factor of 30. We show that HBr treatment is able to activate distinctive trion and free exciton emissions even from highly defective MoSe2 layers. Our results suggest that the HBr treatment not only reduces the n-doping in MoSe2 but also reduces the structural defects. The results provide further insights of the control and tailoring the exciton emission from CVD-grown monolayer TMDCs.

  17. Cation effects on phosphatidic acid monolayers at various pH conditions.

    Science.gov (United States)

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

    2016-10-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  19. Bioavailability of Echinacea Constituents: Caco-2 Monolayers and Pharmacokinetics of the Alkylamides and Caffeic Acid Conjugates

    Directory of Open Access Journals (Sweden)

    R. Lehmann

    2005-10-01

    Full Text Available Many studies have been done over the years to assess the effectiveness of Echinacea as an immunomodulator. We have assessed the potential bioavailability of alkyl- amides and caffeic acid conjugates using Caco-2 monolayers and compared it to their actual bioavailability in a Phase I clinical trial. The caffeic acid conjugates permeated poorly through the Caco-2 monolayers. Alkylamides were found to diffuse rapidly through Caco-2 monolayers. Differences in diffusion rates for each alkylamide correlated to structural variations, with saturation and N-terminal methylation contributing to decreases in diffusion rates. Alkylamide diffusion is not affected by the presence of other constituents and the results for a synthetic alkylamide were in line with those for alkylamides found in an ethanolic Echinacea preparation. We examined plasma from healthy volunteers for 12 hours after ingestion of Echinacea tablets manufactured from an ethanolic liquid extract. Caffeic acid conjugates could not be identified in any plasma sample at any time after tablet ingestion. Alkylamides were detected in plasma 20 minutes after tablet ingestion and for each alkylamide, pharmacokinetic profiles were devised. The data are consistent with the dosing regimen of one tablet three times daily and supports their usage as the primary markers for quality Echinacea preparations.

  20. Formation and Characterization of Self-Assembled Phenylboronic Acid Derivative Monolayers toward Developing Monosaccaride Sensing-Interface

    Directory of Open Access Journals (Sweden)

    Kwangnak Koh

    2007-08-01

    Full Text Available We designed and synthesized phenylboronic acid as a molecular recognitionmodel system for saccharide detection. The phenylboronic acid derivatives that haveboronic acid moiety are well known to interact with saccharides in aqueous solution; thus,they can be applied to a functional interface of saccharide sensing through the formation ofself-assembled monolayer (SAM. In this study, self-assembled phenylboronic acidderivative monolayers were formed on Au surface and carefully characterized by atomicforce microscopy (AFM, Fourier transform infrared reflection absorption spectroscopy(FTIR-RAS, surface enhanced Raman spectroscopy (SERS, and surface electrochemicalmeasurements. The saccharide sensing application was investigated using surface plasmonresonance (SPR spectroscopy. The phenylboronic acid monolayers showed goodsensitivity of monosaccharide sensing even at the low concentration range (1.0 × 10-12 M.The SPR angle shift derived from interaction between phenylboronic acid andmonosaccharide was increased with increasing the alkyl spacer length of synthesizedphenylboronic acid derivatives.

  1. Cu2+ Montmorillonite K10 Clay Catalyst as a Green Catalyst for Production of Stearic Acid Methyl Ester: Optimization Using Response Surface Methodology (RSM)

    OpenAIRE

    Enas A. Almadani; Farah W. Harun; Salina M. Radzi; Syamsul K. Muhamad

    2018-01-01

    Clay catalyst has received much attention to replace the homogeneous catalysts in the esterification reaction to produce fatty acid methyl ester as the source of biodiesel as it is low cost, easily available, as well as environmental friendly. However, the use of unmodified clay, in particular montmorillonite K10 (MMT K10), for the esterification of fatty acids showed that the acid conversion was less than 60% and this is not preferable to the production of biodiesel. In this study, synthesis...

  2. Ternary Surface Monolayers for Ultrasensitive (Zeptomole) Amperometric Detection of Nucleic-Acid Hybridization without Signal Amplification

    Science.gov (United States)

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

    2010-01-01

    A ternary surface monolayer, consisting of co-assembled thiolated capture probe (SHCP) mercaptohexanol (MCH) and dithiothreitol (DTT), is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers (SAMs). Remarkably low detection limits down to 40 zmole (in 4 μL samples) as well as only 1 CFU E. coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3′,5,5′-tetramethylbenzidine (HRP/TMB) system. Such dramatic improvements in the detection limits (compared to common binary alkanethiol interfaces and to most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to non-specific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration ‘backfillers’ that leads to a remarkably low background noise even in the presence of complex sample matrices. A wide range of surface compositions have been investigated and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety and forensic analysis. PMID:20883023

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

    Science.gov (United States)

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

    2010-11-01

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

  4. Adsorption Characteristics of DNA Nucleobases, Aromatic Amino Acids and Heterocyclic Molecules on Silicene and Germanene Monolayers

    KAUST Repository

    Hussain, Tanveer

    2017-09-14

    Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory calculations. Binding energy range for nucleobases, amino acids and heterocyclic molecules with both the sheets have been found to be (0.43-1.16eV), (0.70-1.58eV) and (0.22-0.96eV) respectively, which along with the binding distances show that these molecules bind to both sheets by physisorption and chemisorption process. The exchange of electric charges between the monolayers and the incident molecules has been examined by means of Bader charge analysis. It has been observed that the introduction of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules alters the electronic properties of both silicene and germanene nano sheets as studied by plotting the total (TDOS) and partial (PDOS) density of states. The DOS plots reveal the variation in the band gaps of both silicene and germanene caused by the introduction of studied molecules. Based on the obtained results we suggest that both silicene and germanene monolayers in their pristine form could be useful for sensing of biomolecules.

  5. Application of Box-Behnken design for preparation of levofloxacin-loaded stearic acid solid lipid nanoparticles for ocular delivery: Optimization, in vitro release, ocular tolerance, and antibacterial activity.

    Science.gov (United States)

    Baig, Mirza Salman; Ahad, Abdul; Aslam, Mohammed; Imam, Syed Sarim; Aqil, Mohd; Ali, Asgar

    2016-04-01

    The aim of the present study was to develop and optimize levofloxacin loaded solid lipid nanoparticles for the treatment of conjunctivitis. Box-Behnken experimental design was applied for optimization of solid lipid nanoparticles. The independent variables were stearic acid as lipid (X1), Tween 80 as surfactant (X2) and sodium deoxycholate as co-surfactant (X3) while particle size (Y1) and entrapment efficiency (Y2) were the dependent variables. Further in vitro release and antibacterial activity in vitro were also performed. The optimized formulation of levofloxacin provides particle size of 237.82 nm and showed 78.71% entrapment efficiency and achieved flux 0.2,493 μg/cm(2)/h across excised goat cornea. In vitro release study showed prolonged drug release from the optimized formulation following Korsmeyer-Peppas model. Antimicrobial study revealed that the developed formulation possesses antibacterial activity against Staphylococcus aureus, and Escherichia coli equivalent to marketed eye drops. HET-CAM test demonstrated that optimized formulation was found to be non-irritant and safe for topical ophthalmic use. Our results concluded that solid lipid nanoparticles are an efficient carrier for ocular delivery of levofloxacin and other drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Sulfonic acid-functionalized golf nanoparticles: A colloid-bound catalyst for soft lithographic application on self-assembled monolayers

    NARCIS (Netherlands)

    Li, X.; Paraschiv, V.; Huskens, Jurriaan; Reinhoudt, David

    2003-01-01

    In this report, we present a new lithographic approach to prepare patterned surfaces. Self-assembled monolayers (SAMs) of the acid-labile trimethylsilyl ether (TMS-OC11H22S)2 (TMS adsorbate) was formed on gold. 5-Mercapto-2-benzimidazole sulfonic acid sodium salt (MBS-Na+) was used as a ligand for

  7. Enhancing Cooperativity in Bifunctional Acid–Pd Catalysts with Carboxylic Acid-Functionalized Organic Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Coan, Patrick D. [Department of Chemical and Biological Engineering, University of Colorado—Boulder, Boulder, Colorado 80309, United States; Ellis, Lucas D. [Department of Chemical and Biological Engineering, University of Colorado—Boulder, Boulder, Colorado 80309, United States; Griffin, Michael B. [National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States; Schwartz, Daniel K. [Department of Chemical and Biological Engineering, University of Colorado—Boulder, Boulder, Colorado 80309, United States; Medlin, J. Will [Department of Chemical and Biological Engineering, University of Colorado—Boulder, Boulder, Colorado 80309, United States

    2018-03-01

    Cooperative catalysts containing a combination of noble metal hydrogenation sites and Bronsted acid sites are critical for many reactions, including the deoxygenation (DO) of biomass-derived oxygenates in the upgrading of pyrolysis oil. One route toward the design of cooperative catalysts is to tether two different catalytically active functions so that they are in close proximity while avoiding undesirable interactions that can block active sites. Here, we deposited carboxylic acid (CA)-functionalized organophosphonate monolayers onto Al2O3-supported Pd nanoparticle catalysts to prepare bifunctional catalysts containing both Bronsted acid and metal sites. Modification with phosphonic acids (PAs) improved activity and selectivity for gas-phase DO reactions, but the degree of improvement was highly sensitive to both the presence and positioning of the CA group, suggesting a significant contribution from both the PA and CA sites. Short spacer lengths of 1-2 methylene groups between the phosphonate head and CA tail were found to yield the best DO rates and selectivities, whereas longer chains performed similarly to self-assembled monolayers having alkyl tails. Results from a combination of density functional theory and Fourier transform infrared spectroscopy suggested that the enhanced catalyst performance on the optimally positioned CAs was due to the generation of strong acid sites on the Al2O3 support adjacent to the metal. Furthermore, the high activity of these sites was found to result from a hydrogen-bonded cyclic structure involving cooperativity between the phosphonate head group and CA tail function. More broadly, these results indicate that functional groups tethered to supports via organic ligands can influence catalytic chemistry on metal nanoparticles.

  8. Saturated fatty acid in the phospholipid monolayer contributes to the formation of large lipid droplets

    International Nuclear Information System (INIS)

    Arisawa, Kotoko; Mitsudome, Haruka; Yoshida, Konomi; Sugimoto, Shizuka; Ishikawa, Tomoko; Fujiwara, Yoko; Ichi, Ikuyo

    2016-01-01

    The degree of saturation of fatty acid chains in the bilayer membrane structure is known to control membrane fluidity and packing density. However, the significance of fatty acid composition in the monolayers of lipid droplets (LDs) has not been elucidated. In this study, we noted a relationship between the size of LDs and the fatty acid composition of the monolayer. To obtain large LDs, we generated NIH3T3 cells overexpressing fat-specific protein 27 (FSP27). This induced the fusion of LDs, resulting in larger LDs in FSP27-overexpressing cells compared with LDs in control cells. Moreover, the lipid extracts of LDs from FSP27-overexpressing cells reconstituted large-droplet emulsions in vitro, implying that the lipid properties of LDs might affect the size of LDs. FSP27-overexpressing cells had more saturated fatty acids in the phospholipid monolayer of the LDs compared with control cells. To further investigate the effects of the degree of phospholipid unsaturation on the size of LDs, we synthesized artificial emulsions of a lipid mixed with distearoylphosphatidylcholine (DSPC, diC18:0-PC) and with dioleoylphosphatidylcholine (DOPC, diC18:1n-9-PC) and compared the sizes of the resulting LDs. The emulsions prepared from saturated PC had larger droplets than those prepared from unsaturated PC. Our results suggest that saturated fatty acid chains in phospholipid monolayers might establish the form and/or stability of large LDs. - Highlights: • The lipid extracts of larger LDs from FSP27 cells reconstructed large-droplet emulsions. • Isolated LDs from FSP27 cells had more saturated fatty acids in the phospholipid monolayer compared with the control. • Saturated fatty acids in the phospholipid monolayer are a factor in the formation of large emulsions.

  9. The Rheological Properties of Lipid Monolayers Modulate the Incorporation of l-Ascorbic Acid Alkyl Esters.

    Science.gov (United States)

    Díaz, Yenisleidy de Las Mercedes Zulueta; Mottola, Milagro; Vico, Raquel V; Wilke, Natalia; Fanani, María Laura

    2016-01-19

    In this work, we tested the hypothesis that the incorporation of amphiphilic drugs into lipid membranes may be regulated by their rheological properties. For this purpose, two members of the l-ascorbic acid alkyl esters family (ASCn) were selected, ASC16 and ASC14, which have different rheological properties when organized at the air/water interface. They are lipophilic forms of vitamin C used in topical pharmacological preparations. The effect of the phase state of the host lipid membranes on ASCn incorporation was explored using Langmuir monolayers. Films of pure lipids with known phase states have been selected, showing liquid-expanded, liquid-condensed, and solid phases as well as pure cholesterol films in liquid-ordered state. We also tested ternary and quaternary mixed films that mimic the properties of cholesterol containing membranes and of the stratum corneum. The compressibility and shear properties of those monolayers were assessed in order to define its phase character. We found that the length of the acyl chain of the ASCn compounds induces differential changes in the rheological properties of the host membrane and subtly regulates the kinetics and extent of the penetration process. The capacity for ASCn uptake was found to depend on the phase state of the host film. The increase in surface pressure resultant after amphiphile incorporation appears to be a function of the capacity of the host membrane to incorporate such amphiphile as well as the rheological response of the film. Hence, monolayers that show a solid phase state responded with a larger surface pressure increase to the incorporation of a comparable amount of amphiphile than liquid-expanded ones. The cholesterol-containing films, including the mixture that mimics stratum corneum, allowed a very scarce ASCn uptake independently of the membrane diffusional properties. This suggests an important contribution of Cho on the maintenance of the barrier function of stratum corneum.

  10. Use of atomic force microscopy for imaging the initial stage of the nucleation of calcium phosphate in Langmuir-blodgett films of stearic acid

    International Nuclear Information System (INIS)

    Zhang Yuanjian; He Ping; Xu Xiudong; Li Jinghong

    2004-01-01

    The nucleation of calcium phosphate on the substrate of steatic acid Langmuir-blodgett film at the initial stage was investigated by atomic force microscopy. Nano-dots, nano-wires and nano-islands were observed in sequence for the first time, reflecting the nucleation of calcium phosphate and the molecular arrangement of carboxylic layer. The nucleation rates perpendicular and parallel to the carboxylic terminal group were estimated from the height and diameter of the calcium phosphate crystals, respectively. And this stage was distinct from the late explosive grown stage, in which the change of the morphology was not obvious. The approaches based on this discovery would lead to the development of new strategies in the controlled synthesis of inorganic nano-phases and the assembly of organized composite and ceramic materials

  11. Suitability of using monolayered and multilayered emulsions for microencapsulation of ω-3 fatty acids by spray drying

    DEFF Research Database (Denmark)

    Jiménez-Martín, Estefanía; Gharsallaoui, Adem; Pérez-Palacios, Trinidad

    2015-01-01

    Microencapsulation of ω-3 fatty acids by spray drying was studied using both monolayered (lecithin) and multilayered (lecithin-chitosan) fish oil emulsions with maltodextrin as wall material. Stability of the multilayered emulsions was higher than the monolayered ones, and increased...... with the highest concentration of chitosan (1 % w/w), being related with lower detection of TBARS at high storage temperatures. Overall, this study shows the suitability of microencapsulating ω-3 fatty acids by spray drying using both monolayered and multilayered fish oil emulsions with maltodextrin as wall...... material. Multilayered microcapsules prepared with lecithin-chitosan emulsions provide a great protective effect against lipid oxidation of fish oil during storage at moderate to high temperatures (30 °C and 60 °C). These multilayered microcapsules could be therefore successfully used as a fish oil...

  12. Structural insights into the dual strategy of recognition by peptidoglycan recognition protein, PGRP-S: structure of the ternary complex of PGRP-S with lipopolysaccharide and stearic acid.

    Directory of Open Access Journals (Sweden)

    Pradeep Sharma

    Full Text Available Peptidoglycan recognition proteins (PGRPs are part of the innate immune system. The 19 kDa Short PGRP (PGRP-S is one of the four mammalian PGRPs. The concentration of PGRP-S in camel (CPGRP-S has been shown to increase considerably during mastitis. The structure of CPGRP-S consists of four protein molecules designated as A, B, C and D forming stable intermolecular contacts, A-B and C-D. The A-B and C-D interfaces are located on the opposite sides of the same monomer leading to the the formation of a linear chain with alternating A-B and C-D contacts. Two ligand binding sites, one at C-D contact and another at A-B contact have been observed. CPGRP-S binds to the components of bacterial cell wall molecules such as lipopolysaccharide (LPS, lipoteichoic acid (LTA, and peptidoglycan (PGN from both gram-positive and gram-negative bacteria. It also binds to fatty acids including mycolic acid of the Mycobacterium tuberculosis (Mtb. Previous structural studies of binary complexes of CPGRP-S with LPS and stearic acid (SA have shown that LPS binds to CPGRP-S at C-D contact (Site-1 while SA binds to it at the A-B contact (Site-2. The binding studies using surface plasmon resonance showed that LPS and SA bound to CPGRP-S in the presence of each other. The structure determination of the ternary complex showed that LPS and SA bound to CPGRP-S at Site-1 and Site-2 respectively. LPS formed 13 hydrogen bonds and 159 van der Waals contacts (distances ≤4.2 Å while SA formed 56 van der Waals contacts. The ELISA test showed that increased levels of productions of pro-inflammatory cytokines TNF-α and IFN-γ due to LPS and SA decreased considerably upon the addition of CPGRP-S.

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

    KAUST Repository

    Nava Ocampo, Maria F.

    2017-05-01

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

  14. Transepithelial transport of aliphatic carboxylic acids studied in Madin Darby canine kidney (MDCK) cell monolayers

    International Nuclear Information System (INIS)

    Cho, M.J.; Adson, A.; Kezdy, F.J.

    1990-01-01

    Transport of 14C-labeled acetic, propionic (PA), butyric, valeric, heptanoic (HA), and octanoic (OA) acids across the Madin Darby canine kidney (MDCK) epithelial cell monolayer grown on a porous polycarbonate membrane was studied in Hanks' balanced salt solution (HBSS) at 37 degrees C in both apical-to-basolateral and basolateral-to-apical directions. At micromolar concentrations of solutes, metabolic decomposition was significant as evidenced by [14C]CO2 production during the OA transport. The apparent permeability (Pe) indicates that as lipophilicity increases, diffusion across the unstirred boundary layer becomes rate limiting. In support of this notion, transport of OA and HA was enhanced by agitation, showed an activation energy of 3.7 kcal/mol for OA, and resulted in identical Pe values for both transport directions. Analysis of Pe changes with varying alkyl chain length resulted in a delta G of -0.68 +/- 0.09 kcal/mol for -CH2-group transfer from an aqueous phase to the MDCK cells. When the intercellular tight junctions were opened by the divalent chelator EGTA in Ca2+/Mg2(+)-free HBSS, transport of the fluid-phase marker Lucifer yellow greatly increased because of paracellular leakage. PA transport also showed a significant increase, but OA transport was independent of EGTA. Although albumin also undergoes paracellular transport in the presence of EGTA and OA binds strongly to albumin, OA transport in EGTA solution was unchanged by albumin. These observations indicate that transmembrane transport is the major mechanism for lipophilic substances. The present study, together with earlier work on the transport of polar substances, shows that the MDCK cell monolayer is an excellent model of the transepithelial transport barrier

  15. Importance of Terminal Amino Acid Residues to the Transport of Oligopeptides across the Caco-2 Cell Monolayer.

    Science.gov (United States)

    Ding, Long; Wang, Liying; Yu, Zhipeng; Ma, Sitong; Du, Zhiyang; Zhang, Ting; Liu, Jingbo

    2017-09-06

    The objective of this paper was to investigate the effects of terminal amino acids on the transport of oligopeptides across the Caco-2 cell monolayer. Ala-based tetra- and pentapeptides were designed, and the N- or C-terminal amino acid residues were replaced by different amino acids. The results showed that the oligopeptides had a wide range of transport permeability across the Caco-2 cell monolayer and could be divided into four categories: non-/poor permeability, low permeability, intermediate permeability, and good permeability. Tetrapeptides with N-terminal Leu, Pro, Ile, Cys, Met, and Val or C-terminal Val showed the highest permeability, with apparent permeability coefficient (P app ) values over 10 × 10 -6 cm/s (p transport of tetrapeptides. Pentapeptides with N- or C-terminal Tyr also showed high permeability levels, with P app values of about 10 × 10 -6 cm/s. The amino acids Glu, Asn, and Thr at the N terminus or Lys, Asp, and Arg at the C terminus were also beneficial for the transport of tetra- and pentapeptides, with P app values ranging from 1 × 10 -6 to 10 × 10 -6 cm/s. In addition, peptides with amino acids replaced at the N terminus generally showed higher permeability than those with amino acids replaced at the C terminus (p transport of oligopeptides across the Caco-2 cell monolayer.

  16. Effect of the distribution of saturated fatty acids in the melting and crystallization profiles of high-oleic high-stearic oils; Efecto de la distribución de los ácidos grasos saturados en los perfiles de fusión y cristalización de los aceites alto esteárico alto oleico

    Energy Technology Data Exchange (ETDEWEB)

    Bootello, M.A.; Garces, R.; Martinez-Force, E.; Salas, J.J.

    2016-07-01

    The composition and distribution of fatty acids in triacylglycerol (TAG) molecules are commonly considered as factors that determine the physical properties of a given oil or fat. The distribution of any fatty acid in fats and oils can be described through the α coefficient of asymmetry, which can be calculated from the TAG composition and fatty acid composition of the Sn-2 position of the TAGs determined through lipase hydrolysis. High-oleic high-stearic oils and fats are considered stable and healthy, and they are good substitutes for hydrogenated vegetable oils and palm fractions in many food products, such as spreads and confectionery. Here, different high-oleic high-stearic acid oils were formulated which contained different distributions of saturated fatty acids in their TAGs, while maintaining a similar fatty acid composition. The aim of this work was to discuss the possibility of using the α coefficient to predict the physical properties of fats in function of their chemical composition and their melting and crystallization behavior as examined by differential scanning calorimetry.

  17. Impregnation of 12-tungstophosphoric acid on silica - part II: effect of different solvents on the impregnation and catalytic activity in methyl esterification of stearic acid; Impregnacao do acido 12-tungstofosforico em silica - parte II: efeito de diferentes solventes na impregnacao e atividade catalitica na esterificacao metilica de acido estearico

    Energy Technology Data Exchange (ETDEWEB)

    Scroccaro, Karine Isabel; Yamamoto, Carlos I., E-mail: karineisabel@yahoo.com.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Centro Politecnico. Departamento de Engenharia Quimica; Tanobe, Valcineide O. de A.; Oliveira, Alan Antonio de [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Departamento de Engenharia e Tecnologia Florestal; Wypych, Fernando [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Departamento de Quimica

    2014-04-15

    Materials obtained by the immobilization of 12-tungstophosphoric acid (PTA) on silica using the method of impregnation with excess solution in distinct solvents (aqueous HCl, methanol:H{sub 2}O, and acetonitrile) were evaluated for use as catalysts in the methyl esterification of stearic acid. Optimum conditions were established for the impregnation of 0.5 g (w/w) of PTA on amorphous silica, under stirring at 150 rpm for 24 h, using 20 mL of 0.1 mol L{sup -1} HCl as the solvent. After calcination at 200 deg C, high conversions were obtained under mild reaction conditions, resulting in high turnover numbers. The catalyst was evaluated in ten catalytic cycles of use, where the activity was reduced only slightly, attesting its stability and the possibility to apply it to industrial production of methylesters. (author)

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

    International Nuclear Information System (INIS)

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

    1989-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Lingzi [Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721 (United States); Knesting, Kristina M. [Department of Chemistry, University of Washington, Seattle, WA 98195-1700 (United States); Bulusu, Anuradha [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Sigdel, Ajaya K. [National Renewable Energy Laboratory, Golden, CO 80401 (United States); Giordano, Anthony J.; Marder, Seth R. [School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); Berry, Joseph J. [National Renewable Energy Laboratory, Golden, CO 80401 (United States); Graham, Samuel [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Ginger, David S. [Department of Chemistry, University of Washington, Seattle, WA 98195-1700 (United States); Pemberton, Jeanne E., E-mail: pembertn@email.arizona.edu [Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721 (United States)

    2016-12-15

    Highlights: • Deposition of phosphonic acid monolayers on oxides from ethanol solutions occurs by rapid adsorption within 10 s with slower equilibration complete in 48 h. • The slower equilibration step involves molecular reorientation and vacancy filling on the oxide surface. • Soak-free deposition by spray coating and microcontact printing do not provide reproducible, fully-covered, uniform monolayers without substrate etching. • Adjustments to exposure time, substrate temperature, and solution/substrate contact efficiency are necessary to optimize soak-free methods. - Abstract: Phosphonic acid (PA) self-assembled monolayers (SAMs) are utilized at critical interfaces between transparent conductive oxides (TCO) and organic active layers in organic photovoltaic devices (OPVs). The effects of PA deposition method and time on the formation of close-packed, high-quality monolayers is investigated here for SAMs fabricated by solution deposition, micro-contact printing, and spray coating. The solution deposition isotherm for pentafluorinated benzylphosphonic acid (F{sub 5}BnPA) on indium-doped zinc oxide (IZO) is studied using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) at room temperature as a model PA/IZO system. Fast surface adsorption occurs within the first min; however, well-oriented high-quality SAMs are reached only after ∼48 h, presumably through a continual process of molecular adsorption/desorption and monolayer filling accompanied by molecular reorientation. Two other rapid, soak-free deposition techniques, micro-contact printing and spray coating, are also explored. SAM quality is compared for deposition of phenyl phosphonic acid (PPA), F{sub 13}-octylphosphonic acid (F{sub 13}OPA), and pentafluorinated benzyl phosphonic acid (F{sub 5}BnPA) by solution deposition, micro-contact printing and spray coating using PM-IRRAS. In contrast to micro-contact printing and spray coating techniques, 48–168 h solution

  20. Effect of Time and Deposition Method on Quality of Phosphonic Acid Modifier Self-Assembled Monolayers on Indium Zinc Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Lingzi; Knesting, Kristina M.; Bulusu, Anuradha; Sigdel, Ajaya K.; Giordano, Anthony J.; Marder, Seth R.; Berry, Joseph J.; Graham, Samuel; Ginger, David S.; Pemberton, Jeanne E.

    2016-12-15

    Phosphonic acid (PA) self-assembled monolayers (SAMs) are utilized at critical interfaces between transparent conductive oxides (TCO) and organic active layers in organic photovoltaic devices (OPVs). The effects of PA deposition method and time on the formation of close-packed, high-quality monolayers is investigated here for SAMs fabricated by solution deposition, micro-contact printing, and spray coating. The solution deposition isotherm for pentafluorinated benzylphosphonic acid (F5BnPA) on indium-doped zinc oxide (IZO) is studied using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) at room temperature as a model PA/IZO system. Fast surface adsorption occurs within the first min; however, well-oriented high-quality SAMs are reached only after -48 h, presumably through a continual process of molecular adsorption/desorption and monolayer filling accompanied by molecular reorientation. Two other rapid, soak-free deposition techniques, micro-contact printing and spray coating, are also explored. SAM quality is compared for deposition of phenyl phosphonic acid (PPA), F13-octylphosphonic acid (F13OPA), and pentafluorinated benzyl phosphonic acid (F5BnPA) by solution deposition, micro-contact printing and spray coating using PM-IRRAS. In contrast to micro-contact printing and spray coating techniques, 48-168 h solution deposition at both room temperature and 70 degrees C result in contamination- and surface etch-free close-packed monolayers with good reproducibility. SAMs fabricated by micro-contact printing and spray coating are much less well ordered.

  1. Differential feedback regulation of cholesterol 7α-hydroxylase mRNA and transcriptional activity by rat bile acids in primary monolayer cultures of rat hepatocytes

    NARCIS (Netherlands)

    Twisk, J.; Lehmann, E.M.; Princen, H.M.G.

    1993-01-01

    We have used primary monolayer cultures of rat hepatocytes to study the effects of physiological concentrations of various bile acids, commonly found in bile of normal rats, on the mechanism of regulation of cholesterol 7α-hydroxylase and bile acid synthesis. Addition of taurocholic acid, the most

  2. Influence of Poly(ethylenimine) on the Monolayer of Oleic Acid at the Air/Water Interface.

    Science.gov (United States)

    Hwan Ha, Tai; Kyu Kim, Dai; Choi, Myung-Un; Kim, Kwan

    2000-06-01

    The effect of poly(ethylenimine) (PEI) dissolved in water on the surface pressure-area isotherm of oleic acid (OA) at the air/water interface was investigated. On a concentrated PEI solution, the isotherm of the OA monolayers exhibited a noticeable difference as a function of subphase pH. PEI caused the collapse pressure of the OA monolayer to increase up to 45 mN/m, due to a stronger acid-base-type interaction occurring between the amine group of the PEI and the carboxyl group of OA; on a pure water subphase, the collapse pressure was;28 mN/m. On the other hand, owing to a stronger OA-PEI interaction, the OA monolayers favored a liquid-expanded state more on the PEI-containing water subphase than on the pure water. From the QCM measurement, each OA molecule appeared to interact, on average, with 4.3-5.8 ethylenimine repeating units at basic pHs. We also found that OA multilayers could be assembled on a hydrophilic substrate by a Z-type Langmuir-Blodgett (LB) deposition in a PEI-containing subphase at basic pHs. The ATR-IR spectral data revealed that, in a Z-type LB film, the headgroup of OA was mostly present as carboxylate, interacting in an ionic state with the protonated amine groups of PEI. In acidic conditions, neither a Y-type nor a Z-type deposition was really accomplished. Nonetheless, the ATR-IR spectral data suggested that OA molecules should exist in a monomeric state in a LB film assembled at acidic pHs without PEI while they would form intermolecular hydrogen bridges and/or dimers in the presence of PEI. Copyright 2000 Academic Press.

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

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  4. In vitro bioacessibility and transport across Caco-2 monolayers of haloacetic acids in drinking water.

    Science.gov (United States)

    Melo, A; Faria, M A; Pinto, E; Mansilha, C; Ferreira, I M P L V O

    2016-10-01

    Water disinfection plays a crucial role in water safety but it is also a matter of concern as the use of disinfectants promotes the formation of disinfection by-products (DBPs). Haloacetic acids (HAAs) are one of the major classes of DBPs since they are frequently found in treated water, are ubiquitous, pervasive and have high water solubility, so a great concern emerged about their formation, occurrence and toxicity. Exposure to HAAs is influenced by consumption patterns and diet of individuals thus their bioavailability is an important parameter to the overall toxicity. In the current study the bioacessibility of the most representative HAAs (chloroacetic acid - MCAA, bromoacetic acid - MBAA, dichloroacetic acid - DCAA, dibromoacetic acid - DBAA, and trichloroacetic acid - TCAA) after simulated in vitro digestion (SIVD) in tap water and transport across Caco-2 monolayers was evaluated. Compounds were monitored in 8 points throughout the digestion phases by an optimized LC-MS/MS methodology. MCAA and MBAA were not bioaccessible after SIVD whereas DCAA, DBAA and TCAA are highly bioaccessible (85 ± 4%, 97 ± 4% and 106 ± 7% respectively). Concerning transport assays, DCAA and DBAA were highly permeable throughout the Caco-2 monolayer (apparent permeability and calculated fraction absorbed of 13.62 × 10(-6) cm/s and 90% for DCAA; and 8.82 × 10(-6) cm/s and 84% for DBAA), whereas TCAA showed no relevant permeability. The present results may contribute to efficient risk analysis studies concerning HAAs oral exposure from tap water taking into account the different biological behaviour of these chemically similar substances. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Enhanced tribology durability of a self-assembled monolayer of alkylphosphonic acid on a textured copper substrate

    Energy Technology Data Exchange (ETDEWEB)

    Wan Yong, E-mail: wanyong@qtech.edu.cn [School of Mechanical Engineering, Qingdao Technological University, Qingdao 266033 (China); Wang Yinhu; Zhang Quan; Wang Zhongqian; Xu Zhen; Liu Changsong [School of Mechanical Engineering, Qingdao Technological University, Qingdao 266033 (China); Zhang Junyan [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer A textured surface is prepared on the copper substrate by chemical etching. Black-Right-Pointing-Pointer The alkylphosphonic acid is assembled on the etched copper substrate. Black-Right-Pointing-Pointer Combining texturing and alkylphosphonic acid coating render the films hydrophobicity. Black-Right-Pointing-Pointer The dual-layer films possess low friction with extremely long duration. - Abstract: A simple two-step process was developed to render the copper surface with lower friction and long durability. The copper substrate was immersed in a 0.01 M NaOH solution to fabricate a textured Cu{sub 2}O film. A self-assembled monolayer of alkylphosphonic acid was then deposited on the Cu{sub 2}O film to acquire high hydrophobicity. Scanning electron microscopy, Fourier transform infrared microscopy and water contact angle measurements were used to analyze the morphological features, the chemical composition and hydrophobicity of freshly prepared samples, respectively. Moreover, the friction-reducing behavior of the organic-inorganic composite film sliding against steel was evaluated in a ball-on-plate configuration. It was found that the alkylphosphonic acid films on the textured Cu{sub 2}O film led to decreased friction with significantly extended life. For a constant load, the increase in chain length of alkylphosphonic acid yields the films that are dramatically more stable against tribological deformation and provide low coefficients of friction over much longer periods of time.

  6. Enhanced tribology durability of a self-assembled monolayer of alkylphosphonic acid on a textured copper substrate

    International Nuclear Information System (INIS)

    Wan Yong; Wang Yinhu; Zhang Quan; Wang Zhongqian; Xu Zhen; Liu Changsong; Zhang Junyan

    2012-01-01

    Highlights: ► A textured surface is prepared on the copper substrate by chemical etching. ► The alkylphosphonic acid is assembled on the etched copper substrate. ► Combining texturing and alkylphosphonic acid coating render the films hydrophobicity. ► The dual-layer films possess low friction with extremely long duration. - Abstract: A simple two-step process was developed to render the copper surface with lower friction and long durability. The copper substrate was immersed in a 0.01 M NaOH solution to fabricate a textured Cu 2 O film. A self-assembled monolayer of alkylphosphonic acid was then deposited on the Cu 2 O film to acquire high hydrophobicity. Scanning electron microscopy, Fourier transform infrared microscopy and water contact angle measurements were used to analyze the morphological features, the chemical composition and hydrophobicity of freshly prepared samples, respectively. Moreover, the friction-reducing behavior of the organic-inorganic composite film sliding against steel was evaluated in a ball-on-plate configuration. It was found that the alkylphosphonic acid films on the textured Cu 2 O film led to decreased friction with significantly extended life. For a constant load, the increase in chain length of alkylphosphonic acid yields the films that are dramatically more stable against tribological deformation and provide low coefficients of friction over much longer periods of time.

  7. Frictional response of fatty acids on steel.

    Science.gov (United States)

    Sahoo, Rashmi R; Biswas, S K

    2009-05-15

    Self-assembled monolayers of fatty acids were formed on stainless steel by room-temperature solution deposition. The acids are covalently bound to the surface as carboxylate in a bidentate manner. To explore the effect of saturation in the carbon backbone on friction in sliding tribology, we study the response of saturated stearic acid (SA) and unsaturated linoleic acid (LA) as self-assembled monolayers using lateral force microscopy and nanotribometry and when the molecules are dispersed in hexadecane, using pin-on-disc tribometry. Over a very wide range (10 MPa-2.5 GPa) of contact pressures it is consistently demonstrated that the unsaturated linoleic acid molecules yield friction which is significantly lower than that of the saturated stearic acid. It is argued, using density functional theory predictions and XPS of slid track, that when the molecular backbone of unsaturated fatty acids are tilted and pressed strongly by a probe, in tribological contact, the high charge density of the double bond region of the backbone allows coupling with the steel substrate. The interaction yields a low friction carboxylate soap film on the substrate. The saturated fatty acid does not show this effect.

  8. Carrier-mediated ¿-aminobutyric acid transport across the basolateral membrane of human intestinal Caco-2 cell monolayers

    DEFF Research Database (Denmark)

    Nielsen, Carsten Uhd; Carstensen, Mette; Brodin, Birger

    2012-01-01

    and the anticancer prodrug d-aminolevulinic acid across the apical membrane of small intestinal enterocytes. Little is however known about the basolateral transport of these substances. We investigated basolateral transport of GABA in mature Caco-2 cell monolayers using isotope studies. Here we report that, at least...... two transporters seem to be involved in the basolateral transport of GABA. The basolateral uptake consisted of a high-affinity system with a K(m) of 290µM and V(max) of 75pmolcm(-2)min(-1) and a low affinity system with a K(m) of approximately 64mM and V(max) of 1.6nmolcm(-2)min(-1). The high...

  9. Cyclic voltammetry on n-alkylphosphonic acid self-assembled monolayer modified large area indium tin oxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Habich, Dana Berlinde [Siemens AG, CT T DE HW 3 Organic Electronics, Guenther-Scharowsky-Strasse 1, 91058 Erlangen (Germany); Halik, Marcus [Lehrstuhl fuer Polymerwerkstoffe, Department Werkstoffwissenschaften, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Martensstrasse 7, 91058 Erlangen (Germany); Schmid, Guenter, E-mail: guenter.schmid@siemens.com [Siemens AG, CT T DE HW 3 Organic Electronics, Guenther-Scharowsky-Strasse 1, 91058 Erlangen (Germany)

    2011-09-01

    We show stable bonding of n-alkylphosphonic acid self-assembled monolayers (SAMs) to indium tin oxide electrodes and their direct electrical characterization by cyclic voltammetry (CV). The functional coatings were investigated with regards to the addressability and stability of the electrodes, which are related to small changes in molecular layer thickness. The response of a redox active compound in solution to the faradic current is indirectly proportional to the molecular chain length of the SAMs. We observed a decrease of the electrode sensitivity with enhanced surface protection and slow long term degradation of the SAM under electrochemical stress by CV, and therefore conclude a trade-off optimum for molecules with the C10 chain.

  10. Chemical resistivity of self-assembled monolayer covalently attached to silicon substrate to hydrofluoric acid and ammonium fluoride

    Science.gov (United States)

    Saito, N.; Youda, S.; Hayashi, K.; Sugimura, H.; Takai, O.

    2003-06-01

    Self-assembled monolayers (SAMs) were prepared on hydrogen-terminated silicon substrates through chemical vapor deposition using 1-hexadecene (HD) as a precursor. The HD-SAMs prepared in an atmosphere under a reduced pressure (≈50 Pa) showed better chemical resistivities to hydrofluoric acid and ammonium fluoride (NH 4F) solutions than that of an organosilane SAM formed on oxide-covered silicon substrates. The surface covered with the HD-SAM was micro-patterned by vacuum ultraviolet photolithography and consequently divided into two areas terminated with HD-SAM or silicon dioxide. This micro-patterned sample was immersed in a 40 vol.% NH 4F aqueous solution. Surface images obtained by an optical microscopy clearly show that the micro-patterns of HD-SAM/silicon dioxide were successfully transferred into the silicon substrate.

  11. Filmes compostos de gelatina, triacetina, ácido esteárico ou capróico: efeito do pH e da adição de surfactantes sobre a funcionalidade dos filmes Composite films made with gelatin, tracetin, stearic and caproic acids: effect of pH and surfactants addition on the functionality of films

    Directory of Open Access Journals (Sweden)

    Taciana Davanço

    2007-06-01

    Full Text Available O desenvolvimento de biofilmes tem crescido devido à possibilidade de substituição parcial de materiais plásticos não biodegradáveis. Proteínas e polissacarídeos têm sido utilizados para a produção de filmes com boas propriedades mecânicas. Porém, filmes a partir desses materiais apresentam alta permeabilidade ao vapor de água. Uma alternativa usada para diminuir a permeabilidade ao vapor de água dos filmes é a incorporação de substâncias hidrofóbicas na composição da solução filmogênica, porém essa incorporação não ocorre de maneira homogênea. Com o objetivo de melhorar a incorporação das substâncias hidrofóbicas (ácido esteárico e ácido capróico na matriz protéica (gelatina do filme foram adicionados os surfactantes (SDS e Tween 80, que são substâncias capazes de interagir com a proteína e com o ácido graxo, tornando a matriz filmogênica menos heterogênea. O efeito do pH também foi estudado, com a finalidade de observar se este exerce influência na homogeneidade da matriz filmogênica. A adição do ácido esteárico aos filmes de gelatina foi mais eficiente na redução da permeabilidade ao vapor de água do que o ácido capróico. A adição do surfactante SDS reduziu a permeabilidade ao vapor de água dos filmes contendo ácido esteárico, ou ácido capróico. O ajuste de pH nos filmes sem adição de surfactantes também produziu matrizes mais homogêneas.The development of biofilms has grown considering the possibility of partial substitution of plastic materials which are not biodegradable. Proteins and polysaccharides have been used to produce films with good mechanical properties. However, films produced with these materials present a high permeability in water vapor. An alternative to improve the water vapor barrier of films is to incorporate hydrophobic substances (stearic and caproic fatty acids in the composition of the filmogenic solution, however this incorporation does not occur

  12. Carrier-mediated γ-aminobutyric acid transport across the basolateral membrane of human intestinal Caco-2 cell monolayers.

    Science.gov (United States)

    Nielsen, Carsten Uhd; Carstensen, Mette; Brodin, Birger

    2012-06-01

    The aim of the present study was to investigate the transport of γ-aminobutyric acid (GABA) across the basolateral membrane of intestinal cells. The proton-coupled amino acid transporter, hPAT1, mediates the influx of GABA and GABA mimetic drug substances such as vigabatrin and gaboxadol and the anticancer prodrug δ-aminolevulinic acid across the apical membrane of small intestinal enterocytes. Little is however known about the basolateral transport of these substances. We investigated basolateral transport of GABA in mature Caco-2 cell monolayers using isotope studies. Here we report that, at least two transporters seem to be involved in the basolateral transport of GABA. The basolateral uptake consisted of a high-affinity system with a K(m) of 290 μM and V(max) of 75 pmol cm(-2) min(-1) and a low affinity system with a K(m) of approximately 64 mM and V(max) of 1.6 nmol cm(-2) min(-1). The high-affinity transporter is Na(+) and Cl(-) dependent. The substrate specificity of the high-affinity transporter was further studied and Gly-Sar, Leucine, gaboxadol, sarcosine, lysine, betaine, 5-hydroxythryptophan, proline and glycine reduced the GABA uptake to approximately 44-70% of the GABA uptake in the absence of inhibitor. Other substances such as β-alanine, GABA, 5-aminovaleric acid, taurine and δ-aminolevulinic acid reduced the basolateral GABA uptake to 6-25% of the uptake in the absence of inhibitor. Our results indicate that the distance between the charged amino- and acid-groups is particular important for inhibition of basolateral GABA uptake. Thus, there seems to be a partial substrate overlap between the basolateral GABA transporter and hPAT1, which may prove important for understanding drug interactions at the level of intestinal transport. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Structures and shear response of lipid monolayers

    International Nuclear Information System (INIS)

    Dutta, P.; Ketterson, J.B.

    1993-02-01

    This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases

  14. Integrated electrochemical gluconic acid biosensor based on self-assembled monolayer-modified gold electrodes. Application to the analysis of gluconic acid in musts and wines.

    Science.gov (United States)

    Campuzano, S; Gamella, M; Serra, B; Reviejo, A J; Pingarrón, J M

    2007-03-21

    An integrated amperometric gluconic acid biosensor constructed using a gold electrode (AuE) modified with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA) on which gluconate dehydrogenase (GADH, 0.84 U) and the mediator tetrathiafulvalene (TTF, 1.5 micromol) were coimmobilized by covering the electrode surface with a dialysis membrane is reported. The working conditions selected were Eapp=+0.15 V and 25+/-1 degrees C. The useful lifetime of one single TTF-GADH-MPA-AuE was surprisingly long. After 53 days of continuous use, the biosensor exhibited 86% of the original sensitivity. A linear calibration plot was obtained for gluconic acid over the 6.0x10(-7) to 2.0x10(-5) M concentration range, with a limit of detection of 1.9x10(-7) M. The effect of potential interferents (glucose, fructose, galactose, arabinose, and tartaric, citric, malic, ascorbic, gallic, and caffeic acids) on the biosensor response was evaluated. The behavior of the biosensor in a flow-injection system in connection with amperometric detection was tested. The analytical usefulness of the biosensor was evaluated by determining gluconic acid in wine and must samples, and the results obtained were validated by comparison with those provided by using a commercial enzyme test kit.

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

    Science.gov (United States)

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

    2011-06-21

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

  16. Adsorption Characteristics of DNA Nucleobases, Aromatic Amino Acids and Heterocyclic Molecules on Silicene and Germanene Monolayers

    KAUST Repository

    Hussain, Tanveer; Vovusha, Hakkim; Kaewmaraya, Thanayut; Amornkitbamrung, Vittaya; Ahuja, Rajeev

    2017-01-01

    Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory

  17. Thermodynamic versus non-equilibrium stability of palmitic acid monolayers in calcium-enriched sea spray aerosol proxy systems.

    Science.gov (United States)

    Wellen Rudd, Bethany A; Vidalis, Andrew S; Allen, Heather C

    2018-04-16

    Of the major cations in seawater (Na+, Mg2+, Ca2+, K+), Ca2+ is found to be the most enriched in fine sea spray aerosols (SSA). In this work, we investigate the binding of Ca2+ to the carboxylic acid headgroup of palmitic acid (PA), a marine-abundant fatty acid, and the impact such binding has on the stability of PA monolayers in both equilibrium and non-equilibrium systems. A range of Ca2+ conditions from 10 μM to 300 mM was utilized to represent the relative concentration of Ca2+ in high and low relative humidity aerosol environments. The CO2- stretching modes of PA detected by surface-sensitive infrared reflection-absorption spectroscopy (IRRAS) reveal ionic binding motifs of the Ca2+ ion to the carboxylate group with varying degrees of hydration. Surface tensiometry was used to determine the thermodynamic equilibrium spreading pressure (ESP) of PA on the various aqueous CaCl2 subphases. Up to concentrations of 1 mM Ca2+, each system reached equilibrium, and Ca2+:PA surface complexation gave rise to a lower energy state revealed by elevated surface pressures relative to water. We show that PA films are not thermodynamically stable at marine aerosol-relevant Ca2+ concentrations ([Ca2+] ≥ 10 mM). IRRAS and vibrational sum frequency generation (VSFG) spectroscopy were used to investigate the surface presence of PA on high concentration Ca2+ aqueous subphases. Non-equilibrium relaxation (NER) experiments were also conducted and monitored by Brewster angle microscopy (BAM) to determine the effect of the Ca2+ ions on PA stability. At high surface pressures, the relaxation mechanisms of PA varied among the systems and were dependent on Ca2+ concentration.

  18. Tuning the work function of monolayer graphene on 4H-SiC (0001) with nitric acid

    International Nuclear Information System (INIS)

    Günes, Fethullah; Arezki, Hakim; Alamarguy, David; Alvarez, José; Kleider, Jean-Paul; Boutchich, Mohamed; Pierucci, Debora; Ouerghi, Abdelkarim; Dappe, Yannick J

    2015-01-01

    Chemical doping of graphene is a key process for the modulation of its electronic properties and the design and fabrication of graphene-based nanoelectronic devices. Here, we study the adsorption of diluted concentrations of nitric acid (HNO_3) onto monolayer graphene/4H-SiC (0001) to induce a variation of the graphene work function (WF). Raman spectroscopy indicates an increase in the defect density subsequent to the doping. Moreover, ultraviolet photoemission spectroscopy (UPS) was utilized to quantify the WF shift. UPS data show that the WF of the graphene layer decreased from 4.3 eV (pristine) down to 3.8 eV (30% HNO_3) and then increased to 4.4 eV at 100% HNO_3 concentration. These observations were confirmed using density functional theory (DFT) calculations. This straightforward process allows a large WF modulation, rendering the molecularly modified graphene/4H-SiC(0001) a highly suitable electron or hole injection electrode. (paper)

  19. Self-assembled monolayer based electrochemical nucleic acid sensor for Vibrio cholerae detection

    International Nuclear Information System (INIS)

    Patel, Manoj K; Solanki, Pratima R; Agrawal, Ved V; Khandelwal, Sachin; Ansari, S G; Malhotra, B D

    2012-01-01

    Nucleic acid sensor has been fabricated by immobilization of thiolated (5' end) single stranded deoxyribonucleic acid probe (ssDNA-SH) onto gold (Au) coated glass electrode for Vibriocholerae detection. This ssDNA-SH/Au bioelectrode characterized using atomic force microscopy (AFM),Fourier transforms infrared spectroscopy (FT-IR) and electrochemical technique, has been used for hybridization detection of genomic DNA (dsDNA/Au). This ssDNA-SH/Au bioelectrode can specifically detect up to 100- 500 ng/μL genomic DNA of Vibriocholeare within 60 s of hybridization time at 25°C by cyclic voltammetry (CV) using methylene blue (MB) as electro-active DNA hybridization indicator. The value of sensitivity of the dsDNA/Au electrode has been determined as 0.027μA/ng cm −2 with regression coefficient as 0.978. This DNA bioelectrode is stable for about 4 months when stored at 4°C.

  20. Potential of amino acid/dipeptide monoester prodrugs of floxuridine in facilitating enhanced delivery of active drug to interior sites of tumors: a two-tier monolayer in vitro study.

    Science.gov (United States)

    Tsume, Yasuhiro; Hilfinger, John M; Amidon, Gordon L

    2011-10-01

    To evaluate the advantages of amino acid/dipeptide monoester prodrugs for cancer treatments by assessing the uptake and cytotoxic effects of floxuridine prodrugs in a secondary cancer cell monolayer following permeation across a primary cancer cell monolayer. The first Capan-2 monolayer was grown on membrane transwell inserts; the second monolayer was grown at the bottom of a plate. The permeation of floxuridine and its prodrugs across the first monolayer and the uptake and cell proliferation assay on secondary layer were sequentially determined. All floxuridine prodrugs exhibited greater permeation across the first Capan-2 monolayer than the parent drug. The correlation between uptake and growth inhibition in the second monolayer with intact prodrug permeating the first monolayer suggests that permeability and enzymatic stability are essential for sustained action of prodrugs in deeper layers of tumors. The correlation of uptake and growth inhibition were vastly superior for dipeptide prodrugs to those obtained with mono amino acid prodrugs. Although a tentative general overall correlation between intact prodrug and uptake or cytotoxic action was obtained, it appears that a mixture of floxuridine prodrugs with varying beneficial characteristics may be more effective in treating tumors.

  1. Properties of organogels of high stearic soybean oil

    Science.gov (United States)

    Recently, the U.S. Food and Drug Administration (FDA) announced that food companies have to phase out the use of partially hydrogenated oils containing trans-fats by 2018. The use of high-stearic oils has been recognized as one of the ways to replace trans fats in food. Organogels also have drawn a ...

  2. Avaliação físico-química de bolo de chocolate com coberturas comestíveis à base de gelatina, ácido esteárico, amido modificado ou cera de carnaúba Physical and chemical evaluation of chocolate cake covered with gelatin, stearic acid, modified starch or "carnaúba" wax edible icing

    Directory of Open Access Journals (Sweden)

    Cibele Cristina Osawa

    2009-03-01

    Full Text Available Coberturas comestíveis biodegradáveis são uma alternativa às embalagens sintéticas, que causam preocupações ambientais. Este trabalho avaliou o efeito de diferentes tipos de coberturas sobre propriedades físico-químicas de bolo de chocolate durante a estocagem, em comparação com bolo sem cobertura (CO e bolo sem cobertura embalado em polipropileno (EMB. As seguintes coberturas foram aplicadas sobre os bolos: 10% gelatina (GE, 10% gelatina com 10% ácido esteárico (GE + AE, 18% cera de carnaúba (CE, 10% amido modificado (AM e fondant (FO. Os bolos foram avaliados durante 10 dias de estocagem. FO e EMB apresentaram menor perda de massa, enquanto todos os demais tratamentos apresentaram valores superiores a CO. GE, GE + AE e EMB apresentaram a menor redução da atividade de água, enquanto CE e CO apresentaram a maior redução. As superfícies dos bolos recobertos estavam mais duras que as de CO e EMB. Os maiores valores para dureza e mastigabilidade foram encontrados para CE e CO e os menores, para EMB, GE e GE + AE. Em relação à cor, GE + AE foi diferente dos demais tratamentos, devido à presença do ácido esteárico. Os resultados indicam que a perda de massa dos bolos pode ser atribuída também à perda de água das coberturas.Biodegradable edible icing or frosting is an alternative to synthetic packaging that causes environmental concerns. This work evaluated the effect of different types of frosting on the physical-chemical properties of chocolate cake during storage in comparison to cakes without icing or frosting (C and cakes without frosting packed in polypropylene (CP. The following frostings were applied to the cakes: 10% gelatin (GE, 10% gelatin with 10% stearic acid (GE+SA, 18% "carnaúba" wax (CW, 10% modified starch (MS, and fondant (FO. The cakes were analyzed during 10 days of storage. FO and CP presented the lowest mass loss while all other treatments presented higher values than C. GE, GE+SA, and CP presented

  3. Monolayer covalent modification of 5-hydroxytryptophan on glassy carbon electrodes for simultaneous determination of uric acid and ascorbic acid

    International Nuclear Information System (INIS)

    Lin Xiangqin; Li Yongxin

    2006-01-01

    5-Hydroxytryptophan (5-HTP) was covalently grafted on the surface of glassy carbon electrodes (GCEs) using cyclic voltammetric method in a phosphate buffer solution. The prepared electrode, denoded as 5-HTP/GCE, was characterized by X-ray photoelectron spectroscopy, cyclic voltammetry and differential pulse voltammetry (DPV). Tryptophan grafted GCE (TRP/GCE) and 5-hydroxytryptamine grafted GCE (5-HTP/GCE) were also prepared by the same method for comparison. It was found that the electrocatalytic activities toward the oxidation of uric acid (UA) and ascorbic acid (AA) was in the order of 5-HT/GCE > 5-HTP/GCE > TRP/GCE for UA oxidation and 5-HT/GCE 5-HTP/GCE > TRP/GCE for AA oxidation. However, the CV current sensitivity was estimated as 4:2:1 for 5-HTP/GCE:5-HT/GCE:TRP/GCE. The DPV peaks for UA and AA oxidation appeared at 0.07 V and 0.34 V versus SCE, respectively, allowing simultaneous determination in mixtures. A linearly response in the range of: 5.0 x 10 -7 to 1.1 x 10 -5 M with the detection limit (s/n = 3) of 2.8 x 10 -7 M for UA determination, and a linear response in the range of: 5.0 x 10 -6 to 1.0 x 10 -4 M with the detection limit of 4.2 x 10 -6 M for AA determination were obtained. This electrode was used for UA and AA determinations in human urine samples satisfactorily

  4. Influence of palmitic acid and hexadecanol on the phase transition temperature and molecular packing of dipalmitoylphosphatidyl-choline monolayers at the air-water interface

    Science.gov (United States)

    Lee, Ka Yee C.; Gopal, Ajaykumar; von Nahmen, Anja; Zasadzinski, Joseph A.; Majewski, Jaroslaw; Smith, Gregory S.; Howes, Paul B.; Kjaer, Kristian

    2002-01-01

    Palmitic acid (PA) and 1-hexadecanol (HD) strongly affect the phase transition temperature and molecular packing of dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface. The phase behavior and morphology of mixed DPPC/PA as well as DPPC/HD monolayers were determined by pressure-area-isotherms and fluorescence microscopy. The molecular organization was probed by synchrotron grazing incidence x-ray diffraction using a liquid surface diffractometer. Addition of PA or HD to DPPC monolayers increases the temperature of the liquid-expanded to condensed phase transition. X-ray diffraction shows that DPPC forms mixed crystals both with PA and HD over a wide range of mixing ratios. At a surface pressure (π) of 40 mN/m, increasing the amount of the single chain surfactant leads to a reduction in tilt angle of the aliphatic chains from nearly 30° for pure DPPC to almost 0° in a 1:1 molar ratio of DPPC and PA or HD. At this composition we also find closest packing of the aliphatic chains. Further increase of the amount of PA or HD does not change the lattice or the tilt.

  5. Characterization of 10,12-pentacosadiynoic acid Langmuir–Blodgett monolayers and their use in metal–insulator–metal tunnel devices

    Directory of Open Access Journals (Sweden)

    Saumya Sharma

    2014-11-01

    Full Text Available The characterization of Langmuir–Blodgett thin films of 10,12-pentacosadiynoic acid (PDA and their use in metal–insulator–metal (MIM devices were studied. The Langmuir monolayer behavior of the PDA film was studied at the air/water interface using surface tension–area isotherms of polymeric and monomeric PDA. Langmuir–Blodgett (LB, vertical deposition and Langmuir–Schaefer (LS, horizontal deposition techniques were used to deposit the PDA film on various substrates (glass, quartz, silicon, and nickel-coated film on glass. The electrochemical, electrical and optical properties of the LB and LS PDA films were studied using cyclic voltammetry, current–voltage characteristics (I–V, and UV–vis and FTIR spectroscopies. Atomic force microscopy measurements were performed in order to analyze the surface morphology and roughness of the films. A MIM tunnel diode was fabricated using a PDA monolayer assembly as the insulating barrier, which was sandwiched between two nickel layers. The precise control of the thickness of the insulating monolayers proved critical for electron tunneling to take place in the MIM structure. The current–voltage characteristics of the MIM diode revealed tunneling behavior in the fabricated Ni–PDA LB film–Ni structures.

  6. Effect of uncoated calcium carbonate and stearic acid coated ...

    Indian Academy of Sciences (India)

    Administrator

    ties such as strength, modulus and toughness. Also it has ... Finally, the tensile and impact test specimens were prepared, by ... The thermal stability of the samples was measured by ..... does not help in binding the filler with the PBT matrix.

  7. Boosting the performance of Pt electro-catalysts toward formic acid electro-oxidation by depositing sub-monolayer Au clusters

    International Nuclear Information System (INIS)

    Bi Xuanxuan; Wang Rongyue; Ding Yi

    2011-01-01

    Highlights: → Au decoration on Pt nanoparticles simultaneously increases the activity and stability. → Sub-monolayer Au decoration changes the reaction path and results in the activity improvement. → Increasing the Au coverage will increase the specific activity. → Proper Au coverage results in a maximum mass specific activity. - Abstract: CO poisoning is the main obstacle to the application of Pt nanoparticles as anode catalysts in direct formic acid fuel cells (DFAFCs). Significant types of Pt alloys have been investigated, which often demonstrate evidently improved catalytic performance governed by difference mechanisms. By using a well-known electrochemical technique of under potential deposition and in situ redox replacement, sub-monolayer Au clusters are deposited onto Pt nanoparticle surfaces in a highly controlled manner, generating a unique surface alloy structure. Under optimum conditions, the modified Pt nanoparticles can exhibit greatly enhanced specific activity (up to 23-fold increase) at potential of -0.2 V vs. MSE toward formic acid electro-oxidation (FAEO). Interestingly, the mass specific activity can also be improved by a factor of 2.3 at potential of -0.35 V vs. MSE although significant amount of surface Pt atoms are covered by the overlayer Au clusters. The much enhanced catalytic activity can be ascribed to a Pt surface ensemble effect, which induces change of the reaction path. Moreover, the sub-monolayer Au coating on the surface also contributes to the enhanced catalyst durability by inhibiting the Pt oxidation. These results show great potential to rationally design more active and stable nanocatalysts by modifying the Pt surface with otherwise inactive materials.

  8. A Study by Contact Angle of the Acid-Base Behavior of Monolayers Containing W-Mercaptocarboxylic Acids Absorbed on Gold: An Example of Reactive Spreading

    Science.gov (United States)

    1989-11-01

    1966,22, 138-143. 27 Joos, P. Bull. Soc. Chim. Belges 1971, 80, 277-281. 28 Patil, G. S.; Matthews, R. H.; Cornwell , D. G. In Monolayers; Goddard, E...Commanding Officer 1 Chief of Naval Research Naval Weapons Support Center Special Assistant Attn: Dr. Bernard E. Douda for Marine Corps Matters Crane

  9. Direct patterning of negative nanostructures on self-assembled monolayers of 16-mercaptohexadecanoic acid on Au(111) substrate via dip-pen nanolithography

    International Nuclear Information System (INIS)

    Zheng Zhikun; Yang Menglong; Liu Yaqing; Zhang Bailin

    2006-01-01

    Both bare and self-assembled monolayer (SAM) protected gold substrate could be etched by allyl bromide according to atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometric (ICPMS) analysis results. With this allyl bromide ink material, negative nanopatterns could be fabricated directly by dip-pen nanolithography (DPN) on SAMs of 16-mercaptohexadecanoic acid (MHA) on Au(111) substrate. A tip-promoted etching mechanism was proposed where the gold-reactive ink could penetrate the MHA resist film through tip-induced defects resulting in local corrosive removal of the gold substrate. The fabrication mechanism was also confirmed by electrochemical characterization, energy dispersive spectroscopy (EDS) analysis and fabrication of positive nanopatterns via a used DPN tip

  10. Direct patterning of negative nanostructures on self-assembled monolayers of 16-mercaptohexadecanoic acid on Au(111) substrate via dip-pen nanolithography

    Science.gov (United States)

    Zheng, Zhikun; Yang, Menglong; Liu, Yaqing; Zhang, Bailin

    2006-11-01

    Both bare and self-assembled monolayer (SAM) protected gold substrate could be etched by allyl bromide according to atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometric (ICPMS) analysis results. With this allyl bromide ink material, negative nanopatterns could be fabricated directly by dip-pen nanolithography (DPN) on SAMs of 16-mercaptohexadecanoic acid (MHA) on Au(111) substrate. A tip-promoted etching mechanism was proposed where the gold-reactive ink could penetrate the MHA resist film through tip-induced defects resulting in local corrosive removal of the gold substrate. The fabrication mechanism was also confirmed by electrochemical characterization, energy dispersive spectroscopy (EDS) analysis and fabrication of positive nanopatterns via a used DPN tip.

  11. Synthesis and release of fatty acids by human trophoblast cells in culture

    International Nuclear Information System (INIS)

    Coleman, R.A.; Haynes, E.B.

    1987-01-01

    In order to determine whether placental cells can synthesize and release fatty acids, trophoblast cells from term human placentas were established in monolayer culture. The cells continued to secrete placental lactogen and progesterone and maintained specific activities of critical enzymes of triacylglycerol and phosphatidylcholine biosynthesis for 24 to 72 hr in culture. Fatty acid was rapidly synthesized from [ 14 C]acetate and released by the cells. Palmitoleic, palmitic, and oleic acids were the major fatty acids synthesized from [ 14 C]acetate and released. Small amounts of lauric, myristic, and stearic acids were also identified. [ 14 C]acetate was also incorporated into cellular triacylglycerol, phospholipid, and cholesterol, but radiolabeled free fatty acid did not accumulate intracellularly. In a pulse-chase experiment, cellular glycerolipids were labeled with [1- 14 C]oleate; trophoblast cells then released 14 C-labeled fatty acid into the media as the cellular content of labeled phospholipid and triacylglycerol decreased without intracellular accumulation of free fatty acid. Twenty percent of the 14 C-label lost from cellular glycerolipid could not be recovered as a chloroform-extractable product, suggesting that some of the hydrolyzed fatty acid had been oxidized. These data indicate that cultured placenta trophoblast cells can release fatty acids that have either been synthesized de novo or that have been hydrolyzed from cellular glycerolipids. Trophoblast cells in monolayer culture should provide an excellent model for molecular studies of placental fatty acid metabolism and release

  12. Direct electrochemistry and electrocatalysis of hemoglobin at three-dimensional gold film electrode modified with self-assembled monolayers of 3-mercaptopropylphosphonic acid

    International Nuclear Information System (INIS)

    Chen Yu; Yang Xiaojing; Guo Lirong; Li Jing; Xia Xinghua; Zheng Limin

    2009-01-01

    Multilayered hemoglobin (Hb) molecules were successfully immobilized on three-dimensional gold film electrode modified with self-assembled monolayers (SAMs) of 3-mercaptopropylphosphonic acid. Direct electrochemistry of the immobilized multilayered Hb occurs with high thermal stability and electrochemical stability. In the multilayered Hb film, the most inner Hb molecules can directly transfer electron with the electrode, while the Hb protein beyond this layer communicates electron with the electrode via protein-protein electron exchange. In addition, the proposed functional interface can greatly enhance electron transfer rate of the immobilized Hb protein (k s = 15.8 ± 2.0 s -1 ) due to the increase of roughness of the gold substrate. Under optimized experimental conditions, the multilayered Hb film displays good bioelectrocatalytic activity toward the reduction of hydrogen peroxide. This electrochemical sensor shows fast response (less than 1 s), wide linear range (7.8 x 10 -8 to 9.1 x 10 -5 M) and low detection limit (2.5 x 10 -8 M), which can be attributed to good mass transport, large Hb proteins loading per unit area and fast electron transfer rate of Hb protein.

  13. Conversion of Langmuir-Blodgett monolayers and bilayers of poly(amic acid) through polyimide to graphene

    Science.gov (United States)

    Jo, Hye Jin; Lyu, Ji Hong; Ruoff, Rodney S.; Lim, Hyunseob; In Yoon, Seong; Jeong, Hu Young; Shin, Tae Joo; Bielawski, Christopher W.; Shin, Hyeon Suk

    2017-03-01

    Various solid carbon sources, particularly poly(methyl methacrylate), have been used as precursors to graphene. The corresponding growth process generally involves the decomposition of the solids to hydrocarbon gases followed by their adsorption on metallic substrates (e.g., Cu). We report a different approach that uses a thermally-resistant polyimide (PI) as a carbon precursor. Langmuir-Blodgett films of poly(amic acid) (PAA) were transferred to copper foils and then converted to graphene via a PI intermediate. The Cu foil substrate was also discovered to facilitate the orientation of aromatic moieties upon carbonization process of the PI. As approximately 50% of the initial quantity of the PAA was found to remain at 1000 °C, thermally-stable polymers may reduce the quantity of starting material required to prepare high quality films of graphene. Graphene grown using this method featured a relatively large domain size and an absence of adventitious adlayers.

  14. Immbolization of uricase enzyme in Langmuir and Langmuir-Blodgett films of fatty acids: possible use as a uric acid sensor.

    Science.gov (United States)

    Zanon, Nathaly C M; Oliveira, Osvaldo N; Caseli, Luciano

    2012-05-01

    Preserving the enzyme structure in solid films is key for producing various bioelectronic devices, including biosensors, which has normally been performed with nanostructured films that allow for control of molecular architectures. In this paper, we investigate the adsorption of uricase onto Langmuir monolayers of stearic acid (SA), and their transfer to solid supports as Langmuir-Blodgett (LB) films. Structuring of the enzyme in β-sheets was preserved in the form of 1-layer LB film, which was corroborated with a higher catalytic activity than for other uricase-containing LB film architectures where the β-sheets structuring was not preserved. The optimized architecture was also used to detect uric acid within a range covering typical concentrations in the human blood. The approach presented here not only allows for an optimized catalytic activity toward uric acid but also permits one to explain why some film architectures exhibit a superior performance. Copyright © 2011 Elsevier Inc. All rights reserved.

  15. Studies of endothelial monolayer formation on irradiated poly-L-lactide acid with ions of different stopping power and velocity

    Energy Technology Data Exchange (ETDEWEB)

    Arbeitman, Claudia R. [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); UNQ – IMBICE – CCT – CONICET – LA PLATA (Argentina); Grosso, Mariela F. del [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Ibañez, Irene L. [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Behar, Moni [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); Grasselli, Mariano [UNQ – IMBICE – CCT – CONICET – LA PLATA (Argentina); Bermúdez, Gerardo García [Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina)

    2015-12-15

    In this work we study cell viability, proliferation and morphology of bovine aortic endothelial cells (BAEC) cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. In a previous study comparing ions beams with the same stopping power we observed an increase in cell density and a better cell morphology at higher ion velocities. In the present work we continued this study using heavy ions beam with different stopping power and ion velocities. To this end thin films of 50 μm thickness were irradiated with 2 MeV/u and 0.10 MeV/u ion beams provided the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The results suggest that a more dense and elongated cell shapes, similar to the BAEC cells on the internal surface of bovine aorta, was obtained for stopping power of 18.2–22.1 MeV cm{sup 2} mg{sup −1} and ion velocity of 2 MeV/u. On the other hand, for low ion velocity 0.10 MeV/u the cells present a more globular shapes.

  16. Studies of endothelial monolayer formation on irradiated poly-L-lactide acid with ions of different stopping power and velocity

    International Nuclear Information System (INIS)

    Arbeitman, Claudia R.; Grosso, Mariela F. del; Ibañez, Irene L.; Behar, Moni; Grasselli, Mariano; Bermúdez, Gerardo García

    2015-01-01

    In this work we study cell viability, proliferation and morphology of bovine aortic endothelial cells (BAEC) cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. In a previous study comparing ions beams with the same stopping power we observed an increase in cell density and a better cell morphology at higher ion velocities. In the present work we continued this study using heavy ions beam with different stopping power and ion velocities. To this end thin films of 50 μm thickness were irradiated with 2 MeV/u and 0.10 MeV/u ion beams provided the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The results suggest that a more dense and elongated cell shapes, similar to the BAEC cells on the internal surface of bovine aorta, was obtained for stopping power of 18.2–22.1 MeV cm 2 mg −1 and ion velocity of 2 MeV/u. On the other hand, for low ion velocity 0.10 MeV/u the cells present a more globular shapes.

  17. Bioelectric and Morphological Response of Liquid-Covered Human Airway Epithelial Calu-3 Cell Monolayer to Periodic Deposition of Colloidal 3-Mercaptopropionic-Acid Coated CdSe-CdS/ZnS Core-Multishell Quantum Dots.

    Directory of Open Access Journals (Sweden)

    Aizat Turdalieva

    Full Text Available Lung epithelial cells are extensively exposed to nanoparticles present in the modern urban environment. Nanoparticles, including colloidal quantum dots (QDs, are also considered to be potentially useful carriers for the delivery of drugs into the body. It is therefore important to understand the ways of distribution and the effects of the various types of nanoparticles in the lung epithelium. We use a model system of liquid-covered human airway epithelial Calu-3 cell cultures to study the immediate and long-term effects of repeated deposition of colloidal 3-mercaptopropionic-acid coated CdSe-CdS/ZnS core-multishell QDs on the lung epithelial cell surface. By live confocal microscope imaging and by QD fluorescence measurements we show that the QD permeation through the mature epithelial monolayers is very limited. At the time of QD deposition, the transepithelial electrical resistance (TEER of the epithelial monolayers transiently decreased, with the decrement being proportional to the QD dose. Repeated QD deposition, once every six days for two months, lead to accumulation of only small amounts of the QDs in the cell monolayer. However, it did not induce any noticeable changes in the long-term TEER and the molecular morphology of the cells. The colloidal 3-mercaptopropionic-acid coated CdSe-CdS/ZnS core-multishell QDs could therefore be potentially used for the delivery of drugs intended for the surface of the lung epithelia during limited treatment periods.

  18. Atomic force measurements of 16-mercaptohexadecanoic acid and its salt with CH3, OH, and CONHCH3 functionalized self-assembled monolayers

    International Nuclear Information System (INIS)

    Morales-Cruz, Angel L.; Tremont, Rolando; Martinez, Ramon; Roman-tilde ach, Rodolfo; Cabrera, Carlos R.

    2005-01-01

    Chemical and mechanical properties of different compounds can be elucidated by measuring fundamental forces such as adhesion, attraction and repulsion, between modified surfaces by means of atomic force microscopy (AFM) in force mode calibration. This work presents a combination of AFM, self-assembled monolayers (SAMs), and crystallization techniques to study the forces of interaction between excipients and active ingredients used in pharmaceutical formulations. SAMs of 16-mercaptohexadecanoate, which represent magnesium stereate, were used to modify the probe tip, whereas CH 3 -, OH- and CONHCH 3 -functional SAMs were formed on a gold-coated mica substrate, and used as examples of the surfaces of lactose and theophylline. The crystals of lactose and theophylline were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The modification of gold surfaces with 16-mercaptohexadecanoate, 10-mercapto-1-decanol (OH-functional SAM), 1-decanethiol (CH 3 -functional) and N-methyl-11-mercaptoundecanamide (CONHCH 3 -functional SAM) was studied by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Fourier transform-infrared spectroscopy (FT-IR) in specular reflectance mode. XPS and AES results of the modified surfaces showed the presence of sulfur binding, and kinetic energies that correspond to the presence of 10-mercapto-1-decanol, 1-decanethiol, N-methyl-11-mercaptoundecanamide and the salt of 16-mercaptohexadecanoic acid. The absorption bands in the IR spectra further confirm the modification of the gold-coated substrates with these compounds. Force versus distance measurements were performed between the modified tip and the modified gold-coated mica substrates. The mean adhesion forces between the COO - Ca 2+ functionalized tip and the CH 3 -, OH-, and CONHCH 3 -modified substrates were determined to be 4.5, 8.9 and 6.3 nN, respectively. The magnitude of the adhesion force (ion-dipole) interaction between the modified

  19. Diamondoid monolayers as electron emitters

    Science.gov (United States)

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

    2012-04-10

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

  20. Antibiotic interaction with phospholipid monolayers

    International Nuclear Information System (INIS)

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

    2002-01-01

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

  1. Antibiotic interaction with phospholipid monolayers

    Energy Technology Data Exchange (ETDEWEB)

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

    2002-12-01

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

  2. WSe2 Monolayer

    KAUST Repository

    Zhang, Shuai; Wang, Chen-Guang; Li, Ming-yang; Huang, Di; Li, Lain-Jong; Ji, Wei; Wu, Shiwei

    2017-01-01

    dichalcogenide materials, intrinsic defects in WSe2 arise surprisingly from single tungsten vacancies, leading to the hole (p-type) doping. Furthermore, we found these defects to dominate the excitonic emission of the WSe2 monolayer at low temperature. Our work

  3. Protonation of octadecylamine Langmuir monolayer by adsorption of halide counterions

    Science.gov (United States)

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

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

  4. Transport of monocarboxylic acids at the blood-brain barrier: Studies with monolayers of primary cultured bovine brain capillary endothelial cells

    International Nuclear Information System (INIS)

    Terasaki, T.; Takakuwa, S.; Moritani, S.; Tsuji, A.

    1991-01-01

    The kinetics and mechanism of the transport of monocarboxylic acids (MCAs) were studied by using primary cultured bovine brain capillary endothelial cells. Concentration-dependent uptake of acetic acid was observed, and the kinetic parameters were estimated as follows: the Michaelis constant, Kt, was 3.41 ± 1.87 mM, the maximum uptake rate, Jmax, was 144.7 ± 55.7 nmol/mg of protein/min and the nonsaturable first-order rate constant, Kd, was 6.66 ± 1.98 microliters/mg of protein/min. At medium pH below 7.0, the uptake rate of [3H]acetic acid increased markedly with decreasing medium pH, whereas pH-independent uptake was observed in the presence of 10 mM acetic acid. An energy requirement for [3H]acetic acid uptake was also demonstrated, because metabolic inhibitors (2,4-dinitrophenol and rotenone) reduced significantly the uptake rate (P less than .05). Carbonylcyanide-p-trifluoro-methoxyphenylhydrazone, a protonophore, inhibited significantly the uptake of [3H]acetic acid at medium pH of 5.0 and 6.0, whereas 4,4'-diisothiocyanostilben-2,2'-disulfonic acid did not. Several MCAs inhibited significantly the uptake rate of [3H]acetic acid, whereas di- and tricarboxylic acids did not. The uptake of [3H]acetic acid was competitively inhibited by salicylic acid, with an inhibition constant, Ki, of 3.60 mM, suggesting a common transport system between acetic acid and salicylic acid. Moreover, at the medium pH of 7.4, salicylic acid and valproic acid inhibited significantly the uptake of [3H]acetic acid, demonstrating that the transport of MCA drugs could also be ascribed to the MCA transport system at the physiologic pH

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

    Energy Technology Data Exchange (ETDEWEB)

    Mary Vergheese, T.; Berchmans, Sheela

    2004-02-15

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

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

    International Nuclear Information System (INIS)

    Mary Vergheese, T.; Berchmans, Sheela

    2004-01-01

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

  7. In situ Observation of Direct Electron Transfer Reaction of Cytochrome c Immobilized on ITO Electrode Modified with 11-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}undecylphosphonic Acid Self-assembled Monolayer Film by Electrochemical Slab Optical Waveguide Spectroscopy.

    Science.gov (United States)

    Matsuda, Naoki; Okabe, Hirotaka; Omura, Ayako; Nakano, Miki; Miyake, Koji

    2017-01-01

    To immobilize cytochrome c (cyt.c) on an ITO electrode while keeping its direct electron transfer (DET) functionality, the ITO electrode surface was modified with 11-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}undecylphosphonic acid (CH 3 O (CH 2 CH 2 O) 3 C 11 H 22 PO(OH) 2 , M-EG 3 -UPA) self-assembled monolayer (SAM) film. After a 100-times washing process to exchange a phosphate buffer saline solution surrounding cyt.c and ITO electrode to a fresh one, an in situ observation of visible absorption spectral change with slab optical waveguide (SOWG) spectroscopy showed that 87.7% of the cyt.c adsorbed on the M-EG 3 -UPA modified ITO electrode remained on the ITO electrode. The SOWG absorption spectra corresponding to oxidized and reduced cyt.c were observed with setting the ITO electrode potential at 0.3 and -0.3 V vs. Ag/AgCl, respectively, while probing the DET reaction between cyt.c and ITO electrode occurred. The amount of cyt.c was evaluated to be about 19.4% of a monolayer coverage based on the coulomb amount in oxidation and reduction peaks on cyclic voltammetry (CV) data. The CV peak current maintained to be 83.4% compared with the initial value for a M-EG 3 -UPA modified ITO electrode after 60 min continuous scan with 0.1 V/s between 0.3 and -0.3 V vs. Ag/AgCl.

  8. A Facile Method for Detection of Substituted Salicylic Acids Using Pyrenesulfonamide-Terminated Self-Assembled Monolayers on Silicon Oxide Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Han, Gyeongyeop; Choi, Jaehyuck; Lee, Jungkyu; Kumar, Ashwani; Lee, Ju-Young; Kim, Hong-Seok [Kyungpook Nation al University, Daegu (Korea, Republic of)

    2016-05-15

    We have developed a method for sensing substituted salicylic acids on silicon oxide surfaces. The receptor molecule was successfully immobilized onto the surface by self-assembly, and, as a demonstration, micropatterns of substituted salicylic acids were generated by soft lithography techniques. We believe that this approach used herein will not only widen the understanding of the specific interactions between salicylic acids and pyrenesulfonamide derivatives, but also be applicable to practical devices such as chemo/bio analytical sensors. We have successfully demonstrated the molecular recognition between salicylic acids and pyrene derivatives in solution by fluorescence measurement. Briefly, selective recognition was achieved using intermolecular interactions, including π-π interactions and multi-hydrogen bonds, and intramolecular hydrogen bonding between the phenolic O-H group and the adjacent C=O group.

  9. A Facile Method for Detection of Substituted Salicylic Acids Using Pyrenesulfonamide-Terminated Self-Assembled Monolayers on Silicon Oxide Surfaces

    International Nuclear Information System (INIS)

    Han, Gyeongyeop; Choi, Jaehyuck; Lee, Jungkyu; Kumar, Ashwani; Lee, Ju-Young; Kim, Hong-Seok

    2016-01-01

    We have developed a method for sensing substituted salicylic acids on silicon oxide surfaces. The receptor molecule was successfully immobilized onto the surface by self-assembly, and, as a demonstration, micropatterns of substituted salicylic acids were generated by soft lithography techniques. We believe that this approach used herein will not only widen the understanding of the specific interactions between salicylic acids and pyrenesulfonamide derivatives, but also be applicable to practical devices such as chemo/bio analytical sensors. We have successfully demonstrated the molecular recognition between salicylic acids and pyrene derivatives in solution by fluorescence measurement. Briefly, selective recognition was achieved using intermolecular interactions, including π-π interactions and multi-hydrogen bonds, and intramolecular hydrogen bonding between the phenolic O-H group and the adjacent C=O group

  10. Modulation of saturation and chain length of fatty acids in Saccharomyces cerevisiae for production of cocoa butter-like lipids

    DEFF Research Database (Denmark)

    Bergenholm, David; Gossing, Michael; Wei, Yongjun

    2018-01-01

    Chain length and degree of saturation plays an important role for the characteristics of various products derived from fatty acids, such as fuels, cosmetics, and food additives. The seeds of Theobroma cacao are the source of cocoa butter, a natural lipid of high interest for the food and cosmetics...... as the saturated fatty acid stearic acid is typically found only in low abundance. Demand for cocoa butter is increasing, yet T. cacao can only be cultivated in some parts of the tropics. Alternative means of production of cocoa butter lipids (CBLs) are, therefore, sought after. Yeasts also store fatty acids...... industry. Cocoa butter is rich in saturated fatty acids that are stored in the form of triacylglycerides (TAGs). One of the major TAG species of cocoa butter, consisting of two stearic acid molecules and one oleic acid molecule (stearic acid-oleic acid-stearic acid, sn-SOS), is particularly rare in nature...

  11. Structure of montmorillonite cointercalated with stearic acid and octadecylamine: Modeling, diffraction, IR spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Čapková, P.; Pospíšil, M.; Valášková, M.; Měřínská, D.; Trchová, Miroslava; Sedláková, Zdeňka; Weiss, Z.; Šimoník, J.

    2006-01-01

    Roč. 300, č. 1 (2006), s. 264-269 ISSN 0021-9797 R&D Projects: GA ČR GA205/05/2548; GA ČR GP205/03/D111 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer-clay nanocomposite * intercalation * montmorillonite Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.233, year: 2006

  12. Monolayer Superconductivity in WS2

    NARCIS (Netherlands)

    Zheliuk, Oleksandr; Lu, Jianming; Yang, Jie; Ye, Jianting

    Superconductivity in monolayer tungsten disulfide (2H-WS2) is achieved by strong electrostatic electron doping of an electric double-layer transistor (EDLT). Single crystals of WS2 are grown by a scalable method - chemical vapor deposition (CVD) on standard Si/SiO2 substrate. The monolayers are

  13. Unusual fatty acid substitution in lipids and lipopolysaccharides of Helicobacter pylori.

    OpenAIRE

    Geis, G; Leying, H; Suerbaum, S; Opferkuch, W

    1990-01-01

    Cellular fatty acids, phospholipid fatty acids, and lipopolysaccharide fatty acids of four strains of Helicobacter pylori were analyzed by gas-liquid chromatography. The presence of myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, 19-carbon cyclopropane fatty acid, beta-hydroxypalmitic acid, and beta-hydroxystearic acid was confirmed. In phospholipids, myristic acid and 19-carbon cyclopropane fatty acid were the major fatty acids. Hydroxy fatty acids and unsaturated fatt...

  14. Distribution of fatty acids from dietary oils into phospholipid classes of triacylglycerol-rich lipoproteins in healthy subjects.

    Science.gov (United States)

    Abia, Rocio; Pacheco, Yolanda M; Montero, Emilio; Ruiz-Gutierrez, Valentina; Muriana, Francisco J G

    2003-02-21

    Several studies have suggested that lipoprotein metabolism can be affected by lipoprotein phospholipid composition. We investigated the effect of virgin olive oil (VOO) and high-oleic sunflower oil (HOSO) intake on the distribution of fatty acids in triacylglycerols (TG), cholesteryl esters (CE) and phospholipid (PL) classes of triacylglycerol-rich lipoproteins (TRL) from normolipidemic males throughout a 7 h postprandial metabolism. Particularly, changes in oleic acid (18:1n-9) concentration of PL were used as a marker of in vivo hydrolysis of TRL external monolayer. Both oils equally promoted the incorporation of oleic acid into the TG and CE of postprandial TRL. However, PL was enriched in oleic acid (18:1n-9) and n-3 polyunsaturated fatty acids (PUFA) after VOO meal, whereas in stearic (18:0) and linoleic (18:2n-6) acids after HOSO meal. We also found that VOO produced TRL which PL 18:1n-9 content was dramatically reduced along the postprandial period. We conclude that the fatty acid composition of PL can be a crucial determinant for the clearance of TRL during the postprandial metabolism of fats.

  15. Interference effects from coexisting fatty acids on elaidic acid separation by fractionating crystallization: A model study

    DEFF Research Database (Denmark)

    Jala, Ram Chandra Reddy; Guo, Zheng; Bjerring, Thomas

    2010-01-01

    A multi-stage temperature-programmed fractionating crystallization process was carried out to examine the effects of the presence of stearic acid (SA), oleic acid (OA), and linoleic acid (LA) on the separation of elaidic acid (EA). The results showed that the efficiency of fractionating...

  16. N-Type self-assembled monolayer field-effect transistors for flexible organic electronics

    NARCIS (Netherlands)

    Ringk, A.; Roelofs, Christian; Smits, E.C.P.; van der Marel, C.; Salzmann, I.; Neuhold, A.; Gelinck, G.H.; Resel, R.; de Leeuw, D.M.; Strohriegl, P.

    Within this work we present n-type self-assembled monolayer field-effect transistors (SAMFETs) based on a novel perylene bisimide. The molecule spontaneously forms a covalently fixed monolayer on top of an aluminium oxide dielectric via a phosphonic acid anchor group. Detailed studies revealed an

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

    NARCIS (Netherlands)

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

    2012-01-01

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

  18. Separation of the Stern and diffuse layer in coarse-grained models: the cases of phosphatidyl serine, phosphatidic acid, and PIP2 monolayers.

    Science.gov (United States)

    Vangaveti, S; Travesset, A

    2014-12-28

    We present here a method to separate the Stern and diffuse layer in general systems into two regions that can be analyzed separately. The Stern layer can be described in terms of Bjerrum pairing and the diffuse layer in terms of Poisson-Boltzmann theory (monovalent) or strong coupling theory plus a slowly decaying tail (divalent). We consider three anionic phospholipids: phosphatidyl serine, phosphatidic acid, and phosphatidylinositol(4,5)bisphosphate (PIP2), which we describe within a minimal coarse-grained model as a function of ionic concentration. The case of mixed lipid systems is also considered, which shows a high level of binding cooperativity as a function of PIP2 localization. Implications for existing experimental systems of lipid heterogeneities are also discussed.

  19. Structural investigation of a self-assembled monolayer material 5-[(3-methylphenyl) (phenyl) amino] isophthalic acid for organic light-emitting devices

    Science.gov (United States)

    Saş, E. Babur; Kurt, M.; Can, M.; Okur, S.; İçli, S.; Demiç, S.

    2014-12-01

    The molecular structure and vibrations of 5-[(3-methylphenyl) (phenyl) amino] isophthalic acid (MePIFA) were investigated by infrared and Raman spectroscopies, UV-Vis, 1H and 13C NMR spectroscopic techniques and NBO analysis. FT-IR, FT-Raman and dispersive Raman spectra were recorded in the solid phase. 1H and 13C NMR spectra and UV-Vis spectrum were recorded in DMSO solution. HOMO-LUMO analysis and molecular electrostatic potential (MEP) analysis were performed. The theoretical calculations for the molecular structure and spectroscopies were performed with DFT (B3LYP) and 6-311G(d,p) basis set calculations using the Gaussian 09 program. After the geometry of the molecule was optimized, vibration wavenumbers and fundamental vibration wavenumbers were assigned on the basis of the potential energy distribution (PED) of the vibrational modes calculated with VEDA 4 program. The total (TDOS), partial (PDOS) density of state and overlap population density of state (OPDOS) diagrams analysis were made using GaussSum 2.2 program. The results of theoretical calculations for the spectra of the title compound were compared with the observed spectra.

  20. Phase transitions in surfactant monolayers

    International Nuclear Information System (INIS)

    Casson, B.D.

    1998-01-01

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

  1. Surface-segregated monolayers: a new type of ordered monolayer for surface modification of organic semiconductors.

    Science.gov (United States)

    Wei, Qingshuo; Tajima, Keisuke; Tong, Yujin; Ye, Shen; Hashimoto, Kazuhito

    2009-12-09

    We report a new type of ordered monolayer for the surface modification of organic semiconductors. Fullerene derivatives with fluorocarbon chains ([6,6]-phenyl-C(61)-buryric acid 1H,1H-perfluoro-1-alkyl ester or FC(n)) spontaneously segregated as a monolayer on the surface of a [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) film during a spin-coating process from the mixture solutions, as confirmed by X-ray photoelectron spectroscopy (XPS). Ultraviolet photoelectron spectroscopy (UPS) showed the shift of ionization potentials (IPs) depending on the fluorocarbon chain length, indicating the formation of surface dipole moments. Surface-sensitive vibrational spectroscopy, sum frequency generation (SFG) revealed the ordered molecular orientations of the C(60) moiety in the surface FC(n) layers. The intensity of the SFG signals from FC(n) on the surface showed a clear odd-even effect when the length of the fluorocarbon chain was changed. This new concept of the surface-segregated monolayer provides a facile and versatile approach to modifying the surface of organic semiconductors and is applicable to various organic optoelectronic devices.

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

    DEFF Research Database (Denmark)

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

    1996-01-01

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

  3. Infrared spectroscopy of self-assembled monolayer films on silicon

    Science.gov (United States)

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

    2007-07-01

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

  4. Orientational epitaxy in adsorbed monolayers

    International Nuclear Information System (INIS)

    Novaco, A.D.; McTague, J.P.

    1977-01-01

    The ground state for adsorbed monolayers on crystalline substrates is shown to involve a definite relative orientation of the substrate and adsorbate crystal axes, even when the relative lattice parameters are incommensurate. The rotation angle which defines the structure of the monolayer-substrate system is determined by the competition between adsorbate-substrate and adsorbate-adsorbate energy terms, and is generally not a symmetry angle. Numerical predictions are presented for the rare gas-graphite systems, whose interaction potentials are rather well known. Recent LEED data for some of these systems appear to corroborate these predictions

  5. Transport properties in monolayer-bilayer-monolayer graphene planar junctions

    Institute of Scientific and Technical Information of China (English)

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

    2017-01-01

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

  6. Solution-processable septithiophene monolayer transistor

    NARCIS (Netherlands)

    Defaux, M.; Gholamrezaie, F.; Wang, J.; Kreyes, A.; Ziener, U.; Anokhin, D.V.; Ivanov, D.A.; Moser, A.; Neuhold, A.; Salzmann, I.; Resel, R.; Leeuw, de D.M.; Meskers, S.C.J.; Moeller, M.; Mourran, A.

    2012-01-01

    Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and

  7. Solution-Processable Septithiophene Monolayer Transistor

    NARCIS (Netherlands)

    Defaux, Matthieu; Gholamrezaie, Fatemeh; Wang, Jingbo; Kreyes, Andreas; Ziener, Ulrich; Anokhin, Denis V.; Ivanov, Dimitri A.; Moser, Armin; Neuhold, Alfred; Salzmann, Ingo; Resel, Roland; de Leeuw, Dago M.; Meskers, Stefan C. J.; Moeller, Martin; Mourran, Ahmed

    2012-01-01

    Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and

  8. Phase transitions in polymer monolayers

    NARCIS (Netherlands)

    Deschênes, Louise; Lyklema, J.; Danis, Claude; Saint-Germain, François

    2015-01-01

    In this paper we investigate the application of the two-dimensional Clapeyron law to polymer monolayers. This is a largely unexplored area of research. The main problems are (1) establishing if equilibrium is reached and (2) if so, identifying and defining phases as functions of the temperature.

  9. Activity of the main fatty acid components of the hexane leaf extract ...

    African Journals Online (AJOL)

    The composition of hexane leaf extract of Ricinus communis was determined by gas chromatography– mass spectrometry (GC-MS) to contain four fatty acids: linolenic acid (47.76%), linoleic acid (15.28%), palmitic acid (13.01%), and stearic acid (1.73%). The insectistatic and insecticidal activities of the two major ...

  10. Convenient biosynthetic preparation of isomeric spin-labelled radioactive phosphatidic acids

    Energy Technology Data Exchange (ETDEWEB)

    Stuhne, L.; Stanacev, N.Z. (Toronto Univ., Ontario (Canada). Dept. of Clinical Biochemistry)

    1982-11-01

    A convenient method for the enzymatic preparation of sn-3-(2-/sup 3/H)phosphatidic acids carrying also 5-, 12-, or 16-nitroxide stearic acids, from sn-3-(2-/sup 3/H) glycerophosphate and isolated guinea pig liver microsomes, is described in detail. The procedure allows a simultaneous preparation of three spin-labelled sn-3-(2-/sup 3/H)phosphatidic acids of yields 3-3.5..mu..mol of each compound which is >99% pure in respect to the radioactivity and which contains 25 mol% of spin-labelled fatty acids. These phosphatidic acids were approximately equally distributed between the primary and the secondary hydroxyl when 12- or 16-nitroxide stearic acids were used or predominantly (75%) associated with the secondary hydroxyl of sn-3-(2-/sup 3/H)phosphatidic acid when 5-nitroxide stearic acid was present in the incubation mixture.

  11. Qualitative and quantitative assessment of fatty acids of buddleja asiatica by GC-MS

    International Nuclear Information System (INIS)

    Ali, F.; Ali, I.; Bibi, H.; Malik, A.

    2013-01-01

    To analyze the fatty acid contents of Buddleja asiatica Lour,both the non-volatile oil and fat obtained from the n-hexane soluble sub- fraction were subjected to GC/MS using BSTFA (N,O-bis(trimethylsilyl) trifloroacetamide) derivatization. The oil showed the presence of six fatty acids including palmitic acid (46.75 %), linoleic acid (37.80 %), stearic acid (10.98 %), arachidic acid, margaric acid and lignoceric acid (< 3 %) . Analysis of the fat revealed nine fatty acids including lignoceric acid (43.12 %), behenic acid (26.39 %), arachidic acid (9.29 %) and stearic acid (5.3 %). Cerotic acid, montanic acid, melissic acid and palmitic acid were found in low amounts (< 5 %) while trycosylic acid (4.83 %) was the only fatty acid with odd number of carbon atoms. The oil showed a low thermal stability. (author)

  12. Monolayer atomic crystal molecular superlattices

    Science.gov (United States)

    Wang, Chen; He, Qiyuan; Halim, Udayabagya; Liu, Yuanyue; Zhu, Enbo; Lin, Zhaoyang; Xiao, Hai; Duan, Xidong; Feng, Ziying; Cheng, Rui; Weiss, Nathan O.; Ye, Guojun; Huang, Yun-Chiao; Wu, Hao; Cheng, Hung-Chieh; Shakir, Imran; Liao, Lei; Chen, Xianhui; Goddard, William A., III; Huang, Yu; Duan, Xiangfeng

    2018-03-01

    Artificial superlattices, based on van der Waals heterostructures of two-dimensional atomic crystals such as graphene or molybdenum disulfide, offer technological opportunities beyond the reach of existing materials. Typical strategies for creating such artificial superlattices rely on arduous layer-by-layer exfoliation and restacking, with limited yield and reproducibility. The bottom-up approach of using chemical-vapour deposition produces high-quality heterostructures but becomes increasingly difficult for high-order superlattices. The intercalation of selected two-dimensional atomic crystals with alkali metal ions offers an alternative way to superlattice structures, but these usually have poor stability and seriously altered electronic properties. Here we report an electrochemical molecular intercalation approach to a new class of stable superlattices in which monolayer atomic crystals alternate with molecular layers. Using black phosphorus as a model system, we show that intercalation with cetyl-trimethylammonium bromide produces monolayer phosphorene molecular superlattices in which the interlayer distance is more than double that in black phosphorus, effectively isolating the phosphorene monolayers. Electrical transport studies of transistors fabricated from the monolayer phosphorene molecular superlattice show an on/off current ratio exceeding 107, along with excellent mobility and superior stability. We further show that several different two-dimensional atomic crystals, such as molybdenum disulfide and tungsten diselenide, can be intercalated with quaternary ammonium molecules of varying sizes and symmetries to produce a broad class of superlattices with tailored molecular structures, interlayer distances, phase compositions, electronic and optical properties. These studies define a versatile material platform for fundamental studies and potential technological applications.

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

    International Nuclear Information System (INIS)

    Wang Xinxin; Nagata, Kenji; Higuchi, Masahiro

    2012-01-01

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

  14. Packing of ganglioside-phospholipid monolayers

    DEFF Research Database (Denmark)

    Majewski, J.; Kuhl, T.L.; Kjær, K.

    2001-01-01

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

  15. Structure and shear response of lipid monolayers

    International Nuclear Information System (INIS)

    Dutta, P.; Ketterson, J.B.

    1990-02-01

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

  16. Connexin 26-mediated gap junctional intercellular communication suppresses paracellular permeability of human intestinal epithelial cell monolayers

    International Nuclear Information System (INIS)

    Morita, Hidekazu; Katsuno, Tatsuro; Hoshimoto, Aihiro; Hirano, Noriaki; Saito, Yasushi; Suzuki, Yasuo

    2004-01-01

    In some cell types, gap junctional intercellular communication (GJIC) is associated with tight junctions. The present study was performed to determine the roles of GJIC in regulation of the barrier function of tight junctions. Caco-2 human colonic cells were used as a monolayer model, and barrier function was monitored by measuring mannitol permeability and transepithelial electrical resistance (TER). The monolayers were chemically disrupted by treatment with oleic acid and taurocholic acid. Western blotting analyses were performed to evaluate the protein levels of connexins, which are components of gap junctional intercellular channels. Cx26 expression was detected in preconfluent Caco-2 cells, and its level increased gradually after the monolayer reached confluency. These results prompted us to examine whether overexpression of Cx26 affects barrier function. Monolayers of Caco-2 cells stably expressing Cx26 showed significantly lower mannitol permeability and higher TER than mock transfectants when the monolayers were chemically disrupted. The levels of claudin-4, an important component of tight junctions, were significantly increased in the stable Cx26 transfectant. These results suggest that Cx26-mediated GJIC may play a crucial role in enhancing the barrier function of Caco-2 cell monolayers

  17. Studies of lipid interactions in mixed Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Gzyl-Malcher, Barbara [Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland)], E-mail: gzyl@chemia.uj.edu.pl; Paluch, Maria [Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland)

    2008-10-31

    The mixed monolayers of dipalmitoyl phosphatidylcholine (DPPC) with 3-monopalmitoyl glycerol (PG) and palmitic acid 4-methylumbelliferyl ester (4-MU) were compared. Relevant thermodynamic parameters such as excess area ({delta}A{sup E}) and excess free energy of mixing ({delta}G{sub mix}{sup E}) were derived from the surface pressure data obtained from compression measurements performed in a Langmuir trough. Generally, DPPC formed more condensed monolayers with PG and greater negative values of {delta}A{sup E} and {delta}G{sub mix}{sup E} were observed for DPPC/PG system than for DPPC/4-MU one. The positive values of the excess free entropy of mixing ({delta}S{sub mix}{sup E}) were calculated for DPPC/4-MU system at lower temperatures and for DPPC/PG system at higher temperatures.

  18. Transepithelial transport of flavanone in intestinal Caco-2 cell monolayers

    International Nuclear Information System (INIS)

    Kobayashi, Shoko; Konishi, Yutaka

    2008-01-01

    Our recent study [S. Kobayashi, S. Tanabe, M. Sugiyama, Y. Konishi, Transepithelial transport of hesperetin and hesperidin in intestinal Caco-2 cell monolayers, Biochim. Biophys. Acta, 1778 (2008) 33-41] shows that the mechanism of absorption of hesperetin involves both proton-coupled active transport and transcellular passive diffusion. Here, as well as analyzing the cell permeability of hesperetin, we also study the transport of other flavanones, naringenin and eriodictyol, using Caco-2 cell monolayers. Similar to hesperetin mentioned, naringenin and eriodictyol showed proton-coupled polarized transport in apical-to-basolateral direction in non-saturable manner, constant permeation in the apical-to-basolateral direction (J ap→bl ) irrespective of the transepithelial electrical resistance (TER), and preferable distribution into the basolateral side after apical loading in the presence of a proton gradient. Furthermore, the proton-coupled J ap→bl of hesperetin, naringenin and eriodictyol, were inhibited by substrates of the monocarboxylic acid transporter (MCT), such as benzoic acid, but not by ferulic acid. In contrast, both benzoic and ferulic acids have no stimulatory effect on J ap→bl of each flavanone by trans-stimulation analysis. These results indicates that proton-driven active transport is commonly participated in the absorption of flavanone in general, and that its transport is presumed to be unique other than MCT-mediated transport for absorption of phenolic acids (PAs), sodium-dependent MCT (SMCT) nor anion exchanger-mediated transport

  19. Preparation, characterization and pharmacokinetics of enrofloxacin-loaded solid lipid nanoparticles: influences of fatty acids.

    Science.gov (United States)

    Xie, Shuyu; Zhu, Luyan; Dong, Zhao; Wang, Xiaofang; Wang, Yan; Li, Xihe; Zhou, WenZhong

    2011-04-01

    Enrofloxacin-loaded solid lipid nanoparticles (SLN) were prepared using fatty acids (tetradecanoic acid, palmitic acid, stearic acid) as lipid matrix by hot homogenization and ultrasonication method. The effect of fatty acids on the characteristics and pharmacokinetics of the SLN were investigated. The results showed that the encapsulation efficiency and loading capacity of nanoparticles varied with fatty acids in the order of stearic acid>palmitic acid>tetradecanoic acid. Furthermore, stearic acid-SLN had larger particle size, bigger polydispersity index (PDI) and higher zeta potential compared with the other two fatty acid formulated SLN. The SLN showed sustained releases in vitro and the released enrofloxacin had the same antibacterial activity as that of the native enrofloxacin. Although in vitro release exhibited similar patterns, within 24 h the releasing rates of the three formulations were significantly different (tetradecanoic acid-SLN>palmitic acid-SLN>stearic acid-SLN). Pharmacokinetic study after a single dose of intramuscular administration to mice demonstrated that tetradecanoic acid-SLN, palmitic acid-SLN, and stearic acid-SLN increased the bioavailability by 6.79, 3.56 and 2.39 folds, and extended the mean residence time (MRT) of the drug from 10.60 h to 180.36, 46.26 and 19.09 h, respectively. These results suggest that the enrofloxacin-fatty acid SLN are promising formulations for sustained release while fatty acids had significant influences on the characteristics and performances of the SLN. Copyright © 2010 Elsevier B.V. All rights reserved.

  20. Lateral pressure profiles in lipid monolayers

    NARCIS (Netherlands)

    Baoukina, Svetlana; Marrink, Siewert J.; Tieleman, D. Peter

    2010-01-01

    We have used molecular dynamics simulations with coarse-grained and atomistic models to study the lateral pressure profiles in lipid monolayers. We first consider simple oil/air and oil/water interfaces, and then proceed to lipid monolayers at air/water and oil/water interfaces. The results are

  1. Preparation and Photoluminescence of Tungsten Disulfide Monolayer

    Directory of Open Access Journals (Sweden)

    Yanfei Lv

    2018-05-01

    Full Text Available Tungsten disulfide (WS2 monolayer is a direct band gap semiconductor. The growth of WS2 monolayer hinders the progress of its investigation. In this paper, we prepared the WS2 monolayer through chemical vapor transport deposition. This method makes it easier for the growth of WS2 monolayer through the heterogeneous nucleation-and-growth process. The crystal defects introduced by the heterogeneous nucleation could promote the photoluminescence (PL emission. We observed the strong photoluminescence emission in the WS2 monolayer, as well as thermal quenching, and the PL energy redshift as the temperature increases. We attribute the thermal quenching to the energy or charge transfer of the excitons. The redshift is related to the dipole moment of WS2.

  2. Fatty Acid And Essential Oil Compositions Of The Seed Oil Of Five ...

    African Journals Online (AJOL)

    The fatty acid and essential oil compositions of the seed oil of Annona cherimola, A. muricata, A. reticulata, A. senegalensis and A. squamosa were investigated by GC and GC/MS spectra. About eleven fatty acids were identified of which oleic, gondoic, palmitic and stearic acids predominated in each sample, and others ...

  3. Thermal stability of thiol and silane monolayers: A comparative study

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  4. Effect of dietary fatty acid intake on prospective weight change in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition

    DEFF Research Database (Denmark)

    Nimptsch, Katharina; Berg-Beckhoff, Gabi; Linseisen, Jakob

    2010-01-01

    OBJECTIVE: To evaluate the association between fatty acid (alpha-linolenic acid (ALA), EPA, DHA, palmitic, stearic, oleic, linoleic and arachidonic acids) intake and prospective weight change in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition. DESIGN....... RESULTS: Stearic acid intake was linearly associated with weight gain (P acid intake, significantly so in women. In multinomial models, women in the highest tertile of ALA and stearic acid intake showed increased OR (95 % CI......) and categorised into four groups (weight loss, or =2.5 to or =7.5%/5 years). Energy-adjusted dietary fatty acid intake data were estimated from the FFQ completed at baseline. Multivariate linear regression models as well as multinomial logistic regression analyses (carbohydrate replacement models) were conducted...

  5. Effect of 6 dietary fatty acids on the postprandial lipid profile, plasma fatty acids, lipoprotein lipase, and cholesterol ester transfer activities in healthy young men

    DEFF Research Database (Denmark)

    Tholstrup, T.; Sandstrøm, B.; Bysted, Anette

    2001-01-01

    , plasma fatty acids, and preheparin lipoprotein lipase and cholesterol ester transfer protein (CETP) activities. Design: Six test fats high (approximate to 43% by wt) in stearic acid, palmitic acid, palmitic + myristic acid, oleic acid, elaidic acid (trans 18:1), and linoleic acid were produced...... to the test-fat meals were observed for plasma lipoprotein triacylglycerol and cholesterol concentrations, plasma fatty acid concentrations, and lipoprotein lipase and CETP activities (diet x time interaction: 0.001 acids stearic and palmitic acids resulted......Background: There is increasing evidence that postprandial triacylglycerol-rich lipoproteins may be related to atherogenic risk. Objective: The objective was to investigate the effect of individual fatty acid intakes on postprandial plasma lipoprotein triacylglycerol and cholesterol concentrations...

  6. Large Friction Anisotropy of a Polydiacetylene Monolayer

    International Nuclear Information System (INIS)

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-01-01

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties

  7. Molecular diffusion in monolayer and submonolayer nitrogen

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, Ludwig Walter

    2001-01-01

    The orientational and translational motions in a monolayer fluid of physisorbed molecular nitrogen are treated using molecular dynamics simulations. Dynamical response functions and several approximations to the coefficient of translational diffusion are determined for adsorption on the basal plane...

  8. Dark excitations in monolayer transition metal dichalcogenides

    DEFF Research Database (Denmark)

    Deilmann, Thorsten; Thygesen, Kristian Sommer

    2017-01-01

    Monolayers of transition metal dichalcogenides (TMDCs) possess unique optoelectronic properties, including strongly bound excitons and trions. To date, most studies have focused on optically active excitations, but recent experiments have highlighted the existence of dark states, which are equally...

  9. Method to synthesize metal chalcogenide monolayer nanomaterials

    Science.gov (United States)

    Hernandez-Sanchez, Bernadette A.; Boyle, Timothy J.

    2016-12-13

    Metal chalcogenide monolayer nanomaterials can be synthesized from metal alkoxide precursors by solution precipitation or solvothermal processing. The synthesis routes are more scalable, less complex and easier to implement than other synthesis routes.

  10. Janus Monolayer Transition-Metal Dichalcogenides.

    Science.gov (United States)

    Zhang, Jing; Jia, Shuai; Kholmanov, Iskandar; Dong, Liang; Er, Dequan; Chen, Weibing; Guo, Hua; Jin, Zehua; Shenoy, Vivek B; Shi, Li; Lou, Jun

    2017-08-22

    The crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit has been synthesized and carefully characterized in this work. By controlled sulfurization of monolayer MoSe 2 , the top layer of selenium atoms is substituted by sulfur atoms, while the bottom selenium layer remains intact. The structure of this material is systematically investigated by Raman, photoluminescence, transmission electron microscopy, and X-ray photoelectron spectroscopy and confirmed by time-of-flight secondary ion mass spectrometry. Density functional theory (DFT) calculations are performed to better understand the Raman vibration modes and electronic structures of the Janus SMoSe monolayer, which are found to correlate well with corresponding experimental results. Finally, high basal plane hydrogen evolution reaction activity is discovered for the Janus monolayer, and DFT calculation implies that the activity originates from the synergistic effect of the intrinsic defects and structural strain inherent in the Janus structure.

  11. Nanotubes based on monolayer blue phosphorus

    KAUST Repository

    Montes Muñ oz, Enrique; Schwingenschlö gl, Udo

    2016-01-01

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube

  12. Exciton Binding Energy of Monolayer WS2

    Science.gov (United States)

    Zhu, Bairen; Chen, Xi; Cui, Xiaodong

    2015-03-01

    The optical properties of monolayer transition metal dichalcogenides (TMDC) feature prominent excitonic natures. Here we report an experimental approach to measuring the exciton binding energy of monolayer WS2 with linear differential transmission spectroscopy and two-photon photoluminescence excitation spectroscopy (TP-PLE). TP-PLE measurements show the exciton binding energy of 0.71 +/- 0.01 eV around K valley in the Brillouin zone.

  13. Sensitive detection of plastic explosives with self-assembled monolayer-coated microcantilevers

    Science.gov (United States)

    Pinnaduwage, L. A.; Boiadjiev, V.; Hawk, J. E.; Thundat, T.

    2003-08-01

    We report the detection of 10-30 parts-per-trillion levels of pentaerythritol tetranitrate and hexahydro-1,3,5-triazine within 20 s of exposure to a silicon microcantilever with its gold surface modified with a self-assembled monolayer of 4-mercaptobenzoic acid. These measurements correspond to a limit of detection of a few fg.

  14. Double-brush Langmuir-Blodgett monolayers of alpha-helical diblock copolypeptides

    NARCIS (Netherlands)

    Nguyen, Le-Thu T.; Vorenkamp, Eltjo J.; Daumont, Christophe J. M.; ten Brinke, Gerrit; Schouten, Arend J.; Vukovic, Ivana; Loos, Katja

    2010-01-01

    The synthesis of amphiphilic diblock copolypeptides consisting of poly(alpha-L-glutamic acid) (PLGA) and poly(gamma-methyl-L-glutamate-ran-gamma-stearyl-L-glutamate) with 30 mol % of stearyl substituents (PMLGSLG) and their monolayer behavior at the air-water interface have been studied.

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

    Science.gov (United States)

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

    2009-09-01

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

  16. Complexation of phospholipids and cholesterol by triterpenic saponins in bulk and in monolayers.

    Science.gov (United States)

    Wojciechowski, Kamil; Orczyk, Marta; Gutberlet, Thomas; Geue, Thomas

    2016-02-01

    The interactions between three triterpene saponins: α-hederin, hederacoside C and ammonium glycyrrhizate with model lipids: cholesterol and dipalmitoylphosphatidylcholine (DPPC) are described. The oleanolic acid-type saponins (α-hederin and hederacoside C) were shown to form 1:1 complexes with lipids in bulk, characterized by stability constants in the range (4.0±0.2)·10(3)-(5.0±0.4)·10(4) M(-1). The complexes with cholesterol are generally stronger than those with DPPC. On the contrary, ammonium glycyrrhizate does not form complexes with any of the lipids in solution. The saponin-lipid interactions were also studied in a confined environment of Langmuir monolayers of DPPC and DPPC/cholesterol with the saponins present in the subphase. A combined monolayer relaxation, surface dilational rheology, fluorescence microscopy and neutron reflectivity (NR) study showed that all three saponins are able to penetrate pure DPPC and mixed DPPC/cholesterol monolayers. Overall, the effect of the saponins on the model lipid monolayers does not fully correlate with the lipid-saponin complex formation in the homogeneous solution. The best correlation was found for α-hederin, for which even the preference for cholesterol over DPPC observed in bulk is well reflected in the monolayer studies and the literature data on its membranolytic activity. Similarly, the lack of interaction of ammonium glycyrrhizate with both lipids is evident equally in bulk and monolayer experiments, as well as in its weak membranolytic activity. The combined bulk and monolayer results are discussed in view of the role of confinement in modulating the saponin-lipid interactions and possible mechanism of membranolytic activity of saponins. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Characterization of free and bound fatty acids in human gallstones by capillary gas liquid chromatography

    International Nuclear Information System (INIS)

    Channa, N.A.; Khand, F.D.; Noorani, M.A.; Bhanger, M.I.

    2002-01-01

    Forty-four human gallstone samples either of pure cholesterol or cholesterol and bilirubin were randomly selected and analyzed by capillary gas liquid chromatography for the relative percentage composition of free and total fatty acids. The results showed that bound fatty acids were present in higher amounts than the free fatty acids. Amongst the bound fatty acids the percentage occurrence for palmitic acid was highest followed by stearic, oleic, linoleic and myristic acids. Fatty acids myristic, palmitic and linoleic were present in higher amounts in cholesterol gallstones, whereas stearic acid in cholesterol and bilirubin gallstones. When compared, no significant difference (p < 0.05) in the levels of free and bound fatty acids were seen in gallstones of males and females. The results suggest that bound fatty acids have a role to play in the structure of gallstones. (author)

  18. Multivariate analysis of TOF-SIMS spectra of monolayers on scribed silicon.

    Science.gov (United States)

    Yang, Li; Lua, Yit-Yian; Jiang, Guilin; Tyler, Bonnie J; Linford, Matthew R

    2005-07-15

    Static time-of-flight secondary ion mass spectrometry (TOF-SIMS) was performed on monolayers on scribed silicon (Si(scr)) derived from 1-alkenes, 1-alkynes, 1-holoalkanes, aldehydes, and acid chlorides. To rapidly determine the variation in the data without introducing user bias, a multivariate analysis was performed. First, principal components analysis (PCA) was done on data obtained from silicon scribed with homologous series of aldehydes and acid chlorides. For this study, the positive ion spectra, the negative ion spectra, and the concatentated (linked) positive and negative ion spectra were preprocessed by normalization, mean centering, and autoscaling. The mean centered data consistently showed the best correlations between the scores on PC1 and the number of carbon atoms in the adsorbate. These correlations were not as strong for the normalized and autoscaled data. After reviewing these methods, it was concluded that mean centering is the best preprocessing method for TOF-SIMS spectra of monolayers on Si(scr). A PCA analysis of all of the positive ion spectra revealed a good correlation between the number of carbon atoms in all of the adsorbates and the scores on PC1. PCA of all of the negative ion spectra and the concatenated positive and negative ion spectra showed a correlation based on the number of carbon atoms in the adsorbate and the class of the adsorbate. These results imply that the positive ion spectra are most sensitive to monolayer thickness, while the negative ion spectra are sensitive to the nature of the substrate-monolayer interface and the monolayer thickness. Loadings show an inverse relationship between (inorganic) fragments that are expected from the substrate and (organic) fragments expected from the monolayer. Multivariate peak intensity ratios were derived. It is also suggested that PCA can be used to detect outlier surfaces. Partial least squares showed a strong correlation between the number of carbon atoms in the adsorbate and the

  19. Clofibric Acid Increases the Formation of Oleic Acid in Endoplasmic Reticulum of the Liver of Rats

    OpenAIRE

    広瀬, 明彦; 山崎, 研; 坂本, 武史; 須永, 克佳; 津田, 整; 光本, 篤史; 工藤, なをみ; 川嶋, 洋一

    2011-01-01

    The effects of 2-(4-chlorophenoxy)-2-methylpropionic acid (clofibric acid) on the formation of oleic acid (18:1) from stearic acid (18:0) and utilization of the 18:1 formed for phosphatidylcholine (PC) formation in endoplasmic reticulum in the liver of rats were studied in vivo. [14C]18:0 was intravenously injected into control Wistar male rats and rats that had been fed on a diet containing 0.5% (w/w) clofibric acid for 7 days; and the distribution of radiolabeled fatty acids among subcellul...

  20. Thermal ripples in model molybdenum disulfide monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Remsing, Richard C.; Klein, Michael L. [Institute for Computational Molecular Science, Center for the Computational, Design of Functional Layered Materials, and Department of Chemistry, Temple University, 1925 N. 12th St., 19122, Philadelphia, PA (United States); Waghmare, Umesh V. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560 064, Jakkur, Bangalore (India)

    2017-01-15

    Molybdenum disulfide (MoS{sub 2}) monolayers have the potential to revolutionize nanotechnology. To reach this potential, it will be necessary to understand the behavior of this two-dimensional (2D) material on large length scales and under thermal conditions. Herein, we use molecular dynamics (MD) simulations to investigate the nature of the rippling induced by thermal fluctuations in monolayers of the 2H and 1T phases of MoS{sub 2}. The 1T phase is found to be more rigid than the 2H phase. Both monolayer phases are predicted to follow long wavelength scaling behavior typical of systems with anharmonic coupling between vibrational modes as predicted by classic theories of membrane-like systems. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Phases and phase transition in insoluble and adsorbed monolayers of amide amphiphiles: Specific characteristics of the condensed phases.

    Science.gov (United States)

    Vollhardt, D

    2015-08-01

    For understanding the role of amide containing amphiphiles in inherently complex biological processes, monolayers at the air-water interface are used as simple biomimetic model systems. The specific characteristics of the condensed phases and phase transition in insoluble and adsorbed monolayers of amide amphiphiles are surveyed to highlight the effect of the chemical structure of the amide amphiphiles on the interfacial interactions in model monolayers. The mesoscopic topography and/or two-dimensional lattice structures of selected amino acid amphiphiles, amphiphilic N-alkylaldonamide, amide amphiphiles with specific tailored headgroups, such as amide amphiphiles based on derivatized ethanolamine, e.g. acylethanolamines (NAEs) and N-,O-diacylethanolamines (DAEs) are presented. Special attention is devoted the dominance of N,O-diacylated ethanolamine in mixed amphiphilic acid amide monolayers. The evidence that a first order phase transition can occur in adsorption layers and that condensed phase domains of mesoscopic scale can be formed in adsorption layers was first obtained on the basis of the experimental characteristics of a tailored amide amphiphile. New thermodynamic and kinetic concepts for the theoretical description of the characteristics of amide amphiphile's monolayers were developed. In particular, the equation of state for Langmuir monolayers generalized for the case that one, two or more phase transitions occur, and the new theory for phase transition in adsorbed monolayers are experimentally confirmed at first by amide amphiphile monolayers. Despite the significant progress made towards the understanding the model systems, these model studies are still limited to transfer the gained knowledge to biological systems where the fundamental physical principles are operative in the same way. The study of biomimetic systems, as described in this review, is only a first step in this direction. Copyright © 2014 Elsevier B.V. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-06-15

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

  3. Electrochemical behavior of monolayer and bilayer graphene.

    Science.gov (United States)

    Valota, Anna T; Kinloch, Ian A; Novoselov, Kostya S; Casiraghi, Cinzia; Eckmann, Axel; Hill, Ernie W; Dryfe, Robert A W

    2011-11-22

    Results of a study on the electrochemical properties of exfoliated single and multilayer graphene flakes are presented. Graphene flakes were deposited on silicon/silicon oxide wafers to enable fast and accurate characterization by optical microscopy and Raman spectroscopy. Conductive silver paint and silver wires were used to fabricate contacts; epoxy resin was employed as a masking coating in order to expose a stable, well-defined area of graphene. Both multilayer and monolayer graphene microelectrodes showed quasi-reversible behavior during voltammetric measurements in potassium ferricyanide. However, the standard heterogeneous charge transfer rate constant, k°, was estimated to be higher for monolayer graphene flakes. © 2011 American Chemical Society

  4. Sub-THz Characterisation of Monolayer Graphene

    Directory of Open Access Journals (Sweden)

    Ehsan Dadrasnia

    2014-01-01

    Full Text Available We explore the optical and electrical characteristics of monolayer graphene by using pulsed optoelectronic terahertz time-domain spectroscopy in the frequency range of 325–500 GHz based on fast direct measurements of phase and amplitude. We also show that these parameters can, however, be measured with higher resolution using a free space continuous wave measurement technique associated with a vector network analyzer that offers a good dynamic range. All the scattering parameters (both magnitude and phase are measured simultaneously. The Nicholson-Ross-Weir method is implemented to extract the monolayer graphene parameters at the aforementioned frequency range.

  5. Low temperature photoresponse of monolayer tungsten disulphide

    Directory of Open Access Journals (Sweden)

    Bingchen Cao

    2014-11-01

    Full Text Available High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup, while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  6. Nonlinear optical studies of organic monolayers

    International Nuclear Information System (INIS)

    Shen, Y.R.

    1988-02-01

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

  7. Methylated Fatty Acids from Heartwood and Bark of Pinus sylvestris, Abies alba, Picea abies, and Larix decidua: Effect of Strong Acid Treatment

    Directory of Open Access Journals (Sweden)

    Mohamed Zidan Mohamed Salem

    2015-09-01

    Full Text Available Methylated fatty acid (FA compounds in the heartwood and bark of some softwood species, specifically Pinus sylvestris, Abies alba, Picea abies, and Larix decidua, grown in the Czech Republic were evaluated. Strong H2SO4 was used for methylation of the lipids. The highest content of lipid was found in P. abies bark (40.132 mg/g o.d. sample, and the lowest content was in A. alba wood (11.027 mg/g o.d. sample. The highest concentration of FAs was observed in L. decidua bark. The highest percentages of FAs in wood of P. sylvestris were arachidic acid and oleic acid. In bark, the highest percentages of FAs were stearic acid, palmitic acid, and oleic acid. The FAs with the highest concentrations in A. alba wood were arachidic acid, palmitic acid, pentadecanoic acid, and margarinic, and those in bark were behenic acid, lignoceric acid, and arachidic acid. P. abies wood FAs showed arachidic acid, palmitic acid, and margarinic acid, and the bark contained lignoceric acid and arachidic acid. The FAs of L. decidua wood were arachidic acid, palmitic acid, and stearic acid, and in bark they were pentacosylic acid, docosahexaenoic acid (DHA, lignoceric acid, arachidic acid, and behenic acid. The lack of typically dominant unsaturated fatty acids (e.g. 18:1, 18:2, compared to literature values were attributed to the application of strong acid for the hydrolysis.

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

    Science.gov (United States)

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

    2008-09-02

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-01

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

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-11-30

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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-03-01

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

  15. Molar extinction coefficients of some fatty acids

    DEFF Research Database (Denmark)

    Sandhu, G.K.; Singh, K.; Lark, B.S.

    2002-01-01

    ) and stearic acid (C18H36O2), has been measured at the photon energies 81, 356, 511, 662, 1173 and 1332 keV. Experimental values for the molar extinction coefficient, the effective atomic number and the electron density have been derived and compared with theoretical calculations. There is good agreement......The attenuation of gamma rays in some fatty acids, viz. formic acid (CH2O2), acetic acid (C2H4O2), propionic acid (C3H6O2), butyric acid (C4H8O2), n-hexanoic acid (C6H12O2), n-caprylic acid (C8H16O2), lauric acid (C12H24O2), myristic acid (C14H28O2), palmitic acid (C16H32O2), oleic acid (C18H34O2...

  16. Preparation, characterization, and thermal properties of starch microencapsulated fatty acids as phase change materials thermal energy storage applications

    Science.gov (United States)

    Stable starch-oil composites can be prepared from renewable resources by excess steam jet-cooking aqueous slurries of starch and vegetable oils or other hydrophobic materials. Fatty acids such as stearic acid are promising phase change materials (PCMs) for latent heat thermal energy storage applica...

  17. Crystal network for edible oil organogels: Possibilities and limitations of the fatty acid and fatty alcohol systems

    NARCIS (Netherlands)

    Schaink, H.M.; Malssen, van K.; Morgado-Alves, S.; Kalnin, D.J.E.; Linden, van der E.

    2007-01-01

    The textural and structural properties of organogels made by structuring liquid oil with mixtures of stearic acid (octadecanoic acid) and stearyl alcohol (octadecanol) have been studied. Optical, rheological and X-ray diffraction measurements have been used to investigate the influence of

  18. Surface chemistry and electrocatalytic behaviour of tetra-carboxy substituted iron, cobalt and manganese phthalocyanine monolayers on gold electrode

    International Nuclear Information System (INIS)

    Mashazi, Philani N.; Westbroek, Philippe; Ozoemena, Kenneth I.; Nyokong, Tebello

    2007-01-01

    Surface chemistry and electrocatalytic properties of self-assembled monolayers of metal tetra-carboxylic acid phthalocyanine complexes with cobalt (Co), iron (Fe) and manganese (Mn) as central metal ions have been studied. These phthalocyanine molecules are immobilized on gold electrode via the coupling reaction between the ring substituents and pre-formed mercaptoethanol self-assembled monolayer (Au-ME SAM). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed chemisorption of mercaptoethanol via sulfur group on gold electrode and also coupling reaction between phthalocyanines and Au-ME SAM. Electrochemical parameters of the immobilized molecules show that these molecules are densely packed with a perpendicular orientation. The potential applications of the gold modified electrodes were investigated towards L-cysteine detection and the analysis at phthalocyanine SAMs. Cobalt and iron tetra-carboxylic acid phthalocyanine monolayers showed good oxidation peak for L-cysteine at potentials where metal oxidation (M III /M II ) takes place and this metal oxidation mediates the catalytic oxidation of L-cysteine. Manganese tetra-carboxylic acid phthalocyanine monolayer also exhibited a good catalytic oxidation peak towards L-cysteine at potentials where Mn IV /Mn III redox peak occurs and this redox peak mediates L-cysteine oxidation. The analysis of cysteine at phthalocyanine monolayers displayed good analytical parameters with good detection limits of the orders of 10 -7 mol L -1 and good linearity for a studied concentration range up to 60 μmol L -1

  19. Imidazolide monolayers for versatile reactive microcontact printing

    NARCIS (Netherlands)

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

    2008-01-01

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

  20. Nanotubes based on monolayer blue phosphorus

    KAUST Repository

    Montes Muñoz, Enrique

    2016-07-08

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube diameter and axial strain. The nanotubes are found to be semiconductors with a sensitive indirect band gap that allows flexible tuning.

  1. Integrated circuits based on conjugated polymer monolayer.

    Science.gov (United States)

    Li, Mengmeng; Mangalore, Deepthi Kamath; Zhao, Jingbo; Carpenter, Joshua H; Yan, Hongping; Ade, Harald; Yan, He; Müllen, Klaus; Blom, Paul W M; Pisula, Wojciech; de Leeuw, Dago M; Asadi, Kamal

    2018-01-31

    It is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier mobilities reaching 3 cm 2  V -1  s -1 . The high performance is attributed to the strong interactions of the polymer chains present already in solution leading to pronounced edge-on packing and well-defined microstructure in the monolayer. The high reproducibility enables the integration of discrete unipolar PoM-FETs into inverters and ring oscillators. Real logic functionality has been demonstrated by constructing a 15-bit code generator in which hundreds of self-assembled PoM-FETs are addressed simultaneously. Our results provide the state-of-the-art example of integrated circuits based on a conjugated polymer monolayer, opening prospective pathways for bottom-up organic electronics.

  2. Shadow mask evaporation through monolayer modified nanostencils

    NARCIS (Netherlands)

    Kolbel, M.; Tjerkstra, R.W.; Brugger, J.P.; van Rijn, C.J.M.; Nijdam, W.; Huskens, Jurriaan; Reinhoudt, David

    2002-01-01

    Gradual clogging of the apertures of nanostencils used as miniature shadow masks in metal evaporations can be reduced by coating the stencil with self-assembled monolayers (SAM). This is quantified by the dimensions (height and volume) of gold features obtained by nanostencil evaporation as measured

  3. Fullerene monolayer formation by spray coating

    NARCIS (Netherlands)

    Cervenka, J.; Flipse, C.F.J.

    2010-01-01

    Many large molecular complexes are limited in thin film applications by their insufficient thermal stability, which excludes deposition via commonly used vapour phase deposition methods. Here we demonstrate an alternative way of monolayer formation of large molecules by a simple spray coating method

  4. Semiconductor monolayer assemblies with oriented crystal faces

    KAUST Repository

    Ma, Guijun; Takata, Tsuyoshi; Katayama, Masao; Zhang, Fuxiang; Moriya, Yosuke; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2012-01-01

    Fabrication of two-dimensional monolayers of crystalline oxide and oxynitride particles was attempted on glass plate substrates. X-Ray diffraction patterns of the assemblies show only specific crystal facets, indicative of the uniform orientation of the particles on the substrate. The selectivity afforded by this immobilization technique enables the organization of randomly distributed polycrystalline powders in a controlled manner.

  5. Fullerene monolayer formation by spray coating

    Czech Academy of Sciences Publication Activity Database

    Červenka, Jiří; Flipse, C.F.J.

    2010-01-01

    Roč. 21, č. 6 (2010), 065302/1-065302/7 ISSN 0957-4484 Institutional research plan: CEZ:AV0Z10100521 Keywords : monolayer * spray coating * fullerene * atomic force microscopy * scanning tunnelling microscopy * electronic structure * graphite * gold Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.644, year: 2010

  6. Caveolar fatty acids and acylation of caveolin-1.

    Directory of Open Access Journals (Sweden)

    Qian Cai

    Full Text Available Caveolae are cholesterol and sphingolipids rich subcellular domains on plasma membrane. Caveolae contain a variety of signaling proteins which provide platforms for signaling transduction. In addition to enriched with cholesterol and sphingolipids, caveolae also contain a variety of fatty acids. It has been well-established that acylation of protein plays a pivotal role in subcellular location including targeting to caveolae. However, the fatty acid compositions of caveolae and the type of acylation of caveolar proteins remain largely unknown. In this study, we investigated the fatty acids in caveolae and caveolin-1 bound fatty acids.Caveolae were isolated from Chinese hamster ovary (CHO cells. The caveolar fatty acids were extracted with Folch reagent, methyl esterificated with BF3, and analyzed by gas chromatograph-mass spectrometer (GC/MS. The caveolin-1 bound fatty acids were immunoprecipitated by anti-caveolin-1 IgG and analyzed with GC/MS.In contrast to the whole CHO cell lysate which contained a variety of fatty acids, caveolae mainly contained three types of fatty acids, 0.48 µg palmitic acid, 0.61 µg stearic acid and 0.83 µg oleic acid/caveolae preparation/5 × 10(7 cells. Unexpectedly, GC/MS analysis indicated that caveolin-1 was not acylated by myristic acid; instead, it was acylated by palmitic acid and stearic acid.Caveolae contained a special set of fatty acids, highly enriched with saturated fatty acids, and caveolin-1 was acylated by palmitic acid and stearic acid. The unique fatty acid compositions of caveolae and acylation of caveolin-1 may be important for caveolae formation and for maintaining the function of caveolae.

  7. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    Energy Technology Data Exchange (ETDEWEB)

    Arbeitman, Claudia R.; Grosso, Mariela F. del [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Behar, Moni [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); García Bermúdez, Gerardo, E-mail: ggb@tandar.cnea.gov.ar [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Escuela de Ciencia y Tecnología, UNSAM (Argentina)

    2013-11-01

    In this work we study cell adhesion, proliferation and cell morphology of endothelial cell cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. Thin films of PLLA samples were irradiated with sulfur (S) at energies of 75 MeV and gold (Au) at 18 MeV ion-beams. Ion beams were provided by the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The growth of a monolayer of bovine aortic endothelial cells (BAEC) onto unirradiated and irradiated surfaces has been studied by in vitro techniques in static culture. Cell viability and proliferation increased on modified substrates. But the results on unirradiated samples, indicate cell death (necrosis/apoptosis) with the consequent decrease in proliferation. We analyzed the correlation between irradiation parameters and cell metabolism and morphology.

  8. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    International Nuclear Information System (INIS)

    Arbeitman, Claudia R.; Grosso, Mariela F. del; Behar, Moni; García Bermúdez, Gerardo

    2013-01-01

    In this work we study cell adhesion, proliferation and cell morphology of endothelial cell cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. Thin films of PLLA samples were irradiated with sulfur (S) at energies of 75 MeV and gold (Au) at 18 MeV ion-beams. Ion beams were provided by the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The growth of a monolayer of bovine aortic endothelial cells (BAEC) onto unirradiated and irradiated surfaces has been studied by in vitro techniques in static culture. Cell viability and proliferation increased on modified substrates. But the results on unirradiated samples, indicate cell death (necrosis/apoptosis) with the consequent decrease in proliferation. We analyzed the correlation between irradiation parameters and cell metabolism and morphology

  9. Low-voltage self-assembled monolayer field-effect transistors on flexible substrates.

    Science.gov (United States)

    Schmaltz, Thomas; Amin, Atefeh Y; Khassanov, Artoem; Meyer-Friedrichsen, Timo; Steinrück, Hans-Georg; Magerl, Andreas; Segura, Juan José; Voitchovsky, Kislon; Stellacci, Francesco; Halik, Marcus

    2013-08-27

    Self-assembled monolayer field-effect transistors (SAMFETs) of BTBT functionalized phosphonic acids are fabricated. The molecular design enables device operation with charge carrier mobilities up to 10(-2) cm(2) V(-1) s(-1) and for the first time SAMFETs which operate on rough, flexible PEN substrates even under mechanical substrate bending. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Science.gov (United States)

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

    2007-09-11

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

  11. Molecular tilt on monolayer-protected nanoparticles

    KAUST Repository

    Giomi, L.

    2012-02-01

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

  12. Epitaxial growth by monolayer restricted galvanic displacement

    Directory of Open Access Journals (Sweden)

    Vasilić Rastko

    2012-01-01

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

  13. Collective cell motion in endothelial monolayers

    International Nuclear Information System (INIS)

    Szabó, A; Ünnep, R; Méhes, E; Czirók, A; Twal, W O; Argraves, W S; Cao, Y

    2010-01-01

    Collective cell motility is an important aspect of several developmental and pathophysiological processes. Despite its importance, the mechanisms that allow cells to be both motile and adhere to one another are poorly understood. In this study we establish statistical properties of the random streaming behavior of endothelial monolayer cultures. To understand the reported empirical findings, we expand the widely used cellular Potts model to include active cell motility. For spontaneous directed motility we assume a positive feedback between cell displacements and cell polarity. The resulting model is studied with computer simulations and is shown to exhibit behavior compatible with experimental findings. In particular, in monolayer cultures both the speed and persistence of cell motion decreases, transient cell chains move together as groups and velocity correlations extend over several cell diameters. As active cell motility is ubiquitous both in vitro and in vivo, our model is expected to be a generally applicable representation of cellular behavior

  14. Molecular tilt on monolayer-protected nanoparticles

    KAUST Repository

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

    2012-01-01

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

  15. Electrochemical behaviour of monolayer and bilayer graphene

    OpenAIRE

    Valota, Anna T.; Kinloch, Ian A.; Novoselov, Kostya S.; Casiraghi, Cinzia; Eckmann, Axel; Hill, Ernie W.; Dryfe, Robert A. W.

    2011-01-01

    Results of a study on the electrochemical properties of exfoliated single and multilayer graphene flakes are presented. Graphene flakes were deposited on silicon/silicon oxide wafers to enable fast and accurate characterization by optical microscopy and Raman spectroscopy. Conductive silver paint and silver wires were used to fabricate contacts; epoxy resin was employed as masking coating in order to expose a stable, well defined area of graphene. Both multilayer and monolayer graphene microe...

  16. Conformation, orientation and interaction in molecular monolayers

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  17. Structure of cholesterol/ceramide monolayer mixtures

    DEFF Research Database (Denmark)

    Scheffer, L.; Solomonov, I.; Weygand, M.J.

    2005-01-01

    The structure of monolayers of cholesterol/ ceramide mixtures was investigated using grazing incidence x-ray diffraction, immunofluorescence, and atomic force microscopy techniques. Grazing incidence x-ray diffraction measurements showed the existence of a crystalline mixed phase of the two....... As ceramide incorporates the lipid backbone common to all sphingolipids, this arrangement may be relevant to the understanding of the molecular organization of lipid rafts....

  18. Investigation on gallium ions impacting monolayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xin; Zhao, Haiyan, E-mail: hyzhao@tsinghua.edu.cn; Yan, Dong; Pei, Jiayun [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, P. R. Chinaand Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2015-06-15

    In this paper, the physical phenomena of gallium (Ga{sup +}) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga{sup +} ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga{sup +} ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm{sup 2}. Afterwards, the focused ion beam over 21.6 ion/nm{sup 2} is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  19. Janus monolayers of transition metal dichalcogenides

    KAUST Repository

    Lu, Ang-Yu

    2017-05-15

    Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements.

  20. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

    2015-01-01

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm '2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  1. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua

    2015-02-19

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  2. Affinity of serum apolipoproteins for lipid monolayers

    International Nuclear Information System (INIS)

    Ibdah, J.A.

    1987-01-01

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

  3. Chain length dependence of the helix orientation in Langmuir-Blodgett monolayers of alpha-helical diblock copolypeptides

    NARCIS (Netherlands)

    Nguyen, Le-Thu T.; Ardana, Aditya; Vorenkamp, Eltjo J.; ten Brinke, Gerrit; Schouten, Arend J.

    2010-01-01

    The effect of chain length on the helix orientation of alpha-helical diblock copolypeptides in Langmuir and Langmuir-Blodgett monolayers is reported for the first time. Amphiphilic diblock copolypeptides (PLGA-b-PMLGSLGs) of poly(alpha-L-glutamic acid) (PLGA) and

  4. Dendritic functionalization of monolayer-protected gold nanoparticles

    International Nuclear Information System (INIS)

    Cutler, Erin C.; Lundin, Erik; Garabato, B. Davis; Choi, Daeock; Shon, Young-Seok

    2007-01-01

    This paper describes the facile synthesis of nanoparticle-cored dendrimers (NCDs) and nanoparticle megamers from monolayer-protected gold clusters using either single or multi-step reactions. First, 11-mercaptoundecanoic acid/hexanethiolate-protected gold clusters were synthesized using the Schiffrin reaction followed by the ligand place-exchange reaction. A convergent approach for the synthesis of nanoparticle-cored dendrimers uses a single step reaction that is an ester coupling reaction of hydroxy-functionalized dendrons with carboxylic acid-functionalized gold clusters. A divergent approach, which is based on multi-step reactions, employs the repetition of an amide coupling reaction and a Michael addition reaction to build polyamidoamine dendritic architectures around a nanoparticle core. Nanoparticle megamers, which are large dendrimer-induced nanoparticle aggregates with an average diameter of more than 300 nm, were prepared by the amide coupling reaction between polyamiodoamine [G-2] dendrimers and carboxylic acid-functionalized gold clusters. 1 H NMR spectroscopy, FT-IR spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used for the characterization of these hybrid nanoparticles

  5. Modulation of saturation and chain length of fatty acids in Saccharomyces cerevisiae for production of cocoa butter-like lipids.

    Science.gov (United States)

    Bergenholm, David; Gossing, Michael; Wei, Yongjun; Siewers, Verena; Nielsen, Jens

    2018-04-01

    Chain length and degree of saturation plays an important role for the characteristics of various products derived from fatty acids, such as fuels, cosmetics, and food additives. The seeds of Theobroma cacao are the source of cocoa butter, a natural lipid of high interest for the food and cosmetics industry. Cocoa butter is rich in saturated fatty acids that are stored in the form of triacylglycerides (TAGs). One of the major TAG species of cocoa butter, consisting of two stearic acid molecules and one oleic acid molecule (stearic acid-oleic acid-stearic acid, sn-SOS), is particularly rare in nature as the saturated fatty acid stearic acid is typically found only in low abundance. Demand for cocoa butter is increasing, yet T. cacao can only be cultivated in some parts of the tropics. Alternative means of production of cocoa butter lipids (CBLs) are, therefore, sought after. Yeasts also store fatty acids in the form of TAGs, but these are typically not rich in saturated fatty acids. To make yeast an attractive host for microbial production of CBLs, its fatty acid composition needs to be optimized. We engineered Saccharomyces cerevisiae yeast strains toward a modified fatty acid synthesis. Analysis of the fatty acid profile of the modified strains showed that the fatty acid content as well as the titers of saturated fatty acids and the titers of TAGs were increased. The relative content of potential CBLs in the TAG pool reached up to 22% in our engineered strains, which is a 5.8-fold increase over the wild-type. SOS content reached a level of 9.8% in our engineered strains, which is a 48-fold increase over the wild type. © 2018 Wiley Periodicals, Inc.

  6. Evaluation of conjugated linoleic acid and other health-related lipid ...

    African Journals Online (AJOL)

    Boiled samples preserved the total beneficial lipids of CLA, PUFA, MUFA and omega 3 and 6 fatty acids more than smoked samples. The major fatty acids found in the muscle analyzed are palmitic (C16:0), stearic (C18:0) and octadecenoic (C18:1). Omega 3 fatty acids are 1.05%, 1.16% and 1.30 % for boiled, smoked and ...

  7. Development and characterization of a hydrophobic treatment for jute fibres based on zinc oxide nanoparticles and a fatty acid

    Energy Technology Data Exchange (ETDEWEB)

    Arfaoui, M.A. [CTT Group, Saint-Hyacinthe (Canada); Department of Mechanical Engineering, Ecole de technologie supérieure, Montréal (Canada); Dolez, P.I., E-mail: pdolez@gcttg.com [CTT Group, Saint-Hyacinthe (Canada); Dubé, M.; David, É. [Department of Mechanical Engineering, Ecole de technologie supérieure, Montréal (Canada)

    2017-03-01

    Highlights: • A hydrophobic treatment based on zinc oxide nanoparticles and stearic acid was developed for recycled jute fibres. • The water contact angle was increased from 33° for the scoured fibre to 148° after the ZnO nanorod/stearic acid hydrothermal treatment. • The fibre thermal degradation temperature remained the same throughout the treatment at around 315 °C. • A reduction in the fibre breaking force of 32% was observed between the as-received and the ZnO nanorod/stearic acid treated fibres. - Abstract: This work aims at developing a hydrophobic treatment for jute fibres based on the grafting and growth of zinc oxide (ZnO) nanorods on the fibre surface. The first step consists in removing impurities from the fibre surface with a scouring treatment. In the second step, the jute fibres are coated with a layer of ZnO nanoseeds. A hydrothermal process is carried out as a third step to ensure a uniform growth of ZnO nanorods on the surface of the jute fibres. Finally, a hydrophobic treatment is performed on the ZnO nanorod-covered jute fibres using stearic acid (SA), i.e., a typical fatty acid. A large improvement in the fibre hydrophobicity was obtained without any negative effect on thermal stability and limited reduction in strength. Complementary measurements by scanning electron microscopy and X-ray diffraction were also performed and revealed a hexagonal system for the ZnO nanorods.

  8. [Lipid synthesis by an acidic acid tolerant Rhodotorula glutinis].

    Science.gov (United States)

    Lin, Zhangnan; Liu, Hongjuan; Zhang, Jian'an; Wang, Gehua

    2016-03-01

    Acetic acid, as a main by-product generated in the pretreatment process of lignocellulose hydrolysis, significantly affects cell growth and lipid synthesis of oleaginous microorganisms. Therefore, we studied the tolerance of Rhodotorula glutinis to acetic acid and its lipid synthesis from substrate containing acetic acid. In the mixed sugar medium containing 6 g/L glucose and 44 g/L xylose, and supplemented with acetic acid, the cell growth was not:inhibited when the acetic acid concentration was below 10 g/L. Compared with the control, the biomass, lipid concentration and lipid content of R. glutinis increased 21.5%, 171% and 122% respectively when acetic acid concentration was 10 g/L. Furthermore, R. glutinis could accumulate lipid with acetate as the sole carbon source. Lipid concentration and lipid yield reached 3.20 g/L and 13% respectively with the initial acetic acid concentration of 25 g/L. The lipid composition was analyzed by gas chromatograph. The main composition of lipid produced with acetic acid was palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid, including 40.9% saturated fatty acids and 59.1% unsaturated fatty acids. The lipid composition was similar to that of plant oil, indicating that lipid from oleaginous yeast R. glutinis had potential as the feedstock of biodiesel production. These results demonstrated that a certain concentration of acetic acid need not to be removed in the detoxification process when using lignocelluloses hydrolysate to produce microbial lipid by R. glutinis.

  9. Genetic variability in Cynara cardunculus L. domestic and wild types for grain oil production and fatty acids composition

    International Nuclear Information System (INIS)

    Raccuia, Salvatore Antonino; Piscioneri, Ilario; Sharma, Neeta; Melilli, Maria Grazia

    2011-01-01

    This paper aimed to study the genetic variability within different types of Cynara cardunculus L., domestic and wild types, for their grain oil amount and oil fatty acid composition. The grain oils were extracted from 8 domestic cardoons and 4 wild cardoons, by Soxhlet method, and obtained oils were characterized for palmitic, stearic, oleic and linoleic acids by gas chromatography. The oil amount, resulted on average of accessions 216 g kg -1 DM with a good range of variability (CV = 11.7%). Unsaturated acids (oleic and linoleic) predominated over saturated ones (stearic and palmitic acids), the chemical characterization of extracted oil, showed the main compound (as % of analysed fatty acids), averaged for all populations, was linoleic acid (44.5%), followed by oleic acid (42.6%), palmitic acid (9.8%) and stearic acid (3.1%). In particular referring the oleic acid wild cardoon populations showed a mean value of 289 g kg -1 oil, against a mean value of 472 g kg -1 oil showed by domestic cardoon accessions. Three of the studied domestic cardoon ('DC1', 'DC3' and 'DC7') showed values higher than 795 g kg -1 oil, while all the other accessions had concentration lower than 370 g kg -1 oil. The three types of domestic cardoon 'DC1', 'DC3' and 'DC7' showed a fatty acids profile similar to genetic modified sunflower oil, representing new genetic material that potentially could be used for high quality biodiesel production, characterised by a low Iodine Number. -- Highlights: → The grain oils from 12 cardoons were characterized for fatty acids composition. → The oil amount, resulted on average of accessions 216 g kg -1 DM. → Oleic and linoleic acids predominated over stearic and palmitic acids. → Three domestic cardoons grain oil showed high oleic acid content (795 g kg -1 oil). → This oil could be used for high quality biodiesel production, with a low IN.

  10. Zitterbewegung in monolayer silicene in a magnetic field

    International Nuclear Information System (INIS)

    Romera, E.; Roldán, J.B.; Santos, F. de los

    2014-01-01

    We study the Zitterbewegung in monolayer silicene under a perpendicular magnetic field. Using an effective Hamiltonian, we have investigated the autocorrelation function and the density currents in this material. Moreover, we have analyzed other types of periodicities of the system (classical and revival times). Finally, the above results are compared with their counterparts in two other monolayer materials subject to a magnetic field: graphene and MoS 2 . - Highlights: • We study Zitterbewegung in monolayer silicene in a magnetic field. • We have analyzed other types of periodicities in silicene. • The above results are compared with other monolayer materials (graphene and MoS 2 )

  11. Zitterbewegung in monolayer silicene in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Romera, E. [Departamento de Física Atómica, Molecular y Nuclear and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Roldán, J.B. [Departamento de Electrónica y Tecnología de Computadores and CITIC, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Santos, F. de los [Departamento de Electromagnetismo y Física de la Materia, and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2014-07-04

    We study the Zitterbewegung in monolayer silicene under a perpendicular magnetic field. Using an effective Hamiltonian, we have investigated the autocorrelation function and the density currents in this material. Moreover, we have analyzed other types of periodicities of the system (classical and revival times). Finally, the above results are compared with their counterparts in two other monolayer materials subject to a magnetic field: graphene and MoS{sub 2}. - Highlights: • We study Zitterbewegung in monolayer silicene in a magnetic field. • We have analyzed other types of periodicities in silicene. • The above results are compared with other monolayer materials (graphene and MoS{sub 2})

  12. Testing the effectiveness of monolayers under wind and wave conditions.

    Science.gov (United States)

    Palada, C; Schouten, P; Lemckert, C

    2012-01-01

    Monolayers are highly desirable for their evaporation reducing capabilities due to their relatively minimal cost and ease of application. Despite these positive attributes, monolayers have consistently failed to perform effectively due to the harsh wind and wave conditions prevalent across real-world water reserves. An exhaustive and consistent study testing the influence of wind and wave combinations on monolayer performance has yet to be presented in the literature. To remedy this, the effect of simultaneous wind and wave conditions on a benchmark high-performance monolayer (octadecanol suspension, CH(3)(CH(2))(16)CH(2)OH) has been analysed. Subjected only to waves, the monolayer remained intact due to its innate ability to compress and expand. However, the constant simultaneous application of wind and waves caused the monolayer to break up and gather down-wind where it volatilised over time. At wind speeds above 1.3 m s(-1) the monolayer was completely ineffective. For wind speeds below this threshold, the monolayer had an influence on the evaporation rate dependent on wind speed. From these results a series of application protocols can now be developed for the optimised deployment of monolayers in real-world water reserves. This will be of interest to private, commercial and government organisations involved in the storage and management of water resources.

  13. Nanostructure of polymer monolayer and polyelectrolyte brush at air/water interface by X-ray and neutron reflectometry

    CERN Document Server

    Matsuoka, H; Matsumoto, K

    2003-01-01

    The nanostructure of amphiphilic diblock copolymer monolayer on water was directly investigated by in situ X-ray and neutron reflectivity techniques. The diblock copolymer consists of polysilacyclobutane, which is very flexible, as a hydrophobic block and polymethacrylic acid, an anionic polymer, as a hydrophilic block. The polymers with shorter hydrophilic segment formed a very smooth and uniform monolayer with hydrophobic layer on water and dense hydrophilic layer under the water. But the longer hydrophilic segment polymer formed three-layered monolayer with polyelectrolyte brush in addition to hydrophobic and dense hydrophilic layers. The dense hydrophilic layer is thought to be formed to avoid a contact between hydrophobic polymer layer and water. Its role is something like a 'carpet'. An additional interesting information is that the thickness of the 'carpet layer' is almost 15A, independent the surface pressure and hydrophilic polymer length. Highly quantitative information was obtained about the nanost...

  14. HAMLET forms annular oligomers when deposited with phospholipid monolayers.

    Science.gov (United States)

    Baumann, Anne; Gjerde, Anja Underhaug; Ying, Ming; Svanborg, Catharina; Holmsen, Holm; Glomm, Wilhelm R; Martinez, Aurora; Halskau, Oyvind

    2012-04-20

    Recently, the anticancer activity of human α-lactalbumin made lethal to tumor cells (HAMLET) has been linked to its increased membrane affinity in vitro, at neutral pH, and ability to cause leakage relative to the inactive native bovine α-lactalbumin (BLA) protein. In this study, atomic force microscopy resolved membrane distortions and annular oligomers (AOs) produced by HAMLET when deposited at neutral pH on mica together with a negatively charged lipid monolayer. BLA, BAMLET (HAMLET's bovine counterpart) and membrane-binding Peptide C, corresponding to BLA residues 75-100, also form AO-like structures under these conditions but at higher subphase concentrations than HAMLET. The N-terminal Peptide A, which binds to membranes at acidic but not at neutral pH, did not form AOs. This suggests a correlation between the capacity of the proteins/peptides to integrate into the membrane at neutral pH-as observed by liposome content leakage and circular dichroism experiments-and the formation of AOs, albeit at higher concentrations. Formation of AOs, which might be important to HAMLET's tumor toxic action, appears related to the increased tendency of the protein to populate intermediately folded states compared to the native protein, the formation of which is promoted by, but not uniquely dependent on, the oleic acid molecules associated with HAMLET. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Template-Directed Self-Assembly of Alkanethiol Monolayers: Selective Growth on Preexisting Monolayer Edges

    NARCIS (Netherlands)

    Sharpe, R.B.A.; Burdinski, Dirk; Huskens, Jurriaan; Zandvliet, Henricus J.W.; Reinhoudt, David; Poelsema, Bene

    2007-01-01

    Self-assembled monolayers were investigated for their suitability as two-dimensional scaffolds for the selective growth of alkanethiol edge structures. Heterostructures with chemical contrast could be grown, whose dimensions were governed by both the initial pattern sizes and the process time.

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

    Czech Academy of Sciences Publication Activity Database

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

    2016-01-01

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

  17. Recombinant albumin monolayers on latex particles.

    Science.gov (United States)

    Sofińska, Kamila; Adamczyk, Zbigniew; Kujda, Marta; Nattich-Rak, Małgorzata

    2014-01-14

    The adsorption of recombinant human serum albumin (rHSA) on negatively charged polystyrene latex micro-particles was studied at pH 3.5 and the NaCl concentration range of 10(-3) to 0.15 M. The electrophoretic mobility of latex monotonically increased with the albumin concentration in the suspension. The coverage of adsorbed albumin was quantitatively determined using the depletion method, where the residual protein concentration was determined by electrokinetic measurements and AFM imaging. It was shown that albumin adsorption was irreversible. Its maximum coverage on latex varied between 0.7 mg m(-2) for 10(-3) M NaCl to 1.3 mg m(-2) for 0.15 M NaCl. The latter value matches the maximum coverage previously determined for human serum albumin on mica using the streaming potential method. The increase in the maximum coverage was interpreted in terms of reduced electrostatic repulsion among adsorbed molecules. These facts confirm that albumin adsorption at pH 3.5 is governed by electrostatic interactions and proceeds analogously to colloid particle deposition. The stability of albumin monolayers was measured in additional experiments where changes in the latex electrophoretic mobility and the concentration of free albumin in solutions were monitored over prolonged time periods. Based on these experimental data, a robust procedure of preparing albumin monolayers on latex particles of well-controlled coverage and molecule distribution was proposed.

  18. Cavity plasmon polaritons in monolayer graphene

    International Nuclear Information System (INIS)

    Kotov, O.V.; Lozovik, Yu.E.

    2011-01-01

    Plasmon polaritons in a new system, a monolayer doped graphene embedded in optical microcavity, are studied here. The dispersion law for lower and upper cavity plasmon polaritons is obtained. Peculiarities of Rabi splitting for the system are analyzed; particularly, role of Dirac-like spinor (envelope) wave functions in graphene and corresponding angle factors are considered. Typical Rabi frequencies for maximal (acceptable for Dirac-like electron spectra) Fermi energy and frequencies of polaritons near polariton gap are estimated. The plasmon polaritons in considered system can be used for high-speed information transfer in the THz region. -- Highlights: → Plasmon polaritons in a monolayer doped graphene embedded in optical microcavity, are studied here. → The dispersion law for lower and upper cavity plasmon polaritons is obtained. → Peculiarities of Rabi splitting for the system are analyzed. → Role of Dirac-like wave functions in graphene and corresponding angle factors are considered. → Typical Rabi frequencies and frequencies of polaritons near polariton gap are estimated.

  19. Repair during multifraction exposures: spheroids versus monolayers

    International Nuclear Information System (INIS)

    Durand, R.E.

    1984-01-01

    Many type of mammalian cells, when grown in culture as multicell spheroids, display an increased ability to accumulate and repair sublethal radiation damage which has been called the ''contact effect''. Since this effect has the potential to markedly modify the multifraction radiation response of cells in V79 spheroids relative to cells in monolayer cultures, an investigation was made of regimens ranging from 1 to 100 fractions. Effective dose rates were chosen near 1 Gy h -1 to inhibit cell progression and thus simplify analysis of the results. As expected, larger doses per fraction produced more net cell killing in both systems than lower doses per fraction. Additionally, less killing of spheroid cells was observed in all regimens, in accord with their greater potential for repair. However, when the data were expressed as isoeffect curves, the spheroid and monolayer curves converged as the number of fractions increased. Thus, quite similar inherent sensitivity and repair capabilities would be predicted for ultra-low doses per fraction. High precision techniques for defining survival after doses of radiation from 0.2 to 1 Gy were, however, still able to demonstrate a survival advantage for cells grown as spheroids. (author)

  20. Microwave assisted esterification of free fatty acid over a heterogeneous catalyst for biodiesel production

    International Nuclear Information System (INIS)

    Liu, Wei; Yin, Ping; Liu, Xiguang; Chen, Wen; Chen, Hou; Liu, Chunping; Qu, Rongjun; Xu, Qiang

    2013-01-01

    Highlights: • Microwave assisted esterification of stearic acid with ethanol was catalyzed by D418. • D418 exhibited remarkable catalytic performance for ethyl stearate formation. • It proved possible to prepare biodiesel rapidly and with good conversions by microwave heating. • The relative catalytic kinetics study has been conducted and modeled. - Abstract: Biodiesel fuel is gaining significant attention in recent years because of its environmental benefits and the growing interest in finding new resources and alternatives for conventional fuels. Biodiesel production from waste cooking oil with high free fatty acids usually requires esterification step to produce fatty acid methyl/ethyl ester. In the present work, the heterogeneous catalyst aminophosphonic acid resin D418 has been successfully utilized in the energy-efficient microwave-assisted esterification reaction of fatty acid ethyl ester (FAEE) from free fatty acid (FFA) stearic acid with short-chain alcohol ethanol. Under the reaction conditions of 9 wt% D418 and 11: 1 M ratio of ethanol to stearic acid at 353 K and atmospheric pressure, more than 90% conversion of the esterification was achieved in 7 h by microwave heating, while it took about 12 h by conventional heating. Moreover, the kinetics of this esterification reaction has been studied, and the relevant values of activation energy and pre-exponential factor were obtained

  1. The response of quartz crystals coated with thin fatty acid film to organic gases

    CERN Document Server

    Jin, C N; Kim, K H; Kwon, Y S

    1999-01-01

    We tried to apply a quartz crystal as a sensor by using the resonant frequency and the resistance properties of quartz crystals. Four kinds of fatty acids that have the same head groups were coated on the surfaces of the quartz crystals, and the shift of the resonant frequency and the resistance were observed based on the lengths of the tail groups. Myristic acid (C sub 1 sub 4), palmitic acid (C sub 1 sub 6), stearic acid (C sub 1 sub 8), and arachidic acid (C sub 2 sub 0) were deposited on the surfaces of quartz crystals by using the Langmuir-Blodgett (LB) method. As a result, the resonant frequency change was more sensitive to high molecular-weight fatty acids than to low molecular-weight ones. We also observed the effect of temperature on stearic acid LB films, and the response properties of quartz crystals coated with stearic-acid LB films to organic gases were investigated. As a result, the sensitivity of quartz crystals to organic gases was higher for higher molecular-weight gas, and we found that quar...

  2. Analysis of embryo, cytoplasm and maternal effects on fatty acid components in soybean (Glycine max Merill.)

    Institute of Scientific and Technical Information of China (English)

    NING Hailong; LI Wenxia; LI Wenbin

    2007-01-01

    The quality of oil determined by the constituents and proportion of fatty acid components,and the understanding of heredity of fatty acid components are of importance to breeding good quality soybean varieties.Embryo,cytoplasmic and maternal effects and genotype×environment interaction effects for quality traits of soybean [Glycine max (L.) Merrill.] seeds were analyzed using a general genetic model for quantitative traits of seeds with parents,F1 and F2,of 20 crosses from a diallel mating design of five parents planted in the field in 2003 and 2004 in Harbin,China.The interaction effects of palmitic,stearic,and linoleic acid contents were larger than the genetic main effects,while the genetic main effects were equal to interaction effects for linolenic and oleic acid content.Among all kinds of genetic main effects,the embryo effects were the largest for palmitic,stearic,and linoleic acids,while the cytoplasm effects were the largest for oleic and linolenic acids.Among all kinds of interaction effects,the embryo interaction effects were the largest for fatty acids.The sum of additive and additive× environment effects were larger than that of dominance and dominance×environment effects for the linolenic acid content,but not for other quality traits.The general heritabilities were the main parts of heritabilities for palmitic and oleic acid contents,but the interaction was more important for stearic,linoleic,and linolenic acid contents.For the general heritability,maternal and cytoplasm heritabilities were the main components for palmitic,oleic,and linolenic acid contents.It was shown for the interaction heritabilities that the embryo interaction heritabilities were more important for oleic and linolenic acid contents,while the maternal interaction heritabilities were more important for linoleic acid content.Among selection response components,the maternal and cytoplasm general responses and/or interaction responses were more important for palmitic,stearic

  3. Metal ion interaction with phosphorylated tyrosine analogue monolayers on gold.

    Science.gov (United States)

    Petoral, Rodrigo M; Björefors, Fredrik; Uvdal, Kajsa

    2006-11-23

    Phosphorylated tyrosine analogue molecules (pTyr-PT) were assembled onto gold substrates, and the resulting monolayers were used for metal ion interaction studies. The monolayers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), both prior to and after exposure to metal ions. XPS verified the elemental composition of the molecular adsorbate and the presence of metal ions coordinated to the phosphate groups. Both the angle-dependent XPS and IRAS results were consistent with the change in the structural orientation of the pTyr-PT monolayer upon exposure to metal ions. The differential capacitance of the monolayers upon coordination of the metal ions was evaluated using EIS. These metal ions were found to significantly change the capacitance of the pTyr-PT monolayers in contrast to the nonphosphorylated tyrosine analogue (TPT). CV results showed reduced electrochemical blocking capabilities of the phosphorylated analogue monolayer when exposed to metal ions, supporting the change in the structure of the monolayer observed by XPS and IRAS. The largest change in the structure and interfacial capacitance was observed for aluminum ions, compared to calcium, magnesium, and chromium ions. This type of monolayer shows an excellent capability to coordinate metal ions and has a high potential for use as sensing layers in biochip applications to monitor the presence of metal ions.

  4. A MOLECULAR-DYNAMICS STUDY OF LECITHIN MONOLAYERS

    NARCIS (Netherlands)

    AHLSTROM, P; BERENDSEN, HJC

    1993-01-01

    Two monolayers of didecanoyllecithin at the air-water interface have been studied using molecular dynamics simulations. The model system consisted of two monolayers of 42 lecithin molecules each separated by a roughly 4 nm thick slab of SPC water. The area per lecithin molecule was 0.78 nm(2)

  5. Characterization of self-assembled monolayers on a ruthenium surface

    NARCIS (Netherlands)

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

    2017-01-01

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

  6. Langmuir monolayer formation of metal complexes from polymerizable amphiphilic ligands

    NARCIS (Netherlands)

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

    1996-01-01

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

  7. Mechanical and electronic properties of Janus monolayer transition metal dichalcogenides

    Science.gov (United States)

    Shi, Wenwu; Wang, Zhiguo

    2018-05-01

    The mechanical and electronic properties of Janus monolayer transition metal dichalcogenides MXY (M  =  Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; X/Y  =  S, Se, Te) were investigated using density functional theory. Results show that breaking the out-of-plane structural symmetry can be used to tune the electronic and mechanical behavior of monolayer transition metal dichalcogenides. The band gaps of monolayer WXY and MoXY are in the ranges of 0.16–1.91 and 0.94–1.69 eV, respectively. A semiconductor to metallic phase transition occurred in Janus monolayer MXY (M  =  Ti, Zr and Hf). The monolayers MXY (M  =  V, Nb, Ta and Cr) show metallic characteristics, which show no dependence on the structural symmetry breaking. The mechanical properties of MXY depended on the composition. Monolayer MXY (M  =  Mo, Ti, Zr, Hf and W) showed brittle characteristic, whereas monolayer CrXY and VXY are with ductile characteristic. The in-plane stiffness of pristine and Janus monolayer MXY are in the range between 22 and 158 N m‑1. The tunable electronic and mechanical properties of these 2D materials would advance the development of ultra-sensitive detectors, nanogenerators, low-power electronics, and energy harvesting and electromechanical systems.

  8. Large-area and bright pulsed electroluminescence in monolayer semiconductors

    KAUST Repository

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

    2018-01-01

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

  9. Large-area and bright pulsed electroluminescence in monolayer semiconductors

    KAUST Repository

    Lien, Der-Hsien

    2018-04-04

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

  10. A pentacene monolayer trapped between graphene and a substrate.

    Science.gov (United States)

    Zhang, Qicheng; Peng, Boyu; Chan, Paddy Kwok Leung; Luo, Zhengtang

    2015-09-21

    A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures.

  11. Fatty Acid Compositions of Six Wild Edible Mushroom Species

    Science.gov (United States)

    Günç Ergönül, Pelin; Akata, Ilgaz; Kalyoncu, Fatih; Ergönül, Bülent

    2013-01-01

    The fatty acids of six wild edible mushroom species (Boletus reticulatus, Flammulina velutipes var. velutipes, Lactarius salmonicolor, Pleurotus ostreatus, Polyporus squamosus, and Russula anthracina) collected from different regions from Anatolia were determined. The fatty acids were identified and quantified by gas chromatography and studied using fruit bodies. Fatty acid composition varied among species. The dominant fatty acid in fruit bodies of all mushrooms was cis-linoleic acid (18 : 2). Percentage of cis-linoleic acid in species varied from 22.39% to 65.29%. The other major fatty acids were, respectively, cis-oleic, palmitic, and stearic acids. Fatty acids analysis of the mushrooms showed that the unsaturated fatty acids were at higher concentrations than saturated fatty acids. PMID:23844377

  12. Fatty Acid Compositions of Six Wild Edible Mushroom Species

    Directory of Open Access Journals (Sweden)

    Pelin Günç Ergönül

    2013-01-01

    Full Text Available The fatty acids of six wild edible mushroom species (Boletus reticulatus, Flammulina velutipes var. velutipes, Lactarius salmonicolor, Pleurotus ostreatus, Polyporus squamosus, and Russula anthracina collected from different regions from Anatolia were determined. The fatty acids were identified and quantified by gas chromatography and studied using fruit bodies. Fatty acid composition varied among species. The dominant fatty acid in fruit bodies of all mushrooms was cis-linoleic acid (18 : 2. Percentage of cis-linoleic acid in species varied from 22.39% to 65.29%. The other major fatty acids were, respectively, cis-oleic, palmitic, and stearic acids. Fatty acids analysis of the mushrooms showed that the unsaturated fatty acids were at higher concentrations than saturated fatty acids.

  13. Vector assembly of colloids on monolayer substrates

    Science.gov (United States)

    Jiang, Lingxiang; Yang, Shenyu; Tsang, Boyce; Tu, Mei; Granick, Steve

    2017-06-01

    The key to spontaneous and directed assembly is to encode the desired assembly information to building blocks in a programmable and efficient way. In computer graphics, raster graphics encodes images on a single-pixel level, conferring fine details at the expense of large file sizes, whereas vector graphics encrypts shape information into vectors that allow small file sizes and operational transformations. Here, we adapt this raster/vector concept to a 2D colloidal system and realize `vector assembly' by manipulating particles on a colloidal monolayer substrate with optical tweezers. In contrast to raster assembly that assigns optical tweezers to each particle, vector assembly requires a minimal number of optical tweezers that allow operations like chain elongation and shortening. This vector approach enables simple uniform particles to form a vast collection of colloidal arenes and colloidenes, the spontaneous dissociation of which is achieved with precision and stage-by-stage complexity by simply removing the optical tweezers.

  14. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Rasmussen, Filip Anselm; Kuhar, Korina

    2016-01-01

    Localized electronic states formed inside the band gap of a semiconductor due to crystal defects can be detrimental to the material's optoelectronic properties. Semiconductors with a lower tendency to form defect induced deep gap states are termed defect-tolerant. Here we provide a systematic first...... the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within......-principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only...

  15. Beam damage of self-assembled monolayers

    International Nuclear Information System (INIS)

    Rieke, P.C.; Baer, D.R.; Fryxell, G.E.; Engelhard, M.H.; Porter, M.S.

    1993-01-01

    X-ray and electron beam damage studies were performed on Br-terminated and methyl-terminated alkylsilane self-assembled monolayers. X-ray beam initiated damage was primarily limited to removal of the labile Br group and did not significantly damage the hydrocarbon chain. Some of the x-ray beam damage could be attributed to low-energy electrons emitted by the non-monochromatic source, but further damage was attributed to secondary electrons produced in the sample by x-ray exposure. Electron beams caused significant damage to the hydrocarbon chains. Maximum damage occurred with a beam energy of 600 eV and a dosage of 6x10 -3 C/cm 2

  16. Enhanced photocurrent in engineered bacteriorhodopsin monolayer.

    Science.gov (United States)

    Patil, Amol V; Premaruban, Thenhuan; Berthoumieu, Olivia; Watts, Anthony; Davis, Jason J

    2012-01-12

    The integration of the transmembrane protein bacteriorhodopsin (BR) with man-made electrode surfaces has attracted a great deal of interest for some two decades or more and holds significant promise from the perspective of derived photoresponse or energy capture interfaces. Here we demonstrate that a novel and strategically engineered cysteine site (M163C) can be used to intimately and effectively couple delipidated BR to supporting metallic electrode surfaces. By virtue of the combined effects of the greater surface molecular density afforded by delipidation, and the vicinity of the electrostatic changes associated with proton pumping to the transducing metallic continuum, the resulting films generate a considerably greater photocurrent density on wavelength-selective illumination than previously achievable with monolayers of BR. Given the uniquely photoresponsive, wavelength-selective, and photostable characteristics of this protein, the work has implications for utilization in solar energy capture and photodetector devices.

  17. Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcellos, Kayla B.; McHugh, Sean M.; Dapsis, Katherine J.; Petty, Alexander R.; Gerdon, Aren E., E-mail: gerdoar@emmanuel.edu [Emmanuel College (United States)

    2013-09-15

    Biomineralization of hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 Multiplication-Sign 10{sup -3} to 3.1 Multiplication-Sign 10{sup -3} OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

  18. Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

    Science.gov (United States)

    Vasconcellos, Kayla B.; McHugh, Sean M.; Dapsis, Katherine J.; Petty, Alexander R.; Gerdon, Aren E.

    2013-09-01

    Biomineralization of hydroxyapatite (Ca10(PO4)6(OH)2) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 × 10-3 to 3.1 × 10-3 OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

  19. Bovine and human insulin adsorption at lipid monolayers: a comparison

    Science.gov (United States)

    Mauri, Sergio; Pandey, Ravindra; Rzeznicka, Izabela; Lu, Hao; Bonn, Mischa; Weidner, Tobias

    2015-07-01

    Insulin is a widely used peptide in protein research and it is utilised as a model peptide to understand the mechanics of fibril formation, which is believed to be the cause of diseases such as Alzheimer and Creutzfeld-Jakob syndrome. Insulin has been used as a model system due to its biomedical relevance, small size and relatively simple tertiary structure. The adsorption of insu lin on a variety of surfaces has become the focus of numerous studies lately. These works have helped in elucidating the consequence of surface/protein hydrophilic/hydrophobic interaction in terms of protein refolding and aggregation. Unfortunately, such model surfaces differ significantly from physiological surfaces. Here we spectroscopically investigate the adsorption of insulin at lipid monolayers, to further our understanding of the interaction of insulin with biological surfaces. In particular we study the effect of minor mutations of insulin’s primary amino acid sequence on its interaction with 1,2-Dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) model lipid layers. We probe the structure of bovine and human insulin at the lipid/water interface using sum frequency generation spectroscopy (SFG). The SFG experiments are complemented with XPS analysis of Langmuir-Schaefer deposited lipid/insulin films. We find that bovine and human insulin, even though very similar in sequence, show a substantially different behavior when interacting with lipid films.

  20. Defect Structure of Localized Excitons in a WSe2 Monolayer

    KAUST Repository

    Zhang, Shuai

    2017-07-26

    The atomic and electronic structure of intrinsic defects in a WSe2 monolayer grown on graphite was revealed by low temperature scanning tunneling microscopy and spectroscopy. Instead of chalcogen vacancies that prevail in other transition metal dichalcogenide materials, intrinsic defects in WSe2 arise surprisingly from single tungsten vacancies, leading to the hole (p-type) doping. Furthermore, we found these defects to dominate the excitonic emission of the WSe2 monolayer at low temperature. Our work provided the first atomic-scale understanding of defect excitons and paved the way toward deciphering the defect structure of single quantum emitters previously discovered in the WSe2 monolayer.

  1. Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solids

    Energy Technology Data Exchange (ETDEWEB)

    Greene, J. E. [University of Illinois, Urbana, Illinois 61801 (United States); Linköping University, 581 83 Linköping (Sweden); National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

    2015-03-15

    The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (∼1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ∼78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese “floating-ink” art (suminagashi) developed ∼1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO{sub 2} and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including

  2. Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solids

    International Nuclear Information System (INIS)

    Greene, J. E.

    2015-01-01

    The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (∼1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ∼78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese “floating-ink” art (suminagashi) developed ∼1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO 2 and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including

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

    Science.gov (United States)

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

    2011-11-29

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

  4. {alpha}-Man monolayer formation via Si-C bond formation and protein recognition

    Energy Technology Data Exchange (ETDEWEB)

    Funato, Koji [School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Shirahata, Naoto [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Miura, Yoshiko, E-mail: miuray@jaist.ac.j [School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2009-11-30

    An acetylenyl-terminated saccharide was synthesized and the thin layer formation on the hydrogen-terminated silicon was investigated. The acetylenyl-terminated saccharide was synthesized by the condensation reaction of hexynoic acid and p-aminophenyl saccharide. This was reacted with hydrogen-terminated silicon (Si-H) by a photochemical reaction. The resulting saccharide modified substrate was analyzed by ellipsometry and X-ray photoelectron spectroscopy, which showed the formation of a uniform monolayer. The surface's ability to recognize proteins was analyzed by fluorescent microscopy, and showed specific interactions with sugar recognition proteins.

  5. The comparison of fatty acid and cholesterol profile on fresh and mozarella cheese made by pampangan buffalo milk

    Science.gov (United States)

    Rizqiati, H.; Nurwantoro; Mulyani, S.

    2018-01-01

    This research aimed to investigate the composition of fatty acid and cholesterol profile of Fresh and Mozarella Cheese from Pampangan Buffalo Milk. Material of this reseach was Pampangan buffalo milk and Mozarella cheese made from buffalo milk. Fatty acids composition were analyzed by [1] method. Result showed the major saturated fatty acid found in milk and Mozzarella cheese Pampangan buffalo milk were palmitic, stearic and miristic acid while the unsaturated fatty acid was oleic acid. The total amount of fatty acid in Mozarella cheese was lower than those in Pampangan buffalo milk.

  6. Fluorescein transport properties across artificial lipid membranes, Caco-2 cell monolayers and rat jejunum.

    Science.gov (United States)

    Berginc, Katja; Zakelj, Simon; Levstik, Lea; Ursic, Darko; Kristl, Albin

    2007-05-01

    Membrane transport characteristics of a paracellular permeability marker fluorescein were evaluated using artificial membrane, Caco-2 cell monolayers and rat jejunum, all mounted in side-by-side diffusion cells. Modified Ringer buffers with varied pH values were applied as incubation salines on both sides of artificial membrane, cell culture monolayers or rat jejunum. Passive transport according to pH partition theory was determined using all three permeability models. In addition to that, active transport of fluorescein in the M-S (mucosal-to-serosal) direction through rat jejunum was observed. The highest M-S P(app) values regarding the active transport through the rat jejunum were observed in incubation saline with pH 6.5. Fluorescein transport through the rat jejunum was inhibited by DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) and alpha-CHC (alpha-cyano-4-hydroxycinnamic acid). Thus, we assume that two pH-dependent influx transporters could be involved in the fluorescein membrane transport through the intestinal (jejunal) epithelium. One is very likely an MCT (monocarboxylic acid cotransporter) isoform, inhibited by specific MCT inhibitor alpha-CHC, while the involvement of the second one with overlapping substrate/inhibitor specificities (most probably a member of the organic anion-transporting polypeptide family, inhibited at least partially by DIDS) could not be excluded.

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

    Directory of Open Access Journals (Sweden)

    Guus Rijnders

    2010-03-01

    Full Text Available FePt nanoparticles (NPs were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(onates were used as an adsorbate to form self-assembled monolayers (SAMs on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP or phosphonoundecanoic acid (PNDA SAMs or with poly(ethyleneimine (PEI as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al2O3, which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al2O3 surface and controlling the immersion time of the modified Al2O3 substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N2/4%H2 led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices.

  8. Coexistence of multiple conformations in cysteamine monolayers on Au(111)

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Bilic, A; Reimers, JR

    2005-01-01

    The structural organization, catalytic function, and electronic properties of cysteamine monolayers on Au(111) have been addressed comprehensively by voltammetry, in situ scanning tunneling microscopy (STM) in anaerobic environment, and a priori molecular dynamics (MD) simulation and STM image si...

  9. Evidence of indirect gap in monolayer WSe2

    KAUST Repository

    Hsu, Wei-Ting; Lu, Li-Syuan; Wang, Dean; Huang, Jing-Kai; Li, Ming-Yang; Chang, Tay-Rong; Chou, Yi-Chia; Juang, Zhen-Yu; Jeng, Horng-Tay; Li, Lain-Jong; Chang, Wen-Hao

    2017-01-01

    Monolayer transition metal dichalcogenides, such as MoS2 and WSe2, have been known as direct gap semiconductors and emerged as new optically active materials for novel device applications. Here we reexamine their direct gap properties

  10. Monolayer MoS2 heterojunction solar cells

    KAUST Repository

    Tsai, Menglin

    2014-08-26

    We realized photovoltaic operation in large-scale MoS2 monolayers by the formation of a type-II heterojunction with p-Si. The MoS 2 monolayer introduces a built-in electric field near the interface between MoS2 and p-Si to help photogenerated carrier separation. Such a heterojunction photovoltaic device achieves a power conversion efficiency of 5.23%, which is the highest efficiency among all monolayer transition-metal dichalcogenide-based solar cells. The demonstrated results of monolayer MoS 2/Si-based solar cells hold the promise for integration of 2D materials with commercially available Si-based electronics in highly efficient devices. © 2014 American Chemical Society.

  11. Wavepacket revivals in monolayer and bilayer graphene rings.

    Science.gov (United States)

    García, Trinidad; Rodríguez-Bolívar, Salvador; Cordero, Nicolás A; Romera, Elvira

    2013-06-12

    We have studied the existence of quantum revivals in graphene quantum rings within a simplified model. The time evolution of a Gaussian-populated wavepacket shows revivals in monolayer and bilayer graphene rings. We have also studied this behavior for quantum rings in a perpendicular magnetic field. We have found that revival time is an observable that shows different values for monolayer and bilayer graphene quantum rings. In addition, the revival time shows valley degeneracy breaking.

  12. Atomic defects and doping of monolayer NbSe2

    OpenAIRE

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J.P.; Lawlor, Sean; Sanchez, Ana M.; Sloan, Jeremy; Gorbachev, Roman; Grigorieva, Irina; Krasheninnikov, Arkady V.; Haigh, Sarah

    2017-01-01

    We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reve...

  13. Wavepacket revivals in monolayer and bilayer graphene rings

    International Nuclear Information System (INIS)

    García, Trinidad; Rodríguez-Bolívar, Salvador; Cordero, Nicolás A; Romera, Elvira

    2013-01-01

    We have studied the existence of quantum revivals in graphene quantum rings within a simplified model. The time evolution of a Gaussian-populated wavepacket shows revivals in monolayer and bilayer graphene rings. We have also studied this behavior for quantum rings in a perpendicular magnetic field. We have found that revival time is an observable that shows different values for monolayer and bilayer graphene quantum rings. In addition, the revival time shows valley degeneracy breaking. (paper)

  14. Density determination of langmuir-blodgett monolayer films using x-ray reflectivity technique

    International Nuclear Information System (INIS)

    Damar Yoga Kusuma

    2015-01-01

    Monolayer deposition by Langmuir-Blodgett technique produces monolayer films that are uniform with controllable thickness down to nanometer scale. To evaluate the quality of the monolayer deposition, X-ray reflectivity technique are employed to monitor the monolayers density. Langmuir-Blodgett monolayer with good coverage and uniformity results in film density close to its macroscopic film counterpart whereas films with presence of air gaps shows lower density compared to its macroscopic film counterpart. (author)

  15. Amperometric cholesterol biosensor based on in situ reconstituted cholesterol oxidase on an immobilized monolayer of flavin adenine dinucleotide cofactor.

    Science.gov (United States)

    Vidal, Juan-C; Espuelas, Javier; Castillo, Juan-R

    2004-10-01

    A new amperometric biosensor for determining cholesterol based on deflavination of the enzyme cholesterol oxidase (ChOx) and subsequent reconstitution of the apo-protein with a complexed flavin adenine dinucleotide (FAD) monolayer is described. The charge transfer mediator pyrroquinoline quinone (PQQ) was covalently bound to a cystamine self-assembled monolayer (SAM) on an Au electrode. Boronic acid (BA) was then bound to PQQ using the carbodiimide procedure, and the BA ligand was complexed to the FAD molecules on which the apo-ChOx was subsequently reconstituted. The effective release of the FAD from the enzyme and the successful reconstitution were verified using molecular fluorescence and cyclic voltammetry. The optimal orientation of FAD toward the PQQ mediator and the distances between FAD and PQQ and between PQQ and electrode enhance the charge transfer, very high sensitivity (about 2,500 nAmM(-1)cm(-2)) being obtained for cholesterol determination. The biosensor is selective toward electroactive interferents (ascorbic acid and uric acid) and was tested in reference serum samples, demonstrating excellent accuracy (relative errors below 3% in all cases). The biosensor activity can be successfully regenerated in a simple process by successive reconstitution with batches of recently prepared apo-ChOx on the same immobilized Au/SAM-PQQ-BA-FAD monolayer (it was tested five times); the lifetime of the biosensor is about 45-60 days.

  16. Electrical Contacts in Monolayer Arsenene Devices.

    Science.gov (United States)

    Wang, Yangyang; Ye, Meng; Weng, Mouyi; Li, Jingzhen; Zhang, Xiuying; Zhang, Han; Guo, Ying; Pan, Yuanyuan; Xiao, Lin; Liu, Junku; Pan, Feng; Lu, Jing

    2017-08-30

    Arsenene, arsenic analogue of graphene, as an emerging member of two-dimensional semiconductors (2DSCs), is quite promising in next-generation electronic and optoelectronic applications. The metal electrical contacts play a vital role in the charge transport and photoresponse processes of nanoscale 2DSC devices and even can mask the intrinsic properties of 2DSCs. Here, we present a first comprehensive study of the electrical contact properties of monolayer (ML) arsenene with different electrodes by using ab initio electronic calculations and quantum transport simulations. Schottky barrier is always formed with bulk metal contacts owing to the Fermi level pinning (pinning factor S = 0.33), with electron Schottky barrier height (SBH) of 0.12, 0.21, 0.25, 0.35, and 0.50 eV for Sc, Ti, Ag, Cu, and Au contacts and hole SBH of 0.75 and 0.78 eV for Pd and Pt contacts, respectively. However, by contact with 2D graphene, the Fermi level pinning effect can be reduced due to the suppression of metal-induced gap states. Remarkably, a barrier free hole injection is realized in ML arsenene device with graphene-Pt hybrid electrode, suggestive of a high device performance in such a ML arsenene device. Our study provides a theoretical foundation for the selection of favorable electrodes in future ML arsenene devices.

  17. Specific Ion Effects in Cholesterol Monolayers

    Directory of Open Access Journals (Sweden)

    Teresa Del Castillo-Santaella

    2016-05-01

    Full Text Available The interaction of ions with interfaces and, in particular, the high specificity of these interactions to the particular ions considered, are central questions in the field of surface forces. Here we study the effect of different salts (NaI, NaCl, CaCl2 and MgCl2 on monolayers made of cholesterol molecules, both experimentally (surface area vs. lateral pressure isotherms measured by a Langmuir Film Balance and theoretically (molecular dynamics (MD all-atomic simulations. We found that surface isotherms depend, both quantitatively and qualitatively, on the nature of the ions by altering the shape and features of the isotherm. In line with the experiments, MD simulations show clear evidences of specific ionic effects and also provide molecular level details on ion specific interactions with cholesterol. More importantly, MD simulations show that the interaction of a particular ion with the surface depends strongly on its counterion, a feature ignored so far in most theories of specific ionic effects in surface forces.

  18. Optical absorption in disordered monolayer molybdenum disulfide

    Science.gov (United States)

    Ekuma, C. E.; Gunlycke, D.

    2018-05-01

    We explore the combined impact of sulfur vacancies and electronic interactions on the optical properties of monolayer MoS2. First, we present a generalized Anderson-Hubbard Hamiltonian that accounts for both randomly distributed sulfur vacancies and the presence of dielectric screening within the material. Second, we parametrize this energy-dependent Hamiltonian from first-principles calculations based on density functional theory and the Green's function and screened Coulomb (GW) method. Third, we apply a first-principles-based many-body typical medium method to determine the single-particle electronic structure. Fourth, we solve the Bethe-Salpeter equation to obtain the charge susceptibility χ with its imaginary part being related to the absorbance A . Our results show that an increased vacancy concentration leads to decreased absorption both in the band continuum and from exciton states within the band gap. We also observe increased absorption below the band-gap threshold and present an expression, which describes Lifshitz tails, in excellent qualitative agreement with our numerical calculations. This latter increased absorption in the 1.0 -2.5 eV range makes defect engineering of potential interest for solar cell applications.

  19. Edge Delamination of Monolayer Transition Metal Dichalcogenides.

    Science.gov (United States)

    Ly, Thuc Hue; Yun, Seok Joon; Thi, Quoc Huy; Zhao, Jiong

    2017-07-25

    Delamination of thin films from the supportive substrates is a critical issue within the thin film industry. The emergent two-dimensional, atomic layered materials, including transition metal dichalcogenides, are highly flexible; thus buckles and wrinkles can be easily generated and play vital roles in the corresponding physical properties. Here we introduce one kind of patterned buckling behavior caused by the delamination from a substrate initiated at the edges of the chemical vapor deposition synthesized monolayer transition metal dichalcogenides, led by thermal expansion mismatch. The atomic force microscopy and optical characterizations clearly showed the puckered structures associated with the strain, whereas the transmission electron microscopy revealed the special sawtooth-shaped edges, which break the geometrical symmetry for the buckling behavior of hexagonal samples. The condition of the edge delamination is in accordance with the fracture behavior of thin film interfaces. This edge delamination and buckling process is universal for most ultrathin two-dimensional materials, which requires more attention in various future applications.

  20. Technique for etching monolayer and multilayer materials

    Science.gov (United States)

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

    2015-10-06

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

  1. Defects and oxidation of group-III monochalcogenide monolayers

    Science.gov (United States)

    Guo, Yu; Zhou, Si; Bai, Yizhen; Zhao, Jijun

    2017-09-01

    Among various two-dimensional (2D) materials, monolayer group-III monochalcogenides (GaS, GaSe, InS, and InSe) stand out owing to their potential applications in microelectronics and optoelectronics. Devices made of these novel 2D materials are sensitive to environmental gases, especially O2 molecules. To address this critical issue, here we systematically investigate the oxidization behaviors of perfect and defective group-III monochalcogenide monolayers by first-principles calculations. The perfect monolayers show superior oxidation resistance with large barriers of 3.02-3.20 eV for the dissociation and chemisorption of O2 molecules. In contrast, the defective monolayers with single chalcogen vacancy are vulnerable to O2, showing small barriers of only 0.26-0.36 eV for the chemisorption of an O2 molecule. Interestingly, filling an O2 molecule to the chalcogen vacancy of group-III monochalcogenide monolayers could preserve the electronic band structure of the perfect system—the bandgaps are almost intact and the carrier effective masses are only moderately disturbed. On the other hand, the defective monolayers with single vacancies of group-III atoms carry local magnetic moments of 1-2 μB. These results help experimental design and synthesis of group-III monochalcogenides based 2D devices with high performance and stability.

  2. Nonlinear optical characteristics of monolayer MoSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Le, Chinh Tam; Ullah, Farman; Senthilkumar, Velusamy; Kim, Yong Soo [Department of Physics and Energy Harvest Storage Research Center, University of Ulsan (Korea, Republic of); Clark, Daniel J.; Jang, Joon I. [Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, NY (United States); Sim, Yumin; Seong, Maeng-Je [Department of Physics, Chung-Ang University, Seoul (Korea, Republic of); Chung, Koo-Hyun [School of Mechanical Engineering, University of Ulsan (Korea, Republic of); Park, Hyoyeol [Electronics, Communication and Semiconductor Applications Department, Ulsan College (Korea, Republic of)

    2016-08-15

    In this study, we utilized picosecond pulses from an Nd:YAG laser to investigate the nonlinear optical characteristics of monolayer MoSe{sub 2}. Two-step growth involving the selenization of pulsed-laser-deposited MoO{sub 3} film was employed to yield the MoSe{sub 2} monolayer on a SiO{sub 2}/Si substrate. Raman scattering, photoluminescence (PL) spectroscopy, and atomic force microscopy verified the high optical quality of the monolayer. The second-order susceptibility χ{sup (2)} was calculated to be ∝50 pm V{sup -1} at the second harmonic wavelength λ{sub SHG} ∝810 nm, which is near the optical gap of the monolayer. Interestingly, our wavelength-dependent second harmonic scan can identify the bound excitonic states including negatively charged excitons much more efficiently, compared with the PL method at room temperature. Additionally, the MoSe{sub 2} monolayer exhibits a strong laser-induced damage threshold ∝16 GW cm{sup -2} under picosecond-pulse excitation{sub .} Our findings suggest that monolayer MoSe{sub 2} can be considered as a promising candidate for high-power, thin-film-based nonlinear optical devices and applications. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Controlled electrodeposition of Au monolayer film on ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Qiang; Pang, Liuqing; Li, Man; Zhang, Yunxia; Ren, Xianpei [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Liu, Shengzhong Frank, E-mail: szliu@dicp.ac.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Dalian Institute of Chemical Physics, Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian 116023 (China)

    2016-05-15

    Highlights: • We fabricate Au monolayer film on Ionic liquid substrate using an electrochemical deposition technique. • Au monolayer film was deposited on a “soft substrate” for the first time. • Au monolayer film can contribute extra Raman enhancement. - Abstract: Gold (Au) nanoparticles have been attractive for centuries for their vibrant appearance enhanced by their interaction with sunlight. Nowadays, there have been tremendous research efforts to develop them for high-tech applications including therapeutic agents, sensors, organic photovoltaics, medical applications, electronics and catalysis. However, there remains to be a challenge to fabricate a monolayer Au coating with complete coverage in controlled fashion. Here we present a facile method to deposit a uniform Au monolayer (ML) film on the [BMIM][PF{sub 6}] ionic liquid substrate using an electrochemical deposition process. It demonstrates that it is feasible to prepare a solid phase coating on the liquid-based substrate. Moreover, the thickness of the monolayer coating can be controlled to a layer-by-layer accuracy.

  4. Surface Charge Transfer Doping of Monolayer Phosphorene via Molecular Adsorption.

    Science.gov (United States)

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

    2015-12-03

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

  5. Effect of dietary fatty acids on the postprandial fatty acid composition of triacylglycerol-rich lipoproteins in healthy male subjects

    DEFF Research Database (Denmark)

    Bysted, Anette; Holmer, G.; Lund, Pia

    2005-01-01

    interesterified test fats with equal amounts of palmitic acid ( P fat), stearic acid (S fat), trans-18: 1 isomers (T fat), oleic acid (O fat), or linoleic acid (L fat) were tested. Subjects: A total of 16 healthy, normolipidaemic males ( age 23 +/- 2 y) were recruited. Interventions: The participants ingested fat......Objective: The aim of the present study was to investigate the effect of trans-18: 1 isomers compared to other fatty acids, especially saturates, on the postprandial fatty acid composition of triacylglycerols ( TAG) in chylomicrons and VLDL. Design: A randomised crossover experiment where five......-rich test meals ( 1 g fat per kg body weight) and the fatty acid profiles of chylomicron and VLDL TAG were followed for 8 h. Results: The postprandial fatty acid composition of chylomicron TAG resembled that of the ingested fats. The fatty acids in chylomicron TAG were randomly distributed among the three...

  6. Fatty acids, phenols content, and antioxidant activity in Ibervillea sonorae callus cultures

    OpenAIRE

    Estrada-Zúñiga, M.E.; Arano-Varela, H.; Buendía-González, L.; Orozco-Villafuerte, J.

    2012-01-01

    Ibervillea sonorae callus cultures were established in order to produce fatty acids (lauric, myristic, pentadecanoic, palmitic and stearic acids) and phenolic compounds. Highest callus induction (100%) was obtained in treatments containing 2.32 or 4.65 μM Kinetin (KIN) with 2.26 or 6.80 μM 2,4-Dichlorophenoxyacetic acid (2,4-D). Highest fatty acids (FA) production (48.57 mg g-1), highest total phenol content (TPC; 57.1 mg gallic acid equivalents [GAE] g-1) and highest antioxidant activity (EC...

  7. Comparative proteome analysis of monolayer and spheroid culture of canine osteosarcoma cells.

    Science.gov (United States)

    Gebhard, Christiane; Miller, Ingrid; Hummel, Karin; Neschi Née Ondrovics, Martina; Schlosser, Sarah; Walter, Ingrid

    2018-04-15

    Osteosarcoma is an aggressive bone tumor with high metastasis rate in the lungs and affects both humans and dogs in a similar way. Three-dimensional tumor cell cultures mimic the in vivo situation of micro-tumors and metastases and are therefore better experimental in vitro models than the often applied two-dimensional monolayer cultures. The aim of the present study was to perform comparative proteomics of standard monolayer cultures of canine osteosarcoma cells (D17) and three-dimensional spheroid cultures, to better characterize the 3D model before starting with experiments like migration assays. Using DIGE in combination with MALDI-TOF/TOF we found 27 unique canine proteins differently represented between these two culture systems, most of them being part of a functional network including mainly chaperones, structural proteins, stress-related proteins, proteins of the glycolysis/gluconeogenesis pathway and oxidoreductases. In monolayer cells, a noticeable shift to more acidic pI values was noticed for several proteins of medium to high abundance; two proteins (protein disulfide isomerase A3, stress-induced-phosphoprotein 1) showed an increase of phosphorylated protein species. Protein distribution within the cells, as detected by immunohistochemistry, displayed a switch of stress-induced-phosphoprotein 1 from the cytoplasm (in monolayer cultures) to the nucleus (in spheroid cultures). Additionally, Western blot testing revealed upregulated concentrations of metastasin (S100A4), triosephosphate isomerase 1 and septin 2 in spheroid cultures, in contrast to decreased concentrations of CCT2, a subunit of the T-complex. Results indicate regulation of stress proteins in the process of three-dimensional organization characterized by a hypoxic and nutrient-deficient environment comparable to tumor micro-metastases. Osteosarcoma is an aggressive bone tumor that early spreads to the lungs. Three-dimensional tumor cell cultures represent the avascular stage of micro

  8. Phospholipid fatty acid analysis to monitor the co-composting process of olive oil mill wastes and organic household refuse

    OpenAIRE

    Barje , F.; Amir , S.; Winterton , Peter; Pinelli , Eric; Merlina , Georges; Cegarra , J.; Revel , Jean-Claude; Hafidi , Mohamed

    2008-01-01

    International audience; The co-composting of olive oil mill wastes and household refuse was followed for 5 months. During the thermophilic phase of composting, the aerobic heterotrophic bacteria (AHB) count, showed a significant rise with a slight regression of fungal biomass. In the same way, phospholipid fatty acids PLFAs common in bacteria, showed a significant increase of hydroxyl and branched PLFAs. The evaluation of the ratio of octadecenoic PLFAs to stearic acid (C18:1/C18:0) revealed ...

  9. Bilayers at High pH in the Fatty Acid Soap Systems and the Applications for the Formation of Foams and Emulsions.

    Science.gov (United States)

    Xu, Wenlong; Zhang, Heng; Zhong, Yingping; Jiang, Liwen; Xu, Mengxin; Zhu, Xionglu; Hao, Jingcheng

    2015-08-20

    In our previous work, we reported bilayers at high pH in the stearic acid/CsOH/H2O system, which was against the traditional viewpoint that fatty acid (FA) bilayers must be formed at the pKa of the fatty acid. Herein, the microstructures at high pH of several fatty acid soap systems were investigated systematically. We found that palmitic acid/KOH/H2O, palmitic acid/CsOH/H2O, stearic acid/KOH/H2O, and stearic acid/CsOH/H2O systems can form bilayers at high pH. The bilayer structure was demonstrated by cryogenic transmission electron microscopy (cryo-TEM) and deuterium nuclear magnetic resonance ((2)H NMR), and molecular dynamics simulation was used to confirm the formation of bilayers. The influence of fatty acids with different chain lengths (n = 10, 12, 14, 16, and 18) and different counterions including Li(+), Na(+), K(+), Cs(+), (CH3)4N(+), (C2H5)4N(+), (C3H7)4N(+), and (C4H9)4N(+) on the formation of bilayers was discussed. The stability of foam and emulsification properties were compared between bilayers and micelles, drawing the conclusion that bilayer structures possess a much stronger ability to foam and stronger emulsification properties than micelles do.

  10. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

    KAUST Repository

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

    2016-01-01

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

  11. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

    KAUST Repository

    Zheng, Yu Jie

    2016-01-21

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

  12. Onset wear in self-assembled monolayers

    International Nuclear Information System (INIS)

    D'Acunto, Mario

    2006-01-01

    Self-assembled monolayers (SAMs) are very useful for the systematic modification of the physical, chemical and structural properties of a surface by varying the chain length, tail group and composition. Many of these properties can be studied making use of atomic force microscopy (AFM), and the interaction between the AFM probe tip and the SAMs can also be considered an excellent reference to study the fundamental properties of dissipation phenomena and onset wear for viscoelastic materials on the nanoscale. We have performed a numerical study showing that the fundamental mechanism for the onset wear is a process of nucleation of domains starting from initial defects. An SAM surface repeatedly sheared by an AFM probe tip with enough applied loads shows the formation of progressive damages nucleating in domains. The AFM induced surface damages involve primarily the formation of radicals from the carbon chain backbones, but the deformations of the chains resulting in changes of period lattice also have to be taken into consideration. The nucleation of the wear domains generally starts at the initial surface defects where the energy cohesion between chains is lower. Moreover, the presence of surface defects is consistent with the changes in lateral force increasing the probability of the activation for the removal of carbon debris from the chain backbone. The quantification of the progressive worn area is performed making use of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory for phase transition kinetic processes. The advantage of knowing the general conditions for onset wear on the SAM surfaces can help in studying the fundamental mechanisms for the tribological properties of viscoelastic materials, in solid lubrication applications and biopolymer mechanics

  13. Comparative study on fatty acid composition of olive (Olea europaea L.), with emphasis on phytosterol contents.

    Science.gov (United States)

    Ozkan, Ali; Aboul-Enein, Hassan Y; Kulak, Muhittin; Bindak, Recep

    2017-08-01

    The present study was designed to determine the fatty acid composition and phytosterol contents of Turkish native olive cultivars, namely Kilis Yağlık and Nizip Yağlık cv. In this context, olive fruits from 34 locations were sampled and then screened for their components in comparison. Fifteen different fatty acids were found in both olive oils. In the order of abundance, the most important ones were oleic acid (18:1) > palmitic acid (16:0) > linoleic acid (18:2) > stearic acid (18:0). Significant differences were observed in the contents of oleic acid (18:1), palmitic acid (16:0), linoleic acid (18:2) but not for stearic acid content in comparison both oils (p < 0.01). There were significant differences in terms of unsaturated fatty acids, saturated fatty acids and polyunsaturated fatty acids (p < 0.01). The seven phytosterols - cholesterol, campesterol, stigmasterol, β-sitosterol, Δ-5-avenasterol, Δ-7-stigmastenol and Δ-7-avenasterol - were studied in both oil sources. The predominant sterols were β-sitosterol, Δ5-avenasterol and campesterol in the samples analysed. However, no significant differences were found in the levels of the phytosterols between the two olive cultivars. Copyright © 2017 John Wiley & Sons, Ltd.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-17

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

  15. Efficient inverted bulk-heterojunction polymer solar cells with self-assembled monolayer modified zinc oxide.

    Science.gov (United States)

    Kim, Wook Hyun; Lyu, Hong-Kun; Han, Yoon Soo; Woo, Sungho

    2013-10-01

    The performance of poly(3-hexylthiophen) (P3HT) and [6, 6]phenyl C61 butyric acid methyl ester ([60]PCBM)-based inverted bulk-heterojunction (BHJ) polymer solar cells (PSCs) is enhanced by the modification of zinc oxide (ZnO)/BHJ interface with carboxylic-acid-functionalized self-assembled monolayers (SAMs). Under simulated solar illumination of AM 1.5 (100 mW/cm2), the inverted devices fabricated with SAM-modified ZnO achieved an enhanced power conversion efficiency (PCE) of 3.34% due to the increased fill factor and photocurrent density as compared to unmodified cells with PCE of 2.60%. This result provides an efficient method for interface engineering in inverted BHJ PSCs.

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

    Science.gov (United States)

    Ito, Juri; Kajikawa, Kotaro

    2016-02-01

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

  17. Evidence of indirect gap in monolayer WSe2

    KAUST Repository

    Hsu, Wei-Ting

    2017-10-09

    Monolayer transition metal dichalcogenides, such as MoS2 and WSe2, have been known as direct gap semiconductors and emerged as new optically active materials for novel device applications. Here we reexamine their direct gap properties by investigating the strain effects on the photoluminescence of monolayer MoS2 and WSe2. Instead of applying stress, we investigate the strain effects by imaging the direct exciton populations in monolayer WSe2–MoS2 and MoSe2–WSe2 lateral heterojunctions with inherent strain inhomogeneity. We find that unstrained monolayer WSe2 is actually an indirect gap material, as manifested in the observed photoluminescence intensity–energy correlation, from which the difference between the direct and indirect optical gaps can be extracted by analyzing the exciton thermal populations. Our findings combined with the estimated exciton binding energy further indicate that monolayer WSe2 exhibits an indirect quasiparticle gap, which has to be reconsidered in further studies for its fundamental properties and device applications.

  18. Enhanced piezoelectricity of monolayer phosphorene oxides: a theoretical study.

    Science.gov (United States)

    Yin, Huabing; Zheng, Guang-Ping; Gao, Jingwei; Wang, Yuanxu; Ma, Yuchen

    2017-10-18

    Two-dimensional (2D) piezoelectric materials have potential applications in miniaturized sensors and energy conversion devices. In this work, using first-principles simulations at different scales, we systematically study the electronic structures and piezoelectricity of a series of 2D monolayer phosphorene oxides (POs). Our calculations show that the monolayer POs have tunable band gaps along with remarkable piezoelectric properties. The calculated piezoelectric coefficient d 11 of 54 pm V -1 in POs is much larger than those of 2D transition metal dichalcogenide monolayers and the widely used bulk α-quartz and AlN, and almost reaches the level of the piezoelectric effect in recently discovered 2D GeS. Furthermore, two other considerable piezoelectric coefficients, i.e., d 31 and d 26 with values of -10 pm V -1 and 21 pm V -1 , respectively, are predicted in some monolayer POs. We also examine the correlation between the piezoelectric coefficients and energy stability. The enhancement of piezoelectricity for monolayer phosphorene by oxidation will broaden the applications of phosphorene and phosphorene derivatives in nano-sized electronic and piezotronic devices.

  19. Piezoelectric effect on the thermal conductivity of monolayer gallium nitride

    Science.gov (United States)

    Zhang, Jin

    2018-01-01

    Using molecular dynamics and density functional theory simulations, in this work, we find that the heat transport property of the monolayer gallium nitride (GaN) can be efficiently tailored by external electric field due to its unique piezoelectric characteristic. As the monolayer GaN possesses different piezoelectric properties in armchair and zigzag directions, different effects of the external electric field on thermal conductivity are observed when it is applied in the armchair and zigzag directions. Our further study reveals that due to the elastoelectric effect in the monolayer GaN, the external electric field changes the Young's modulus and therefore changes the phonon group velocity. Also, due to the inverse piezoelectric effect, the applied electric field induces in-plane stress in the monolayer GaN subject to a length constraint, which results in the change in the lattice anharmonicity and therefore affects the phonon mean free path. Furthermore, for relatively long GaN monolayers, the in-plane stress may trigger the buckling instability, which can significantly reduce the phonon mean free path.

  20. Thermal conductivity of a h-BCN monolayer.

    Science.gov (United States)

    Zhang, Ying-Yan; Pei, Qing-Xiang; Liu, Hong-Yuan; Wei, Ning

    2017-10-18

    A hexagonal graphene-like boron-carbon-nitrogen (h-BCN) monolayer, a new two-dimensional (2D) material, has been synthesized recently. Herein we investigate for the first time the thermal conductivity of this novel 2D material. Using molecular dynamics simulations based on the optimized Tersoff potential, we found that the h-BCN monolayers are isotropic in the basal plane with close thermal conductivity magnitudes. Though h-BCN has the same hexagonal lattice as graphene and hexagonal boron nitride (h-BN), it exhibits a much lower thermal conductivity than the latter two materials. In addition, the thermal conductivity of h-BCN monolayers is found to be size-dependent but less temperature-dependent. Modulation of the thermal conductivity of h-BCN monolayers can also be realized by strain engineering. Compressive strain leads to a monotonic decrease in the thermal conductivity while the tensile strain induces an up-then-down trend in the thermal conductivity. Surprisingly, the small tensile strain can facilitate the heat transport of the h-BCN monolayers.

  1. Growth of cells superinoculated onto irradiated and nonirradiated confluent monolayers

    International Nuclear Information System (INIS)

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

    1990-01-01

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

  2. An investigation into the mechanisms of drug release from taste-masking fatty acid microspheres.

    Science.gov (United States)

    Qi, Sheng; Deutsch, David; Craig, Duncan Q M

    2008-09-01

    Fatty acid microspheres based on stearic and palmitic acids are known to form effective taste masking systems, although the mechanisms by which the drug is preferentially released in the lower gastrointestinal tract are not known. The objective of the present study was to identify the mechanisms involved, with a particular view to clarify the role of acid soap formation in the dissolution process. Microspheres were prepared by a spray chilling process. Using benzoic acid as a model drug and an alkaline dissolution medium, a faster drug release was observed in the mixed fatty acid formulation (50:50 stearic:palmitic acid (w/w)) compared to the single fatty acid component systems. Thermal and powder X-ray diffraction studies indicated a greater degree of acid soap formation for the mixed formulation in alkaline media compared to the single fatty acid systems. Particle size and porosity studies indicated a modest reduction in size for the mixed systems and an increase in porosity on immersion in the dissolution medium. It is proposed that the mixed fatty acid system form a mixed crystal system which in turn facilitates interaction with the dissolution medium, thereby leading to a greater propensity for acid soap formation which in turn forms a permeable liquid crystalline phase through which the drug may diffuse. The role of dissolution of palmitic acid into the dissolution medium is also discussed as a secondary mechanism.

  3. Determination of fruit characteristics, fatty acid profile and total antioxidant capacity of Mespilus germanica L. fruit

    Directory of Open Access Journals (Sweden)

    Hale Seçilmiş Canbay

    2015-11-01

    Full Text Available Objective: To determine fruit characteristics, fatty acid profile and total antioxidant capacitiy of first cultured Mespilus germanica L. Methods: A total of 15 fruits were taken randomly from four directions of adult trees. Then the physical and chemical properties of first cultured medlar fruit (Istanbul/Turkey were measured by using refractometer, colorimeter, spectrophotometer and gas chromatograph mass spectrometer, respectivly. Results: In the fruit studied, the results showed that palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid and behenic acid were the most abundant fatty acids (FAs, and the main FA was palmitic acid [(35.35 ± 1.20%]. The percentage of linoleic acid and stearic acid in this fruit oil were (29.10 ± 1.70% and (8.53 ± 0.25%, respectively. As a result of the analysis, the total antioxidant capacity of medlar fruit was (1.1 ± 0.2 mmol trolox equivalents/L. Conclusions: The present study has demonstrated the concentrations of FAs and the antioxidantive capacity of first cultured Istanbul medlar fruits by using many tested methods. It is proved that in our daily life, medlar fruit plays a significant role with its nutrition and health effect.

  4. Fullerene nanostructures, monolayers and thin films

    International Nuclear Information System (INIS)

    Cotier, B.N.

    2000-10-01

    The interaction of submonolayer, monolayer and multilayer coverages of C 60 with the Ag/Si(111)-(√3x√3)R30 deg. (√3Ag/Si) and Si(111)-7x7 surfaces has been investigated using atomic force microscopy (AFM), photoelectron spectroscopy (PES) and ultra high vacuum scanning tunneling microscopy (UHV-STM). It is shown that it is possible to preserve the √3Ag/Si surface, normally corrupted by exposure to air, in ambient conditions when immersed beneath a few layers of C 60 molecules. Upon removal of the fullerene layers in the UHV-STM some corruption is observed which is linked to the morphology of the fullerene film (defined by the nature of the interaction of C 60 with √3Ag/Si). This technique opens up the possibility of performing experiments on the clean √3Ag/Si surface outside of UHV conditions. With the discovery of techniques whereby structures may be formed that are composed of only a few atoms/molecules, there is a need to perform electrical measurements in order to probe the fascinating properties of these 'nano-scale' devices. Using AFM, PES and STM evaporated metals and ion implantation have been investigated as materials for use in forming sub-micron scale contacts to nanostructures. It is found that ion implantation is a more promising approach after studying the response to annealing of treated surfaces. Electrical measurements between open/short circuited contacts and through Ag films clearly demonstrate the validity of the method, further confirmed by a PES study which probes the chemical nature of the near surface region of ion-implanted samples. Attempts have been made to form nanostructure templates between sub-micron scale contacts as a possible precursor to forming nanostructures. The bonding state of C 60 molecules on the Si(111)-7x7 surface has been in dispute for many years. To properly understand the system a comprehensive AFM, PES and STM study has been performed. PES results indicate covalent bond formation, with the number of bonds

  5. Lateral Interactions in Monolayer Thick Mercury Films

    Science.gov (United States)

    Kime, Yolanda Jan

    An understanding of lateral adatom-adatom interactions is often an important part of understanding electronic structure and adsorption energetics in monolayer thick films. In this dissertation I use angle-resolved photoemission and thermal desorption spectroscopies to explore the relationship between the adatom-adatom interaction and other characteristics of the adlayer, such as electronic structure, defects, or coexistent structural phases in the adlayer. Since Hg binds weakly to many substrates, the lateral interactions are often a major contribution to the dynamics of the overlayer. Hg adlayer systems are thus ideal for probing lateral interactions. The electronic structures of Hg adlayers on Ag(100), Cu(100), and Cu_3Au(100) are studied with angle-resolved ultraviolet photoemission. The Hg atomic 5d_{5/2} electronic band is observed to split into two levels following adsorption onto some surfaces. The energetic splitting of the Hg 5d_{5/2} level is found to be directly correlated to the adlayer homogeneous strain energy. The existence of the split off level also depends on the order or disorder of the Hg adlayer. The energetics of Hg adsorption on Cu(100) are probed using thermal desorption spectroscopy. Two different ordered adlayer structures are observed for Hg adsorption on Cu(100) at 200 K. Under some adsorption conditions and over a range of exposures, the two phases are seen to coexist on the surface prior to the thermal desorption process. A phase transition from the more dense to the less dense phase is observed to occur during the thermal desorption process. Inherent differences in defect densities are responsible for the observed differences between lateral interactions measured previously with equilibrium (atom beam scattering) and as measured by the non-equilibrium (thermal desorption) technique reported here. Theoretical and experimental evidence for an indirect through-metal interaction between adatoms is also discussed. Although through

  6. Amino acid and fatty acid compositions of Rusip from fermented Anchovy fish (Stolephorussp)

    Science.gov (United States)

    Koesoemawardani, D.; Hidayati, S.; Subeki

    2018-04-01

    Rusip is a typical food of Bangka Belitung Indonesia made from fermented anchovy. This study aims to determine the properties of chemistry, microbiology, composition of amino acids and fatty acids from fermented fish spontaneously and non spontaneously. Spontaneous rusip treatment is done by anchovy fish (Stolephorussp) after cleaning and added salt 25% (w/w) and palm sugar 10% (w/w). While, non-spontaneous rusip is done by adding a culture mixture of Streptococcus, Leuconostoc, and Lactobacillus bacteria 2% (w/v). The materials are then incubated for 2 weeks. The data obtained were then performed t-test at the level of 5%. Spontaneous and non-spontaneous rusip fermentation process showed significant differences in total acid, reducing sugar, salt content, TVN, total lactic acid bacteria, total mold, and total microbial. The dominant amino acid content of spontaneous and non-spontaneous rusip are glutamic acid and aspartic acid, while the dominant fatty acids in spontaneous and non-spontaneous rusip are docosahexaenoic acid, palmitic acid, oleic acid, arachidonic acid, stearic acid, eicosapentaenoic acid, palmitoleic acid, and myristic acid.

  7. Fatty Acid Methyl Esters and Solutol HS 15 Confer Neuroprotection After Focal and Global Cerebral Ischemia

    OpenAIRE

    Lin, Hung Wen; Saul, Isabel; Gresia, Victoria L.; Neumann, Jake T.; Dave, Kunjan R.; Perez-Pinzon, Miguel A.

    2013-01-01

    We previously showed that palmitic methyl ester (PAME) and stearic acid methyl ester (SAME) are simultaneously released from the sympathetic ganglion and PAME possesses potent vasodilatory properties which may be important in cerebral ischemia. Since PAME is a potent vasodilator simultaneously released with SAME, our hypothesis was that PAME/SAME confers neuroprotection in rat models of focal/global cerebral ischemia. We also examined the neuroprotective properties of Soluto...

  8. Radiolytic products of irradiated authentic fatty acids and triacylglycerides

    International Nuclear Information System (INIS)

    Kim, K.-S.; Lee, Jeong-Min; Seo, Hye-Young; Kim, Jun-Hyoung; Song, Hyun-Pa; Byun, Myung-Woo; Kwon, Joong-Ho

    2004-01-01

    Radiolytic products of authentic fatty acids (palmitic, stearic, oleic, linoleic and linolenic acids) and triacylglycerides (tripalmitin, tristearin, triolein, trilinolein and trilinolenin) were determined. Concentrations of hydrocarbons from the saturated fatty acids were higher than the unsaturated fatty acids. Authentic fatty acids were mainly decomposed in the α-carbon position and C n-1 hydrocarbons occurred in higher than C n-2 hydrocarbons. Concentrations of 2-alkylcyclobutanones from the saturated fatty acids were lower than the unsaturated fatty acids. Concentrations of hydrocarbons from tripalmitin and tristearin were not a significant change compared with triolein, trilinolein and trilinolenin. For all triacylglycerides except triolein, C n-1 hydrocarbons were higher than C n-2 hydrocarbons. Radioproduction rates of 2-alkylcyclobutanones from tripalmitin and tristearin were higher than triolein, trilinolein and trilinolenin

  9. Effects of Fatty Acid Inclusion in a DMPC Bilayer Membrane

    DEFF Research Database (Denmark)

    Peters, Günther H.J.; Hansen, Flemming Yssing; Møller, Martin S.

    2009-01-01

    Free fatty acids in biomembranes have been proposed to be a central component in several cellular control and regulatory mechanisms. To elucidate some fundamental elements underlying this, we have applied molecular dynamics simulations and experimental density measurements to study the molecular...... packing and structure of oleic acid (HOA) and stearic acid (HSA) in fluid bilayers of dimyristoylphosphatidylcholine (DMPC). The experimental data show a small but consistent positive excess volume for fatty acid concentrations below 10 mol %. At higher concentrations the fatty acids mix ideally...... with fluid DMPC. The simulations, which were benchmarked against the densitometric data, revealed interesting differences in the structure and location of the fatty acids depending on their protonation status. Thus, the protonated (uncharged) acid is located rather deeply in the membrane with an average...

  10. Polysarcosine-Based Lipids: From Lipopolypeptoid Micelles to Stealth-Like Lipids in Langmuir Blodgett Monolayers

    Directory of Open Access Journals (Sweden)

    Benjamin Weber

    2016-12-01

    Full Text Available Amphiphiles and, in particular, PEGylated lipids or alkyl ethers represent an important class of non-ionic surfactants and have become key ingredients for long-circulating (“stealth” liposomes. While poly-(ethylene glycol (PEG can be considered the gold standard for stealth-like materials, it is known to be neither a bio-based nor biodegradable material. In contrast to PEG, polysarcosine (PSar is based on the endogenous amino acid sarcosine (N-methylated glycine, but has also demonstrated stealth-like properties in vitro, as well as in vivo. In this respect, we report on the synthesis and characterization of polysarcosine based lipids with C14 and C18 hydrocarbon chains and their end group functionalization. Size exclusion chromatography (SEC and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS analysis reveals that lipopeptoids with a degree of polymerization between 10 and 100, dispersity indices around 1.1, and the absence of detectable side products are directly accessible by nucleophilic ring opening polymerization (ROP. The values for the critical micelle concentration for these lipopolymers are between 27 and 1181 mg/L for the ones with C18 hydrocarbon chain or even higher for the C14 counterparts. The lipopolypeptoid based micelles have hydrodynamic diameters between 10 and 25 nm, in which the size scales with the length of the PSar block. In addition, C18PSar50 can be incorporated in 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC monolayers up to a polymer content of 3%. Cyclic compression and expansion of the monolayer showed no significant loss of polymer, indicating a stable monolayer. Therefore, lipopolypeptoids can not only be synthesized under living conditions, but my also provide a platform to substitute PEG-based lipopolymers as excipients and/or in lipid formulations.

  11. 1-Dodecanethiol based highly stable self-assembled monolayers for germanium passivation

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  12. 1-Dodecanethiol based highly stable self-assembled monolayers for germanium passivation

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-30

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

  13. Self assembled monolayers of octadecyltrichlorosilane for dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-04-13

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

  14. Measuring the Edge Recombination Velocity of Monolayer Semiconductors.

    Science.gov (United States)

    Zhao, Peida; Amani, Matin; Lien, Der-Hsien; Ahn, Geun Ho; Kiriya, Daisuke; Mastandrea, James P; Ager, Joel W; Yablonovitch, Eli; Chrzan, Daryl C; Javey, Ali

    2017-09-13

    Understanding edge effects and quantifying their impact on the carrier properties of two-dimensional (2D) semiconductors is an essential step toward utilizing this material for high performance electronic and optoelectronic devices. WS 2 monolayers patterned into disks of varying diameters are used to experimentally explore the influence of edges on the material's optical properties. Carrier lifetime measurements show a decrease in the effective lifetime, τ effective , as a function of decreasing diameter, suggesting that the edges are active sites for carrier recombination. Accordingly, we introduce a metric called edge recombination velocity (ERV) to characterize the impact of 2D material edges on nonradiative carrier recombination. The unpassivated WS 2 monolayer disks yield an ERV ∼ 4 × 10 4 cm/s. This work quantifies the nonradiative recombination edge effects in monolayer semiconductors, while simultaneously establishing a practical characterization approach that can be used to experimentally explore edge passivation methods for 2D materials.

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

    Directory of Open Access Journals (Sweden)

    Jinxuan Liu

    2017-04-01

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

  16. Controlled electrodeposition of Au monolayer film on ionic liquid

    Science.gov (United States)

    Ma, Qiang; Pang, Liuqing; Li, Man; Zhang, Yunxia; Ren, Xianpei; Liu, Shengzhong Frank

    2016-05-01

    Gold (Au) nanoparticles have been attractive for centuries for their vibrant appearance enhanced by their interaction with sunlight. Nowadays, there have been tremendous research efforts to develop them for high-tech applications including therapeutic agents, sensors, organic photovoltaics, medical applications, electronics and catalysis. However, there remains to be a challenge to fabricate a monolayer Au coating with complete coverage in controlled fashion. Here we present a facile method to deposit a uniform Au monolayer (ML) film on the [BMIM][PF6] ionic liquid substrate using an electrochemical deposition process. It demonstrates that it is feasible to prepare a solid phase coating on the liquid-based substrate. Moreover, the thickness of the monolayer coating can be controlled to a layer-by-layer accuracy.

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  18. Monolayer structures of alkyl aldehydes: Odd-membered homologues

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  19. Magnetism of Ta dichalcogenide monolayers tuned by strain and hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Manchanda, Priyanka; Sellmyer, D. J.; Skomski, Ralph [Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Sharma, Vinit [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Yu, Hongbin [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States)

    2015-07-20

    The effects of strain and hydrogenation on the electronic, magnetic, and optical properties of monolayers of Ta based dichalcogenides (TaX{sub 2}; X = S, Se, and Te) are investigated using density-functional theory. We predict a complex scenario of strain-dependent magnetic phase transitions involving paramagnetic, ferromagnetic, and modulated antiferromagnetic states. Covering one of the two chalcogenide surfaces with hydrogen switches the antiferromagnetic/nonmagnetic TaX{sub 2} monolayers to a semiconductor, and the optical behavior strongly depends on strain and hydrogenation. Our research opens pathways towards the manipulation of magnetic as well as optical properties for future spintronics and optoelectronics applications.

  20. Unconventional fractional quantum Hall effect in monolayer and bilayer graphene

    Science.gov (United States)

    Jacak, Janusz; Jacak, Lucjan

    2016-01-01

    The commensurability condition is applied to determine the hierarchy of fractional fillings of Landau levels in monolayer and in bilayer graphene. The filling rates for fractional quantum Hall effect (FQHE) in graphene are found in the first three Landau levels in one-to-one agreement with the experimental data. The presence of even denominator filling fractions in the hierarchy for FQHE in bilayer graphene is explained. Experimentally observed hierarchy of FQHE in the first and second Landau levels in monolayer graphene and in the zeroth Landau level in bilayer graphene is beyond the conventional composite fermion interpretation but fits to the presented nonlocal topology commensurability condition. PMID:27877866

  1. Disorder-dependent valley properties in monolayer WSe2

    KAUST Repository

    Tran, Kha

    2017-07-19

    We investigate the effect of disorder on exciton valley polarization and valley coherence in monolayer WSe2. By analyzing the polarization properties of photoluminescence, the valley coherence (VC) and valley polarization (VP) are quantified across the inhomogeneously broadened exciton resonance. We find that disorder plays a critical role in the exciton VC, while affecting VP less. For different monolayer samples with disorder characterized by their Stokes shift (SS), VC decreases in samples with higher SS while VP does not follow a simple trend. These two methods consistently demonstrate that VC as defined by the degree of linearly polarized photoluminescence is more sensitive to disorder, motivating further theoretical studies.

  2. Evaluation of Fatty Acid and Amino Acid Compositions in Okra (Abelmoschus esculentus Grown in Different Geographical Locations

    Directory of Open Access Journals (Sweden)

    Rokayya Sami

    2013-01-01

    Full Text Available Okra has different uses as a food and a remedy in traditional medicine. Since it produces many seeds, distribution of the plant is also quite easy. Although seed oil yield is low (4.7%, since the linoleic acid composition of the seed oil is quiet high (67.5%, it can still be used as a source of (UNSAT unsaturated fatty acids. In this study, samples of okra grown in four different locations were analyzed to measure fatty acid and amino acid compositions. The content of the lipid extraction ranged from 4.34% to 4.52% on a dry weight basis. Quantitatively, the main okra fatty acids were palmitic acid (29.18–43.26%, linoleic acid (32.22–43.07%, linolenic acid (6.79–12.34%, stearic acid (6.36–7.73%, oleic acid (4.31–6.98%, arachidic acid (ND–3.48%, margaric acid (1.44–2.16%, pentadecylic acid (0.63–0.92%, and myristic acid (0.21–0.49%. Aspartic acid, proline, and glutamic acids were the main amino acids in okra pods, while cysteine and tyrosine were the minor amino acids. Statistical methods revealed how the fatty acid and amino acid contents in okra may be affected by the sampling location.

  3. Composition evaluation of the tallow and meat fatty acids of the cattle and determining their atherogenesis and thrombogenesisindexes in South Khorasan Province

    Directory of Open Access Journals (Sweden)

    Mohammad Malekaneh

    2015-01-01

    Conclusion: It was found that the sum of trans and stearic fatty acids was more in tallow. The hypocholesterolemic fatty acids levels were higher in the meat in the whole province. The cattle’s meat had lower atherogenetic and thrombogenetic properties compared with the animals’ fat.The consumed cattle’s meat and fat in the province appear to have a proper condition.

  4. Emergence of Dirac and quantum spin Hall states in fluorinated monolayer As and AsSb

    KAUST Repository

    Zhang, Qingyun; Schwingenschlö gl, Udo

    2016-01-01

    Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer As and AsSb. While the pristine monolayers are semiconductors (direct band gap at the Γ point), fluorination results in Dirac cones at the K

  5. Cadmium Alters the Concentration of Fatty Acids in THP-1 Macrophages.

    Science.gov (United States)

    Olszowski, Tomasz; Gutowska, Izabela; Baranowska-Bosiacka, Irena; Łukomska, Agnieszka; Drozd, Arleta; Chlubek, Dariusz

    2018-03-01

    Fatty acid composition of human immune cells influences their function. The aim of this study was to evaluate the effects of known toxicant and immunomodulator, cadmium, at low concentrations on levels of selected fatty acids (FAs) in THP-1 macrophages. The differentiation of THP-1 monocytes into macrophages was achieved by administration of phorbol myristate acetate. Macrophages were incubated with various cadmium chloride (CdCl 2 ) solutions for 48 h at final concentrations of 5 nM, 20 nM, 200 nM, and 2 μM CdCl 2 . Fatty acids were extracted from samples according to the Folch method. The fatty acid levels were determined using gas chromatography. The following fatty acids were analyzed: long-chain saturated fatty acids (SFAs) palmitic acid and stearic acid, very long-chain saturated fatty acid (VLSFA) arachidic acid, monounsaturated fatty acids (MUFAs) palmitoleic acid, oleic acid and vaccenic acid, and n-6 polyunsaturated fatty acids (PUFAs) linoleic acid and arachidonic acid. Treatment of macrophages with very low concentrations of cadmium (5-200 nM) resulted in significant reduction in the levels of arachidic, palmitoleic, oleic, vaccenic, and linoleic acids and significant increase in arachidonic acid levels (following exposure to 5 nM Cd), without significant reduction of palmitic and stearic acid levels. Treatment of macrophages with the highest tested cadmium concentration (2 μM) produced significant reduction in the levels of all examined FAs: SFAs, VLSFA, MUFAs, and PUFAs. In conclusion, cadmium at tested concentrations caused significant alterations in THP-1 macrophage fatty acid levels, disrupting their composition, which might dysregulate fatty acid/lipid metabolism thus affecting macrophage behavior and inflammatory state.

  6. Screening of self-assembled monolayer for aflatoxin B1 detection using immune-capacitive sensor

    Directory of Open Access Journals (Sweden)

    Alvaro V. Gutierrez R

    2015-12-01

    Full Text Available A capacitive biosensor was used for detection of aflatoxin B1. Two different methods for cleaning gold electrodes were evaluated using cyclic voltammetry in the presence of ferricyanide as redox couple. The methods involve use of a sequence of cleaning steps avoiding the use of Piranha solution and plasma cleaner. Anti-aflatoxin B1 was immobilized on self-assembled monolayers (SAM. The immune-capacitive biosensor is able to detect aflatoxin B1 concentrations in a linear range of 3.2 × 10−12 M to 3.2 × 10−9 M when thiourea was used to form the SAM; 3.2 × 10−9 M to 3.2 × 10−7 M when thioctic acid was used. When the gold surface was isolated with tyramine-electropolymerization linear ranges of 3.2 × 10−13 M to 3.2 × 10−7 M and 3.2 × 10−9 M to 3.2 × 10−7 M where obtained, respectively. The results obtained show the difference in linear range, limit of detection, and limit of quantification when different self-assembled monolayers are used for aflatoxin B1 detection.

  7. Electroactive oligoaniline-containing self-assembled monolayers for tissue engineering applications.

    Science.gov (United States)

    Guo, Yi; Li, Mengyan; Mylonakis, Andreas; Han, Jingjia; MacDiarmid, Alan G; Chen, Xuesi; Lelkes, Peter I; Wei, Yen

    2007-10-01

    A novel electroactive silsesquioxane precursor, N-(4-aminophenyl)-N'-(4'-(3-triethoxysilyl-propyl-ureido) phenyl-1,4-quinonenediimine) (ATQD), was successfully synthesized from the emeraldine form of amino-capped aniline trimers via a one-step coupling reaction and subsequent purification by column chromatography. The physicochemical properties of ATQD were characterized using mass spectrometry as well as by nuclear magnetic resonance and UV-vis spectroscopy. Analysis by cyclic voltammetry confirmed that the intrinsic electroactivity of ATQD was maintained upon protonic acid doping, exhibiting two distinct reversible oxidative states, similar to polyaniline. The aromatic amine terminals of self-assembled monolayers (SAMs) of ATQD on glass substrates were covalently modified with an adhesive oligopeptide, cyclic Arg-Gly-Asp (RGD) (ATQD-RGD). The mean height of the monolayer coating on the surfaces was approximately 3 nm, as measured by atomic force microscopy. The biocompatibility of the novel electroactive substrates was evaluated using PC12 pheochromocytoma cells, an established cell line of neural origin. The bioactive, derivatized electroactive scaffold material, ATQD-RGD, supported PC12 cell adhesion and proliferation, similar to control tissue-culture-treated polystyrene surfaces. Importantly, electroactive surfaces stimulated spontaneous neuritogenesis in PC12 cells, in the absence of neurotrophic growth factors, such as nerve growth factor (NGF). As expected, NGF significantly enhanced neurite extension on both control and electroactive surfaces. Taken together, our results suggest that the newly electroactive SAMs grafted with bioactive peptides, such as RGD, could be promising biomaterials for tissue engineering.

  8. Mechanical Adaptability of the MMP-Responsive Film Improves the Functionality of Endothelial Cell Monolayer.

    Science.gov (United States)

    Hu, Mi; Chang, Hao; Zhang, He; Wang, Jing; Lei, Wen-Xi; Li, Bo-Chao; Ren, Ke-Feng; Ji, Jian

    2017-07-01

    Extracellular matrix and cells are inherent in coordinating and adapting to each other during all physiological and pathological processes. Synthetic materials, however, show rarely reciprocal and spatiotemporal responses to cells, and lacking self-adapting properties as well. Here, a mechanical adaptability based on the matrix metalloproteinase (MMPs) sensitive polyelectrolyte film is reported. Poly-lysine (PLL) and methacrylated hyaluronic acid (HA-MA) nanolayers are employed to build the thin film through the layer-by-layer assembly, and it is further crosslinked using MMP sensitive peptides, which endows the films with changeable mechanical properties in response to MMPs. It is demonstrated that stiffness of the (PLL/HA-MA) films increases with the crosslinking, and then decreases in response to a treatment of enzyme. Consequently, the crosslinked (PLL/HA-MA) films reveal effective growth of endothelial cells (ECs), leading to fast formation of EC monolayer. Importantly, significantly improved endothelial function of the EC monolayer, which is characterized by integrity, biomolecules release, expression of function related gene, and antithrombotic properties, is achieved along with the decrosslinking of the film because of EC-secreted MMPs. These results suggest that mechanical adaptability of substrate in Young's modulus plays a significant role in endothelial progression, which shows great application potential in tissue engineering, regenerative medicine, and organ-on-a-chip. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Chitosan-modified porous silicon microparticles for enhanced permeability of insulin across intestinal cell monolayers.

    Science.gov (United States)

    Shrestha, Neha; Shahbazi, Mohammad-Ali; Araújo, Francisca; Zhang, Hongbo; Mäkilä, Ermei M; Kauppila, Jussi; Sarmento, Bruno; Salonen, Jarno J; Hirvonen, Jouni T; Santos, Hélder A

    2014-08-01

    Porous silicon (PSi) based particulate systems are emerging as an important drug delivery system due to its advantageous properties such as biocompatibility, biodegradability and ability to tailor the particles' physicochemical properties. Here, annealed thermally hydrocarbonized PSi (AnnTHCPSi) and undecylenic acid modified AnnTHCPSi (AnnUnTHCPSi) microparticles were developed as a PSi-based platform for oral delivery of insulin. Chitosan (CS) was used to modify the AnnUnTHCPSi microparticles to enhance the intestinal permeation of insulin. Surface modification with CS led to significant increase in the interaction of PSi microparticles with Caco-2/HT-29 cell co-culture monolayers. Compared to pure insulin, the CS-conjugated microparticles significantly improved the permeation of insulin across the Caco-2/HT-29 cell monolayers, with ca. 20-fold increase in the amount of insulin permeated and ca. 7-fold increase in the apparent permeability (P(app)) value. Moreover, among all the investigated particles, the CS-conjugated microparticles also showed the highest amount of insulin associated with the mucus layer and the intestinal Caco-2 cells and mucus secreting HT-29 cells. Our results demonstrate that CS-conjugated AnnUnTHCPSi microparticles can efficiently enhance the insulin absorption across intestinal cells, and thus, they are promising microsystems for the oral delivery of proteins and peptides across the intestinal cell membrane. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Advanced chemistry of monolayers at interfaces trends in methodology and technology

    CERN Document Server

    Imae, Toyoko

    2007-01-01

    Advanced Chemistry of Monolayers at Interfaces describes the advanced chemistry of monolayers at interfaces. Focusing on the recent trends of methodology and technology, which are indispensable in monolayer science. They are applied to monolayers of surfactants, amphiphiles, polymers, dendrimers, enzymes, and proteins, which serve many uses.Introduces the methodologies of scanning probe microscopy, surface force instrumentation, surface spectroscopy, surface plasmon optics, reflectometry, and near-field scanning optical microscopy. Modern interface reaction method, lithographic tech

  11. Serum Paraoxonase 1 Activity Is Associated with Fatty Acid Composition of High Density Lipoprotein

    Directory of Open Access Journals (Sweden)

    Maryam Boshtam

    2013-01-01

    Full Text Available Introduction. Cardioprotective effect of high density lipoprotein (HDL is, in part, dependent on its related enzyme, paraoxonase 1 (PON1. Fatty acid composition of HDL could affect its size and structure. On the other hand, PON1 activity is directly related to the structure of HDL. This study was designed to investigate the association between serum PON1 activity and fatty acid composition of HDL in healthy men. Methods. One hundred and forty healthy men participated in this research. HDL was separated by sequential ultracentrifugation, and its fatty acid composition was analyzed by gas chromatography. PON1 activity was measured spectrophotometrically using paraxon as substrate. Results. Serum PON1 activity was directly correlated with the amount of stearic acid and dihomo-gamma-linolenic acid (DGLA. PON1/HDL-C was directly correlated with the amount of miristic acid, stearic acid, and DGLA and was inversely correlated with total amount of ω6 fatty acids of HDL. Conclusion. The fatty acid composition of HDL could affect the activity of its associated enzyme, PON1. As dietary fats are the major determinants of serum lipids and lipoprotein composition, consuming some special dietary fatty acids may improve the activity of PON1 and thereby have beneficial effects on health.

  12. Serum paraoxonase 1 activity is associated with fatty acid composition of high density lipoprotein.

    Science.gov (United States)

    Boshtam, Maryam; Razavi, Amirnader Emami; Pourfarzam, Morteza; Ani, Mohsen; Naderi, Gholam Ali; Basati, Gholam; Mansourian, Marjan; Dinani, Narges Jafari; Asgary, Seddigheh; Abdi, Soheila

    2013-01-01

    Cardioprotective effect of high density lipoprotein (HDL) is, in part, dependent on its related enzyme, paraoxonase 1 (PON1). Fatty acid composition of HDL could affect its size and structure. On the other hand, PON1 activity is directly related to the structure of HDL. This study was designed to investigate the association between serum PON1 activity and fatty acid composition of HDL in healthy men. One hundred and forty healthy men participated in this research. HDL was separated by sequential ultracentrifugation, and its fatty acid composition was analyzed by gas chromatography. PON1 activity was measured spectrophotometrically using paraxon as substrate. Serum PON1 activity was directly correlated with the amount of stearic acid and dihomo-gamma-linolenic acid (DGLA). PON1/HDL-C was directly correlated with the amount of miristic acid, stearic acid, and DGLA and was inversely correlated with total amount of ω 6 fatty acids of HDL. The fatty acid composition of HDL could affect the activity of its associated enzyme, PON1. As dietary fats are the major determinants of serum lipids and lipoprotein composition, consuming some special dietary fatty acids may improve the activity of PON1 and thereby have beneficial effects on health.

  13. Milk fat globules: fatty acid composition, size and in vivo regulation of fat liquidity.

    Science.gov (United States)

    Timmen, H; Patton, S

    1988-07-01

    Populations of large and small milk fat globules were isolated and analyzed to determine differences in fatty acid composition. Globule samples were obtained by centrifugation from milks of a herd and of individual animals produced under both pasture and barn feeding. Triacylglycerols of total globule lipids were prepared by thin layer chromatography and analyzed for fatty acid composition by gas chromatography. Using content of the acids in large globules as 100%, small globules contained fewer short-chain acids, -5.9%, less stearic acid, -22.7%, and more oleic acids, +4.6%, mean values for five trials. These differences are consistent with alternative use of short-chain acids or oleic acid converted from stearic acid to maintain liquidity at body temperature of milk fat globules and their precursors, intracellular lipid droplets. Stearyl-CoA desaturase (EC 1.14.99.5), which maintains fluidity of cellular endoplasmic reticulum membrane, is suggested to play a key role in regulating globule fat liquidity. Possible origins of differences between individual globules in fatty acid composition of their triacylglycerols are discussed.

  14. Pressure-dependent optical and vibrational properties of monolayer molybdenum disulfide

    KAUST Repository

    Nayak, Avinash P.; Pandey, Tribhuwan; Voiry, Damien; Liu, Jin; Moran, Samuel T.; Sharma, Ankit; Tan, Cheng; Chen, Changhsiao; Li, Lain-Jong; Chhowalla, Manish U.; Lin, Jungfu; Singh, Abhishek Kumar; Akinwande, Deji

    2015-01-01

    vibrational dynamics of the distorted monolayer 1T-MoS2 (1T′) and the monolayer 2H-MoS2 via a diamond anvil cell (DAC) and density functional theory (DFT) calculations. The direct optical band gap of the monolayer 2H-MoS2 increases by 11.7% from 1.85 to 2.08 e

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

    NARCIS (Netherlands)

    de Boer, B; Hadipour, A; Mandoc, MM; van Woudenbergh, T; Blom, PWM

    2005-01-01

    Work functions of gold and silver are varied by over 1.4 and 1.7 eV, respectively, by using self-assembled monolayers. Using these modified electrodes, the hole current in a poly(2-methoxy-5-(2'-ethylhexyloxy)- 1,4-phenylene vinylene) light-emitting diode is tuned by more than six orders of

  16. Applications of self-assembled monolayers in materials chemistry

    Indian Academy of Sciences (India)

    Unknown

    Physical and Materials Chemistry Division, National Chemical Laboratory,. Pune 411 008, India e-mail: viji@ems.ncl.res.in. Abstract. Self-assembly provides a simple route to organise suitable organic molecules on noble metal and selected nanocluster surfaces by using monolayers of long chain organic molecules with ...

  17. Melting mechanism in monolayers of flexible rod-shaped molecules

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Taub, H.

    1992-01-01

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

  18. Direct measurement of the microscale conductivity of conjugated polymer monolayers

    DEFF Research Database (Denmark)

    Bøggild, Peter; Grey, Francois; Hassenkam, T.

    2000-01-01

    The in-plane conductivity of conjugated polymer monolayers is mapped here for the first time on the microscale using a novel scanning micro four-point probe (see Figure). The probe allows the source, drain, and voltage electrodes to be positioned within the same domain and the mapping results...

  19. Suppressing segregation in highly phosphorus doped silicon monolayers

    NARCIS (Netherlands)

    Keizer, Joris; Kölling, Sebastian; Koenraad, Paul; Simmons, Michelle Y.

    2015-01-01

    Sharply defined dopant profiles and low resistivity are highly desired qualities in the microelectronic industry, and more recently, in the development of an all epitaxial Si:P based quantum computer. In this work, we use thin (monolayers thick) room temperature grown silicon layers, so-called

  20. Formation and optical characterisation of colloidal gold monolayers

    NARCIS (Netherlands)

    Kooij, Ernst S.; Brouwer, E.A.M.; Wormeester, Herbert; Poelsema, Bene

    2003-01-01

    We study the deposition of charge-stabilised gold nanocolloids on silicon substrates, which have been derivatised with (aminopropyl)triethoxysilane. Atomic force microscopy (AFM) and spectroscopic ellipsometry are employed to investigate the nanocrystal monolayers ex situ. Analysis of AFM images

  1. Electrical Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide

    Science.gov (United States)

    2014-07-14

    Lou, Sina Najmaei, Matin Amani, Matthew L. Chin, Zheng Se. TASK NUMBER Liu Sf. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 8...Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide Sina Najmaei,t.§ Matin Ama ni,M Matthew L. Chin,* Zhe ng liu/ ·"·v: A. Gle n

  2. Theory of lithium islands and monolayers: Electronic structure and stability

    International Nuclear Information System (INIS)

    Quassowski, S.; Hermann, K.

    1995-01-01

    Systematic calculations on planar clusters and monolayers of lithium are performed to study geometries and stabilities of the clusters as well as their convergence behavior with increasing cluster size. The calculations are based on ab initio methods using density-functional theory within the local-spin-density approximation for exchange and correlation. The optimized nearest-neighbor distances d NN of the Li n clusters, n=1,...,25, of both hexagonal and square geometry increase with cluster size, converging quite rapidly towards the monolayer results. Further, the cluster cohesive energies E c increase with cluster size and converge towards the respective monolayer values that form upper bounds. Clusters of hexagonal geometry are found to be more stable than square clusters of comparable size, consistent with the monolayer results. The size dependence of the cluster cohesive energies can be described approximately by a coordination model based on the concept of pairwise additive nearest-neighbor binding. This indicates that the average binding in the Li n clusters and their relative stabilities can be explained by simple geometric effects which derive from the nearest-neighbor coordination

  3. Permethylated 12-Vertex p-Carborane Self-Assembled Monolayers

    Czech Academy of Sciences Publication Activity Database

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

    2011-01-01

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

  4. Overcrowding drives the unjamming transition of gap-free monolayers

    Science.gov (United States)

    Lan, Ganhui; Su, Tao

    Collective cell motility plays central roles in various biological phenomena such as wound healing, cancer metastasis and embryogenesis. These are demonstrations of the unjamming transition in biology. However, contradictory to the typical density-driven jamming in particulate assemblies, cellular systems often get unjammed in highly packed, sometimes overcrowding environments. Here, we investigate monolayers' collective behaviors when cell number changes under the gap-free constraint. We report that overcrowding can unjam gap-free monolayers through increasing isotropic compression. We show that the transition boundary is determined by the isotropic compression and the cell-cell adhesion. Furthermore, we construct the free energy landscape for the T1 topological transition during monolayer rearrangement, and discover that the landscape evolves from single-barrier W shape to double-barrier M shape during the unjamming process. We also discover a distributed-to-disordered morphological transition of cells' geometry, coinciding with the unjamming transition. Our analyses reveal that the overcrowding and adhesion induced unjamming reflects the mechanical yielding of the highly deformable monolayer, suggesting an alternative mechanism that cells may robustly gain collective mobility through proliferation in confined environments, which differs from those caused by loosing up a packed particulate assembly. This work is supported by the GWU College Facilitating Funds.

  5. Illustrative view on the magnetocrystalline anisotropy of adatoms and monolayers

    Czech Academy of Sciences Publication Activity Database

    Šipr, Ondřej; Mankovsky, S.; Polesya, S.; Bornemann, S.; Minár, J.; Ebert, H.

    2016-01-01

    Roč. 93, č. 17 (2016), s. 1-13, č. článku 174409. ISSN 2469-9950 R&D Projects: GA ČR(CZ) GAP108/11/0853 Institutional support: RVO:68378271 Keywords : magnetic anisotropy * adatom * monolayer * spin-orbit coupling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  6. Monolayer II-VI semiconductors: A first-principles prediction

    Science.gov (United States)

    Zheng, Hui; Chen, Nian-Ke; Zhang, S. B.; Li, Xian-Bin

    A systematic study of 32 honeycomb monolayer II-VI semiconductors is carried out by first-principles methods. It appears that BeO, MgO, CaO, ZnO, CdO, CaS, SrS, SrSe, BaTe, and HgTe honeycomb monolayers have a good dynamic stability which is revealed by phonon calculations. In addition, from the molecular dynamic (MD) simulation of other unstable candidates, we also find two extra monolayers dynamically stable, which are tetragonal BaS and orthorhombic HgS. The honeycomb monolayers exist in form of either a planar perfect honeycomb or a low-buckled 2D layer, all of which possess a band gap and most of them are in the ultraviolet region. Interestingly, the dynamically stable SrSe has a gap near visible light, and displays exotic electronic properties with a flat top of the valence band, and hence has a strong spin polarization upon hole doping. The honeycomb HgTe has been reported to achieve a topological nontrivial phase under appropriate in-plane tensile strain and spin-orbital coupling (SOC). Some II-VI partners with less than 5% lattice mismatch may be used to design novel 2D heterojunction devices. If synthesized, potential applications of these 2D II-VI families could include optoelectronics, spintronics, and strong correlated electronics. Distinguished Student (DS) Program of APS FIP travel funds.

  7. Topography and instability of monolayers near domain boundaries

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  8. Vertical uniformity of cells and nuclei in epithelial monolayers.

    Science.gov (United States)

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

    2016-01-22

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

  9. Photocarrier dynamics in monolayer phosphorene and bulk black phosphorus.

    Science.gov (United States)

    Zereshki, Peymon; Wei, Yaqing; Ceballos, Frank; Bellus, Matthew Z; Lane, Samuel D; Pan, Shudi; Long, Run; Zhao, Hui

    2018-06-13

    We report a combined theoretical and experimental study on photocarrier dynamics in monolayer phosphorene and bulk black phosphorus. Samples of monolayer phosphorene and bulk black phosphorus were fabricated by mechanical exfoliation, identified according to their reflective contrasts, and protected by covering them with hexagonal boron nitride layers. Photocarrier dynamics in these samples was studied by an ultrafast pump-probe technique. The photocarrier lifetime of monolayer phosphorene was found to be about 700 ps, which is about 9 times longer than that of bulk black phosphorus. This trend was reproduced in our calculations based on ab initio nonadiabatic molecular dynamics combined with time-domain density functional theory in the Kohn-Sham representation, and can be attributed to the smaller bandgap and stronger nonadiabatic coupling in bulk. The transient absorption response was also found to be dependent on the sample orientation with respect to the pump polarization, which is consistent with the previously reported anisotropic absorption of phosphorene. In addition, an oscillating component of the differential reflection signal at early probe delays was observed in the bulk sample and was attributed to the layer-breathing phonon mode with an energy of about 1 meV and a decay time of about 1.35 ps. These results provide valuable information for application of monolayer phosphorene in optoelectronics.

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

    NARCIS (Netherlands)

    Yildirim, O.

    2010-01-01

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

  11. Effect of Structure and Disorder on the Charge Transport in Defined Self-Assembled Monolayers of Organic Semiconductors.

    Science.gov (United States)

    Schmaltz, Thomas; Gothe, Bastian; Krause, Andreas; Leitherer, Susanne; Steinrück, Hans-Georg; Thoss, Michael; Clark, Timothy; Halik, Marcus

    2017-09-26

    Self-assembled monolayer field-effect transistors (SAMFETs) are not only a promising type of organic electronic device but also allow detailed analyses of structure-property correlations. The influence of the morphology on the charge transport is particularly pronounced, due to the confined monolayer of 2D-π-stacked organic semiconductor molecules. The morphology, in turn, is governed by relatively weak van-der-Waals interactions and is thus prone to dynamic structural fluctuations. Accordingly, combining electronic and physical characterization and time-averaged X-ray analyses with the dynamic information available at atomic resolution from simulations allows us to characterize self-assembled monolayer (SAM) based devices in great detail. For this purpose, we have constructed transistors based on SAMs of two molecules that consist of the organic p-type semiconductor benzothieno[3,2-b][1]benzothiophene (BTBT), linked to a C 11 or C 12 alkylphosphonic acid. Both molecules form ordered SAMs; however, our experiments show that the size of the crystalline domains and the charge-transport properties vary considerably in the two systems. These findings were confirmed by molecular dynamics (MD) simulations and semiempirical molecular-orbital electronic-structure calculations, performed on snapshots from the MD simulations at different times, revealing, in atomistic detail, how the charge transport in organic semiconductors is influenced and limited by dynamic disorder.

  12. Nanostructure of polymer monolayer and polyelectrolyte brush at air/water interface by X-ray and neutron reflectometry

    Energy Technology Data Exchange (ETDEWEB)

    Matsuoka, Hideki; Mouri, Emiko; Matsumoto, Kozo [Kyoto Univ., Dept. of Polymer Chemistry, Kyoto (Japan)

    2003-03-01

    The nanostructure of amphiphilic diblock copolymer monolayer on water was directly investigated by in situ X-ray and neutron reflectivity techniques. The diblock copolymer consists of polysilacyclobutane, which is very flexible, as a hydrophobic block and polymethacrylic acid, an anionic polymer, as a hydrophilic block. The polymers with shorter hydrophilic segment formed a very smooth and uniform monolayer with hydrophobic layer on water and dense hydrophilic layer under the water. But the longer hydrophilic segment polymer formed three-layered monolayer with polyelectrolyte brush in addition to hydrophobic and dense hydrophilic layers. The dense hydrophilic layer is thought to be formed to avoid a contact between hydrophobic polymer layer and water. Its role is something like a 'carpet'. An additional interesting information is that the thickness of the 'carpet layer' is almost 15A, independent the surface pressure and hydrophilic polymer length. Highly quantitative information was obtained about the nanostructure of polymer brush under water by neutron reflectometry with the aid of contrast variation technique. X-ray and neutron reflectivity is a very powerful technique to investigate the nanostructure of surface and interfaces, which is important not only for surface nanotechnology but also industrial and medical applications. (author)

  13. ATR-IR spectroscopy for the detection of induced-phase transition in Langmuir-Blodgett monolayer film

    International Nuclear Information System (INIS)

    Widayati, Suci

    1996-01-01

    The rate at which a solid substrate is transferred through the Air/Water interface in the Langmuir-Blodgett process of preparing monomolecular films influences the final structure of the transferred film. This phenomenon has been observed from the attenuated total reflectance infra-red (ATR-IR) spectra of fatty acid monolayer transferred onto germanium substrate. This transfer-induced effect is most evidence when the monolayer is transferred from an expanded region of the surface-pressure-molecular area isotherm, but has limited influence on the hydrocarbon chain conformation of film molecules transferred in the condensed phases at high surface pressure. Such a conformational ordering may due to a kinetically limited phase transition taking place in the meniscus formed between the solid substrate and aqueous sub phase. In addition, these results suggest that the structure of the amphiphilic molecules may modulate the extent and nature of the dipping-speed-induced structural changes taking place in the monomolecular L-B film. In order to use monomolecular L-B films to accurately characterize the structure, orientation and phase properties of monolayers at the Air/Water interface, the L-B transfer must be performed at transfer speeds that minimize this structural phase transition

  14. Proton and hydrogen transport through two-dimensional monolayers

    International Nuclear Information System (INIS)

    Seel, Max; Pandey, Ravindra

    2016-01-01

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

  15. Proton and hydrogen transport through two-dimensional monolayers

    Science.gov (United States)

    Seel, Max; Pandey, Ravindra

    2016-06-01

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

  16. Influence of fatty acids on the binding of warfarin and phenprocoumon to human serum albumin with relation to anticoagulant therapy

    DEFF Research Database (Denmark)

    Vorum, H; Honoré, B

    1996-01-01

    of palmitic, stearic, oleic or linoleic acids with energetic couplings for co-binding of one molecule of each of the fatty acids and one molecule of warfarin of 0.9, 1.1, 0.7 and 0.6 kJ mol-1, respectively. The affinity of phenprocoumon was only increased slightly on addition of palmitate with an energetic...... of warfarin but not of phenprocoumon was correlated to the increasing plasma fatty acid concentration. Anticoagulant therapy with phenprocoumon may thus be less sensitive than warfarin to changes in the fatty acid concentration of plasma. Udgivelsesdato: 1996-Aug...

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

    Science.gov (United States)

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

    2018-05-01

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

  18. Inactivation of catalase monolayers by irradiation with 100 keV electrons

    International Nuclear Information System (INIS)

    Hahn, M.; Seredynski, J.; Baumeister, W.

    1976-01-01

    A catalase monolayer adsorbed on a layer of arachidic acid deposited on a solid support was irradiated with 100 keV electrons simulating the conditions of electron microscopic imaging. Effective doses were calculated taking into account the angular and energy distribution of backscattered electrons. Enzymatic inactivation was chosen as the criterion for damage and was monitored by a rapid and quantifiable but nevertheless sensitive assay. Dose-response curves revealed that inactivation is a one-hit--multiple-target phenomenon, which is consistent with biochemical evidence for a cooperative function of subunits. The experimentally determined target size coincides fairly well with both calculated cross sections for inelastic interactions based on the atomic composition of catalase and with calculated cross sections for ionizing events based on the chemical bonds involved. This legitimates both types of calculations even for complex biomolecules

  19. Fatty acids composition of Spanish black (Morus nigra L.) and white (Morus alba L.) mulberries.

    Science.gov (United States)

    Sánchez-Salcedo, Eva M; Sendra, Esther; Carbonell-Barrachina, Ángel A; Martínez, Juan José; Hernández, Francisca

    2016-01-01

    This research has determined qualitatively and quantitatively the fatty acids composition of white (Morus alba) and black (Morus nigra) fruits grown in Spain, in 2013 and 2014. Four clones of each species were studied. Fourteen fatty acids were identified and quantified in mulberry fruits. The most abundant fatty acids were linoleic (C18:2), palmitic (C16:0), oleic (C18:1), and stearic (C18:0) acids in both species. The main fatty acid in all clones was linoleic (C18:2), that ranged from 69.66% (MN2) to 78.02% (MA1) of the total fatty acid content; consequently Spanish mulberry fruits were found to be rich in linoleic acid, which is an essential fatty acid. The fatty acid composition of mulberries highlights the nutritional and health benefits of their consumption. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Structural, electronic and magnetic properties of Au-based monolayer derivatives in honeycomb structure

    Energy Technology Data Exchange (ETDEWEB)

    Kapoor, Pooja, E-mail: pupooja16@gmail.com; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh, India 171005 (India); Kumar, Ashok [Centre for Physical Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, India, 151001 (India)

    2016-05-23

    We present electronic properties of atomic layer of Au, Au{sub 2}-N, Au{sub 2}-O and Au{sub 2}-F in graphene-like structure within the framework of density functional theory (DFT). The lattice constant of derived monolayers are found to be higher than the pristine Au monolayer. Au monolayer is metallic in nature with quantum ballistic conductance calculated as 4G{sub 0}. Similarly, Au{sub 2}-N and Au{sub 2}-F monolayers show 4G{sub 0} and 2G{sub 0} quantum conductance respectively while semiconducting nature with calculated band gap of 0.28 eV has been observed for Au{sub 2}-O monolayer. Most interestingly, half metalicity has been predicted for Au{sub 2}-N and Au{sub 2}-F monolayers. Our findings may have importance for the application of these monolayers in nanoelectronic and spintronics.

  1. Emergence of Dirac and quantum spin Hall states in fluorinated monolayer As and AsSb

    KAUST Repository

    Zhang, Qingyun

    2016-01-21

    Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer As and AsSb. While the pristine monolayers are semiconductors (direct band gap at the Γ point), fluorination results in Dirac cones at the K points. Fluorinated monolayer As shows a band gap of 0.16 eV due to spin-orbit coupling, and fluorinated monolayer AsSb a larger band gap of 0.37 eV due to inversion symmetry breaking. Spin-orbit coupling induces spin splitting similar to monolayer MoS2. Phonon calculations confirm that both materials are dynamically stable. Calculations of the edge states of nanoribbons by the tight-binding method demonstrate that fluorinated monolayer As is topologically nontrivial in contrast to fluorinated monolayer AsSb.

  2. Modulation of salt (NaCl)-induced effects on oil composition and fatty acid profile of sunflower (Helianthus annuus L.) by exogenous application of salicylic acid.

    Science.gov (United States)

    Noreen, Sibgha; Ashraf, Muhammad

    2010-12-01

    Salicylic acid (SA) is a potential endogenous plant hormone that plays an important role in plant growth and development. Since sunflower yield and its seed oil yield are adversely affected by salinity, in this study the role of SA in modulating salt (NaCl)-induced effects on various yield and oil characteristics of sunflower was investigated. For this purpose a greenhouse experiment comprising two sunflower hybrid lines (Hysun-33 and SF-187), two NaCl levels (0 and 120 mmol L(-1)) and four SA levels (0, 100, 200 and 300 mg L(-1)) was conducted. Salt stress markedly reduced yield, oil content, linoleic acid and δ-tocopherol in both sunflower lines, while it increased linolenic acid, palmitic acid, stearic acid and α- and γ-tocopherols. However, increasing levels of foliar-applied SA resulted in improved achene yield and hundred-achene weight in both lines. Foliar-applied SA caused a significant decrease in oil stearic acid and α- and γ-tocopherols in both lines under non-saline and saline conditions. Salt-induced harmful effects on achene yield and oil characteristics of sunflower could be alleviated by exogenous application of SA. High doses of SA caused a marked increase in sunflower achene oil content as well as some key fatty acids. Copyright © 2010 Society of Chemical Industry.

  3. Changes in cholesterol content and fatty acid composition of serum lipid in irradiated rat

    International Nuclear Information System (INIS)

    Ohashi, Shigeru

    1979-01-01

    The effect of a single dose of whole body irradiation on the serum cholesterol content and fatty acid composition of serum lipids in rats was investigated. A change in the fatty acid composition of liver lipids was also observed. After 600 rad of irradiation, the cholesterol content increased, reached a maximum 3 days after irradiation, and then decreased. After irradiation, an increase in cholesterol content and a marked decrease in triglyceride content were observed, bringing about a change in the amount of total serum lipids. The fatty acid compositions of normal and irradiated rat sera were compared. The relative percentages of palmitic and oleic acids in total lipids decreased while those of stearic and arachidonic acids increased. Serum triglyceride had trace amounts of arachidonic acid and the unsaturated fatty acid component decreased after irradiation. On the other hand, unsaturated fatty acid in cholesterol ester increased after irradiation, while linoleic and arachidonic acids made up 29% and 22% in the controls and 17% and 61% after irradiation, respectively. The fatty acid composition of total liver lipids after irradiation showed a decrease in palmitic and oleic acids and an increase in stearic and arachidonic acids, the same trend as observed in serum lipid fatty acid. Liver cholesterol ester showed trace amounts of linoleic and arachidonic acids and an increase in short-chain fatty acid after irradiation. The major component of serum phospholipids was phosphatidylcholine while palmitostearyl lecithine and unsaturated fatty acid were minor components. Moreover, phosphatidylcholine and phosphatidylethanolamine were the major components of liver phospholipids, having highly unsaturated fatty acids. The changes in fatty acid composition were similar to the changes in total phospholipids. (J.P.N.)

  4. High Fat Diet Administration during Specific Periods of Pregnancy Alters Maternal Fatty Acid Profiles in the Near-Term Rat

    Directory of Open Access Journals (Sweden)

    Marlon E. Cerf

    2016-01-01

    Full Text Available Excessive fat intake is a global health concern as women of childbearing age increasingly ingest high fat diets (HFDs. We therefore determined the maternal fatty acid (FA profiles in metabolic organs after HFD administration during specific periods of gestation. Rats were fed a HFD for the first (HF1, second (HF2, or third (HF3 week, or for all three weeks (HFG of gestation. Total maternal plasma non-esterified fatty acid (NEFA concentrations were monitored throughout pregnancy. At day 20 of gestation, maternal plasma, liver, adipose tissue, and placenta FA profiles were determined. In HF3 mothers, plasma myristic and stearic acid concentrations were elevated, whereas docosahexaenoic acid (DHA was reduced in both HF3 and HFG mothers. In HF3 and HFG mothers, hepatic stearic and oleic acid proportions were elevated; conversely, DHA and linoleic acid (LA proportions were reduced. In adipose tissue, myristic acid was elevated, whereas DHA and LA proportions were reduced in all mothers. Further, adipose tissue stearic acid proportions were elevated in HF2, HF3, and HFG mothers; with oleic acid increased in HF1 and HFG mothers. In HF3 and HFG mothers, placental neutral myristic acid proportions were elevated, whereas DHA was reduced. Further, placental phospholipid DHA proportions were reduced in HF3 and HFG mothers. Maintenance on a diet, high in saturated fat, but low in DHA and LA proportions, during late or throughout gestation, perpetuated reduced DHA across metabolic organs that adapt during pregnancy. Therefore a diet, with normal DHA proportions during gestation, may be important for balancing maternal FA status.

  5. Towards modelling the vibrational signatures of functionalized surfaces: carboxylic acids on H-Si(111) surfaces

    Science.gov (United States)

    Giresse Tetsassi Feugmo, Conrard; Champagne, Benoît; Caudano, Yves; Cecchet, Francesca; Chabal, Yves J.; Liégeois, Vincent

    2012-03-01

    In this work, we investigate the adsorption process of two carboxylic acids (stearic and undecylenic) on a H-Si(111) surface via the calculation of structural and energy changes as well as the simulation of their IR and Raman spectra. The two molecules adsorb differently at the surface since the stearic acid simply physisorbs while the undecylenic acid undergoes a chemical reaction with the hydrogen atoms of the surface. This difference is observed in the change of geometry during the adsorption. Indeed, the chemisorption of the undecylenic acid has a bigger impact on the structure than the physisorption of the stearic acid. Consistently, the former is also characterized by a larger value of adsorption energy and a smaller value of the tilting angle with respect to the normal plane. For both the IR and Raman signatures, the spectra of both molecules adsorbed at the surface are in a first approximation the superposition of the spectra of the Si cluster and of the carboxylic acid considered individually. The main deviation from this simple observation is the peak of the stretching Si-H (ν(Si-H)) mode, which is split into two peaks upon adsorption. As expected, the splitting is bigger for the chemisorption than the physisorption. The modes corresponding to atomic displacements close to the adsorption site display a frequency upshift by a dozen wavenumbers. One can also see the disappearance of the peaks associated with the C=C double bond when the undecylenic acid chemisorbs at the surface. The Raman and IR spectra are complementary and one can observe here that the most active Raman modes are generally IR inactive. Two exceptions to this are the two ν(Si-H) modes which are active in both spectroscopies. Finally, we compare our simulated spectra with some experimental measurements and we find an overall good agreement.

  6. Towards modelling the vibrational signatures of functionalized surfaces: carboxylic acids on H-Si(111) surfaces

    International Nuclear Information System (INIS)

    Tetsassi Feugmo, Conrard Giresse; Champagne, Benoît; Liégeois, Vincent; Caudano, Yves; Cecchet, Francesca; Chabal, Yves J

    2012-01-01

    In this work, we investigate the adsorption process of two carboxylic acids (stearic and undecylenic) on a H-Si(111) surface via the calculation of structural and energy changes as well as the simulation of their IR and Raman spectra. The two molecules adsorb differently at the surface since the stearic acid simply physisorbs while the undecylenic acid undergoes a chemical reaction with the hydrogen atoms of the surface. This difference is observed in the change of geometry during the adsorption. Indeed, the chemisorption of the undecylenic acid has a bigger impact on the structure than the physisorption of the stearic acid. Consistently, the former is also characterized by a larger value of adsorption energy and a smaller value of the tilting angle with respect to the normal plane. For both the IR and Raman signatures, the spectra of both molecules adsorbed at the surface are in a first approximation the superposition of the spectra of the Si cluster and of the carboxylic acid considered individually. The main deviation from this simple observation is the peak of the stretching Si-H (ν(Si-H)) mode, which is split into two peaks upon adsorption. As expected, the splitting is bigger for the chemisorption than the physisorption. The modes corresponding to atomic displacements close to the adsorption site display a frequency upshift by a dozen wavenumbers. One can also see the disappearance of the peaks associated with the C=C double bond when the undecylenic acid chemisorbs at the surface. The Raman and IR spectra are complementary and one can observe here that the most active Raman modes are generally IR inactive. Two exceptions to this are the two ν(Si-H) modes which are active in both spectroscopies. Finally, we compare our simulated spectra with some experimental measurements and we find an overall good agreement. (paper)

  7. The LB Films of Dansyl Chloride Labeled Octadecylamine and Its Fluorescence Lifetime

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Octadecylamine was derivatized with dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride) in order to simplify and understand the LB films of fluorescent probe labeling proteins.Its monolayer and multilayers in the absence and presence of stearic acid were deposited by LB technique.Fluorescence spectra and lifetimes of the fluorescent products were studied to elucidate the microenvironment of molecules in the LB films.

  8. Neutron Reflectivity Measurement for Polymer Dynamics near Graphene Oxide Monolayers

    Science.gov (United States)

    Koo, Jaseung

    We investigated the diffusion dynamics of polymer chains confined between graphene oxide layers using neutron reflectivity (NR). The bilayers of polymethylmetacrylate (PMMA)/ deuterated PMMA (d-PMMA) films and polystyrene (PS)/d-PS films with various film thickness sandwiched between Langmuir-Blodgett (LB) monolayers of graphene oxide (GO) were prepared. From the NR results, we found that PMMA diffusion dynamics was reduced near the GO surface while the PS diffusion was not significantly changed. This is due to the different strength of GO-polymer interaction. In this talk, these diffusion results will be compared with dewetting dynamics of polymer thin films on the GO monolayers. This has given us the basis for development of graphene-based nanoelectronics with high efficiency, such as heterojunction devices for polymer photovoltaic (OPV) applications.

  9. Organosilicon derivatives of BTBT for monolayer organic field effect transistors

    Science.gov (United States)

    Agina, Elena V.; Polinskaya, Marina S.; Trul, Askold A.; Chekusova, Viktoria P.; Sizov, Alexey S.; Borshchev, Oleg V.; Ponomarenko, Sergey A.

    2017-08-01

    Synthesis of novel organosilicon derivatives of [1]benzothieno[3,2-b][1]-benzothiophene (BTBT) linked though flexible aliphatic spacers to a disiloxane anchor group is reported. They were successfully used in monolayer OFETs with the charge carrier mobilities up to 0.02 cm2 /Vs, threshold voltage close to 0 V and On/Off ratio up to 10,000. Influence of the chemical structure of the molecules synthesized on the morphology, molecular 2D ordering in the monolayers and their semiconducting properties is considered. The effect of different methods of the ultrathin semiconducting layer preparation, such as Langmuir-Blodgett, Langmuir-Schaefer, spin coating or doctor blade, on the OFET performance is discussed.

  10. Defective interfering particles in monolayer-propagated Newcastle disease virus

    International Nuclear Information System (INIS)

    Roman, J.M.; Simon, E.H.

    1976-01-01

    Newcastle disease virus (NDV) serially passaged in chick embryo fibroblasts (M-NDV) gives rise to defective interfering (NDV-DI) particles, while NDV passaged in embryonated eggs (E-NDV) does not. Co-infection with these particles and infectious virions results in a 99 percent reduction in yield. Interference is not due to interferon or to prevention of absorption of infectious virions and is specific for NDV. The particles mediating interference sediment at the same velocity as infectious virions. The accumulation of NDV-DI particles in monolayers but not in eggs may be a consequence of the fact that M-NDV virions are larger and probably contain more RNA, or it may reflect differences in NDV replicative processes in eggs and monolayers, or both

  11. Intact penetratin metabolite permeates across Caco-2 monolayers

    DEFF Research Database (Denmark)

    Birch, Ditlev; Christensen, Malene Vinther; Stærk, Dan

    . Previous studies have demonstrated that cell-penetrating peptides (CPPs) may be used as carriers in order to improve the bioavailability of a therapeutic cargo like insulin after oral administration. Penetratin, a commonly used CPP, has been shown to increase the uptake of insulin across Caco-2 cell......-2 cells cultured on permeable filter inserts and in cell lysates, respectively. The epithelial permeation of penetratin and the formed metabolites was assessed by using Caco-2 monolayers cultured on permeable filter inserts. Results Preliminary data revealed that at least one specific metabolite...... is formed upon both intracellular and extracellular degradation of penetratin (figure 1A). Following incubation with epithelium for 4 hours, the metabolite permeated the Caco-2 monolayer and the concentration increased approximately 10-fold when compared to a sample collected following 15 minutes...

  12. Point defect weakened thermal contraction in monolayer graphene.

    Science.gov (United States)

    Zha, Xian-Hu; Zhang, Rui-Qin; Lin, Zijing

    2014-08-14

    We investigate the thermal expansion behaviors of monolayer graphene and three configurations of graphene with point defects, namely the replacement of one carbon atom with a boron or nitrogen atom, or of two neighboring carbon atoms by boron-nitrogen atoms, based on calculations using first-principles density functional theory. It is found that the thermal contraction of monolayer graphene is significantly decreased by point defects. Moreover, the corresponding temperature for negative linear thermal expansion coefficient with the maximum absolute value is reduced. The cause is determined to be point defects that enhance the mechanical strength of graphene and then reduce the amplitude and phonon frequency of the out-of-plane acoustic vibration mode. Such defect weakening of graphene thermal contraction will be useful in nanotechnology to diminish the mismatching or strain between the graphene and its substrate.

  13. Microculture system for studying monolayers of functional beta-cells.

    Science.gov (United States)

    Dobersen, M J; Scharff, J E; Notkins, A L

    1980-04-01

    A method is described for growing monolayers of newborn rat beta-cells in microculture trays. After disruption of the pancreas with collagenase, islets were isolated by Ficoll density gradient centrifugation, trypsinized to obtain individual cells, and plated in 96-well tissue culture trays. The cells were incubated for the first 3 days in growth medium containing 0.1 mM 3-isobutyl-1-methylxanthine to promote monolayer formation. The cultures could be maintained in a functional state, as defined by their responsiveness to known modulators of insulin secretion, for at least 2 weeks. As few as 1 X 10(3) islet cells/well gave results that were reproducible within +/- 10%. It is suggested that the microculture system for islet cells might prove to be a rapid and reproducible screening technique for studying drugs, viruses, or other agents that affect beta-cell function.

  14. MgO monolayer epitaxy on Ni (100)

    Science.gov (United States)

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

    2017-11-01

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

  15. Structures of sub-monolayered silicon carbide films

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  16. Integrated quantitative fractal polarimetric analysis of monolayer lung cancer cells

    Science.gov (United States)

    Shrestha, Suman; Zhang, Lin; Quang, Tri; Farrahi, Tannaz; Narayan, Chaya; Deshpande, Aditi; Na, Ying; Blinzler, Adam; Ma, Junyu; Liu, Bo; Giakos, George C.

    2014-05-01

    Digital diagnostic pathology has become one of the most valuable and convenient advancements in technology over the past years. It allows us to acquire, store and analyze pathological information from the images of histological and immunohistochemical glass slides which are scanned to create digital slides. In this study, efficient fractal, wavelet-based polarimetric techniques for histological analysis of monolayer lung cancer cells will be introduced and different monolayer cancer lines will be studied. The outcome of this study indicates that application of fractal, wavelet polarimetric principles towards the analysis of squamous carcinoma and adenocarcinoma cancer cell lines may be proved extremely useful in discriminating among healthy and lung cancer cells as well as differentiating among different lung cancer cells.

  17. Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers

    Energy Technology Data Exchange (ETDEWEB)

    Piquemal-Banci, M.; Galceran, R.; Bouzehouane, K.; Anane, A.; Petroff, F.; Fert, A.; Dlubak, B.; Seneor, P. [Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau 91767 (France); Caneva, S.; Martin, M.-B.; Weatherup, R. S.; Kidambi, P. R.; Robertson, J.; Hofmann, S. [Department of Engineering, University of Cambridge, Cambridge CB21PZ (United Kingdom); Xavier, S. [Thales Research and Technology, 1 avenue Augustin Fresnel, Palaiseau 91767 (France)

    2016-03-07

    We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

  18. Monolayers and thin films of dextran hydrophobically modified

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  19. Atomic Defects and Doping of Monolayer NbSe2.

    Science.gov (United States)

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

    2017-03-28

    We have investigated the structure of atomic defects within monolayer NbSe 2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe 2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

  20. Channel formation in single-monolayer pentacene thin film transistors

    International Nuclear Information System (INIS)

    Park, B-N; Seo, Soonjoo; Evans, Paul G

    2007-01-01

    The geometrical arrangement of single-molecule-high islands and the contact between them have large roles in determining the electrical properties of field effect transistors (FETs) based on monolayer-scale pentacene thin films. As the pentacene coverage increases through the submonolayer regime there is a percolation transition where islands come into contact and a simultaneous rapid onset of current. At coverages just above the percolation threshold, the electrical properties vary with geometrical changes in the contacts between the pentacene islands. At higher coverages, the FET mobility is much lower than the mobility measured by the van der Pauw method because of high contact resistances in monolayer-scale pentacene film devices. An increase in the van der Pauw mobility of holes as a function of pentacene coverage shows that second layer islands take part in charge transport

  1. Acoustic analog of monolayer graphene and edge states

    International Nuclear Information System (INIS)

    Zhong, Wei; Zhang, Xiangdong

    2011-01-01

    Acoustic analog of monolayer graphene has been designed by using silicone rubber spheres of honeycomb lattices embedded in water. The dispersion of the structure has been studied theoretically using the rigorous multiple-scattering method. The energy spectra with the Dirac point have been verified and zigzag edge states have been found in ribbons of the structure, which are analogous to the electronic ones in graphene nanoribbons. The guided modes along the zigzag edge excited by a point source have been numerically demonstrated. The open cavity and 'Z' type edge waveguide with 60 o corners have also been realized by using such edge states. -- Highlights: → Acoustic analog of monolayer graphene has been designed. → The energy spectra with the Dirac point have been verified. → The zigzag edge states have been found in ribbons of the structure. → The guided modes excited by a point source have been demonstrated. → The open cavity and 'Z' type edge waveguide have been realized.

  2. Plasmonic light-sensitive skins of nanocrystal monolayers

    Science.gov (United States)

    Akhavan, Shahab; Gungor, Kivanc; Mutlugun, Evren; Demir, Hilmi Volkan

    2013-04-01

    We report plasmonically coupled light-sensitive skins of nanocrystal monolayers that exhibit sensitivity enhancement and spectral range extension with plasmonic nanostructures embedded in their photosensitive nanocrystal platforms. The deposited plasmonic silver nanoparticles of the device increase the optical absorption of a CdTe nanocrystal monolayer incorporated in the device. Controlled separation of these metallic nanoparticles in the vicinity of semiconductor nanocrystals enables optimization of the photovoltage buildup in the proposed nanostructure platform. The enhancement factor was found to depend on the excitation wavelength. We observed broadband sensitivity improvement (across 400-650 nm), with a 2.6-fold enhancement factor around the localized plasmon resonance peak. The simulation results were found to agree well with the experimental data. Such plasmonically enhanced nanocrystal skins hold great promise for large-area UV/visible sensing applications.

  3. Actinide Sequestration Using Self-Assembled Monolayers on Mesoporous Supports

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  4. Functional Molecular Junctions Derived from Double Self-Assembled Monolayers.

    Science.gov (United States)

    Seo, Sohyeon; Hwang, Eunhee; Cho, Yunhee; Lee, Junghyun; Lee, Hyoyoung

    2017-09-25

    Information processing using molecular junctions is becoming more important as devices are miniaturized to the nanoscale. Herein, we report functional molecular junctions derived from double self-assembled monolayers (SAMs) intercalated between soft graphene electrodes. Newly assembled molecular junctions are fabricated by placing a molecular SAM/(top) electrode on another molecular SAM/(bottom) electrode by using a contact-assembly technique. Double SAMs can provide tunneling conjugation across the van der Waals gap between the terminals of each monolayer and exhibit new electrical functions. Robust contact-assembled molecular junctions can act as platforms for the development of equivalent contact molecular junctions between top and bottom electrodes, which can be applied independently to different kinds of molecules to enhance either the structural complexity or the assembly properties of molecules. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Energy Technology Data Exchange (ETDEWEB)

    ADZIC,R.

    2000-12-01

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

  6. Mixed 2D molecular systems: Mechanic, thermodynamic and dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Beno, Juraj [Department of Physics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 812 19-SK Bratislava (Slovakia); Weis, Martin [Department of Physics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 812 19-SK Bratislava (Slovakia)], E-mail: Martin.Weis@stuba.sk; Dobrocka, Edmund [Department of Physics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 812 19-SK Bratislava (Slovakia); Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravska cesta 9, 841 04-SK Bratislava (Slovakia); Hasko, Daniel [International Laser Centre, Ilkovicova 3, 812 19-SK Bratislava (Slovakia)

    2008-08-15

    Study of Langmuir monolayers consisting of stearic acid (SA) and dipalmitoylphosphatidylcholine (DPPC) molecules was done by surface pressure-area isotherms ({pi}-A), the Maxwell displacement current (MDC) measurement, X-ray reflectivity (XRR) and atomic force microscopy (AFM) to investigate the selected mechanic, thermodynamic and dielectric properties based on orientational structure of monolayers. On the base of {pi}-A isotherms analysis we explain the creation of stable structures and found optimal monolayer composition. The dielectric properties represented by MDC generated monolayers were analyzed in terms of excess dipole moment, proposing the effect of dipole-dipole interaction. XRR and AFM results illustrate deposited film structure and molecular ordering.

  7. Properties of thiolate monolayers formed on different amalgam electrodes

    Czech Academy of Sciences Publication Activity Database

    Josypčuk, Bohdan; Mareček, Vladimír

    2011-01-01

    Roč. 653, 1-2 (2011), s. 7-13 ISSN 1572-6657 R&D Projects: GA AV ČR IAA400400806; GA ČR GAP206/11/1638; GA MŠk(CZ) LC06063 Institutional research plan: CEZ:AV0Z40400503 Keywords : thiolate monolayer * reductive desorption * charge effect Subject RIV: CG - Electrochemistry Impact factor: 2.905, year: 2011

  8. Immobilization of transition metal ions on zirconium phosphate monolayers

    International Nuclear Information System (INIS)

    Melezhik, A.V.; Brej, V.V.

    1998-01-01

    It is shown that ions of transition metals (copper, iron, vanadyl, titanium) are adsorbed on zirconium phosphate monolayers. The zirconium phosphate threshold capacity corresponds to substitution of all protons of hydroxyphosphate groups by equivalent amounts of copper, iron or vanadyl. Adsorption of polynuclear ions is possible in case of titanium. The layered substance with specific surface up to 300 m 2 /g, wherein ultradispersed titanium dioxide particles are intercalirated between zirconium-phosphate layers, is synthesized

  9. Superior Gas Sensing Properties of Monolayer PtSe2

    KAUST Repository

    Sajjad, Muhammad

    2016-12-15

    First-principles calculations of the structural and electronic properties of monolayer 1T-PtSe2 with adsorbed (a) NO2, (b) NO, (c) NH3, (d) H2O, (e) CO2, and (f) CO molecules are discussed. The results point to great potential of the material in gas sensor applications. Superior sensitivity is demonstrated by transport calculations using the nonequilibrium Green\\'s function method.

  10. Influence of calcium on ceramide-1-phosphate monolayers

    Directory of Open Access Journals (Sweden)

    Joana S. L. Oliveira

    2016-02-01

    Full Text Available Ceramide-1-phosphate (C1P plays an important role in several biological processes, being identified as a key regulator of many protein functions. For instance, it acts as a mediator of inflammatory responses. The mediation of the inflammation process happens due to the interaction of C1P with the C2 domain of cPLA2α, an effector protein that needs the presence of submicromolar concentrations of calcium ions. The aim of this study was to determine the phase behaviour and structural properties of C1P in the presence and absence of millimolar quantities of calcium in a well-defined pH environment. For that purpose, we used monomolecular films of C1P at the soft air/liquid interface with calcium ions in the subphase. The pH was varied to change the protonation degree of the C1P head group. We used surface pressure versus molecular area isotherms coupled with other monolayer techniques as Brewster angle microscopy (BAM, infrared reflection–absorption spectroscopy (IRRAS and grazing incidence X-ray diffraction (GIXD. The isotherms indicate that C1P monolayers are in a condensed state in the presence of calcium ions, regardless of the pH. At higher pH without calcium ions, the monolayer is in a liquid-expanded state due to repulsion between the negatively charged phosphate groups of the C1P molecules. When divalent calcium ions are added, they are able to bridge the highly charged phosphate groups, enhancing the regular arrangement of the head groups. Similar solidification of the monolayer structure can be seen in the presence of a 150 times larger concentration of monovalent sodium ions. Therefore, calcium ions have clearly a strong affinity for the phosphomonoester of C1P.

  11. A microfluidic device for the automated derivatization of free fatty acids to fatty acid methyl esters.

    Science.gov (United States)

    Duong, Cindy T; Roper, Michael G

    2012-02-21

    Free fatty acid (FFA) compositions are examined in feedstock for biodiesel production, as source-specific markers in soil, and because of their role in cellular signaling. However, sample preparation of FFAs for gas chromatography-mass spectrometry (GC-MS) analysis can be time and labor intensive. Therefore, to increase sample preparation throughput, a glass microfluidic device was developed to automate derivatization of FFAs to fatty acid methyl esters (FAMEs). FFAs were delivered to one input of the device and methanolic-HCl was delivered to a second input. FAME products were produced as the reagents traversed a 29 μL reaction channel held at 55 °C. A Design of Experiment protocol was used to determine the combination of derivatization time (T(der)) and ratio of methanolic-HCl:FFA (R(der)) that maximized the derivatization efficiencies of tridecanoic acid and stearic acid to their methyl ester forms. The combination of T(der) = 0.8 min and R(der) = 4.9 that produced optimal derivatization conditions for both FFAs within a 5 min total sample preparation time was determined. This combination of T(der) and R(der) was used to derivatize 12 FFAs with a range of derivatization efficiencies from 18% to 93% with efficiencies of 61% for tridecanoic acid and 84% for stearic acid. As compared to a conventional macroscale derivatization of FFA to FAME, the microfluidic device decreased the volume of methanolic-HCl and FFA by 20- and 1300-fold, respectively. The developed microfluidic device can be used for automated preparation of FAMEs to analyze the FFA compositions of volume-limited samples.

  12. Nutritional quality evaluation of rabbit meat (Flemish Giant breed corelated with fatty acids content

    Directory of Open Access Journals (Sweden)

    Gabriela Frunză

    2016-10-01

    Full Text Available The aim of this study was to assess the nutritional quality of rabbit meat (Flemish Giant breed in terms of content of fatty acids. The biological material consisted of 42 rabbits (17 females and 15 males from which were collected Longissimus dorsi, Semimembranosus and Triceps Brachii muscles immediately after slaughter. The samples were vacuum packaged, frozen at -80 0C, and immediately after thawing have been minced and freeze-dried at -110 0C (using lyophilizer CoolSafe Scanvac. The content in fatty acids was followed through NIRS methodology, using FOSS 6500 spectrophotometer, by gender. Was determined: the saturated fatty acids: C14:0 (Myristic acid, C15: 0 (Pentadecanoic acid, C16: 0 (Palmitic acid, C17: 0 (Heptadecanoic acid and C18: 0 (Stearic acid; monounsaturated fatty acids: Palmitoleic acid (C16: 1n-7, Vaccenic acid, cis-isomer of oleic acid (C18: 1n-7 and oleic acid (C18: 1n-9 and the polyunsaturated fatty acids (ω3 and ω6: C18: 2n-6 (linoleic acid, C18: 3n-3 (Linolenic acid, C20: 2n-6 (Eicosadienoic acid, C20: 3n-6 (Eicosatrienoic acid, C20: 4n-6 (arachidonic acid, C20: 5n-3 (Eicosapentaenoic acid, C22: 4n-6 (Docosatetraenoic acid, C22: 5n-3 (Docosopentaenoic acid and C22: 6n- 3 (docosahexaenoic acid. The results were statistically analyzed, including analysis of variance (ANOVA and was observed significant differences between gender.

  13. Platinum Monolayer Electrocatalysts for Anodic Oxidation of Alcohols.

    Science.gov (United States)

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

    2012-12-06

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

  14. Nanoscale Trapping and Squeeze-Out of Confined Alkane Monolayers.

    Science.gov (United States)

    Gosvami, N N; O'Shea, S J

    2015-12-01

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

  15. Measurement of Exciton Binding Energy of Monolayer WS2

    Science.gov (United States)

    Chen, Xi; Zhu, Bairen; Cui, Xiaodong

    Excitonic effects are prominent in monolayer crystal of transition metal dichalcogenides (TMDCs) because of spatial confinement and reduced Coulomb screening. Here we use linear differential transmission spectroscopy and two-photon photoluminescence excitation spectroscopy (TP-PLE) to measure the exciton binding energy of monolayer WS2. Peaks for excitonic absorptions of the direct gap located at K valley of the Brillouin zone and transitions from multiple points near Γ point of the Brillouin zone, as well as trion side band are shown in the linear absorption spectra of WS2. But there is no gap between distinct excitons and the continuum of the interband transitions. Strong electron-phonon scattering, overlap of excitons around Γ point and the transfer of the oscillator strength from interband continuum to exciton states make it difficult to resolve the electronic interband transition edge even down to 10K. The gap between excited states of the band-edge exciton and the single-particle band is probed by TP-PLE measurements. And the energy difference between 1s exciton and the single-particle gap gives the exciton binding energy of monolayer WS2 to be about 0.71eV. The work is supported by Area of excellency (AoE/P-04/08), CRF of Hong Kong Research Grant Council (HKU9/CRF/13G) and SRT on New Materials of The University of Hong Kong.

  16. Immobilization of Colloidal Monolayers at Fluid–Fluid Interfaces

    Directory of Open Access Journals (Sweden)

    Peter T. Bähler

    2016-07-01

    Full Text Available Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle spacing can be formed, as required, for instance, in surface patterning and sensing applications. At the same time, the immobilization of particles locked into desired structures to be transferred to solid substrates remains challenging. Here, we describe three different strategies to immobilize monolayers of polystyrene microparticles at water–decane interfaces. The first route is based on the leaking of polystyrene oligomers from the particles themselves, which leads to the formation of a rigid interfacial film. The other two rely on in situ interfacial polymerization routes that embed the particles into a polymer membrane. By tracking the motion of the colloids at the interface, we can follow in real-time the formation of the polymer membranes and we interestingly find that the onset of the polymerization reaction is accompanied by an increase in particle mobility determined by Marangoni flows at the interface. These results pave the way for future developments in the realization of thin tailored composite polymer-particle membranes.

  17. Monolayer MoS{sub 2} self-switching diodes

    Energy Technology Data Exchange (ETDEWEB)

    Al-Dirini, Feras, E-mail: alf@unimelb.edu.au; Hossain, Md Sharafat [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Victorian Research Laboratory, National ICT Australia, West Melbourne, Victoria (Australia); Hossain, Faruque M.; Skafidas, Efstratios [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Mohammed, Mahmood A. [Princess Sumaya University for Technology, Amman (Jordan); Nirmalathas, Ampalavanapillai [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Melbourne Networked Society Institute (MNSI), University of Melbourne, Victoria (Australia)

    2016-01-28

    This paper presents a new molybdenum disulphide (MoS{sub 2}) nanodevice that acts as a two-terminal field-effect rectifier. The device is an atomically-thin two-dimensional self-switching diode (SSD) that can be realized within a single MoS{sub 2} monolayer with very minimal process steps. Quantum simulation results are presented confirming the device's operation as a diode and showing strong non-linear I-V characteristics. Interestingly, the device shows p-type behavior, in which conduction is dominated by holes as majority charge carriers and the flow of reverse current is enhanced, while the flow of forward current is suppressed, in contrast to monolayer graphene SSDs, which behave as n-type devices. The presence of a large bandgap in monolayer MoS{sub 2} results in strong control over the channel, showing complete channel pinch-off in forward conduction, which was confirmed with transmission pathways plots. The device exhibited large leakage tunnelling current through the insulating trenches, which may have been due to the lack of passivation; nevertheless, reverse current remained to be 6 times higher than forward current, showing strong rectification. The effect of p-type substitutional channel doping of sulphur with phosphorus was investigated and showed that it greatly enhances the performance of the device, increasing the reverse-to-forward current rectification ratio more than an order of magnitude, up to a value of 70.

  18. A trough for improved SFG spectroscopy of lipid monolayers

    Science.gov (United States)

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

    2017-05-01

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

  19. Photo-induced travelling waves in condensed Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Tabe, Y [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yamamoto, T [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yokoyama, H [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan)

    2003-06-01

    We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. The dynamics can be qualitatively explained by the modified reaction-diffusion model proposed by Reigada, Sagues and Mikhailov.

  20. Strain engineering on transmission carriers of monolayer phosphorene.

    Science.gov (United States)

    Zhang, Wei; Li, Feng; Hu, Junsong; Zhang, Ping; Yin, Jiuren; Tang, Xianqiong; Jiang, Yong; Wu, Bozhao; Ding, Yanhuai

    2017-11-22

    The effects of uniaxial strain on the structure, band gap and transmission carriers of monolayer phosphorene were investigated by first-principles calculations. The strain induced semiconductor-metal as well as direct-indirect transitions were studied in monolayer phosphorene. The position of CBM which belonged to indirect gap shifts along the direction of the applied strain. We have concluded the change rules of the carrier effective mass when plane strains are applied. In band structure, the sudden decrease of band gap or the new formation of CBM (VBM) causes the unexpected change in carrier effective mass. The effects of zigzag and armchair strain on the effective electron mass in phosphorene are different. The strain along zigzag direction has effects on the electrons effective mass along both zigzag and armchair direction. By contrast, armchair-direction strain seems to affect only on the free electron mass along zigzag direction. For the holes, the effective masses along zigzag direction are largely affected by plane strains while the effective mass along armchair direction exhibits independence in strain processing. The carrier density of monolayer phosphorene at 300 K is calculated about [Formula: see text] cm -2 , which is greatly influenced by the temperature and strain. Strain engineering is an efficient method to improve the carrier density in phosphorene.

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

    Science.gov (United States)

    Shigenobu, Hayato; McNamee, Cathy E

    2012-12-15

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

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

    Science.gov (United States)

    Miura, Manabu; Fujimoto, Keiji

    2006-12-01

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

  3. Monolayer-protected clusters of gold nanoparticles: impacts of stabilizing ligands on the heterogeneous electron transfer dynamics and voltammetric detection.

    Science.gov (United States)

    Pillay, Jeseelan; Ozoemena, Kenneth I; Tshikhudo, Robert T; Moutloali, Richard M

    2010-06-01

    Surface electrochemistry of novel monolayer-protected gold nanoparticles (MPCAuNPs) is described. Protecting ligands, (1-sulfanylundec-11-yl)tetraethylene glycol (PEG-OH) and (1-sulfanylundec-11-yl)poly(ethylene glycol)ic acid (PEG-COOH), of three different percent ratios (PEG-COOH:PEG-OH), 1:99 (MPCAuNP-COOH(1%)), 50:50 (MPCAuNP-COOH(50%)), and 99:1 (MPCAuNP-COOH(99%)), were studied. The electron transfer rate constants (k(et)/s(-1)) in organic medium decreased as the concentration of the surface-exposed -COOH group in the protecting monolayer ligand is increased: MPCAuNP-COOH(1%) (approximately 5 s(-1)) > MPCAuNP-COOH(50%) (approximately 4 s(-1)) > MPCAuNP-COOH(99%) (approximately 0.5 s(-1)). In aqueous medium, the trend is reversed. The surface pK(a) was estimated as approximately 8.2 for the MPCAuNP-COOH(1%), while both MPCAuNP-COOH(50%) and MPCAuNP-COOH(99%) showed two pK(a) values of about 5.0 and approximately 8.0. These results have been interpreted in terms of the quasi-solidity and quasi-liquidity of the terminal -OH and -COOH head groups, respectively. MPCAuNP-COOH(99%) excellently suppressed the voltammetric response of the ascorbic acid but enhanced the electrocatalytic detection of epinephrine compared to the other MPCAuNPs studied. This study reveals important factors that should be considered when designing electrode devices that employ monolayer-protected gold nanoparticles and possibly for some other redox-active metal nanoparticles.

  4. Long Chain Saturated and Unsaturated Carboxylic Acids: Filling a Large Gap of Knowledge in Their Enthalpies of Formation.

    Science.gov (United States)

    Rogers, Donald W; Zavitsas, Andreas A

    2017-01-06

    Despite their abundance in nature and their importance in biology, medicine, nutrition, and in industry, gas phase enthalpies of formation of many long chain saturated and unsaturated fatty acids and of dicarboxylic acids are either unavailable or have been estimated with large uncertainties. Available experimental values for stearic acid show a spread of 68 kJ mol -1 . This work fills the knowledge gap by obtaining reliable values by quantum theoretical calculations using G4 model chemistry. Compounds with up to 20 carbon atoms are treated. The theoretical results are in excellent agreement with well established experimental values when such values exist, and they provide a large number of previously unavailable values.

  5. Targeted association mapping demonstrating the complex molecular genetics of fatty acid formation in soybean.

    Science.gov (United States)

    Li, Ying-hui; Reif, Jochen C; Ma, Yan-song; Hong, Hui-long; Liu, Zhang-xiong; Chang, Ru-zhen; Qiu, Li-juan

    2015-10-23

    The relative abundance of five dominant fatty acids (FAs) (palmitic, stearic, oleic, linoleic and linolenic acids) is a major factor determining seed quality in soybean. To clarify the currently poorly understood genetic architecture of FAs in soybean, targeted association analysis was conducted in 421 diverse accessions phenotyped in three environments and genotyped using 1536 pre-selected SNPs. The population of 421 soybean accessions displayed significant genetic variation for each FA. Analysis of the molecular data revealed three subpopulations, which reflected a trend depending on latitude of cultivation. A total of 37 significant (p seed quality of soybean with benefits for human health and for food processing.

  6. Unanticipated C=C bonds in covalent monolayers on silicon revealed by NEXAFS.

    Science.gov (United States)

    Lee, Michael V; Lee, Jonathan R I; Brehmer, Daniel E; Linford, Matthew R; Willey, Trevor M

    2010-02-02

    Interfaces are crucial to material properties. In the case of covalent organic monolayers on silicon, molecular structure at the interface controls the self-assembly of the monolayers, which in turn influences the optical properties and electrical transport. These properties intrinsically affect their application in biology, tribology, optics, and electronics. We use near-edge X-ray absorption fine structure spectroscopy to show that the most basic covalent monolayers formed from 1-alkenes on silicon retain a double bond in one-fifth to two-fifths of the resultant molecules. Unsaturation in the predominantly saturated monolayers will perturb the regular order and affect the dependent properties. The presence of unsaturation in monolayers produced by two different methods also prompts the re-evaluation of other radical-based mechanisms for forming covalent monolayers on silicon.

  7. Esterification of Fatty Acids with Short-Chain Alcohols over Commercial Acid Clays in a Semi-Continuous Reactor

    Directory of Open Access Journals (Sweden)

    Mohamed H. Frikha

    2009-11-01

    Full Text Available Production of fatty acid esters from stearic, oleic, and palmitic acids and short-chain alcohols (methanol, ethanol, propanol, and butanol for the production of biodiesel was investigated in this work. A series of montmorillonite-based clays catalysts (KSF, KSF/0, KP10, and K10 were used as acidic catalysts. The influence of the specific surface area and the acidity of the catalysts on the esterification rate were investigated. The best catalytic activities were obtained with KSF/0 catalyst. The esterification reaction has been carried out efficiently in a semi-continuous reactor at 150°C temperature higher than the boiling points of water and alcohol. The reactor used enabled the continuous removal of water and esterification with hydrated alcohol (ethanol 95% without affecting the original activity of the clay.

  8. Neutrophil-endothelial cell interactions on endothelial monolayers grown on micropore filters.

    Science.gov (United States)

    Taylor, R F; Price, T H; Schwartz, S M; Dale, D C

    1981-01-01

    We have developed a technique for growing endothelial monolayers on micropore filters. These monolayers demonstrate confluence by phase and electron microscopy and provide a functional barrier to passage of radiolabeled albumin. Neutrophils readily penetrate the monolayer in response to chemotaxin, whereas there is little movement in the absence of chemotaxin. This system offers unique advantages over available chemotaxis assays and may have wider applications in the study of endothelial function. Images PMID:7007441

  9. Interferon induction in bovine and feline monolayer cultures by four bluetongue virus serotypes.

    OpenAIRE

    Fulton, R W; Pearson, N J

    1982-01-01

    The interferon inducing ability of bluetongue viruses was studied in bovine and feline monolayer cultures inoculated with each of four bluetongue virus serotypes. Interferon was assayed by a plaque reduction method in monolayer cultures with vesicular stomatitis virus as challenge virus. Interferon was produced by bovine turbinate, Georgia bovine kidney, and Crandell feline kidney monolayer cultures in response to bluetongue virus serotypes 10, 11, 13 and 17. The antiviral substances produced...

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

    DEFF Research Database (Denmark)

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

    Pulmonary surfactant forms the alveolar monolayer at the air/aqueous interface within the lung. During the breathing process, the surface pressure periodically varies from ~40mN/m up to ~70mN/m. The film is mechanically stable during this rapid and reversible expansion. The monolayer consists...... of the alveolae monolayer and at the same time allows reduction of the interfacial tension to ~0mN/m....

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  12. Comparative Study of Fatty Acids Profile in Eleven Wild Mushrooms of Boletacea and Russulaceae Families.

    Science.gov (United States)

    Dimitrijevic, Marija V; Mitic, Violeta D; Jovanovic, Olga P; Stankov Jovanovic, Vesna P; Nikolic, Jelena S; Petrovic, Goran M; Stojanovic, Gordana S

    2018-01-01

    Eleven species of wild mushrooms which belong to Boletaceae and Russulaceae families were examined by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) analysis for the presence of fatty acids. As far as we know, the fatty acid profiles of B. purpureus and B. rhodoxanthus were described for the first time. Twenty-six fatty acids were determined. Linoleic (19.5 - 72%), oleic (0.11 - 64%), palmitic (5.9 - 22%) and stearic acids (0.81 - 57%) were present in the highest contents. In all samples, unsaturated fatty acids dominate. Agglomerative hierarchical clustering was used to display the correlation between the fatty acids and their relationships with the mushroom species. Based on the fatty acids profile in the samples, the mushrooms can be divided into two families: Boletaceae and Russulaceae families, using cluster analysis. © 2018 Wiley-VHCA AG, Zurich, Switzerland.

  13. Chemotaxonomic Evaluation of Species of Turkish Salvia: Fatty Acid Composition of Seed Oils. II

    Directory of Open Access Journals (Sweden)

    Turgut Kılıç

    2007-05-01

    Full Text Available Fatty acids composition of seed oil of Salvia viridis, S. hydrangea, S. blepharochleana, S. chianantha, S. staminea, S. hypergeia,, S. cilicica, S. caespitosa, S. sclarea, S. cadmica, S. microstegia, S. pachystachys and S. verticillata were analyzed by GC/MS. The main compound were found to be as linoleic acid (18:2; 12.8 % to 52.2 %, linolenic acid (18:3; 3.2 % to 47.7 %, oleic acid (18:1; 11.3 % to 25.6 %, palmitic acid (16:0; 0.7 % to 16.8 % and stearic acid (18:0; 1.8 % to 4.8 %. A phylogenetic tree of species of Salvia were reported and compared to 18:3/18:2 ratio of the seed oils. Fatty acid composition of Salvia seed oils could be used as a chemotaxonomical marker.

  14. In vivo incorporation of labeled fatty acids in rat liver lipids after oral administration

    International Nuclear Information System (INIS)

    Leyton, J.; Drury, P.J.; Crawford, M.A.

    1987-01-01

    Striking differences were found in the compartmentalization of fatty acids into liver lipid fractions. The saturated fatty acids--lauric, myristic, palmitic and stearic--were incorporated into phosphoglycerides at faster rates with increasing chain lengths, while triglyceride incorporation was almost uniform. The degree of incorporation of the unsaturated fatty acids into phosphoglycerides (structural) compared to triglyceride (storage and energy) was the converse of their oxidation rates. The incorporation of oleic, linoleic and alpha-linolenic acids was mainly into triglyceride, whereas dihomo-gamma-linolenic acid and arachidonic acid were preferentially incorporated into phosphoglycerides. The data suggest that distribution of each fatty acid is different depending on its destination for structural or energy function

  15. Expression of a fatty acid-binding protein in yeast

    International Nuclear Information System (INIS)

    Scholz, H.

    1991-06-01

    The unicellular eukaryotic microorganism, Saccharomyces cerevisiae, transformed with a plasmid containing a cDNA fragment encoding bovine heart fatty acid-binding protein (H-FABP C ) under the control of the inducible yeast GAL10 promoter, expressed FABP during growth on galactose. The maximum level of immunoreactive FABP, identical in size and isoelectric point to native protein, was reached after approximately 16 hours of induction. In contrast, transcription of the gene was induced within half an hour. Both, protein and mRNA were unstable and degraded within 1 h after repression of transcription. Analysis of subcellular fractions showed that FABP was exclusively associated with the cytosol. FABP expressed in yeast cells was functional as was demonstrated by its capacity to bind long chain fatty acids in an in vitro assay. Growth of all transformants on galactose as the carbon source showed no phenotype at temperatures up to 37 deg C, but the growth of FABP-expressing cells at 37 deg C was significantly retarded. Among the biochemical effects of FABP expression on lipid metabolism is a marked reduction of chain elongation and desaturation of exogenously added 14 C-palmitic acid. This effect is most pronounced in triacylglycerols and phospholipids when cells grow at 30 deg C and 37 deg C, respectively. In an in vitro assay determining the desaturation of palmitoyl CoA by microsomal membranes cytosol with or without exo- or endogenous FABP showed the same stimulation of the reaction. The desaturation of exogenously added 14 C-stearic acid, the pattern of unlabelled fatty acids (saturated vs. unsaturated) and the distribution of exogenously added radioactive fatty acids (palmitic, stearic or oleic acid) among lipid classes was not significantly affected. Using high concentrations (1 mM) the uptake of fatty acids was first stimulated and then inhibited when FABP was expressed. (author)

  16. Electron transfer dynamics across self-assembled N-(2-mercaptoethyl) octadecanamide/mycolic acid layers: impedimetric insights into the structural integrity and interaction with anti-mycolic acid antibodies

    CSIR Research Space (South Africa)

    Ozoemena, KI

    2010-01-01

    Full Text Available The integrity and properties of mycolic acid (MA) antigens integrated into a self-assembled monolayer (SAM) of N-(2-mercaptoethyl)octadecanamide, (MEODA), on a gold electrode have been interrogated using cyclic voltammetry (CV) and electrochemical...

  17. Thermodynamic and real-space structural evidence of a 2D critical point in phospholipid monolayers

    DEFF Research Database (Denmark)

    Nielsen, Lars K.; Bjørnholm, Thomas; Mouritsen, Ole G.

    2007-01-01

    The two-dimensional phase diagram of phospholipid monolayers at air-water interfaces has been constructed from Langmuir compression isotherms. The coexistence region between the solid and fluid phases of the monolayer ends at the critical temperature of the transition. The small-scale lateral...... structure of the monolayers has been imaged by atomic force microscopy in the nm to mu m range at distinct points in the phase diagram. The lateral structure is immobilized by transferring the monolayer from an air-water interface to a solid mica support using Langmuir-Blodgett techniques. A transfer...

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

    International Nuclear Information System (INIS)

    Dutta, P.; Ketterson, J.B.

    1990-01-01

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

  19. Atomic scattering from an adsorbed monolayer solid with a helium beam that penetrates to the substrate

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, L.W.; Dammann, Bernd

    2013-01-01

    Diffraction and one-phonon inelastic scattering of a thermal energy helium atomic beam are evaluated in the situation that the target monolayer lattice is so dilated that the atomic beam penetrates to the interlayer region between the monolayer and the substrate. The scattering is simulated......(1 × 1) commensurate monolayer solid of H2/KCl(001). For the latter, there are cases where part of the incident beam is trapped in the interlayer region for times exceeding 50 ps, depending on the spacing between the monolayer and the substrate and on the angle of incidence. The feedback effect...

  20. Active cell-matrix coupling regulates cellular force landscapes of cohesive epithelial monolayers

    Science.gov (United States)

    Zhao, Tiankai; Zhang, Yao; Wei, Qiong; Shi, Xuechen; Zhao, Peng; Chen, Long-Qing; Zhang, Sulin

    2018-03-01

    Epithelial cells can assemble into cohesive monolayers with rich morphologies on substrates due to competition between elastic, edge, and interfacial effects. Here we present a molecularly based thermodynamic model, integrating monolayer and substrate elasticity, and force-mediated focal adhesion formation, to elucidate the active biochemical regulation over the cellular force landscapes in cohesive epithelial monolayers, corroborated by microscopy and immunofluorescence studies. The predicted extracellular traction and intercellular tension are both monolayer size and substrate stiffness dependent, suggestive of cross-talks between intercellular and extracellular activities. Our model sets a firm ground toward a versatile computational framework to uncover the molecular origins of morphogenesis and disease in multicellular epithelia.

  1. Transport of curcumin derivatives in Caco-2 cell monolayers.

    Science.gov (United States)

    Zeng, Zhen; Shen, Zhe L; Zhai, Shuo; Xu, Jia L; Liang, Hui; Shen, Qin; Li, Qing Y

    2017-08-01

    Curcumin (Cur) is a strong natural antioxidant, who can prevent multiple diseases such as anti-cancer, anti-inflammatory, have a resistance to alzheimer's disease and various malignant diseases. But it has poor oral bioavailability due to its poor aqueous solubility, as well as instability. While its novel derivatives (CB and FE), showed better anti-tumor activity, better anti-oxidant activity and better stability than the original drug (Cur). The aim of this study was to study the intestinal transport of Cur, CB and FE using an in vitro Caco-2 cell monolayer model. The results showed that Cur had a lower permeability coefficient (1.13×10 -6 ±0.11×10 -6 cm/s) for apical-to-basolated (AP-BL) transport at 25μM, while the transport rate for AP to BL flux of CB (3.18×10 -6 ±0.31×10 -6 cm/s) and FE (5.28×10 -6 ±0.83×10 -6 cm/s) were significantly greater than that of Cur. The efflux ratio (ER) value at the concentration of 25μM was 1.31 for Cur, 1.26 for CB and 1.33 for FE, suggesting there was no active efflux involved in the translocation across the Caco-2 cell monolayers for the three compounds. Furthermore, the transport flux of CB and FE was in a concentration dependent manner, suggesting the intestinal transport mechanism in them was passive transport. In summary, the results demonstrated that both the intestinal permeability of CB and FE across Caco-2 cell monolayers was significantly improved compare to Cur. Thus they might show a higher oral bioavailability in vivo, and show the potential application in clinic or nutraceutical. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Polycyclic aromatic hydrocarbons in model bacterial membranes - Langmuir monolayer studies.

    Science.gov (United States)

    Broniatowski, Marcin; Binczycka, Martyna; Wójcik, Aneta; Flasiński, Michał; Wydro, Paweł

    2017-12-01

    High molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) are persistent organic pollutants which due to their limited biodegradability accumulate in soils where their increased presence can lead to the impoverishment of the decomposer organisms. As very hydrophobic PAHs easily penetrate cellular membranes of soil bacteria and can be incorporated therein, changing the membrane fluidity and other functions which in consequence can lead to the death of the organism. The structure and size of PAH molecule can be crucial for its membrane activity; however the correlation between PAH structure and its interaction with phospholipids have not been investigated so far. In our studies we applied phospholipid Langmuir monolayers as model bacterial membranes and investigated how the incorporation of six structurally different PAH molecules change the membrane texture and physical properties. In our studies we registered surface pressure and surface potential isotherms upon the monolayer compression, visualized the monolayer texture with the application of Brewster angle microscopy and searched the ordering of the film-forming molecules with molecular resolution with the application of grazing incidence X-ray diffraction (GIXD) method. It turned out that the phospholipid-PAH interactions are strictly structure dependent. Four and five-ring PAHs of the angular or cluster geometry can be incorporated into the model membranes changing profoundly their textures and fluidity; whereas linear or large cluster PAHs cannot be incorporated and separate from the lipid matrix. The observed phenomena were explained based on structural similarities of the applied PAHs with membrane steroids and hopanoids. Copyright © 2017. Published by Elsevier B.V.

  3. Metal adsorption on monolayer blue phosphorene: A first principles study

    Science.gov (United States)

    Khan, Imran; Son, Jicheol; Hong, Jisang

    2018-01-01

    We investigated the electronic structure, adsorption energies, magnetic properties, dipole moment and work function of metal adatoms (Mg, Cr, Mo, Pd, Pt, and Au) adsorption on a blue phosphorene monolayer. For Mg, Pt and Au metals, the most stable state was found in hollow site while for Cr, Mo and Pd metals we found an adsorption in valley site. We suggest that the Pd and Pt atoms prefer 2D growth mode while the Mg, Cr, Mo and Au atoms prefer 3D island growth mode on monolayer phosphorene. The electronic band structures and magnetic properties were dependent on the doping site and dopant materials. For instance, the semiconducting features were preserved in Mg, Pd, Pt, and Au doped systems. However, the Cr and Mo doped systems displayed half-metallic band structures. The total magnetic moment of 4.05, 2.0 and 0.77 μB /impurity atom were obtained in Cr, Mo and Au doped systems whereas the Mg, Pd and Pt doped systems remained nonmagnetic. We also investigated the magnetic interaction between two transition metal impurities. We observed ferromagnetic coupling between two transition metal impurities in Cr and Mo doped systems while the Au doped system displayed almost degenerated magnetic state. For Mg, Cr, and Mo adsorptions, we found relatively large values of dipole moments compared to those in the Pd, Pt and Au adsorptions. This resulted in a significant suppression of the work function in Mg, Cr and Mo adsorptions. Overall, adsorption can tune the physical and magnetic properties of phosphorene monolayer.

  4. Fabrication of an electrically conductive mixed self-assembled monolayer and its application in an electrochemical immunosensor

    International Nuclear Information System (INIS)

    Lee, Jung Bae; Namgung, Miok; Lee, Sang-Baek; Oh, Se Young

    2008-01-01

    Oligophenylethynylene thiol containing carboxylic acid in the tail group as a conducting wire bioreceptor was synthesized, and then its electrical property was investigated from the measurement of scanning tunneling microscopy (STM). Mixed self-assembled monolayer (SAM) consisting of 4-(2-(4-acetylthio)phenyl)ethynyl) benzoic acid (APBA) and butanethiol was fabricated in order to improve the electrical conductivity owing to the molecular orientation. We have examined the molecular orientation and the electrochemical activity of mixed SAM via X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Especially, the prepared mixed SAM used as a bioreceptor in electrochemical prostate specific antigen (PSA) immunosensor showed higher electrochemical activity than that of the other SAMs

  5. Self-assembled monolayer resists and nanoscale lithography of silicon dioxide thin films by chemically enhanced vapor etching (CEVE)

    Science.gov (United States)

    Pan, M.; Yun, M.; Kozicki, M. N.; Whidden, T. K.

    1996-10-01

    We report on the use of electron-beam exposed monolayers of undecylenic acid in the etch rate enhancement of silicon dioxide films in HF vapor for the formation of nanoscale features in the oxide. Variations of the etching characteristics with electron beam parameters are examined and the results analyzed in terms of proposed models of the etching mechanism. Apparent variations in the relative concentrations of etch initiator with the thermal history of the samples prior to etching provides support for the dominant etch initiator within this system as the carboxylic acid moiety bound at the oxide surface. Other variations in the etching characteristics are discussed in terms of differences in localized concentrations of hydrocarbon crosslinks and the effect that this has upon the etch initiation. The process has been employed in the production of features in silicon dioxide surface masks with sizes down to 50 nm.

  6. Chemical stability of nonwetting, low adhesion self-assembled monolayer films formed by perfluoroalkylsilanization of copper.

    Science.gov (United States)

    Hoque, E; DeRose, J A; Hoffmann, P; Bhushan, B; Mathieu, H J

    2007-03-21

    A self-assembled monolayer (SAM) has been produced by reaction of 1H,1H,2H,2H-perfluorodecyldimethylchlorosilane (PFMS) with an oxidized copper (Cu) substrate and investigated by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), friction force microscopy (FFM), a derivative of AFM, and contact angle measurement. FFM showed a significant reduction in the adhesive force and friction coefficient of PFMS modified Cu (PFMS/Cu) compared to unmodified Cu. The perfluoroalkyl SAM on Cu is found to be extremely hydrophobic, yielding sessile drop static contact angles of more than 130 degrees for pure water and a "surface energy" (which is proportional to the Zisman critical surface tension for a Cu surface with 0 rms roughness) of 14.5 mJm2(nMm). Treatment by exposure to harsh conditions showed that PFMS/Cu SAM can withstand boiling nitric acid (pH=1.8), boiling water, and warm sodium hydroxide (pH=12, 60 degrees C) solutions for at least 30 min. Furthermore, no SAM degradation was observed when PFMS/Cu was exposed to warm nitric acid solution for up to 70 min at 60 degrees C or 50 min at 80 degrees C. Extremely hydrophobic (low surface energy) and stable PFMS/Cu SAMs could be useful as corrosion inhibitors in micro/nanoelectronic devices and/or as promoters for antiwetting, low adhesion surfaces or dropwise condensation on heat exchange surfaces.

  7. Chemical stability of nonwetting, low adhesion self-assembled monolayer films formed by perfluoroalkylsilanization of copper

    International Nuclear Information System (INIS)

    Hoque, E.; DeRose, J. A.; Hoffmann, P.; Bhushan, B.; Mathieu, H. J.

    2007-01-01

    A self-assembled monolayer (SAM) has been produced by reaction of 1H,1H,2H,2H-perfluorodecyldimethylchlorosilane (PFMS) with an oxidized copper (Cu) substrate and investigated by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), friction force microscopy (FFM), a derivative of AFM, and contact angle measurement. FFM showed a significant reduction in the adhesive force and friction coefficient of PFMS modified Cu (PFMS/Cu) compared to unmodified Cu. The perfluoroalkyl SAM on Cu is found to be extremely hydrophobic, yielding sessile drop static contact angles of more than 130 degree sign for pure water and a 'surface energy' (which is proportional to the Zisman critical surface tension for a Cu surface with 0 rms roughness) of 14.5 mJ/m 2 (nM/m). Treatment by exposure to harsh conditions showed that PFMS/Cu SAM can withstand boiling nitric acid (pH=1.8), boiling water, and warm sodium hydroxide (pH=12, 60 degree sign C) solutions for at least 30 min. Furthermore, no SAM degradation was observed when PFMS/Cu was exposed to warm nitric acid solution for up to 70 min at 60 degree sign C or 50 min at 80 degree sign C. Extremely hydrophobic (low surface energy) and stable PFMS/Cu SAMs could be useful as corrosion inhibitors in micro/nanoelectronic devices and/or as promoters for antiwetting, low adhesion surfaces or dropwise condensation on heat exchange surfaces

  8. Nanocomposite Materials of Alternately Stacked C60 Monolayer and Graphene

    Directory of Open Access Journals (Sweden)

    Makoto Ishikawa

    2010-01-01

    Full Text Available We synthesized the novel nanocomposite consisting alternately of a stacked single graphene sheet and a C60 monolayer by using the graphite intercalation technique in which alkylamine molecules help intercalate large C60 molecules into the graphite. Moreover, it is found that the intercalated C60 molecules can rotate in between single graphene sheets by using C13 NMR measurements. This preparation method provides a general way for intercalating huge fullerene molecules into graphite, which will lead to promising materials with novel mechanical, physical, and electrical properties.

  9. Nanocomposite Materials of Alternately Stacked C60 Monolayer and Graphene

    International Nuclear Information System (INIS)

    Ishikawa, M.; Miura, K.; Kamiya, S.; Yoshimoto, S.; Suzuki, M.; Kuwahara, D.; Sasaki, N.

    2010-01-01

    We synthesized the novel nanocomposite consisting alternately of a stacked single graphene sheet and a C 60 monolayer by using the graphite intercalation technique in which alkylamine molecules help intercalate large C 60 molecules into the graphite. Moreover, it is found that the intercalated C 60 molecules can rotate in between single graphene sheets by using C 13 NMR measurements. This preparation method provides a general way for intercalating huge fullerene molecules into graphite, which will lead to promising materials with novel mechanical, physical, and electrical properties.

  10. Friction anisotropy-driven domain imaging on exfoliated monolayer graphene.

    Science.gov (United States)

    Choi, Jin Sik; Kim, Jin-Soo; Byun, Ik-Su; Lee, Duk Hyun; Lee, Mi Jung; Park, Bae Ho; Lee, Changgu; Yoon, Duhee; Cheong, Hyeonsik; Lee, Ki Ho; Son, Young-Woo; Park, Jeong Young; Salmeron, Miquel

    2011-07-29

    Graphene produced by exfoliation has not been able to provide an ideal graphene with performance comparable to that predicted by theory, and structural and/or electronic defects have been proposed as one cause of reduced performance. We report the observation of domains on exfoliated monolayer graphene that differ by their friction characteristics, as measured by friction force microscopy. Angle-dependent scanning revealed friction anisotropy with a periodicity of 180° on each friction domain. The friction anisotropy decreased as the applied load increased. We propose that the domains arise from ripple distortions that give rise to anisotropic friction in each domain as a result of the anisotropic puckering of the graphene.

  11. Fractal growth in impurity-controlled solidification in lipid monolayers

    DEFF Research Database (Denmark)

    Fogedby, Hans C.; Sørensen, Erik Schwartz; Mouritsen, Ole G.

    1987-01-01

    A simple two-dimensional microscopic model is proposed to describe solidifcation processes in systems with impurities which are miscible only in the fluid phase. Computer simulation of the model shows that the resulting solids are fractal over a wide range of impurity concentrations and impurity...... diffusional constants. A fractal-forming mechanism is suggested for impurity-controlled solidification which is consistent with recent experimental observations of fractal growth of solid phospholipid domains in monolayers. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

  12. Kinetics of monolayer graphene growth by segregation on Pd(111)

    Energy Technology Data Exchange (ETDEWEB)

    Mok, H. S.; Murata, Y.; Kodambaka, S., E-mail: kodambaka@ucla.edu [Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, California 90095 (United States); Ebnonnasir, A.; Ciobanu, C. V. [Department of Mechanical Engineering and Materials Science Program, Colorado School of Mines, Golden, Colorado 80401 (United States); Nie, S.; McCarty, K. F. [Sandia National Laboratories, Livermore, California 94550 (United States)

    2014-03-10

    Using in situ low-energy electron microscopy and density functional theory calculations, we follow the growth of monolayer graphene on Pd(111) via surface segregation of bulk-dissolved carbon. Upon lowering the substrate temperature, nucleation of graphene begins on graphene-free Pd surface and continues to occur during graphene growth. Measurements of graphene growth rates and Pd surface work functions establish that this continued nucleation is due to increasing C adatom concentration on the Pd surface with time. We attribute this anomalous phenomenon to a large barrier for attachment of C adatoms to graphene coupled with a strong binding of the non-graphitic C to the Pd surface.

  13. Stability of FDTS monolayer coating on aluminum injection molding tools

    DEFF Research Database (Denmark)

    Cech, Jiri; Taboryski, Rafael J.

    2012-01-01

    microns can obliterate small features. The nanoimprint lithography community extensively uses functional monolayer coatings on silicon/SiO2 lithographic stamps [7–11]. This treatment dramatically reduces stiction, and improves yield and quality of replicated nanostructures. Here we report on a fluorinated...... trichloro-silane based coating deposited on aluminum or its alloys by molecular vapor deposition. We have tested the stability of this coating in challenging conditions of injection molding, an environment with high shear stress from the molten polymer, pressures up to 200 MPa, temperatures up to 250 ◦C...

  14. Spreading dynamics of 2D dipolar Langmuir monolayer phases.

    Science.gov (United States)

    Heinig, P; Wurlitzer, S; Fischer, Th M

    2004-07-01

    We study the spreading of a liquid 2D dipolar droplet in a Langmuir monolayer. Interfacial tensions (line tensions) and microscopic contact angles depend on the scale on which they are probed and obey a scaling law. Assuming rapid equilibration of the microscopic contact angle and ideal slippage of the 2D solid/liquid and solid/gas boundary, the driving force of spreading is merely expressed by the shape-dependent long-range interaction integrals. We obtain good agreement between experiment and numerical simulations using this theory.

  15. Comparison of electronic structure between monolayer silicenes on Ag (111)

    Science.gov (United States)

    Chun-Liang, Lin; Ryuichi, Arafune; Maki, Kawai; Noriaki, Takagi

    2015-08-01

    The electronic structures of monolayer silicenes (4 × 4 and ) grown on Ag (111) surface are studied by scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations. While both phases have similar electronic structures around the Fermi level, significant differences are observed in the higher energy unoccupied states. The DFT calculations show that the contributions of Si 3pz orbitals to the unoccupied states are different because of their different buckled configurations. Project supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) through Grants-in-Aid for Scientific Research (Grant Nos. 24241040 and 25110008) and the World Premier International Research Center Initiative (WPI), MEXT, Japan.

  16. Kinetics of monolayer graphene growth by segregation on Pd(111)

    International Nuclear Information System (INIS)

    Mok, H. S.; Murata, Y.; Kodambaka, S.; Ebnonnasir, A.; Ciobanu, C. V.; Nie, S.; McCarty, K. F.

    2014-01-01

    Using in situ low-energy electron microscopy and density functional theory calculations, we follow the growth of monolayer graphene on Pd(111) via surface segregation of bulk-dissolved carbon. Upon lowering the substrate temperature, nucleation of graphene begins on graphene-free Pd surface and continues to occur during graphene growth. Measurements of graphene growth rates and Pd surface work functions establish that this continued nucleation is due to increasing C adatom concentration on the Pd surface with time. We attribute this anomalous phenomenon to a large barrier for attachment of C adatoms to graphene coupled with a strong binding of the non-graphitic C to the Pd surface

  17. Conduction quantization in monolayer MoS2

    Science.gov (United States)

    Li, T. S.

    2016-10-01

    We study the ballistic conduction of a monolayer MoS2 subject to a spatially modulated magnetic field by using the Landauer-Buttiker formalism. The band structure depends sensitively on the field strength, and its change has profound influence on the electron conduction. The conductance is found to demonstrate multi-step behavior due to the discrete number of conduction channels. The sharp peak and rectangular structures of the conductance are stretched out as temperature increases, due to the thermal broadening of the derivative of the Fermi-Dirac distribution function. Finally, quantum behavior in the conductance of MoS2 can be observed at temperatures below 10 K.

  18. The dependence of lipid monolayer lipolysis on surface pressure.

    OpenAIRE

    Hall, D G

    1992-01-01

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

  19. Structure of adsorbed monolayers. The surface chemical bond

    International Nuclear Information System (INIS)

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

    1984-06-01

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

  20. Oleic acid biosynthesis in cyanobacteria

    International Nuclear Information System (INIS)

    VanDusen, W.J.; Jaworski, J.G.

    1986-01-01

    The biosynthesis of fatty acids in cyanobacteria is very similar to the well characterized system found in green plants. However, the initial desaturation of stearic acid in cyanobacteria appears to represent a significant departure from plant systems in which stearoyl-ACP is the exclusive substrate for desaturation. In Anabaena variabilis, the substrate appears to be monoglucosyldiacylglycerol, a lipid not found in plants. The authors examined five different cyanobacteria to determine if the pathway in A. variabilis was generally present in other cyanobacteria. The cyanobacteria studied were A. variabilis, Chlorogloeopsis sp., Schizothrix calcicola, Anacystis marina, and Anacystis nidulans. Each were grown in liquid culture, harvested, and examined for stearoyl-ACP desaturase activity or incubated with 14 CO 2 . None of the cyanobacteria contained any stearoyl-ACP desaturase activity in whole homogenates or 105,000g supernatants. All were capable of incorporating 14 CO 2 into monoglucosyldiacylglycerol and results from incubations of 20 min, 1 hr, 1 hr + 10 hr chase were consistent with monoglucosyldiacylglycerol serving as precursor for monogalctosyldiacylglycerol. Thus, initial evidence is consistent with oleic acid biosynthesis occurring by desaturation of stearoyl-monoglucosyldiacylglycerol in all cyanobacteria

  1. Study on fatty acids composition of lipid class in fish oil, proximate analysis and calorie value of kijar in Iran

    Directory of Open Access Journals (Sweden)

    Ali Aberoumand

    2017-01-01

    Full Text Available 14.00 This aim of this research was to determine fatty acids and raw proximate composition and calorie value of fish Kijar in Iran. The fatty acids and proximate composition Kijar was determined. The established AOAC (Association of Official Agricultural Chemist, USA methods were followed for composition bio chemical of fish. Mean moisture, fat, protein, ash, carbohydrate contents and calorie value of raw fish were 70.81%, 5.88%, 17.80%, 3.41%, 2.1% and 132.52 kcal, respectively. Among fatty acids, palmitic acid was a major fatty acid while stearic acid was the other major constituent. Unsaturated monoenoic fatty acids (oleic and palmitoleic acids were major constituents. Important unsaturated fatty acids such as EPA and DHA, were also identified. percentage composition of fatty acids in the lipid classes of oil of Saurida undosquamis which the saturated fatty acids ranges from 58% to 72.14%. Palmitic acid is predominant and its composition ranges 38.64% to 48.98% while stearic acid ranges from 11.35% to 19.50%. Among unsaturated fatty acids, monoenoic are the major fatty acids. Oleic acid ranges from 12.15% to 27.48%. It is concluded that fish kijar found as health seafood for Iranian southern peoples form point of view of nutritional values and valuable fatty acids. Therefore it is recommended people put this fish in diet basket and it consumed three times in the week. Normal 0 false false false EN-US X-NONE AR-SA

  2. Relationship between fatty acid composition and biodiesel quality for nine commercial palm oils

    Directory of Open Access Journals (Sweden)

    Chanida Lamaisri

    2015-08-01

    Full Text Available Biodiesel is an alternative fuel consisting of alkyl esters of fatty acids from vegetable oils or animal fats. The fatty acid compositions in the oils used as feedstock can influence quality of the biodiesel. In the present study, oil content and fatty acid composition of mesocarp and kernel oil were examined from nine commercial oil palm Elaeis guineensis cultivars. Saponification number, iodine value and cetane number were calculated from palm oil fatty acid methyl ester compositions. Fruits of tenera oil palm were collected from a farmer’s plantation in Dan Makham Tia District, Kanchanaburi Province in 2009. Variation between cultivars was observed in oil content and fatty acid profile of mesocarp oil rather than kernel oil. The percentage of oil in dry mesocarp ranged from 63.8% to 74.9%. The mesocarp oil composed of 41.5 - 51.6% palmitic acid, 3.58-7.10% stearic acid, 32.8-42.5% oleic acid and 9.3-13.0% linoleic acid. Likewise saponification number, iodine value and cetane number of mesocarp oil fatty acid methyl ester showed more variation among cultivars, ranging from 196.5-198.9, 45.7-54.6 and 61.8-63.6, respectively. While those of kernel oil fatty acid methyl ester showed no different among cultivars, ranging from 229-242, 13.6-16.4 and 65.3-66.5, respectively. The cetane number of fatty acid methyl ester positively correlated with contents of myristic, palmitic and stearic acids in palm oil and saponification number of biodiesel, but negatively correlated with iodine value

  3. Biotransformation of hydralazine (HDZ) in monolayer cultures of rabbit hepatocytes

    International Nuclear Information System (INIS)

    McQueen, C.A.; Rosado, R.R.

    1990-01-01

    Adverse reactions to HDZ have been associated with the acetylator polymorphism; slow acetylators are more likely to develop HDZ-induced lupus erythematosus. In studying the role of this polymorphism in susceptibility to HDZ toxicity, the biotransformation of HDZ was investigated in rabbit hepatocytes. New Zealand white rabbits, like humans, are classified as rapid or slow acetylators. Heptocytes were isolated from rapid acetylator rabbits by collagenase perfusion. Monolayer cultures were initiated and exposed to 14 C-HDZ. Since HDZ is unstable at neutral pH, parallel incubations were done in the absence of cells. Metabolites in the media were determined by reverse phase HPLC. Phthalazine (P), phthalazinone (PZ), triazoloph-thalazine (TP), methyl TP (MTP) and 3-hydroxy MTP were identified. In the absence of cells, more TP was formed than MTP, probably resulting from reaction of HDZ with components in the medium. In the presence of cells, there was a three-fold increase in MTP, while the amount of TP was relatively constant. Only trace amounts of P, PZ 3-hydroxy MTP were detected. These data indicate that monolayer cultures of rapid acetylator rabbit hepatocytes were capable of metabolizing HDZ with acetylation playing a major role. These studies are being extended to cells from slow acetylator rabbits

  4. Thermodynamics of interaction of ionic liquids with lipid monolayer.

    Science.gov (United States)

    Bhattacharya, G; Mitra, S; Mandal, P; Dutta, S; Giri, R P; Ghosh, S K

    2018-06-01

    Understanding the interaction of ionic liquids with cellular membrane becomes utterly important to comprehend the activities of these liquids in living organisms. Lipid monolayer formed at the air-water interface is employed as a model system to follow this interaction by investigating important thermodynamic parameters. The penetration kinetics of the imidazolium-based ionic liquid 1-decyl-3-methylimidazolium tetrafluoroborate ([DMIM][BF4]) into the zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid layer is found to follow the Boltzmann-like equation that reveals the characteristic time constant which is observed to be the function of initial surface pressure. The enthalpy and entropy calculated from temperature-dependent pressure-area isotherms of the monolayer show that the added ionic liquids bring about a disordering effect in the lipid film. The change in Gibbs free energy indicates that an ionic liquid with longer chain has a far greater disordering effect compared to an ionic liquid with shorter chain. The differential scanning calorimetric measurement on a multilamellar vesicle system shows the main phase transition temperature to shift to a lower value, which, again, indicates the disordering effect of the ionic liquid on lipid membrane. All these studies fundamentally point out that, when ionic liquids interact with lipid molecules, the self-assembled structure of a cellular membrane gets perturbed, which may be the mechanism of these molecules having adverse effects on living organisms.

  5. Coherent quantum dynamics of excitons in monolayer transition metal dichalcogenides

    KAUST Repository

    Moody, Galan

    2016-03-14

    Transition metal dichalcogenides (TMDs) have garnered considerable interest in recent years owing to their layer thickness-dependent optoelectronic properties. In monolayer TMDs, the large carrier effective masses, strong quantum confinement, and reduced dielectric screening lead to pronounced exciton resonances with remarkably large binding energies and coupled spin and valley degrees of freedom (valley excitons). Coherent control of valley excitons for atomically thin optoelectronics and valleytronics requires understanding and quantifying sources of exciton decoherence. In this work, we reveal how exciton-exciton and exciton-phonon scattering influence the coherent quantum dynamics of valley excitons in monolayer TMDs, specifically tungsten diselenide (WSe2), using two-dimensional coherent spectroscopy. Excitation-density and temperature dependent measurements of the homogeneous linewidth (inversely proportional to the optical coherence time) reveal that exciton-exciton and exciton-phonon interactions are significantly stronger compared to quasi-2D quantum wells and 3D bulk materials. The residual homogeneous linewidth extrapolated to zero excitation density and temperature is ~1:6 meV (equivalent to a coherence time of 0.4 ps), which is limited only by the population recombination lifetime in this sample. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  6. Simvastatin Ameliorates Matrix Stiffness-Mediated Endothelial Monolayer Disruption.

    Directory of Open Access Journals (Sweden)

    Marsha C Lampi

    Full Text Available Arterial stiffening accompanies both aging and atherosclerosis, and age-related stiffening of the arterial intima increases RhoA activity and cell contractility contributing to increased endothelium permeability. Notably, statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase inhibitors whose pleiotropic effects include disrupting small GTPase activity; therefore, we hypothesized the statin simvastatin could be used to attenuate RhoA activity and inhibit the deleterious effects of increased age-related matrix stiffness on endothelial barrier function. Using polyacrylamide gels with stiffnesses of 2.5, 5, and 10 kPa to mimic the physiological stiffness of young and aged arteries, endothelial cells were grown to confluence and treated with simvastatin. Our data indicate that RhoA and phosphorylated myosin light chain activity increase with matrix stiffness but are attenuated when treated with the statin. Increases in cell contractility, cell-cell junction size, and indirect measurements of intercellular tension that increase with matrix stiffness, and are correlated with matrix stiffness-dependent increases in monolayer permeability, also decrease with statin treatment. Furthermore, we report that simvastatin increases activated Rac1 levels that contribute to endothelial barrier enhancing cytoskeletal reorganization. Simvastatin, which is prescribed clinically due to its ability to lower cholesterol, alters the endothelial cell response to increased matrix stiffness to restore endothelial monolayer barrier function, and therefore, presents a possible therapeutic intervention to prevent atherogenesis initiated by age-related arterial stiffening.

  7. Acamprosate permeability across Caco-2 cell monolayer is predominantly paracellular

    DEFF Research Database (Denmark)

    Antonescu, Irina-Elena; Steffansen, Bente

    support area, thickness, and porosity). Results. The mean (± SD) Papp, exp of acamprosate and [14C]-mannitol across Caco-2 cell monolayers was measured as 0.19 ± 0.07 x 10-6 cm/s (n = 2, N = 3) and 0.35 ± 0.17 x 10-6 cm/s (n = 3, N = 4), respectively. Acamprosate PUBL and Pf were estimated as 200 - 3150 x...... role in acamprosate permeability, as only a very low fraction of acamprosate is in the neutral form at pH 7.4. The estimated acamprosate Ppara accounts for nearly 100% of the mathematically determined acamprosate Papp, calc (0.20 ± 0.10 x 10-6 cm/s), which matches well with the experimentally...... to the overall acamprosate apparent permeability. Methods. Acamprosate apparent permeability (Papp, exp) was determined across Caco-2 monolayers in the apical-to-basolateral transport direction using a buffer pH of 7.4 and several cell passages (N). Acamprosate concentrations were quantified by LC...

  8. Fabrication and surface transformation of FePt nanoparticle monolayer

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  9. Lipid dip-pen nanolithography on self-assembled monolayers

    International Nuclear Information System (INIS)

    Gavutis, Martynas; Navikas, Vytautas; Rakickas, Tomas; Vaitekonis, Šarūnas; Valiokas, Ramūnas

    2016-01-01

    Dip-pen nanolithography (DPN) with lipids as an ink enables functional micro/nanopatterning on different substrates at high process speeds. However, only a few studies have addressed the influence of the physicochemical properties of the surface on the structure and phase behavior of DPN-printed lipid assemblies. Therefore, by combining the scanning probe and optical imaging techniques in this work we have analyzed lipid microdomain formation on the self-assembled monolayers (SAMs) on gold as well-defined model surfaces that displayed hydrophilic (protein-repellent) or hydrophobic (protein-adhesive) characteristics. We have found that on the tri(ethylene glycol)-terminated SAM the lipid ink transfer was fast (∼10 –1 μm 3 s −1 ), quasi-linear and it yielded unstable, sparsely packed lipid microspots. Contrary to this, on the methyl-terminated SAM the lipid transfer was ∼20 times slower, nonlinear, and the obtained stable dots of ∼1 μm in diameter consisted of lipid multilayers. Our comparative analysis indicated that the measured lipid transfer was consistent with the previously reported so-called polymer transfer model (Felts et al 2012, Nanotechnology 23 215301). Further on, by employing the observed distinct contrast in the DPN ink behavior we constructed confined lipid microdomains on pre-patterned SAMs, in which the lipids assembled either into monolayer or multilamellar phases. Such microdomains can be further utilized for lipid membrane mimetics in microarray and lab-on-a-chip device formats. (paper)

  10. Formation of intra-island grain boundaries in pentacene monolayers.

    Science.gov (United States)

    Zhang, Jian; Wu, Yu; Duhm, Steffen; Rabe, Jürgen P; Rudolf, Petra; Koch, Norbert

    2011-12-21

    To assess the formation of intra-island grain boundaries during the early stages of pentacene film growth, we studied sub-monolayers of pentacene on pristine silicon oxide and silicon oxide with high pinning centre density (induced by UV/O(3) treatment). We investigated the influence of the kinetic energy of the impinging molecules on the sub-monolayer growth by comparing organic molecular beam deposition (OMBD) and supersonic molecular beam deposition (SuMBD). For pentacene films fabricated by OMBD, higher pentacene island-density and higher polycrystalline island density were observed on UV/O(3)-treated silicon oxide as compared to pristine silicon oxide. Pentacene films deposited by SuMBD exhibited about one order of magnitude lower island- and polycrystalline island densities compared to OMBD, on both types of substrates. Our results suggest that polycrystalline growth of single islands on amorphous silicon oxide is facilitated by structural/chemical surface pinning centres, which act as nucleation centres for multiple grain formation in a single island. Furthermore, the overall lower intra-island grain boundary density in pentacene films fabricated by SuMBD reduces the number of charge carrier trapping sites specific to grain boundaries and should thus help achieving higher charge carrier mobilities, which are advantageous for their use in organic thin-film transistors.

  11. Performance of monolayer graphene nanomechanical resonators with electrical readout.

    Science.gov (United States)

    Chen, Changyao; Rosenblatt, Sami; Bolotin, Kirill I; Kalb, William; Kim, Philip; Kymissis, Ioannis; Stormer, Horst L; Heinz, Tony F; Hone, James

    2009-12-01

    The enormous stiffness and low density of graphene make it an ideal material for nanoelectromechanical applications. Here, we demonstrate the fabrication and electrical readout of monolayer graphene resonators, and test their response to changes in mass and temperature. The devices show resonances in the megahertz range, and the strong dependence of resonant frequency on applied gate voltage can be fitted to a membrane model to yield the mass density and built-in strain of the graphene. Following the removal and addition of mass, changes in both density and strain are observed, indicating that adsorbates impart tension to the graphene. On cooling, the frequency increases, and the shift rate can be used to measure the unusual negative thermal expansion coefficient of graphene. The quality factor increases with decreasing temperature, reaching approximately 1 x 10(4) at 5 K. By establishing many of the basic attributes of monolayer graphene resonators, the groundwork for applications of these devices, including high-sensitivity mass detectors, is put in place.

  12. Coherent quantum dynamics of excitons in monolayer transition metal dichalcogenides

    KAUST Repository

    Moody, Galan; Hao, Kai; Dass, Chandriker Kavir; Singh, Akshay; Xu, Lixiang; Tran, Kha; Chen, Chang-Hsiao; Li, Ming-yang; Li, Lain-Jong; Clark, Genevieve; Bergh ä user, Gunnar; Malic, Ermin; Knorr, Andreas; Xu, Xiaodong; Li, Xiaoqin

    2016-01-01

    Transition metal dichalcogenides (TMDs) have garnered considerable interest in recent years owing to their layer thickness-dependent optoelectronic properties. In monolayer TMDs, the large carrier effective masses, strong quantum confinement, and reduced dielectric screening lead to pronounced exciton resonances with remarkably large binding energies and coupled spin and valley degrees of freedom (valley excitons). Coherent control of valley excitons for atomically thin optoelectronics and valleytronics requires understanding and quantifying sources of exciton decoherence. In this work, we reveal how exciton-exciton and exciton-phonon scattering influence the coherent quantum dynamics of valley excitons in monolayer TMDs, specifically tungsten diselenide (WSe2), using two-dimensional coherent spectroscopy. Excitation-density and temperature dependent measurements of the homogeneous linewidth (inversely proportional to the optical coherence time) reveal that exciton-exciton and exciton-phonon interactions are significantly stronger compared to quasi-2D quantum wells and 3D bulk materials. The residual homogeneous linewidth extrapolated to zero excitation density and temperature is ~1:6 meV (equivalent to a coherence time of 0.4 ps), which is limited only by the population recombination lifetime in this sample. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  13. Mixed carboranethiol self-assembled monolayers on gold surfaces

    Science.gov (United States)

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

    2017-08-01

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

  14. Effects of chronic fly ash exposure on golden hamsters: changes in lung phospholipids and their fatty acid composition as a result of inhalation

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, I; Negishi, T; Kamihira, M

    1986-01-01

    Changes in lung phospholipids of golden hamsters exposed to 2 mg/mT coal fly ash for 180 days, 7 days/week, 20 hours/day were examined. In the exposed group the amount of phospholipids in lavaged lung organ increased significantly compared with the control group, but in pulmonary surfactant did not. As regards lipid composition of phospholipids in lavaged lung organ, phosphatidylcholine was slightly increased but sphingomyelin was decreased by exposure. Some significant changes in fatty acid composition of phospholipids were observed between exposed and control group. In pulmonary surfactant, palmitic acid showed no change but myristic acid and oleic acid decreased. On the other hand, in lavaged lung organ, palmitic acid increased but stearic acid and decosatetraenoic acid decreased. Arachidonic acid composition increased in both parts of lung. An increase in the proportion of polyunsaturated fatty acid in whole fatty acid of phospholipids was found in pulmonary surfactant of exposed hamsters. 24 refs., 2 figs., 3 tabs.

  15. Characterization of cider apples on the basis of their fatty acid profiles.

    Science.gov (United States)

    Blanco-Gomis, Domingo; Mangas Alonso, Juan J; Margolles Cabrales, Inmaculada; Arias Abrodo, Pilar

    2002-02-27

    In the current study, the fatty acids composition of 30 monovarietal apple juices from six cider apple varieties belonging to two categories was analyzed. The different apple juices were obtained from three consecutive harvests (1997, 1998, and 1999). The fatty acids concentration in apple juice together with chemometric techniques such as principal components analysis (PCA), soft independent modeling of class analogy (SIMCA), and linear discriminant analysis (LDA), allowed us to differentiate apple juices on the basis of the sweet or sharp category to which the cider apple variety belongs. Fatty acids such as the unsaturated oleic and linoleic acids, and saturated caprylic, capric, stearic, and palmitic acids were related to the sweet cider apple category, while pentadecanoic acid is related to the sharp class.

  16. Radiolabeled 9- or 10-monoiodostearic acid and 9- or 10-monoiodostearyl carnitine: Pt. 1

    International Nuclear Information System (INIS)

    Reed, K.W.; Ueda, C.T.; Murray, W.J.; Augustine, S.C.

    1989-01-01

    The purpose of this investigation was to synthesize and purify radiolabeled 9- or 10-monoiodostearyl carnitine for potential use as a perfusion and metabolic imaging agent for the heart. Oleic acid was iodinated via a free radical addition reaction of Hl across the double bond to give 9- or 10-monoiodostearic acid which in turn was esterified with carnitine. The identity of 9- or 10-monoiodostearic acid and 9-or 10-monoiodostearyl carnitine was determined using nuclear magnetic resonance (NMR), infrared (i.r.), ultraviolet (u.v.), and mass spectroscopy. The purity of the fatty acid and carnitine ester was established by thin layer chromatography. 9- or 10-Monoiodo[ 125 I]stearic acid and 9- or 10-monoiodo[ 125 I]stearyl carnitine were synthesized via the isotopic exchange of 125 I for cold iodine bonded to 9- or 10-monoiodostearic acid and 9- or 10-monoiodostearyl carnitine. (author)

  17. Exploitation of genetic resources for improvement of unsaturated fatty acid in sunflower

    International Nuclear Information System (INIS)

    Haq, U.A.; Mehmood, K.

    2008-01-01

    Twenty-five inbred lines (Cytoplasmic male sterile and 12 fertility restorer) annuus synthesized at the oilseeds research institute Faisalabad. Pakistan were analyzed on gas chromatograph for their fatty acid status. The palmitic, stearic, oleic and linoleic acid ranged form 5.62-11.02% 1.09-3.08%, 21.40-50.70% and 40.60-69.10% respectively. The saturate fatty acid may increase the cholesterol level in the blood. This deposition of cholestrol in the blood vesels is a major cause of heart attack. By screening our germplasm on the basis of fatty acid profile, we can use their inbred lines having low percentage of saturated high percentage of unsaturated fatty acids which may benefit sunflower industry through increased consumer performance for a low saturated fatty acid sunflower products. RL-58, RL-52, ORI-85 and ORI-2 are recommended for the development of commercial hybrids with quality edible oil. (author)

  18. Fatty acids profile of chia oil-loaded lipid microparticles

    Directory of Open Access Journals (Sweden)

    M. F. Souza

    Full Text Available ABSTRACT Encapsulation of poly-unsaturated fatty acid (PUFAis an alternative to increase its stability during processing and storage. Chia (Salvia hispanica L. oil is a reliable source of both omega-3 and omega-6 and its encapsulation must be better evaluated as an effort to increase the number of foodstuffs containing PUFAs to consumers. In this work chia oil was extracted and encapsulated in stearic acid microparticles by the hot homogenization technique. UV-Vis spectroscopy coupled with Multivariate Curve Resolution with Alternating Least-Squares methodology demonstrated that no oil degradation or tocopherol loss occurred during heating. After lyophilization, the fatty acids profile of the oil-loaded microparticles was determined by gas chromatography and compared to in natura oil. Both omega-3 and omega-6 were effectively encapsulated, keeping the same omega-3:omega-6 ratio presented in the in natura oil. Calorimetric analysis confirmed that encapsulation improved the thermal stability of the chia oil.

  19. Micelles versus Ribbons: How Congeners Drive the Self-Assembly of Acidic Sophorolipid Biosurfactants.

    Science.gov (United States)

    Dhasaiyan, Prabhu; Le Griel, Patrick; Roelants, Sophie; Redant, Emile; Van Bogaert, Inge N A; Prevost, Sylvain; Prasad, B L V; Baccile, Niki

    2017-03-17

    Sophorolipids (SLs), a class of microbially derived biosurfactants, are reported by different research groups to have different self-assembled structures (either micelles or giant ribbons) under the same conditions. Here we explore the reasons behind these contradictory results and attribute these differences to the role of specific congeners that are present in minute quantities. We show that a sample composed of a majority of oleic acid (C18:1) sophorolipid in the presence of only 0.5 % (or more) of congeners with stearic acid (C18:0) or linoleic acid (C18:2) results in the formation of micelles that are stable over long periods of time. Conversely, the presence of only 10 to 15 % of congeners with a stearic acid chain gives fibrillar structures instead of micelles. To study the mechanisms responsible, oleic acid SLs devoid of any other congeners were prepared. Very interestingly, this sample can self-assemble into either micelles or fibers depending on minute modifications to the self-assembly conditions. The findings are supported by light scattering, small-angle X-ray scattering, transmission electron microscopy under cryogenic conditions, high-pressure liquid chromatography, and NMR spectroscopy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Metallic Langmuir and Langmuir-Blodgett films based on TTF derivatives and fatty acid

    International Nuclear Information System (INIS)

    Ohnuki, H.; Ishizaki, Y.; Suzuki, M.; Desbat, B.; Delhaes, P.; Giffard, M.; Imakubo, T.; Mabon, G.; Izumi, M.

    2002-01-01

    Recent progress in the metallic conducting Langmuir-Blodgett (LB) films built from TTF derivative and fatty acids is reported. A simple LB method of transferring the mixed Langmuir (L) film of BEDO-TTF (BO) and stearic acid (SA) onto substrates provided metallic conducting LB films. A homogeneous L film formation on the water surface observed by Brewster angle microscope (BAM) is an essential factor for the well-ordered LB films. In the L film, the carboxylate group of fatty acid forms anion layer bringing about a spontaneous formation of mixed valence state (MVS) of BO layer. Similar spontaneous formation was also found in the molecular combination of nonoxygen-substituted donor of EDT-TTF and octadecanesulfonic acid (OS). This type of reaction would be useful for obtaining conducting LB films. For the LB films of BEDO-TTF and stearic acid, we found a negative transverse magnetoresistance at low temperature that was interpreted in the weak localization of a two-dimensional (2D) electronic system based on the well-defined conducting layer